Ultrasonic preparation of graphene
Since the special properties of graphite are well known, several methods of preparing graphite have been developed. In addition to the chemical production of graphene from graphene oxide in a multi-step process, very strong oxidation and reducing agents are required. In addition, graphene prepared under these severe chemical conditions often contains a large number of defects even after reduction, compared to graphene obtained from other methods. However, ultrasound is a proven alternative to producing large quantities of high quality graphene. Researchers use ultrasound to develop methods that vary slightly, but in general, graphene production can be done in one step.
An example of a particular graphene production process is the addition of graphite to a mixture of a dilute organic acid, an alcohol and water, and then exposing the mixture to ultrasonic radiation. The acid acts as a "molecular wedge" to separate the graphene sheets from the parent graphite. Through this simple process, a large amount of undispersed, high quality graphene dispersed in water is produced.
Direct stripping of graphene
Ultrasonic waves can be used to prepare graphene in organic solvents, surfactants/aqueous solutions or ionic liquids. This means that the use of strong oxidation or reducing agents can be avoided. Stankovich et al. (2007) produced graphene by spalling under the action of ultrasound. Ultrasonic treatment of a 1 mg/ml graphene oxide melt. The AFM image shows that there is always a sheet of uniform thickness (1 nm). These good graphene oxide stripped samples have no graphene with a thickness greater than 1 nm or a thickness less than 1 nm. The flakes, from which it was concluded that under these conditions, complete flaking of graphene oxide was achieved to obtain a single graphene oxide sheet.