Research On The Luminescent Properties And Mineralization Of Rare Earth(Eu³⁺,Sm³⁺,Gd³⁺) Doped Tricalcium Silicate

Tricalcium silicate(Ca3SiOs,C3S)is the main constitute of traditioal ordinary portland cement(OPC).In recent years,much researchs confirmed that tricalcium silicate posses excellent bioactivity,and has the ability to induce the formation of hydroxyapatite(Ca10(P04)6(OH)2,HA)in SBF,can bond with natural bone after it was iplanted into human body,effectively stimulate the formation of new bone,promote the recovery of bone defects.Currectly.tricalcium silicate has attracted much attention in the research and development of bone cement and bioceramic showing great application potentials.Rare erath ions also have been verified showing good biocompatibility,no toxicity to human body in suitable amount,can reduce the cycle of bone remodelling.Now rare earth ions have been widly used in bioimaging and luminescent probe which is important for docrots in preoperative diagnosis and postoperative observation,showing great advantages,such as low cost,high eficiency,good sensitivity and no toxicity.In clinic,if the degradation of tricalcium silicate could be observed in real time conveniently,it is helpful for doctors to make rehabilitation plan for patients.In this paper,Several rare earth ions(Ln3+)-doped tricalcium silicate was synthesised,the phase composition and crystal structure,optical properties and bioactivity of Ln3+-doped tricalcium silicate was systematically syudied,we hope to monitor the degradation of tricalcium siicate by the luminescence of rare earth ions in mineralization,and provide the experimental evidence for the potential clinical application.The paper has six chapters totally.The first chapter is introduction,the second chapter introduce the materisls,equipments and characteristic techniques in experiments.The third chapter introduce the three preparation methods of tricalcium silicate,including precipitation method,sol-gel method and high temperature solid-phase method.The resulting samples was characterized using XRD.The bioactivity of tricalcium silicate was researched using phosphate solution as mineralizaiton solution.The forth to sixth chapters introduce Eu3+,Sm3+,Gd3+doped tricalcium silicate,respectively.The effects of the three rare earth ions on the phase composition and crystal structure,optical properties and bioactivity of tricalcium silicate was discussed.The third chapter introduced the experimental process of precipitation method,sol-gel method and solid-phase method in detail.The resulting samples of the three methods were characterized using XRD and SEM.The results show that pure tricalcium silicate can be synthesised in 1400℃ by precipitation method and the average size of particles is 5-10 pm,however pure tricalcium silicate can be prepared in 1450℃ by sol-gel method and the average size is 30-50 μm.In this paper,rice husk was firstly used as Si source of tricalcium silicate synthesised by solid-phase method.The XRD of sample calcined at 1500℃ shows good crystalline and no obvious inpurity.K2HPO4 aqueous solution(0.25 M)was used as mineralization solution to characterize the bioactivity of tricalcium.The XRD pattern shows that tricalcium silicate shows excellent ability of inducing the formation of hydroxyapatite in phosphate solution.SEM image shows that the morphology of mineralized hydroxyapatite in the surface of tricalcium silicate is needle-likeIn the forth chapter,Eu3+-doped tricalcium silicate(Ca3SiO5)was synthesized by precipitation 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 Ca3SiOs can be monitored through the evolution of optical properties with prolonged soaking time.In the fifth chapter,Sm3+-doped tricalcium silicate was synthesised by precipitation method.The phase composition,crystal structure and luminescent properties of samples were characterized by XRD,Rietveld refinement,FTIR,emission and excitation spectra,respectively.The results showed that the doping of Sm3+ can effectively promote the formation of tricalcium silicate and decrease the content of CaO.Sm3+can stabilize T1,T2,T3 polymorphs in sequence with doping concentration increasing from 0.1 mol%to 3mol%.The luminescent intensity reached maximum at doping concentration of 0.25mol%,than concentration quenching occured.The emitting color of sample under UV-lamp(365 nm)is orange-red,and decay time decreased with increasing doping concentration.Sm3+has inhibitory effect on the bioactivity of tricalcium silicate,decrease the mineralizing speed of tricalcium silicate.In the mineralization process of tricalcium silicate,the emission intenstiy of Sm3+ decreased gradually with prolonged soaking time.Therefore,the change of emission intesnity can be used to monitor the minerlization of tricalicum silicate.In the sixth chapter,Gd3+-doped tricalcium silicate was synthesised by precipitation method.The phase composition,crystal structure and luminescent properties of samples were characterized by XRD,Rietveld refinement,FTIR,emission and excitation spectra,respectively.The results showed that the doping of Gd3+ can effectively promote the formation of tricalcium silicate and decrease the content of CaO.Sm3+ can stabilize T2,T3 polymorphs in sequence with doping concentration increasing from 0.1 mol%to 3mol%.The luminescent intensity reached maximum at doping concentration of 2mol%,than concentration quenching occured.Gd3+-doped tricalcium silicate exhibited a narrow-band emission peak at wavelength of 3 13 nm corresponding to the 6P7/2→8S7/2 transition,and decay time decreased with increasing doping concentration.Gd3+ has inhibitory effect on the bioactivity of tricalcium silicate,decreases the mineralizing speed of tricalcium silicate.In the mineralization process of tricalcium silicate,the emission intenstiy of Gd3+decreased slowly with prolonged soaking time.