Recent progress in graphenes: synthesis, covalent functionalization and environmental applications

Graphene is a 2D monolayer assembly of carbon atoms organized in a hexagonal fashion. Due to their exclusive structural, opto-mechanical, and electrical attributes, graphene-based nanostructures have found diverse applications in chemistry, physics, electronics, environment, and so on. We, herein, undertake an in-depth review of the available approaches to fabricate and chemically functionalize graphene and graphene-based nanostructures for diverse environmental implications. Different covalent functionalization approaches, including nucleophilic addition, electrophilic substitution, cycloaddition, and free radical additions, have been highlighted with their general schemes, supported by some relevant citations. The oxygenated moieties on graphenes provide reactive sites to extend their novel functionalities. The choice of chemical functionalities present on graphenes may determine and tailor their desirable properties for diverse environmental applications. Some major environmental implications of graphene-based materials have been presented, herein, including organic, heavy metals and toxic gaseous removal and detection, water desalination, and photocatalysis as well as sustainability aspects of functionalized graphenes. The study concludes with current opportunities and future recommendations in this domain.