Au NUs@SiO₂ sensors for sensitive and selective optical sensing of volatile compounds

Plasmonic sensors has been widely used to detect the refractive index change in liquids, while it is challenging to apply the plasmonic sensors to the selective detection of organic vapors that adsorb non-specifically and induce extremely low refractive index change. Herein, silica shell was directly grown on Au nano-urchins (Au NUs) through sol-gel hydrolysis method to improve its vapor molecules anchoring capability and generate the selectivity to different vapors. According to the vapor sensing experiments to ethanol, acetone and hexane, the refractive index sensitivity (RIS) of Au NUs@SiO₂ sensors was four times higher than that of bare Au NUs. In addition, Au NUs@SiO₂ sensors demonstrate different vapor sensing performance to different organic vapors. The sensing characteristics is attributed to the large contacting area and the affinity between Au NUs@SiO₂ sensors and the target molecules. These findings provide a basis for the development of novel plasmonic sensors and the RIS enhancement, which abroad their application as contactless sensors.