Detection of amine gases by inverse opal photonic crystals infiltrated with precursor HPQ-Ac of aggregation-induced emission luminogen

In this study, to detect amine gases such as ammonia, a kind of biological gas, with high sensitivity, we fabricated a device that combines an inverse opal photonic crystal (IOPC) and 2-(4-oxo-3,4-dihydroquinazolin-2-yl)phenyl acetate (HPQ-Ac), a precursor of the aggregation-induced emission luminogen. IOPC silica structures (200IOPC, 350IOPC, 500IOPC) with SiO2 were respectively obtained after calcination with 200, 350, and 500 nm polystyrene (PS) nanoparticles used as templates and tetraethyl orthosilicate (TEOS) formed by self-assembly on a slide glass. Furthermore, mesopore-introduced IOPC (50 nm-350IOPC) was prepared by mixing 350 nm and 50 nm PS particles in TEOS solution. Each IOPC was infiltrated with HPQ-Ac, reacted with ammonia, and the rate of change in emission intensity owing to fluorescence was examined. The highest response was obtained for 350IOPC infiltrated with HPQ-Ac among the three IOPCs without mesopores. The 50 nm-350IOPC had higher sensitivity than 350IOPC and was found to be able to detect 50 ppb ammonia gas.