A facile, inexpensive and green electrochemical sensor for sensitive detection of imidacloprid residue in rice using activated electrodes

Subtle adjustment of the cyclic potential on electro-activated glassy carbon electrodes for sensitive sensing of methyl parathion

Facile electro-activated glassy carbon electrodes (e-GCEs), which are prepared in electrolyte solution with a certain potential for a few seconds, have been verified to improve analytical performance toward not a few electro-active molecules recently. Nevertheless, how and why the potential plays an important role is not clear, and has even not received enough consideration. In this paper, we found that the mode and the range of applied potential significantly impacted the sensitivity of methyl parathion (MP), which is a typical pesticide with the electro-active group of -NO2. Compared with constant potential, the e-GCE with cyclic potential provided a much more stable baseline during MP detection. Additionally, the electro-oxidation peak current of MP at around -0.1 V on it was higher than another changeable potential (constant current). What's more interesting, with cyclic potential for 50 segments from -2 to 1.5 V, the peak current value increased by 30 times in comparison with a bare GCE, but only 2 times from -2 to 1 V. Then after systematic investigation including structures of the electrode surface and functional groups, we speculated that the produced group of O-CO in the process of activation and remaining groups of C-O and CO on the bare GCE surface are beneficial for adsorbing MP molecules leading to enhanced peak current. Employing the proposed e-GCE, the limit of detection of MP reached 0.015 μM and the reproducibility was perfect. This work elucidates the potent impact of electro-activation potential parameters on electroanalysis behaviors.

Electrochemical sensors of neonicotinoid insecticides residues in food samples: From structure to analysis

Most food samples are detected positive for neonicotinoid insecticides, posing a severe threat to human health. Electrochemical sensors have been proven effective for monitoring the residues to guarantee food safety, but there needs to be more review to conclude the development status comprehensively. On the other hand, various modified materials were emphasized to improve the performance of electrochemical sensors in relevant reviews, rather than the reasons why they were selected. Therefore, this paper reviewed the electrochemical sensors of neonicotinoid insecticides according to bases and strategies. The fundamental basis is the molecular structure of neonicotinoid insecticides, which was disassembled into four functional groups: nitro group, saturated nitrogen ring system, aromatic heterocycle and chlorine substituent. Their relationships were established with strategies including direct sensing, enzyme sensors, aptasensors, immunosensors, and sample pretreatment, respectively. It is hoped to provide a reference for the effective design of electrochemical sensors for small molecule compounds.

Developments in food neonicotinoids detection: novel recognition strategies, advanced chemical sensing techniques, and recent applications

Neonicotinoid insecticides (NEOs) are a new class of neurotoxic pesticides primarily used for pest control on fruits and vegetables, cereals, and other crops after organophosphorus pesticides (OPPs), carbamate pesticides (CBPs), and pyrethroid pesticides. However, chronic abuse and illegal use have led to the contamination of food and water sources as well as damage to ecological and environmental systems. Long-term exposure to NEOs may pose potential risks to animals (especially bees) and even human health. Consequently, it is necessary to develop effective, robust, and rapid methods for NEOs detection. Specific recognition-based chemical sensing has been regarded as one of the most promising detection tools for NEOs due to their excellent selectivity, sensitivity, and robust interference resistance. In this review, we introduce the novel recognition strategies-enabled chemical sensing in food neonicotinoids detection in the past years (2017-2023). The properties and advantages of molecular imprinting recognition (MIR), host-guest recognition (HGR), electron-catalyzed recognition (ECR), immune recognition (IR), aptamer recognition (AR), and enzyme inhibition recognition (EIR) in the development of NEOs sensing platforms are discussed in detail. Recent applications of chemical sensing platforms in various food products, including fruits and vegetables, cereals, teas, honey, aquatic products, and others are highlighted. In addition, the future trends of applying chemical sensing with specific recognition strategies for NEOs analysis are discussed.

Electrochemical activation of oxygen vacancy-rich TiO2@MXene as high-performance electrochemical sensing platform for detecting imidacloprid in fruits and vegetables

Heterostructured TiO₂@MXene rich in oxygen vacancies defects (VO-TiO₂@MXene) has been developed to construct an electrochemical sensing platform for imidacloprid (IMI) determination. For the material design, TiO₂ nanoparticles were firstly in situ grown on MXene and used as a scaffolding to prevent the stack of MXene nanosheets. The obtained TiO₂@MXene heterostructure displays excellent layered structure and large specific surface area. After that, electrochemical activation is utilized to treat TiO₂@MXene, which greatly increases the concentration of surface oxygen vacancies (VOs), thereby remarkably enhancing the conductivity and adsorption capacity of the composite. Accordingly, the prepared VO-TiO₂@MXene displays excellent electrocatalytic activity toward the reduction of IMI. Under optimum conditions, cyclic voltammetry and linear sweep voltammetry techniques were utilized to investigate the electrochemical behavior of IMI at the VO-TiO₂@MXene/GCE. The proposed sensor based on VO-TiO₂@MXene presents an obvious reduction peak at -1.05 V(vs. Hg|Hg₂Cl₂) with two linear ranges from 0.07 - 10.0 μM and 10.0 - 70.0 μM with a detection limit of 23.3 nM (S/N= 3). Furthermore, the sensor provides a reliable result for detecting IMI in fruit and vegetable samples with a recovery of 97.9-103% and RSD≤ 4.3%. A sensitive electrochemical sensing platform was reported for imidacloprid (IMI) determination based on heterostructured TiO₂@MXene rich in oxygen vacancy defects.

WS2-Nanosheet-Modified Electrodes as an Efficient Electrochemical Sensing Platform for the Nonenzymatic Detection of the Insecticide Imidacloprid

Imidacloprid (IMI) is a systemic insecticide, which is widely used for seed treatment and pest control in vegetables. The unwarranted presence of traces of IMI in vegetables and groundwater is a matter of grave concern which needs to be detected and quantified in order to effect remedial measures for the sake of food safety. In this work, we communicate the fabrication of tungsten sulfide (WS₂) nanosheets and the construction of an amperometric sensor for the precise determination of IMI. The sensor performances were evaluated by using cyclic voltammetry (CV). The presence of surface-active sites and the fast electron transfer on WS₂/GCE favored the electrochemical reduction of the aromatic nitro group in IMI. The developed IMI sensor displayed a linear range of IMI detection from 10 to 90 μM with a detection limit of 0.28 μM. The developed WS₂/GCE sensor also displayed good sensitivity, with a value of 3.98 μA μM^-1 cm^-2. The electrochemical measurements demonstrated the superior selectivity of the constructed WS₂/GCE sensor for IMI detection, which makes it suitable for practical applications.

Highly Sensitive Electrochemical Sensor for Sunset Yellow Based on Electrochemically Activated Glassy Carbon Electrode

Electrochemically activated glassy carbon electrode (AGCE) was fabricated and applied for sensitive and selective detection of sunset yellow (SY). The electroanalysis of SY was investigated by square wave voltammetry (SWV). Owed to the specific oxygen-contained functional groups and the outstanding conductivity of AGCE, the proposed sensor exhibits an enhanced oxidation peak current of SY when compared with non-activated glass carbon electrode (GCE). Under the optimal analytical conditions, the oxidation peak current is linear with SY concentration in the range of 0.005–1.0 μM. The low limit of detection is 0.00167 μM (S/N = 3). This method is applied for the detection of SY in the actual samples. The recovery is between 96.19 and 103.47%, indicating that AGCE is suitable for the determination of SY in beverage sample.

Micro-/Mesoporous Fluorescent Polymers and Devices for Visual Pesticide Detection with Portability, High Sensitivity, and Ultrafast Response

The residue of pesticides in crops, soil, and water continues to be a widespread concern due to the threat to human health and food safety. With the aim to develop highly sensitive sensing materials and portable detection devices, two dicarbazole-based fluorescent micro-/mesoporous polymers (JYs) with a larger specific surface area and pore sizes ranging from 1.1 to 34.2 nm are synthesized. The Stern-Volmer constants of JY fluorescence quenching for imidacloprid (50,063 M^-1) exceed 23-51 times those of the reported porous organic polymers (980-2173 M^-1). Of particular interest is the observation that JYs show rapid fluorescence response (2 s) and ultralow detection limit (30 ppb) for imidacloprid in water medium. The pronounced chemsensing property is attributed to the synergistic role of the hierarchical pore structure, large π-conjugation of chromophore groups, and strong inner filter effect between the polymer and imidacloprid molecule. Moreover, the pesticide detection of JYs exhibits good interference resistance in complicated service environments such as the extract liquids of the apple peel and field soil as well as aqueous solutions of various cations and anions. Because of the portability, excellent reusability, and sensitive fluorescence response, the prepared JYs and detection devices have promising applications in the on-site monitoring and early warning of the pesticide residues.