ENVIRONMENT EFFECTS ON SURFACE-PLASMON SPECTRA IN GOLD-ISLAND FILMS POTENTIAL FOR SENSING APPLICATIONS

The effects of the local dielectric environment on the surface-plasmon resonances of annealed gold-island films as a potential for sensing a pplications are studied experimentally and modeled theoretically. Gold -island films were annealed at 600 degrees C to produce spheroidal sha pe particles that exhibit well-resolved resonances in polarized, angle -resolved, absorption spectra. These resonances are shifted in differe nt amounts by the depolarization effect of the surrounding medium (liq uids with various refraction indices). Cross-section calculations base d on nonretarded, single-particle, dielectric interaction for these va rious configurations are presented and are found to be in good agreeme nt with the experimental observations. The results show an interesting potential for biosensing or environmental monitoring applications. (C ) 1998 Optical Society of America.