Research On Photoelectrochemical Sensors Based On MOF Materials And Photocurrent Signal Sensitization Amplification

In recent years,photoelectrochemical analysis technology has attracted extensive attention of researchers due to its simple equipment,easy operation,high sensitivity,separation of excitation signal and detection signal,etc.It has been studied and applied in environmental detection,biological analysis and food analysis.The development of novel photoelectrochemical analysis technology mainly has the following two paths:one is to develop new photoelectric active materials.Photoelectric active materials have an important influence on the photoelectric conversion efficiency and analytical performance of photoelectrochemical sensors;the second is to develop new sensing systems and signal transduction pathways,which also play a role in amplifying the signal,improving detection sensitivity and practicality.Metal-Organic Framework（MOF）materials are a new class of organic-inorganic hybrid porous materials,which are formed by self-assembly of inorganic units（metal ions or clusters）and organic units through coordination bonds,etc.It has the advantages of large specific surface area,high porosity,adjustable structure and function,and has shown important application value in many fields such as gas adsorption,separation,and chemical sensing.In this paper,the following researches were carried out on the application of MOF materials in photoelectrochemical sensors:（1）The zeolite imidazolate framework material-ZIF-8 was prepared by hydrothermal method,and then calcined under nitrogen protection to obtain the carbonized ZIF-8（C-ZIF-8）.C-ZIF-8 was adsorbed on the NiO/ITO electrode to prepare a high-efficiency photocathode（C-ZIF-8/NiO/ITO）.Lead ion(Pb²⁺)was used to induce the configuration change of potassium ion（K⁺）-stabilized hemin（Hemin）embedded G-quadruplex,and Hemin was released.The released Hemin has a sensitizing effect on the C-ZIF-8/NiO/ITO electrode,which improves the light absorption capacity and carrier separation capability of the electrode and enhances the photocurrent.Based on this,the correlation between the photocurrent and the concentration of Pb²⁺was established and a photoelectrochemical biosensor for the determination of Pb²⁺was constructed.The study found that the photoelectrochemical sensor has excellent analytical performance for Pb²⁺,showing a good linear relationship in the concentration range of 10 p M～5 n M,and the detection limit was as low as 2.6 p M（S/N=3）.（2）MOF materials can be used not only as photoelectrode materials,but also as packaging materials for the encapsulation of biomolecules,etc.In this chapter,the zeolite imidazolate framework material ZIF-90 was used to encapsulate the photoactive dye Methyl Violet（MV）to form the MV@ZIF-90 hybrid material.The encapsulated MV can be released by adenosine triphosphate（ATP）induced cleavage of ZIF-90.The released MV not only exhibited fluorescence emission characteristics,but also sensitized the ZnInS photoanode and increased the photocurrent signal due to the formation of dye-sensitized heterojunction.Based on the sensitization effect of MV on the ZnInS photoelectrode and its fluorescence emission signal,a photoelectrochemistry（PEC）and fluorescence（FL）dual-signal analysis method was established for the detection of ATP.The sensing system can realize enzyme-free and label-free detection of ATP with a wide linear range and low detection limit（PEC 3.2 p M,FL 4.1 p M）.Moreover,the two signals can be verified interactively and improves the reliability of the detection.（3）On the basis of study above,ZIF-8 was used as the encapsulation carrier to study the effect of ZIF-8 with different sizes and morphologies on ATP detection.First,two ZIF-8 materials with different morphologies and sizes were prepared by different preparation methods,and the photoactive dye Methyl Blue（MB）was encapsulated in them during the preparation process,resulting two kinds of MB@ZIF-8 materials labeled as MB@ZIF-8（W,M）and MB@ZIF-8（W,M,CATB）,respectively.Then,the sensing performance of the two MB@ZIF-8 hybrid materials on ATP were investigated.The study found that the PEC biosensing system based on MB@ZIF-8（W,M,CATB）has a wider linear range（10 f M～1μM）,a lower detection limit（5.32 f M）,and shorter detection time.In addition,the sensing system has high selectivity and shows satisfactory recovery test results in actual sample detection,which has a broad practical application prospect.