A novel organic–inorganic hybrid optical sensor (HQS-SBA-15) was prepared by a two-step post synthesis of SBA-15: functionalization with 3-(iodopropyl)-trimethoxysilane followed by the covalent attachment of 8-hydroxyquinoline-5-sulfonic acid. XRD, N₂ adsorption–desorption, TEM and FT-IR were used for the characterization of the prepared materials. A fluorescence study showed that the suspension of HQS-SBA-15 in water was able to detect selectively and sensitively two ions with opposite charges, i.e. Pb²⁺ in the presence of different cations, including Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Mn²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg⁺, as well as I⁻ among different anions, including NO₂⁻, NO₃⁻, CN⁻, Cl⁻, F⁻, Br⁻, CO₃²⁻, SO₄²⁻, HCO₃⁻, and H₂PO₄⁻. The effects of pH, its applicability in real samples and reversibility are also discussed.