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.