Microstructure and optical absorption property of Au nanoparticles and Au, Ag bimetal nanoparticles separately dispersed Al2O3 composite films

Au nanoparticles and Au, Ag bimetal nanoparticles separately dispersed Al2O3 composite films were prepared by sol-gel method. The microstructure and optical property of the films were studied by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV/vis) absorption spectra. Gold in Au/Al2O3, and gold and silver in AuAg/Al2O3 composite films exist in the state of metal Au and Ag, and they are basically spherical nanoparticles. The optical absorption peaks of Au nanoparticles due to the surface plasmon resonance (SPR) in Au/Al2O3 films were observed in the range of 530-550 nm, and their absorptions intensity with the increase of Au contents. There are two SPR peaks corresponding to Au and Ag nanoparticles, which were observed in the range of 530-550 nm, 400-420 nm, respectively. The intensities of two SPR peaks change with various molar ratios of Au and Ag nanoparticles. The SPR peaks of Au nanoparticles intensity, and those of Ag nanoparticles weaken with the increase of Au contents, and decrease of Ag contents. The SPR speaks of Au and Ag nanoparticles shift slightly to the longer wavelength with an increase of Au and Ag contents in AuAg/Al2O3 composite films.