“…Concerning 1 H NMR characterizations of the already complex systems of mesoporous
silica coexisting with its heterogeneous surface layer of calcium
phosphates, these NMR peaks are a nuisance and may lead to assignment
ambiguities—even as to the precise organic source molecules, as shown below. However, these NMR signals are worth
discussing in more depth because similar (but distinct) NMR responses
are frequently observed across the shift range 0.8–1.4 ppm
from apatites, encompassing HA, 13−16,22 HCA, 6,13,14,19−21 fluoro-hydroxyapatite, 15,87 as well as bone mineral. 6,13,14 These resonances are usually
very weak from well-crystalline HA, as may be verified
from the 1 H NMR spectra of Figure 6(a, b).…”