The Influence of Water Content on the Growth of the Hybrid-Silica Particles by Sol-Gel Method

This paper investigates the change in size and morphology of the silica network with the change of water content by sol-gel method. Methyl triethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) were used as co-precursors. The results reveal that the morphology controllable silica network are prepared by changing water content, the size of silica network is in the range in 17–176 nm. There are two ways for the silica nanoparticles to grow in the sol media, condensing with the newly hydrolyzed precursor named monomer-addition model or condensing with the existing silica structure called controlled-aggregation model. As the molar ratio of water/siloxane increases from 1 to 12, the growth process change from the aggregation of oligomers to the condensation between oligomer and hydrolyzed precursor, and the final morphology of silica nanoparticles changes from a network structure to a monodisperse particle structure. When the water content reaches a very high value with the molar ratio of water/siloxane ≥12, the growth process of silica nanoparticles is dominated by the monomer-addition mechanism. The addition of MTES as co-precursor favors the formation of the network structure.