A DFT study of In doped Tl2O: a superior NO2 gas sensor with selective adsorption and distinct optical response

Sensitivity and selectivity are important factors for Tl2O monolayer to be the sensitive material. In this work, the sensing performance of NO2 on pure and X-Tl2O (X = In, Cd, Y, Pb, Ga, Si) sheets has been detailed investigated by means of DFT. The results show that the doped systems have a better sensing performance for NO2 and it is most evident in the In-Tl2O substrate. And In-Tl2O has a unique response to NO2 with appropriate adsorption energy (-1.79 eV) and charge transfer (-0.51 e) which are far more than B-C3N (-1.15 eV, 0.44 e). Besides, although In-Tl2O monolayer and SO2 have formed the chemical bond, the adsorption effect of NO2 on the substrate hardly changes when the co-adsorption of SO2 and NO2 occurs on it. In addition, the reflectivity and optical absorption of the gas/In-Tl2O (gas = NO, NO2 and SO2) adsorption system are calculated, and the results indicate optical absorption and reflectivity of NO2/In-Tl2O system are all far greater than that of other systems in the visible and near infrared regions. So it is easy to be distinguished by infrared detection. These all show that the In-Tl2O is an excellent sensing material for NO2 detection.