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Öğe A comprehensive study of cytosine-ZnO interactions: Theoretical and experimental insights(Elsevier, 2025) Bulut, Niyazi; Keser, Serhat; Zanchet, Alexandre; Zuchowski, Piotr S.; Ates, Tankut; Kilic, Irfan; Kaygili, OmerThis paper presents a comprehensive investigation of the adsorption of cytosine, a DNA base, on ZnO model clusters, specifically Zn2O2, Zn3O3, Zn4O4, Zn6O6, Zn8O8 ring (R) and cubic rocksalt. A density functional theory (DFT) method was used to simulate the adsorption of cytosine on ZnO (C/ZnO) clusters. The B3LYP/LanL2DZ method, which includes a correction for the dispersion contribution, was used. The calculated energy gap (Eg) for cytosine showed a strong dependence on the cluster size, highlighting variations corresponding to the dimensions of the clusters. The proposed physisorption mechanism involves the formation of an N...Zn bond between cytosine and the active Zn site on ZnO. In addition, experimental data, including microscopic and spectroscopic evidence, were integrated to further elucidate the interactions between cytosine and ZnO. A composite of C and ZnO was prepared by the wet chemical method and characterised by SEM, XRD and FT-IR analyses. The interaction of cytosine with ZnO nanoparticles was observed by UV-vis spectroscopy. The experimental results were then compared with those obtained from DFT calculations, taking into account the new insights into the cytosine-ZnO interactions. This comparison provided a holistic understanding of the system.Öğe Advances in metallic ion-doped hydroxyapatite: unlocking enhanced structural, biological, and functional properties for cutting-edge biomedical applications(Springer, 2026) Kareem, Rebaz Obaid; Barzinjy, Azeez A.; Ates, Tankut; Bulut, Niyazi; Keser, Serhat; Kaygili, OmerHydroxyapatite (HAp) is a biomaterial that has been extensively studied for its exceptional biocompatibility, osteoconductivity and non-toxic nature, making it highly suitable for applications in bone and dental tissue engineering. This review evaluates the incorporation of metallic ions into the HAp lattice as a strategic approach to optimize its structural integrity, mechanical performance and biological functionality. Quantitative findings from recent studies show that Ag+ doping at 1 wt% reduces bacterial growth by over 95%, but higher doses ( > 3 wt%) can reduce cell viability by up to 20%. Sr2 + (5 wt%) improves bone regeneration by 25%, though excessive levels may alter lattice stability. Zn2 + at 3 wt% enhances osteoblast proliferation by 60% but can slightly reduce thermal stability. Cu2 + improves angiogenesis and antimicrobial efficacy, but high concentrations can induce cytotoxicity. Furthermore, metallic ion doping enhances the dielectric properties and contributes to anti-cancer capabilities, expanding HAp's therapeutic potential. The review also highlights advanced applications of metallic ion-doped HAp, including its role in drug delivery systems, implant surface coatings, and even environmental remediation. By synthesizing findings from recent studies, this comprehensive analysis underscores the transformative impact of metallic doping in optimizing HAp for diverse biomedical applications. These advances represent an important step in the development of multifunctional biomaterials, paving the way for innovative solutions to medical and environmental challenges.Öğe Ce/Sm co-doped hydroxyapatites: synthesis, characterization, and band structure calculation(Springer, 2020) Kaygılı, Ömer; Vural, Gülay; Keser, Serhat; Yahia, İ.S.; Bulut, Niyazi; Ateş, Tankut; Köytepe, Süleyman; Temüz, Mehmet Mürşit; Ercan, Filiz; İnce, TuranIn this paper, Ce/Sm co-doped hydroxyapatites (HAps) were synthesized by a wet chemical route. The amount of Ce was kept at constant at the value of at.% 0.4, and the second dopant of Sm was used at different amounts of at.% 0, 0.6, 1.2, and 1.8, respectively. The effects of these co-dopants on the crystal structure, morphology, and thermal properties of HAp were determined experimentally using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), and thermogravimetric analysis (TGA). Furthermore, the band structure of the prepared samples was modeled theoretically using the quantum calculations of the density of states and band structure. A gradual increase from 26.56 to 36.23 nm in the crystallite size was observed. Although the amounts of the co-dopants of Ce and Sm did not affect the thermal stability and microstructure of HAp, its crystal structure-related parameters were affected by the amount of these co-additives. The partial substitution of both co-dopants was detected. The 0.4Ce-1.2Sm-HAp sample may be considered as the best crystal structure with a steady-state. It was seen that the band structure and density of states were also affected by these co-dopants. The bandgap value decreased gradually from 4.6078 to 4.0477 eV due to these dopants.Öğe Characterization of SrO samples produced at two different temperatures(Niyazi BULUT, 2021) Ince, Turan; Ateş, Tankut; Bulut, Niyazi; Keser, Serhat; Kaygili, Omer[Abstract Not Available]Öğe Comprehensive analysis of the impact of iron and terbium co-dopant levels on the structural, thermal, and spectroscopic properties of hydroxyapatite(Elsevier Sci Ltd, 2025) Kaygili, Omer; Duskun, Yusuf; Barzinjy, Azeez A.; Kareem, Rebaz Obaid; Ates, Tankut; Keser, Serhat; Ince, TuranIn recent years, there has been a growing interest in biomaterials for improving human living conditions. Hydroxyapatite (HAp), a biomaterial widely used in bone and teeth restoration, has been doped with iron (Fe) and terbium (Tb) to enhance its electronic properties and potential biomedical applications. Theoretical calculations revealed a decreasing trend in bandgap values with increasing concentrations of Fe and Tb, suggesting a shift from insulating to semiconducting behavior. The synthesized Fe and Tb doped HAp samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results showed that the addition of Fe and Tb dopants led to changes in the lattice parameters, crystallinity, and morphology of HAp structure. The doped HAp samples exhibited improved thermal stability, and their FTIR and Raman spectra confirmed the presence of the phosphate group. SEM analysis revealed sphere-like nanoparticles and EDX results confirmed the presence of Fe and Tb in the doped samples. The (Ca + Tb + Fe)/P molar ratios were close to the ideal value of 1.667. The study demonstrates the potential of Fe and Tb-doped HAp as multifunctional materials in biomedicine and other fields requiring tunable electrical properties.Öğe Comprehensive structural characterization of chromium-doped zinc oxides(Springer-Verlag Italia Srl, 2025) Ates, Tankut; Keser, Serhat; Bulut, Niyazi; Kaygili, OmerThis study presents a comprehensive investigation of the effects of chromium (Cr) on the structural properties of zinc oxide (ZnO). X-ray diffraction (XRD) analysis confirmed the formation of the ZnO wurtzite phase for all samples. At lower Cr concentrations (up to 1.4 at%), Cr3(+) ions were successfully incorporated into the ZnO lattice without forming secondary phases, indicating effective substitutional doping. However, at higher Cr contents (>= 2.8 at%), the formation of a secondary ZnCr2O4 spinel phase was observed, suggesting that the Cr solubility limit in ZnO was exceeded. Cr content influenced various crystal-structure-related parameters such as crystallinity, crystallite size, lattice parameters, Zn-O bond length, lattice strain, and stress. The texture coefficient (TC(hkl)) analyses revealed a shift in preferential growth orientation from the (200) plane to the (004) plane with increasing Cr concentration. FTIR spectra supported the presence of Zn-O vibrational modes and changes in surface chemistry, while SEM images showed morphology evolution and increased surface complexity with doping.Öğe Effects of gallic acid and quercetin on the structural, thermal, spectroscopic, in vitro biocompatibility and electronic properties of Au-based hydroxyapatite structure(Elsevier Science Sa, 2024) Keser, Serhat; Dogan, Ahmet; Ates, Tankut; Barzinjy, Azeez A.; Ates, Burhan; Tekin, Suat; Kaygili, OmerThe aim of this study is investigating the structural, thermal, spectroscopic, electronic and biocompatibility properties of the Au-based hydroxyapatites containing quercetin (Q) or gallic acid (GA) at various concentration. Different characterization techniques including; XRD analysis, FTIR and Raman spectroscopies, differential thermal analysis, SEM and EDX analysis were utilized. Cell cytotoxicity test was conducted with the cells of MG63 human bone cancer, hFOB 1.19 human osteoblast and Caco-2 human colon cancer. It has been shown that the utilized samples had no cytotoxic activity on the L-929, hFOB 1.19 and MG-63 cells. However, these samples had cytotoxic activity on Caco-2. The current study showed that the bandgap of the un-doped HAp structure was 4.976 eV. The crystallite size is also affected by Au-doping, type of the as-used biological additive and its amount. Also, the as-produced samples were thermally stable in the range from room temperature to 1000 degrees C. The particle size distributions of the samples were found at variable ranges. The molar ratios were close to the stoichiometric value of 1.667. These novel findings not only expand our appreciation for the role of dopants in materials science but also opens avenues for deliberate engineering of electronic properties for enhanced performance in various applications.Öğe Effects of pyrocatechol on the computational, structural, spectroscopic and thermal properties of silver-modified hydroxyapatite(Springer, 2025) Keser, Serhat; Yildiz, Aykut; Barzinjy, Azeez A.; Kareem, Rebaz Obaid; Mahmood, Bahroz Kareem; Agid, Riyadh Saeed; Bulut, NiyaziThis study investigates the synthesis and characterization of hydroxyapatite (HAp) ceramic biomaterials doped with silver (Ag) and pyrocatechol. HAp, commonly utilized in the treatment of hard tissues including teeth and bones, was produced and analyzed to assess the structural, morphological, elemental, and thermal properties of the materials. The phase and crystal structures of the synthesized HAp biomaterials were examined using X-ray diffraction (XRD), revealing that the incorporation of Ag and pyrocatechol influenced the crystallinity and lattice parameters. Fourier transform infrared (FT-IR) spectroscopy verified the presence of the characteristic OH- and PO4(3)(-) groups of HAp, while scanning electron microscopy (SEM) displayed consistent morphologies across all samples, free of residues or impurities. Elemental compositions were determined by energy dispersive X-ray (EDX) spectroscopy, and thermal stability was assessed through differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Additionally, computational studies using density functional theory (DFT) were conducted to further investigate the electronic and structural properties of 0.44% Ag-doped HAp. The DFT calculations revealed that Ag atoms replace calcium (Ca1 and Ca2) positions in the lattice, leading to slight distortions in the lattice structure and changes in the electronic density distribution. Minor changes were observed in the band structure and electronic properties, indicating the stability and tunability of the doped system. A small amount of beta-tricalcium phosphate (beta-TCP) phase was also detected alongside the main HAp phase. These results underscore the importance of incorporating pyrocatechol and silver doping into HAp for biomedical applications. The resulting biomaterials exhibit enhanced structural, thermal, and electronic properties, with improved biocompatibility and antimicrobial activity.Öğe Experimental and theoretical characterization of Dy-doped hydroxyapatites(Springer, 2023) Isen, Fatih; Kaygili, Omer; Bulut, Niyazi; Ates, Tankut; Osmanlioglu, Fatih; Keser, Serhat; Kareem, Rebaz ObaidThe effects of adding Dy to the hydroxyapatite (HAp) structure were investigated experimentally and theoretically. The as-obtained experimental results with an increasing amount of Dy are as follows. X-ray diffraction, Raman, and Fourier transform infrared measurements verified the HAp structure for each specimen. The crystallinity, lattice parameters, lattice stress, strain, and anisotropic energy density were affected. Thermal stability and stoichiometry were not affected. It was observed that all the Dy-doped HAps have smaller crystallite size values compared to the un-doped HAp. The cell viability obtained from mouse fibroblast cell (L929) was higher than 82%, indicating all the samples were biocompatible. The theoretical findings, obtained from the density functional theory (DFT) calculations, exhibited a continuous decrease in the bandgap from 4.7109 to 3.7982 eV, an increase in the density from 3,155 to 3,189 kg m(-3), and an increase in the linear absorption coefficient.Öğe Exploring Electronic and Structural Properties of Titanium-Doped Chlorapatite: A Theoretical and Experimental Investigation(Niyazi BULUT, 2023) Keser, Serhat; Ateş, Tankut; Bulut, Niyazi; Kaygılı, Omer[Abstract Not Available]Öğe Farklı Element Katkılı Sodyum Fosfat Camlarının Sentez ve Karakterizasyonu(Bilecik Şeyh Edebali Üniversitesi, 2021) Keser, Serhat; Tatar, Cengiz; Ateş, Tankut; İnce, Turan; Kaygılı, ÖmerBu çalışmada, yaş kimyasal yöntemi ile üretilen Ba ve Li katkılı sodyum fosfat (NaPO3) camları karakterize edildi. Ba katkılı numunelerin tamamının ve en yüksek Li katkısına sahip numunenin amorf yapıya sahip olduğu görüldü. Bunların haricindeki tüm numunelerin kristal yapıya sahip olduğu gözlendi. Fourier dönüşümlü kızılötesi (FTIR) spektroskopisi sonuçları NaPO3 yapısının oluşumunu desteklemektedir. Morfoloji, katkıların türü ve bunların miktarından etkilendi.Öğe Impact of pyrocatechol on the structural, spectroscopic, thermal characteristics, and in vitro bioactivity of gadolinium-enhanced hydroxyapatites(Elsevier, 2025) Keser, Serhat; Demirbilek, Fatos; Barzinjy, Azeez A.; Kareem, Rebaz Obaid; Mahmood, Bahroz Kareem; Ates, Tankut; Kaygili, OmerIn this study, the effects of pyrocatechol content on the structural, thermal, spectroscopic, and biocompatibility properties of gadolinium (Gd) based hydroxyapatites (HAs) were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetric analysis, and scanning electron microscopy. The results, of this study, show that the energy bandgap (Egap) of Gd-doped HAs decreases to 4.1978 eV, indicating a narrowing of the electronic energy levels compared to pure HAs. The doping of Gd3+ further enhances these effects, as confirmed by enhanced photoluminescence intensity attributed to cooperative energy transfer mechanisms between the dopants. The two most biocompatible materials in the HAs series were determined as 0.42Gd-HA (94%) and P16-0.42Gd-HA (91%). These results demonstrate that even small concentrations of dopant like Gd can meaningfully impact the material's electronic and optical properties, offering potential for its application in areas where a higher bandgap and insulating properties are essential, such as in biomedical implants, coatings, or electronic insulators.Öğe Impact of quercetin and gallic acid on the electronic, structural, spectroscopic, thermal properties and in vitro bioactivity of silver-modified hydroxyapatite(Elsevier Science Sa, 2025) Keser, Serhat; Firat, Melikehatun; Barzinjy, Azeez A.; Kareem, Rebaz Obaid; Ates, Tankut; Ates, Burhan; Kaygili, OmerHydroxyapatite (HAp) possesses outstanding characteristics, for instance biocompatibility and osteoconductivity, which are vital for bone reconstruction. Nevertheless, it remains passive against infectious bacteria that can cultivate in compromised bone tissue, and its usage in some individuals under care might result in some objectionable provocative responses. Gallic acid (GA) and quercetin (Que) are recognised for their explicit biological activites. Connecting these properties with silver-modified HAp is remarkably interesting. The current study examined the preparation of un-doped HAp and Ag-based samples in the presence of various extents of GA and Que using the neutralization method at room temperature. The impact of GA and Que on the electronic, structural, thermal, spectroscopic, and biocompatibility properties of HAp and Ag-modified HAp were investigated intensively. Also, mouse fibroblast (L929), human osteoblast (hFOB 1.19), human bone cancer (MG-63) and human colon cancer (Caco-2) cell lines obtained from the ATCC were used for cytotoxic and biocompatibility assays. The bandgap of the distinct regions (occupation of Ca(I) and Ca(II) sites) using DFT were 3.837 and 4.211 eV, respectively. This study showed that introducing Ag as a dopant reduced the bandgap dramatically. X-ray diffraction analysis revealed that the as-prepared samples possess polycrystalline structure. While, the lattice parameters and volume of the unit cell were increased after adding Ag as a dopant. However, both GA and Que containing samples, remarkably decrease these parameters. Both FTIR and Raman spectroscopy utilized to investigate the nature of bonding structure for the utilized samples. It has been shown that the addition of Ag into the HAp causes an increase in the specific heat capacity. SEM images and EDX analysis confirm the distribution of the utilized elements and the purity of the samples. Overall, the prepared Ag-HAp/GA and Ag-HAp/Que samples offered structural and chemical characteristics close to those of ordinary bone that make them a good candidate for bone tissue regeneration.Öğe Investigation of structural properties of Pr-doped hydroxyapatites synthesized via an ultrasonic-assisted wet chemical method(Niyazi BULUT, 2023) Ateş, Tankut; Bulut, Niyazi; Kaygılı, Omer; Keser, Serhat[Abstract Not Available]Öğe Investigation of the effects of glycerol addition as a catalyst on the morphology and structural properties of Gd/Er co-doped hydroxyapatite(Niyazi BULUT, 2024) Mohammed, Bast Ahmed; Ateş, Tankut; Mahmood, Bahroz Kareem; Kareem, Rebaz Obaıd; Keser, Serhat; Bulut, Niyazi; Kaygılı, Omer[Abstract Not Available]Öğe Investigation of the effects of immersion period of simulated body fluid on the morphology and structural properties of Fe/Ni co-doped chlorapatites(Niyazi BULUT, 2023) Keser, Serhat; Ateş, Tankut; Bulut, Niyazi; Kaygılı, Omer[Abstract Not Available]Öğe Investigation of the effects of quercetin on the structure and properties of zinc-modified hydroxyapatites(Univ Novi Sad, Fac Technology, 2026) Keser, Serhat; Kaya, Semih; Barzinjy, Azeez A.; Mahmood, Bahroz Kareem; Kareem, Rebaz Obaid; Temuz, Mehmet Mursit; Bulut, NiyaziIn this study, hydroxyapatite (HAp) samples, co-doped with 0.44 at.% of zinc and different amount of quercetin (Zn/Que-HAp), were synthesised using a wet-chemical method and calcined at 900 degrees C. XRD shows HAp as the primary phase with minor beta-TCP. Compared to the Zn-doped sample without quercetin (Q1), quercetin co-doping induces clear structural changes (shifts of lattice parameters a from-0.0017 to +0.0006 nm and c from-0.0026 to-0.0005 nm), accompanied by changes in crystallinity (from-3.6% to +2.5%) and crystallite size (from-3.5 to +0.6 nm), evidencing a distinct co-doping effect. DTA/TGA reveal reduced total mass loss for the Que-containing compositions relative to the Zn-doped sample, indicating enhanced thermal stability of the co-doped lattice. SEM reveals granular morphologies with interconnected porosity, while EDX yields (Ca+Zn)/P ratios greater than 1.67, consistent with Ca-sufficient apatite and modified defect chemistry. DFT calculations resolve the site-specific effects of Zn substitution and predict a preference for perturbation at Ca2 sites. The electronic density of states retains a wide-gap, insulating character, with localised states sensitive to the dopant configuration. By correlating experiment and theory, we demonstrate that the organic-inorganic co-dopant pair offers an effective means to tune lattice metrics, phase balance, and thermal response without compromising the intrinsic insulating nature of HAp.Öğe Investigation of the structural, thermal, magnetic and cell viability properties of Ce/Sr co-doped hydroxyapatites(Elsevier, 2023) Ates, Hulya Gunes; Kaygili, Omer; Bulut, Niyazi; Osmanlioglu, Fatih; Keser, Serhat; Tatar, Beyhan; Ozcan, ImrenThe present study aims to give a more detailed report on the structural, thermal, magnetic and in vitro cell viability properties of the hydroxyapatites (HAps) co-doped with Sr and Ce at different amounts. Besides these experimental analyses, this study also includes the theoretical calculation results obtained from the modeled systems for the as-prepared samples. Diamagnetic behavior was observed for all the samples, as well as their high cell compatibilities. All the samples showed a thermally stable behavior, and the mass change mechanism and specific heat capacity were affected by the amount of the codopants. The bandgap value and linear absorption coefficient varied with the amount of both co-dopants. (c) 2023 Elsevier B.V. All rights reserved.Öğe Quercetin and Gallic Acid containing Hydroxyapatites: Synthesis and Characterization(Niyazi BULUT, 2024) Ateş, Tankut; Keser, Serhat; Köytepe, Süleyman; Bulut, Niyazi; Kaygılı, Omer[Abstract Not Available]Öğe Structural, magnetic, thermal, biocompatibility, and electronic properties of lanthanum doped-magnesium hydroxyapatite(Elsevier Sci Ltd, 2025) Mahmood, Bahroz Kareem; Kareem, Rebaz Obaid; Bulut, Niyazi; Ates, Tankut; Keser, Serhat; Kaygili, Omer; Kurucay, AliThis study presents the preliminary experimental and theoretical results on Mg/La co-substituted in hydroxyapatite (HAp) structure. Four Mg-based HAps were synthesized with La doping by keeping the Mg concentration constant at 0.45 at.%, while the La content was varied from 0.45 to 1.80 at.% in 0.45 at.% increments by a wet chemical method. Experimentally, the major phase for all samples was HAp and the minor phase was beta-TCP. The presence of La as a dopant for the HAp structure was found to affect the lattice parameters. The values of lattice parameters and unit cell volume were observed to increase gradually. The crystallinity percentage ranged from 85 % to 89 %. Analysis using the Scherrer and Williamson-Hall approaches revealed that the crystallite size values of the samples were in the range of 22-29 nm and 23-33 nm respectively. In addition, the values of lattice stress, strain and anisotropic energy density were influenced by the concentration of La. The magnetic saturation decreased from 0.0439 to 0.0383 emu/g with an increase in the amount of La. All samples showed biocompatible properties. A slight change in morphology was also observed. The EDX results showed that the presence of La at different levels resulted in calcium deficiency. Thermogravimetric analysis and differential thermal analysis, carried out over a temperature range of 25-850 degrees C, showed that each sample had thermal stability, with no exothermic or endothermic peaks detected. Theoretical results derived from Density Functional Theory (DFT) calculations showed that the band gap values decreased steadily from 4.578 to 4.438 eV.
