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Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications
Published on: November 10, 2017
Direct imaging the upconversion nanocrystal core/shell structure at the subnanometer level: shell thickness
Fan Zhang1, Renchao Che, Xiaomin Li
1Department of Chemistry, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, P. R. China. zhang_fan@fudan.edu.cn
Nano Letters
|May 2, 2012
Summary
Researchers developed a method to precisely control the shell thickness of upconversion nanoparticles. This control establishes a direct link between shell thickness and enhanced optical properties, improving their use in bioimaging and lasers.
Area of Science:
- Materials Science
- Nanotechnology
- Optics
Background:
- Lanthanide-doped upconversion nanoparticles (UCNPs) are promising for lasers, displays, solar cells, and bioimaging.
- Epitaxial shells on UCNPs can enhance emission, but the link between shell thickness and optical properties is unclear.
Purpose of the Study:
- To demonstrate a reproducible method for growing hexagonal NaGdF(4) shells with monolayer thickness control on NaYF(4):Yb,Er nanocrystals.
- To establish a direct correlation between shell thickness and the optical properties of core/shell UCNPs.
Main Methods:
- Epitaxial growth of hexagonal NaGdF(4) shells on NaYF(4):Yb,Er nanocrystal cores with monolayer control.
- Cryo-transmission electron microscopy (cryo-TEM) and electron energy loss spectroscopy (EELS) for subnanometer imaging.
- High-angle annular dark-field (HAADF) imaging at low temperatures (96 K).
Main Results:
- Direct subnanometer imaging of NaYF(4):Yb,Er@NaGdF(4) core/shell structures was achieved for the first time.
- A strong linear relationship was established between NaGdF(4) shell thickness and optical response.
- Passivation of surface defects by shell growth enhanced UCNP emission intensity and lifetime.
Conclusions:
- The study presents a novel method for precise shell thickness control in UCNPs.
- Established a direct link between shell thickness and enhanced optical properties, crucial for UCNP applications.
- Demonstrated improved UCNP performance and water-resistance due to defect passivation.
