The inherent behavior of graphene flakes in water: A molecular dynamics study

Abstract

Graphene-water interaction has been under scrutiny ever since graphene discovery and realization of its exceptional properties. Several computational and experimental reports exist that have tried to look into the interactions involved, however, none of them addresses the issue in its entirety. Most computational analysis doesn't go beyond the atomistic scale and report graphene to be hydrophobic. Meanwhile, several experimental and molecular dynamics (MD) studies show an active interaction between graphene and water. We have, therefore, tested the inherent hydrophobic behavior of a small graphene in water droplet by the means of MD simulations. The analysis has been extended to multiple graphene flakes in water and their respective size dependent responses to water droplet. Graphene retreats from water droplet to encapsulate it from the surface. This response was highly dependent upon graphene size with respect to water content. Additionally, we also report self-assembly of multilayered graphene in water by means of MD simulations, an observation which can be utilized to synthesize such structures in a cost-effective way by experimentalists. To fully comprehend graphene behavior in water, graphene deformation was analyzed in the presence of water molecules. It was noticed that graphene wrinkled to wrap around water molecules and resisted complete failure, one that is seen in case of a sole graphene sheet. Our work will not only address the question about whether graphene is hydrophobic or hydrophilic but also provide insight into the behavior of graphene surface and mobility when exposed to water which can be exploited in numerous applications.

Computational study of the water-driven graphene wrinkle life-cycle towards applications in flexible electronics

“…We used TIP4P potential for water (H 2 O) [49], and Lennard-Jones type of pair potential for C and H 2 O interactions [50]. We used TIP4P potential before for water modeling [3,37], and our computational results were in good agreement with the experimental findings [3]. The methodology of Phase I is summarized in the 'Wrinkle Evolution' part of the flow-chart shown in Figure 3.…”

“…The self-folding mechanics of surface wettability on patterned graphene nanoribbons by water evaporation was studied by Zhang et al [36]. We also investigated the interaction of graphene nanoribbons with water droplets [3,37]. The effect of diffused hydrogen molecules in between graphene and copper substrate on the size of wrinkle formation was studied by Wang et al [38].…”

Tuning the wettability of metal surface with electrodeposited porous copper and graphene coatings

“…It was observed that water molecules do not strongly bind to a graphene sheet [190]. However, it is still controversial that whether graphene is hydrophobic or hydrophilic, but some experimental reports show that the initial process of producing graphene is reflected that the graphene sheet is hydrophobic or hydrophilic [191]. Some reports showed a changeable behavior of graphene hydrophobicity to hydrophilicity by using chemical additives or ultraviolet radiation [115,192].For instance a combination of acetone and water as a solvent shows a wide range of water contact angles on the graphene surface due to chemisorption of acetone on graphene in any defects of graphene surface [192].…”