Electrochemical Sensors Based on Au Nanoparticles Decorated Pyrene-Reduced Graphene Oxide for Hydrazine, 4-Nitrophenol and Hg2+ Detection in Water.

Monitoring hazardous chemical compounds such as hydrazine (N2H4), 4-nitrophenol (4-NP) and Hg2+ in natural water resources is a crucial issue due to their toxic effects on human health and catastrophic impact on the environment. Electrochemical nanostructured platforms integrating hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are of great interest for such a purpose. In this work, disposable screen-printed carbon electrodes (SPCEs) have been modified with a hybrid nanocomposite formed by reduced graphene oxide (RGO), functionalized by 1-pyrene carboxylic acid (PCA), and decorated by colloidal Au NPs. These hybrid platforms have been tested for the electrocatalytic detection of N2H4 and 4-NP by differential pulse voltammetry and have been modified with an electropolymerized film of Hg2+ ions imprinted polycurcumin for the electroanalytical detection of Hg2+ by DPV. LODs, lower and in line with the lowest ones reported for state-of-the-art electrochemical sensors, integrating similar Au-graphene < nanocomposites, have been estimated. Additionally, good repeatability, reproducibility, and storage stability have been assessed, as well as a high selectivity in the presence of a 100-fold higher concentration of interfering species. The applicability of the proposed platforms for the detection of the compounds in real complex matrices, such as tap and river water samples, has been effectively demonstrated.

Machine learning-based prediction of toxic metals concentration in an acid mine drainage environment, northern Tunisia.

In northern Tunisia, Sidi Driss sulfide ore valorization had produced a large waste amount. The long tailings exposure period and in situ minerals interactions produced an acid mine drainage (AMD) which contributed to a strong increase in the mobility and migration of huge heavy metal (HM) quantities to the surrounding soils. In this work, the soil mineral proportions, grain sizes, physicochemical properties, SO42- and S contents, and Machine Learning (ML) algorithms such as the Random Forest (RF), Support Vector Machine (SVM), and Artificial Neural Network (ANN) models were used to predict the soil HM quantities transferred from Sidi-Driss mine drainage to surrounding soils. The results showed that the HM concentrations had significantly increased with the increase of decomposition and oxidation of galena, marcasite, pyrite, and sphalerite-marcasite and Fe-oxide-hydroxides quantities and the sulfate dissolution (marked with SO42- ions increase) that produced the decreased soil pH. Compared to SVM, and ANN models outputs, the RF model that revealed higher R2val, RPD, RPIQ, and lower error indices had satisfactorily predicted the soil HM accumulation coming from the AMD environment.

Molecularly imprinted curcumin nanoparticles decorated paper for electrochemical and fluorescence dual-mode sensing of bisphenol A.

A molecularly imprinted paper-based analytical device (MIP-µPAD) was developed for the sensing of bisphenol A (BPA). The platform was screen-printed onto a filter paper support, where the electrodes and the fluorescence µPADs were designed. Owing to its dual electrochemical and fluorescence responses, molecularly imprinted curcumin nanoparticles were used to sense BPA. The µPAD design was characterized by transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, and electrochemical techniques. The sensor design comprised a wide linear range from 1 to 200 µg L-1 with limits of detection of 0.47 ± 0.2 and 0.62 ± 0.3 µg L-1 (LOD, S/N = 3) for electrochemical and fluorescence sensing, respectively. Furthermore, the system showed good analytical performance such as selectivity, stability, and reproducibility. The feasibility of the MIP-µPAD was demonstrated for the sensing of BPA in seawater, foods, and polycarbonate plastic packaged water with recovery values of 97.2 and 101.8%.

Effect of Fe2+ ions on gypsum precipitation during bulk crystallization of reverse osmosis concentrates.

In reverse osmosis desalination, the concentrate is a saline solution that may become supersaturated. Heterogeneous nucleation of salts occurs at the membrane surface, resulting in the buildup of inorganic deposits on the membrane. The inorganic nucleation process, however, is complex in natural waters. Most studies focused primarily on single salt fouling of membranes, and related treatment for single solute systems. However, scale formation, especially gypsum, is affected by the presence of different salts and metals. In this wok, for the first time, we investigate the mixed precipitation of iron oxides and gypsum. The role of citric acid in the inhibition of precipitation was studied for different concentrations in both the absence and the presence of Fe2+. Conductivity and ion concentration measurements were used to estimate the formation time of gypsum. Scanning electron microscopy, X-Ray Diffraction (XDR) analysis, and Infra-Red spectroscopy analysis were used to provide structural information. Collected data showed that the presence of Fe2+ accelerates gypsum precipitation and shortens its induction time. Analytic results showed that gypsum crystals are greatly affected by the presence of Fe2+ ions, which generated needle shaped crystals. Citric acid can delay the induction time of gypsum precipitation. It also affects the morphology of gypsum crystals through adsorption mechanism. XDR diagrams revealed that the presence of citric acid (20 mg/L) can stabilize the bassanite phase (CaSO4·½H2O) for much longer periods. In the presence of Fe2+ ions, citric acid extends the induction time of calcium sulfate and minimizes the acceleration effect of Fe2+ ions. SEM images showed that the presence of ferrous ions during the chemical inhibition generates the ß-hemihydrate form of calcium sulfate.

Curcumin graphite pencil electrode modified with molybdenum disulfide nanosheets decorated gold foams for simultaneous quantification of nitrite and hydrazine in water samples.

A non-enzymatic sensor based on a curcumin modified pencil graphite electrode, loaded with molybdenum disulfide nanosheets decorated gold foam, was constructed. Herein, the electrochemical deposition strategy was adopted throughout the sensing platform design stepwise. The electroactivity of the pencil electrode platform enables sensitive simultaneous quantification of hydrazine and nitrite where the respective working potentials typically are at + 0.2 V for hydrazine and + 0.75 V for nitrite (both vs. Ag/AgCl, saturated KCl). It is shown that the resulting sensor demonstrates excellent analytical performances in terms of limits of detection (18.3, 21.7 nM), sensitivities (0.051, 0.061 µA µM-1), and reproducibility standard deviations (RSD) of 3.1 and 2.7% for hydrazine and nitrite, respectively. Furthermore, long term stability studies showed that the electrodes exhibited an effectively unchanged response after some 30 days. The sensor was used to analyze spiked samples of river water and industrial wastewater.

Reduced graphene oxide nanosheets modified with nickel disulfide and curcumin nanoparticles for non-enzymatic electrochemical sensing of methyl parathion and 4-nitrophenol.

A method was designed for simultaneous voltammetric determination of methyl parathion pesticide (MP) and 4-nitrophenol (4-NP). Curcumin nanoparticles were deposited on reduced graphene oxide nanosheets that were modified with nickel disulfide. The material was placed on a screen-printed carbon electrode and then displayed high electrocatalytic activities toward MP and 4-NP, with a peak potential near -0.9 and - 0.7 V (vs. pseudo Ag/AgCl), respectively. Figures of merit include (a) good electrochemical sensitivities (7.165 and 6.252 µA·µM-1·cm-2), (b) wide linear ranges (from 0.25 to 80 µM), (c) low limits of detection (8.7 and 6.9 nM at S/N = 3) for MP and 4-NP, respectively, and (d) good selectivity, repeatability, reproducibility, and storage stability. The method was applied in the determination of MP and 4-NP in tomato and apple juices and spiked river water. Graphical abstract A novel electrocatalysis platform based on reduced graphene oxide-nickel disulfide nanosheets decorated with curcumin nanoparticles for simultaneous quantification of methyl parathion and 4-nitrophenol in various vegetarian juices and water samples.

Voltammetric simultaneous quantification of p-nitrophenol and hydrazine by using magnetic spinel FeCo2O4 nanosheets on reduced graphene oxide layers modified with curcumin-stabilized silver nanoparticles.

A sensor based on a screen-printed carbon electrode loaded with curcumin-stabilized silver nanoparticle-coated reduced graphene oxide magnetic spinel (FeCo2O4) nanosheets was constructed. The electrocatalytic activity of the electrode enables sensitive simultaneous quantification of hydrazine and p-nitrophenol. The respective working potentials typically are at +0.15 V for hydrazine and at -0.75 V for p-nitrophenol (both vs. pseudo Ag/AgCl), and the detection limits are 23 nM and 18 nM (at S/N = 3). Good selectivity, repeatability, reproducibility and storage stability are shown. The sensor was used to analyze spiked samples of river water and industrial wastewater. Graphical abstract Schematic of an electrochemical sensor for simultaneous quantification of hydrazine and 4-nitrophenol in various natural and wastewater samples. The electrocatalyst in this sensor is composed of graphene oxide nanosheets modified with a magnetic spinel of type FeCo2O4 and os curcumin-stabilized silver nanoparticles.

Graphene nanosheets modified with curcumin-decorated manganese dioxide for ultrasensitive potentiometric sensing of mercury(II), fluoride and cyanide.

A glassy carbon electrode (GCE) was modified by electropolymerization of curcumin on MnO2-Gr nanosheets to obtain a detection method for Hg(II) and for the anions fluoride and cyanide. The complexation by curcumin can be monitored by potentiometry. The results revealed a cathodic shift for the simultaneous detection of fluoride and cyanide and an anodic shift for the mercury(II) sensing, with peak potentials of -0.24, 0.12 and 0.82 V, respectively (vs. Ag/AgCl). The modified GCE is fairly selective, reproducible and repeatable. The detection limits are 19.2 nM for Hg(II), 17.2 nM for fluoride, and 28.3 nM for cyanide (LOD, S/N = 3). The method was successfully applied to the analysis of spiked samples of tap water, river water and petrochemical refinery wastewater. Graphical abstract Schematic of an electrochemical curcumin-MnO2-graphene nanosheet platform for the simultaneous assay of fluoride, cyanide and mercury(II) in the ppb concentration range in various natural and wastewater samples.