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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, Omer
Hydroxyapatite (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.
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, Turan
In 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.
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, Niyazi
This 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.
Epinephrine Compound: Unveiling Its Optical and Thermochemical Properties via Quantum Computation Methods
(Iranian Chemical Science and Technologies Association, 2023) Kareem, Rebaz Obaid; Kebiroğlu, Mehmet Hanifi; Hamad, Othman Abdulrahman; Kaygili, Omer; Bulut, Niyazi
This study employs Density Functional Theory (DFT) methodology to comprehensively investigate the structural and physicochemical characteristics of epinephrine, a molecule of physiological relevance. By employing DFT approaches, a more precise description of epinephrine's structure and properties is achieved compared to prior studies. A detailed examination of epinephrine's structure and various properties, such as the Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO), Band Gap (BG), Density of States (DOS), Fourier-Transform Infrared Spectroscopy (FT-IR), Ultraviolet (UV) absorption, and Natural Bond Orbital (NBO) analysis. Furthermore, we explore non-covalent interactions (NCI) through the examination of Reduced Density Gradient (RDG) and Molecular Electrostatic Potential (MEP) maps. Incorporating FT-IR results, we delve into the vibrational properties of epinephrine, highlighting C-H vibrations at 3700, 3176.20, and 2986.14 cm-1, along with specific vibrational modes of the benzene ring at 1558.43 and 1461.14 cm-1. Additionally, we provide a comprehensive analysis of epinephrine's thermochemical properties at temperatures ranging from 100 to 200 K under constant pressure conditions (1 atm), including optical transitions. This comprehensive investigation enhances our understanding of epinephrine's structure and properties, paving the way for a more profound comprehension of its biological and pharmacological significance. © 2023, Iranian Chemical Science and Technologies Association. All rights reserved.
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, Omer
This 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.
Experimental and theoretical characterization of Bi-based hydroxyapatites doped with Ce
(Elsevier Sci Ltd, 2022) Kareem, Rebaz Obaid; Kaygili, Omer; Ates, Tankut; Bulut, Niyazi; Koytepe, Suleyman; Kurucay, Ali; Ercan, Ismail
This study deals with the theoretical and experimental characterizations of Bi-based hydroxyapatites (HAps) codoped with Ce. Five samples of Bi-based HAp (at a constant amount of 0.125 at.%) with additions of the Ce in various amounts (0, 0.125, 0.25, 0.375, and 0.500 at. %) were synthesized by using the wet chemical method. The prepared samples were investigated experimentally by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). All the samples were also modeled by using a density functional theory (DFT), and theoretical results were obtained. Both experimental and theoretical results showed that the lattice parameters and unit cell volume were significantly affected by Ce content. Calculated bandgap energy results of the samples gradually reduced from 4.6308 eV to 4.5299 eV. The bandgap decreased with increasing Ce content, and the densities of states (DOS) values were also affected by the amount of Ce. It was found that the sample doped with 0.500 at. % Ce showed the best biocompatibility among all the as-synthesized samples. The linear absorption coefficient increased with increasing amounts of Ce in all samples, while this parameter decreased with increasing photon energy. The density increases with the increasing Ce content ranging from 3.1615 g cm-3 to 3.1772 g cm- 3. Both crystallite size and crystallinity decreased gradually with the increasing amount of Ce. FTIR and Raman spectra confirm the formation of the HAp structure for all the samples.
Experimental and theoretical characterization of Dy-doped hydroxyapatites
(Springer, 2023) Isen, Fatih; Kaygili, Omer; Bulut, Niyazi; Ates, Tankut; Osmanlioglu, Fatih; Keser, Serhat; Kareem, Rebaz Obaid
The 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.
Exploring the Influence of Various Solvents on the Structural, Optical, and Spectroscopic Properties of MgO
(TUBITAK, 2024) Mohammed, Bast Ahmed; Kareem, Rebaz Obaid; Bulut, Niyazi; Demirci, Tuna; Elibol, Erdem; Ercan, Filiz; Kaygili, Omer
Magnesium oxide (MgO) samples were manufactured at different temperatures using various solvents of water and ethanol. MgO structure was also modeled and its vibration modes were calculated. The kind of solvent as-used in the synthesis and calcination temperature caused changes in the lattice parameter, crystallinity, and crystallite size. The crystallite size increased with increasing production temperature for both series of the MgO. The morphology and bandgap energy were also affected significantly by the solvent and calcination temperature. © 2024, TUBITAK. All rights reserved.
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, Omer
In 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.
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, Omer
Hydroxyapatite (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.
Investigation of Electronic and Spectroscopic Properties of Phosphosilicate Glass Molecule (BioGlass 45S5) and Ti-BioGlass 45S5 by Quantum Programming
(Eurasian Science Society (ESS), 2023) Kebiroğlu, Mehmet Hanifi; Kareem, Rebaz Obaid; Hamad, Othman Abdulrahman
In this study, when a Ti atom is added to Phosphosilicate (BioGlass 45S5), its characterization is investigated using quantum chemical calculations. The STO-ground-state molecular 3G base-set HF approach was used to ensure that the shape of both Phosphosilicate and titanium Phosphosilicate (Ti-Phosphosilicate) was optimized. Many other quantum chemical properties were determined, such as the energy gap (EHOMO-ELUMO ), electronic properties, global reactivity, molecule electrostatic potential (MEP) on surfaces, and nuclear magnetic resonance (NMR), FT-IR were calculated at the B3LYP/STO-3G theory level. NMR shows eight peaks of the chemical shift values of the (H, O, P, and Si) molecule both Phosphosilicate and Ti-Phosphosilicate. Some examples of thermodynamic quantities include entropy (S), molar heat capacity (Cv), and thermal energy (E). According to MEP the negative-charged electrophilic reactivity region of the molecule is orange-red. Blue represents the positively charged nucleophilic reactive zone. The HOMO and LUMO energy gaps were smaller in Ti-Phosphosilicate, indicating that the moleculee under study had major chemical reactivity, biological activity, and polarizing ability. © 2023, Eurasian Science Society (ESS). All rights reserved.
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, Niyazi
In 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.
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, Omer
This 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.
Mg-Dopant Effects on Band Structures of Zn-Based Hydroxyapatites: A Theoretical Study
(Springer Int Publ Ag, 2023) Bulut, Niyazi; Kaygili, Omer; Hssain, Ala Hamd; Dorozhkin, Sergey V.; Abdelghani, Benahmed; Orek, Cahit; Kareem, Rebaz Obaid
The band structures of Zn-based hydroxyapatites co-doped with Mg at varying amounts from 0 to 2.0 at. % have been investigated theoretically in more detail. The calculations were done to obtain the band structure, density of states, and band gap for all the modeled structures to study their electronic properties. It was seen that the co-doping has an effect on the structural and electronic properties of all the as-investigated structures. The bandgap energy for all samples in each group was found to be reduced gradually with varying doping rates of Mg into Zn-doped HAp. The band gap decreased from 4.54 to 3.84 eV for samples of 0.4Zn-0.4 Mg-HAp and 2.0Zn-0.4 Mg-HAp with the same amount of Mg, respectively, as a result of increasing the doping levels of Zn from 0.4 to 2.0 at.%. The lattice parameters, unit cell volume, and density decrease with increase in doping of Zn-containing HAp and in addition of second dopant Mg at varying amounts 0.4, 0.8, 1.2, 1.6, and 2.0 at. % in all of the modeled sample group. Furthermore, it is observed that the declining values of the aforementioned parameters are significantly impacted by the increasing Zn doping rates.
Quantum Computing Analysis of Naphthalene Compound: Electronic Structure, Optical, and Thermochemical Approaches using DFT and HF
(Sami Publishing Company, 2024) Hamad, Othman Abdulrahman; Kareem, Rebaz Obaid; Azeez, Yousif Hussein; Kebiroğlu, Mehmet Hanifi; Omer, Rebaz Anwar; Zebari, Osama Ismail Haji
The novelty of the work lies in the application of quantum computing analysis, specifically employing density functional theory (DFT) and Hartree-Fock (HF) techniques with various basis sets (aug-cc-pVQZ, 3-21G, 6-31G, 6-311G, and SDD), this work examined the structure and characteristics of naphthalene. The theoretical nature of naphthalene's structure and characteristics: Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO), band gap BG, density of state (DOS), Ultraviolet (UV), and Natural Bond Orbital (NBO) are explored. Several additional characteristics have been studied: thermochemical properties at standard temperature and pressure, and their optical properties (Optical BG with the indirect and direct transition). The DFT/aug-cc-pVQZ basis was used with a fixed value of 4.75 eV to determine the HOMO-LUMO gap of naphthalene in this investigation. We find that the gaps of 4.71, 4.873, and 4.74 eV, respectively, in a recent density-functional theory (DFT) study that agrees with our results. © 2024 by SPC (Sami Publishing Company).
Spectroscopic Properties and Computational Studies of Phosphosilicate-Doped Compounds Including (F, Cl, Br)
(Eurasian Science Society (ESS), 2024) Kareem, Rebaz Obaid; Mohammed, Bast Ahmed; Kebiroğlu, Mehmet Hanifi; Hamad, Othman Abdulrahman
In this work, we added Cl, Br, and F atoms to the phosphate-silicate (PHS) molecule using the density functional theory (DFT) approach using a 6-31G basis set and the B3LYP level of theory. Numerous characteristics, including HOMO-LUMO, reduced density gradient (RDG), density of states (DOS), non-covalent interaction (NCI) theory, and molecular electrostatic potential (MEP) maps, were determined. The PHS molecule was found to have the higest softness (0.330 eV-1) and electronegativity (5.117 eV), along with a lower energy gap (3.029 eV). These features point to improved inhibitor efficiency, polarizability, and higher chemical activity. On the other hand, it also implies that compounds with pure PHS are less stable when analyzed through the lens of density functional theory, which results in a greater degree of chemical reactivity. © 2024, Eurasian Science Society (ESS). All rights reserved.
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, Ali
This 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.
The electronic structure and physicochemical characteristics of chlorohydroquinone compounds using density functional theory and Hartree-Fock techniques
(Bureau Scientific Publ, 2024) Mohammed, Bast Ahmed; Kareem, Rebaz Obaid; Hamad, Othman Abdulrahman; Kebiroglu, Hanifi
In the present research, the computer program Gaussian 5.0.9W was used to perform all calculations and physicochemical characteristics of 2-chlorobenzene-1,4-diol, 2,5-dichlorobenzene-1,4-diol, and 2,3,5,6-tetrachlorobenzene-1,4-diol molecules. The novelty of the work lies in the application of quantum computing analysis, specifically employing density functional theory (DFT) and Hartree-Fock (HF) techniques with a variety of basis sets (3-21G, 6-31G and 6-311G) to study the structure and characteristics of title compounds. In the current investigation, the influence of an increasing concentration of Cl compound on the electronegativity, dipole moment, and ionization potential was investigated. The following quantum chemical properties were derived: E (HOMO) -E (LUMO) energy band gap (BG), energy ground state, ultraviolet (UV) spectroscopy, molecule electrostatic potential (MEP) on surfaces, density of states (DOS), reduced density gradient (RDG), nuclear magnetic resonance (NMR) including ground state energy E (B3LYP), thermodynamic parameters including thermal energy (E), entropy (S), molar heat capacity (Cv). Using a 6-31G basis set for DFT, the maximum amount of BG energy that can be transferred between HOMO and LUMO in a 2-chlorobenzene-1,4-diol molecule is 5.46 eV. Finally, based on our findings, the HF technique has a larger energy gap than the DFT approach. According to this, chlorohydroquinone compounds are less stable when using the DFT method, which suggests a higher degree of chemical reactivity.
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, Tankut
This 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.
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, Niyazi
Hydroxyapatite (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.

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