| In this thesis, 3,5-Dihydroxybenzylalcohol (DHBA) based dendrimers of generations 0-5 (G0-G5) were used as templates in the construction of hybrid silica networks via a simple sol-gel condensation methodology. Two types silane reagent Si(NMe2)4 and ClSi(NEt2)3 were used to react with the periphery situated hydroxyl groups in these dendrimers, followed by hydrolysis and polycondensation, leading to highly cross-linked, porous silica based hybrid materials. The removal of dendrimer templates was achieved via in situ or acid hydrolysis. In situ removal of dendrimer templates was carried out as the use of ClSi(NEt 2)3, while in the case of Si(NMe2)4, the dendrimers were subsequently removed upon treatment with HCl. The detailed studies of silica network structures and surface morphology before and after removal of dendrimers and salt were carried out using techniques including solid-state NMR, FT-IR spectroscopies, transmission electron microscopy (TEM), and nitrogen adsorption (BET), showing that the aggregation of DHBA based dendrimers controls the evolution of the network structure and their pore sizes. The resulting dendrimer templated silica networks were found to be water repellant on their surfaces with a hydrophilic interior.;The application of silica networks synthesized using DHBA based dendrimers as templates was successfully demonstrated in tailoring the preparation of silver metal nanoparticles. Due to the internal and external environment of the silica networks, G1-3 silica networks wet slowly with aqueous silver acetate, resulting in chemisorption of silver ions with internal silanol groups, and followed by the growth of silver oxide nanoparticles as higher local water content around silver ions inside the networks. G4 silica networks with residual of dendrimer templates mixed with aqueous silver acetate solution. Silver ions that were chemisorbed with silanol groups were reduced photolytically to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles exclusively. |
