Engineering a surface functionalized Pt@SnS2/Ti3C2Tx MXene sensor with humidity tolerance and high sensitivity at room temperature for NH3 detection†

The design of hierarchical heterostructures that can detect volatile organic compounds (VOCs) at room temperature with good selectivity, sensitivity, and humidity tolerance is an intriguing and practically useful area of research. In this study, Pt@SnS₂/MXene with a 0D@2D/2D hybrid structure was successfully fabricated by selectively etching Ti₃C₂T_x MXene with HF and following this with SnS₂ solvothermal growth and finally decorating with Pt nanoparticles. Decoration of few layered vertically grown SnS₂ nanoflakes with rich active sites provided an electron reservoir that promoted the selectivity, conductivity, and stability of the MXene-based ternary heterostructure during sensing applications. Post-functionalization with trimethoxypropylsilane (TES) formed a monolayer on the ternary heterostructure of Pt@SnS₂/MXene by self-assembly, improved moisture resistance and sensitivity, and maximized sensor durability. Interfacial contact of the TES functionalized mixed metal interface facilitated charge transport and the spectral separation required for NH₃ sensing at room temperature (R_a/R_g = 22.7, 10 ppm NH₃), which was 14.2, 12.6, 8.1, and 3.3-fold greater higher than those of MXene, SnS₂, SnS₂/MXene, and Pt@SnS/MXene, respectively. The functionalized heterostructure exhibited high response, remarkable relative response (98.7%), a low theoretical detection limit (23 ppb), and long-term stability (nearly 30 days). Furthermore, TES functionalization protected the sensor from humidity and the sensor sensitivity was ascribed to a Schottky barrier and p–n junction at the Pt@SnS₂/MXene heterostructure interface. Superior sensing responses were retained at various humidity levels due to the hydrophobicity of TES alkyl chains. In addition, TES captured free electrons on the sensing surface, and thus, maximized the width of the electron depletion layer. The functionalized Pt@SnS₂/MXene heterostructure-based template offers a potential means of constructing highly sensitive and durable gas sensors suitable for practical NH₃ responsive, flexible wearable electronics.