UC Riverside

The unique structure and properties of graphene initiated broad fundamental and technological research in recent years, and highlighted graphene as an alternative for various applications such as energy storage and nanoelectronics. Chemical vapor deposition (CVD) of graphene on copper is believed to be the most promising method for large-scale synthesis of continuous sheets. The exceptional properties of graphene however, are governed by its microstructure. The size of graphene grains and the grain boundaries affect the carrier mobility. Therefore understanding the formation mechanism of graphene is critical to control the microstructure and physical properties. We implemented Fluorescence Quenching Microscopy (FQM) in conjunction with other methods to understand a trend which is pertinent in large-scale. In order to investigate the nucleation and growth mechanism of graphene on copper and its subsequent microstructure, effect of key parameters such as density of defects in copper foils and growth pressure in the CVD chamber have been altered. Results point out that microstructure of copper regulates the structure and properties of graphene and heat treatment and electropolishing of the foil substrates as well as controlling the saturation pressure of the carbon precursor yield to large graphene domains.

Water decontamination and oil/water separation are principal motives in the surge to develop novel means for sustainability. In this prospect, supplying clean water for the ecosystems is as important as the recovery of the oil spills since the supplies are scarce. Inspired to design an engineering material which not only serves this purpose, but can also be altered for other applications to preserve natural resources, a facile template-free process is suggested to fabricate a superporous, superhydrophobic graphene-based sponge. Moreover, the process is designed to be inexpensive and scalable. The fabricated sponge can be used to clean up different types of oil, organic solvents, toxic and corrosive contaminants. This versatile microstructure can retain its functionality even when pulverized. The sponge is applicable for targeted sorption and collection due to its ferromagnetic properties. We hope that such cost-effective process can be embraced and implemented widely.