改性石墨烯HCN气敏特性的第一性原理研究

First principles study of the HCN gas sensitivity of modified graphene

为了寻求高灵敏度的石墨烯基的HCN气体传感器,采用基于密度泛函理论的第一性原理计算方法系统地研究了纯净石墨烯(PG)、单空位缺陷石墨烯(SVG)及14种元素Li、B、N、Mg、Al、S、Ca、Ti、Cr、Mn、Fe、Co、Ni、Pt替位掺杂石墨烯(XG)对HCN气体分子的吸附和气敏特性.研究结果表明,HCN分子和PG、BG、NG、SG间由于较小的吸附能和较大的吸附距离而隶属于较弱的物理吸附,且该分子的吸附未能引起费米能级附近态密度的变化,故上述基底对HCN分子吸附的敏感性差;单空位缺陷的引入尽管增大了基底与HCN分子间的结合,但分子吸附前后体系的电子结构几乎不变;HCN分子化学吸附于LiG、MgG、AlG、CaG、TiG、CrG、MnG、FeG、CoG、NiG和PtG.其中该分子的吸附导致LiG从金属过渡到半导体,MnG从半金属过渡到半导体,可见电导率明显减小,而其他基底仍旧保持原来的性质.因此,LiG和MnG更适合作为检测HCN分子的石墨烯基底.该研究将为设计新型石墨烯气体传感器提供理论参考.

To search for high sensitivity of graphene-based gas sensors for HCN gas,the adsorption and gas sensitivity of hydrogen cyanide （HCN） molecules on pristine graphene （PG） and modified graphene,including single vacancy defect graphene （SVG） and Li,B,N,Mg,Al,S,Ca,Ti,Cr,Mn,Fe,Co,Ni and Pt substitutional doped graphene （XG）,have been systematically explored by using first-principles analysis based on density functional theory （DFT）.It has been found that HCN undergoes weakly physisorption on PG,BG,NG and SG due to low adsorption energy and large adsorption length,and HCN adsorption failed to cause the change of the density of states near the Fermi level.Therefore,the substrates （PG,BG,NG and SG） are not sensitive to HCN molecule.Although the introduction of single vacancy defect increases interaction between the substrate and HCN molecule,the electronic structure of the system hardly change before and after HCN adsorption.HCN molecule is chemisorbed on LiG,MgG,AlG,CaG,TiG,CrG,MnG,FeG,CoG,NiG and PtG.Among them,LiG transforms from metallic to semiconducting and MnG transforms from half-metallic to semiconducting owning to HCN adsorption,suggesting that the electrical conductivity decreases obviously.However,other substrates still retain original property.Therefore,LiG and MgG are more suitable for HCN detection among all of mentioned substrates.Our work provides theoretical reference to design novel graphene-based gas sensor.