Anomalous Long-Range Attraction in Colloidal Binary Mixtures at Fluid–Fluid Interfaces

Zonglin Yi,To Ngai

doi:10.3390/colloids4030036

Abstract

The properties of binary colloidal systems have gained the interest of researchers because they have much richer structures than their one-component counterpart. Continuing efforts are being made on the theoretical side on binary colloidal systems, while many issues remained unsolved for the lack of solid experimental supports, especially for study in the field of two-dimensional (2D) binary colloids system. Oil–water interfaces can serve as a good stringent 2D confinement for colloidal particles and can avoid anomalous problems caused by the quasi-two-dimensional environment in previous experimental reports. In this work, we conduct experimental research of binary colloids system in an oil–water interface to revisit theoretical predication. We measure an ultra-long-range attraction and discuss the possible mechanism of this attraction by comparing the experimental result with existing model and theory. This study could contribute more understanding of the binary colloidal system in both experimental aspects and theoretical aspects.

Highlights

Colloidal particles have garnered considerable interest given their good performance in both fundamental study and application-related material study
We reported an experimental result of interactions between large particles in binary systems containing large and small particles at a stringent 2D environment at oil–water interface, which has not been reported before to our knowledge
An ultra-long-range attraction between large particles caused by introduction of small particles to system was measured

Summary

Introduction

Colloidal particles have garnered considerable interest given their good performance in both fundamental study and application-related material study. In terms of fundamental research, researchers have long used colloidal particles as an experimental model system to study phase transitions and dynamics in condensed matter physics since the 1940s, the time commercial latex became available. In comparison with atomic crystals where atoms interact through complex and predetermined potentials, colloidal particles can often be described by simpler interaction potentials, which can be more readily controlled at the particle level or via external forces. Their easy observability by conventional optical microscopy and an instrumentally detectable time duration make them an ideal model system to fundamentally study the self-organization phenomena [5]. Mixtures of binary species demonstrated richer phase behaviors and structures than a single-species system, such as the formation of superlattices [12,13,14]

Methods

Results

Conclusion