Journal of The Electrochemical Society, 159 (4) E73-E81 (2012) E73 0013-4651/2012/159(4)/E73/9/$28.00 © The Electrochemical Society In Situ UV-Visible Spectroelectrochemistry and Cyclic Voltammetry of Conducting N-Methylpyrrole: Indole Copolymers on Gold Electrode Jalal Arjomandi, z Samaneh Safdar, and Mahdi Malmir Department of Physical Chemistry, Faculty of Chemistry, Buali Sina University, Hamedan 65178, Iran Electrochemical copolymerization of N-methylpyrrole (NMPy) and indole (In) in various monomer ratios were carried out by potentiodynamically methods in acetonitrile electrolyte containing LiClO 4 on gold electrode. The obtained homopolymers and copolymers were characterized with cyclic voltammetry (CV), in situ UV-Visible, FT-IR spectroscopy, scanning electron microscopy (SEM) and in situ resistivity measurements. The cyclic voltammetry study shows that the onset potential for the monomers and co monomers curves is located at the different values for N-methylpyrrole, indole and N-methylpyrrole-indole. There is a nucleation process followed by growth of nuclei to continuous films. The oxidation and reduction peaks for copolymer, P(NMPy-In), which synthesized from the 1:1 mole-mole ratio concentration of the relevant monomers, located between those for poly N- methylpyrrole (PNMPy) and polyindole (PIn) films. The observed values were showed a decreased [NMPy]/[In] ratio concentration in the copolymers shifts the peak potential to more positive. The in situ UV-Visible, FT-IR spectroscopy and SEM analysis of homopolymers and copolymers were also studied. The result shows the intermediate spectroscopic properties between homopolymers and copolymers. The in situ resistivity measurements showed that the copolymers have a lower conductivity than the corresponding parent homopolymers. © 2012 The Electrochemical Society. [DOI: 10.1149/2.023204jes] All rights reserved. Manuscript submitted September 1, 2011; revised manuscript received January 1, 2012. Published January 23, 2012. Organic conducting polymers such as polypyrrole, poly N-methylpyrrole, polyfuran, polythiophene, polyindole and its substi- tuted derivatives have been studied extensively 1–11 due to their poten- tial and electronic application including energy storage devices, 12, 13 solid state devices, 14 electrochemical/chemical sensors, 15 diodes 16, 17 and others. Electro copolymerization offers the advantages of prepar- ing a wide array of materials with redox activity, varying conductivity and stability. 2, 12, 18 The polymerization of pyrrole, N-methylpyrrole and pyrrole-indole, and their derivative compounds have been done by several groups to generate copolymers. 19–22 In situ spectroelectro- chemistry and in situ characterization of some conducting polymers and copolymers have been published recently. 23–32 The electrochemi- cal synthesis of polyindole on nickel-coated mild steel 33 and on 304- stainless steel 34 has been reported. Electrochemical copolymerization of indole and pyrrole on platinum electrode has been reported. 18, 22 It is also reported that pyrrole-indole copolymer electrode materials with higher redox potentials could offer the possibility of increasing the energy density when used as cathode materials in rechargeable batteries. 18 In the present paper, we report the electrosynthesis and characterize the PNMPy, PIn and new copolymers, P(NMPy-In), with different concentrations by cyclic voltammetry on gold electrode in nonaqueous media, in situ UV-Visible and FT-IR spectroscopy. Experimental Reagents and solvent.— N-methylpyrrole (Aldrich, 99%) was used as received. Indole (Aldrich) was purified by recrystallization from petroleum ether. LiClO 4 (Aldrich) used as an electrolyte was dried under a vacuum. Acetonitrile (Merck), water content as deter- mined by the Karl Fischer method <0.05%) was used as received and kept over a molecular sieve. Electrochemistry, spectroelectrochemistry, SEM and FT-IR measurement.— Cyclic voltammograms were performed using a Beh- pajoh model BHP/2062 and an Auto lab model PGSTAT 20 poten- tiostat/galvanostat. For cyclic voltammetry (CV), the working and auxiliary electrodes used were gold sheets of ∼0.4 and 1.0 cm 2 (from AZAR electrode), respectively. For UV-Vis. spectroscopy an ITO coated glass sheet (Praezisions Glas & Optik, Germany, R = 20 ± 5  cm −2 ), and for in situ resistivity measurements, a band-gap gold setup described elsewhere 35 (from AZAR electrode) were used z E-mail: jalal.arjomandi@s2004.tu-chemnitz.de as working electrodes. The two strips of the bandgap electrode can be easily bridged through the deposition of conducting polymers as the separation between them is only a few micrometers. The surface area of both strips is very small. Therefore, due to the brittle nature of the electrochemically synthesized conducting polymers, one cannot deposit thick films. Otherwise the films will not be uniform, some- thing which can considerably affect the experimental results. 36 The instrument for resistivity measurement was made by Sama Research Center. UV-Vis-spectra were recorded with the polymer and copoly- mer films deposited on an optically transparent ITO-glass electrode in the supporting electrolyte solution (acetonitrile + 0.1 M LiClO 4 ) in a standard 10 mm cuvette using a UV-Visible spectrophotometer Perkin Elmer, 55 OSD. A cuvette with the same solution and an uncoated ITO glass was placed in the reference beam. Spectra were recorded at increasingly positive electrode potentials; in a few cases, spectra were recorded in the negative-going potential direction in order to test reversibility. The morphological study was carried out by scan- ning electron microscopy with a Hitachi model S-4160 microscope. For this purpose, films were peeled back from the gold electrode and glued with graphite paste to a copper holder. Infrared spectra were recorded on a Perkin Elmer FT-IRGX spectrometer using the KBr pellet technique. All experiments were performed at room tempera- ture with nitrogen-purged solutions. PNMPy, PIn and P(NMPy-In) films electrosynthesis in nonaque- ous solution.— Monomers and electrolyte concentrations were [N- methylpyrrole] = 0.1 M, [Indole] = 0.1 M and [LiClO 4 ] = 0.1 M and 1:1, 2:1, 3:1, 1:2, 1:3 (mole-mole) ratio of (NMPy-In) solutions was prepared in acetonitrile + 0.1 M LiClO 4 separately. After vigor- ous mixing and nitrogen purging (10 min) electropolymerization was effected by scanning the electrode potential initially toward positive potentials and then between −0.10 < E SCE < 0.90 V at a scan rate of 50 mV · s −1 . The electrosynthesis for PNMPy, PIn, P(NMPy- In) (1mole-1mole), P(NMPy-In) (3mole-1mole) and P(NMPy-In) (1mole-3mole) films were stopped after 40, 400, 200, 110 and 440 cycles, respectively. Electrosynthesis for P(NMPy-In) (2mole- 1mole) and P(NMPy-In) (1mole-2mole) films were stopped after150 and 300 cycles, respectively. Results and Discussion Cyclic voltammetry.— Initial CVs of three different monomers of NMPy, In and 1:1 mole-mole ratio [NMPy]/[In] of a gold electrode Downloaded 25 Jan 2012 to 130.101.20.196. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp