Synthetic Metals 157 (2007) 432–436 Tailoring the gold–polypyrrole nanostructures at water–toluene interphase Chepuri R.K. Rao, D.C. Trivedi ∗ Center for Studies in Conducting Polymers, Electrochemical Materials Science Division, Central Electrochemical Research Institute, Karaikudi 630006, India Received 15 January 2007; received in revised form 30 April 2007; accepted 30 April 2007 Available online 2 July 2007 Abstract A method is described to obtain gold–polypyrrole nanostructures by reacting gold chloride with pyrrole at toluene–water interphase. By adjusting the concentration of the stabilizer, namely, pyridine-3-sulphonate, the shape of the nanostructures formed at the interphase can be tailored. This novel method facilitates the fabrication of Au–Ppy composite material that gives wider scope for biosensing applications. © 2007 Elsevier B.V. All rights reserved. Keywords: Interphase; Nanostructures; Gold; Polypyrrole; Biosensing 1. Introduction In recent times nanomaterials have received tremendous attention due to their potential applications in important areas such as biology, medicine [1] and are now limelight for many scientists research programmes. Gold nanoparticles are biocom- patible, nontoxic, bind readily to large range of biomolecules such as aminoacids, proteins/enzymes and DNA [2]. On the other hand, conducting polymers (CPs), better known as advanced materials, are now foci of materials science and many applications are in vogue such as electrochromic displays [3], corrosion protection [4], electrostatic discharge/EMI shielding [5], batteries [6,7], sensors and electrocatalysis [8,9]. Polypyr- role (Ppy), an important CP, has excellent film forming property with good conductivity and is known for its unique biosens- ing/drug delivery [10] due to its biocompatibility. The drawback of this polymer is that the adsorption of desired biomolecules sometimes is difficult and not stable. The aim of the present work is to fabricate a nanocomposite, Au(0)–PPY, by incorporating a biologically active metal, gold, into biocompatible conduct- ing polymer polypyrrole and thereby enhancing the utility for biosensing. ∗ Corresponding author. Fax: +91 4565 227713. E-mail address: rkkousik@rediffmail.com (D.C. Trivedi). In our efforts to synthesize such metal–CP composite materi- als, we recently demonstrated method to incorporate palladium particles into Ppy matrix [11a] and modified Ppy surface with silver nanoparticles [11b]. Synthesis of conducting polymers such as polypyrrole and polyaniline using auric acid as oxi- dizing agent is known in literature [12–14]. Selvam et al. first synthesized gold–polypyrrole composite in a diblock copolymer micellor solution with HAuCl 4 as an oxidizing agent [12]. Liu et al. investigated [13] the pathways of auto-polymerization using complexes that contain chloride and gold. Report [14] on syn- thesis of polyaniline using tetrachloroaurate showed that gold colloids and short chained polyaniline are rapidly formed. The short chained polyaniline slowly transformed into long chain polyaniline. In the present communication, for the first time, we describe an effective and novel method to incorporate gold nanoparti- cles into conducting polypyrole matrix, at an interphase. We used AuCl 3 as an oxidizing agent which oxidatively polymer- izes pyrrole and concomitantly gets into the formed polymer as a nanosized metal particles at the toluene–water interphase. The morphology of Au–Ppy composite can be tailored to nanorods/colloids by adjusting the concentration of the stabi- lizer, namely, sodium pyridine-3-sulfonate (SPS). In the absence of the stabilizer, a copper colored powdery Au–Ppy material composed of nanosized particles is obtained. The results are presented and discussed. 0379-6779/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2007.04.013