Atomically dispersed Pb ionic sites in PbCdSe quantum dot gels enhance room-temperature NO₂ sensing

Atmospheric NO₂ is of great concern due to its adverse effects on human health and the environment, motivating research on NO₂ detection and remediation. Existing low-cost room-temperature NO₂ sensors often suffer from low sensitivity at the ppb level or long recovery times, reflecting the trade-off between sensor response and recovery time. Here, we report an atomically dispersed metal ion strategy to address it. We discover that bimetallic PbCdSe quantum dot (QD) gels containing atomically dispersed Pb ionic sites achieve the optimal combination of strong sensor response and fast recovery, leading to a high-performance room-temperature p-type semiconductor NO₂ sensor as characterized by a combination of ultra-low limit of detection, high sensitivity and stability, fast response and recovery. With the help of theoretical calculations, we reveal the high performance of the PbCdSe QD gel arises from the unique tuning effects of Pb ionic sites on NO₂ binding at their neighboring Cd sites.