The interactions of glycine (Gly) with TiO2, graphene (G), graphene oxide (GO), TiO2/G and TiO2/GO nano-composites were investigated by density functional theory (DFT). The results indicate that the interactions between Gly and TiO2 in TiO2/G nanocomposites are stronger than that between Gly and bare TiO2 surfaces, which suggests G helps to strengthen the interaction of amino acids with TiO2 surfaces. In TiO2/GO nanocomposites, the interactions of Gly and TiO2 are slightly weaker than that between Gly and bare TiO2 surfaces, which reveals that GO is not conducive to the interaction of amino acids with TiO2 surfaces. (C) 2014 Elsevier B. V. All rights reserved.