The mechanical and photochemical properties of titania coated silica nanowires

Dense layers of silica nanowires, grown directly on Au-coated Si substrates via simple active oxidation processes, were coated with a Ti-alkoxide solution and annealed at different temperatures. Mechanical measurements of the resulting anatase and rutile titania coated silica nanowire samples showed that although the volume fraction of nanowires increased with increasing indentation load, a comparative global effective elastic modulus and hardness could be calculated. The rutile coated samples were found to be more robust under low indentation loads, but more readily suffered from brittle failure at higher loads. The photochemical activity of the coated layers, measured by the photodissociation of deuterium oxide vapor, was found to increase with ultra-violet exposure time, most likely due to the desorption of atmospheric N2 or alkoxide residues. This increase in photoactivity was found to be more pronounced for the anatase coated nanowire samples, consistent with the anatase phase having a greater effective reactive surface.