High-performance electrochemical sensing of hazardous pesticide Paraoxon using BiVO4 nano dendrites equipped catalytic strips

Metallic Dendrites: How Far Can We Go?

Metallic dendrites, novel hierarchical nanostructures with a distinctive fern- or tree-like appearance, introduce a new era in sensing and wearable technologies. They possess several properties, including high surface area, crystal defects, grain boundaries, and edge sites, all of which contribute to an increased number of catalytic sites for sensing and wearable platforms, as well as functionalization sites for antibodies and drug molecules' adhesion. The aforementioned characteristics endow them with superior conductivity and enhanced catalytic activity, thereby facilitating improved mass and charge transfer rates of analytes in catalytic platforms. Since their discovery, there has been substantial progress in their synthesis, nanoengineering with composites, and extensive analytical applications in diverse domains, such as sensor platforms and wearables, fuel cells, supercapacitors, and drug delivery. Although platforms based on dendrites have performed well over the past ten years, their commercialization has yet to take place for a variety of reasons, primarily being the challenge to achieve homogeneity in large-scale synthesis due to uncontrolled development. Besides this, other challenges include transitioning to non-noble metals while still maintaining high activity and stability, as well as their sluggish metabolism in vivo following drug delivery and poor excretion by the body, which collectively hinder their translation. This Perspective encompasses important breakthroughs of metallic dendrites and analytical platforms based upon them, crucial knowledge gaps, and bottlenecks in commercialization with an eye towards the future of dendrite-based sensing, wearable electronics, as well as other such platforms.

Reductive pathway profiling of chemical warfare agent simulant in complex matrices using hydrothermally engineered mixed-valent Y2NiMnO6 double perovskite

The detection of chemical warfare agent (CWA) simulants in complex matrices remains a critical challenge for safeguarding environmental and public health. In this study, we report the development of a highly sensitive and selective electrochemical sensor utilizing hydrothermally engineered Y2NiMnO6 (YNMO), a mixed-valent double perovskite, for the detection of paraoxon ethyl (PXE), a representative CWA simulant. The YNMO-modified glassy carbon electrode (YNMO/GCE) exhibited exceptional electrocatalytic performance, owing to the synergistic redox activity of Ni2+/Ni3+ and Mn3+/Mn4+ redox couples that significantly enhanced interfacial charge transfer kinetics. The sensor achieved an impressively low detection limit of 0.08 nM and a quantification limit of 5 nM, with a wide linear detection range spanning from 0.19 μM to 2147.51 μM. It demonstrated high analytical robustness, with excellent repeatability (relative standard deviation < 2.57 %), reproducibility (inter-electrode variation <1.7 %), and operational stability over a 30-day testing period. Notably, the sensor retained functionality under complex conditions, exhibiting strong anti-interference capability against structurally related organophosphates and coexisting environmental or biological species. Real-sample analyses in diverse matrices including river, pond, and tap water; synthetic saliva and sweat; and various food items yielded high recovery rates (98.6-101.8 %), confirming the sensor's practical applicability.

Enhanced electrochemical sensing of methyl parathion using AgNPs@IL/GO nanocomposites in aqueous matrices

Methyl parathion (MP) is a widely used pesticide; it is recognized as being toxic to both target and non-target species, posing serious risks to environmental and human health. Monitoring and controlling MP residues is thus essential, necessitating the development of innovative sensors that are highly sensitive, selective, and reproducible. In the present study, an efficient electrochemical MP sensor is proposed based on silver nanoparticles (AgNPs) in conjunction with graphene oxide/ionic liquid (GO/IL) on screen printed electrodes (AgNPs@GO/IL@SPCE). The AgNPs were synthesized via a cost-effective wet-chemical process and characterized using UV-Vis spectroscopy and transmission electron microscopy (TEM). The modified electrodes were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The active surface area and charge transfer were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. The modified electrodes' electrocatalytic performance towards the reduction of MP was investigated by CV, complemented by semiempirical quantum chemistry calculations to elucidate the interaction and the electrochemical reduction mechanism of MP. The sensor demonstrates a remarkable limit of detection of 0.009 μmol L-1 within a linear range of 0.025 to 200 μmol L-1. It has an excellent analytical performance in terms of selectivity, reproducibility, and long-term stability over 60 days. The designed sensor was effectively used to inspect MP in groundwater and surface water samples, with recovery values ranging from 95.60% to 99.68%.

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.

Ultrasensitive non-enzymatic electrochemical detection of paraoxon-ethyl in fruit samples using 2D Ti3C2Tx/MWCNT-OH

This study reports on the development of a highly sensitive non-enzymatic electrochemical sensor based on a two-dimensional Ti3C2Tx/MWCNT-OH nanocomposite for the detection of paraoxon-based pesticide. The synergistic effect between the Ti3C2Tx nanosheet and the functionalized multi-walled carbon nanotubes enhanced the sensor's conductivity and catalytic activity. The nanocomposite demonstrates superior electrochemical and electroanalytical performance compared to the pristine Ti3C2Tx and MWCNT-OH in detecting paraoxon-ethyl in fruit samples (green and red grapes), with a linear response range from 0.1 to 100 μM, a low limit of detection (LOD) of 10 nM, limit of quantitation (LOQ) of 70 nM, and sensitivity of 0.957 µA μM-1 cm-2 at pH 8. Furthermore, the sensors maintain excellent selectivity and effectiveness in detecting paraoxon-ethyl even in the presence of various interferents, including diazinon, carbaryl, Fe2+, NO2-, NO3-, ascorbic acid, and glucose. The facile fabrication and enhanced sensing capabilities of the Ti3C2Tx/MWCNT-OH nanocomposite position it as a reliable, cost-effective, and sustainable alternative to conventional detection systems for monitoring pesticide residues in agricultural products.

A novel polycaprolactone/polypyrrole/β-cyclodextrin electrochemical flexible sensor for dinotefuran pesticide detection

The monitoring and the rapid quantification of pesticides and their residues are becoming increasingly important in the field of food safety. Herein, the polycaprolactone/polypyrrole/β-cyclodextrin (PCL/PPy/β-CD) flexible sensor was developed for the electrochemical determination of new neonicotinoid insecticide Dinotefuran (DNF). The morphology, structure, and hydrophilicity of PCL/PPy/β-CD sensor probes were characterized by SEM, FTIR spectroscopy and static contact angle test. Under optimum conditions, the fabricated PCL/PPy/β-CD sensor exhibited excellent electrochemical sensing performance for DNF with a low detection limit of 0.05 μM in the linear concentration range from 0.2 μM to 50 μM and high sensitivity 14.07 μA·μM-1·cm-2, which attributed to the two-stage porous structure, good electron transfer rate and the adsorption effect. The PCL/PPy/β-CD sensor also showed reproducibility (RSD = 4.76%), stability, and high selectivity towards DNF. In addition, a real samples investigation in rice with recoveries of 96.67 % ∼ 103.65 % implied the good application potential of PCL/PPy/β-CD in DNF monitoring.

Electrochemical Sensors based on Gold-Silver Core-Shell Nanoparticles Combined with a Graphene/PEDOT:PSS Composite Modified Glassy Carbon Electrode for Paraoxon-ethyl Detection

Herein, a nonenzymatic detection of paraoxon-ethyl was developed by modifying a glassy carbon electrode (GCE) with gold-silver core-shell (Au-Ag) nanoparticles combined with the composite of graphene with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS). These core-shell nanoparticles (Au-Ag) were synthesized using a seed-growth method and characterized using UV-vis spectroscopy and high-resolution transmission electron microscopy (HR-TEM) techniques. Meanwhile, the structural properties, surface morphology and topography, and electrochemical characterization of the composite of Au-Ag core-shell/graphene/PEDOT:PSS were analyzed using infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) techniques. Moreover, the proposed sensor for paraoxon-ethyl detection based on Au-Ag core-shell/graphene/PEDOT:PSS modified GCE demonstrates good electrochemical and electroanalytical performance when investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry techniques. It was found that the synergistic effect between Au-Ag core-shell nanoparticles and the composite of graphene/PEDOT:PSS provides a higher conductivity and enhanced electrocatalytic activity for paraoxon-ethyl detection at an optimum pH of 7. At pH 7, the proposed sensor for paraoxon-ethyl detection shows a linear range of concentrations from 0.2 to 100 μM with a limit of detection of 10 nM and high sensitivity of 3.24 μA μM-1 cm-2. In addition, the proposed sensor for paraoxon-ethyl confirmed good reproducibility, with the possibility of being further developed as a disposable electrode. This sensor also displayed good selectivity in the presence of several interfering species such as diazinon, carbaryl, ascorbic acid, glucose, nitrite, sodium bicarbonate, and magnesium sulfate. For practical applications, this proposed sensor was employed for the determination of paraoxon-ethyl in real samples (fruits and vegetables) and showed no significant difference from the standard spectrophotometric technique. In conclusion, this proposed sensor might have a potential to be developed as a platform of electrochemical sensors for pesticide detection.

Advances in Microfluidics Techniques for Rapid Detection of Pesticide Residues in Food

Food safety is a significant issue that affects people worldwide and is tied to their lives and health. The issue of pesticide residues in food is just one of many issues related to food safety, which leave residues in crops and are transferred through the food chain to human consumption. Foods contaminated with pesticide residues pose a serious risk to human health, including carcinogenicity, neurotoxicity, and endocrine disruption. Although traditional methods, including gas chromatography, high-performance liquid chromatography, chromatography, and mass spectrometry, can be used to achieve a quantitative analysis of pesticide residues, the disadvantages of these techniques, such as being time-consuming and costly and requiring specialist staff, limit their application. Therefore, there is a need to develop rapid, effective, and sensitive equipment for the quantitative analysis of pesticide residues in food. Microfluidics is rapidly emerging in a number of fields due to its outstanding strengths. This paper summarizes the application of microfluidic techniques to pyrethroid, carbamate, organochlorine, and organophosphate pesticides, as well as to commercial products. Meanwhile, the study also outlines the development of microfluidics in combination with 3D printing technology and nanomaterials for detecting pesticide residues in food.

Label-free ultra-sensitive colorimetric detection of hepatitis E virus based on oxidase-like activity of MnO2 nanosheets

Hepatitis E virus (HEV) is an evolving infectious entity that causes viral hepatitis infections worldwide. Current routine methods of identifying and diagnosing HEV are someway laborious and costly. Based on the biomimicking oxidase-like activity of MnO₂ nanosheets, we designed a label-free, highly sensitive colorimetric sensing technique for HEV detection. The prepared MnO₂ catalyst displays intrinsic biomimicking oxidase-like catalytic activity and efficiently oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate from colorless to blue colored oxidized TMB (oxTMB) product which can be measured at 652 nm by UV-visible spectrum. When the HEV-DNA was added, DNA adsorbed easily on MnO₂ surface through physical adsorption and electrostatic interaction which hinders the oxidase-like catalytic activity of MnO₂. Upon the introduction of target, the HEV target DNA binds with its complementary ssDNA on the surface of MnO₂, the hybridized DNA releases from the surface of MnO₂, which leads to recovery of oxidase-like catalytic activity of MnO₂. This strategy was applied to construct a colorimetric technique for HEV detection. The approach works in the linear range of 1 fM-100 nM DNA concentration with the limit of detection (LOD) of 3.26 fM (S/N = 3) and quantitative limit (LOQ) of 36.08 fM. The TMB-MnO₂ platform was highly selective for HEV target DNA detection when compared with potential interferences. Result of serum sample analysis demonstrates that this sensing system can be used for clinical diagnostic applications.

Nano-Engineered Surface Comprising Metallic Dendrites for Biomolecular Analysis in Clinical Perspective

Metallic dendrites, a class of three-dimensional nanostructured materials, have drawn a lot of interests in the recent years because of their interesting hierarchical structures and distinctive features. They are a hierarchical self-assembled array of primary, secondary, and terminal branches with a plethora of pointed ends, ridges, and edges. These features provide them with larger active surface areas. Due to their enormous active areas, the catalytic activity and conductivity of these nanostructures are higher as compared to other nanomaterials; therefore, they are increasingly used in the fabrication of sensors. This review begins with the properties and various synthetic approaches of nanodendrites. The primary goal of this review is to summarize various nanodendrites-engineered biosensors for monitoring of small molecules, macromolecules, metal ions, and cells in a wide variety of real matrices. Finally, to enlighten future research, the limitations and future potential of these newly discovered materials are discussed.

A Z-scheme CdS/BiVO4 photocatalysis towards Eriochrome black T: An experimental design and mechanism study

The synergistic photocatalytic activity was obtained when CdS and BiVO₄ nanoparticles (NPs) were coupled. The samples were characterized by XRD, FTIR, SEM-EDX, and UV-DRS techniques, and their pHpzc was also estimated. The crystallite size of the coupled sample was estimated at 37.3 and 12.5 nm by the Scherrer and Williamson-Hall equations, respectively. The band gaps and the potential positions of VB and CB levels of the semiconductors used were determined. The highest boosted photocatalytic activity was obtained when the CdS: BiVO₄ mole ratio was 1:1. RSM studied the simultaneous interactions between the selected variables, and the model F-value of 110.61> F_{0.05, 14, 13} = 2.4 accompanied by the LOF F-value of 5.20 < F_{0.05, 10, 3} = 8.79 confirm the model significance. The correlation coefficients of R² = 0.9861, the adjusted R² = 0.9710, and the predicted R² = 0.9417, also establish a satisfactory model for processing the experimental data. In the scavenging agent study, photodegradation mechanisms were suggested; among them, the direct Z-scheme mechanism is more favorable for illustrating the EBT-photodegradation by the binary CdS-BiVO₄ photocatalyst. The proposed system, especially the direct Z-scheme mechanism, is suitable as a potential hydrogen production system.

In Situ Synthesis of a Bismuth Vanadate/Molybdenum Disulfide Composite: An Electrochemical Tool for 3-Nitro-l-Tyrosine Analysis

The quantification of 3-nitro-l-tyrosine (NO₂-Tyr), an in vivo biomarker of nitrosative stress, is indispensable for the clinical intervention of various inflammatory disorders caused by nitrosative stress. By integrating the unique features of BiVO₄ and MoS₂ with matching bandgap energies, electrode materials with amplified response signals can be developed. In this regard, we introduce a hydrothermally synthesized bismuth vanadate sheathed molybdenum disulfide (MoS₂@BiVO₄) heterojunction as a highly sensitive electrode material for the determination of NO₂-Tyr. Excellent electrochemical behavior perceived for the MoS₂@BiVO₄ augments the performance of the sensor and allows the measurement of NO₂-Tyr in biological media without any time-consuming pretreatments. The synergistic interactions between BiVO₄ and MoS₂ heterojunctions contribute to low resistance charge transfer (R_ct = 159.13 Ω·cm²), a reduction potential E_pc = -0.58 V (vs Ag/AgCl), and a good response range (0.001-526.3 μM) with a lower limit of detection (0.94 nM) toward the detection of NO₂-Tyr. An improved active surface area, reduced charge recombination, and high analyte adsorption contribute to the high loading of the biomarker for improved selectivity (in the presence of 10 interfering compounds), operational stability (1000 s), and reproducibility (six various modified electrodes). The proposed sensor was successfully utilized for the real-time determination of NO₂-Tyr in water, urine, and saliva samples with good recovery values (±98.94-99.98%), ascertaining the reliability of the method. It is noteworthy that the electrochemical activity remains unaffected by other redox interferons, thus leading to targeted sensing applications.

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.