Grafenes

Grafenes refer to graphene-based carbon materials that exist as two-dimensional sheets about one atom thick, with graphene as the core. The term also covers related derivatives such as graphene oxide, reduced graphene oxide, and few- or multi-layer graphene, which share a common hexagonal carbon lattice.

Graphene, the core material, is a single layer of carbon atoms in a hexagonal lattice. It combines high electrical and thermal conductivity, exceptional stiffness, and optical transparency. A monolayer absorbs about 2.3% of visible light; its in-plane Young's modulus is about 1 TPa and intrinsic strength around 130 GPa. Electron mobility in pristine samples is extremely high, enabling potential high-speed electronics.

Grafenes are produced by several methods. Mechanical exfoliation yields high-quality flakes but limited area. Chemical vapor deposition can grow large-area films on copper or nickel, which are then transferred. Chemical reduction of graphene oxide and liquid-phase or surfactant-assisted exfoliation produce solution-processable grafenes for composites and coatings. Other approaches include epitaxial growth on silicon carbide and bottom-up synthesis.

Applications span electronics, energy storage, and materials engineering. In electronics, grafenes show promise for high-frequency devices and flexible circuits. In energy storage, they enhance electrode conductivity and surface area for batteries, supercapacitors, and electrolyzers. In composites, grafenes improve stiffness and toughness; in sensors, they enable sensitive detectors for gases and biomolecules; in membranes, they offer selective transport.

History and challenges: Graphene was isolated in 2004 by Geim and Novoselov, earning the Nobel Prize in 2010. Grafenes face hurdles in scalable, cost-effective production, consistent quality control, and integration with existing manufacturing. Safety considerations include handling nanoscale materials to prevent inhalation exposure and environmental implications of nanomaterials.