Yazar "Simsek, Murat" seçeneğine göre listele

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    Detection of Diazinon Organophosphates Using Magnetoelastic Sensor
    (Ieee-Inst Electrical Electronics Engineers Inc, 2022) Atalay, Selcuk; Ates, Burhan; Balcioglu, Sevgi; Inan, Orhan Orcun; Kolak, Seda; Simsek, Murat; Kolat, Veli Serkan
    In this study, 2826MB (Fe40Ni38Mo4B18) amorphous ferromagnetic ribbons were used as a magnetoelastic sensor (MES) to detect diazinon organophosphates (OP). Since enlarging the sensor surface area makes a significant contribution to the sensitivity of the sensor, nanofibers were coated on the sensor surface, and then, the nanofibers were functionalized with glutaraldehyde (GA) in order to covalently bind acetylcholinesterase (AChE) enzyme to the surface. It was found that binding of OPs to the AChE enzyme at the functional amorphous ribbon surface, a large change in the resonance frequency was observed. The results showed that functionalized MES shows a linear change according to the amount of OP detected in the range of 0-140 nL or 0-150 ppm in the solution.
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    Fabrication of electrospun polycaprolactone/chitosan nanofiber-modified screen-printed electrode for highly sensitive detection of diazinon in food analysis
    (Elsevier Sci Ltd, 2022) Topsoy, Oguz Kagan; Muhammad, Fakhriy; Kolak, Seda; Ulu, Ahmet; Gungor, Oznur; Simsek, Murat; Koytepe, Suleyman
    In the present study, a screen-printed electrode for Diazinon (DZN) detection was modified with nanofibers prepared via electrospinning technique. The chemical structure, morphology, and crystallinity of the nanofibers were characterized in detail. The electrochemical behaviors of the modified screen-printed electrode were evaluated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The spinning time, pH value and scan rates were optimized at 6 min, 5.25, and 50 mVs(-1), respectively. The limit of detection as 2.888 nM was obtained over a linear concentration range (3 nM-100 nM). Besides, DZN selectivity, repeatability, and storage stabilities of the developed sensor were proven. Meanwhile, the sensor was successfully applied for the determination of DZN in the tomato juice sample with recovery values in the range of 93.27-108.30%. The developed sensor could be a promising candidate to detect the presence and level of DZN in real samples.
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    Fabrication, characterization, and in vivo biocompatibility evaluation of titanium-niobium implants
    (Sage Publications Ltd, 2021) Yolun, Abdurrahman; Simsek, Murat; Kaya, Mehmet; Annac, Ebru Elibol; Kom, Mustafa; Cakmak, Omer
    In this study, biocompatible titanium-niobium (Ti-Nb) alloys were fabricated by using powder metallurgy methods. Physical, morphological, thermal, and mechanical analyses were performed and their in vivo compatibility was evaluated. Besides alpha, beta, and alpha '' martensitic phases, alpha+beta Widmanstatten phase due to increasing sintering temperature was seen in the microstructure of the alloys. Phase transformation temperatures of the samples decreased as Nb content increased. The ratio of Nb in the samples affected their mechanical properties. No toxic effect was observed on implanted sites. This study shows that Ti-Nb alloys can be potentially used for orthopedic applications without any toxic effects.
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    Multifunctional colloidal nanofiber composites including dextran and folic acid as electro-active platforms
    (Elsevier Sci Ltd, 2017) Rzayev, Zakir M. O.; Bunyatova, Ulviye; Simsek, Murat
    This work presents the fabrication and characterization of novel colloidal multifunctional polymer nanofiber composites (NFCs) from water dispersion blends of intercalated silicate layered nanocomposites of poly (2-vinyl-N-pyrrolidone)/octadecyl amine-montmorillonite (ODA-MMT) and dextran/ODA-MMT as matrix and partner polymer intercalated nanocomposites in the presence of NaOH and folic acid (FA) as doping agents by green reactive electrospinning. Chemical and physical structures, surface morphology and electrical properties were investigated. Effects of matrix/partner polymer ratios, doping agents, absorption time of NaOH, and temperature on electrical parameters of NFCs were evaluated. The presence of FA and increasing dextran fraction in NFCs resulted in reducing fiber diameter and improving diameter distribution. High complexing behaviors of matrix/partner polymer chains, organoclay, FA, and NaOH significantly improved conductivity parameters, especially 5-min of absorption time (approximate to 10(-2)-10(-3) Sm-1). The conductivity of the samples decreased with increasing temperature. NFCs fabricated for the first time are promising candidates for various biomedical, electrochemical and electronic applications as electro-active platforms. (C) 2017 Elsevier Ltd. All rights reserved.
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    Multifunctional electroactive electrospun nanofiber structures from water solution blends of PVA/ODA-MMT and poly(maleic acid-alt-acrylic acid): effects of Ag, organoclay, structural rearrangement and NaOH doping factors
    (Iop Publishing Ltd, 2016) Simsek, Murat; Rzayev, Zakir M. O.; Bunyatova, Ulviya
    Novel multifunctional colloidal polymer nanofiber electrolytes were fabricated by green reactive electrospinning nanotechnology from various water solution/dispersed blends of poly (vinyl alcohol-co-vinyl acetate) (PVA)/octadecyl amine-montmorillonite (ODA-MMT) as matrix polymer nanocomposite and poly(maleic acid-alt-acrylic acid) (poly(MAc-alt-AA) and/or its Ag-carrying complex as partner copolymers. Polymer nanofiber electrolytes were characterized using FTIR, XRD, thermal (DSC, TGA-DTG), SEM, and electrical analysis methods. Effects of partner copolymers, organoclay, in situ generated silver nanoparticles (AgNPs), and annealing procedure on physical and chemical properties of polymer composite nanofibers were investigated. The electrical properties (resistance, conductivity, activation energy) of nanofibers with/without NaOH doping agent were also evaluated. This work presented a structural rearrangement of nanofiber mats by annealing via decarboxylation of anhydride units with the formation of new conjugated double bond sites onto partner copolymer main chains. It was also found that the semiconductor behaviors of nanofiber structures were essentially improved with increasing temperature and fraction of partner copolymers as well as presence of organoclay and AgNPs in nanofiber composite.
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    Random/aligned electrospun PCL fibrous matrices with modified surface textures: Characterization and interactions with dermal fibroblasts and keratinocytes
    (Elsevier, 2022) Poyraz, Seyma; Altinisik, Zeynep; Cakmak, Anil Sera; Simsek, Murat; Gumusderelioglu, Menemse
    Micro- or nano-surface topography of a biomaterial can improve various cellular activities for obtaining functional tissues. Electrospun fibers can gain further functionality when introduced topographic details to their surfaces. In this regard, we produced random and aligned polycaprolactone (PCL) micron/submicron fibers by the electrospinning method. Simultaneously, the surface structure of the fibers was altered by applying phase separation processes including non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) mechanisms. As a result, PCL fibers with porous, wrinkled, grooved, and crater-like morphology were obtained. Human dermal fibroblasts (BJ cells) and human keratinocytes (HS2) were cultured onto the fiber surfaces and the data were evaluated in terms of cell-material interactions. Results showed that not only the orientation of fibers but also fiber topography affected both cell-fiber and cell-cell interactions in different manners. It was observed that the wrinkled topography is the most suitable for both dermal fibroblasts and keratinocytes in terms of cell attachment and proliferation. We also concluded that cellular behavior was varied according to the morphology of the cells used. Morphological observations showed that HS2 cells proliferated more intensively on all surfaces compared to BJ cells. All these findings can be evaluated in terms of the design of tissue scaffolds, especially in skin tissue engineering.
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    Tuning surface texture of electrospun polycaprolactone fibers: Effects of solvent systems and relative humidity
    (Cambridge Univ Press, 2020) Simsek, Murat
    In this study, the surface morphology of electrospun polycaprolactone (PCL) fibers was investigated. PCL was dissolved in various solvent/nonsolvent systems (acetone/dimethylformamide (DMF), tetrahydrofuran (THF)/DMF, dichloromethane (DCM)/DMF, chloroform (CF)/DMF, acetone/dimethyl sulfoxide (DMSO), THF/DMSO, DCM/DMSO, CF/DMSO) at a fixed ratio of 80/20 v/v. PCL solutions from these solvent systems were electrospun under varying high relative humidity (60-90%), and also room humidity. Characterization of fibers was evaluated by a scanning electron microscope, an atomic force microscope, water contact angle measurements, the Brunauer-Emmett-Teller method, and a strain-stress test. Results revealed that the surface texture of individual fibers changed with the presence of different types of pores and surface roughness depending on both humidity and solvent/nonsolvent properties. Miscibility with water was another factor to be taken into account for understanding mechanisms that contributed to the formation of surface defects. Fibrous materials having such a surface architecture, especially the porous ones, are potential candidates for various applications such as tissue engineering, drug delivery, catalysis, and filtration.