Ion transport in nanoparticle membranes and superlattices

This work surveys recent advances in ion transport through nanoparticle (NP) membranes and arrays, also known as NP superlattices. In these systems, ions diffuse and/or migrate through the interstitial voids between particles, where transport is strongly influenced by the surface charge of the particles and the properties of their surface-bound ligands. Over the past decades, methods for assembling ordered NP arrays have advanced rapidly, enabling the fabrication of highly organized structures in which building blocks with diverse core properties and surface chemistries are positioned with precise control in well-defined lattice sites. This unprecedent level of structural definition has opened new opportunities in nanofluidics, iontronics, energy storage, and filtration, where nano- and microparticles have been exploited to achieve ion selectivity, signal generation and processing, responsiveness to chemical or physical stimuli, and diode-like transport behaviors. This review addresses this emerging field by first discussing the fundamental physical phenomena governing ion transport at the nanoscale and by establishing a connection between NP-based membranes and membranes based on cylindrical and conical nanopores, which have been extensively studied in the literature. We then review theoretical and computational approaches developed to describe these materials, followed by a comprehensive survey of experimental studies and application examples. Finally, we critically assess the advantages and limitations of NP membranes relative to other nanoporous systems, as well as the current capabilities of theory and simulation to provide mechanistic insights and guide the rational design of functional NP-based membranes.