1. Origin, characterization and reactivity of silanol groups in MCM-41 and MCM-48. 2. Semiconductor inclusion within the pores of MCM-41, MCM-48 and zeolite HY

The utility of crystalline mesoporous hosts for the inclusion of a variety of semiconductor materials was examined. These materials possess three features that provide a unique opportunity to synthesize novel composite semiconductor nano materials: periodic structure, large channel diameters and accessible wall hydroxyls that are chemically reactive. The purposes of this research are (i) to use this novel combination of host properties along with a variety of semiconductor precursor materials to assess the potential of the host as both a reactive surface and passivating container for the confinement of semiconductor crystallites; and (ii) to then quantum confine semiconductors in a unique periodic array. A variety of precursor materials were evaluated. Germane, digermane, trimethylgermaniumchloride, tetraethylgermane, disilane, trimethylsiliconchloride, trimethylgallium and lead iodide were included over a range of temperatures by chemisorption and physisorption from both the gas and liquid phases. Prior to the formation of these composites the generation and nature of the wall silanol groups in the siliceous MCM-41 and MCM-48 were explored since these sites were to be used as internal probes and points of attachment for the fabrication of semiconductor/mesoporous composites. The wall silanols were generated by template removal at both low temperature (LT) (room temperature to 95{dollar}spcirc{dollar}C) and at high temperature (HT) (calcination to 500{dollar}spcirc{dollar}C). Using {dollar}sp1{dollar}H and {dollar}sp{lcub}29{rcub}{dollar}Si NMR, PGAA, TGA and TMSiCl as a probe for accessible surface silanol groups the LT material had a surface accessible population of silanols of 1.8 per nm{dollar}sp2{dollar} and approximately 1.6 per nm{dollar}sp2{dollar} for inaccessible wall silanols. The accessible surface silanol density of the HT material was found to be 1.44 per nm{dollar}sp2{dollar}. The formation of semiconductor/mesoporous composites was monitored by TEM, XRD, {dollar}sp1{dollar}H and {dollar}sp{lcub}29{rcub}{dollar}Si NMR, UV-VIS, room temperature photoluminescence (PL). TEM established the formation of filaments contained with the channels of MCM-41 in both the Ge and PbI{dollar}sb2{dollar}/mesopore composites. Size dependent UV-VIS and PL were established in the GaAs and PbI{dollar}sb2{dollar} mesopore composites.