First-principles study of the heavy metals adsorption on SnS2 and Janus monolayers

Heavy metal contamination in water bodies caused serious threats to health and ecosystems, necessitating adsorbing materials for rapid decrease in heavy metals. Therefore, we have conducted a first-principles study on the rapid decrease of heavy metals (Hg, As, Pb) by SnXS (X = S, O, Se) monolayer. Compared with SnS₂, Janus structure SnXS (X = O, Se) narrows the band gap, and increases the electronic interactions between SnXS (X = O, Se) and heavy metals (Hg, As, Pb), thus exhibiting excellent adsorption capacity. In detail, the minimum increase in adsorption capabilities for SnOS and SnSeS are 67.6 % and 27.2 %, respectively. Moreover, the optical properties indicate that at the wavelength of 1550 nm, the refractive indexes of SnSeS reduced after adsorbing As and Pb. Similarly, at the wavelength of 1310 nm, the refractive index of SnOS reduced after adsorbing Hg. Hence, SnXS (X = O, Se) shows a prominent refractive index change characteristic, which has the potential as a functional nanomaterial in the field of optical fiber heavy metal ion detection.