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13C, 14N, 15N, 17O, and 35Cl NMR parameters, including chemical shift tensors and quadrupolar tensors for 14N, 17O, and 35Cl, are calculated for the crystalline forms of various amino acids under periodic boundary conditions and complemented by experiment where necessary. The 13C shift tensors and 14N electric field gradient (EFG) tensors are in excellent agreement with experiment. Similarly, static 17O NMR spectra could be precisely simulated using the calculation of the full chemical shift (CS) tensors and their relative orientation with the EFG tensors. This study allows correlations to be found between hydrogen bonding in the crystal structures and the 17O NMR shielding parameters and the 35Cl quadrupolar parameters, respectively. Calculations using the two experimental structures for L-alanine have shown that, while the calculated isotropic chemical shift values of 13C and 15N are relatively insensitive to small differences in the experimental structure, the 17O shift is markedly affected.

Polyhedral octahydridosilsesquioxanes, [HSiO1.5]8 (1) and [(HSiMe2O)SiO1.5]8 (3) were hydrosilylatively copolymerized with stoichiometric amounts of the octavinylsilsesquioxanes, [vinylSiO1.5]8 (2) and [(vinylSiMe2O)SiO1.5]8 (4) in toluene using platinum divinyltetramethyldisiloxane, “Pt(dvs)”, as catalyst. The degree of condensation of the resultant four copolymers ranges from 43% to 81% depending on intercube chain lengths, as determined by solid state 13C and 29Si MAS NMR analyses, using cross-polarization (CP) techniques. The presence of residual functional groups was confirmed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Polymer porosities were measured using nitrogen sorption, positron annihilation lifetime spectroscopy (PALS), and small angle X-ray scattering (SAXS) methods. The combination of these three techniques allows a relatively complete description of the pore sizes and pore size distributions in these materials. The pores in the cube interiors are ∼0.3 nm in diameter, while those between the cubes range from 1 to 50 nm in diameter (for polymer 3 + 4). Nitrogen sorption analyses give specific surface areas (SSAs) of 380 to 530 m2/g with “observable” pore volumes of 0.19−0.25 mL/g.

The incorporation of Mg in hydroxyapatite (HA) was investigated using multinuclear solid state NMR, X-ray absorption spectroscopy (XAS) and computational modeling. High magnetic field 43 Ca solid state NMR and Ca K-edge XAS of a ~10% Mg-substituted HA were performed, bringing direct evidence of the preferential substitution of Mg in the Ca(II) position. 1 H and 31 P solid state NMR show that the environment of the anions is disordered in this substituted apatite phase. Both Density Functional Theory (DFT) and interatomic potential computations of Mg-substituted HA structures are in agreement with these observations. Indeed, the incorporation of low levels of Mg in the Ca(II) site is found to be more favourable energetically, and the NMR parameters calculated from these optimized structures are consistent with the experimental data. Calculations provide direct insight in the structural modifications of the HA lattice, due to the strong contraction of the M•••O distances around Mg. Finally, extensive interatomic potential calculations also suggest that a local clustering of Mg within the HA lattice is likely to occur.

Combination of one-dimensional and two-dimensional solid state magic angle spinning nuclear magnetic resonance (MAS NMR) experiments has been used to investigate the hybrid organicinorganic interfaces in surfactant templated silicas. Samples prepared with cetyltrimethylammonium 2 bromide (CTAB) under acidic (HCl) and basic (NaOH) conditions have been compared. The use of sequences based on the 29 Si-1 H heteronuclear dipolar interactions allows us to selectively filter the NMR response of the protons close to the Si surface sites showing directly the clear difference between the two systems. The basic sample is characterised by a small amount of Si-OH groups, and a short distance between the Si-Osurface groups and the surfactant polar head group, while the acidic sample exhibits a silanol-rich surface with a longer distance between the Si surface sites and the polar head groups. The nature of the interface induces consequent differences in the structure of the adsorbed water layers present at the interface, and this has been revealed by near infrared experiments, as well as 1 H MAS NMR spectra recorded on dehydrated and partially re-hydrated samples. One objective of this work was also to show that the use of standard solid state NMR conditions (magnetic field of 7 T and magic angle spinning frequency less than 15 kHz) can be largely sufficient to get extremely valuable information regarding the silica/surfactant interfaces.

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The interfaces within bones, teeth and other hybrid biomaterials are of paramount importance but remain particularly difficult to characterize at the molecular level because both sensitive and selective techniques are mandatory. Here, it is demonstrated that unprecedented insights into calcium environments, for example the differentiation of surface and core species of hydroxyapatite nanoparticles, can be obtained using solid-state NMR, when combined with dynamic nuclear polarization. Although calcium represents an ideal NMR target here (and de facto for a large variety of calcium-derived materials), its stable NMR-active isotope, calcium-43, is a highly unreceptive probe. Using the sensitivity gains from dynamic nuclear polarization, not only could calcium-43 NMR spectra be obtained easily, but natural isotopic abundance 2D correlation experiments could be recorded for calcium-43 in short experimental time. This opens perspectives for the detailed study of interfaces in nanostructured materials of the highest biological interest as well as calcium-based nanosystems in general.

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