摘要
Titanium dioxide (TiO 2 ) has been acknowledged as one of the efficient photocatalysts in the UV region. To extend the photo-absorption region toward visible lights, the TiO 2 nanowires enclosed with carbon shells (TiO 2 @carbon core-shell nanowires) were synthesized by a chemical vapor deposition technique at various temperatures from 650 to 950 °C. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that TiO 2 cores and carbon shells are rutile and graphitic structures, respectively. From Raman spectra, the peak intensity of the E g mode was observed to be redshifted with elevated growth temperatures due to the increase in oxygen vacancies in the TiO 2 @carbon core-shell nanowires. From X-ray photoelectron spectroscopy (XPS) results, the oxygen vacancies were strongly related to the Ti 3+ ions. The UV–visible spectroscopic studies show a possible decrease in photocatalytic energy from 3.1 to 2.7 eV for the TiO 2 @carbon core-shell nanowires, indicating that the light absorption was enhanced in the visible-light region. The optical absorbance results confirmed the presence of the mid-gap states due to the oxygen vacancies, which are responsible for the visible-light absorption. The photocatalytic activity of the TiO 2 @carbon core-shell nanowires studied by methylene blue (MB) dye degradation is effective under visible lights.