Ethylenediamine tetraacetic acid (EDTA) is considered as an effective crystal growth modifier for template-assisted hydrothermal synthesis of hydroxyapatite (HA) materials. In this work, flowerlike carbonated HA (CHA) microspheres were synthesized using EDTA via a one-step hydrothermal route. The phase, functional groups, morphology, and particle size distribution of the products were examined by X-ray diffraction, Fourier transform infrared spectrometer, field-emission scanning electron microscopy as well as laser diffraction particle size analysis. Results show that the morphology of the products can be well controlled by adjusting the EDTA concentration. With an increase of the EDTA concentration, the particle size of flowerlike microspheres decreased from tens of microns down to a few microns. The underlying mechanism for the morphological transition of CHA microspheres with different concentrations of EDTA under the hydrothermal conditions was proposed. This work provides a simple way to controllably fabricate CHA microspheres with various sizes using the same synthesis system for biomedical applications, such as cell carriers and drug delivery.

Flowerlike CHA microspheres with different sizes were obtained via a hydrothermal synthesis. During the experiment, Ca(NO₃)₂ (0.01 mol/L), (NH₄)₂HPO₄ (0.06 mol/L) and urea (0.1 mol/L) were mixed homogeneously on a magnetic stirrer (Zhengzhou, Henan, China). Then dilute HNO₃ solution (volume ratio of nitric acid to DI water=1:2) were added to the mixture dropwise till the pH value reached 3.50. After mixing well, EDTA (0.01 M, 0.2 M, 2 M) was added into the above clear solution, respectively. Finally, 80 ml of the reactants were moved to 100 ml stainless steel autoclaves and treated at 180°C for 5 h. After the reaction, the resultants were washed by DI water and ethanol thoroughly, and dried at 80°C.

With the help of X-ray diffractometer (XRD, Bruker D8 Advance, Cu Kα radiation source, λ = 1.5418 Å) and Fourier transform infrared (FTIR, Bruker Tensor 27) spectroscopy, the phase identification information and functional groups of the products were obtained. A field emission scanning electron microscope (FE-SEM, SU-70) was applied to characterize the products’ morphology. Due to the inconductivity of the samples, they need to be sprayed with gold before the FE-SEM test to increase the conductivity. The particle size distribution was evaluated by a laser particle analyzer (PSD, LS13320) and DI water was chosen as the dispersion medium.

There are no missing values.