DOI: 10.1002/elan.201900217 Silver Nanoparticles-silsesquioxane Nanomaterial Applied to the Determination of 4-nitrophenol as a Biomarker PaolaZimmermann Crocomo, [a] JoãoPaulo Winiarski, [a] MaríliaReginatodeBarros, [a] Eloah Latocheski, [a] GlaucioRégis Nagurniak, [b] RenatoLuisTameParreira, [c] DiogoAlexandre Siebert, [a] GustavoAmadeu Micke, [a] HéricaAparecida Magosso, [a] andCristianeLuisaJost* [a] Abstract: Anovelsilsesquioxanematerialwassynthetized and used as a stabilizing agent for silver nanoparticles. This hybrid material was characterized by FTIR, 29 Si CP- MAS NMR, 13 C DEPT 135° NMR and TGA techniques and the silver nanoparticles were characterized from DLS, UV-Vis spectroscopy, zeta-potential, TEM and SAXS results. The silver nanoparticles obtained were spherical in shape with a diameter of 3.74nm. The nanomaterial was successfully applied in the modification of a glassy carbon electrode and a pronounced current response was obtained in the determination of the biomarker 4-nitrophenol. Quantum chemical calculations, using density functional theory, were also performed in ordertoevaluatetheredoxpropertiesoftheanalyte.Two different linear ranges were obtained applying optimal square wave voltammetry conditions. The reduction peak currents obtained were linear for 4-NP concentrations in the ranges of 0.29 to 1.50μmolL 1 (E d = 0.6Vandt d = 20s)and2.75to31.5μmolL 1 , with a theoretical (signal to noise = 3)limitofdetectionof0.05μmolL 1 (t d = 20s). The proposed method was successfully applied to the determination of 4-NP in synthetic serum samples at different levels of 4-NP with a recovery range of 94– 101%. Validation was performed using a comparative methodthroughthecapillaryelectrophoresis(CE)techni- que. Keywords: hybrid material · silver nanoparticles electrochemical sensor · 4-nitrophenol · quantum chemical calculations · biomarker 1 Introduction The compound 4-nitrophenol (4-NP) is included in the List of Priority Pollutants of the U.S. Environmental Protection Agency (USEPA) due to its toxicity and persistence [1]. This compound has been described as potentially carcinogenic, teratogenic and mutagenic [2,3]. It is released as a product of the hydrolysis of the pesticides parathion and methyl parathion in aquatic environments[4,5].Themolecularstructuresforthethree above-mentionedcompoundsareshowninFigure1. Thebiodegradationofparathionandmethylparathion occurs quickly, with a half-life time of seven days in soils, after a breakdown of the O  P bond in their chemical structure[6,7].Thecompound4-NPcanbeconsideredas a biomarker in biological monitoring for establishing the presence and magnitude of exposure to both pesticides throughthemeasurementof4-NPinurine[8]. Unfortunately, parathion sprays are still used for crop cultivation by farm workers worldwide [9]. Despite the prohibition (in 2016) by the regulatory agencies in Brazil [10], methyl parathion is employed particularly in border areas where cotton and soybeans are grown. Organo- phosphatepesticides,suchasmethylparathion,havebeen related to depression and suicide cases involving crop farmers in southern Brazil [11,12] and worldwide [13,14]. Thus, the development of analytical procedures for the determination of the biomarker 4-NP in biological samplesisofgreatinterest. Several techniques are recommended for the determi- nation of 4-NP in different types of samples, such as HPLC[15,16],electrophoresis[17,18]chemiluminescence [19], and GC coupled to mass spectrometry [20]. How- ever, electroanalytical techniques, such as voltammetry, have been attracting greater attention in recent years due to the reduction of analysis costs without compromising the figures of merit. The advent of electrodes modified with metal nanoparticles in combination with efficient stabilizingagentshascontributedtothisdemand.Electro- des modified with nanomaterials allow lower costs in comparison to bare electrodes while enhancing the selectivity and sensitivity and even providing electro- catalysisinsomereactions[21–26]. [a]P.Z.Crocomo,J.P.Winiarski,M.R.deBarros, E.Latocheski,D.A.Siebert,G.A.Micke,H.A.Magosso, C.L.Jost Universidade Federal de Santa Catarina, Departamento de Química, 88040-900 Florianópolis – SC, Brazil Tel.: + 55 48 37214538 E-mail:cristiane.jost@gmail.com [b]G.R.Nagurniak Universidade Federal de Pelotas, Departamento de Física, P. O. Box 354, Pelotas – RS, Brazil [c]R.L.T.Parreira Universidade de Franca, Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, 14404-600 Franca – SP, Brazil Supporting information for this article is available on the WWWunderhttps://doi.org/10.1002/elan.201900217 Full Paper www.electroanalysis.wiley-vch.de © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2019, 31, 1 – 12 1 These are not the final page numbers! ��