NM08.06.03 : Structure and Stabilization of Graphene Oxide in 1-Alcohols, with Application to Desalination

5:00 PM–7:00 PM Apr 4, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Mursal Ashrafi1 Michael Pope1

1, University of Waterloo, Waterloo, Ontario, Canada

Graphene oxide has become one of the most widely used 2D materials, not only for use as a solution-processable precursor to graphene but also due to its own unique properties, such as its liquid crystalline behavior. Graphene oxide exhibits high colloidal stability in aqueous environments, and under specific temperature and concentration conditions, can spontaneously align via liquid crystallinity. However, graphene oxide continuously undergoes chemical transformation in water due to water’s nucleophilic nature, thus losing its unique properties over time, as demonstrated recently by Dimiev et al. The step usually taken to remediate this in experiments is to synthesize a fresh batch, which is time-consuming and futile because the fresh batch also goes through the same chemical transformation as soon as water is introduced during the washing process. In this work, we study the physical and chemical stability of graphene oxide in simple alcohol-based solvents. We demonstrate several unique phenomena that make a subset of these solvents ideal for processing. X-ray diffraction carried out on concentrated slurries of graphene oxide in the alcohol dispersions indicate that they form crystalline domains of alternating graphene oxide and oriented 1-alcohol layers. This and their colloidal stability suggest that alcohol acts as a strong steric stabilizer preventing restacking. In addition, chemical degradation is slowed or inhibited for longer-chain water-immiscible alcohols. We demonstrate that these attributes allow us to process graphene oxide dispersions in water-immiscible solvents for the high yield transfer of graphene oxide monolayers as Langmuir-Blodgett films. Furthermore, the ability to retain a high oxidation degree enables higher flux membranes for water desalination. These membranes from the graphene oxide alcohol dispersions demonstrate fluxes of 14.3 L/m2h at 35 °C while maintaining NaCl salt rejection at >99.8%.