Phosphorene and phosphorene oxides as a toxic gas sensor materials: a theoretical study.

A systematic study of the adsorption of several harmful gases (CO2, NO, SO2, NH3y H2S) onto black phosphorene and three different black phosphorene oxides (BPO) is carried out through density functional theory calculations. In general, it is shown that BPOs are more suitable adsorbents than pure black phosphorene. Smaller values of adsorption energy correspond to CO2molecules, whilst those exhibiting larger ones are NH3, H2S, NO y SO2. It is found that SO2shows the greater difference in electronic charge transfer as well as the longer time of recovery among all species, being an electron acceptor molecule. Besides, it is revealed that physisorption induces changes of different order in the electronic, magnetic and optical responses of phosphorene systems involved. Greater changes in the electronic structure are produced in the case of NO adsorption. In that case, semiconductor nature and magnetization features of black phosphorene band structure become significantly modified. Moreover, a notorious effect of an externally applied electric field on the molecule adsorption onto BPOs has been detected. In accordance, adsorption energy changes with the applied electric field direction, in such a way that the higher value is favored through an upwards-directed orientation of NO y SO2adsorbates. Results presented could help to enhancing the understanding of BPOs as possible candidates for applications in gas sensing.