Construction Of Metal-Organic Frameworks/Upconversion Nanoparticles Composites For Detection Application

Nanocomposites are composed of two or more solid phases with nanometer size.Nanocomposites can usually promote the interaction between different components,so as to combine the advantages of each component and reduce its disadvantages.More importantly,the interaction between different components may significantly increase the activity,or even produce synergistic effect,thus showing better performance than single component.Metal-organic frameworks（MOFs）are a kind of crystal porous material which are self-assembled by the central metal ions through coordination bonds or formed by clusters of two or multiple teeth organic ligands.Because of its various and adjustable structures,highly ordered pore structure and high specific surface area,MOFs have become an ideal matrix material for the construction of nanocomposites.At present,MOFs have been combined with metal nanoparticles,metal compounds,carbon materials,enzymes,polymers and other functional materials to construct composite materials with excellent properties,which are widely used in gas adsorption,catalysis,sensors,drug delivery,magnetic materials and optical devices.Upconversion nanoparticles（UCNPs）have gradually come into the field of researchers due to their unique and excellent properties.UCNPs are a kind of luminescent materials that can emit visible light under infrared excitation.UCNPs have the advantages of suitable size（small enough to pass through many biological hosts,such as cytoplasm,nucleus,etc.）,high chemical stability,low cytotoxicity,high signal-to-noise ratio,low background fluorescence,low background fluorescence,etc.The composites constructed by MOFs and UCNPs can obtain near-infrared photons,which endows MOFs with additional functions and have great potential in catalysis,biological detection,biological imaging and tumor therapy.However,at present,the research of MOFs/UCNPs composites mainly focuses on the core-shell structure and dimer structure,which may be limited by the lack of effective synthesis strategy.The composite of MOFs and UCNPs with complex structure is of great significance.In this study,we propose a simple two-step synthesis strategy for the synthesis of MOFs/UCNPs composite,study its growth mechanism,and explore the application potential of the composite in the field of detection.The main research contents are as follows:（1）A simple two-step synthesis strategy was proposed.Firstly,stick like UCNPs were modified with surfactants,and then MOFs/UCNPs composites were successfully prepared by oil bath reaction.We explored the growth mechanism of MOFs/UCNPs composites,and studied the effect of the amount of UCNPs on the morphology of MOFs/UCNPs composites,which provided a reference for the development of UCNPs and MOFs composites.（2）The optical properties of MOFs/UCNPs composite were studied,and based on this,the H₂O₂ optical sensor was constructed.Next,we studied the efficiency and sensitivity of the H₂O₂ sensor.The sensor has high sensitivity and rapid response to H₂O₂,which provides a new idea for H₂O₂ detection.（3）A series of M-MOFs/UCNPs composites（M=Mn,Cu,Co,Fe）were synthesized.M-MOFs/UCNPs composites show different morphologies,which have certain application potential in catalysis,detection,biological imaging and tumor therapy.