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Adsorption and crystallization of particles at the air–water interface induced by minute amounts of surfactant

Anyfantakis, Manos; Vialetto, Jacopo; Best, Andreas; Auernhammer, Günter K.; Butt, Hans-Jürgen; Binks, Bernard P.; Baigl, Damien

Authors

Manos Anyfantakis

Jacopo Vialetto

Andreas Best

Günter K. Auernhammer

Hans-Jürgen Butt

Damien Baigl



Abstract

Controlling the organization of particles at liquid-gas interfaces usually relies on multiphasic preparations and external applied forces. Here, we show that micromolar amounts of a conventional cationic surfactant induce, in a single step, both adsorption and crystallization of various types of nanometer- to micrometer-sized anionic particles at the air-water interface, without any additional phase involved or external forces other than gravity. Contrary to conventional surfactant-induced particle adsorption through neutralization and hydrophobization at a surfactant concentration close to the critical micellar concentration (CMC), we show that in our explored concentration regime (CMC/1000-CMC/100), particles adsorb with a low contact angle and maintain most of their charge, leading to the formation of two-dimensional assemblies with different structures, depending on surfactant ( Cs) and particle ( Cp) concentrations. At low Cs and Cp, particles are repulsive and form disordered assemblies. Increasing Cp in this regime increases the number of adsorbed particles, leading to the formation of mm-sized, highly ordered polycrystalline assemblies because of the long-range attraction mediated by the collective deformation of the interface. Increasing Cs decreases the particle repulsion and therefore the interparticle distance within the monocrystalline domains. A further increase in Cs (≈CMC/10) leads to a progressive neutralization of particles accompanied by the formation of disordered structures, ranging from densely packed amorphous ones to loosely packed gels. These results emphasize a new role of the surfactant to mediate both adsorption and crystallization of particles at liquid-gas interfaces and provide a practical manner to prepare two-dimensional ordered colloidal assemblies in a remarkably robust and convenient manner.

Citation

Anyfantakis, M., Vialetto, J., Best, A., Auernhammer, G. K., Butt, H., Binks, B. P., & Baigl, D. (2018). Adsorption and crystallization of particles at the air–water interface induced by minute amounts of surfactant. Langmuir : the ACS journal of surfaces and colloids, 34(50), 15526-15536. https://doi.org/10.1021/acs.langmuir.8b03233

Journal Article Type Article
Acceptance Date Oct 23, 2018
Online Publication Date Nov 11, 2018
Publication Date Dec 18, 2018
Deposit Date Apr 4, 2019
Publicly Available Date Nov 12, 2019
Journal Langmuir
Print ISSN 0743-7463
Electronic ISSN 1520-5827
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 34
Issue 50
Pages 15526-15536
DOI https://doi.org/10.1021/acs.langmuir.8b03233
Public URL https://hull-repository.worktribe.com/output/1547195
Publisher URL https://pubs.acs.org/doi/10.1021/acs.langmuir.8b03233

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Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.langmuir.8b03233.






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