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Publication Metadata only Al-Sm alloys under far-from-equilibrium conditions(Springer International Publishing AG, 2021) Okuyucu, Can; Kaygusuz, Burçin; Işıksaçan, Cemil; Meydanoğlu, Onur; Özerinç, Sezer; Kalay, Yunus Eren; N/A; Motallebzadeh, Amir; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/ATraditional Al alloys have shown tremendous potential in the aerospace industry due to their attractive properties such as ductility, fracture toughness, and fatigue resistance. However, modern aerospace applications call for next-generation Al alloys with a stringent combination of properties such as high strength, low density, and excellent environmental stability. In that sense, we studied highly driven Al-Rare-Earth (RE) alloys under far-from-equilibrium conditions to investigate the possible effects of cooling rate on the expected microstructure, thus mechanical properties. Al94Sm6 was produced using a copper wheel melt spinner. XRD analysis showed the Sm is entirely trapped within the Al matrix. The heat-treated specimens resulted in the formation of the nanocrystalline Al4Sm phase embedded in the Al matrix, with a two-step precipitation sequence. The hardness values determined by nanoindentation shows that the initial supersaturated solid solution has 3.83 GPa hardness, while the heat-treated ones have 3.34 GPa. The mechanisms behind this extreme strength and ductility through solute trapping, and subsequent heat-treatments were discussed in detail using a combined study of micromechanical characterization, nanoindentation , electron microscopy, XRD, and DSC.Publication Metadata only Ammonia decomposition on a highly-dispersed carbon-embedded iron catalyst derived from Fe-BTC: stable and high performance at relatively low temperatures(Elsevier, 2020) N/A; N/A; Department of Chemical and Biological Engineering; Akarçay, Özge; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; 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); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 384798; 59917Fe-BTC (iron 1,3,5-benzenetricarboxylic acid), a commercially available metal organic framework (MOF), was used as a sacrificial template to produce a series of carbon-embedded Fe catalysts upon its pyrolysis at different temperatures. The catalyst prepared by pyrolyzing Fe-BTC at 400 degrees C under flowing N-2 provided a high graphitic degree on the carbon support hosting highly dispersed Fe species at a Fe loading of 34 wt%. Performance measurements on ammonia decomposition to produce COx-free hydrogen showed that this catalyst provided an ammonia conversion of 73.8% at a space velocity of 6000 cm(3) NH3 h(-1) g(cat)(-1) and at 500 degrees C for at least 120 h. This stable performance, exceeding that of some of the best non-noble metal catalysts, was associated with the presence of highly-dispersed Fe species at a significantly high Fe loading, embedded in a carbonaceous shell. The presence of the carbonaceous shell not only protected the active species against sintering, but also made them electron rich owing to its high level of graphitization.Publication Metadata only An ultra-compact and wireless tag for battery-free sweat glucose monitoring(Elsevier Advanced Technology, 2022) N/A; Department of Mechanical Engineering; N/A; N/A; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Mirzajani, Hadi; Abbasiasl, Taher; Mirlou, Fariborz; İstif, Emin; Bathaei, Mohammad Javad; Dağ, Çağdaş; Deyneli, Oğuzhan; Dereli, Dilek Yazıcı; Beker, Levent; Researcher; PhD Student; PhD Student; Other; PhD Student; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Koç Üniversitesi İş Bankası Enfeksiyon Hastalıkları Uygulama ve Araştırma Merkezi (EHAM) / Koç University İşbank Center for Infectious Diseases (KU-IS CID); n2STAR-Koç University Nanofabrication and Nanocharacterization Center for Scientifc and Technological Advanced Research; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; School of Medicine; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 171914; 179659; 308798Glucose monitoring before, during, and after exercise is essential for people with diabetes as exercise increases the risk of activity-induced hyper- and hypo-glycemic events. The situation is even more challenging for athletes with diabetes as they have impaired metabolic control compared to sedentary individuals. In this regard, a compact and noninvasive wearable glucose monitoring device that can be easily worn is critical to enabling glucose monitoring. This report presents an ultra-compact glucose tag with a footprint and weight of 1.2 cm(2) and 0.13 g, respectively, for sweat analysis. The device comprises a near field communication (NFC) chip, antenna, electrochemical sensor, and microfluidic channels implemented in different material layers. The device has a flexible and conformal structure and can be easily attached to different body parts. The battery-less operation of the device was enabled by NFC-based wireless power transmission and the compact antenna. Femtosecond laser ablation was employed to fabricate a highly compact and flexible NFC antenna. The proposed device demonstrated excellent operating characteristics with a limit of detection (LOD), limit of quantification (LOQ), and sensitivity of 24 mu M, 74 mu M, and 1.27 mu A cm(-2) mM(-1), respectively. The response of the proposed sensor in sweat glucose detection and quantification was validated by nuclear magnetic resonance spectroscopy (NMR). Also, the device's capability in attachment to the body, sweat collection, and glucose measurement was demonstrated through in vitro and in vivo experiments, and satisfactory results were obtained.Publication Metadata only COx-free hydrogen production from ammonia decomposition over sepiolite-supported nickel catalysts(Pergamon-Elsevier Science Ltd, 2018) Soyer-Uzun, Sezen; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Sarp, Seda; Akkaya, Ceren Yılmaz; Yağcı, Mustafa Barış; Uzun, Alper; PhD Student; Undergraduate Student; Researcher; Researcher; 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; College of Engineering; N/A; College of Engineering; 384798; N/A; N/A; N/A; 59917Sepiolite, a clay mineral, was utilized as a support for nickel-based catalysts for COx-free hydrogen production from ammonia decomposition. First, the physical and chemical properties of sepiolite were changed by calcining it at temperatures varying from 500 to 1000 degrees C, then nickel was impregnated on these calcined supports and tested for ammonia decomposition at various temperatures following reduction at 650 degrees C. Results indicated that even though the catalysts contained almost the same amount of nickel, they showed different hydrogen production performance. Detailed characterization of the catalysts before and after reaction illustrated that the support obtained by calcining sepiolite at 700 degrees C shows good basic properties with a high surface area offering a high degree of nickel dispersion. These properties lead to promising hydrogen production rates which are on par, if not higher, than most of the nickel-based catalysts prepared on supports, which are either not cheap or require tedious preparation procedures.Publication Metadata only Detection of human kappa-opioid antibody using microresonators with integrated optical readout(Elsevier advanced Technology, 2010) N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Timurdoğan, Erman; Özber, Natali; Nargül, Sezin; Yavuz, Serhat; Kılıç, M. Salih; Kavaklı, İbrahim Halil; Ürey, Hakan; Alaca, Burhanettin Erdem; PhD Student; Master Student; PhD Student; Master Student; Resercher; Faculty Member; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 40319; 8579; 115108Label-free detection of the interaction between hexahistidine-tagged human kappa-opioid receptor membrane protein and anti-His antibody is demonstrated in liquid by an optical microelectromechanical system utilizing electromagnetically actuated microresonators Shift in resonance frequency due to accretion of mass on the sensitive surface of microresonators is monitored via an integrated optical readout a frequency resolution of 2 Hz is obtained Together with a sensitivity of 7 ppm/(ng/ml)) this leads to a minimum detectable antibody concentration of 57 ng/ml for a 50-kHz device the measurement principle is shown to impart immunity to environmental noise, facilitate operation in liquid media and bring about the prospect for further miniaturization of actuator and readout leading to a portable biochemical sensor.Publication Metadata only Directing chemiluminescent dioxetanes to mitochondria: a cationic luminophore enables in vitro and in vivo detection of cancer cells upon enzymatic activation(Elsevier B.V., 2023) Department of Chemistry; N/A; N/A; Department of Chemistry; N/A; N/A; N/A; N/A; N/A; Department of Chemistry; Gündüz, Hande; Acari, Alperen; Çetin, Sultan; Almammadov, Toghrul; Değirmenci, Nareg Pınarbaşı; Dırak, Musa; Cingöz, Ahmet; Kılıç, Eda; Önder, Tuğba Bağcı; Kölemen, Safacan; Researcher; Master Student; PhD Student; Researcher; PhD Student; PhD Student; Researcher; Master Student; Faculty Member; Faculty Member; Department of Chemistry; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); N/A; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); N/A; N/A; N/A; College of Sciences; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; School of Medicine; College of Sciences; 224496; N/A; N/A; N/A; N/A; N/A; N/A; N/A; 184359; 272051A mitochondrion targeted and leucine aminopeptidase (LAP) activatable 1,2-dioxatane based chemiluminescent probe (MCL) for detection of LAP activity in living cancer cells and tumor bearing mice was reported. MCL displayed a selective and sensitive turn-on response in aqueous solutions upon reacting with the LAP enzyme. In cell culture studies, a selective luminescence intensity increase was observed in cancer cell lines, suggesting that MCL can differentiate between cancer and normal cells and allows detection of varying endogenous LAP concentrations. Using fluorescence imaging with a commercial Mitotracker dye, MCL was also shown to localize mitochondria in cancer cell lines. Furthermore, MCL was used to image tumors in mice models. MCL marks not only the first ever example of a mitochondria targeted chemiluminescent probe, but also the first ever example of an organelle targeted 1,2-dioxetane derivative. © 2023 Elsevier B.V.Publication Open Access Electrochemical deposition of Mn:ZnO films under hydrothermal conditions(Electrochemical Society (ECS), 2013) N/A; Department of Chemistry; Akkaya, Ceren Yılmaz; Ünal, Uğur; PhD Student; 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 SciencesThis study demonstrated the electrochemical deposition of Mn-doped ZnO films under hydrothermal conditions at 130 degrees C in 50% v/v DMSO-H2O mixture. X-ray diffraction analysis showed that the deposition of the ZnO structures was along (002) direction. However, the presence of Mn2+ affected the thickness of ZnO structures and we believe that the interaction of Mn2+ with the nonpolar surface of ZnO restricts lateral growth. Mn appears in the mixed oxide state in ZnO lattice. The photoluminescence spectra of the films show only UV emission indicating high crystal quality. The blueshift of the UV emission is observed after the introduction of Mn impurity into the ZnO lattice. The surface morphology, lattice structure, Mn content, chemical binding characteristics, and optical properties of the deposits were examined by scanning electron microscopy, X-ray diffraction, X-ray photoelectron-spectroscopy and photoluminescence spectroscopy, respectively.Publication Metadata only Electrochemical-hydrothermal synthesis of manganese oxide films as electrodes for electrochemical capacitors(Elsevier, 2015) N/A; Department of Chemistry; Öztuna, Feriha Eylül Saraç; Ünal, Uğur; PHD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Science and Engineering; College of Sciences; N/A; 42079Electrochemical capacitors have attracted great interest because they can maintain high power density along with high energy density. In this study, manganese oxides were electrodeposited onto nickel mesh substrate under hydrothermal conditions to be used as electrodes for electrochemical capacitors. Obtained Mn3O4 (hausmannite) phase was electrochemically oxidized to mixed-valent MnO2 during potential cycling. MnO2 electrodes showed excellent pseudocapacitative behaviour in cyclic voltammetry (CV) and charge-discharge (CD) measurements. Produced electrodes had specific capacitance of 518.8 F g(-1) at 0.1 mA cm(-2). Also, the electrodes maintained their capacitative properties at high scan rates/current densities and after 10,000 cycles of CV measurement. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only Enhanced photoelectrochemical activity of magnetically modified TiO2 prepared by a simple ex-situ route(Springer, 2022) Kuyumcu, Ozge Kerkez; Bayazit, Sahika Sena; Akyuz, Duygu; Koca, Atif; N/A; N/A; Yılmaz, Seda; PhD Student; PhD Student; N/A; N/A; N/A; N/AModified TiO2 nanocomposites have been recognized as attractive photocatalytic materials in solar energy conversion. The aim of this study is to enhance the photoelectrochemical performance under visible light region by magnetically modified TiO2 nanocomposites (Fe3O4/TiO2 and NiFe2O4/TiO2) prepared by a simple ex-situ non-thermal route. The magnetic TiO2 nanocomposites were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectra (DRS), photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), vibrational scanning magnetometry (VSM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Photoelectrochemical analysis was performed; chronoamperometry and Mott-Schottky curves were obtained. Results indicated that these non-noble, low-cost photocatalysts have shown the desired features; NiFe2O4/TiO2 have a suitable band gap to harvest visible range of solar light; they have reduced electron-hole recombination; and it is magnetically separable from reaction media. The most promising nanocomposite was found as NiFe2O4/TiO2 with a maximum photocurrent density 132 mu A cm(-2). The possible mechanism accounting for the improved photoelectrochemical performance of NiFe2O4/TiO2 is proposed.Publication Metadata only Fabrication of 1D ZNO nanostructures on mems cantilever for VOC sensor application(Elsevier, 2014) Kosemen, Arif; Öztürk, Sadullah; Yerli, Yusuf; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; Researcher; PhD Student; Other; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; 59959; N/A; N/A; 8579This study reports the fabrication method and sensing performance for novel 1D zinc oxide (ZnO) nanorods and nanotubes grown on nickel MEMS cantilevers. The fabrication of the nanostructures and the cantilevers are simple and low-cost using standard lithography, electrodeposition, and hydrothermal etching processes. 1D ZnO nanostructures increase the total sensitive area for biological and chemical sensor applications. We performed experiments with various VOCs with a real-time sensor system developed in our laboratory. While Ni microcantilevers produced no signal, ZnO nanostructure coated microcantilevers showed good sensitivity and repeatable changes. Furthermore, the nanotube coated microcantilevers showed more than 10 fold increase in sensitivity compared to the nanorod coated microcantilevers which can be explained to the fact that ZnO nanotubes have higher surface area and subsurface oxygen vacancies and these provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods. The tests are performed using dynamic mode of operation near resonant frequency using magnetic actuation and optical sensing. The phase stability and the limit of detection of ZnO nanotube coated microcantilevers exposed to diethylamine (DEA) were 0.02 degrees and lower than 10 ppm, respectively. ZnO nanostructure coated microcantilevers have good potential for VOC sensor applications especially for amine groups.