Photocontrol of nitrogen sites for poisoning-free NO₂ sensing

In this communication, we present a comprehensive investigation of the UV photoactivation mechanism in nitrogen-doped carbon-based sensing materials. Here, tailored nitrogen incorporation enables rapid and effective NO₂ detection, driven by the synergistic interplay between the chemical nature and electronic properties of fundamentally graphitic-, pyridinic- and pyrrolic-N species. The influence of 275 nm UV power density is probed via in-situ confocal Raman microscopy measurements. The results reveal its critical role in the desorption process and its correlation with microstructural features and nitrogen species functionalization. Interestingly, the combination of hierarchical porous structure with high S BET (2783 m 2 /g), a large number of structural defects, and nitrogen doping through different species, promotes p- and n-type behaviors. This scenario leads to superior sensing performance. At 7 mW/cm 2 , the device shows poisoning-free operation, 11.76%/ppm sensitivity, and a detection limit of 2.55 ppb. Therefore, the work advances a technologically demanding solution to achieve practical monitoring of NO₂ at room temperature in the sub-ppm range, with high sensitivity, rapid recovery, and stability against poisoning.