LAUSR

Abstract This paper describes the electrochemical behavior of poly-bithiophene (PBTh), poly-ethylene-3,4-dioxythiophene (PEDOT), and poly-3,4-ortho-xylendioxythiophene (PXDOT) in an EtOH/H2O (1:1) mixture using 0.1 M LiClO4 as supporting electrolyte and AcOH/AcONa to buffer pH. PBTh suffers fast degradation, whereas PEDOT and PXDOT show reasonable stability in the EtOH/H2O mixture. A strong interaction between the 3,4-alkoxythiophene polymers and the EtOH/H2O mixture was evidenced by a charge/discharge process limited by ionic movement and slow electron transfer (as signaled by a large ΔEp). Both of these processes were faster in ACN. The stability of the prepared films was studied through 100 charge/discharge cycles in ACN and in the EtOH/H2O mixture. Considerable electroactivity loss for PEDOT and PXDOT was observed in ACN, which may be caused by charge trapping phenomena and oligomer release. This loss diminished substantially in the EtOH/H2O mixture showing a current higher than 75% of the initial value and an electrochemical reversibility (i.e., the Qc/Qa ratio) higher than 90%. Due to the stability of the PEDOT and PXDOT films in the EtOH/H2O mixture, it was possible to use them in modified electrodes for Cu (II) detection using anodic stripping voltammetry, where concentration-dependent current signals were observed.