Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 16Citation - Scopus: 15Characterization of Silk Fibroin Based Films Loaded With Rutin-Ss Inclusion Complexes(Kluwer Academic Publishers, 2014) Şamlı, Merve; Bayraktar, Oğuz; Korel, FigenIn this study, cyclodextrin inclusion complexes with rutin were prepared via co-precipitation method. Stability constant and solubility energy of beta-cyclodextrin complex were calculated as 262 M-1 and 1,737 kJ mol-1, respectively. Aqueous solubility of rutin was increased with inclusion complex of beta-cyclodextrin. The effect of temperature on both aqueous solubility of free rutin, and its inclusion complex was also studied. Characterization of cyclodextrin complexes were conducted with UV-Vis spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffractometry, differential scanning calorimetry, thermal gravimetric analysis, nuclear magnetic resonance spectroscopy and scanning electron microscopy techniques. Characterization results supported formation of inclusion complexes. Dissolution profiles of rutin, physical mixture and inclusion complex of rutin were observed at 37 °C. Dissolution results proved the effect of cyclodextrin addition on solubility rate of rutin. After loading rutin and its complexes into silk fibroin based films, release tests were performed at 37 °C in neutral pH conditions for 24 h. Most of the rutin were released from silk fibroin films within the first 5 h and the rest of it was released slowly (sustained release). Electron microscope analyses showed that films had homogenous and dense morphologies. These results revealed that silk fibroin is useful for preparing bioactive films loaded with natural compounds and for modifying their release behaviour at physiological conditions.Article Citation - WoS: 48Citation - Scopus: 58Micro-Encapsulation of Ozonated Red Pepper Seed Oil With Antimicrobial Activity and Application To Nonwoven Fabric(John Wiley and Sons Inc., 2013) Özyıldız, Figen; Karagönlü, S.; Başal, Güldemet; Uzel, Ataç; Bayraktar, OğuzIn recent years, functional fabrics possessing antimicrobial activity have drawn significant interest because antibiotic resistance is becoming widespread among pathogenic micro-organisms. The aim of this study was to produce microcapsules incorporating ozonated red pepper seed oil (ORPSO) with antimicrobial properties and apply them to nonwoven fabrics to prepare functional textiles. Red pepper seed oil (RPSO) was ozonated and micro-encapsulated via a complex coacervation method using gelatin (GE) and gum arabic (GA) as wall materials. While micro-encapsulation yield and oil loading decreased with increases in the amount of surfactant, the mean particle size increased. The antimicrobial activity of the oil was tested via the disc diffusion method. The microcapsules were also tested using the agar well method. While RPSO had no effect on the test micro-organisms, the ORPSO and microcapsules containing ORPSO were found to be active against the test micro-organisms. The microcapsules were then applied to nonwoven fabric using the padding method to produce a disposable functional textile. The microcapsule-impregnated functional fabrics provided a 5 log decrease in 1 h. It is therefore possible to functionalize nonwoven fabrics to have antimicrobial activity against antibiotic-resistant micro-organisms, using microcapsules containing ORPSO.Article Citation - WoS: 53Citation - Scopus: 60Properties of N-Eicosane Silk Fibroin-Chitosan Microcapsules(John Wiley and Sons Inc., 2011) Başal, Güldemet; Şirin Deveci, Senem; Yalçın, Dilek; Bayraktar, OğuzPCM microcapsules containing n-eicosane were prepared by complex coacervation of silk fibroin (SF) and chitosan (CHI). Chemical characterization of microcapsules was carried out using Fourier-transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of microencapsulated n-eicosane were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). FTIR spectra confirmed the encapsulation of n-eicosane within the microcapsules. Results from thermal analyses showed that microcapsules consisted of an average of 45.7 wt % n-eicosane, and had a thermal energy storage and release capacity of about 93.04 J/g and 89.68 J/g, respectively.Article Citation - WoS: 22Citation - Scopus: 21A Novel Silk Fibroin-Supported Iron Catalyst for Hydroxylation of Phenol(John Wiley and Sons Inc., 2006) Pekşen, Bahar Başak; Üzelakçil, Caner; Güneş, Alev; Malay, Özge; Bayraktar, OğuzThe aim of this study was to explore the potential use of silk fibroin (SF) as a catalyst support material for phenol hydroxylation reactions. Iron-substituted silk fibroin fibers were prepared using formic acid at room temperature and characterized using inductively coupled plasma atomic-emission spectrometry, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and optical microscopy. Measurement of an FTIR spectrum showed that the secondary structure was β-structure before and after iron substitution. To evaluate the catalytic properties of prepared catalyst, phenol hydroxylation reaction was carried out using aqueous hydrogen peroxide as an oxidant. An excellent transformation of phenol into dihydroxybenzenes (catechol and hydroquinone) was achieved. Phenol conversions of 3.3%, 61.2%, and 80.3% were obtained at room temperature, 40°C and 60°C respectively. It was found that no further phenol conversion proceeded because catalysts became separated from the reaction system during the reaction. No significant leaching of the iron was detected. Catalyst could be reused several times without a significant change in activity. Parent silk fibroin fibers without iron were inactive.Article Citation - WoS: 29Citation - Scopus: 32Visualization of the Equilibrium Fcc Catalyst Surface by Afm and Sem-Eds(Kluwer Academic Publishers, 2003) Bayraktar, Oğuz; Kugler, Edwin L.The deposition of metal contaminants (e.g., Ni, V, and Fe) from the hydrocarbon feed causes the deactivation of fluid catalytic cracking (FCC) catalyst used in petroleum refining. It is very important to understand the changes in the morphology and chemical composition on the catalyst surface and how these structural and chemical changes affect the catalyst performance. In this research, metal-contaminated FCC catalysts from a commercial unit have been characterized using AFM together with SEM-EDS. The AFM images showed the surface pores as well as the features that surround the pore's entrance on the catalyst surface. Catalyst surface contains debris that appear as bright spots in AFM images. SEM-EDS results have shown the presence of iron in these bright spots. Fe enrichment at the catalyst particle surface was also confirmed by XPS analyses.