Water/ionic liquid interfaces as fluid scaffolds for the two-dimensional self-assembly of charged nanospheres

Takuya Nakashima, Nobuo Kimizuka

    Research output: Contribution to journalArticlepeer-review

    22 Citations (Scopus)

    Abstract

    Liquid-liquid interfaces formed between water and ionic liquids serve as fluid scaffolds to self-assemble anionic nanospheres two-dimensionally. When aqueous dispersions of anionic fluorescent polystyrene nanospheres (diameter ∼500 nm) are layered on ionic liquids, ordered monolayers are spontaneously formed at the interface. Fluorescent nanospheres are hexagonally packed in the interfacial monolayers, as observed by confocal laser scanning microscopy (CLSM). The adsorption and alignment of nanospheres at the interface are affected by the ionic strength and pH of the aqueous phase, indicating electrostatic interaction as the primary driving force for the self-assembly. CLSM observation of the water/ionic liquid interface reveals that the lower hemisphere of nanospheres is exposed to the ionic liquid phase, which effectively alleviates lateral electrostatic repulsion between charged nanospheres and promotes their close packing. The densely packed monolayer structure of nanospheres is stably immobilized on the surface of CLSM glass dishes simply by rinsing the ionic liquid layer with pure water, probably as a consequence of the gluing effect exerted by imidazolium cations. The fluidic nature of the water/ionic liquid interface facilitates the diffusion and ordering of nanospheres into a hexagonal lattice, and these features render the interface promising soft scaffolds to self-assemble anionic nanomaterials two-dimensionally.

    Original languageEnglish
    Pages (from-to)1281-1285
    Number of pages5
    JournalLangmuir
    Volume27
    Issue number4
    DOIs
    Publication statusPublished - Feb 15 2011

    All Science Journal Classification (ASJC) codes

    • General Materials Science
    • Condensed Matter Physics
    • Surfaces and Interfaces
    • Spectroscopy
    • Electrochemistry

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