Plohl Olivija, Kralj Slavko, Majaron Boris, Fröhlich Eleonore, Ponikvar-Svet Maja, Makovec Darko, Lisjak Darja
Jožef Stefan Institute, Department for Materials Synthesis, Jamova 39, 1000 Ljubljana, Slovenia.
Dalton Trans. 2017 May 30;46(21):6975-6984. doi: 10.1039/c7dt00529f.
Upconverting nanoparticles (UCNPs) of β-NaYF, co-doped with Yb and Tm and 21-36 nm large, were synthesized using a modified thermal decomposition method. The as-synthesized UCNPs were coated with oleic acid and dispersed in nonpolar media. Their morphology, size and crystal structure were analysed with transmission electron microscopy and X-ray diffraction. The UCNPs showed a fluorescence emission spectrum characteristic of Tm. Their dissolution in water (pH ∼ 4-5) and phosphate buffered saline (PBS, pH = 7.4) was determined from the fraction of dissolved fluoride ions using a fluoride-ion-selective electrode. The dissolution of bare UCNPs was much more prominent in PBS than in water. Two amphiphilic coatings, poly(maleic anhydride-alt-1-octadecene)-bis(hexamethylene)triamine (PMAO-BHMT) and d-α-tocopheryl polyethylene glycol succinate (TPGS) were tested for their effects on the dissolution of the UCNPs. The coatings were formed directly on the as-synthesized UCNPs as was confirmed with electrokinetic measurements, infrared spectroscopy and thermogravimetric analyses. Both coatings enabled the dispersion of UCNPs in water, and improved the fluorescence emission intensity with respect to the bare UCNPs. However, only the PMAO-BHMT coating provided an effective protection against the dissolution of the UCNPs and long-term colloidal stability in PBS, and did not show cytotoxicity in EAhy926 endothelial cells.
采用改进的热分解方法合成了共掺杂镱（Yb）和铥（Tm）的β-NaYF上转换纳米颗粒（UCNPs），其尺寸为21 - 36纳米。合成后的UCNPs用油酸包覆并分散在非极性介质中。用透射电子显微镜和X射线衍射分析了它们的形态、尺寸和晶体结构。UCNPs呈现出铥的荧光发射光谱特征。通过使用氟离子选择性电极测定溶解的氟离子分数，确定了它们在水（pH约为4 - 5）和磷酸盐缓冲盐水（PBS，pH = 7.4）中的溶解性。未包覆的UCNPs在PBS中的溶解比在水中更显著。测试了两种两亲性涂层，聚（马来酸酐-alt-1-十八烯）-双（六亚甲基）三胺（PMAO-BHMT）和d-α-生育酚聚乙二醇琥珀酸酯（TPGS）对UCNPs溶解的影响。通过电动测量、红外光谱和热重分析证实，涂层直接形成在合成后的UCNPs上。两种涂层都能使UCNPs分散在水中，并相对于未包覆的UCNPs提高了荧光发射强度。然而，只有PMAO-BHMT涂层能有效防止UCNPs在PBS中溶解并提供长期的胶体稳定性，并且在EAhy926内皮细胞中未显示出细胞毒性。
