Electrochemical SERS for in Situ Monitoring the Redox States of PEDOT and Its Potential Application in Oxidant Detection

Abstract

In response to recent developments for applying conducting polymers on various biomedical applications, the development of characterization techniques for evaluating the states of conducting polymers in liquids is beneficial to the applications of these materials. In this study, we propose a platform using electrochemical surface-enhanced Raman scattering (EC-SERS) technology, which allows a direct measurement of the redox states of conducing polymers in liquids. A thiophene-based conducting polymer, hydroxymethyl poly (3,4-ethylenedioxythiophene) or poly(EDOT-OH), was used to demonstrate this concept. Poly(EDOT-OH) films were coated on Au nanoparticle-coated ITO glass as SERS-active substrates. Taking the advantage of Raman enhancement, we can in situ and clearly monitor the redox behavior of poly(EDOT-OH) in aqueous solutions. The Raman peak intensity decreases as the poly(EDOT-OH) film is oxidized. Furthermore, we demonstrated our idea to utilize this phenomenon as the sensing mechanism for oxidant detection. The Raman intensity of conducting polymers reduces faster when oxidants exist, and we obtain a quantitative analysis for the detection of oxidants. Moreover, the oxidized poly(EDOT-OH) films can be reused for detection of oxidants simply by applying a reduction potential to activate the poly(EDOT-OH) films. The film stability was also confirmed, and the detection of two other oxidants, namely ammonium persulfate and iron chloride, were also demonstrated. The results show different SERS spectra of poly(EDOT-OH) films oxidized by using different oxidants. Besides, the oxidized films can be easily recovered simply by applying a cathodic potential, which allows repeating usage and makes it possible for continuous monitoring applications. To the best of our knowledge, this is the first time to apply PEDOT's Raman feature for detection purposes.

SERS Activity of Silver Nanosphere, Triangular Nanoplates, Hexagonal Nanoplates and Quasi-Spherical Nanoparticles: Effect of Shape and Morphology

“…For this reason, Surface Enhanced Raman Scattering (SERS) is a powerful vibrational spectroscopic technique that can extend the sensitivity of conventional Raman spectroscopy to the single molecule level [2][3][4]. The power of SERS can be exploited for its versatility and feasibility in a wide variety of fields including polymers, materials science, biochemistry and bio-sensing, catalyst, electrochemistry, pesticides, and food additives [5][6][7][8][9]. SERS technique increases drastically the Raman signals of an analyte molecule by the presence of roughened metal noble-metals (Ag and Au) near or in proximity of the analyzed samples [10,11].…”

Spectroscopic Characterization of Pedot:pss Conducting Polymer by Resonance Raman and Serrs Spectroscopies

“…[7][8][9] Many efforts have been done to parameterize the polymeric dispersion syntheses in order to find the most suitable applications. Due to the electronic structures of conducting polymers, the use of resonance Raman (RR) [10][11][12] and surface-enhanced resonance Raman scattering (SERRS) 13,14 spectroscopies can provide valuable information for the characterization of their dispersions and films. These techniques could lead to infer the structural parameters along with the molecular systems chemical environment, which interferes in the properties of interest.…”

Spectroelectrochemical Sensing: Current Trends and Challenges

“…From a quantitative point of view, the most used SEC techniques are UV/Vis absorption SEC , fluorescence SEC and Raman SEC . For this reason, and taking into account the objectives of this review, these three techniques are those that will be described in more detail below.…”

“…Indirect measurements are an interesting strategy that can be used for analysis. For example, EC‐SERS can provide in‐situ and real‐time monitoring of the doping/dedoping conversion of poly(EDOT‐OH) and a quantitative measurement of oxidant concentration . Real‐time monitorization of the Raman spectra change of poly(EDOT‐OH) at dedoped state can be used for the determination of H 2 O 2 solutions of different concentrations.…”