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

Abstract

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) synthesis was monitored by resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies and both the oxidation of the polymer and the effects of chain length were assessed by vibrational analysis. It was supported by theoretical models of oligomers, with charge ranging from 0 to +6 and size varying from 2 to 16 3,4-ethylenedioxythiophene (EDOT) repeat units, described through density functional theory. The symmetric C α C β stretching band observed at ca. 1426 cm-1 shifts to higher wavenumbers for reaction times varying from 2 to 9 hours and stabilizes at intermediate wavenumbers for longer times. The former behavior was ascribed to the increase of concentration of oxidized species, which was corroborated by calculated wavenumbers for oligomer models when their charges changed from neutral to +6. The behavior observed for longer reaction times was associated with the growth of chains. It was also observed through SERRS spectroscopy that small chains of the polymer, obtained in the early time of the synthesis, adsorbs on gold nanoparticle surfaces through interactions via oxidized residues. In this way, RR and SERRS spectroscopies were valuable tools to follow the synthetic procedures of PEDOT:PSS, allowing the determination of the structural evolution of the polymer.

Raman Spectroscopy and Thermoelectric Characterization of Composite Thin Films of Cu2ZnSnS4 Nanocrystals Embedded in a Conductive Polymer PEDOT:PSS

“…The good crystallinity of the synthesized NCs is confirmed by observing distinct overtones of the main CZTS peak at about 650 and 1000 cm −1 . The spectrum of pure PEDOT:PSS exhibits a set of characteristic peaks in good agreement with data in the literature [ 19 , 21 , 23 , 37 , 38 , 39 , 40 ]. The difference in the position of the characteristic bands of PEDOT:PSS are not only caused by changes in the structure but also depend on the excitation wavelength [ 41 ].…”

Bio‐Inspired Adaptive Sensing through Electropolymerization of Organic Electrochemical Transistors

“…Concerning the doping level, the peak for the C α = C β symmetric vibrations shifted from 1439 cm −1 for the spin-coated PEDOT to 1444 cm −1 for both electropolymerized PEDOT. This shifts indicates a higher level of oxidation for the polymer [26,[28][29][30][31][32][33] in correlation with the peaks at 1266 cm −1 that corresponded to the oxidized state of PEDOT. [26,[28][29][30][31][32][33] In addition, these blue-shifts (i.e., to higher wavenumbers) could be associated to oxidized states with quinoid form of polymer chains, which may have a key role to play on the conductivity of the polymers.…”

“…This shifts indicates a higher level of oxidation for the polymer [26,[28][29][30][31][32][33] in correlation with the peaks at 1266 cm −1 that corresponded to the oxidized state of PEDOT. [26,[28][29][30][31][32][33] In addition, these blue-shifts (i.e., to higher wavenumbers) could be associated to oxidized states with quinoid form of polymer chains, which may have a key role to play on the conductivity of the polymers. [31] Moreover, electropolymerized PEDOT at 0.6 V presented the narrowest peak at 1444 cm −1 which suggested a larger rate of π-σ-π conjugation and thus higher crystallinity and conductivity as shown by Zhao et al [29,34] On the other hand, the decrease in the intensity of the peaks in the 400-1000 cm −1 region (dioxyethylene ring deformation) whereas an increase is observed at 1450-1650 cm −1 (C α = C β vibrations region) for both electropolymerized PEDOT relatively to spin-coated PEDOT indicated a perpendicular orientation of the thiophene rings with respect to the surface and thus an edge on the growth of PEDOT:PSS on the surface.…”

Electrical/Spectroscopic Stability of Conducting and Biodegradable Graft‐Copolymer

“…For CPs, Raman spectroscopy is a powerful tool to access structural changes only in the conductive component once typically, CPs have larger cross‐sections or could even have their intensity enhanced by the Raman resonance effect. [ 77–79 ] This point is further illustrated by comparing the calculated nonresonant cross‐sections of a two and four‐unit EDOT oligomer to a three‐unit PDLLA oligomer, shown in Supporting Information Figure S9. Thus, we will focus on the spectroscopic changes occurring on PEDOT in this work.…”