Abstract
The need for highly sensitive toxic gas sensors is significant, and achieving this sensitivity is possible. Researchers have utilized density functional theory (DFT) computations to examine adsorption of different gas molecules (COX2, where X is F, Cl, or Br) over Au-doped and pristine graphene. This investigation aims to determine possibility of employing Au-doped graphene as a basis for gas sensors. Multiple adsorption positions and orientations were examined for each gas molecule. The configuration that exhibited the highest stability was identified, and adsorption energy (Eads) values, considering van der Waals (vdW) interactions, have been computed using NCI analyses. In addition, the electronic properties, including LUMOHOMO orbital density and charge transfer, were analyzed to acquire a deeper understanding of process by which adsorption occurs. Findings indicated that gas molecules under investigation exhibited weak adsorption on pristine graphene, with low Eads values. In contrast, Eads values of every gas molecule on Au-doped graphene displayed varying degrees of increase. Notably, COX2 exhibited a high sensitivity to Au-doped graphene. Furthermore, in the effect of doping Au into graphene, the Eads absorption of COCl2 gas has increased from 0.155 to 1.028 eV. This indicates the strong tendency of Au-doped graphene to interact with gas COCl2 compared to two other COX2 gas species. This strong adsorption can be ascribed to significant substantial charge transfer (CT) between COCl2 and Au-doped graphene and orbital hybridization. The charge transfer amount of the doped states has increased by more than double compared to the pure state. The band gap of Au-doped graphene has decreased from 2.14 to 1.83 eV due to the absorption of gas COCl2, indicating the highest amount of reduction compared to other gases. Moreover, the enhanced electrical conductivity of Au-doped graphene renders it more valuable and sensitive in the context of sensing COX2 gases.
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