We have established NMR as a tool for characterizing nanocomposites, typically consisting of inorganic nanoparticles dispersed in an organic polymer, not only in terms of composition, but also in terms of the location of various components relative to the organic-inorganic interface. The composition of the surface layers of both the nanoparticles and the matrix, which are particularly important since they are responsible for the interactions between the components, can be determined by selective NMR techniques, often based on heteronuclear dipolar couplings across the interface.
 This approach has enabled us to demonstrate the presence of citrate strongly bound to apatite nanocrystals in bone, which stabilizes the thin crystals at thicknesses of only 3 – 4 unit cells. [PNAS, 2010)]