Investigation on the Three-Dimensional Nanostructure and the Optical Properties of Hydroxyapatite/Magnetite Nanocomposites Prepared from Natural Resources

Hydroxyapatite, which has been widely used in the medical field in the last couple of years, is a superior biomaterial due to its biocompatibility and nontoxicity. Hydroxyapatite requires highly magnetic materials to perform maximally in specific medical fields. In this study, hydroxyapatite/ magnetite composites mainly composed of limestone and natural iron sand were synthesized through a coprecipitation method, and composites having different hydroxyapatite-to-magnetite mass ratios were compared. The crystal structure, particle size, fractal dimension, morphology, functional group, and energy gap were characterized using X-ray diffraction (XRD), synchrotron X-ray scattering (SAXS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and ultraviolent-visible (UV-Vis) spectroscopy. The research results showed that the hydroxyapatite and magnetite phases had a hexagonal structure and cubic structure, respectively. In general, from the FTIR data analysis, the hydroxyapatite and magnetite particles were identified from the functional groups of phosphate, iron-oxygen, carbonate, and hydroxyl. Moreover, depending on particle size, the samples consisting of 3.7-nm primary particles formed a cluster with a massive three-dimensional structure. Meanwhile, the energy gap showed various values ranging between 3.25 and 3.86 eV.