Thermal stabilization of thin gold nanowires by surfactant-coating: a molecular dynamics study

TL;DR

This study uses molecular dynamics simulations to show that surfactant coatings can significantly stabilize thin gold nanowires against melting by suppressing surface atom mobility and thermal motions.

Contribution

It demonstrates that surfactant coatings can reverse melting point depression in gold nanowires through isotropic pressure effects, a novel insight into nanowire stabilization.

Findings

Surfactant coating raises melting temperature of nanowires.

Surface instability patterns dominate melting in coated nanowires.

Surfactants suppress large atomic motions, stabilizing nanowires.

Abstract

The thermal stabilization of thin gold nanowires with a diameter of about 2 nm by surfactants is investigated by means of classical molecular dynamics simulations. While the well-known melting point depression leads to a much lower melting of gold nanowires compared to bulk gold, coating the nanowires with surfactants can reverse this, given that the attractive interaction between surfactant molecules and gold atoms lies beyond a certain threshold. It is found that the melting process of coated nanowires is dominated by surface instability patterns, whereas the melting behaviour of gold nanowires in vacuum is dominated by the greater mobility of atoms with lower coordination numbers that are located at edges and corners. The suppression of the melting by surfactants is explained by the isotropic pressure acting on the gold surface (due to the attractive interaction) which successfully suppresses large-amplitude thermal motions of the gold atoms. (Note that this is a pre-peer-reviewed version which has been submitted to Nanoscale.)