Self-assembled Core–Shell Au@Pd Nanoparticle Arrays for Optical Hydrogen Sensing

The development of optical hydrogen sensors using wet-chemical methods often faces significant challenges, including slow response times and limited repeatability. This study presents an optical hydrogen sensor with a rapid response time, low detection limit, and excellent recyclability. The sensor uses core–shell Au@Pd NPs as the hydrogen response material. These NPs are self-assembled into a thin film by using an interfacial self-assembly method and then transferred onto a glass slide to form an Au@Pd nanoparticle array (NAs) sensor. The unique morphology of the Pd layer, which offers a high surface area with numerous reactive sites, significantly reduces the response time. By adjusting the Pd layer thickness, an optimal Au0.31Pd0.69 NPs composition was achieved, yielding a low detection limit (0.1%) and a fast response time (t90 of 3% H2 is about 6.2 s) at room temperature(abouts 23 °C). Incorporating PMMA improved the sensor’s cycling performance while maintaining a fast response (t90 of about 8 s for 3% H2) and low detection limit (0.5%). This work demonstrates a cost-effective and high-performance hydrogen sensor with superior response time, excellent repeatability, and a broad detection range fabricated through wet-chemical methods.