Near infrared light enhanced room-temperature NO2 gas sensing by hierarchical ZnO nanorods functionalized with PbS quantum dots

•Room-temperature NO2 sensors based on PbS/ZnO nanocomposites.•Near infrared (NIR) light was utilized in NO2 sensing for the first time.•NIR enhanced the radial modulation of the conduction channel of the ZnO nanorods. Here we report the near infrared light (NIR) activated room-temperature NO2 gas sensors based on ZnO/PbS nanocomposites. The nanocomposites were composed of PbS quantum dots (QDs)-decorated ZnO nanorods with an urchin-like hierarchical mesoporous structure. The nanocomposites showed NIR adsorption derived from the PbS QDs with a narrow band gap. Compared to the pristine ZnO nanorods, the ZnO/PbS nanocomposites-based sensor with the optimal loading amount of PbS exhibited higher response and quicker response/recovery rates to parts per million (ppm) level of NO2 at room temperature under NIR illumination. Moreover, the sensor exhibited full reversibility, low detection limit, good selectivity and long-term stability to NO2. Photoluminescence and I–V characterization revealed the electron transfer from the excited PbS QDs to ZnO nanorods under NIR illumination, which enhanced the radial modulation of the conduction channel of ZnO nanorods, leading to the improved NO2 sensing performances of the ZnO/PbS nanocomposites at room temperature.