| As a neurotransmitter,dopamine?DA?plays an important role in the diagnosis and treatment of mental diseases,drug detection and food safety guarantee.Therefore,the research on dopamine analysis and detection has certain practical value.Taking advantage of the characteristics of dopamine that can be oxidized by electrochemically,it can be efficiently and sensitively detected by electrochemical method,and the key to achieving excellent detection performance is to prepare electrochemical analysis sensors with high specific surface area,outstanding electron conductivity,and high stability electrode material.Porphyrin metal-organic-frameworks?MOFs?have high crystalline,adjustable pore size,open metal active sites,high specific surface area.They have extraordinary performance in the field of electrochemical detection of dopamine.At present,the research on porphyrin MOFs electrochemical analysis sensors in the field of dopamine detection is mainly focused on the development of new porphyrin-based MOFs materials to improve their detection performance.However,in the practical application of electrochemical analysis sensors,the arrangement and combination of sensing materials on the electrode surface will also have a greater impact on the performance of the electrochemical analysis sensors,but there are only a few researches about this.The in-situ construction of a regular-shaped porphyrin MOFs films with an electrode as the substrate can not only effectively regulate the arrangement of active porphyrin MOFs on the substrate,but also improve the binding force between the porphyrin MOFs films and the substrate,and is expected to achieve high performance of dopamine electrochemical analysis sensors.The in-situ electrochemical synthesis MOFs membrane has attracted wide attention because of its simple operation,controllability and time-saving.Compared with the cathodic reduction method and the electrophoretic method,the anodic oxidation method directly uses the metal electrode to provide the metal node to prepare the MOFs films in situ,which can not only get wonderful electrical and mechanical contact between the films and the substrate,but also avoid the occurrence of bulk coordination.Therefore,the electrochemical anodic oxidation method for in-situ construction of porphyrin MOFs sensing materials is expected to prepare high-performance dopamine electrochemical analysis sensors.Based on the above issues,this paper specifically develops the following two aspects of work:1.In-situ growth and characterization of porphyrin MOFs films by anodization.Zinc metal sheet is used as working electrode,tetraphenyl carboxyporphyrin?H2TCPP?is used as organic ligand,and porphyrin-based MOFs films is grown on the surface of zinc sheet by anodizing method.Through electrochemical anodic oxidation,these zinc atoms on the surface of the zinc metal sheet are oxidized to zinc ions,and then,these zinc ions coordinate the porphyrin ligand at the interface of zinc electrode and electrolyte.By adjusting the applied potential or current can controll the precipitation rate of metal ions,the Zn-H2 TCPP MOFs films?Zn-H2 TCPP MOFs/Zn?with regular morphology are prepared in situ on the zinc metal sheet.To further explore the universality of the anodic oxidation method for the preparation of porphyrin MOFs,for example,metal copper sheet can also obtain uniform and dense membranes,which initially indicates that the anodization method can prepare different porphyrin MOFs or porphyrin complexes on different substrates have a certain universality.This provides the possibility for the further application of this type of in-situ MOFs membrane materials.2.Preparation of Zn-H2 TCPP MOFs/GCE electrochemical analysis sensors and research on its detection performance.Due to the poor electrochemical stability of metal in water systems,the application of metal electrodes in electrochemical analysis sensors is limited.In order to overcome this problem,the electrochemical inert glass carbon electrode?GCE?is used as the working electrode to plate a thin layer of metal zinc on its surface.According to the anodizing process of preparing Zn-H2 TCPP MOFs/Zn in the first part of the work,the thin layer of metallic zinc on the surface of GCE is gradually oxidized to zinc ions,and these zinc ions coordinate the porphyrin ligand at the interface of GCE and electrolyte.Finally,the Zn-H2 TCPP MOFs/GCE electrochemical analysis sensors directly applies in the detection of dopamine,which shows good electrocatalytic oxidation performance.Compared with other reported electrochemical analysis sensors,Zn-H2 TCPP MOFs/GCE has the advantages of wide linear range,high sensitivity and low detection limit.The excellent detection performance mainly comes from: The First,Zn-H2 TCPP MOFs films obtained by in-situ growth has good electrical and mechanical contact with the substrate;The Second,the porphyrin single molecule as a ligand is evenly dispersed in the hole wall of MOFs,which can make full use of the electrostatic attraction between the porphyrin molecule and dopamine to promote the enrichment of dopamine in the Zn-H2 TCPP MOFs membrane material;Last but not least,Zn-H2 TCPP MOFs membrane materials have a regular lamellar microstructure,which is conducive to the mass transfer of dopamine and its oxidation products.The inherently slower charge transfer rate of MOF limits the improvement of the electrochemical detection performance of dopamine.According to the strategy of "building a boat in a bottle",we first synthesize MOFs and then load GNPs.We prepare GNPs/Zn-H2 TCPP MOFs composite by using electrochemical cyclic voltammetry.The presence of gold nanoparticles not only effectively improves the charge transfer speed of Zn-H2 TCPP MOFs,but also increases the number of active sites of electrochemical analysis sensors,and then,ultimately promotes its performance in detecting dopamine. |
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