Quenching performance of surfactant-containing and surfactant-free fluorophore-doped mesoporous silica films for nitroaromatic compound detection

Various surfactant-templated, mesoporous silica thin films containing a phenyl-substituted pyrene fluorophore were prepared and tested as sensors for the nitroaromatic compound 2,4-dinitrotoluene (DNT). The effects of materials parameters on quenching efficiency were evaluated, including the influence of mesopore architecture (wormlike, cubic, or hexagonal mesopores), the presence or absence of the templating surfactant in the mesopores, and the mode of fluorophore incorporation (doping, impregnating, or grafting). Among films with similar components, films with wormlike mesopore architecture exhibited a better quenching performance than those with 2D-hexagonal or 3D-hexagonal mesopore structure. Surfactant-free, fluorophore-bridged films with wormlike mesopores showed the best quenching performance (43% after 5 s and 88% after 60 s), which compares favorably with state-of-the-art sensors based on fluorescent conjugated polymers. Surfactant-containing, fluorophore-doped films with wormlike mesopores were also effectively quenched by DNT, with 39% quenching after 45 s and 94% of quenching after 405 s. It is notable that the surfactant blocks the diffusion of DNT only slightly while it enhances the binding of DNT to the film, boosting the quenching performance.