A novel nanosilver/nafion composite electrode for electrochemical sensing of methyl parathion and parathion

Fabrication of FeVO4/RGO Nanocomposite: An Amperometric Probe for Sensitive Detection of Methyl Parathion in Green Beans and Solar Light-Induced Degradation

Pesticide usage is one of the significant issues in modern agricultural practices; hence, monitoring pesticide content and its degradation is of utmost importance. A novel and simple one-pot deep eutectic solvent-based solvothermal method has been developed for the synthesis of FeVO₄/reduced graphene oxide (FeV/RGO) nanocomposite. The band gap of FeV decreased upon anchoring with RGO. Enhanced activity in the detection and photocatalytic degradation has been achieved in the FeV/RGO nanocomposite compared to pure FeV and RGO. FeV/RGO was used to modify glassy carbon electrode (GCE), and the fabricated electrode was evaluated for its electrochemical detection of methyl parathion (MP). The amperometric technique was found to be more sensitive with a 0.001-260 μM (two linear ranges; 0.001-20 and 25-260 μM) wide linear range and low limit of detection value (0.70 nM). The practical applicability of modified GCE is more selective and sensitive to real samples like river water and green beans. Photocatalytic degradation of MP has been examined using FeV, RGO, and FeV/RGO nanocomposite. FeV/RGO managed to degrade 95% of MP under solar light in 80 min. Degradation parameters were optimized carefully to attain maximum efficiency. Degradation intermediates were identified using liquid chromatography-mass spectrometry analysis. The degradation mechanism has been studied in detail. FeV/RGO could serve as a material of choice in the field of electrochemical sensors as well as heterogeneous catalysis toward environmental remediation.

Silver nanoparticle-modified electrodes for the electrochemical detection of neonicotinoid pesticide: clothianidin

For the first time, stable silver nanoparticles with a diameter less than 20 nm were prepared using SDS as a reducing and stabilizing agent and characterized, and then used to construct modified electrodes. The developed electrodes are more catalytically active towards the reduction of clothianidin. Clothianidin undergoes reduction at -300 mV vs. Ag/AgCl on the silver nanoparticle-modified electrode, whereas no reduction peak was observed on a bare glassy carbon electrode (GCE). The detection limit was found to be 2.4 nM. The reduction potential and detection limits reported in this work are lower than ever reported in the literature. The analytical validity of clothianidin was tested using tomatoes. Validation of electrochemical results has been achieved by comparing them to HPLC results. There is a good agreement between the results and those obtained by HPLC. The proposed sensor opens up new possibilities for the sensing of clothianidin in environmental samples.

A nonenzymatic reduced graphene oxide-based nanosensor for parathion

Organophosphate-based pesticides (e.g., parathion (PT)) have toxic effects on human health through their residues. Therefore, cost-effective and rapid detection strategies need to be developed to ensure the consuming food is free of any organophosphate-residue. This work proposed the fabrication of a robust, nonenzymatic electrochemical-sensing electrode modified with electrochemically reduced graphene oxide (ERGO) to detect PT residues in environmental samples (e.g., soil, water) as well as in vegetables and cereals. The ERGO sensor shows a significantly affected electrocatalytic reduction peak at -0.58 V (vs Ag/AgCl) for rapid quantification of PT due to the amplified electroactive surface area of the modified electrode. At optimized experimental conditions, square-wave voltammetric analysis exhibits higher sensitivity (50.5 μA·μM^-1·cm^-2), excellent selectivity, excellent stability (≈180 days), good reproducibility, and repeatability for interference-free detection of PT residues in actual samples. This electrochemical nanosensor is suitable for point-of-care detection of PT in a wide dynamic range of 3 × 10^-11-11 × 10^-6 M with a lower detection limit of 10.9 pM. The performance of the nanosensor was validated by adding PT to natural samples and comparing the data via absorption spectroscopy. PT detection results encourage the design of easy-to-use nanosensor-based analytical tools for rapidly monitoring other environmental samples.

Electrocatalysis of Endosulfan Based on Fe3O4: An Experimental and Computational Approach

The present work reports the electrocatalytic oxidation of the organochlorine pesticide endosulfan (EDS) using iron oxide (Fe₃O₄) nanoparticles synthesized from Callistemon viminalis leaf extracts. As a sensor for EDS, Fe₃O₄ was combined with functionalized multiwalled carbon nanotubes (f-MWCNTs) on a glassy carbon electrode (GCE). Cyclic voltammetry, electrochemical impedance spectroscopy, and the differential pulse voltammetry experiment were conducted to investigate the electrochemistry of EDS on the GCE/f-MWCNT/Fe₃O₄ sensor. Based on optimized experimental conditions, the reports of analytical parameters show a limit of detection of 3.3 μM and an effective sensitivity of 0.06464 μA/μM over a range of concentrations from 0.1 to 20 μM. With the proposed method, we were able to demonstrate recoveries between 94 and 110% for EDS determinations in vegetables. Further, a series of computational modeling studies were carried out to better understand the EDS surface adsorption phenomenon on the GCE/f-MWCNT/Fe₃O₄ sensor. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap (-5.18 eV) computed by density functional theory (DFT) supports the layer-by-layer electrode modification strategy's charge transfer and stability. Finally, transition state modeling was able to predict and confirm the mechanism of endosulfan oxidation.

Electrodeposition of silver onto carbon graphite and their catalysis properties toward thiamethoxam reduction: application in food and beverage samples

The purpose of this paper is the electrodeposition of silver particles on graphite electrode (Ag@GrCE) using chronoamperometry and the use of this electrode for the determination of thiamethoxam. The electrode was prepared by chronoamperometry and characterized by X-Ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), EDX analysis and electrochemical impedance spectroscopy. The obtained electrode exhibits excellent electrocatalytic activity toward thiamethoxam reduction. The voltammetric response was linear as function of TXM concentration with a limit of detection around to 1.92 × 10⁻⁶ mol L⁻¹. The proposed electrode was successfully used to analyze thiamethoxam residue in some food samples including orange and tomato juices.

Sensitive, simple and fast voltammetric determination of pesticides in juice samples by novel BODIPY-phthalocyanine-SWCNT hybrid platform

The present work describes the first synthesis of novel asymmetric zinc (II) phthalocyanine (ZnPc) including three boron dipyrromethene (BODIPY) and one ethyloxy azido moieties. Moreover, single walled carbon nanotube (SWCNT) surface was functionalized by this ZnPc containing BODIPY; using the azide-alkyne Huisgen cycloaddition (Click) reaction to obtain SWCNT-ZnPc hybrid material. Structural, thermal and morphological characterizations of both ZnPc and SWCNT-ZnPc hybrid were carried out in-depth by spectroscopic, thermal and microscopic techniques. In this study, the synthesized SWCNT-ZnPc material was decorated on composite glassy carbon electrode (GCE) by means of an easy and a practical drop cast method. The modified electrode was tested as a non-enzymatic electrochemical sensor in various common pesticides such as methyl parathion, deltamethrin, chlorpyrifos and spinosad. Electrochemical behavior of non-enzymatic electrode (GCE/SWCNT-ZnPc) was determined via cyclic voltammetry and differential pulse voltammetry. The non-enzymatic sensor demonstrated high selectivity for methyl parathion in a wide linear range (2.45 nM-4.0 × 10^-8 M), low limit of detection value (1.49 nM) and high sensitivity (0.1847 μA nM^-1). Also, the developing non-enzymatic sensor exhibited good repeatability (RSD = 2.3% for 10 electrodes) and stability (85.30% for 30 days). Validation guidelines by HPLC and statistical analysis showed that the proposed voltammetric method were precise, accurate, sensitive, and can be used for the routine quality control of methyl parathion determination in juice samples.

A novel, biocompatible and electrocatalytic stearic acid/nanosilver modified glassy carbon electrode for the sensing of paraoxon pesticide in food samples and commercial formulations

A simple, biocompatible and an enzyme-free sensing platform was developed for detection of paraoxon. The surface of a glassy carbon electrode was modified with an electrodeposition of stearic acid/nanosilver composite at -0.7 V for 40 s. The paraoxon undergoes electro-reduction at -550 mV on the modified electrode, and the limits of detection (LOD) was calculated as 0.1 nM (S/N = 3) using differential pulse voltammetry which is lower than that of the existing materials reported. The high stability observed with the modified electrode for prolonging period indicated that the sensitivity of the electrode remains active for several runs of the analysis. The developed analytical strategy was implemented for onion and paddy grain samples and good recovery rates were observed. Also, it was applied for analyzing the purity of the commercial paraoxon sample. The reliability of the developed strategy was confirmed by comparing the results of electrochemical approach with that of HPLC technique.

VXC-72R/ZrO2/GCE-Based Electrochemical Sensor for the High-Sensitivity Detection of Methyl Parathion

In this work, a carbon black (VXC-72R)/zirconia (ZrO2) nanocomposite-modified glassy carbon electrode (GCE) was designed, and a VXC-72R/ZrO2/GCE-based electrochemical sensor was successfully fabricated for the high-sensitivity detection of methyl parathion (MP). Electrochemical measurements showed that the VXC-72R/ZrO2/GCE-based electrochemical sensor could make full use of the respective advantages of the VXC-72R and ZrO2 nanoparticles to enhance the MP determination performance. The VXC-72R nanoparticles had high electrical conductivity and a large surface area, and the ZrO2 nanoparticles possessed a strong affinity to phosphorus groups, which could achieve good organophosphorus adsorption. On the basis of the synergistic effect generated from the interaction between the VXC-72R and ZrO2 nanoparticles, the VXC-72R/ZrO2/GCE-based electrochemical sensor could show excellent trace analysis determination performance. The low detection limit could reach up to 0.053 μM, and there was a linear concentration range of 1 μM to 100 μM. Such a high performance indicates that the VXC-72R/ZrO2/GCE-based electrochemical sensor has potential in numerous foreground applications.

Electrochemical biosensor for methyl parathion based on single-walled carbon nanotube/glutaraldehyde crosslinked acetylcholinesterase-wrapped bovine serum albumin nanocomposites

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s-SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu-s-SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10^-10 M to 5 × 10^-6 M with a limit of detection (LOD) of 3.75 × 10^-11 M. In addition, the BSA/AChE-Glu-s-SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu-s-SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE-s-SWCNTs/GCE, s-SWCNTs/GCE and bare GCE.

Electrochemical co-deposition synthesis of Au-ZrO2-graphene nanocomposite for a nonenzymatic methyl parathion sensor

For the first time, a simple electrochemical co-deposition was utilized to synthesis the gold and zirconia nanocomposites modified graphene nanosheets on glassy carbon electrode (Au-ZrO₂-GNs/GCE) for electrocatalytic analysis of methyl parathion (MP). According to Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM) and X-Ray Diffraction (XRD), the gold nanoparticles were uniformly distributed on the surface of graphene-based nanocomposite. The Au-ZrO₂-GNs/GCE based sensor exhibited superior capacity for MP detection, ascribed to the strong affinity of zirconia towards the phosphoric group, as well as the high catalytic activity and good conductivity of Au-GNs. The best fabrication and work conditions were then obtained by systematically optimization of the electrodeposition process, pH value and enrichment time. Compared to the gold nanoparticles, zirconia or graphene modified electrodes, AuZrO₂-GNs/GCE sensor displayed superior electro-catalytic response toward MP oxidation. The sensor response current of square wave voltammetry was highly linearly correlated with the MP concentrations range of 1-100 ng mL^-1 and 100-2400 ng mL^-1 with the detection limit of 1 ng mL^-1. The Au-ZrO₂-GNs/GCE nanocomposite sensor showed excellent accuracy and reproducibility for detection of MP in Chinese cabbage samples, providing a new method for efficient pesticide detection in practical applications.

Electrochemical determination of methyl parathion based on pillar[5]arene@AuNPs@reduced graphene oxide hybrid nanomaterials

The detection of pesticides has become a very important and critical research area because of the rapid development of agriculture and strict environmental protection regulations.

A review of the advanced developments of electrochemical sensors for the detection of toxic and bioactive molecules

The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.

Methyl parathion detection in vegetables and fruits using silver@graphene nanoribbons nanocomposite modified screen printed electrode

We have developed a sensitive electrochemical sensor for Organophosphorus pesticide methyl parathion (MP) using silver particles supported graphene nanoribbons (Ag@GNRs). The Ag@GNRs nanocomposite was prepared through facile wet chemical strategy and characterized by TEM, EDX, XRD, Raman, UV-visible, electrochemical and impedance spectroscopies. The Ag@GNRs film modified screen printed carbon electrode (SPCE) delivers excellent electrocatalytic ability to the reduction of MP. The Ag@GNRs/SPCE detects sub-nanomolar concentrations of MP with excellent selectivity. The synergic effects between special electrocatalytic ability of Ag and excellent physicochemical properties of GNRs (large surface area, high conductivity, high area-normalized edge-plane structures and abundant catalytic sites) make the composite highly suitable for MP sensing. Most importantly, the method is successfully demonstrated in vegetables and fruits which revealed its potential real-time applicability in food analysis.

In situ synthesis of high swell ratio polyacrylic acid/silver nanocomposite hydrogels and their antimicrobial properties

Silver nanocomposites embedded within a polymer matrix have attracted attention in recent years. Ionic polymer hydrogels comprise networks of chemically or physically cross-linked polymers that swell considerably in an appropriate solvent. In this study, we used a solution of the carboxylic monomer acrylic acid and silver nitrate to prepare nanocomposite hydrogels through ultraviolet (UV)-light irradiation. Silver-impregnated biomaterial composed of acrylic acid contains only a monomer and no cross-linker. The formation of hydrogels and reduction of silver nanoparticles were affected by the preparation parameters, that is, the monomer concentration and silver nitrate concentration. The morphology, structure, and size of the silver nanocomposite hydrogels were evaluated through field emission scanning electron microscopy and UV-visible absorption. The antimicrobial activity of the samples was tested against fourstandard strains Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli; and five clinical bacterial isolates Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumonia. The silver nanocomposite hydrogels exhibited an interconnected porous structure and could absorb 400 to 550g of deionized water per gram of dried hydrogel. Moreover, these hydrogels produced a strong antibacterial effect, which can be useful in developing new superabsorbent antimicrobial pharmaceutical products.

Environmentally-friendly in situ plated bismuth-film electrode for the quantification of the endocrine disruptor parathion in skimmed milk

An in situ bismuth-film electrode (BiFE) together with square-wave cathodic voltammetry (SWCV) was used to determine the concentration of the endocrine disruptor parathion in skimmed milk. The experimental conditions (deposition time, deposition potential and Bi (III) concentration) were optimized for the preparation of the BiFE. A glassy carbon electrode was used as the substrate. The selection of the chemical composition of the supporting electrolyte and the solution pH was aimed at improving the reduction of parathion at the BiFE surface. In addition, the parameters of the square-wave cathodic voltammetry were adjusted to improve the sensor performance. A cathodic current identified at -0.523 V increased linearly with the parathion concentration in the range of 0.2-2.0 μmol L(-1) (R=0.999). The sensitivity of the calibration curve obtained was 4.09 μA L μmol(-1), and the limits of detection (LOD) and quantification (LOQ) were 55.7 nmol L(-1) and 169.0 nmol L(-1), respectively. The performance of the sensor was tested using a sample of skimmed milk with parathion added. The same determination was carried out by UV-vis spectroscopy and the results obtained were used for the statistical evaluation of the data obtained.

Ultrasensitive electrochemical sensor for p-nitrophenyl organophosphates based on ordered mesoporous carbons at low potential without deoxygenization

p-Nitrophenyl organophosphates (OPs) including paraoxon, parathion and methyl parathion, etc, are highly poisonous OPs, for which sensitive and rapid detection method is most needed. In this work, an ultrasensitive electrochemical sensor for the determination of p-nitrophenyl OPs was developed based on ordered mesoporous carbons (OMCs) modified glassy carbon electrode (GCE) (OMCs/GCE). The electrochemical behavior and reaction mechanism of p-nitrophenyl OPs at OMCs/GCE was elaborated by taking paraoxon as an example. Experimental conditions such as buffer pH, preconcentration potential and time were optimized. By using differential pulse voltammetry, the current response of the sensor at -0.085 V was linear with concentration within 0.01-1.00 μM and 1.00-20 μM paraoxon. Similar linear ranges of 0.015-0.5 μM and 0.5-10 μM were found for parathion, and 0.01-0.5 μM and 0.5-10 μM for methyl parathion. The low limits of detection were evaluated to be 1.9nM for paraoxon, 3.4 nM for parathion and 2.1 nM for methyl parathion (S/N=3). Common interfering species had no interference to the detection of p-nitrophenyl OPs. The sensor can be applicable to real samples measurement. Therefore, a simple, sensitive, reproducible and cost-effective electrochemical sensor was proposed for the fast direct determination of trace p-nitrophenyl OPs at low potential without deoxygenization.

Resonance scattering detection of trace melamine using aptamer-modified nanosilver probe as catalyst without separation of its aggregations

Nanosilver was modified by aptamer (ssDNA) to obtain a resonance scattering (RS) probe (AgssDNA) for melamine (MA). Based on the catalytic effect of the probe on the Fehling particle reaction, a nanocatalytic RS assay is proposed for the determination of 0.02-1.06 μg L(-1) MA.