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: 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: 8Citation - Scopus: 9Sublattice Engineering and Voltage Control of Magnetism in Triangular Single and Bi-Layer Graphene Quantum Dots(John Wiley and Sons Inc., 2016) Güçlü, Alev Devrim; Potasz, P.; Hawrylak, PawelWhen a Dirac electron is confined to a triangular graphene quantum dot with zigzag edges, its low-energy spectrum collapses to a shell of degenerate states at the Fermi level leading to a magnetized edge. The shell degeneracy and the total magnetization are proportional to the edge size and can be made macroscopic. In this review, we start with a general discussion of magnetic properties of graphene structures and its relation to broken sublattice symmetry. Then, we discuss single electronic properties of single and bilayer triangular graphene quantum dots, focusing on the nature of edge states. Finally, we investigate the role of electronic correlations in determining the nature of ground state and excitation spectra of triangular graphene quantum dots as a function of dot size and filling fraction of the shell of zero-energy states. The interactions are treated by a combination of tight-binding, Hartree-Fock and configuration interaction methods. We show that the spin polarization of the triangular graphene quantum dots can be controlled through gating, i.e., by adding or removing electrons. In bilayer graphene dots, the relative filling of edge states in each layer and the magnetization can be tuned down to single localized spin using an external vertical electrical field.Article Citation - WoS: 8Citation - Scopus: 8Influence of Applied Current Density on the Nanostructural and Light Emitting Properties of N-Type Porous Silicon(World Scientific Publishing Co. Pte Ltd, 2015) Çetinel, A.; Artunç, N.; Şahin, Gündoğdu; Tarhan, EnverEffects of current density on nanostructure and light emitting properties of porous silicon (PS) samples were investigated by field emission scanning electron microscope (FE-SEM), gravimetric method, Raman and photoluminescence (PL) spectroscopy. FE-SEM images have shown that below 60 mA/cm2, macropore and mesopore arrays, exhibiting rough morphology, are formed together, whose pore diameter, pore depth and porosity are about 265-760 nm, 58-63 μ m and 44-61%, respectively. However, PS samples prepared above 60 mA/cm2 display smooth and straight macropore arrays, with pore diameter ranging from 900-1250 nm, porosity of 61-80% and pore depth between 63-69 μm. Raman analyses have shown that when the current density is increased from 10 mA/cm2 to 100 mA/cm2, Raman peaks of PS samples shift to lower wavenumbers by comparison to crystalline silicon (c-Si). The highest Raman peak shift is found to be 3.2 cm-1 for PS sample, prepared at 90 mA/cm2, which has the smallest nanocrystallite size, about 5.2 nm. This sample also shows a pronounced PL, with the highest blue shifting, of about 12 nm. Nanocrystalline silicon, with the smallest nanocrystallite size, confirmed by our Raman analyses using microcrystal model (MCM), should be responsible for both the highest Raman peak shift and PL blue shift due to quantum confinement effect (QCE).