Simulation-ready graphene oxide structures with hierarchical complexity: a modular tiling strategy

Abstract

Graphene oxide (GO) sheet structures are highly variable and depend on preparation conditions. The use of molecular simulation is a complementary strategy to explore how this complexity influences the ion transport properties of GO membranes. However, despite recent advances, computational models of GO typically lack the required complexity as suggested by experiment. The labor required to create such an ensemble of such structural models with the required complexity is impractical without recourse to automated approaches, but no such code currently can meet this challenge. Here, a modular tiling concept is introduced, along with the HierGO suite of code; an automated approach to producing highly complex hierarchically-structured models of GO with a high degree of control in terms of holes and topological defects, and oxygen-group placement, that can produce simulation-ready input files. The benefits of the code are exemplified by modeling and contrasting the properties of three types of GO membrane stack; the widely-modeled Lerf-Klinowski structure, and two types of highly heterogeneous GO sheet reflecting differing processing conditions. The outcomes of this work clearly demonstrate how the introduction of the complexity modeled here leads to new insights into the structure/property relationships of GO with respect to permeation pathways of water, ions and molecular agents that are inaccessible using previously-considered models.

Experimental and Theoretical Insights into Interfacial Properties of 2D Materials for Selective Water Transport Membranes: A Critical Review

“…The investigation delved into the evolution of the electronic structure of GO with varying coverage. Noteworthy discoveries encompass: (a) full coverage of GO at 100% is less energetically advantageous compared to 75%, (b) functionalization involving both oxygen and hydroxyl groups is more favorable for 25% coverage than functionalization with hydroxyl groups alone, (c) diminishing GO from 75% to 6.25% coverage (C:O ratio 16:1) is relatively facile, but further reduction appears challenging, and (d) GO transitions to a conducting state at 25% coverage, acting as an insulator at higher coverage levels. , …”

Decoding the Interplay between Topology and Surface Charge in Graphene Oxide Membranes During Humidity Induced Swelling

“…11 Garcia et al proposed a framework on producing a complex GO flake that could include defects and spatial distribution of oxygenated functional groups to capture the complexity of GO. 44 Another method of fabricating the complex morphology of GO membrane models was also proposed by Chen et al based on a pressure-assisted ultrafiltration self-assembly method. This model was then used to study the separation of heavy metal ions from water and the rejection mechanism.…”

“…The procedure has been used by Reddy et al to study the purification of pharmaceutical effluent, showing that GO membranes are promising candidates also for such filtration processes . Garcia et al proposed a framework on producing a complex GO flake that could include defects and spatial distribution of oxygenated functional groups to capture the complexity of GO . Another method of fabricating the complex morphology of GO membrane models was also proposed by Chen et al based on a pressure-assisted ultrafiltration self-assembly method.…”