Electron Paramagnetic Resonance studies on silver atoms and clusters in regularly interstratified clay minerals

Phyllosilicates, regularly interstratified clay minerals, are objects of presented studies. The regularly interstratified clay minerals were loaded with silver cations, dried, irradiated at 77 K in a 60Co source with a dose of 4 kGy. After irradiation the EPR spectra of dehydrated trioctahedral Ag-smectite/chlorite (Ag-tri-Sm/Ch) and dioctahedral Ag-smetite/mica (Ag-di-Sm/M) recorded and analyzed. When dehydrated Ag-tri-Sm/Ch and Ag-di-Sm/M samples were exposed to water vapor and then irradiated at 77 K the EPR spectra recorded just after the radiation treatment and in the course of annealing are similar to those of dehydrated samples. On the contrary, the samples exposed to methanol vapor show completely different spectra after irradiation. The observed spectral lines were assigned to the Ag2+ and Ag33+ clusters. The effective scavenging of positive holes by methanol molecules, which limits the geminate recombination and increases the number of Ag0 atoms initiating the agglomeration process, is proposed to explain the formation of silver clusters with bigger nuclearity in the presence of methanol