DOI: 10.1002/celc.201402087 Synthesis of Hybrid Electroactive Materials by Low- Potential Electropolymerization of Gold Nanoparticles Capped with Tailored EDOT-Thiophene Precursor Units** Ali Yassin, [a] MaitØna OÅafrain, [a] Philippe Blanchard,* [a] Romain Mallet, [b] and Jean Roncali* [a] 1. Introduction Electrogenerated conducting polymers (ECPs) based on thio- phene derivatives (PTs) have been the focus of sustained scien- tific interest for several decades. [1, 2] Besides the advantages of electrochemical polymerization in terms of simplicity, rapidity, and direct grafting of an electroactive material onto an elec- trode surface, the possibility of modulating the electronic properties of the p-conjugated backbone by tailoring the structure of the precursor has received much attention and driven the development of rich synthetic chemistry focused on the synthesis of functional ECPs for energy storage, [3] electro- chromics, [4] electrocatalysis, [5] or sensors. [6] Since the beginning of research on PTs, modification of the structure and properties of these polymers has been devel- oped along two main lines, namely, the polymerization of monomers modified by covalently attached functional groups [2] and the association of PTs with other organic or inor- ganic substances to develop hybrid materials based on syner- gistic combinations of the two components. [2, 7, 8] In this con- text, PTs containing metallic nanoparticles of, for example, plat- inum, copper, or palladium for applications in electrocatalysis have been developed at an early stage. [9] More recently, PTs containing gold nanoparticles (GNPs) have been prepared by several groups with the aim of combining the mechanical, op- tical, and electrical properties of conducting polymers with the optical, electrical, and catalytic properties of GNPs. [10–18] These hybrid PT/GNP materials have been synthesized by different chemical methods. Thus, the use of tetraalkylammonium or poly(vinylpyridine) derivatized with pendant terthienyl (3T) groups to reduce solutions of HAuCl 4 gives GNPs larger than 15 nm in the first case and those of 6 to 100 nm with an aver- age of 33 nm with the second approach. [11, 12] A related method involves the oxidative polymerization of EDOT by HAuCl 4 with the concomitant formation and incorporation of GNPs in the polymer. [13–15] Alternative methods are based on the reduction of HAuCl 4 by NaBH 4 in the presence of poly(3-hexylthio- phene), [16] the addition of HAuCl 4 to solutions of chemically synthesized PT with polyether side chains, [17] or the entrap- ment of encapsulated GNPs during the electrochemical poly- merization of EDOT. [18] Relatively few groups have investigated the direct electro- chemical synthesis of GNP/PT by using GNPs capped with elec- tropolymerizable groups as precursors. [19–23] Thus, the electro- chemical co-polymerization of 3-alkylthiophenes with GNPs stabilized by 2-mercapto-3-octylthiophene or 3-(11-mercapto- 1-undecanoxyl)thiophene has been reported. [19, 20] The electro- deposition of GNPs capped with terthiophenes attached to GNPs through phosphine groups was first described by Wolf et al. , [21] whereas other groups have investigated the electroox- idation of GNPs capped with short-chain oligothiophenes [22] or with oligoethyleneoxy–terthiophene templates. [23] It is worth noting that, in spite of detailed characterization of the compo- sition and structure of the resulting electrogenerated materials, their detailed electrochemical and spectroelectrochemical properties have barely been investigated. One of the key problems to achieve efficient electrochemical synthesis of a hybrid GNP/PT material is related to the choice The synthesis of gold nanoparticles (GNPs) capped with alka- nethiols with terminal bithiophenic polymerizable groups, con- sisting of 3,4-ethylenedioxythiophene (EDOT) and 3-alkylsulfa- nylthiophene, is described. Transmission electron microscopy (TEM) and light diffusion show that these stabilized GNPs have an average size of 2–3 nm with low polydispersity. The electro- chemical behavior of C 10 S-Au is investigated in dichlorome- thane in the presence of Bu 4 NPF 6 . The results show that these capped GNPs undergo straightforward and efficient electropo- lymerization under potentiodynamic or potentiostatic condi- tions. TEM images show that the electrodeposited films of the composite material present a very homogeneous structure, in which the size of the GNPs incorporated into the polythio- phene matrix is unchanged. Results of cyclic voltammetry and spectroelectrochemistry obtained on polymer films deposited on platinum electrodes and transparent indium tin oxide elec- trodes, respectively, show that the reversible charging–dis- charging process and electrochromic behavior typical of poly- (thiophenes) are preserved in the hybrid electroactive material. [a] Dr. A. Yassin, Dr. M. OÅafrain, Dr. P. Blanchard, Dr. J. Roncali Group Linear Conjugated Systems, CNRS, Moltech-Anjou University of Angers, 2 Bd Lavoisier F-49045 (France) E-mail : jeanroncali@gmail.com [b] R. Mallet Service Commun d’Imageries et Analyses microscopiques SCIAM University of Angers (France) [**] EDOT = 3,4-ethylenedioxythiophene. Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/celc.201402087.  2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemElectroChem 0000, 00,1–8 &1& These are not the final page numbers! ÞÞ CHEMELECTROCHEM ARTICLES