Graphene nanoribbons (GNRs) have recently emerged as alternative 2D semiconductors owing to their fascinating electronic properties that include tunable band gaps and high charge-carrier mobilities. Identifying the atomic-scale edge structures of GNRs through structural investigations is very important to fully understand the electronic properties of these materials. Herein, we report an atomic-scale analysis of GNRs using simulated X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Tetracene with zigzag edges and chrysene with armchair edges were selected as initial model structures, and their XPS and Raman spectra were analyzed. Structurally expanded nanoribbons based on tetracene and chrysene, in which zigzag and armchair edges were combined in various ratios, were then simulated. The edge structures of chain-shaped nanoribbons composed only of either zigzag edges or armchair edges were distinguishable by XPS and Raman spectroscopy, depending on the edge type. It was also possible to distinguish planar nanoribbons consisting of both zigzag and armchair edges with zigzag/armchair ratios of 4:1 or 1:4, indicating that it is possible to analyze normally synthesized GNRs because their zigzag to armchair edge ratios are usually greater than 4 or less than 0.25. Our study on the precise identification of GNR edge structures by XPS and Raman spectroscopy provides the groundwork for the analysis of GNRs.

Reactive surface species present on SiO2 in a mixture with inert ones is one likely origin of charge puddles observed in supported graphenes.

CO2 separation from CO2/CH4 and CO2/H2 mixtures is essential in H2 production from biogas. Although amine-functionalized carbon materials are excellent candidates for selective CO2 adsorption, their adsorption performance depends on the amine edge position, which requires further clarification. Herein, 19 graphene nanoflakes (GNFs) bearing two amines at various positions on the zigzag, corner, and armchair edges were evaluated. All structures exhibited better CO2 adsorption compared to CH4 and H2. In the GNFs with isolated amines, only one main bond (H2 N – C O2) was involved in CO2 adsorption, which was influenced by charge transfer from the GNFs to CO2. GNFs with adjacent amines had an additional hydrogen bond ( H 2N–C O 2) that became stronger with decreasing steric hindrance. The CO2 adsorption performance of amines decreased as the number of methyl groups on the nitrogen increased, which interfered with CO2 adsorption. The presence of H2O hindered the interaction of amines and CO2 owing to the strong hydrogen bond between H2O and amines.

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