Tuning selective detection of asthma biomarkers (H2S and NO) on MoSe2 monolayers via Pd decoration and vacancy substitution

Gas sensing technologies capable of selectively detecting asthma biomarkers are of great importance for non-invasive respiratory disease diagnosis. In this work, first-principles density functional theory (DFT) calculations were employed to systematically investigate the sensing performance of MoSe 2 monolayers toward two representative asthma biomarkers, H 2 S and NO, through two Pd functionalization strategies: surface decoration and Se-vacancy substitution. Both modification modes introduce localized Pd-4d states near the Fermi level, significantly enhancing orbital hybridization with adsorbed gas molecules and activating the MoSe 2 surface. Adsorption analysis reveals that NO exhibits stronger interaction with the Pd sites than H 2 S, resulting in more pronounced electronic perturbation and band gap modulation, particularly in the Pd-substituted system. Anti-interference evaluations further confirm that common exhaled gases (N 2 , O 2 , CO 2 , CH 4 , and H 2 O) interact weakly with the Pd-modified surfaces, demonstrating excellent selectivity toward the target biomarkers. Sensitivity analysis based on band-gap modulation indicates that Pd substitution dramatically enhances the sensing response to NO, while Pd decoration exhibits strong responses to both gases. Recovery-time estimations suggest that Pd-decorated MoSe 2 is suitable for high-temperature H 2 S detection, whereas Pd-substituted MoSe 2 enables rapid H 2 S sensing at room temperature and effective NO detection at elevated temperatures. These findings reveal how Pd functionalization modes regulate surface reactivity and electronic response, providing theoretical insights for the rational design of high-performance MoSe 2 -based gas sensors for biomarker detection.