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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.

Journal Article Type Article
Publication Date Dec 18, 2018
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
APA6 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
DOI https://doi.org/10.1021/acs.langmuir.8b03233
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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