Optical properties of thin films of Au@SiO2 particles

Homogeneous films of Au@SiO2 particles have been deposited on glass as a pr ototype 3D "artificial solid" using the LBL method. The film thickness is c ontrolled by the number of dipping cycles and is measured by AFM. Each cycl e results in approximately one monolayer of particles being deposited. The particle films are dense, but disordered. The optical properties of the res ulting thin films have been analyzed as a function of the particle volume f raction, which is controlled through the silica shell thickness. We find th at the surface plasmon peak position in films with volume fractions up to p hi > 0.5 is accurately predicted by the Maxwell-Garnett model. The films ex hibit remarkably uniform, transmitted colors and display metallic reflectio n at low angles of incidence, even at low volume fractions. The films can b e annealed at T > 500 K to provide extremely stable, optical films.