Room-Temperature Selectivity Switching via Nanoporous Au Film-Integrated SnO₂ Hybrid Sensors

Metal oxide chemiresistive sensors operating at room temperature offer a promising route toward low-power gas monitoring, but their selectivity remains largely governed by the intrinsic surface chemistry of the oxide. Here, we report a transport-engineered Au nanoporous metal film (Au NPMF)-integrated tin dioxide (SnO₂) hybrid structure (Au NPMF@SnO₂) that reverses the native sensing preference of SnO₂ at room temperature. A continuous Au NPMF is conformally integrated with glancing-angle-deposited SnO₂ nanorods through a plasma-assisted dry process, producing a permeable metal/oxide interface while preserving the structural and chemical identity of the oxide scaffold. The Au NPMF does not merely function as a catalytic decoration, but as an interconnected transport-regulating overlayer that modulates gas access, adsorption, and release before molecules reach the SnO₂ surface. Consequently, the intrinsic NO₂-dominant behavior of pristine SnO₂ is switched to H₂S-selective sensing, with improved H₂S recovery, stable cycling performance, and a theoretical detection limit of 0.0087 ppm. This behavior is primarily associated with the continuous nanoporous Au architecture, which couples morphology-controlled gas accessibility with gas-specific adsorption-desorption behavior and interfacial electronic interactions. These findings establish nanoporous metal overlayers as programmable interfacial layers for room-temperature selectivity control in metal oxide gas sensors.