Engineering Bright and Mechanosensitive Alkaline-Earth Rare-Earth Upconverting Nanoparticles

Area of Science:

• Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Upconverting nanoparticles (UCNPs) are promising for nanoscale mechanical force sensing.
• A key challenge is balancing high mechanical responsivity with bright optical emission.

Purpose of the Study:

• To develop and characterize UCNPs for sensitive nanometer-scale mechanical force detection.
• To optimize UCNP composition and structure for enhanced mechano-sensing performance.

Main Methods:

• Synthesis and optical spectroscopy of UCNPs using a diamond anvil cell.
• Analysis of ratiometric emission changes under applied pressure.
• Determination of noise equivalent sensitivity using single-particle brightness measurements.

Main Results:

• Five types of UCNPs, including cubic NaYF4 and alkaline-earth hosts (CaLuF, SrLuF, SrYbF, BaLuF), were synthesized and tested.
• SrYb0.72Er0.28F@SrLuF particles demonstrated a strong ratiometric emission change and bright luminescence under pressure.
• An optimal noise equivalent sensitivity of 0.26 ± 0.04 GPa/√Hz was achieved.

Conclusions:

• Developed UCNPs exhibit bright emission and high mechanical responsivity for nanometer-scale force sensing.
• Optimized SrYb0.72Er0.28F@SrLuF particles show excellent noise equivalent sensitivity.
• These UCNPs offer a robust platform for advanced mechano-sensing applications.