Thin Films Containing Metal Nanoparticles: Preparation and Characterization
S.H. Lee, T.R. Lee, A.J. Jacobson
University of Houston, US
Keywords: nanoshells, nanoparticles, layer-by-layer self assembly
Abstract:Gold shells grown on silica core nanoparticles have received much attention due to their unique and tunable optical properties. To synthesize these composite particles, the surface of the silica particles (~150 nm in diameter) were functionalized with (3-aminopropyl)trimethoxysilane (APTMS) and then seeded with small gold nanoparticles (e.g., 2 nm). The gold-seeded silica particles were coated with a thin layer of gold via solution-phase reduction of a gold salt. The resulting composite particles were ~200 nm in diameter with shells that were ~25 nm thick. The morphologies of the nanoparticles were characterized with SEM and TEM. Powder X-ray diffraction (XRD) demonstrated that the outer gold layers are composed of well-crystallized structures. Thin films containing the nanoparticles were developed by dip-coating techniques, using layer-by-layer self assembly. These uniformly dispersed composite nanoparticles were imaged by SEM, and the optical properties were analyzed by UV-vis spectroscopy, which showed strong absorptions ranging from the visible to the near-IR region. X-ray photoelectron spectra (XPS) were also obtained to determine the elements present and the oxidation states of these elements.