Graphene is a new carbon nanomaterial that was first discovered in 2004. Under the action of external forces, the bonding bonds between graphene carbon atoms will be deformed and the structure is stable. Therefore, graphene has very good strength performance. Crystal lattice of graphene is carbon hexagons with stable structure, and the thermal conductivity of graphene is excellent. Due to the special structure, graphene has strong thermal stability which does not change with temperature. The ideal graphene structure is a planar hexagonal lattice, which can be seen as a layer of stripped graphite molecules. In graphene structure, each carbon atom is SP2 hybridized, and it can contribute a remaining electron to form a large π bond. The π electrons can move freely, giving graphene good electrical conductivity. Moreover, at room temperature, the electron transfer rate is much faster than ordinary conductive materials. Furthermore, graphene is only one atom thick and has a light transmittance of 97.7%, which is very transparent. From an optical point of view, graphene is a "transparent" conductor that could very well replace liquid crystal materials.
Figure 1. An example of graphene designed as a gas sensor.
Figure 2. An example of graphene used as hydrogen storage material.
Graphene can be divided into single-layer graphene, double-layer graphene, few-layer graphene and multi-layer graphene.