Abstract
The hydroxyapatite nanopowders of the Eu3+-doped, Cu2+-doped, and Eu3+/Cu2+-co-doped Ca10(PO4)6(OH)2 were prepared by a microwave-assisted hydrothermal method. The structural and morphological properties of the products were investigated by X-ray powder diffraction (XRD), transmission electron microscopy techniques (TEM), and infrared spectroscopy (FT-IR). The average crystal size and the unit cell parameters were calculated by a Rietveld refinement tool. The absorption, emission excitation, emission, and luminescence decay time were recorded and studied in detail. The 5D0 → 7F2 transition is the most intense transition. The Eu3+ ions occupied two independent crystallographic sites in these materials exhibited in emission spectra: one Ca(1) site with C3 symmetry and one Ca(2) sites with Cs symmetry. The Eu3+ emission is strongly quenched by Cu2+ ions, and the luminescence decay time is much shorter in the case of Eu3+/Cu2+ co-doped materials than in Eu3+-doped materials. The luminescence quenching mechanism as well as the schematic energy level diagram showing the Eu3+ emission quenching mechanism using Cu2+ ions are proposed. The electron paramagnetic resonance (EPR) technique revealed the existence of at least two different coordination environments for copper(II) ion.
Highlights
Apatite-type materials can be applied in many industrial fields, e.g., as sorbents, biocompatible and biodegradable materials for bone and teeth reconstruction, catalysts, materials for the wastewater treatment, fertilizers, and luminescent materials [1,2]
The Ca10(PO4)6(OH)2 nanopowders doped with Eu3+ and Cu2+ ions were synthesized by a microwave-assisted hydrothermal method
The theoretical fit with the observed X-ray powder diffraction (XRD) pattern was found to be in good agreement, which indicated the success of the Rietveld refinement method
Summary
Apatite-type materials can be applied in many industrial fields, e.g., as sorbents, biocompatible and biodegradable materials for bone and teeth reconstruction, catalysts, materials for the wastewater treatment, fertilizers, and luminescent materials [1,2]. HAp) is used in medicine as a bone implant material due to its biocompatibility, bioactivity, and similarity to bone mineral [3,4] It is still widely investigated in order to improve its properties by obtaining appropriate grain size, morphology, mechanical strength, and solubility and by adding some dopants that are, e.g., naturally built into bone apatite, ions possessing antibacterial properties, or ions enabling bio-imaging [5,6]. Ag+ and Cu2+ ions have the ability to complex anions such as –NH2, –S–S–, and –CONH– of the proteins or enzymes in the bacterial cells. It provides bacterial DNA and RNA damage and inhibits proliferation [7,11,12]. Recent studies have shown that copper-doped apatite-type materials are very promising as a new kind of ow-toxic pigment that can be used in the paint and varnish industry [1,15,16,17,18]
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