Sol–gel synthesis and spectrometric structural evaluation of strontium substituted hydroxyapatite

Abstract

Investigations of the electronic structures of substituted strontium apatites were carried out by using X-ray photo electron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction technique (XRD) has been used to determine the structural parameters. Electron microprobe microanalysis technique was used to estimate the elemental concentrations in each substituted apatite material. The present work aims at studying the changes in the electronic structure of Sr 5(PO 4) 3OH (Sr-HAP) upon isomorphic substitution by F and Cl at the OH site of apatite and Sr by Na at trans Sr-HAP. The ion exchange between Na + in sodium alginate and aqueous Ca 2+ was important for the preparation of calcium hydroxyapatite. In contrast, the reaction of sodium alginate with the mixture of Na 4P 2O 7 and aqueous Sr 2+ afforded strontium hydroxyapatite at the specific ratio. The structure of calcium and strontium phosphates prepared from the sol–gel process evidently depended on the amount of sodium alginate introduced into the mixture of Na 4P 2O 7 and the corresponding divalent cations. The findings have ensured that substitution of Sr-HAP by Na enhances the binding energy of O and Sr core levels. It was also noticed that the same substitution decreases the binding energy of P 2s-level. These observations point out to a decrease in the electron density at P and an increase in the electron density at O in Sr atoms.