WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
9 results
Search Results
Article Citation - WoS: 4Citation - Scopus: 6Electrospinning of Fatty Acid-Based and Metal Incorporated Polymers for the Fabrication of Eco-Friendly Fibers(Wiley, 2022) Erdem, Çağlar; Isık, Tuğba; Horzum, Nesrin; Hazer, Baki; Demir, Mustafa MuammerAccumulation of plastic wastes occupies large space in gyres of the oceans called the 7th continent. This high-level concentration of toxic plastic wastes causes harmful consequences for marine life, therefore petroleum-originated plastics must be replaced (or at least partially) with natural resources. The environmental trends in material preparation promote the utilization of greener methods and materials when the limited primary sources are considered. Starting from the fatty acid macroperoxide initiators, synthesis of bio-based polymers using less commercial chemicals and stepwise green synthesis schemes could be possible in the near future. In this research, autoxidized vegetable oil initiators (castor, limonene, and soybean oil) containing metal nanoparticles (silver, platinum, and gold) are employed for free radical polymerization of vinyl monomers. The metal loaded and vegetable oil-based polymers are processed by electrospinning and end up with the successful fabrication of continuous fibers. Ag-loaded ricinoleic acid based polymers show notable antibacterial activity against Escherichia coli. This approach offers a remarkable minimization of the initiator consumption in the synthesis of such synthetic macromolecules as well as nanoparticle containing polymer composites while still maintaining the ease of processing. Transforming the obtained graft copolymers to electrospun nanofibers facilitates the use as support materials for antibacterial surfaces.Article Citation - WoS: 9Citation - Scopus: 9Synthesis and Characterization of Novel High Temperature Structural Adhesives Based on Nadic End Capped Mda-Btda Copolyimide(IOP Publishing Ltd., 2018) Acar, Oktay; Varış, Serhat; Işık, Tuğba; Tirkeş, Seha; Demir, Mustafa MuammerA series of novel copolyimide structural adhesives were synthesized using 4,4′-diaminodiphenylmethane (MDA), 3,4′-oxydianiline (ODA) and 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T g) about 400 °C, with thermal stability up to 500 °C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA:ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance.Article Citation - WoS: 84Citation - Scopus: 85A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications(John Wiley and Sons Inc., 2018) Güner, Tuğrul; Demir, Mustafa MuammerIn the last decade, halide perovskites have attracted great interest due to many reasons, including their low cost, solution-processability, superior PL properties, broad range of color tunability, color purity, and defect tolerance, among others. They are in increasing demand for a wide range of applications, such as solar cells, light emitting diodes (LEDs), white LEDs (WLED), and lasers. Yellow phosphors have been heavily employed in solid-state lighting, since its illumination by blue yields white light with various optical features, such as high/low CRI, CCT, and luminous efficiency. However, phosphors as pigments are seldom found and are costly material. In this sense, halide perovskites may offer a promising alternative to phosphors for future solid-state lighting. In this study, the synthesis and optical properties of halide perovskites, as well as their application in WLED as a conversion layer are investigated.Article Citation - WoS: 2Citation - Scopus: 4Use of Electrospun Fiber Mats for the Remediation of Hypersaline Geothermal Brine(Desalination Publications, 2017) Çelik, Aslı; Koç, Gonca; Erdoğan, Emre; Shahwan, Talal; Baba, Alper; Demir, Mustafa MuammerGeothermal brines display high contents of various metal ions that can adversely affect surface and groundwater resources. Nevertheless, it is possible to sequestrate these metals and use some of them in certain engineering applications. The aim of this study was to fabricate electrospun chitosan fiber mats and remove heavy metal cations from geothermal brine of the Tuzla geothermal field (TGF) by employing these mats. TGF is located on the Biga Peninsula in the northwestern part of Turkey. The brine of TGF has high salinity (EC > 91 mS/cm) and high temperature (reservoir temperature is 173°C). The brine is rich in terms of metal cations. For instance, the concentration of lithium ion in geothermal fluid ranges from 17 to 35 mg/L, with little seasonal variations. A horizontal electrospinning setup was employed to obtain a non-woven mat comprising submicron diameter chitosan fibers at 2.0 kV∙cm−1. This material was then utilized as a stable membrane for the removal of metal ions present in the brine through sorption at 25°C overnight. The results showed that the chitosan fiber mats sequestrate various ions in the brine. Under the studied conditions, the material was capable of removing 46%, 44%, 50%, 44%, 40%, 67% and 48% of Li+, Mg2+, Ba2+, Sr2+, Mn2+, Ca2+ and K+ from the geothermal brine, respectively.Article Citation - WoS: 23Citation - Scopus: 23Use of Polyethylene Glycol Coatings for Optical Fibre Humidity Sensing(Springer Verlag, 2008) Açıkgöz, Sabriye; Bilen, Bukem; Demir, Mustafa Muammer; Menceloğlu, Yusuf Z.; Skarlatos, Yani; Aktaş, Gülen; İnci, Mehmet N.Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.Article Citation - WoS: 30Citation - Scopus: 30Glycidyl-Methacry Late-Based Electrospun Mats and Catalytic Silver Nanoparticles(John Wiley and Sons Inc., 2008) Demir, Mustafa Muammer; Uğur, Gökçe; Gülgün, Mehmet A.; Menceloğlu, Yusuf Z.P(AN-GMA) and PGMA fibers coated with monodisperse silver nanoparticles have been prepared by a combination of electrospinning and electroless plating. The morphology of the electrospun fibers remains unchanged after surface hydrazination. Oxidation of hydrazine in an ammoniacal solution of AgNO 3 reduces and deposits silver atoms along the fiber surface, which then coalesce to Ag particles. The size of the silver nanoparticles is varied between 20-60 nm. Since the density of the active sites for silver reduction is lower in P(AN-GMA), a smaller particle size could be obtained. The catalytic activity of the silver nanoparticles has been confirmed.Article Citation - WoS: 15Aggregation of Fillers Blended Into Random Elastomeric Networks: Theory and Comparison With Experiments(John Wiley and Sons Inc., 2006) Demir, Mustafa Muammer; Menceloğlu, Yusuf Ziya; Erman, BurakA theoretical model describing aggregation of filler particles in amorphous elastomers is proposed. The model is based on a counting technique originally used in genome analysis to characterize the size and distribution of overlapping segments randomly placed on a DNA molecule. In the present model, the particles are first assumed to aggregate randomly upon mixing into the elastomer and then-sizes are calculated. The sizes and distributions of aggregates are also studied in the presence of attractive interparticle forces. Results of the proposed model are compared with experimental data on silica-filled end-linked poly(dimethyl-siloxane) networks. Comparison of the theory and experiment shows that the random aggregation assumption where no attractive forces exist between the particles is not valid and a significant attraction between the silica particles is needed in the theory to justify the experimental data obtained using atomic force microscopy. For filler content below 1.45 vol.-%, the model agrees, qualitatively, with experiment and shows the increase in cluster size with increasing amount of filler. It also explains the increase in the dispersion of aggregate sizes with increasing amount of filler.Article Citation - WoS: 20Citation - Scopus: 23Rhodamine-Immobilised Electrospun Chitosan Nanofibrous Material as a Fluorescence Turn-On Hg2+ Sensor(John Wiley and Sons Inc., 2016) Horzum, Nesrin; Mete, Derya; Karakuş, Erman; Üçüncü, Muhammed; Emrullahoğlu, Mustafa; Demir, Mustafa MuammerA turn-on fluorescence sensing system for mercuric (Hg2+) ions relying on a modified rhodamine B–chitosan fluorophore moiety was developed. This novel sensing approach relies on the simultaneous electrospinning of chitosan and rhodamine B hydrazide with phenylisothiocyanate functionality in hexafluoroisopropanol solution at 3.4 kV cm−1. The electrospun mats exhibited not only considerably enhanced fluorescence intensity in the presence of mercury ions, a result attributed to the ring opening of the spirolactam unit of the rhodamine-based fluorophore, but also a remarkably high sensitivity and selectivity toward Hg2+. In effect, the strategy has the potential to open new avenues in the design and development of other high-performance nanofibrous sensing materials for detecting target metal species of environmental interest.Article Citation - WoS: 49Citation - Scopus: 51Voc Sensors Based on a Metal Oxide Nanofibrous Membrane/Qcm System Prepared by Electrospinning(Royal Society of Chemistry, 2014) Horzum Polat, Nesrin; Taşçıoğlu, Didem; Özbek, Cebrail; Okur, Salih; Demir, Mustafa MuammerWe report a simple synthetic route to fabricate crystalline ZnO and CeO2/ZnO nanofibrous mats and their sensing characteristics against volatile organic compounds (VOCs) such as benzene, propanol, ethanol, and dichloromethane. Precursor fibers were fabricated by electrospinning of poly(vinyl alcohol) and metal salt(s) at 2.5 kV cm-1 in aqueous solution. The fibers were directly deposited on the crystal surface of a quartz crystal microbalance (QCM). The crystal, which was coated by nanostructured PVA/metal precursor(s) fibers, was subjected to calcination in air at 500 °C for 5 h. The formation of an oxide based nanofiber mat was revealed by scanning electron microscopy and X-ray diffraction. Upon exposure of the nanofiber mats to the VOCs, the compounds adsorbed onto the surface of oxidic fibers. The physisorption of the compounds was confirmed by FTIR and QCM. Both systems showed sensitivity to the VOCs and they hold a broad promise particularly for sensing applications of volatile alcoholic compounds. The introduction of CeO2 into the ZnO structure reduced the sensitivity of ZnO most probably due to the decrement of oxygen vacancies.