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

Ultrasensitive adsorptive stripping voltammetry-free electrochemical sensor for Cu2 + based on its specific catalytic etching to cytosine-rich oligonucleotide templated silver nanoparticles

The development of reliable and highly sensitive copper ions (Cu2+) detection technologies is crucial for both environmental conservation and health surveillance. To address the challenges associated with conventional adsorptive stripping voltammetry, such as potential matrix interference, lengthy pre-electrolysis times, and limited detection sensitivity, we herein introduce an innovative electrochemical sensing approach for Cu2+. This method utilizes the unique catalytic etching capability of Cu2+ on cytosine-rich oligonucleotide (CRO)-templated silver nanoparticles (AgNPs). The thiolated CRO was assembled onto the Au electrode through the Au-S bond. Subsequently, the AgNPs were generated by in-situ chemical reduction of Ag+, which pre-absorbed on CRO via the cytosine-Ag+-cytosine (C-Ag+-C) structure. The results demonstrated that Cu2+ could markedly speed up the etching of AgNPs, which in turn reduced the solid-state electrochemical response of AgNPs. This reduction allowed for the detection of Cu2+ within a wide concentration range from 0.1 pM to 1.0 nM, with an impressively low detection limit of 0.03 pM. The practicality of this method has been validated through its successful application in analyzing Cu2+ levels of the actual water samples.

Application of nanomaterials in the detection of pesticide residues in spices

With the development of global trade and the improvement of consumer safety awareness, the problem of pesticide residues in spices has received considerable attention. At the same time, with the advancement of nanotechnology, nanomaterials have shown great potential in pesticide residue detection. Given the wide variety of spices and their complex matrices, there has been a lack of a comprehensive review on the application of nanomaterials in pesticide residue detection in spices until now. In this study, the advancements in research on newly developed nanomaterials were examined for the detection of pesticide residues in spices over the last 10 years, focusing on the applications of carbon nanotubes, graphene and its derivatives, metal nanoparticles, metal-organic frameworks, molecularly imprinted polymers, and quantum dots. Additionally, this study also explores the advantages and challenges of different nanomaterials' applications and predicts their development trends, aiming to provide a reference for future research.

Preconcentration-enhanced electrochemical detection of paraoxon in food and environmental samples using reduced graphene oxide-modified disposable sensors

Organophosphates, such as paraoxon, are widely used as insecticides in agriculture, making their detection in environmental and food samples crucial due to their high toxicity. This study presents the development of an electrochemical sensor for the detection of paraoxon, using a screen-printed carbon electrode (SPCE) modified with electrochemically reduced graphene oxide (rGO). The modification enhanced the sensor's electrical conductivity and electrochemical performance. A novel preconcentration approach, involving potential pulses at -1.0 and 0.0 V, was employed to improve the adsorption of paraoxon on the electrode surface. Detection was performed by square wave voltammetry, and under optimized conditions, the rGO-SPCE sensor exhibited a linear range from 1.0 to 30 μmol L-1, with detection and quantification limits of 0.26 and 0.86 μmol L-1, respectively. The sensor demonstrated excellent repeatability (RSD = 4.22%), reproducibility (RSD = 7.14%), and selectivity (RSD < 9.22%). The method was successfully applied to tap water, grape and apple juices, and canned corn water samples, achieving recoveries of approximately 98% at the lowest concentration (1.0 μmol L-1) with minimal matrix effects. This approach offers a simple, low-cost, and rapid method for paraoxon detection in water and food samples.

Summer profiles: Tracing currently used organophosphorus pollutants in the surface seawater of the Arctic Ocean

We investigate the spatial distribution and potential ecological impact of Currently Used Organophosphorus Pollutants (CUOPPs) in the Arctic Ocean, focusing on the East Siberian Sea, Laptev Sea, and high Arctic regions. Analyzing surface water samples collected during a scientific expedition aboard the "Xuelong 2" in August and September 2021, we detected 38 out of 83 targeted CUOPPs, including Phorate, Paraoxon, and Azinphos-ethyl, with concentrations exhibiting significant geographical variance. The results reveal a pronounced increase in CUOPP concentrations towards the Arctic poles, diverging markedly from the patterns observed in the East China Sea, thereby highlighting distinct regional pollution profiles and environmental interactions. Our findings suggest various potential sources and transport mechanisms for CUOPPs, indicating complex pollutant dynamics. Furthermore, the study delves into the influence of Arctic sea ice dynamics on the distribution patterns of CUOPPs, underscoring the pivotal role of environmental factors such as surface currents. Ecological risk assessments conducted for essential Arctic species pose a high ecological risk in the Arctic Ocean, with a "Summer Alert" effect. This investigation elucidates the intricate relationship between CUOPPs dispersal in the Arctic and the broader implications of climate change, offering critical insights into the emerging environmental challenges in polar ecosystems.

Graphene oxide-cerium oxide nanocomposite modified gold electrode for ultrasensitive detection of chlorpyrifos pesticide

This research presents a novel approach for the detection of the pesticide chlorpyrifos (CLP) using a gold working electrode immobilized with a graphene oxide-cerium oxide (GO-CeO2) nanocomposite in a phosphate buffer (PBS) solution with a pH of 7.0. Graphene oxide (GO) was synthesized via a modified Hummer's method, while cerium oxide (CeO2) nanoparticles were prepared using a coprecipitation technique. The GO-CeO2 nanocomposite was synthesized via sonochemical methods. Structural and morphological characterization of the prepared material was conducted using X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDX). Fourier transform infrared (FTIR) spectroscopy has been conducted for the confirmation of functional group presence in the prepared materials. Cyclic voltammetry (CV) was employed to investigate the interaction between the prepared material and the analyte. Further investigations using varying scan rates (5 mV s-1 to 300 mV s-1) revealed a diffusion-controlled process at the electrode-electrolyte interface. Linear sweep voltammetry (LSV) experiments were conducted across a pH range of 5 to 9, with pH 7.0 showing enhanced response for the target pesticides in the presence of the buffer solution. Subsequent electrochemical measurements were performed at pH 7.0. Chronocoulometry was utilized to measure the effective electrode area for electrochemical interactions. Ultrasensitive square wave voltammetry (SWV) was employed for investigating the sensitivity over a concentration range of 1 fM to 100 μM and yielded the limit of detection (LOD) and limit of quantification (LOQ) as 47.7 fM and 159 fM respectively. Interference studies confirmed the selectivity of the prepared sensor, while stability and reproducibility were assessed through controlled experiments. Electrochemical impedance spectroscopy (EIS) was performed to investigate the interactions at the interface. This study provides insights into the development of selective electrochemical sensors for pesticide detection, with potential applications in environmental monitoring.

A novel acetylcholinesterase inhibition based colorimetric biosensor for the detection of paraoxon ethyl using CUPRAC reagent as chromogenic oxidant

A novel colorimetric biosensor for the sensitive and selective detection of an organophosphate pesticide, paraoxon ethyl (POE), was developed based on its inhibitory effect on the acetylcholine esterase (AChE) enzyme. The bis-neocuproine copper (II) complex ([Cu(Nc)2]2+) known as the CUPRAC reagent, was used as a chromogenic oxidant in the AChE inhibition-based biosensors for the first time. To initiate the biosensor, an enzymatic reaction takes place between AChE and its substrate acetylthiocholine (ATCh). Then, enzymatically produced thiocholine (TCh) reacts with the light blue [Cu(Nc)2]2+ complex, resulting in the oxidation of TCh to its disulfide form. On the other hand, [Cu(Nc)2]2+ reduces to a yellow-orange cuprous complex ([Cu(Nc)2]+) which gives maximum absorbance at 450 nm. However, the absorbance of [Cu(Nc)2]+ proportionally decreased with the addition of POE because the inhibition of AChE by the organophosphate pesticide reduced the amount of TCh that would give a colorimetric reaction with the CUPRAC reagent. Based on this strategy, the linear response range of a colorimetric biosensor was found to be between 0.15 and 1.25 μM with a detection limit of 0.045 μM. The fabricated biosensor enabled the selective determination of POE in the presence of some other pesticides and metal ions. The recovery results between 92% and 104% were obtained from water and soil samples spiked with POE, indicating that the determination of POE in real water and soil samples can be performed with this simple, accurate, sensitive, and low-cost colorimetric biosensor.

An enzyme-free, ultrasensitive strategy for simultaneous screening of the p-nitrophenyl substituent organophosphorus pesticides

An enzyme-free, sensitive, and convenient approach was reported for the P-nitrophenyl substituent organophosphorus pesticides (NSOPs) of paraoxon-methyl (PM), paraoxon-ethyl (PE), parathion-methyl (PTM) and parathion-ethyl (PTE)) by indirectly quantification of the 4-nitrophenol (4-NP, hydrolysis product of the NSOPs). NaOH instead of hydrolase/nanozyme was applied, and temperature, pH, ultrasound was investigated to improve the NSOPs hydrolysis. Under the optimized conditions, the hydrolysis efficiencies were up to 99.9 %, 99.9 %, 99.6 %, 96.0 % for PM (10 min), PE (30 min), PTM (90 min) and PTE (120 min), based on which a low detection limits of 0.06 (PM), 0.07 (PE), 0.06 (PTM) and 0.07 (PTE) ppb were calculated with the 4-NP detection limit (0.03 ppb). Furthermore, the method exhibited good performance for the NSOPs with recoveries from 88.87 % to 100.33 % in real samples. This indirect approach offered an ultrasensitive alternative for the NSOPs detection, which holds great potential in practical application for the assessment of food safety and environmental risks.

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.

Recent Progress in Non-Enzymatic Electroanalytical Detection of Pesticides Based on the Use of Functional Nanomaterials as Electrode Modifiers

This review presents recent advances in the non-enzymatic electrochemical detection and quantification of pesticides, focusing on the use of nanomaterial-based electrode modifiers and their corresponding analytical response. The use of bare glassy carbon electrodes, carbon paste electrodes, screen-printed electrodes, and other electrodes in this research area is presented. The sensors were modified with single nanomaterials, a binary composite, or triple and multiple nanocomposites applied to the electrodes' surfaces using various application techniques. Regardless of the type of electrode used and the class of pesticides analysed, carbon-based nanomaterials, metal, and metal oxide nanoparticles are investigated mainly for electrochemical analysis because they have a high surface-to-volume ratio and, thus, a large effective area, high conductivity, and (electro)-chemical stability. This work demonstrates the progress made in recent years in the non-enzymatic electrochemical analysis of pesticides. The need for simultaneous detection of multiple pesticides with high sensitivity, low limit of detection, high precision, and high accuracy remains a challenge in analytical chemistry.

A novel paraoxon imprinted electrochemical sensor based on MoS2NPs@MWCNTs and its application to tap water samples

Organophosphorus pesticides are widely utilized in agricultural fertility. However, their long-term accumulations result in serious damage to human health and ecological balance. Paraoxon (PAR) can block acetylcholinesterase in the human body, resulting in death. Thus, in this study, a molecularly imprinted electrochemical PAR sensor based on multiwalled carbon nanotubes (MWCNTs)/molybdenum disulfide nanoparticles (MoS₂NPs) nanocomposite (MoS₂NPs@MWCNTs) was proposed for selective tap water determination. A hydrothermal fabrication approach was firstly implemented to prepare MoS₂NPs@MWCNTs nanocomposite. Afterwards, the formation of PAR imprinted electrochemical electrode was performed on nanocomposite modified glassy carbon electrode (GCE) in presence of PAR as template and pyrrole (Py) as a monomer by cyclic voltammetry (CV) technique. Just after determining the physicochemical features of as-fabricated nanostructures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), Raman spectroscopy, and atomic force microscopy (AFM), the electrochemical behavior of the fabricated sensors was determined through CV, differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The suggested imprinted electrode provided the acceptable limit of quantification (LOQ) and limit of detection (LOD) values of 1.0 × 10^-11 M, and 2.0 × 10^-12 M, respectively. As a consequence, the proposed PAR imprinted electrochemical sensor can be offered for the determining safe tap water and its utility.

Nano-engineered materials for sensing food pollutants: Technological advancements and safety issues

Food spoilage and safety are key concerns of the modern food sector. Among them, several types of polluting agents are the prime grounds of food deterioration. In this context, nanotechnology-based measures are setting new frontiers to strengthen food applications. Herein, we summarize the nanotechnological dimension of the food industry for both processing and packaging applications. Active bioseparation, smart delivery, nanoencapsulation, nutraceuticals, and nanosensors for biological detection are a few emerging topics of nanobiotechnology in the food sector. The development of functional foods is another milestone set by food nanotechnology by building the link between humans and diet. However, the establishment of optimal intake, product formulations, and delivery matrices, the discovery of beneficial compounds are a few of the key challenges that need to be addressed. Nanotechnology provides effective solutions for the aforementioned problem giving various novel nanomaterials and methodologies. Various nanodelivery systems have been designed, e.g., cochleate, liposomes, multiple emulsions, and polysaccharide-protein coacervates. However, their real applications in food sciences are very limited. This review also provides the status and outlook of nanotechnological systems for future food applications.

Fabrication and application of three-dimensional nanocomposites modified electrodes for evaluating the aging process of Huangjiu (Chinese rice wine)

In this study, three modified glassy carbon electrodes based on three-dimensional conducting polymer nanocomposites (TDCPNs) were fabricated for evaluating the aging process of Huangjiu (Chinese rice wines). The electrochemical activity and experimental conditions of the TDCPNs modified electrodes were investigated by cyclic voltammetry, the aging information obtained by the modified electrodes were optimized by variance inflation factor (VIF). Principal components analysis (PCA), locally linear embedding (LLE), and locality preserving projection (LPP, which presented the best classification result) based on the optimized data were applied to classify the wine samples. Then, the dimensionality reduction data of PCA, LLE, and LPP were used as input variables of the logistic regression and extreme learning machine (ELM) for evaluating the aging process of Huangjiu, and the LLE-ELM method exhibited the best prediction results. These results demonstrated that the TDCPNs modified electrodes presented the potential for the quality analysis of food and beverages.

Emerging vistas on pesticides detection based on electrochemical biosensors - An update

Organophosphates and carbamates pesticides are widely used to increase crop production globally causing a threat to human health and the environment. A variety of pesticides are applied during different stages of vegetable production. Therefore, monitoring the presence of pesticide residues in food and soil has great relevance to sensitive pesticide detection through distinct determination methods that are urgently required. Conventional techniques for the detection of pesticides have several limitations that can be overcome by the development of highly sensitive, fast, reliable and easy-to-use electrochemical biosensors. Herein, we describe the types of biosensors with the main focus on electrochemical biosensors fabricated for the detection of OPPs and carbamates pesticides. An overview of conventional techniques employed for pesticide detection is also discussed. This review aims to provide a glance of recently developed biosensors for some common pesticides like chlorpyrifos, malathion, parathion, paraoxon, and carbaryl which are present in food and environment samples.

Preparation of magnetic molecularly imprinted polymer based on multiwalled carbon nanotubes for selective dispersive micro-solid phase extraction of fenitrothion followed by ion mobility spectrometry analysis

A novel molecularly imprinted polymer based on magnetic multi-walled carbon nanotubes was fabricated and applied for selective dispersive micro-solid phase extraction of fenitrothion prior its determination by ion mobility spectrometry. The composite was synthesized using magnetic multi-walled carbon nanotubes as the support. Methacrylic acid was used as the functional monomer, fenitrothion as the template, ethylene glycol dimethacrylate as the cross-linker and 2,2-azoisobutyronitrile as the initiator. The resultant polymer was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, Brunauer-Emmet-Teller analysis, thermogravimetric analysis and vibrating sample magnetometer techniques. Experimental factors affecting the extraction efficiency such as pH and amount of sorbent were evaluated. Under optimum experimental conditions, the developed method displayed the linear range of 5-220 μg L^-1 with a detection limit (LOD) of 1.3 μg L^-1 . The intra and inter-day relative standard deviations (RSD%) for determination of fenitrothion were 3.6 and 4.7% (n = 6), respectively. Ultimately, the proposed method was used to monitoring of trace amounts of fenitrothion in fruit,vegetable and water samples. This article is protected by copyright. All rights reserved.

Detection of organophosphorus pesticides: exploring oxime as a probe with improved sensitivity by CeO2-modified electrode

In this paper, the catalytic activity of CeO₂ NPs toward oxime oxidation was adopted for the first time to develop an electrochemical sensor with improved sensitivity toward the direct detection of organophosphorus pesticides (OPs) without electrochemical redox activity. To enhance the conductivity of the sensor, CeO₂ NPs together with multi-walled carbon nanotubes (MWCNTs) were deposited onto a bare glassy carbon electrode (GCE) by the simple method of drop-casting. The electrochemical properties of the as-prepared sensor were evaluated in K₃[Fe(CN)₆] solution and the oxidation behavior of pralidoxime (PAM) chloride on the electrodes was characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the modification of CeO₂ onto the electrode not only increases the electroactive area of the electrode but also significantly increases the peak current of PAM chloride oxidation, which confirms that CeO₂ has an electrocatalytic effect toward oxime oxidation. To evaluate the sensitivity of the as-fabricated sensor, the inhibition rate of PAM chloride peak current was tested in PAM chloride solution containing different concentrations of chlorpyrifos, which shows a very small detection limit of 2.5 × 10^-9 M. In addition, the sensor successfully achieved a convenient and sensitive determination of OPs in vegetable extracts.

Determination of quinclorac by adsorptive stripping voltammetry in rice samples without sample pretreatment

A novel voltammetric method with practically no sample pretreatment was developed for determination of Quinclorac (QNC) in rice samples by using a working Carbon Paste Electrode (CPE) modified with ionic liquid, with deposition potential (E_D) of -1.43 V for 30 s in NaOH 0.01 mol L^-1. The systematic influence of cations and anions of imidazole ionic liquids on the composition of CPE has evaluated. The best electrode composition was 65% (w/w) of graphite powder, 30% (w/w) of mineral oil and 5.0% (w/w) of C₄min⁺BF₄^- ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate). The matrices analyzed were deionized water and extracts of upland rice: white, brown, peel and seed. The limits of quantification ranged between 0.954 mg kg^-1 and 3.61 mg kg^-1. The recovery percentages of QNC in rice samples ranged between 90% and 121%. The simplicity and good analytical frequency enable the proposed method to be used to obtain preliminary information on the presence of QNC, prior to the implementation of more detailed, costly and elaborate quantitative analyses. The technique can be applied in the study and evaluation of sorption mechanisms, metabolization of the herbicide in plants and its persistence and degradation in the environment.

Recent Advances in (Bio)Chemical Sensors for Food Safety and Quality Based on Silver Nanomaterials

There is a continuing need for tools and devices which can simplify, quicken and reduce the cost of analyses of food safety and quality. Chemical sensors and biosensors are increasingly being developed for this purpose, reaping from the opportunities provided by nanotechnology. Due to the distinct electrical and optical properties of silver nanoparticles (AgNPs), this material plays a vital role in (bio)sensor development. This review is an analysis of chemical sensors and biosensors based on silver nanoparticles with application in food and beverage matrices. It consists of academic research published from 2015 to 2020. The paper is structured to separately explore the designs of two major (bio)sensor classes: electrochemical (including voltammetric and impedimetric sensors) and optical sensors (including colourimetric and luminescent), with special focus on the type of silver nanomaterial and its role in the sensor system. The review indicates that diverse nanosensors have been developed, capable of detecting analytes such as pesticides, mycotoxins, fertilisers, microorganisms, heavy metals, and various additives with exceptional analytical performance. Current trends in the design of such sensors are highlighted and challenges which need to be overcome in the future are discussed.