Broad-range flow velocimetry enabled by pulse-width-dependent luminescence of core-multishell upconversion nanoprobes

Area of Science:

• Nanotechnology
• Optical Sensing
• Materials Science

Background:

• Lanthanide-doped upconversion nanoparticles (UCNPs) possess unique optical properties valuable for sensing.
• UCNP-based probes are promising for microfluidic flow velocity calibration.
• Developing UCNPs with efficient luminescence modulation for wide-range flow velocimetry is challenging.

Purpose of the Study:

• To engineer a core-multishell UCNP probe for advanced flow velocimetry.
• To achieve real-time dynamic optical modulation using dual emissions.
• To establish a quantitative emission ratio-velocity mapping for precise calibration.

Main Methods:

• Fabrication of a core-multishell UCNP probe: NaGdF4:Tm3+/Yb3+@NaGdF4@NaGdF4:Eu3+@NaYF4.
• Utilizing spatially isolated Tm3+ (blue) and Eu3+ (red) activators for dual emissions.
• Correlating the intensity ratio of dual emissions with laser pulse width for optical modulation.

Main Results:

• The engineered UCNP probe demonstrated laser pulse-width-dependent dual emission intensity ratios.
• A quantitative relationship between fluid velocity and emission ratio was established.
• The method enabled precise calibration and significantly broadened the measurable velocity range.

Conclusions:

• The developed core-multishell UCNP probe enables precise, broad-range flow velocimetry through optical modulation.
• This sensing paradigm advances fluid velocimetry and highlights the versatility of UCNPs in photonic technologies.