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: 14Citation - Scopus: 13Investigations of Polyamide Nano-Composites Containing Bentonite and Organo-Modified Clays: Mechanical, Thermal, Structural and Processing Performances(Walter de Gruyter GmbH, 2021) Akar, Alinda Öykü; Yıldız, Ümit Hakan; Tayfun, ÜmitPolyamide 6 (PA) matrix was reinforced with Na-activated bentonite, amino functional silane treated bentonite and organo-modified clays at different concentrations. The preparation of composites was carried out using melt-blending method and the test samples were prepared by injection-molding process. Mechanical, thermal, structural and processing investigations of PA based composites were reported performing via tensile, hardness, and impact tests, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and force measurements, respectively. According to mechanical test results, additions of fillers to PA matrix caused slight improvements for tensile strength and modulus parameters. Silane treated BNT exhibited improvement in mechanical results compared to Na-activated bentonite additions. Thermal studies revealed that decomposition and melting temperatures of PA shifted to higher values after inclusion of clay into polymer matrix. Results confirmed that organo-clay and bentonite additions with their lower filling ratios yielded enhancements for the mechanical and thermal performance of polyamide.Article Citation - WoS: 27Citation - Scopus: 34Chitosan/Montmorillonite Composite Nanospheres for Sustained Antibiotic Delivery at Post-Implantation Bone Infection Treatment(IOP Publishing Ltd., 2019) Kımna, Ceren; Değer, Sibel; Tamburacı, Sedef; Tıhmınlıoğlu, FundaDespite the advancements in bone transplantation operations, inflammation is still a serious problem that threatens human health at the post-implantation period. Conventional antibiotic therapy methods may lead to some side effects such as ototoxicity and nephrotoxicity, especially when applied in high doses. Therefore, local drug delivery systems play a vital role in bone disorders due to the elimination of the disadvantages introduced by conventional methods. In the presented study, it was aimed to develop Vancomycin (VC) and Gentamicin (GC) loaded chitosan-montmorillonite nanoclay composites (CS/MMT) to provide required antibiotic doses to combat post-implantation infection. CS/MMT nanocomposite formation was supplied by microfluidizer homogenization and spherical drug carrier nanoparticles were obtained by electrospraying technique. Three factors; voltage, distance and flowrate were varied to fabricate spherical nanoparticles with uniform size. Emprical model was developed to predict nanosphere size by altering process variables. Nanospheres were characterized in terms of morphology, hydrodynamic size, zeta potential, drug encapsulation efficiency and release profile. Drug loaded nanospheres have been successfully produced with a size range of 180-350 nm. Nanocomposite drug carriers showed high encapsulation efficiency (80%-95%) and prolonged release period when compared to bare chitosan nanospheres. The drug release from nanocomposite carriers was monitored by diffusion mechanism up to 30 d. The in vitro release medium of nanospheres showed strong antimicrobial activity against gram-positive S. aureus and gram-negative E. coli bacteria. Furthermore, it was found that the nanospheres did not show any cytotoxic effect to fibroblast (NIH/3T3) and osteoblast (SaOS-2) cell lines. The results demonstrated that the prepared composite nanospheres can be a promising option for bone infection prevention at the post implantation period.Article Citation - WoS: 39Citation - Scopus: 39Polarized Emission From Cspbbr3 Nanowire Embedded-Electrospun Pu Fibers(IOP Publishing Ltd., 2018) Güner, Tuğrul; Topçu, Gökhan; Savacı, Umut; Genç, Aziz; Sarı, Emre; Demir, Mustafa MuammerInterest in all-inorganic halide perovskites has been increasing dramatically due to their high quantum yield, band gap tunability, and ease of fabrication in compositional and geometric diversity. In this study, we synthesized several hundreds of nanometer long and ∼4 nm thick CsPbBr3 nanowires (NWs). They were then integrated into electrospun polyurethane (PU) fibers to examine the polarization behavior of the composite fiber assembly. Aligned electrospun fibers containing CsPbBr3 NWs showed a remarkable increase in the degree of polarization from 0.17-0.30. This combination of NWs and PU fibers provides a promising composite material for various applications such as optoelectronic devices and solar cells.Article Citation - WoS: 8Citation - Scopus: 13Anticorrosion Coating for Magnesium Alloys: Electrospun Superhydrophobic Polystyrene/Sio2 Composite Fibers(TUBITAK, 2018) Horzum Polat, Nesrin; Kap, Özlem; Farzaneh, AmirSuperhydrophobic nanocomposite coatings for magnesium surfaces with remarkable corrosion resistance were fabricated by electrospinning in the presence of fluorosilane-functionalized silica (SiO2) nanoparticles. The effects of surface-modified silica (mod-SiO2) nanoparticles on the superhydrophobicity and corrosion resistance of polystyrene (PS)/mod-SiO2 fiber coatings were evaluated. The incorporation of the SiO2 nanoparticles endows PS fibers with rough surfaces exhibiting a water contact angle (WCA) of 165◦. The surface wettability, corrosion resistance, and their relation to the inorganic content in the PS fibers and the contact angle of the composite coatings were explored. Analysis of the corrosion results confirmed that the PS/mod-SiO2 coating protected the Mg surface from corrosion. In addition, PS fibers containing mod-SiO2 nanoparticles showed improved hydrophobicity, and excellent corrosion resistance was achieved with PS fibers containing 4 wt% SiO2 nanoparticles.Article Citation - WoS: 34Citation - Scopus: 36Effects of Organo-Modified Clay Addition and Temperature on the Water Vapor Barrier Properties of Polyhydroxy Butyrate Homo and Copolymer Nanocomposite Films for Packaging Applications(Springer Verlag, 2018) Akın, Okan; Tıhmınlıoğlu, FundaPolymer nanocomposites, based on bacterial biodegradable thermoplastic polyester, poly(hydroxy-butyrate) (PHB), poly(hydroxyl-butyrate-co-hydroxy-valerate) (PHBHV), and commercial organo-modified montmorillonite (OMMT-Cloisite 10A) were prepared by solution casting method. This work aims to investigate the effect of Cloisite 10A type clay addition on the water vapour permeability properties of PHB/OMMT, and PHBHV/OMMT nanobiocomposite films. Temperature dependence of water vapor permeabilities of the films were also evaluated at various temperatures, and semi empirical permeability models were used to predict the permeability of polymer systems as a function of clay concentration and aspect ratio of nanoplates. Moreover, thermal, optical, and mechanical properties of the composites were examined by using varieties of techniques including differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and thin-film X-ray diffractometer (TF-XRD) respectively. Test results indicated that addition of highly intergallery swollen Cloisite 10A to the PHB/PHBHV, reduced the water vapor permeability up to 41 and 25% compared to native PHB and PHBHV films, respectively. Regarding the all mechanical properties measured, the maximum improvement was achieved for 3 wt% clay loaded samples for both PHB and PHBHV polymer composites. An increase of about 152 and 73% in tensile strength and of 77 and 18% in strain at break was achieved for PHB and PHBHV polymers, respectively. As a result of X-ray diffraction analysis, exfoliated structure was achieved at low clay loaded sample (1% w/w), however at higher concentration (3% w/w) the structure found as intercalated. Therefore, it is an evident that enhancement of characteristic properties highly depend on the dispersion level of clay particles in polymer matrix. The results obtained in this study show the feasibility of improvement of the properties of PHB based polymers with incorporation of nanoclay.Article Citation - WoS: 19Citation - Scopus: 20Transparent Pullulan/Mica Nanocomposite Coatings With Outstanding Oxygen Barrier Properties(MDPI Multidisciplinary Digital Publishing Institute, 2017) Uysal Ünalan, İlke; Boyacı, Derya; Trabattoni, Silvia; Tavazzi, Silvia; Farris, StefanoThis study presents a new bionanocomposite coating on poly(ethylene terephthalate) (PET) made of pullulan and synthetic mica. Mica nanolayers have a very high aspect ratio (α), at levels much greater than that of conventional exfoliated clay layers (e.g., montmorillonite). A very small amount of mica (0.02 wt %, which is φ ≈ 0.00008) in pullulan coatings dramatically improved the oxygen barrier performance of the nanocomposite films under dry conditions, however, this performance was partly lost as the environmental relative humidity (RH) increased. This outcome was explained in terms of the perturbation of the spatial ordering of mica sheets within the main pullulan phase, because of RH fluctuations. This was confirmed by modelling of the experimental oxygen transmission rate (OTR) data according to Cussler’s model. The presence of the synthetic nanobuilding block (NBB) led to a decrease in both static and kinetic coefficients of friction, compared with neat PET (≈12% and 23%, respectively) and PET coated with unloaded pullulan (≈26% reduction in both coefficients). In spite of the presence of the filler, all of the coating formulations did not significantly impair the overall optical properties of the final material, which exhibited haze values below 3% and transmittance above 85%. The only exception to this was represented by the formulation with the highest loading of mica (1.5 wt %, which is φ ≈ 0.01). These findings revealed, for the first time, the potential of the NBB mica to produce nanocomposite coatings in combination with biopolymers for the generation of new functional features, such as transparent high oxygen barrier materials.Article Citation - WoS: 13Citation - Scopus: 15Synthesis of Poly-2 Methacrylate-Montmorillonite Nanocomposite Via in Situ Atom Transfer Radical Polymerization(Cambridge University Press, 2008) Oral, Ayhan; Shahwan, Talal; Güler, ÇetinThe poly-2-hyroxyethyl methacrylate (PHEMA)/clay nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. To produce organically modified montmorillonite (MMT) that has ATRP initiator moiety, a new catalyst that consists of quaternary ammonium salt moiety and an initiator moiety was synthesized. This initiator was intercalated into the interlayer spacing of the MMT. The polymerization reaction was carried out in a mixed solvent system consisting of methyl ethyl ketone and 1-propanol at 50 °C, using the initiator that has been already synthesized with a copper bromide catalyst. The 2, 2′-bipyridyl (bpy) complex was used as ligand. The products were characterized via Fourier transform infrared, nuclear magnetic resonance (1H NMR, 12C NMR), transmission electron microscopy, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. © 2008 Materials Research Society.Article Citation - WoS: 16Citation - Scopus: 18Polyglycolide-Montmorillonite as a Novel Nanocomposite Platform for Biosensing Applications(Royal Society of Chemistry, 2017) Ünal, Betül; Yalçınkaya, Esra Evrim; Gümüştaş, Sıla; Sönmez, Burak; Özkan, Melek; Balcan, Mehmet; Odacı Demirkol, Dilek; Timur, SunaIn catalytic biosensors, the immobilization of biomolecules in a suitable matrix is one of the vital parameters for obtaining improved systems. Clays, which are intercalated with various organic compounds, have a great tendency to develop biosensors with high stability, sensitivity and reproducibility. Herein, a polymer/clay nanocomposite based on natural silicate montmorilonite (Mt) and a biodegradable polymer polyglycolide (PGA) was prepared and characterized by FT-IR, thermogravimetric analysis, differential thermogravimetric analysis and X-ray diffraction. Then, the resulting matrix was used as a fixation matrix for pyranose oxidase (POx), which was selected as a model enzyme. The bioactive layer was fabricated by immobilization of POx on glassy carbon electrodes by means of PGA-Mt and bovine serum albumin. The POx biosensor revealed a good linear range from 0.01 to 0.5 mM glucose with a LOD of 1.2 μM. After the optimization of the working and preparation conditions, characterization studies were performed for glucose detection. Finally, the PGA-Mt/POx biosensor was confirmed to have detected glucose in beverages without needing any sample pre-treatment.Article Citation - WoS: 59Citation - Scopus: 64Interfacial Thermal Resistance Between the Graphene-Coated Copper and Liquid Water(Elsevier Ltd., 2016) Pham, An T.; Barışık, Murat; Kim, BohungThe thermal coupling at water-solid interfaces is a key factor in controlling thermal resistance and the performance of nanoscale devices. This is especially important across the recently engineered nano-composite structures composed of a graphene-coated-metal surface. In this paper, a series of molecular dynamics simulations were conducted to investigate Kapitza length at the interface of liquid water and nano-composite surfaces of graphene-coated-Cu(1 1 1). We found that Kapitza length gradually increased and converged to the value measured on pure graphite surface with the increase of the number of graphene layers inserted on the Cu surface. Different than the earlier hypothesis on the "transparency of graphene," the Kapitza length at the interface of mono-layer graphene coated Cu and water was found to be 2.5 times larger than the value of bare Cu surface. This drastic change of thermal resistance with the additional of a single graphene is validated by the surface energy calculations indicating that the mono-layer graphene allows only ∼18% van der Waals energy of underneath Cu to transmit. We introduced an "overall interaction strength" value for the nano-composites based the quantitative contribution of pair interaction potentials of each material with water into the total surface energy in each case. Similar to earlier studies, results revealed that Kapitza length shows exponentially variation as a function of the estimated interaction strength of the nano-composite surfaces. The effect of Cu/graphene coupling on thermal behavior between the nano-composite with water was characterized. The Kapitza length was found to decrease significantly with increased Cu/graphene strength in the case of weak coupling, while this behavior becomes negligible with strong coupling of Cu and graphene.Article Citation - WoS: 33Citation - Scopus: 33Folic Acid Modified Clay/Polymer Nanocomposites for Selective Cell Adhesion(Royal Society of Chemistry, 2014) Barlas, Fırat Barış; Ağ Şeleci, Didem; Özkan, Melek; Demir, Bilal; Şeleci, Muharrem; Aydın, Muhammed; Taşdelen, M. A.; Zareie, Hadi M.; Timur, Suna; Özçelik, Serdar; Yağcı, YusufA folic acid (FA) modified poly(epsilon-caprolactone)/clay nanocomposite (PCL/MMT-(CH2CH2OH)2-FA) resulting in selective cell adhesion and proliferation was synthesized and characterized as a cell culture and biosensing platform. For this purpose, first the FA modified clay (MMT-(CH2CH2OH)2-FA) was prepared by treating the organo-modified clay, Cloisite 30B [MMT-(CH2CH 2OH)2] with FA in chloroform at 60°C. Subsequent ring opening polymerization of ε-caprolactone in the presence of tin octoate (Sn(Oct)2) using MMT-(CH2CH2OH)2-FA at 110°C resulted in the formation of MMT-(CH2CH 2OH)2-FA with an exfoliated clay structure. The structures of intermediates and the final nanocomposite were investigated in detail by FT-IR spectral analysis and DSC, TGA, XRD, SEM and AFM measurements. The combination of FA, PCL and clay provides a simple and versatile route to surfaces that allows controlled and selective cell adhesion and proliferation. FA receptor-positive HeLa and negative A549 cells were used to prove the selectivity of the modified surfaces. Both microscopy and electrochemical sensing techniques were applied to show the differences in cell adherence on the modified and pristine clay platforms. This approach is expected to be adapted into various bio-applications such as 'cell culture on chip', biosensors and design of tools for targeted diagnosis or therapy.