Single Er³⁺, Yb³⁺: KGd₃F₁₀ Nanoparticles for Nanothermometry

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Luminescence thermometry is a versatile optical non-contact thermometry method.
• Lanthanide-based nanothermometers utilize upconversion (UC) mechanisms for biological applications, converting near-infrared radiation to visible light.
• UC nanothermometers enable local temperature determination via spectroscopic investigation.

Purpose of the Study:

• To synthesize highly crystalline Er³⁺, Yb³⁺ co-doped KGd₃F₁₀ nanoparticles (NPs) for upconversion thermometry.
• To characterize the structure, morphology, and optical properties of the synthesized NPs.
• To evaluate the potential of these NPs as primary nanothermometers for biological applications.

Main Methods:

• EDTA-assisted hydrothermal synthesis of Er³⁺, Yb³⁺: KGd₃F₁₀ NPs.
• Characterization using transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and dynamic light scattering.
• Nonlinear spectroscopic studies and Luminescence Intensity Ratio (LIR) technique for thermometry evaluation.

Main Results:

• Synthesized highly crystalline Er³⁺, Yb³⁺: KGd₃F₁₀ NPs with intense green and red UC emissions.
• Demonstrated two- and three-photon UC processes under 980 and 1,550 nm excitation.
• Achieved a thermal sensitivity of 1.17% at the single NP level for dry NPs at 300 K, with potential NIR-II emission.

Conclusions:

• Er³⁺, Yb³⁺: KGd₃F₁₀ NPs are promising for upconversion thermometry.
• The developed nanothermometers are suitable for temperature sensing in the biological range.
• This work presents the first thermometry based on single KGd₃F₁₀ particles, with potential as biomarkers.