Exploring Adsorption Of R6G Molecule On Graphene By The First-principle Calculations

Graphene has attracted the researchers’ much attention in both theoretical and experimental investigations since it was found for the first time in 2004. Graphene has many excellent properties. Firstly, the electronic property is important, which derives from its unique electronic structure. Secondly, graphene has good thermal conductivity, high strength, large specific surface area, excellent magnetic properties and so on. It is so many excellent properties that lead graphene to having a very wide range of applications, such as electrode materials, sensors, supercapacitors and so on. In addition to the intrinsic excellent properties, the electronic structures of graphene can be tailored by adsorption and doping, and thus it is possible to modify its properties and expand its applications. Consequently, it widely attracted researchers’ interests. For example, graphene can be used as substrate materials to attract atoms or small gas molecules on it, especially the adsorption of inorganic small molecules, such as hydrogen, ammonia and so on, which graphene can be functional and its application can be expanded. However, there are a few researches about adsorption of organic macromolecules on graphene. For example, R6G(Rhodamine 6G) is a kind of organic dye molecules, and graphene can be used as a substrate to enhance the Raman signal of R6 G molecule, but the interaction about between R6 G molecule and graphene is not very clear. The research about R6 G molecule adsorption on defective graphene and functionalized graphene are very rare. Therefore, it is very meaningful to take a systematic investigation about the adsorption of R6 G molecule on perfect graphene, defective graphene and functionalized graphene surface and their interaction.In this thesis, we will explore the adsorption of R6 G molecule on perfect graphene, defective graphene and functionalized graphene surfaces as well as their interaction by first principles method based on density functional theory(DFT). The package used in this thesis included DMol3 and DFTB +.Through the formation enthalpy, electronic density difference, electronic density of states, orbital distribution, population analysis and electron transport properties, we analyzed the stability and electronic properties of R6G-graphene. The thesis contains following three parts:1. In the first part, we studied the adsorption of R6 G on perfect graphene, intrinsic defect graphene surfacesto explore the influence of introducing defects into grapheneon adsorption of R6 G molecule. Our calculated results showed that the adsorption of R6 G on perfect graphene was physical adsorption. However, the adsorption of R6 G on different intrinsic defects graphene could be physical adsorption or chemical adsorption depending on defects.2. In the second part, we studied the adsorption of R6 G on perfect graphene or defect graphene surfaces modified by O or OH to explore the influence of functionalizing graphene on R6 G adsorption behaviour. Our results induced that the perfect graphene modified by O/OH was reduced due to R6 G molecule adsoption. The physical adsorption or chemical adsorption could occur when R6 G molecules adsorpting on defects graphene/doped graphene modified by O/OH. However, they could not be reduced.3. In the third part, we studied the adsorption of R6 G on B/N-doped graphene to explore the influence of B or N doping on R6 G adsorption behaviour. Our results showed that the adsorptions of R6 G on B/N-doped graphene were physical adsorption. Chemical adsorption could only occur on B-doped monovacancy graphene surface.