Characterization and Luminescence of Eu3+- and Gd3+-Doped Hydroxyapatite Ca10(PO4)6(OH)2

Veronica Paterlini,Giancarlo Della Ventura,Marco Bettinelli,Francesco Capitelli,Asmaa El Khouri,Rosanna Rizzi,Manuela Rossi

doi:10.3390/cryst10090806

Abstract

Luminescence properties of europium-doped Ca10-xEux(PO4)6(OH)2 (xEu = 0, 0.01, 0.02, 0.10 and 0.20) and gadolinium-doped hydroxyapatite Ca9.80Gd0.20(PO4)6(OH)2 (HA), synthesized via solid-state reaction at T = 1300 °C, were investigated using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), and luminescence spectroscopy. Crystal structure characterization (from unit cell parameters determination to refined atomic positions) was achieved in the P63/m space group. FTIR analyses show only slight band shifts of (PO4) modes as a function of the rare earth concentration. Structural refinement, achieved via the Rietveld method, and luminescence spectroscopy highlighted the presence of dopant at the Ca2 site. Strong luminescence was observed for all Eu- and Gd-doped samples. Our multi-methodological study confirms that rare-earth (RE)-doped synthetic hydroxyapatites are promising materials for bio-imaging applications.

Highlights

Synthetic hydroxyapatite Ca10 (PO4 )6 (OH)2 (HA) is the calcium phosphate compound having the most close affinities with the mineral component of human bones and teeth, with excellent biocompatibility and bioactivity, due to its non-toxic and noninflammatory properties [1]
We investigate the luminescence behaviour of a set of Eu3+ -doped Ca10-x REx (PO4 )6 (OH)2 hydroxyapatite, with x = 0, 0.01, 0.02, 0.10 and 0.20, and of Ca9.80 Gd0.20 (PO4 )6 (OH)2, through a multidisciplinary study based on scanning electron microscopy (SEM), powder X-Ray diffraction (PXRD), Fourier transform infrared (FTIR), and luminescence spectroscopies
High-resolution aggregates are higher.SEM investigation of Eu-doped hydroxyapatite Ca9.80Gd0.20(PO4)6(OH)2 (HA) samples showed the presence of three different morphologies: compact and porous aggregates

Summary

Introduction

Synthetic hydroxyapatite Ca10 (PO4 ) (OH) (HA) is the calcium phosphate compound having the most close affinities with the mineral component of human bones and teeth, with excellent biocompatibility and bioactivity, due to its non-toxic and noninflammatory properties [1] For these reasons, the most common applications of HA are in biomedical sciences, a wide range of other applications, e.g., as material suitable for laser ablation [2], host for toxic substances [3], and gas sensors [4] have been explored. In biomedical sciences, HA is used in: orthopedics, such as coating for metallic prothesis, bone filler [5] and as composite materials HA/poly (L-lactide) for bone tissue scaffolds [6]; orthodontics, e.g., cements and dental implants [7]; oncology (cancer treatments) [8]; carrier in drug delivery applications [9,10], and so on. Incorporation of RE into the HA matrix overcome the risk of toxicity deriving from RE ions in view of biomedical applications [13]

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Conclusion