Sensor based on β - NiOx hybrid film/multi-walled carbon nanotubes composite electrode for groundwater salinization inspection

The enrichment of groundwater with different nutrients (Na+, Ca2+, Mg2+, Cl−, CO32−, among others) triggers the salinization of the aquifer and makes it inappropriate for many purposes. In this work, we developed a highly sensitive and selective electrochemical sensor, based on Ni-inorganic films electrosynthetized in situ onto multi-walled carbon nanotubes composite paste electrode (MWCNE), which allows the early detection of salinization. The working sensor (β-NiOx/MWCNE) was derivatized from nickel hexacyanoferrate modified electrode in strong alkaline medium (pH = 12), producing a hybrid film composed by β-Ni(OH)2 and β-NiO(OH). The electrochemical properties, morphology and chemical composition of the formed β-NiOx thin films were evaluated by voltammetry, scanning electron microscopy and X-ray spectroscopy. The developed β-NiOx/MWCNE sensor was highly sensitive to the presence of Na+ cation by ion-exchange, and the increase of Na+ concentration in the range 4.46 × 10−7 to 4.93 × 10−6 mol L−1 inhibited linearly the reversible electrochemical signal of the device, allowing to determine trace concentrations of this ion (LOD = 9.86 × 10−8 mol L−1) with high correlation coefficient of the data (r = 0.999) and suitable precision/reproducibility of the measurements (RSD < 9%). Using Na+ as salinization marker and β-NiOx/MWCNE as electroanalytical device, we found evidences of groundwater salinization in Grossos, a Brazil coast city, whose inhabitants have hypertension above the national average. The attained results were comparable to those obtained by the standard methods for Na+ analysis (percentage error ranging from 0.5 to 1.6%), confirming the accuracy of the proposed electroanalytical platform.info:eu-repo/semantics/publishedVersio

Removal and sensing of emerging pollutants released from (micro)plastic degradation: Strategies based on boron-doped diamond electrodes

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).info:eu-repo/semantics/publishedVersio

Trends and frontiers in graphene-based (bio)sensors for pesticides electroanalysis

Undoubtedly, 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.info:eu-repo/semantics/publishedVersio

Laccase–Prussian blue film–graphene doped carbon paste modified electrode for carbamate pesticides quantification

A novel enzymatic biosensor for carbamate pesticides detection was developed through the direct immobilization of Trametes versicolor laccase on graphene doped carbon paste electrode functionalized with Prussianblue films (LACC/PB/GPE). Graphene was prepared by graphite sonication-assisted exfoliation and characterized by transmission electron microscopy and X-ray photoelectron spectro- scopy. The Prussian blue film electrodeposited onto graphene doped carbon paste electrode allowed considerable reduction of the charge transfer resistance and of the capacitance of the device.The combined effects of pH, enzyme concentration and incubation time on biosensor response were optimized using a 23 full-factorial statistical design and response surface methodology. Based on the inhibition of laccase activity and using 4-aminophenol as redox mediator at pH 5.0,LACC/PB/GPE exhibited suitable characteristics in terms of sensitivity, intra-and inter-day repeatability (1.8–3.8% RSD), reproducibility (4.1 and 6.3%RSD),selectivity(13.2% bias at the higher interference: substrate ratios tested),accuracy and stability(ca. twenty days)for quantification of five carbamates widely applied on tomato and potato crops.The attained detection limits ranged between 5.2×10−9 mol L−1(0.002 mg kg−1 w/w for ziram)and 1.0×10−7 mol L−1 (0.022 mg kg−1 w/w for carbofuran).Recovery values for the two tested spiking levels ranged from 90.2±0.1%(carbofuran)to 101.1±0.3% (ziram) for tomato and from 91.0±0.1%(formetanate)to 100.8±0.1%(ziram)for potato samples.The proposed methodology is appropriate to enable testing pesticide levels in food samples to fit with regulations and food inspections