Design of PbS quantum dots-PbMoO4-MoS2 ternary nanocomposites for highly selective NO2 sensing at room temperature

Traditional resistive semiconductor gas sensors suffer from high operating temperature and poor selectivity. Herein, a highly selective NO2 sensor based on PbS quantum dots-PbMoO4-MoS2 ternary nanocomposites operating at room temperature was fabricated to address the issue. The ternary nanocomposites were synthesized via an in-situ method, yielding PbS quantum dots (QDs) with an average size of ~10 nm and PbMoO₄ nanoparticles in the 10-20 nm range, uniformly distributed on ultrathin MoS₂ nanosheets with an average thickness of ~7 nm. The optimized sensor demonstrated a significant improvement in response to 1 ppm NO₂ at 25°C, achieving a response of 44.5%, which is approximately seven times higher than that of the pure MoS₂-based sensor (6.4%). The sensor also achieved relatively short response/recovery times and full recovery properties. Notably, the optimal sensor displayed extraordinary selectivity towards NO2, showing negligible responses to different interfering gases. Density functional theory calculations were conducted to elucidate the underlying sensing mechanism, which was attributed to the enhanced specific surface area, the receptor function of both PbS QDs and PbMoO4 nanoparticles, along with the transducer function of MoS2 nanosheets.