Fig. 1: Identification of oxygen sites by 1D 17O MAS NMR and 2D 17O 3QMAS NMR.
From: Mapping the oxygen structure of γ-Al2O3 by high-field solid-state NMR spectroscopy
a 1D 17O MAS NMR spectrum of γ-Al2O3 acquired at 35.2 T and partially enlarged 17O spectrum, b sheared 2D 17O 3QMAS spectrum of γ-Al2O3 recorded on 35.2 T and projection (blue) in isotropic dimension with the simulated spectrum (purple) deconvoluted by five individual Gaussian lines (black, A-E denote as five individual oxygen sites), c sheared 2D 17O 3QMAS spectrum of γ-Al2O3 recorded at 18.8 T. Green lines in 2D spectra represent chemical shift/diagonal axis (CQ = 0). OIV and OIII denote 4-coordinated and 3-coordinated oxygen sites, respectively. d, e The best-fit simulation spectra (purple) of the 1D 17O MAS NMR spectra (black) of γ-Al2O3 obtained at 35.2 T and 18.8 T. The 1D spectra are deconvoluted with the DMFIT program57 according to the NMR parameters of five oxygen sites (A-E) in Table S1. The acquisition times of the 2D 17O 3QMAS spectra at 35.2 T and 18.8 T are ca. 0.53 h and ca. 40 h, respectively. Asterisks denote spinning sidebands.
