Research On The Bioactivity And Luminescence Intensity Of β-Ca₂SiO₄:Eu And CaAl₂O₄:Eu

Bioceramics have been widely used in hard tissue repair materials,such as bone and teeth repair or filler material.Nevertheless,the use in clinical of inert bioceramics has been limited by lacking of biological activity.If the inert bioceramics were implanted for a long time,it would cause loose and pull out.β-Ca₂SiO₄,as a structure ceramic,it has excellent biological activity.After soaking in simulated body fluid,a bone-like apatite（Ca10（PO₄）6（OH）2,HA）coating forms on the surface of β-Ca₂SiO₄.Eu³⁺ ions have been widely researched in the field of luminescence.On the one hand,it can be used as a structure probe to research the structure symmetry properties by analyzing the relative intensity and the peak splitting of the spectrum.On the other hand,Eu³⁺ ions are apply to the fluorescent labeling for biomolecules.The right quality of Eu³⁺ is nontoxic,and suitable for biological environments.In addition,there is a currently research into the phase transformation of CaAl₂O₄ during the sintering process.The results show that the single test methods can not characterize the phase transformation clearly during the sintering process.To cure the above problems,this paper presents new methods on the base of current research about doping Eu ions into β-Ca₂SiO₄ and CaAl₂O₄.In this paper,it was the first time to monitor the dynamic forming process of HA during mineralization by doping Eu³⁺ ions as a fluorescence probe.β-dicalcium silicate（β-Ca₂SiO₄）doped with Eu³⁺ was synthesized by sol-gel method,and the prepared powders were soaked in the phosphate solution to analyze the biological activity.Moreover,CaAl₂O₄:Eu was prepared by Pechini method.XRD,FTIR,SEM,ICP,EDX,TG/DTA were used to characterize the main group,microstructure,the change of ions during the process of mineralization and the phase transformation of CaAl₂O₄.The results have shown that the β-Ca₂SiO₄:Eu has an excellent biological activity after soaking in 0.25 M K2HPO₄ solution with a starting pH value of 7.0 at 37 oC.The rare earth ions play a significant role in monitoring the process of mineralization.With the prolonged soaking time,the luminescence intensity of Eu³⁺ decreased with the forming of HA.After soaking for 3 days,the luminescence intensity could hardly be detected with the complete transformation from β-Ca₂SiO₄:Eu³⁺ to hydroxyapatite.In response to this issue,we developed a qualitative model for the mineralization mechanisms.During the process of mineralization,Eu³⁺ released gradually from the β-Ca₂SiO₄ crystal to the phosphate solution.That is a prescription for the decreasing of the luminescence intensity with the prolonged soaking time.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.Precursor of Europium doped calcium aluminate（CaAl₂O₄:Eu）were prepared by the Pechini technique.Eu was used as a probe to research the change of the crystal structure.With the increase of calcination temperature,the phosphors exhibit color change from bright red to violet upon excitation by UV-light and it showed that an abnormal reduction of Eu³⁺→Eu2+ was observed in monoclinic phase of CaAl₂O₄:Eu samples calcined in air atmosphere at high temperature.Therefore,Eu2+ ions could be used as the local probe to explore the phase transformation of CaAl₂O₄ according to the change of the luminescence properties.The biological activity of CaAl₂O₄ material has been discussed.After soaking in 0.25 M K2HPO₄ solution with a starting pH value of 7.0 at 37 oC for a week,HA was not deposited on the surface of CaAl₂O₄.To this phenomenon,we added some biological materials into CaAl₂O₄ to improve the biological activity.Then CaAl₂O₄ material can be used in the application of hard tissue repair materials with the excellent biological activity and favorable mechanical properties.The novelties of this dissertation are as follows: The rare earth ions play a significant role in monitoring the process of mineralization by analyzing the luminescence intensity.With the increase of the soaking time,Eu³⁺ released gradually from the β-Ca₂SiO₄ crystal to the phosphate solution leading to the change of the luminescence intensity.The results have important reference values in monitoring hydroxyapatite conversion during the process of mineralization.In the meantime,Eu ion could be used as a local probe to explore the phase transformation of CaAl₂O₄ according to the change of the luminescence properties.This feature and the test are complementary to each other to explore the crystal structure change.