Influence of doping strategies on Hydroxyapatite: Modeling approach of structural changes and formation energy of calcium vacancy with stability of Ti4+

This research examines the synthesis, characterization, and computational analysis of hydroxyapatite (HAp) doped with zinc oxide (ZnO) and titanium dioxide (TiO2) to improve structural and antibacterial characteristics. Two approaches for synthesising were employed: Method 1 involved incorporating oxides during the HAp synthesis from CaO, whereas Method 2 introduced oxides after synthesis, simulating a composite structure. Characterization was carried out utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), and antibacterial assessments. XRD verified effective doping, as Zn enhanced crystallite size while Ti generated lattice strain. SEM and EDS analyses revealed a more uniform distribution of dopants in Method 1. Antibacterial assays showed greater efficacy for Zn-doped HAp (Method 1) and Ti-doped HAp (Method 2). DFT calculations highlighted the site preferences of Zn and Ti, and showed a decrease in the formation energy of cation vacancies in presence of non-isovalent dopants and a decrease in the band gap. This research illustrates the impact of synthesis techniques and dopant interactions on HAp-based biomaterials intended for biomedical uses.