Hydrodynamic cavitation for scalable exfoliation of few layered graphene nanosheets

Abstract

<p>A simple method for scalable exfoliation of biocompatible few layered graphene (FLG) dispersions is developed using an inexpensive hydrodynamic cavitation setup. Hydrodynamic cavitation is used for the exfoliation. Unlike acoustic cavitation, the primary way of bubble collapse in hydrodynamic cavitation is caused laterally, thereby separating two adjacent flakes by a shear effect. The process utilizes a known protein, Bovine Serum Albumin (BSA), which acts as an effective exfoliation agent and provides stability by preventing restacking of the graphene layers. This is because BSA possesses both hydrophobic as well as hydrophilic sections. The hydrophobic section is absorbed on graphene, which also is hydrophobic. This assists in the formation of dispersions and potentially prevents restacking of graphene. Development of potentially scalable biocompatible methods are critical for producing costeffective non-toxic graphene, enabling numerous possible biomedical and biological applications. A methodical study was performed to identify the effect of time in a novel hydrodynamic cavitation system for graphene exfoliation. The fabricated product was characterized using Raman spectroscopy and Transmission electron microscopy. It was found that with time the number of layers of graphene seem to decrease based on the I2D/IG ratio where at 6 hours the ratio was at 0.307 but along with that disorder in graphene seem to increase based on the ID/IG ratio which reached up to .33 from .25 at 4.5 hours. Based on the data in the study, evidence of a direct relationship between graphene exfoliation and cavitation is found. Therefore, the paper provides the theoretical and the computational analysis needed to create an optimized cavitation model to potentially improve graphene exfoliation using hydrodynamics.</p>