Colloidal metal particles as probes of nanoscale thermal transport in fluids

We investigate suspensions of 3-10 nm diameter Au, Pt, and AuPd nanoparticles as probes of thermal transport in fluids and determine approximate values for the thermal conductance G of the particle/fluid interfaces. Subpicosecond lambda=770 nm optical pulses from a Ti:sapphire mode-locked laser are used to heat the particles and interrogate the decay of their temperature through time-resolved changes in optical absorption. The thermal decay of alkanethiol-terminated Au nanoparticles in toluene is partially obscured by other effects; we set a lower limit G>20 MW m(-2)K(-1). The thermal decay of citrate-stabilized Pt nanoparticles in water gives Gapproximate to130 MW m(-2) K-1. AuPd alloy nanoparticles in toluene and stabilized by alkanethiol termination give Gapproximate to5 MW m(-2) K-1. The measured G are within a factor of 2 of theoretical estimates based on the diffuse-mismatch model.