Construction Of Novel Ratio Fluorescence Probe Based On Carbon Dots And Terbium Coordination Polymer And Application In Detection Of Heavy Metal Ions And Pesticides

Fluorescence analysis is widely used in environmental monitoring,optoelectronic devices,bioimaging and drug transport.Carbon Dots（CDs）is a kind of zero-dimensional carbon-based nano-material,which has good water-solubility,excellent light stability,high quantum yield and abundant surface functional groups.The carbon dots can detect heavy metal ions,as a fluorescent single probe.Lanthanide coordination polymers（Ln CPs）exhibit long fluorescence lifetime,narrow fluorescence emission peak and large Stokes shift.In the self-assembly process,organic dyes,metal nano-ions or quantum dots can be encapsulated in the Ln CPs to form a ratio fluorescent probe with two fluorescent emission centers,the ratio fluorescence signal can significantly reduce the background interference and improve the detection sensitivity.In this study,three fluorescent probes based on CDs and Ln CPs were constructed for the detection of different targets.The main work is as follows:1.Microwave synthesis of nitrogen-doped carbon dots derived from malic acid for Hg²⁺detectionNitrogen-doped carbon dots（MU-CDs）were prepared by microwave irradiation.Urea and malic acid were used as nitrogen source and carbon source respectively.MU-CDs has good optical properties and light stability.The quantum yield of MU-CDs is 24%.The linear range of Hg²⁺was 0.05-100μM and the detection limit was as low as 10 n M.The results of energy level calculation and fluorescence lifetime analysis show that the electrons of MU-CDs can transfer to the D orbit of Hg²⁺empty,and the fluorescence quenching mechanism is dynamic quenching.2.Ratio fluorescent probes based on carbon dots to Lanthanide Coordination Polymer for Ag⁺detectionIn the process of self-assembly of adenylate with terbium ions to form polymer,a kind of Lanthanide Coordination Polymer can be formed by introducing a carbon dots as an guest molecule.MU-CDs@AMP/Tb only showed the characteristic peak of carbon dots at 450 nm,and the characteristic peak of Tb³⁺at 545 nm was significantly enhanced when Ag⁺was added.The linear range of silver ion is 1-100μM and the detection limit is 0.42μM.AMP/Tb and AMP/Tb-Ag⁺were characterized by FT-IR,SEM and XPS,and the binding sites of AMP with Tb³⁺and Ag⁺were investigated.3.Detection of cartap by self-assembled ratio fluorescence probe based on Tb³⁺and nitrogen-phosphorus codoped carbon dotsHydrothermal synthesis of nitrogen-phosphorus co-doped carbon spots（AMP-CDs）using adenosine monophosphate as a source of carbon,nitrogen and phosphorus.A novel fluorescent probe AMP-CDs@Tb with double emission centers was prepared by adding Tb³⁺into the polymer,and encapsulating the carbon dots in the polymer.AMP-CDs@Tb can be used for the determination of cartap,which is a common organic sulfur pesticide.The linear range of 0.1-10μM and a detection limit of 14 n M.