Abstract
In this study, different fluoridated hydroxyapatite doped with Eu3+ ion nanoparticles were prepared by the hydrothermal method. The relationship between luminescence enhancement of Eu3+ ions and a fluorine substitution ratio for hydroxyl group in hydroxyapatite was discussed. Moreover, the effect of fluorine substitution for a hydroxyl group on phase composition, crystallinity, and crystal size was studied. Phase composition and chemical structures were identified by X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) Spectroscopy analyses. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) patterns were performed to analyze the morphology and particle size. X-ray Photoelectron Spectroscopy (XPS) patterns were observed to analyze fluorine substitution for the hydroxyl group and chemical state of Eu3+ ions in fluoridated hydroxyapatite. The results of these experiments indicated that the samples with a different fluorine substitution ratio were prepared successfully by maintaining the apatite structure. With an increasing fluorine substitution ratio, the morphology maintained a rod-like structure but the aspect ratio tended to decrease. XPS patterns displayed that the fluorine replaced the hydroxyl group and brought environmental variation. The fluorine ions could affect the crystal field environment and promote luminescence conversion. There was a linear relationship between the fluorine substitution ratio and luminescence enhancement.
Highlights
Hydroxyapatite (Ca10(PO4)6(OH)2), which is known as HAp, is the main inorganic ingredient of hard tissues similar to its mineral constituents [1,2,3], which have outstanding biocompatibility and bioactivity [4,5]
The rare earth (RE) ions doped HAp nanoparticles have better features as luminescence imaging agents including low toxicity, photostability, thermal and chemical stability, and real-time imaging [4,7,8,9]. Their luminescence imaging ability is affected by a degree of crystallinity, size distribution, and dispersion of nanoparticles as well as crystal field contributions [1,5,10]
More attention has been put by the researchers toward the luminescence performance of RE ions in natural as well as synthesized apatites
Summary
Hydroxyapatite (Ca10(PO4)6(OH)2), which is known as HAp, is the main inorganic ingredient of hard tissues similar to its mineral constituents [1,2,3], which have outstanding biocompatibility and bioactivity [4,5]. The RE ions doped HAp nanoparticles have better features as luminescence imaging agents including low toxicity, photostability, thermal and chemical stability, and real-time imaging [4,7,8,9]. Their luminescence imaging ability is affected by a degree of crystallinity, size distribution, and dispersion of nanoparticles as well as crystal field contributions [1,5,10]. Fluoride ions (F− ) are usually used for Crystals 2020, 10, 191; doi:10.3390/cryst10030191 www.mdpi.com/journal/crystals
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