Hydrothermal Preparation and Characterization of Zn, Si, Mg, Fe Doped Hydroxyapatite

Doping of trace elements is an effective way to endow hydroxyapatite with more biological functions. But the behaviors of different element doping remained to be further revealed. Here, nine kinds of hydroxyapatite particles containing zinc, silicon, magnesium, iron, manganese, copper, strontium, selenium, and cobalt, respectively, were prepared by parallel hydrothermal synthesis, and their physicochemical properties were studied. The results show that the morphology and crystal growth direction of hydroxyapatite particles are significantly changed, while the phase composition is maintained. The peak intensity of（211） and（112） plane diffraction peaks decreased, accompanied by decreased crystallinity. Analysis results show that the actual doping efficiency obeys the tendency of manganese > zinc >magnesium > iron（trivalent） > strontium > cobalt > copper > selenium > silicon. Among these elements, doping amounts of Mn, Zn and Mg are higher, because their ion radii are closed to that of Ca2+. The low doping efficiency of copper is caused by its complexation with ammonia in synthetic solution, while silicon and selenium are caused by different geometry and charge of SiO32–, SeO32– from that of PO43–. This study reveals the reasonable relationship between doping behavior and ion characteristics, providing a useful reference for design and development of functionalized hydroxyapatite.