Novel insights into the unique intrinsic sensing essences of 2D tin chalcogenides for ethanol: From hexagonal SnS2 to orthorhombic SnS

Abstract

Introducing orthorhombic SnS phase into two-dimensional (2D) hexagonal SnS2 crystal to form in-plane heterojunctions has become a promising approach to facilitate the sensitivity of SnS2 towards trace gases. However, its surface sensitization mechanism remains to be exploited in addition to the heterointerface effect. Hence, to dig into it, we explored the surface adsorption of SnS and SnS2 from unique surface electron configurations by combing experimental, computational and bionic approaches. Taking ethanol vapor as the target gas, orthorhombic SnS shows rapid detection of trace ethanol with a sub-ppm level at room temperature (RT). In contrast, hexagonal SnS2 is more suitable for detecting ethanol vapor with much higher concentrations (above 50 ppm). First-principles calculations and porcupine quill models further reveal that unlike the inactive symmetry of electrons on SnS2 surface, the rotational symmetry breaking of the stereochemically-active SnS surface leads to the oriented rearrangement of its surface electrons, which greatly facilitates the adsorption of trace ethanol molecules on SnS. On these basis, we renew the design concept of SnS–SnS2 in-plane heterostructures. This work reveals the structure-property relationship between the crystalline structures and gas-sensitive characteristics of 2D tin chalcogenides from a brand-new perspective, and helps the design and research of novel lateral heterostructures.