Structural characterization, optical properties and in vitro bioactivity of mesoporous erbium-doped hydroxyapatite

We report the successful synthesis of mesoporous erbium doped hydroxyapatite (Er-HA, Ca10−xEr2x/3□x/3(PO4)6(OH)2) by using a rapid and efficient microwave assisted wet precipitation method. Characterization techniques like X-ray diffraction (XRD), Fourier transform infra-red (FTIR), X-ray fluorescence spectrometer (XRF), Brunauer, Emmett and Teller (BET) and transmission electron microscopy (TEM) were used to determine lattice parameters, particle size, degree of crystallinity, elemental composition, surface area and morphology of Er-HA. Results confirmed the formation of crystalline Er-HA having crystallite size of 25 nm with spherical and rod like morphology, while the TEM analysis confirmed the mesoporous nature of the particles. Optical spectra of Er-HA contained seven electron transitions, whereas blue shift in the energy band gap (Eg) was observed upon increase in Er3+ content. The photoluminescence (PL) spectra contained green and red emissions. In vitro bioactivity study conducted in SBF revealed that the incorporation of Er3+ ions into HA structure lead to the faster discharge of Er3+ ions resulting in intense growth of apatite grains on the surface of the Er-HA pellets with Ca/P ratio of 1.72.