Oxygen is a key chemical element and solid state NMR can provide unique insight into the its local environment. In the last decade there have been significant advances (sensitivity, resolution) in the NMR methodology for non-integer spin quadrupole nuclei such as oxygen and the background to these techniques is presented in this tutorial review. The information that the NMR parameters can provide about the local environment is explained through a series of illustrations from different areas of solid state chemistry and structural science of inorganic materials.

Despite the numerous studies of bone mineral, there are still many questions regarding the exact structure and composition of the mineral phase, and how the mineral crystals become organised with respect to each other and the collagen matrix. Bone mineral is commonly formulated as hydroxyapatite, albeit with numerous substitutions, and has previously been studied by ³¹P and ¹H NMR, which has given considerable insight into the complexity of the mineral structure. However, to date, there has been no report of an NMR investigation of the other major component of bone mineral, calcium, nor of common minority cations like sodium. Here, direct analysis of the local environment of calcium in two biological apatites, equine bone (HB) and bovine tooth (CT), was carried out using both ⁴³Ca solid state NMR and Ca K-edge X-ray absorption spectroscopy, revealing important structural information about the calcium coordination shell. The ⁴³Ca δ_iso in HB and CT is found to correlate with the average Ca–O bond distance measured by Ca K-edge EXAFS, and the ⁴³Ca NMR linewidths show that there is a greater distribution in chemical bonding around calcium in HB and CT, compared to synthetic apatites. In the case of sodium, ²³Na MAS NMR, high resolution 3Q-MAS NMR, as well as ²³Na{³¹P} REDOR and ¹H{²³Na} R³-HMQC correlation experiments give the first direct evidence that some sodium is located inside the apatite phase in HB and CT, but with a greater distribution of environments compared to a synthetic sodium substituted apatite (Na-HA).

New natural-abundance ${}^{43}\mathrm{Ca}$ magic angle spinning (MAS) NMR data measured at high magnetic field $\left(14.1\mathrm{T}\right)$ is presented for a range of crystalline calcium-containing binary and ternary inorganic compounds. The combination of high field, moderate MAS (up to $4.5\mathrm{kHz}$), and large sample volume (a $9.5\mathrm{mm}$ diameter MAS rotor) means that a good signal-to-noise ratio can generally be obtained in a time ($\sim 12\mathrm{h}$) that makes ${}^{43}\mathrm{Ca}$ NMR a feasible approach for determining information about calcium siting in a wide range of materials of physical interest. This study greatly increases the number of ${}^{43}\mathrm{Ca}$ NMR parameters determined for solid materials in the literature, extending reports to local nearest-neighbor coordinations to other than oxygen. These data show that the isotropic chemical shift range is $>250\mathrm{ppm}$ and typically that the quadrupole interaction is $<4\mathrm{MHz}$. In ternary compounds where Ca is coordinated in the nearest-neighbor shell by only oxygen, the isotropic ${}^{43}\mathrm{Ca}$ chemical shift correlates well to the mean Ca-O distance, consistent with the only previous study. In binary compounds the isotropic ${}^{43}\mathrm{Ca}$ chemical shift does not appear to be correlated with the mean $\mathrm{Ca}\text{−}X$ bond length. The extension of natural-abundance ${}^{43}\mathrm{Ca}$ MAS NMR studies to amorphous materials are reported by examining sol-gel prepared calcium silicate materials. The data show that in the initial amorphous mixture at lower temperatures $(120–350°\mathrm{C})$ the calcium environment is more like that in the parent calcium nitrate than a silicate, and that further heat treatment causes very significant broadening of the calcium resonance. The implications of this observation for the use of natural-abundance ${}^{43}\mathrm{Ca}$ MAS NMR structural studies of amorphous materials are examined.

This study demonstrates the utility of the novel Field Sweep Fourier Transform (FSFT) method for acquiring wideline ¹⁹⁵Pt NMR data from various sized Pt nanoparticles, Pt–Sn intermetallics/bimetallics used to catalyse oxidative processes in fuel cell applications, and various other related Pt₃X alloys (X = Al, Sc, Nb, Ti, Hf and Zr) which can facilitate oxygen reduction catalysis. The ¹⁹⁵Pt and ¹¹⁹Sn NMR lineshapes measured from the PtSn intermetallic and Pt₃Sn bimetallic systems suggest that these are more ordered than other closely related bimetallic alloys; this observation is supported by other characterisation techniques such as XRD. From these reconstructed spectra the mean number of atoms in a Pt nanoparticle can be accurately determined, along with detailed information regarding the number of atoms present effectively in each layer from the surface. This can be compared with theoretical predictions of the number of Pt atoms in these various layers for cubo-octahedral nanoparticles, thereby providing an estimate of the particle size. A comparison of the common NMR techniques used to acquire wideline data from the I = 1/2 ¹⁹⁵Pt nucleus illustrates the advantages of the automated FSFT technique over the Spin Echo Height Spectroscopy (SEHS) (or Spin Echo Integration Spectroscopy (SEIS)) approach that dominates the literature in this area of study. This work also presents the first ¹⁹⁵Pt NMR characterisation of novel small Pt₁₃ nanoclusters which are diamagnetic and thus devoid of metallic character. This unique system provides a direct measure of an isotropic chemical shift for these Pt nanoparticles and affords a better basis for determining the actual Knight shift when compared to referencing against the primary IUPAC shift standard (1.2 M Na₂PtCl_6(aq)) which has a very different local chemical environment.