UC San Diego

Graphene plays important roles in technological developments regarding electronic device, environment and energy management and the motivation to prepare two-dimensional (2D) nanomaterials. As the pioneer for 2D nanomaterials, graphene has been shown to be not only thermodynamically stable, but also superior in terms of electronic and mechanical properties and that it can be processed into a wide variety of novel materials. However, they are still limited to the challenges such as multi-stacked layers and low efficiency towards a scalable and cost-effective manufacturing process.

In this dissertation, we develop an aqueous arc discharge process as a novel method to produce graphene. This novel graphene production process has the following features: (1) Low energy power consumption process to exfoliate graphene from graphite rather than to evaporate carbon molecules. (2) Water used as a dielectric medium uses a coolant to maintain the temperature during the process. (3) Controllable graphene layers and the number of oxygen-related functional groups. (4) A seamless process for morphological transition of graphene from 2D to three-dimensional (3D) construction.

The graphene produced by our aqueous arc discharge is investigated as transparent electrodes and water desalination membranes. For the transparent electrodes, bi- and trilayers of graphene are adopted to be at high electrical conductance and transmittance, which are collected by vacuum-assisted filtration and then transferred to a flexible transparent polymer films. In the case of the application for water desalination, the effect of the degree of graphene oxidation is investigated and found that the affinity of 2D nanochannels to water molecules and ions affected to the flow rate and salt rejection rate due to the interfacial friction at the interface.

The seamless process of the aqueous arc discharge has been achieved to crumple 2D graphene into 3D graphene nanospheres with the controllable degree of crumpling of graphene. The formation of oil-in-water emulsion during arc discharge can entrap and crumple the exfoliated graphene, simultaneously. The degree of graphene deformation can be controlled by adjusting the flow rate of oil into the plasma zone.