Downshifting Luminescence Rare-Earth Nanoparticles for High-Resolution In Vivo Imaging at NIR IIb/c Window

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Imaging

Background:

• Rare-earth nanoparticles (RENPs) are promising for NIR-IIb/c bioimaging (1600-2000 nm) due to deep tissue penetration and high resolution.
• Current challenges include achieving high brightness and precise emission control in RENPs.

Purpose of the Study:

• To rationally design and synthesize highly Tm3+-doped core@shell@shell@shell RENPs with a cascade Nd3+-sensitized energy transfer architecture.
• To optimize RENPs for enhanced quantum yield (QY) and emission efficiency in the NIR-IIb/c window.

Main Methods:

• Fabrication of α-phase core@shell@shell@shell RENPs with controlled doping of Tm3+ and Nd3+.
• Characterization of QY under different excitation wavelengths (980 nm and 808 nm).
• Investigation of the effect of Yb3+ shell thickness on emission efficiency for varying Tm3+ doping levels.

Main Results:

• Optimized RENPs achieved a QY of ~23.5% (980 nm excitation) and ~11.3% (808 nm excitation) in the NIR-IIb/c region.
• Emission efficiency in highly Tm3+-doped RENPs (≥8%) strongly correlated with Yb3+ shell thickness.
• Low Tm3+ doping levels (≤4%) showed minimal sensitivity to shell thickness.

Conclusions:

• Engineered RENPs demonstrate excellent biocompatibility and enable high-contrast in vivo deep-tissue vascular imaging.
• The developed cascade energy transfer architecture offers a promising strategy for next-generation RENPs.
• These RENPs are tailored for high-performance, noninvasive NIR-IIb/c bioimaging applications.