Enhancing multiphoton upconversion through energy clustering at sublattice level
Enhancing multiphoton upconversion through energy clustering at sublattice level
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DOI：
10.1038/nmat3804
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发表时间：
2014-02-01
期刊：
影响因子：
41.2
通讯作者：
Liu, Xiaogang
中科院分区：
文献类型：
--
作者：
Wang, Juan;Deng, Renren;Liu, Xiaogang
镧系元素掺杂的上转换纳米晶体在生物成像、光子学、光致发光学和治疗学中的应用促进了对合理控制纳米晶体的发射分布的日益增长的需求（1-14）。用于调节上转换发光的常见策略是控制镧系元素离子的掺杂浓度（15，16）。然而，在高掺杂水平下激发态的浓度猝灭现象构成了显著的限制。因此，镧系元素离子必须严格地保持在相对低的浓度以使发光猝灭最小化（17）。在这里，我们描述了一类新的上转换纳米晶体，采用正交晶体结构，其中镧系元素离子分布在四分体簇阵列。重要的是，这种独特的安排，使激发能量的亚晶格域内的保存，并有效地减少了迁移的激发能量的缺陷，即使在化学计量的化合物与高Yb 3+含量（计算为98摩尔%）。这使我们能够从Er 3+产生一种不寻常的四光子促进的紫色上转换发射，其强度比以前报道的高出8倍以上。我们的研究结果强调，通过在亚晶格水平上的能量聚集来增强上转换的方法可能为光引发的生物反应和光动力治疗提供新的机会。
The applications of lanthanide-doped upconversion nanocrystals in biological imaging, photonics, photovoltaics and therapeutics have fuelled a growing demand for rational control over the emission profiles of the nanocrystals(1-14). A common strategy for tuning upconversion luminescence is to control the doping concentration of lanthanide ions(15,16). However, the phenomenon of concentration quenching of the excited state at high doping levels poses a significant constraint. Thus, the lanthanide ions have to be stringently kept at relatively low concentrations to minimize luminescence quenching(17). Here we describe a new class of upconversion nanocrystals adopting an orthorhombic crystallographic structure in which the lanthanide ions are distributed in arrays of tetrad clusters. Importantly, this unique arrangement enables the preservation of excitation energy within the sublattice domain and effectively minimizes the migration of excitation energy to defects, even in stoichiometric compounds with a high Yb3+ content (calculated as 98 mol%). This allows us to generate an unusual four-photon-promoted violet upconversion emission from Er3+ with an intensity that is more than eight times higher than previously reported. Our results highlight that the approach to enhancing upconversion through energy clustering at the sublattice level may provide new opportunities for light-triggered biological reactions and photodynamic therapy.