First - Principles Study On The Adsorption Of Gaseous Molecules By Graphene

Graphene has attracted enormous scientific and technological interests since the publication of Geim and Novoselov’s paper on graphene in Science in 2004. Due to its unique geometric construction and physicochemical properties, such as high surface area, excellent thermal and electric conductivity, and great mechanical strength, graphene becomes an important new material for numerous potential applications, ranging from nano electronic devices, solar cell technology, and gas sensors and so on. Graphene-based nanostructures are considered to have a potential application in sensors of various types. This is not only owing to the fact that a 2D crystal maximizes the interaction between the surface and adsorbates on the layer, but also due to the fact that a small change of carrier concentration can cause a notable variation of electrical conductivity. Besides, in order to improve the sensitivity for gases and the electronic structures in graphene, the methods of defect and doping are usually used. In this article, the calculations are performed within first-principle approach based on the density-functional theory (DFT) using the Vienna ab initio simulation package (VASP). We theoretically studied the stable consructions and the conductivity and magnetism change of chlorine adsorption configuration, formaldehyde adsorption configuration and sulfur dioxide adsorption configuration, respectively. Some important results are concluded as follows:(1) Graphene and B-doped graphene are not sensitive for Cl2 molecule because of weak physisorption. The other doped graphene for Cl2 molecule are strong chemisorption, and Ti-doped graphene and Au-doped graphene are the two most reactive ones in terms of Cl2 adsorption among all the doped graphenes. TiG can be used to detect this toxic molecule by detecting the conductivity change, and AuG can be used to detect this toxic molecule by detecting the conductivity and magnetism change.(2) B-doped graphene and N-doped graphene with all atoms in the same plane and physisorbed H2CO. Therefore, B-doped graphene and N-doped graphene are not sensitive for H2CO molecule. The other doped graphene for H2CO molecule are strong chemisorption, and Al-doped graphene and Mn-doped graphene are the two most reactive ones in terms of H2CO adsorption among all the doped graphenes. Al-doped graphene and Mn-doped graphene can be more suitable for detecting the conductivity and magnetism change before and after the adsorption of H2CO.(3) The interactions between SO2 molecules and intrinsic graphene, SW-defected graphene, Al-doped graphene, Al-doped SW defect combination are in turn increases. It is found that SO2 molecule are weakly adsorbed on the intrinsic graphene and SW-defected graphene, and the electronic properties were slightly changed upon the adsorption of SO2 molecule. In contrast, the SO2 molecule shows strong interactions with the Al-doped graphene and Al-doped SW defect combination, and the electronic properties were changed upon the adsorption of SO2 molecule. Compared with the Al-doped graphene adsorption system, the presence of SW defects enhance the stability of the Al-doped SW defect combination and make the adsorption of SO2 on Al-doped SW defect combination occur large change in the conductivity and magnetism of the detect-dopant graphene layers, which indicates that the Al-doped SW defect combination sheet can be more suitable for the detection of SO2 molecules.