Doping
with impurities as well as introducing oxygen vacancies has been recognized
as an important means to enhance photocatalytic activity of TiO2 under visible-light irradiation. Here we report that simple
ethanol impregnation followed with mild heat treatment (150–400
°C) can color TiO2 nanoparticles and enhance visible-light
photocatalytic activity of the material. The coloration and photocatalytic
activity for β-naphthol and rhodamine B (RhB) degradation were
observed to be dependent on heat-treatment temperature, and the highest
activity as well as the most coloration was obtained at temperatures
around 200 to 250 °C. Comprehensive analyses based on X-ray photoelectron
spectroscopy (XPS) and electron paramagnetic resonance (EPR) investigations
as well as first-principle density functional calculation suggest
that the simple ethanol impregnation treatment leads to the generation
of oxygen vacancy on TiO2 surface which should be responsible
for the coloration and enhanced photocatalytic activity.