The Preparation Of Rare Earth Up-conversion Nano-materials And Its Biomedical Applications

In recent years, with the development of nano-science and nano-technology, much attention has been pay to the rare-earth-doped conversion fluorescent nanoparticles as novel biomarkers applied to the biomedical field. Compare to the traditional fluorescent markers (such as organic dyes, quantum dots, etc.), the conversion nanoparticles were excited by infrared light that could effectively avoid the interference of organism autofluorescence, and improve the detection sensitivity and signal to noise ratio. Infrared light has deep tissue penetration and show very small damage to the biological tissue. In addition, upconversion nanoparticles show a low toxicity, a good stability, a high fluorescence intensity and a large Stokes shift. They may have a good application potential in biological markers and biological detection fields. Therefore, the development of such materials controlled synthesis and surface modification technologies have very important theoretical research value and practical significances.Contents of this paper consists of two parts, the first is using thermal decomposition the trifluoroacetate salts to prepare the rare-earth double-ion-doped upconversion fluorescent nanomaterials with different morphologies, scales and substrates. The second part is using bovine fetal albumin modify the rare earth fluorescent materials. The main contents are as follows:1.The synthesis and characterization of hexagonal phase NaYF4:Yb,Er upconversion nanoparticles. The hexagonal phase NaYF4:Yb,Er upconversion nanoparticles with an average particle size about20nm were prepared by thermal decomposing trifluoroacetate salts in an oleic acid/oleylamine/octadecene (OA:OM:OME) mixed phase system. The prepared nanoparticles show high fluorescence intensity. The particles were characterized by the means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence spectroscopy. g Finally, we found that under the conditions of the reaction temperature of310℃, the reaction time of1.5h, and the solvent ratio of OA:OM:OME=1:1:2, the obtained particles show uniform morphology and highest fluorescence intensity.2. The synthesis and characterization of tetragonal octahedral LiYF4:Yb,Er upconversion nanoparticles. The tetragonal octahedral LiYF4:Yb,Er nanoparticles with uniform particle size and morphology was prepared by thermal decomposition of trifluoroacetate salts in an oleic acid/oley lamine/octadecene mixed-phase system.The fluorescence properties of LiYF4:Yb,Er and NaYF4:Yb,Er nanoparticles under the same concentration were studied by the fluorescence spectroscopy. Under the excitation with980nm wavelength light, the green emission fluorescence from the2H11/2-4I15/2and4S3/2-4I15/2level transition, the red emission fluorescence from the4F9/2-4I15/2level transition and the faint violet emission fluorescence from the2H9/2-4I15/2level transition were observed, respectively. The results showed that:the fluorescence intensity of LiYF4:Yb,Er nanoparticles is much higher than that of NaYF4:Yb,Er nanoparticles.3. The surface modification and biological applications of LiYF4:Yb,Er nanoparticles. We have successfully prepared carboxylated modified bovine serum albumin (BSA) modified LiYF4:Yb,Er nanoparticles. Then the nanoparticles were conjugated with the mPEG-NH2. The transmission electron microscopy (TEM), fourier transform infrared spectrophotometer (FTIR) and fluorescence spectrometer have clearly demonstrated that the LiYF4:Yb,Er nanoparticles were successful modified with BSA and mPEG-NH2. The cytotoxicity of modified nanoparticles was test by MTS assay using Hela cells, and the modified nanoparticles showed a lower toxicity and have potential application values in biomedical field.