Guest-Mediated Defect Healing in Layered Metal Chalcogenides for Humidity-Resilient NO₂ Sensing

Precise defect control is pivotal for advancing nanomaterial performance, yet layered metal chalcogenides are plagued by coupled, multidimensional defects that degrade their electronic, optical, and chemical functions. Here, we introduce a guest-mediated defect healing (GMDH) strategy that concurrently heals multidimensional defects in layered chalcogenides under mild conditions. In a cascade process, hydrothermally synthesized SnS₂ nanosheets undergo vacuum-sealed annealing that expels intercalated guest molecules (e.g., thioacetamide), driving interlayer lattice rearrangement; simultaneously, thermal decomposition of these guests further replenishes sulfur vacancies. This one-route treatment avoids external sulfur sources and high temperatures, lowering defect density while improving crystal integrity and carrier transport. As a proof of concept, GMDH-treated SnS₂ enables trace NO₂ detection under high humidity with fast and reversible response (response time = 64 s), strong humidity tolerance (up to 90% RH), and long-term operational stability (180 days under 75% RH), directly linking simultaneous defect repair to device robustness. GMDH provides a general and scalable pathway for precision defect engineering in two-dimensional layered chalcogenides and underscores their promise for humidity-resilient, reliable electronic and sensing technologies.