Chemical polymerization of a 3,4-ethylenedioxythiophene (EDOT) derivative bearing a sulfonate group (EDOT-S) is reported. The polymer, PEDOT-S, is fully water-soluble and has been produced by polymerizing EDOT-S in water, using Na₂S₂O₈ and a catalytic amount of FeCl₃. Thus obtained polymer can be used as doping polyanion of poly-pyrrole (PPY). Interestingly, the PPY/PEDOT-S bipolymeric composite can be synthesized in acidic aqueous solution of PY and PEDOT-S without any external oxidized. Ambient oxygen is efficient oxidizer of the binary mixture and the biopolymer forms as a dark gel after 24h in r.t. Certain cleaning produces suspensions of PPY/PEDOT-S in water or organic solvents. The cast deposits of the biopolymer on voltammetric electrodes show substantial electrochemical activity typical of conjugated conducting polymers. The acceleration of electrode kinetics at the biopolymer modified electrodes compared to the unmodified electrodes was observed for many redox systems.

Fig. 1.  (A) Linear sweep voltammograms recorded at a rotating glassy carbon electrode  (1000 r.p.m.) in 0.1 M HClO₄ before (a) and after addition of 10 mM Fe³⁺ (b). The same experiment performed at the bipolymer-modified electrode is reflected by lines (c) and (d), respectively. Sweep rate: 2 mV s^-1. (B) Constant potential amperometry recorded at +0.3 V vs. Ag/AgCl at the modified rotating disk electrode (1000 r.p.m.) following addition of 2.5 (a), 5 (b), 10 (c), 15 (d), 20 (e), 25 (f), 37.5 (g), 50 (h), 75 (i), 100 (j), 150 (k), 200 (l), 250 (m), 300 (n), 400 (o) and 500 μM (p) (black line). The same experiment performed on the bare electrode is reflected by the red line.

For instance, Fig. 1A compares reductive single sweep voltammograms of Fe³⁺ cation at unmodified and biopolymer-modified electrodes. As it seen, in the latter case the voltammogram shows a clear current plateau indicating diffusion-controlled reduction reaction. Moreover, the current onset point is shifted significantly toward higher electrode potentials. This implies that the biopolymer modified electrode can be used as amperommetric sensor of Fe³⁺ ions in solution. This was experimentally verified by measuring current changes following additions of increasing concentrations of Fe³⁺ ions. The obtained current-time tracing is shown in Fig. 1B. It is evident that the observed responses are many times higher than at the unmodified electrode. The sensitivity factor calculated from the slope of the linear regression line was 0.28 μA μM cm^-2.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/24885 must be provided.

1. Polymeric and nanostructured composites containing lignin derivatives