Characterization of Tb-doped hydroxyapatite for biomedical applications: optical properties and energy band gap determination

In the present work, the synthesis, by means of the sol–gel method, of calcium-deficient hydroxyapatite and Tb-doped calcium-deficient hydroxyapatite with dopant content of 10 and 12 wt% is reported. The synthesized samples exhibit diffraction patterns and structural characteristics consistent with those reported in the literature for synthetic hydroxyapatite. The results of the chemical characterization show that the synthesized samples are suitable for biomedical applications, and the incorporation of Tb³⁺ in the host structure occurs both substitutional and by dopant insertion in calcium vacancy sites. In addition, using spectroscopic techniques, the values of the valence band, optical band gap energies, and luminescent response were determined for all samples, concluding that the increase in dopant has the consequence of decreasing the value of the optical band gap, as it was expected; However, it is also observed that the maximum luminescent emission is obtained for the sample synthesized with 10 wt% of terbium.