Controlling the formation of silver nanoparticles on silica by photochemical deposition and other means.

Silver nanoparticles (Ag-NP) on silica were produced in aqueous solution by deposition of silver on colloidal silica in a small cuvette using radiation from a xenon-mercury lamp. Ag-NP were also synthesized on a much larger scale with low-level, long-term visible light irradiation for several months. In both cases, the nanoparticle production was monitored by the appearance of the surface plasmon resonance (SPR) band at around 410 nm. The growth of the nanoparticles was directly related to the time exposed to radiation, which could be tracked spectrophotometrically over time. We also investigated the possibilities of rapid nanoparticle production without the assistance of radiation though silver oxide by adding alkali hydroxide, which is a relatively unexplored approach for syntheses of Ag-NP on silica. The SPR absorption of Ag-NP was used as a tool in evaluating the size and shape of the resulting nanoparticles along with dynamic light scattering and transmission electron microscopy data. In order to better utilize and understand Ag-NP, we present various ways to control their production through initial concentration adjustments, irradiation effects, gravitational fractionation, sonication and silver oxide formation.