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

21 September 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


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 non-oxidizing and 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 intensity, shape and position of the Raman spectra. However, we demonstrated that the same effects can be obtained either by increasing the concentration of non-oxidizing 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 to revise most of the Raman results reported in literature with a clear model, setting a new basis for investigating the dynamics of mixed electronic/ionic charge transfer in conductive polymers.


ion diffusion dynamics
charge transfer
saline buffers
optical sensors

Supplementary materials

Supporting Information
S1. Details of setup for Raman experiments on PEDOT:PSS-based OECTs S2. Raman spectra of PEDOT:PSS. Literature-based assignment of the main bands. S3. Scheme of the oxidation states of PEDOT S4. Raman spectra of PEDOT:PSS in non-oxidizing halide salts


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