Topotactic reduction of oxide nanomaterials: unique structure and electronic properties of reduced TiO2 nanoparticles

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, TiO_1.83, that is oxygen rich compared with that of (100)-oriented single crystals reduced under the same conditions (TiO_1.48); the latter, however, have unique electronic properties compared with typical Ti₂O₃. The structure of TiO_1.83 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.