Topotactic reduction of oxide nanomaterials: unique structure and electronic properties of reduced TiO2nanoparticles

Abstract

Reduced titanium oxide nanomaterials are of great scientific and industrial interest. Herein we analyze corundum-like titanium oxide nanomaterials synthesized by topotactic reduction of TiO2 nanoparticles. The structure is probed using X-ray pair distribution functions, and the electronic properties are examined using hard X-ray photoelectron spectroscopy and electron energy loss spectroscopy. Topotactically reduced nanoparticles have a composition, TiO1.83, that is oxygen rich compared with that of (100)-oriented single crystals reduced under the same conditions (TiO1.48); the latter, however, have unique electronic properties compared with typical Ti2O3. The structure of TiO1.83 was found to contain both the unique Ti2O3 and Ti4O7, and the conductivity was lower than the single crystal-derived materials due to interparticle resistance. The findings confirm that topotactic reactions can create nanomaterials having unique structures and properties that cannot be realized in bulk materials.