Double cross-polarization MAS NMR in the assignment of abundant-spin resonances: 19F-{29Si}-19F FBCP/MAS NMR of fluoride ions incorporated in calcium silicate hydrate (C-S-H) phases

A new version of the double cross-polarization MAS NMR experiment, which transfers polarization Forth and Back (FBCP) between high- and low-gamma spin nuclei, is presented. The pulse sequence is demonstrated by F-19-{Si-29}-F-19 and F-19-{C-13}-F-19 FBCP NMR spectra of a mixture of cuspidine (Ca4Si2O7F2) and Teflon (-CF2-)(n). The experiment is useful for assignment of the high-gamma spin resonances, as demonstrated by F-19-{Si-29}-F-19 FBCP NMR of a fluoride-containing calcium-silicate-hydrate (C-S-H) phase, where the F-19 resonance from fluoride ions incorporated in the interlayer structure of the C-S-H phase is identified. (C) 2012 Elsevier Inc. All rights reserved.