Room temperature NH3 detection in agricultural greenhouses using SnS2/MoS2@c-MOF sensors: Experimental and theoretical analysis

Abstract

Intrinsic SnS₂, MoS₂, and conductive metal organic frameworks (c-MOF) were synthesized through a hydrothermal method, followed by in situ synthesis of c-MOF on the surfaces of SnS₂ and MoS₂ to achieve various ratios of SnS₂@c-MOF and MoS₂@c-MOF composites. The successful preparation of these materials was confirmed using comprehensive characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Subsequently, planar sensors based on SnS₂@c-MOF and MoS₂@c-MOF were fabricated, and their responses to NH₃ concentration, recovery time, and stability were rigorously assessed. Comparative gas sensing tests indicated that the SnS₂@c-MOF-based sensor exhibited superior sensitivity towards NH₃, demonstrating stability and reliability. A response of 16.65 % was observed for 10 ppm NH₃, with a theoretical limit of detection as low as 419.05 ppb, demonstrating selectivity for NH₃ at room temperature. Furthermore, first-principles calculations utilizing density functional theory provided detailed insights into the adsorption capabilities of the SnS₂@c-MOF composite material, analyzing parameters such as adsorption energy, distance, charge transfer, energy gap, density of states distribution, deformation charge density distribution, and frontier molecular orbital distribution. This research lays a robust foundation for the development of high-performance SnS₂@c-MOF sensors aimed at detecting toxic NH₃ emissions generated in greenhouse environments.