Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA.
J Am Chem Soc. 2010 Apr 28;132(16):5672-6. doi: 10.1021/ja9030243.
Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D (13)C double-quantum/single-quantum correlation SSNMR spectrum of (13)C-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp(2), 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). (13)C chemical shift anisotropy (CSA) patterns measured by a 2D (13)C CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems.
化学改性石墨烯和其他基于石墨的材料因其作为轻质电子和结构纳米材料的独特潜力而引起了越来越多的关注。根据 NMR 或其他光谱数据构建非晶态石墨基材料的结构模型是一个重要的挑战。为了解决这一挑战，提出了一种基于固态 NMR（SSNMR）的结构建模方法，用于研究氧化石墨（GO），GO 是一种重要的前体和改性石墨烯的有趣基准体系。通过比较（13）C 标记 GO 的二维（13）C 双量子/单量子相关 SSNMR 实验谱与使用从头算几何优化和化学位移计算模拟的不同结构模型的谱，对该方法进行了验证。结果表明，GO 样品的光谱特征通过基于 Lerf-Klinowski 模型（Lerf，A.等人，Phys. Chem. B 1998，102，4477）的几何优化结构模型得到了最好的重现，该模型由相互连接的 sp（2）、1,2-环氧和 COH 碳原子组成。该研究还令人信服地排除了其他先前提出的模型的可能性，包括涉及 1,3-环氧碳原子的高度氧化结构（Szabo，I.等人，Chem. Mater. 2006，18，2740）。通过二维（13）C CSA/各向同性位移相关 SSNMR 测量的（13）C 化学位移各向异性（CSA）模式通过从头算计算得到的化学位移张量得到了很好的重现。本文提出的方法可能适用于其他化学改性石墨烯和基于石墨的系统。
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