Determination of Absolute Coverages for Small Aliphatic Alcohols on TiO2(110)

The absolute coverages of water and small aliphatic alcohols (C1-C4) were determined on TiO2(110) using a combination of temperature-programmed desorption and liquid nitrogen cooled quartz crystal microbalance measurements. The absolute saturation coverages of water on Ti4+ and bridging oxygen, O-b, sites are found to be equal to 1 monolayer with respect to the number of Ti4+ and/or O-b sites (1 ML equivalent to 5.2 x 10(14) cm(-2)) in good agreement with prior studies. The saturation coverages of primary alcohols on Ti4+ sites are found to be approximately constant and equal to 0.77 ML. This indicates that the increasing length of the alkyl chains does not contribute to added steric hindrance. Additional steric hindrance is observed with increased branching as shown for secondary alcohols and tertiary t-butanol where the saturation coverage decreases to 0.62 and 0.44 ML, respectively. On O-b rows, a monotonic decrease of the alcohol coverages is observed for both increasing length of the alkyl chains and the chain number.