Tunable Ag@Au core–shell nanoparticles synthesized by pulsed laser ablation for dual H2S and NO2 gas sensing on porous silicon

Hydrogen sulfide (H 2 S) and nitrogen dioxide (NO[Formula: see text], two of the most dangerous environmental toxins, pose significant threats to human health and safety. In this study, we report a new approach to fabricating Ag@Au core@shell with controllable Au shell thickness using two-step pulsed laser ablation in liquid (PLAL). This approach enables accurate tuning of the Au shell thickness to maximize gas-sensing properties. In contrast to traditional methods, in which the shell’s characteristics are always uncontrolled, the PLAL method for adjusting the shell’s thickness yields a more sensitive and selective sensor. The Ag@Au core–shell NPs were used for dual gas sensing on PS, and sensitivities of up to 68% and 54% to H2S and NO 2 , respectively, were achieved between 200 ∘ C and 250 ∘ C. The sensor with an Au shell layer deposited over a period as short as 1 min exhibited excellent response time (52–55[Formula: see text]s) and recovery time (23–33[Formula: see text]s). In contrast, the 2[Formula: see text]min Au-induced shell sensor displayed an outstanding balance between sensitivity (51% for H 2 S and 41% for NO[Formula: see text] and long-term stability, which has potential for repeated, reliable detection in many real-world situations. This work emphasizes the unparalleled benefit of facile, systematic adjustment of the Au shell thickness via PLAL, resulting in a significant enhancement in dual-gas sensing. It also highlights the practical feasibility of this method for fabricating high-performance gas sensors for environmental monitoring and industrial safety.