Photodynamic optical sensor for buffer capacity and pH based on hydrogel-incorporated spiropyran

We introduce here a dynamic optode for buffer capacity sensing based on photochromic spiropyran (Sp). It represents the first reversible optical sensor for buffer capacity. Sensing was possible using a non-equilibrium readout mode, a novelty for photoswitchable optical ion sensors. In addition to the buffer capacity, the final point of each measurement sequence provides the pH of the solution.