Investigation of structural, photoluminescence, and electronic density of states of terbium-doped hydroxyapatite nanostructures

The understanding of the incorporation of rare-earth elements in hydroxyapatite has not yet been comprehensively studied. In this work, hydroxyapatite (HAp) and terbium-doped (1%) hydroxyapatite (THAp) are prepared by a wet chemical route. X-ray diffraction (XRD) reveals the semicrystalline nature of THAp than that of HAp. There is a contraction of the P-O bonding on THAp. Field Emission-Scanning Electron Microscopy (FE-SEM) shows a nanosphere, nanorod, and nanoplate morphology of the samples. Photoluminescence (PL) of the incorporated sample exhibits a prominent green emission. X-ray photoemission spectroscopy (XPS) reveals an increase in the charge state of Ca in THAp compared to HAp. The Fermi level of HAp and THAp is 8.25 eV and 11.07 eV, respectively. Projected density of states reveals that the Ca 4p states are dominant in the conduction band. Furthermore, the Ca 4p states hybridize well with the P 2p/O 2p states in THAp. These experimental and theoretical results disclose that the terbium-doped hydroxyapatite is a potential candidate for the development of rare-earth-based calcium phosphate for an optoelectronic device application.