Bulk Production of Any Ratio <sup>12</sup>C:<sup>13</sup>C Turbostratic Flash Graphene and Its Unusual Spectroscopic Characteristics
Kevin M. Wyss, Zhe Wang, Lawrence B. Alemany, Carter Kittrell, James M. Tour
Abstract
As graphene enjoys worldwide research and deployment, the biological impact, geologic degradation, environmental retention, and even some physical phenomena remain less well studied. Bulk production of 13C-graphene yields a powerful route to study all of these questions. Gram-scale synthesis of high-quality and high-purity turbostratic flash graphene with varying amounts of 13C-enrichment, from 5% to 99%, is reported here. The material is characterized by solid state NMR spectroscopy, Raman spectroscopy, IR spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. Notably, an unusual enhancement in the Raman spectroscopic D′ peak is observed, resulting from the modification in vibrational frequency through isotopic enrichment favoring intravalley phonon scattering modes. While the IR absorbance spectrum of graphene is for the most part silent, we prepare here 13C-enhanced graphene samples that show a large aromatic 12C═13C stretch that reveals this IR-active mode.