Silver doped ORMOSIL-an investigation on structural and physical properties

초록

Doping of classical silicate glass prepared by sol-gel technique by Ag or other nanometer size particles have made a major stride in past decade. But studies of metallic particle incorporated organically modified silicates (ORMOSIL) are quite scarce. The present work attempt to study the effect of Ag doping on the structural physical properties of poly(dimethylsiloxane)[PDMS] modified silica xerogels. The choice of tetraethoxysilane[TEOS] and PDMS as the starting inorganic and organic components respectively, for the preparation of ORMOSIL was dictated by the siliarity in their backbone structure (-Si-O-). Ag nano particles were incorporated by two routes: (i) directly into the sol by adding calculated amount of AgNO3 prior to gelation, and (ii) in this case preformed porous matrix was obtained first and then Ag doping was done by immersion of that matrix in AgNO3 solution for several days and subsequent heat treatment. Microstructure (SEM, TEM, XRD), particle size distribution, infared response (FTIR) and density have been studied. The merits and demerits of two methods have been discussed. It was found that exposure to humid air transforms the samples from transparent to opaque. This is, however, found to be reversible when treated above 300℃. This phenomenon exhibits its potential to be used as humidity sensor.