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.