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Desenvolvimento de dispositivos baseados em (nano)materiais de carbono para a detecção eletroquímica de espécies de interesse

  • Gevaerd, Ava
Publication Date
Sep 12, 2019
Repositório Digital Institucional da UFPR
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Abstract: Nanostructured materials have offered excellent opportunities for the construction of new electrochemical sensors. Carbon nanomaterials have been ahead prominence and are continuously described in literature due to their structures and properties such as excellent electrical conductivity, high electrocatalytic effect and surface area, which allows the development of sensors with low limits of detection and high sensitivity. In this way, the present project explores the characteristics of different carbon nanomaterials, for the construction of electrochemical devices for the determination of different species of interest, such as hormones, pesticides and mycotoxins. For the determination of progesterone, a glassy carbon electrode was modified with graphene oxide functionalized with imidazole. The synergistic effect of the components was fundamental for the good performance of the device that presented a linear region of 0.22 to 14.0 ?mol L-1, with a detection limit of 68 nmol L-1. The electrode was successfully used for determination of progesterone in pharmaceutical sample, presenting results concordant to those obtained for the comparative method (UV-Vis). For the determination of diethylstilbestrol, a screenprinted electrode was modified by electrodeposition with graphene quantum dots. When compared to an unmodified electrode, the proposed device presented better performance in terms of current, due to the lower values of resistance to charge transfer. The methodology for this determination presented a linear range of 0.05 to 7.5 ?mol L-1 and a detection limit of 8.8 nmol L-1. The application of the method for the determination of diethylstilbestrol in spiked water and urine samples presented good performance at different levels of concentration, with recovery percentages between 80 and 117%. Graphene quantum dots was used as a platform for attaching gold nanoparticles, and the composite was employed as a modifier of a screen-printed carbon electrode for the determination of aflatoxin B1 in fortified samples of malted barley, obtaining good recovery. The electrocatalytic effect presented by the composite is strongly evidenced by the voltammetric profile that presents less positive potential values for mycotoxin oxidation. Under optimized conditions, an analytical curve with linear region of 1.0 to 50.0 nmol L-1, reaching limits of detection of 0.47 nmol L-1. The determination of paraoxon was carried out in a non-enzymatic methodology using imidazole-functionalized carbon nanotubes. The interaction between imidazole and the pesticide allowed the proposed device to perform better than the others. The analysis of fortified samples can be performed, starting from the analytical curve with linear region of 1.0 to 14.0 ?mol L-1, with detection limit of 0.12 ?mol L-1. Fenamiphos was determined using a carbon electrode with electrochemically reduced graphene oxide, which presented a superior response to the unmodified device, which was attributed, besides other factors, to the low value of resistance to transfer of charge. With the optimized parameters, an analytical curve was constructed with a useful working region of 0.25 to 25.0 ?mol L-1 and limits of detection and quantification of 0.067 and 0.22 ?mol L-1. From this, the use of carbon nanomaterials combined with electroanalytical devices lead to versatile strategies that can be employed for the determination of different classes of species of interest. Keywords: Carbon Nanomaterials, Electroanalytical Devices, Hormones, Pesticides, Mycotoxin.

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