Recent advances in engineering 2D transition metal dichalcogenides for high-performance gas sensing

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising materials for gas sensing due to their atomic thickness, high surface to volume ratio, and tunable electronic structure. This review surveys recent advances in TMD based gas sensors, with emphasis on synthesis routes such as chemical vapor deposition, liquid phase exfoliation, mechanical exfoliation, and plasma assisted functionalization, and explains how these processes control defect density and distribution, drive phase transformations, and tailor surface chemistry. We evaluate the sensing performance of key TMDs such as MoS₂, WS₂, MoSe₂, WSe₂ and metallic-phase/Janus variants, analyzing mechanisms such as charge-transfer, defect-mediated adsorption, and photoactivation. We focus on engineering strategies that raise sensitivity to ppb levels and sharpen selectivity. We also prioritize faster response and recovery and reliable operation at ambient temperature. The review also discusses scalable integration approaches, including thin-film and heterostructured sensor architectures, as well as implementation in flow-through reactors, wearable platforms, and IoT systems. This review integrates material design, performance metrics, and system-level engineering to outline a roadmap toward commercially viable, high performance TMD gas sensors.