Yb, Er Preparation And Characterization Of: Converting The Water-soluble Nano-phosphor NaYF 4

Due to the unique up-converting optical property, up-conversion luminescentmaterials NaYF4:Yb,Er have been widely used in many fields, such as biomedicine,solid-state lasers, solar cell, IR imaging, optical-fiber-based telecommunications,three-dimensional displays and optical storage. Among which, the biomedicalapplication has led the study of up-conversion luminescent materials to a very hottopic. Up-conversion luminescent materials NaYF4:Yb,Er has received increasedattention as a new type of fluorescent markers in the molecular detection in recentyears, but under the premise of being water soluble and with high luminescenceefficiency. So it is a key to synthesize high quality, water-soluble NaYF4:Yb,Erconversion nanoparticles.In this study, we do a research on the synthetic methods of water-solubleNaYF4:Yb,Er nanoparticles. The major contributions are summarized as follows:(1) Through the analysis of the coordination effect between surfaces ofup-conversion luminescent nanoparticles NaYF4:Yb,Er and the coating oleic acid, aphysical method-ultrasonic deoiling was proposed to break the coordination energybetween them and change the NaYF4:Yb,Er nanoparticles to be water-soluble. Thenthe experimental process had been studied in detail and the mechanism of oleateligand removing was expounded as well. At last, the characterization of samples withXRD, TEM, TGA, HNMR and fluorescence spectroscopy showed that the oleate-freeNaYF4:Yb,Er nanoparticles were soluble in water stably and uniformly, besides theparticle size, crystal morphology were not obvious changed, while the upconversionluminescence efficiency became higher.(2) High-temperature solution is the main method to obtain NaYF4:Yb,Ernanoparticles, in this study we avoided the complex preparation process andstringent conditions(high-temperature, N2assistance etc.) of this method,and transferred the reaction system into reaction kettle and exploited thesolvothermal method to synthetize NaYF4:Yb,Er nanoparticles. The morphology andsize of product could be regulated by means of adjusting the reaction time,temperature and whether to use methanol. What’s more the crystal morphology,optical properties of the samples and the existence of oleic acid onthe surfaces of nanocrystallines were characterized by TEM, FTIR and fluorescence spectroscopy. Finally, the synthesis methods of NaYF4:Yb,Er nanoparticles werecompared.(3) Synthesizing the water-soluble up-conversion nanoparticles NaYF4:Yb,Er byhydrothermal synthesis with LnCl3(Ln=Y, Yb, Er), NaF as reactants andethylenediamine tetraacetic acid disodium salt (EDTA) as chelating agent. Themorphology and size of product could be regulated by adjusting the EDTA dosage,reaction temperature, reaction time, the molar ratio of LnCl3and NaF, and the order ofthe reactants. The samples were characterized by TEM, XRD and fluorescencespectroscopy.