SILVER NANOCRYSTALS IN SILICA BY SOL-GEL PROCESSING

Silver nanocrystal doped silica films were prepared by the sol-gel pro cess. The sol was prepared from 1:0.12:12:0.2:6:7 molar ratios of C2H5 )(4):AgNO3:H2O:HNO3:(C3H7OH)-H-n:(C4H9OH)-H-i. The glassy, highly tran sparent film with high dopant concentration (silver/silicon atomic rat io = 0.12) was successfully prepared by the dip-coating method. After drying in air at 60 degrees C for 30 min, samples were heat-treated, i n air, at 300, 350, 400, 450, 500 and 550 degrees C using 30-100 min s oaking periods for each step in a cumulative heating procedure. Measur ements on the films were made by ultraviolet-visible and infrared spec troscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry and transmission electron microscopy. Mechanisms of silve r colloid formation in the densified silica matrix with respect to the thermal treatment are discussed. To understand the formation of silve r nanocrystals from the silver silicate network, the corresponding dop ed bulk gel samples were analyzed by X-ray diffraction and differentia l scanning calorimetry.