In chemical, industrial, medical, biochemical andclinical analysis, the continuous and accurate detection of dissolved and/orgaseous CO2 is very important. In recent studies, 8-hydroxypyrene-1, 3,6-trisulfonic acid (HPTS) dye,which is a pH sensitive fluorescent indicator with high sensitivity to CO2gas, is preferred. Researches relating to the improvement of gas sensitivity ofHPTS-based optical sensors are very popular. The aim of this study is toenhance the CO2 response of HPTS along with the sol-gel synthesized TiO2and TiO2@Ag nanoparticles (NPs) as additives. Thecharacterizations of the synthesized metal oxide powders were carried outthrough XPS, XRD, FT-IR, SEM, and PL spectroscopy. The sensing slides were prepared in the form of a thinfilm by immobilizing the HPTS dye and TiO2 and TiO2@Ag NPs additives into theethyl cellulose polymer matrix. Steady state and decay time based spectralresponses of the HPTS-based composites were measured as analytical signal in the concentration range of 0–100% [CO2]. Additions ofTiO2-based additives to HPTS resulted in many advances such as highrelative signal change and larger linear response range, improved sensordynamics, and higher sensitivity with respect to the additive-free forms. Whereasthe CO2 sensitivities were measured as %39, 52% and 70% for undopedform and TiO2 andTiO2@Ag NPs doped forms of the HPTS-based thin films, respectively. The response and the recovery times of the HPTS-basedsensing slide along with TiO2@AgNPs have been measured as 15 and 45 s. These resultsmake the HPTS along with the metal oxide additives promising candidates as CO2probes.</p
