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In situ laser heating with transmission electron microscopy (ILH-TEM) is utilized as a neoteric method to probe the thermal behavior and stability of metal- (Pt, Au-) metal oxide (Fe3O4) heterodimer (HD) nanoparticles. Two different supporting membrane types are used for the laser heating: pure-carbon and silicon-nitride, requiring different amounts of laser power to induce morphological changes. Diffraction pattern analysis and scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) are utilized to analyze reduction of the iron oxide under laser heating, which has differing effects depending on the support film heating mode and the heterodimer particle. A unique wetting behavior of Pt and Au onto Fe3O4 is observed in both heterodimers of Au and Pt. However, this wetting behavior is found to be partially reversible only in the case of the Au-Fe3O4 HD system, whereas for the Pt-Fe3O4 HD system, this wetting process was found to be irreversible under the applied experimental conditions. This observation of a novel wetting behavior has future implications for understanding the performance of oxide supported metal nanoparticles in high temperature applications, such as catalysis. |
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