Nanoparticle Assembly at Liquid–Liquid Interfaces: From the Nanoscale to Mesoscale

Abstract

In the past few decades, novel syntheses of a wide range of nanoparticles (NPs) with well-defined chemical composition and structure have opened tremendous opportunities in areas ranging from optical and electronic devices to biomedical markers. Controlling the assembly of such well-defined NPs is important to effectively harness their unique properties. The assembly of NPs at liquid-liquid interfaces is becoming a central topic both in surface and colloid science. Hierarchical structures, including 2D films, 3D capsules, and structured liquids, have been generating significant interest and are showing promise for physical, chemical, and biological applications. Here, a brief overview of the development of the self-assembly of NPs at liquid-liquid interfaces is provided, from theory to experiment, from synthetic NPs to bio-nanoparticles, from water-oil to water-water, and from "liquid-like" to "solid-like" assemblies.

Cell‐Inspired All‐Aqueous Microfluidics: From Intracellular Liquid–Liquid Phase Separation toward Advanced Biomaterials

“…[95] In recent years, the fundamental understanding on the macromolecular assembly at aqueous-aqueous interfaces has been propelled, and new surfactant systems have been experimentally developed to stabilize all-aqueous emulsions and to fabricate vesicles in near-physiological environments. [131,176,177] It is worth stating that the distribution of complexes at the liquid-liquid interfaces is heterogeneous. Particularly, when the adsorption energy is relatively high, large nanoparticles and nanofibrils can be irreversibly trapped at the aqueous-aqueous interface with certain contact angles, leading to the heterogeneous distribution of solid complexes across the liquid-liquid interfaces.…”

Interfacial Activity of Amine‐Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS): A Simple Strategy To Structure Liquids

“…[2,[22][23][24][25][26] Here,u nlike in colloidosomes, [1,27] colloidal capsules, [28][29][30] or Pickering emulsions, [31][32][33][34] which are stabilized with micronsized particles (Scheme 1a), functionalized nanoparticles dispersed in an aqueous phase interact with end-functionalized oligomeric ligands dissolved in an oil phase at the interface to form nanoparticle surfactants (NP-surfactants; Scheme 1b), where the number of ligands anchored to the NPs is self-regulated to minimize the energy holding each NPsurfactant at the interface. [2,[22][23][24][25][26] Here,u nlike in colloidosomes, [1,27] colloidal capsules, [28][29][30] or Pickering emulsions, [31][32][33][34] which are stabilized with micronsized particles (Scheme 1a), functionalized nanoparticles dispersed in an aqueous phase interact with end-functionalized oligomeric ligands dissolved in an oil phase at the interface to form nanoparticle surfactants (NP-surfactants; Scheme 1b), where the number of ligands anchored to the NPs is self-regulated to minimize the energy holding each NPsurfactant at the interface.…”

“…[2,[22][23][24][25][26] Here,u nlike in colloidosomes, [1,27] colloidal capsules, [28][29][30] or Pickering emulsions, [31][32][33][34] which are stabilized with micronsized particles (Scheme 1a), functionalized nanoparticles dispersed in an aqueous phase interact with end-functionalized oligomeric ligands dissolved in an oil phase at the interface to form nanoparticle surfactants (NP-surfactants; Scheme 1b), where the number of ligands anchored to the NPs is self-regulated to minimize the energy holding each NPsurfactant at the interface. [22,26] Now,w hen ac ompressive force is applied, the individual NP-surfactants are not ejected from the interface and the NP-surfactant assemblies can jam as the interfacial area decreases.T his arrests any further change in the shape of the interface,and can therefore be used to lock in highly non-equilibrium shapes of one liquid in asecond liquid, that is,tostructure the liquid. NP-surfactants constitute av ersatile alternative to Pickering emulsions and afford ap athway to generate adaptive interfacial assemblies that can respond to external stimuli.…”

Interfacial Capillary‐Force‐Driven Self‐Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors

“…Though many efforts have been devoted to directly assemble the highquality MCCs with hydrophilic colloidal particles without any surface modification in polar solvents, to date, the quality of MCCs is still poor with high agglomerates, vacancy, and microcosmic disorder in a large area, resulting in unsat isfied device performances. [14,15] An essential and arresting reason is that the selfassembly process is still facing great chal lenges in controlling the particle aggregation, deposition and transfer, which will be influenced greatly by the dispersants, assembly speed, electrostatic force, intermolecular force, and convective motion of solvents. Besides, the uniformity of the space between the colloidal particles on a largearea substrate is also difficult to be controlled, resulting in low repeatability.…”