where q r is the radial heat rate and T (r i ) is the temperature of the spherical shell at radius r i . This model assumes thermal resistance is additive for a series of concentric spherical shells, each with a well-defined average temperature, surface area, and a constant heat rate that traverses all of the shells. For the nanoparticles, this is essential as the interface is a broad region that extends outward from the metal surface by roughly 10 Å. Estimating interfacial conductance between a nanoparticle and solvent using a series approximation for the Kapitza resistance (Eq. ( )). The number of spherical shells contributing to interfacial resistance can be varied easily. Top: a thin interfacial region comprising a radius of 17.75 (inside the gold particle) to 24.25 Å (just outside the first solvation shell). Bottom: a thicker interfacial region ending at 26.25 Å. The advantage of using Kaptiza resistance is that the width of the interfacial region can be used as a convergence parameter, which is not possible when estimating temperature drops from solid and liquid temperatures projected onto a single interface, e.g. Eq. ( ). 11