SYNTHESIS AND CHARACTERIZATION OF SHELL/CORE NANOPARTICLES AND THE FABRICATION OF NANOPARTICLE THIN FILMS

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2012-08

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Abstract

Due to their unique optical and electronic properties, metal nanoparticles have been used as nanoscale materials for various applications in the fields of opto-electronics, solar cells, lithium ion batteries, gas sensors, and catalysis. Our research focuses on the synthesis of shell/core nanoparticles and the design of thin films that incorporate these nanoparticles. We have examined the stability of colloidal gold nanoparticles coated with tin oxide (SnO2) and silicon dioxide (SiO2), where the shell/core nanoparticles were dispersed in solution over wide range of pHs. The stabilities of the particles were monitored visually and by UV-vis spectroscopy, since these particles could potentially be used in harsh environments in applications such as chemical sensing and solar cells. The systematically designed experiments showed that the tin oxide-coated Au nanoparticles were more stable in basic solutions than the corresponding silica-coated Au nanoparticles.
We also developed a sol-gel-based approach to fabricate tin oxide semiconductor thin films with tin oxide-coated Au nanoparticles dispersed within the layer. These composite nanoparticles were dispersed homogeneously in a SnO2 sol-gel precursor because the SnO2 coating prevented aggregation of the metal core particles and enhanced their miscibility with the 2-propanol-based SnO2 sol-gel precursor. The morphologies, sizes, and/or dimensions of the composite nanoparticles and thin films were characterized by SEM, TEM, XRD, and UV-vis spectroscopy.
We also synthesized Zn(II)- and Sb(V)-doped SnO2-coated Au nanoparticles using a hydrothermal method. Antimony-doped tin oxide (ATO) and zinc-doped tin oxide (ZTO) are promising transparent conducting oxide materials due to their high mobility and optical transmittance. The sizes and morphologies of these unique particles were characterized by SEM and TEM, and the growth and nature of the metal oxide shell was evaluated by XRD, XPS, and UV-vis spectroscopy. Finally, we demonstrated that gold nanoshell-dispersed polymeric thin films could be fabricated via electrostatic layer-by-layer assembly. In this process, negatively charged gold nanoshells were adsorbed electrostatically on positively charged organic polymers that were deposited on transparent glass substrates. The SEM images verified that the gold nanoshells were homogeneously dispersed in the polymeric thin film. The optical properties of the nanoshell thin films were evaluated by UV-vis spectroscopy.

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Keywords

Core-shell, Tin oxide, Gold nanoparticles, Thin films, SnO2-coated nanoparticles, Silica-coated nanoparticles, Colloidal stability, Nanoshell

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