Efficient Plasmonic Gas Sensing Based on Cavity-Coupled Metallic Nanoparticles

Here, we demonstrate the gas sensing ability of cavity coupled metallic nanoparticle systems, comprising gold nanoparticles separated from a gold mirror with a polymer spacer. An increase in relative humidity (RH) causes the spacer to expand, which induces a significant reduction of nanoparticle scattering intensity, as the scattering is highly dependent on the cavity nanoparticle coupling that closely relates to the nanoparticle mirror distance. With high structural tolerance, i.e., no requirement for high-precision nanoparticle geometry, this lithography-free system enables a remarkable average sensitivity at 0.12 dB/% RH and 0.25 dB/% RH over a wide RH range (45-75%) and full reversibility with much faster response time than the commercial electrochemical sensors, possessing the characteristics to be used for notable gas sensing.