NEW PROCEDURES FOR THE PREPARATION OF CDS AND HETEROGENEOUS CR CDS PHASES IN HYBRID XEROGEL MATRICES - PORE STRUCTURE-ANALYSIS AND CHARACTERIZATION/

A CdS phase dispersed in a porous poly(1,4-phenylene)-bridged silsesqu ioxane (PPS) xerogel was prepared from a sol-gel solution containing C d2+ ions. Both wet and dried Cd2+-doped gels and xerogels were exposed to a sulfide source to produce ''low-dimensional'' microcrystalline C dS phases dispersed in the polysilsesquioxane xerogel. The CdS phase w as characterized by EDAX, electron diffraction, UV, XPS, and fluoresce nce analyses. The doping procedure produces xerogels with surface area s and average pore sizes that were somewhat lower and smaller that the undoped materials, but in all cases an open cell porous xerogel struc ture was retained. Related technology has been used to prepare dispers ed heterogeneous phases consisting of intimate mixtures of CdS and chr omium metal in a porous polysilsesquioxane xerogel. In this case, the chromium metal precursor, a sol-gel processable aryl tricarbonyl chrom ium(0) complex, is homogeneously incorporated into the xerogel matrix. A microcrystalline CdS phase was independently prepared by successive diffusion of Cd2+ and S2- ions in the dried xerogel. This was followe d by heat treatment under vacuum (120 degrees C, (1 mmHg) to liberate chromium atoms, which produced the mixed Cr/CdS phase in the xerogel m atrix. TEM images show domains rich in microcrystalline CdS and Cr/CdS clusters in the xerogel. The Cr and CdS crystalline phases in these x erogels were identified by both electron diffraction and EDAX experime nts.