Membrane Growth of Nanoporous Silicates via the Self-Assembly Monolayer

The self-assembly monolayer (SAM) method was used for membrane fabrication, in which Si wafers were treated separately with N-trimethoxysilylpropyl-n,n,n-tri-n-butylammonium bromide (TMSP-TBA) and N-trimethoxysilylpropyl-n,n,n-trimethylammonium chloride (TMSP-TMA) to form monolayers on the Si surfaces. To grow silicate membranes on the organosilyl-treated Si wafers, a series of silicate sols were prepared with composites of tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as silicate sources, and tetrapropylammonium bromide (TPABr) was used as an organic template. Their microstructures were investigated in detail by comparing them using SEM and XRD. The use of MTES hindered the formation of microporous channels in the calcined silicate samples. The calcined silicate samples became totally amorphous over 20% loading of MTES. In addition, their structural information was supported by spectroscopic (FT-IR and solid-state ²⁹Si NMR) analyses.