Local work function analysis of Pt/TiO_2 photocatalyst by a Kelvin probe force microscope

Nanometre-sized Pt clusters were prepared on a TiO_2(110)-(1 × 1) surface, and the lateral distribution of work function was examined by using a Kelvin probe force microscope. Local work function on the Pt clusters was smaller than that on the surrounding TiO_2 surface. Assuming that the dipole moments which perturb work function are produced by uneven electron distribution, the decrease of the work function indicates electron transfer from the clusters to the TiO_2 surface. After decomposition of pivalate anions on the surfaces by UV irradiation, the work function increased on some Pt clusters. It is known that holes photoexcited in TiO_2 attach to pivalate anions to cause a decomposition reaction. Hence the increase of the observed work function by UV irradiation can be ascribed to the trapping of the accompanying electrons to the Pt clusters

An atomic force microscope study of vanadium-benzene sandwich clusters soft-landed on self-assembled monolayers

Multiple-decker vanadium-benzene sandwich clusters Vn(benzene)n+1 produced by a laser-vaporization synthesis method were soft-landed onto self-assembled monolayers of alkanethiol (C18H-SAM) and fluorinated alkanethiol (C10F-SAM) at 200 K. Noncontact atomic force microscopy has been used to examine the resulting adsorption states of the clusters landed on the SAMs at room temperature. For each SAM substrate, the aggregates of the deposited clusters were observed at the vacancy islands and near the steps of the SAM surface. The result indicates that, at room temperature, the clusters landed on the SAM substrate thermally diffuse on the surface to form columnar-shape islands around the defect sites of the SAM surface