Mesoporous silica films as catalyst support for microstructured reactors: Preparation and characterization

Mesoporous silica thin films with hexagonal and cubic mesostructure have been deposited by the evaporation induced self-assembly assisted sol–gel route on microchannels etched in a Pyrex® 7740 borosilicate glass substrate. Prior to the synthesis, a 50 nm TiO2 film has been deposited on the substrate by atomic layer deposition from titanium tetrachloride and water to increase adhesion of the mesoporous films to the walls of the substrate. The mesoporous films were produced by templating a silica precursor (TEOS) with the non-ionic surfactant Pluronic F127 (EOxPOyEOx, EO, ethylene oxide; PO, propylene oxide; x = 106; y = 70). The effect of the channel aspect ratio on the uniformity of the silica films was investigated in the channels with a depth of 50 (mu)m and with a width of 100–250 (mu)m. Depending on the microchannel geometry, the thickness along the channels varies in the range of 0.3–1.0 (mu)m. The most uniform films across the whole channel cross-section were obtained at the width-to-depth ratio of 3. Afterwards, the mesoporous films were impregnated with an ether–dichloromethane suspension of [PPN]2[Ru10Pt2C2(CO)28] mixed-metal cluster precursor to obtain well-dispersed, isolated and anchored bimetallic nanoparticles of 3–4 nm in diameter.