Browsing by Author "Horzum Polat, Nesrin"

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Citation - WoS: 7
Citation - Scopus: 13
Anticorrosion Coating for Magnesium Alloys: Electrospun Superhydrophobic Polystyrene/Sio2 Composite Fibers
(TUBITAK, 2018) Horzum Polat, Nesrin; Kap, Özlem; Farzaneh, Amir
Superhydrophobic 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.
Applications of Electrospun Nanofibers in Filtration Processe
(Izmir Institute of Technology, 2013) Horzum Polat, Nesrin; Elçi, Latif
Electrospinning is a simple and versatile method to fabricate ultrathin fibrous mats from a wide variety of organic and/or inorganic materials. Since it allows fabricating fiber diameter and surface/internal structures by solution and instrumental parameters, electrospun fibers provide much enhanced functionalities, which can not be obtained by bulk materials. This thesis examines the filtration, sensing and catalytical applications associated with the remarkable features of electrospun nanofibers. The systems studied are reported herein; (i) The first part of this dissertation deals with the filtration applications of electrospun nanofibrous membranes.  Nano-sized chitosan fibers were utilized for sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions.  The surface of chitosan fibers were further functionalized by monodisperse nano zero-valent iron (nZVI) particles for the removal of inorganic arsenic species.  Sorption of radioactive U(VI) ions from aqueous systems via column sorption under continuous flow was performed using amidoximated polyacrylonitrile fibers. (ii) The second part of this dissertation presents sensing applications of ceramic fibers.  Humidity sensing properties of electrospun ZnO fiber mats were investigated by quartz crystal microbalance (QCM) method and electrical measurements.  Electrospinning technique was used as coating process for deposition of CeO2/ZnO and ZnO based nanofibers on the electrode of QCM. The fiber-coated QCM sensors were used for the detection of volatile organic compounds (VOCs). (iii) The last part of this dissertation describes an approach to fabricate hierarchically structured composite nanofibers. The nanostructured materials prepared by the simultaneous electrospinning of CeO2 and LiCoO2 precursors and SiO2 nanoparticles were used for the photocatalytic degradation of Rhodamine B.
Citation - WoS: 109
Citation - Scopus: 124
Chitosan Fiber-Supported Zero-Valent Iron Nanoparticles as a Novel Sorbent for Sequestration of Inorganic Arsenic
(Royal Society of Chemistry, 2013-06) Horzum Polat, Nesrin; Demir, Mustafa Muammer; Nairat, Muath; Shahwan, Talal
This study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 ± 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L -1 over a wide range of pH values. Based on XPS analysis, As(iii) was found to undergo oxidation to As(v) upon sorption, while As(v) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise.
Circulating Nucleic Acid (cna) Separation From Serum by Electrospun Membranes
(Izmir Institute of Technology, 2015-07) Işık, Tuğba; Demir, Mustafa Muammer; Horzum Polat, Nesrin
Early detection of diseases is a key factor that can be made provision and successfully treated. There is a wide array of methods to diagnose cancer like biopsy, endoscopy, magnetic resonance imaging (MRI) and blood tests. In blood, while some nucleic acids are found in intracellular fluids, circulating nucleic acids (CNAs) circulate freely in extracellular fluids. They are located at genomic regions and increased levels of CNAs imply a connection with cancer and tumor initiation. For further analysis, separation and concentration of CNAs have high potential in early cancer detection. A model system was constructed with bovine serum albumin (BSA) and single stranded Deoxyribonucleic acid (ss-DNA) for the investigation of membrane separation efficiency. The membranes made of poly styrene (PS) and poly(methylmethacrylate) (PMMA) were fabricated by electrospinning and they were placed in syringe columns. By using the absorption spectroscopy, the sorption efficiency of membranes was determined. The electrospun membranes are promising for BSA uptake over a wide pH range. Under the same circumstances, thanks to PS fibers, ss-DNA uptake is very with respect to BSA uptake. Our results revealed that PS membranes show a better affinity to BSA molecules by hydrophobic interactions. In the mixture of BSA and ss-DNA, ss- DNA cannot be held on the surface of the membrane and pass through with low sorption efficiency. By altering the membrane amount in syringe column and modifiying the surface of the membranes, the separation could be enhanced. The proposed technology promises fast and effective separation of CNAs from whole blood and body fluids.
Citation - WoS: 12
Citation - Scopus: 11
Controlled Surface Mineralization of Metal Oxides on Nanofibers†
(Royal Society of Chemistry, 2015) Horzum Polat, Nesrin; Mari, Margherita; Wagner, Manfred; Fortunato, Giuseppino; Popa, Ana-Maria; Demir, Mustafa Muammer; Landfester, Katharina; Crespy, Daniel; Mu˜noz-Espi, Rafael
We report a versatile approach for the preparation of metal oxide/polymer hybrid nanofibers by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers. Poly (styrene-covinylphosphonic acid) fibers were produced by electrospinning and used as supports for the in situ formation of ceria nanocrystals without further thermal treatment. The crystallization of ceria was induced by the addition of an alkaline solution to fibers loaded with the corresponding precursor. The formation of the inorganic material at the fiber surface was investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The extension of the approach to prepare polymer/titania hybrid nanofibers demonstrates its versatility.
Citation - WoS: 64
Citation - Scopus: 67
Hierarchically Structured Metal Oxide/Silica Nanofibers by Colloid Electrospinning
(American Chemical Society, 2012-11) Horzum Polat, Nesrin; Mun˜oz-Espí, Rafael; Glasser, Gunnar; Demir, Mustafa Muammer; Landfester, Katharina; Crespy, Daniel
We present herein a new concept for the preparation of nanofibrous metal oxides based on the simultaneous electrospinning of metal oxide precursors and silica nanoparticles. Precursor fibers are prepared by electrospinning silica nanoparticles (20 nm in diameter) dispersed in an aqueous solution of poly(acrylic acid) and metal salts. Upon calcination in air, the poly(acrylic acid) matrix is removed, the silica nanoparticles are cemented, and nanocrystalline metal oxide particles of 4-14 nm are nucleated at the surface of the silica nanoparticles. The obtained continuous silica fibers act as a structural framework for metal oxide nanoparticles and show improved mechanical integrity compared to the neat metal oxide fibers. The hierarchically nanostructured materials are promising for catalysis applications, as demonstrated by the successful degradation of a model dye in the presence of the fibers.
Citation - WoS: 74
Humidity Sensing Properties of Zno-Based Fibers by Electrospinning
(Elsevier Ltd., 2011-08) Horzum Polat, Nesrin; Taşçıoğlu, Didem; Okur, Salih; Demir, Mustafa Muammer
Zinc oxide (ZnO) based fibers with a diameter of 80-100 nm were prepared by electrospinning. Polyvinyl alcohol (PVA) and zinc acetate dihydrate were dissolved in water and the polymer/salt solution was electrospun at 2.5 kV cm-1. The resulting electrospun fibers were subjected to calcination at 500 °C for 2 h to obtain ZnO-based fibers. Humidity sensing properties of the fiber mats were investigated by quartz crystal microbalance (QCM) method and electrical measurements. The adsorption kinetics under constant relative humidity (RH) between 10% and 90% were explained using Langmuir adsorption model. Results of the measurements showed that ZnO-based fibers were found to be promising candidate for humidity sensing applications at room temperature.
Macromol. Mater. Eng. 7/2016
(Wiley, 2016) Isık, Tuğba; Horzum Polat, Nesrin; Yıldız, Ümit Hakan; Liedberg, Bo; Demir, Mustafa Muammer
An easy-to-use test platform toward the rapid diagnosis of many life-threating diseases was developed. DNA was isolated from the mixture of BSA+DNA using fibrous commodity polystyrene, which was extremely cheap and can be readily electrospun under ambient conditions. Surface modification with Au nanoparticles improved the performance of the fibrous membrane.
Citation - WoS: 69
Citation - Scopus: 82
Sorption Efficiency of Chitosan Nanofibers Toward Metal Ions at Low Concentrations
(American Chemical Society, 2010-11-16) Horzum Polat, Nesrin; Boyacı, Ezel; Eroğlu, Ahmet Emin; Shahwan, Talal; Demir, Mustafa Muammer
Chitosan fibers showing narrow diameter distribution with a mean of 42 nm were produced by electrospinning and utilized for the sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The filtration efficiency of the fibers toward these ions was studied by both batch and microcolumn methods. High efficiency in sorption of the metal ions was obtained in the both methods. The effects of sorbent amount (0.10−0.50 mg), shaking time (15−120 min), initial metal ion concentration (10.0−1000.0 μg·L−1), and temperature (25 and 50 °C) on the extent of sorption were examined. The sorbent amount did not significantly alter the efficiency of sorption; however, shaking time, temperature, and metal ion concentration were found to have a strong influence on sorption. By virtue of its mechanical integrity, the applicability of the chitosan mat in solid phase extraction under continuous flow looks promising.
Synthesis and Characterization of Mgb2 Superconducting Wires
(Izmir Institute of Technology, 2008) Horzum Polat, Nesrin; Özgen, Tamerkan
In this study, the superconducting properties of laboratory synthesized MgB2 was investigated. In the first part, MgB2 synthesis using commercial magnesium and boron (95-97% purity), and its microstructural and electrical characterization was investigated.Effects of sheath material and annealing temperatures were also examined. The microstructural studies showed that when Cu tubes were used as sheath material, MgCu2 forms instead of MgB2 even at 700oC, while on Fe clad cores, the major phase was MgB2 with minor MgO constituent. The transition temperatures of Fe clad wires were measured between 39K and 40K, whereas no transition temperature was observed for Cu clad wires. The Ic value of the Fe clad MgB2 wire was about 25 A at 4K, while the copper clad wire could not carry current and formed resistance. In Fe clad wires, better results were obtained at annealing temperature of 800°C for 30 minutes. In the second part, MgB2 synthesis using commercial magnesium and boron (90% purity) was tried. 0-5-10-15 wt% of Mg doping and, additionally annealing temperatures were examined. Powder-In-Tube method was used for wire production. 10 wt% Mg addition was seen to be beneficial as compared to the stoichiometric MgB2. 750°C was found to be the most suitable temperature for the formation of MgB2 phase. The Ic value of the wire was measured as 13 A at 4K and it showed a broader transition with non-zero resistivity, transition temperature of 24K.In the third part, 200 m long four filament MgB2/Cu wire was successfully produced in laboratory conditions.
Citation - WoS: 108
Citation - Scopus: 117
Synthesis of Amidoximated Polyacrylonitrile Fibers and Its Application for Sorption of Aqueous Uranyl Ions Under Continuous Flow
(Elsevier Ltd., 2012-12) Horzum Polat, Nesrin; Shahwan, Talal; Parlak, Onur; Demir, Mustafa Muammer
This study reports a feasible method for the removal of radioactive U(VI) ions from aqueous systems via column sorption under continuous flow. Electrospun polyacrylonitrile (PAN) fibers were used as sorbent materials in a homemade minicolumn. The nitrile groups on the fibers' surface were modified to amidoxime groups using hydroxylamine hydrochloride. Surface modification was observed to enhance the sorption capacity of PAN fibers toward uranium ions by more than 4-fold by virtue of the chelating ability of the amidoxime groups. The experiments investigated the effect of pH, initial concentration, and repetitive loading on the sorption properties of amidoximated PAN fibers. Based on the overall results, the surface-modified fibers seem to be a suitable potential sorbent material for applications in environmental cleanup, particularly for nuclear plants.
Citation - WoS: 49
Citation - Scopus: 51
Voc 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 Muammer
We 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.