Optical Monitoring of Electrochemical Processes With ITO-Based Lossy-Mode Resonance Optical Fiber Sensor Applied as an Electrode

In this paper, we discuss the application of optical fiber sensors based on lossy-mode resonance (LMR) phenomenon for real-time optical monitoring of electrochemical processes. The sensors were obtained by a reactive high power impulse magnetron sputtering of indium tin oxide (ITO) on a 2.5 cm long core of polymer-clad silica fibers. The LMR effect made monitoring of changes in optical properties of both ITO and its surrounding medium possible. Moreover, since ITO is electrically conductive and electrochemically active, it was used as a working electrode in a three-electrode cyclic voltammetry setup. The investigations have shown that the sensor's optical response strongly depends on the potential applied to the sensor, as well as on electrochemical modification of its surface. The obtained LMR effect can be applied in parallel to electrochemical measurements for real-time optical monitoring of the electrode conditions and properties of the surrounding medium.