A Highly Selective Electrochemical Sensor Based on Molecularly Imprinted Copolymer Functionalized with Arginine for the Detection of Chloramphenicol in Honey.

Developing an efficient method for chloramphenicol (CAP) detection is of great significance for food safety. Arginine (Arg) was selected as a functional monomer. Benefiting from its excellent electrochemical performance, which is different from traditional functional monomers, it can be combined with CAP to form a highly selective molecularly imprinted polymer (MIP) material. It overcomes the shortcoming of poor MIP sensitivity faced by traditional functional monomers, and achieves high sensitivity detection without compounding other nanomaterials, greatly reducing the preparation difficulty and cost investment of the sensor. The possible binding sites between CAP and Arg molecules were calculated by molecular electrostatic potential (MEP). A low-cost, non-modified MIP electrochemical sensor was developed for the high-performance detection of CAP. The prepared sensor has a wide linear range from 1 × 10-12 mol L-1 to 5 × 10-4 mol L-1, achieves a very low concentration CAP detection, and the detection limit is 1.36 × 10-13 mol L-1. It also exhibits excellent selectivity, anti-interference, repeatability, and reproducibility. The detection of CAP in actual honey samples was achieved, which has important practical value in food safety.

High sensitivity electrochemical detection of ultra-trace imidacloprid in fruits and vegetables using a Fe-rich FeCoNi-MOF.

High sensitivity and ultra-trace detection of imidacloprid are important and challenging in the field of food. In this study, we prepared a Fe-rich FeCoNi-MOF in-situ modified nickel foam working electrode by one-step hydrothermal method, and achieved a highly sensitive detection of the imidacloprid. The characterization techniques confirmed that Fe-rich FeCoNi-MOF had excellent crystallinity, tighter structure, and exposed rich active sites. The detection results showed that Fe-rich FeCoNi-MOF electrochemical sensor had a minimum detection limit of 0.04 pmol/L (100 times lower than that of the bioelectrochemical sensors), a wide response range (1 pmol/L-120 µmol/L), and high sensitivity (124 µA pmol/L-1 cm-2). These advantages of the electrochemical sensor were revealed theoretically by the valence change of active metal and the first principle calculation. Lastly, the Fe-rich FeCoNi-MOF electrochemical sensor was applied to detect imidacloprid in apple, fresh tea leaves, tomato, cucumber, and had an excellent recovery of 98-102.8 %.

Trimetallic metal-organic frameworks (Fe, Co, Ni-MOF) derived as efficient electrochemical determination for ultra-micro imidacloprid in vegetables.

The excessive use of imidacloprid in agricultural production leads to a large number of residues that seriously threaten human health. Therefore, the detection of imidacloprid has become very important. But how to quantitatively detect imidacloprid at ultra-low levels is the main challenges. In this work, trimetallic metal-organic frameworks Fe, Co, Ni-MOF (FCN-MOF) isin situprepared on nickel foam (NF) and then used to make an electrochemical sensor in the detection of imidacloprid. FCN-MOF exhibits the characteristics of ultra-micro concentration detection for imidacloprid with high specific surface area and rich active metal centers. The high conductivity and 3D skeleton structure of the NF electrode enhance the contact site with imidacloprid and promote the transmission of electrons efficiently. All results show that the prepared electrochemical sensor has the advantages of ultra-low detection limits (0.1 pM), wide linear detection ranges (1-5 × 107pM) and good sensitivity (132.91µA pM‒1cm‒2), as well as good reproducibility, excellent anti-interference ability, and fantastic stability. Meanwhile, the electrochemical sensor is used to determine imidacloprid in lettuce, tomato, and cucumber samples with excellent recovery (90%-102.7%). The novel electrochemical sensor is successfully applied to the ultra-micro detection of imidacloprid in vegetables, which provides a new way for the efficient monitoring of imidacloprid in agriculture.

A novel non-enzymatic glucose electrochemical sensor with high sensitivity and selectivity based on CdIn2O4nanoparticles on 3D Ni foam substrate.

Due to the poor conductivity of Fe based, Cu based and Co based electrode materials commonly used in the electrochemical detection of glucose, and the uneven stirring and poor conductivity of the traditional preparation method based on glassy carbon electrode. In order to solve the above problems, in this work, CdIn2O4with high electrical conductivity was directly grown on three-dimensional (3D) Ni foam to prepare electrode materials for non-enzymatic glucose sensors. CdIn2O4nanoparticles is prepared from cadmium acetate and indium nitrate hydrate in benzyl alcohol by non-aqueous sol-gel method. The electrocatalytic oxidation performances of CdIn2O4electrode material for non-enzymatic glucose are studied. The results show that the proposed CdIn2O4electrode material has good electrochemical properties and sensing performance for glucose detection. The electrochemical response of CdIn2O4electrode material to glucose is recorded that calibration plot for glucose concentrations ranging from 1.0µM to 1.0 mM (R2 = 0.99), a limit detection of 0.08µM, an excellent sensitivity of 3.2925 mA.mM-1.cm-2, a rapid response time of 1.58 s, a good selectivity and a good long-term stability. These demonstrate the significant potential of CdIn2O4electrode material based on 3D Ni foam as non-enzymatic glucose sensors, which makes it possible to use it as a practical glucose detector. This work could introduce a new concept of nanoparticles modified electrode material grown directly on 3D Ni foam, thus a simple and reliable electrochemical glucose sensor platform is realized. This study was completed in 2019 in the school of materials and energy, Yunnan University.