A team of physicists led by VU Amsterdam have developed the first optical sensor for hydrogen gas with a sensitivity in the parts-per-billion (ppb) range. It may prove a safer alternative for electrical sensors, which carry an inherent safety risk because the electrical currents involved may induce sparks. Optical sensors don’t need any electrical components near the sensing area.
Previous optical hydrogen sensor implementations were usually based on palladium (Pd) or palladium alloys. When used as a plasmonic hydrogen sensor, palladium produces broad optical spectra, which then gives rise to a signal with high noise and thus limited resolution to detect low concentrations. The researchers tackled this problem by designing a sample comprising periodic arrays of Pd nanoparticles that support so-called surface lattice resonances, optical resonances with very narrow spectra and therefore very high sensitivity.
To find the array with the highest sensitivity, an artificial intelligence approach was used called particle swarm optimization. With this algorithm, the structure of the nanoparticle array can be optimized in such a way as to obtain the strongest optical response under exposure to hydrogen. The method has general applicability and can be combined with other optimization strategies aimed at improving other sensor performance indicators, such as detection speed (using other materials and alloys) and selectivity (with an optimal polymer layer acting as the coating).