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: 22Citation - Scopus: 26Flexible Metal/Semiconductor Type Photodetectors Based on Manganese Doped Zno Nanorods(Elsevier, 2023) Karagöz, Emine; Altaf, Çiğdem Tuç; Yaman, Ecenaz; Yıldırım, İpek Deniz; Erdem, Emre; Çelebi, Cem; Fidan, Mehmet; Sankir, Mehmet; Demirci Sankir, NurdanHigh-performance flexible photodetectors are one of the most interesting research areas due to their great possibilities for a variety of applications such as portable and wearable optoelectronics. This study verifies the performance of flexible metal/semiconductor/metal-type photodetector based on pristine and manganese doped ZnO nanorods (ZnO-NRs) prepared in two different concentrations of zinc precursors and manganese dopant at low temperatures. The photodetectors having ZnO-NRs with high aspect ratios were investigated by various material characterization techniques such as electron paramagnetic resonance and photoluminescence spectroscopy to confirm the relationship between defect concentrations and photodetector performance parameters. It has been calculated that the detectivity (D*) and responsivity (R) of the ZnO nanorod-based photodetectors increased 20 and 18 folds, respectively by increasing the concentration of zinc precursor. Besides the D* and R values of the photodetectors, prepared by the 16.5 mM zinc precursor, increased 18 and 4.5-fold, respectively, after manganese doping. We confirmed that even a very low concentration of zinc precursor could produce a photodetector with high performance in photo-response characteristics, flexibility, and stability against 10,000 cycles of convex/concave bending.(c) 2023 Elsevier B.V. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 9Zno Nanostructures for Photocatalytic Degradation of Methylene Blue: Effect of Different Anodization Parameters(Springer, 2022) Öksüz, Ahmet Emrecan; Yurddaşkal, Metin; Kartal, Uğur; Dikici, Tuncay; Erol, MustafaIn this paper, the photocatalytic activity of ZnO nanostructures formed by anodization method with different parameters was investigated. The synthesis of ZnO nanostructures with different morphology by varying anodic oxidation parameters containing electrolytes, molarity, voltage, and duration was analyzed. ZnO nanostructures were prepared through different parameters consisting of six samples. The produced ZnO nanostructures were investigated by using X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and UV-Vis spectrophotometer. It was found that the morphology of ZnO structures was formed as nanorods, needle-like, flower-like, heterogeneous, and homogeneous of mixed structures. ZnO nanostructures were identified by matching X-Ray diffraction peaks due to the international center for diffraction data database. Experiments on photocatalytic degradation of methylene blue demonstrated that the photocatalytic activity of ZnO samples. The best photocatalytic performance was observed by the sample anodized for an hour in 0.05 M of KHCO3 electrolytes with 40 V electrical potential. It was observed that the removal of methylene blue increased 3 times (photocatalytic degradation efficiency similar to 31% for methylene blue vs similar to 90% by the best sample) thanks to the obtained ZnO nanostructured photocatalysts. The results showed that an increment of the voltage has a significant effect on the photocatalytic activity of ZnO while keeping other parameters including molarity, time, and electrolyte type constant.Article Citation - WoS: 5Citation - Scopus: 6Degradation Behaviour of Ti-12nb Alloy Coated With Zno/Tin Double Layer(Elsevier, 2021) Çaha, İhsan; Alves, A. C.; Affonco, L. J.; da Silva, J. H. D.; Rodrigues, I. R.; Grandini, C. R.; Rocha, L. A.; Pinto, Ana Maria Pires; Lisboa Filho, P. N.; Toptan, FatihTi and its alloys have attracted attention for biomedical applications, but their low tribocorrosion resistance, lack of bioactivity and antimicrobial properties are still major clinical concerns. In this study a ZnO coating, intended to act as an antibacterial agent, was deposited on a Ti-12Nb alloy, which was previously coated with a TiN hard coating, for improving tribocormsion resistance. The idea behind is the proof-of -concept that ZnO is able to provide interesting tribological properties to the surface, thus inspiring new ZnO-containing surfaces that can combine antimicrobial properties and tribocormsion resistance. Thus, the corrosion behaviour was studied by open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization tests in phosphate buffered solution at body temperature. The tribocormsion behaviour was carried out at open circuit potential under 0.5 N of normal load, 1 Hz frequency, during 3600 s sliding in phosphate buffered solution at body temperature. The results indicated that duplex coating sample showed better corrosion resistance and drastically better tribocorrosion resistance compared to uncoated and single TiN coating samples.Article Citation - WoS: 31Citation - Scopus: 34Dual Remediation of Waste Waters From Methylene Blue and Chromium (vi) Using Thermally Induced Zno Nanofibers(Elsevier, 2020) Elhousseini, Mohamed Hilal; Isık, Tuğba; Kap, Özlem; Verpoort, Francis; Horzum, NesrinElectrospun zinc oxide (ZnO) nanofibers have been significantly improved via a simple heat treatment modification. The present work reports an intriguing cost-effective microstructure tuning, by drastically dropping the temperature of the calcined sample during the cooling period, to get highly photocatalytically active ZnO nanofibers. The calcination temperatures are deducted from thermogravimetric analysis, the phase and purity are confirmed by X-ray diffraction, while the morphology and texture have been revealed by field emission scanning electron microscopy and high-resolution transmission electron spectroscopy. X-ray photoelectron spectroscopy was conducted to get further insight on the surface composition and oxidation states, while N-2-adsorption isotherms were analyzed using the Brunauer-Emmet-Teller methodology. The crystallinity, surface area, and porosity of the ZnO nanofibers, as well as the exposure of active sites, have been enhanced by the rapid cooling method. Photodegradation activity toward methylene blue was improved from 88% to 94%, and 85% to 97%, for free cooled and rapid cooled samples calcined at 300 degrees C and 500 degrees C respectively. The adsorption of chromium (VI) was also tested and reached around 85 mg/g at 100 ppm without being saturated, thereby highlighting one of the most cost-effective performance-enhancing modifications so far that could be extended on different metal oxide nanomaterials.Article Citation - WoS: 70Citation - Scopus: 76Humidity-Sensing Properties of a Zno Nanowire Film as Measured With a Qcm(Elsevier Ltd., 2011) Erol, Ayşe; Okur, Salih; Yağmurcukardeş, Nesli; Arıkan, M. ÇetinThe humidity-sensing properties of ZnO nanowires synthesized by carbothermal catalyst-free vapor solid (VS) technique were studied. The morphology and the crystal structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The humidity adsorption and desorption kinetics of the synthesized ZnO nanowires were investigated via quartz crystal microbalance (QCM) measurements. The observed positive frequency shift of ZnO nanowires when loaded on the QCM crystal under varying relative humidity conditions can be explained in terms of visco-elastic variations in their mechanical stiffness.Article Citation - WoS: 138Citation - Scopus: 146Humidity Sensing Properties of Zno Nanoparticles Synthesized by Sol-Gel Process(Elsevier Ltd., 2010) Erol, Ayşe; Okur, Salih; Comba, B.; Mermer, Ömer; Arıkan, M. Ç.ZnO nanoparticles have been synthesized by the sol-gel method with approximately 10 nm diameter and the humidity adsorption and desorption kinetics of ZnO nanoparticles were investigated by quartz crystal microbalance (QCM) technique. The morphology and crystal structure of the ZnO nanoparticles have been characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The roughness of the surface has been investigated using atomic force microscope (AFM). The dynamic Langmuir adsorption model was used to determine the kinetic parameters such as adsorption and desorption rates and Gibbs free energy under relative humidity between 45% and 88%. The relative sensitivity of the ZnO nanoparticles-based humidity sensor was determined by electrical resistance measurements. Our reproducible experimental results show that ZnO nanoparticles have a great potential for humidity sensing applications at room temperature operations. © 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 41Citation - Scopus: 42Characterization of Materials Used in the Execution of Historic Oil Paintings by Xrd, Sem-Eds, Tga and Libs Analysis(Elsevier Ltd., 2009) Şerifaki, Kerem; Böke, Hasan; Yalçın, Şerife; İpekoğlu, BaşakIn this study, material characteristics of historic oil paintings in a 19th century church in Ayvali{dotless}k/Turkey were investigated to propose the treatments to be used in their conservation and protection. For this purpose, physical, chemical and mineralogical compositions and the microstructure of the paintings were determined by X-ray Diffraction, Scanning Electron Microscope, Thermo Gravimetric Analyzer, Differential Scanning Calorimeter, Infrared Spectroscopy and Laser Induced Breakdown Spectroscopy. Analysis results showed that the paintings were composed of very thin binding and white priming layers on which the pigments were applied. Binding layers were composed of polymerized vegetable oil with Zinc Oxide. Priming layers were composed of anglesite mineral in polymerized vegetable oil. Pigments used in paintings were mainly green earth, red chrome and iron oxide.Article Citation - WoS: 3Citation - Scopus: 4Isothermal Corrosion Testing of Frit Furnace Refractories(Elsevier Ltd., 2009) Balıkoğlu, Fatih; Akkurt, SedatIn this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al2O3 precipitation observed along the frit-refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al2O3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite.Article Citation - WoS: 20Citation - Scopus: 19The Catalytic Reforming of Bio-Ethanol Over Sio2 Supported Zno Catalysts: The Role of Zno Loading and the Steam Reforming of Acetaldehyde(Elsevier Ltd., 2008) Şeker, ErolIn this study, the activity and the product distributions of sol-gel made SiO2 supported ZnO catalysts in the steam reforming of ethanol and acetaldehyde is presented as a function of ZnO loading and temperature. We show that although highly dispersed ZnO in SiO2 (upto 50% ZnO loading) can be prepared using a single step sol-gel method, a precise control of crystallite size could not be achieved. From CO2 TPD measurements, we found that the basic site densities of ZnO/SiO2 catalysts stays < 0.05 μ mol / m2 and do not increase linearly with ZnO loading. The highest basic site density among the catalysts occurs on pure ZnO. All ZnO/SiO2 catalysts are active at 350 °C whereas pure ZnO catalyst is active at 450 °C. Iso-conversion activity tests show that ethanol steam reforming activities of the catalysts seem to be dependent on the ZnO crystallite size rather than the basic site density of the catalysts when the surface coverage of the basic site density is < 0.32 % but acetone is not formed only on catalysts with ZnO crystallite size < 5 nm regardless of their basic site densities. Interestingly, we found that ethanol was mostly dehydrogenated to acetaldehyde and hydrogen although H2O/C2H5OH molar ratio in the feed was 12. CO was not also produced in the steam reforming of ethanol over all the catalysts. Acetone and propene are produced from acetaldehyde as observed in the steam reforming of acetaldehyde. The steam reforming of acetaldehyde as compared to its decomposition was found to be more favorable over the catalysts with small ZnO crystals, such as 30% and 50% ZnO catalysts.Article Citation - WoS: 195Optical Properties of Composites of Pmma and Surface-Modified Zincite Nanoparticles(American Chemical Society, 2007) Demir, Mustafa Muammer; Koynov, Kaloian; Akbey, Ümit; Bubeck, Christoph; Park, Insun; Lieberwirth, Ingo; Wegner, GerhardLocate full-text(opens in a new window)|Full Text(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Macromolecules Volume 40, Issue 4, 20 February 2007, Pages 1089-1100 Optical properties of composites of PMMA and surface-modified zincite nanoparticles (Article) Demir, M.M.a, Koynov, K.a, Akbey, Ü.a, Bubeck, C.a, Park, I.ab, Lieberwirth, I.a, Wegner, G.a a Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany b Seoul National University, School of Chemistry, Korea, South Korea View references (65) Abstract Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage. Particle size and graft density of -PO3H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (0) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 μm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm-1 vol %-1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula.