Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Combining electrochemically reduced graphene oxide and Layer-by-Layer films of magnetite nanoparticles for carbofuran detection Celina M. Miyazaki a, *, Angela M. Adriano a , Rafael J.G. Rubira b , Carlos J.L. Constantino b , Marystela Ferreira a, * a Universidade Federal de São Carlos, CCTS, Sorocaba, SP, Brazil b Universidade Estadual Paulista, Presidente Prudente, SP, Brazil ARTICLE INFO Editor: Zhang Xiwang Keywords: Layer-By-Layer film Carbofuran Electrochemical sensor Magnetite Reduced-Graphene oxide ABSTRACT Carbofuran (CBF) is a pesticide currently prohibited in many countries. It can cause serious damages in the nervous system and has been associated with cancer. However, CBF residues are still found in food samples around the world. Here, we develop an electrochemical non-enzymatic sensor for rapid and low-cost detection of CBF. Commercial indium tin oxide (ITO) electrodes were modified with a two-step Layer-by-Layer (LbL) ap- proach: i) an LbL film of poly(diallyldimethyl ammonium) (PDDA) and graphene oxide (GO), which is further electrochemically reduced to produce (PDDA/ERGO)-modified ITO electrodes; and ii) an LbL film of magnetite nanoparticles (MNP) and poly(styrene sulfonate) (PSS) to form the ITO/(PDDA/ERGO) 5 /(MNP/PSS) 5 , with 5 representing the number of bilayers. The growth mechanism and morphology of the modified electrode were characterized by combining microscopy and optical spectroscopy. The ITO/(PDDA/ERGO) 5 /(MNP/PSS) 5 was applied in the electrochemical detection of CBF by differential pulse voltammetry (DPV) in standard solutions, reaching a sensitivity of 0.2543 (μA cm -2 )(μmol L -1 ) and LOD of 0.407 μmol L -1 , and then in real samples of tap water and soil. 1. Introduction Carbofuran (CBF), 2,3-Dihydro-2,2-dimethyl-7-benzofuranol N-me- thylcarbamate, is a pesticide widely used in agriculture to eradicate insects, mites, and parasites. By contact or ingestion, CBF is capable of inhibiting the activity of acetylcholinesterase (AChE) [1,2], resulting in the accumulation of acetylcholine in the synapse and causing mal- functioning of the nervous system [2]. CBF also affects the metabolism of steroids in mammals, and it may be related to cases of lung cancer and lymphoma [2]. CBF is prohibited in the United States and the European Union. In Brazil, it was also prohibited in October 2017 with a discontinuation period within 6 months for cultures of banana, sugar- cane and coffee. However, a report delivered in 2019 by the Brazilian regulatory agency (ANVISA) named Program of Analysis of Pesticides Residues in Food (PARA, from the Portuguese Programa de Análise de Resíduos de Agrotóxicos em Alimentos) show up CBF residues in oranges, sweet potatoes, lettuce, peppers, grapes, and others. Although its origin was associated with the possible conversion of the carbosulfan, this can be related to the illegal application of the CBF. The development of fast, sensitive, and low-cost methods for the monitoring of soil, food and water is extremely important. Currently, the quantification of CBF has been performed by sophisticated, time- consuming and costly methods, which usually require prior treatment of the samples, such as chromatographic methods combined with mass spectrometry techniques [3] and UV–vis absorbance [4,5], or other methods based on the enzyme inhibition [6,7]. In this scenario, elec- trochemical sensors are low cost, easy to handle, and can be moulded to be selective and sensitive. Enzymatic sensors based on the AChE inhibition were developed for CBF detection [6,7]. Chen et al. [6] developed a sensor through the immobilization of the AChE enzyme on a glass-carbon electrode mod- ified with carbon nanotubes, using Prussian Blue as an electron med- iator. However, enzymatic sensors exhibit a high manufacturing cost and require special care for the maintenance of enzymatic activity, i.e. https://doi.org/10.1016/j.jece.2020.104294 Received 7 May 2020; Received in revised form 17 June 2020; Accepted 20 July 2020 Abbreviations: CBF, carbofuran; MNP, magnetite nanoparticles; AChE, acetylcholinesterase; GO, graphene oxide; RGO, reduced graphene oxide; ERGO, electro- chemically-reduced graphene oxide; LbL, Layer-by-Layer; DPV, differential pulse voltammetry; PDDA, poly(diallyldimethylammonium chloride); PSS, poly(styr- enesulfonate) sodium salt ⁎ corresponding authors at: Universidade Federal de São Carlos, CCTS, Rod. João Leme dos Santos, KM 110, Bairro Itinga, CEP 18052-780, Sorocaba, São Paulo, Brazil. E-mail addresses: celinammiyazaki@gmail.com (C.M. Miyazaki), marystela@ufscar.br (M. Ferreira). Journal of Environmental Chemical Engineering 8 (2020) 104294 Available online 25 July 2020 2213-3437/ © 2020 Elsevier Ltd. All rights reserved. T