A β-CD/MWCNT-modified-microelectrode array for rapid determination of imidacloprid in vegetables

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.

Research on a three-dimensional SERS substrate based on a CNTs/Ag@Au/SiO2 composite for detection of fipronil and imidacloprid pesticides

Surface-enhanced Raman scattering (SERS) has a unique fingerprint spectrum, which allows for rapid, highly sensitive, and non-destructive detection without the need for sample pretreatment. However, SERS substrates have disadvantages such as short storage time and poor reproducibility. In this study, carbon nanotubes, gold, and silver were combined to take advantage of their inherent structural and characteristic properties that enhance the Raman effect. A new type of SERS composite substrate, CNTs/Ag@Au/SiO2, was prepared using a hydrothermal method and seed growth method. The substrate was characterized using transmission electron microscopy (TEM), and the average distance between the core-shell nanoparticles was found to be 3.1 nm, which is more suitable than other gold-silver combined core-shell structures and significantly improves the SERS enhancement factor. The substrate demonstrated high sensitivity even at low concentrations of probe molecules and good uniformity at five randomly selected locations. After storage for 45 days, the substrate still exhibited good stability. In most gold-silver combined core-shell structures, the detection limit for Rhodamine 6G (R6G) is 10-9 mol L-1, while in this substrate, the detection limit for R6G is 10-11 mol L-1. Furthermore, the contribution of the substrate's enhancement was deeply investigated using finite-difference time-domain (FDTD), which revealed that the substrate's hotspots were present in two forms: the "hotspots generated between Ag@Au nanoparticles" and the "hotspots generated between Ag@Au nanoparticles and carbon nanotubes". These two forms of hotspots also demonstrated that the performance brought about by the preparation of the substrate structure was reliable. The simulation results were compared with the experimental results, and the analysis showed that the real environment would have an impact on the substrate's structure during the actual substrate preparation process. Finally, the substrate was used for detecting the pesticide fipronil, and the results showed clear peaks even at a concentration of 0.1 mg L-1. The results indicated that the Raman intensity was linearly exponential with the fipronil solution concentration, with a determination coefficient of R2 = 0.991. This study provides a new SERS substrate for pesticide residue detection and further explores the improvement of pesticide detection limits.

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.

Microporous carbon for fast and simple electrochemical detection of imidacloprid insecticide in fruit and water samples

Herein, a fast and sensitive electrochemical sensor was developed for imidacloprid detection using low-cost disposable microporous carbon screen-printed electrodes. The electrochemical behaviour of imidacloprid at the microporous material was investigated in detail. The developed sensor allowed imidacloprid detection in the linear range of 0.00-1.00 mM with a sensitivity of 14.43 ± 0.42 μA mM^-1 and a detection limit of 2.54 μM (3s _B/m). The sensor showed excellent selectivity and high tolerance to possible interference from other tested insecticides and ions. Excellent repeatability (3.42%, n = 3) and reproducibility (2.23%, n = 3) were demonstrated. Application of the sensor in various fruit and water samples without any treatment showed 96.2-103.0% recoveries. The developed sensor further revealed that the most effective method for removing imidacloprid residue from fruit samples was via washing with a mixture of 5% w/v NaCl and 5% w/v bicarbonate at 40 °C.

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

The development of sensitive, facile, cost-effective and eco-friendly sensors is essential for monitoring imidacloprid (IDP) residue on a large scale. Compared with popular modification of electrodes with advanced materials, electrochemical activation is promising at this point. In this paper, we found that strongly basic electrolytes (e.g. KOH and K₃PO₄) and applying cyclic potential during the activating process are beneficial to greatly amplify the electro-reduction response of IDP by nearly 16 times. Combining the characterization of activated electrodes with electrochemical behavior analysis of IDP, it is speculated that specific oxygen-contained functional groups were formed to bond with IDP molecules, leading to fast electron transfer kinetics. Then a sensitive IDP sensor has been developed with a low limit of detection (LOD) of 0.03 μM in the range of 0.1-100 μM. The methodological evaluation including reproducibility, stability and recovery has been also carefully studied, verifying the potential of proposed activated electrodes for application in rice samples.

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Synthesis of imprinted chitosan/AuNPs/graphene-coated MWCNTs/Nafion film for detection of lead ions

An ultrasensitive electrochemical platform based on ion-imprinted nanocomposites for monitoring Pb²⁺ was proposed for environmental protection and food safety applications.