Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Full Length Article Sensitive nitrite detection at core-shell structured Cu@Pt nanoparticles supported on graphene R.M. Abdel Hameed ⁎ , Shymaa S. Medany Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt ARTICLE INFO Keywords: Core-shell structure Biosensor Selectivity Real samples Detection limit ABSTRACT Although nitrite is a carcinogenic material, it is widely used in food preservation. Accordingly, suitable elec- troanalytical tools are necessary to estimate nitrite ions concentration. In this work, core-shell structured Cu@Pt nanoparticles supported on graphene [Cu@Pt/Gr] were developed in simple two-step route through ethylene glycol as a reducing agent. The fabricated nanomaterial was characterized using X-ray diffraction, transmission electron microscopy and electrochemical techniques. Gathering graphene with copper and platinum in special architecture efficiently enhanced its electrocatalytic performance during nitrite determination. The prepared nanocomposite linearly responded to nitrite ions in the concentration ranges of 1 μM–1 mM and 1–15 mM with respective sensitivity values of 21.03 and 62.69 μA mM -1 cm -2 . Cu@Pt/Gr possessed high selectivity for nitrite in presence of many common interfering species. Satisfactory results were obtained when this fabricated na- nocomposite was applied to estimate nitrite concentration in real water samples. This synthesized nano- composite presents a good active component for efficient determination of carcinogens in food industry. 1. Introduction Nowadays, nitrites have received a great attention as fertilizing agents and preservatives. Increasing the concentration of nitrite ions over a definite level could be dangerous to animal and human health. The ingestion of nitrites could lead to the oxidation of hemoglobin into metahemoglobin, and converting amines into nitrosamines, which are known as carcinogenic components [1]. Nitrites could be also in- dustrially employed as a corrosion inhibitor in the industrial water. The potential carcinogenic effect of dietary nitrites and nitrates was studied by Ferrucci et al. [2]. An increased level of bladder cancer was re- corded. Consequently, estimating nitrite levels in drinking water, an- imal feeds, vegetables, water resources, various food products, etc. could be essentially preserve human health and livestock. The determination of nitrite was carried out using several techni- ques including spectroscopy [3], chemiluminescence [4], capillary electrophoresis [5], chromatography [6] and electrochemical methods [7]. Spectrophotometric techniques are generally complex and time consuming. This could be recovered by applying the electrochemical methods. They could provide low cost, fast, ease use and accurate es- timation of nitrite with high sensitivity and selectivity [8–12]. The electrochemical methods rely on nitrite oxidation or nitrite reduction. Nitrite oxidation is the most favorable where there is no interference from nitrate ions or molecular oxygen that could impede the cathodic determination [13,14]. Lin et al. [15] have investigated the electro- catalytic activity of poly (3,4-ethylenedioxythiophene)/iron phthalo- cyanine/multi-walled carbon nanotubes modified screen-printed carbon electrode towards nitrite oxidation. The oxidation overpotential value was reduced by ≈330 mV in conjunction with 3.5 times en- hancement in the oxidation peak current density in relation to those at unmodified electrode. High sensitivity of 638 mA cm -2 M -1 and low detection limit of 71 nM (S/N = 3) were also measured. Rajalakshmi et al. [16] have successfully fabricated electropolymerized 5-amino- 1,3,4-thiadiazole-2-thiol on acid functionalized multi-walled carbon nanotubes. It exhibited a linear current response for nitrite oxidation in the range of 10–1000 nM with a detection limit of 0.2 nM (S/N = 3). On the other hand, multi-walled carbon nanotubes decorated with silver nanoparticles demonstrated fast response towards nitrite oxidation with good reproducibility and long-term stability up to 15 days [17]. Core-shell structured design for electrocatalysts manufacture was developed to enhance the selectivity and platinum surface area utili- zation that in turn improved the measured electrocatalytic activity. The deposition of a thin layer of platinum shell on the transition metal core significantly affected the electronic and structural properties of core- shell nanocomposite [18,19] resulting in higher electrocatalytic activity and stability when related to the electrochemical behavior of pure Pt. https://doi.org/10.1016/j.apsusc.2018.07.079 Received 27 March 2018; Received in revised form 29 June 2018; Accepted 11 July 2018 ⁎ Corresponding author. E-mail address: randa311eg@yahoo.com (R.M. Abdel Hameed). Applied Surface Science 458 (2018) 252–263 0169-4332/ © 2018 Elsevier B.V. All rights reserved. T