Impact of supporting nanometric membranes on the thermo-optical dynamics of individual plasmonic nanodisks.

The thermal dynamics and transient optical response of individual gold nanodisks supported on thin silicon nitride membranes were investigated using optical time-resolved pump-probe spectroscopy and finite-element modeling. The effect of reducing the membrane thickness from 50 nm to 15 nm on the nanodisk thermal dynamics was explored. A significant deceleration of the nanodisk cooling kinetics was observed, and linked to a quasi-two-dimensional heat diffusion process within the 15 nm thick membrane, without detectable modification of its thermal conductivity.

Cooling Dynamics of Individual Gold Nanodisks Deposited on Thick Substrates and Nanometric Membranes.

The cooling dynamics of individual gold nanodisks synthesized using colloidal chemistry and deposited on solid substrates with different compositions and thicknesses were investigated using optical time-resolved spectroscopy and finite-element modeling. Experiments demonstrate a strong substrate-dependence of these cooling dynamics, which require the combination of heat transfer at the nanodisk/substrate interface and heat diffusion in the substrate. In the case of nanodisks deposited on a thick sapphire substrate, the dynamics are found to be mostly limited by the thermal resistance of the gold/sapphire interface, for which a value similar to that obtained in the context of previous experiments on sapphire-supported single gold nanodisks produced by electron beam lithography is deduced.

Ultrafast nano generation of acoustic waves in water via a single carbon nanotube.

Generation of ultra high frequency acoustic waves in water is key to nano resolution sensing, acoustic imaging and theranostics. In this context water immersed carbon nanotubes (CNTs) may act as an ideal optoacoustic source, due to their nanometric radial dimensions, peculiar thermal properties and broad band optical absorption. The generation mechanism of acoustic waves in water, upon excitation of both a single-wall (SW) and a multi-wall (MW) CNT with laser pulses of temporal width ranging from 5 ns down to ps, is theoretically investigated via a multiscale approach.

Versatile template-directed synthesis of gold nanocages with a predefined number of windows.

Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures.

Spin stress contribution to the lattice dynamics of FePt.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments.