Synthesis of Multicolor Core/Shell NaLuF₄:Yb3+/Ln3+@CaF₂ Upconversion Nanocrystals.
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:Yb3+/Ln3+@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.
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. huili@hit.edu.cn.
Hui
H
Li
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. haosw@hit.edu.cn.
Shuwei
S
Hao
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. yangchh@hit.edu.cn.
Chunhui
C
Yang
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. chenguanying@hit.edu.cn.|Institute for Lasers, Photonics and Biophotonics, State University of New York at Buffalo, Buffalo, NY 14260, USA. chenguanying@hit.edu.cn.
Guanying
G
Chen
core/shell nanocrystals; liquid-solid-solution method; multicolor emissions; thermal decomposition