Local photo-mechanical stiffness revealed in gold nanoparticles supracrystals by ultrafast small-angle electron diffraction

Abstract

We demonstrate that highly-ordered two-dimensional crystals of ligand-capped gold nanoparticles display a local photo-mechanical stiffness as high as that of solids such as graphite. In out-of equilibrium electron diffraction experiments, a strong temperature jump is induced in a thin film with a femtosecond laser pulse. The initial electronic excitation transfers energy to the underlying structural degrees of freedom, with a rate generally proportional to the stiffness of the material. With femtosecond small-angle electron diffraction, we observe the temporal evolution of the diffraction feature associated to the nearest-neighbor nanoparticle distance. The Debye-Waller decay for the octanethiol-capped nanoparticles supracrystal, in particular, is found to be unexpectedly fast, almost as fast as the stiffest solid known and observed by the same technique, i.e. graphite. Our observations unravel that local stiffness in a dense supramolecular assembly can be created by Van der Waals interactions up to a level comparable to crystalline systems characterized by covalent bonding.

References in corpus (10)

• Disentangling the electronic and phononic glue in a high-Tc superconductor
• Coherent and incoherent electron-phonon coupling in graphite observed with radio-frequency compressed ultrafast electron diffraction
• Direct observation of optically induced transient structures in graphite using ultrafast electron crystallography
• Snapshots of the retarded interaction of charge carriers with ultrafast fluctuations in cuprates
• X-ray cross-correlation analysis and local symmetries of disordered systems. I. General theory
• Direct Role of Structural Dynamics in Electron-Lattice Coupling of Superconducting Cuprates
• X-ray cross-correlation analysis applied to disordered two-dimensional systems
• Order/disorder dynamics in a dodecanethiol-capped gold nanoparticles supracrystal by small-angle ultrafast electron diffraction
• Evidence for a Peierls phase-transition in a three-dimensional multiple charge-density waves solid
• The role of the coherence in the cross-correlation analysis of diffraction patterns from two-dimensional dense mono-disperse systems