Tracking Photothermal Heat Generation in ITO Nanocrystals and Its Dissipation to Their Surrounding Environment.

Plasmonic metal oxide nanocrystals can readily transduce infrared light into heat for applications in catalysis, therapeutics, and soft robotics. Here, we investigate photothermal pathways in oleate-capped tin-doped indium oxide (ITO) nanocrystals dispersed in toluene, mapping heat transfer dynamics from the ITO lattice to its surface and surrounding solvent. Using rhodamine B dyes adhered to nanocrystal surfaces and toluene as temperature probes, we track photothermal heat dissipation via transient absorption spectroscopy. We find heat transfer from ITO nanocrystals to surface-adsorbed molecules unfolds over tens of picoseconds, followed by heat dissipation into the surrounding solvent over hundreds of picoseconds. We have developed a theoretical model that quantitatively reproduces these kinetics and identifies nanocrystal surface-to-solvent heat transfer as the primary bottleneck in heat dissipation. These insights advance our understanding of nanoscale heat transport involving ITO nanocrystals and offer insights into how to design these materials for heat-driven applications.