TiO2 Quantum Dot-Functionalized Porous SnO2 for NO2 Detection

Ultrasensitive, highly responsive, and rapid detection of NO2 at ultralow concentrations remains a critical challenge for metal oxide semiconductor gas sensors. Here, TiO2 quantum dots were employed as functional modifiers to engineer porous SnO2, yielding a UV-enhanced TiO2/SnO2 heterointerface sensing material via a simple physical mixing route. The optimized 1 mol % TiO2/SnO2 sensor delivered a response of 5.8 to 100 ppb NO2 at 140 °C under UV illumination, with markedly reduced response and recovery times of 70 and 60 s, respectively, compared with those under dark conditions, together with excellent selectivity and good long-term stability. Such enhanced performance can be mainly ascribed to the synergistic effects of enhanced light absorption by TiO2 quantum dots, the formation of heterointerfaces, and the increased abundance of oxygen vacancies. This study establishes an effective quantum dot functionalization strategy for porous semiconductor gas sensors, offering a promising platform for ultralow-concentration NO2 sensing.