Journal of Electroanalytical Chemistry 447 (1998) 1 – 3 Preliminary note Electrochemical molecular recognition by thin films of ether-substituted polythiophenes Leonid M. Goldenberg a,c , Isabelle Le ´vesque b , Mario Leclerc b , Michael C. Petty a, * a School of Engineering and Centre for Molecular Electronics, Uniersity of Durham, Durham DH13LE, UK b Department of Chemistry, Uniersity of Montreal, Montreal, Quebec H3C 3J7, Canada c Institute of Chemical Physics in Chernogoloka, Russian Academy of Science, Chernogoloka, 142432 Moscow Region, Russia Received 7 August 1997; received in revised form 16 December 1997 Abstract The electrochemical behaviour of cast films of poly(3-oligo(oxyethylene)-4-methylthiophene) is reported. These films exhibit electrochemical recognition for alkali metal cations with selectivity in the order K + Na + Li + . © 1998 Elsevier Science S.A. All rights reserved. Keywords: Molecular recognition; Polythiophene; Thin organic films; Ion sensing 1. Introduction The synthesis of various functionalised polythiophenes has led to the development of processable materials with interesting electrochemical, electrical and optical proper- ties [1]. Recent studies have revealed potentially useful molecular recognition behaviour of polyheterocycles, based on non-covalent interactions with ions and neutral species, for ether, crown-ether groups and other receptors [2–16]. In particular, polythiophenes with attached crown ether receptors have been used to detect alkali metal cations [2]. Soluble conjugated polymers and oligomers may be processed into thin films by casting or spin-coating. Here we present a study of the electrochemical properties of a novel ether-substituted polythiophene, in the form of cast films. The chemical formula of the material used (PT350) is as shown. 2. Experimental Details regarding the polymeric material have been reported previously [17]. An EG and G PARC model 273 potentiostat with an Advanced Bryans XY recorder was used for electrochem- ical experiments. Pt wire served as the counter electrode and a Pt disk electrode (1.6 mm diameter, BAS) with a cast film was the working electrode. Polymer films were cast on the electrode disk from chloroform (BDH, Aristar) solution. All potentials were recorded versus AgAg + (corrected to FcFc + as 0.35 V vs. AgAgCl). CH 3 CN (Aldrich, HPLC or anhydrous), Bu 4 NClO 4 (Fluka, electrochemical grade), LiClO 4 (Fluka, microse- lect), NaClO 4 and KClO 4 (both Aldrich, A.C.S. reagents) were used for the preparation of electrolyte solutions. * Corresponding author. Tel.: +44 191 3742389; fax: +44 191 3747492; e-mail: m.c.petty@durham.ac.uk 0022-0728/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved. PII S0022-0728(98)00003-5