X-ray absorption spectroscopy analysis of formation and structure of Ag nanoparticles in soda-lime silicate glass

Ag nanoparticles of 2.8–7 nm mean size were fabricated in soda-lime glass of varying iron oxide content by Na+/Ag+ ion exchange and subsequent thermal treatment. Fe2+ ions have been identified as reducing agent for Ag ions by analysis of the X-ray absorption near edge structure at the Fe K-edge and of the extended X-ray absorption fine structure (EXAFS) at the Ag K-edge. EXAFS analysis accompanied by electron microscopy investigation has shown that crystalline Ag particles in glass with high content of iron oxide (0.865% Fe2O3) exhibit a lattice dilatation. Furthermore, the calculated data demonstrate that with decreasing particle size lattice disorder and anharmonic effects, and hence also the thermal expansion coefficient, increase. This size effect is more distinctly pronounced for glass samples of reduced thickness as well as upon gradual thermal treatment applied for particle preparation. The results indicate substantial influence of the surrounding glass matrix on formation, structure and thermodynamic properties of Ag particles.