|
|Section2= |Section3= }} Graphane is a two-dimensional polymer of carbon and hydrogen with the formula unit (CH)n where ''n'' is large. Graphane should not be confused with graphene, a two-dimensional form of carbon alone. Graphane is a form of hydrogenated graphene. Graphane's carbon bonds are in ''sp''3 configuration, as opposed to graphene's ''sp''2 bond configuration, thus graphane is a two-dimensional analog of cubic diamond. The structure was found, using a cluster expansion method, as the most stable of all the possible hydrogenations ratios of graphene by Marcel H. F. Sluiter and Yoshiyuki Kawazoe in 2003. In 2007, Jorge O. Sofo, Ajay S. Chaudhari, and Greg D. Barber found that the compound has a remarkable stability compared with other compounds containing carbon and hydrogen, such as benzene, cyclohexane, and polyethylene. This group named the predicted compound graphane, because it is the fully saturated version of graphene. They also showed that the new compound is an insulator, suggested chemical functionalization of graphene with hydrogen as a suitable method to open a band gap in graphene, and pointed out the potential of this compound for hydrogen storage.〔 Full hydrogenation from both sides of a graphene sheet results in graphane,〔 but partial hydrogenation leads to hydrogenated graphene. Now they usually imply that the term graphane is used for a case when all graphene's bonds are saturated with hydrogen atoms. All other configurations with partly covered surface of graphene usually named as "graphane-like" structures. Graphane and graphane-like structures can be formed by electrolytic hydrogenation of graphene or few-layer graphene or high-oriented pyrolytic graphite. In the last case mechanical exfoliation of hydrogenated top layers can be used. If graphene rests on a silica surface, hydrogenation on only one side of graphene preserves the hexagonal symmetry in graphane. One-sided hydrogenation of graphene becomes possible due to the existence of ripplings. Because the latter are distributed randomly, the obtained graphane is expected to be a disordered material in contrast to two-sided graphane.〔 Annealing allows the hydrogen to disperse, reverting to graphene,〔Konstantin Novoselov. "Beyond the wonder material". ''Physics World'' August 2009, 27-30.〕 the underlying kinetic mechanism of which has been revealed by theoretical simulations. p-doped graphane is postulated to be a high-temperature BCS theory superconductor with a Tc above 90 K. Any disorder in hydrogenation conformation tend to contract the lattice constant by about 2.0 percent, but hydrogenation will decrease the dependence of the lattice constant on temperature, which indicates the possible application of Graphane in precision instruments. Density functional theory calculations suggested that hydrogenated and fluorinated forms of other group IV (Si, Ge and Sn) nanosheets also present properties similar to graphane. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「graphane」の詳細全文を読む スポンサード リンク
|