Preparation Of Carbon Dots-metal Organic Framework Composite Materials And Their Applications In Fluorescence Analyses

Carbon dot（CDs）is a new type of fluorescent carbon-based nanomaterials,which has attracted much attention due to its unique optical properties,good biocompatibility and low toxicity.It has been widely used in fluorescence sensing,biological imaging,drug delivery,photocatalysis and other fields.Metal-organic frameworks（MOFs）are highly ordered porous coordination polymers formed by self-assembly of inorganic metal ions or metal clusters with organic ligands.Their ultra-high porosity and adjustable pore size make them become potentially valuable carriers for encapsulating nanoparticles.Therefore,by encapsulating CDs with fluorescence properties into the pores of MOFs,make the porous properties of MOFs can be combining with the optical properties of CDs,so that some novel MOFs based materials can be designed and synthesized.In this thesis,three different types of CDs@MOFs composites were designed and synthesized by combining the porosity of MOFs with the optical properties of CDs,and their applications in environmental analysis was further investigated.The thesis is divided into three parts as follows:（1）By introducing the CDs with blue fluorescence synthesized using citric acid and ethylenediamine as raw materials into the reaction mixture of ZIF-8,a new type of MOFs based composite（CDs@ZIF-8）was synthesized by one-pot solvothermal method.The obtained CDs@ZIF-8 composite has both excellent optical properties of CDs and strong adsorption and accumulation effect of ZIF-8,as well as good structure and fluorescence stability in extreme environments.Based strong quenching action of Cu²⁺on the fluorescence of the composite solution,a highly sensitive and selective analytical method for Cu²⁺was developed with a wide linear range of 0.5-550μM and a low detection limit of 0.26μM.（2）Blue fluorescent CDs prepared by hydrothermal method with black wolfberry as carbon source were in situ encapsulated by Eu-MOFs fabricated with a simple one-step hydrothermal method to synthesize a novel dual-emission CDs@Eu-MOFs composite.The obtained composite effectively combined with the advantages including high adsorptive property of Eu-MOFs and the reduction of background interference with the ratio fluorescence probe.It can be applied for the detection of Hg²⁺in environmental water samples,delivering a wide linear range of 0.01-300μM and a low detection limit of 0.12 n M.（3）By respectively selecting the citric acid and urea as carbon source and nitrogen source,blue fluorescent carbon dots（N-CDs）were synthesized,and using green biomass raw spinach as carbon source,red fluorescence carbon dots（R-CDs）were obtained.And then the synthesized N-CDs and R-CDs were simultaneously introduced into the synthesis environment of ZIF-8,and a novel ratio fluorescent probe material（N-CDs/R-CDs@ZIF-8）with excellent fluorescence properties has been successfully prepared.The composite material not only has the advantages of the ratio fluorescence probe,but also has the strong adsorption performance of ZIF-8,which can be used for the specific detection of Pb²⁺in environmental water samples.