Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Academician Lavrentiev ave., 630090 Novosibirsk, Russia.
ACS Nano. 2013 Jan 22;7(1):65-74. doi: 10.1021/nn305268b. Epub 2012 Dec 18.
Highly oriented pyrolytic graphite characterized by a low misorientation of crystallites is fluorinated using a gaseous mixture of BrF(3) with Br(2) at room temperature. The golden-colored product, easily delaminating into micrometer-size transparent flakes, is an intercalation compound where Br(2) molecules are hosted between fluorinated graphene layers of approximate C(2)F composition. To unravel the chemical bonding in semifluorinated graphite, we apply angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and quantum-chemical modeling. The strong angular dependence of the CK and FK edge NEXAFS spectra on the incident radiation indicates that room-temperature-produced graphite fluoride is a highly anisotropic material, where half of the carbon atoms are covalently bonded with fluorine, while the rest of the carbon atoms preserve π electrons. Comparison of the experimental CK edge spectrum with theoretical spectra plotted for C(2)F models reveals that fluorine atoms are more likely to form chains. This conclusion agrees with the atomic force microscopy observation of a chain-like pattern on the surface of graphite fluoride layers.
高取向热解石墨具有小角度晶面取向，其在室温下用 BrF(3)与 Br(2)的混合气体进行氟化。得到的金黄色产物容易剥离成微米大小的透明薄片，是一种插层化合物，其中 Br(2)分子位于氟化石墨烯层之间，其组成近似为 C(2)F。为了阐明半氟化石墨中的化学键，我们应用了角分辨近边 X 射线吸收精细结构（NEXAFS）光谱和量子化学建模。CK 和 FK 边 NEXAFS 光谱对入射辐射的强烈角度依赖性表明，在室温下制备的氟化石墨是一种各向异性材料，其中一半的碳原子与氟原子形成共价键，而其余碳原子保留π电子。将实验的 CK 边谱与为 C(2)F 模型绘制的理论谱进行比较表明，氟原子更有可能形成链。这一结论与原子力显微镜对氟化石墨层表面链状图案的观察结果一致。
