Exfoliation is a process that separates layered materials into nanomaterials by breaking the bonds between layers using mechanical, chemical, or thermal procedures.
While exfoliation has historical roots dating back centuries, significant advances and widespread research gained momentum after Novoselov and Geim's discovery of graphene using Scotch tape in 2004. Their Nobel Prize-winning research primarily relied on mechanical exfoliation for the production of graphene which sparked an immediate interest in the exfoliation process. Today, exfoliation is regarded as the most widely used nanomaterial production technique.
Exfoliation typically involves breaking weak bonds called van der Waals bonds to create two-dimensional materials, such as graphene or transition metal dichalcogenide monolayers. While various reversible chemical processes, such as intercalation can disrupt the weak bonds in a lamellar structure and introduce guest species, many of them fail to produce single-sheet materials as the processes are not strong enough to cancel the interlayer attractions.[1] However, during exfoliation, the high energy input leads to an extreme bond-breaking process that irreversibly separates the layers into single sheets. Lately, it has been shown that if the energy input is substantial enough, the procedure can even break much stronger, bonds such as metallic or ionic bonds to create non-van der Waals materials like hematene or other nanoplatelets.[2]
In recent years, exfoliation has found practical applications in a wide range of fields, from electronics to biomedical and beyond. It plays a vital role in creating advanced materials with properties tailored for specific uses, such as high-performance electronics, efficient energy storage devices, and lightweight yet robust materials for aerospace applications. This versatility and adaptability make exfoliation a crucial technique in cutting-edge material research and various industrial sectors.