A novel organic-inorganic hybrid optical sensor (NUS) was designed and prepared in two steps: the grafting of 3-(isocyanatopropyl)trimethoxysilane onto the surface of SBA-15, and then the attachment of naphthalene-1-amine. The obtained materials were characterized using low-angle XRD, N₂ adsorption-desorption, TGA, FT-IR, and TEM techniques. A fluorescence study revealed that the NUS was a highly selective optical sensor for the detection of Cr₂O₇²⁻ among various anions, including F⁻, I⁻, Cl⁻, Br⁻, CO₃²⁻, HCO₃⁻, NO₃⁻, H₂PO₄⁻, CH₃COO⁻, and NO₂⁻ with a good linearity between the fluorescence intensity and the concentration of Cr₂O₇²⁻ as well as a detection limit of 1.2 × 10⁻⁷ M in a 100% aqueous medium. Moreover, the applicability of real samples of the sensor is also discussed.