Graphene oxide in generation of nanobubbles using controllable microvortices of jet flows

Abstract

Spontaneous generation of nanobubbles (NBs) was developed by using a controllable platform of superfast microvortices, based on turbulent jet flows in the presence of graphene oxide (GO) sheets. Very high energy dissipation rates through discharging warm water into cold N2 aqueous solutions resulted in creation of micro/submicro-vortices. Shear stresses in these domains generated gas local supersaturations, leading to the formation of high concentration (∼109 mL−1) of stable NBs. Introducing GO sheets into the microvortex system resulted in effective manipulation of NBs by providing energetically favorable sites for prompt heterogeneous nucleation as well as stronger shear rate fluctuations. Furthermore, hydrophilic nature of GO sheets induced releasing surface NBs into the bulk. Decreasing the average dimensions of GO sheets from ∼800 to 150 nm significantly reduced the size of NBs from ∼180 to 40 nm while caused a drastic increase (∼two orders of magnitude) in their concentrations. It was found that in the microvortex platform, NBs are able to screen GO surfaces. These results not only show the role of GO in effective and controllable production of NBs, but also suggest the possibility of surface modification of GO sheets by NBs for various upcoming bioapplications as drug carriers.