Abstract

Analysis of liquids performed in multiple domain, e.g., optical and electrochemical (EC), has recently focus significant attention. Our previous works have shown that a simple device based on indium-tin-oxide (ITO) coated optical fiber core may be used for optical monitoring of EC processes. At satisfying optical properties and thickness of ITO a lossy-mode resonance (LMR) effect can be obtained and used for monitoring of optical properties of an analyte in proximity of the ITO surface. However, EC response of the ITO-LMR device to a redox probe has not been achieved for ITO-LMR sensor whereas it is generally observed for commercially available ITO electrodes. The changes in the response to a redox probe are typically used as a sensing parameter when EC label-free sensing is considered, so it is crucial for further development of combined LMR-EC sensing concept. In this work, we focus on enhancing the EC activity of the device by tuning ITO magnetron sputtering deposition parameters. Influence of the deposition pressure on the ITO properties has been the main consideration. Both optical and EC readouts in 0.1 M KCl containing such redox probes as 1 mM of K3[Fe(CN)6] or 1 mM 1,1′-Ferrocenedimethanol were discussed at different scan rate. The performed studies confirm that for optimized ITO properties the ITO-LMR sensor used as the EC electrode may also show excellent EC performance. The observed EC processes are quasi-reversible and diffusion-controlled. Moreover, for the devices, which offer improved EC response, an optical monitoring of the EC process is also possible. According to our best knowledge, fully functional combined optical and EC sensor, where optical effect is resonance-based and other than well-known surface plasmon resonance, is presented for the first time.

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Authors (10)