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    Effects of Yttrium Doping on Erbium-Based Hydroxyapatites: Theoretical and Experimental Study
    (Mdpi, 2022) Ahmed, Lana Omar; Bulut, Niyazi; Kebiroglu, Hanifi; Alkhedher, Mohammad; Ates, Tankut; Koytepe, Suleyman; Ates, Burhan
    This is the first investigation of yttrium (Y) and erbium (Er) co-doped hydroxyapatite (HAp) structures, conducted using theoretical and experimental procedures. By using a wet chemical method, the materials were synthesized by varying the concentration of Y amounts of 0.13, 0.26, 0.39, 0.52, 0.65, and 0.78 at.% every virtual 10 atoms of calcium, whereas Er was kept fixed at 0.39 at.%. Spectroscopic, thermal, and in vitro biocompatibility testing were performed on the generated samples. Theoretical calculations were carried out to compute the energy bandgap, density of states, and linear absorption coefficient. The effects of Y concentration on thermal, morphological, and structural parameters were investigated in detail. Raman and Infrared (FTIR) spectroscopies confirmed the formation of the HAp structure in the samples. Theoretical investigations indicated that the increasing amount of Y increased the density from 3.1724 g cm(-3) to 3.1824 g cm(-3) and decreased the bandgap energy from 4.196 eV to 4.156 eV, except for the sample containing 0.39 at. % of the dopant, which exhibited a decrease in the bandgap. The values of linear absorption appeared reduced with an increase in photon energy. The samples exhibited cell viability higher than 110%, which revealed excellent biocompatibility for biological applications of the prepared samples.
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    Exploring the electronic band structure, spectroscopic signatures, and structural properties of Er3+-based hydroxyapatites co-doped with Ce3+ions
    (Elsevier, 2023) Ahmed, Lana Omar; Bulut, Niyazi; Banares, Luis; Kaygili, Omer; Kebiroglu, Hanifi; Ates, Tankut; Koytepe, Suleyman
    In this work, we have investigated Ce3+ and Er3+ co-doped hydroxyapatite (HAp) structures both theoretically and experimentally for the first time. The Ce3+ content was incrementally varied in steps of 0.13 at. %, ranging from 0.13 at. % to 0.78 at. %. Meanwhile, the Er3+ content remained constant at 0.39 at. % for all samples. We employed X-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry, and in vitro biocompatibility tests to examine the prepared samples. Our findings demonstrate that the thermal behavior, morphology, and other crystal structure-related parameters are significantly influenced by the con-centration of Ce3+. The formation of HAp structures was confirmed through FTIR and Raman spectroscopic analyses. Furthermore, we conducted theoretical calculations to determine the linear absorption coefficient, density of states, and bandgap. These calculations revealed that the addition of Ce3+ atoms at varying concen-trations resulted in an increase in density from 3.174 to 3.195 g cm-3, while the bandgap gradually decreased from 4.16 to 4.10 eV, except for the 0.26Ce-0.39Er-HAp and 0.52Ce-0.39Er-HAp compositions, where the energy bandgap exhibited an increase.
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    Theoretical and experimental characterization of Sn-based hydroxyapatites doped with Bi
    (Springer, 2022) Korkmaz, A. Aksogan; Ahmed, Lana Omar; Kareem, Rebaz Obaid; Kebiroglu, Hanifi; Ates, Tankut; Bulut, Niyazi; Kaygili, Omer
    This is the first report, including both theoretical and experimental results, on Bi and Sn co-doped hydroxyapatite (HAp) structures. Sn content was kept at a constant amount of 0.22 at.%, and Bi content was changed from 0 to 0.44 at.% by using the steps of 0.11at.%. Theoretical results from density functional theory (DFT) calculations revealed an increase in density from 3.154 g cm(-3) to 3.179 g cm(-3), as well as gradual decreases in the bandgap from 4.5993 eV to 4.4288 eV and the linear absorption coefficient. The spectroscopic data obtained from both Raman and Fourier transform infrared (FTIR) spectra confirmed the HAp structure for all the samples. The thermal behavior and morphology, as well as all X-ray diffraction (XRD) related parameters, were all considerably impacted by Bi-content. In vitro assays showed that all the samples can be accepted as the biocompatible materials.
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    Theoretical and experimental investigation of the effects of Pr dopant on the electronic band structure, thermal, structural, in vitro biocompatibility of Er-based hydroxyapatites
    (Elsevier, 2023) Ahmed, Lana Omar; Bulut, Niyazi; Osmanlioglu, Fatih; Tatar, Beyhan; Kebiroglu, Hanifi; Ates, Tankut; Koytepe, Suleyman
    Pr and Er co-doped hydroxyapatites (HAps) have undergone their first theoretical and experimental re-search. Pr content was changed in 0.13 percent increments from 0.13 to 0.78 percent. Er content was kept constant at 0.39 at.%. Theoretical results demonstrated an increase in the density from 3.154 to 3.179 g cm -3, as well as steady decreases in the bandgap from 4.1739 to 4.0618 eV. X-ray diffraction (XRD) pat-terns point out that all the samples consist of the single phase of the HAp. The crystallinity decreased steadily with adding of Pr. Pr-content has a considerable impact on all the XRD-related parameters, ther-mal behavior and morphology. The cell viability was affected by the co-dopant content, and this value was found to be higher than 83% for all the samples. (c) 2023 Elsevier B.V. All rights reserved.