6 th Nanoscience and Nanotechnology Conference, zmir, 2010 Oral - - PDF document

LXIV

6th Nanoscience and Nanotechnology Conference, İzmir, 2010

6th Nanoscience and Nanotechnology Conference, İzmir, 2010

Oral Presentations June 15-18

Golden Dolphin Hotel Çeşme İzmir

Production of CdO Nanoparticles from Cd(OH)2 Precursor by Calcination

Ahmet Avci, Volkan Eskizeybek, Okan Demir

1Department of Mechanical Engineering, Selcuk University, Konya 42075, Turkey

Abstract— In this study, cadmium hydroxide (Cd(OH)2) nanowires were synthesized in yield by a simple arc-dischage method in de-ionized

• water. These precipitates were calcinated at 400 oC for 1 hour and CdO nanoparticles are formed. XRD and SEM, TEM were used to

characterize the product, which revealed that the product consist of nanowires about 40 nm in diameter and nanodots about 20 nm in diameter. The X-ray diffraction study revealed that the as deposited particles consists of cadmium oxide (CdO) phase.

Cadmium oxide is an n-type semiconductor with a direct bandgap of 2.5 eV and an indirect bandgap of 1.98 eV [1]. CdO nanostructures have low ohmic resistivity (even without doping) and high optical transmittance in the visible region of the solar spectrum along with amoderate refractive index (2.49) [2] which offer promising applications in optoelectric fields such as photovoltaic cells, photo-diodes, photo- transistors, gas sensors and transparent electrodes [3]. For these applications, particle size, porosity, and specific surface area are of major importance.Up to the present time, various

• ne-dimensional CdO nanostructures such as nanowires,

nanoneedles, nanobelts and nanorods have been synthesized by solid-state transformation metal-organic framework [4], vapor phase transport [5], template-assisted [6] and solvothermal methods [7]. In this work, Cd(OH)2 nanowires were synthesized in de- ionized water by arc-dischage. High purity cadmium rods were used as anode and cathode. The arc discharge was initiated in the water by touching the anode to the cathode. The applied arc current of 50 A and the voltage 20-30 V were supplied by a dc. current welding power supply. The cadmium hydroxide particles dispersed in the water and some of them floated on the surface. After production, nanoparticles were were characterized by TEM (JEOL 2100 HRTEM) and X-ray Diffraction analysis (Shimadzu XRD-6000). As seen in Figure 1-a, cadmium nanowires are branced form and has 20-30 nm

• diameters. XRD analsis prove that Cd(OH)2 are in crystalline

form and can be indexed as the hexagonal Cd(OH)2 with cell constants a=3.49 2, c=4.71 2, which are consistent with its values in the literature (JCPDS 31-0228) as seen in Figure 1-b. As produced nanoparticles then were heated up to 400 oC for 1 hour and the same analysis were repeated. In figure 1-c, TEM

• bservations showed that new nanoparticles are especially

nanodot form after calcination. A few nanowires are also seen during investigation. After calcination at 400

• C five
• and 69.28 which are associated with (1 1 1), (2 0 0), (2 2 0), (3

1 1) and (2 2 2) as seen in figure 1-d. The planes have d- spacing values of 2.71, 2.35, 1.66, 1.42 and 1.36Å respectively, corresponding to pure CdO crystalline phase. The crystal lattice parameter was calculated from the crystallographical relations to be a = 4.698Å which is consistent with the CdO ASTM value (card 05-0640), 4.695 Å. In summary, CdO nanodots and nanowires were producted by calcination of Cd(OH)2 precursor. The XRD analysis prove the transformation of nanoparticles from Cd(OH)2 to CdO.

• Figure1. a) TEM image of Cd(OH)2 nanowires b) XRD pattern of Cd(OH)2 nanowires c) TEM

image of CdO nanodots d) XRD pattern of CdO nanodots

*Corresponding author: aavci@selcuk.edu.tr

[1] M. Ortega, G. Santana, A. Morales-Acevedo, Optoelectronic properties of CdO/Si photodetectors, Solid State Electron. 44 (2000) (1765). [2] S.H. Wang, S.H. Yang, Spectroscopic characterization of the copper sulphide core/shell nanowires, Mater. Sci. Eng. C 16 (2001) 37. [3] F.A. Benko, F.P. Koffyberg, Quantum efficiency and optical transitions of CdO photoanodes, Solid State Commun. 57 (1986) 901. [4] F. Zhang, F. Bei, J. Cao, X. Wang, The preparation of CdO nanowires from solidstate transformation of a layered metal-organic framework, J. Solid State Chem. 181 (2008) 143. [5] T. Kuo, M.H. Huang, Gold-catalyzed low-temperature growth of cadmium oxide nanowires by vapor transport, J. Phys. Chem. B 110 (2006) 13717. [6] Y.W.Wang, C.H. Liang, G.Z. Wang, T. Gao, S.X. Wang, J.C. Fan, L.D. Zhang, Preparation and characterization of ordered semiconductor CdO nanowire arrays, J. Mater. Sci. Lett. 20 (2001) 1687. [7] N. Varghese, L.S. Panchakarla, M. Hanapi, A. Govindaraj, C.N.R. Rao, Solvothermal synthesis of nanorods of ZnO, N-doped ZnO and CdO, Mater. Res. Bull. 42 (2007) 2117.

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a b c d Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 1

Chemometric approach for optimized synthesis of nano titanium oxide utilizing central composite design of experiment

• A. Bagheri Garmarudia,b, M. Khanmohammadia, N. Khoddamia , K. Ghasemia

aChemistry Department, Faculty of Science, IKIU, Qazvin, Iran bDepartment of Chemistry & Polymer Laboratories, Engineering Research Institute, Tehran, Iran

Abstract— Some conditions for synthesis of nano TiO2 were chosen by design of experiment. Central composite design (CCD) was applied to obtain the optimum condition for synthesis. The crystalline structures and morphologies of the nano particles were characterized by XRD and SEM. Also, the activation energies of gel degradation during the synthesis were

• btained by TGA. The optimum condition obtained by experimental design method is 417.96 and 12 for H2O:TTIP and acid:

TTIP molar ratios respectively. In the other hand, aging temperature, aging time and calcination temperature where optimized at 56.3 °C, 12 h and 278.2 °C respectively. The smallest size of TiO2 powder, obtained by controlling the parameters is 20 nm while the best range of particle size was obtained as 20-45 nm.

Porous nano TiO2 has been prepared by sol–gel route demonstrating high photocatalytic activity with high specific surface area [1-4]. The photocatalytic performance of nano TiO2 depends strongly on its grain size [5]. One of the main ideas which help to reduce the high amount of chemical consumption during a chemical synthesis research is to plan an

• ptimization vision of synthesis affecting parameters e.g.

reaction condition [6-8]. Experimental designs can be employed for a large variety of purposes, one of the most wide spread being optimization. Most statistical approaches normally involve forming a mathematical model of a process and either computationally or algebraically, optimizing this model to determine the best conditions. Design of Experiments (DOE), has been reported as an efficient approach for optimization aims [9]. It is also noticeable that

• ne factor-at-a-time optimization technique requires a

considerable amount of work and time. An alternate strategy is a statistical approach, e.g. factorial experimental design and response surface methodology (RSM), involving a minimum number of experiments for a large number of factors [10]. In this study, central composite design (CCD) was used to evaluate the coefficients in linear and interaction mathematical

• models. Also, response surface method was used to predict the
• ptimum condition for synthesis of nano TiO2.

All the samples were studied by SEM to determine the minimum, maximum and range of their particle size. It was clearly observed that the particle size of final product depends

• n designed parameters during the synthesis procedure. The

smallest particle size and the narrowest size range were for sample 7 (20-45 nm). In order to compare the patterns, the best particle size distributed samples were analyzed. The

• btained XRD patterns were investigated in relation with

synthesis situation. It was observed that by increment in solvent concentration and calcinations temperature, the intensity of signals due to anatase phase are reduced and the intensity of rutile phase signals are increased. In fact, it was concluded that solvent would suppress the hydrolysis of titanium precursor and rapid crystallization of the TiO2 by adsorption on its surface. A set of experiments was designed for synthesis of TiO2 nano particles. A factorial, central composite design for five factors with replicates at the center point and star points was

• used. The used variables were aging time, aging temperature,

calcination temperature, molar ratio of H2O:TTIP and acid:TTIP at five coded levels as shown in table 1. The CCD contained a total of 32 experimental trials that included 11 trials for factorial design, 10 trials for axial points (two for each variable) and nine trials for replication of the central points. Table 1- The independent variables applied in DOE strategy and their levels for CCD

Symb. Coded levels

• ∞
• 1

+1 +∞ Aging time (h) A 4 8 11 14 18 Aging temp. (°C) B 45 60 70 80 95 Calcination temp. (°C) C 145 350 500 650 855 H2O:TTIP D 65 200.0 300.0 400.0 650 acid:TTIP E 1.5 5.0 7.5 10.0 13.5

Finally, the optimum condition was concluded, which would demonstrate the smallest particle size and range for nano TiO2

• sample. CCD was used to find the optimum situation in

synthesis of TiO2 nano particles. A CCD always contains twice as many star points as factors in the design. The star points represent new extreme values (low and high) for each factor in this design [12,13]. If the factorial is a full factorial then α = [2k]1/4 In this study there are 5 main factors (k = 5) factors and thus the previous equation can be written as: α = 2.37 The experimental results of by a complete five -factor-two- level factorial experiment design with nine replications of the central point and ten axial points were studied. Based on CCD,

• ptimum condition for synthesis was estimated by 0.99 of

composite desirability and was 417.96 and 12 for H2O:TTIP and acid:TTIP molar ratios respectively. In the other hand, aging temperature, aging time and calcination temperature where optimized at 56.3 °C, 12 h and 278.19 °C respectively.

*Corresponding author: violamir@gmail.com [1] An-Cheng Lee , et al., Mat. Chem. Phys. 109 (2008) 275–280 [2] Liqun Mao , et al., Mat. Res. Bul. 40 (2005) 201–208 [4] S.B. Deshpande, et al., Mat. Chem. Phys. 97 (2006) 207–212 [3] N. Venkatachalam, et al., Mat. Chem. Phys. 104 (2007) 454–459 [5] Tomoya Ohno, et al., Mat. Chem. Phys. 113 (2009) 119–123 [6] Chantal Guillard, et. al., Appl. Catal.B 39 (2002) 331–342 [7] Zilong Tang, et. al., Mat. Chem. Phys. 77 (2002) 314–317 [8] ki Do Kim,et. al., Physicochem.Eng.Aspects254(2005)99-105 [9] Richard G.Brereton,chemometrics data analysis for the laboratory and chemical plants,University of Bristol,UK,John Wiely&Sons,Ltd(2003) [10] Mir Mohammad Alavi Nikje , et al., J.Macromol. Sci. A,2009,116-120 Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 2

Effect of Shear on CaCO3

Murat Molva

Morphology

1 and Ekrem Özdemir1*

1Department of -Izmir, Turkey

Abstract-Progress in crystal formation and effect of shear on the CaCO 3 morphology were investigated. CaCO 3 crystals were produced in the presence of 30 mM Ca(OH)2 slurry under the CO 2 atmosphere. Although the CaCO 3 were continuously produced by time, the complete conversion of Ca(OH)2 was observed at 11th min. The particle size distribution varied, especially, when pH reduced to below 8.3. The needle- like calcite was produced under the influence of shear instead of cubic or spheroidal shapes.

CaCO3 is easily produced by the precipitation of CO2 by carbonation process [1]. The overall carbonation process (chemical reaction, nucleation, and crystal growth) occurs at pH > 7 in a reactor with a slurry of Ca(OH)2. Calcite, vaterite and aragonite are the various polymorph forms of the

• CaCO3. The most stable polymorph form is calcite and it can

be seen in various crystal structures such as rhombic-trigonal- hexagonal, or scalenohedral. Vaterite and aragonite are metastable polymorphs and they are almost ready to transform into the stable calcite form [2,3]. CaCO3 In this study, precipitated calcium carbonate crystals were produced by CO polymorphs should be modified or changed with various techniques by making them narrow sized, uniform shaped and stabilized crystal forms in order to use for industrial applications [4]. With the changing of the shape and morphology, the mechanical strength and toughness of the structures exceed those of current synthetic ceramics by several orders of magnitude [5].

2 - H2O - Ca(OH)2 system under the

influence of shear caused by a vortex formation in the region

• f a neck in a 250 ml volumetric flask. The liquid level was

250 ml and the CO2 was introduced at the top of the liquid level and diffuse into the Ca(OH)2 slurry in the flask. Stirring rate was constant as 800 rpm. The crystallization was performed in the mini reactor during the influence of shear and affected the morphology of the produced CaCO3. The conversion of Ca(OH)2 dissolved initially was not complete until 11th min, and totally disappeared within the products after 11th min as indicated in the XRD (Figure 1) and FTIR data (data not shown). The particles were more apart each

• ther above pH 8.3, however, they became more aggregated

when pH was reduced below 8.3. The progress in morphological development of CaCO3 under the influence of shear will be presented in detail during the presentation.

10 20 30 40 50 60 70 80 2 Theta intensity, A.U 110 min 23 min 10 min 5 min 0 min 60 min 53 min 30 min

Figure 1. XRD patterns of CaCO 3 showing the conversion of Ca(OH)2 to the CaCO 3 by time.

0 min pH=12.6 5 min pH=12.4 15 min pH=12.1 22.5 min pH=11.8

30 min pH=11.6 75 min pH=7.0 Figure 2. SEM images of CaCO 3 under the influence of shear.

0T*Corresponding Author: ekremozdemir@iyte.edu.tr

[1] Sahebian, S., Zebarjad, S. M., Khaki, J. V., and Sajjadi, S. A. (2009). "The effect of nano-sized calcium carbonate on thermodynamic parameters of HDPE." Journal of Materials Processing Technology, 209(3), 1310-1317 [2] Hernandez-Hernandez, A., Vidal, M. L., Gomez-Morales, J., Rodriguez-Navarro, A. B., Labas, V., Gautron, J., Nys, Y., and Ruiz, J. M. G. (2008). "Influence of eggshell matrix proteins on the precipitation of calcium carbonate (CaCO3)." Journal of Crystal Growth, 310(7-9), 1754-1759. [3] Wang, C. Y., Zhao, J. Z., Zhao, X., Bala, H., and Wang, Z. C. (2006). "Synthesis of nanosized calcium carbonate (aragonite) via a polyacrylamide inducing process." Powder Technology, 163(3), 134-138. [4] Lam, T. D., Hoang, T. V., Quang, D. T., and Kim, J. S. (2009). "Effect of nanosized and surface-modified precipitated calcium carbonate on properties of CaCO3/polypropylene nanocomposites." Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, 501(1-2), 87-93 [5] Wada, N., Nakamura, M., Tanaka, Y., Kanamura, K., and Yamashita, K. (2009). "Formation of calcite thin films by cooperation of polyacrylic acid and self-generating electric field due to aligned dipoles of polarized substrates." Journal of Colloid and Interface Science, 330(2), 374-379

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 3

LOW TEMPERATURE SYNTHESIS OF ZINC OXIDE (ZnO) NANOPARTICLES BY PRECIPITATION

Ozlem Altintas Yildirim1*, Caner Durucan1

1 Department of Metallurgical and Materials Engineering, Middle East Technical University, 06531 Ankara, TURKEY

Abstract- Phase pure zinc oxide (ZnO) nanoparticles with different size and morphology were synthesized by using precipitation method. The formation of zinc oxide nanoparticles was achieved by altering reaction temperature and NaOH concentration. It is seem that reaction temperature influences only particle size and the concentration of the NaOH used for precipitation reaction changes both size and morphology of ZnO nanoparticles.

Zinc oxide (ZnO) is one of the well known semiconductor materials with a wide direct band gap (3.37 eV) and large exciton binding energy (60 meV). Controlled synthesis of ZnO nanoparticles in terms of size and morphology has been investigated because optical properties of nanostructures can be altered by changing size and shape. Among a variety of synthetic routes including spray pyrolysis [1], hydrothermal synthesis [2], sol-gel [3] and microemulsion process [4], precipitation technique is one of the potential methods which provides synthesizing of ZnO nanoparticles at low temperature with different size and morphology by using a facile way for low cost and large scale production. In this work, phase pure ZnO nanoparticles were synthesized by using zinc acetate dihydrate (C4H6O4Zn.2H2O), sodium hydroxide (NaOH) and polyvinyl pyrrolidone ((C6H9NO)n, PVP) as precursors. Ethylene glycol (C2H6O2) and deionized water were used as solvents. The effects of zinc precursor and PVP concentrations, reaction temperature and pH value on morphology and size of ZnO nanoparticles have been

• investigated. Characterization of ZnO nanoparticles was

performed by using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV- visible spectroscopy (UV-vis) and photoluminescence spectroscopy (PL).

Figure 1. XRD pattern of precipitation product synthesized at a) different temperature and b) different NaOH concentration value.

Figure 1 shows the XRD patterns of the precipitation products for investigation of effects of different temperature and NaOH concentration value on particle size and morphology. In Figure 1a, at all reaction temperature, phase pure ZnO nanoparticles were synthesized by using 2 M NaOH addition. In Figure 1b, synthesis of phase pure ZnO nanoparticles were achieved by using higher amount

• f NaOH addition at 25 °C.

a) b) Figure 2. FESEM image of precipitation product synthesized a) at different temperature and b) different NaOH concentration value.

Figure 2a shows that FESEM micrographs of ZnO nanoparticles synthesized at different temperatures. ZnO nanoparticles exhibit a spherical morphology with a narrow size distribution and the average particle size varies in the range from 17 to 6 nm and decreases with increasing reaction temperature from 25 to 80 °C. As shown in Figure 2b, distinctly different morphologies of ZnO nanoparticles such as hollow, triangle and plate structures were achieved with different concentration of NaOH addition at 25 °C. In summary, the proposed precipitation system is advantageous for obtaining size controlled spherical ZnO nanoparticles with narrow size distribution by changing the precipitation temperature and it also allows attaining variation in ZnO morphology which can be achieved by controlling NaOH amount. This work is supported through Middle East Technical University grant no BAP-03-08-07. ÖAY also thank The Scientific and Technological Research Council of Turkey, TUBITAK, for the support through National Scholarship Program for PhD Students and also METU-ÖYP Program. *Corresponding author: altintas@metu.edu.tr

[1] T. Tani, L. Mädler, S.E. Pratsinis, 2002, J. Nanopart. Res. 4 337- 343. [2] J. Wang, L. Gao, 2003, J. Mater. Chem. 13 2551-2554. [3] M. Ristic, S. Music, M. Ivanda, S. Popovic, 2005, J. Alloy Compd. 397 L1-L4. [4] X. Li, G. He, G. Xiao, H. Liu, M. Wang, 2009, J. Colloid Interf.

• Sci. 333 465-473.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 4

CoxZn1-xFe2O4 Synthesized by Microwave Method

(x = 0, 0.2, 0.4, 0.8) Nanoparticles

• F. Gözüak 1*,2, A. Baykal 3

1 2 Department of Physics, Fatih University, 34500 Buyukcekmece, Istanbul, Turkey 3

Department of Chemistry, Fatih University, 34500 Buyukcekmece, Istanbul, Turkey Abstract-We present a systematic investigation on the structural and magnetic properties of CoxZn1-xFe2O 4 nanoparticles synthesized by using Microwave Combustion Method. Metal nitrates and chlorides are used as starting materials to synthesize CoxZn1-xFe2O 4

The magnetism of spinel ferrites has been the topic of extensive research. They have useful electrical and magnetic properties and applications in information storage systems, magnetic bulk cores, magnetic fluids, microwave absorbers and medical diagnostics. So, the scientists focus their attention

• n producing magnetic nanoparticles of spinel ferrites by

using effective, easy and economic ways [1-4].

• nanoparticles. XRD,

FTIR, TEM and VSM were used for the structural, spectroscopic, morphological and magnetic investigation of products, respectively. Magnetization measurements have shown that while the materials with high Zn substitution are superparamagnetic at room temperature and ferromagnetic at temperature lower than the blocking temperature, the materials with less Zn substitution are ferromagnetic below room temperature.

Co xZn 1-xFe2O4 is taken as a basic system for the following

• reasons. This basic system compose of CoFe2O4 that has long

range ferrimagnetic transition temperature at 790 K and ZnFe2O4 that has antiferromagnetic Neel temperature at 9 K. CoFe2O4 is a good candidate for magnetic recording media and magnetic fluids whereas, ZnFe2O4 In this study, we investigate the magnetic and structural properties of cobalt-substituted nanocrystalline zinc ferrites. In the FTIR spectrum of the products, the is used as a catalyst [3–7].

1 band, observed at

561 cm-1 for ZnFe2O4 can be assigned to tetrahedral Zn2+ stretching and the 2 band, observed at 425 cm-1, involves the Fe3+ The X-ray diffraction patterns of the prepared samples indicate the presence of the spinel cubic structure [8]. vibration at the octahedral site [2-4].

Figure 1. M-H curves taken at different temperatures for Co0.2Zn0.8Fe2O 4 nanoparticles.

All magnetic measurements have been carried out by using Quantum Design Vibrating Sample Magnetometer (QD- VSM). The hysteresis loops of the ZnFe2O4, Co 0.2Zn0.8Fe2O4 (Fig.1) and Co 0.4Zn 0.6Fe2O4 The magnetic properties of Co nanoparticles synthesized by microwave combustion method shows that the M-H curves

• btained at high temperatures are almost linear with the

external field and has an s-shape at the origin. At room temperature, non-hysteric behavior and nonsaturated magnetization indicated the presence of superparamagnetic behavior at high temperatures [3,4].

0.8Zn0.2Fe2O4

(Fig.2) nanoparticles synthesized by microwave combustion method displays M-H curve at room temperature that has a small coercivity and the magnetization does not reach to saturation. These results showed that the sample does not show superparamagnetic behavior, it shows ferromagnetic behavior at all measuring temperatures.

Figure 2. M-H curves taken at different temperatures for Co0.8Zn0.2Fe2O nanoparticles.

4

As a result The samples showing superparamagnetic behavior can be used for hypothermia, cancer treatment and as a drug carrier. The samples showing ferromagnetic behavior can be used for high density recording, read-write heads, microwave absorbtion, etc. *Corresponding author: 1Tfgozuak@gyte.edu.tr

[1] D. S. Mathew, R. S. Juang. Chemical Engineering Journal, 129 (1-3) (2007) 51. [2]

• B. Aktas, Journal of Alloys and Compounds, 462 (2008) 209.

[3] F. Gözüak, Journal of Magnetism and M agnetic Materials, 321 (2009) 2170. [4] F. Gözüak, H. Kavas, Polyhedron, 28 (14) (2009) 2887. [ 5] J.L. Dorman, M. Nogues, J. Phys.: Condens. Matter 2 (1990) 1223. [ 6] D. Fiorani, S. Vitticoli, Solid State Commun. 29 (1979) 239. [ 7] K.P. Belov, A.N. Goryaga, A.N. Lymzin, Sov. Phys. Solid State 30 (1988) 715. [ 8] A.M. El Sayed, Ceram. Int. 28 (2002) 363.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 5

Use of low cost sonication technique for the synthesis of zinc oxide nanoparticles

Yasir Jamil1*, M. Raza Ahmad1, Humaima Saeed1, Tabinda Maryam1 and Abdul Hafeez1

1

Zinc Oxide is one of the richest families of nanostructures of all materials, both in structure and in properties.In the rapidly growing electronic industries, ZnO has been used as a multifunctional semiconductinh material [1].Zinc Oxide delivers greater antibacterial power without the need for UV light as catalyst [3]. ZnO is technologically very important material for many piezoelecrical applications [4]

Department of Physics, University of Agriculture, Faisalabad, Pakistan

In this work, nanocrystalline Zinc Oxide powder has been prepared by sonochemical method. The main advantage of using sonochemical technique is its low cost to get started in the field. The main event in sonochemistry is the creation, growth and collapse of a bubble that is formed in the liquid. The control of particle size is quite easy when using

• sonochemistry. The more dilute the solution, the smaller are

the particles. The sonochemical method has the advantage

• ver other method being a seedless, surfactant free and

template free method [5] The crystallinity and crystal phases

• f the synthesized nanostructures were analyzed by the X-ray

diffraction (XRD, Rigaku) spe

• Å) in the range of 20º -70º The optical properties
• f the samples were studied by the UV-Visible (UV-Vis)

absorption double beam spectrophotometer (PG instruments; T 60, UV-Visible spectrophotometer). Table 1. Average particle size of five samples Average particle size (nm) Concentration (M) Sonication time (hours) 79.48522 0.25 2 90.4540 0.30 2 58.5285 0.35 2 60.6815 0.45 2 Figure 1. Average particle distribution obtained from XRD. Here, in this work, the maximum size nanocrystallite (~ 173nm) of ZnO powder has been obtained for pH value of 13.5. The UV-Visible spectra for ZnO nanoparticles synthesized in aqueous madia displayed excitonic absorption peak at 363 nm which implies the lower particle size ZnO. The band gap calculated from the UV cut-off is found to be 3.41 eV ZnO nanoparticles. The band gap of sample A is ( Eg Temperature dependence of the lattice constants showed linear increase in their value [6]. Whereas, in the present work, the samples have been prepared at room temperature. It has been observed that the crystallite size varied according to room temperature. he sample A of 0.25 M concentration having the lattice constants a = 3.251 Å and c = 5.2118Å are in good agreement with ICSD card No. 01-076-0704 of ZnO. = 1240/360) , 3.44 eV which is in agreement with ZnO prepared through other method reported in [7]. Similarly the band gap of sample C, D and E , for wavelength of 360 nm has been found to be 3.44eV. Corresponding author: yasirjamil@yahoo.com

[1] Wang, J., V . Sallet, F . Jomard, A . M . B . do Rego , E . Elamurugu, R . Martins and E. Fortunato. 2007. Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering. Thin Solid Films, 515 : 8785-8788 [2] Zhu, Y., Y. Chen, X. Zhang, Q. Chen and Y. Shao. 2009. Urchin- like ZnO nanostructures: synthesis, characterization and optical

• properties. Materials Letters, 63:1242-1244

[3] Li, J. H., R. Y. Hong, M. Y. Li, H. Z. Li, Y. Zheng and J. Ding.

• 2009. Effect of ZnO nanoparticles on the mechanical and

antibacterial properties of polyurethane coatings. Progress in organic Coatings, 64: 504-509 [4] Xiao, J. 2009. Growth and field emission properties of chessman- like and tower-like ZnO nanostructures. Materials Chemistry and Physics, 115:771-774 [5] Wahab, R., S. G. Ansari, Y. S. Kim, G. Khang and H. S. Shin.

• 2008. Effect of hydroxylamine hydrochloride on the floral decoration
• f Zinc Oxide synthesized by solution method. Applied Surface

Science,254:2037-2042 [6] Singh, P., A. Kumar, Deepak and D. Kaur. 2008. ZnO nanocrystalline powder synthesized by ultrasonic mist-chemical vapour deposition. Optical Materials, 30:1316-1322 [7] Sridevi, D. and K. V. Rajendran. 2009. Synthesis and optical characteristics of ZnO nanocrystals. Bull. Mater. Sci., 32:165-168

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 6

Synthesis of Nano Zinc Oxide Powder

1* and Devrim Balköse1

1

Izmir Institute of Technology Chemical Engineering Department Gülbahçe köyü 35430 Urla- Abstract- Synthesis nano sized zinc oxide(ZnO) was aimed in this study. Monodispersed nano ZnO powders were obtained by using triethyl amine template and ultrasonic mixing during precipitation method. Volumetric resistivity of nano ZnO powder was found as 1.3 1017

• hm-cm. The room temperature fluorescence spectrum of the powder revealed a strong and sharp UV emission band at 391 nm and a weak

and broad blue emission band at 405 nm due to free exciton or bound exciton of ZnO in the UV region and zinc vacancy, respectively. Absorption spectrum of the powder showed absorption peak at UV-A region.

Nano crystalline materials have found an increasing research area on the material science, chemical and electronic engineering during the past years. ZnO has a hexagonal crystal structure and composed of tetrahedrally coordinated O2- and Zn2+ The investigation was focused on the preparation of monodisperse nano zinc oxide powder by precipitation

• method. The electrical conductivity, thermal conductivity

and optical properties of synthesized nano zinc oxide powder were determined. ions, stacked along the c-axis and ZnO has partial ionic characteristics. ZnO is a semiconducting material with a band gap of about 3.2 eV and a large exciton binding energy of 60 meV [1]. ZnO can exhibit unique optical, photocatalytic, piezoelectric, and pyroelectric properties, produces an efficient blue- green luminescence, and displays excitonic ultraviolet (UV) laser action [2]. There are many methods for the preparation of nano ZnO powder and precipitation method is a good choice in the industrial point of view because of the low growth temperature and good potential for scale- up [3]. This synthesis method has large advantages for preparing highly crystallized particles with narrow size distribution and high purity without further treatment at higher temperature. Size and morphology can be controlled by controlling reaction temperature, reaction time and additives [3]. Analytical grade chemicals, zinc chloride (ZnCl2) (98%; Aldrich), potassium hydroxide-KOH (85%; Pancreac) and triethylamine (TEA )(C6H15N, Merck), were used for the preparation of zinc oxide powders throughout the experimental study. Ultrasonic treatment was applied to the mixture (Elma; Transsonic 660/H) at approximately 30

• C for 30 minutes. Mechanical mixing at 500 rpm was

made using Ika RW 20 mechanical mixer. The solid and liquid phases were separated by centrifuging using Hettich, Rotofix 32. The solid phase was then washed for three times with water, dried at 50 o For the characterization

• f

powder X-Ray diffractometer, SEM and FTIR spectrum were used. The particle size of the powders was determined by dynamic light scattering. The volumetric resistivity of the ZnO powders was determined by recording I-V data with Keithley 2420. Helium pycnometer was used to determine the powder densities. The N C for 15 h.

2

BET surface area of the nanopowder was 21.2 m adsorption/desorption analysis were performed to determine the surface area of the powders. Reflection and absorption spectra and emission spectrum of ZnO were obtained by using UV-Vis spectrometer and fluorescence spectrometer respectively.

2/g and

density of the powder was 4.8 g/cm3. XRD pattern and SEM image of the powder is shown in Figure 1. The precipitate 2theta values were detected as 31.6 o, 34.26 o, 36.1 o, 47.35 o, 56.4 o, 62.66 o, 66.2 o, 67.76 o, 68.86 o, 72.2 o, 76.78 o and give the characteristic XRD pattern of ZnO powders (JCPDS Card No: 79-0207). The SEM image of the powder shows, big triangular shaped aggregates but they are obtained from rod shaped/needle like crystals and they are very small about 15-20 nm. However these aggregates are hard to break.

500 1000 1500 2000 20 40 60 80

• )

a.u.

Figure 1. XRD pattern of nano ZnO powder. Figure 2. SEM image of nano ZnO powder.

Nano, monodispersed and repeatable ZnO powders were prepared by precipitation method. Template addition creates nucleation centers and large numbers of nuclei forms and slow crystal growth occurs thus nano ZnO powders were obtained. The crystals of the powder were elipsoidally shaped and the crystal size was calculated as 25.7 nm from Scherer equation. Nano ZnO powder electrical conductivity found 1.3 107 ohm-cm and found moderately electrical conductive. The room temperature fluorescence spectrum of the powder revealed a strong and sharp UV emission band at 391 nm and a weak and broad blue emission band at 405 nm showing to free exciton or bound exciton of ZnO in the UV region and zinc vacancy,

• respectively. Absorption spectrum of the powder showed

absorption peak at UV-A region. We express appreciation to Dr. Salih Okur for his great help in I-V measurements and for letting use his graduate laboratories anytime. We would like to thank to Dr. Serdar Özçelik for his help and permission to use Fluorescence spectrometer. *Corresponding author: filizozmihci@iyte.edu.tr

[1] Wang, Z. L., Zinc Oxide Nanostructures: Growth, Properties and Applications. Journal of Physics: Condensed Matter, 2004, 16, R829–R858. [2] Satyanarayana V.N.T., Kuchibhatla A.S., Karakoti D., Seal S., Progress in Materials Science; Inpress; 2007. [3] Bangal, M.; Ashtapure, S.; Marathe, S.; Ethiraj, A.; Hebalkar, N., Gosavi, S.W.; Urban, J.; Kulkarni, S. K. Semiconductor

• Nanoparticles. Hyperfine Interactions, 2005, 160, 81–94.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 7

Synthesis and physicochemical characterization of monodisperse borosilicate nanoparticles

Ekin Öztürk1 and Serdar Özçelik1*

1Department of Chemistry , Izmir Instute of Technology, Gülbahçe-Urla 35430 Izmir

Abstract- Borosilicate nanoparticles were synthesized by the Stöber method. The Stöber synthesis, the ammonia-catalyzed reaction of TEOS with water in low molecular weight alcohols, was used to produce monodisperse spherical nanoparticles. Tri-methoxy boroxine was used as boron source. Ammonia and ethanol determine the size of nanoparticles.

Nanoparticles are enable to bind and concentrate many molecules on their surface and therefore play a significant role in chemical and biological sciences. Borosilicates are an important class of materials finding applications in various industrial fields as well. The purpose of this study is to develop a method to produce monodisperse borosilicate nanoparticles. Both silica and borosilicate nanoparticles have been synthesized by using Stöber method. [1] The Stöber synthesis includes sol-gel processing in which hydrolysis and condensation reactions take place. [2, 3] A proper amount of ethanol and ammonium hydroxide were mixed and TEOS (tetraethyl orthosilicate) was added to the mixture. The mixture was stirred for 20 hours at room temperature and then the second TEOS (245 L) was added and the reaction kept on another 20 hours to synthesize silica

• nanoparticles. To prepare borosilicate nanoparticles TMB (tri-

methoxy boroxine) was used instead of secondly added TEOS. (a) (b)

Figure 1. DLS results for (a) silica nanoparticles and (b) borosilicate nanoparticles with size about 100 nm.

(a) (b)

Figure 2. SEM images of (a) silica nanoparticles and (b) borosilicate nanoparticles with the size about 400 nm.

(a) (b)

Figure 3. EDX analysis of silica nanoparticles and (b) borosilicate nanoparticles

Both nanoparticles were thoroughly washed before analysis. DLS (Dynamic Light Scattering), SEM (Scanning Electron Microscopy), EDX (Energy-dispersive X-ray spectroscopy) were used to characterize the particles. Also titration method was used to prove the presence of boron in the borosilicate

• nanoparticles. EDX analysis and titration methods showed

that the amount of boron in the borosilicate nanoparticles was 5 % by mass. The size and monodispersity of nanoparticles were precisely tuned by the initial mole ratio of reactants. Ammonia and ethanol are the most effective to control the size of the

• nanoparticles. While increasing amount of ammonia yields

larger nanoparticles higher amount of ethanol forms smaller nanoparticles down to 10 nm. Addition of TMB enlarges further the size of borosilicate nanoparticles. *Corresponding author: serdarozcelik@iyte.edu.tr

[1] Stöber, W.; Fink, A. Journal Colloidal Interface Science 1968, 26, 62. [2] Imhof, M. Mengens, J. J. Engelberts, J. Phys. Chem. B., 1999, 103, 1408-1415 [3] M. Rosenholm, Annika Meinander, Emilia Peuhu, Rasmus Niemi, NanoACS 2009, Vol.3, No.1, 197-206

S iz e d is t r ib u t io n ( s ) 5 1 0 5 0 5 0 0 D ia m e t e r ( n m ) 5 1 0 1 5

% i n c l a s

% in class

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 8

Environmental Friendly, Antibacterial and Easy to Clean Nano-Coating

Esin Burunkaya1,2,*, Ömer Kesmez1,2, Nadir Kiraz1,2, Zerin Yeil1,2, Nedim Erinç2, Erturul Arpaç1,2

1 Department of Chemistry, Akdeniz University, 07058, Antalya, Turkey 2 NANOen R&D Ltd., Antalya Technopolis, Akdeniz University, Antalya, Turkey

Abstract-Environmental friendly, antibacterial and easy to clean transparent thin films have been prepared on different kind of substrates including glass, metal, wood, cotton, ceramic and plastic surfaces by the sol-gel process using a non-fluorinated inorganic-organic hybrid sols. The antibacterial activity of the coatings was investigated against gram negative Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae and gram positive Staphylococcus aureus. Easy to clean properties were investigated by using contact angle goniometer and some in-house comparative tests.

Our lives surrounded by a nano-life including bacteria, fungi, algae viruses and other forms of microscopic life. Even under 'clean' conditions we may inhale several thousand fungal spores per day. Many of them are harmless

• r even useful but others can be lethal or severely

disabling. We increasingly work in air-conditioned offices, attend large hospitals in which infections can spread rapidly, expect to travel from one country to another at high speed and short notice. All aspects of this evolving lifestyle increase our risks of encountering more micro-organisms and varieties to which we have no immunity. Methods used to keep the levels of this nano-life down to acceptable levels gain a great interest in the design and development of the so-called “hygienic surfaces”, referring to surfaces that not only provides antibacterial activity but also to those that are easy to clean and dirt repellent. A surface that inhibits soil and organisms adhering to it, that is easy to clean and which actively reduces the growth of bacteria, will make the cleaning job easier for a wide variety of industries and the achievement of such a coating means, not only a reduction in the problems of corrosion and in health risks, but also a reduction or elimination the consumption of biocides and toxic industrial detergents. Achieving these properties on a surface is possible by means of coatings and treatments on specific surfaces. Most of these coatings acquire their antibacterial/self- cleaning/easy to clean capacity by incorporating specific nano-particles and materials: basically silver (Ag), titanium

• xide (TiO2) and fluorinated compounds [1-3].

Although the fluorinated compounds are low surface energy materials which possess very good easy to clean surface properties, they are hazardous to the ozone layer and human health in the spray form. Incorporation of Ag and TiO2 nano-particles to the surface usually needs an after-treatment like heat [4]. A nano-level easy to clean and antibacterial surface has been developed using a non-fluorinated inorganic-organic hybrid sols. The main advantage of the system is the easy application on to the many surfaces and needs no after treatment so that the coating solution can also be used on the existing surfaces which have not antibacterial and easy to clean properties. SiO2 colloidal sol was prepared by hydrolysis and condensation reactions of alkoxysilane in the presence of acid/baz catalyzer. Synthesized nano-SiO2 particle surfaces modified by reaction with long-chain alkylsilane and

• rganic antibacterial agent to obtain respectively easy to

clean and antibacterial property.

Figure 1. A zone of inhibition around the coated coin for S. aureus (Courtesy of NANOEN)

Particle size distribution of the SiO2 sol was determined by a particle size analyzer and average particle size of the SiO2 colloid was determined as 9 nm. The films were characterized by Scanning Electron Microscopy and Atomic Force Microscopy. The antibacterial activity of the coatings was investigated against gram negative Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae and gram positive Staphylococcus aureus. Easy to clean properties were investigated by using contact angle goniometer and some in-house comparative

• tests. The results showed that transparent hybrid thin film

has effective antibacterial and easy to clean properties. Technical and financial support of NANOen is gratefully acknowledged. *esinburunkaya@gmail.com

[1] Tatar P, Kiraz N, Asilturk M, et al. 2007. Antibacterial thin films on glass substrate by sol-gel process, Journal of Inorganic and Organometallic Polymers and Materials, 17:3:525-533 [2] Saylkan, F., Asiltürk, M., Kiraz, N., et al. 2009. Photocatalytic antibacterial performance of Sn4+-doped TiO2 thin films on glass substrate, Journal of Hazardous Materials, 162:2-3:1309-1316 [3] Yoshino, N., Sato, T., Miyao, K., Furukawa, M., Kondo, Y., 2006. Synthesis of novel highly heat-resistant fluorinated silane coupling agents, J. Fluorine Chem. 127:1058-1065. [4] Tatar, P., 2007. Antibakteriyel Kaplamalar, Yüksek Lisans Tezi, T.C. Akdeniz Üniversitesi, Fen Bilimleri Enstitüsü, Antalya

nhibition zone

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 9

Study of Possibility to Use Zeolites for Immobilization of Proteins in Conductometric and Potentiometric Biosensors

Esin Soy1*, Burcu Akata Kurç1,2

1Micro and Nanotechnology Department, Middle East Technical University, 06531 Ankara, Turkey 2Central Laboratory, Middle East Technical University, 06531 Ankara, Turkey

Abstract-A conductometric and potentiometric biosensors based on protein immobilized with different types of zeolites have been investigated and compared with the convential adsorption method.. It was shown that activity and stability of proteins are strongly affected by the distinct properties of zeolites.

Research and development in biosensors have gained increasing importance in the last few years for their advantageous properties as analytical tools, namely the simplicity of use, potential miniaturization, portability and low cost, in comparison with well-established lab- based methods. Nowadays it is well established that the performance of biosensors depends greatly on the influence imposed on biomolecules by immobilization. Immobilization is the key-step in biosensor construction, but, regardless their peculiar advantages, the conventional methods for biomolecule immobilization (physical adsorption, covalent binding, cross-linking and entrapment in gels or membranes) have, in general, low reproducibility and poor spatially controlled deposition, a crucial problem for the development of commercial miniaturized biosensors [1]. In this context, the use of nanomaterials for the construction of biosensing devices constitutes one of the most exciting approaches. The extremely promising prospects of these devices accrue from the unique properties of nanomaterials. Application of nanomaterials in biosensors allows the use of many new signal transduction technologies in their manufacture. Nanomaterials can be used in a variety of electrochemical biosensing schemes thereby enhancing the performance of these devices and

• pening new horizons in their applications.

The success of immobilization of proteins depends strongly on the properties of the carriers employed. The carrier material should have a high capacity to bind protein, should be mechanically stable and must not have reduced the protein stability. The organic supports like polymers lead to a number of problems such as poor stability and disposal issues [2]. In contrast, inorganic materials such as silica and alumina are thermally and mechanically stable and strong [3,4]. Among different alternatives for carriers, zeolites have been showing great promise as carriers.

Figure 1. Zeolite Beta samples with different Si/Al ratio.

For all these reasons we synthesized zeolite samples with different diameters and Si/Al ratios as some of them can be seen in Figure 1, to see how it effects stability and response of the enzyme biosensor.

Figure 2. Stability of urease with different types of zeolite samples (ES 1-6).

In summary there is no study investigating the effect

• f changing zeolitic properties on different biosensor
• performances. In the current study, zeolite Beta and

LTA nanoparticles with controllably varying hydrophobicities, particle sizes, and surface charges were synthesized. The effect of incorporation of these zeolites into enzymatic membranes was investigated using conductometric and potansiometric urease

• biosensors. It was shown for the first time that certain

zeolite properties affect the activity and stability of proteins in different levels. This study was partly supported by Scientific and Technical Research Council o and partly by a European Union project with the project number PIRSES-GA-2008-230802. The support provided by METU-Central Laboratory is greatly acknowledged.

*Corresponding author: esinsoy@gmail.com

[1]

• S. V. Dzyadevych, A. P. Soldatkin. Solid-State

electrochemical enzyme biosensors. Kyiv: IMBG, 2008, 222 p. [2] D. Norouzian, Iranian Journal of Biotech.1(4)2003. [3] Journal of Molecular Catalysis B: Enzymatic 56 (2009) 13-19 [4] M. Johnson, Z. Li, J. Wang, Y. Yan, Thin Solid Films 515 (6) (2007) 3164-3170.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 10

Fabrication of PHBV/HA nanocomposite for medical applications

Mazyar Sharifzadeh Baei1*, Ghasem Najafpour Darzi1, Fatemeh Tabandeh2 and Habibollah younesi3

1Faculty of Chemical Engineering, Noshirvani University of Technology, Babol, Iran 2Biotechnology Department, National Institute of Genetic Engineering and Biotechnology (NIGEB), P.O. Box: 14155-6343, Tehran, Iran 3Department of Environmental Science, Faculty of Natural Resources & Marine Sciences, Tarbiat Modarres University, Imam Reza Street, Noor,

Iran B.O. Box: 46414-356 Abstract-Biopolymer composite materials for potential medical applications are of current research interest. In this study, a nanocomposite based

• n bioresorbable polymer poly(3-hydroxybutyrate-co-3-hydroxyval) (PHBHV) was prepared by the incorporation of nano-sized hydroxyapatite

(nano-HA) using a solution casting method. Homogeneous distribution of nanoparticles in the polymer matrix was validated by the observation

• f scanning electron microscope (SEM)..

Poly(3-hydroxybutyrate) (PHB) is a fully biodegradable, thermoplastic aliphatic polyester with biocompatibility and ecological safety, produced in nature by at least 75 different genera of bacteria as an energy storage material [1]. Its physical properties are

• ften

compared to isotactic polypropylene since they have similar melting points and crystallinity [2]. However, it has several drawbacks, such as stiffness, brittleness and very low thermal stability at processing temperatures that prevent its larger commercial

• applications. The thermal instability of PHB in the melt

prevents it from substituting the non-biodegradable polymeric materials in commercial products [3]. That is why improvement of the thermal stability of PHB is very important.To overcome these drawbacks of PHB we have prepared PHB nanocomposites with organically modified montmorillonite [4].Polymer nanocomposites are commonly defined as the combination of a polymeric matrix and fillers that have at least one dimension (i.e. length, width or thickness) in the nanometer size range [5]. It has been shown that only a few percent of nanofillers (usually from 1 to 5 wt.%) leads to greatly improved thermal, mechanical and barrier properties of polymers [6–8]. In this work, PHBHV solution in chloroform were prepared by fermentation of whey by Hydrogenophaga pseudoflava and followed by addition of a certain amount of nano-HA

• powders. After 10 min ultrasonication in a water bath at 50°C,

the resulting mixtures were vigorously stirred again at the same temperature for 3 h. Subsequently, the well-mixed PHBHV/HA solution was poured , and the nanocomposite film was obtained after being dried for fabrication of testing samples. Ultrasonication stirring has been proven to be an effective strategy to overcome the agglomeration of particles in the polymer [9]. In this research, in order to improve the dispersion of nanoparticles in the polymer matrix, a solution casting method combined with a strong ultrasonication was introduced. The SEM examinations revealed that HA particles have been well dispersed and evenly distributed in the polymer matrix. No clear evidence of agglomeration can be found in the nanocomposites. The good dispersion of inorganic fillers in the nanocomposite.inevitably benefits the improvement of mechanical properties of composite materials. Finally In this work, the PHBHV/HA nanocomposite has been successfully fabricated by using solution casting method with an aid of strong ultrasonication. But the nobility of this research is using microbial synthesized biopolymer which was produced experimentally from whey fermentation by Hydrogenophaga pseudoflava. *Corresponding author: 1TMazyar.sharifzadeh@gmail.com

[1] D.Z. Bucci, L.B.B. Tavares, I. Sell, Polym. Test 24 (2005) 564– 571. [2] C. Chen, B. Fei, S. Peng, Y. Zhuang, L. Dong, Z. Feng, Eur.

• Polym. J. 38 (2002)1663–1670.

[3] S.N. Lee, M.Y. Lee,W.P. Park, J. Appl. Polym. Sci. 83 (2002) 2945–2952. [4] M. Erceg, T. Kova (2008) 57–62. [5] J. Collister, in: R. Krishnamoorti, R.A. Vaia (Eds.), Polymer Nanocomposites:Synthesis, Characterization and Modeling, American Chemical Society, Washington,2001, pp. 7–14. [6] K.E. Strawhecker, E. Manias, Chem. Mater. 12 (2000) 2943– 2949. [7] M.-A. Paul, M. Alexandre, P. Degée, C. Henrist, A. Rulmont, P. Dubois, Polymer 44 (2003) 443–450. [8] C.F. Ou, M.T. Ho, J.R. Lin, J. Appl. Polym. Sci. 91 (2004) 140– 145. [9] Wu CL, Weng WG, Wu DJ, Yan WL. Preparation of polystyrene/ graphite nanosheet composite. Polymer 2003;44:1781–4.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 11

Theory of metal nanocontacts: structure, conductance, magnetism

• E. Tosatti (*)

SISSA, ICTP, and CNR-IOM Democritos Trieste, Italy The physics of nanosized metal contacts is an intriguing and fast developing subject. Although interest this area is largely curiosity-driven, one may as usual expect that the understanding gained will be of later use in a variety of fields including contact mechanics and friction, electrical contacting and conduction (also through molecules) and control of current by means of magnetism. In this lecture I intend to exploit some recent and less recent theory and simulation results from our group to provide a brief flash of this subject. The geometric structure of nanowire-shaped contacts will be addressed first, including the noncrystalline and helical shapes first predicted by Gulseren et al [1]. Time evolution and spontaneous thinning of these contacts will be described in terms of the nanowire string tension, whose ab initio calculation [2] provided early on a microscopic explanation of the striking helical nanowires observed in Au by Takayanagi's group [3]. The electronic structure of nanocontacts is addressed next. Based on that the Landauer formulation permits a direct calculation of electric conductance in the ballistic limit.[4] In transition metals, a rather different role of s and

• f d electrons emerges. Moreover, due to locally higher spin polarization at the nanocontacts in a

ferromagnetic metal, the minority character of the carriers is predicted to be even more dominant than in bulk.[5] In addition, the locally changed crystal field at the nanocontact leads to the prediction of

• rbital moment "dequenching" with and unexpectedly strong role of spin-orbit interaction and a

consequent upsurge of magnetocrystalline anisotropy, way above the bulk value. [6,7] At the nanocontact, even metals that are not magnetic in bulk may locally magnetize. Density functional electronic structure calculations predict in particular that Pt[7,8] and Pd [9,10] atomic nanocontacts could actually do that. In that case, the conductance should be modified by the spontaneous local magnetism. An experimental detection of this phenomenon is still pending, and represents a challenge. Finally, whenever a magnetic impurity, molecule, or locally magnetic group of atoms (as in the case above), finds itself along the contact conduction path, there is the possibility of a Kondo effect, reflecting the screening of the magnetic impurity by the conduction electron spins. The presence of a Kondo cloud shows up as a conductance "zero bias anomaly" at bias values below the Kondo energy scale, and temperature below the Kondo temperature. The problem posed by the ab initio calculation of a realistic Kondo effect and zero bias anomaly is exemplified by an idealized Au-Ni-Au nanocontact, [11] and by magnetic impurities on single wall

• nanotubes. [12] In metals close to ferromagnetism a very different and unconventional ferromagnetic

Kondo "antiscreening" may instead be expected at a nanocontact.[13] (*) Recent work in collaboration with P. Baruselli, A. Dal Corso, A. Delin, M. Fabrizio, P. Gava, P. Gentile, P. Lucignano,

• R. Mazzarello, A. Smogunov, R. Weht.

[1] O. Gulseren, et al., Phys. Rev. Lett. 80, 3775 (1998). [2] E. Tosatti, et al., Science 291, 288 (2001). [3] Y. Kondo, et al., Science 289, 606 (2000) [4] A. Smogunov, et al., Phys. Rev. B 70, 045417 (2004). [5] A. Smogunov, et al., Phys. Rev. B 73, 075418 (2006). [6] G. Autes, et al., J. Phys. Cond. Matt. 18, 6785 (2006). [7] A. Smogunov, et al., Nature Nanotech. 3, 22 (2008). [8] A. Delin and E. Tosatti, Phys. Rev. B 68, 144434 (2003). [9] A. Delin and E. Tosatti, Phys. Rev. Lett. 92, 057201 (2004). [10] P. Gava, et al., to be published [11] P. Lucignano, et al., Nature Mat. 8, 563 (2009). [12] P. Baruselli, et al., in preparation. [13] P. Gentile, et al., EPL 87, 27014 (2009).

Plenary <<11>>

Lyrotropic Mesophases and Nanostructured Materials: Synthesis and Characterization

Cüneyt Karakaya,1 Yurdanur Türker,1 Cemal Albayrak,1 and Ömer Dag1*

1Department ofChemistry, Bilkent University, Ankara 06800, Turkey

Abstract— Salt-surfactant liquid crystalline mesophases can be used to synthesize mesoporous metal oxides-silica (meso- MO-SiO2) thin films (where M is Cd(II) and Zn(II)). The metal oxide/silica mole ratio can be increased up to 1.43 in the mesopore walls that can be converted to metal sulfide-silica (meso-MS-SiO2) and metal selenide-silica (meso-MSe-SiO2) films by H2S and H2Se reactions, respectively.

Since the discovery of mesostructured materials in 1990’s[1] tremendous efforts have been devoted to synthesize new and functional porous materials. One of an important synthesis approach was surfactant templating in their lyotropic liquid crystalline (LLC) mesophase.[2] Preparation of mesoporous transition metal oxides, sulfides, selenides, and metals in the form of ordered thin films are still the challenges of the field. Using true LLC templating approach for the synthesis of mesostructured sulfides and metals have been created [2] in the form of small particles (50-100 nm particles) that collapse upon removing the surfactants from the pores. We have explored transition metal salt (TMS) containing LLC mesophases towards producing new nano/mesostructured materials.[3] Recently, we have also investigated that addition of a second surfactant, a charged surfactant, such as CTAB or SDS that further improved the TMS/surfactant ratio of the media.[5] To prepare nanostructured networks or to design mesostructures from the LLC mesophases, the metal ion concentration must be high enough to keep the mesostructures during the formation dense pore walls. An excessive amount of metal nitrate salt can be incoorporated into the two surfactants LLC mesophases in presence of a small amount of water.[4] The LLC mesophase can be processed in the form of thin films by dissolving in a solvent such as water, ethanol,

• r acetone, and spin or dip coating on a substrate. The thickness of

the film samples can be controlled between 50 nm to a few μm by controlling the amount of solvent and spinning speed. However, the LLC mesophases are soft such that harsh reactions may lead phase separation of the inorganic from the organic mesophase. To make the media harder and to minimize the phase separation, we have also incorporated silica species together with metal ions. We found that the metal nitrate species can be assembled together with silica up to a metal ion/silicon mole ratio of 2.0. Calcination of the film samples result mesoporous metal oxide-silica thin films.

• Fig. 1.The SEM image of the film sample of meso-CdO-SiO2. Inset

is a detailed image with a scale bar of 1.0 m. A representative SEM image of a film sample is shown in Figure 1. The structure has two pore system, mesopores (4-6 nm) and macro-pores (30-200 nm). The calcined film samples can be reacted with H2S or H2Se to convert the metal oxides to metal sulfides or metal selenides, respectively. Figure 2 display two FTIR spectra after calcination of the mesostructured ZnO- SiO2 films and H2Se reaction. The trend in the spectra clearly shows that the pore walls are made up of silica, silica-cadmium

• xide and cadmium oxide. The broad peak at 965 cm-1 is due to
• Si-OZn mode and the peak at 556 cm-1 is due is ZnO layer.

Both peaks show responds to H2Se reaction due to breaking the Si-O-Zn bonds and converting the ZnO to ZnSe.

• Fig. 2. The FTIR spectra of calcined meso-ZnO-SiO2 film,

before and after H2Se reaction. The detail of the salt-surfactant LLC mesophases, synthesis and characterization of the mesostructured oxides, sulfides and selenides will be discussed using SEM, POM, XRD, FTIR, EDS, Raman techniques. This work was supported by TUBITAK (107T837), UNAM-REGPOT under contract No: 203953 and the Turkish Academy of Science. *corresponding author dag@fen.bilkent.edu.tr [1] C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli, J.

• S. Beck, Nature 359, 710 (1992). b) T. Yanagisawa, T.

Shimizu, K. Kuroda, C. Kato, Bull. Chem. Soc. Jpn. 63, 988 (1990). [2] G. S. Attard, J. C. Glyde, C. G. Göltner, Nature 378, 366 (1995). P. V. Braun, P. Osenar and S. I. Stupp, Nature 380, 325 (1996). Y. Yamauchi, T. Momma, T. Yokoshima, K. Kuroda,

• T. Osaka, J. Mater. Chem. 15, 1987 (2005).

[3] Ö. Çelik and Ö. Dag, Angew. Chem., Int. Ed. 40, 3800 (2001), A. F. Demirörs, B. E. Eser and Ö. Dag, Langmuir 21, 4156 (2005). [4] C. Albayrak, A. M. Soylu, Ö. Dag, Langmuir 24, 10592 (2008).

400 800 1200 1600 3000 3600 0.0 0.1 0.2 0.3 0.4 0.5

Absorbance (a.u.) Wavenumber (cm-1)

556 946 1075

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 12

Self-organized Formation of Hexagonal Pore Arrays in Anodic Alumina Fabrication

Hossein Ghaforyan,1* Majid Ebrahimzadeh2

1Department of Physics, Payame Noor University of Miandoab, West Azarbayjan, Iran 2Department of Physics, Shiraz University, Shiraz , Iran

Abstract— Nanostructure materials have potential technological applications due to their characteristic dimensions. In this experimental paper, we focuses on a reliable method for fabricating nanoporous alumina with high regularity. Starting from study of nanostructure materials synthesize methods. After that, porous alumina are fabricated in the laboratory by anodization of aluminum oxide. The conditions for the self-

• rganized formation of ordered hexagonal structures in anodic alumina were investigated for 0.3 M oxalic as an electrolyte. Highly ordered pore

arrays were obtained for oxidation in 0.3 M oxalic acids. The size of the ordered domains depends strongly on the anodizing voltage. This effect is correlated with a voltage dependence of the volume expansion of the aluminum during oxidation and the current efficiency for oxide

• formation. The resulting mechanical stress at the metal/oxide interface is proposed to cause repulsive forces between the neighboring pores which

promote the formation of ordered hexagonal pore arrays. Hard anodization process are employed to fabricate the nanoporous alumina using 0.3M

• xalic acid and 90, 120, 130 and 140 anodized voltages. The nanoporous template were characterized by SEM and FFT. The nanoporous

templates using 130 and 140 voltages have high ordered. The pore formation, influence of the experimental conditions on the pore formation, the structural characteristics of the pore and the oxide chemical reactions involved in the pore growth are discuss.

Porous oxide growth on aluminum under anodic bias in various electrolytes has been studied for more than 40 years [1]. Because of their relatively regular structure with narrow size distributions of pore diameters and interpore spacings, porous alumina membranes are used for the fabrication of nanometer scale composites. Masuda et al.[2-3] reported self-

• rganized pore growth, leading to a densely packed hexagonal

pore structure for certain sets of parameters. In this experimental paper, We describe the set-up to grow nanoporous self organized alumina templates using anodic aluminum. Experimental section Fabrication of an ordered nanopore arrays is first introduced by Masuda and Fukuda [1]. Masuda and Fukuda used two step anodization process. The steps of anodization process is applying electric current to a substrate in the presence of acid electrolyte to obtain an oxide layer with self organized nanopores [2,3]. Nanoporous alumina films are obtained by electrochemical

• xidation
• f

high-purity (>99.998%) aluminum foils. Prior to anodization, several cleaning treatments are employed. The substrate is first degreased in ethanol, followed by soft chemical polishing in sodium hydroxide solution (1M), which removes the native oxide layer, being then rinsed in deionized water. A hard anodization procedure is used in order to achieve the desired organization

• f pore structure. In the work here presented, the anodizations

were performed at constant voltages of 90, 120, 130 and 140 V during 1hours. As electrolyte a 0.3 M oxalic acid solution was used and the temperature was kept constant within 0ºC.

Figure 1.SEM micrographs and FFT image of nanoporous alumina formed in 0,3M oxalic acid (4×4µm2) ( a,d) 90V (b,e) 120V and ( c,f)140 V. Figure 2.Sem Image of highly ordered nanoporous array formed in 0.3 M

• xalic acids and 140 V anodized voltage implemented in this work

Result and Conclusion As shown in Figure 1, well order nanopore arrays can be

• btained by 0.3 M oxalic acid solution and 140 V anodization
• voltage. From SEM analysis, an anodization in 0.3M oxalic

acid solution at 0ºC, carried out at a potential of 140V for 1 hours, gives the best conditions, suitable for the appearance of a long-range hexagonal-pattern organization Figure 2. We can conclude that an applied potential of 140 V gives the best conditions for the appearance of organized patterns, as it is clearly seen in the FFTs in the insets. Anodic alumina template is a well studied material that is used for fabrication

• f nanotubes or nanowires that have uniform diameter and
• length. Its fabrication method is very simple and inexpensive.

We conclude that in porous anodic alumina, ordered hexagonal pore arrays formed by a self-organization process during growth with oxalic as well as other acid as an

• electrolyte. We suggest that the mechanical stress, which is

associated with the expansion of the aluminum during oxide formation is the cause of repulsive forces between neighboring pores during the oxidation process, which lead to self-organized formation of hexagonal pore arrays.

*Corresponding author: pasiran@gmail.com [1] H. Masuda, K. Fukuda, “Ordered Metal Nanohole Arrays Made by a Two-Step Replication of Honeycomb Structures of Anodic Alumina” Science 268 pp. (1995)1466. [2] H. Pan, J. Lin, Y. Feng, H. Gao, “Electrical-Bridge Model on the Self- Organized Growth of Nanopores in Anodized Aluminum Oxide” IEEE Transactions on Nanotechnology 3 no 4 pp. (2004) 462. [3] A. Sarkar, J. Khan, G. G. Basumallick. Nanowires: properties, applications and synthesis via porous anodic aluminum oxide template. Bulletin of Materials Science, 30(3), (2007). 271. Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 13

5 10 15 20 25 30 35 40 100 200 300 Equilibrium Concentiration(mg/g) Initial Concentrations(ppm) Copper Adsorption CS AC RHA rRHA CS:AC

COMPARISON OF HEAVY METAL ADSORPTION PROPERTIES OF CALCIUM SILICATE WHICH PRODUCED FROM RICE HULL ASH (RHA) AND ACTIVATED CARBON

Polat Tugrul YAZOGLU, Ozgul TASPINAR

Istanbul Technical University,Chemical Engineering Department,Istanbul, 34469,Turkey Abstract- In this study, heavy metal adsorption abilities of synthetic meso-prous calcium silicate which was produced from the rice hull ash (RHA) and activated carbon is going to be researched. Activated Carbon is a porous material used as adsorbent in different industrial

• applications. In chemical industry activated carbon is commonly used for heavy metal adsorption from water. It is going to be searched

whether calcium silicate is an alternative of activated carbon or not .Copper, Lead and Zinc metals are adsorbed by both calcium silicate and activated carbon. Also in this study, raw raw rice hull ash and reburned rice hull ash is used as adsorbents for reducing cost of adsorption process.

Accumulation of heavy metals in the food chain and their persistence in nature, once they are discharged by numerous industrial activities, are well known phenomena. There are many treatment processes that can be used for the removal of metal ions from wastewater [1]. It may be added that most wastewaters contain heavy metals in concentrations greater than permissible limits, and therefore need to be removed. Because of their toxicity, the presence of any of these metals in excessive quantities will interfere with many beneficial uses of the water [2].Treatment processes for metal contaminated waste streams include chemical precipitation, membrane filtration, ion exchange, carbon adsorption, and co-precipitation/adsorption [3].

Table 1. Initial concentrations and, equilibrium concentrations of Copper after adsorption

Initial Cu concentration (ppm) qt(mg/g) Calcium Silicate AC RHA rRHA CS:AC 2 0,892 0,940 0,783 0,848 0,880 4 1,785 1,870 1,495 1,790 1,755 6 2,805 2,755 2,610 2,765 2,550 12 5,589 5,249 5,529 5,704 5,169 16 7,742 6,717 7,867 7,417 7,792 36 17,900 11,083 11,833 10,483 17,903 50 25,011 11,815 11,365 9,815 24,469 100 33,466 13,576 13,586 11,516 22,301 200 20,310 2,310 8,370 300 9,991 Table 1, illustrates how adsorption capacities changes while initial concentrations increase from 2 to 300 ppm. Experiments don’t yields reliable results for high concentrations for adsorbents instead of Calcium Silicate. Because of that, for higher concentrations higher than 100 ppm only calcium silicate experiments have significant results for adsorption of copper. As it seen by table, calcium silicate is the most capable adsorbent for adsorption of copper from water and it can be used for copper removal applications especially up to 100 ppm concentrations.

Figure 1. Equilibrium Concentration Curves for Cooper Adsorption

Figure 1 includes the equilibrium concentration curves for cooper adsorption. This graph plotted by data given in Table 1,and demonstrates adsorption capacities of adsorbents clearly. From figure 1, it is observed that calcium silicate is the best adsorbent for removal of copper ions from water at any concentrations. In many filtration applications activated carbon uses as adsorbent of heavy metals or other contaminants. But by this study calcium silicate is found as a alternative of that.Also RHA is an alternative for adsorbent of copper up to 100 ppm concentrations Corresponding author:yazoglu@itu.edu.tr

[1]Sciban,M.,Radetic.,B.,Kevresan,Z.,Klasnja,M.,2005, Adsorption of heavy metals from electroplating wastewater by wood sawdust, Department of Biotechnology and Pharmaceutical Engineering, Faculty of Technology, University of Novi Sad, Bulevar Cara Lazara [2] Bhatnagara,A., Minochaa, K.A.,2009,Utilization of industrial waste for cadmium removal from water and immobilization in cement Environmental Science and Technology Division, Central Building Research Institute (CBRI), India,Department of Environmental Engineering (YIEST), Yonsei University, Wonju South Korea [3] Aziz,H.,Adlan,N., Ariffin,S.,2007,Heavy metals (Cd, Pb, Zn, Ni, Cu and Cr(III)) removal from waterin Malaysia: Post treatment byhigh quality limestone, School of Civil Engineering, University

• f Science Malaysia

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 14

Oil soluble CdS nanoparticles as Component for Functional Ink-Jet Inks

Mahmut Kus1*, 2, Jens Hammerschmidt2, Stan Farnsworth3, Faruk Ozel1, Serhad Tilki1, and Reinhard R. Baumann2

1Selçuk University, Faculty of Engineering and Architecture, Department of Chemical Engineering, Konya, Turkey 2Chemnitz University of Technology, Institute for Print and Media Technology, Reichenhainer Straße 70, D-09126 Chemnitz, Germany 3Novacentrix, Austin, Texas, USA

Abtsract-We report fabrication of a basic electronics building block e.g. Schottky diodes, based on ink-jet printed amorphous oxide and metal contacts as active and passive device layers. Oil soluble CdS nanoparticles was employed as device active layer. Presented approach may open a novel route for development of a next generation of Large Area Printed Electronics based on printed amorphous Oxides

The ink-jet printing technology allows direct patterning

• f functional materials such as conductors, insulators, and

semiconductors onto the substrate. Amorphous oxides have numerous advantages due to their atmospheric and temperature stability, relatively high field-effect mobility, which make them competitive candidates to be integrated in functional devices and smart systems [1]. Employing printable amorphous oxides and processing them by digital fabrication is a promising route which may enable fabrication

• f

high-end and cost-effective printed electronics. In the last decade, colloidal nanocrystals (NCs) have been widely investigated due to their possible applications in fields as optoelectronic, photocatalysis and biological labeling [2-4]. Semiconductor quantum dots can be fabricated via several techniques [5-6]. Highly luminescent CdSe/CdS and CdSe/ZnS core-shell nanocrystals have been prepared through organometallic approaches [7]. However, organometallic reactions are carried out in

• rganic phase or aqueous phase. Therefore, both

nucleation and growth of the nanocrystals only were happened in a homogeneous system. It is very difficult for

• rganic-phase

approaches to synthesize

• il-soluble

nanocrystals by using various water-soluble precursors [7,]. Pan et. al. reported two phase method which occurs under mild conditions and results in highly luminescent nanoparticles. Here we report fabrication of a basic electronics building block e.g. Schottky diodes, based on ink-jet printed amorphous oxide and metal contacts as active and passive device layers. Printed components are based on originally synthesized semiconductive oxides and metallic inks. The CdS, synthesized in two phase synthetic routes to obtain

• il soluble CdS nanoparticles was employed as device

active layer, After printing, low temperature sintering methods (close to room temperature) were performed in

• rder to form the device active and passive layers. That

was accomplished combining high intensity lamp sintering method and wet-chemical treatment allowing us to use low-cost plastic film, such as Polyethylene terephthalate (PET) as substrate material. Figure 1 shows I-V characteristic of CdS based Schottky diode and device structure (inset).

Figure 1. I-V characteristic of CdS based Schottky diode and device structure (inset).

Presented approach may open a novel route for development of a next generation of Large Area Printed Electronics based on printed amorphous Oxides. *Corresponding author: mahmut_kus@yahoo.com

[1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and

• H. Hosono Nature, 432, 488 – 492, 2004

[2] Klabunde, K. J. Nanoscale Materials in Chemistry; Wiley- Interscience: New York, 2001. [3] Weller, H. Angew. Chem., Int. Ed. Engl. 1993, 32, 41. [4] Alivisatos, A. P. Science 1996, 271, 933. [5] D. Bimberg, M. Grundmann, N.N. Ledentsov, M.H. Mao,

• Ch. Ribbat, R. Sellin, V.M. Ustinov, A.E. Zhukov, Zh.I. Alferov,

J.A. Lottet al, Phys. Status Solidi B 224 (2001) 787. [6] C.B. Murray, D.J. Norris, M.G. Bawendi, J. Am. Chem. Soc. 115 (1993) 8706. [7] Daocheng Pan, Qiang Wang, Shichun Jiang, Xiangling Ji, and Lijia An, J. Phys. Chem. C 2007, 111, 5661-5666

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 15

Graphite Intercalation with Perfluoroalkylanions by Chemical and Electrochemical Oxidation

Bahar Özmen-Monkul*, Michael M. Lerner

Department of Chemistry, Oregon State University, 238 Gilbert Hall, Corvallis, OR 97331, USA

Abstract-Graphite intercalation compounds (GICs) containing anions with perfluoroalkyl substituents have been prepared by chemical or electrochemical oxidation, their structures and compositions determined. The anionic groups include borate, sulfonyl amides and phosphate. The potassium salts as well as an ionic liquid (IL) are used as the anion sources. Gallery heights of 0.84- 0.87 nm have been obtained for stage 2 GICs of this type. The co-intercalation of fluoride ion occurs when HF is used as the reaction solvent; a new analytical method has been developed to evaluate the ratios of fluoride to fluoroanion intercalate in the

• products. The gallery heights of the GICs are calculated from X-ray diffraction data and compared with the ones seen from the

energy minimized anion models calculated by Gaussian 03 software. These observations will be discussed in terms of the most stable anion type and orientation in between the graphene sheets. TGA data indicate how stable the anions are in the GICs compared to their alkali metal salts. Graphite can intercalate various guests in between its parallel sheets where it forms GICs. Uniquely, graphite allows either anions or cations as intercalates, in the former case carbon sheets are oxidized and become positively charged (acceptor-type GIC) where in the latter, they are reduced and become negatively charged (donor-type GIC). Graphite intercalation is therefore a redox reaction and the reactions require the use of either strong oxidizing or reducing agents,

• r the application of a potential in an electrochemical cell. The
• nset potential for oxidative graphite intercalation exceeds 4 V
• vs. Li/Li+, and this potential increases as the intercalation

reaction proceeds to lower stages. The ordering sequence of the occupied galleries and the neighboring graphene layers is known as staging. In a GIC, not every adjacent graphene sheet is necessarily separated by an intercalate for example for a stage 3 GIC, in every third layer of graphene sheets the galleries are occupied and for a stage 2 GIC, in alternating layers of graphene sheets there are intercalates. The most commercially important donor-type GIC is LiCx compound; the LiCx/Cx redox couple is the active component in the negative electrodes in Li-ion cells [1]. Acceptor-type GICs have found application in exfoliated form as gas or oil adsorbents, and when pressed into sheets these materials are used as high-temperature gaskets or seals, and as packing materials [2]. Exfoliated graphite is produced by the rapid volatilization of anionic intercalates at elevated temperatures. Related methods can form graphene nanoplatelets [3]. Graphene-based nanoscale materials have extraordinary mechanical, electronic and thermal properties and have been proposed for a range of applications including electronically- conducting composites [4], transparent electrodes [5] and photovoltaic devices [6]. GICs with fluoro-tris(pentafluoroethyl)borate anions can be obtained by either chemical or electrochemical methods [7]. The calculated gallery heights, di are 0.86-0.89 nm for stages 2 and mixed of stages 2,3. The occupancy of fluoride co-intercalate positions is dependent on reaction time (Fig. 1a) for the chemically prepared GICs. For a stage 2 Cx[FB(C2F5)3]·F, x=52 and =0.03 values are calculated. GICs with tris(pentafluoroethyl)trifluorophosphate anion, [(C2F5)3PF3]- are prepared for the first time by electrochemical method [8]. They are the unique examples of the phosphate including acceptor-type GICs after the GICs with PF6

• and

PO4

3-[8] (Fig. 1b). Stages 2-4 with gallery heights changing

from 0.86 to 0.82 nm are observed respectively. The cyclo-hexafluoropropane-1,3-bis(sulfonyl)amide anion, [CF2(CF2SO2)2N]- produced a stage 2 GIC (Fig. 2) with electrochemical method, however using the chemical

• xidation in either hydrofluoric acid or anhydrous HF, a GIC

was not observed instead, graphite bifluoride (CxHF2·HF) was produced [9].

(a) (b) Figure 1. Energy minimized anion models of stage 2 GICs of (a) Cx[FB(C2F5)3]·F (with boron either facing up or down shown together with the co-intercalated fluoride anions) (b) Cx[PF3(C2F5)3].

The “lying down” anion orientations in the GIC galleries are shown for the relatively small intercalates of linear and cyclic amides. The stabilities of these GICs in a K2MnF6/HF environment are discussed.

(a) (b) Figure 2. The energy minimized anion orientation (a) for Cx[CF2(CF2SO2)2N] and calculated surface charge density (b) for the anion are shown

In summary, the first syntheses and the characterization of the fluroalkylborate and phosphate anion GICs will be

• described. GIC structure models are provided and the

stabilities of the linear and cyclic amides in the GICs are

• discussed. The relative instability of the cyclic anion GIC

makes for facile displacement by smaller intercalate anions such as bifluoride.

*Corresponding author: ozmenb@onid.orst.edu

[1] N.A. Kaskhedikar and J. Maier, Adv. Mater., 21, No. 25-26, 2664 (2009). [2] A.V. Yakovlev et al., Russ. J. Appl. Chem.,79, No. 11, 1741 (2006). [3] S. Stankovich, D.A. Dikin et al., Carbon, 45, No. 7, 1558 (2007). [4] S. Stankovich, D.A. Dikin et al., Nature, 442, No.7100, 282 (2006). [5] S. Watcharotone, D.A. Dikin et al., Nano Lett.,7, No. 7, 1888 (2007). [6] Z. Liu, Q. Liu et al., Adv. Mater., 20, 3924 (2008). [7] B. Özmen-Monkul, M.M. Lerner, G. Pawelke, H. Willner, Carbon, 47, 1592 (2009). [8] B. Özmen-Monkul, M.M. Lerner, Carbon, in review [9] B. Özmen-Monkul, M.M. Lerner, R. Hagiwara, J. Fluorine Chem., 130, 581 (2009). Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 16

Three Dimensional Imaging of Clathrin Coat and Adaptor Protein Dynamics in Living Cells

Comert Kural*, Steeve Boulant, Tomas L. Kirchhausen

200 Longwood Avenue, WAB 133, Harvard Medical School, Boston, MA 02115 Abstract- We generated a tracking algorithm that enables us to determine the three dimensional trajectories of fluorescent objects within live cells imaged by a spinning disk confocal microscope. Using this tracking scheme we can locate an organelle labeled with fluorescent proteins within less than 50 nm in the lateral dimensions. For the Z axis we use a single Gaussian curve fitted to the total intensities calculated from the regions of interests of different focal planes and obtained ~50 nm localization precision in less than 0.5 seconds. Our analysis enabled us to extract for the first time the temporal and spatial behavior of AP3 and AP1 containing clathrin structures as they traffic between membranous organelles of BSC1 monkey cells. We found out that AP1 and AP3 adapter protein coats have strong co-localization with clathrin and have average lifetimes of ~30 seconds. Our results also suggest that, within the same organelle, AP1 and AP3 can form multiple partial coats which behave independently. Transportation of these adaptor protein complexes is mainly performed by microtubule dependent molecular motors.

Endocystosis is a biological process where live cells take in extracellular molecules such as nutrients, hormones and signaling molecules. The fact that viral and bacterial pathogens often hijack endocytic routes to infect cells makes endocytosis an interesting topic for biology research. Clathin- mediated endocytosis is one of these pathways where numerous clathrin proteins form cages (or coats) around the molecules that are marked for internalization. In this work we use a tracking scheme that enables to localize fluorescently labeled structures within ~50 nm in lateral and axial dimensions in order to study endocytosis in three dimensions (Figure 1).

Figure 1. 3D traces of AP2 adapter protein punctae moving with retrograde flow at the dorsal surface of U373 glioblastoma- astrocytoma cells.

Our three dimensional tracking of clathrin associated proteins have revealed that a subset of endocytic events move with a significant displacement in Z axis at the very end of their lifetimes. We named these events as 'lifters' (Figure 2). The rest of the population, where the structure remains at the same axial position, is named as 'stables'. We have shown that lifting of clathrin structures depend on actin filament dynamics for the percentage of lifters has reduced significantly upon treatment of drugs interfering with actin filament dynamics (such as jasplakinolide) (Figure 3).

5 25 45 65 85 105

• 50

50 100 150 200 250 Intensity (a.u.) Z Position (nm) Percentage of Lifetime 4.0k 8.0k 12.0k 16.0k 20.0k 24.0k

Figure 2. The average intensity and Z displacement of lifter coats.

Interestingly, lifter population increased up to two-fold when the cellular membrane tension is raised by incubating cells in hypotonic solution (data not shown). Increasing membrane tension by other means have also resulted in a higher fraction of clathrin structures that depend on actin dynamics.

Figure 3. The sizes of some microscopic objects, in decreasing

• rder of size [2]

Our results suggest that membrane tension is an important factor regulating the involvement of actin machinery during clathrin-mediated endocytosis. This study was supported by National Institute of Health and Helen Hay Whitney Foundation, US. *kural@idi.harvard.edu

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 17

Figure: (a) Atomic Force Microscopy image of the GeNC-in-Si. Peak- to-peak surface roughness is 120 nm. RMS roughness is 38.4 nm. (b) Photoluminescence spectrum of the GeNC-in-Si sample and reference (bare Silicon) for the visible range, excitation wavelength = 300 nm. (c) Low magnification TEM Image of a similar but thinner sample (scale bar: 100 nm) (d) Quantum dots shown in high magnification (scale bar: 5 nm)

Silicon Germanium Nanocrystal Technology for Thin Film Photovoltaics and Integrated Optoelectronics

Abstract—Germanium nanocrystals were obtained in Silicon host by a recently developed heteroepitaxy technique. The nanocrystals were imaged by transmission electron microscopy. The grown films were characterized by atomic force microscope and photoluminescence spectroscopy. Strong absorption enhancement in photoluminescence spectrum was

• bserved corresponding to resonance wavelengths of the quantum dots.

Silicon is near-infrared blind because of its large indirect (~1.1eV) and direct (~3.4eV) bandgap energies and that is why, it cannot be used as the absorbing layer for near-infrared photodetection (especially for >1100 nm). Germanium, however, can circumvent Silicon’s spectral limitation and can be used as the absorbing layer. Okyay and coworkers have recently introduced a new method called Multiple Hydrogen Annealing Heteroepitaxy (MHAH) for growing high crystal quality Germanium on Silicon [1,2]. Using this technique, it is also possible to produce Germanium nanocrystals (NC) on and inside Silicon. With this technique, it is possible to engineer the nanoparticle sizes through the control of the thickness of the Germanium wetting layer. This enables the preparation and integration of engineered absorbing materials spanning visible and near-infrared parts of the spectrum. Doping thin film silicon solar cells with nanocrystals of varying sizes can also enhance the absorption of solar cells, significantly. In this study, we grew Germanium nanoparticles of multiple sizes inside the same silicon host and characterized them in terms of nanostructural, photoluminescence and surface properties. Lowly doped, Silicon (100) wafers were used as starting

• substrates. The wafers were cleaned by RCA 1 clean followed

by immediately loading them into the reaction chamber. The native oxide on Si surface was removed by hydrogen baking and an ultrathin Si epitaxial layer was grown. The growth temperature was then set to 400 °C for Ge NC formation. The growth time and pressure and the gas flows were varied to

• btain various size nanocrystals. Thin Ge layers incubate and

grow in an island fashion before coalescence. Silicon cap layers were deposited before coalescence, leaving Ge NC layers sandwiched in Si matrix. After the growth, the GeNC-in-Si samples were characterized. To confirm the reliability

• f
• ptical

characterization, first, the surface depth profile of the samples were measured using the tapping mode of the atomic force

• microscope. Then, the surface roughness information has been

extracted (Fig.1a) as follows: for 1063 nm thick sample (BT2) which includes 10 layers of quantum dots embedded inside silicon, rms surface roughness is 38.4 nm and maximum peak- to-peak roughness: 120 nm, for a thinner sample (BT4) of 845 nm thickness, rms surface roughness and maximum peak-to- peak roughness are 14 nm and 80 nm, respectively. For a thinner sample (C4) of 123 nm total thickness, rms and maximum peak-to-peak roughness are 15 nm and 80 nm. In order to understand the electronic band structure of the GeNC-in-Si samples, photoluminescence measurements at different excitation wavelengths were performed. In Fig. 1, the photoluminescence spectrum of one of the samples and that of reference bulk silicon is shown. The excitation wavelength was 300 nm and because the 300 nm excitation was not filtered, there are two major peaks at 300 nm and 600 nm (i.e. second harmonic of the excitation). The quantum dot layers not only enhanced existing peaks (arrows on the figure), but also introduced new peaks and amplified the luminescence broadband, due to the size dispersion among the nanocrystals. To confirm the prescence of nanocrystals and further understand the layer structure, we have taken the transmission electron microscope images of the thinnest sample. In Fig.1c, the layer structure is sandwiched among the Silicon substrate and ion beam deposited Platinum. The top Platinum layer is used to protect the silicon surface during ion beam preparation

• f the sample for TEM and to avoid charging effects. The

layers have micro particles which embed Germanium nanocrystals inside. In conclusion, we have demonstrated a novel method of embedding Germanium nanocrystals inside Silicon layers. This opens up advantageous applications for thin film Si photovoltaics and silicon CMOS compatible photodetectors. This work was supported by TUBITAK 108E163, 109E044, EU FP7 PIOS.

[1] Ali K. Okyay, PhD Thesis, Stanford University, September 2007 [2] Ali K. Okyay et. al. Optics Letters, Vol. 31, Issue 17, 2565 Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 18

Cd:Zn (1:1) (1:0.33) (1:1.36) 587 nm 566 nm Normalized Fluoreccence Intensity wavelength(nm) 1 4 6 556 nm

200 min

Normalized Absorption Intensity wavelength(nm)

Normalized Fluorescence Intensity

Composition tunable spectroscopic properties of ZnxCd1-x

L

Te ternary colloidal quantum dots

1 and Serdar Özçelik1*

1Izmir Instute of Technology, Faculty of Science, Department of Chemistry, Urla-

Abstract-We synthesized water dispersible ZnxCd1-xTe ternary colloidal quantum dots (QD) in single step process by allowing the reaction of Cd and Zn sources with Te in the presence of thioglycolic acid as a surfactant. To characterize the ternary nanoparticles UV-vis and photoluminescence spectroscopies, XRD, SEM-EDX, and SAXS techniques were used. The color-tunable emission of the colloidal alloy has been observed by adjusting the initial mole ratio of Cd and Zn sources. We demonstrate that the ternary alloy quantum dots are highly luminescent.

Semiconductor alloy nanocrystals such as Zn xCd 1-x In this work, Zn E (E:S, Se, Te) are important nanoscale man-made materials due to continuous tunability of their chemical and optical properties through gradual variation of the composition variable x in which 0 < x < 1. To date much time and effort have been spend to synthesize and use the binary QDs such as CdS, CdSe, CdTe, etc., for the applications in LEDs, solar cell, lasers, and bioimaging. In recent years, more interest have been focused on the preparation

• f ternary alloyed QDs because reduced number of

defects led to better nanocrystals [1,2]. The added degree

• f freedom (0 < x < 1) in alloy QDs may modify the

crystal structure and allow the tuning of band gap energy

• f the particles by the composition [3]. So it is possible to

achieve a wide range of emission colors from nanoparticles

• f the same

diameter with varied composition.

xCd 1-xTe ternary alloy

semiconductor nanoparticles have been preferred to study because there is

• nly one report just published in the literature [4].

Li et al. synthesized Cd xZn 1-xTe alloyed quantum dot coated with glutathione as the stabilizer. In our laboratory the direct synthesis of Cd xZn 1-xTe ternary semiconductor QDs in water by using thioglycolic acid as stabilizing agent was performed in single step. During all reactions, the total number of moles

• f the metal salts were kept constant and the mole ratio of

Cd:Zn (such as 1:1, 1:0.33, 1:1.36) varied to control the alloy effect of Cd2+ and Zn2+ on the emission properties. The quantum confinement effect was achieved by tuning the composition of the alloy (Figure 1).

Figure 1. Normalized PL emission spectra of CdxZn1-xTe nanoparticles with different Cd:Zn ratio (the growth time was 200 min).

The peak of the PL emission is at 566 nm when the mole ratio of Cd:Zn was equivalent. The PL peak relatively shifted to blue when Cd:Zn ratio was 1:0.33 and but to red with an increase in the amount of zinc, 1:1.36. Growth kinetics of the reactions showed that the different initial mole ratio of metal salts resulted in different nucleation rate and controlled photophysical properties. (Figure 2).

Figure 2. (a) Temporal evolution of the spectra of alloys and (b) the growth kinetics of CdxZn1-xTe nanoparticles having three different Cd:Zn ratio.

XRD analysis showed the formation of zinc-blende Zn 1-

xCd xTe colloidal alloy. (Figure 3) The diffraction peaks

systematically shift to larger angles by the increasing amount

• f Zn in the crystal structure, indicating formation of

homogeneous alloy.

Figure 3. XRD diffractogram of ZnxCd1-xTe alloys synthesized with different Cd:Zn ratio.

*Corresponding author: serdarozcelik@iyte.edu.tr

[1] Zhong, X., Feng, Y., Knoll, W., and Han, M., 2003. Alloyed ZnxCd1-x [2] Jang, E., Jun, S., Pu, L.,2003. High quality CdSeS nanocrystals synthesized by facile single injection process and their

• electroluminescence. Chemical Communications, 10, 2964-2965

S with Highly Narrow Luminescence Spectral Width, Journal of American Chemical Society, 125, 13559-13563 [3] Gurusinghe, N. P., Hewa-Kasakarage, N. N., and Zamkov, M., 2008. Composition-Tunable Properties

• f

CdSxTe1-x [4] Li, W. , Liu,J., Sun,K., Dou,H., and Tao, K., 2010, Highly fluorescent water soluble Cd Alloy Nanocrystals, J. Phys. Chem. C, 112, 12795–12800

xZn1-x

40 80 120 160 200 240 520 560 600

Cd:Zn (1:1) (1:0.33) (1:1.36) rxn 1 rxn 4 rxn 6 fluorescence maxima(nm) time (min)

Te alloyed quantum dots prepared in aqueous solution: one-step synthesis and the alloy effect of Zn.

• J. Mater. Chem., 20, 2133–2138.

10 20 30 40 50 60 70

rxn6(1:1.33) rxn4(1:0.33) rxn1(1:1) ZnTe CdTe

46.6 39 23.7 49.5 41.8

Counts 2Theta

25.3

Cd:Zn

(a) (b)

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 19

DEVELOPMENT OF LUMINESCENT- MAGNETIC HYBRID NANOPARTICLES Havva Yağcı Acar*1, Recep Kaş1, Uğur Topal2

1Koç University, Department of Chemistry, Rumelifeneri Yolu, Sariyer-34450, Istanbul, Turkey 2TUBITAK-UME, Magnetic Measurements Lab., PK.54, 41470 Gebze, Kocaeli, Turkey

E-mail: fyagci@ku.edu.tr

• Abstract. Hybrid nanoparticles composed of quantum dots and superparamagnetic iron oxide were prepared in a simple

extraction process. Hybrids luminesing from green to red and respınding to a magnetic field were prepared in samll sizes with excellent stability.

Superparamagnetic iron oxide (SPIOs) nanoparticles have been extensively studied for biotechnology and medical applications. They are applied in a variety of fields from sensors, to separation, from diagnosis to therapy.1 Its applications heavily depend on the ability of superparamagnetic iron oxides (SPIO) to respond to an external magnetic field either to generate a signal or to drag or hold particles. Semiconductor Quantum Dots (QDs) are also attractive nanoparticles with unique size dependent luminescence properties, photo-stability and broad absorption-narrow emission profile. These properties made QDs also invaluable for especially labeling in biotechnology. More recently, there is an intensive research focused on the use of QDs for

• ptical imaging and therapy.2

Besides, QDs offer new opportunities in different fields such as sensors, optics, solar cells, barcodes, lasers, etc.. Research in the mentioned fields of science and technology is evolved towards doing more with less. In this perspective development of hybrid nanoparticles such as nanoparticles having both luminescent and superparamagnetic properties are highly desirable. Actions such as multiplexing, dual imaging, combined actions

• f

imaging/dragging/therapy, combined actions of multiplexing/separation/detection are tremendously advantages in these mentioned fields. There are different approaches in preparing such hybrid nanostructures.3 But, most of these methods have different disadvantages or difficulties such as large particle size, significant loss of luminescence, low yield, etc. Here, we would describe a very simple and efficient extraction method for the development of hybrid nanoparticles (MDOT) composed of magnetic nanoparticles (SPIOs) and luminescent quantum dots (QDs). SPIOs are coated with –COOH functionalized QDs in water to produce stable and luminescent ferrofluids (Figure 1) in a chloroform/water biphasic system. MDOTs luminesce in the color of the original QDs as seen in Figure 1. Quantum yield of the MDOTs can be tuned by adjusting the SPIO/QD ratio. QDs maintain their optical properties after MDOT formation. MDOTs show superparamagnetic behavior (Figure 2). Hybrid structures harnessing properties of different materials could have a differentiating impact on the current technologies.

Figure 1. A) Aqueous MDOTs (under UV excitation, (B) under daylight (a) and UV excitation (b) responding to a hand-held magnet. Figure 2. M-H loop for two different MDOTs. RK034H (larger SPIO/QD ratio) and RK032H.

References:

• 1. Laurent, S.; Forge, D.; Port, M.; Roch, A.;

Robic, C.; Elst, L. V.; Muller, R. N. Chemical Reviews 2008, 108, 2064.

• 2. S. Mazumder, R. Dey, M.K. Mitra, S.

Mukherjee, G.C.Das, Journal

• f

Nanomaterials, 2009, pages 1-17.

• 3. Quarta, A.; Di Corato, R.; Manna, L.; Ragusa,

A.; Pellegrino, T. Ieee Transactions on Nanobioscience 2007, 6, 298. Acknowledgement: This project was partially funded by MC IRC # 31071.

(a) (b) (c) (d) (a) (b)

A B

RK034-H RK032-H

• 15000
• 10000
• 5000

5000 10000 15000

• 8
• 6
• 4
• 2

2 4 6 8 10

M(emu/g) H(Oe) emu/g

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 20

Effects of Cucurbit(n)uril on Dissolution and Light Emitting Properties of Fluorene-Based Non- Ionic Conjugated Polymers

Müge Artar1*, Saltuk B. Hanay1, Eun Ju Park1, Dönüs Tuncel1

1

Abstract-Effects of cucurbit[n]uril on dissolution and light emitting properties of non-ionic conjugated fluorine-based polymers were

• investigated. Firstly, green and blue light emitting fluorine-based polymers, poly[9,9-bis{6(N,N.dimethylamino)hexyl}fluorene-co-2,5-

thienylene (PFT) and poly[(9,9-bis (Dimethylamino-propyl)-9H-fluorene)-benzene]), were synthesized. Then, their interacitons with cucurbit[n]uril derivatives were studied. It was shown that while CB6 and CB7 have no effect on the dissolution and the photo luminescent enhancement of PFT and poly[(9,9-bis (Dimethylamino-propyl)-9H-fluorene)-benzene] but CB8 could enhance fluorescence quantum yield . These results are rationalized by structural investigation which reveals that some part of the aromatic backbone is encapsulated by CB[8] and this prevents interaction between the polymer chains caused by - stacking. Our results offers a significant contribution to the area of water soluble-light emitting polymers and they will open a new approach in the development of biological and chemical sensors owing to the solubility of non-ionic conjugated polymers in water. Department of Chemistry and Institute of Materials Science Institution and Nanotechnology, Bilkent University, Bilkent, 06800 Ankara, Turkey

Conjugated polyfluorenes and related derivatives are widely used in various fields due to their exceptional electrooptical characteristics that can be listed as high photo- luminescent quantum yields, chemical and thermal stability. Moreover, fluorene based polymers are especially used

• wing to the ease in modification of side chains attached to

the fluorene backbone at the 9th position without distrupting their aromatic backbones to adjust their solubility and optical properties [1]. Mostly in biological applications or any application that take place in water media, water-soluble conjugated polymers are needed. For this reason conjugated polymers’ side chains are tuned by attaching ionic or hydrophilic groups but remaining hydrophobic aromatic backbone causes an intrinsic aggregation which results in poor solubility in water and also decrease in fluorescence quantum yields

[2]

In this work, it was shown that encapsulating fluorene based non-ionic conjugated polymers with macromolecules, cucurbiturils,

increased photo/electroluminescence efficiencies. . To handle this problem various approaches were proposed such as incorporation of bulky groups, interaction with surfactants and encapsulated the backbone of the conjugated polymer with a suitable macrocycle. [a] [b]

Figure 1. (a) Structures

• f

(poly[9,9-bis {6(N,N.dimethylamino)hexyl} fluorene-co-2,5 thienylene (PFT)) and (b) (poly[(9,9-bis (Dimethylamino-propyl)-9H-fluorene)- benzene]).

Firstly, we synthesized non-ionic fluorine-based polymers, namely, poly[9,9-bis{6(N,N.dimethylamino)hexyl}fluorene- co-2,5-thienylene (PFT) and poly[(9,9-bis (Dimethylamino- propyl)-9H-fluorene)-benzene]. Next, solubility properties of these polymers and CB[6], CB[7], CB[8] were investigated in water; polymers was soluble in THF, CHCl3, TOLUENE, DMF, DMSO, MeOH while not in water and only CB[7] was soluble in water among other CB derivatives. However, CB[8]-PFT complex was soluble in aqueous media, while CB[8] and PFT were not soluble in water before complex formation. Selective 1D-NOESY NMR spectra of PFT@CB8 indicated that the some part of the aromatic backbone of the PFT was encapsulated by CB8 and the methyl groups of the side chains are in a close proximity with CB8. Next, we have focused on effect of complex formation with CB[8] on photo/electroluminescence efficiencies of PFT. We have compared the absorption and emission spectra of PFT in MeOH, protonated PFT in water and PFT@CB8 inclusion complex in water and an enhancement in emission of PFT@CB8 compared to PFT in methanol was observed.

Figure 2. (a) UV-Vis Absorption of PFT in methanol, protonated PFT in water and PFT@CB8 in water, (b) Emission spectra of PFT in methanol, protonated PFT in water and PFT@CB8 in water

In summary, CB6 and CB7 have no effect on the dissolution and the photo luminescent enhancement of PFT and poly[(9,9-bis (Dimethylamino-propyl)-9H- fluorene)-benzene] but CB8 has. This results are rationalized by structural investigation which reveals that some part of the aromatic backbone is encapsulated by CB[8] and this prevents interaction between the polymer chains caused by - stacking. This findings offers a significant contribution to the area of water soluble-light emitting polymers and they will have great impact in the development of biological and chemical sensors owing to the solubility of non-ionic conjugated polymers in water. *Corresponding author: m_artar@fen.bilkent.edu.tr

[1] U. Koldemir, Conjugated Polymers Based on Polyfluorene Derivatives and Polypyrrole (M.S. Thesis, 2007) [2] Lee S, Kim J-M. Macromolecules 2007; 40. 9201.

S N N n

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 21

Tuning superconductivity by carrier injection into intrinsic Josephson stacks

Paul Müller*

Department of Physics and Center for Molecular Materials, Universität Erlangen-Nürnberg, Germany

*Corresponding author

E-mail address: phm@physik.uni-erlangen.de [keywords] Intrinsic Josephson effects, carrier doping, dc transport, macroscopic quantum tunneling.

In layered high-temperature superconductors, like Bi2Sr2CaCu2O8+, superconductivity is controlled by carrier doping of the conducting planes. Usually this is achieved by a non- stoichiometric composition. The current transport perpendicular to the planes of these layered materials shows intrinsic Josephson effects. Normally, current flow inside superconductors is never expected to be able to change the material itself. However, we were able to show that by extensive current injection along the c-axis the superconducting properties of Bi2Sr2CaCu2O8+ can be changed effectively and reversibly. By injecting current perpendicular to the planes, we show that critical temperature, c-axis resistivity and critical current of intrinsic Josephson junctions can be tuned in a large range from underdoping to extreme overdoping. This effect is reversible and room-temperature stable. Apparently, the insulating layers are charged by injected carriers, and work as a floating gate. The result is hole doping of the conducting layers. This flash memory concept seems to be a general property of layered materials where the insulating charge reservoir layers are separated from the conducting planes.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 22

Atomic and Electronic Properties of Boron Clusters and Their Stability Analyses

Nurten Akman,1* Murat Tas,2 Cem Ozdogan,3 Ihsan Boustani

4 and Ziya B. Guvenc5

1Department of Physics, Mersin University, Mersin 33343, Turkey 2Department of Physics , Bilkent University, Ankara 06800, Turkey 3Department of Computer Engineering, Çankaya University, Ankara 06530, Turkey 4Theoretische Chemie, Bergische Universitat Wuppertal, D-42097 Wuppertal, Germany 5

Department of Electronic and Communication Engineering, Çankaya University, Ankara 06530, Turkey Abstract— We study boron clusters consisting of 2 through 13 atoms arranged in planar or quasi-planar geometry. The vibrational frequency analyses and the optimized geometries are obtained by using the first prinsiple calculations within the density functional theory (DFT) . The average binding energies, bond lengths, adiabatic and vertical electron affinities as well as ionization potentials are calculated for each neutral and multicharged boron clusters. We also provide the stability analyses of boron clusters by investigating the dissociation channel energies as a function of cluster size and charge state.

Boron is a light semiconductor with low density and high melting point. Its hardness is comparable with the diamond. Besides it shows metallic or superconducting behaviors under very high pressure. These striking properties make boron quite attractive for device applications. Due to sp2 hybridization of three valence electrons, large coordination numbers and short covalent radius, boron prefers to form strong covalent bond with various elements. Similar to carbon, boron clusters can form a variety of stable architectures like fullerenes, nanotubes, 2D sheets, planar, and 3D cages. Small boron clusters have already been realized experimentally by using laser ablation technique [1] and obtained some fragmentation

• channels. The electronic, geometrical and vibrational analyses

have been performed for both neutral and anionic small boron clusters by using photoelectron spectroscopy and ab initio

• techniques. All these studies [2-4] proved that small sized

neutral and charged boron clusters prefer to form planar or quasi-planar type atomic arrangements. Besides, clusters with 2D planar geometry are more stable than the 3D clusters.

Figure 1. Top view of optimized geometries of neutral boron clusters

• f n atoms.

In this study, we explored the optimized geometries of boron clusters Bn

m, where 2. The charge m ranges from -2 to

the value at which the cluster dissociates into fragments. We solved the Kohn-Sham equations by using the first principles calculations within the DFT scheme. The exchange-correlation potential was approximated by generalized gradient potential using functional of Becke’s three parameter hybrid exchange functional and the Lee-Yang-Parr (LYP) nonlocal correlation

• functional. Our computations were done with the Gaussian03

package employing the basis set 6-311++G. Note that none of the ground states we obtained have imaginary frequency. As an example, we present optimized geometries for neutral Bn up to n=13 in Figure 1. We have seen oscillations in the variation of average bond lengths with the number of boron atoms for small m values. However the average bond lengths were found to decrease with the number of atoms for large m

• values. We also calculated the average binding energy Eb for

each neutral and singly charged anionic and cationic boron

• clusters. As expected, Eb

We next computed the first and second energy differences to discuss the stability of boron clusters. The most stable cluster was determined from the second energy difference analyses. Besides we investigated the possible fragmentation channels

• f boron clusters as a function of cluster size and their charge

state by calculating the dissociation energy E decreases with increasing number of atoms in the cluster approaching the bulk cohesive energy.

n m

E as

n m = En m - daughters

Positive .

n m means that, the energy is released and the

fragmentation is spontaneous. This process is known as the Coulomb explosion. However, a negative n

m means that the

parent cluster is stable against that particular dissociation channel and one must supply energy external to the cluster for this process. In Figure 2, we display an example of fragmentation channels for boron clusters.

Figure 2. Dissociation energies for the fragmentation Bn

m Bn-2 m-1

+ B2

+1.

*Corresponding author: 1Takmann@mersin.edu.tr

[1] L. Hanley and S. L. Anderson, J. Phys. Chem. 91, 5161 (1987). [2] H. J. Zhai, B. Kiran, J. Li and L. –S. Wang, Nature Mat. 2, 827 (2003). [3] H. J. Zhai, L. –S. Wang, A. N. Alexandrova and A. I. Boldyrev, J.

• Chem. Phys. 117, 7917 (2002).

[4] I Boustani, Phys. Rev. B 55, 16426 (1997).

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 23

Interlamellar Controlled/Living Radical Copolymerization of Maleic Anhydride and Itaconic Acid with Butylmethactylate Via Preintercalated RAFT-Agent/Organoclays Complexes

Zakir M. O. Rzayev1* Ernur A. Söylemez1,

1

Department of Chemical Engineering, Faculty of Engineering, Hacettepe University, Beytepe, 06800 Ankara, Turkey Abstract-We have developed a new approach for the synthesis of polymer nanocomposites using a bifunctional reversible addition- fragmentation chain transfer (RAFT) agent, two types of organo-montmorillonites, such as a non-reactive dimethyldodecyl ammonium (DMDA)- MMT and a reactive octadecyl amine (ODA)-MMT organo-clays), and a radical initiator. This simple and versatile method can be applied to a wide range of monomers and donor-acceptor type monomer/comonomer systems for the preparation of completely exfoliated nanoarchitectures for high performance engineering nanomaterial applications.

In the last years, many researchers attempt to utilize the controlled/living polymerization methods [1-5] tion of the polymer/silicate nanocomposites. Of the methods for the prepara- used in the preparation of polymer-silicate nanocomposites, in situ polymerization offers the ability to impart significant con- troll over both the polymer architecture and the final structure

• f the composite. The polymer/silicate nanocomposites, with

well-dispersed (exfoliated) silicatelayers, can be produced using atom transfer radical polymerization and nitroxide mediated polymerization methods. The interlamellarcontrolled / living radical (co)polymerization of monomers using eversible addi- tion-fragmentation chain transfer (RAFT) technique in the presence of mineral clay has been scarcely investigated. In this work, we have been described our preliminary results

• n synthesis and characterization of new RAFT...O-MMT com-

plexes as the reactive RAFT-nanofillers and their utilization in the interlamellar conrolled/living complex-radical copolymeri- zation of MA and IA with BMA as a internal plastisization agent in-situ processing to prepare new generation of polymer nanocomposites with complete exfoliated nanoarchitectures, lower (2.5 wt. %) and controlled content of organo-MMT, molecular weight, and polydispersity of matrix-polymer chains. Synthetic partways of these pre-intercalated complexes and functional copolymer/organo-clay nanosystems may be re- presented as follows:

Figure 1. Complex-radical interlamellar controlled/living RAFT copolymerization

Figure 2. SEM images (scale: 1 m at x1000 magnification) of (a) MA and (b) IA containing nanosystems prepared by controlled/living radical RAFT copolymerization in the presence of RAFT...O-MMT complexes. Figure 3. TEM images of (a) MA and (b) IA-containing nanocomposites.

SEM and TEM images of synthesized nanocomposites were illus- strated in Figures 1 and 2. In the case of reactive organoclay (ODA- MMT), relative fine distributed morphology was observed. As seen from these images, the dispersed phase significantly reduced in the IA containing nanosystem and in the nanocomposites prepared with RAFT…ODA-MMTcomplex. This observed fact can be explained by chemical in situ processing through amine/anhydride (or acid) reactions which are carried out in nano scale. We have developed a facile and effective strategy for the design and synthesis of polymer/organo-silicate nanoarchitectures by an interlamellar RAFT copolymerization method. Unlike the known methods, the novel approach involves the use of physically and chemically modified and intercalated RAFT/organo-MMT nanofillers in interlamellar complex-radical copolymerizations of functional monomer systems and synthesis of well exfoliated polymer/silicate layered nanocomposites with a relatively low concentration of organo- MMT (2.5-5.0 wt. %) and high performance thermal and mechanical

• properties. This strategy can also be broadly utilized to other hydro-

philic/hydrophobic polymer/silicate hybrid nanomaterials. *Corresponding author: zmo@hacettepe.edu.tr

[1]. Matyjaszewski K. et al. J. Am. Chem. Soc. 1997, 119, 674.

[2]. Hawker C. J. Acc. Chem. Res. 1997, 30, 373. [3]. .Puts R. D., Sogah, D. Y. Macromolecules 1996, 29, 3323. [4]. Zeng C. H., J. Macromol. Sci. Part C: Polym. Rev. 2005, 45, 171. [5]. Di J., Sogah, D. Y. Macromolecules 2006, 39, 1020.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 24

Hydroxyapatite Deposition on Ordered Nanotubular Titanium Oxide Plates

Abstract— Titanium and its alloys with various nanofunctionalized surfaces are used in dental and orthopaedic applications. Surface preparation and hydroxyapatite coating is critical in bioactivation of these surfaces in order to enhance osteointegration. In a previous study, hydroxyapatite deposition on pure titanium, anodized titania and ordered titanium dioxide nanotubular plates using electrochemistry at 80ºC and 37ºC had been compared, showing that by providing a larger surface area for hydroxide ion generation, surfaces having nanotubular structures enabled HA deposition at both temperatures. Here, hydroxyapatite coating using a modified SBF solution and pulsed electrodeposition process at 37ºC, with a current density of -20mA/cm2 to ensure hydroxyapatite formation was optimized. Calcium phosphate deposition was characterized using XRD, FTIR and FE-SEM. Our results indicated that biomineralization starts from the bottom and walls of the tubes and progresses upwards and radially inwards. With the optimized coating parameters, increased deposition in the nanotubes, homogenous coating and a surface without cracks can be achieved.

Design and production of innovative functional biotechnological composite nanomaterials and systems is possible by mimicking processes like biomineralization [1]. Composite materials made of nanofunctionalized titanium structures can be used in dental and orthopaedic implant materials for load-bearing applications [2]. However, surface preparation and coating is essential for increased biocompatibility of these implants. Formation of an oxide layer has been shown to enhance osteointegration indicating that response of bone tissue to titanium based implant materials depends on the chemical and physical properties of titanium surfaces [3]. Hydroxyapatite coating of titanium dioxide surfaces provides additional means for improved

• steointegration. As microcrack formation during the

coating process and bond strength which may lead to implant failure are factors to be considered when choosing an appropriate coating method, electrochemical hydroxyapatite deposition has been preferred, as it enables coating of implants of any size and shape at low temperatures, with easily controlled coating thickness and reduced expenses [4]. In this study, a composite material was prepared using nanofunctionalized titanium plates and the electrochemical deposition method [5]. Nanotubular bundles with a uniform average diameter of 90nm and a length of 2.5-3 micrometer were bioactivated using NaOH, on which hydroxyapatite (HAp) was deposited from a modified SBF solution with a Ca/P ratio of 1.5. Hydroxyapatite deposition was carried out as a two step process pulsing the current density to - 10mA/cm2 for 0.2 seconds from a base current density of 10μA/cm2 at every 10 seconds. After 100 pulsing cycles, the deposition was carried out at a constant current density of - 10mA/cm2 at 80°C and repeated at 37°C at a deposition density of -20 mA/cm2 to ensure HAp deposition. Surface coating was characterized using XRD, FTIR and SEM (Fig. 1), indicating formation of HAp crystal [6]. Progress of deposition was visualized using FE-SEM by freeze-fracturing the specimen to reveal the vertical cross- section of the nanotubes displaying that HAp deposition begins both at the bottom, as well as the walls of the tubes and continues upwards and radially inwards during the course of pulse cycles (Fig. 2). After the completion of pulsing cycles, HAp continues to deposit on the plate

• surface. As some of the nanotubes were not completely

filled, deposition parameters were optimized by increasing the duration of anodic pulse, the number of pulse cycles as well as Ca/P ratio of solution to 1.67 and imaged using FE- SEM (Fig. 3). XRD analysis of the coating indicated that Hap was deposited on the nanotubular titania plates. Acknowledgements: This study has been supported by TUBITAK BIDEB 2218 Post-doc Research Project and Advanced Technologies in Engineering, TR-SPO. We thank Hüseyin Sezer, Talat Apak, Berk Alkan and Sevgin Türkeli for their help in the characterization of HAp coatings. References: [1]. M Sarikaya, C Tamerler, AY Jen, K Schulten, F Baneyx, Nature Mater, 2, 577-85, (2003). [2]. Zhu X, DW Son, J.L Ong, K Kim, Journal of Materials Science: Materials in Medicine, 14(7)629-634(2003). [3]. Zhang, JM, CJ Lin, ZD Feng, ZW Tian, Journal of Electroanalitical Chemistry, 452: 235-240, 1998. [4]. Narayanan, R, SK Seshadri, TY Kwon, KH Kim, Journal

• f Biomedical Materials Research, 85B (1) 279–299, 2007.

[5]. Kar, A, KS Raja and M Misra, Surface Coatings and Technology, 201: 3723-3731, 2006. [6]. Utku, FS, E Seckin, G Goller, C Tamerler, M Urgen, Nanomats2009, Istanbul Technical University, Ayazaga, İstanbul, 2009.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 25

Synthesis of Nanomaterials for Energy Applications

Wolfgang Sigmund

Department of Materials Science, University of Florida, Gainesville, Florida, USA and Department of Energy Engineering, Hanyang University, Seoul, S. Korea. Email: wsigm@mse.ufl.edu Nanomaterials offer benefits for many applications. Especially in the field of energy conversion, energy storage and energy efficiency novel nanostructures demonstrate superior performance to bulk materials. This talk will highlight novel synthesis strategies and nano architectures. While there are numerous techniques to create nanostructures, electrospinning is the only technique that allows fabrication of nanofibers at long length scales. These uniquely shaped fibers are applied to several energy related devices. This review is an in-depth summary of the uses of electrospun fibers in dye sensitized solar cells, batteries, capacitors, fuel cells, and hydrogen storage devices. Developments in electrospinning technologies to create novel fiber morphologies are also discussed.

Continued depletion of natural resources and population growth create an increasing demand for materials with enhanced properties that enable higher efficiencies in energy conversion, harvesting, and storage devices. These technologies, which include solar cells, fuel cells, batteries, and capacitors, offer the potential to: significantly lower energy related carbon footprints, decrease dependence on fossil fuels, and create new areas for economic growth. A report released by the US Energy Information Administration (EIA) in 2008 indicated that approximately half of the electrical energy in the United States was generated from coal [1]. Only a small portion is generated from renewable resources, which is primarily due to high upfront installation costs and lengthy amortization times. Development of inexpensive materials along with processing methods to create highly efficient devices will assist in the transition to sustainable technologies. Additionally, an economic

• pportunity exists in creating a renewable infrastructure, if

the cost per kilowatt hour of renewable technologies can be brought to a comparable level of existing technologies. Electrospinning and electrospraying are exciting novel approaches to synthesize a variety of nanostructures, be it nanoparticles, nanotubes, nanofibers, ribbons, or ceramic fiber mats. Using strong electric fields (kV/cm) to achieve nanostructured materials seems to yield one of the most versatile processing strategies under ambient conditions for many materials including metals, polymers, ceramics, composites and hybrids. This talk will present an overview of the history of the fabrication process and highlight recent advances in nanostructure synthesis. Material properties and the potential commercial applications of these novel nanostructures will be discussed such as energy harvesting, storage and conversion as well as water purification, and air filtration. This research was supported by WCU (World Class University) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-2008-000-10092-0). sigmund@nanotr.com 1. Energy Information Administration. Available

• nline at http://www.eia.doe.gov/emeu/aer Last

accessed August 2009.

• 2. M. Laudenslager, R. Scheffler, W. Sigmund,

Electrospun materials for energy harvesting, conversion, and storage: a review, J. of Applied and Pure Chemistry, 2010, in press.

• 3. R. Scheffler, N.S. Bell, W. Sigmund, Electrospun

Teflon AF fibers for superhydrophobic membranes,

• J. of Materials Research, 2010, in press.
• 4. Karran Woan, Georgios Pyrgiotakis, and Wolfgang

Sigmund, Photocatalytic Carbon-Nanotube TiO2 Composites, Adv. Mater. 2009, 21, 1–7.

• 5. Maneeratana, V.; Sigmund, W. M., Continuous

hollow alumina gel fibers by direct electrospinning

• f an alkoxide-based precursor. Chemical

Engineering Journal 2008, 137 (1), 137-143.

• 6. Sigmund W, Yuh J, Park H, Maneeratana V,

Pyrgiotakis G, Daga A, Taylor J, Nino JC, Processing and structure relationships in electrospinning of ceramic fiber systems , J. Am.

• Ceram. Soc. 89 (2): 395-407, 2006.
• 7. Sung-Hwan Lee and Wolfgang M. Sigmund,

Synthesis of Anatase-Silver Nanocomposite Fibers via Electrospinning, J. Nanosc. and Nanotechn. (2): 554-557, 2006.

• 8. Yuh J, Nino JC, Sigmund W, Synthesis of barium

titanate (BaTiO3) nanofibers via electrospinning, Materials Letters 59 (28): 3645-3647, 2005.

• 9. Sung-Hwan Lee, Cagri Tekmen, and Wolfgang M.

Sigmund, Three-point bending of electrospun TiO2 nanofibers, Materials Science and Engineering A 398: 77–81, 2005.

Plenary Talk <<25>>

Nanomaterials and Nanostructures: Preparation-Applications

Fahrettin Yakuphanoglu

Fırat University, Faculty of Arts and Sciences, Department of Physics, Elazığ, Turkey.

Currently, there is an increasing activity in synthesis and fabrication of organic and inorganic nanostructures with manipulated morphology and size due to their fundamental importance and electronic applications. Nanomaterials materials have a wide application in the electronic technology, such as Schottky diodes, solar cell, field effect transistor, light emitting diodes etc. Nanophysics and nanochemisty are new disciplines with a bright perspective in basic research and offer novel possibilities in designing materials properties. Controlling the physical size of materials can be used to tune the material properties. In the nanometer size regime, the electronic and optical properties of metals and semiconductors strongly depend on crystallite size in the nanometer size regime. In this talk, the preparation, properties and applications of nanomaterials and nanostructures for electronic device applications will be discussed.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 26

A Study for Investigation of Natural Convection of Nanofluids

Hikmet . Aybar, Sedighe Tadrisi

Department of Mechanical Engineering, Eastern Mediterranean University, G.Magosa, North Cyprus, Mersin 10 Turkey Abstract- In this experimental study, behavior of nanofluid on natural convection is investigated. The nanofluid used in this study includes Cu2O nanoparticles in ethanol. The heat transfer performance of the nanofluid is shown as Nu versus Ra.

The performance of the heat transfer fluids such as water, mineral oil, ethylene glycol, and ethanol are very important in many process industries. The performance of these conventional heat transfer fluids is often limited due to their low thermal conductivities. The concept of nanofluids refers to a new kind of heat transport fluids by suspending nano scaled metallic or nonmetallic particles in base fluids. The base fluids which are used in nanofluids are common heat transfer fluids such as water, engine oil, ethylene glycol, and ethanol. Some nanoparticle materials used in nanofluids are oxide ceramics (Al2O3, CuO, Cu2O), nitride ceramics (AlN, SiN), carbide ceramics (Sic, TiC), metals (Ag, Au, Cu, Fe), semiconductors (TiO2), single, double or multi-walled carbon nano tubes (SWCNT, DWCNT, MWCNT), and composite materials such as nanoparticle core-polymer shell composites. 1 There are some studies about thermophysical properties

• f nanofluids [1] such as conduction heat transfer
• coefficient. Some other studies about nanofluids investigate

the performance of forced convection [2] and free convection of nanofluids [3]. In this experimental study, natural convection heat transfer is investigated. The nanofluid, Cu2O solid particles in ethanol, is used with different solid particle concentration. The cavity used in the experiment is shown in Fig.1. The dimensions of the cavity are 11 cm (length) and 11 cm (height) and 8 cm (width). The front, back, bottom and top sides of the enclosure are made of Plexiglas which has 1 cm

• thickness. Left and right sides of the enclosure have heat

exchangers which are made of brass. Water is supplied to those heat exchangers from two separate constant- temperature baths. Hot water bath from right side and cold water bath from left part of cavity are connected by flexible tubes.

Figure 1. A top view of cavity: [A] Plexiglas Plates, [B] Heat exchangers (right side is hot wall and left side is cold wall), [C] Insulation Material, [E] Output Pipes, [D] Input Pipes, [T10 to T13] Pipe Thermocouples.

The nanofluid used in the experiment is Cu2O in ethanol and solid particle volume fraction is 1.5 %. Three samples are prepared in terms of volume fraction () of

• nanoparticle. The conduction heat transfer coefficient (k) of

the samples depends on the volume fraction. The volume fraction and the heat transfer coefficients are given in Table.1.

Table 1. The Properties of Nanofluid Samples

(%) k (W/m C) Sample1 (S1) 0.245 0.1702 Sample2 (S2) 0.381 0.1708 Sample3 (S3) 0.636 0.1721

Figure 2. Effect of nanoparticles concentrations on the cold surface temperature for the three samples at (T) bath = 10 C.

The variation of cold surface temperature within time is shown in Fig.3 for the samples. Higher concentration cause higher temperature within same time. The variation of Nusselt Number versus Rayleigh Number is shown in Fig.3. It can be seen that the Nusselt number decreases while the Rayleigh number increases. It is assumed that there is a relation between Nu Number and Ra Number in the form of Nu=C×Ran. In the case of Sample1, the C=8×1015, and n=-1.54.

Figure 3. Nusselt Number versus Rayleigh Number for the Sample S1 at (T) bath = 10C.

* hikmet.aybar@emu.edu.tr

[1] S.M.S. Murshed, K.C. Leong, C. Yang, Review Thermophysical and electrokinetic properties of nanofluids – A critical review, Applied Thermal Engineering, 28 (2008) 2109–2125. [2] D. Wen, Y. Ding, Experimental investigation into convective heat transfer of nanofluids at the entrance region under laminar flow conditions, International Journal of Heat and Mass Transfer, 47 (2004) 5181– 5188. [3] E. Abu-Nada, Effects of variable viscosity and thermal conductivity of Al2O3–water nanofluid on heat transfer enhancement in natural convection, International Journal of Heat and Fluid Flow, 30 (2009) 679–690.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 27

Compact Heat Removal System with Magnetic Nanoparticles

Muhsincan Sesen1, Erman Arslanalp1, Kursat Sendur1, M.Pinar Menguc2, H.Yagci Acar3 and Ali Kosar1,*

1Sabanci University, Tuzla 34956, Turkey 2Ozyegin University, Uskudar 34662, Turkey 3Koc University, Sariyer 34450, Turkey

Abstract— A miniature heat transfer enhancement system is developed. The compact system consists of a pool boiler filled with a nanofluid including ferromagnetic nanoparticles, a heater and a magnetic stirrer. The ferromagnetic particles within the pool were actuated with a magnetic stirrer and heat transfer characteristics of the system was investigated at constant heat flux and was compared to pure water.

Most of the micro/nano devices tend to shrink in size while the escalation in their power densities becomes inevitable every day. This trend asks for an urgent need for enhancement of heat transfer because these devices find applications in many important areas including electronics, microreactors, micropropulsion, biotechnology, fuel cells and air conditioning. In order to keep up with the miniaturization process heat transfer and fluid flow at micro and nano scale have been rigorously studied in the literature to achieve higher heat removal capabilities. Nanofluids have priorly been used since their thermal conductivities are higher compared to their base agents and they have also been used for deposition of nanoparticles on pool surfaces to promote heat transfer [1-7]. Different from the state of art, magnetic nanoparticles are utilized in this study to remove heat from excessive heat generating surfaces. Magnetic nanoparticles are actuated and utilized as heat transporters so that the system could be operated efficiently even at lower temperatures. Motivated by the results in the above mentioned studies, the focus of this paper is to propose a compact pool boiler for thermal management applications in microscale. Preliminary experiments with the pool boiler were conducted and boiling curves were obtained from a nanofluid actuated by a magnetic stirrer and distilled water. The potential for such compact pool boilers in the use in microscale cooling applications was exploited (up to about 8.5 W/cm2) and promising results were

• btained.

Nanofluids are fluids having suspended nanoparticles of nanometer-size and chemistry (metals, oxides, carbides, nitrides, or nanotubes). In this study a nanofluid containing ferromagnetic particles have been used. This nanofluid can be actuated by the application of a magnetic field. The actuation

• f these ferromagnetic nanoparticles should drive its base

liquid's molecules along so that a flow could be created. For this purpose, a nanofluid sample was prepared, namely

• AKY028. To decrease their viscosities and thus facilitate their

motion inside the liquid, nanoparticles were coated with specific solutions. AKY028 was coated with NH2. The sizes

• f the ferromagnetic nanoparticles in the sample AKY028 are

23 nm.

ID [Fe] Si/Fe (mole %) Base/Fe (mole %) Dh-I (nm) Dh-I washed (nm) Dh- N (nm) Dh-N washed (nm) (M) AKY028 0,175 1,25 1,5 23- 100 23 32- 100 28 Table 1. Nanofluid Properties

Table 1 shows some properties of the nanofluid used in this

• study. Dh-I refers to hydrodynamic diameter measured with

Dynamic Light Scattering (DLS) using scattered light intensity and Dh-N uses DLS with numerical averaging.

Figure 1. Heat Flux vs. Surface Temperature (Single-Phase and Two-Phase)

Nanofluid with magnetic stirrer (MS) slightly decreases the surface temp relative to the results with the nanofluid without the magnetic stirrer and this can be observed from Fig. 1 which shows both the single-phase and two-phase results. The results gathered from the experiments properly indicate the advantageous effects of a nanofluid (containing ferromagnetic particles integrated with magnetic stirrer) on heat transfer magnification and flow circulation. With such a compact setup, the magnetic stirrer integrated to this cooling system acts efficiently. Using these tabulated results, further investigations and models, nanofluids of ferromagnetic particles can be utilized in various cooling applications of small electronic devices, microreactors, micropropulsion, biotechnology, fuel cells and air conditioning. Further studies include two-phase pool boiling experiments of various nanofluids with and without a magnetic stirrer and their comparisons amongst themselves and distilled water. The fraction of magnetic nanoparticles inside the nanofluid will also be modified in order to account for its advantageous

• effects. The magnetic flux densities of the magnets will be

modified in order to see its effects on the pool boiling enhancement.

*Corresponding author: kosara@sabanciuniv.edu [1] Kim, H., Kim, J., and Kim, M., International Journal of Heat and Mass Transfer, 49(25-26), pp.5070-5074, 2006. [2] Bang, I.C. and Chang, S.H., International Journal of Heat and Mass Transfer, 48(12), pp. 2407-2419, 2005. [3] Vassallo, P., Kumar, R., and D'Amico, S., International Journal of Heat and Mass Transfer, 47(2), pp. 407-411, 2004. [4] Milinova, D. and Kumar, R., Appl. Phys. Lett. 87, 233107, 2005. [5] You, S.M., Kim, J.H. and Kim, K.H., Appl. Phys. Lett. 83, pp. 3374–3376, 2003. [6] Kim, H., Kim, J., and Kim, M., Nucl. Eng. Technol., 38(1), pp. 61-68, 2006. [7] Kim, S.J., Bang, I.C., Buongiorno, J., and Hu, L.W., International Journal

• f Heat and Mass Transfer, 50, pp. 4105-4116.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 28

Synthesis and Magnetic Characterization of Cobalt Doped Zinc Ferrite Magnetic Nanoparticles via A Peg Assisted Route

1*, F. Gözüak1, A. Baykal2

1Fatih University, Department of Physics, 34500 Buyukcekmece, Istanbul-Turkey 2

Fatih University, Department of Chemistry, 34500 Buyukcekmece, Istanbul-Turkey Abstract-We present an investigation of properties of CoxZn1-xFe2O 4 (x=0.0-1.0) nanoparticles synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating scanning magnetometry (VSM) were used to characterize the structural, morphological and magnetic properties. The particle size obtained from TEM and XRD are consistent with each other. It was observed that the lattice constant for each composition decreases with increasing Co substitution and follows Vegard’s law. Magnetization measurements show that while the materials with high Zn substitution are superparamagnetic at room temperature, they are ferromagnetic at temperatures lower than the blocking temperature. The materials with less Zn substitution are ferromagnetic below room temperature. Magnetizations and the coercivities

• f the samples decrease with the Zn substitution. The resultant overall magnetic behavior of the superparamagnetic samples are found to be

considerably different than that of conventional superparamagnetic systems due to the antiferromagnetic interactions both in intra-cluster and inter-cluster spins, and size (effective moment) distribution of the particles.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 29

Electronic structure and magnetic properties of Ni0.2Cd0.3Fe2.5-xAlx

Khalid Mujasam Batoo

O4 (0 nanoparticles

1*, Shalendra Kumar2

1Department of Applied Physics, Aligarh Muslim University, Aligarh, UP 202002, India 2

School of Nano and Advanced Materials Engineering, Changwon National University, 9 Sarim dong, Changwon-641-773, Republic of Korea Abstract-Structural, magnetic and electronic structural properties of Ni0.2Cd0.3Fe2.5_xAlxO4 ferrites nanoparticles have been studied x-ray diffraction (XRD), transmission electron microscopy (TEM), dc magnetization, and near edge x-ray absorption fine structure spectroscopy (NEXAFS) measurements. Nanoparticles of Ni0.2Cd0.3Fe2.5-xAlxO4 (0-gel method. The XRD and TEM measurements show that all samples have single phase nature with cubic structure and have nanocrystalline behavior. From the XRD and TEM analysis, it is observed that particle size increases with Al doping. DC magnetization measurements infer that magnetic moment decreases whereas blocking temperature increases with increase in Al doping. It is observed that the magnetic moment decreases with Al doping which may be due to the dilution of the sublattice by the doping of Al ions. The NEXAFS measurements performed at room temperature indicates that Fe exist in mixed valence state.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 30

Nano-Sized Iron Precipitation in Ni-Al-Fe Alloys

Nagehan Duman,1,* Amdulla O. Mekhrabov1 and M. Vedat Akdeniz1

1Department of Metallurgical and Materials Engineering, Middle East Technical University, Ankara 06531, Turkey

Abstract- Iron precipitation behavior has been investigated for different annealing treatments in Ni50Al50-xFex ternary alloys. The formation of ferromagnetic nano-sized α-Fe precipitates, as evidenced by transmission electron micrographs and magnetic measurements, provides enhancements in magnetic properties.

Nickel-Aluminum (NiAl) is the most promising intermetallic alloy for high temperature structural applications [1]. The NiAl compound possesses high melting point, excellent

• xidation

and corrosion resistance and low density; however, room temperature ductility and high temperature strength requires to be improved for use as desirable high temperature materials. Recently, the incorporation of Fe in the NiAl alloy systems has been shown to induce specific alterations in structural properties of the materials [2-4]. The addition

• f Fe into NiAl alloys together with a convenient

annealing heat treatment is known to allow for the precipitation of BCC α-phase Fe [5]. The mentioned Fe precipitates improve both the high temperature strength (by means of precipitation strengthening) [4,5] and magnetic properties of Ni-Al-Fe alloys [6]. Accordingly, the formation of Fe precipitates could be detected by measuring variations in magnetic properties for Ni-Al-Fe alloys. This study aims to investigate the influence of annealing on the formation of BCC α-Fe precipitates for a variety of alloy compositions, i.e. Ni50Al50-xFex alloys with x=20, 25, 30. The BCC α-Fe precipitation has been

• bserved by microstructural evaluations and magnetic

properties.

Figure 1. Room temperature magnetization values of annealed Ni50Al50-xFex alloys.

Alloys are prepared from high purity 99.9% Ni, Fe and Al through arc melting in a zirconium-gettered argon atmosphere, remelted for four times for compositional

• homogeneity. Isothermal annealing heat treatments have

been conducted in quartz tubes filled with argon gas at temperatures of 473, 673, 873 and 1073 K for 7 days, followed by furnace cooling. Structural characterizations

• f the investigated materials have been carried out by X-

ray diffraction (XRD) whereas evolution of the microstructure upon annealing has been followed by scanning electron microscopy (SEM). The formation of ferromagnetic Fe precipitates has been determined by transmission electron microscopy (TEM) observations and conducting magnetic measurements by a vibrating sample magnetometer (VSM). XRD results and SEM images display that in alloy with 20 at.% Fe, a single BCC β phase, and in alloys with 25, 30 at.% Fe, both β phase and FCC γ phase have been

• bserved at room temperature, respectively. According to

the VSM measurements, Curie transition temperature (TC) and magnetization raise with increasing Fe content. Additionally, annealing treatments lead to rise in TC. However magnetization of Ni50Al50-xFex ternary alloys, consisting of β and β + γ phases, except in Fe precipitating alloys do not vary with different annealing

• temperature. Increased magnetization values for alloys

annealed at 673 K, displayed in Figure 1, are attributed to the formation of ferromagnetic Fe precipitates.

Figure 2. TEM micrograph showing the Fe precipitates (bright-field image) and SADP pattern of Ni50Al25Fe25 alloy

annealed at 673 K. Further investigations by TEM confirm the formation

• f Fe precipitates. Bright-field TEM micrographs and the

corresponding selected area diffraction patterns (SADP)

• f the β phase matrix in the Ni50Al25Fe25 alloy annealed at

673 K are shown in Figure 2. TEM observations reveal precipitates below 5 nm size which are distributed uniformly within the matrix. The extra ring pattern indicates the formation of BCC Fe precipitates in the nano-scale. *Corresponding author: nduman@metu.edu.tr

[1] D. B. Miracle, Acta Metall. Mater. 41 (1993) 649-684. [2] E. P. George, C. T. Liu, J. A. Horton, C. J. Sparks, M. Kao, H. Kunsmann, T. King, Mater. Charact. 39 (1997) 665. [3] R. Kainuma, S. Imano, H. Ohtani, K. Ishida, Intermetallics 4 (1996) 37-45. [4] A. Misra, R. Gibala, Metall. Mater. Trans. A 28 (1997) 795-807. [5] S. Guha, I. Baker, P. R. Munroe, J. R. Michael, Mater.

• Sci. Eng., A 152 (1992) 258-263.

[6] H. S. Ko, H. S. Park, K. T. Hong, K. S. Lee, M. J. Kaufman, Scr. Mater. 39 (1998) 1267-1272. Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 31

Photo-patterning of PMMA Films with Gold Nanoparticles

Eda 1*1

1

Department of Chemistry, Bilkent University, 06800 Ankara, Turkey Abstract- Gold nanoparticles were synthesized within Poly(methymethacrylate) films using UV irradiation. With this in-situ synthesis method, photo-patterning applications are eligible. Another interesting property of such films is the “ion free regions” observed between the irradiated and masked regions of the photo-patterned films. The ion free regions can help understand the diffusion of gold in polymer matrices better as well as helping to produce more stable photo-patterned films.

Polymer-nanoparticles are technologically important composite systems, gaining increasing interest from many different fields of science in the last decade.[1] Production of such systems can be achieved by many different approaches. Nanoparticles (NPs) may be synthesized before the integration to polymer or in the polymer to produce these composite

• systems. Both methods may have their advantages and

disadvantages depending on the usage and many examples for both are available in literature. An efficient approach, used for the production of nanoparticles within the polymer matrix is employment of irradiation. Energetic light is widely employed for reduction of metal salts and it can be used in solution phase synthesis and also for solid state synthesis. Here we present in-situ synthesis of gold nanoparticles within poly(methylmethacrylate) (PMMA) films by UV irradiation.[2] This process can be easily monitored by UV- Vis spectrometer step by step. (Fig.1) In the beginning the spectrum of the PMMA film containing gold ions, a peak around 320 nm is observed belonging to gold ions. After 30 minutes of irradiation of the film this peak disappears, indicating that the reduction of gold ions to gold atoms is

• completed. In the following spectrum taken after 1 hour of

irradiation, gold NP’s plasmon resonance band starts to appear showing the formation of gold NPs. The formation of gold NPs can be completed from 12 hours to 24 hours depending

• n the concentration of gold in the film. [3]

200 300 400 500 600 700 800 0.0 0.5 1.0 1.5 2.0

A Wavelength (nm)

Production of Au NPs Reduction of Au

3+

no rad. 30 min rad. 60 min rad. 210 min rad.

Figure 1. UV-Vis spectrum of gold nanoparticles produced in PMMA film at various radiation times.

An advantage of synthesizing gold NPs within polymer films is the opportunity of photo-patterning. Films having patterns made of regions with and without gold NPs can be produced by using masks designed to cut off the UV radiation at desired places.(Fig.2) With SEM investigation of the photo- patterned films, interesting clues on the diffusion mechanism

• f gold atoms within the polymer were also obtained.

Figure 2. Light microscope image of photo-patterned PMMA film with gold.

In such photo-patterned films, dark regions between irradiated and masked regions were observed. These dark regions are concluded to be “ion depleted regions” after our investigation of such films. We believe that gold ions tend to diffuse to the irradiated regions during photo-patterning and this process takes place for a region with about 10 microns

• width. To understand the nature of this process fluorescence

was also employed since fluorescent molecules like Rhodamine 6G can be quenched or enhanced by different forms of gold.[4] Films prepared with Rhodamine 6G can provide beautiful contrast between masked regions, ion depleted regions and irradiated regions. (Fig.3) Also with XPS, the gold count profile can be measured for such films as given in Fig.3. The XPS line scans for such films present another evidence for the formation of ion free regions.

Figure 3. Fluorescence image of photo-patterned PMMA film with gold nanoparticles and Rhodamine 6G. Inlet shows the XPS counts profile for gold.

To summarize, we showed a novel method for in-situ synthesis of Au nanoparticles within PMMA matrix with UV

• radiation. This method is

particularly useful for photo- patterning applications, using simple masking any shape in a large range of sizes can be imprinted. Besides the newly discovered ion free regions can provide the desired durability to such films. *Corresponding author: edaoz@bilkent.edu.tr

[1] Daniel, M. C., Astruc, D., Chem. Rev., 2004, 104(1), 293-346. [2] Karadas, F., Ertas, G., Ozkaraoglu, E., Suzer, S., Langmuir, 2005, 21 [3] Ozkaraoglu, E., Tunc, I., Suzer, S., Polymer, 2009, 50(2), 462- 466. (1), 437-442. [4] Tanaka, T., Yamaguchi, K., Yamamoto, S., Optics Commun., 2002, 212, 45-50.

Au counts profile (24 hours radiated)

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 32

AR Coating of Organic Substrates by Thermionic Vacuum Arc Technique (TVA)

Murat Ozmumcu,1* Naci Ekem,1 Suat Pat,1 M.Zafer Balbag,2 Mehmet Ozkan,1 Sadan Korkmaz1

1Meselik 2

EducaMeselik, Abstract-Antireflective or anti-reflection (AR) coatings are a type of optical coating applied to the surface of lenses and other optical devices to reduce reflection. This improves the efficiency of the system since less light is lost. In this study, organic substrates were coated with SiO 2 and ZrO 2 and transmittances were determined by UV-Vis spectrophotometer. Additionally, SEM, EDX, AFM were used for surface morphologies.

Thermionic Vacuum Arc (TVA) system is a new type discharge for pure thin film deposition. This discharge in pure metal vapors can be ignited in any kind of metal vapors including refractory metals. The electrons emitted from the cathode are accelerated toward the anode by the applied voltage accross the electrodes, the flux of electrons being concentrated on a small area of the anode surface which becomes a melted metal spot [1-4]. In this work, SiO2, ZrO2 layers were deposited on the

• rganic substrates by TVA.

Figure 1. Transmission of the SiO 2 and ZrO2 coated organic substrate Figure 2. AFM image (3D) of SiO 2 coated organic substrate Figure 3. AFM image (3D) of ZrO 2 coated organic substrate

(a) (b)

Figure 4. Surface roughnesses of coated substrates, a)SiO 2 b)ZrO 2 Figure 5. SEM images of SiO 2 coated organic substrate Table 1. EDX measurements of SiO 2 coated substrate

Elt. Line Intensity (c/s) Error 2-sig Conc Units O Ka 270.24 10.394 44.205 wt.% Si Ka 1,571.82 25.068 55.795 wt.% 100.000 wt.% Total

UV spectra, AFM and SEM measurements of SiO2 and ZrO2 coated substrates were analized. This research activity has been supported by TUBITAK numbered with 108M608. *Corresponding author: 1Tmuratozmumcu@gmail.com

[1] S. Pat et al., Journal of Optoelectronics and Advanced Materials, 7 (5), 2495-2499, (2005) [2] N. Ekem, et al., Journal of Optoelectronics and Advanced Materials, Vol.10, No:3, 672–674, (2008) [3] R. Vladoiu et al., Journal of Optoelectronics and Advanced Materials, 5 (1), 325-330, (2003) [4] C. P. Lungu, et al., Journal of Optoelectronics and Advanced Materials Vol. 8, No. 1, 74—77, (2006)

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 33

1 Low temperature preparation of TiO2/SiO2 Nanocomposites and study of their phase transformations

Simin Janitabar Darzi, Abdolreza Nilchi, Somayeh Rasouli Garmarodi

Nuclear Science and Technology Research Institute, P.O.Box 11365/8486, Tehran, Iran Abstract-TiO2/SiO2 nanocomposite was synthesized by a free calcination sol-gel method. Thermal phase transformation studies of the as-prepared composite were carried out up to 1100C by means of XRD analysis. The studies showed existence of anatase phase in all the tested temperatures. When temperature exceeds 400°C, brookite phase was formed beside anatase phase. At 950°C amorphous silica matrix was transformed to crystobalite and brookite phase disappeared. Finally, small peaks of rutile phase were detectable at 1100°C.

According to XRD patterns of prepared materials (Fig. 1), as-synthesized TiO2/SiO2 nanocomposite (TSR) without calcination is crystalline anatase phase in amorphous silica matrix. Amorphous silica transforms to crystobalite at 950°C but anatase phase is present in all of the synthesized composite samples up to 1100ºC. The XRD patterns related to the TS400, TS600 and TS800 exhibit diffraction lines attributed to brookite phase beside the anatase. Only at very high temperature (1100°C), small peaks

• f

rutile phase appears in the nanocomposite. According to the Scherrer equation, the sizes of the anatase crystallites in the TSR, TS400, TS600, TS800, TS950, and TS1100 samples calculated to be 5, 5.09, 5.6, 7.8, 15.12, and 26.69nm.

350 20 30 40 50 60 70 80

2 Theta/degree Intensity/a.u ▲ ▲ ▲ ▲

• ▲

▲ ▲ ▲ ▲ ▲ ▲

• ▲

▲ ▲ ▲ ▲

• ▲

▲

• ▲

□

• TSR

TS400 TS600 TS800 TS950 TS1100 ■ ▲

• Fig. 1. XRD spectra of as-prepared TiO2/SiO2 composite and

samples heat-treated at different temperatures.

The XRF analysis shows that the composite consists of 50% TiO2 and 46% SiO2. There is a characteristic band at around 950 cm-1 in FT-IR spectra of composites (Fig. are not shown) that has been assigned to the stretching

• f the Si-O¯ species of Si-O-Ti.
• Fig. 2 shows the typical TEM image of as-

prepared TiO2/SiO2 nanocomposite (TSR) and SEM images of calcined nanocomposites. The images show that all of composites have agglomerated grainy structure and the particles size of the samples increases with increasing calcination temperature. Fig. 3 shows N2 adsorption-desorption Isotherms of TS400 and TS1100 composites. For TS400 the hysteresis loop is a H2 type with a triangular shape and a steep desorption branch. Such behavior was attributed to the pore connectivity effects. For TS1100 composite, hysteresis loop is an H4 type that has been attributed to adsorption-desorption in narrow slitlike pores [1]. Pore diameters of TS400 and TS1100 based on BJH plots obtained to be around 4.65 and 2.4 nm, respectively.

• Fig. 2. TEM image of as-prepared composite (TSR) and SEM

images of calcined composite TS400, TS600, TS800, TS950, TS1100.

• Fig. 3. N2-adsorption-desorption isotherms, and BJH pore

size distribution curve of TS400 and TS1100.

It can be deduced that the calcination temperature governs on morphology, size and phase of the TiO2 nanoparticles dispersed in SiO2 matrix and formation of the Ti-O-Si bond could effectively increase the stability of anatase, limit the growth of crystallites, and so significant increasing surface area. *sjanitabar@aeoi.org.ir [1] Michal, K., Jaroniec, M., 2001. Chem. Mater. 3169.

TS400 100 200 300 0.5 1 1.5 Relative Pressure (P/P0) Volume (cm3/g)

0.04 0.08 0.12 0.16 1 2 3 4 5 6 7 8 9 10 Pore Diameter (nm) dV/dD (cm3/g/nm) TS400 TS1100 5 10 15 0.5 1

Relative Pressure (P/P0) Volume (cm

Pore Diameter (nm) dV/dD (cm

TS1100

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 34

Synthesis of Nanosilver Particles and Nanocable Production through Coaxial Electrospinning

Simge Cinar1,2, Gungor Gunduz1, Uner Colak3, and Bora Mavis4

1Department of Chemical Engineering, Middle East Technical University, Ankara 06531, Turkey 2Iowa State University, Department of Material Science and Engineering, 50011, IA, USA 3 Hacettepe Üniversitesi, Department of Nuclear Engineering, 06800, Ankara 4 Hacettepe Üniversitesi, Department of Mechanical Engineering, 06800, Ankara

Abstract— The aim of this study is to demonstrate the possibility to produce silver core-polymer shell nanocable structure via coaxial electrospinning method. For this purpose, silver nanoparticles were produced by a chemical reduction method

• separately. Oleylamine and oleic acid were used as reducing and capping agents in the reduction step and produced particles

were placed at the center of Polyvinylpyrolidone (PVP), or Polycaprolactone (PCL) shell polymers by electrospinning method.

Nanocables are one dimensional composite structures consisting of a core at the center and shell covering this core. In this study we proposed to produce a metal core-polymer shell nanocable structure (Figure 1). The study of Song et al constitutes the only example of production of nanocable structures consisting of a metal core [1]. It was reported that iron-platinum particles covered by oleylamine can be placed in the center of polycaprolactone fibers by coaxial electrospinning method. In the present study, silver was used as a core metal due to its antimicrobial property and its wide application in the areas of catalysis, information storage and sensing.

Figure 1. Nanocable Structure.

Oleylamine and oleic acid system are used separately or together in many different systems [2-4]. In these studies

• leylamine and oleic acid were used as both reducing and

capping agents. Since they have weak reducing effect, in the absence of any other stronger agent, they can act as a

• reducer. On the other hand, their long aliphatic tales and

functional groups, give them the property of strong capping. When oleylamine or oleic acid is used alone in the system, reduction takes long time or requires high temperatures to

• btain monodisperse particles. It was reported that better

results could be obtained when they were used together; however, to our knowledge, none of the studies in the literature explain the mechanism of the reduction and effects

• f oleylamine and oleic acid in the system completely. In the

present study, not only monodisperse silver particle were synthesized by oleylamine-oleic acid system, but also their effects on the system were investigated and reduction mechanism were clarified. In the metal particle production step, XRD, TEM, PCS and SPR techniques were used to analyze morphological, structural and optical properties of particles. XRD, PCS and TEM techniques were correlated in terms of the particle size and size distribution of the particles (Table 1). As a result of this study, silver particles with sizes between 1.7nm and 4.8nm and volume weight average of 2.7 nm were produced. It was also shown that the size and size distribution of particles can be adjusted by tuning the system parameters like composition of ingredients, time and temperature.

Table 1. Particle sizes of samples prepared in different conditions and calculated from different characterization methods.

Sample TEM (nm) PCS (nm) (volume-weight average) XRD (nm) (Scherrer eqn) 115°C 2.8±1.9 2.7 1.5 150°C 3.8±1.3 4.0 1.7 Sonication but no mixing 2.8±1.3 3.0 2.0 In the coaxial electrospinning part, PVP in dimethylene formamide(DMF) solution and PCL in trifluoroethanol (TFE) solutions were used as shell solutions of coaxial electrospinning process. In order to characterize produced nanocable structures, TEM and SEM techniques were used. Figure 2 shows the TEM micrographs of the produced silver nanoparticles and the nanocable structure. (a) (b)

Figure 2. TEM micrographs of oleylamine capped silver nanoparticles (a) and nanocables produced by covering these particles with polymer shell by coaxial electrospinning method (b). Acknowledgement: This work is supported by TUBTAK under Grant No. 107M024

*www.nanomative.org

[1] Song, T., Zhang, Y., Zhou, T., Lim, C.T., Ramakrishna S., Liu B., 2005, Encapsulation of self assembled FePt magnetic nanoparticles in PCL nanofibers by coaxial electrospinning, Chemical Physics Letters, 415:317-322.

[2] Z. Deng, M. Mansuipur, A. J. Muscat, 2008, New method to

single-crystal micrometer-sized ultra-thin nanosheets synthesis and characterization, The Journal of Physical Chemistry C,113:867-873

[3] Z. Xu, C. Shen, Y. Hou, H. Gao, S. Sun, 2009, Oleylamine as

both reducing agent and stabilizer in a facile synthesis of magnetite nanoparticles, Chemistry of Materials, 21:1778.

[4] V. Mazumder, S. Sun, 2009, Oleylamine mediated synthesis

• f Pd nanoparticles for catalytic formic acid oxidation, Journal of

the American Chemical Society, 131:4588

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 35

Figure 1. General representation of polycarbynes

Diamond/DLC thin film on ceramics using polymeric precursors

Yusuf Nur1 and Levent Toppare1*

1

Abstract -Poly(hydridocarbyne) and poly(methylcarbyne) were synthesized via electropolymerization of chloroform and trichloro ethane monomers respectively. The procedure is very easy and cheap. Since the polymers are soluble in or ganic solvents, they can be coated on a surface in any thickness and shape then converted to diamond/DLC thin film via sintering. UV/Vis, FTIR and NMR of the polymers showed that they were synthesized succesfully and naked eye seen film was characterized with optical microscope, digital camera photograph and Raman spectroscopy, and results are quite remarkable. Department of Chemistry, METU, Ankara 06531, Turkey

Due to high optical transparency in the infra-red, high electrical resistivity, high thermal conductivity, high chemical inertness, good biocompatibility, high hardness, low fraction coefficient and high wear resistance of a diamond/diamond- like carbon (DLC) film, these characteristics make it so much desired material for a wide range of applications in the field of

• ptical, electric, thermal

management, biomedical and tribological implementations. The techniques used to obtain a thin film on a surface are Chemical Vapor Deposition (CVD), Combustion Method, Oxygene-Acetylene Welding Torch etc. Those have some drawbacks, since they are expensive and require complex techniques. The films are not homogenous and smooth. Moreover, the thickness of obtained film is not good enough for several applications. Nowadays, a new concept has appeared to overcome them, polycarbynes, used to make ceramics. These special polymers are poly(hydridocarbyne), poly(phenylcarbyne) and poly(methylcarbyne). Polycarbynes are polymeric precursors to form diamond/DLC thin films on surfaces. The polymers consist of carbon backbone where each carbon has sp3 hybridization with three neighbor carbons having hydrogen, or methyl, or phenyl pendant group (Figure 1). These polymers can be converted to diamond under inert atmosphere at 1000

• The polymers have been recently synthesized using

ultrasound and explosive reagents (NaK alloy)

• r

electrochemical methods [1-4]. The former method is an expensive, complex, explosive and a low yield method. Thus it is not possible to be used for industrial implementations. Instead, electrochemical synthesis of these polymers can be used to overcome this deficiency [1-2]. It can be widely used in industry and research laboratories since the synthesis of them via electrochemistry is cheap, easy and high yield. The polymers are soluble in common organic solvents like acetone, THF and chloroform. Owing to solubility, any surface can be coated in any thickness and shape. After a surface is coated with one of these special polymers, the film can be converted to diamond/DLC thin film heating to 1000 C [1-3].

• C under Ar or N2

in a tube furnace. In this study, electrochemically synthesized poly(hydridocarbyne) and poly(methylcarbyne) from chloroform and trichloroethane respectively were used to form Diamond/DLC film on ceramic surfaces [6]. The polymers were characterized using UV/Vis, FTIR and NMR. Then, they were dissolved in THF and coated on ceramic surfaces. Polymeric films were converted to diamond/DLC film via sintering procedure as explained above. Diamond/DLC film

• btained on the surfaces was characterized by optical

microscope, digital camera photograph (Figure 2), Raman spectroscopy (Figure 3).

Figure 2. Digital photographs of Diamond/DLC films obtained from a) poly(hydridocarbyne) b) poly(methylcarbyne) on ceramic surfaces Figure 3. Raman spectra of Diamond/DLC films obtained from a) poly(hydridocarbyne) b) poly(methylcarbyne) on ceramic surfaces

Raman shift at 1332 cm-1 *Corresponding author: proved that the film is diamond/DLC [1-5]. toppare@metu.edu.tr

[1]. Nur, Y., Pitcher, M.W., , S., Toppare, L., 2008, Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, 45, 358. [2]. Nur, Y., Cengiz, H., Pitcher, M.W., Toppare, 2009, L., Journal of Material Science, 44, 2274. [3]. Bianconi, P.A., Joray, S. J., Aldrich, B.L., Sumranjit, R. et al., 2004, Journal of American Chemical Society, 126, 3191. [4]. Rieke, RD., Chen, T.A., 1994, Chemistry of Materials, 6, 576. [5]. Prawer, S., Nugent, K.W., Amieson, D.N. J., Orwa, Bursill, L.A., Peng, J.L., 2000, Chemical Physics Letters, 332, 93. [6] Pitcher, M. W., Toppare L., PCT Patent WIPO- PCT/TR2007/00012-WO2008010781A.

a b Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 36

A simple analytical EAM model for the binary immiscible alloy systems

Ibrahim H. Dursun 1, Ziya B. Güvenç2

1 Faculty of Science and Literature, University of Aksaray, TR-68100, Aksaray, Turkey 2 Electronic and Communication Engineering, Cankaya University, TR-06500 Balgat Ankara, Turkey

Abstract-An analytical embedded atom method which can treat fcc was presented and a modified term has been introduced to fit the negative Cauchy pressure

• 2

/

44 12

C C P

C

• for fcc ansition metals and
• alloys. In this model type potentials have been constructed for six binary immiscible alloy systems: Ag Ni, Fe

Ta, Cu acancy formation energy and elastic constants for

• nly pure metals which consist the immiscible alloy systems. In order to test the reliability of the constructed new potentials, formation

enthalpies of disordered alloys for those six binary immiscible alloy systems have been calculated. The calculated results are in general agreement with the experimental data available and those theoretical results calculated by other authors. As only very limited experimental information is available for alloy properties in immiscible alloy systems, the analytical embedded atom method is demonstrated to be a reasonable method to construct the interatomic potentials for immiscible alloy systems because only the properties of pure elements are needed in calculation.

Immiscible alloy systems, the source of many functional materials, have received a greatly increased interest owing to their metastable structure formation in non-equilibrium process and technological merits. It had been revealed that alloys could be synthesized in such systems with highly non- equilibrium processing methods such as mechanical alloying (MA) [1]. However, the mechanisms for non-equilibrium structure formation in immiscible alloy systems during the process of MA are still under debate [2]. Also some important details of MA process are difficult to be observed, even by high-resolution electron microscopy, for MA is a continuous and complex process of deformation, fracture and cold weld in which diffusion and phase transition are involved. Nowadays, computer simulations such as molecular dynamic simulation, firstprinciple simulation and Monte Carlo simulation et al. have become the increasingly useful tool for studying the structure and properties of metals and alloys. So interesting

• pportunities are therefore available to

investigate some details of non-equilibrium process during MA by computer simulation. The interatomic potentials for the alloy systems play a key role in the atomic computer simulations, as the accuracy of the potentials will obviously affect the result of the computer

• simulations. Many different potential models have been

developed to describe the interatomic potentials for metallic alloys, however, few of them have been applied in the immiscible alloy systems. Foiles constructed interatomic potentials for NiCu and AgCu alloy systems with embedded atom method [3]. Landa et al. constructed the glue- type potential for the Al/Pb immiscible alloy system using the ‘force matching’ method [4]. Till now no potential model has been applied to systemically construct the interatomic potentials for the binary immiscible alloy systems. The approach often used in the reported potential construction in immiscible alloy systems is to fit the potentials to the properties of metals and alloys such as the lattice constant, elastic constant and cohesive energy et al. As only very limited experimental information is available for the properties of alloys in the immiscible alloy systems because of lacking the related experiments. Researchers tried ways to get the quantities needed in fitting the potentials to properties. For example, Landa et al. [4] constructed a hypothetical Pb3Al intermediate alloy phase so as to fit the potentials for Al/Pb immiscible alloy system to its properties. Therefore, the agreement between their calculation and the experimental data available needs improvement because such assumption was made in their model. Compared with other potential models, the Analytic Embedded Atom Method may be a reasonable

• ne in constructing the interatomic potentials for immiscible

alloy systems because the Analitic Embedded Atom Method potentials for alloys can be built with only inputting the physical parameters of pure metals [5]. The purpose of the present paper is to construct suitable interactomic potentials for binary immiscible alloy systems with Analitic Embedded Atom Method and then to calculate the formation enthalpies for those binary immiscible alloys and compare the result with the available thermodynamic data. In summary, we showed that the Analitic Embedded Atom Method potentials for 6 binary immiscible alloy systems have been constructed: and Ag Cu Cu These potentials were fitted to the lattice constant, cohesive energy, unrelaxed monovacancy formation energy and elastic constant for only pure metals which consist the immiscible alloy systems. The constructed potentials were used to calculate the formation enthalpies for those seven binary immiscible alloy systems. The results were in reasonable agreement with the calculations by Miedema et al. and the experimental data available. It is demonstrated that Analitic Embedded Atom Method is an effective and successful method for constructing the potentials in immiscible alloy systems with only using the properties of pure metals. The constructed Analitic Embedded Atom Method potentials can be used in further modeling of thermodynamic and other properties of those seven binary immiscible alloy systems with molecular dynamic and Monte Carlo simulations. *Corresponding author: 1Thidursun@aksaray.edu.tr

[1] C.C. Koch, Mater. Trans. JIM 36 (1995) 85. [2] J. Eckert, J.C. Holzer, C.E. Krill, III, W.L. Johnson, J. Appl.

• Phys. 73 (1993) 2794.

[3] S.M. Foiles, Phys. Rev. B 32 (1985) 7865. [4] A. Landa, P. Wynblatt, D.J. Siegel, et al., Acta Mater. 48 (2000) 1753. [5] Y.F. Ouyang, B.W. Zhang, S.Z. Liao, Z.P. Jin, Z. Physik B101(1996) 161.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 37

Investigation of the relation between the morphological and optical properties of gold nanoparticles in and on a glass matrix

11 and 1*

1

Thermally evaporated gold thin-films on glass substrates have different

• ptical

and morphological properties depending on their thickness. The gold islands/clusters that form the films can be manipulated relatively easily by physical methods [1, 2]. Because of these properties and ease

• f manipulation gold films find a wide range of use in

physical, chemical and biological applications. These applications actually utilize the plasmonic properties

• f the gold nanoclusters. Plasmons are the quantized,

collective, oscillations of free electrons in a metal. At surfaces of thin metal films, the phenomenon of surface plasmon polaritons and their confinement in nano sized islands present themselves as a very useful tool and they are widely researched [3, 4]. In this study a high vacuum thermal evaporator was used to deposit gold films on glass microscope slides. Films with varying thicknesses are prepared. As a function of the film thickness the color varies from blue to usual gold. After preparation of the films, annealing techniques have been

• used. Oven annealing (OA) and flame annealing (FA) cause

different effects on the film and substrate. The one which anneals both of the substrate and the sample is OA, which is performed by using a muffle furnace at 500

University, Department of Physics, Maslak, 34469, l, Turkey Abstract- Optical properties of gold films on glass and mica depend greatly on their morphological structure. Films grown by thermal evaporation of gold under high vacuum are investigated after different annealing processes in order to see the relation between morphological and

• ptical properties as well as the effect of the annealing processes.
• C and 900 o

Color variations of the films are shown in figure-1. (a) is the pink gold which is relatively thin and annealed at 500 C with different durations. Surface melting of the substrate resulted in the partial sinking of the gold clusters in the glass. Effects of this on optical properties have been studied in this work. Although OA effects both the glass substrate and Au films, FA only effects the surface, so

• nly the Au films .
• Surface morphology of the film was studied by atomic

force microscopy (AFM). Surface images recorded under atmospheric conditions are shown in Figure 2. C for half an hour. (b) is the blue gold, not annealed thin film, c) is the usual gold colored sample which is thicker than the

• thers.

Transmittance spectroscopies at visible wavelengths of these films are given in figure 3. The transmittance and absorption peaks correlate with the color of each sample.

Figure 2. AFM images of the films, a) is annealed one for 500 oC for half an hour and appears pink, b) is not annealed but thin enough to be transparent an looks blue, c) not annealed and appears yellow Figure 3. Uv-Vis spectroscopy measurement. Transmittance and absorbance peaks at the wave length the same of the film colors. a)pink, b) blue, c) gold.

We investigated the island sizes and their distribution in relation to the optical properties of the films and studied the confinement of the plasmon resonances in the gold nano

• clusters. Moreover we studied the position of the gold

clusters in the glass substrates in order to see whether the coloration between the morphology of the Au clusters and the sample colors of the Au coated and thermally processed glass samples is truly due to the surface clusters as mentioned in the literature [5]. Corresponding author: 2Tgurlu@itu.edu.tr

[1] Doron-Mor I et al, 2004, Chem. Mater. 16, 3476-3483 [2] Gupta G. et al et al, 2009, Nanotechnology 20 025703 [3] Kelly K. Lance et al, 2003, J. Phys. Chem. B 107, 668-677 [4] Maier S. A. Plasmonics: Fundamentals and applications, United Kingdom: Springer Science and Business Media, 2007 [5]Mishara Y K et al, 2007, J. Opt. A: Pure Appl. Opt. 9, 410-414 Figure 1. a) Pink gold, b) Blue gold, c) Yellow gold

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 38

Tuning the Physical Properties of Diamondoids

Dogan Erbahar1*, Savas Berber1

1Gebze Institute of Technology Physics Department

Abstract- We report density functional calculations for diamondoids. We fully optimized the atomic structures of all the isomers, and

• btained electronic structures. After investigating the pure diamondoids, we concentrated on the substitutional doping of these diamondoids

with Boron and Nitrogen. We find that B and N doping has considerable effects on the electronic structure of diamondoids, and thus on

• ptical properties. Our comparison of B and N doped diamondoids and the doped bulk diamond reveal the size and surface effects on the

doping energetics and the electronic and optical properties. Unlike the common assumption, the surface substitution sites are more favorable than inner substitution sites. We find that the electronic and optical properties of both the single and double doped diamondoids can be tuned for different applications by the dopant type and concentration.

Diamondoids are variants of the carbon cage molecule known as adamantane (C10H16 The recent identification and separation of higher diamondoids allowed to envision several applications, such as electron emission devices, chemical sensors, biomarkers, and pharmaceuticals. Diamondoids are considered promising functional building blocks for nanotechnology applications. These nanoscale building blocks are very different, but compare well in stability and being light-weight with fullerenes and nanotubes. ), the smallest unit cage structure of the diamond crystal lattice. Diamondoids also known as nanodiamonds or condensed adamantanes may include one or more cages (adamantane, diamantane, triamantane, and higher polymantanes) as well as numerous isomeric and structural variants of adamantanes and

• polymantanes. These diamondoids occur naturally in

petroleum deposits and have been extracted and purified into large pure crystals of polymantane molecules having more than a dozen adamantane cages per molecule. Being essentially hydrogen-terminated nanosized diamond fragments, they may occur in a large variety of shapes, as shown in Figure 1.

Figure 1. The ball-and-stick models of diamondoids. The yellow color denotes C, and the blue color H atoms

These uncommon organic molecules can be chemically functionalized by substituting carbon or hydrogen atoms at the surface by other atoms or groups to promote the formation of specific polymers. Given that diamondoids are essentially hydrogen-terminated diamond fragments, we anticipate that in the absence of significant structural changes, they share the toughness and insulating properties with their bulk diamond counterpart. The diamondoids, similar to bulk diamonds, can be substitutionally doped by B and N impurities. The pure diamondoids exhibit unexpected electronic and optical properties, such as unusual size dependence of optical properties. The electronic and optical properties may be modified for obtaining desired electronic properties by B and N substitution. However, the detailed atomic configuration of B and N dopants in diamondoids, and the origin of the observed optical and electronic properties. First, we have investigated single dopant atoms in isolated diamondoids by ab initio density functional calculations. Later, we have calculated the energetics and physical properties of double-doped diamondoids. Our calculations provide valuable information about the relative stability of doping sites, and dopant levels as well as the surface reconstruction after doping. Our results for the electronic structure of pure and doped diamondoids reveal the origin of the key electronic and optical properties of diamondoids. Diamondoids have the general formula of C4n+6H4n+12. We conducted a research on various diamondoids beginning from adamantane (n = 1) to hexamantane (n = 6). Since there are several isomers for the same n as illustrated in Fig. 1, we included all the isomers for from n=1 to 5, and selected isomers for n-6. We fully optimized the atomic structures of all the isomers, and obtained electronic structures. After investigating the pure diamondoids, we concentrated on the substitutional doping of these diamondoids with Boron and

• Nitrogen. We found that it is energetically more favorable for

a diamondoid to release the surface hydrogen atom after the doping both in the B and N case. This originates from the lack of unpaired electrons of dopant B and N atoms compared to the substituted C atoms. We find that B and N doping has considerable effects on the electronic structure of diamondoids, and thus on optical properties. Our electronic density of states results indicate that the energy gap could be adjusted for technologically important optical applications. Our comparison of B and N doped diamondoids and the doped bulk diamond reveal the size and surface effects on the doping energetics and the electronic and optical properties. Unlike the common assumption, the surface substitution sites are more favorable than inner substitution sites. In the case

• f 2 dopant atoms per diamondoid molecule we observe the

tendency of the dopant atoms to cluster. Since the homonuclear bonds are weaker and undesirable, doping by a B-N pair is more favorable than B-B or N-N doping. We find that the electronic and optical proerties of both the single and double doped diamondoids can be tuned for different applications by the dopant type and concentration. *Corresponding author: erbahar@gyte.edu.tr

[1] J. E. Dahl, S. G. Liu, and R. M. K. Carlson, Science 299, 96 (2003). [2] J. R. Schnell and J. J. Chou, Nature (London) 451, 591 (2008). [3] R. C. Merkle, Nanotechnology 11, 89 (2000). [4] J. E. Dahl, J. M. Moldowan, K. E. Peters, G. E. Claypool, M. A. Rooney, G. E. Michael, M. R. Mello, and M. L. Kohnen, Nature (London) 399, 54 (1999).

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 39

• Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials

6th Nanoscience and Nanotechnology Conference, zmir, 2010 40

Radiation Effects on MOS structure with Ge Nanocrystals embedded in SiO2

Ercan Y1*, Aliekber A1, uran2, And Nader A. P. Mogaddam2

1Physics Department, Abant Izzet Baysal University, 14280 Bolu, Turkey 2

Abstract-SiO Physics Department, Middle East Technical University, 06531 Ankara, Turkey

2 films containing small particles of Ge were grown using the r.f.-magnetron sputtering technique. The use of SiO 2 + Ge dielectric

in the MOS structure has been investigated. The responses of the MOS devices have been compared with conventional MOS capacitors with SiO 2 dielectric. The study includes the gamma radiation effects with dose up to 4000 Gray to the strucuture with SiO 2 + Ge and 150 G ray to the structure with SiO 2

In recent years, group IV nanocrystals embedded in SiO

. The effect of radiation has been determined from the valance band shift in the C-V curves. We conclude that MOS structure with Ge Nanocrystals embedded in SiO2 is a good candidate to be used in radiation sensors in space applications.

2

have attracted much attention. The main focus has been on Si nanocrystals in SiO2 [1], but also Ge nanocrystals have been studied [2–4]. The primary reason to study group IV nanocrystals is twofold. Firstly, the nanocrystals have been shown to serve as efficient light emitters and are, therefore, interesting for optical applications. Secondly, these materials are fully compatible with silicon based electronics that completely dominates the electronic industry. This makes group IV nanocrystals a promising candidate in electronic applications [5, 6]. Ge nanoclusters in SiO2 layers have in particular been produced by either ion implantation of Ge into SiO2 layers or by magnetron sputtering of SiO2

• 6
• 4
• 2

2 4 6 175 200 225 250 275 300 325 350 375 400 Capacitance pF Gate Bias (Volt) 500 Gy 650 Gy 800 Gy 1000 Gy 1300 Gy 1800 Gy 2800 Gy 4000 Gy

co-doped with Ge, in both cases followed by heat treatment.

Figure 1. C-V Curves for MOS with Ge-SiO 2 irradiated to gamma radiation

The samples used in this work were 100 nm Ge rich SiO2 layer sandwiched between two SiO2 films deposited on n-type Si<100> substrate by RF magnetron co-sputtering from two independent target materials. The effect of using a Ge-rich layer on the radiation sensing has been studied in this work. SiO2+Ge, which is believed to be an alternative dielectric in the microelectronic technology, has been employed in the MOS capacitors used for radiation sensing. Radiation effect on the MOS capacitors with SiO2 dielectric layer has previously been studied to some extend [7,8]. We investigated the radiation effect on the MOS capacitors with SiO2+Ge. The flatband voltage shifts are given in Fig.1. In one of our previous work [9] we have investigated the radiation effect on the MOS device with SiO2

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 240 280 320 360 400 440

No Rad 2 Gy 16 Gy 64 Gy 150 Gy

Capacitance pF Gate Bias (Volt) . The radiation effect on the flatband voltage shift is given in Fig.2.

Figure 2. C-V Curves for MOS with SiO 2 irradiated to gamma radiation.

In this paper, we present an evaluation of SiO2+Ge based MOS devices as a radiation sensor and a direct comparison with SiO2 based devices from the sensitivity point of view. It is shown that MOS capacitor with SiO2+Ge dielectric exhibits better sensitivity to the ionization radiation at high radiation

• doses. This means that MOS structure with Ge Nanocrystals

embedded in SiO2 is a good candidate to be used in radiation sensors in space applications. This work is supported by Abant Izzet Baysal University under contract number AIBU, BAP.2008.03.02.289. *Corresponding author: yilmaz@ibu.edu.tr

[1] L. Pavesi, L.D. Negro, C. Mazzoleni, G. Franzo, F. Priolo, Nature 408, 440 (2000) [2] S. Takeoka, M. Fujii, S. Hayashi, K. Yamamoto, Phys. Rev. B 58, 7921 (1998) [3] A.V. Kolobov, S.Q. Wei, W.S. Yan, H. Oyanagi, Y. Maeda, K. Tanaka, Phys. Rev. B 67, 195 314 (2003) [4] H. Seifarth, R. Grotzschel, A. Markwitz, W. Matz, P. Nitzsche, L. Rebohle, Thin Solid Films 330, 202 (1998) [5] N.T.V. Oanh, N.A. Viet, Int. J. Mod. Phys. B 14, 1559 (2000) [6] M.S. Hybertsen, Phys. Rev. Lett. 72, 1514 (1994) [7] K. Naruke, M. Yodshida, J. Maegushi and H. Tango, Radiation induced interface states of poly-Si gate MOS capacitors using low temperature gate oxidation, IEEE Trans. Nucl. Sci. 30 (6) (1983) 4054. [8] G. J. Brucker, O. Van Gunten, E.G. Stassinopoulos, P. Sapiro, L.

• S. August, and T. M. Jordan, Recovery of Damage in Rad-hard MOS

Devices during and after Irradiation by Electrons, Protons, Alphas and Gamma Rays, IEEE Trans. Nucl. Sci. 30 (6) (1983) 4157.

• Type Radiation Sensors”, Nuclear Instruments and Methods in

Physics Research B, 264, Iss 2, P.287-292, 2007.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 41

Figure 1. Net spin density for substitutionally Cr doped diamantine, which indicates these clusters may find use in spintronic applications.

Cr doped diamondoids for spintronics

Semran Ipek1*and Savas Berber1

1

Abstract-We perform first principles calculations using local density approximation to predict the structural and electronic properties of Cr atom substituted diamondoid (clusters having general chemical formula C Department of Physics, Gebze Institute of Technology, Gebze, KOCAELI 41400, Turkey

4n+6H 4n+2

Due to the down scaling of electronic devices, the clusters

and cluster based devices will be the building blocks of future electronic devices. Among the clusters, diamondoid molecules with the formula of C

) starting from adamantane (n=1) to tetramantane (n=4). We find that the Cr atom energetically prefers the inner sites than surface sites of the diamondoid as the size of the diamondoid increases. We find this behavior unexpected, since the surface atoms that constitute a large fraction of the whole structure should make the surface more prone to chemical reactions. The highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO-LUMO) gaps are drastically lowered as much as 2 eV by introducing the Cr atom. The calculated spin density contour plots reveal that the magnetic coupling between the dop ant Cr atom and the neighboring atoms is antiferromagnetic, which results in decreasing the net magnetic moment.

4n+6H4n+2

In this study, we performed the density functional theory calculations based on the local density approximation with Perdew-Zunger exchange correlation density functional implemented in the SIESTA code. The optimized structures of Cr substituted diamondoids are given in Figure. Since there are two kinds of C atoms with respect to the number of H atoms bonding to the C atoms, there are two possible sites for the Cr atom to occupy in these structures. We find that Cr atoms energetically prefer the sites with one hydrogen atom for both adamantane and diamantane. Our geometry

• ptimization results show that the Cr substitution does not

destroy the diamondoid structures significantly. Based on the total energy calculations, the formation energies of Cr substituted diamondoids are also calculated. have received much interest recently because of possible applications in microelectronics and in optoelectronics.[1]. Due to the feasibility of arranging these molecules in a self assembly manner [2], new generation assemblers from carbon based diamondoids having different physical and electronic properties from the bulk form should be investigated extensively. Since the diamondoid molecules are known as cage hydrocarbons, which are free from both angle and torsional strain, they can be used for encapsulation

• f other compounds like drugs in pharmacology. Because of

their lower size (1-2 nm) and high surface/volume ratio, the electronic and structural properties of diamondoids could be altered by linking some functional groups or by substituting

• ther atoms. Recently, it was found that the optical properties
• f stoichiometrically identical diamond clusters depend on the

atomic configuration strictly.[4] It has been theoretically predicted that diamondoids have significant quantum size effects due to their lower size with the large highest occupied molecular orbital and lowest unoccupied molecular gap (HOMO-LUMO) up to 7.6 eV. In the case of bulk diamond the electronic band gap is 5.47 eV. However, to the best of

• ur knowledge, the structural and electronic effects of

transition metal atom substitution in these carbon cage molecules have not been theoretically investigated. The formation energies vary in the range of 8.24 eV -8.42 eV from adamantane to tetramantene. The spin polarized calculations show that all the structures have a net magnetic moment as much as 2 B In order to interpret the effect of the Cr subtitution on the electronic properties, HOMO-LUMO gap is also calculated for all structures. Cr atom makes the HOMO-LUMO gap lower as compared to bare diamondoids . regardless of type of the diamondoid. Since the energy cost brought by the additional perturbation of the host molecule in substituting the Cr atom is high, the antiferromagnetic coupling stabilizes the ground states of the

• diamondoids. This coupling between Cr atom and diamantane

molecule is depicted in Figure. In conclusion, we find that Cr atom substitution in lower diamondoids changes their electronic and magnetic properties

• drastically. Because of having net magnetic moment after the

substitution Cr atom in diamondoids, these structures could be possible candidates for future spintronic electronic devices, while the formation energies are only accessible by experimental processes requiring high energies. *Corresponding author: seipek@gyte.edu.tr

[1] L.Landt, W.Kielich, D. Wolter , M. Staiger , A. Ehresmann, T. Möller ,C.Bostedt, Physical Review B. 80, 205323 (2009). [2] N.Tsuzuki, T. Hama, M. Kawada, A. Hasui, R. Konishi, S. Shiwa,

• Y. ochi, S. Futaki, and K. Kitagawa, J. Pharmaceutical Sci. 83, 481

(1994). [3] L. Landt, K. Klunder, J. E. Dahl, R. M. K. Carlson, T. Moller,1 and C. Bostedt, Physical Review Letters 103, 047402 (2009). [4] Yayu Wang, Emmanouil Kioupakis, Xinghua Lu, Daniel Wegner, Ryan Yamachika, Jeremy E. Dahl, Robert M. K. Carlson, Steven G. Louie, and Michael F. Crommie, Nature Materials 7, 38 (2008).

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 42

Synthesis and characterization of nanocrystalline yittrium silicate materials doped with neodymium

Murat Erdem,*1 Gonul Ozen2 and Cumali Tav1

1Marmara University, Department of Physics, Goztepe, 34722, Istanbul, Turkey 2İstanbul Technical University, Physics Engineering, Maslak, 34469, Istanbul, Turkey

Abstract-Sol-gel technique was used to prepare the yttrium silicate powders doped with 0.01Nd3+. The XRD patterns of the powders annealed at 960oC for 72 hours were used to determine the crystallization behaviors and the crystallite sizes which were found to be 23±0.1nm. The Y4.67 (SiO4)3O, Y2Si2O7 and Y2SiO5 crystalline phases were observed.

Studies on the technical applications of yttrium silicate system (SiO2-Y2O3) exhibit interesting optical features with a variety of preparing

• techniques. Doping with rare earth elements resulted

in samples with promising

• ptical

memory applications [1], producing diode pumps [2], and making potential candidates for the production of laser materials [3] or high energy phosphors [4,5]. The SiO2-Y2O3 phase diagram [6] indicates a two phase region between 1:1 and 1:2 molar ratios in which Y2SiO5 and Y2Si2O7 form a stable mixture. The yttrium orthosilicate (Y2SiO5) crystal has two different monoclinic structures: X1 type (X1- Y2SiO5) and X2 types (X2-Y2SiO5). The X1 and X2 types formed by varying annealing temperature are known as crystallographic groups of P21/c, and B2/b, respectively [7]. The yttrium pyrosilicate (Y2Si2O7) investigated from a structural point of view due to its complex high temperature polymorphism was reported for the first four forms [8]:

1225 1445 1535

• C

C C

• . In the

respective stability range, these four modifications were synthesized from appropriate reagents using solid state reactions [9]. In this work, an amorphous phase of neodymium (Nd3+) doped yttrium silicate phosphors synthesized by the sol gel technique was

• bserved at 900oC. While the other studies report the

X1-Y2SiO5 and α-Y2Si2O7 form at higher temperatures and larger nanocrystal-size, our results reveal smaller nanocrystal-size and Y4.67 (SiO4)3O phase in 0.5 and 0.67 molar ratios of SiO2 at 960oC in addition to Y2Si2O7 and Y2SiO5 We have observed amorphous phases of three powder-samples at 900oC. In Figure 1, the diffraction pattern of α-Y2Si2O7 for SYN75,α- Y2Si2O7,Y4.67(SiO4)3O and X1-Y2SiO5 for SYN65, X1 - Y2SiO5 for SYN55, are illustrated, respectively. The SiO2-Y2O3 phase diagram [6] shows the crystal structures of Y2SiO5+Y2Si2O7 in the molar region of 50% -67% from 1500oC to 1650oC. In our work, we

• bserved α-Y2Si2O7, Y4.67 (SiO4)3O and X1 -Y2SiO5

for SYN65 and X1-Y2SiO5 for SYN55 at 960oC in the same molar region. While Y2Si2O7+SiO2 crystal structures were observed from 1500oC to 1660oC through the molar region of 67%-100% in that only α- Y2Si2O7 crystal structure at 960oC was occurred in

• ur work. The average crystallite sizes for all three

powder-sample calculated from Scherrer’s formula [10] are to be 23±0.1nm.

Figure 1.The diffraction pattern of α-Y2Si2O7 for SYN75, α-Y2Si2O7,Y4.67(SiO4)3O and X1-Y2SiO5 for SYN65, X1 -Y2SiO5 for SYN55, after annealing temperature.

Nanocrystalline phosphors of neodymium-doped yttrium silicate are highly important in lasers. We successfully synthesized nanocrystalline yttrium silicate doped with neodymium by the sol-gel technique. This work was supported by Science Institute of Marmara University with the project number FEN-C- DRP-090409-0079. *merdem@marmara.edu.tr

[1] M.Mitsunaga, R.Yano, N.Uesugi, Opt.Lett. 16, 1890, (1991) [2]F.Thibault,D.Pelenc, F.Druon, Y.Zaouter, M.Jacquement and P.Georges, Opt.Lett. 31, 1555, (2006) [3]M.Jacquement, F.Balembois, S.Chenais, F.Druon, P.Georges, R.Gaume, B.Ferrand, Appl. Phys. B 78, 13, (2004) [4]P.Zhou, X.Yu, L.Yang, S.Yang, W.Gao, J.Lumin. 124, 241, (2007) [5]D.Hreniak, P.Gluchowski, W.Strek, M.Bettinelli, A.Kozlowska, M.Kozlowski, Mater. Sci. 24, 405, (2006) [6]J.J.Chambers and G.N. Parsons, Journal of Applied Physics 90, 2, (2001). [7]C.Cannas,M.Mainas,A.Musinu,G.Piccaluga, A.Speghini, M.Bettinelli, Opt. Mater. 27, 1506, (2005) [8]J.Ito and H. Johnson, Am.Miner. 53, 1940, (1968) [9]N.Taghavinia,G.Leronda,H.Makino,T.Yao, Nanotechnology 15, 549, (2004) [10]X.Qin, Y.Ju, S.Bernhard, N.Yao, Mater.Res.Bull. 42 1440, (2007)

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 43

Synthesis and Characterization of NaxCo2O4 PVA Polymerized Complex Thermoelectric Material using

Mehmet Okan Erdal1*, Arda Aytimur2 slu3, Mustafa Koyuncu4

1Selcuk University, Institute of Science and Technology, Department of Physics, Esentepe, Konya, Turkey 2 3 4

Selcuk University, Faculty of Science, Department of Physics, Esentepe, Konya, Turkey Abstract- For the first time, sodium cobalt oxide (NaxCo2O 4) crystalline thermoelectric materials were obtained using polyvinyl alcohol (PVA) polymerized complex sol-gel solution. PVA was used as polymer solution with sodium acetate/cobalt acetate, followed by calcination at 800 oC. The sodium cobalt oxide calcined crystal structures were characterized by X-ray diffraction (XRD). The sol-gel solution calcined at 800 oC were single crystal and XRD results have an agreement with the literature values. The results indicated that samples after calcination should be sintered more than one to obtain pure crystalline phase.

Thermoelectric energy conversion is widely recognized as a promising technology especially for both waste heat recovery and cooling of various electronic devices employed in high

• technology. The thermoelectric material is a material that

shows large thermopower; low resistivity, low thermal conductivity and [1] chemically and thermally stable. Sodium–cobalt oxide (NaxCo 2O4 Various methods were tried to prepare Na ) has been revealed to have potential as a thermoelectric material [2] because of chemical and thermal stabilty and thus can be used at high temperatures without deterioration of their performance due to oxidation. Moreover, the production costs of these materials are comparatively low.

xCo 2O4 such as

mechanical grinding and mixing of related oxides or spark plasma sintering technology to prepare a fine ultra homogenous microstructure but both of them result a lower thermoelectric performance. Recently a precursor mixture of sodium acetate/cobalt acetate/ Polyacrylonitrile (PAN) is used fort he homogenous synthesis NaxCo 2O4. In this study, poly vinyl alcohol was used instead of PAN and the sintered samples showed that polymerized sol-gel complex synthesis of NaxCo 2O4 In this study, PVA had molecular weight of 72000 g/mol and sodium and cobalt acetate was obtained from Sigma Aldrich and deionized water was used as a solvent. Aqueous PVA solution (10%) was first prepared by dissolving PVA powder in distilled water and heating at 80 showed a high density, a fine microstructure and improved thermoelectric performance compared to a sample prepared by the conventional solid state reaction method. [3]

• C with stirring for

3 h, then cooling to room temperature. 0,3 g of the sodium acetate solution and 2 g of cobalt acetate solution were added to the 100 g aqueous PVA at 60 oC separately and drop by drop and the solution was vigorously stirred for one hour at this temperature. Stirring was continued for 2 hr at room

• temperature. Thus, a viscous gel of PVA/Na-Co acetate

solution was obtained. This mixture was aged at room temperature for about 12 hours. The hybrid polymer solution were dried in an oven0T under vacuum at 80 °C for 6 hours and sintered at 800 o According to the diffraction patterns given in Fig. 1 a) and b), 2 theta values as 16.3 (0 0 2), 33.1 (0 0 4), 36.4 (1 0 0), 44.5 (1 0 3) planes obtained from the diffraction images coincide with those of polycrystalline Na C at atmospheric conditions for 2 hrs.

xCo 2O4 (JCPDS card

• No. 27-0682) and this card number shows they were indexed

as the -phase. It should be noted that this phase of NaxCo 2O4 shows a large Seebeck coefficient. This results are also agree with results of S. Yoshimoto and coworkers which calcined the polymerized PAN precursor at the same temperature.[4]. The peak at 26.6o corresponds to pure graphite like structure (The interlayer distance of pure graphite is 3.35 A° (2h = 26.6) [5] and this peak was disappeared when the samples sintered at the same

• temperature. This result shows that samples should be sintered

at least two or much more times to obtain ultra pure crystalline structures. given in Fig. 1 (a)

Figure 1. NaxCo2O 4 polymerized complex a) calcined at 800 oC b) sintered at 800 oC

This study was supported by Selcuk University Research Coordination Office. We also thank to Prof.Dr. M. L. Aksu who opened his research laboratory in Gazi University for this

• study. We also thank to Assoc.Prof.Dr. M. K. Öztürk from

Gazi University for the XRD analysis. *Corresponding author: mehmeterdal@ttmail.com

[1] Mahan G.D., 1998. Solid State Phys. 51, 81. [2] I. Terasaki, 2003. Physica B 328, 63. [3] M. Ito, Nagira T., Furumoto D., Oda Y. and Hara S., 2004. Science and Technology of Advanced Materials, Volume 5, Issues 1- 2. [4] Maensiri S., Nuansing W., 2006. Materials Chemistry and Physics 99, 104. [5] Yoshimoto S., Amano J., Miura K., 2010. J Mater Sci 45, 1955.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 44

Synthesis, Structure and Properties of Pre-intercalated Allyl Amine-Clay and Its Nanocomposites by Interlamellar Copolymerization

Amir Sepehrianazar1*, Nagihan Caylak2 and Zakir M. O. Rzayev3

1Department of Chemical Engineering, Islamic Azad University, Ahar Branch, Ahar 54516, Iran 2Department of Physics, Sakarya University, Sakarya 54187, Turkey 3Department of Chemical Engineering, Hacettepe University, Ankara 06800, Turkey

Abstract— Functional copolymer/silicate [poly(allyl amine) (AAm) surface modified montmorillonite (MMT)] layered nanocomposites have been synthesized by interlamellar complex-radical copolymerization of pre-intercalated complex of PAAm...MMT as a ‘nano-reactor’ with acrylic acid (AA). It was demonstrated that intercalation and exfoliation in situ processes are accompanied by physical (H-bonding) and chemical (amidization) interfacial interactions of PAAm with AA comonomer which are responsible for the formation of nanostructural hybrid architectures.

In last decade, considerable attention is given to developing various methods for synthesizing polymer nanocomposites, emphasizing layered silicate reinforcement, especially alkyl amine surface modified montmorillonite clay (organo-MMT) [1-6]. Generally, such nanocomposites prepared by intercalative polymerization of vinyl and acrylic monomers, and compounding compatibilized thermoplastic blends in melt in the presence of different type of organo-silicate clays as a nano-reactor. Clear property advantages demonstrated by nanocomposites in comparison to conventional thermoplastic and thermosetting polymers and inorganic fillers. In the last years, nanomaterials have attracted substantial attention due to their high performance physical and mechanical properties, when compared with those of the conversional polymer composites. Taking into the consideration that nature of interaction between functional (co)polymers and the organo-clay is importance, and the structure and morphology of the resulting nanocomposites strongly depend on the such interactions, we have been investigated physical (H-bonding) and chemical (amidization) interactions between functional monomers, such as acrylic (AA) and allyl amine, and MMT clay layered silicate polymer nanocomposites were synthesized by intercalative (co)polymerization of AAm or PAAm modified MMT with acrylic acid in the presence of an ionizable water- soluble radical initiator in aqueous medium, and by intercalation/exfoliation of copolymer of AAm and AA via interlamellar complex-formation or amidization reactions. General scheme of the synthetic partways can be represented as follows:

Figure

• 1. Complex formation, amidization and interlamellar

complex-radical copolymerization

The formations of intercalated complexes of AAm or PAAm with AA monomer, as well as nano-structures in the studied systems were confirmed by FTIR, X-ray powder diffraction and SEM morphology analyses. This new approach in synthesis polymer nanocomposites my utilized for a widely range of functional monomers exhibiting yielding to formation

• f H-bonding with various amine compounds.

The results of the comparative XRD and SEM analyses of nanocomposites indicate that the observed effects of interlayer complex formation and internal amidization reaction play an important role in interlamellar copolymerization and intercalation/exfoliation in situ processes, as well as in the local chain folding and crystallization process. On the other hand, complex-formation between AAm units and MMT clay layered surface increases the force of interfacial interaction between organic (polymer chains) and inorganic phases. This pre-intercalated complex also plays an important role as a reactive compatibilizer in the formation of nano-structural architectures with given thermal properties.

Figure 2. SEM images

• f

poly(AAc)/poly(AAm)-MMT nanocomposite: Effect of initiator content.

Synthesized hybrids may be utilized as nano-films and nano-coatings in the in-line coating processing for surface modification of various thermoplastic films, as reactive compatibilizer-nanofillers for the reactive thermoplastic polymer blends, especially for the acrylic polymer based systems, and also as components of the various nanomaterials prepared in melt by reactive extrusion in situ processing. This study was supported by TUBITAK and Science and Research Unit (BAB) of Hacettepe University for the financial supports of this work through Projects TBAG-HD/249 and BAB(DPT)-K120930, respectively. *Corresponding author: amir@hacettepe.edu.tr References

[1] H. Nasegawa, et. al. J. Appl. Polym. Sci. 93, 758 (2004). [2] D. H. Kim, P. D. Fasulo, et al. Polymer 48, 5308 ( 2007). [3] G. D. Liu, L. C. Zhang, et al. J. Appl. Polym. Sci. 98, 1932 (2005). [4] M. Alexandre, P. Dubois, Mater. Sci. Eng.R: 28, 1 (2000). [5] Z. M.O. Rzayev, A.Yilmazbayhan, E. Alper, Adv. Polym. Technol. 26, 41 (2007). [6] E. Söylemez, N. Çaylak, Z. M. O. Rzayev, eXPRESS Polym. Lett.

2, 639 (2008). Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 45

SYNTHESIS AND CHARACTERIZATION OF POLYMERS WIT TRIPTYCENE UNITES BY PHOTOPOLYMERIZATION AND CLICK CHEMISTRY PROCESSESOF

Lokman Torun,1 Sahin Ates,1,2 Binnur Aydogan,2 Yasemin D. Yuksel,2 Yusuf Yagci2

1Chemistry Institute, TUBITAK MRC, Gebze, Kocaeli, 41470, Turkey 2Istanbul Technical University, Department of Chemistry, Maslak, 34469, Istanbul, Turkey

Abstract— We predict that a single ethylene molecule can form a stable complex with two transition metals (TM) such as Ti. The resulting TM-ethylene complex then absorbs up to ten hydrogen molecules, reaching to gravimetric storage capacity of ~14 wt%. Our results are quite remarkable and open a new approach to high-capacity hydrogen-storage materials discovery. In this work, we herein report synthesis, characterization and photocuring behavior of a new cross-linker based on triptycene molecule. Photopolymerizations were performed with the formulations containing triptycene hydroquinone diacrylate (THDA) together with monofunctional monomers glycidyl methacrylate (GMA), 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl ethacrylate (HEMA), and 2-ethylhexyl methacrylate (EHMA), by using 2,2- dimethoxy-2-phenylacetophenone (DMPA) as the photoinitiator. Comparative photopolymerization studies were also performed by using structurally similar cross-linker, hydroquinone diacrylate (HDA) which does not possess triptycene unit. Photopolymerization kinetics was analyzed for different compositions of monofunctional monomers and cross-linked agents by using photo-differential scanning calorimeter (photo-DSC). Each monofunctional monomer was reacted with varied percentages of a difunctional monomer HDA and THDA respectively to observe the influence of triptycene based cross-linker on rate of polymerization.1 Scheme 1. Overall process for copolymerization of azide terminated bifunctional polystyrene (N3-PS-N3) by “click” chemistry. In addition, In this work, we report synthesis of polystyrene possessing triptycene unit in the main chain by the combination of ATRP and click chemistry process. Bromine terminal groups of polystyrene obtained by ATRP converted to azide functionality by simple nucleophilic substitution by using NaN3. Bisalkyne functional triptycene compound was independently synthesized for the subsequent click

• reaction. Bisazide and bisalkyne functional

compounds with long alkyl chain were also prepared and used as

• comonomers. 2

The cross-linkers were synthesized by the acylation of the respective hydroquinone compounds with acryloyl chloride (Scheme 2). Scheme 2. Synthesis of the cross linkers. The H NMR spectrum of HDA showed characteristic peaks for acrylic protons at 5.6 ppm, 6.0 ppm and 6.4 ppm, and aromatic protons at 7.1 ppm. In the spectrum of THDA, while the signal at 8.9 ppm corresponding to –OH protons of the precursor TH completely disappeared, new signals originating from acrylic protons appeared at 6.1 ppm, 6.5 ppm and 6.7 ppm. Photopolymerizations of several monomers using either HDA or THDA were followed by DSC under identical conditions of temperature (30 _C) and UV light intensity (18.4mWcm_2). Schematic representation of photoinduced cross-linking is shown in Figure 1. As can be seen triptycene units are chemically incorporated to the network after photocuring process. Figure 1. Schematic representation of photoinduced cross-linking of vinyl monomers using triptycene hydroquinone diacrylate (THDA). In conclusion, in the first part we report synthesis of polystyrene possessing triptycene moiety in the structure by combination of ATRP and “click” chemistry. The intermediates and the resulting polymers were caharacterized by spectral and thermal analyses methods. The effect of the triptycene moiety on the thermal properties was demonstrated. In the light of present study and the general behavior of triptycene molecules in polymer chains it is expected that polymers with enhanced properties such as ductility and stiffness can be obtained by ATRP combined with “click” chemistry. Further studies on the investigation of these properties are now in progress.

In the second part, we report synthesis of a new cross-linker possessing triptycene moiety in the structure and characterized. Moreover, its photopolymerization behavior in the UV curable formulations containing different monofunctional monomers was

• studied. Comparative kinetic studies revealed that the polymerization

kinetics are governed mainly by the structure of the monofunctional monomer employed in the formulation and triptycene type cross- linker acts in a manner similar to the conventional cross-linkers. In the light of present study and the general behavior of triptycene molecules in polymer chains it is expected that cross-linked networks with enhanced properties such as ductility and stiffness can be

• btained by photoinitiated free radical polymerization.

1

Sahin Ates, Binnur Aydogan, Lokman Torun, Yusuf Yagci Polymer 51 (2010) 825–831.

2

Sahin Ates, Yasemin Yuksel Durmaz, Lokman Torun, Yusuf Yagci, In

• press. Journal of Macromolecular Science.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 46

Effect of different additions on crystallization behavior and magnetic properties of magnetic glass ceramic

Salwa A. M. Abdel-Hameeda & Abeer.Y.El-Kadyb

a Glass Research Department, National Research Center, Dokki, Cairo, Egypt b Biomaterial Department, National Research Center, Dokki, Cairo, Egypt

Abstract: This work pointed out the preparation of magnetic glass ceramic in the system Fe2O3.ZnO.CaO.SiO2.The base composition was designed to crystallize ~60% magnetite. The influences of adding different additions as TiO2, Na2O and P2O5 individual or as mixture from them were studied. Thermal behavior of the samples was studied using DTA which revealed decrease in the thermal effects by adding P2O5, TiO2 and Na2O respectively. The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The crystallization of magnetite was increased by adding, TiO2, P2O5 respectively while decreased by adding Na2O. Heat treatment in the temperature range 1000-1050ºC for different times leads to appearance of hematite and

• wollastonite which slightly increased by adding P2O5, TiO2 and largely

enhanced by adding Na2O. Sample contains mixture from TiO2, Na2O, and P2O5 shows summation of the effects of these oxides. The microstructure was studied using TEM which revealed crystallite size in the range 52-90nm. Magnetic hysteresis cycles were analyzed using a vibrating sample magnetometer with a maximum applied field of 10 kOe, at room temperature, in quasi-static conditions. From the obtained hysteresis loops, the saturation magnetization (Ms), remanance magnetization (Mr) and coercivity (Hc) where

• determined. The results showed that these materials are expected to be

useful in the localized treatment of cancer.

Oral Presentation, Theme A: Nanomaterials including Nanoparticles, Nanocavities, Nanocrystals, Nano-porous materials 6th Nanoscience and Nanotechnology Conference, zmir, 2010 47