PHYSICAL STRUCTURE, OPTICAL RESONANCE, AND SURFACE-ENHANCED RAMAN-SCATTERING OF SILVER-ISLAND FILMS ON SUSPENDED POLYMER LATEX-PARTICLES

A new approach to producing SERS activity on dispersed particles is de scribed. Silver islands are deposited onto submicron latex and glass p articles, and the particles are dispersed into aqueous suspensions. Th e physical structure of the metal islands is investigated by transmiss ion electron and atomic force microscopies and compared with the optic al absorption and SERS efficiencies for several particulate substrates and silver deposition methods. Thermal vapor deposition onto poly(met hyl methacrylate) particles produced a latex that supported silver isl ands with optical properties and SERS activities similar to silver-isl and films deposited on flat surfaces. Like silver colloids, the materi al could be handled as an aqueous suspension to generate SERS from a d ispersed surface; unlike silver colloids, however, the optical and phy sical properties of the material were stable upon storage for periods as long as several months.