First Principles Calculations Of The Adsorption Properties Of SO₂ Molecules On Graphene

Since the single graphene has been prepared by Geim and others at the University of Manchester in 2004,graphene has been widely used in sensors,semiconductor devices,nanoscale devices and biological medicine because of its completely two-dimensional crystal structure and good electrical,optical and magnetic properties.Graphene has good specific surface area and good adsorption performance for gas.It has important application value in gas sensors.Based on the application of graphene in gas sensors,we study the adsorption properties of SO₂ gas on graphene by first principles calculation.First of all,we use the Castep module of Materials Studio software to create 3×3×1intrinsic graphene supercell,and optimize the ground state structure.On the basis of the optimized eigengraphene,the relationship of 0 degrees,90 degrees and-90 degrees between the SO₂ and the plane of the intrinsic graphene is constructed,and the SO₂ is placed in three high symmetric positions（B,H and T）of graphene,and then we get 9 systems named M1-M9.We optimize the 9 systems and get their stable structures.The calculated results show that the M8,where the SO₂ molecule is in T high symmetry point,and the angle between the SO₂ and graphene is 90 degree,is the most stable.The calculation for M8 indicates that when graphene material is intrinsic graphene,it is not suitable for detector material.Finally,on the basis of M8,the doping calculation of a graphene with Al,N and B atoms was studied.The geometric structure,energy band and state density of the doped M8 structures were analyzed.The results show that doping can change the electronic properties of graphene.In the Al and B atom doped systems,the carrier type is hole,and the valence band of the system moves up through the Fermi level.In the N atom doped system,the carrier type is electron,and the conduction band of the system moves down through the Fermi level.After doping with Al,N and B atoms,the M8 system changes from the original semiconductor to the conductor,which enhances the conductivity of the system.And N doping has the greatest influence on the conductivity of the system.