Room Temperature Resistive NO₂ Sensor Based on SnS₂ Quantum Dots/Ti₃C₂T_x MXene Heterostructures

Detecting nitrogen dioxide (NO 2 ) at room temperature (RT) is crucial for advancing environmental monitoring technologies, enabling efficient and practical air quality assessment. Two-dimensional (2D) MXene nanomaterials, recognized for their large specific surface area (SSA), abundant functional groups, and tunable electrical properties, have attracted considerable attention as promising candidates for room temperature gas-sensing applications. However, despite their potential, challenges, such as low gas adsorption efficiency, limited sensitivity, and poor selectivity, hinder their broader application and development, highlighting the need for further research. Here, we introduce a zero-dimensional (0D)/2D heterojunction gas-sensitive structure by synthesizing SnS 2 quantum dot (QD)-sensitized Ti 3 C 2 T x MXene nanocomposites via a hydrothermal method. The carefully designed gas sensor exhibits a significantly enhanced response value (RV) of 5.83% for 10 ppm of NO 2 and a low detection limit of 500 ppb at RT, achieving an RV that is 5.8 times higher than that of pure Ti 3 C 2 T x . Additionally, the sensor demonstrates high sensitivity (0.76 ppm –1 in the 0.5–5 ppm range), excellent selectivity, and outstanding stability, with a performance degradation of only 3.2% over 4 weeks. The exceptional performance arises from the synergistic effects of the quantum confinement properties of SnS 2 QDs and the superior conductivity of Ti 3 C 2 T x, which together provide abundant active sites for gas adsorption and facilitate efficient charge transfer pathways. Furthermore, the formation of the heterojunction modulates the resistance, enhancing room temperature sensing capabilities. The synthesized nanomaterials offer significant potential for advancing the design of heterostructures that integrate 0D QDs with 2D nanomaterials, paving the way for highly efficient NO 2 detection at RT. Moreover, maintaining an optimal operating temperature further enhances the accuracy and reliability of real-time NO 2 monitoring systems.