Gold Nanofilms at Liquid–Liquid Interfaces: An Emerging Platform for Redox Electrocatalysis, Nanoplasmonic Sensors, and Electrovariable Optics

Abstract

The functionality of liquid-liquid interfaces formed between two immiscible electrolyte solutions (ITIES) can be markedly enhanced by modification with supramolecular assemblies or solid nanomaterials. The focus of this Review is recent progress involving ITIES modified with floating assemblies of gold nanoparticles or "nanofilms". Experimental methods to controllably modify liquid-liquid interfaces with gold nanofilms are detailed. Also, we outline an array of techniques to characterize these gold nanofilms in terms of their physiochemical properties (such as reflectivity, conductivity, catalytic activity, or plasmonic properties) and physical interfacial properties (for example, interparticle spacing and immersion depth at the interface). The ability of floating gold nanofilms to impact a diverse range of fields is demonstrated: in particular, redox electrocatalysis, surface-enhanced Raman spectroscopy (SERS) or surface plasmon resonance (SPR) based sensors, and electrovariable optical devices. Finally, perspectives on applications beyond the state-of-the-art are provided.

Collapse mechanisms and extreme deformation of particle-laden interfaces

“…For particles with anisotropic surface chemistry, a comparison of homogenous polystyrene particles with gold-polystyrene Janus colloids of the same size reveals that while the homogeneous particles form monolayers that buckle upon compression, the Janus particles form bilayers upon monolayer collapse due to the anisotropic particle-particle and particle-interface interactions [55]. Monolayer collapse can be an undesirable phenomenon in the application of nanoparticle monolayers to advanced functional materials, for instance made from gold nanoparticles [58], or graphene and graphene oxide sheets [59].…”

Ion transfer at polarised liquid-liquid interfaces modified with adsorbed silica nanoparticles

“…The interface formed between two immiscible electrolyte solutions (ITIES) is a highly reproducible, defect-free surface that allows the assembly of a large variety of nanoscale objects [1][2][3][4]. The adsorption of nano-objects at a liquid-liquid interface is governed by their dimensions, the organic-aqueous interfacial tension and the wettability of the material [2,[5][6][7][8].…”

Debye screening, overscreening and specific adsorption in solutions of organic ions

“…As reviewed before 10,11 , ITIES encompass a wide range of applications, such as phase-transfer-catalysis or photochemical energy conversion. More recently, ITIES have been successfully employed to trap metallic nanoparticles in two dimensional arrays, enabling the design of self-assembled tuneable nanoplasmonic optical metasurface mirrors [12][13][14] . The accuracy of mean field approaches (Gouy-Chapman) to describe ion distribution at these interfaces has been addressed recently, and the structure of the interface examined using x-ray reflectivity 15 .…”