Selective Triethylamine Gas Sensor Based on a CdIn ₂ S ₄ @ZnIn ₂ S ₄ Heterojunction with a Hydroxyl Radical-Mediated Response Mechanism

To develop a sensitive and fast-response sensor toward triethylamine (TEA), a CdIn2S4@ZnIn2S4 heterostructure with well-defined nanoscale interfacial features was constructed via a one-step hydrothermal method. The resulting composite exhibits an improved sensing performance compared with the individual components. At 120 °C and 50 ppm TEA, the sensor delivers a response value of 87, with a response ratio S(TEA):S(trimethylamine) of 21.3, and response/recovery times of 19 and 10 s (with the assistance of an external current), indicating high sensitivity and selective response toward TEA. The improved sensing behavior is associated with the heterostructure providing abundant interfacial contact and a suitable surface reaction environment. ESR results suggest the possible involvement of ·OH radicals in the surface reaction process, while molecular simulations provide supportive insights into the reaction pathway, indicating that hydrogen abstraction at the α-C–H site of TEA is thermodynamically feasible. Overall, this work highlights the role of nanoscale heterostructure construction in modulating surface reaction behavior and suggests a feasible strategy for the design of amine-sensitive gas sensors.