Thulium doped LaF₃ for nanothermometry operating over 1000 nm

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Engineering

Background:

• Rare-earth luminescent nanoparticles are increasingly used as nanothermometers for minimally invasive thermal sensing in nanomedicine.
• Developing nanothermometers with high brightness and sensitivity, especially operating above 1000 nm, remains a significant challenge.

Purpose of the Study:

• This work investigates the potential of thulium (Tm3+) emissions around 1.23 and 1.47 μm for ratiometric thermometry.
• The study aims to utilize Tm3+ doped LaF3 nanoparticles for enhanced thermal sensing capabilities.

Main Methods:

• Exploration of Tm3+ emissions at 1.23 and 1.47 μm under 690 nm excitation.
• Analysis of the temperature dependence of the 1.23 μm emission band in Tm3+ doped LaF3 nanoparticles.
• Investigation of physical mechanisms including multiphonon decays and cross-relaxations.

Main Results:

• Demonstrated effective temperature dependence of the 1.23 μm emission band, not observable in other systems like NaNbO3:Tm.
• Achieved a high relative thermal sensitivity of 1.9% °C-1.
• Successfully applied the developed nanothermometers for ex vivo tissue property assessment via thermal relaxation dynamics.

Conclusions:

• Tm3+ doped LaF3 nanoparticles are effective for ratiometric thermometry, offering high sensitivity and brightness.
• The understanding of thermal dependence mechanisms provides a basis for further nanothermometer development.
• The nanothermometers show potential for practical applications in biological and medical thermal sensing.