Yazar "Mutlu, Mehmet" seçeneğine göre listele

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    Modification of quartz crystal microbalance surfaces via electrospun nanofibers intended for biosensor applications
    (Amer Scientific Publishers, 2013) Rodoplu, Didem; Şen, Yasin; Mutlu, Mehmet
    The major aim of this study is to increase the performance of mass sensitive biosensor surfaces by making modifications on quartz crystal microbalance (QCM) surfaces via electrospinning and plasma polymerization techniques. Polyvinyl alcohol (PVA) nanofibers with a diameter of approximately 150 nm were collected on the QCM surfaces by electrospinning technique. Allylamine monomer was used to create specific groups on these nanofiber coated surfaces by plasma polymerization technique. Modified surfaces were characterized by contact angle measurements, scanning electron microscopy, atomic force microscopy, fourier transform infrared spectroscopy and QCM frequency measurements in order to determine the physical and chemical characteristics of the surfaces after each experimental stage. N-H, C-N, C-H and C=O group bands were determined in the IR spectra of the materials. Decrease in the contact angle values of the modified materials indicated the increase in hydrophilicity. Those results showed that amine containing films on the surfaces were successfully deposited using plasma. The performance of modified QCM surfaces was tested via resonance frequency shifts measurements after bovine serum albumin immobilization. In this group of tests, "dip and dry" method and "flow-cell method" were performed and 548 +/- 4 Hz and 50 +/- 5 Hz frequency shifts were obtained respectively. Results of this study revealed that plasma treated electrospun PVA nanofiber modified surfaces can be used for further biosensor applications.
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    Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensor applications
    (SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2012) Turhan, Adil Burak; Ataman, Demet; Şen, Yasin; Mutlu, Mehmet; Özbay, Ekmel
    The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JNP.6.061602]
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    Plasma processing of materials for biotechnological applications
    (Current Biology, 2011) Şen, Yasin; Ataman, Demet; Mutlu, Mehmet
    [Abstract Not Available]
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    Öğe
    Preparation of superhydrophobic membranes by HMDSO plasma modified electrospun nanofibers
    (Elsevier, 2012) Şen, Yasin; Rodoplu, Didem; Mutlu, Mehmet
    [Abstract Not Available]
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    Sterilization of food contacting surfaces via non-thermal plasma treatment: A model study with Escherichia coli-contaminated stainless steel and polyethylene surfaces
    (SPRINGER, 2013) Şen, Yasin; Mutlu, Mehmet
    This study focuses on the utilization of glow discharge technique for the reduction of microorganisms on food contacting surfaces to determine whether non-thermal, low-pressure plasma could provide an effective alternative to current sterilization methods. Radio frequency (13.6 MHz) plasma environment was developed and tested for the inactivation of E. coli K12. Different plasma parameters (discharge power 0-100 W, exposure time 0-30 min) and selected gases (nitrogen, oxygen, air, water vapor) were tested. Following plasma treatment, survival curves and D values were determined. Contact angle measurements were performed to state the change of surface hydrophilicity. Determinations of structural changes on microorganisms were accomplished by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Improved bacterial inactivation efficiency was achieved when air was used instead of pure oxygen or nitrogen gases. Water vapor was found to be the most effective (approximately 7 log(10) reduction) agent in destruction of the microorganisms. The results showed that surface topography and hydrophilicity also have an effect on the efficiency of plasma treatment. In this study, the E. coli inoculated on polyethylene surfaces showed more resistance to plasma treatment. Fragmentation of bacterial cell wall and leakage of cytoplasmic matter were observed following plasma experiments. This study demonstrates that plasma is a promising technology for sterilization of food contacting surfaces, because of its safety, easy handling, capability of processing at low-temperature ( < 44 A degrees C), relatively rapid sterilization.
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    Surface modification of polyethersulfone membrane to improve its hydrophobic characteristics for waste frying oil filtration: Radio frequency plasma treatment
    (Wiley-Blackwell, 2012) Tur, Eren; Önal-Ulusoy, Baran; Akdoğan, Ebru; Mutlu, Mehmet
    In this study, polyethersulfone (PES) membrane was subjected to surface modification using hexamethyldisiloxane (HMDSO) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) in radio frequency (RF) plasma system to improve its hydrophobic property for recovery of waste frying oil. Structural and morphological changes on the membrane surfaces were characterized by contact angle measurements, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and atomic force microscopy (AFM). Permeate fluxes, physical and chemical properties of waste frying oil and waste frying oil-methanol micella (oil/methanol 1/3, 1/1, 1/3, v/v) after filtration through unmodified and modified PES membranes were investigated. The results showed that PES membranes modified with HMDSO at 75 W for 5 min (discharge power-exposure time) selectively rejected total polar compounds (TPC) and free fatty acids (FFAs) of waste frying oil to the extent of 46.9-48% and 35.3-40%, respectively. Furthermore, the viscosity of waste frying oil was reduced to the extent of 9.4-12.8%. RF-plasma-treated PES membranes appeared to improve the regeneration of waste frying oils and allow these oils to be used for either repeated frying operations or biodiesel production. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3402-3411, 2012