Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 7Citation - Scopus: 7Synthesis and Characterization of Single-Walled Carbon Nanotube: Cyto-Genotoxicity in Allium Cepa Root Tips and Molecular Docking Studies(Wiley, 2022) İnce Yardımcı, Atike; İstifli, Erman Salih; Açıkbaş, Yaser; Liman, Recep; Yağmurcukardeş, Nesli; Yılmaz, Selahattin; Ciğerci, İbrahim HakkıHerein, single-walled carbon nanotubes (SWCNTs) were synthesized by the thermal chemical vapor deposition (CVD) method, and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Raman spectroscopy, dynamic light scattering (DLS), and thermo-gravimetric analysis (TGA). The results indicated that obtained nanotubes were SWCNTs with high crystallinity and their average diameter was 10.15 ± 3 nm. Allium cepa ana–telophase and comet assays on the root meristem were employed to evaluate the cytotoxic and genotoxic effects of SWCNTs by examining mitotic phases, mitotic index (MI), chromosomal aberrations (CAs), and DNA damage. A. cepa root tip cells were exposed to SWCNTs at concentrations of 12.5, 25, 50, and 100 μg/ml for 4 h. Distilled water and methyl methanesulfonate (MMS, 10 μg/ml) were used as the negative and positive control groups, respectively. It was observed that MIs decreased statistically significantly for all applied doses. Besides, CAs such as chromosome laggards, disturbed anaphase–telophase, stickiness and bridges and also DNA damage increased in the presence of SWCNTs in a concentration-dependent manner. In the molecular docking study, the SWCNT were found to be a strong DNA major groove binder showing an energetically very favorable binding free energy of −21.27 kcal/mol. Furthermore, the SWCNT interacted effectively with the nucleotides on both strands of DNA primarily via hydrophobic π and electrostatic interactions. As a result, cytotoxic and genotoxic effects of SWCNTs in A. cepa root meristematic cells which is a reliable system for assessment of nanoparticle toxicology were demonstrated in this study.Article Citation - WoS: 25Citation - Scopus: 27Osteogenic Differentiation of Mesenchymal Stem Cells on Random and Aligned Pan/Ppy Nanofibrous Scaffolds(SAGE Publications, 2019) Selamet, Yusuf; İnce Yardımcı, Atike; Baskan, Öznur; Yılmaz, Selahattin; Meşe, Gülistan; Özçivici, EnginThe aim of this study was to develop random and aligned polyacrilonitrile (PAN)/polypyrrole (PPy) nanofibrous scaffolds by electrospinning technique for osteogenic differentiation of mesenchymal stem cells. Nanofibers were fabricated successfully as straight, smooth, and free from bead formation. The average diameter of random and aligned nanofibers was 268(+/- 49) nm and 225(+/- 72) nm, respectively. Alignment process increased the tensile strength of nanofibers 3.9-fold, while the tensile strain of nanofibers decreased by 78%. PAN/PPy nanofibers were hydrophilic with the contact angle value of about 32 degrees and alignment did not affect the contact angle value. Random and aligned PAN/PPy nanofibers were investigated as a scaffold material for osteogenic differentiation of D1 ORL UVA mouse bone marrow mesenchymal stem cells. Cells were able to attach and grow on nanofibers confirmed by cell viability results. Stem cells that were cultured with osteogenic induction were able to mineralize on electrospun nanofibers based on alizarin red and Von Kossa dye staining. For aligned PPy nanofibers, mineralization occurred in the fiber alignment direction. Consequently, PAN/PPy nanofibrous mats in both random and aligned forms would be potential candidates for bone tissue engineering.Article Citation - WoS: 30Citation - Scopus: 31Esterification of Cetyl Alcohol With Palmitic Acid Over Wo3/Zr-sba-15 and Zr-Sba Catalysts(Elsevier Ltd., 2016) Mutlu, Nahide Nuran; Yılmaz, SelahattinTungsten loaded and Zr incorporated SBA-15 catalysts (WO3/Zr-SBA-15 and Zr-SBA-15) were developed for esterification of cetyl alcohol and palmitic acid. The influence of the Zr content, tungsten loading amount, calcination temperature, feed composition and catalyst amount has been studied. Higher tungsten loading decreased the acidity due to formation of WO3 crystals whereas calcination temperature enhanced the acidity by favoring the dispersion of WOx species. Activities of the catalyst changed depending on their amount of Brønsted sites and total number of acid sites. Zr-SBA-15 catalyst which had the highest amount of Brønsted acid sites gave maximum cetyl palmitate yield (63.1%). This catalyst retained its activity up to 3 reuse cycles without significant loss of activity.Article Citation - WoS: 41Citation - Scopus: 42Fructose Dehydration To 5-Hydroxymethylfurfural Over Sulfated Tio2-Sio2, Ti-Sba Zro2, Sio2, and Activated Carbon Catalysts(American Chemical Society, 2015) Kılınç, Emre; Yılmaz, SelahattinDifferent sulfated catalysts including SO4/TiO2-SiO2, SO4/Ti-SBA-15, SO4/ZrO2, SO4/AC, and SO4/SiO2 were tested in fructose dehydration to 5-hydroxymethylfurfural (HMF). Reactions were carried out in dimethyl sulfoxide (DMSO) at 110 °C. Characterization results indicated that no sulfur leaching was observed from SO4/ZrO2, SO4/TiO2-SiO2, and SO4/Ti-SBA-15 catalysts in the reaction tests. The SO4/TiO2-SiO2 catalyst had a high amount of strong acid sites and the highest amount of Bronsted sites. The highest selectivity to HMF at high conversion, that is, 89% selectivity at 77% fructose conversion was obtained over this catalyst. It preserved its activity after four times reuse.Activated carbonCarbonCatalystsDehydrationArticle Citation - WoS: 28Citation - Scopus: 31The Effects of Catalyst Pretreatment, Growth Atmosphere and Temperature on Carbon Nanotube Synthesis Using Co-mo/Mgo Catalyst(Elsevier Ltd., 2015) İnce Yardımcı, Atike; Yılmaz, Selahattin; Selamet, YusufThe growth of high quality and high yield carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of CH4 over Co-Mo/MgO catalyst was investigated for different growth temperatures and H2 flow rates. It was observed that CNT yield decreased with the H2 flow rate, however, quality increased with increasing H2 flow rate. CNT yield increased for the temperatures 850-950 °C but dropped significantly above 950 °C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950 °C. The optimum H2 flow rate was 200 sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H2 and the mixture of both gases were also analyzed and it was observed that the highest quality CNTs were obtained for both pretreatment and growth carried out with H2. This gave a high yield of 292%. On the other hand, CNT growth carried out under Ar atmosphere gave higher CNT yield of 368%, however, the CNTs grown with Ar were more defective and had larger diameters. Prime novelty statement We demonstrate a sorbitol added catalysis synthesis method and importance of the ideal growth conditions to improve high quality single walled carbon nanotube yield up to 1500%.Article Citation - WoS: 53Citation - Scopus: 60Supercritical Deposition of Pt on Sno2-Coated Al2o3 Foams: Phase Behaviour and Catalytic Performance(Elsevier Ltd., 2008) Garrido, G. Incera; Patcas, F. C.; Upper, G.; Türk, M.; Yılmaz, Selahattin; Kraushaar-Czarnetzki, B.Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378 K at 0.1 MPa to 360 K at 25.6 MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9 × 10-4 mol/mol at 11.2 MPa and 313 K to 3.4 × 10-3 mol/mol at 29.6 MPa and 353 K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3 nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.Article Citation - WoS: 11Citation - Scopus: 13Liquid-Phase Oxidation of Carvacrol Using Zeolite-Encapsulated Metal Complexes(American Chemical Society, 2006) Güneş, Alev; Bayraktar, Oğuz; Yılmaz, SelahattinWe report here the use of zeolite-encapsulated metal (salpn) complexes as catalysts in the oxidation reaction of the natural compound carvacrol in acetonitrile with hydrogen peroxide as the oxidant. No previous studies on the oxidation of carvacrol in the presence of metal salpn complexes have been reported. By using a general flexible ligand method, Cr(III), Fe(III), Bi(III), Ni(II), and Zn(II) complexes of N,N′-bis(salicylidene)propane1,3-diamine (H2salpn) encapsulated in NaY zeolite were prepared. All catalysts were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses to confirm the complex encapsulation. The activities of all prepared catalysts for the oxidation of carvacrol and hydrogen peroxide were tested. The performances of all catalysts were compared on the basis of the leaching test results and carvacrol conversions. Thymohydroquinone and benzoquinones were observed as byproducts at high conversions of carvacrol. No product was formed in the absence of a catalyst. Fe(salpn)-NaY catalyst exhibited the highest carvacrol conversion of 27.6% with a yield of 22.0%, followed by Cr(salpn)-NaY catalyst with 23.5% carvacrol conversion and a yield of 17.6%. Other catalysts have shown relatively lower performances in terms of carvacrol conversion and leaching. The Cr(salpn)-NaY catalyst was found to be a more efficient catalyst than others on the basis of leaching and activity tests. With the selected catalyst Cr (salpn)-NaY, the effects of temperature and carvacrol/hydrogen peroxide molar ratio on carvacrol oxidation reactions were investigated. Increasing the temperature from 40 to 60 °C caused an increase in the thymoquinone yield from 6.2% to 16.0%. An increase in carvacrol/hydrogen peroxide molar ratio from 1 to 3 resulted in a decrease in the thymoquinone yield.Article Citation - WoS: 32Citation - Scopus: 35Liquid Phase Transformation of ?-Pinene Over Beta Zeolites Containing Aluminium or Boron, Titanium and Vanadium as Lattice Ions(Elsevier Ltd., 2005) Gündüz, Gönül; Dimitrova, Raina D.; Yılmaz, Selahattin; Dimitrov, LjubomirBeta zeolites with different modules (SiO2/Al2 O3) and containing B, Ti or V in lattice positions were synthesised by different methods and tested as catalysts in liquid phase transformation of α-pinene at 100 °C in a batch reactor. It was established that the hydrogen forms of Beta samples with a SiO2/Al2O3 module of about 55-66 and containing both micro- and mesopores displayed high catalytic activity in liquid phase isomerization of α-pinene. Samples with boron, titanium or vanadium, as lattice ions possess insignificant catalytic activity.Article Citation - WoS: 36Citation - Scopus: 40The Kinetics of Citral Hydrogenation Over Pd Supported on Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Yılmaz, Selahattin; Uçar, Şule; Artok, Levent; Güleç, HilalThe liquid phase hydrogenation of citral has been investigated over Pd (2.42%) supported on clinoptilolite rich natural zeolite catalyst for different reaction conditions. The zeolite support did not affect the active metal properties. This was attributed to the large size of Pd particles on the support. High selectivity (90%) to citronellal was obtained at complete conversion of citral. The catalytic activity increased with reaction temperature (80, 100, 120°C) following an Arrhenius behaviour, while selectivity remained constant for a given conversion. Selectivity to citronellal increased from 78 to 90% with increase in the amount of catalyst in the reaction solution (Citral/Pd mole ratio 293, 176 and 105). The spent catalyst regained its fresh activity and selectivity upon regeneration.Article Citation - WoS: 4Citation - Scopus: 4A Chromatographic Study of Carbon Monoxide Adsorption on a Clinoptilolite-Containing Natural Zeolitic Material(Taylor and Francis Ltd., 2004) Narin, Güler; Yılmaz, Selahattin; Ülkü, SemraIn this study, the equilibrium and kinetic parameters for CO adsorption on clinoptilolite-rich natural zeolitic material were determined by the concentration pulse chromatography technique. Experiments were carried out at different column temperatures (60-120°C) and interstitial carrier gas velocities (3.1-16.3 cm/s) using a clinoptilolite-rich natural zeolitic material packed column. The equilibrium and kinetic parameters were determined by matching the moments of the experimentally obtained response curves to the parameters in the mathematical model. The Henry's Law constants were found to decrease from 700 to 49 with increasing temperature. The heat of adsorption at low coverage was found to be 50.73 kJ/molK. The contributions from external film, macropore, and micropore diffusion resistances to mass transfer were determined, and the micropore diffusion resistance was found to be the major contributor. The micropore diffusivity as a function of crystal radius (Dc/rc 2) was determined and found to change between 5.72 × 10-4 and 1.34 × 10-2 s-1 in the temperature range studied.