Reversible Photodynamic Chloride-Selective Sensor Based on Photochromic Spiropyran

[Image: see text] We report here for the first time on a reversible photodynamic bulk optode sensor based on the photoswitching of a spiropyran derivative (Sp). The photoswitching of Sp induces a large basicity increase in the polymeric phase, which triggers the extraction of Cl(–) and H(+). Cl(–) is stabilized by a lipophilic chloride-selective ionophore inside the membrane, while H(+) binds with the open form of Sp and induces a spectral change, hence providing the sensor signal. The system was studied with spectroscopic and electrochemical methods.