Xu Jiating, Sun Mingdi, Kuang Ye, Bi Huiting, Liu Bin, Yang Dan, Lv Ruichan, Gai Shili, He Fei, Yang Piaoping
Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin, 150001, P. R. China.
Dalton Trans. 2017 Jan 31;46(5):1495-1501. doi: 10.1039/c6dt04529d.
Rare-earth-doped up-conversion nanoparticles (UCNPs), which are capable of converting infrared light to shorter-wavelength photons, have attracted worldwide attention due to their unique characteristics. However, the emission brightness of UCNPs is greatly limited by the unsatisfactory absorptivity of lanthanide ions. Herein, we adopted a novel strategy to enhance the up-conversion intensity using NIR dye IR-808 as an antenna to sensitize the core-shell-shell structured NaGdF:Yb,Er@NaGdF:Yb@NaNdF:Yb UCNPs. When excited with 808 nm light, the IR-808 emitted a broadband peak, which perfectly overlapped with the absorption of Nd and Yb ions. Thus, the active shell of NaNdF:Yb can efficiently capture the emitted NIR photons and transfer them to the transition layer of NaGdF:Yb. The transition layer acted as an energy bridge to connect the active shell and up-converting zone, avoiding the energy back-transfer from the activators to Nd ions. The optimized dye sensitization combined with the well-designed core-shell-shell structure tremendously enhances the NIR photon absorptivity of UCNPs and eliminates the deleterious cross-relaxation between the activators and sensitizers, eventually leading to dramatic enhancement of the up-conversion intensity. This study provides a new insight into the dye-sensitized up-conversion luminescence of rare earth-based nanoparticles and facilitates their practical applications.
稀土掺杂的上转换纳米粒子（UCNPs）能够将红外光转换为波长更短的光子，因其独特的特性而受到全球关注。然而，镧系离子的吸收性不尽人意，极大地限制了UCNPs的发射亮度。在此，我们采用了一种新策略，使用近红外染料IR-808作为天线来敏化核-壳-壳结构的NaGdF:Yb,Er@NaGdF:Yb@NaNdF:Yb UCNPs，以增强上转换强度。当用808 nm光激发时，IR-808发射出一个宽带峰，该峰与Nd和Yb离子的吸收完美重叠。因此，NaNdF:Yb的活性壳层能够有效地捕获发射出的近红外光子，并将其转移到NaGdF:Yb的过渡层。过渡层作为能量桥连接活性壳层和上转换区域，避免了能量从激活剂反向转移到Nd离子。优化后的染料敏化与精心设计的核-壳-壳结构相结合，极大地提高了UCNPs对近红外光子的吸收能力，并消除了激活剂和敏化剂之间有害的交叉弛豫，最终导致上转换强度显著增强。本研究为基于稀土的纳米粒子的染料敏化上转换发光提供了新的见解，并促进了它们的实际应用。
