AMORPHOUS POLYSILSESQUIOXANES AS A CONFINEMENT MATRIX FOR QUANTUM-SIZED PARTICLE GROWTH - SIZE ANALYSIS AND QUANTUM-SIZE EFFECT OF CDS PARTICLES GROWN IN POROUS POLYSILSESQUIOXANES

Microporous polysilsesquioxane xerogels were prepared by sol-gel proce ssing of 1,4-bis(triethoxysilyl)benzene and 1,6-bis(triethoxysilyl)hex ane. By the BET and BJH methods, the surface areas and average pore di ameters of phenyl- and hexyl-bridged polysilsesquioxane (PPS and HPS) xerogels were found to be 531 and 533 m2/g and 34 and 43 angstrom, res pectively. These amorphous materials are potential candidates for a no vel confinement matrix for the growth of quantum-sized semiconductor p articles or metal clusters. The xerogels were treated successively wit h Cd2+ and S2- ions, resulting in the formation of quantum-sized CdS p articles. Confirmation of their identity was established by high-resol ution EDAX and by analysis of the resulting electron diffraction patte rn. The diameter of quantum-sized CdS doped into PPS was calculated by the Brus method (from the blue shift of the UV absorption band edge o f the CdS particles) to be 56 angstrom. HRTEM images permitted direct and independent evaluation of the size distribution of CdS particles. The measured diameters of CdS doped into PPS and HPS were approximatel y 60 and 90 angstrom, respectively. These findings provide support for the use of amorphous, microporous polysilsesquioxanes as a confinemen t matrix for the growth of quantum-sized semiconductor particles over a range of particle sizes.