Introduction. Carbon is one of the most abundant elements in nature and is capable of forming stable and highly flexible bonds in low-dimensional materials. The different structures and properties of carbon materials are due to these different carbon–carbon bonds, such as sp3, sp2, and sp hybrids. Carbon atoms form various allotrope through these three hybrid states, including sp3 hybrid diamond1,2, sp3 and sp2 hybrid carbon nanotubes3,4,5,6,7, fullerenes8,9,10,11, and graphene12,13,14,15....