Research ArticleCONDENSED MATTER PHYSICS

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

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Science Advances  25 Nov 2020:
Vol. 6, no. 48, eabb8675
DOI: 10.1126/sciadv.abb8675
  • Fig. 1 Attachment of NPs to sparsely populated water-oil interface.

    (A) Schematic diagram showing the attachment of a NP to the pristine water–oil interface. (B) Confocal microscopy images showing the attachment of 500-nm NPs to the water-oil interface. (C) Number of attached 500-nm NPs as a function of time, where the slope follows at power law of 0.5. (D) In situ AFM image of 100- and 300-nm NPs assembled at the water-oil interface at different times: t0 and t0 + 3.0 min, with a circle highlighting an attachment event. (E) Section data along arrow in (D) showing fit for NP diameter size and position in the interface. (F) Positions of the assembled NPs at different times: t0 (red) and t0 + 3.0 min (blue), where the open blue circle represents the newly attached NP. Scale bars, 20 μm (B) and 200 nm (D and F).

  • Fig. 2 Attachment of 300-nm NPs to thoroughly populated water-oil interface.

    (A) Schematic diagram of the attachment of a 300-nm NP where previous NPs are displaced laterally and vertically. (B) Time-dependent in situ AFM showing the attachment of 300-nm NP to the water-oil interface, where the white circle indicates the newly adsorbed NP. (C) NPS positions at t0 (red) and t0 + 5.3 min (blue), where the faded blue dot represents the newly attached NP and the faded red dots represent NPSs that cannot be located by AFM after attachment of the newly attached NP. Scale bars, 200 nm.

  • Fig. 3 Attachment of NPs to the water-oil interface with assembled NPs.

    (A) LSCM images showing the attachment of 500-nm NPs to the water-oil interface with assembled 70-nm NPSs. (B) Number of 500-nm NPSs in the field of view as a function of time. (C) In situ AFM images show the coassembly of 30- and 300-nm NPSs at the water-oil interface. (D) In situ AFM images showing the attachment of 300-nm NPs to the water-oil interface with assembled 30- and 300-nm NPSs. (E) Time-dependent in situ AFM images showing the attachment of a 300-nm NP to the water-oil interface covered by 100- and 300-nm NPSs, where the yellow rectangles indicate the affected areas. (F) Line profiles of the region shown in (E) indicate the relaxation of the newly attached 300-nm NP. Scale bars, 20 μm (A), 100 nm (C), 500 nm (D), and 200 nm (E).

  • Fig. 4 Attachment of 70- and 500-nm NPs to the water-oil interface.

    (A) LSCM images showing the attachment of both 70-nm (yellow) and 500-nm (green) NPs. (B) Zoomed-in view of (A) showing the crack of the assemblies and the attachment of 500-nm NPs to the open area. (C) Zoomed-in view of (A) showing the attachment of a 500-nm NP to the water-oil interface already assembled with 70-nm NPSs. Scale bars, 20 μm (A) and 2 μm (B and C).

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