Synthesis And Characterization Of NaYF₄:Yb³⁺/Er³⁺ For Biological

Upconversion nanoparticles were synthesized through a solvothermal method in this paper.The samples were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,infrared spectroscopy（IR）and fluorescence spectrophotometer（FL）.In the experiment,the modified upconversion luminescent nanoparticles were successfully synthesized by repeated experiments and applied to the imaging work of HeLa cells.The main results are as follows:（1）NaYF₄:Yb³⁺/Er³⁺ were synthesized through solvothermal method which is convenient and simple by using rare earth stearate as precursors.In order to use the samples at the filed of biological imaging,the optimum reaction conditions were determined: the reaction temperature is 120 ℃,the reaction time is 24 h,the volume ratio of water and olic acid is 10:5.The effect of chelaing agents of EDTA and citrate on structure of samples was also explored.The adding of EDTA can prevent to form more stable hexagonal phase and increase the intensity of particles even at low reaction temperature.And we also detect the effect of the the amount of doped ions on luminous intensity.The up-conversion fluorescence efficiency of NaYF₄:Yb³⁺/Er³⁺ is highest when the molar ratio of Y3+:Yb3+:Er3+is 78:20:2.（2）There are two main methods for samples’ surface hydrophilic modification:select different hydrophilic polymers,PEI,PVP,PAA,PEG were added to the reaction system respectively,and got samples with different functional groups,-NH2,-C=O,-COO-,and-OH;oxidize-C=C-which adsorbed on the sample surface to-COO-use strong oxidizing Lemieux-von Rudloff agents.The hydrophilic groups were coated on thesurface of the sample successfully which can be proved by IR spectra.（3）Upconversion nanoparticles coated by hydrophilic groups were used for bioimaging.The effects of different materials and different labeling time on the bioimaging were investigated.The surface-coated carboxyl-based material obtained by oxidation with a strong oxidizing agent has a better imaging mark effect after co-cultivation with the cells for 2 hours.（4）The preparation of a core-shell structure of the luminescent material were further studied.NaYF4:Yb3+were coated on the surface of NaYF₄:Yb³⁺/Er³⁺.After coating,the intensity of samples increased a lot.And in this article,the effect of reaction time and the ratio of Y and Yb on the luminous intensity were detected.We found that,samples have the most strong intensity when the reaction time is 4 h,thickness of coating layer is about 15-25 nm,the molar ratio of Y:Yb is 7:3.