Synthesis and Characterization of Gold Nanoparticles (2020/05/02 - - PowerPoint PPT Presentation

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Synthesis and Characterization of Gold Nanoparticles (2020/05/02 - - PowerPoint PPT Presentation

Sep 27, 2022 469 likes •645 views

Synthesis and Characterization of Gold Nanoparticles (2020/05/02 revised) Collect Apparatus Amount Apparatus Amount Wash with aqua regia in hood: 50 mL round-bottomed flask Cuvettes 1 2 Condenser 1 Stir bar (TA) 1 Sand bath Timer

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SLIDE 1

1

Synthesis and Characterization of Gold Nanoparticles

Collect

Apparatus Amount Apparatus Amount Wash with aqua regia in hood: 50 mL round-bottomed flask 1 Cuvettes 2 Condenser 1 Stir bar (TA) 1 Sand bath 1 Timer (TA) 1 Extension clamp (small) 1 Rubber tube 2 Extension clamp (large) 1 Dropper 1 Latex gloves 2 2 mL Measuring pipet Shared Linen gloves 2 15 mL Transfer pipet Shared

*Clean the top of hot plate with wet cloth first

(2020/05/02 revised)

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SLIDE 2

2

Objective

  • Use sodium citrate (Na3C6H5O7) as reducing agent to

reduce tetrachloroaurate(III) ion to gold nanoparticles

  • Synthesize gold nanoparticles with various sizes
  • Measure and compare the surface plasmon resonance

(SPR) spectra

  • Observe Tyndall effect of gold nanoparticles

Citrate ion

Au(s)

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SLIDE 3

3

Techniques

 Prepare aqua regia to clean up the

surface of reacting apparatus

 Manipulate graduated pipette and

pipette filler

 Set up reflux system  Use magnetic stirrer / hot plate  Operate spectrophotometer

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SLIDE 4

4

Preparation of Gold Nanoparticles

Reduction of tetrachloroaurate(III) ions by sodium citrate HAuCl4(aq) + C6H5O7Na3(aq)  Au(s) + CO2(g) + HCOOH… Reducing agent nano-gold (< 100 nm)

Control the amount of citrate (1.8 or 1.0 mL) used

to prepare gold nanoparticles of different diameters (15 or 33 nm)

Reference:

  • K. C. Grabar; R. G. Freeman; M. B. Hommer; M. J. Natan; Anal.
  • Chem. 1995, 67, 735-743.
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SLIDE 5

5

Outline of Procedure

  • I. Clean up apparatus
  • II. Synthesis of gold

nanoparticles

  • III. Vis. absorption

Spectrum

  • IV. Tyndall effect of

Colloid

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SLIDE 6

Procedure I. Clean up the Apparatus

  • Wear latex gloves
  • Operate the followings in fume hood

－Mix 5 mL conc. HNO3 and 15 mL

  • conc. HCl in a beaker to prepare

aqua regia －Clean magnetic stir bar, round- bottomed flask, condenser, and 2 cuvette with aqua regia －Aqua regia can be used repeatedly

  • Rinse the apparatus with D.I. water
  • nce

=== Back to bench =============================

  • Wash off the acids with large amounts of D.I. water
  • Drip-dry the washed apparatus

6

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SLIDE 7

Procedure II. Set up Reflux System

Condenser 50 mL Round- bottomed flask Sand Bath Stirrer / hot plate

Measure 15 mL of Au(III) with transfer pipet to round-bottomed flask

Fix the round-bottomed flask with small- sized extension clamp

Set round-bottomed flask in the sand bath container and place on the top center of hot plate

Test the stirring to make sure the stir-bar can stir smoothly.

Fix the condenser with large-sized extension clamp

Cooling water:

Connect the rubber tubes firmly

Run the cooling water from the bottom to the top

Adjust the water flow properly

Lastly, add sea-sand in sand bath container

Heat the soln. after checking by TA Note:

  • Wipe the top of hot plate with

wet cloth before setting up

  • Electric wires and rubber tubes

should not contact the hot plate

7 Cooling water

  • ut

Cooling water in

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SLIDE 8
  • Keep stirring on while Au(III)(aq) boils vigorously
  • Obtain 1.8 mL (odd groups) or 1.0 mL (even groups)
  • f sodium citrate with 2 mL graduated pipet
  • Add through condenser all at once
  • Observe color change with reaction time

Procedure II. React with Sodium Citrate

8

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SLIDE 9

Note: Put cotton gloves on when removing the sand bath to avoid burns

Procedure II. Synthesis of Gold Nanoparticles

Keep on heating and stirring until solution boils for 10 min.

Turn off heating

Remove sand bath, continue stirring while cooling for 10 min.

9

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SLIDE 10

Expected Gold Nanoparticles

(B) 1.0 mL sodium citrate 33 nm gold nanoparticles (A) 1.8 mL sodium citrate 15 nm gold nanoparticles

10

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SLIDE 11

Obtain two cuvettes

 One filled with half volume of D.I. water as Blank  One filled with half volume of diluted gold nanoparticles as Sample soln

* Dilute 1 mL of gold nanoparticle soln. with 4 mL D.I. water as sample

  • soln. Transfer half of soln to cuvette and the rest to a test tube.

 Notice

 Do not brush the cuvettes  Use lens tissue to wipe clean the cuvettes before putting into

spectrophotometer

Align cuvettes in fixed direction

Procedure III. Absorption Spectrum of Gold Nanoparticles

Sample soln. Blank Cuvette

11

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SLIDE 12

400 ~ 700 nm: measured in 20 nm intervals 510 ~ 540 nm: measured in 5 nm intervals

Calibration and Measurement (1) Turn on power to warm up (2) Empty the cuvette holder (3) Set the mode to A (4) Set wavelength to 400 nm (5) Press [BLANK] to adjust zero (6) Place blank soln to cuvette holder (7) Press [BLANK] to calibrate (8) Place sample soln into cuvette holder and record the Abs (9) Change wavelength (420 nm), repeat (6)~(8) to calibrate and measure the absorbance

Note: Repeat calibration while changing the wavelength (1) (2) (3) (4) (5)

12

Procedure III. Absorption Spectrum of Gold Nanoparticles

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SLIDE 13

13

Plot Absorption Spectrum

  • Absorbance as y axis and wavelength as x axis
  • Excel: insert XY scattering diagram with smooth

curve fitting

  • Indicate max

(520, 0.614) (525, 0.617)

, nm 1.8 mL 1.0 mL 400 0.402 0.418 420 0.402 0.420 440 0.396 0.412 460 0.412 0.419 480 0.458 0.454 500 0.548 0.533 510 0.588 0.578 515 0.606 0.596 520 0.614 0.608 525 0.602 0.617 530 0.573 0.602 535 0.538 0.573 540 0.506 0.524 560 0.348 0.384 580 0.223 0.260 600 0.140 0.162 620 0.090 0.096 640 0.072 0.075 660 0.059 0.061 680 0.047 0.053 700 0.039 0.043

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 400 450 500 550 600 650 700

Abs. wavelength (nm) Absorption spectrum of gold nanoparticles

小粒徑 大粒徑

1.8 mL citrate 1.0 mL citrate

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SLIDE 14

(A)

50 nm

5 10 15 20 25 30 35 40 45 50 5 10 15 20 25 30

(B) Dia.= 33 + 3 nm (50 particles) Polydispersity= 9% (A) Dia.= 15 + 1 nm (50 particles) Polydispersity= 7%

Counts Diameter (nm)

(B) 1.0 mL Citrate (A) 1.8 mL Citrate (A) (B)

400 450 500 550 600 650 700 0.0 0.1 0.2 0.3 0.4 0.5

max = 520 nm (15 nm) max = 528 nm (33 nm) Absorbance Wavelength (nm)

Expected Color, Spectra and Particle Size Analysis (TEM)

14

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SLIDE 15

15

Colloid Property of Gold- nanoparticles

  • Colloids: solute with diameter in 1-1000 nm
  • Tyndall effect: light scattering by colloids

Gold nanoparticle solution

NaCl(aq)

 Effect of electrolyte on colloids

  • Add 1 M NaCl(aq) drop by drop to

diluted sample soln in test tube

  • Observe the coagulation of gold

nanoparticles and color changes

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SLIDE 16

16

Notice (Full report)

  • Be cautious while operating aqua regia which is corrosive
  • Recycle aqua regia into specific waste bin after lab
  • DO NOT waste HAuCl4 which is expensive
  • Wash apparatus thoroughly with plenty of D.I. water

before synthesis

  • Be careful with hot plate and sand bath to avoid burning
  • You may fill some gold nanoparticles solution in a sample

vial as a souvenir or discard into gold nanoparticles recycling bin

  • Wash specific equipment with water and put back in

place

  • Clean up hot plate, benchtop, and apparatus
  • Hand in lab report next weak