Surface engineered hollow hydroxyapatite microspheres: Hydrothermal synthesis and growth mechanisms

• Published in: Solid state sciences 2020-08, Vol.106, p.106301, Article 106301
• Main Authors: Daryan, Sahar Hashemi, Khavandi, Alireza, Javadpour, Jafar
• Format: Article
• Language: English
• Subjects: Citrate; Hierarchical microspheres; Hollow; Hydrothermal synthesis; Hydroxyapatite; Nanosheet
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2020.106301

Well-organized hollow hierarchical hydroxyapatite microspheres were prepared hydrothermally via a template free process. Citrate was used as chelating or morphology regulating agent in this study. In the presence of regulating agent two-dimensional monetite phase evolved into three-dimensional hollow hydroxyapatite microspheres with an average diameter of 4 μm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the importance of Citrate/Calcium (Cit/Ca) ratio in regulating the particle morphology. The results indicate that the surface morphology of microspheres can be engineered from nanosheets to nanorods by regulating agent concentration. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed crystallinity and purity in the synthesized powders. Brunauer-Emmett-Teller (BET) indicated an increase in the specific surface area with the change from hydroxyapatite microspheres with nanosheets (HAMNS) to hydroxyapatite microspheres with nanorods (HAMNR) on the surface. Thermodynamic and kinetic theories are proposed to account for the observed changes in the surface morphology and crystal growth. [Display omitted] •Synthesis of hollow hierarchical hydroxyapatite microspheres hydrothermally.•Investigation of surface morphology change as a function of Citrate/Calcium ratio.•The study of the crystal growth mechanisms of hydroxyapatite and the thermodynamic evolution of surface morphology.