Colloidal Electrostatic Interactions Near a Conducting Surface

TL;DR

This paper investigates unexpected long-range attractions between like-charged colloidal spheres near a conducting surface, revealing how surface properties influence interparticle interactions in confined colloidal systems.

Contribution

It demonstrates that conducting surfaces suppress anomalous attractions, highlighting the role of surface conductivity in colloidal interactions near boundaries.

Findings

Conducting gold coatings eliminate the observed attractions.

Electrostatic repulsions can mask the attractions at low ionic strengths.

Surface conductivity influences colloidal pair potentials near boundaries.

Abstract

Charge-stabilized colloidal spheres dispersed in deionized water are supposed to repel each other. Instead, artifact-corrected video microscopy measurements reveal an anomalous long-ranged like-charge attraction in the interparticle pair potential when the spheres are confined to a layer by even a single charged glass surface. These attractions can be masked by electrostatic repulsions at low ionic strengths. Coating the bounding surfaces with a conducting gold layer suppresses the attraction. These observations suggest a possible mechanism for confinement-induced attractions.