单层石墨烯带传输模式及其对气体分子振动谱的传感特性研究

Transmission mode of a single layer graphene and its performance in the detection of the vibration spectrum of gas molecular

自2004年石墨烯被成功制备以来,相关研究引起了广泛关注,其中,传感应用是一个重要方向.目前,有关石墨烯传感特性的研究都集中在低频,即根据分子附着引起的电导率变化来实现检测.然而,由于大部分分子吸附都会使电导率发生变化,因此该方法难以区分不同分子的特征.论文基于Kubo公式,结合数值仿真方法研究了单层石墨烯带的传输模式,分析了有效模式指数与模式传输特性的关联,证实了波导模的局域性和宽带特性.同时,利用一阶波导模与气体作用引起的传输强度的变化反演分子振动谱.以SO2,CO和C7H8气体的传感为例,基于本征分析验证了方法的有效性.结果表明,传输模式与分子作用能够产生耦合共振增强,并且其变化趋势与气体分子振动谱一致;在传输方向上,分子与传输模式的作用范围越大,则模式传输强度的变化越大.该研究为实现气体分子指纹的识别和检测奠定了理论基础.

Since its successful preparation in 2004, graphene has attracted a great deal of attention, and the sensing application is an important research field. But nearly all the researches about graphene sensors focus on low frequency band, of which the mechanism is mainly dependent on the detection of charge carrier concentration and conductivity variation induced by the absorption of molecules. However, due to the fact that most of the molecules absorbed on the surface of graphene will induce the change of conductivity, this method is incapable of distinguishing different molecules. Transmission mode of a single molecular layer is studied based on Kubo formula and combined with a numerical method. The relation between transmission properties and effective mode index is analyzed, and the broadband localization capability of the waveguide mode is demonstrated. Meanwhile, the variation of the transmission intensity which is due to the interaction between the first order waveguide mode and the gas is adopted to retrieve the vibration spectrum of molecules. Taking the sensing of SO2, CO and C7H8 as examples, the effectiveness of this method is verified based on eigenmode analysis. Results show that the transmission spectrum is consistent with the variation spectrum of gas molecules; besides, in the transmission direction, the larger the interaction range, the greater the attenuation of mode transmission intensity will be. This study has provided a theoretical foundation for the realization of the detection and identification of gas moleculan fingerprints.