N-doped TiO2 nanooctahedra, nanoparticles and nanospheres were successfully synthesized through nitrification of the corresponding TiO2 nanostructures in the presence of ammonia gas at 700 degrees C for 30 min. The crystal phase and compositions of N-doped TiO2 samples were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The product morphology was characterized with scanning microscopy (SEM) and transmission electron microscopy (TEM). UV-vis absorption results show that all the as-synthesized N-doped TiO2 samples present red-shift absorption up to similar to 410 nm, which can be ascribed to the addition energy level between TiO2 valence and conducion band. Surface areas of all samples were measured through nitrogen absorption-desorption isothermal. In order to evaluate the photocatalytic activity of N-doped TiO2 samples, photodecomposition for methyl orange (MO) was performed under UV-vis light irradiation for 30 min, indicating that N-doped TiO2 nanooctahedra with the exposed {1 0 1} crystallized surfaces show good photocatalytic behavior in comparison with other samples. (C) 2013 Elsevier B.V. All rights reserved.