Graphene Domain Signature of Raman Spectra of sp2 Amorphous Carbons

Abstract

The standard D-G-2D pattern of Raman spectra of sp2 amorphous carbons is considered from the viewpoint of graphene domains presenting their basic structure units (BSUs) in terms of molecular spectroscopy. The molecular approximation allows connecting the characteristic D-G doublet spectra image of one-phonon spectra with a considerable dispersion of the C=C bond lengths within graphene domains, governed by size, heteroatom necklace of BSUs as well as BSUs packing. The interpretation of 2D two-phonon spectra reveals a particular role of electrical anharmonicity in the spectra formation and attributes this effect to a high degree of the electron density delocalization in graphene domains. A size-stimulated transition from molecular to quasi-particle phonon consideration of Raman spectra was experimentally traced, which allowed evaluation of a free path of optical phonons in graphene crystal.

sp2 Carbon Stable Radicals

“…Therefore, having been known for more than one-and-a-half thousand years, amorphous carbon is undergoing a rebirth and appears as agglomerative compositions of framed graphene molecules, thus becoming a special subject of modern nanotechnology. A recent extended study was devoted to a detailed investigation of the structure and chemical composition of amorphous carbons of the highest carbonization [79][80][81][82]. For the first time, reasonable models of graphene molecules, which are the basic structural units (BSUs) of the studied solids and which correspond to both their structure and chemical composition, including a definite C:O:H atom relation, were suggested.…”

“…Bright spots on the N DA distribution maps reveal the radical character of the species. Later on, the models were corrected based on IR reflection [81] and Raman scattering [82] data. The correction concerned the structure-chemical pattern of the heteroatom distribution around the pristine (5,5) NGr molecule, keeping the relation of C:O:H components fixed and the radical character of the models conserved.…”

Lateral Structured Phototransistor Based on Mesoscopic Graphene/Perovskite Heterojunctions

“…The graphene edges can also be testified by the Raman spectra in Figure 1 b. Since the D peak (~1350 cm −1 ) requires a defect for its activation and the G peak (1580 cm −1 ) corresponds to the doubly degenerate zone center E 2g mode, we can see that, the longer the growth time of GNWs used, the larger the intensity ratio of the D to G (I D /I G ), which means more graphene edge defects and a higher degree of disorder shaped [ 30 , 31 ]. However, from the increasing intensity of the D peak and the increasing full width at half maximum (FWHM) of the 2D peak, it could be inferred that a longer growth time leads graphene nanosheets to nanocrystalline graphite.…”

Application of design of experiments (DoE) for optimised production of micro- and mesoporous Norway spruce bark activated carbons

“…The lower I D /I G value indicates that ACs exhibit more perfect and orderly graphite structures with a high graphitisation degree [52][53][54], while a higher I D /I G peak intensity ratio reveals more structural defects in carbon materials. Moreover, I D /I G values also serve to identify the size of the sp 2 domain, related to graphene structure, in the AC structure [53,55]. Figure 5 shows that AC6 (700 °C, 2 h, 2) had the highest graphitisation degree, followed by AC14 (700 °C, 1 h, 1.5)-presenting I D /I G values of 0.85 and 0.88, respectively.…”