Molecular Dynamics Study of the Aggregation Process
of Graphene Oxide in Water
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Abstract
Molecular
dynamics (MD) simulations were performed to provide molecular
insight into the aggregation process of graphene oxide (GO) in water.
The aggregation was found to be a point–line–plane
process. Five forces were involved during the process: van der Waals
attraction, electrostatic interaction, hydrogen-bond interaction,
π–π stacking, and the collision of water molecules.
The dominant forces were different in the three stages. The connection
“line” was important to the aggregation process and
the final overlapping area of the GO aggregate. To study the effect
of oxygen content and functional group on the aggregation of GO, four
different GOs were used: C<sub>10</sub>O<sub>1</sub>(OH)<sub>1</sub>(COOH)<sub>0.5</sub>, C<sub>30</sub>O<sub>1</sub>(OH)<sub>1</sub>(COOH)<sub>0.5</sub>, C<sub>10</sub>O<sub>1</sub>(COOH)<sub>0.5</sub>, and C<sub>10</sub>O<sub>1</sub>(OH)<sub>1</sub> (termed OGO, RGO,
GO-COOH, and GO-OH, respectively). RGO aggregated faster than OGO,
and GO-OH aggregated faster than GO-COOH. A quantitative analysis
showed the difference in aggregation rate of these four GOs should
be attributed to the hydrogen bonds. Additionally, the closer GOs
were to each other initially, the faster they aggregated. This study
reveals the aggregation process of GO and will be helpful in understanding
its behavior in water