Preparation And Application Of Electrochemical Sensors Based On Functional Composites And Molecular Imprinting Technology

Electrochemical sensor is a detection method that combines electrochemical analysis and sensor technology.The construction of electrochemical sensors with high sensitivity,high stability,high reproducibility and high selectivity is a goal pursued by many researchers.The modification of electrodes is the key for the preparation of excellent electrochemical sensors.However,using only one kind of material to modify the electrode cannot achieve the ideal effect.If two or more materials are used to modify the electrode,their maximum effectiveness can be achieved through their synergy,so that an electrochemical sensor with excellent performance can be constructed.This paper mainly builds electrochemical sensors based on carbon materials and metal oxides?sulfides?with excellent conductivity properties,metal-organic frameworks?MOFs?with large specific surface areas,and the highly selective molecularly imprinted polymeric membranes for the detection of drugs and tumor markers.Detecting the concentration of drugs in human serum and urine samples can monitor the concentrations of drugs in the human body and reduce the adverse reactions of drugs.At the same time,the monitoring of tumor markers in biological samples can help early diagnosis of cancer.The main contents of the paper are as follows:?1?NiO-ZnO composites were prepared by sodium citrate-assisted precipitation method,then carboxylated multi-wall carbon nanotubes and NiO-ZnO composites were respectively modified on the glass carbon electrodes?GCE?to construct Ni O-ZnO/MWCNT-COOH/GCE sensor.The electrochemical sensor was used for the simultaneous determination of imatinib?IMA?and itraconazole?ITZ?.In this experiment,the electrochemical sensor for simultaneous detection of IMA and ITZ was constructed for the first time,and the detection limits of IMA and ITZ were 2.4 nM and 4.1 n M?S/N=3?,respectively.The sensor was successfully applied to detect IMA and ITZ in human serum and urine samples with satisfactory results.?2?In this chapter,we first constructed an electrochemical sensor?MIP/Pt@MnO₂/g-C₃N₄/GCE?with rapid detection,high sensitivity and good selectivity for the detection of tigecycline?TCG?in human serum.The MnO₂/g-C₃N₄ with 2D/2D structure provided a high specific surface area and good conductive effect,and then Pt nanoparticles were evenly loaded on the surface of MnO₂/g-C₃N₄,which could significantly improve the sensitivity of the sensor.The detection limit is 7.3 nM?S/N=3?in the concentration range of 0.03?M to 8.6?M.The electrochemical sensor was successfully applied to the detection of TCG in human serum samples.?3?An electrochemical sensor for the detection cholyglycine?CG?,a liver cancer marker,was constructed in this experiment.First,MIL-88A was synthesized using L-lysine as structural directing agent,Fe3+as metal node and fumaric acid as organic ligand.The L-lysine could significantly accelerate the growth of MIL-88A crystals and adjust the particle sizes of MIL-88A.Then the conductive material carbon black?XC-72?was uniformly loaded onto MIL-88A by an ultrasonic method,the composites of MIL-88A and XC-72 was prepared.The composites was modified to GCE to obtain the electrode of MIL-88A/XC-72/GCE.In order to improve the selectivity of the working electrode,a molecularly imprinted polymeric film of CG was prepared on the surface of MIL-88A/XC-72/GCE by electropolymerization using pyrrole as functional monomer to obtain the MIP/MIL-88A/XC-72/GCE sensor.Under the optimal experimental conditions,the detection limit?LOD?of CG was calculated to be 3.4 pM?S/N=3?.In addition,the molecularly imprinted sensor was successfully applied for the detection of CG in human serum samples with satisfactory results.?4?For the first time,Cu_1.96S-Fe S₂ was synthesized using the metal organic frameworks of Cu-MOF-NH₂ and Fe-MOF-NH₂?Cu/Fe-MOF-NH₂?as a precursors.Dopamine was used as additional nitrogen and carbon source,and calcined at high temperature to obtain N-doped carbon materials.It could play the role as a protective layer for the Cu_1.96S-FeS₂composites,and could not only effectively prevent the agglomeration of Cu_1.96S-FeS₂ composites,but also improved the conductivity of composites through synergy.Meanwhile,in order to enhance the selectivity of the sensor,o-phenylenediamine?o-PD?and chitosan?CS?were used as dual-functional monomers,a molecularly imprinted polymer film was prepared on the surface of electrode.The MIP/Cu_1.96S-FeS₂@NC/GCE electrochemical sensor was successfully constructed and a sensitive electrochemical method was established to detect the content of aristolochic acid I?AAI?in Asarum and human serum samples.Under the optimal experimental conditions,AAI was detected in the linear range of0.02?M-3.52?M with a detection limit of 5.3 nM.