Characterization of water/AOT/benzene microemulsions during photoreduction to produce silver particles

Abstract

Colloidal dispersions of silver (Ag) particles were prepared by the photoreduction of silver perchlorate (AgClO 4) in water/AOT/benzene water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), water and benzene. Formation mechanisms of Ag particles prepared in the presence of benzoin by photoreduction from Ag +-containing w/o microemulsions were investigated by UV–vis, transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS) measurements. By a combination of TEM and EXAFS results, Ag particles show a metallic nature after the photoreduction and the diameter of Ag particles ranges between 5 and 30 nm. In situ time-resolved SAXS measurements show that the integrated rate equation can be applied in the reduction process of Ag + ions to Ag 0 atoms, and the autocatalytic Ag particle growth proceeds in the association process of Ag 0 atoms during the photoreduction of Ag +-containing w/o microemulsions. The nanometer-sized water droplets microemulsified by AOT in benzene continuous-phase regulated the size of Ag particles, and the size and shape of water droplets were retained during the Ag particle formation.