Colloidal metal particles as probes of nanoscale thermal transport in fluids

Abstract

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 $\lambda =770\mathrm{}\mathrm{nm}$ 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 $G>\mathrm{}20{\mathrm{MW}\mathrm{m}}^{-2}{\mathrm{K}}^{-1}.$ The thermal decay of citrate-stabilized Pt nanoparticles in water gives $G\approx 130{\mathrm{MW}\mathrm{m}}^{-2}{\mathrm{K}}^{-1}.$ AuPd alloy nanoparticles in toluene and stabilized by alkanethiol termination give $G\approx 5{\mathrm{MW}\mathrm{m}}^{-2}{\mathrm{K}}^{-1}.$ The measured G are within a factor of 2 of theoretical estimates based on the diffuse-mismatch model.