Mineralization and optical properties of Eu3+-doped tricalcium silicate soaked in dilute K2HPO4 aqueous solution

Eu3+-doped tricalcium silicate (Ca3SiO5) was synthesized by two-step precipitation and combinated calcination method. The samples were investigated before and after soaking in dilute K2HPO4 aqueous solution for different times using X-ray diffraction method (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray energy-dispersive spectra (EDS). The optical properties of as-prepared and mineralized samples were evaluated using luminescence spectroscopy respectively. The results showed that, with prolonged soaking time, Eu3+-doped tricalcium silicate gradually transformed into hydroxyapatite and showed good bioactivity. Meanwhile, the luminescence intensity of Eu3+ ion gradually decreased; the intensity ratio between electric dipole transition (5D0→7F2) and magnetic dipole transition (5D0→7F1) increased; the emitting color of mineralized samples under UV-lamp and its CIE coordinates changed from orange-red to deep-violet. These phenomena revealed that the mineralization of Eu3+-doped Ca3SiO5 can be monitored through the evolution of optical properties with prolonged soaking time.