Synthesis and in-situ oxygen functionalization of deposited graphene nanoflakes for nanofluid generation

Graphene nanoflakes (GNFs) are a stack of 5-20 layers of highly crystalline graphene sheets having a planar size of approximately 100 by 100 nm and low defect concentration. They are produced here through homogeneous nucleation following the plasma decomposition of a carbon source in an inductively coupled thermal plasma reactor. Following synthesis within the plasma reactor, the GNFs are functionalized downstream in the plasma recombination zone with the addition of oxygen to the main plasma stream. Tunable oxygen functionalization is obtained and values up to 14.2 atomic percent are reached on the surface of the particles. While the non-functionalized GNFs are hydrophobic, the oxygen-functionalized GNFs (O-GNFs) show full stability of all the produced powders when directly dispersed in water or ethanol without any surfactant. The O-GNFs keep their structural integrity even after the implementation of the hydrophilic groups on the surface of the nanoparticles, and maintain their dispersion stability in water and ethanol over a long period of time.