Scientific Publications 2004

U

Uetsuka H, H Onishi, MA Henderson, and JM White. 2004. "Photoinduced Redox Reaction Coupled with Limited Electron Mobility at Metal Oxide Surface." Journal of Physical Chemistry B 108(30):10621-10624. Abstract Photoinduced oxidation of an organic adsorbate was examined on an atomically flat surface of titanium dioxide by scanning tunneling microscopy combined with macroscopic analysis of desorbed products. The rate of oxidation was coupled with limited surface mobility of photoexcited electrons, and thereby spatially modulated on the surface exposed to oxygen gas. The dimension of the modulations as small as a few lattice constants of the oxide demonstrates that photoexcited electrons are localized to this extent on the surface covered by adsorbed chemicals.

Uetsuka H, MA Henderson, A Sasahara, and H Onishi. 2004. "Formate Adsorption on the (111) Surface of Rutile TiO2 ." Journal of Physical Chemistry B 108(36):13706-13710. Abstract The (111) surface of rutile TiO2 was prepared with argon-ion sputtering and vacuum annealing at 970 K. Scanning tunneling microscope observation revealed nanometer-scale domains of (1 x 1) and (1 x 2) phases covering the surface. Formic acid was dissociatively adsorbed on the surface at room temperature. The recombination and decomposition temperatures of adsorbed formate were similar to those reported on rutile surfaces of different orientations. The CH-related and COO-related stretching modes probed by high-resolution electron energy loss showed two types of formate. The wavenumbers of the vibrational modes can be interpreted with a mixture of monodentate, bidentate, or bridge form of adsorption. The number density and limited mobility of formate evaluated in microscope topography supports monodentate and bidentate forms.