Vortex ring processes allowing shape control and entrapment of antibacterial agents in GO-based particles

Abstract

Vortex ring (VR) processes have proved highly effective in tailoring the morphology/shape of particles prepared from nanoclays, silica nanocolloids, magnetic nanoparticles and different polysaccharides. Herein, we have prepared toroidal-, teardrop-, jellyfish-, and cap-shaped vortex ring particles by drip- ping an aqueous suspension of graphene oxide (GO) into a cetyl trimethylammonium bromide (CTAB) aqueous solution that played the role of coagulating agent. Interestingly, the GO suspension exhibited liquid crystalline features. We demonstrated how controlling the drop impact force against the liquid surface was critical to produce VR particles with such intriguing shapes. With the purpose of controlling the drop impact force, we studied the drop density/viscosity, the speed at which the drop impacts the surface of the liquid pool and the surface tension of the CTAB solution. Finally, we also demonstrated the antibacterial activity of the resulting GO-based VR particles against Escherichia coli and Bacillus subtilis, and discussed about the origin of such a behaviour. In particular, we investigated the occurrence of (1) membrane damage by physical contact between GO and bacteria, (2) GO-induced oxidative stress, or (3) CTAB released into the bacteria culture, the antiseptic and disinfectant action of which may ultimately kill bacteria.