Engineering efficient upconverting nanothermometers using Eu³⁺ ions

Area of Science:

• Materials Science
• Nanotechnology
• Optical Physics

Background:

• Upconversion nanothermometry enables optical temperature sensing in microscale environments.
• Existing methods face limitations in spectral range and heat transfer.
• Lanthanide ion luminescence offers potential for enhanced sensing capabilities.

Purpose of the Study:

• To develop a novel ratiometric upconversion nanothermometer using lanthanide ions.
• To investigate the temperature sensitivity of Eu3+ luminescence activated via Yb3+/Tm3+ co-sensitization.
• To create nanoparticles for precise temperature measurements in microfluidic and microelectronic applications.

Main Methods:

• Synthesized tridoped SrF2:Yb3+,Tm3+,Eu3+ nanoparticles (17 nm average size).
• Utilized near-infrared (NIR) excitation (980 nm) with Yb3+ as a sensitizer.
• Employed a ratiometric strategy based on Eu3+ ion luminescence for temperature readout.

Main Results:

• Achieved a relative thermal sensitivity of 1.1% K-1 at 25.0 °C.
• Demonstrated effective energy transfer from Yb3+ to Tm3+, then to Eu3+.
• Showcased luminescence sensitive to temperature changes.

Conclusions:

• The developed nanoparticles offer high thermal sensitivity for upconversion nanothermometry.
• This approach enables the use of lanthanide ions not directly excitable by NIR light.
• The design provides a stable readout, addressing spectral gaps in current nanothermometry.