Synthesis And Luminance Of Water Soluble Fluoride Nanocrystals

Rare earth doped upconversion fluorescent materials have important applications in the fields of photoluminescence (PL) bioimaging and photodynamic therapy of human diseases based on their virtue of being excited by the near infrared laser, absence of photodamage and so on. However, there are still many problems for upconversion materials, for example disability of dispersion in aqueous media, low upconversion efficiency, etc. Because of these problems, their applications in bioimaging are limited. Thus, it is imperative that straightforward postsynthesis routes be developed that allow for the dispersion of these upconverting NPs in aqueous media if they are ever to be useful for biolabeling applications.Based on rare-earth-ion-doped fluoride materials, we have investigated upconversion water solubility enhancement and emission enhancement.Size- and morphology-controllable fluoride nanocrystals were prepared, the upconversion emissions of NaYbF4:Tm³⁺ have been investigated. Hexagonal NaYbF4:Tm³⁺ nanocrystals with small uniform size and monodispersition have been synthesized via modulating reaction time and temperature by solvent hot method. Ultral small NaYF4:Yb³⁺/Er³⁺ and NaYF4:Yb³⁺/ Tm ³⁺ nanocrystals are successfully acheived. The XRD and TEM images showed size and morphology of the nanoctrstals. By codoping Tm ³⁺ ions in NaYbF4:Tm³⁺nanocrystals, the effect of Tm ³⁺ ions on the UC efficiency of NaYbF4:Tm³⁺ nanocrystals have been investigated. NaYbF4:1%Tm³⁺with high UC efficiency was successfully achieved.NaYbF4:2%Tm³⁺ UC photoluminescence intensity at 800 nm was shown 17 times the same as UC photoluminescence intensity at 345 nm. Optical imaging experiments demonstrated that NaYbF4:Tm³⁺ nanocrystals can be used in bioimaging under the excitation wavelength (980 nm).The new phenomena that the upconvertion intensity of NaYbF4: Tm³⁺ nanocrystals decrease with time under the excitation of 980nm laser has been found.The water-soluble modification of fluoride nanocrystalline and the fluorescence properties in liquid were studied. Here, we employ the PEG ligand to render hydro-phobic upconverting NaYF4:Yb³⁺/Tm³⁺,NaYF4:Yb³⁺/Er³⁺ NPs dispersible in aqueous environments. Two new methods to prepare hydrophilic rare earth upconverted nanoparticles were developed: the preparation rare-earth-ion-doped fluoride materials capped by PEG-4000 via solvent hot method; the preparation of PLA-PEG capped rare-earth-ion-doped fluoride materials via phase separation method. The synthesized NaYbF4:1%Tm³⁺ and NaYF4:20%Yb³⁺/20%Er³⁺ can steadily disperse in water solution. The TEM images and FT-IR shows that PEG has been successfully capped. We then employ the 980 nm laser to examine the effect the PEG capping has on the luminescent properties of NaYF4:Yb³⁺/Tm³⁺, NaYF4:Yb³⁺/Er³⁺ and NaYbF4:Tm³⁺.