Lijuan Li Santa Barbara City College Mechanical Engineering - - PowerPoint PPT Presentation

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Feb 09, 2023 142 likes •366 views

Lijuan Li Santa Barbara City College Mechanical Engineering Postdoctoral mentor: Jayna Jones Faculty advisor: David Awschalom Why nanodiamonds? Electron spin Carbon Properties Biocompatibility & nontoxicity Chemical stability nitrogen

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Lijuan Li Santa Barbara City College Mechanical Engineering Postdoctoral mentor: Jayna Jones Faculty advisor: David Awschalom

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Why nanodiamonds?

Properties

Biocompatibility & nontoxicity Chemical stability Fluorescence from its defects

Potential applications

Single particle tracking Cellular biomarkers (tumor targeting and cell imaging)

nitrogen Vacancy Electron spin

http://awsch-web.physics.ucsb.edu/research/solid_state/polarization/d2_figure_01.jpg

Carbon

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Problems

Background noise complicates experiments Suspect they come from surface(50nm~100nm diamond has large surface area to volume ratio)

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Goals

Create a method to approximate

nanodiamond concentration

Surface cleaning
Study of surface charge properties

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Concentration vs absorption

Dilution Run absorption scan using UV‐vis spectrophotometer Analyze the absorption as a function of concentration Develop a method of figuring out the concentration of a nanodiamond solution easily

UV-vis spectrophotometer

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0.00 0.02 0.04 0.06 0.08 0.10

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Absorption (a.u.) Concentration(weight%)

Abs@300nm Abs@350nm Abs@400nm Abs@450nm Abs@488nm Abs@500nm

Linear fit data of absorption vs concentration

Abs@400nm =26.948*(concentration) - 0.01603

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Surface cleaning

Centrifuge nanodiamond Acetone treatment Rinse with millipore water and centrifuge the

sample. Repeat 3 ‐4 times

Resuspend treated nanodiamond in water for experiments

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After surface treatment

Excitation at 532nm Emission scan with fluorimeter Fluorescence comparison Fluorimeter vs UV‐vis spectrophotometer

Cary Eclipse Fluorimeter

Fluorimeter UV‐vis spectrophotometer

Measures the light that is emitted from the sample, which is called fluorescence Measures how much light being absorbed by the sample

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600 650 700 750 800 1 10

Intensity(a.u.) Wavelength(nm) untreated 0.05wt% washed 0.05wt%

The fluorescent peaks of the washed nanodiamond are sharper than the untreated one

Emission scan at 532nm

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600 650 700 750 800

1 10

Intensity (a.u.) Wavelength(nm) untreated 0.025wt% washed 0.025wt%

The untreated nanodiamond has a sharper peak

Emission scan at 532nm

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What is zeta potential?

Measures the amount of surface charge Potential between the diffuse layer and fixed layer is zeta potential Factors

Speed of particle
Strength of E field
Distance between the electrodes

http://nition.com/en/products/zeecom_s.htm

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Zeta potential vs pH

2 3 4 5 6 7 8 9 10

untreated ND acetone washed ND

zeta potential(mV) measured pH

Surface charge varies with pH Acetone wash does not change the surface charge a lot

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Future studies

Clean the nanodiamonds with strong acid at

high temperature

Study if the surface charge properties affects the

fluorescence of nanodiamonds through the emission scan with different pH in solution

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Acknowledgements

Mentor: Jayna Jones Advisor: David Awschalom Fellow INSET students and advisors Funding source: U.S. Air Force Reference: “Detonation nanodiamonds as UV radiation filter”

“The particle size‐dependent photoluminescence

f nanodiamonds”

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Energy band diagram

Red region

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Nanodiamond in solution

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Nanodiamonds photobleaching

Laser: 160mW, 532 nm

Photobleaching is the photochemical destruction of a fluorophore.

In microscope, photobleaching may complicate the observation of fluorescent molecules, since they will eventually be destroyed by the light exposure necessary to stimulate them into fluorescing. This is

especially problematic in time‐lapse microscopy.

600 1200 1800 2400 3000 40 60 80 100 Fluorescence (counts per millisecond) Time (s)

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Equation of zeta potential

µe= 2 ε ζ f(Ka)/3η

µe=the electrophoretic

mobility (µ/s)/(V/cm)

ζ= zeta Potential (mV)
ε= dielectric constant of the

medium

η= viscosity of the medium
F(ka)=Function of particle

radius

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Light spectrum

http://www.dnr.sc.gov/ael/personals/pjpb/lecture/spectrum.gif

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Questions

How is the orientation of spin relate to intensity of

fluorescence? Does it relate to the energy band?

Why single photon emission results in high

resolution imaging in application

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