Concurrent quantification of magnetic nanoparticles temperature and relaxation time

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Magnetic nanoparticles (MNPs) offer insights into their microenvironment via harmonic spectrum analysis.
• Current methods struggle to accurately measure simultaneous changes in temperature and relaxation time.
• Existing scaling techniques for temperature or relaxation time are limited when both parameters vary.

Purpose of the Study:

• To develop a method for simultaneous estimation of temperature and relaxation time for MNPs.
• To overcome the limitations of previous scaling methods that could not handle simultaneous variations.
• To enhance the characterization of MNP microenvironments.

Main Methods:

• Expanded existing 1D scaling methods to a 2D approach analyzing magnetic field amplitude and frequency.
• Verified the 2D scaling method using a magnetic nanoparticle spectrometer with samples at varying temperatures and relaxation times.
• Conducted simulations to determine optimal nanoparticle sizes for the 2D scaling method.

Main Results:

• The 2D scaling method achieved high accuracy: 0.83% error for relaxation time and 1.03°C for temperature.
• Simultaneously measured MNP temperature and viscosity with low errors (1.03°C and 0.011 mPas).
• Simulations identified optimal core (16 nm) and hydrodynamic (23 nm) radii for monodisperse particles with Brownian relaxation.

Conclusions:

• The 2D scaling method enables simultaneous and accurate estimation of temperature and relaxation time.
• Optimizing particle size and utilizing harmonic ratios/phases can further improve measurement accuracy.
• This technique provides a more robust way to characterize MNP behavior in complex environments.