一氧化氮在氧、氮掺杂石墨烯表面吸附的光学特性研究

Study on the micro-mechanism and optical properties ofnitric oxide adsorption on graphene surface

利用基于密度泛函理论的第一性原理平面波超软赝势计算方法,对一氧化氮(NO)分子在石墨烯表面上吸附的光学特性进行了理论研究,计算了石墨烯表面顶位、桥位和空位3个位点吸附NO分子的吸附能、Mulliken分布、差分电荷密度、态密度和光学性质。研究结果表明,单O掺杂、单N掺杂和O-N双掺杂的石墨烯表面均易吸附NO分子,其吸附方式是化学吸附;3种掺杂均会在石墨烯的费米能级附近形成新的杂质能级,为电子跃迁提供帮助,提升石墨烯的光学性能;在可见光360~780 nm范围内,O-N双掺杂石墨烯表面C-N键桥位吸附NO分子的光学性能最优,其吸收系数和反射系数的峰值较未掺杂时分别提高了约1.40倍和1.84倍。工作加深了对石墨烯表面吸附NO分子的理解,为基于石墨烯材料的NO传感研究提供了理论支持。

In this paper,the microscopic mechanism and optical properties of nitric oxide(NO)molecules adsorbed on the surface of graphene were studied theoretically by using the first principles of plane wave ultra-soft pseudopotential calculation method based on density functional theory.In order to obtain more accurate results,the effects of dispersion interaction,long-range electron correlation effect and Van der Waals force are taken into account.The exchange correlation functional of DFT-D and generalized step approximation of PBE is used to optimize the geometric structure.The plane wave ultra-soft pseudopotential method is used to describe the interaction between electron and ion.The Kohn-Sham equation and the energy functional are solved by self-consistent method.According to the three adsorption sites on the surface of graphene-top site,bridge site and vacancy site,the adsorption model of NO molecules on the surface of 14 kinds of graphene was constructed.The adsorption energy,Mulliken distribution,differential charge density,state density and optical properties of NO molecules adsorbed on graphene surface were calculated.The results show that NO molecules are easily adsorbed on the surface of single-O doped,single-N doped and O-N double-doped graphene by chemical adsorption.All three kinds of doping will form a new impurity level near the Fermi level of graphene,which will help the electronic transition and improve the optical properties of graphene.In the range of visible light 360-780 nm,the optical properties of NO molecules adsorbed by C-N bond bridge site on the surface of O-N double-doped graphene are the best,and the peak absorption coefficient and reflection coefficient of O-N double-doped graphene are increased by about 1.40 times and 1.84 times,respectively,compared with that of undoped graphene.This work deepens the understanding of the process of NO molecule adsorption on graphene surface and its microscopic mechanism,and provides theoretical support for the study of NO sensing based on graphene materials.