Enhanced charge separation efficiency of sulfur-doped TiO2 nanorod arrays for an improved photoelectrochemical glucose sensing performance

Improving the electron-hole separation efficiency and accelerating the reaction kinetics of semiconductors are effective methods for improving the photoelectric catalytic activity of TiO2. In this study, sulfur-doped TiO2 (S-TiO2) nanorod arrays grown on a fluorine-doped SnO2 transparent conductive glass were successfully prepared using a microwave-assisted method for the photoelectrochemical (PEC) biosensing of glucose. The charge separation efficiency on S-TiO2 was evaluated by subjecting the prepared material to X-ray photoelectron spectroscopy, PEC measurements, and theoretical calculations based on density functional theory. The results clearly showed that the sulfur impurity state could not only reduce the bandgap but also serve as "stairs" to facilitate the electron transfer. Sulfur atoms that were successfully doped into TiO2 significantly promote the separation of the photogenerated carriers and improve the photocatalytic activity of the photoelectrode. Consequently, excellent glucose-detection sensitivities of 54 and 19 mu A mM(-1) cm(-2) were achieved for fragments with sizes of 0.1-1.5 and 2-12 mM, respectively.