Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, Xiangtan University, Xiangtan 411105, China.
J Colloid Interface Sci. 2012 Feb 15;368(1):49-55. doi: 10.1016/j.jcis.2011.10.072. Epub 2011 Nov 10.
Lanthanide doping not only works as sensitizer and activator, but also plays an important role to facilitate the growth of nanocrystal and to control the size, shape, and property of nanocrystals. Here, reported was the synthesis of monodisperse Ba(2)LaF(7) nanocrystals with the size of sub-10nm through a solvothermal method. We found the dopants of Ho(3+), Er(3+), or Yb(3+) facilitated the growth of Ba(2)LaF(7) nanocrystals obviously to a certain size within a shorter reaction time. Similar phenomenon can also be observed in the synthesis of LaF(3) nanocrystals. We find that Ln(3+) (e.g., Ho(3+), Er(3+), or Yb(3+)) with smaller radius can reduce the nucleation energy and lead to heterogeneous nucleation, which favors the growth of Ba(2)LaF(7) nanocrystals obviously. In addition, intense upconversion emission can be observed from Ln(3+)-doped Ba(2)LaF(7) nanocrystals under the 980 nm laser excitation, providing great potential application in biological imaging. Especially, Ba(2)LaF(7):Yb/Er (20/1 mol%) nanocrystals present more intense upconversion emission than α-NaYF(4):Yb/Er (20/1 mol%) nanocrystals under the same conditions.
镧系元素掺杂不仅可以作为敏化剂和激活剂，而且对于促进纳米晶体的生长以及控制纳米晶体的尺寸、形状和性质也起着重要作用。在这里，我们通过溶剂热法合成了具有亚 10nm 尺寸的单分散 Ba(2)LaF(7)纳米晶体。我们发现，Ho(3+)、Er(3+)或 Yb(3+)等掺杂剂在更短的反应时间内，明显促进了 Ba(2)LaF(7)纳米晶体的生长到一定尺寸。在 LaF(3)纳米晶体的合成中也可以观察到类似的现象。我们发现，半径较小的 Ln(3+)（例如 Ho(3+)、Er(3+)或 Yb(3+)）可以降低成核能，导致异质成核，从而明显有利于 Ba(2)LaF(7)纳米晶体的生长。此外，在 980nm 激光激发下，Ln(3+)掺杂的 Ba(2)LaF(7)纳米晶体可以观察到强烈的上转换发射，这为生物成像提供了巨大的潜在应用。特别是，在相同条件下，Ba(2)LaF(7):Yb/Er(20/1mol%)纳米晶体的上转换发射比α-NaYF(4):Yb/Er(20/1mol%)纳米晶体更强烈。
