Tuning the Properties of Colloidal Magnetic Particles for Thermometry on the Nanoscale

Accurate, local, remote, and real-time temperature measurements are essential for many technological applications. While conventional thermometry can accurately measure the temperature of a microscale spot on a surface, magnetic nanothermometry is being developed to measure temperature at comparable spatial resolution throughout a volume. However, commercially available nanomaterials display only modest magnetic thermosensitivity; this response must be strengthened to improve the signal-to-noise ratio as a prerequisite to practical volumetric nanothermometry. Here, we engineer solution-synthesized nanoparticles and measure their magnetization dependence on the temperature of their local environment. Modulation of composition, size, and structure allows for different magnetic transition temperature regimes and sensitivities to improve these nanothermometers’ performance. Over the range 100 K to 350 K, under an applied magnetic field of 0.01 T, these structurally complex samples show considerable temperature-dependent change to their magnetization. Results collected from X-ray scattering and diffraction, Raman spectroscopy, and high-resolution electron microscopies provide correlations between the nanoscale structure of these particles with their magnetic thermosensistivity.