Selective Voltammetric Sensor for the Simultaneous Quantification of Tartrazine and Brilliant Blue FCF

Tartrazine and brilliant blue FCF are synthetic dyes used in the food, cosmetic and pharmaceutical industries. The individual and/or simultaneous control of their concentrations is required due to dose-dependent negative health effects. Therefore, the paper presents experimental results related to the development of a sensing platform for the electrochemical detection of tartrazine and brilliant blue FCF based on a glassy carbon electrode (GCE) modified with MnO₂ nanorods, using anodic differential pulse voltammetry. Homogeneous and stable suspensions of MnO₂ nanorods have been obtained involving cetylpyridinium bromide solution as a cationic surfactant. The MnO₂ nanorods-modified electrode showed a 7.9-fold increase in the electroactive surface area and a 72-fold decrease in the electron transfer resistance. The developed sensor allowed the simultaneous quantification of dyes for two linear domains: in the ranges of 0.10-2.5 and 2.5-15 μM for tartrazine and 0.25-2.5 and 2.5-15 μM for brilliant blue FCF with detection limits of 43 and 41 nM, respectively. High selectivity of the sensor response in the presence of typical interference agents (inorganic ions, saccharides, ascorbic and sorbic acids), other food dyes (riboflavin, indigo carmine, and sunset yellow), and vanillin has been achieved. The sensor has been tested by analyzing soft and isotonic sports drinks and the determined concentrations were close to those obtained involving the chromatography technique.

Recent Advances in Rapid Detection Techniques for Pesticide Residue: A Review

As an important chemical pollutant affecting the safety of agricultural products, the on-site and efficient detection of pesticide residues has become a global trend and hotspot in research. These methodologies were developed for simplicity, high sensitivity, and multiresidue detection. This review introduces the currently available technologies based on electrochemistry, optical analysis, biotechnology, and some innovative and novel technologies for the rapid detection of pesticide residues, focusing on the characteristics, research status, and application of the most innovative and novel technologies in the past 10 years, and analyzes challenges and future development prospects. The current review could be a good reference for researchers to choose the appropriate research direction in pesticide residue detection.

Recent advancements in the detection of organophosphate pesticides: a review

Organophosphorus pesticides (OPPs) are generally utilized for the protection of crops from pests. Because the use of OPPs in various agricultural operations has expanded dramatically, precise monitoring of their concentration levels has become the critical issue, which will help in the protection of ecological systems and food supply. However, the World Health Organization (WHO) has classified them as extremely dangerous chemical compounds. Taking their immense use and toxicity into consideration, the development of easy, rapid and highly sensitive techniques is necessary. Despite the fact that there are numerous conventional ways for detecting OPPs, the development of portable sensors is required to make routine analysis considerably more convenient. Some of these advanced techniques include colorimetric sensors, fluorescence sensors, molecular imprinted polymer-based sensors, and surface plasmon resonance-based sensors. This review article specifically focuses on the colorimetric, fluorescence and electrochemical sensors. In this article, the sensing strategies of these developed sensors, analytical conditions and their respective limit of detection are compiled.

Roll-to-Roll Manufactured Sensors for Nitroaromatic Organophosphorus Pesticides Detection

A fully roll-to-roll manufactured electrochemical sensor with high sensing and manufacturing reproducibility has been developed for the detection of nitroaromatic organophosphorus pesticides (NOPPs). This sensor is based on a flexible, screen-printed silver electrode modified with a graphene nanoplatelet (GNP) coating and a zirconia (ZrO₂) coating. The combination of the metal oxide and the 2-D material provided advantageous electrocatalytic activity toward NOPPs. Manufacturing, scanning electron microscopy-scanning transmission electron microscopy image analysis, electrochemical surface characterization, and detection studies illustrated high sensitivity, selectivity, and stability (∼89% current signal retention after 30 days) of the platform. The enzymeless sensor enabled rapid response time (10 min) and noncomplex detection of NOPPs through voltammetry methods. Furthermore, the proposed platform was highly group-sensitive toward NOPPs (e.g., methyl parathion (MP) and fenitrothion) with a detection limit as low as 1 μM (0.2 ppm). The sensor exhibited a linear correlation between MP concentration and current response in a range from 1 μM (0.2 ppm) to 20 μM (4.2 ppm) and from 20 to 50 μM with an R² of 0.992 and 0.991, respectively. Broadly, this work showcases the first application of GNPs/ZrO₂ complex on flexible silver screen-printed electrodes fabricated by entirely roll-to-roll manufacturing for the detection of NOPPs.

Fe3O4-Polyaniline Nanocomposite for Non-enzymatic Electrochemical Detection of 2,4-Dichlorophenoxyacetic Acid

This study proposes the development of an electrochemical sensor based on fabrication of a glassy carbon electrode (GCE) with Fe3O4-polyaniline (Fe3O4-PANI) nanocomposite, which was further used for enzyme-less detection of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous medium. Spectroscopic studies, microstructural studies, and elemental analysis established the formation of Fe3O4 nanoparticles with polyaniline coating. The fabricated Fe3O4-PANI-GCE was characterized by electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical response of 2,4-D on Fe3O4-PANI-GCE was evaluated by performing cyclic voltammetry and amperometry experiments. The synergistic effect of the composite causes the superior electrochemical behavior of Fe3O4-PANI-GCE toward the detection of 2,4-D. Amperometric measurements exhibited a linear concentration range from 1.35 to 2.7 μM. The sensitivity and detection limit were evaluated from the amperometric responses, which were found to be 4.62 × 10-7 μA μM-1 cm-2 and 0.21 μM, respectively. The electrochemical sensing response could be attributed to adsorption of 2,4-D onto the Fe3O4-PANI-modified GCE (Fe3O4-PANI-GCE) surface. Fe3O4-PANI-GCE is found to be a simple, low-cost, and biocompatible non-enzymatic sensor for detection of 2,4-D in aqueous medium at ambient temperature.

Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine

Amorphous zirconium oxide nanoparticles (ZrO₂) have been used for the first time, to modify carbon paste electrode (CPE) and used as a sensor for the electrochemical determination of gallic acid (GA). The voltammetric results of the ZrO₂ nanoparticles-modified CPE showed efficient electrochemical oxidation of gallic acid, with a significantly enhanced peak current from 261 µA ± 3 to about 451 µA ± 1. The modified surface of the electrode and the synthesised zirconia nanoparticles were characterised by scanning electrode microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDXA), X-ray powdered diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, the electrochemical behaviour of GA on the surface of the modified electrode was studied using differential pulse voltammetry (DPV), showing a sensitivity of the electrode for GA determination, within a concentration range of 1 × 10⁻⁶ mol L⁻¹ to 1 × 10⁻³ mol L⁻¹ with a correlation coefficient of R² of 0.9945 and a limit of detection of 1.24 × 10⁻⁷ mol L⁻¹ (S/N = 3). The proposed ZrO₂ nanoparticles modified CPE was successfully used for the determination of GA in red and white wine, with concentrations of 0.103 mmol L⁻¹ and 0.049 mmol L⁻¹ respectively.

Novel electrochemical aptasensor with dual signal amplification strategy for detection of acetamiprid

In this work, a novel dual signal amplification strategy for aptasensor employing reduced graphene with silver nanoparticles and prussian blue-gold nanocomposites was developed for detection of acetamiprid. To improve the sensitivity of aptasensors, reduced graphene oxide-silver nanoparticles (rGo-AgNPs) were modified on a bare glassy carbon electrode surface, which provided a large specific surface area for subsequent material immobilization and amplified current signal. The electrical signal output and sensitivity of the aptasensor was significantly improved after the immobilization of prussian blue-gold nanoparticles (PB-AuNPs) as a catalyst for the redox reaction. The analysis experiment exhibited that it had super-high sensitivity with a detection limit of 0.30 pM (S/N = 3), which met the requirements of the vast majority of daily leaf vegetable testing. Under optimized conditions, the proposed aptasensor showed a wide linear detection range from 1 pM to 1 μM. This aptasensor also had good stability and high selectivity for acetamiprid detection without an interfering effect of some other pesticides. The proposed aptasensor displayed good recovery rates in real samples, which proposed a new method for constructing electrochemical sensors and provided a novel tool for rapid, sensitive analysis of pesticides with low cost.

Zirconia nanocomposites with carbon and iron(iii) oxide for voltammetric detection of sub-nanomolar levels of methyl parathion

This study reports the synthesis of zirconia nanoparticles loaded on various carbon substrates, namely, reduced graphene oxide (Zr-r-GO), carbon nanotubes (Zr-CNT), and activated carbon (Zr-AC). In addition, a composite of zirconia-iron mixed oxide loaded on activated carbon (FeZr-AC) was also synthesized. The materials were characterized using SEM-EDX, HRTEM, FTIR, Raman spectroscopy, TGA and XRD. The FeZr-AC sample was found to have a nanorod like morphology. The samples were evaluated for their sensing potential towards methyl parathion (MP) using differential pulse voltammetry in a range of 0.0 V to -0.9 V (vs. Ag/AgCl) by drop casting on a glassy carbon electrode (GCE). All the modified GCEs best operated at a working potential of 0.4-0.9 V vs. Ag/AgCl/Cl-. FeZr-AC was found have the best limit of detection followed by Zr-AC, Zr-CNT and Zr-r-GO with their detection limits being 1.7 × 10-9 M, 17.2 ×10-9 M, 243.3 × 10-9 M and 534.0 × 10-9 M respectively. These materials were then used to detect MP in spiked sewage samples and showed good recoveries.

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.

Nanostructured Diatom-ZrO2 composite as a selective and highly sensitive enzyme free electrochemical sensor for detection of methyl parathion

In the current work we report a simple and scalable technique for synthesis of ordered nanoporous Si-ZrO₂ composite derived from the diatom Phaeodactylum tricornutum. The composite was well characterized using SEM, TEM-EDX, FTIR, TGA, BET and DLS. The diatom-ZrO₂ was found to have a specific surface area of 140 m²/g, Si:Zr ratio of 1:4 and a particle size of 80 ± 2 nm. This composite was evaluated as an enzyme free electrochemical sensor towards the detection of methyl parathion (MP) and showed excellent sensing ability at extremely low detection limits of 54.3 pM and a linear concentration range of 3.4 nM to 64 μM. The diatom-ZrO₂ composite was also found to be highly selective towards MP as shown by its response even in the presence of high concentrations of other interfering molecules and ions.

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.

Ultrasensitive electrochemical detection of methyl parathion pesticide based on cationic water-soluble pillar[5]arene and reduced graphene nanocomposite

We report a rapid, sensitive and selective electrochemical sensor based on pillar[5]arene (CP5) reduced graphene (rGO) nanohybrid-modified glassy carbon electrode CP5-rGO/GCE for the trace detection of methyl parathion (MP) by differential pulse voltammetry (DPV) for the first time. Compared to beta-cyclodextrin (β-CD)-functionalized reduced graphene (rGO)-modified GCE β-CD-rGO/GCE, the proposed CP5-rGO/GCE sensor exhibits excellent electrochemical catalytic activity, rapid response, high sensitivity, good reproducibility and anti-interference ability towards MP. The recognition mechanism of β-CD/MP and CP5/MP was studied by ¹H NMR. The results indicate a higher supramolecular recognition capability between CP5 and MP compared to that between β-CD and MP. The β-CD-rGO and CP5-rGO nano-composites were prepared via a wet chemistry approach. The resulting nano-composites have been characterized by thermogravimetric analysis (TGA), fourier transform infrared spectrometry (FTIR), charge transfer resistance (R_ct) and zeta potential. The CP5-rGO/GCE combines the merits of CP5 and rGO, and is used for quantitative detection of MP. It has a low detection limit of 0.0003 μM (S/N = 3) and a linear response range of 0.001–150 μM for MP. This method has been used to detect MP in soil and waste water samples with satisfactory results. This study provides a promising electrochemical sensing platform and is a promising tool for the rapid, facile and sensitive analysis of MP.

A promising electrochemical sensing platform for the detection of methyl parathion based on cationic water-soluble pillar[5]arene reduced graphene nanocomposite.

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.

Application of pristine and doped SnO2 nanoparticles as a matrix for agro-hazardous material (organophosphate) detection

With an increasing focus on applied research, series of single/composite materials are being investigated for device development to detect several hazardous, dangerous, and toxic molecules. Here, we report a preliminary attempt of an electrochemical sensor fabricated using pristine Ni and Cr-doped nano tin oxide material (SnO2) as a tool to detect agro-hazardous material, i.e. Organophosphate (OP, chlorpyrifos). The nanomaterial was synthesized using the solution method. Nickel and chromium were used as dopant during synthesis. The synthesized material was calcined at 1000 °C and characterized for morphological, structural, and elemental analysis that showed the formation of agglomerated nanosized particles of crystalline nature. Screen-printed films of powder obtained were used as a matrix for working electrodes in a cyclic voltammogram (CV) at various concentrations of organophosphates (0.01 to 100 ppm). The CV curves were obtained before and after the immobilization of acetylcholinesterase (AChE) on the nanomaterial matrix. An interference study was also conducted with hydroquinone to ascertain the selectivity. The preliminary study indicated that such material can be used as suitable matrix for a device that can easily detect OP to a level of 10 ppb and thus contributes to progress in terms of desired device technology for the food and agricultural-industries.

Recent Progresses in Nanobiosensing for Food Safety Analysis

With increasing adulteration, food safety analysis has become an important research field. Nanomaterials-based biosensing holds great potential in designing highly sensitive and selective detection strategies necessary for food safety analysis. This review summarizes various function types of nanomaterials, the methods of functionalization of nanomaterials, and recent (2014-present) progress in the design and development of nanobiosensing for the detection of food contaminants including pathogens, toxins, pesticides, antibiotics, metal contaminants, and other analytes, which are sub-classified according to various recognition methods of each analyte. The existing shortcomings and future perspectives of the rapidly growing field of nanobiosensing addressing food safety issues are also discussed briefly.

ZrO2 supported Nano-ZSM-5 nanocomposite material for the nanomolar electrochemical detection of metol and bisphenol A

ZrO₂ decorated Nano-ZSM-5 was synthesized by the calcination of the physical mixture of ZrO₂ and Nano-ZSM-5. Electrochemical sensor based on this material was investigated in the determination of hazardous organic water pollutants.

Radially oriented nanostrand electrodes to boost glucose sensing in mammalian blood

Architecture of nanoscale electrochemical sensors for ultra-trace detection of glucose in blood is important in real-life sampling and analysis. To broaden the application of electrochemical sensing of glucose, we fabricated, for the first time, a glucose sensor electrode based on radially oriented NiO nanostrands (NSTs) onto 3D porous Ni foam substrate for monitoring, as well as selective and sensitive sensing of glucose in mammalian blood. The simple, scalable one-pot fabrication of this NST-Ni sensor design enabled control of the pattern of radially oriented NSTs onto 3D porous Ni foam substrate. The radial orientation of NST-Ni electrode onto the interior of the 3D porous substrate with controlled crystal structure size and atomic arrangement along the axis of the strands, intrinsic surface defects, and superior surface properties, such as hydrophilicity, high surface energy, and high density led to highly exposed catalytic active sites. The hierarchical NST-Ni electrode was used to develop a sensitive and selective sensor over a wide range of glucose concentrations among actively competitive ions, chemical species and molecular agents, and multi-cyclic sensing assays. The NST-Ni electrode shows significant glucose sensing performance in terms of unimpeded diffusion pathways, a wide range of concentration detection, and lower limit of detection (0.186 µM) than NiO nanosheet (NS)-Ni foam electrode pattern, indicating the effectiveness of the shape-dependent structural architecture of NST-Ni electrode. In this study, the NST-Ni electrode is fabricated to develop a simple, selective method for detecting glucose in physiological fluids (e.g., mammalian blood).

A highly sensitive multi-catalytic sensing system for organophosphorus and organochlorine pesticides based on the peroxidase-like activity of ferric ions

A novel and highly sensitive multi-catalytic sensing system was successfully developed for OPs and organochlorine pesticides, on the basis of the color reaction of TMB catalyzed by Fe³⁺ ions.