Structural Characterization of Carbon‐Doped and Carbon‐Coated TiO ₂ Core–Shell Nanoparticles

ABSTRACT Carbon‐doped TiO ₂ nanoparticles were prepared by a facile carbothermal treatment at different temperatures. The synthesis was conducted in a rotary tube furnace under an acetylene/nitrogen gas flow. A detailed analysis of the morphology of the particles revealed a layered graphene structure surrounding the TiO ₂ core with a temperature‐dependent shell thickness of 1–1.5 nm. The material exhibits a significant shift in the Raman E _g(1) mode toward higher wavenumbers. High carbon contents were determined by X‐ray photoelectron spectroscopy. This led to the conclusion that in addition to the carbon in the shell, carbon is also incorporated into the TiO ₂ structure. Substitutional doping in favor of titanium or oxygen atoms could be excluded based on XPS measurements due to the absence of Ti–C bonds and the lack of changes in lattice parameters of the unit cell or microstrain. An interstitial incorporation of carbon is therefore most likely. Either the incorporation of carbon or the carbon shell suppressed the phase transition from anatase to the thermodynamically stable rutile which is expected above 600. Additionally, the process inhibits the crystallite growth at higher treatment temperatures.