Nanocomposites Visible-Light-Driven Production of Poly(a-terthiophene)–Au Nanoparticle Functional Hybrid Material Raj Kumar Bera, Prasenjit Bhunia, Sukanta Chakrabartty, and C. Retna Raj* [a] Abstract: A novel one-step visible-light-driven synthesis of Au nanoparticle–poly(a-terthiophene) (nAu-poly(a-TT)) func- tional nanocomposites and their electrocatalytic and photo- electrocatalytic applications are described. The visible-light- induced electron transfer between a-TT and Au III ion yields nAu-poly(a-TT) nanocomposite material. The nAu-poly(a-TT) shows characteristic diffraction corresponding to the well-or- ganized lamellar structure of the polymer and Au nanoparti- cles. The nanoparticles inside the polymer matrix increase the interlayer spacing and stacking distance of the polymer planes. Remarkable enhancement in the Raman signature of poly(a-TT) due to the embedded Au nanoparticles was ob- served. The nanocomposite favors the selective electrochem- ical oxidation of hydrophobic analytes. The photoexcitation of the nanocomposite with white light at potentials more negative than 0.3 V (Ag/AgCl) yields cathodic photocur- rent, which is > 500 times higher than that of the free poly(a-TT). Introduction Functional nanocomposite materials derived from conducting polymers and metal nanoparticles are very promising for vari- ous applications due to the synergistic properties of the parent components. In recent years, the potential benefits of these composite materials have been well-recognized for fun- damental and technological applications. For instance, they have been exploited in the development of energy conversion and storage interfaces, microelectronics, biosensing and bio- electronic devices, etc. [1, 2] The metal nanoparticles of the com- posite significantly improve the electronic and optoelectronic properties of the polymer. Both metal nanoparticles and con- ducting polymers complement each other in enhancing the overall performance of the composite material. The develop- ment of conductive composite materials with polymers having the donor and acceptor functionalities is one of the promising approaches in the fabrication of bulk-heterojunction solar cells and photoelectrochemical platforms. [3, 4] The incorporation of metal particles of suitable shape and size onto such polymers is known to increase the charge separation. [5, 6] The functional properties of these composite materials largely depends on the size, shape, and distribution of the nanoparticles in the polymer network and nature of the polymer. [7, 8] The controlled growth of metal nanoparticles of desired shape and size is a challenging task. Polymer–metal nanoparticle hybrid materials have been syn- thesized by various approaches including: [9–17] 1) direct in situ synthesis by the oxidative polymerization of the monomer using the metal precursor as an oxidizing agent, which in- volves the polymerization and growth of metal nanoparticle in one-pot without using any additional reducing/oxidizing agent; [18–24] 2) synthesis using redox-active polymers that are thermodynamically capable of reducing the metal precursor; and 3) physical mixing of ex situ synthesized polymers and metal nanoparticles using suitable procedures. The direct route is very promising and has many advantages over the other available methods as homogeneous distribution as well as controlled growth of metal nanoparticles in the polymer matrix can be achieved in one-step. It does not require any ex- ternal reducing agent as the monomer itself plays the role of reducing agent. For the direct synthesis of the nanocomposite materials, chemical, electrochemical, and photochemical meth- ods have been employed in the past. For instance, Jung et al. chemically polymerized thiophene using Au III complex as an oxidizing agent to obtain the composite material of polythio- phene–Au nanoparticle. [19] Pringle et al. demonstrated the one- step chemical synthesis of polymer–noble metal nanoparticle in ionic liquid. [20] The electrochemical methods require a con- ducting support where both polymer and metal nanoparticles have been simultaneously deposited. [23, 24] Takahashi et al. ex- plored the electrochemical polymerization of thiophene on Au nanoparticle electrostatically pre-deposited electrodes. [23] Peng et al. demonstrated the incorporation of metal nanoparticles into the polymer network during electrochemical polymeri- zation. [24] The photochemical methods have some advanta- geous over the electrochemical methods: 1) They do not re- [a] Dr. R. K. Bera, Dr. P. Bhunia, S. Chakrabartty, Prof. C. R. Raj Functional Materials and Electrochemistry Lab Department of Chemistry Indian Institute of Technology Kharagpur Kharagpur 721302 (India) E-mail : crraj@chem.iitkgp.ernet.in Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cnma.201500111. ChemNanoMat 2015, 1, 586 – 592 # 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 586 Full Paper DOI: 10.1002/cnma.201500111