Department of Rare Earths, Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznan, Poland.
Sci Rep. 2021 Sep 22;11(1):18846. doi: 10.1038/s41598-021-98240-0.
Water-dispersible up-converting nanoparticles (UCNPs) are known to be very effective in biomedical applications. Research groups have paid special attention to the synthesis of hydrophilic UCNPs with good physicochemical properties. Being aware of this, we decided to improve the ligand-free modification method of OA-capped NaYF:Yb,Er/NaYF UCNPs prepared by precipitation in high-boiling-point solvents as the thus-far reported methods do not provide satisfactory results. Different molarities of hydrochloric acid and various mixing times were selected to remove the organic ligand from the NPs' surface and to discover the most promising modification approach. Highly water-stable colloids were obtained with a very high reaction yield of up to 96%. Moreover, the acid treatment did not affect the morphology and the size of the product. All of the crystals exhibited a bright up-conversion emission under 975-nm excitation, which confirmed the two-photon excitation and effective energy transfer between the used dopant ions. Thus, we could establish the most successful ligand-free modification procedure.
水相分散上转换纳米粒子（UCNPs）在生物医学应用中被证明是非常有效的。研究小组特别关注具有良好物理化学性质的亲水性 UCNPs 的合成。有鉴于此，我们决定改进无配体修饰的 OA 封端的 NaYF:Yb,Er/NaYF UCNPs 的沉淀法合成，因为迄今为止报道的方法没有提供令人满意的结果。选择不同浓度的盐酸和不同的混合时间来去除 NPs 表面的有机配体，并发现最有前途的修饰方法。得到了高度稳定的胶体，反应收率高达 96%。此外，酸处理并没有影响产物的形貌和尺寸。所有晶体在 975nm 激发下都表现出明亮的上转换发射，这证实了所用掺杂离子的双光子激发和有效的能量转移。因此，我们可以建立最成功的无配体修饰程序。
