Structure of graphene oxide membranes in solvents and solutions.

Alexey Klechikov,Junchun Yu,Diana Thomas,Tiva Sharifi,Alexandr V Talyzin

doi:10.1039/c5nr04096e

Alexey Klechikov, Junchun Yu + Show 3 more

Open Access

https://doi.org/10.1039/c5nr04096e

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Journal: Nanoscale	Publication Date: Jan 1, 2015
Citations: 103	License type: cc-by

Affiliation: Umeå University, MAX IV Laboratory, Lund University

Abstract

The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite oxide powder samples. Intercalation of liquid dioxolane, acetonitrile, acetone, and chloroform into the GO membrane structure occurs with maximum one monolayer insertion (Type I), in contrast with insertion of 2-3 layers of these solvents into the graphite oxide structure. However, the structure of GO membranes expands in liquid DMSO and DMF solvents similarly to precursor graphite oxide (Type II). It can be expected that Type II solvents will permeate GO membranes significantly faster compared to Type I solvents. The membranes are found to be stable in aqueous solutions of acidic and neutral salts, but dissolve slowly in some basic solutions of certain concentrations, e.g. in NaOH, NaHCO3 and LiF. Some larger organic molecules, alkylamines and alkylammonium cations are found to intercalate and expand the lattice of GO membranes significantly, e.g. up to ∼35 Å in octadecylamine/methanol solution. Intercalation of solutes into the GO structure is one of the limiting factors for nano-filtration of certain molecules but it also allows modification of the inter-layer distance of GO membranes and tuning of their permeation properties. For example, GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents.

Highlights

Thanks to the hydrophilic structure, graphite oxides can be dispersed in water to give stable solutions of singlelayered graphene oxide (GO).[1]
GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents
It is interesting to discuss the possible reasons for the strong difference between swelling of graphite oxide powders and GO membranes

Summary

Introduction

Thanks to the hydrophilic structure, graphite oxides can be dispersed in water to give stable solutions of singlelayered graphene oxide (GO).[1]. Many recent studies have aimed at demonstration of selective permeation of certain ions and molecules through GO membranes for nano-filtration applications.[23,24,25,26,27,28] Some studies suggested simple models, considering the interlayer distance in GO membranes (“channels”) to be equal to the value observed for membranes immersed in pure water (∼12–13 Å) without assuming the effects of solutes on the GO lattice In this case the size of hydrated ions or molecules was speculated to be the only parameter which determines the permeability of a GO membrane.[11] We believe that such models are over-simplified and can be applied only to limited range of salts or molecules. The limitations of GO membranes for nano-filtration applications are demonstrated on examples of some basic salts, amines and alkylammonium salts

Experimental

Results

GO membranes in polar solvents

GO membranes in aqueous solutions

GO membranes in alkylamines and methanol solutions of alkylammonium salts

Discussion