Gold moves faster than platinum at the atomic scale (w/video)

(Nanowerk News) Researchers at the University of Antwerp, Belgium, the CIC biomaGUNE laboratory in San Sebastián, Spain and Thermo Fisher Scientific recently investigated the thermal stability of gold nanoparticles covered by a platinum shell (ACS Nano, "Thermal Activation of Gold Atom Diffusion in Au@Pt Nanorods").
Nanoparticles composed of two different metals in a core-shell configuration are of great interest since they combine the unique properties of each counterpart in one system.
For Au@Pt, it becomes possible to exploit the excellent optical properties of Au together with the outstanding catalytic properties of Pt, which is of interest for several photo-and electrocatalytic reactions.
The BioNanoplasmonics Lab at CIC biomaGUNE is one of the pioneers in the synthesis of metal nanoparticles, which can nowadays be performed with high control over morphology and composition. This is of great importance since the materials properties strongly depend on these parameters.
Unfortunately, the carefully designed properties of (bi)metallic nanpoparticles may significantly alter during actual applications. For example, complex changes in morphology and elemental distribution may occur at high temperature during catalysis and consequently, the activity will degrade.
To understand such processes, researchers of the electron microscopy group EMAT at the university of Antwerp investigated the 3D structure and composition of Au@Pt nanorods at different temperatures using a variety of advanced transmission electron microscopy techniques.
Surprisingly, they observed significant changes in morphology and elemental distribution for Au@Pt nanorods already at 200 °C, a temperature that is hundreds of degrees below the bulk melting temperatures of the individual elemental components.
To obtain a better understanding of the underlying processes, 3D reconstructions of the Au@Pt nanorods were used as input for molecular dynamics simulations. In this manner, it became clear that the structural transformations took place because the system aims to reach a thermodynamically favorable structure and such deformations largely depend on the morphology and coverage of the platinum shell around gold core.
Such insights are of great importance to control the desired structure-dependent functional properties of gold-platinum core-shell structures and optimize their design for several novel applications.
Source: University of Antwerpen
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