The average values and standard errors of the thermal interface conductance G values were estimated by block averaging of the temperature profile. For each block, ∆T was estimated as the temperature difference between the outermost gold spatial bin and the innermost water spatial bin. To account for the possibility of thermal expansion of the gold, the gold size (diameter for AuNPs and thickness for planar slab) was estimated from the outermost gold spatial bin position (Table , Supporting Information). The corresponding G for the block was estimated according to Equation 1. Block sizes of 200 ps, 250 ps, 500 ps, and 750 ps were used for the block averages for the 3, 5, and 10 nm AuNPs and planar slab, respectively. In the poor wetting case, the block sizes were adjusted to 200 ps, 250 ps, 400 ps, and 300 ps for the 3, 5, and 10 nm AuNPs and planar slab, respectively. The gold temperature was examined using blocked standard error analysis with varying block sizes (Figure and Figure , Supporting Information) to confirm that these block sizes resulted in uncorrelated data for block averaging. The reported error in G values was taken as 1.96 times the standard error estimate (from block averaging) and thus represents an estimate of the 95% confidence interval.