Enhancement of CO detection in Al doped graphene

A principle of enhancement CO adsorption was developed theoretically by using density functional theory through doping Al into graphene. The results show that the Al doped graphene has strong chemisorption of CO molecule by forming Al−CO bond, where CO onto intrinsic graphene remains weak physisorption. Furthermore, the enhancement of CO sensitivity in the Al doped graphene is determined by a large electrical conductivity change after adsorption, where CO absorption leads to increase of electrical conductivity upon via introducing large amount of shallow acceptor states. Therefore, this newly developed Al doped graphene would be an excellent candidate for sensing CO gas. * To whom correspondence should be addressed. e-mail: [email protected] (S. Li), e-mail: [email protected] (Q. Jiang). † Jilin University ‡ The University of New South Wales 1 Solid-state gas sensors are renowned owing their high sensitivity, robustness and a wide range of applications as well as low cost and potential for miniaturization [1]. Carbon nanotubes (CNTs) is one of the promising nanoscale molecular sensors used to detect gas molecules with fast response time and high sensitivity at room temperature [2,3,4]. The semiconducting CNTs are sensitive to variation of electrical conductivity in the presence of gas molecules at the concentration range of ppb (parts per 10). However, higher sensitive sensor is desirable for the virtual applications of industrial, environmental and military monitoring. It was reported that the detectable range and sensitivity of the single wall carbon nanotubes (SWCNTs) can be widened and enhanced substantially through either doping technology or surface engineering [4,5,6]. For example, SWCNT coated with Pb nanoparticles has high sensitivity to H2 [5], SnO2/SWCNTs hybrid material shows an enhanced sensitivity to NO2 [6]. The high sensitivity of boron doped SWCNT to CO and H2O absorptions has been demonstrated [4]. Most recently, Al-cluster and Al doped SWCNT assembly were suggested to be promising systems for novel molecular sensors to NH3 [7] and CO [8], and the B doped SWCNTs are highly sensitive to the gaseous cyanide and formaldehyde molecules [9]. However, the devices with higher sensitivity to these toxic gases are apparently required for environmental safety issues both in workplaces and residential areas, especially in some industrial and military fields. Graphene based device may be a solution for ultra-high sensitivity gas sensor for such applications [10,11,12]. Similar to CNT, the working principle of graphene