One-Step Fabrication of a Multifunctional Magnetic Nickel Ferrite/Multi-walled Carbon Nanotubes Nanohybrid-Modified Electrode for the Determination of Benomyl in Food

Ti3C2Tx/laser-induced graphene-based micro-droplet electrochemical sensing platform for rapid and sensitive detection of benomyl

The design and fabrication of high-performance electrode devices are highly important for the practical application of electrochemical sensors. In this study, flexible three-dimensional porous graphene electrode devices were first facilely fabricated using common laser ablation technique at room temperature. After then, hydrophilic two-dimensional MXene (Ti3C2Tx) nanosheet was decorated on the surface of the laser-induced graphene (LIG), resulting in disposable Ti3C2Tx/LIG electrode devices. After introducing Ti3C2Tx nanosheet, the electrochemical active area, electron transfer ability of LIG electrode device and its adsorption efficiency toward organic pesticide benomyl was significantly boosted. As a result, the fabricated Ti3C2Tx/LIG electrode device exhibited significantly enhanced electrocatalytic activity toward benomyl oxidation. Based on this, a novel and ultra-sensitive electrochemical platform for micro-droplet detection of benomyl was achieved in the range of 10 nM-6000 nM with detection sensitivity of 169.9 μA μM-1 cm-2 and detection limit of 5.8 nM. Considering the low-cost Ti3C2Tx/LIG electrode devices are rarely used for electrochemical analysis, we believed this research work will contribute to exploring the broader application of MXene/LIG electrode devices in the field of electrochemical sensing.

Electrochemical determination of benomyl using MWCNTs interspersed graphdiyne as enhanced electrocatalyst

Graphdiyne (GDY) has attracted a lot of interest in electrochemical sensing application with the advantages of a large conjugation system, porous structure, and high structure defects. Herein, to further improve the sensing effect of GDY, conductive MWCNTs were chosen as the signal accelerator. To get a stable composite material, polydopamine (PDA) was employed as connecting bridge between GDY and MWCNTs-NH₂, where DA was firstly polymerized onto GDY, followed by covalently linking MWCNTs-NH₂ with PDA through Michael-type reaction. The formed GDY@PDA/MWCNTs-NH₂ composite was then explored as an electrochemical sensor for benomyl (Ben) determination. GDY assists the adsorption and accumulation of Ben molecules to the sensing surface, while MWCNTs-NH₂ can enhance the electrical conductivity and electrocatalytic activity, all of which contributing to the significantly improved performance. The proposed sensor displays an obvious oxidation peak at 0.72 V (vs. Hg|Hg₂Cl₂) and reveals a wide linear range from 0.007 to 10.0 µM and a low limit of detection (LOD) of 1.8 nM (S/N = 3) toward Ben detection. In addition, the sensor shows high stability, repeatability, reproducibility, and selectivity. The feasibility of this sensor was demonstrated by detecting Ben in apple and cucumber samples with a recovery of 94-106% and relative standard deviations (RSDs) less than 2.3% (n = 5). A sensitive electrochemical sensing platform was reported for benomyl (Ben) determination based on a highly stable GDY@PDA/MWCNTs-NH₂ composite.

Low-cost electrochemical detection of l-tyrosine using an rGO-Cu modified pencil graphite electrode and its surface orientation on a Ag electrode using an ex situ spectroelectrochemical method

A low cost reduced graphene oxide–copper hybrid nano thin-film modified Pencil Graphite Electrode has been employed to detect the l-tyrosine enantiomer. The free-standing rGO–Cu hybrid nano-thin film was prepared by a simple one-step liquid–liquid interface method. Electrochemical Cyclic Voltammetry, Differential Pulse Voltammetry, pH-dependent and scan rate dependent studies on bare PGE, Cu, rGO, and rGO–Cu for l-tyrosine have been explained in detail. The rGO–Cu modified PGE based biosensor exhibits good detection of l-tyrosine. The linear range detection limit was estimated to be 1 × 10⁻⁷ M. The calculated sensitivity is 0.4 μA ppm⁻¹ mm². This electroactive biosensor is easily fabricated and controlled and is cost-effective. The surface orientation of l-tyrosine on the Ag electrode at a particular potential and its comparison with vibrational DFT calculations have been studied for the first time.

A low cost reduced graphene oxide–copper hybrid nano thin-film modified pencil graphite electrode has been employed to detect the l-tyrosine enantiomer.

The synthesis of CoxNi1−xFe2O4/multi-walled carbon nanotube nanocomposites and their photocatalytic performance

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized, where Co_xNi_1−xFe₂O₄ was synthesized via a one-step hydrothermal approach. Simultaneously, methylene blue (MB) was used as the research object to investigate the catalytic effect of the catalyst in the presence of hydrogen peroxide (H₂O₂). The results showed that all the photocatalysts exhibited enhanced catalytic activity compared to pure ferrite. In addition, compared with the other photocatalysts, the reaction time was greatly shortened a significantly higher removal rate was achieved using 3-CNF/MWCNTs. There was no significant decrease in photodegradation efficiency after three catalytic cycles, suggesting that Co_xNi_1−xFe₂O₄/MWCNTs are recyclable photocatalysts for wastewater treatment. Our results indicate that the Co_xNi_1−xFe₂O₄/MWCNT composite can be effectively applied for the removal of organic pollutants as a novel photocatalyst.

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized. The results implied that this composites can be effectively applied for the removal of organic pollutant as novel photocatalysts.

Simultaneous Electrochemical Detection of Benzimidazole Fungicides Carbendazim and Thiabendazole Using a Novel Nanohybrid Material-Modified Electrode

In this work, a novel ZnFe₂O₄/SWCNTs nanohybrid was successfully synthesized as electrode material and applied to the simultaneous quantitative determination of carbendazim (CBZ) and thiabendazole (TBZ). The electrochemical behaviors of CBZ and TBZ on the ZnFe₂O₄/SWCNTs/GCE were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrochemical active area of modified electrode was calculated, which is nearly 5.5 times that of the bare electrode. The influence of various factors such as accumulation time, pH and scan rates, type of surfactant, and the electrochemical reaction mechanism was studied. The results showed that the reaction of CBZ/TBZ was controlled by adsorption/diffusion and was a quasi-reversible/an irreversible process at the ZnFe₂O₄/SWCNTs/GCE. In the pH 7.0 phosphate-buffered saline (PBS) containing 10.0 μg/mL CTAB, the electrochemical responses of CBZ and TBZ were separately investigated and were linearly dependent on their concentrations ranging from 0.5 to 100.0 μM, with relatively low detection limits of 0.09 and 0.05 μM, respectively. The concentration range for the simultaneous determination of CBZ and TBZ was 1.0-100.0 μM. Furthermore, with satisfactory results, the proposed electrochemical sensor was successfully applied to the determination of CBZ and TBZ in the real samples.

A Novel Acetylcholinesterase Biosensor: Core-Shell Magnetic Nanoparticles Incorporating a Conjugated Polymer for the Detection of Organophosphorus Pesticides

To construct a sensing interface, in the present work, a conjugated polymer and core-shell magnetic nanoparticle containing biosensor was constructed for the pesticide analysis. The monomer 4,7-di(furan-2-yl)benzo[c][1,2,5]thiadiazole (FBThF) and core-shell magnetic nanoparticles were designed and synthesized for fabrication of the biosensing device. The magnetic nanoparticles were first treated with silica and then modified using carboxyl groups, which enabled binding of the biomolecules covalently. For the construction of the proposed sensor a two-step procedure was performed. First, the poly(FBThF) was electrochemically generated on the electrode surface. Then, carboxyl group modified magnetic nanoparticles (f-MNPs) and acetylcholinesterase (AChE), the model enzyme, were co-immobilized on the polymer-coated surface. Thereby, a robust and novel surface, conjugated polymer bearing magnetic nanoparticles with pendant carboxyl groups, was constructed, which was characterized using Fourier transform infrared spectrometer, cyclic voltammetry, scanning electron microscopy, and contact angle measurements. This novel architecture was then applied as an immobilization platform to detect pesticides. To the best of our knowledge, a sensor design that combines both conjugated polymer and magnetic nanoparticles was attempted for the first time, and this approach resulted in improved biosensor characteristics. Hence, this approach opens a new perspective in the field of enzyme immobilization and sensing applications. Paraoxon and trichlorfon were selected as the model toxicants. To obtain best biosensor performance, optimization studies were performed. Under optimized conditions, the biosensor in concern revealed a rapid response (5 s), a low detection limit (6.66 × 10(-3) mM), and high sensitivity (45.01 μA mM(-1) cm(-2)). The KM(app) value of poly(FBThF)/f-MNPs/AChE were determined as 0.73 mM. Furthermore, there was no considerable activity loss for 10 d for poly(FBThF)/f-MNPs/AChE biofilm.