Carbon doping of self-organized TiO2 nanotube layers by thermal acetylene treatment

Self-organized layers of TiO2 nanotubes were formed by electrochemical anodization of Ti in a HF/Na2HPO4 electrolyte. The tubes were treated at 500 degrees C under a mixed flux of N-2 and acetylene (C2H2). The samples were characterized using SEM, XRD and photoelectrochemical measurements. The results show that the acetylene treated tube layers exhibit a significant photoresponse over the whole range of visible light up to the near-IR region (1.5 eV). This carbon doping treatment at comparable mild conditions does not lead to any structural damage to the morphology of the nanotubes.