Browsing by Author "Sousa, Camila P."
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- Chitosan-magnetite nanocomposite as a sensing platform to bendiocarb determinationPublication . Oliveira, Raissa C. de; Sousa, Camila P.; Freire, Tiago M.; Freire, Rafael M.; Denardin, Juliano C.; Fechine, Pierre B. A.; Becker, Helena; Morais, Simone; Lima-Neto, Pedro de; Correia, Adriana N.A novel platform for carbamate-based pesticide quantification using a chitosan/magnetic iron oxide (Chit-Fe3O4) nanocomposite as a glassy carbon electrode (GCE) modifier is shown for an analytical methodology for determination of bendiocarb (BND). The BND oxidation signal using GCE/Chit-Fe3O4 compared with bare GCE was catalyzed, showing a 37.5% of current increase with the peak potential towards less positive values, showing method's increased sensitivity and selectivity. Using square-wave voltammetry (SWV), calibration curves for BND determination were obtained (n = 3), and calculated detection and quantification limits values were 2.09 × 10-6 mol L-1 (466.99 ppb) and 6.97 × 10-6 mol L-1 (1555.91 ppb), respectively. The proposed electroanalytical methodology was successfully applied for BND quantification in natural raw waters without any sample pretreatment, proving that the GCE/Chit-Fe3O4 modified electrode showed great potential for BND determination in complex samples. ᅟ Graphical abstract.
- Chlorhexidine digluconate on chitosan-magnetic iron oxide nanoparticles modified electrode: Electroanalysis and mechanistic insights by computational simulationsPublication . Sousa, Camila P.; Oliveira, Raissa C. de; Freire, Tiago. M.; Fechine, Pierre B.A.; Salvador, Michele A.; Homem-de-Mello, Paula; Morais, Simone; Lima-Neto, Pedro de; Correia, Adriana N.In this work, an electrochemical sensor based on modification of a glassy carbon electrode (GCE) with magnetic iron oxide nanoparticles (Fe3O4) and chitosan (CS) was developed to quantify chlorhexidine digluconate (CHD), a worldwide used antiseptic. Cyclic voltammetric and electrochemical impedance spectroscopy assays showed that the permeable Fe3O4/CS film on the GCE surface improved the conduc-tivity and facilitated electron transfer. CHD response at GCE/Fe3O4/CS corresponds to an irreversible anodic diffusion-controlled process (at about 1.13 V in 0.04 mol L−1 Britton-Robinson buffer, pH 4.0) involving the transfer of two electrons and an equal number of proton. Quantum mechanics and Monte Carlo simulations were performed to give insights on the CHD oxidation process. The modification with Fe3O4/CS induced alterations in CHD geometry that led to degeneration of the highest occupied molecular orbitals (HOMO and HOMO−1), facilitating the oxidation process because both sides of the molecule contribute to these orbitals. It facilitated also, at least thermodynamically, the first electron lost. The oxidation of CHD probably conducts to the formation of two p-chloroaniline and, possibly, two biguanidine molecules. GCE/Fe3O4/CS exhibited suitable electroanalytical characteristics in terms of sensitivity (8.78 ± 0.58 A mol−1 L), linearity range (2.10 × 10−8–2.09 × 10−7 mol L−1), detection limit (5.7 × 10−9 mol L−1; 0.005 mg kg−1), intra-day repeatability (2.8% RSD), and reproducibility (4.6% RSD). To evaluate the accuracy and applicability of the proposed electroanalytical methodology, two CHD com-mercial formulations were analysed and the attained results were in agreement with those attained by the chromatographic reference method. Overall, the developed GCE/Fe3O4/CS exhibits appropriate performance and relevant advantages for CHD electroanalysis in commercial products.
- Dispersion of multi-walled carbon nanotubes in [BMIM]PF 6 for electrochemical sensing of acetaminophenPublication . Gomes, Rayane N.; Sousa, Camila P.; Casciano, Paulo N.S.; Ribeiro, Francisco Wirley P.; Morais, Simone; Lima-Neto, Pedro de; Correia, Adriana N.The influence of functionalized multi-walled carbon nanotubes (fMWCNT) in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) in different ratios was investigated on the acetaminophen (ACOP) electrochemical determination. The electrochemical behavior of the ACOP exhibited a pair of well-defined redox peaks, suggesting that the reversibility of ACOP was significantly improved in comparison to irreversible oxidation peak on bare GCE. The redox process was controlled by adsorption, involves two electrons and the value of apparent rate constant (ks) was equal to 14.7 s-1 ± 3.6 s-1. The analytical curves were obtained for concentrations of ACOP ranging from 0.3 to 3.0 μmol L-1. The values of the detection limit were calculated from SWV and found to be 6.73 × 10-8 mol L-1. The proposed electrochemical sensor exhibited good stability and reproducibility and was applied for ACOP determination in tablets (Tylenol® and Tylenol®DC) with satisfactory results.
- Electroanalysis of Imidacloprid Insecticide in River Waters Using Functionalized Multi-Walled Carbon Nanotubes Modified Glassy Carbon ElectrodePublication . Paiva, Wyslley Douglas A.; Oliveira, Thiago Mielle B. F.; Sousa, Camila P.; Neto, Pedro de Lima; Correia, Adriana N.; Morais, Simone; Silva, Djalma R.; Castro, Suely Souza LealIn this work, a functionalized multi-walled carbon nanotubes modified glassy carbon electrode (GCE/MWCNT-f) was optimized for the direct determination of imidacloprid (IMC) insecticide in river water. The functionalized material was characterized by infrared spectroscopy with Fourier transform (FTIR) and the modified electrode by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Results revealed that the GCE/MWCNT-f effectively increased the response toward IMC reduction by enhancing the reduction peak current and decreasing the peak potential in comparison with the bare electrode. After optimizing the electroanalytical conditions, the GCE/MWCNT-f showed a linear voltammetric response at concentration ranging from 2.40 × 10−7 to 3.50 × 10−6 mol L−1, with detection and quantification limits of 4.15 × 10−7 mol L−1 and 1.38 × 10−6 mol L−1, respectively. The recovery rate of IMC in spiked river water samples varied from 90–95%. Thus, this sensor can be a promising tool for the analysis and monitoring of IMC in complex environmental matrices.
- Electroanalysis of Pharmaceuticals on Boron‐Doped Diamond Electrodes: A ReviewPublication . Sousa, Camila P.; Ribeiro, Francisco W. P.; Oliveira, Thiago M. B. F.; Salazar‐Banda, Giancarlo R.; Lima‐Neto, Pedro de ; Morais, Simone; Correia, Adriana N.Boron‐doped diamond (BDD) electrodes possess outstanding physical, chemical, and electronic properties and have been successfully, yet in a limited way, explored in the electroanalysis of substances with therapeutic action (analgesics, antipyretics, antibiotics, anti‐inflammatories, antihypertensives, antidepressants, vitamins, and others) in diverse milieus (pharmaceutical formulations, urine, serum, whole blood, surface waters, seawaters, groundwater, wastewaters, etc.). Therefore, in this Review, a broad overview of the available scientific information on recent progress and achievements of the application of bare or modified BDD electrodes to the bioanalytical and environmental detection of pharmaceutical compounds is presented. The main parameters, for example boron concentration, applied operational conditions during pretreatment, chemical and physical structure, and other influential factors on the electroanalytical BDD electrodes performance, are discussed.
- Electroanalysis of Pharmaceuticals on Boron‐Doped Diamond Electrodes: A ReviewPublication . Sousa, Camila P.; Ribeiro, Francisco W. P.; Oliveira, Thiago M. B. F.; Salazar‐Banda, Giancarlo R.; Lima‐Neto, Pedro de; Morais, Simone; Correia, Adriana N.Boron‐doped diamond (BDD) electrodes possess outstanding physical, chemical, and electronic properties and have been successfully, yet in a limited way, explored in the electroanalysis of substances with therapeutic action (analgesics, antipyretics, antibiotics, anti‐inflammatories, antihypertensives, antidepressants, vitamins, and others) in diverse milieus (pharmaceutical formulations, urine, serum, whole blood, surface waters, seawaters, groundwater, wastewaters, etc.). Therefore, in this Review, a broad overview of the available scientific information on recent progress and achievements of the application of bare or modified BDD electrodes to the bioanalytical and environmental detection of pharmaceutical compounds is presented. The main parameters, for example boron concentration, applied operational conditions during pretreatment, chemical and physical structure, and other influential factors on the electroanalytical BDD electrodes performance, are discussed.
- Experimental and computational studies of the interactions between carbon nanotubes and ionic liquids used for detection of acetaminophenPublication . Salvador, Michele A.; Sousa, Camila P.; Maciel, Cleiton D.; Gomes, Rayane N.; Morais, Simone; Lima-Neto, Pedro de; Coutinho-Neto, Maurício D.; Correia, Adriana N.; Homem-de-Mello, PaulaThe interactions between multi-walled carbon nanotubes and different amounts of an ionic liquid (IL), as well asthe interactions between this system (used as electrochemical sensor) and acetaminophen (ACOP), were in-vestigated through both experimental and theoretical methodologies. Experiments indicated that there is anoptimal concentration of ionic liquid for ACOP detection. A host of techniques and model systems were em-ployed to investigate the adsorption and oxidation processes. To investigate the source of the increased elec-trochemical current in the presence of an IL, we computed the adsorption energy values of ACOP in the nanotube–IL system via Monte Carlo simulations and Density Functional Theory (DFT). DFT allowed us to explore thechanges in adsorption energy due to oxidation. Our theoretical results support the experimentalfindings thatmoderate amounts of IL modulates ACOP/ACOP+adsorption, pointing to a cooperative effect that tends to wanewith increasing amounts of IL pairs. We observed that the IL favors desorption of the oxidized species andfacilitates charge transfer from the ACOP to the nanotube. Therefore, our studies point towards multifactorialeffects with clear physical basis that modulates binding leading to an optimal ratio to promote ACOP detection
- Trends and frontiers in graphene-based (bio)sensors for pesticides electroanalysisPublication . Sousa, Camila P.; Ribeiro, Francisco W.P.; Oliveira, Thiago M.B.F.; Correia, Adriana N.; de Lima-Neto, Pedro; Morais, SimoneUndoubtedly, carbonaceous (nano)materials are the most widely used feedstock to obtain improvements in electrochemical devices, but graphene has attracted strong scientific and technological interest due to its exceptional physicochemical properties. Graphene-sheets functionalization, integration with metallic nanoparticles, organic and inorganic molecules and/or groups, synthesis method, and chemical or thermal reduction of graphite oxide can greatly influence the performance of the devices. In general, graphene-based (bio)sensors overcome the conventional ones in terms of sensitivity, electrocatalytic activity, potential window, and charge-transfer processes. They can be a key tool for the miniaturization and development of fast, sensitive, versatile, environment-friendly, and in situ electroanalytical methods for pesticides, in particular for carbamates, organophosphates, organochlorines, benzimidazole, and neonicotinoids, among others. The constant advances in the application of these devices are unquestionable, but there are still questions about the interfacial redox phenomena that are not fully understood and deserve to be investigated. This chapter describes the exciting progress and challenges in this field, emphasizing the main scientific findings.