Gas detection using quenching fluorescence of dye-immobilised silica nanoparticles

A novel oxygen (O2) and sulphur dioxide (SO2) gas sensor was produced by incorporating fluorophores within silica nanoparticles (SiNPs). The fluorophore rhodamine B isothiocyanate (RBITC) was encapsulated within SiNPs (208 ± 9 nm) to produce a nanosensor that is sensitive to SO2, while ruthenium-tris(4,7-diphenyl-1,10-phenanthroline) dichloride (Ru(dpp)3) was encapsulated within silica nanoparticles (192 ± 8 nm) to sense O2. The sensor utilises the fluorescence quenching phenomena as a detection mechanism. Core–shell SiNPs were immobilised in organically modified sol–gel (ormosil) composed of octyltriethoxysilane (OTEOS) and methyltriethoxysilane (MTEOS). The surfaces of SiNPs were modified with carboxylic acid groups in order to bind the SiNPs within the ormosil matrix. A film was produced where Ru(dpp)3 encapsulated silica nanoparticles were combined with RBITC encapsulated silica nanoparticles within a sol–gel matrix. The fluorescence of Ru(dpp)3 was highly quenched by O2 whilst RBITC was highly quenchable by SO2. Furthermore, the nanosensor was capable of detecting oxygen levels as low as 0.018% and SO2 gas at 50%. These novel nanosensors demonstrate potential to develop multisensor systems capable of detecting multiple gasses simultaneously in a single matrix for a magnitude of future applications that require small robust gas sensing.