Surface and interface functionalization of graphene and beyond: strategies for targeted applications

Graphene's exceptional electrical, mechanical, and interfacial properties can be systematically tuned through chemical functionalization, enabling its integration into advanced technological systems. The structure, electrical behaviour, and surface chemistry of graphene are all altered by covalent, non-covalent, and hybrid functionalization techniques, which are all rigorously examined in this review. Non-covalent interactions maintain π-conjugation and allow reversible, selective interfaces, while covalent alterations provide stable, high-density functional groups but decrease carrier mobility through lattice disruption. These benefits are combined in hybrid techniques, which enhance stability, charge transfer, and conductivity retention. Performance improvements in sensors, energy storage, catalysis, environmental remediation, and biomedical platforms are demonstrated by application-focused study; functionalized graphene provides increased sensitivity, larger capacitances, greater catalytic turnover, and biocompatible drug delivery. Scalability, chemical accuracy, stability, and sustainability are important obstacles. Green chemistry, and hierarchical hybrid architectures are examples of emerging ideas that have the potential to spur innovation. Structure-property design guidelines for upcoming functionalized graphene materials are provided in this review.