Achieving the Sensing Property of Hg0 Molecules on Black Phosphorene Nanosheets Using Anisotropy as a Response Signal

Elemental mercury (Hg⁰) molecules have received great attention as a neurotoxic environmental pollutant. However, the chemical inertness of Hg⁰ molecules hinders discovery by gas sensors. In this work, we explore the gas sensing property of Hg⁰ molecules on black phosphorene nanosheets. The results show that the Hg⁰ molecules can form chemical adsorption on the black phosphorene nanosheet with a suitable adsorption energy of 0.85 eV. Chemical bonds can be formed between Hg⁰ molecules and the black phosphorene nanosheet via the orbital interaction. Although the chemical adsorption slightly changes the band gap of 0.08 eV and the work function of 0.11 eV, the adsorption of Hg⁰ molecules will remarkably influence the behavior of frontier orbitals. The difference of electron effective mass decreases from 9.54 to 6.82 times between armchair and zigzag directions; as a result, when applying a bias of 2.0 V, the anisotropy of current remarkably decreases from 41.34 to 7.67 times between armchair and zigzag directions, which can be an effective response signal to detect Hg⁰ molecules. This work not only reports a gas sensor for Hg⁰ molecules but also provides a physical factor of anisotropy to monitor environmental pollutants.