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Shielding Upconversion by Surface Coating: A Study of the Emission Enhancement Factor
Tianying Sun1, Ronghua Ma2, Xvsheng Qiao3
1Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR, P. R. China.
Summary
Surface coating enhances upconversion luminescence in nanoparticles. However, this effect diminishes with lower Ytterbium doping and higher excitation power due to stepwise excitation and energy hopping mechanisms.
Area of Science:
- Materials Science
- Nanotechnology
- Luminescence
Background:
- Surface coating is crucial for improving upconversion luminescence by preventing surface quenching of luminescent cores.
- Lanthanide-doped nanoparticles, such as NaYF4:Yb/Er, are widely studied for their upconversion properties.
Purpose of the Study:
- To investigate the impact of surface coating on upconversion luminescence in NaYF4:Yb/Er nanoparticles.
- To explore the influence of Ytterbium (Yb3+) dopant concentration and excitation power on the coating's effectiveness.
Main Methods:
- Comparative study of NaYF4:Yb/Er nanoparticles and NaYF4:Yb/Er@NaYF4 core-shell nanoparticles.
- Systematic variation of Yb3+ dopant concentration and excitation power.
- Analysis of upconversion emission enhancement factors.
Main Results:
- Observed a decrease in emission enhancement with reduced Yb3+ concentration.
- Emission enhancement factor declined as excitation power increased.
- Mechanistic insights point to stepwise excitation and Yb3+ energy hopping as key factors.
Conclusions:
- Surface coating effectiveness in upconversion nanoparticles is dependent on dopant concentration and excitation power.
- Understanding these dependencies, driven by stepwise excitation and energy hopping, is vital for designing advanced core-shell nanoparticles.
- Findings contribute to the rational design of lanthanide-doped core-shell nanomaterials for diverse applications.
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