Dynamics of water between graphene and mica

The behavior of water under confinement is of utmost importance for the field of electrocatalysis, nanofluidics and lubrication. The dynamics of water under confinement are significantly different as compared to bulk water. Experimental knowledge of confined water is challenging to obtain due to the confined nature of the water, and therefore limited access to the water structures. With the discovery of the two-dimensional material graphene in combination with scanning probe microscopy, a new approach to in-situ study confined water layers was born. The mechanical properties of graphene like its flexibility, impermeability and atomic thickness make it a perfect cover to study the water molecules. In this thesis, I cover the dynamic properties of water on mica, covered with a graphene coating. Different dynamics are studied, e.g. electrolysis of the confined water molecules to hydrogen nanobubbles, the influence of charges on the graphene, and the influence of the confined molecules on the mechanical properties of the graphene. The studies expand our experimentally obtained knowledge of confined water which will find applications in future devices

Water confined in two-dimensions: Fundamentals and applications

The behavior of water in close proximity to other materials under ambient conditions is of great significance due to its importance in a broad range of daily applications and scientific research. The structure and dynamics of water at an interface or in a nanopore are often significantly different from those of its bulk counterpart. Until recently, experimental access to these interfacial water structures was difficult to realize. The advent of two-dimensional materials, especially graphene, and the availability of various scanning probe microscopies were instrumental to visualize, characterize and provide fundamental knowledge of confined water. This review article summarizes the recent experimental and theoretical progress in a better understanding of water confined between layered Van der Waals materials. These results reveal that the structure and stability of the hydrogen bonded networks are determined by the elegant balance between water-surface and water-water interactions. The water-surface interactions often lead to structures that differ significantly from the conventional bilayer model of natural ice. Here, we review the current knowledge of water adsorption in different environments and intercalation within various confinements. In addition, we extend this review to cover the influence of interfacial water on the two-dimensional material cover and summarize the use of these systems in potential novel applications. Finally, we discuss emerged issues and identify some flaws in the present understanding

Tuning the Friction of Graphene on Mica by Alcohol Intercalation

The friction of graphene on mica was studied using lateral force microscopy. We observed that intercalation of alcohol molecules significantly increases the friction of graphene, as compared to water. An increase of 1.8, 2.4, and 5.9 times in friction between the atomic force microscopy tip and single-layer graphene was observed for methanol, ethanol, and 2-propanol, respectively. Moreover, the friction of graphene is found to be higher for single-layer graphene than for multilayer graphene. We attribute the increase in friction to the additional vibrational modes of alcohol molecules. The significant variation of the frictional characteristics of graphene at the nanoscale by altering the intercalant could open up applications for the next-generation nanolubricants and nanodevices

Electrochemically Induced Nanobubbles between Graphene and Mica

We present a new method to create <i>dynamic</i> nanobubbles. The nanobubbles are created between graphene and mica by reducing intercalated water to hydrogen. The nanobubbles have a typical radius of several hundred nanometers, a height of a few tens of nanometers and an internal pressure in the range of 0.5–8 MPa. Our approach paves the way to the realization of nanobubbles of which both size and internal pressure are tunable