Study On Photoelectrochemical Biosensing Based On Metal-Organic Framework Compounds

Photoelectrochemical（PEC）biosensors are an emerging analytical detection technology that quantitatively analyzes substances through a combination of electrochemical detection and photoexcitation.Due to the advantages of high sensitivity,good stability,and strong anti-interference ability,PEC sensors are widely used in food testing,biological analysis,and environmental monitoring.The generation of PEC signal mainly relies on the transfer of electrons generated after the photosensitive material absorbs visible light,thereby converting light energy into electrical energy and outputting it as an electrical signal.Therefore,the substance can be quantitatively detected according to the photocurrent change caused by the interaction between the analyte and the photoactive material.Photosensitive materials are the basis for the construction of PEC biosensors.In recent years,metal-organic frameworks（MOFs）have attracted extensive attention due to their large specific surface area and porous structure.In this thesis,MOFs are combined with inorganic materials to prepare a novel PEC biosensor based on MOFs materials,which realizes highly sensitive detection of small molecules and antibiotics.The main work contents are as follows:1.The MIL-100（Fe）@Cd S nanocomposite was synthesized by a simple solvothermal method,and modified on the electrode surface,and then further immobilized Ag nanoparticles on this basis,and a PEC biosensor based on Ag NPs/MIL-100（Fe）@Cd S composite was developed for the highly sensitive detection of small molecule L-cysteine（Cys）.Due to the large specific surface area and excellent porous structure of MIL-100（Fe）,Cd S can be uniformly attached to the surface,and the photoelectric performance of PEC sensor can be effectively improved by the synergistic effect between the two.Ag nanoparticles have surface plasmon resonance effect,which can accelerate electron transfer,effectively inhibit the recombination of electron（e^-）-hole（h⁺）pairs,and increase the photoelectric conversion efficiency.Under illumination conditions,the Ag NPs/MIL-100（Fe）@Cd S electrode has high photoelectric properties,which can oxidize Cys to generate a strong photocurrent.The change of photocurrent is related to the concentration of Cys,so that Cys can be realized quantitative detection.After experimental verification,the PEC sensor can show high sensitivity and anti-interference ability,and has a wide detection range:0.005-100μM,and the detection limit is 0.82 n M,which provides a new idea for the detection of cysteine in actual samples.2.UIO-66-NH₂metal-organic framework was synthesized by solvothermal method and modified on ITO electrode,and then Ag I was modified on the electrode surface by ion adsorption.On this basis,Au NPs were further modified on the electrode.Thus,a photocathode PEC aptamer sensor based on Au NPs/Ag I/UIO-66-NH₂composite was constructed and used for highly sensitive detection of ampicillin.The recombination of UIO-66-NH₂and Ag I accelerates the electron transfer at the electrode interface,effectively suppresses the recombination of electron-hole pairs,and enhances the photoelectric conversion efficiency.The modification of Au NPs,on the one hand,it can fix the aptamer on the electrode surface through the Au-S bond;On the other hand,due to its own surface plasmon resonance effect,the absorption of visible light by the electrode material can be enhanced,the electron transport efficiency can be improved,and the photoelectrochemical performance can be enhanced.Due to the presence of K₃Fe（CN）₆in the solution,it can be reduced by the conduction band as an electron acceptor,which can further accelerate the electron transfer,increase the photocurrent signal,and generate a stable cathode photocurrent.Under the optimal conditions,the aptamer specifically recognizes ampicillin and exhibits strong photocurrent changes,realizing the quantitative analysis of ampicillin.The PEC aptamer sensor has a wide linear range（0.01 p M-10 n M）,low detection limit（0.00142 p M）,high sensitivity and strong specificity,which provide a new method for the detection of ampicillin in actual samples.