| Abstract
| - Surfactant-templated silica thin films are potentially important materials for applications such as chemicalsensing. However, a serious limitation for their use in aqueous environments is their poor hydrolyticstability. One convenient method of increasing the resistance of mesoporous silica to water degradationis addition of alumina, either doped into the pore walls during material synthesis or grafted onto the poresurface of preformed mesophases. Here, we compare these two routes to Al-modified mesoporous silicawith respect to their effectiveness in decreasing the solubility of thin mesoporous silicate films. Directsynthesis of templated silica films prepared with Al/Si = 1:50 was found to limit film degradation, asmeasured by changes in film thickness, to less than 15% at near-neutral pH over a 1 week period. Inaddition to suppressing film dissolution, addition of Al can also cause structural changes in silica filmstemplated with the nonionic surfactant Brij 56 (C16H33(OCH2CH2)n∼10OH), including mesophasetransformation, a decrease in accessible porosity, and an increase in structural disorder. The solubilitybehavior of films is also sensitive to their particular mesophase, with 3D phases (cubic, disordered) possessingless internal but more thickness stability than 2D phases (hexagonal), as determined with ellipsometricmeasurements. Finally, grafting of Al species onto the surface of surfactant-templated silica films alsosignificantly increases aqueous stability, although to a lesser extent than the direct synthesis route.
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