Photoactivities of the carbon-containing nano-structured titanium dioxide (TiO2) prepared using a modified sol-gel method as visible-light-responsive photocatalysts were studied. This research aimed to compare four carbon-containing TiO2 samples, prepared in different conditions, with a commercial nano-structured TiO2 powders. The prepared titanium dioxide powders were analyzed using Raman spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy. It is found carbon-containing TiO2 nanoparticles prepared under calcinations at 200 degrees C exhibited high photocatalytic activity for decoloring of methylene blue and the removal of nitrogen monoxide under both ultraviolet and visible-light illumination. The calcination temperature and incorporated carbons affect the particle size and lattice structure of TiO2, and hence the photoactivities. The superior photocatalytic effects were attributed to the carbon-containing mixed anatase and rutile phase in the crystal structure of the TiO2. (C) 2007 Elsevier B.V. All rights reserved.