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 (N2AA). Scanning tunneling microscopy and spectroscopy (STM and STS) of NG revealed the presence of localized states in the conduction band induced by N2AA-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.

Novel Physical Phenomena may arise from co-axial nanotube structuresHighly crystalline and pure double-walled carbon nanotubes (DWNTs) are needed in order to probe electronic properties, thermal transport and mechanical behavior of individual DWNTs.Here we report the fabrication of a new type of a paper-like material consisting of high-purity DWNTs in high yields using a catalytic chemical vapor deposition (CVD) method in conjunction with an optimized purification treatment. These tubes are hexagonally packed in bundles and show a narrow diameter distribution.DWNTs, which consist of two concentric graphene cylinders, have attracted the attention of numerous scientists because these hybrid structures [lying between single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs)], may exhibit intriguing electronic and mechanical properties that have not been reported hitherto. Therefore, various attempts to produce high purity DWNTs have been published [1][2][3][4][5][6][7] . Unfortunately, these reports usually generate mixtures of DWNTs and SWNTs, in addition to metal particles, amorphous carbon and multi-layer carbon nanotubes. The CCVD method is considered to be most efficient in dealing with the large-scale production of nanotubes 8, 9 . Arc-discharge methods and thermal treatments of C 60 peapods result in DWNTs as well as unwanted carbon nanomaterials 1, 4 , and the cross-sections of the DWNTs (using high resolution transmission electron microscope (HRTEM)) were never shown because the uniformity and purity of the DWNT material has not yet reached that of SWNTs [1][2][3][4][5][6][7] .The synthesis of DWNTs was carried out using a conditioning catalyst (Mo/Al 2 O 3 ) on one end of the furnace, and the nanotube catalyst (Fe/MgO) in the middle part of the furnace (see supplemental information). Subsequently, a CH 4 +Ar gas mixture (1:1) was fed into the reactor for 10 minutes at 875°C. When using the conditioning catalyst 10 , preferential growth of DWNTs over SWNTs occurred, possibly due to an increased portion of active carbon species. In order to obtain a pure DWNT paper (Fig. 1a), a two-step purification process was applied to the synthesized products. In particular, HCl treatments (18wt%HCl, 373K, 10hrs) were carried out in order to remove iron catalyst and the supporting material, followed by air oxidation at 500 o C for 30 minutes. The latter process is used to remove amorphous carbon and chemically active SWNTs. After a filtering process, we obtained a dark and stable paper-like sheet, which is very flexible and mechanically stable (tough) (Fig. 1a). Careful HRTEM (JEOL JEM-2010FEF) observations revealed an extremely high-yield of DWNTs (more than 95%) arranged in bundles (Fig. 1c).The DWNT paper (see Fig. 1b and 1c) contains nanotubes with a narrow diameter distribution, exhibiting a hexagonal packing (Fig. 1d). Raman studies were carried out in order to determine the radial breathing mode (RBM) frequency, which is inversely related to the tube diameter.Raman peaks appear above 25...

We report the use of chemical vapor deposition (CVD) for the bulk production (grams per day) of long, thin, and highly crystalline graphene ribbons (<20-30 microm in length) exhibiting widths of 20-300 nm and small thicknesses (2-40 layers). These layers usually exhibit perfect ABAB... stacking as in graphite crystals. The structure of the ribbons has been carefully characterized by several techniques and the electronic transport and gas adsorption properties have been measured. With this material available to researchers, it should be possible to develop new applications and physicochemical phenomena associated with layered graphene.