Preparation Of Rare Earth Doped Fluoride-Matrixed Upconversion Nanoparticles And Their Applications In Biolabeling

The rapid development of life sciences makes biolabeling more and more significant。 Making desied biomarker has become a study hotpoint. The usual biolabels such as organic dyes and quantum dots (QDs) can cause autofluorescence owing to the high energy of exciting source, so the detection sensitivity is low. The emerging of rare-earth (RE) doped upconversion (UC) luminescent nanoparticles (NPs) solved this problem. Compared with traditional biolabels, UCNPs are excited by infrared (IR) radiation with lower energy, which results in the absence of autofluorescence and minor damage to organism. Meanwhile, UCNPs have several advantages, such as high emission intensity, low toxicity and good stability, showing great application prospect in biolabeling. In recent years, ionic liquids(ILs) have attracted extensive attention for their great "green" characteristic and good stability. ILs can dissolve many inorganics and organics. If ILs were used instead of organic solvents as solvents and reactants in chemical reactions, environment pollution can be reduced. Therefore, finding a suitable ILs as the reactant, template and co-solvent to synthesize rare-earth doped fluoride-matrixed upconversion nanoparticles is of very important and practical value.In this research,1-butyl-3-methylimidazolium tertrafluoroborate ([Bmim][BF]) was used as the F source, template and co-solvent, to hydrothermally synthesize YF3:Yb,Er UCNPs. Meanwhile, hexagonal phased (p-phase) NaYF4nanoparticles co-doped with Yb3+-Er3+ion couple were prepared by hydrothermal and solvothermal, respectively. The reaction mechanisms of each method were discussed while the size, crystal structure and fluorescent properties of the nanoparticles were characterized. The effects of reaction parameters on luminescence intensity and crystal structure were also investigated in detail. The results showed that (3-NaYF4:Yb,Er UCNPs prepared by solvothermal method have a mean size of35nm and disperse well in water. The as-prepared particles can be directly applied to biolabeling without further modify because the surface of these UCNPs was capped with amino groups. The as synthesized NaYF4:Yb,Er UCNPs were coupled with folate and used for the cell labeling based on the specific conjugation of folate with the folate receptor on HT-29cells. The in vivo imaging of Caenorhabditis elegans was carried out by incubating NaYF4:Yb,Er UCNPs produced by three different methods with C. elegans. The effects of nanoparticle concentration, size, ligand groups on the surface of nanoparticles and incubation time on the C. elegans imaging were investigated. The results showed that in a certain range, the higher concentration and the longer incubation time make C. elegans swallow more nanoparticles. The C. elegans have difficulty in swallowing nanoparticles with large size and the C. elegans did not show apparent difference in swallowing nanoparticles covered by various groups. In addation, by means of observing the survival rate of C. elegans swallowed nanoparticles, the low toxicity of NaYF4:Yb,Er UCNPs was verified.