Theoretical Study Of The Absorption Of Topic Gaseous Molecules On Gold-doped (Au-doped)Single-walled (8,0) Carbon Nanotube (SECNT)

Single-walled carbon nanotubes (SWCNT), which were first discovered by Iijima, especially, SWNT modified by gold atom significantly have attracted intense interest because of their novel gas sensitivity properties in recent years.In order to explore a novel sensor to detect the topic gaseous molecules, we investigate reactivities of the intrinsic and gold-doped (Au-doped) single-walled (8,0) carbon nanotube (SWCNT) with CO and HCN by using the Density Functional Theory (DFT)based upon the first-principle. All calculations are used the DMol3package of Materials Studio4.0.The study mostly included three aspects.(1) Geometry structure of the (8,0) intrinsic and gold doped (Au-doped) single-walled carbon nanotube (SWCNT) has been optimized. We find that the distance between carbon atoms is consistent with those reported, which shows that our calculation are reliable(2) The absorption behavior of CO on the (8,0) Semiconducting intrinsic and gold doped (Au-doped) single-walled carbon nanotube (SWCNT) has been investigated by the density functional theory because of its superior sensitivity to many toxic gases. It is shown that CO molecules can be absorbed to Au atoms on the wall of Au-doped SWCNT with bingding energies as high as2.1eV, and can attract lager charge transfer0.23. Compared with the intrinsic SWCNT, The Au-doped SWCNT presents high sensitivity to CO in terms of the calculated geometrical structures and electronic properties, Furthermore, the calculated electron density of two representative adsorption positions show that Au-doped SWCNT electron clouds overlap more on the top of carbon adsorbed CO. By comparison to oxygen absorption on SWCNT, we infer that molecular CO absorbed on Au-doped SWCNT can induce significant change in the conductivity of SWCNT. So Au-doped SWCNT is expected to be a potential candidate for detecting the presence of CO.(3)To search for a novel sensor to detect the presence of HCN, we investigate reactivities of the intrinsic and gold-doped (Au-doped) single-walled (8,0) carbon nanotube (SWCNT) with HCN using density functional theory calculations. Compared with the intrinsic SWCNT, the Au-doped SWCNT presents high sensitivity to HCN. This is attributed to the strongly chemical interaction between the electron-rich nitrogen atom of HCN and the electron-scarce gold atom of the doped SWCNT according to the analysis of the adsorption energy, geometry structure, charge transfer. To further evaluate the electronic properties of these intrinsic and Au-doped SWCNT systems, we also calculated their HOMO-LUMO energy gap. By comparison with the intrinsic SWCNT, The energy gaps (Eg) between the highest-occupied molecular orbitals (HOMO) and the lowest-unoccupied mo-lecular orbitals (LUMO) becomes smaller, Which is more conducive to cause the changes of electrical conductivity. Au-doped SWCNTs are expected to be a potential candidate for detecting the presence of HCN.