锰离子对镥基纳米晶体的荧光调控与增强

通过调控Mn²⁺的掺杂浓度，在镥基纳米晶体成功地实现了六方、四方混合相到纯四方相的相位转变，并详细讨论了其相变机理. 时域和频域光谱的分析表明，立方相Na₅Lu₉F₃₂：40% Mn²⁺，20% Yb³⁺，2% Ln³⁺（Ln=Er³⁺，Ho³⁺）纳米晶体内的准纯红色荧光发射主要由Mn²⁺和Ln³⁺之间的两步能量转移引起. Mn²⁺掺杂后引起了发光离子附近局域对称性的降低，使得电偶极跃迁的辐射速率明显增加，进而导致了上转换、下转换荧光的极大增强. 该研究结果在生物荧光成像、太阳能电池效率的提高方面具备潜在的、广阔的应用前景. 关键词： 镥基纳米晶体 电偶极跃迁 两步能量转移 局域对称性

Mn2+ induced luminescence regulation and enhancement of Lu-based nanocrystals

Transformation from Lu-based nanocrystals in hexagonal and cubic mixed phases to pure cubic phase was observed through adjusting the doping concentration of Mn²⁺. The mechanism for the phase transformation was discussed in detail. Studies on the time and frequency domain spectra indicated that the semi-pure red emissions in cubic Na₅Lu₉F₃₂: 40% Mn²⁺, 20% Yb³⁺, 2% Ln³⁺ (Ln=Er³⁺, Ho³⁺) nanocrystals were caused by a two-step energy transfer between Mn²⁺ and Ln³⁺ ions. After incorporating of Mn²⁺ ions into the host lattices, the local symmetry around the luminescent ion was reduced, which induced the increase of radiative rates for transitions that were mainly contributed by electric dipole radiations. Considerable enhancements in upconversion and downconversion luminescence were accompanied. The result of the current study has great application potential in bioimaging and solar cells.
Keywords： Lu-based nanocrystals electric dipole transition two-step energy transfer local symmetry