Why PEDOT:PSS Should Not Be Used for Raman Sensing of Redox States (and How It Could Be)

Year: 2022

Authors: Alessandri I., Torricelli F., Cerea B., Speziani M., Romele P., Kovacs-Vajna ZM., Vassalini I.

Autors Affiliation: Univ Brescia, Dept Informat Engn, I-25123 Brescia, Italy; INSTM Natl Consortium Mat Sci & Technol, UdR Brescia, I-25123 Brescia, Italy; UdR Brescia, CNR INO, I-25123 Brescia, Italy.

Abstract: Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been recently proposed for Raman sensing of redox-active species in solution. Here, we investigated the rationale of this approach through systematic experiments, in which the Raman spectrum of PEDOT:PSS was analyzed in the presence of either nonoxidizing or oxidizing electrolytes. The results demonstrated that Raman spectra precisely reflect the conformation of PEDOT units and their interactions with PSS. Two different responses were observed. In the case of oxidizing electrolytes, the effect of charge transfer is accurately transduced in Raman spectrum changes. On the other hand, reduction induces a progressive separation between the PEDOT and PSS chains, which decreases their mutual interaction. This stimulus determines characteristic variations in the intensity, shape, and position of the Raman spectra. However, we demonstrated that the same effects can be obtained either by increasing the concentration of nonoxidizing electrolytes or by deprotonating PSS chains. This poses severe limitations to the use of PEDOT:PSS for this type of Raman sensing. This study allows us to revise most of the Raman results reported in the literature with a clear model, setting a new basis for investigating the dynamics of mixed electronic/ionic charge transfer in conductive polymers.

Journal/Review: ACS APPLIED MATERIALS & INTERFACES

Volume: 14 (50)      Pages from: 56363  to: 56373

More Information: I.V. was partially supported by the Italian Ministry of University and Research (MUR) through the PRIN project NOMEN (2017MP7F8F) .
KeyWords: PSS; Raman; electrolyte; ion diffusion dynamics; charge transfer; saline buffers; optical sensors; PEDOT
DOI: 10.1021/acsami.2c17147

Citations: 7
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