Instantaneous spatial temperature profiles for gold and water were computed separately with a spatial binning of width ∼ 1 Å (radial shells for AuNPs and rectangular blocks along the z-direction for the planar slab) every 1 ps during non-equilibrium steady state simulations. Subsequently, bins with < 100 atoms at any time point were dropped from the profile to reduce errors in the temperature estimation. The steady-state temperature profiles were then estimated by time averaging the instantaneous profiles within the designated steady-state portions of each trajectory.