Enhancing electrochemical properties of an ITO-coated lossy-mode resonance optical fiber sensor by electrodeposition of PEDOT:PSS

Abstract

A sensor working in multiple domains may offer enhanced information about the properties of an investigated analyte, including those containing biological species. It has already been shown that a dual-domain sensing capability, i.e., in optical and electrochemical domains, can be offered by lossy-mode resonance (LMR) sensors based on indium-tin-oxide (ITO) thin film. The spectral response of the LMR sensors depends on the refractive index (RI) at the ITO surface. In this work, we discuss a capability for enhancing the electrochemical properties of these sensors by electrodeposition of poly(3,4-ethylenedioxythiophene)–poly(4-styrenesulfonate) (PEDOT:PSS) on the ITO surface. This conjugated polymer shows high electrical conductivity, high optical transmittance, as well as good chemical stability, and thus can be used as a transparent electrode. We have found that the PEDOT:PSS deposition improves the reversibility of the electrochemical reduction/oxidation reactions by 2.5 times with no negative impact on LMR-based measurements of the RI of the analyte.