Experimental observation of thermoplasmonic heat transfer at the nanoscale by polymerization. A step towards nanoscale heat sources.

The thermoplasmonic effect, arising from the relaxation of a metal nanostructure excited at plasmon resonance, has garnered significant interest in recent years. While this effect has been extensively studied across various spatial and temporal scales, there is currently no experimental technique for investigating the spatial distribution of heat exchange at the nanoscale. In this paper, we introduce a chemical approach to map the temperature distribution around nanoparticles. Formulations that crosslink at specific temperatures are placed in contact with gold nanotriangles and irradiated under controlled power and polarization conditions. At moderate power, the polymerized regions, corresponding to the zones of maximum field, exhibit local temperatures exceeding the polymerization temperature. At higher power, anisotropic melting of the gold within the gold nanotriangles was observed. This new methodology reveals that, contrary to common assumptions, significant heat exchange occurs between the nanoparticle and the surrounding medium before temperature homogenization within the nanoparticle. We have thus demonstrated the potential to generate nanoscale heat sources, representing a major advance on a fundamental level and opening up numerous new prospects in nanofabrication.