CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 9207–9214 Thiourea assisted one-pot easy synthesis of CdS/rGO composite by the wet chemical method: Structural, optical, and photocatalytic properties Satheesh Kaveri a , Lavanya Thirugnanam b,c , Mrinal Dutta b , Jayavel Ramasamy a , Naoki Fukata b,n a Centre for Nanoscience and Technology, Anna University, Chennai 600025, India b International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan c Department of Physics, Anna University, Chennai 600025, India Received 22 March 2013; received in revised form 7 May 2013; accepted 7 May 2013 Available online 14 May 2013 Abstract We report on the synthesis of CdS/reduced graphene oxide (rGO) composite by a wet chemical method. Thiourea was used both as a sulfur source and as a reducing agent to convert graphene oxide to rGO. The structural and morphological confirmation for the reduction of graphene oxide and the formation of the CdS/rGO composite was demonstrated by X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. Photoluminescence spectra of the composite exhibited a more efficient luminescence quenching in comparison with pure CdS nanoparticles. The composite demonstrated 99% photodegradation of methyl orange under UV irradiation, which is much superior than the photodegradation of methyl orange under similar conditions exhibited by CdS nanoparticles (72%). & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: C. Optical properties; Wet chemical synthesis; CdS/rGO composite; Luminescence quenching; Photocatalytic properties 1. Introduction Graphene, an sp 2 hybridized hexagonal arrangement of two dimensional honeycomb carbon lattice, has become the focus of recent research because of its extraordinary optical, thermal, electrical, and mechanical properties [1–4]. These properties hold great promise for technological applications in different areas such as nanoelectronics [5], sensors [6], photovoltaics [7], and energy storage materials [8,9]. Graphite oxide is the starting precursor for synthesizing graphene oxide (GO) sheets. GO has many oxygen-containing functional groups such as epoxy, hydroxyl, carbonyl, and carboxyl groups [10,11]. A growing interest has been evidenced in decorating the inorganic nanoparticles with graphene sheets to enhance their photocatalytic properties. The oxygen-containing functional groups of GO are very useful in attaching inorganic nanopar- ticles within graphene sheets. However, these functional groups act as scattering centers and alter the sp 2 in-plane bonding, thereby reducing the optical and electrical properties of graphene. Hence, regaining sp 2 aromaticity by reducing these functional groups becomes necessary to enable reduced GO (rGO) to be effectively used as an efficient charge carrier shuttle and a photocatalytic support material. So far, different approaches for this purpose, such as chemical reduction with reducing agents like hydrazine, hydrothermal reduction, and photochemical reduction using semiconductors, have been demonstrated [12]. Hydrazine and its derivatives have been proved the best GO reducing agents; however, owing to their toxicity, the search for alternate non-toxic compounds is still on. In the recent years, nanocrystalline semiconductor materi- als have attracted much attention because of their unique optical and electronic properties [13–15]. By controlling the particle size, the band gap of semiconductor nanoparticles can www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.05.025 n Corresponding author. Tel.: +81 29 8513354 4769. E-mail address: FUKATA.Naoki@nims.go.jp (N. Fukata).