Mn-N-codoped TiO2 nanocrystal photocatalysts responsive to visible light were synthesized by a simple sol-gel method and calcined at different temperatures. The catalysts with different Mn contents were characterized by XRD, BET, UV-vis DRS, XPS and ESR analyses and their photocatalytic activities for Rhodamine B degradation were studied under visible light irradiation. The results showed that the codoping of Mn and N ions inhibited the growth of crystalline size and the transformation from anatase to rutile phase. The XPS results showed that the introduction of a small amount of Mn facilitated further N uptake. Mn-Ti0(2) and Mn-N-TiO2 exhibited strong visible light absorptions at 400-650 nm. Mn-TiO2 showed significant photocatalytic activity under visible light irradiation compared to pure TiO2, and the activity was further enhanced by codoping Mn and N into TiO2. The highest photocatalytic activity was achieved on 0.(2)5%Mn-N-TiO2 calcined at 400 degrees C. The synergistic effect of Mn and N ions narrowed the band gap of TiO2 and inhibited the recombination of the photogenerated electrons and holes, leading to a great improvement in the photocatalytic activity in the visible light region. (C) 2014 Elsevier B.V. All rights reserved.