Preparation,Characterization And Computational Simulation Of Sr²⁺/Eu³⁺ Co-doped Hydroxyapatite

Rare earth doped hydroxyapatite fluorescent materials play an increasingly important role in the field of fluorescence imaging.A large number of studies have demonstrated that it is a novel fluorescent probe material with excellent biological and properties through in vitro and in vivo imaging experiments.Rare earth Eu³⁺has characteristic red light,and Sr can promote bone formation.In this paper,Sr²⁺/Eu³⁺co-doped hydroxyapatite material was prepared by chemical co-precipitation method using europium as the luminescent center and strontium doped hydroxyapatite as the luminescentmatrix.By adjusting the composition of luminescent matrix,Eu³⁺mono-doped hydroxyapatite material,Sr²⁺low-doped and Sr²⁺highly-doped europium hydro-xyapatite material were prepared,respectively.The structure of the materials and the relationship between the luminescence behavior and the luminescent matrix were studied by XRD,FT-IR,PL spectra,DFT calculations,Rietveld refinement,and luminescence kinetics.The main results are as follows:?1?The structure and properties of Eu_y-HAp were characterized.The results showed that the structure of hydroxyapatite was less affected by Eu³⁺doping.The fluorescence intensity of the sample increases gradually with the increasing of Eu³⁺content,and tends to be stable in the Eu_0.7-HAp samples,and it can be inferred that it gradually approaches the quenching point of Eu³⁺concentration.The fluorescence lifetime of Eu_y-HAp samples increased firstly and then decreased with the increasing of Eu³⁺content,and the strongest peak appeared in the Eu_0.7-HAp samples,which is about 0.815 ms.?2?The structure and properties of Sr_x-Eu_y-HAp were tested and compared with that of Eu_y-HAp.The results showed that the structure of HAp channel can be expanded in the presence of Sr²⁺.The doping of a small amount of Sr²⁺has low impact on the structure of HAp.However,the fluorescence intensity of Sr²⁺containing materials is increased and the growth rate is about 100%.The fluorescence lifetime of the sample is improved when the content of Sr²⁺is higher than that of Eu³⁺.?3?The structure properties and calculation simulation of Sr_x-Eu-Ca_10-x-HAp material are carried out.The XRD patterns and Rietveldrefinementof samples showed that the doping of Eu had no significant effect on the structure of the samples,while the unit cell parameters and cell volume increased with the increasing of Sr content.The DFT calculation results show that the substitution of Ca?I?site atoms is more prone to occur than the Ca?II?site.The PL analysis indicates that at 394 nm excitation the fluorescence intensity of Sr_x-Eu-Ca_10-x-HAp samples at 596 nm and 618 nm increased firstly and then decreased with the increaseng of Sr content,and the strongest peak appeared in the Sr₇-Eu-Ca₃-HAp samples.At the same time,the fluorescence lifetime of the samples showed the same tendency with the increase of Sr content.In addition,the ratio of magnitude between electric dipole and magnetic dipole transition?I_R/I_O?also increased firstly and decreased subsequently along with the increasing of Sr content in the matrix.Furthermore,the energy transfer parameters?f?calculated from luminescent dynamic of Eu³⁺correlating to different sites and transitions present the reverse change.It is concluded that the doped sites of Eu³⁺ions in the host lattice were affected by the content and location of Sr²⁺ions in the matrix.Thereby a tunable luminescent property of Sr₇-Eu-Ca₃-HAp samples can be obtained by changing the site of Eu ions in the matrix through adjusting the value of Sr/Ca.