Li Hui, Hao Shuwei, Yang Chunhui, Chen Guanying
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering & Key Laboratory of Micro-systems and Micro-Structures, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China.
Institute for Lasers, Photonics and Biophotonics, State University of New York at Buffalo, Buffalo, NY 14260, USA.
Nanomaterials (Basel). 2017 Feb 7;7(2):34. doi: 10.3390/nano7020034.
The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF₄:Yb/Ln@CaF₂ (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF₄). We exploited the liquid-solid-solution method to synthesize the NaLuF₄ core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF₂) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals.
从高效主体晶格合成高质量分级核/壳纳米晶体的能力对于实现从生物成像到太阳能电池等应用中的有效光子上转换至关重要。在此，我们描述了一种基于新建立的氟化镥钠（NaLuF₄）主体晶格来制备多色核@壳α-NaLuF₄:Yb/Ln@CaF₂（Ln = Er、Ho、Tm）上转换纳米晶体（UCNCs）的策略。我们利用液-固-溶液法合成纯立方相的NaLuF₄核，并采用热分解方法在核UCNCs上外延生长氟化钙（CaF₂）壳，得到尺寸为15.6±1.2 nm（核约9±0.9 nm，壳约3.3±0.3 nm）的立方核/壳纳米晶体。我们表明，由于有效抑制了表面相关的猝灭效应，那些核/壳UCNCs能够发射出由激活剂定义的多色发射，其效率比核纳米晶体高出约772倍。我们的结果为从胶体纳米晶体增强多色上转换光致发光的异质核/壳结构提供了一种新范例。
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