▎ 摘　　要

The exploration of novel sensors for NO2 detection is particularly important in material and environmental sciences. In this work, the HOMO-LUMO gap of graphene, Ti- or N-doped graphene is investigated by DFT methods. The adsorption of NO2, NO, and O-2 on Ti- or N-doped graphene of different sizes is also explored. Results reveal that the interactions between gases (NO2, NO, and O-2) and Ti- or N-doped graphenes is not affected by the size of graphene. The doped Ti greatly improves the interactions between gases and graphene whereas the doped N has no effect on those interactions. The HOMO-LUMO gap of Ti-doped graphene can be modulated by adsorption of the gases. The cross effect of the NO and O-2 is also investigated, and it is demonstrated that Ti-doped graphene has specific interactions with NO2. Thus, Ti-doped graphene can be a candidate for NO2 sensor materials. Furthermore, doping the graphene with Ti or N improves the sensitivity of the sheets toward NO2, which can be trapped and detected by the intrinsic graphene. Efficient sensors are rationally designed to diversify their applications in environmental science and engineering. (C) 2015 Elsevier Inc. All rights reserved.