Yazar "Dorozhkin, Sergey, V" seçeneğine göre listele

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    The effects of Mn and/or Ni dopants on the in vitro/in vivo performance, structural and magnetic properties of ?-tricalcium phosphate bioceramics
    (Elsevier Sci Ltd, 2019) Ates, Tankut; Dorozhkin, Sergey, V; Kaygili, Omer; Kom, Mustafa; Ercan, Ismail; Bulut, Niyazi; Firdolas, Fatih
    The present study describes the effects of dopants of Mn and/or Ni on the structural, magnetic and in vivo/in vitro performances of beta-tricalcium phosphate (beta-TCP) bioceramics synthesized by a sol-gel method. Both types of dopants caused significant effects on the structure-related parameters of beta-TCP, including the crystallite dimensions and lattice parameters. The magnetic properties of as-prepared samples were found to be affected by the type and amount of the dopant(s). The in vitro antimicrobial activities of doped beta-TCPs against American Type Culture Collection (ATCC) reference bacterial and fungal strains were evaluated. Among them, only 1.35Ni-TCP displayed an effective antimicrobial activity against Gram-positive bacteria (50 mu g/mL Minimum Inhibitory Concentration (MIC) range), while other types of doped beta-TCPs did not possess with such effect. The in vivo tests showed that each formulation could be a good nominate for bone healing and bone treatment.
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    Effects of strontium - erbium co-doping on the structural properties of hydroxyapatite: An Experimental and theoretical study
    (Elsevier Sci Ltd, 2020) Mahmood, Bahroz Kareem; Kaygili, Omer; Bulut, Niyazi; Dorozhkin, Sergey, V; Ates, Tankut; Koytepe, Suleyman; Gurses, Canbolat
    Five different samples of Sr-based Er-doped hydroxyapatites (HAps) in the dissimilar quantities like 0, 0.35, 0.70, 1.05 and 1.40 at% were produced via a wet chemical process. The prepared samples were investigated experimentally by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA), and in vitro biocompatibility tests. In addition, the density of states (DOS) and band structures were investigated theoretically. It was found that the presence of Er as a dopant affected the lattice parameters, while the EDX measurements confirmed that the presence of Er at various concentrations caused a Ca-deficiency because the addition of Er decreased the Calcium/Phosphorus molar ratio from 1.67 to 1.61. For all samples, the single-phase distribution of HAp was observed. The crystallinity percentage of the samples was found to be 89% or more according to two different methods. The calculations with respect to Scherrer and Williamson-Hall methods showed that the crystallite sizes of the samples were found to be in the ranges of 29-34 nm and 25-42 nm, respectively. DTA investigations revealed that all samples exhibited thermal stability in the temperature range of 25 degrees C - 1000 degrees C. No remarkable morphological alterations were observed. Furthermore, the theoretical studies confirmed that the band structures narrowed with an increase in Er concentration.
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    Experimental characterization and theoretical investigation of Ce/Yb co-doped hydroxyapatites
    (Elsevier Science Sa, 2022) Acar, Serdar; Kaygili, Omer; Ates, Tankut; Dorozhkin, Sergey, V; Bulut, Niyazi; Ates, Burhan; Koytepe, Suleyman
    In the present study, the effects of variable amounts of Yb addition on the structural, thermal, and in vitro biocompatibility properties of Ce-doped hydroxyapatite (HAp) samples synthesized via the wet chemical method were investigated. Besides, the prepared formulations were also modeled for making the theoretical investigations. The single-phase compositions were detected for all samples, and no formation of additional phases was observed. Doping with Yb was observed to produce some variations in the lattice parameters, unit cell volume, lattice strain, and lattice stress. While a decreasing trend in the crystallite size and crystallization percent with increasing Yb content was found, a gradual increase in the anisotropic energy density was observed. All samples were found to be thermally stable from room temperature to 1000 degrees C with negligible mass losses during heating. No significant morphological changes were caused by the addition of Yb. For all samples, the numerical values of (Ca + Ce + Yb)/P molar ratio were found to be close to that for stoichiometric HAp (1.67). It was observed that the increased Yb additive caused a decrease in cell viability values. A continuous decrease in the bandgap energy with the increasing amounts of Yb added to the Ce-based HAp structure was observed from the theoretical investigations. A sharp decrease in the cell viability of the Ce-based HAp was observed with the addition of Yb.
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    Investigation of the effects of Pr doping on the structural properties of hydroxyapatite: an experimental and theoretical study
    (Springer, 2020) Agid, Riyadh Saeed; Kaygili, Omer; Bulut, Niyazi; Dorozhkin, Sergey, V; Ates, Tankut; Koytepe, Suleyman; Ates, Burhan
    Five samples of hydroxyapatite (HAp) doped with praseodymium (Pr) at various amounts (2, 4, 6, 8, and 10 at.%) were synthesized by using the wet chemical route. The effects of Pr doping on the structural and thermal properties, as well as on the in vitro performance of HAp, were investigated experimentally. The band structure and density of states (DOS) of HAp were studied theoretically. Incorporation of Pr into the crystal lattice of HAp was observed. A gradual increase in the crystallite size, lattice parametera, and unit cell volume was found, and a gradual decrease in the crystallinity degree was seen. Pr content from 2 to 10 at.% did not affect the thermal stability of HAp. The theoretical results showed that the bandgap energy of HAp decreased steadily from 3.82 to 1.32 eV with the adding of Pr, and the DOS was also affected by the Pr content. The cell viability tests showed that among all the as-synthesized samples, the best biocompatible properties were found for the sample which was doped with 10 at.% Pr, and the amount of Pr affected significantly the cell viability property of HAp. Except for the sample having 6 at.% Pr, all the remaining samples appeared to be potentially good candidates for biomedical applications.