Graphene is one of the most attractive carbon allotropes due to its unique physicochemical, mechanical, electronic, and optical properties. Its increased use necessitates systematic environmental evaluation of this nanomaterial. Surface functionalization has gained tremendous interest to overcome zero band-gap limitation of graphene surfaces. However, the effect of surface coatings on graphene's environmental behavior has not been systematically evaluated. This study will be the first to understand the role of non-covalent surface coatings on aggregation kinetics of graphene suspensions in environmentally relevant conditions. Graphene, coated with poly(vinyl pyrrolidone) or PVP, 1-pyrene sulphonic acid sodium salt or PySASS, 1-pyrenesulfonic acid hydrate or Py-SAH and 2, 3, 6, 7, 10, 11-hexakis (10-carboxydecyloxy) triphenylene or C10 have been used to study aggregation kinetics in aqueous suspensions. Time-resolved dynamic light scattering was employed. A range of mono- and di-valent cations and Suwannee River humic acid (at 2.5 mg/L TOC) were considered. Graphene coated with PySASS and Py-SAH showed typical DLVO type aggregation behavior, while non-ionic PVP-coated ones resisted aggregation under the influence of cations. C10 coated graphene on the other hand, showed rapid aggregation compared to the other coatings. The difference in observed aggregation behavior with C10 has likely resulted from the long chained alkenes connected to the aromatic rings, which likely have prevented effective surface coverage on graphene. Observed results demonstrate that structure of the coatings heavily influence graphene aggregation in aqueous systems.

Surface coating dependent aggregation kinetics of graphene suspensions

247th National Meeting (2014)

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