Effect of trapped water on the frictional behavior of graphene oxide layers sliding in water environment

Two-dimensional materials have great potential for applications in the wide-reaching areas of sensing, drug delivery, and biomolecule nano-transportation. When considering graphene for possible applications, interactions with the surrounding environment should be always kept in mind, as they can cause wear and damage of the films and thus largely affect the overall performance of graphene-based devices. In this paper, we use Quartz Crystal Microbalance (QCM) to explore interactions of graphene oxide (GO) films with water at solid/liquid interface. We demonstrate that water trapped between GO layers during deposition from the water solution largely affects the response of the QCM in the liquid environment by unexpectedly increasing the resonant frequency of oscillations. Once the trapped water is released in the DI water environment or eliminated in case of graphene deposited from an ethanol solution, the resonant frequency decreases upon immersion as predicted from viscosity effect on the oscillations. The trapped water also increases friction against the QCM movement in the liquid environment, as indicated by 2-3 times larger mechanical resistance values. Our observations confirm the importance of GO composition and deposition procedures and propose a new method for releasing the trapped water from the structures and improving the tribological performance of the film in solid/liquid interface.

175