Long-Range Hydrophobic Attraction Between Graphene and Oil–Water Interfaces

Graphene has become one of the most studied materials over the past two decades due to its outstanding properties. Though it has a wide variety of applications, the mass production of high-quality graphene in a cost-effective way is still a challenge. As a solution for this problem, a simple, inexpensive and scalable method called 'Interface trapping method' was found to produce graphene by exfoliating graphite at the interface of oil and water. To understand this behavior of graphene further, we quantified the interactions between graphene and oil–water interfaces via force spectroscopy using functionalized AFM colloidal probes with graphene at different reduction levels. Our force data showed that graphene is attracted to the oil–water interface with an interaction ranging several 100 nm. The interaction increased with the degree of graphene reduction, which supported our hypothesis that the forces were due to long-range hydrophobic interactions between graphene and the oil–water interface. We were further able to determine the receding and advancing water contact angles on graphene as a function of reduction. This insight on these interactions will enable further development and optimization of the interface trapping method to yield high-quality graphene at industrial scale.