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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Item Metadata only A facile tert-butyl nitrite-assisted preparation of deamino graphitic carbon nitride (DA-gCN) as a photocatalyst for the C-H arylation of heteroarenes using anilines as radical source(Tubitak Scientific and Technological Research Council Turkey, 2023) 0000-0003-1622-4992; N/A; 0000-0002-6922-3187; Department of Chemistry; N/A; N/A; Metin, Önder; Palani, Natarajan; Karapınar, Begümhan; Faculty Member; Researcher; PhD Student; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; N/A; Graduate School of Sciences and Engineering; 46962; N/A; N/AIn pristine graphitic carbon nitride (g-CN), amino groups often function as structural defects that trap photogenerated charges, resulting in low photocatalytic activity as well as reaction with nitrite, aldehyde, etc., ensuing in poor product yield. Without significantly altering the optical characteristics, the removal of amino groups is necessary to increase the photocatalytic activity and structural stability of pristine g-CN. The deamino graphitic carbon nitride (DA-gCN-5) was prepared by tert-butyl nitrite (TBN)treatment, characterized and used as a photocatalyst for the radical C-H arylation of heteroarenes using anilines as radical source. Indeed, the photophysical characteristics of DA-gCN-5 and those of pristine g-CN are very comparable, except that DA-gCN-5 has a fewer residual amino groups, higher crystallinity, and compressed structure with a different morphology. Moreover, DA-gCN-5- catalyzed C-H arylation reaction offers greater product yield in a shorter reaction time compared to that of pristine g-CN in the coupling between heteroarenes and the in situ generated aryl diazonium salts from anilines under visible light irradiation. The amino groups in pristine g-CN absorbed the TBN that was added to convert aniline into the appropriate diazonium ions during the reaction. As a result, deamino graphitic carbon nitride produced by chemical treatment has better photophysical properties and catalytic activity than pristine g-CN. Additionally, this is the first method that uses diazotization reaction for the preparation of deamino graphitic carbon nitride, as far as we are aware.Publication Metadata only Influence of soft segment structure, hydrogen bonding, and diisocyanate symmetry on morphology and properties of segmented thermoplastic polyurethanes and polyureas(Tubitak Scientific & Technological Research Council Turkey, 2023) Department of Chemistry; Department of Chemistry; Yılgör, Emel; Yılgör, İskender; College of SciencesA comprehensive review of the structure-morphology-property relations in segmented thermoplastic polyurethanes and polyureas (TPU) is provided. Special emphasis is given to the influence of the soft segment structure, polarity, and molecular weight, diisocyanate symmetry and the nature, extent, and strength of hydrogen bonding on the morphology and thermal and mechanical properties of TPUs. Experimental results obtained on composition-dependent TPU morphology and properties by various techniques were also compared by the morphology profiles generated by computational methods such as quantum mechanical calculations and molecular dynamics simulations.Publication Metadata only Exploration of novel 6,8,9-trisubstituted purine analogues: synthesis, in vitro biological evaluation, and their effect on human cancer cells(Tubitak Scientific & Technological Research Council Turkey, 2024) Polat, Muhammed Fatih; Atalay, Rengul; Tuncbilek, Meral; N/A; Şahin, İrem Durmaz; Koç University Research Center for Translational Medicine (KUTTAM); School of MedicineCancer, a leading global cause of mortality, demands continuous advancements in therapeutic strategies. This study focuses on the design and synthesis of a novel series of purine derivatives, specifically 6 -(substituted phenyl piperazine)-8-(4-phenoxyphenyl)9-cyclopentyl purine derivatives (5-11). The motivation behind this endeavor lies in addressing acquired resistance mechanisms in cancer cells, a significant hurdle in current treatment modalities. The synthesis, starting from 4,6-dichloro-5-nitropyrimidine, involves a multi -step process, resulting in seven new purine derivatives. Biological evaluation against human liver, colon, and breast cancer cells (Huh7, HCT116, and MCF7, respectively) was performed using the SRB assay. Among the synthesized analogs, compounds 5 and 6, exhibited notable cytotoxic activity, surpassing clinically used positive controls 5-Fluorouracil and Fludarabine in terms of efficacy. This research underscores the potential of purine derivatives with a phenyl group at the C-8 position as a scaffold for developing compounds with improved anticancer properties. The findings offer insights for future exploration and development of novel agents in cancer pharmaceutical research.Publication Metadata only A coarse graining approach in molecular simulations: fuzzy potentials(Istanbul Technical University, 2003) Department of Chemistry; Department of Chemistry; Department of Chemistry; Yurtsever, İsmail Ersin; Eşsiz, Şebnem; Faculty Member; Undergraduated Student; College of Sciences; College of Sciences; 7129; 191615A new representation for interaction potential functions is presented. Unlike the orthodox approaches, the potential function is not a fixed function in terms of internuclear coordinates but a probabilistic one which contains information over a wide range of angular degrees of freedom. It is shown that such approaches can provide practical solutions for bulk systems of high density.Publication Metadata only A two-dimensional Monte Carlo polymerization of 5-membered rings(Scientific Technical Research Council Turkey, 1997) Esentürk, O.; Pamuk, H. A.; Department of Chemistry; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; College of Sciences; 7129A modification of the kinetic growth model in two dimensions for the polymerization of 5-membered rings is presented. The preliminary results reveal the validity of the modified model.Publication Metadata only Lanthanide doped bismuth tungstates: an investigation for led and photocatalysis applications(Eskişehir Teknik Üniversitesi, 2018) Department of Chemistry; Department of Chemistry; Department of Chemistry; Akkaya, Ceren Yılmaz; Ünal, Uğur; Researcher; Faculty Member; College of Sciences; College of Sciences; N/A; 42079In this work, we studied optical, photocatalytic and photoelectrochemical properties of a series of lanthanide-doped double layered Aurivillius type bismuth oxides. The visible-light harvesting photocatalysts doped with Eu, Pr, Nd, Tm, Ho and Ce ions were synthesized by solid-state synthesis method. Doping amount was varied between 0.2-to-10 percent. X-ray diffraction (XRD) analysis revealed that lanthanide atoms were incorporated into the Bi2W2O9 lattice successfully up to 5%. Higher dopant ratios resulted in formation of secondary phases. Particles crystallized in micro-platelet morphology. Furthermore, luminescence of Pr3+ and Eu3+ ion doped catalysts are evaluated and the study showed that red emission intensity of Pr3+ doped powder is 29 times higher than that of Eu3+ doped ceramics. Lanthanide doped powders absorb in the visible regions. Especially, doping double layered bismuth oxide with Ce significantly narrowed down the band gap from ~3.3 eV to ~2.1 eV. Photoelectrochemical behaviour of the powders was also investigated and rare-earth dependent enhanced photocurrent production is demonstrated. Best photoelectrochemical response is achieved with Tm3+ ion doped sample.Publication Metadata only The synthesis of binary and ternary cobalt based metal borides by inorganic molten salt technique(TENMAK Bor Araştırma Enstitüsü, 2020) N/A; N/A; Department of Chemistry; Department of Chemistry; Department of Chemistry; Altıntaş, Zerrin; Khoshsima, Sina; Somer, Mehmet Suat; Balcı, Özge; Researcher; Researcher; Faculty Member; Researcher; 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); N/A; N/A; College of Sciences; College of Sciences; N/A; N/A; 178882; 295531Crystalline metal boride powders were synthesized via low temperature method in inorganic molten salt medium, and binary and ternary metal boride composite powders were investigated using anhydrous metal chlorides and sodium borohydride powder mixtures. The reactions were carried out in an aluminum crucible placed in a silica tube under argon which was put in a vertical tube furnace. At the end of the reaction, the resulting powder mixture was leached with hot water to remove any undesirable chloride phases. In order to improve crystalline properties, some of pure powders were selected and annealed at 1100°C. Characterization of synthesized and annealed powders was carried out using X-ray diffractometer (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM / EDX) and dynamic light scattering technique (DLS). The results showed the positive effect of inorganic molten salt technique (LiCl/ KCl eutectic mixture) on the formation of phases during the reaction between CoCl2 , NiCl2 and NaBH4 powder mixtures. Following the reactions at between 750-950 °C, the binary and ternary metal boride powders consisting of CoB-Ni2 BCoBx , CoB-Ni4 B3 ve CoB-NiB-Ni2 Co0.67B0.33 phases were obtained. The measured particle size of the final particles had an average of 60 nm. / Öz: Kristalin metal borür tozları inorganik ergimiş tuz ortamında düşük sıcaklık yöntemi ile sentezlenmiş, ikili ve üçlü metal borür kompozit tozlarının eldesi susuz metal klorürler ve sodyum borhidrür toz karışımları kullanılarak incelenmiştir. Reaksiyonlar, argon altında dikey bir tüp fırında silika tüp içine yerleştirilmiş alüminyum pota içinde gerçekleştirilmiştir. Reaksiyon sonunda elde edilen toz karışımına sıcak su ile liç işlemi yapılarak istenmeyen klorür fazları giderilmiştir. Seçilen bazı saf tozlar, kristalin özelliği geliştirmek amacıyla 1100°C’de tavlama işlemine tabi tutulmuştur. Sentezlenen ve tavlanmış tozların karakterizasyonu, X-ışını difraktometresi (XRD), X-ışını floresans spektrometresi (XRF), taramalı elektron mikroskobu (SEM/EDX) ve dinamik ışık saçma tekniği (DLS) kullanılarak analiz edilmiştir. Sonuçlar, inorganik ergimiş tuz tekniğinin (LiCl/KCl ötektik karışımı) CoCl2 , NiCl2 ve NaBH4 toz karışımları arasındaki reaksiyon sırasında oluşan fazlar üzerindeki olumlu etkisini ortaya koymuştur. 750-950°C sıcaklıkları arasında gerçekleşen reaksiyonlarda CoB-Ni2 B-CoBx , CoB-Ni4 B3 ve CoB-NiB-Ni2 Co0.67B0.33 fazlarını içeren ikili ve üçlü metal borür tozları nano boyutta elde edilmiştir. Sentezlenen tozların partikül boyutu ortalama 60 nm civarında hesaplanmıştır.Publication Metadata only The effect of different carbon sources on the phase formation and microstructure of boron carbide powders(TENMAK Bor Araştırma Enstitüsü, 2019) N/A; N/A; Department of Chemistry; N/A; Department of Chemistry; Department of Chemistry; Kiraz, Kamil; Balcı, Özge; Çoşut, Özge; Somer, Mehmet Suat; Researcher; Researcher; Researcher; Faculty Member; 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); N/A; College of Sciences; N/A; College of Sciences; N/A; 295531; N/A; 178882The objective of this study is to synthesize boron carbide powders starting with boron oxide (B2 O3 ) and varying carbon sources such as graphite and activated carbon by using carbothermal method. Powder mixtures are mechanically activated with ball mill, pelletized in cold hydraulic press and reacted under Argon atmosphere at 1450°C. Milling speed and time; reaction duration; varying carbon source and the ratio of the starting materials are experimented to observe the results upon the phase structure and the yield of the B4 C. The product characterization is carried out via XRD, SEM, particle size analyzer and organic elemental analysis methods. Mechanical pretreatment significantly reduces the amount of the unreacted carbon and lowers the theoretical reaction temperature down to 1360°C. Under the optimum conditions, the yield contains 4 % remaining carbon and approximately 10 µm boron carbide particles. / Bu çalışmada, bor oksit ve farklı karbon kaynaklarından hareketle karbotermik yöntemle bor karbür tozu üretimi amaçlanmıştır. Hammadde olarak, B2 O3 ve grafit ya da aktif karbon kullanılmış olup, toz karışımları bilyalı değirmende mekanik olarak aktive edilmiştir. Mekanik olarak aktive edilen tozlar, hidrolik preste peletler haline getirilmiş ve Ar atmosferi altında 1450°C’de reaksiyona tabi tutulmuştur. Öğütme süresi/hızı, reaksiyon süresi, başlangıç toz miktarları ve farklı karbon kaynaklarının son ürün verimi ve faz yapısı üzerindeki etkisi incelenmiştir. Elde edilen toz ürünlerin karakterizasyonu, XRD, SEM ve organik element analizi yöntemleri ile gerçekleştirilmiştir. Öğütme ve presleme işlemleri sayesinde, son ürün yapısındaki kalıntı karbon miktarı önemli ölçüde azaltılmış ve teorik oluşum sıcaklığı 1360°C’ye kadar düşürülmüştür. Optimum koşullarda elde edilen tozlar, yapısında en fazla % 4 kalıntı karbon içeren ve ortalama 10 µm partikül boyutuna sahip bor karbür tozlarıdır.Publication Metadata only Enhanced ionic conductivity and mechanical strength in nanocomposite electrolytes with nonlinear polymer architectures(TÜBİTAK, 2023) N/A; Department of Chemical and Biological Engineering; N/A; Department of Chemical and Biological Engineering; Bakar, Recep; Şenses, Erkan; Darvishi, Saeid; PhD Student; Faculty Member; PhD Student; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 280298; N/ASolvent-free polymer-based electrolytes (SPEs) have gained significant attention to realize safer and flexible lithium-ion batteries. Among all polymers used for preparing SPEs electrolytes, poly(ethylene oxide), a biocompatible and biodegradable polymer, has been the most prevalent one mainly because of its high ionic conductivity in the molten state, the capability for the dissolution of a wide range of different lithium salts as well as its potential for the environmental health and safety. However, linear PEO is highly semicrystalline at room temperature and thus exhibits weak mechanical performance. Addition of nanoparticles enhances the mechanical strength and effectively decreases the crystallization of linear PEO, yet enhancement in mechanical performance often results in decreased ionic conductivity when compared to the neat linear PEO-based electrolytes; new strategies for decoupling ionic conductivity from mechanical reinforcement are urgently needed. Herein, we used lithium bis(trifluoromethane-sulfonyl)-imide (LiTFSI) salts dissolved in various nonlinear PEO architectures, including stars (4-arms and 8-arms) and hyperbranched matrices, and SiO2 nanoparticles (approximately equal to 50 nm diameter) as fillers. Compared to the linear PEO chains, the room temperature crystallinity was eliminated in the branched PEO architectures. The electrolytes with good dispersion of the nanoparticles in the nonlinear PEOs significantly enhanced ionic conductivity, specifically by approximately equal to 40% for 8-arm star, approximately equal to 28% for 4-arms star, and approximately equal to %16 for hyperbranched matrices, with respect to the composite electrolyte with the linear matrix. Additionally, the rheological results of the SPEs with branched architectures show more than three orders of magnitude enhancement in the low-frequency moduli compared to the neat linear PEO/Li systems. The obtained results demonstrate that the solvent-free composite electrolytes made of branched PEO architectures can be quite promising especially for irregularly shaped and environmentally benign battery applications suitable for medical implants, wearable devices, and stretchable electronics, which require biodegradability and biocompatibility. © TÜBİTAK.Publication Metadata only In silico design of novel and highly selective lysine-specific histone demethylase inhibitors(Scientific Technical Research Council Turkey-Tubitak, 2011) Akdogan, Ebru Demet; Yelekci, Kemal; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Erman, Burak; Faculty Member; College of Engineering; 179997Histone lysine-specific demethylase (LSD1) is involved in a wide range of epigenetic processes and plays important roles in gene silencing, DNA transcription, DNA replication, DNA repair, and heterochromatin formation. Its active site shows a resemblance to those of 2 homologous enzymes, monamine oxidase A and B (MAO-A and MAO-B.) In the present work, starting from suitable scaffolds and generating thousands of structures from them, 10 potential inhibitors were obtained with structural and physicochemical properties selectively suitable for inhibiting LSD1. iLib Diverse software was used to generate the diverse structures and 3 docking tools, CDOCKER, GOLD, and AutoDock, were used to find the most probable potential inhibitor based on its binding affinity. The dispositions of the candidate molecules within the organism were checked by ADMET_PSA_2D (polar surface area) versus ADMET_AlogP98 (the logarithm of the partition coefficient between n-octanol and water), and their suitability is discussed. The LSD1 inhibition activities of the candidates were compared with the properties of trans-2-phenylcyclopropylamine (tranylcypromine) and 2-(4-methoxy-phenyl) cyclopropylamine, which are the 2 known inhibitors of LSD1.