Temperature Measurement Based on Electron Paramagnetic Resonance of Magnetic Nanoparticles

Magnetic nanoparticles (MNPs) have significant temperature-to-magnetization transition effect at nanoscale. Yet temperature measurement based on MNPs is currently seriously interfered by their on-site concentration. By utilizing the electron paramagnetic resonance (EPR), we report a highly sensitive temperature measurement approach independent of concentration. MNP’s temperature will affect the anisotropic field and thus affecting the resonance magnetic field and g-value. Therefore, g-value can be used to characterize the temperature of MNP. Experiments show that g-value is independent of MNP’s concentration. The influence of particle size and the data analysis method on temperature estimation are also studied. Finally, the optimal temperature sensitivity is achieved with 15-nm MNPs, while Gaussian smoothing method allows an optimal accuracy at Fe concentration of 5 mg mL $^{-1}$ with a root mean squared error of 0.07 K.