This paper presents a high-performance fiber-optic carbon dioxide (CO 2) sensor based on sol-gel matrix composed of n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) doped with pH-sensitive fluorescent dye and silica particles. The sensor film consists of 1-hydroxy-3,6,8- pyrenetrisulfonic acid trisodium salt (HPTS, PTS-), silica particles, tetraoctylammonium cation (TOA+), and a tetraoctylammonium hydroxide (TOAOH) phase transfer agent (i.e. the base) immobilized within the sol-gel matrix. The sensor has a sensitivity of approximately 26 and exhibits a uniquely linear response for CO2 concentrations in the range 0∼100 %. The response time of the sensor is 9.8 s when switching from a pure N2 atmosphere to a pure CO2 atmosphere and 195.4 s when switching from CO2 to N2.