Mesoporous structure development during calcination of titania-doped mesoporous silica thin films is characterized by in situ grazing-incidence small-angle Xray scattering (GISAXS). Varying amounts of titania (≤6 mol %) are incorporated in cetyltrimethylammonium bromide (CTAB)-templated films by two methods in this study: dispersion of titania in the silica matrix and fixing titania at the pore surface by complexation of the titania precursor with a sugar-based cosurfactant, dodecyl maltoside (C 12 G 2 ). Before calcination, films templated with only CTAB display a mesoporous structure with a mixture of in-plane two-dimensional (2D) hexagonal and randomly oriented porous structure, while the C 12 G 2 -complexed film possessed randomly oriented mesostructure only. Both methods yield a final structure of hexagonal close-packed pores orthogonally oriented to the substrate after calcination at 500 °C. This is attributed to weak Si−O−Ti bonds, which allow sintering to occur at 500 °C, combined with unidirectional thermal contraction of the film in the vertical direction. Anisotropic stress and annealing of the films allow the randomly oriented pores to merge vertically and form channels with a pore diameter of 2.3 ± 0.3 nm. Titania doping greater than 1% is required for this transformation in films with no C 12 G 2 surfactant used, while transformation was observed for films with C 12 G 2 complexation even at low (0.005%) titania doping, perhaps accentuated by orientational disorder introduced by the sugar surfactant.

The transport of two redox probes, 1,1′-ferrocenedimethanol (FDM, hydrophilic) and 1,1′-dioctadecyl-4,4′-bipyridinium dibromide (DBD, hydrophobic), through ionic liquidfilled and/or functionalized silica nanoporous thin films is compared as a function of pore size (2.5 and 8 nm diameter pores). Electrochemical impedance spectroscopy (EIS) was used to measure the permeability of these aqueous probes through the bare silica films and silica films with pores containing a physically confined ionic liquid (IL, 1-butyl-3-methylimidazolium hexafluorophosphate (Functionalization of the nanoporous thin films with an IL-like group provides a barrier to the hydrophilic redox probe (a 40-fold decrease in permeability relative to bare 2.5 nm porous silica films), with only a 50% corresponding decrease in the permeability of the hydrophobic probe. The selectivity to hydrophobic solutes suggested by the barrier properties of IL-functionalized silica is less pronounced in the films with the larger 8 nm pores. Physically confining an IL in the pores of both bare and IL-functionalized pores results in similar transport as the corresponding non-IL filled pores. The ability to tune solute transport through nanoconfined ILs using pore size and surface functionalization is critical to the design of composite thin films for IL-based separation and energy storage applications.