Nanoparticle Taylor dispersion near charged surfaces with an open boundary

TL;DR

This study investigates how electrostatic interactions and absorption influence the dispersion of charged nanoparticles near charged surfaces in shear flows, revealing a significant reduction in spreading due to boundary effects at the nanoscale.

Contribution

It provides experimental insights into nanoparticle dispersion near charged boundaries, highlighting the impact of electrostatic repulsion and absorption on particle distribution and spreading.

Findings

Electrostatic repulsion and absorption significantly alter particle distribution.

A ten-fold reduction in dispersion dynamics compared to non-interacting particles.

Deviations from Gibbs-Boltzmann distribution at the nanoscale.

Abstract

The dispersive spreading of microscopic particles in shear flows is influenced both by advection and thermal motion. At the nanoscale, interactions between such particles and their confining boundaries become unavoidable. We address the roles of electrostatic repulsion and absorption on the spatial distribution and dispersion of charged nanoparticles in near-surface shear flows, observed under evanescent illumination. The electrostatic repulsion between particles and the lower charged surface is tuned by varying electrolyte concentrations. Particles leaving the field of vision can be neglected from further analysis, such that the experimental ensemble is equivalent to that of Taylor dispersion with absorption. These two ingredients modify the particle distribution, deviating strongly from the Gibbs-Boltzmann one at the nanoscale studied here. The overall effect is to restrain the accessible space available to particles, leading to a striking, ten-fold reduction in the spreading dynamics as compared to the non-interacting case.