Defected and Functionalized Germanene-based Nanosensors under Sulfur Comprising Gas Exposure.

Efficient sensing of sulfur containing toxic gases like HS and SO is of the utmost importance due to the adverse effects of these noxious gases. Absence of an efficient 2D-based nanosensor capable of anchoring HS and SO with feasible binding and an apparent variation in electronic properties upon the exposure of gas molecules has motivated us to explore the promise of a germanene nanosheet (Ge-NS) for this purpose. In the present study, we have performed a comprehensive computational investigation by means of DFT-based first-principles calculations to envisage the structural, electronic, and gas sensing properties of pristine, defected, and metal substituted Ge-NSs. Our initial screening has revealed that although interaction of SO with pristine Ge-NSs is within the desirable range, HS binding however falls below the required values to guarantee an effective sensing. To improve the binding characteristics, we have considered the interactions between HS and SO with defected and metal substituted Ge-NS. The systematic removals of Ge atoms from a reasonably large super cell lead to monovacancy, divacancies, and trivacancies in Ge-NS. Similarly, different transition metals like As, Co, Cu, Fe, Ga, Ge, Ni, and Zn have been substituted into the monolayer to realize substituted Ge-NS. Our van der Waals corrected DFT calculations have concluded that the vacancy and substitution defects not only improve the binding characteristics but also enhance the sensing propensity of both HS and SO. The total and projected density of states show significant variations in electronic properties of pristine and defected Ge-NSs before and after the exposure to the gases, which are essential in constituting a signal to be detected by the external circuit of the sensor. We strongly believe that our present work would not only advance the knowledge towards the application of Ge-NS-based sensing but also provide motivation for the synthesis of such efficient nanosensor for HS and SO based on Ge monolayer.