Upconversion Nanomaterials And Coumarin-based Composite Materials And The Applications In Biosensing

In recent years,fluorescent sensors have received extensive attention in the field of biological substance detection due to their high sensitivity,speed and simplicity.Fluorescence sensors based on upconverting nanomaterials show unique advantages in bioprotein detection,including: anti-Stokes shifts,narrow-band emission,easy-toadjust spectra,etc.Most importantly,such materials are excited by infrared light.Obtaining visible light emission not only has a large depth of tissue penetration,but also effectively avoids background fluorescence and improves detection sensitivity.In addition,coumarin derivatives are a class of excellent fluorescent molecules which have a good planar enlarged ?-? conjugated system and exhibit excellent optical properties.The probe molecules based thereon have such large Stokes.The advantages of displacement,high fluorescence quantum yield,excellent light stability,etc.are hot topics in the field of organic light-emitting materials.In this thesis,the advantages of near-infrared excitation of upconverting nanomaterials were firstly combined with silver nanoparticles to design a tumor marker CA-125 sensor.The NaYF4: Yb/Tm-PEI upconversion nanocrystal synthesis was realized by one-step synthesis.The tumor marker antibody modification is achieved by the amino group extending from the surface,and then the silver nanoparticle is used to label the CA-125 tumor marker,and the CA-125 is used to connect the upconversion nanocrystal and the silver nanoparticle.The important innovation of this work is that the plasmon resonance absorption spectrum of silver nanoparticles has a good overlap with the emission spectrum of upconverting nanocrystals,and achieves a high absorption efficiency.Since the sandwich structure centered on the tumor marker can be a distance of less than 10 nm,thereby achieving efficient energy transfer,we achieve high sensitivity detection of tumor markers by fluorescence signal changes,and the detection sensitivity reach 120pg/ml.Second,we explore iron ion probes based on coumarin fluorophores.At present,because of its excellent molecular design function,organic fluorescent small molecule probes can achieve high selectivity of different ions and become the main research direction of ion detection.The fluorophore is mainly a hydrophobic fused ring structure,which reduces the water solubility of the ion probe,and thus becomes a major problem to be solved for further application.In order to improve the water solubility of molecular probes,this paper adopts the design concept of “internal hydrophobicity,external hydrophilicity”,introduces hydrophobic benzene ring structure as the core,and connects coumarin probe molecules to achieve high water solubility of oligomers.And greatly improved the detection limit of iron ions to reach the picomolar / liter(pM)level.In this work,we explore the molecular weight of the hydrophilic and hydrophobic parts of the molecule through a large number of experiments,and clarify the molecular design rules for improving water solubility.Due to the greatly improved water solubility,the biocompatibility is further improved,and the oligomer probe molecule successfully achieves the detection of iron ions at the cellular level,and the detection limit is up to 9 pM,and the probe molecule can be excited by sunlight.For naked eye detection,the lower limit of detection is 50 ?M.In this paper,we design a new method for the detection of tumor markers by designing bio-probes based on upconverting nanomaterials and small molecules of coumarin oligomers,while greatly reducing the detection limit of iron ions,both in basic research and in the practical application areas are of great significance.