Enhanced Refractive Index Sensitivity through Combining a Sol-Gel Adsorbate with a TiO Nanoimprinted Metasurface for Gas Sensing.

We combine a gas-adsorbent microporous hybrid silica layer and a dense TiO Mie resonator array (metasurface), both obtained by sol-gel deposition and nanoimprint lithography, to form nanocomposite systems with high sensitivity for refractive index (RI) variations induced by gas adsorption. Using optical transduction based on direct specular reflection, we show spectral shifts of 4470 nm/RIU corresponding to 0.2 nm/ppm gas (air concentration) and reflection intensity changes of * = 17 (R/RIU) and 0.