The sensor was modified with metal-organic framework (MOF), silver nanoparticles (AgNPs) and walnut shell biomass carbon (BC). Among them, AgNPs are grown on the surface of Cr-MIL-101 to obtain Cr-MIL-101/Ag, and then calcined with BC to obtain composite material BC/Cr2O3/Ag. This material increases the current response by increasing the effective specific surface area and electron transfer capability of the electrode. Adding molecularly imprinted polymer (MIP) to the surface of the composite material can improve the specific recognition ability of the NFZ modified electrode. Using acrylamide (AM) and α-methacrylic acid (MAA) as bifunctional monomers and NFZ as template, MIP was prepared by precipitation polymerization. In a suitable experimental environment, the differential pulse voltammetry (DPV) current response of the modified electrode (BC/Cr2O3/Ag/MIP/GCE) to NFZ shows a good range of 5×10−9-1×10−5 M Linear relationship, detection limit of 3×10−9M, the sensor has high sensitivity, selectivity, reproducibility and stability. In addition, BC/Cr2O3/Ag/MIP/GCE is also applied to the detection of NFZ in actual samples. BC/Cr2O3/Ag/MIP/GCE provides a reliable method for the determination of NFZ in biological fluids.
NFZ is an antibiotic with good antibacterial effect, high resistance to a variety of gram-positive and negative bacteria, and can treat skin infections and trypanosomiasis. However, NFZ is potentially teratogenic and carcinogenic, and can be ingested by humans through the food chain. The Ministry of Agriculture of China has banned the use of NFZ in humans and animals. However, due to its high antibacterial efficiency and low cost, NFZ is still used illegally. Therefore, it is necessary to develop a sensitive, fast, convenient and efficient NFZ analysis method.
A molecularly imprinted electrochemical sensor modified with BC/Cr2O3/Ag (BC/Cr2O3/Ag/MIP) coating and applied to the analysis of NFZ. Conductive AgNPs were grown on Cr-MIL-101, and then calcined with BC with larger active specific surface area under nitrogen atmosphere to obtain nanocomposite material (BC/Cr2O3/Ag). The Cr2O3/Ag from MOF not only maintains the large specific surface area of the frame structure, but also improves the electrical conductivity to enhance the current response. MIP was dropped onto the surface of the composite material, and NFZ was specifically recognized through hydrogen bonds. The resulting molecularly imprinted electrochemical sensor showed high sensitivity, wide linear range and low detection limit. The electrochemical sensor has a high potential for rapid determination of NFZ in human blood, urine and drugs.
The synthesized Cr-MIL-101 has a uniform octahedral morphology with a particle size of about ~400nm, as shown in SEM image A. AgNPs were synthesized in situ outside of Cr-MIL-101 (Figure B). AgNPs are uniformly distributed on the surface of Cr-MIL-101, and the morphology of MOF remains unchanged. The mature walnut shell is treated with nitric acid to obtain amorphous BC (Figure C). On the one hand, it helps to increase the conductivity, on the other hand, it helps electron transfer, thereby improving the electrochemical response. As shown in Figure D, BC/Cr-MIL-101/Ag is calcined at 900°C to obtain BC/Cr2O3/Ag, which can maintain the octahedral shape of Cr-MIL-101, and the composite frame structure remains unchanged after calcination. The MIP obtained by the precipitation polymerization method exhibits a spherical shape (Figure E), and the MIP can specifically recognize NFZ through hydrogen bonds, thereby improving the sensitivity of the modified electrode. As shown in the SEM image (Figure F), the surface of the electrode modified with BC/Cr2O3/Ag/MIP is very rough and has a large number of voids. The existence of voids promotes electron transfer and increases the electrochemical response of NFZ.
The sensor is based on the molecular imprinting of biomass carbon, metal oxides derived from metal-organic frameworks, metal nanoparticles and bifunctional monomers. The BC nanomaterials and Cr2O3 that maintain the MOF framework structure have a large specific surface area, and AgNPs promote electron transport, so it can effectively enhance the electrochemical response. The introduction of MIP allows the sensor to increase the selectivity of NFZ. Under better experimental conditions, the BC / Cr2O3/ Ag / MIP / GCE electrochemical sensor shows a good linear relationship within the concentration range of 5×10 -9-1 ×10 -5 M, and the detection limit is 3×10- 9 M (S/N = 3). The electrochemical sensor has good repeatability, selectivity and stability for the quantitative analysis of NFZ. This provides a promising method for monitoring NFZ in biological fluids.
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zzj 2021.3.18