Acoustic vibrations in nanosized gold-shell particles

Abstract

We demonstrate and discuss acoustic vibrations in spherical shell particles. The particles consist of 38-nm-thick gold shells, sandwiched between an inner silica core of 456 nm in diameter and an outer silica shell of 10 nm in thickness. Employing standard and asynchronous optical sampling (ASOPS) ultrafast pump-probe experiments, we excite acoustic vibrations of the shells and detect the oscillations via modulations of the optical reflectivity. Two kinds of vibrations were excited and observed. One oscillation with 400 ps period corresponds to the prediction of Lamb theory for breathing modes of free thin gold shells. The other oscillation with 25ps-period corresponds to resonant longitudinal thickness vibrations of the gold shells. At later times, echoes appear corresponding to the travel time through the silica core.

Optical Studies of Dynamics in Noble Metal Nanostructures

“…The samples have been produced both by solution phase chemistry, and by lithographic techniques. The solution phase studies include Au and Ag nanorods, ,, Ag triangles, − Ag nanocubes, core−shell particles with both metal and dielectric cores, , hollow cubic shaped particles, Au bipyramids, and nanowires of various metals. − The lithographically defined particles that have been studied include Au and Ag nanopyramids produced by nanosphere lithography, − and nanocubes and nanodisks made by electron-beam lithography. , …”

Filtering of Elastic Waves by Opal-Based Hypersonic Crystal

“…As HC we have chosen synthetic opal films which have been widely used as photonic structures and nowadays are known as the technologically most easily accessible objects for studying the properties of 3D HCs. ,,− We studied the coherent elastic vibrations in silica opal films consisting of seven monolayers of close-packed in fcc lattice SiO 2 spheres with diameters D ≈ 350 nm deposited on silica substrate. A scanning electron microscope (SEM) image of a studied film is shown in Figure .…”

“…Details of the film growth procedure can be found elsewhere . The experimental setup was based on the femtosecond pump−probe optical technique developed earlier for studying the coherent vibrations in opal films and colloidal crystals. ,− , Coherent elastic vibrations were excited by pulsed optical pump excitation (wavelength 800 nm) of a thin Al layer deposited on the surface of the opal film. For detecting the temporal evolution of the coherent vibrations the reflectivity of the probe beam incident from the back (substrate) side of the film was measured as function of the delay t between the pump and probe pulses.…”