Formation of TiO2 nanoparticles by reactive-layer-assisted deposition and characterization by XPS and STM.

Stoichiometric TiO2 nanoparticles (1-5 nm) were prepared by reactive-layer-assisted deposition (RLAD), in which Ti was initially deposited on a multilayer of H2O (or NO2) on a Au(111) substrate at approximately 90 K. The composition and atom-resolved structure of the nanoparticles were studied by XPS and STM. The approximately 5 nm TiO2 particles had either a rutile or anatase phase with various crystal facets. STS of the nanoparticles suggests size-dependent electronic structure. These well-defined nanoparticles can be used in molecular-level studies of the reactions and mechanisms of photocatalytic processes on TiO2 nanoparticle surfaces.