Self-assembly of dandelion-like hydroxyapatite nanostructures via hydrothermal method

Self-assembled dandelion-like hydroxyapatite (HAp) nanostructures were successfully synthesized via a mild template-free hydrothermal process, using ethylenediaminetetraacetic acid (EDTA) as the surfactant. The obtained dandelion-like HAp nanostructures were between 5 and 8 μm in diameter and were composed of radially oriented nanorods with an average diameter of about 200 nm. The X-ray diffraction analysis and Fourier transform infrared spectroscopy were used to characterize the crystalline phase and purity of the synthesized nanostructures. The Brunauer-Emmett-Teller surface area of the dandelion-like nanostructures was measured to be about 39 m²/g. The results of thermal analysis revealed that dandelion-like HAp nanostructures have appropriate thermal stability up to 1200°C. Scanning electron microscopy and transmission electron microscopy analyses showed that EDTA plays an important role in obtaining the dandelion-like morphology, because without it, only monodispersed HAp nanoparticles with an average diameter of about 125 nm were formed. The mechanism for the formation of dandelion-like HAp nanostructures was suggested based on the radial self-assembly of Ca-EDTA molecular complexes.