Damping of the acoustic vibrations of a suspended gold nanowire in air and water environments

Abstract

The lifetimes of the acoustic vibrations of metal nanostructures depend sensitively on the properties of the environment, such as the acoustic impedance and viscosity. In order to accurately study these effects, they have to be separated from the damping processes that are inherent to the nanostructure. Here we show that this can be done experimentally by investigating individual gold nanowires suspended over a trench in air and liquid environments. The experiments were done by ultrafast pump-probe microscopy, recording transient absorption traces at the same point on the nanowire in both environments. These first experiments were performed with water, and the measured vibrational quality factors due to the presence of water were compared to continuum mechanics calculations for a cylinder in a homogeneous environment. Good agreement was found between the experimental quality factors and the calculated values. The continuum mechanics analysis shows that damping is dominated by the acoustic impedance of the solvent rather than by its viscosity for the nanowires in the present experiments. This experimental technique opens up the possibility of studying the effect of viscosity on the high frequency vibrational motions of nanostructures for a variety of liquids.

Acoustic Vibrations of Au Nano-Bipyramids and their Modification under Ag Deposition: a Perspective for the Development of Nanobalances

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“…20,21 These studies addressed different kinds of high-interest nanomaterials such as nanotubes, 3 quantum dots, 1,2 nano-wires, 4 and noble metal nanoparticles. 5À21 Due to tremendous progress in metallic colloidal chemistry synthesis, 22,23 a wide vari-ety of shapes have been investigated: spheres, 5,6,13,18 rods, 11,12 prisms and triangles, 7,10,15,16 dimers, 17 cubes, 19 and bipyramids.…”

Size and nanocrystallinity controlled gold nanocrystals: synthesis, electronic and mechanical properties

“…6,[22][23][24][25]38,[43][44][45][46][47][48] These lattice vibrations can be monitored either in the frequency domain (using low-frequency Raman spectroscopy), allowing the observation of the NP quadrupolar vibration modes, or in the time domain (through pump-probe spectroscopy), enabling the investigation of the NP radial breathing modes (RBMs). 26,44,[49][50][51] How these ultrafast relaxation processes in metal NPs are affected by nanocrystallinity is still a matter of debate.…”

Spatiotemporal Imaging of the Acoustic Field Emitted by a Single Copper Nanowire

“…Because of the electrons fast diffusion, this ultrafast heating is not confined to the surface of the nano-object, the whole width of the nanowire subsequently undergoes periodic radial contrac- tions and expansions. These isotropic volume oscillations correspond to the fundamental breathing mode of the nanowire [24,26]. These periodic lattice oscillations induce a modulation of the metal refractive index, which shows up by a periodic variation of the relative probe reflectivity ∆R/R (Figure 2b).…”