FIGURE 1.

Sensing Mechanism and spectral behavior of HPTS dye. (A) HPTS exhibits a strong emission peak at 515 and 455 nm in its deprotonated and protonated forms, respectively. Exposure of the dye in an aqueous media to CO₂ lowers the pH and HPTS is increasingly protonated with increasing percent CO₂ levels. (B) Fluorescence emission spectra of HPTS entrapped in PDMS upon exposure to increasing CO₂ concentrations show as HPTS is protonated by an increasingly acidic environment, the deprotonated dye peak decreases and the protonated dye peak increases.