A Ratiometric Optical Dual Sensor for the Simultaneous Detection of Oxygen and Carbon Dioxide.

Simultaneous detection of carbon dioxide (CO) and oxygen (O) has attracted considerable interest since CO and O play key roles in various industrial and domestic applications. In this study, a new approach based on a fluorescence ratiometric referencing method was reported to develop an optical dual sensor where platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) complex used as the O-sensitive dye, CdSe/ZnS quantum dots (QDs) combined with phenol red used as the CO-sensitive dye, and CdSe/ZnS QDs used as the reference dye for the simultaneous detection of O and CO. All the dyes were immobilized in a gas-permeable matrix poly (isobutyl methacrylate) (PolyIBM) and subjected to excitation using a 380 nm LED. The as-obtained distinct fluorescence spectral intensities were alternately exposed to analyte gases to observe changes in the fluorescence intensity. In the presence of O, the fluorescence intensity of the Pt (II) complex was considerably quenched, while in the presence of CO, the fluorescence intensity of QDs was increased. The corresponding ratiometric sensitivities of the optical dual sensor for O and CO were approximately 13 and 144, respectively. In addition, the response and recovery for O and CO were calculated to be 10 s/35 s and 20 s/60 s, respectively. Thus, a ratiometric optical dual gas sensor for the simultaneous detection of O and CO was successfully developed. Effects of spurious fluctuations in the intensity of external and excitation sources were suppressed by the ratiometric sensing approach.