SAXS and XAFS Analysis in Forming of Metal Nanoparticles in Water-in-scCO₂ Microemulsions

Metal particles of silver (Ag) and copper (Cu) have been synthesized in the presence of Aerosol-OT (AOT) or fluorinated surfactants in water-in-scCO2 microemulsions by the chemical reduction of AgClO4 and Cu(ClO4)2. The formation of Ag particles by the photo-reduction using UV-light have been confirmed by in-situ UV-Vis, X-ray absorption fine structure (XAFS), and small angle X-ray scattering (SAXS) measurements. Cu particles have also been prepared by the addition of a reducing reagent sodium borohydride, and the electronic structure of Cu ionic species has been investigated after reduction in the water-in-scCO2 microemulsions. The average size of aggregates of Ag particles in the microemulsions by means of in-situ SAXS measurements also has been estimated.