Department of Chemical Engineering

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DEVELOPMENT OF PLATINUM CONTAINING ELECTROCATALYSTS SUPPORTED ON HYBRID MATERIAL OF PEM FUEL CELL
(2023-01-27) ALJANABI, Ahmed; YAMAN, Şeniz Özalp; DEVRİM, Yılser
Increasing energy demand in the world has increased the need for alternative energy technologies. Fuel cells using hydrogen, an important alternative energy source, have attracted great interest in recent years. Among the fuel cell types, proton exchange membrane fuel cells (PEMFC) are the most interesting fuel cell type due to their modular structure, high efficiency and low operating temperatures. Particularly, component development studies attract attention to increase the performance of PEMFCs. In this thesis multiwalled carbon nanotube-graphene MWCNT-supported Pt catalysts are synthesized using the microwave-assisted approach to examine the method to investigate the PEMFC performance. MWCNT-supported platinum catalysts were prepared for PEMFC application by using [(NH4)2[Pt2(HPO4)4(H2O)2] (Ptcomplex-1) & [(NH4)2[Pt2(SO4)4(H2O)2] (Ptcomplex-2) complexes as starting materials. TGA, XRD, HR-TEM and XPS analyzes were applied to examine the microstructure and morphology of the catalysts. Among the prepared catalysts Ptcomplex-1/MWCNT-3 and Ptcomplex-2/MWCNT-3 catalysts were tested in PEMFC with H2/air at the range of 60- 80 °C. The maximum power density values were determined for a membrane electrode assembly (MEA) prepared using Ptcomplex-1/MWCNT-3 catalyst as 0.36, 0.39, 0.41, and 0.26 W/cm2 and 0.38, 0.423, 0.44 and 0.28 W/cm2 for Ptcomplex-2/MWCNT-3 catalyst at 60, 65, 70 and 80 ⁰C, respectively. It was determined that the prepared Ptcomplex/MWCNT catalysts showed a better PEMFC performance than that of the Pt/C catalyst. The performance of the catalysts can be further improved with MEA optimization studies to be carried out with the catalysts prepared in the future.
INVESTIGATION OF THE EFFECT OF SENESCENCE ON ANTIOXIDANT RESPONSES FOR MG-63 (HUMAN OSTEOSARCOMA) AND MC3T3-E1 (MOUSE PRE-OSTEOBLAST) CELL LINES
(2023-02-01) AYAN, Fırat; İŞGÖR, Sultan Belgin
Aging and its effects have been revealed by many researchers, the effects of aging on living systems are still being investigated today. In this study, antioxidant enzyme responses of mouse osteosarcoma (MG-63) and mouse preosteoblast cells (MC3T3- E1) against aging, which are used in many scientific studies; Superoxide Dismutase Glutathione-S-Transferase (GST), Glutathione Peroxidase (GPx) and DPPH activities were investigated. In this study before performing the enzyme assays, the protein contents of the cells were found, and they were determined as 0.05 mg/mL for MG-63 young, 0.05 mg/mL for MG-63 young, 0.05 mg/mL for MC3T3-E1 young and 0.03 mg/mL for MC3T3-E1 young were found, respectively. Enzyme activities were analyzed comparatively for passages 10, 15, 20, 25, 30, 35, 40 and 45. As can be seen, GST, GPX activities are higher in senescent cancer cells. However, SOD activity was found to be higher in aging progenitor bone cells. In DPPH activity, senescent cancer cells were found to have the highest oxidant scavenging effect with 71.2%. On the other hand, both cell lines were stained with S-A-β-Galactosidase, and β-Galactosidase accumulations due to senescence were qualitatively investigated, and blue stain accumulation was found to be higher in aged osteosarcoma cells. Finally, cell kinetics were examined, and doubling times and specific growth rates were found for the old and young passages of both cell lines used. Doubling times of cells were found to be as respectively, 4.45 hours for MG-63 young, 2.48 hours for MG-63 young, 3.04 hours for MC3T3-E1 old and 3.30 hours for MC3T3-E1 young.
INFLUENCE OF SURFACE TREATMENTS OF FELDSPAR AND QUARTZ MINERALS TO ELASTOMERIC POLYURETHANE BASED COMPOSITES
(2022-06-20) BOUZMANE, Hajar; TİRKEŞ, Seha; TAYFUN, Ümit
In this thesis study, surface treatment routes including silane modifications were applied to quartz and feldspar minerals (purchased from Eczacıbaşı Esan, Istanbul, Türkiye) to achieve a compatible mineral surface with the polymer matrix. Surface characteristics of minerals were examined using chemical analysis and surface functionality by Fourier transformed infrared spectroscopy (FTIR) method. Thermoplastic polyurethane-TPU (supplied by Ravago Petrochemicals, Izmir, Türkiye) was compounded with pristine and modified minerals by melt-blending technique. TPU-based composites were fabricated at a constant adding amount of 10% by weight for each additive. The dogbone-shaped test samples were prepared using an injection molding process. Mechanical, thermo-mechanical, melt-flow, and morphological characterizations of TPU and composites were performed by tensile and Shore hardness tests, dynamic mechanical analysis (DMA), melt flow index (MFI) measurements, and scanning electron microscopy (SEM), respectively. Effects of surface treatments were discussed comparing the findings of composites filled with pristine and modified minerals with the help of test data.
SYNTHESIS, CHARACTERIZATION AND INVESTIGATIONS OF THERMAL BEHAVIOR OF THE NITRO-IMIDAZOLE-BASED ENERGETIC COORDINATION COMPOUNDS
(2022-06-16) YAMAN, Vahide Selen; ÖZALP YAMAN, Şeniz; EKİNCİ MACHIN, Nesrin
Energetic materials produced in various structures have different applications both in the military as explosives and in the civilian field as propellant and pyrotechnics. However, due to the adverse effects of these materials on the environment and health as well as their high sensitivity to light and friction, it is desired to replace them with environmentally friendly, toxic metal-free and easy-handling alternatives. The main aim of this study is to synthesize and explore the performance of novel energetic organic and coordination compounds. In this scope, 5-(chloro(nitro)methyl)-4-nitro 1H-imizadole (HL) and its sodium (NaL) and ammonium (NH4L) salts were designed and synthesized as a first time. Next, totally 34 cobalt(II/III), copper(II), iron(II/III) and zinc(II) complexes containing 5-(chloro(nitro)methyl)-4-nitro-1H-imizadole were designed in octahedral and tetrahedral structures, [M(NH3)x(L)y] n [x:0, 2-4; y:1, 2, 4 or 6; n:(+1)-(-4)]. However, only 26 of these complexes could be synthesized successfully and characterized via various spectroscopic techniques (HRMS, NMR, FTIR). Especially, 6 L coordinated cobalt(II)/III) and iron(II)/III) complexes were found to be unstable due to the steric effect as it was also indicated by their optimized geometry calculations carried out as a part of the TUBITAK Project 117Z391 [1]. Thermo-gravimetric and differential thermal analyses (TGA-DSC) of these newly generated energetic coordination compounds were achieved and their thermal stability, thermal decomposition characteristics and kinetic parameters were determined to explore their potential to be used as an energetic material. The simultaneous TGA-DSC curves pointed out the similar decomposition processes with the high thermal stability within the range of 25-1200 oC for all the studied complexes. Among all these compounds; HL, NaL, NH4L and only five of the metal complexes showed exothermic behavior at around 800-1100 oC. It was observed that the exothermic decomposition temperature of the HL and its salts moved from 800 oC to 1100 oC upon coordination to the metal ions. It was very suprising that solely Co(II), Fe(II) and Cu(II) complexes including one or two L showed an exothermic character. Impact and friction sensitivity tests applied to the most promising two energetic compounds, [Co(NH3)4(L)2] and [Fe(NH3)4(L)2], revealed that these complexes were very resistant to impact and insensitive to friction. The agreement between the desired energy and sensitivity results indicated that our complexes can be applied as propellants in rocket systems and as additives in small amounts to modify the ballistic properties of propellants.
SYNTHESIS OF CHEMILUMINESCENT COMPOUNDS AND THEIR USAGE IN METAL ION RECOGNITION AND BLOOD DETECTION
(2022-06-13) BALCI, BURCU; Cihaner, Atilla
Luminescent compounds have gained great importance recently due to their wide application areas. In addition, chemiluminescent compounds have been used for many studies in analytical chemistry due to their high luminescence sensitivity. In this thesis, a new series of chemiluminescent compounds, namely 5,8-di(furan-2-yl)-2,3- dihydrophthalazine-1,4-dione (F2B-Lum), 5,8-di(selenophene-2-yl)-2,3- dihydrophthalazine-1,4-dione (S2B-Lum) and 5,7-di(selenophen-2-yl)-2,3- dihydrothieno[3,4-d] pyridazine-1,4-dione (S2T-Lum), was synthesized via electron donor-acceptor-donor approach. Their structures were confirmed by using NMR, FTIR and HRMS techniques. Then, the chemiluminescence reactions of compounds with hydrogen peroxide in an alkaline solution (0.1 M NaOH(aq)) in the presence of different metal ions, hemin and blood samples were investigated and the results were compared with luminol. As expected, the compounds were sensitive to copper(II), iron(III) ions and blood. It can be easily concluded that the corresponding compounds as new derivatives of luminol are potential candidates for the detection of blood findings in forensic science. In addition, the sensitivity of the compounds to copper(II) ion makes them usable for copper ion recognition in analytical applications. Furthermore, cyclic voltammetry technique was used to investigate the redox behaviors of the compounds and they exhibited irreversible oxidation peaks. Also, reactive oxygen species can be detected by using these compounds via square wave potential method by applying an external potential of -1.05 V. Finally, among the compounds, S2T-Lum was successfully polymerized electrochemically. The corresponding polymer PS2T-Lum can be a precious member of luminol type polymers since it is electroactive and bears chemiluminescent active appendages in its polymeric structure.
SYNTHESIS AND CHARACTERIZATION OF A NEW SELENOPHENE BASED ELECTROCHROMIC POLYMER
(2015-01-31) KARABAY, Barış; CİHANER, Atilla
A new derivative of 3,4-propylenedioxyselenophene bearing naphtyl appendages on the bridge, called 3,4-dihydro-3,3-bis ((naphthalen-1-yl)methyl)-2H selenopheno[3,4-b][1,4]dioxepine (ProDOS-Np2), was synthesized and polymerized via potentiostatic and potentiodynamic methods. Electrochemically obtained polymer film (PProDOS-Np2) is pure blue at the neutral state and highly transparent at the oxidized state. An increase in the size of the substituents on the bridge resulted in an increase in the optical contrast ratio. Upon moving from naked bridge to benzyl and to naphtyl substituents on the bridge center, the optical contrast changed from 51% to 65% and finally to 84%. When compared to polythiophene analogue, the PProDOS Np2 has lower oxidation potential and band gap, higher optical contrast ratio, coloration efficiency, robustness and stability. The polymer film preserved its properties even after thousands of cycles under ambient conditions.
SYNTHESIS AND CHARACTERIZATION OF NEW DITHIENOSILOLE BASED CHROMIC POLYMERS
(2015-06-27) AL-JUMAILI, MOHAMMED; CİHANER, Atilla
2-Ethylhexyl substituted dithienosilole based soluble polymers including thiophene (P1) and bithiophene (P2) units were synthesized via Stille Coupling reaction. The polymers were characterized by using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) techniques. The presence of 2- ethylhexyl substituents on the silole ring gave solubility property to the polymers in common solvents. According to GPC measurements, weight average molecular weights of the polymers P1 and P2 were found to be as 70977 with a polydispersity index (PDI) of 2.30 and 110439 with a PDI of 1.42, respectively. Fluorescent polymers in toluene solution have maximum emisssion bands at 634 nm for P1 and 613 for P2. Chemical and electrochemical doping of the polymers in solution and film forms were monitored by using ultraviolet-visible (Uv-vis) spectroscopic technique. The polymers exhibited chromic (chemochromic and electrochromic) properties. While the colors of the neutral polymer films are purple for P1 and reddish brown for P2, both polymers are transparent sky blue at their oxidized states. The band gaps of polymers in film forms were calculated as 1.81 eV for P1 and 1.92 eV for P2. Also, electrochromic device applications of the polymers were done. Electrochemical and optical behaviors of the polymer demonstrated that they can be good candidates for optoelectronic applications.
SYNTHESIS AND CHARACTERIZATION OF NEW POLYMERIC MATERIALS FROM ELEMENTAL SULFUR
(2015-06-26) SALMAN, Mohamed Khalifa; CİHANER, Atilla
New elemental sulfur based polymeric materials called poly(sulfur-random divinylbenzene) (poly(S-r-DVB)) were synthesized by ring opening polymerization in the presence of a mixture of o-, m- and p-diviniylbenzene (DVB) as a crosslinker. In order to get the copolymers, the elemental sulfur was melted at 160 oC and therefore ring-opening polymerization of the S8 was promoted and a clear yellow/orange colored liquid was obtained. Then, various amounts of DVB were added to this liquid directly via a syringe and continued to further mixing at 200 oC for 10 minutes to get viscous reddish brown polymeric materials. The copolymers are soluble in common solvents like tetrahydrofuran, dichloromethane and chloroform, and they can be coated on any surface as thin film. The characterization of the materials were performed by using nuclear magnetic resonance, fourier transform infrared and Raman spectroscopies. The morphological properties were monitored via scanning electron microscope technique. Thermal analysis showed that an increase in the amount of DVB in the copolymers resulted in an increase in the termal decomposition temperature. On the other hand, poly(S-r-DVB) copolymers exhibited good percent transmittance as 50 %T between 1500 and 13000 nm in electromagnetic radiation spectrum, which make them good candidates to be amenable use in military and surveillance cameras.
SYNTHESIS AND POLYMERIZATION OF BENZIMIDAZOLE BASED MONOMERS VIA A DONOR – ACCEPTOR APPROACH
(2015-06-25) AL-OGAİDİ, Saad; CİHANER, Atilla
A new series of fluorescent donor-acceptor-donor (D-A-D) type monomers based on benzimidazole acceptor unit bearing cycloalkane appendages, called 4,7-di-2,3- dihydrothieno[3,4-b][1,4]dioxin-5-ylspiro[benzimidazole-2,1'-cyclopentane] (E5E), 4,7-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-ylspiro[benzimidazole-2,1'- cyclohexane] (E6E) and 4,7-di-2-thienylspiro[benzimidazole-2,1'-cyclohexane] (T6T), were synthesized and polymerized via potentiostatic and potentiodynamic methods. The effect of ring size on benzimidazole unit and the kind of donor moiety in D-A-D system has been studied systematically on the electrochemical and optical properties. The optical studies showed that ring size of the benzimidazole unit has no effect on the absorbance and fluorescence properties, whereas the oxidation potential of E5E, E6E and T6T monomers varied with respect to both the ring size and donor unit: 0.89 V, 0.83 V and 1.22 V vs Ag/AgCl, respectively. All polymers have ambipolar (p- and n-type doping) and electrochromic properties. While the polymer films PE5E and PE6E are green at neutral state and transparent at oxidized state, the polymer PT6T has no appreciable color change between its neutral and oxidized state. The polymers bearing 3,4-ethylenedioxythiophene unit as donor units (PE5E and PE6E) exhibited lower band gap values (1.21 eV and 1.18 eV, respectively) than PT6T (1.53 eV). When compared to PT6T, PE5E and PE6E polymers are more stable under ambient condition. While PE5E retained 76% of its electroactivity after 4000 cycles, PE6E has 65% of its electroactivity after 2000 cycles.
PREPARATION AND CHARACTERIZATION OF SILVER-PESeE FILM DEPOSITED ON ITO GLASS SURFACE AS A SURFACE ENHANCED RAMAN SCATTERING SUBSTRATE
(2015-06-25) ALSHUWAİLİ, Kadhim Taresh Raisan; KAYA, Murat; CİHANER, Atilla
Surface enhanced Raman scattering (SERS) is known as a very attractive technique for the characterization and detection of a variety of chemical and biological molecules due to their impressive characteristics such as giving spectral fingerprint of vibrations, high sensitivity and insensitivity to water. One of the most important points of the SERS technique is the requirement for producing a substrate having an ideal surface morphology to facilitate the achievement of the most favorable enhancement. Here a novel, simple, reliable, and reproducible one-step electrochemical method for the preparation of surface enhanced Raman-active polymer-mediated silver nanoparticles (Ag NPs) on planar indium tin oxide (ITO) coated glass substrates was reported. Poly (4,7-di-2,3-dihydrothieno [3,4-b] [1,4] dioxin-5-yl-2,1,3 benzoselena diazole) (PESeE) film was used as a support material for dispersing silver nanostructures on the surface homogeneously. The morphologies of the prepared substrates have been investigated by field emission scanning electron microscopy (FE-SEM). The effect of the thickness of PESeE polymer film and the amount of silver particles on the polymer film on the SERS response were studied as well as repeatability and stability of prepared substrates. Brilliant cresyl blue (BCB) has been used as Raman probes to evaluate the properties of the new SERS substrates.
PREPARATION AND CHARACTERIZATION OF PALLADIUM-COPPER BIMETALLIC NANOPARTICLES SUPPORTED ON SILICA COATED COBALT FERRITE MAGNETIC PARTICLES FOR HYDROLYTIC DEHYDROGENATION OF AMMONIA BORANE
(2015-06-25) AL-AQBI, Talaat Hikmat Hashim; KAYA, Murat; CİHANER, Atilla
Metal nanoparticles have attracted much attention over the last decade due to their desired applications in catalytic systems and the usage of these particles in such systems are considered to be a promising way for bridging homogenous and heterogenous catalysis, that is to say for “quasihomogeneous” (or soluble heterogeneous) systems. Naked nanoparticles are due to high surface energy not stable and prone to coagulate while catalytic transformation is taking place. On the other hand, filtration techniques are not efficient to separate nanoparticles that have diameters of less than 100 nm. Under such circumstances, expensive ultracentrifugation is preferred to separate the product and catalyst. In order to get rid of the disadvantages of naked nanoparticles and to enhance the stability and to obtain reusable catalysts, immobilization of nanoparticles onto inorganic supports provide the desired properties for catalytic efficiency. Due to high hydrogen storage capacity (19.6 % wt) and low molecular weight, the innovations in the development of nanocomposite catalysts for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3) is essential to use these catalysts as solid hydrogen carrier. In this thesis, new and reproducible catalyst system consists of palladium-copper bimetallic nanoparticles supported on silica coated magnetic particles has been prepared by wet-impregnation method. After addition of Pd2+ and Cu2+ ions on silica coated cobalt ferrite nanoparticles, nanoparticles formed by in situ reduction of the Pd2+ and Cu2+ ions with NH3BH3 on the surface of silica coated magnetic nanoparticles. The characterization of nanocomposite catalysts were done by inductively coupled plasma/optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution- transmission electron microscopy (HR-TEM) and N2 adsorption–desorption technique. Palladium-Copper bimetallic nanoparticles supported on silica coated cobalt ferrite (PdCuNPs/SiO2-CoFe2O4) provide an initial turnover frequency (TOF) of 238 min-1 at room temperature that shows higher catalytic activity than both non-noble metal catalysts and noble metal based homogenous and heterogeneous catalysts that is used in the reaction of hydrolytic dehydrogenation of ammonia-borane. One of the most important opportunity of such catalyst system is that, catalysts can be collected with a magnet in the reactor wall and they are reusable for up to 5 recycles with the sustainable catalytic activity that exhibited excellent reusability of the catalyst.
DESIGN, SYNTHESIS AND BIOLOGICAL ACTIVITY OF NOVEL ANTITUMOR ACTIVE PLATINUM AND COPPER BASED COMPLEXES CONTAINING QUINOXALINE LIGANDS
(2022-03-10) El- Beshti, Hager Sadek; ÖZALP YAMAN, Şeniz; chemistry
Across the globe, today, cancer accounts for many fatalities, thus calling for better and updated antineoplastic agents within biomedicine and health sciences. In this regard, inorganic chemistry for pharmaceutic purposes is essential in creating drugs based in metal to fight cancer as such medicine has been shown to be potentially effective to fight cancer in humans. In light of this background, this research focuses on synthesis and anticancer activity of (2,3-di-pyridin-2-yl-quinoxaline), (2,3-di-thenyl-2-yl quinoxaline), (2,3,2',3'-tetra-pyridin-2-yl-[6,6']biquinoxaline) and (2,3,2',3'-tetra thenyl-2-yl-[6,6']biquinoxaline) containing copper(II) and platinum(II) compounds as prodrug candidates. The binding interaction of these compounds with calf thymus DNA (CT-DNA) and human serum albumin (HSA) of the complexes were assessed with UV titration, thermal decomposition, viscometric, and fluorometric measurements. The nature of the binding of the complexes on DNA were revealed as electrostatic interaction between the cationic metal complex ions and the negative phosphate groups of CT DNA upon removal of one or two labile chloride ion(s), except Pt(tpbq)Cl2, Pt(ttbq)Cl2, and Cu(tpbq)Cl2; van der Waals and hydrogen bonds interaction were proposed for these complexes. In addition, our complexes induced a surface contact through the hygroscopic region of serum albumin. Antitumor activity of the complexes against human glioblastoma A172, LN229, and U87 cell lines and human lung A549, human breast MDA-231, human cervix HeLa, and human prostate PC-3 cell lines were investigated by examining cell viability (MTT), oxidative stress, apoptosis-TUNEL, in vitro migration an invasion, in vitro Comet DNA demage, and plasmid DNA interaction assays. The U87 and HeLa cells were investigated as the cancer cells most sensitive to our complexes. The exerted cytotoxic effect of complexes was attributed to the formation of the reactive oxygen species in vitro. It is clearly demonstrated that Cu(dtq)2Cl2, Cu(ttbq)Cl2, Pt(ttbq)Cl2 and Pt(tpbq)Cl2 have the highest DNA degradation potential and anticancer effect among the tested complexes by leading apoptosis. Wound healing and invasion analysis results also supported the higher anticancer activity of those complexes.
DNA INTERACTION AND CYTOTOXICITY OF THE PLATINUM BLUE COMPLEX CONTAINING 2-AMINOTHIOPHENOL
(2017-01-07) SALEM, SAFIA; ÖZALP YAMAN, Şeniz
Since the discovery of cisplatin, metal based agents have gained significant interest of researchers as potential anticancer drugs. Several drugs have been rationally synthesized to overcome the hurdles of cisplatin, majorly its toxicity and resistance. Search for less toxic, but still potent anti-cancer platinum compounds revealed a class of platinum complexes with pyrimidines called platinum-pyrimidine complexes also known as “platinum blue” (Pt-blue) complexes. Here, we describe DNA binding ability of the Pt-blue complex [Pt4(2-atp)8(H2O)(OH)] (2-atp: 2- aminothiophenol). In order to investigate the nature of the interaction between the Pt-blue complex and DNA, spectroscopic measurements were made and the results of UV titration, thermal behavior, viscosity and fluorometric titration of the Pt-blue treated DNA were evaluated. Our results suggested that the compound was able to partially intercalate DNA that related to the anticancer activities of the drugs.
THE EFFECT OF PHELLINUS TORULOSUS MUSHROOM EXTRACT ON ANTIOXIDANT ENZYMES
(2017-01-07) ALSAMRRAEY, Maiser Zaid; İŞGÖR, S. Belgin
In order to prevent free radical damages there has been an increasing interest in finding natural sources which can play as antioxidant. Even though several studies were done on mushrooms, Phellinus torulosus was not examined in details. In this study, the free radical scavenging capacity of the total phenolic and flavonoid contents of Phellinus torulosus mushroom extract was evaluated by DPPH and the antioxidant property was tested by catalase (CAT), superoxide dismutase (SOD) and glutathione- S-transferase (GST). In this study, four different mushroom extracts have been prepared using cold water, hot water, methanol, and ethanol. As ethanol extract resulted in the highest contents of total phenolic and flavonoid (as 625.125 µg/ml and 463.5 µg/ml respectively), the ethanol extract was used in the following steps for determining the radical scavenging capacity and antioxidant property of the mushroom. The free radical scavenging capacity of Phellinus torulosus ethanol extract was examined by using DPPH free radical. In this experiment by using quercetin and gallic acid as standards, DPPH radical scavenging capacity of mushroom extract was observed and IC50 value was calculated as 0.04353 g/l. The antioxidant property of Phellinus torulosus ethanol extract was determined by observing its effect on GST. The result showed that the mushroom extract inhibited the activities of GST about 60%. The effect of ethanol extract of Phellinus torulosus on GST was shown with IC50 calculated in the range of 0.1609 to 0.9076 g/l. Again in the same experiment Phellinus torulosus ethanol extract was found to have no effect on CAT and SOD enzymes with less than 15% inhibition for both enzymes.
DESIGN, SYNTHESIS AND DNA BINDING ABILITY OF NOVEL PLATINUM(II) COMPLEXES CONTAINING BIDENTATE NITROGEN AND SULPHUR DONOR LIGAND
(2017-01-07) ABDUSALAM, MOHAMED; ÖZALP YAMAN, Şeniz
One of the main challenges in bioinorganic chemistry is to synthesize new DNA targeting complexes as a potential anticancer drug leads providing better efficiency with low tissue resistance compared to cisplatin. For this purpose, three novel platinum(II) complexes containing 5,6-di-2-thienyl-2,3-dihydropyrazine in asymmetric- (asy-), cis and bis- geometry have been synthesized, identified and their DNA binding ability has been studied by spectroscopic techniques and gel electrophoresis. Spectroscopic data and the calculated binding constant values were demonstrated that the synthesized drugs bind DNA in different types. While Cis and Asy complexes perform base binding covalently, bis complex interact with DNA by intercalating mode but in weaker extend. Gel electrophoresis results were in agreement with the spectroscopic findings. All the complexes induce an oxidative single strand cleavage in the presence of a reductant (ascorbic acid) on the double helix structure of DNA with the decreasing activity order from Asy to Bis. On the other hand, cytotoxicity experiments carried out at the neutral conditions, suggested that the Bis complex is the most promising anticancer agent for the treatment of Human Glioblastoma.
THE EFFECT OF FOMITOPSIS PINCOLA MUSHROOM EXTRACT ON ANTIOXIDANT ENZYME ACTIVITES
(2017-01-07) ELMUBARK, Marwa; İŞGÖR, S. Belgin
A long time ago, mushrooms and their extracts had been widely used for medicinal and food purposes. Nutritionally, mushrooms are low in energy and fat but high in protein, carbohydrate and dietary fiber. Mushrooms are also an important source of biologically active compounds with potential medicinal value. Bioactive secondary metabolites found in mushrooms include phenolic compounds, sterols and triterpenes. In different studies with mushrooms and isolated bioactive constituents have many pharmacological effects such as anti-tumors, antioxidant, antiviral, hypocholesterolemia and hypoglycemic effects. Using of mushroom or mushroom products in our daily diet may provide health benefits. In this study, Fomitopsis pinicola mushroom extracted with seven different methods, by using three different solvents; water, methanol, and ethanol. Total phenol and flavonoid contents of all this extracts were determined to evaluate their antioxidant potency that can act as secondary defense in the biological system, beside the primary defense enzyme systems, such as catalase (CAT), superoxide dismutase, and glutathione-S- transferase. Also the effect of this mushroom on DPPH (1,1-Diphenyl-2- picrylhydrazyl) radical scavenging activity was examined. Since hot water boiled for one hour, and repeated for two times extracts has highest total phenolic contents (TPC) and total flavonoid contents (TFC) valves; 658.900 µg of GAE/ml of extract, and 245.800 µg of QE /ml of extract respectively. DPPH and all enzyme assays were continued by using this extract. This extract has ability to stabilize free radical DPPH about 70%, with IC50 value of 0.272 g/L. also this extract inhibits CAT enzyme activity as 50%, and on the other hand GST enzyme activity was inhibited by the same extract as 85%. The IC50 values of CAT and GST for this extract were calculated as 1.951×10-5 g/L, and 0.086-0.593g/L respectively. While this extract has not significant effect on SOD enzyme and IC50 value calculated as 0.001 g/L.
INVESTIGATION OF THE PHOTOCATALYTIC ACTIVITY OF PALLADIUM NANOPARTICLES ADDED PEDOT
(2017-01-07) AHMED, Matira Miud Alaribi; KAYA, Murat
Investigation and development of efficient and low-cost method for wastewater treatment to effectively eliminate the pollutants is so important for environmental remediation. Among the wastewater treatment methods, advanced oxidation processes (AOP’s) consists of the usage of homogenous and heterogeneous photocatalysts, known as the most effective way. The development of photocatalytic materials used in AOP’s is so important. The advancement of photocatalysts which sensitive to solar light would allow more effective utilization of solar light brings sustainable ways to various environmental problems. Recently conductive polymers noted as a new types of effective photocatalytic materials under solar light. Poly(3,4-ethylenedioxythiophene) (PEDOT) considered as one of the most important candidate among the conjugated polymers. In this thesis, photocatalytic activity of the palladium added PEDOT (PdNPs/PEDOT) polymer was investigated. In this study, a facile production procedure was demonstrated to fabricate the PdNPs/PEDOT as a photocatalyst. The phtocatalytic activity of PdNPs/PEDOT nanocomposite material was checked into the decolorization of MB under UV and solar light exposure. The photocatalytic behavior of bare PEDOT, TiO2 nanoparticles and PdNPs/TiO2 nanostructure were also investigated in order to make comparison with PdNPs/PEDOT nanostructure. The characterization of nanocomposite catalysts were done by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) energy dispersive X-Ray (EDX) coupled with SEM and Raman Spectroscopy.
PREPARATION AND CHARACTERIZATION OF POLYCARBONATE/GLASS FIBER –MICA HYBRID COMPOSITES
(2017-02-07) ALHAJ, Ibrahim Alsadig Mohammedkhair; TİRKEŞ, Seha
The improvement of physical properties of polycarbonate is still great interest of scientists due to the huge application areas. In this study polycarbonate matrix was reinforced with glass fiber (GF), mica (MC) and in hybrid form. The preparation of composites was carried out using co-rotating twin screw micro-compounder at 280 oC and the test samples were prepared by laboratory scale injection-molding device. The percent compositions of added fillers for PC/GF and PC/MC composites were 5%, 10%, 20%, and 30%. The total percentage of both filler was kept as 30% for hybrid composites (MC%/GF%) of which comspositions were 5/25, 10/20, 20/10, 25/5, respectively. The characterizations of obtained composites were examined via tensile test, impact test, melt flow index test, differential scanning calorimetry analysis and scanning electron microscopy methods. The obtained results showed that the best values of tensile strength were obtained for the lowest mica concentration and 20% glass fiber containing composites gave the optimum value. The concentration increment of the additives more than these values caused agglomerations and reduction of homogeneous distribution of them in the PC matrix, which were revealed by scanning electron microscopy.
PREPARATION AND CHARACTERIZATION OF THERMOPLASTIC POLYURETHANE NANOCOMPOSITES AND THEIR HYBRID COMPOSITES
(2017-03-04) Mohamed, Salma A. Taher; TİRKEŞ, Seha
The improvement of physical properties of thermoplastic polyurethane (TPU) is still great interest of scientists due to the possible wide application areas. In this study, polyurethane matrix was reinforced with polyhedral oligomeric silsesquioxane (POSS), halloysites nanotubes (HNT) and in hybrid form. The preparation of composites were carried out using co-rotating twin-screw micro-compounder at 210 oC and the test samples were prepared by laboratory scale injection-molding device. The weight percentages compositions of added fillers for TPU/POSS and TPU/HNT nanocomposites were 0.5%, 1.0%, 1.5%, and 2.0% respectively. As for TPU/POSS HNT hybrid composites the weight percentages were (0.5%, 0.5%), (1.0%, 1.0%), (0.5%, 1.5%), (1.5%, 0.5%) respectively. The characterizations of obtained composites were examined via tensile test, impact test, melt flow index test, hardness test, dynamic mechanical analysis and scanning electron microscopy methods. The obtained results showed that the best value of tensile strength was obtained for the lowest HNT content of 0.5%. For the impact test, the maximum impact strength was achieved when the POSS value was 0.5%. POSS nanoparticles are homogeneously dispersed in TPU matrix for the lowest loading (0.5%). Further additions of POSS cause formation of agglomerations. HNT and POSS nanoparticles seem to be well mixed in micro image of TPU/ 0.5% POSS 0.5%HNT hybrid composites. Homogeneity of their mixing in TPU matrix decreases as the concentrations of POSS and HNT increase, which were revealed by scanning electron microscopy.
THEORETICAL INVESTIGATION OF CARBONYL SULFIDE CAPTURE BY AQUEOUS DIETHANOLAMINE SOLUTION
(2017-05-02) Hadia, Abubaker; Kayı, Hakan
Carbonyl sulfide (COS), an unwanted impurity, released with a variety of processing gases. Capturing of COS can be achieved with liquid absorbents. Two different mechanisms are proposed in the literature for COS and diethanolamine (DEA) reaction, and both drive to a formation of thiocarbamate. The first mechanism is zwitterion intermediate mechanism, which takes two reaction steps. The first step is the forming of the zwitterion, and the second one is the deprotonation of the formed zwitterion. The second mechanism is termolecular mechanism in which a complex forms as intermediate in a single step reaction. Four different termolecular reactions among COS, DEA and water were investigated through the quantum chemical calculations, and structural, energetic and thermochemical properties were revealed. Theoretical standard free energy of activation (∆ ‡G ° ) and reaction (∆G°rxn), equilibrium constant (Keq) and reaction rate constant (k) values for these four termolecular reactions were calculated. Density Functional Theory (DFT) was applied during the theoretical investigations of this study utilizing the B3LYP hybrid functional, and 6-311G(d) basis set. In conclusion, calculated activation energy and reaction rate constant values obtained in this study were compared with the experimental data available in the literature, and under the guidance of these findings, the most probable termolecular reaction mechanism for the COS capture by aqueous DEA solution was revealed.

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