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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access In situ formation of copper phosphate on hydroxyapatite for wastewater treatment(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Rahmani, Fatemeh; Ghadi, Arezoo; Khaksar, Samad; Doustkhah, Esmail; PhD Student; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM)Here, we control the surface activity of hydroxyapatite (HAp) in wastewater treatment which undergoes peroxodisulfate (PDS) activation. Loading the catalytically active Cu species on HAp forms a copper phosphate in the outer layer of HAp. This modification turns a low active HAp into a high catalytically active catalyst in the dye degradation process. The optimal operational conditions were established to be [Cu-THAp](0) = 1 g/L, [RhB](0) = 20 mg/L, [PDS](0) = 7.5 mmol/L, and pH = 3. The experiments indicate that the simultaneous presence of Cu-THAp and PDS synergistically affect the degradation process. Additionally, chemical and structural characterizations proved the stability and effectiveness of Cu-THAp. Therefore, this work introduces a simple approach to water purification through green and sustainable HAp-based materials.Publication Open Access Predicting new iron garnet thin films with perpendicular magnetic anisotropy(Elsevier, 2020) N/A; Department of Electrical and Electronics Engineering; Zanjani, Saeedeh Mokarian; Onbaşlı, Mehmet Cengiz; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 258783Magnetic iron garnets are insulators with low Gilbert damping with many applications in spintronics. Many emerging spintronic applications require perpendicular magnetic anisotropy (PMA) although garnets have only a few PMA types (i.e. terbium and samarium garnet). More and stable PMA garnet options are needed for investigating new spintronic phenomena. In this study, we predict 20 new epitaxial magnetic iron garnet film/substrate pairs with stable PMA at room temperature. The effective anisotropy energies of 10 different garnet films that are lattice-matched to 5 different commercially available garnet substrates (total 50 film/substrate pairs) have been calculated using shape, magnetoelastic and magnetocrystalline anisotropy terms. Strain type, tensile or compressive depending on substrate choice, as well as the sign and the magnitude of the magnetostriction constants of garnets determine if a garnet film may possess PMA. We show the conditions in which Samarium, Gadolinium, Terbium, Holmium, Dysprosium and Thulium garnets may possess PMA on the investigated garnet substrate types. New PMA garnet films with tunable saturation moment and field may improve spin-orbit torque memory and compensated magnonic thin film devices.Publication Open Access Lead halide perovskite quantum dots for photovoltaics and photocatalysis: a review(American Chemical Society (ACS), 2022) Department of Chemistry; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Aydemir, Umut; Researcher; PhD Student; Faculty Member; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; 58403Lead halide-based perovskite quantum dots (PQDs) have recently emerged as an important class of nanocrystal (NC) materials for optoelectronic and photoelec-trochemical applications. Thanks to their intriguing features including tunable band gap, narrow emission, high charge carrier mobility, remarkable light-absorbing factors, and long charge diffusion length, there has been a surge in research on lead halide-based PQDs and their applications. In this review, we showcase the fundamentals of PQDs and two principal applications including PQD solar cells (PQDSCs) and photocatalytic conversion. First, a thorough discussion on PQDSCs, their structure, surface treat-ment, and interface engineering along with their recent progress are presented. It is highlighted that the improvement of the efficiency of PQDSCs from below 10% to beyond 16% in a matter of a few years has turned them into promising candidates for future SC applications. Subsequently, the application of PQDs in photocatalytic reactions such as hydrogen production, CO2 reduction, and organic compounds' degradation is summarized. Not to mention that, despite the remarkable properties of PQDs in SCs and photocatalysis, the inferior stability of PV devices based thereon under operation as well as their poor tolerance under air, water, light, and heat impede their widespread application. For this, the practical efforts and possible solutions are extensively addressed. Finally, an outlook is provided, addressing further merits, and demerits of each application as well as prospective opportunities.Publication Open Access Fast and selective adsorption of methylene blue from water using [BMIM][PF6]-incorporated UiO-66 and NH2-UiO-66(American Chemical Society (ACS), 2020) Department of Chemical and Biological Engineering; N/A; Kulak, Harun; Keskin, Seda; Uzun, Alper; Kavak, Safiyye; Polat, Hüsamettin Mert; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; N/A; 40548; 59917; N/A; N/AIncorporation of ionic liquids (ILs) into metal-organic frameworks (MOFs) offers a broad potential in various applications. However, their applications in wastewater treatment have remained unexplored. Here, we investigate their potential in wastewater treatment and demonstrate a new concept of IL incorporation in ligand-functionalized MOFs, introducing IL/FMOFs. The composites were prepared by incorporating 1-n-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], into UiO-66 and NH2-UiO-66 and tested for the adsorption of methylene blue (MB) and methyl orange (MO) from aqueous solutions. Data showed that NH2-functionalization and [BMIM][PF6] incorporation improved MB removal performance of UiO-66 by 16- and 48-times, as the capacity increased from 84.8 to 144.7 mg g(-1) and 174.1 mg g(-1), respectively. When considering both modifications together, [BMIM][PF6]/NH2-UiO-66 was almost 300 times faster than that of UiO-66, and the capacity exceeded 200 mg g(-1). Data further suggested that IL incorporation almost doubled MB/MO selectivity because of the strong electrostatic interactions and hydrogen bonding between [PF6](-) and MB, and pi-pi interactions between the [BMIM](+) cation and MB molecules. These results are the first to demonstrate the prospect of combining ligand functionalization with IL incorporation for modifying MOFs, introducing IL/FMOF composites for fast and selective removal of pollutants from wastewater.
Publication Metadata only Predicting new iron garnet thin films with perpendicular magnetic anisotropy(Elsevier, 2020) Department of Electrical and Electronics Engineering; Zanjani, Saeedeh Mokarian; Onbaşlı, Mehmet Cengiz; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 258783Magnetic iron garnets are insulators with low Gilbert damping with many applications in spintronics. Many emerging spintronic applications require perpendicular magnetic anisotropy (PMA) although garnets have only a few PMA types (i.e. terbium and samarium garnet). More and stable PMA garnet options are needed for investigating new spintronic phenomena. In this study, we predict 20 new epitaxial magnetic iron garnet film/substrate pairs with stable PMA at room temperature. The effective anisotropy energies of 10 different garnet films that are lattice-matched to 5 different commercially available garnet substrates (total 50 film/substrate pairs) have been calculated using shape, magnetoelastic and magnetocrystalline anisotropy terms. Strain type, tensile or compressive depending on substrate choice, as well as the sign and the magnitude of the magnetostriction constants of garnets determine if a garnet film may possess PMA. We show the conditions in which Samarium, Gadolinium, Terbium, Holmium, Dysprosium and Thulium garnets may possess PMA on the investigated garnet substrate types. New PMA garnet films with tunable saturation moment and field may improve spin-orbit torque memory and compensated magnonic thin film devices.Publication Open Access Quantum dot to nanorod transition for efficient white-light-emitting diodes with suppressed absorption losses(American Chemical Society (ACS), 2022) Melikov, Rustamzhon; N/A; Department of Electrical and Electronics Engineering; N/A; Önal, Asım; Sadeghi, Sadra; Karatüm, Onuralp; Nizamoğlu, Sedat; Eren, Güncem Özgün; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A; 130295; N/AColloidal nanocrystals have great potential for next-generation solid-state lighting due to their outstanding emission and absorption tunability via size and morphology, narrow emission linewidth, and high photoluminescence quantum yield (PLQY). However, the losses due to self-and interabsorption among multitudes of nanocrystals significantly decrease external quantum yield levels of light-emitting diodes (LEDs). Here, we demonstrate efficient white LEDs via CdSe/CdS dot to ""dot-in-rod"" transition that enabled a large Stokes shift of 780 meV and significantly reduced absorption losses when used in conjunction with near-unity PLQY ZnCdSe/ZnSe quantum dots (QDs) emitting at the green spectral range. The optimized incorporation of nanocrystals in a liquid state led to the white LEDs with an ultimate external quantum efficiency (EQE) of 42.9%, with a net increase of EQE of 10.3% in comparison with white LEDs using CdSe/CdS dots. Therefore, combinations of nanocrystals with different nanomorphologies hold high promise for efficient white LEDs.Publication Open Access Computational investigation of multifunctional MOFs for adsorption and membrane-based separation of CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 mixtures(Royal Society of Chemistry (RSC), 2023) Department of Chemical and Biological Engineering; Keskin, Seda; Demir, Hakan; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 40548; N/AThe ease of functionalization of metal-organic frameworks (MOFs) can unlock unprecedented opportunities for gas adsorption and separation applications as the functional groups can impart favorable/unfavorable regions/interactions for the desired/undesired adsorbates. In this study, the effects of the presence of multiple functional groups in MOFs on their CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 separation performances were computationally investigated combining grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The most promising adsorbents showing the best combinations of selectivity, working capacity, and regenerability were identified for each gas separation. 15, 13, and 16 out of the top 20 MOFs identified for the CH4/H-2, CH4/N-2, and N-2/H-2 adsorption-based separation, respectively, were found to have -OCH3 groups as one of the functional groups. The biggest improvements in CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 selectivities were found to be induced by the presence of -OCH3-OCH3 groups in MOFs. For CH4/H-2 separation, MOFs with two and three functionalized linkers were the best adsorbent candidates while for N-2/H-2 separation, all the top 20 materials involve two functional groups. Membrane performances of the MOFs were also studied for CH4/H-2 and CH4/N-2 separation and the results showed that MOFs having -F-NH2 and -F-OCH3 functional groups present the highest separation performances considering both the membrane selectivity and permeability.