Direct observation of nanoparticle-surfactant assembly and jamming at the water-oil interface

Yu Chai; Jaffar Hasnain; Kushaan Bahl; Matthew Wong; Dong Li; Phillip Geissler; Paul Y Kim; Yufeng Jiang; Peiyang Gu; Siqi Li; Dangyuan Lei; Brett A Helms; Thomas P Russell; Paul D Ashby

doi:10.1126/sciadv.abb8675

Direct observation of nanoparticle-surfactant assembly and jamming at the water-oil interface

Sci Adv. 2020 Nov 25;6(48):eabb8675. doi: 10.1126/sciadv.abb8675. Print 2020 Nov.

Authors

Yu Chai^{1

2}, Jaffar Hasnain³, Kushaan Bahl⁴, Matthew Wong³, Dong Li¹, Phillip Geissler^{3

5}, Paul Y Kim⁵, Yufeng Jiang^{5

6}, Peiyang Gu^{5

7}, Siqi Li⁸, Dangyuan Lei⁹, Brett A Helms^{1

5}, Thomas P Russell^{10

11

12

13}, Paul D Ashby^{14

5}

Affiliations

¹ The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
² Department of Physics, The City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China.
³ Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.
⁴ Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA.
⁵ Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
⁶ Department of Applied Science and Technology, University of California, Berkeley, Berkeley, CA 94720, USA.
⁷ College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation, Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, China.
⁸ Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, SAR, Hong Kong, China.
⁹ Department of Materials Science and Engineering, The City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, SAR, Hong Kong, China.
¹⁰ Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA. tprussell@lbl.gov pdashby@lbl.gov.
¹¹ Polymer Science and Engineering Department, Conte Center for Polymer Research, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA.
¹² Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
¹³ Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan.
¹⁴ The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA. tprussell@lbl.gov pdashby@lbl.gov.

Abstract

Electrostatic interactions between nanoparticles (NPs) and functionalized ligands lead to the formation of NP surfactants (NPSs) that assemble at the water-oil interface and form jammed structures. To understand the interfacial behavior of NPSs, it is necessary to understand the mechanism by which the NPSs attach to the interface and how this attachment depends on the areal coverage of the interface. Through direct observation with high spatial and temporal resolution, using laser scanning confocal microscopy and in situ atomic force microscopy (AFM), we observe that early-stage attachment of NPs to the interface is diffusion limited and with increasing areal density of the NPSs, further attachment requires cooperative displacement of the previously assembled NPSs both laterally and vertically. The unprecedented detail provided by in situ AFM reveals the complex mechanism of attachment and the deeply nonequilibrium nature of the assembly.

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