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 $\ensuremath{\lambda}=770\mathrm{nm}$ 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 $G>20\phantom{\rule{0ex}{0ex}}{\mathrm{MW}\mathrm{m}}^{\ensuremath{-}2}{\mathrm{K}}^{\ensuremath{-}1}.$ The thermal decay of citrate-stabilized Pt nanoparticles in water gives $G\ensuremath{\approx}130{\mathrm{MW}\mathrm{m}}^{\ensuremath{-}2}\phantom{\rule{0ex}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}.$ AuPd alloy nanoparticles in toluene and stabilized by alkanethiol termination give $G\ensuremath{\approx}5{\mathrm{MW}\mathrm{m}}^{\ensuremath{-}2}\phantom{\rule{0ex}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}.$ The measured G are within a factor of 2 of theoretical estimates based on the diffuse-mismatch model.