Morphology, Structure Evolution and Site‐Selective Occupancy of Eu³⁺ in Ca₁₀(PO₄)₆(OH)₂ Nanorods Synthesized via Subcritical Hydrothermal Method

Abstract

The structure and composition evolution of hydroxyapatite in bone and teeth play important roles on their strength and durability, especially of the local chemical environment of Ca evolution, that determines bone demineralization and osteoporosis. In this paper, we synthesized a series of Eu-doped (2-10%) hydroxyapatite nanorod via subcritical hydrothermal method at high temperature (220-280 o C) with the doped ions fully occupied at Ca1-site. The as-synthesized samples are grown with uniform particle size and shape distribution. Crystal morphology formation mechanism has been discussed based on the Bravais-Friedel-Donnay-Harker method and crystal structure of hydroxyapatite. Powder X-ray diffraction result and Pawley fitting of the diffraction pattern for Eu-doped hydrox-yapatite samples indicate a linear structure evolution with increasing doping level. FTIR spectra suggest the minimal structure change for Eu-doped hydroxyapatite nanocrystals. Photoluminescent spectra of Ca 10 (PO 4 ) 6 (OH) 2 :Eu indicates the doping of Eu happens at the Ca1-site, which shows a concentration-dependent emission intensity evolution behavior. Decay curves for the 5 D 0 ! 7 F 2 transition of Eu 3 + in each samples suggested a longer lifetime in our samples than the similar composition that prepared via other methods. The siteselective occupancy of Eu-doped hydroxyapatite luminescent phenomenon may serve as a potential indicator for monitoring the Ca-loss in bones and teeth that caused osteoporosis in aging people.[a] Dr.