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Particles at Interfaces

Interest in understanding the behavior of colloidal particles near interfaces has grown in recent years. Among motivations for such studies is the attraction of colloids to interfaces, which is of considerable importance for many applications such as foam and emulsion stabilization, oil recovery, and self-assembly processes. Analogous to surfactants, colloidal particles are surface-active materials as they can spontaneously accumulate at the fluid interfaces, either liquid-vapor or liquid-liquid, a behavior first reported by Ramsden at the beginning of the last century. This phenomenon was further explored by Pickering after whom solid-stabilized emulsions are named, so-called Pickering Emulsions. Despite their surface activity, colloidal particles with homogeneous chemical composition and surface properties are not amphiphilic in nature. In contrast to homogeneous particles with uniform wettability, Janus particles with anisotropic surface wettability, described by de Gennes on the occasion of the 1991 noble prize lecture as a "new animal", possess the typical Pickering character coupled with the amphiphilicity of a classical surfactant. Consequently, an enhanced surface activity is expected for these Janus colloids in comparison to homogeneous particles. Our research is focused on studying the behavior of Janus particles near and at the interface of two immiscible liquids using both simulation and experimentaltools with the goal of gaining insight into their stabilizing impact on fluid interfaces. In other words, we are interested in investigating the dynamics of particle adsorption to a liquid-liquid interface and the particle-particle interactions at the interface in order to comprehend their influence on emulsion stability.

Figure 1. Molecular Dynamics simulation of a particle entering an interface.

Current Graduate Students: Sepideh Razavi
Current Undergraduate Students: Jannatul Ferdaous, Alismari Read
Collaborators: Prof. K. Y. Lee, Prof. J. Koplik, Prof. R. Tu, Prof. V. Manoharan, Dr. D. Harbottle, Dr. C.E. Colosqui, A. Wang
Former Contributors: Mamdou Bah, Wenyi Xia, Jessica Lenis, Elin Osterberg, Karol Gonzales, Martin Ugwu


Relevant Literature:

• This work is supported by the Nanoscale Science Foundation under NSF Award Number CBET-PMP-1067501.
• This research is supported, in part, by a grant of computer time from the City University of New York High Performance Computing Center under NSF Grants CNS-0855217 and CNS-0958379.
• CCNY-Chicago PREM Program.