Natively porous films as halide anion fluorescence optical sensors

•Hybrid porous films with linked quinolinium dyes are effective halogen anion sensors.•Measurements of chloride in the physiological range are possible.•Bromide and iodide anions are detected in sub-millimolar concentrations.•Dynamic quenching constants of dyes are unaffected by inclusion in silica matrix.•Response time is tens of minutes for dry films due their hydrophobic character.

A halogen-anion fluorescent solid-state sensor based on natively porous films doped with a quinolinium derivative is reported. The sensitive films are prepared with a low temperature sol–gel synthesis starting from bridged silsesquioxane precursors, and 6-methoxyquinolinium moieties are covalently linked to the organic–inorganic hybrid network. This sensor system is reversible and allows selective detection and measurement of halogen anion concentrations in the physiological range by a dynamic quenching effect of the sensitive fluorophore. The quenching constants are unaffected by dye inclusion in the bridged polysilsesquioxane matrix.