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Graphene is the only form of carbon (or solid material) in which every atom is available for chemical reaction from two sides (due to the 2D structure). Atoms at the edges of a graphene sheet have special chemical reactivity. Graphene has the highest ratio of edge atoms of any allotrope. Defects within a sheet increase its chemical reactivity. [1]
The graphene sheet thus displays a semimetallic (or zero-gap semiconductor) character. Two of the six Dirac points are independent, while the rest are equivalent by symmetry. In the vicinity of the K-points the energy depends linearly on the wave vector, similar to a relativistic particle.
Graphene oxide flakes in polymerss display enhanced photo-conducting properties. [222] Graphene is normally hydrophobic and impermeable to all gases and liquids (vacuum-tight). However, when formed into a graphene oxide-based capillary membrane, both liquid water and water vapor flow through as quickly as if the membrane were not present.
The hydrophobic effect represents the tendency of water to exclude non-polar molecules. The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect.
[1] [2] The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. [3]
It is also frequently referred to by the symbol P, especially in the English literature. It is also known as n-octanol-water partition ratio. [63] [64] [65] K ow, being a type of partition coefficient, serves as a measure of the relationship between lipophilicity (fat solubility) and hydrophilicity (water solubility) of a substance. The value ...
It is widely agreed that the water repellency of biological objects is due to the Cassie-Baxter equation. If water has a contact angle between 0 < θ < 90 ∘ {\displaystyle 0<\theta <90^{\circ }} , then the surface is classed as hydrophilic, whereas a surface producing a contact angle between 90 ∘ < θ < 180 ∘ {\displaystyle 90^{\circ ...
Side view of ABA layer stacking in graphite. Graphite consists of stacked sheets of covalently bonded carbon. [5] [6] The individual layers are called graphene.In each layer, each carbon atom is bonded to three other atoms forming a continuous layer of sp 2 bonded carbon hexagons, like a honeycomb lattice with a bond length of 0.142 nm, and the distance between planes is 0.335 nm. [7]