Heterogeneous and anisotropic dynamics of a 2D gel

TL;DR

This study uses X-ray Photon Correlation Spectroscopy to reveal that a 2D gold nanoparticle gel exhibits anisotropic, heterogeneous, and super-diffusive nanoscale dynamics, with multiple distinct time scales.

Contribution

It provides the first experimental measurement of the fourth order correlation function in a 2D gel, revealing complex anisotropic and heterogeneous dynamics.

Findings

Dynamics are anisotropic and heterogeneous.

Super-diffusive behavior observed at the nanoscale.

Multiple time scales identified for different motion regimes.

Abstract

We report X-ray Photon Correlation Spectroscopy (XPCS) results on a bidimensional (2D) gel formed by a Langmuir monolayer of gold nanoparticles. The system allows an experimental determination of the fourth order time correlation function which is compared to the usual second order correlation functions and to the mechanical response measured on macroscopic scale. The observed dynamics is anisotropic, heterogeneous and super-diffusive on the nanoscale. Different time scales, associated with fast heterogeneous dynamics inside 2D cages and slower motion of larger parts of the film, can be identified from the correlation functions.