The Applications Of Iron-Based Metal-Organic Framework In Colorimetric Sensing And Antibacterial Therapy

Metal-organic frameworks（MOFs）are porous network materials composed of metal centers and organic ligands.Due to the large specific surface area,high porosity,active sites,and easy functionalization of structures,MOF s exhibit broad application prospects in storage,adsorption and separation,catalysis,sensing and biomedicine.In this paper,colorimetric sensing analysis and antibacterial research were carried out by modifying iron-based MOFs,which based on the redox properties of metal clusters in iron-based MOFs.Aiming at the problems that the colorimetric detection process based on iron-based MOFs is complicated and the catalytic activity is easily affected by p H,a fast and simple strategy was constructed for colorimetric detection of ascorbic acid（AA）by complexing with a chromogenic agent.Considering that the ultraviolet-visible excitation light of iron-based MOFs is harmful to organisms,a photodynamic antibacterial platform combining up-conversion nanomaterials with iron-based MOF was fabricated.The up-conversion nanomaterials were used to convert near-infrared light into ultraviolet-visible light,excite the iron-based MOFs to generate photogenerated holes,and generate active oxygen for sterilization in the presence of H₂O₂,which solves the safety problem of the antibacterial system.MIL-101（Fe）and MIL-100（Fe）,which are zeolite-like iron-based MOFs with supertetrahedral configuration,were selected to carry out experiments respectively.The details are as follows:（1）The MIL-101（Fe）/1,10-phenanthroline colorimetric sensing system was constructed to detect AA.Based on the strong reducibilit y of AA,the valence state of the iron metal center in the MIL-101（Fe）material changes,resulting in the collapse of the MOF structure.Then,Fe（Ⅱ）is released and reacts with 1,10-phenanthroline to form[Fe(C₁₂H₈N₂)₃]²⁺,which is an orange-red complex and has a board absorption band in the range of 370-600 nm with the strong absorbance at 510 nm.The absorption intensity at 510 nm had a linear and positive correlation with the concentration of AA when the concentration range wa s from 0.1μM to 60μM.The colorimetric sensing system provided a higher selectivity.Therefore,the colorimetric sensing system was successfully used for the quantitative analysis of AA in drinking water.（In chapter two）（2）A photodynamic antibacterial platform ofβ-NaYF₄:Yb,Tm,Gd@MIL-100（Fe）+H₂O₂ was designed.β-NaYF₄ with high up-conversion luminescence efficiency was used as the matrix material.β-NaYF₄:Yb,Tm,Gd nanorods was synthesized by hydrothermal method.Then the optimal fluorescence intensity of UCNRs w as explored by adjusting the Yb³⁺doping concentration.MIL-100（Fe）was coated on the surface of the up-conversion nanorods by layer-by-layer self-assembly method,which has a strong and broad absorption band in the range of 200-600 nm.Under 980 nm laser excitation,the up-conversion nanorods emit ultraviolet-visible light,which overlaps well with the absorption band of MIL-100（Fe）,and excites MIL-100（Fe）to produce electron/hole.In addition,H₂O₂ can enhance the oxidation capability of MIL-100（Fe）through inducing Fenton reaction and consume electrons to suppress the rapid recombination of the electron/hole.The optimal thickness of MIL-100（Fe）shell was explored,the cytotoxicity assay of UCNR@MIL-100（Fe）was assessed.Reactive oxidizing species（ROS）detection and the antibacterial performances indicated the biosafety of the UCNR@MIL-100（Fe）composites,which produced ROS under the excitation at 980 nm,and showed excellent bactericidal effect against Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）.（In chapter three）...