Nanoparticle-Induced Disorder at Complex Liquid–Liquid Interfaces: Effects of Curvature and Compositional Synergy on Functional Surfaces

Abstract

The self-assembly of surfactant monolayers at interfaces plays a sweeping role in tasks ranging from household cleaning to the regulation of the respiratory system. The synergy between different nanoscale species at an interface can yield assemblies with exceptional properties, which enhance or modulate their function. However, understanding the mechanisms underlying coassembly, as well as the effects of intermolecular interactions at an interface, remains an emerging and challenging field of study. Herein, we study the interactions of gold nanoparticles striped with hydrophobic and hydrophilic ligands with phospholipids at a liquid–liquid interface and the resulting surface-bound complexes. We show that these nanoparticles, which are themselves minimally surface active, have a direct concentration-dependent effect on the rapid reduction of tension for assembling phospholipids at the interface, implying molecular coassembly. Through the use of sum frequency generation vibrational spectroscopy, we reveal that nanoparticles impart structural disorder to the lipid molecular layers, which is related to the increased volumes that amphiphiles can sample at the curved surface of a particle. The results strongly suggest that hydrophobic and electrostatic attractions imparted by nanoparticle functionalization drive lipid–nanoparticle complex assembly at the interface, which synergistically aids lipid adsorption even when lipids and nanoparticles approach the interface from opposite phases. The use of tensiometric and spectroscopic analyses reveals a physical picture of the system at the nanoscale, allowing for a quantitative analysis of the intermolecular behavior that can be extended to other systems.

Enhancing membrane-based soft materials with magnetic reconfiguration events

“…The EMG 507 tension was estimated to be 0.88 mN m −1 in the 2:1 hexadecane: silicone oil AR20 and 0.84 mN m −1 in the 1:1 hexadecane: silicone oil AR20. These lower estimated monolayer tension values potentially align with modified monolayer formation expected with nanoparticle-lipid interactions at the oil–water interface 64 .…”

Ion Pairing and Molecular Orientation at Liquid/Liquid Interfaces: Self-Assembly and Function

“…Although these properties make SFG a versatile tool in surface/interface sciences, it has not been widely adopted in studies in probing liquid/liquid interfaces. In fact, only a few research groups have used SFG to study such interfaces, specifically in the context of amphiphile adsorption, − polymer assembly, − liquid extraction, droplet stabilization, and protein/surfactant interactions . Associated challenges in probing these buried interfaces typically limit available information, but their importance to chemical separations, self-assembly, and a range of applied sciences makes them extremely important.…”

Squeezing Out Interfacial Solvation: The Role of Hydrogen-Bonding in the Structural and Orientational Freedom of Molecular Self-Assembly

“…Lipids are a main constituent of biological membranes and of bioinspired platforms of drug delivery and cell mimics, among other applications. − In recent years, advances in extending the use of lipid bilayers, namely in building two-terminal memory elements, have inspired new opportunities to develop artificial neural networks. , However, the fragility and short lifetimes of lipids have limited the realization of stable soft-matter electronics. To address this problem, much effort has been devoted to the synthesis of lipid analogues with improved material and structural properties, including stability.…”