refractive index sensitivity of dye-doped silica-coated gold nanorods in various organic solvents...
TRANSCRIPT
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Refractive Index Sensitivity of Dye-Doped Silica-Coated Gold Nanorods In Various
Organic Solvents Kayla Love
Langston University
Dr. Katherine Willets Research Group
Department of Chemistry and Biochemistry, University of Texas at Austin
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Importance of Nanoparticles
Noble metal nanoparticles have optical properties that can be beneficial for
• biological applications
• surface enhanced spectroscopy
• catalysis
Where do these optical properties come from?
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Plasmon
Plasmon: a collective oscillation of surface conduction electrons in materials with a negative real and small positive imaginary dielectric constant.
• The plasmon provides the color for a nanoparticles. • The plasmon resonance is sensitive to the local refractive index.
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Key Terms
• Refractive index: also called index of refraction is a measure of the bending of a ray of light when passing from one medium into another.
• UV-Vis Spectrometer: measures the amount of light that is absorbed by a molecule.
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Experimental Setup
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Purpose of Study
• It is known that silica coated AuNRs have a linear wavelength response to increasing refractive index.
n max
Do we still maintain a linear response if we include dye in the silica shell of gold nanorods rinsed in various organic solvents?
Langmuir 25 (2009) 9441- 9446
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Overview Of Purpose
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Nanoparticle Shape
• The wavelength for a nanoparticle shape becomes smaller as the curvature of a metal nanoparticle gets shorter.
• Nanospheres appear at 530 to 550 nm and Nanorods appear between 650 and 850 nm
850 800 750 700 650 600 550 500(nm)
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Au Nanorods• Prepare AuNR seed solution from a mixture of sodium
borohydride, chloroauric acid, and cetyltrimethylammonium bromide (CTAB).
• Prepare growth solution from a mixture of chloroauric acid, CTAB, ascorbic acid, hydrochloric acid, and silver nitrate.
• Mix the growth solution with the diluted seed solution.
Transmission Electron Microscopy (TEM) image of AuNR UV-Vis Spectrum
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Etching
• Add AuNR solution with hydrochloric acid and heat in water bath at 55° Celsius.
• Monitor the blue shift over time.
Time
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Dye-Doped Silica Coating
Synthesis Procedure •Mix AuNR solution with tetraethyl orthosilicate (TEOS) in methanol and NaOH to form a porous silica shell •Nile red dye is added to the reaction mixture for dye doping.
•The pores allow solvent to access the AuNR core
Nano Lett. 9, (2009) 3896- 3903.
TEM images of dye-doped silica-coated AuNRs
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Refractive Index Sensitivity UV-Vis spectra of dye-doped silica-coated AuNRs in different solvents.
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Refractive Index Sensitivity
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Significance
One would no longer be stuck having to chose between two excitation source because now you can use either.
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Summary
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Conclusion
• The dye did alter the bulk UV-Vis Spectra• Maintained the linear trend between the
refractive index and the wavelength of gold nanorods rinsed in various organic solvents
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Future Studies
Conduct test to determine whether nile red dye is capable of leeching out of the pores of the silica shell and into the solution.
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References• Chen, Huanjun, Lei Shao, Kat Choi Woo, Tian Ming, Hai-Qing
Lin, and Jianfang Wang. "Shape-Dependent Refractive Index Sensitivities of Gold Nanocrystals with the Same Plasmon Resonance Wavelength." The Journal of Physical Chemistry C 113 (2009) 17691-7697
• Mayer, Kathryn M., Seunghyun Lee, Hongwei Liao, Betty C. Rostro, Amaris Fuentes, Peter T. Scully, Colleen L. Nehl, and Jason H. Hafner. "A Label-Free Immunoassay Based Upon Localized Surface Plasmon Resonance of Gold Nanorods." ACS Nano 2 (2008) 687-92
• Ming, Tian, Lei Zhao, Zhi Yang, Huanjun Chen, Lingdong Sun, Jianfang Wang, and Chunhua Yan. "Strong Polarization Dependence of Plasmon-Enhanced Fluorescence on Single Gold Nanorods." NanoLetters 11 (2009) 3896- 3903
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Acknowledgments
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Questions?