Ru- and Nb-doped Janus PtSSe Monolayer for Hazardous Gas Sensing of HCHO, C6H6 and Rn: a First-Principles Investigation

Indoor air quality in archival environments is critically threatened by hazardous gases such as HCHO, C6H6, and Rn, which originate from collection materials and building structures remain largely undetected. Using first-principles theory, this study investigates the structural stability, electronic properties, and gas adsorption performance of noble metal (Ru and Nb)-doped Janus PtSSe monolayers as potential resistive sensing materials for three target gases. The results reveal that both Ru and Nb dopants preferentially substitute at the Se site, and Nb-doping enhances the electron-donating capability of the substrate, leading to stronger adsorption energies and greater charge transfer compared to Ru-doping. Band structure analysis shows that Nb-PtSSe exhibits larger bandgap modulations with somewhat higher sensing response. Specifically, HCHO and C6H6 are chemisorbed behaving chemiresistive detection, while Rn, as noble gas with low chemical reactivity, behave weak physisorption and polarization-induced charge redistribution that achieves a tiny response. Recovery time analysis reveals that Nb-PtSSe suffers from long desorption times, while Ru-PtSSe achieves significantly faster recovery at 398 K. Thus, Ru-PtSSe emerges as a practically viable candidate for fast-recovery applications. This work not only provides a theoretical foundation for developing PtSSe-based gas sensors but also highlights the critical role of dopant selection in tailoring sensing performance for cultural heritage preservation applications.