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Hydrothermal synthesis of perfectly shaped micro- and nanosized carbonated apatite
Although carbonated apatite (CAp)-based nanomaterials are considered suitable as bone substitutes, for
effective treatment, it is necessary to develop synthetic methods for preparing particles with controlled
sizes and morphologies. Herein, perfectly shaped CAp crystals with uniform sizes and morphologies were
successfully obtained by the reaction of the N,N’-ethylenediaminetetraacetic acid complex of Ca2+ (Ca
[EDTA]) with sodium (di)hydrophosphate and sodium (hydro)carbonate under mild conditions
(120–160 °C, 1–5 h, pH ∼6 or ∼9). Depending on the initial pH value, reaction time, temperature, and
reagent ratio, a wide range of plate-like, rod-like, and prism-like crystal species with different aspect ratios
were synthesized for the first time. X-ray diffraction analysis confirmed that the obtained samples were
mainly B-type CAp species. Energy-dispersive X-ray spectroscopy revealed high Na/Ca ratios (up to 0.3),
whereas Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA) confirmed high
CO32− contents (C/P ratios up to 0.48). The TGA data also showed that the thermal decomposition of the
obtained CAp species involved step-by-step dehydration and CO2 elimination. Furthermore, sintering of
the CAp samples revealed the optimal temperature (850 °C) for preparing the apatite phase, which is
highly active for vancomycin absorption and therefore has potential for applications in biomedicine.