An optical sol-gel-based co2 sensor strip was fabricated using a fluorescent pH indicator, 1-hydroxypyrene-3, 6, 8-trisulfonate (HPTS) (Bultzingsloween et al., 2002). exhibited fast and reversible response to carbon dioxide over a wide range of concentrations (0-100% Co2) with sufficient resolution (t2%). The dye was immobilized in hydrophobic organically modified silica matrix. Cetyltrimethylammonium hydroxide (CTA-oH), a quater nary ammonium base, was used as an ion-pairing agent for a polar pH indicator in a non-polar gas permeable membrane, and also it functions as internal buffer. The Dual Luminophore Referencing (DLR) sensing method, an internal ratiometric method, is used for measuring the fluorescence. In which, the analyte-sensitive fluor rescence intensity signal is converted into the phase domain by co-immobilizing an inert long-lifetime reference luminophore