Monitoring of hydroxyapatite conversion by luminescence intensity of Eu3+ ions during mineralization of Eu3+-doped β-Ca2SiO4

• β-Ca2SiO4:Eu3+ powders were prepared by sol–gel process.
• Ca10(PO4)6(OH)2 formed when β-Ca2SiO4 was immersed in phosphate solution.
• Eu3+ was used as a luminescence probe to monitor the process of mineralization.
• The technique may be used for biomaterials to monitor the in vivo mineralization.

β-Dicalcium silicate (β-Ca2SiO4) doped with Eu3+ was synthesized by sol–gel method. The luminescence intensity of the mineralization products formed during the hydroxyapatite (Ca10(PO4)6(OH)2, HA) conversion of Eu3+-doped β-Ca2SiO4, in 0.25 M K2HPO4 solution, were detected using luminescence spectroscopy. The results indicated that the luminescence intensity of Eu3+ ion gradually depressed with prolonged mineralization time, and it could hardly be detected with the complete transformation from β-Ca2SiO4:Eu3+ to hydroxyapatite. The change of Eu3+ ionic concentrations in the mineralization products and the final solutions after conversion reaction, were further examined using energy-dispersive X-ray and inductively-coupled plasma mass spectrometry, respectively. This suggested that the process of mineralization can be monitored with the luminescence intensity of Eu3+ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring hydroxyapatite conversion with a fiber luminescence spectrometer.