Size distribution and EPR of silver nanoparticles in SiO2 matrix

Metallic silver nanoparticles were prepared by the sol-gel method in a SiO2 matrix. The process includes complexation of silicon alkoxides with metal salts, hydrolysis, polycondensation, formation of powder, and subsequent thermal treatment first in oxidizing and second in reducing atmosphere. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measurements revealed sizes of metallic particles between 1 and 20 nm, depending upon processing conditions. The magnetic properties were investigated using the electron paramagnetic resonance spectroscopy in the temperature range between 4 and 300 K. The variation of the intensity of the resonance line with the temperature can be approximated by the Curie law indicative for the quantum size effect. (C) 1998 Elsevier Science B.V.