Advancing neodymium single-band nanothermometry

Area of Science:

• Materials Science
• Biomedical Engineering
• Nanotechnology

Background:

• Near-infrared (NIR) emitting contrast agents with integrated optical temperature sensing are crucial for subcutaneous visualization and thermodynamic property measurement.
• Developing multifunctional nanoprobes requires small, uniformly sized, and engineerable nanoparticles.

Purpose of the Study:

• To explore the potential of Neodymium (Nd³⁺) doped Lithium Lutetium Tetrafluoride rare-earth nanoparticles (RENPs) as NIR photoluminescent nanothermometers.
• To evaluate the suitability of these RENPs for biomedical applications requiring precise temperature sensing.

Main Methods:

• Synthesized Nd³⁺ doped LiLuF₄ RENPs with controlled size distribution.
• Investigated the Stark structure of Nd³⁺ optical transitions (⁴F₃/₂→⁴I<0xE2><0x82><0x99>/₂, ⁴I₁₁/₂, ⁴I₁₃/₂) for single-band NIR nanothermometry.
• Defined and compared thermometric parameters for Nd³⁺ emissions at 880, 1050, and 1320 nm.
• Performed transient temperature measurements through tissue at varying depths.

Main Results:

• The LiLuF₄ host enabled observation of fine Stark structure for Nd³⁺ emissions.
• The thermometric parameter for the 1050 nm emission exhibited high temperature sensitivity (∼0.49% °C⁻¹) and low uncertainty (0.3 °C).
• RENPs successfully assessed fast temperature changes at 3 mm tissue depth and slower changes at greater depths.

Conclusions:

• Nd³⁺ doped LiLuF₄ RENPs offer significant improvements for Nd³⁺-based single-band photoluminescence nanothermometry.
• These RENPs are suitable for subcutaneous visualization and thermodynamic measurements in biomedical applications.
• Potential for integration into advanced multifunctional theranostic nanostructures exists.