The thermal transport properties of surface-functionalized gold nanorods in aqueous solution are investigated with transient absorption, following femtosecond pumping of the longitudinal localized surface plasmons. The thermal conductivities and heat capacities of surfactant and polymer coating layers are extracted from transient absorption; thicknesses of the layers are measured by dynamic light scattering. The rate of change of the absorption of gold nanorods in aqueous solution varies with the probe laser wavelength due to the shift in the plasmon resonance created by heating of media surrounding the particles. The measurements of the cooling dynamics of gold nanorods are optimized by pumping and probing at the absorption peak of the sample. The heat capacity of the surfactant cetyltrimethylammonium bromide (CTAB) layer is ~2.0 J cm-3 K-1; the thermal conductivity of the CTAB layer drops from 0.24 W m-1 K-1 to 0.18 W m-1 K-1 at solution concentrations above the CTAB critical micelle concentration. Layer-by-layer polyelectrolyte coatings using poly(acrylic acid) (PAA) and polyallyamine hydrochloride (PAH) increase the thermal conductivity and heat capacity of the surface layer; greater water penetration into PAH-terminated surface layers have increased the thickness, thermal conductivity, and heat capacity relative to PAA-terminated layers.

Ultrafast thermal analysis of surface functionalized gold nanorods in aqueous solution

245th National Meeting (2013)

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