Dynamics of Size-Selected Gold Nanoparticles Studied by Ultrafast Electron Nanocrystallography

TL;DR

This study uses ultrafast electron nanocrystallography to explore size-dependent surface melting, recrystallization, and phase transformations in gold nanoparticles, revealing detailed dynamics at sub-picosecond timescales.

Contribution

It provides new insights into the ultrafast structural dynamics and phase transitions of size-selected gold nanoparticles supported on molecular interfaces.

Findings

Size influences melting and recrystallization behavior.

Ultrafast photoinduced melting involves non-equilibrium electron-phonon processes.

Distinct structural pathways for melting and recrystallization were observed.

Abstract

We report the studies of ultrafast electron nanocrystallography on size-selected Au nanoparticles (2-20 nm) supported on a molecular interface. Reversible surface melting, melting, and recrystallization were investigated with dynamical full-profile radial distribution functions determined with sub-picosecond and picometer accuracies. In an ultrafast photoinduced melting, the nanoparticles are driven to a non-equilibrium transformation, characterized by the initial lattice deformations, nonequilibrium electron-phonon coupling, and upon melting, the collective bonding and debonding, transforming nanocrystals into shelled nanoliquids. The displasive structural excitation at premelting and the coherent transformation with crystal/liquid coexistence during photomelting differ from the reciprocal behavior of recrystallization, where a hot lattice forms from liquid and then thermally contracts. The degree of structural change and the thermodynamics of melting are found to depend on the size of nanoparticle.