SnS monolayers based heavy metal sensors: DFT and NEGF analysis

Abstract

Monitoring heavy metals helps prevent heavy metal contamination from affecting human health. However, existing monitoring technologies encounter challenges in real-time detection. Using density functional theory and non-equilibrium Green's function method, sensing capacities of SnS monolayer towards heavy metals are analyzed by adsorption energy, charge transfer, energy band structure, the density of states, differential charge density, recovery time, and transport performance. SnS monolayers exhibit high selectivity and good sensitivity of 13527% and 368860% for detecting As and Pb at the coverage of 1, respectively. With recovery times of 2.99 s for As and 76.44 s for Pb at 598 K, SnS monolayers can detect As or Pb at ambient temperature and be reused at high temperatures. SnS monolayers can selectively detect As and Pb through their response peaks at different bias voltages. SnS monolayers can detect Cd with a sensitivity of 442% in the concentration as low as coverage 1, when desorb at a recovery time of 31.2 μs at 298 K, showing strong potential for ambient temperature sensors for Cd. SnS monolayers require Hg in high concentration, as high as coverage of more than 7, to reach the detection limit. The highest sensitivity of SnS monolayers towards Hg is 326% at the condition of a 0.6-V bias voltage and 8 coverage. Overall, our research provides fresh insight into low-cost, environmentally friendly materials for online heavy metal detection.