Ultrasonic exfoliation of graphene in water: A key parameter study

Liquid Phase Exfoliation (LPE) is an efficient method for graphene flake exfoliation and considered to be compatible with industrial production requirements. However, most of available LPE methods require the use of harmful and expensive solvents for chemical exfoliation prior to mechanical dispersion of the flakes, and therefore an additional step is needed to remove the contamination caused by the added chemicals, making the process complex, costly, unsafe and detrimental to the environment. By studying the effects of key ultrasonic LPE parameters, our study demonstrates the possibility to control the production and quality of few-layer graphene flakes in pure water in a relatively short period of time. The driving frequency of an ultrasonic source, a higher acoustic cavitation intensity and uniform distribution of the cavitation events in the sonicated volume are the key parameters for controlling the thickness, surface area and production yield of few-layer graphene flakes. The results are discussed in the context of mechanical exfoliation. This opens a direction for developing LPE into a cost effective, clean, environmentally friendly, and scalable manufacturing process for the next generation of two-dimensional nanomaterials for industrial-scale applications.