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The negative impacts of microplastics on the environment and human health cannot be unnoticed. Several classes of emerging pollutants with endocrine-disrupting properties such as bisphenol A and its analogs, phthalates, among others, have been reported to migrate out of plastics entering the aquatic environment. Thus, this review aims to draw attention to the significant potential of the boron-doped diamond electrode to contribute to the implementation of mitigation actions for microplastic pollutants. The latest studies in the two main fields of the use of the boron-doped diamond electrode, that is, treatment of wastewater by electrochemical oxidation and a as sensor for pollutants monitoring, are herein reviewed and their main findings highlighted., T.M.B.F. Oliveira and F.W.P. Ribeiro thank FUNCAP (Proc. BP4-0172-00111.01.00/20 and BP4-0172-00150.01.00/20), CNPq (Proc. 308108/2020-5, 420261/2018-4, and 406135/2018-5), and UFCA for their financial support. S. Morais acknowledges UIDB/50006/2020 and UIDP/50006/2020 fundings and PTDC/ASP-PES/29547/2017 (POCI-01-0145-FEDER-029547) funded by FEDER funds through the POCI and by National Funds through FCT. P. de Lima-Neto and A.N. Correia gratefully thank CNPq (proc. 408626/2018-6, 304152/2018-8, 305136/2018-6, and 405596/2018-9) and FCT/Funcap (proc. FCT-00141-00011.01.00/18).

Electroanalytical methodology by boron-doped diamond electrode (BDDE) associated to the square-wave voltammetry (SWV) for the determination of hydrolyzed dipyrone (DIP) in commercial formulations, raw natural waters and in human urine was developed. Through cyclic voltammetry (CV), it was shown that the oxidation of the DIP on the BDDE was irreversible with diffusional control. Computational studies suggested that the oxidation mechanism of DIP occurred with participation of two electrons and one proton. The analytical curves were obtained for concentrations of DIP ranging from 1.0 × 10−6 to 6.5 × 10−5 mol L−1 (r = 0.9994). The values of detection limit (LOD) and quantification limit (LOQ) of DIP were calculated from SWV and found to be 2.6 × 10−7 mol L−1 and 8.8 × 10−7 mol L−1. The methodology was effectively applied to real samples with the values of calculated recoveries varying between 91.0% and 117.3% and validated by iodometric titration experiments whose values were between 93.3% and 106.9%. The proposed methodology with BDDE represents an alternative tool and it has advantageous, such as very easy handling, low cost, no need for modification, low detection limit. Furthermore, it can be used for the routine analysis of DIP in different real samples.

A simple and robust sensor (fMWCNT-Nafion®0.5%/GCE) for determination of imidacloprid (IMI), a widely used neonicotinoid, was developed using a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (fMWCNT) and Nafion®. The obtained data suggest that IMI reduction is an irreversible process, due to the reduction of the nitro group to hydroxylamine derivatives, with the participation of two protons and four electrons, and a charge transfer coefficient of 0.141. The optimized square-wave voltammetric conditions were: McIlvaine buffer at pH 6.0, 0.5% of Nafion® in the fMWCNT suspension, -0.6 V and 180 s as accumulation potential and time, respectively. A linearity in the range of 2.00 × 10-7 to 1.77 × 10-6 mol L-1 IMI, with the values of limit of detection and limit of quantification were equal to 3.74 × 10-8 mol L-1 and 1.25 × 10-7 mol L-1, respectively. Repeatability and reproducibility displayed relative standard deviations lower than 5%. Recovery tests performed in tap water, melon, and shrimp yielded mean values of 94 ± 6%, 97 ± 10% and 93 ± 10%, respectively. Moreover, several inorganic and organic compounds did not significantly interfere (0.6 to 4.5%) on the IMI signal, proving the selectivity and applicability of the developed sensor for IMI detection in complex samples.

Ternary Zn-Sn-In coatings were successfully electrodeposited for the first time on 1020 carbon steel substrates from a choline chloride and ethylene glycol base bath to improve the corrosion resistance of Zn-Sn alloys. The micrographs of the coatings revealed that increasing the concentration of indium (In) in the alloy reduced the grain size, and the electrodeposition performed at –1.3 V produced denser and more compact coatings rich in Zn. The diffractograms showed the deposition of metallic Zn, Sn, and In, as well as the presence of an In-Sn4 intermetallic phase. The electrochemical corrosion tests in 3.5% NaCl solution showed that the addition of indium in the Zn-Sn coatings increased the corrosion resistance of the protective layer, with the Zn64Sn23In13 coating, electrodeposited at –1.3 V, showing corrosion resistance superior to the other investigated coatings.

The water influence on electrochemical behaviour of Ag+ ions in urea and choline chloride mixture was investigated by cyclic voltammetry technique, while the molecular insights about the investigated systems were obtained from molecular dynamic (MD) simulation. The water content was variated from 0 up to 10% (v/v). Cyclic voltammetry technique showed that the peak potential for Ag+/Ag redox couples shifted in direction to more positive potentials with the gradual increase of water content in solution, indicating that the addition of water electrocatalyses the kinetics of the reduction of Ag+ ions. The MD simulations demonstrated that water molecules do not interact strongly with Ag+ ions but induce a small reduction in the number of urea molecules around of the ion and that the water molecules adjust to free spaces in the mixture.

The water influence on electrochemical behaviour of Ag

Pharmaceuticals, as a contaminant of emergent concern, are being released uncontrollably into the environment potentially causing hazardous effects to aquatic ecosystems and consequently to human health. In the absence of well-established monitoring programs, one can only imagine the full extent of this problem and so there is an urgent need for the development of extremely sensitive, portable, and low-cost devices to perform analysis. Carbon-based nanomaterials are the most used nanostructures in (bio)sensors construction attributed to their facile and well-characterized production methods, commercial availability, reduced cost, high chemical stability, and low toxicity. However, most importantly, their relatively good conductivity enabling appropriate electron transfer rates—as well as their high surface area yielding attachment and extraordinary loading capacity for biomolecules—have been relevant and desirable features, justifying the key role that they have been playing, and will continue to play, in electrochemical (bio)sensor development. The present review outlines the contribution of carbon nanomaterials (carbon nanotubes, graphene, fullerene, carbon nanofibers, carbon black, carbon nanopowder, biochar nanoparticles, and graphite oxide), used alone or combined with other (nano)materials, to the field of environmental (bio)sensing, and more specifically, to pharmaceutical pollutants analysis in waters and aquatic species. The main trends of this field of research are also addressed., This work was financially supported by: projects UID/QUI/50006/2019 and PTDC/ASP-PES/29547/2017 (POCI-01-0145-FEDER-029547) funded by FEDER funds through the POCI and by National Funds through FCT - Foundation for Science and Technology. This proposal was also subsidized by the Brazilian agencies CNPq (Proc. 420261/2018-4) and CAPES (Proc. 88881.140821/2017-01; Finance code 001). F.W.P. Ribeiro acknowledges funding provided by FUNCAP-BPI (Proc. BP3-0139-00301.01.00/18). Acknowledgments T.M.B.F. Oliveira thanks the UFCA’s Pro-Rectory of Research and Innovation for initiating his investigations. F.W.P. Ribeiro thanks the CNPq (proc. 406135/2018-5) and all support provided by the UFCA‘s Pro-Rectory of Research and Innovation. A.N. Correia thanks the CNPq (proc. 305136/2018-6).

The corrosion behavior of the 18Ni 300-grade maraging steel in 0.6 mol L−1 NaCl solution, containing 1 mmol L−1 H2S, and saturated with CO2, was investigated by measurement of the open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The maraging steel was solution-treated at 840 °C for 1 h and aged at 650 °C for 3 h. All corrosion electrochemical tests proved that the austenitic phase formed during the aging thermal treatment was detrimental to corrosion resistance of the 18Ni 300-grade maraging steel. The analysis of the XPS spectra suggested that FeCO3, Fe2O3, FeS2, FeSO4, NiO, Ni(OH)2, NiS, NiSO4, MoO2, MoO3 and MoS2 were the corrosion products deposited on the surface of both maraging steel samples after 29 days of immersion in the testing solution. Lastly, for industrial application requiring the corrosion resistance property of the 18Ni 300 grade maraging steel, it is recommended that it be thermal solution-treated before its use.

Fe-P, Ni-P and Ni-Fe-P alloys were prepared by galvanostatic electrodeposition over copper electrodes in aqueous media in order to obtain a corrosion resistant layer. All electrodeposits were prepared in optimized conditions at acidic medium (pH

This work describes the electroanalytical determination of Chlorpyriphos pesticide in natural waters using hanging mercury drop electrode allied to square wave adsorptive cathodic stripping voltammetry. The best responses were obtained in Britton‒Robinson buffer solutions at pH 2.0, using a frequency of 100 s–1, a scan increment of 5 mV, a square wave amplitude of 25 mV and an accumulation potential of–0.4 V during 60 s. Therefore, voltammetric responses showed the presence of one well-defined and irreversible reduction peak, at–1.08 V vs. Ag/AgCl/KCl 1.0 M, which involves two electrons in the reduction of carbon‒nitrogen bond in the N-heterocyclic system with the participation of protonation equilibrium preceding the electron transfer reaction. Analytical curves were constructed and compared to similar curves performed by gas chromatograph coupled to a selective nitrogen‒phosphorus detector, which demonstrates that the proposed methodology is suitable for determining contamination by Chlorpyriphos in complex samples.

Ni0.5Zn0.5Fe2O4 nanocrystals were successfully synthesized under different pure hydrothermal conditions (no organic solvent). The effects of the NaOH content and reaction time on the growth mechanism, as well as structural, morphological and magnetic properties were investigated. High-resolution electron microscopy transmission (HRTEM) revealed the formation of the nanocrystals, mainly via oriented attachment or in addition by a coalescence mechanism depending on the NaOH concentration (3.7–5.2 M). This secondary mechanism was found to give rise to defects in the network and structural disorder on the surface of the nanocrystals. By extending the reaction time (6–24 h), a morphology transition from truncated-hexagonal to rounded structures was seen, which evidenced a self-integration mechanism to achieve the most stable shape. Moreover, preferential exposure of the (111) plane was observed. Electrochemical measurements using [Fe(CN)6]3─/4─ to check the surface status further supported this statement. This indicated an adsorption effect of the NaOH on the surface of the MNPs allowing an oriented growth of the nanocrystals. In addition, the blocking temperature ( T B ) was affected by different factors (rearrangement of the atoms on the surface or increase of the magnetically-ordered core) depending on the hydrothermal conditions used.

The effect of water on the physicochemical properties of an ethylene glycol and choline chloride mixture containing Cu2+ ions was investigated by electrochemical techniques and molecular dynamics simulation. The experiments and computational calculations were carried out by increasing the water content from 0 up to 10% (v/v). The cyclic voltammetry and chronopotentiometry techniques showed that the diffusion coefficient of Cu2+ ions increased and that the peak potentials for both the Cu2+/Cu+ and Cu+/Cu redox couples shifted towards more positive potentials with the increase in the water content in the solution. The molecular dynamics simulation indicated that the water molecules replaced the ethylene glycol molecules that were coordinated with Cu2+ ions, while the interactions between Cu2+ and Cl− ions were not influenced by the presence of water.

Zn and ZnSn coatings were electrodeposited on carbon steel surfaces from choline chloride and ethylene glycol solvent (1ChCl:2EG). The corrosion resistance of the coatings was investigated in a 3.5% NaCl solution, and the results revealed that Zn deposition was favored by increasing bath temperature and electrodeposition potential. Besides, Zn-enriched coatings were also obtained from Sn-rich Zn/Sn baths, and the coating morphologies were affected by these parameters. Finally, the ZnSn layer (14% Sn) electrodeposited at −1.3 V and 363 K increased the corrosion resistance up to 6 times towards the pure Zn layer under the same conditions.

The present study aimed at investigating the influence of the electrodeposition current density and pH of the plating solution on chemical composition, electrodeposition current efficiency and on the roughness factor of the electrodeposited Co-Mo coatings. The coatings with higher roughness factor were evaluated as cathodes for hydrogen evolution reaction in alkaline medium. The electrodeposition current densities were 30 mA cm −2 , 45 mA cm −2 and 60 mA cm −2 and the values of pH of the plating solutions were 6, 7 and 8. The two-level and centre-point factorial design was applied. Coatings showed cracks and amorphous structures. The pH had a positive effect on the Mo percentage and on the roughness factor of the coatings. The current density had the highest effect on the current efficiency and electroactive area of the coatings. Increasing the value of this parameter, the current efficiency decreased from 31.63% to 17.65% and roughness factor presented relative increase of 27.53–78.74. The Volmer reaction was the determining step and the apparent activation energy was 18.40 kJ mol −1 in the hydrogen evolution reaction.

Monte Carlo simulations were performed to evaluate the interaction between acetaminophen (ACOP) and polyethylenimine-functionalized multi-walled carbon nanotubes (PEI- f MWCNT), followed by quantum mechanics studies concerning the oxidation mechanism. Simulations demonstrated that the polymer enhances adsorption by more than 10 kcal mol −1 and that it is important to reproduce the diameter of the nanotube in the simulation models because the adsorption occurs preferentially inside the nanotube. Using square-wave voltammetry (SWV) coupled with a glassy carbon electrode (GCE) surface modified with the dispersion of f MWCNT in the presence of PEI, it was possible to develop an analytical methodology for identification and quantification of ACOP in tablets. The analytical curves were obtained for concentrations of ACOP ranging from 9.99 × 10 −8 to 6.95 × 10 −6 mol L −1 (r = 0.9953). The detection limit and quantification limit of ACOP was determined from SWV and found to be 5.58 × 10 −8 mol L −1 and 1.86 × 10 −7 mol L −1 . The method was successfully applied to real samples detection with the recovery in the range from 95.5% and 111.0% with good stability and reproducibility. Density functional calculations suggested that the oxidation mechanism of ACOP in the presence of the composite may occur in a reversible way, involving H + or H abstraction, in a different path from the metabolic reactions.

The electrodeposition of Indium on Copper substrate was investigated using 0.05 mol L −1 InCl 3 dissolved in a mixture of choline chloride (ChCl) and ethylene glycol (EG) in molar ratio 1:2. The In electrodeposition was controlled by diffusion and the diffusion coefficient of In 3+ species in 1ChCl:2EG as a function of temperature was fitted by a like-Arrhenius equation and the apparent activation energy for the diffusion of In 3+ species was 32.50 kJ mol −1 . Analysis of the current-time curves using the Scharifker-Hills’ model indicated that the In deposition occurred by progressive nucleation and three-dimensional growth. The morphology of the electrodeposits, obtained between 25 and 65 °C, were characterised by grains and rods in micrometer regime randomly distributed. In addition, In nanorods arrays, with diameter ranging between 75 and 250 nm, were observed in the In coating obtained at 80 °C. X-ray diffraction analysis revealed the existence of the metal In and CuIn alloy phase and that the (101) was the preferential plane to the growth of the In nanorods.

This paper describes the development of an electroanalytical procedure proposal for the determination of tricyclic antidepressant imipramine (IMP) in commercial pharmaceutical formulations using boron-doped diamond electrode and square-wave voltammetry. The electrochemical oxidation of imipramine was studied in 0.04 mol L− 1 Britton-Robinson buffer solution. The voltammetric results showed two well-defined oxidation peaks with potentials of 0.04 V and 0.82 V vs. Ag/AgCl/3 mol L− 1 Cl− for peaks 1 and 2, respectively. The effect of the experimental and voltammetric parameters was evaluated and the best performance was obtained in pH 7.4, pulses application frequency of potential of 100 Hz, amplitude of 50 mV and potential increment of 2 mV. Under these conditions, the analytical curves were obtained in the linear range of concentration from 1.73 × 10− 7 mol L− 1 to 2.53 × 10− 6 mol L− 1 (r = 0.9984), with detection and quantitation limits 4.35 × 10− 8 mol L− 1 and 1.45 × 10− 7 mol L− 1, respectively. The proposed method was applied with success in the determination of IMP in commercial pharmaceutical formulations and validated by comparison with standard method for determination of imipramine. The obtained results were in close agreement, at a 95% confidence level, with those obtained using an official method of the British Pharmacopeia.

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 conductivity 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 commercial 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.

Six amino acids were evaluated as corrosion inhibitors for carbon steel and copper in 0.5 mol L−1 H2SO4 solution by potentiodynamic polarization and electrochemical impedance techniques allied to Density Functional Theory (DFT) and Monte Carlo computations The corrosion inhibitor rankings were: Arg > Gln > Asn > Met > Cys > Ser, for copper, and Met > Cys > Ser > Arg > Gln > Asn, for carbon steel. The DFT approach failed to explain the corrosion inhibition rating based on the HOMO and LUMO energies of the isolated amino acid molecules, while the simpler classical Monte Carlo approach, performed considering the interaction energies between the corrosion inhibitor and the metallic substrate, was successful.

An analytical methodology for determination of diethylstilbestrol (DES) based on electrochemical response of this compound on glassy carbon electrode modified with gold nanoparticules (AuNPTs), multiwall carbon nanotubes (MWCNTs) and cobalt phtolocyanine (CoPc) was proposed. The modified electrode catalysed the electrochemical oxidation of DES and also improved the sensitivity in comparison with unmodified electrode. The experimental conditions were optimized and also the kinetic electrochemical parameters were also evaluated. From square wave voltammograms, the calibration curve for DES determination were obtained and the calculated detection and quantification limits were equal to 1.99 × 10 −7 mol L −1 and the 6.64 × 10 −7 mol L −1 , respectively. The proposed electroanalytical methodology was successfully applied for DES determination in water, and meat with satisfactory results, showing that fabricated sensor has potential do be applied in laboratory practices for DES determination in complex samples.

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., Funding Information: CNPq-INCT. Grant Numbers: 573925/2008-9, 573548/2008-0 CAPES/Funcap. Grant Numbers: 2133/2012/proc. 23038.007973/2012-90, PNE-0112-00048.01.00/16 CNPq. Grant Numbers: 400223/2014-7, 303596/2014-7, 302801/2014-6, 408790/2016-4 PRONEX/Funcap. Grant Number: PR2-0101-00030.01.00/15 FCT/Funcap. Grant Number: FCT-00141-00011.01.00/18 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brasil (CAPES). Grant Number: 001 CAPES-PNPD FUNCAP-BPI. Grant Number: BP3-0139-00301.01.00/18 CNPq CAPES FUNCAP UFCA's Pro-Rectory CNPq. Grant Number: 304419/2015-0 European Union (FEDER funds through COMPETE) National Funds (Fundação para a Ciência e Tecnologia-FCT). Grant Numbers: UID/QUI/50006/2013, PTDC/ASP-PES/29547/2017 FCT/MEC Norte Portugal Regional Operational Programme (NORTE 2020). Grant Numbers: Norte-01-0145-FEDER-000011, Norte-01-0145-FEDER-000024

A new cardanol-based salophen (hpbp) ligand and its manganese complex [Mn(hpbp)] were obtained by microwave-assisted synthesis method, with yields and reaction times of 65% in 20 min and 85% in 5min, respectively. The structural features of compounds were confirmed by electronic (UV–vis and fluorescence), infrared and NMR (1H, 13C) spectroscopic techniques. The photophysical study of the ligand showed ketoenamine-enolimine tautomeric equilibrium, which was discussed based on the excited state intramolecular proton transfer (ESIPT) mechanism and was dependent on the solvent, concentration and molecular structure. The energy of the HOMO and LUMO orbitals (−5.41 and −2.12 eV, respectively), determinated by cyclic voltammetry and UV–Vis, the energy was very close to the values determined by the theoretical calculations. The studies revealed that the hpbp is a tetradentate ligand bonded to the metal ion by phenolic oxygens and by azomethine nitrogens. Therefore, this work contributes to the science of salophen compounds, in addition to stimulating the synthesis of new ligands from renewable sources for the coordination chemistry.

Fe–Co coatings were electrodeposited on Cu substrates from a choline chloride-urea eutectic solution. The influence of Fe and Co content on the magnetic, morphological, and electrocatalytic properties of the electrodeposits was duly studied. The coercivity and quadrature of the magnetic hysteresis curves revealed that all coatings had soft magnetic properties that varied with the coating composition. A hyperfine magnetic field between 36 and 38 T in their Mossbauer spectra indicated the formation of Fe–Co alloy in the samples Fe87Co13, Fe64Co36, and Fe44Co56. All coatings with Fe content higher than 25% showed magnetic texture along their growth axis with orientation angles ranging from θ = 5.1 to 42.8∘. The Fe, Co, and Fe–Co coatings showed good electrocatalytic performance for the hydrogen evolution reaction, with mainly the Fe-rich coatings presenting the lowest values of overpotential. Remarkably, an Fe coating afforded a current density of 10 cm−1 at a low overpotential of 89.2 mV, as well as exhibiting a small Tafel slope of 44.6 mV dec−1 in 0.5 mol L−1 NaOH. The results showed that the use of choline chloride-urea eutectic solution provides a promising and ecological strategy for the production of Fe–Co coatings since it is not necessary to add other chemicals besides the corresponding metallic salts.

Chitosan-based magnetite nanocomposites were synthesized using a versatile ultrasound assisted in situ method involving one quick step. This synthetic route approach results in the formation of spheroidal nanoparticles (Fe 3 O 4 ) with average diameter between 10 and 24 nm, which were found to be superparamagnetic with saturation magnetization (Ms) ranges from 32–57 emu g −1 , depending on the concentration. The incorporation of Fe 3 O 4 into chitosan matrix was also confirmed by FTIR and TG techniques. This hybrid nanocomposite has the potential application as electrochemical sensors, since the electrochemical signal was excepitionally stable. In addition, the in situ strategy proposed in this work allowed us to synthesize the nanocomposite system in a short time, around 2 min of time-consuming, showing great potential to replace convencional methods. Herein, the procedure will permit a further diversity of applications into nanocomposite materials engineering.

Here we described the development of a simple methodology for quantification of acetaminophen (ACOP) using square-wave voltammetry (SWV). A glassy carbon electrode modified with gold nanoparticles, functionalized multi-walled carbon nanotubes and cobalt (II) phthalocyanine was prepared and characterized with cyclic voltammetry, SWV and electrochemical impedance spectroscopy. The optimum experimental conditions, such as pH, buffer and square-wave voltammetric parameters were investigated. From the data analysis of the optimization of experimental conditions, the oxidation of ACOP was characterized as a quasi-reversible and proton-dependent process, where the reaction mechanism presents the participation of equal number of protons and electrons (two protons and two electrons) and k s value is equal to 59.0 ± 2.5 s − 1 . Under the optimized conditions, calibration curves were linear in the concentration range of 1.49 μmol L − 1 to 47.6 μmol L − 1 and 47.6 μmol L − 1 to 107.0 μmol L − 1 with a limit of detection of 0.135 μmol L − 1 . Other analytical parameters such as equations of the analytical curves, correlation coefficients, recovery efficiency and relative standard deviation for repeatability and reproducibility experiments were compared to results obtained by the use of UV–Vis spectrophotometry.

The inhibition of laccase enzymatic catalytic activity by formetanate hydrochloride (FMT) was investigated by cyclic voltammetry and by quantum chemical calculations based on density functional theory with a protein fragmentation approach. The cyclic voltammograms were obtained using a biosensor prepared by enzyme immobilization on gold electrodes modified with gold nanoparticles and 4-aminophenol as the target molecule. The decrease in the peak current in the presence of FMT was used to characterize the inhibition process. The calculations identified Asp206 as the most relevant moiety in the interaction of FMT with the laccase enzymatic ligand binding domain. The amino acid residue Cys453 was important, because the Cys453-FMT interaction energy was not affected by the dielectric constant, although it was not a very close residue. This study provides an overview of how FMT inhibits laccase catalytic activity.

This study characterizes the electroanalytical behavior of the carbamate pesticide formetanate hydrochloride (FMT) at a cobalt phthalocyanine (CoPc) functionalized multiwalled carbon nanotubes ( f MWCNT) modified glassy carbon electrode (CoPc- f MWCNT/GCE). Nafion ® was used to improve solubility and dispersibility of f MWCNT. The construction of the developed electrode was characterized by high-resolution field-emission gun scanning electron microscopy, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. FMT exhibited a behavior consistent with a three-step reaction of the electrochemical-chemical-electrochemical mechanistic type at CoPc- f MWCNT/GCE (three anodic peaks at 0.26, 0.55 and 1.2 V, and two cathodic peaks at 0.35 and 0.50 V vs . Ag/AgCl/3 M KCl). Highly reproducible and well-defined peaks were obtained at the optimum experimental conditions (Britton-Robinson buffer at pH 5.0, accumulation potential 1.55 V, accumulation time 5 s, frequency 100 s −1 , amplitude 30 mV, and scan increment 3 mV). Peak currents were found to be proportional to the FMT concentrations in the range of 9.80 × 10 −8 to 3.92 × 10 −6 mol dm −3 with a detection limit (LOD) of 9.7 × 10 −8 mol dm −3 . The modification of GCE with CoPc- f MWCNT enhanced the electrocatalytic activity and provided high sensitivity (3.51 A mol −1 dm 3 ). The developed electroanalytical methodology was successfully applied to FMT residue analysis in mango and grape samples with recoveries in the range of 94.2 ± 4.5 to 105.7 ± 1.8%. The proposed electroanalytical approach represents a reliable, sensitive and environmental friendly analytical alternative for determination of FMT.

The low toxicity and environmentally compatible ionic liquids (ILs) are alternatives to the toxic and harmful cyanide-based baths used in industrial silver electrodeposition. Here, we report the successful galvanostatic electrodeposition of silver films using the air and water stable ILs 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIM]TfO) and 1-H-3-methylimidazolium hydrogen sulphate ([HMIM(+)][HSO4(-)]) as solvents and AgTfO as the source of silver. The electrochemical deposition parameters were thoughtfully studied by cyclic voltammetry before deposition. The electrodeposits were characterized by scanning electron microscopy coupled with X-ray energy dispersive spectroscopy and X-ray diffraction. Molecular dynamics (MD) simulations were used to investigate the structural dynamic and energetic properties of AgTfO in both ILs. Cyclic voltammetry experiments revealed that the reduction of silver is a diffusion-controlled process. The morphology of the silver coatings obtained in [EMIM]TfO is independent of the applied current density, resulting in nodular electrodeposits grouped as crystalline clusters. However, the current density significantly influences the morphology of silver electrodeposits obtained in [HMIM(+)][HSO4(-)], thus evolving from dendrites at 15 mA cm(-2) to the coexistence of dendrites and columnar shapes at 30 mA cm(-2). These differences are probably due to the greater interaction of Ag(+) with [HSO4(-)] than with TfO(-), as indicated by the MD simulations. The morphology of Ag deposits is independent of the electrodeposition temperature for both ILs, but higher values of temperature promoted increased cluster sizes. Pure face-centred cubic polycrystalline Ag was deposited on the films with crystallite sizes on the nanometre scale. The morphological dependence of Ag electrodeposits obtained in the [HMIM(+)][HSO4(-)] IL on the current density applied opens up the opportunity to produce different and predetermined Ag deposits.

Silver electrodeposition is essential for industry and commerce, such as aesthetical products or electronic devices, and is regularly carried out in strongly corrosive and toxic alkaline cyanide baths. This paper introduces a methodology using the room temperature protic ionic liquid (RTPIL) 1-H-3-methylimidazolium hydrogen sulfate [HMIM+][HSO4−] as the electrolyte for silver electrodeposition on a gold disk electrode. Cyclic voltammograms for the Ag+/Ag pair show one process for Ag reduction (cathodic peak potential, Ecp = −0.06 V vs. Ag wire) and oxidation (anodic peak potential, Eap = 0.06 V vs. Ag wire), being then a quasi-reversible process. The temperature effect over Ag+ ions electrodeposition shows to be limited above 45 °C due to the equilibrium between Ag+ cations and HSO4− anions brought by RTPIL, a hypothesis that can be found in the literature for similar systems. Cottrell plots were obtained in different temperatures to calculate the Ag+ diffusion coefficient in [HMIM+][HSO4−] RTPIL. The diffusion coefficient changes nonlinearly when temperature increased, and the Arrhenius-type plot for this system is convex (i.e., not linear and dependent upon other quantity). This fact leads to a polynomial fit for the Arrhenius-type plot rather than linear, and the activation energy is dependent upon temperature. This dependency is related to the equilibrium hypothesis, which is further confirmed by DFT calculations. The formation constant of the AgHSO4 complex has a negative Gibbs energy, and this thermodynamic calculation shows to be exergonic. The morphology of Ag electrodeposits changes when temperate, and deposition mode (potentiostatic and galvanostatic) change, varying the bulk layer and sub-micrometer Ag morphologies.

A sensor based on polyethylenimine-functionalized multi-walled carbon nanotubes/glassy carbon electrode (fMWCNT-PEI/GCE) was developed for promethazine hydrochloride (PMZ) detection in pharmaceutical samples. PMZ is oxidized at the modified electrode at more negative potentials and with higher sensitivity than at the bare electrode. The morphological characterization of the sensor surface showed a homogeneous layer with size distribution of the diameters of the PEI-fMWCNT ranging from 22-47 nm. The characterization of the electrochemical behavior suggested that an equal number of electrons and protons participate in the PMZ irreversible oxidation on the fMWCNT-PEI/GCE. The optimized conditions were Sorensen buffer at pH 2.0, frequency of 90 s−1, amplitude of the pulse of 40 mV, and height of the potential step of 2 mV. Based on the most sensitive peak, at ca. 0.75 V, which is related to the formation of the phenazothiazonium ion, the PMZ calibration curve was obtained with sensitivity of 3.21 × 10−3 A mol−1 L, a linearity range of 4.97 × 10−7 to 5.03 × 10−6 mol L−1, and a detection limit of 2.31 × 10−7 mol−1 L. This methodology was successfully validated in pharmaceutical samples by comparison with the standard method of the Pharmacopoeia, showing high potential applicability of the fMWCNT-PEI/GCE.

The study describes the electroanalytical approach for benzimidazole pesticide/drug thiabendazole (TBZ) determination using cathodically pretreated boron-diamond doped electrode (BDDE). TBZ exhibited an irreversible oxidation process with peak current and potential values proton-dependent. The TBZH+ that provided the most intense peak current for TBZ oxidation. The reaction mechanism is diffusion-controlled, involving the participation of one electron. The voltammetric and experimental optimized conditions were pH 3.0, potential pulse frequency (f) of 20 s−1, amplitude of the pulse (a) of 20 and the height of the potential step (ΔEs) of 3 mV. The analytical curves were linear from 4.98 × 10−7 to 1.12 × 10−5 mol L−1 with a limit of detection of 1.27 × 10−7 mol L−1. The BDDE was successfully applied to TBZ determination in the several real samples (mango, sugar cane, natural waters and pharmaceutical formulation) with recovery ranged from 71.0 to 103.3% and RSD from 0.91 to 5.3%. The results indicated that the electrochemical methodology based on BDDE presented suitable characteristics in terms of sensitivity, linearity, accuracy and precision.

Carbamate pesticides (CBMs) are esters and thioesters derived from carbamic acid, which are widely used to increase agricultural productivity and to protect human and animal health from insect-vector-mediated diseases. However, they can be highly toxic when not appropriately applied. Electrochemical carbon-based sensors and biosensors gather a plethora of advantages for reliable, low cost, rapid and even in loco quality control and surveillance of CBMs levels in all systems related to environmental and human health. Thus, this review presents a broad overview of the state-of-art of design and applications of these (bio)sensors for CBMs electroanalysis in environmental, food and biological matrices with emphasis in the role of the carbon (nano)materials. The latest advances and trends but also the main (bio)sensors limitations and research gaps are highlighted. Highly selective, robust and novel carbon-based (bio)sensors with multiplexing CBMs capability are envisaged to emerge shortly for in-field applicability.

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., The authors gratefully acknowledge the funding provided by the following Brazilian agencies: CNPq-INCT (proc. 573925/2008-9 and 573548/2008-0), CAPES/Funcap (2133/2012/proc. 23038.007973/2012-90 and PNE-0112-00048.01.00/16), CNPq (proc. 400223/2014-7, 303596/2014-7, 302801/2014-6 and 408790/2016-4), PRONEM/FUNCAP/CNPq (PNE-0112-00048.01.00/16) and PRONEX/Funcap (proc. PR2-0101-00030.01.00/15). The Fundação para a Ciência e a Tecnologia (FCT) and the FEDER, under Programme PT2020 (Project UID/QUI/50006/2013) and the project Qualidade e Segurança Alimentar- uma abordagem (nano) tecnológica (NORTE-01-0145-FEDER-000011) are also acknowledged for the financial funding. R.M.F. and J.C.D. acknowledge the financial support by Fondecyt 3170240 and Basal Program for Centers of Excellence, Grant FB0807 CEDENNA, CONICYT. C.P.S. thanks CAPES-PNPD for her grant.

The effect of water on the physicochemical properties of an ethylene glycol and choline chloride mixture containing Cu2+ ions was investigated by electrochemical techniques and molecular dynamics simulation. The experiments and computational calculations were carried out by increasing the water content from 0 up to 10% (v/v). The cyclic voltammetry and chronopotentiometry techniques showed that the diffusion coefficient of Cu2+ ions increased and that the peak potentials for both the Cu2+/Cu+ and Cu+/Cu redox couples shifted towards more positive potentials with the increase in the water content in the solution. The molecular dynamics simulation indicated that the water molecules replaced the ethylene glycol molecules that were coordinated with Cu2+ ions, while the interactions between Cu2+ and Cl- ions were not influenced by the presence of water.

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., The authors gratefully acknowledge funding provided by the following Brazilian agencies: CNPq-INCT (Proc. 573925/2008-9 and 573548/2008-0), CAPES/Funcap (2133/2012/Proc. 23038.007973/2012-90), CNPq-PVE (Proc. 400223/2014-7 and 303596/2014-7), PRONEX/FUNCAP (Proc. PR2-0101-00030.01.00/15) and CNPq (Proc. 302801/2014-6). R.N. Gomes thanks CAPES and C.P. Sousa thanks CAPES-PNPD for their grants. The authors also are grateful to the Central Analítica-UFC/CT-INFRA/MCTI-SISNANO/Pró-Equipamentos CAPES for technical support and Prof. Pierre Basílio Almeida Fechine and MsC. Davino Machado Andrade Neto for Zeta potential analysis.

In 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.

This study describes the development of a simple and accurate methodology for carbamate pesticide formetanate (FMT) analysis in fruits based on the use of a boron-diamond doped electrode (BDDE) cathodically pretreated and on the forward component of the current of square-wave voltammetry (SWV). FMT exhibits a well-defined irreversible oxidation process, which reaction mechanism is diffusion-controlled, involves the participation of one electron and is influenced by the electrolyte pH. However, protonation does not participate in the rate-determining step in the redox process. The optimum experimental and voltammetric conditions were pH 7.0 (0.04 mol L−1 Britton-Robinson buffer), pulse potential frequency of 20 s−1, amplitude of the pulse of 25 mV, and height of the potential step of 3 mV. Under the optimum conditions, calibration curve was linear from 4.98 × 10−7 to 1.70 × 10−5 mol L−1 FMT with a limit of detection of 3.7 × 10−7 mol L−1. FMT sensing was performed in different fruits (mango and grape). Recoveries ranged from 95.2 ± 2.8 to 104.0 ± 3.5% for mango and 96.5 ± 2.5 to 105.2 ± 3.5% for grape proving the accuracy and precision of the electroanalytical methodology. The attained data validated the applicability of the developed approach for FMT quantification in fruits.

The 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, The authors wish to thank the Brazilian research funding institu-tions Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq) and Fundação de Amparo à Pesquisa do Estado de São Paulo(FAPESP) for theirfinancial support (CNPq proc. 400223/2014-7,303596/2014-7, 306177/2016-1, 302801/2014-6, 154089/2016-8,573925/2008-9 and 573548/2008-0; FAPESP 2017/23416-9) andCAPES (Funcap–2133/2012/proc. 23038.007973/2012-90),PRONEM/FUNCAP/CNPq (PNE-0112-00048.01.00/16), PRONEX/FUNCAP (proc. PR2-0101-00030.01.00/15). This study wasfinanced inpart by the Coordenação de Aperfeiçoamento de Pessoal de NívelSuperior–Brasil (CAPES)–Finance Code 00. Camila P. Sousa thanksCAPES- PNPD for her grant

Herein, a highly sensitive and selective simultaneous electrochemical method to monitor the emerging organic contaminants tartrazine (TRT), dexamethasone (DMZ) and diclofenac (DCL) in sewage treatment plants was developed. The sensing was based on electroreduction of TRT (−0.22 V), DMZ (−0.93 V) and DCL (−1.12 V) on hanging mercury drop electrode (HMDE), using citrate buffer pH 2.5 as electrolyte. The fast electrodic kinetics of these chemicals provided improvements on selectivity at high scan rates. The unique electrochemical properties of HMDE were associated to analytical performance of the square-wave voltammetry to quantify trace concentrations of TRT, DMZ and DCL, with detection limits ranging from 2.78 × 10 −8 to 1.48 × 10 −7 mol L −1 . After wastewater treatment by using solid-phase extraction, the proposed procedure was successfully applied for the direct quantification of the studied compounds with high precision, accuracy and stability of the measurements, even in the presence of other electroactive contaminants.

This paper describes the use of electrochemical methods and accelerated oxidation experiments (EN 14112, Rancimat method) for the determination of antioxidant activity of phenolic compounds (cardanol, cardol and tert- butylated cardanol) derived from cashew nut shell liquid (CNSL), a byproduct obtained during the processing of cashew nuts classified as a renewable raw material, natural of low-value. Through the electrochemical study, having as reference the anodic peak potential (Epa) and peak current (Ip), was observed that the cardol had the best performance, followed by tert -butylated cardanol and this by cardanol, showing that the presence of electron-donating groups as tert- butyl and hydroxyl exerts a positive influence on the antioxidant action of these compounds. These analyzes showed also that unsaturated compounds presented current values superior than saturated ones, indicating that the unsaturated molecules participate in greater number of the electro-oxidation process. The accelerated oxidation experiments were performed through analysis of biodiesel samples additivated with CNSL-based antioxidants at 500 ppm, and the same sequence of activity presented by the electrochemical study was observed, showing that this class of compounds can be applied effectively to inhibit the oxidative process of biofuel.

The effect of the Bi doping of PbO2 coatings on the electrochemical degradation of the pesticide tebuconazole (TBC) was investigated. The insertion of 8% Bi (relative to the amount of Pb) in the PbO2 structure afforded a well-defined texturing in the direction of the (2 0 0) plane to the PbO2 coatings, as well as, a decrease in the size of the coherent domain of the crystal, an increase in the electrochemical roughness and in the oxidation power of the Bi-doped PbO2 compared with PbO2. Through ultraviolet-visible spectrometry and total organic carbon (TOC) analyses for TCB electrodegradation was possible to chose the current density of 40 mA cm−2 as optimized one, with 68% of TOC removed by the Bi-doped electrode and 56% removed by the PbO2 electrode. High resolution liquid chromatography coupled with electrospray ionisation high resolution mass spectrometry helped to propose an oxidation pathway for the electrochemical degradation of TBC. Nine electrooxidation products were identified; which were produced by hydroxylation of the TBC phenyl group and its consequent oxidation to a ketone (including both mono- and dihydroxylated products), by dechlorination (two different products), and by multiple oxidative steps with ring opening (two different products). It was possible to conclude that the electrooxidation of TBC using Bi-doped PbO2 anodes generated products that were less harmful than TBC itself, thus recommending this electrode as an alternative material for wastewater decontamination.