Department of Chemistry, National University of Singapore, 117543, Singapore.
Nat Mater. 2011 Oct 23;10(12):968-73. doi: 10.1038/nmat3149.
Photon upconversion is promising for applications such as biological imaging, data storage or solar cells. Here, we have investigated upconversion processes in a broad range of gadolinium-based nanoparticles of varying composition. We show that by rational design of a core-shell structure with a set of lanthanide ions incorporated into separated layers at precisely defined concentrations, efficient upconversion emission can be realized through gadolinium sublattice-mediated energy migration for a wide range of lanthanide activators without long-lived intermediary energy states. Furthermore, the use of the core-shell structure allows the elimination of deleterious cross-relaxation. This effect enables fine-tuning of upconversion emission through trapping of the migrating energy by the activators. Indeed, the findings described here suggest a general approach to constructing a new class of luminescent materials with tunable upconversion emissions by controlled manipulation of energy transfer within a nanoscopic region.
上转换是一种很有前途的技术，可应用于生物成像、数据存储或太阳能电池等领域。在这里，我们研究了一系列组成不同的基于钆的纳米粒子的上转换过程。我们表明，通过合理设计核壳结构，并在精确定义的浓度下将一组镧系离子掺入到分离的层中，可以通过钆亚晶格介导的能量迁移，在没有长寿命中间能态的情况下，实现高效的上转换发射，适用于广泛的镧系元素激活剂。此外，使用核壳结构可以消除有害的交叉弛豫。这种效应可以通过将迁移能量捕获到激活剂上来精细调节上转换发射。实际上，这里描述的发现提出了一种通用的方法，通过在纳米尺度范围内控制能量转移，构建一类具有可调上转换发射的新型发光材料。
