Surface plasmon resonance (SPR) sensors based on evanescent-wave interactions have been widely used in the detection of biological and chemical analytes due to their advantages of label-free detection and real-time monitoring. However, highly sensitive SPR gas sensors with cost-effective fabrication processes remain a challenge because gas molecules are usually much smaller than biomolecules, resulting in poor detection of gas adsorption. In this work by Zhang and co-authors, the authors demonstrate a sensitive SPR gas sensor using nanoporous gold (NPG) films, which were cleverly fabricated by a sputtering-dealloying combined method. The porous structures of NPG increase the adsorption area of gas molecules, and significantly improve the detection sensitivity. By controlling the sputtering time and dealloying time to adjust film thickness and porosity, they optimized the performance of the NPG-SPR sensor obtaining a spectral shift of approximately 34 nm at 100 ppm H₂S gas, a sensitivity more than six times higher than that of a conventional Au-SPR sensor. This work indicates a potentially fruitful approach for sensitive SPR gas sensors for practical applications with ultimate sensitivity.

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