Please cite this article in press as: A. Safavi, et al., Electrocatalytic oxidation of thiourea on graphene nanosheets–Ag nanoparticles hybrid ionic liquid electrode, Sens. Actuators B: Chem. (2014), http://dx.doi.org/10.1016/j.snb.2014.10.057 ARTICLE IN PRESS G Model SNB-17554; No. of Pages 5 Sensors and Actuators B xxx (2014) xxx–xxx Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo ur nal home page: www.elsevier.com/locate/snb Electrocatalytic oxidation of thiourea on graphene nanosheets–Ag nanoparticles hybrid ionic liquid electrode Afsaneh Safavi ∗ , Raheleh Ahmadi, Farzaneh Aghakhani Mahyari, Maryam Tohidi Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran a r t i c l e i n f o Article history: Received 2 August 2014 Received in revised form 1 October 2014 Accepted 14 October 2014 Available online xxx Keywords: Graphene nanosheets Silver nanoparticles Ionic liquid electrode Thiourea Amperometric method a b s t r a c t A simple, selective and sensitive graphene nanosheets–Ag nanoparticles hybrid ionic liquid electrode (GNSs-AgNPs/ILE) was used for the electrochemical determination of thiourea (TU). Cyclic voltammo- gram of TU showed two well defined oxidation signals at the potentials of -0.2 and 0.1 V vs. Ag/AgCl. Amperometric method was used for quantification of TU in the range of 1.0–3000 M. The theoretical detection limit was obtained as 0.7 M. The sensor was successfully applied for TU determination in orange juice and waste water. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Thiourea (TU) is known to be a serious environmental organic pollutant, with harmful effects on mammalian species and nitri- fying bacteria [1,2]. It is a carcinogenic [3] and allergenic [4] substance. Furthermore, TU causes the disturbance of carbohydrate metabolism [5], induce hypothyroidism [6] and inhibits nitrifi- cation in soil and water [7]. However, it has a widespread use in various fields of science and technology such as electroplat- ing industry [8], rubber industry [9], photography [2], analytical chemistry [10], agriculture [11] and for induction of early ripen- ing in several fruits [12]. Thus, a convenient, selective, sensitive, rapid and cost-effective method is demanded for the analysis of this hazardous material in waste water and environment. Several analytical methods have been reported for determina- tion of TU such as titrimetry [13], piezoelectric method [14], high performance liquid chromatography (HPLC) [15], Fourier transform infrared (FT-IR) spectrometry [16], chemiluminescence [10], flow injection methods [11], UV–vis spectrophotometry [17,18] and electrochemical methods [1,8,19–24]. Compared with other meth- ods, electrochemical techniques have some advantages including simplicity, rapidity, high selectivity and sensitivity. The unique electronic, catalytic and optical properties of metal nanoparticles make them attractive for potential applications in ∗ Corresponding author. Tel.: +98 711 6137150; fax: +98 711 2286008. E-mail address: safavi@chem.susc.ac.ir (A. Safavi). the electrochemical and optical sensors [25,26]. Recently, sev- eral metal nanoparticles modified electrochemical sensors have been reported for the determination of different important ana- lytes [26–30]. In the case of electrochemical sensors, the important functions provided by metal nanoparticles include the catalysis of electrochemical reactions and the enhancement of electron trans- fer [25]. Graphene nanosheets (GNSs), a new member of carbon mate- rials has become a hot topic of interest in different fields of chemistry owing to its unique nanostructure and its extraor- dinary electronic, mechanical and catalytic properties [31]. In recent years, GNSs has attracted tremendous attention as a new support of metal nanoparticles mainly due to its chemical stabil- ity, high electrical conductivity and the high surface to volume ratio [32–35]. Metal nanoparticles-embedded GNS hybrids display special features in sensors, catalysis and electrical applications [32–35]. Recently, a facile and rapid one-step procedure has been reported in our research group for the preparation of graphene nanosheets–Ag nanoparticles hybrid (GNSs-AgNPs) [35]. GNSs- AgNPs/ILE was prepared using GNSs-AgNPs as the conductive phase and octylpyridinium hexafluorophosphate (OPFP) as a binder [35]. OPFP was introduced for the first time in our research group as a very suitable binder for preparation of carbon ionic liquid electrode (CILE) [36,37]. It shows an excellent performance compared to con- ventional organic binders due to high conductivity, high thermal stability, wide electrochemical window, non-volatility and non- inflammability [36,37]. CILE exhibits highly desirable features such as simple preparation, renewable surface, low background current, http://dx.doi.org/10.1016/j.snb.2014.10.057 0925-4005/© 2014 Elsevier B.V. All rights reserved.