Fine tuning and orientation control of surface Cu complexes on TiO2(110) premodified with mercapto compounds: the effect of different mercapto group positions

Abstract

Three-dimensional structures of vacuum-deposited Cu species formed on TiO₂(110) surfaces premodified with three mercaptobenzoic acid (MBA) isomers were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). We explored the possibility of fine tuning and orientation control of the surface Cu structures, including their coordination and configuration against the surface, according to the different mercapto group positions of the three MBA isomers (o-, m-, and p-MBA). Almost linear S–Cu–O (lattice O of TiO₂) surface compounds were formed on the three MBA-modified TiO₂(110) surfaces; however, the orientation of the Cu species on the o- and m-MBA-modified TiO₂(110) surfaces (40–45° inclined from the surface normal) was different from that on the p-MBA-modified TiO₂(110) surface (60° from the surface normal). This work suggests that the selection of a different MBA isomer for premodification of a single crystal TiO₂(110) surface enables fine tuning and orientation control of surface Cu complexes.