Ab-initio study of vacancy-defective aluminium nitride nanosheets as trifluoroacetonitrile gas sensor

Abstract

Trifluoroacetonitrile (CF3CN) is a decomposition product from the promising dielectric heptafluoro-isobutyronitrile (C4F7N) under partial discharge process, so can be used to detect failures in gas-insulated switchgear. In this work, we study through density functional theory (DFT) calculations the adsorption of CF3CN on pristine aluminium nitride nanosheets (AlNNS) and defective Al-vacancy (vAl) and N-vacancy (vN) AlNNS, in order to explore the potential of these nanomaterials as sensors for this gas. Our energetic analysis shows negligible adsorption energy for the pristine surface but strong interactions can be observed between the molecule and the monovacancy-defected surfaces, with adsorption energy values estimated to be about −2.2 and −3.1 eV for CF3CN/vN-AlNNS and CF3CN/vAl-AlNNS, respectively, which suggests chemisorption processes. Furthermore, our geometric and bonding studies revealed the formation of new N—Al interactions between gas and monovacancy-defected surfaces, with serious distortions for the vAl-AlNNS nanosheet. The electronic density of states and band structure analysis reveals moderate band gap variations after gas adsorption. In contrast, significant changes in the work function and the magnetic moment of defective AlNNS were computed after gas exposition, for all optimized adsorption configurations. Therefore, based on our results, vacancy-defected AlNNS could be suggested as possible material for CF3CN gas sensing.