Recent multiple experiments have shown that the local temperature of magnetic nanoparticles during induction heating may be higher than that in a non-magnetic environment. Although this nanoscale hot spot effect is particularly attractive in biomedical and catalytic fields, its existence still remains a subject of scientific controversy. Therefore, we simultaneously measured the internal temperatures of magnetic nanoparticles and their solid support materials during the induction heating process. The support was a dry, non-magnetic and non-conductive porous powder used to separate the magnetic nanoparticles. The temperature was measured using in-situ synchrotron X-ray diffraction, utilizing the shift in X-ray diffraction peak positions due to the thermal expansion of the material. At an atomic Kelvin temperature resolution and a 0.1-second time resolution, we found that there was no measurable temperature difference between the magnetic nanoparticles and the support, meaning no significant hot spot, which is consistent with existing theories. We obtained the same results for three different combinations of magnetic nanoparticles and supports. We encourage further integration of X-ray diffraction thermal measurements with other local temperature measurement techniques to clarify whether the local temperature increase observed in previous experimental studies may be mistakenly attributed to non-thermal effects causing the increase in temperature. This study was published in ACS Nano under the title "Sub-Kelvin Resolution X-ray Diffraction Thermometry Defies the Existence of Nanoscale Hotspots in Induction Heated Magnetic Nanoparticles".
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DOI: 10.1021/acsnano.5c10818