Photoactivities of the carbon-containing nano-structured titanium dioxide (TiO 2 ) prepared using a modified sol–gel method as visible-light-responsive photocatalysts were studied. This research aimed to compare four carbon-containing TiO 2 samples, prepared in different conditions, with a commercial nano-structured TiO 2 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 TiO 2 nanoparticles prepared under calcinations at 200°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 TiO 2 , 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 TiO 2 .