Far-field optical nanothermometry using individual sub-50 nm upconverting nanoparticles

Area of Science:

• Nanotechnology
• Optical Physics
• Materials Science

Background:

• Accurate temperature measurement at the nanoscale is crucial for understanding and controlling processes in various fields.
• Conventional thermometry methods struggle with the spatial resolution required for individual nanoparticles.
• Rare-earth-doped nanoparticles offer unique optical properties suitable for sensing applications.

Purpose of the Study:

• To demonstrate far-field optical thermometry for individual, sub-50 nm nanoparticles.
• To characterize the temperature-dependent luminescence response of these nanoparticles.
• To assess the applicability of standard thermometry models and particle-to-particle uniformity.

Main Methods:

• Utilized far-field optical imaging to identify individual sodium yttrium fluoride (NaYF4) nanoparticles doped with erbium (Er3+) and ytterbium (Yb3+).
• Confirmed particle identification and dimensions using scanning electron microscopy (SEM).
• Characterized the luminescence thermometry response of single nanoparticles over a temperature range of 300 K to 400 K.

Main Results:

• Successfully identified and characterized individual NaYF4 nanoparticles as small as 20 × 20 × 40 nm(3).
• Demonstrated that a standard Arrhenius model accurately describes the thermometry response for these sub-50 nm particles.
• Observed good particle-to-particle uniformity, with response coefficients showing standard deviations below 5%.

Conclusions:

• Far-field optical thermometry is effective for individual nanoscale particles.
• The technique achieves spatial resolution on the order of 50 nm, surpassing the diffraction limit.
• This method holds significant potential for fundamental thermal measurements and nanoscale metrology in industrial applications.