Deformation, alignment and anisotropic optical properties of gold nanoparticles embedded in silica

Gold nanoparticles resist deformation by swift heavy ion irradiation when embedded in a crystalline matrix

“…For example, one study found that particles smaller than 5 and larger than 50 nm do not deform [20] or that a deformation threshold of 7 nm exists [21]; both studies concerned room-temperature irradiation. Our own studies on gold in silica irradiated at liquid nitrogen temperature (the same temperature used in the present experiment) showed clear deformation of 4 nm particles in core-shell colloid [2] as well as 6 nm particles in a gold-silica composite [17]. The particle size distribution in the present experiment (2-12 nm) falls squarely in the range of deformable particles, were they embedded in silica.…”

“…The deformation of gold nanoparticles under swift heavy ion irradiation has been argued to be a consequence of the anisotropic growth of the amorphous matrix [2,7,17,18], a phenomenon known as hammering [6,7]. The hammering effect creates large compressive stresses in the plane perpendicular to the ion beam, and it is not surprising that the gold particles would relax these stresses by expanding in the direction of the ion beam, perpendicular to the applied stress.…”

Zn nanoparticles irradiated with swift heavy ions at low fluences: Optically-detected shape elongation induced by nonoverlapping ion tracks

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Here we summarize early discussion of the elongation mechanism, while any decisive mechanisms have yet to be proposed. D'Orleans et al 7 pointed out that the lattice temperature of smaller NPs increases to a greater extent based on the thermal spike model.…”

Elongation of gold nanoparticles in silica glass by irradiation with swift heavy ions

“…Anisotropic metal colloids can be fabricated controllably by irradiating colloidal particles, each consisting of a Au core surrounded by a silica shell, with ions of megaelectron volt ͑MeV͒ energies at 77 K. 5,6 We hypothesized that optical losses could be reduced by fabricating an array of Au nanorods with their long axes aligned parallel to the direction of light propagation. Recently, fabrication by using ion beams was examined as a means of controlling the size and spatial distribution of Au nanorods.…”