This work presents a systematic study of the ratio between the integrated intensities of the disorder-induced $D$ and $G$ Raman bands $(I_D∕I_G)$ in nanographite samples with different crystallite sizes $\left(L_a\right)$ and using different excitation laser energies. The crystallite size $L_a$ of the nanographite samples was obtained both by x-ray diffraction using synchrotron radiation and directly from scanning tunneling microscopy images. A general equation for the determination of $L_a$ using any laser energy in the visible range is obtained. Moreover, it is shown that $I_D∕I_G$ is inversely proportional to the fourth power of the laser energy used in the experiment.

Graphene is a two-dimensional network in which sp²-hybridized carbon atoms are arranged in two different triangular sub-lattices (A and B). By incorporating nitrogen atoms into graphene, its physico-chemical properties could be significantly altered depending on the doping configuration within the sub-lattices. Here, we describe the synthesis of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding a unique N-doping site composed of two quasi-adjacent substitutional nitrogen atoms within the same graphene sub-lattice (N₂^AA). Scanning tunneling microscopy and spectroscopy (STM and STS) of NG revealed the presence of localized states in the conduction band induced by N₂^AA-doping, which was confirmed by ab initio calculations. Furthermore, we demonstrated for the first time that NG could be used to efficiently probe organic molecules via a highly improved graphene enhanced Raman scattering.

Double-walled carbon nanotubes are needed in a pure, highly crystalline form before features such as their electronic properties, thermal transport and mechanical behaviour can be investigated. Here we fabricate a paper-like material that consists of hexagonally packed bundles of clean, coaxial carbon nanotubes whose double walls vary little in diameter; it is prepared in high yields using chemical-vapour deposition with a conditioning catalyst and two-step purification. Our results will enable investigation of the physical properties of double-walled carbon nanotubes, which are predicted to be superior to those of both their single- and multiwalled relatives.