The Bhattacharyya coefficient (BC) quantifying the level of overlap between the gold and water vibrational density of states was computed using numerical estimation of the following integral: BC = VDOS Au (ω) × VDOS W ater (ω)dω , (11) where ω is the vibrational frequency and VDOS Au (ω) and VDOS W ater (ω) are the vibrational density of states (VDOS) of gold and water, respectively. The integral was taken on the entire range of frequencies over which the VDOS was computed (0-32 THz).