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 w ith metal salts, hydrolysis, polycondensation, formation of powder, an d subsequent thermal treatment first in oxidizing and second in reduci ng atmosphere. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measure ments revealed sizes of metallic particles between 1 and 20 nm, depend ing upon processing conditions. The magnetic properties were investiga ted using the electron paramagnetic resonance spectroscopy in the temp erature range between 4 and 300 K. The variation of the intensity of t he resonance line with the temperature can be approximated by the Curi e law indicative for the quantum size effect. (C) 1998 Elsevier Scienc e B.V.