| Due to their unique optical properties and chemical stability, the rare-earth nanocrystals (RENPs) have great potential biomedical application in both in-vitro and in-vivo. Firstly, the prerequisite for the biomedical application is to gain monodisperse and strong luminescence nanoctystals. Secondly, the RENPs must have functional groups such as–NH2, -COOH, -SH and good water solubility. Lastly, the biomolecule that has targeting property should been conjugated to the RENPs. For these requisite, a few biological luminescent labeling materials have been prepared and characterized.1) NaYF4:Eu3+ nanocrystals with remarkably uniform morphology and size have been synthesized via a facile thermal decomposition route using trifluoroacetates as precursors in hot solutions of oleic acid and oleylamine. The high-quality cubicα-phase and hexagonalβ-phase NaYF4:Eu3+ with different shape were obtained at different temperature, respectively. The relationship between the morphology and the luminescence via the excitation and emission spectra was investigated.2) A novel preparative method to synthesize monoamine-terminated poly (ethylene glycol) (MPEG-NH2) coated RENPs was developed. NaYF4:Ce/Tb nanocrystals with oleic acid on the surface were firstly prepared via a modified thermal decomposition method. The oleic acid on the surface of nanocrystals was converted into azelaic acid by the Lemieux-von Rudloff oxidation method. Next, the carboxylic acid-functionlized NaYF4:Ce/Tb was conjugated with poly(ethylene glycol) bis(3-aminopropyl) terminated (NH2-PEG-NH2). At last, the folic acid (FA)-functionlized NaYF4:Ce/Tb nanocrystals were obtained for targeted bio-imaging.3) A series of multicolor up-conversion the rare earth nanocrystals were synthesized by adjusting the doping rare earth ion and its concentration. Furthermore, the water-soluble nanocrystals was obtained through changing the oleic acid on the surface of nanocrystals into azelaic acid by the Lemieux-von Rudloff oxidation method.
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