Preparation And Surface Modification Of Erbium-ion Doped Rare Earth Near Infrared Luminescent Materials

Optical imaging has received great attention in vivo imaging due to its high spatial and temporal resolution.However,a great deal of studies have shown that optical imaging has some limited tissues,such as low penetration depth,obvious tissue fluorescence and obvious background noise in visible light window and near infrared region I window(NIR-I),which will eventually affect the contrast and resolution of the whole image.Compared with traditional fluorescent materials,because the particularity of electronic energy levels of rare earth elements,RENPs have unique luminescent properties and advantages in biomedical imaging,including large resistance to stokes shift,deep penetration of biological tissue,photobleaching resistance,low autofluorescence background,significant chemical stability and low toxicity,rare earth luminescent nanoparticles(RENPs)are a kind of luminescent probe with great application potentials.In addition,the efficiency of RENPs in the near infrared second region biological window(NIR-?)are higher than that of RENPs in the visible window and NIR-I,and they have the deeper imaging penetration depth,high spatial resolution and imaging fidelity and lower background autofluorescence of RENPs in NIR-?.Therefore,RENPs have a better potential application in NIR-? imaging.Based on these reasons,the biocompatibility of RENPs has been improved by surface modification,and their luminescence intensity of RENPs in NIR-? was regulated by doping Ce³⁺.Finally,the cell and animal imaging have been investigated as well.1.In this chapter,the up conversion of rare earth luminescent nanoparticles based on Er³⁺{UCNPs(Na YF₄:Yb,Er)}was prepared.To improve biocompatibility,the surface of rare earth luminescent materials(Na YF₄:Yb,Er)have been modificated by a simple and effective method.Oxidized sodium alginate(OAlg)as a surface ligand was formed by the oxidation of sodium alginate(Alg)by sodium periodate(Na IO₄).Then,OAlg was exchanged to the surface of UCNPs to obtain UCNPs-OAlg through hydrophilic and hydrophobic ligands.Finally,the effect of surface modification on cytotoxicity was tested.The upconversion luminescence(UCL)of UCNPs-OAlg was investigated by a cell imaging test and the potential of UCL bioimaging with fluorescent probes(UCNPs-OAlg)was discussed as well.2.In this chapter,to investigate the effect of crystal phase and Ce³⁺doping on the luminescence properties of Er³⁺-based RENPs,the effect of the RENPs with doping amount of Ce³⁺were discussed.Firstly,cubic phase UCNPs(Na YF₄:Yb,Er,Ce)doped with different proportions of Ce³⁺were prepared by pyrolytic method.Then,the luminescence intensities of cubic phase UCNPs doped with different amount of Ce³⁺in visible light imaging window and NIR-? were tested.The inert core-shell calcium fluoride(Ca F₂)were coated on the surface of cubic-phase UCNPs with different amount of Ce³⁺doping to regulate the emission intensity in visible light window and NIR-?.The emission intensity of UCNPs@Ca F₂in NIR-? was tested comparied with those without modification.The hexagonal RENPs(Er,Ce)with different amount of Ce³⁺doping were prepared by a hydrothermal method,and the luminescent intensity of Er,Ce with different amount of Ce³⁺doping in visible light imaging window and NIR-? was tested.Finally,the effects of different amount of Ce³⁺doping on the luminescence intensity of the hexagonal phase UCNPs@Ca F₂and Er,Ce in visible light window and NIR-? were discussed as well.In addition,silicas were coated on the surface of ER,Ce@SiO₂to provide better modification possibility.And Er,Ce@SiO₂were further modified by oxidizing sodium alginate(OALg)to improve its biocompatibility.The cytotoxicity and upconversion luminescence(UCL)was investigated as well.