Geometry scaling of thermal boundary resistance in plasmonic nanostructures

Heat exchange between metal nanoparticles and their surrounding liquid plays a central role in thermoplasmonics, photonics, and nanoscale sensing. Yet it remains difficult to predict how particle shape influences interfacial thermal resistance. Here we introduce a geometry-driven scaling theory supported by experiments that identifies shape as the primary determinant of interfacial resistance and demonstrates that this resistance scales linearly with the number of nanoscale heat sources within a given fluid volume. Using a reduced single-time-constant description of thermal relaxation, time-domain measurements yield volume-normalised interfacial resistances independent of the surrounding fluid pathway. When expressed through appropriate geometric normalisation, these resistances fall onto a master scaling trend across nano stars, spheres, and rods. The resulting scaling law, R_int,vol (A_NP/V_NP)/R_K0 plotted against the geometry factor D/L + α (h_spike/r_tip) unifies the structures of these different shapes by linking their interfacial thermal behaviour to a single dimensionless geometry factor. This formulation shows that geometry sets the governing law for interfacial heat transport at the nanoscale, offering a compact design principle for engineering heat flow in a wide range of nanostructured systems.