ABSTRACT
Phenomenon ................................................................................... 93 2.2.4 Relaxation Phenomena .................................................................. 97 2.2.5 Nuclear Spin Interactions ............................................................ 100 2.2.6 Solid-State NMR Methods .......................................................... 102
2.2.6.1 Dipolar Decoupling....................................................... 103 2.2.6.2 Magic-Angle Spinning (MAS) ..................................... 104 2.2.6.3 Cross-Polarization (CP) ................................................ 107
2.3 Practical Aspects of Solid-State 13C NMR in Carbon Science ............... 109 2.3.1 Chemical Shifts ........................................................................... 109 2.3.2 Direct-versus Cross-Polarization .................................................110 2.3.3 Dipolar Dephasing, Spectral Editing, and Spectral
Parameters Derived from 13C NMR Spectra ................................114 2.3.4 Magnetic Field Strength ...............................................................117 2.3.5 Spinning, Tuning, and Related Matters ....................................... 120 2.3.6 Referencing and Setting Up the NMR Experiment ..................... 123 2.3.7 Processing the Free Induction Decay (FID) and Obtaining
the 13C NMR Spectrum ............................................................... 127
LIST OF ABBREVIATIONS AND ACRONYMS: 1D: one-dimensional 2D: two-dimensional CP: cross-polarization CRAMPS: combined rotation and multiple-pulse spectroscopy CSA: chemical shift anisotropy CVD: chemical vapor deposition CW: continuous wave DAS: dynamic angle spinning DD: dipolar dephasing DNP: dynamic nuclear polarization DOR: double rotation EFG: electric ƒeld gradient ESR: electron spin resonance FID: free induction decay GIC: graphite intercalation compound HETCOR: heteronuclear correlation HOPG: highly oriented pyrolytic graphite MAS: magic-angle spinning MQ-MAS: multiple-quantum magic-angle spinning NMR: nuclear magnetic resonance NQR: nuclear quadrupole resonance RAMP CP: ramped amplitude cross-polarization REDOR: rotational echo double resonance RF: radiofrequency S/N: signal-to-noise SPE: single pulse excitation TMS: tetramethylsilane
2.4 Survey of Selected Applications of Solid-State NMR to Carbon Materials .................................................................................................. 129 2.4.1 13C NMR Studies ......................................................................... 129 2.4.2 NMR of Other Nuclides .............................................................. 129
2.5 Concluding Remarks .................................................................................. 133 2.5.1 Routine 13C NMR Analyses ........................................................... 133 2.5.2 13C NMR Studies of New Carbon Forms .................................... 137 2.5.3 NMR Spectroscopy Using Other Nuclides .................................. 139 2.5.4 Advanced Methods in Solid-State NMR Spectroscopy of
Carbons ........................................................................................ 142 Acknowledgments ............................................................................................. 146 References ......................................................................................................... 146
TOSS: total suppression of spinning sidebands TPPM: two pulse phase modulation VACP: variable amplitude cross-polarization VCT: variable contact time VSL: variable spin-lock WISE: wide-line separation
Nuclear magnetic resonance (NMR) has been long recognized as a powerful tool for the chemical and physical investigation of both organic and inorganic substances. If in the more remote past high-resolution NMR studies were almost entirely conƒned to liquid substances or solutions, the advent of high-resolution solid-state methods in the 1970s made solid-state NMR an equally widespread and useful spectroscopic technique [1,2]. As such, NMR has been used for the study of many forms of carbon-based materials, including graphite, diamond, fullerenes, coals, pitches, cokes, and chars. By far the most commonly used approach in these studies involves the recording of 1H and 13C NMR spectra, obviously due to the large contents of these dominant elements in carbon materials. But other nuclei such as 7Li, 14N, 17O, 23Na, 29Si, 31P, and 129Xe, among others, have been used as local probes of chemical and structural features in speciƒc investigations as well.
