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Publication Metadata only 3D coffee stains(Royal Soc Chemistry, 2017) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Chemistry; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Söz, Çağla Koşak; Press, Daniel Aaron; Melikov, Rustamzhon; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Yılgör, Emel; Yılgör, İskender; Nizamoğlu, Sedat; PhD Student; PhD Student; Researcher; PhD Student; PhD Student; PhD Student; PhD Student; Faculty Member; Researcher; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; N/A; N/A; N/A; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 206349; N/A; 24181; 130295When a liquid droplet (e.g., coffee, wine, etc.) is splattered on a surface, the droplet dries in a ring-shaped stain. This widely observed pattern in everyday life occurs due to the phenomenon known as a coffee stain (or coffee ring) effect. While the droplet dries, the capillary flow moves and deposits the particles toward the pinned edges, which shows a 2D ring-like structure. Here we demonstrate the transition from a 2D to a 3D coffee stain that has a well-defined and hollow sphere-like structure, when the substrate surface is switched from hydrophilic to superhydrophobic. The 3D stain formation starts with the evaporation of the pinned aqueous colloidal droplet placed on a superhydrophobic surface that facilitates the particle flow towards the liquid-air interface. This leads to spherical skin formation and a cavity in the droplet. Afterwards the water loss in the cavity due to pervaporation leads to bubble nucleation and growth, until complete evaporation of the solvent. In addition to the superhydrophobicity of the surface, the concentration of the solution also has a significant effect on 3D coffee stain formation. Advantageously, 3D coffee stain formation in a pendant droplet configuration enables the construction of all-protein lasers by integrating silk fibroin with fluorescent proteins. No tools, components and/or human intervention are needed after the construction process is initiated; therefore, 3D coffee-stains hold promise for building self-assembled and functional 3D constructs and devices from colloidal solutions.Publication Open Access A new class of porous materials for efficient CO2 separation: ionic liquid/graphene aerogel composites(Elsevier, 2021) Department of Chemical and Biological Engineering; N/A; Department of Chemistry; Zeeshan, Muhammad; Yalçın, Kaan; Keskin, Seda; Uzun, Alper; Öztuna, Feriha Eylül Saraç; Ünal, Uğur; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; 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; College of Sciences; N/A; N/A; 40548; 59917; N/A; 42079Here, we report a new post-synthesis modification strategy for functionalizing reduced graphene aerogels (rGAs) towards an exceptional CO2 separation performance. 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was impregnated on a rGA, prepared by reducing GA at 700 degrees C, at various ionic liquid (IL) loadings of 5, 10, 30, and 50 wt%. The resulting composites were characterized in deep detail by X-ray photoelectron spectroscopy, X-ray diffraction, N-2 physical adsorption measurements, scanning electron microscopy, Fourier transform infrared and Raman spectroscopies, and thermogravimetric analysis. Results indicated the presence of interactions between the rGA surface and the anion of the IL, potentially improving the CO2 affinity. Volumetric gas adsorption measurements using these materials showed that the deposition of [BMIM][PF6] on rGA surface at an IL loading of 50 wt% boosts the CO2/CH4 selectivity by more than 20-times, exceeding an absolute value of 120, a remarkably higher CO2/CH4 selectivity compared to that of other functionalized materials under similar operating conditions. Tunability of both the IL structure and the surface characteristics of rGA offer a tremendous degree of flexibility for the rational design of these IL/rGA composites towards high performance in gas separation applications.Publication Metadata only A water-soluble Irgacure 2959-based diallylammonium salt system for antibacterial coatings(Wiley, 2024) Balaban, Burcu; Avci, Duygu; Department of Chemistry; Güner, Pınar Tatar; Acar, Havva Funda Yağcı; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of SciencesA water-soluble mixture of a novel diallylammonium salt photoinitiator based on 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-1-propanone (Irgacure 2959 or I2959) and diallylammonium tosylate has been prepared. It shows excellent water-solubility of 6.8 wt% in water, much greater than the solubility of I2959 (<2 wt%). It has a strong absorbance at 269 nm (epsilon similar to 15731) in methanol. It exhibits 15.6 times higher migration stability than I2959 due to its monomeric nature. Its photoinitiating efficiency of 2-hydroxyethylmethacrylate (HEMA) and poly(ethylene glycol) diacrylate (PEGDA, M-n = 575 D) was found to be similar to I2959. PEGDA hydrogels prepared using the synthesized photoinitiator (PI) were found to have highly porous structures (15.44 mu m) compared with those using I2959. PEGDA film prepared using this PI has demonstrated antibacterial properties against gram-negative Pseudomonas aeruginosa (ATCC 15442) and gram-positive Staphylococcus aureus (ATCC 23235) bacterial species.Publication Metadata only ALD-engineered CuxO overlayers transform ZnO nanorods for selective production of CO in electrochemical CO2 reduction(American Chemical Society, 2024) Department of Chemistry; Yusufoğlu, Muhammed; Tafazoli, Saeede; Jahangiri, Hadi; Yağcı, Mustafa Barış; Balkan, Timuçin; Kaya, Sarp; Department of Chemistry; 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 SciencesThe electrochemical CO2 reduction reaction (CO2RR) holds tremendous promise as a strategy for lowering atmospheric CO2 levels and creating new clean energy sources. The conversion of CO2RR to CO, in particular, has garnered significant scientific interest due to its industrial feasibility. Within this context, the CuZn-based electrocatalyst presents an attractive alternative to conventional CO-selective electrocatalysts, which are often costly and scarce. Nevertheless, the wide-range utilization of CuZn electrocatalysts requires a more comprehensive understanding of their performance and characteristics. In this study, we synthesized ZnO nanorods through electrodeposition and subsequently coated them with CuxO overlayers prepared by atomic layer deposition (ALD). CuxO significantly enhanced CO selectivity, and 88% CO selectivity at a relatively low potential of -0.8 V was obtained on an optimized CuxO overlayer thickness (CuxO-250/ZnO). The addition of CuxO on ZnO was found to dramatically increase the electrochemical surface area (ESCA), lower the charge-transfer resistance (R-ct), and introduce new active sites in the epsilon-CuZn4 phase. Furthermore, electrochemical Raman spectroscopy results showed that the CuxO-250/ALD electrode developed a ZnO layer on the surface during the CO2RR, while the bare ZnO electrode showed no evidence of ZnO during the reaction. These results suggest that the addition of CuxO by ALD played a crucial role in stabilizing ZnO on the surface. The initial amount of CuxO was shown to further affect the redeposition of the ZnO layer and hence affect the final composition of the surface. We attribute the improvement in CO selectivity to the introduction of both epsilon-CuZn4 and ZnO that developed during the CO2RR. Overall, our study provides new insights into the dynamic behavior and surface composition of CuZn electrocatalysts during CO2RR.Publication Open Access An in vitro study on the cytotoxicity and genotoxicity of silver sulfide quantum dots coated with meso-2,3-dimercaptosuccinic acid(Galenos Yayınevi, 2019) N/A; Department of Chemistry; Gözüaçık, Devrim; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of SciencesObjectives: Silver sulfide (Ag2S) quantum dots (QDs) are highly promising nanomaterials in bioimaging systems due to their high activities for both imaging and drug/gene delivery. There is insufficient research on the toxicity of Ag2S QDs coated with meso-2,3-dimercaptosuccinic acid (DMSA). In this study, we aimed to determine the cytotoxicity of Ag2S QDs coated with DMSA in Chinese hamster lung fibroblast (V79) cells over a wide range of concentrations (5-2000 mu g/mL). Materials and methods: cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red uptake (NRU) assays. The genotoxic and apoptotic effects of DMSA/Ag2S QDs were also assessed by comet assay and real-time polymerase chain reaction technique, respectively. Results: cell viability was 54.0 +/- 4.8% and 65.7 +/- 4.1% at the highest dose (2000 mu g/mL) of Ag2S QDs using the MTT and NRU assays, respectively. Although cell viability decreased above 400 mu g/mL (MTT assay) and 800 mu g/mL (NRU assay), DNA damage was not induced by DMSA/Ag2S QDs at the studied concentrations. The mRNA expression levels of p53, caspase-3, cospose-9, Box, Bcl-2, and survivin genes were altered in the cells exposed to 500 and 1000 mu g/mL DMSA/Ag2S QDs. Conclusion: the cytotoxic effects of DMSA/Ag2S QDs may occur at high doses through the apoptotic pathways. However, DMSA/Ag2S QDs appear to be biocompatible at low doses, making them well suited for cell labeling applications. / Amaç: Gümüş sülfür (Ag2 S) kuantum noktaları (QD), hem görüntüleme hem de ilaç/gen hedefleme için büyük aktiviteleri nedeniyle biyo-görüntüleme sisteminde oldukça gelecek vaad eden nanomalzemelerdir. Mezo-2,3-dimerkaptosüksinik asit (DMSA) ile kaplanmış Ag2 S QD’lerin toksisitesi hakkında yeterli çalışma yoktur. Bu çalışmada Çin hamster akciğer fibroblast (V79) hücrelerinde DMSA ile kaplanmış Ag2 S QD’lerin geniş bir konsantrasyon aralığında (5-2000 µg/mL) sitotoksisitesini belirlemeyi amaçladık. Gereç ve yöntemler: hücre canlılığı 3-(4,5-dimetiltiyazol-2-il)-2,5-difeniltetrazolium bromid (MTT) ve nötral kırmız alım (NRU) deneyleri ile belirlendi. DMSA/Ag2 S QD’lerin genotoksik ve apoptotik etkileri sırasıyla komet analizi ve gerçek zamanlı polimeraz zincir reaksiyonu tekniği ile değerlendirildi. Bulgular: Ag2 S QD’lerin en yüksek dozlarında hücre canlılığı MTT ve NRU deneylerinde sırasıyla 54.0±4.8% ve 65.7±4.1% olarak bulundu. Ancak hücre canlılığı 400 µg/mL (MTT deneyi) ve 800 µg/mL (NRU deney) üzerinde azalmıştır. İncelenen konsantrasyonlarda DNA hasarının DMSA/Ag2 S QD’ler tarafından indüklenmediği belirlenmiştir. P53, kaspaz-3, kaspaz-9, Bax, Bcl-2 ve survivin genlerinin mRNA ekspresyon düzeyleri 500 ve 1000 µg/mL DMSA/Ag2 S QD’lere maruz kalan hücrelerde değişmiştir. Sonuç: DMSA/Ag2 S QD’lerin yüksek dozlarda sitotoksik etkilerinin apoptotik yollarla ortaya çıkabileceği görülmektedir. Bununla birlikte, DMSA/ Ag2 S QD’ler, düşük dozlarda biyolojik olarak uyumlu görünmektedir, bu da onları hücre görüntüleme uygulamaları için uygun kılmaktadır.Publication Open Access An integrated computational-experimental hierarchical approach for the rational design of an IL/UiO-66 composite offering infinite CO2 selectivity(Wiley, 2022) Department of Chemical and Biological Engineering; Department of Chemistry; Zeeshan, Muhammad; Gülbalkan, Hasan Can; Durak, Özce; Haşlak, Zeynep Pınar; Ünal, Uğur; Keskin, Seda; Uzun, Alper; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; 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); College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; 42079; 40548; 59917Owing to the possibility of generating theoretically unlimited numbers of ionic liquid (IL)-metal-organic framework (MOF) combinations, experimental studies on IL/MOF composites for gas separation applications are mostly conducted on a trial-and-error basis. To address this problem, an integrated computational-experimental hierarchical approach is presented for selecting the best IL-MOF combination for a target gas separation application. For this purpose, UiO-66 and pyrrolidinium-based ILs are chosen as the parent MOF and IL family, respectively, and three powerful computational tools, Conductor-like Screening Model for Realistic Solvents calculations, density functional theory calculations, and grand canonical Monte Carlo simulations, are integrated to identify the most promising IL-UiO-66 combination as 1-n-butyl-1-methylpyrrolidinium dicyanamide/UiO-66, [BMPyrr][DCA]/UiO-66. Then, this composite is synthesized, characterized in deep detail, and tested for CO2/N-2, CO2/CH4, and CH4/N-2 separations. Results demonstrate that [BMPyrr][DCA]/UiO-66 offers an extraordinary gas separation performance, with practically infinite CO2 and CH4 selectivities over N-2 at 15 degrees C and at low pressures. The integrated hierarchical approach proposed in this work paves the way for the rational design and development of novel IL/MOF composites offering exceptional performance for any desired gas separation application.Publication Metadata only Anticorrosion efficiency of ultrasonically deposited silica coatings on titanium(Elsevier Science Bv, 2013) N/A; N/A; Department of Chemistry; N/A; Ertan, Fatoş Sibel; Kaş, Recep; Miko, Annamaria; Birer, Özgür; Master Student; Master Student; Teaching Faculty; Researcher; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; 163509; N/AWe utilized high intensity ultrasound to prepare coatings of silica and organically modified silica composed of multiple layers of densely packed nanoparticles. Ultrasound was used to collide nanoparticles onto an activated titanium surface with high speed. Large areas could be homogeneously coated by this method. These coatings were characterized by spectroscopy and microscopy methods and the anticorrosion efficiency in NaCl solution was evaluated by electrochemical measurements. The results indicated that the composite coatings provided good quality barrier layer on bare titanium and decreased the anodic corrosion rate. It was found that increase in the organic content of the coating shifted the passivation potential towards more positive direction. The comparison of the impedance results recorded at the corrosion potential pointed out that in each case a good quality barrier layer was formed on the titanium surface. The outstanding corrosion resistance of the composite coatings with only similar to 200 nm thickness shows that ultrasound assisted deposition can be a competitive method to obtain corrosion protective layers. (c) 2013 Elsevier B.V. All rights reserved.Publication Open Access Balanced intersystem crossing in iodinated silicon-fluoresceins allows new class of red shifted theranostic agents(American Chemical Society (ACS), 2021) Elmazoğlu, Zübeyir; Karaman, Osman; Günbaş, Görkem; Department of Chemistry; Çetin, Sultan; Kölemen, Safacan; Gündüz, Hande; PhD Student; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; 272051; N/AIodination of the silicon-fluorescein core revealed a new class of highly cytotoxic, red-shifted and water-soluble photosensitizer (SF-I) which is also fairly emissive to serve as a theranostic agent. Singlet oxygen generation capacity of SF-I was evaluated chemically, and up to 45% singlet oxygen quantum yield was reported in aqueous solutions. SF-I was further tested in triple negative breast (MDA MB-231) and colon (HCT-116) cancer cell lines, which are known to have limited chemotherapy options as well as very poor prognosis. SF-I induced efficient singlet oxygen generation and consequent photocytotoxicity in both cell lines upon light irradiation with a negligible dark toxicity while allowing cell imaging at the same time. SF-I marks the first ever example of a silicon xanthene-based photosensitizer and holds a lot of promise as a small-molecule-based theranostic scaffold.Publication Metadata only Bidisperse magneto-rheological fluids consisting of functional SPIONs added to commercial MRF(Elsevier Science inc, 2020) N/A; N/A; Department of Chemistry; Department of Chemistry; Nejatpour, Mona; Ünal, Uğur; Acar, Havva Funda Yağcı; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; 42079; 178902Magnetorheological fluids (MRFs) are smart materials with a reversible and fast transition from a liquid to a semi-solid state when an external magnetic field is applied (magnetorheological effect). the sedimentation of micron-sized magnetic particles in commercial MRFs is a crucial problem limiting the long-term use in industrial applications. Here, we develop a new MRF based on commercial 140-CG LORD (R) with the addition of surface functional superparamagnetic iron oxide nanoparticles (SPIons). these new bidisperse MRFs are comprised of either poly(acrylic acid) (Paa) coated SPIons or lauric acid (La) coated SPIons and micron-sized fatty acid-coated magnetic particles of the commercial MRF. SPIons have specific coatings to interact with the fatty acid coating of the micron-sized Fe-particles. Sedimentation behaviour and the magnetorheological properties of these bidisperse MRFs with 6-12 wt % SPIon were examined. Bidisperse MRFs improved the stability and redispersibility of MRFs. Bidisperse MRFs with 12 wt% SPIon-Paa showed similar or better magnetorheological behaviour than the commercial MRF despite lower content of the micron size Fe-particles. Hence, A combination of magnetizable nano and micron-sized particles and utilization of correct surface chemistry that allows their favourable interaction improves the stability of MRFs without sacrificing magnetic response but even by improving it.Publication Metadata only Black phosphorus/WS2-TM (TM: Ni, Co) heterojunctions for photocatalytic hydrogen evolution under visible light illumination(MDPI, 2023) Acar, Emineguel Genc; Çekceoglu, Ilknur Aksoy; Aslan, Emre; Patir, Imren Hatay; Department of Chemistry; Yılmaz, Seda; Eroğlu, Zafer; Metin, Önder; Department of Chemistry; 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 SciencesBlack phosphorus (BP) has recently emerged as a versatile photocatalyst owing to its unique photophysical properties and tunable bandgap. Nonetheless, the rapid recombination of the photogenerated charges of pristine BP samples has significantly hindered its practical applications in photocatalysis. Herein, we report, for the first time, the effect of transition metal nanoparticles (Ni and Co) as co-catalysts on the photocatalytic activity of BP/tungsten disulfide (WS2) binary heterojunctions (BP/WS2-TM (TM: Ni, Co)) in the hydrogen evolution reaction (HER) under visible light irradiation (& lambda; > 420 nm). Ternary heterojunctions named BP/WS2-TM (TM: Ni, Co) were synthesized via a chemical reduction method, leading to the formation of an S-scheme heterojunction, in which BP acts as a reduction catalyst and WS2 serves as an oxidation catalyst. BP/WS2-Ni and BP/WS2-Co performed substantial amounts of hydrogen generation of 9.53 mmol h(-1)g(-1) and 12.13 mmol h(-1)g(-1), respectively. Moreover, BP/WS2-Co exhibited about 5 and 15 times higher photocatalytic activity compared to the binary BP/WS2 heterojunctions and pristine BP, respectively. The enhanced photocatalytic activity of the heterojunction catalysts is attributed to the extended light absorption ability, enhanced charge separation, and larger active sites. This study is the first example of photocatalytic hydrogen evolution from water by using Ni- and Co-doped binary BP/WS2 heterojunctions.