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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 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 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 analysis of bismuth Co-doped erbium-based hydroxyapatites(Springer, 2025) Ali, Aenas Laith; Mahmood, Bahroz Kareem; Kareem, Rebaz Obaid; Ates, Tankut; Barzinjy, Azeez A.; Bulut, Niyazi; Kaygili, OmerThis study explores the impact of bismuth (Bi) and erbium (Er) co-doping on the structural, morphological, and electronic properties of hydroxyapatites (HAp). Bi/Er co-doped HAp samples at varying concentrations were synthesized through a wet chemical process and characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Additionally, density functional theory (DFT) was employed to analyze band structure (BS), energy gap (Eg), density of states (DOS), and linear attenuation coefficient (LAC). Results revealed a systematic decrease in the energy gap from 4.0340 eV to 3.9222 eV with increasing Bi content, highlighting a reduced band gap energy trend as the Bi and Er concentrations increase. Higher Bi concentration also influenced the DOS and BS, and reduced crystallite size (D) across samples. Among them, the 0.26Bi-0.39Er-HAp sample exhibited the lowest crystallinity (76.56%) and smallest crystallite size (27.84 nm). This study provides valuable insights into how co-doping affects HAp properties, with potential implications for biomedical and environmental applications.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 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, Spectroscopic, and Electronic Properties of Praseodymium-based Hydroxyapatites Co-doped with Silver and Zinc in Varying Concentrations(Budapest Univ Technology Economics, 2025) Kareem, Rebaz Obaid; Ates, Tankut; Barzinjy, Azeez A.; Temuz, Mehmet Mursit; Ince, Turan; Bulut, Niyazi; Kaygili, OmerThis study investigates the crystal structure, energy gap, band structure, spectroscopy, thermal, and electrical properties of Pr3+-based hydroxyapatites (HAp) co-doped with Zn2+ and Ag+ in varying concentrations. The synthesized samples, designated as 0.25Zn-0.25PrHAp, 0.50Zn-0.25Pr-HAp, 0.75Zn-0.25Pr-HAp, 0.25Ag-0.25Pr-HAp, 0.50Ag-0.25Pr-HAp, and 0.75Ag-0.25Pr-HAp, were prepared using a wet chemical method. The materials were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetric analysis (TGA). Additionally, theoretical calculations employing density functional theory (DFT) were conducted to analyze the band structure (BS), energy gap (Eg; EHOM & oacute;ELUMO), and density of states (DOS). Results revealed a progressive reduction in the bandgap with increasing dopant concentrations, particularly in Ag-doped samples. Notably, 0.75Ag-0.25Pr-HAp exhibited the smallest bandgap of 3.983 eV, indicating enhanced electronic conductivity and potential applications in bioelectronics and medical sensors. Furthermore, the co-doped samples demonstrated reduced crystallinity, larger crystallite sizes, and excellent stability in biological environments, alongside superior biocompatibility and antibacterial properties. Among the synthesized materials, 0.75Ag-0.25Pr-HAp exhibited promising characteristics as a biomedical material for bone-related applications, owing to its structural stability, enhanced electrical properties, and suitability in antibacterial and bioelectronic devices. This investigation highlights the versatility of Zn/Ag co-doped Pr-HAp materials for advanced biomedical and technological applications.Öğe The role and importance of rare earth elements as dopants for hydroxyapatite structure: a comprehensive review(Elsevier, 2025) Kareem, Rebaz Obaid; Mahmood, Bahroz Kareem; Barzinjy, Azeez A.; Bulut, Niyazi; Kaygili, Omer; Keser, Serhat; Ates, TankutThis comprehensive review delves into the significance of rare earth elements (REEs) as dopants in hydroxyapatite (HAp) structures, highlighting their role in modulating the material's crystallinity, solubility, and bioactivity. The unique properties of REEs, such as their ability to form ionic bonds with hydroxyapatite, are discussed in relation to their impact on the material's interactions with biological molecules. The review also examines the effects of REE doping on the in vitro and in vivo behavior of HAp, including its influence on cell proliferation, differentiation, and mineralization. Furthermore, the potential applications of REE-doped HAp in orthopedic and dental implants, as well as its potential in bone tissue engineering, are explored. This review provides a thorough understanding of the role and importance of REEs as dopants in HAp structures, shedding light on their potential to revolutionize the development of biomaterials for biomedical applications, especially in bone tissues engineering.Öğe The structural, thermal, spectroscopic, morphologic and in vitro biocompatibility properties of boron-doped hydroxyapatites co-doped with dysprosium: An experimental and theoretical investigation(Elsevier Ltd, 2026) Cihangir, Samet; Kaygili, Omer; Barzinjy, Azeez A.; Kareem, Rebaz Obaid; Goldberg, Margarita A.; Komlev, Vladimir S.; Bulut, NiyaziHydroxyapatite (HA) stands as a pivotal biomaterial in orthopedic applications due to its chemical similarity to natural bone mineral. This study presents a comprehensive experimental and theoretical investigation into the structural, thermal, spectroscopic, morphological, and biocompatibility properties of Boron (B)-doped HA co-doped with varying concentrations of Dysprosium (Dy). Samples were synthesized via a wet chemical method and characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopy, thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). Complementing the experimental work, Density Functional Theory (DFT) calculations were employed to analyze the electronic structure, density, and radiation shielding parameters. XRD analysis confirmed the formation of the hexagonal HA phase alongside a minor beta-tricalcium phosphate (β-TCP) secondary phase (0.8-2.3%). The introduction of dopants induced lattice distortions and a systematic reduction in crystallite size, ranging from 34.65 nm for pure HA to 29.30 nm for the highest Dy-containing sample (1.6Dy-0.8B-HA), with crystallinity indices decreasing from 1.17 to 0.70 upon B doping and varying between 0.66 and 0.92 for the co-doped compositions. Theoretically, while B doping slightly widened the band gap from 4.35 eV to 4.56 eV, the incorporation of Dy systematically narrowed it from 4.43 eV (0.4Dy-0.8B-HA) to 4.12 eV (1.6Dy-0.8B-HA), attributed to the introduction of localized Dy-4f states within the forbidden gap. The theoretical and experimental density values showed excellent agreement, with densities increasing from approximately 3115 - 3119 kg m−3 for B-doped HA to 3188 - 3320 kg m−3 for the highest Dy content, reflecting the progressive substitution of Ca2+ by the significantly heavier Dy3+ cation.Notably, the linear attenuation coefficient (LAC) increased significantly with Dy concentration, from 1.832 cm−1 (pure HA) to 2.139 cm−1 (1.6Dy - 0.8B-HA) at 50 keV, with corresponding reductions in half-value layer (HVL) from 0.378 cm to 0.324 cm at the same energy, indicating progressively enhanced radiation shielding capabilities. These findings collectively suggest that B-Dy co-doped HA possesses tunable electronic and structural properties alongside improved radiation shielding potential, making it a promising multifunctional candidate for advanced bone tissue engineering, bioimaging, and biomedical radiation protection applications. © 2026 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Öğe Theoretical and experimental investigation of structural, spectroscopic, and thermal properties of Bismuth- and Gadolinium-doped hydroxyapatites(Elsevier, 2026) Ates, Tankut; Acar, Emine Nur; Barzinjy, Azeez A.; Koytepe, Suleyman; Keser, Serhat; Adam, Ibrahim Muhammad; Kaygili, OmerIn this study, hydroxyapatite (HAp) materials doped with bismuth (Bi) and gadolinium (Gd) were synthesized using the wet chemical precipitation method and comprehensively characterized through both theoretical and experimental approaches. Density functional theory (DFT) calculations were employed to investigate the effects of co-doping with Bi and Gd on the electronic structure, lattice parameters, and unit cell volume. Results revealed a consistent reduction in bandgap energy with increasing dopant concentration, highlighting the tunability of HAp's electronic properties for advanced functional applications. Structural analyses revealed subtle reductions in lattice constants and unit cell volume, confirming the incorporation of dopants and lattice contraction. Experimental characterizations included X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopy, thermal analyses (DTA/TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). XRD confirmed phase purity with minor beta-TCP formation, while FTIR and Raman spectra validated the presence of phosphate and hydroxyl groups typical of HAp. Thermal analyses indicated excellent stability up to 900 degrees C with minimal mass loss, especially in doped samples. SEM images revealed nanostructured spherical morphologies with homogenous elemental distribution, while EDX confirmed the successful integration of Bi and Gd into the HAp lattice. Biocompatibility assays using l-929 fibroblast cells showed high cell viability (>80%) for all samples, indicating excellent biocompatibility with negligible cytotoxicity. Notably, Gd-doped and co-doped samples showed improved biological responses. These findings suggest that Bi/Gd co-doped HAp materials hold strong potential for biomedical applications such as bone implants and dental restorations, where enhanced electronic, thermal, and biocompatibility properties are crucial.Öğe Tuning electronic properties of hydroxyapatite through controlled doping using zinc, silver, and praseodymium: A density of states and experimental study(Elsevier Sci Ltd, 2024) Sahin, Binnur; Ates, Tankut; Acari, Idil Karaca; Barzinjy, Azeez A.; Ates, Burhan; Ozcan, Imren; Kaygili, OmerThis study presents a comprehensive exploration of the electronic properties of hydroxyapatite (HA) doped with zinc (Zn), silver (Ag), and praseodymium (Pr). Five distinct compositions-0.4Pr-HA, 0.4Zn-0.4Pr-HA, 0.8Zn0.4Pr-HA, 0.4Ag-0.4Pr-HA, and 0.8Zn-0.4Pr-HA were systematically investigated through Density of States (DOS) and band structure calculations. The computed band gap values, ranging from 4.4037 to 4.1554 eV, revealed a progressive decrease in band gap energy from 0.4Pr-HA to 0.8Ag-0.4Pr-HA, emphasizing the substantial impact of dopant composition on electronic properties. Additionally, the incorporation of Pr induced distinct bands and peaks in the density of states, signifying the emergence of specific energy levels associated with Pr and suggesting a clear effect on the electronic structure. Furthermore, the study explores the influences of dopant type and quantity on the electronic structure, microstructure, spectral, thermal, and in vitro cell viability properties of Pr-based HA samples. Theoretical results demonstrated a continuous decrease in the bandgap with Ag or Zn dopants, and the study observed controllable changes in LAC values based on co-dopant type and quantity. Experimental outcomes revealed significant effects on crystallinity, crystallite size, lattice parameters, and unit cell volume, confirmed through XRD, SEM, EDX, FTIR, and Raman analyses. These findings provide valuable visions into the tunability of the electronic properties of HA through controlled doping with Zn, Pr, and Ag. This knowledge is crucial for modifying materials with desirable electronic properties, and thus holds promise for various applications in electronic devices and biocompatible coatings.
