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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 Digital monitoring of the microchannel filling flow dynamics using a non-contactless smartphone-based nano-liter precision flow velocity meter(Elsevier Advanced Technology, 2024) Xu, Weiming; Köydemir, Hatice Ceylan; Department of Mechanical Engineering; Atik, Abdulkadir Yasin; Beker, Levent; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of EngineeringMicrofluidic systems find widespread applications in diagnostics, biological research, chemistry, and engineering studies. Among their many critical parameters, flow rate plays a pivotal role in maintaining the functionality of microfluidic systems, including droplet-based microfluidic devices and those used in cell culture. It also significantly influences microfluidic mixing processes. Although various flow rate measurement devices have been developed, the challenge remains in accurately measuring flow rates within customized channels. This paper presents the development of a 3D-printed smartphone-based flow velocity meter. The 3D-printed platform is angled at 30 degrees to achieve transparent flow visualization, and it doesn't require any external optical components such as external lenses and filters. Two LED modules integrated into the platform create a uniform illumination environment for video capture, powered directly by the smartphone. The performance of our platform, combined with a customized video processing algorithm, was assessed in three different channel types: uniform straight channels, straight channels with varying widths, and vessel-like channel patterns to demonstrate its versatility. Our device effectively measured flow velocities from 5.43 mm/s to 24.47 mm/s, with video quality at 1080p resolution and 60 frames per second, for which the measurement range can be extended by adjusting the frame rate. This flow velocity meter can be a useful analytical tool to evaluate and enhance microfluidic channel designs of various lab-on-a-chip applications.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 Metadata only Disulfonated polyarylene ether sulfone membrane for graphitic carbon nitride/zinc oxide based photo-supercapacitors(Pergamon-Elsevier Science Ltd, 2023) Altaf, Cigdem Tuc; Colak, Tuluhan Olcayto; Erdem, Emre; Misirlioglu, Feray Bakan; Condorelli, Guglielmo Guido; Sankir, Nurdan Demirci; Sankir, Mehmet; Department of Chemistry; Ünal, Uğur; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of SciencesPhoto-supercapacitors (PSCs) are environmentally friendly devices that directly convert and store solar energy into electricity and have a high potential to eliminate the need for grid electricity for a sustainable future. In this study, lithiated (Li+) biphenol-based disulfonated poly (arylene ether sulfone) random copolymer (BPS) mem-brane has been successfully integrated into graphitic carbon nitride/zinc oxide nanowire composite-based PSC to increase the efficiency and to offer simpler and more cost-effective designs. It has been observed that after UV illumination specific capacitance (C-p) and energy density (E-d) increased 2.8 and 2.7-fold, respectively, indicating that the PSC with BPS-Li(+)performs approximately 3 times better under illumination than dark conditions. Furthermore, at elevated temperatures and 100% relative humidity C-p and E-d of the PSC increased to 23.61 Fg(-1) and 47.22 Whkg(-1) at 85 degrees C, respectively. This enhancement can be linked to the temperature-boosted ionic conductivity of the membrane.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 Experimental and theoretical assessment of the enhanced hydrogen adsorption on polycyclic aromatic hydrocarbons upon decoration with alkali metals(Elsevier, 2024) Reider, Anna Maria; Kollotzek, Siegfried; Scheier, Paul; Calvo, Florent; Pirani, Fernando; Bartolomei, Massimiliano; Hernandez, Marta I.; Gonzalez-Lezana, Tomas; Campos-Martinez, Jose; Department of Chemistry; Yurtsever, İsmail Ersin; Department of Chemistry; College of SciencesHydrogen storage by physisorption on carbon-based materials is limited by comparatively low adsorption energies. However, decoration of the carbon substrate with alkali, alkaline earth, or other metal atoms has been proposed as a means to enhance adsorption energies. The decoration affects also the stability of these materials since it makes them more stable and resilient in the repeated cycles of charge and discharge that would be required for a good material devoted to storage. We investigate hydrogen storage capacities of small polycyclic aromatic hydrocarbons (PAHs) cations grown in ultracold helium nanodroplets by analyzing the ion abundances and stabilities. The observations are assessed with quantum chemical calculations and atomistic simulations. It is experimentally shown that the addition of an alkali ion significantly enhances the hydrogen adsorption of the studied PAHs, up to 25% over the bare PAH in the experimental conditions studied here, and the simulations confirm this general trend except for some minor residual discrepancies in the special stabilities (magic numbers). Several approaches to study larger and different PAH compounds are also proposed, and for all cases it is found that alkali decoration increases energy stability by more than 100%.Publication Metadata only Graphene aerogel supported pt electrocatalysts for oxygen reduction reaction by supercritical deposition(Elsevier, 2017) Yu, Haibo; Aindow, Mark; N/A; N/A; N/A; Department of Chemistry; Department of Chemical and Biological Engineering; Öztuna, Feriha Eylül Saraç; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Ünal, Uğur; Erkey, Can; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; 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; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; 42079; 29633Mesoporous graphene aerogel (GA) supported Pt nanoparticles with narrow size distribution were prepared via supercritical deposition (SCD) using supercritical CO2 (scCO(2)). Pt(cod)me(2) precursor was dissolved in scCO(2) and adsorbed onto GA at 35 degrees C and 10.7 MPa. The Pt precursor was converted to its metal form under atmospheric pressure at various temperatures. The effects of precursor conversion temperature (400, 600, and 800 degrees C) on the structural properties of the composites were investigated using Raman Spectroscopy, XRD, XPS, and TEM. The average particle size increased from 1.2 to 2.9 nm when the conversion temperature was increased from 400 to 800 degrees C. The electrocatalytic activity of the samples towards the Oxygen Reduction Reaction were evaluated using cyclic voltammetry (CV) and rotating disc electrode (RDE) measurements. SCD helped to preserve the textural properties of the GA after the Pt nanoparticle deposition, and thus Pt/GA converted at 600 degrees C exhibited an enhanced mass activity of 30.6 mA mg(Pt)(-1), outperforming the mass activities reported in the literature for Pt/GA electrocatalysts prepared using conventional routes. (C) 2017 Elsevier Ltd. All rights reserved.Publication Metadata only Hydrogen sensing properties of ZnO nanorods: effects of annealing, temperature and electrode structure(Pergamon-Elsevier Science Ltd, 2014) Öztürk, Sadullah; Torun, Imren; Kosemen, Arif; Sahin, Yasin; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959In this study, the hydrogen (H-2) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H2 sensor performance, the nanorods were heated at 500 C in dry air. H2 sensing measurements were done in the temperature range of 25-200 degrees C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the uncoated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure.Publication Metadata only In situ synthesis of dendrimer-encapsulated palladium(0) nanoparticles as catalysts for hydrogen production from the methanolysis of ammonia borane(Pergamon-Elsevier Science Ltd, 2020) Eghbali, Paria; Gurbuz, Mustafa Ulvi; Erturk, Ali Serol; Department of Chemistry; Metin, Önder; Faculty Member; Department of Chemistry; College of Sciences; 46962Addressed herein is the in situ synthesis of a PAMAM dendrimer-encapsulated palladium(0) NPs (Pd(0)/Dnd) during the methanolysis of ammonia borane (AB) and the catalytic performance of the yielded Pd(0)/Dnd nanocatalysts in hydrogen production from the methanolysis of AB under ambient conditions. A two-step procedure that includes the impregnation of Pd(II) ions via their coordination to -NH2 groups of the dendrimer and then reduction of Pd(II) ions into the dendrimer-encapsulated Pd(0) NPs by AB during the methanolysis reaction was followed for the synthesis of Pd(0)/Dnd nanocatalysts. However, apart from the existing reports on the synthesis of dendrimer-encapsulated metal NPs, the present study includes for the first time the examination of effect of generation size (G4-G6), core type (ethylene diamine (E) or Jeffamine (P)) and terminal groups (-NH2, -COOH and -OH) of a PAMAM dendrimer on the stability, particle size, morphology and catalytic activity of metal NPs. After finding the optimum Pd(0)/Dnd catalysts considering all these effects, a detailed kinetic study comprising the effect of catalyst and AB concentrations as well as temperature was conducted by monitoring the hydrogen production from the methanolysis of AB. The best catalytic activity in the methanolysis of AB was obtained by using a PAMAM dendrimer with generation G6, amine terminal groups and Jeffamine core (P6.NH2) encapsulated Pd(0) NPs, providing the highest initial turnover frequency (TOF) of 55.8 mol H-2.mol pd(-1).min(-1) and apparent activation energy (Ea(app)) of 48 +/- 3 kJ.mol(-1) at room temperature.Publication Open Access Nanocrystalline cobalt-nickel-boron (metal boride) catalysts for efficient hydrogen production from the hydrolysis of sodium borohydride(Elsevier, 2021) N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Paksoy, Aybike; Altıntaş, Zerrin; Khoshsima, Sina; Öztulum, Samira Fatma Kurtoğlu; Dizaji, Azam Khodadadi; Uzun, Alper; Balcı, Özge; Researcher; Researcher; Faculty Member; Researcher; Department of Chemical and Biological Engineering; 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); 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; N/A; N/A; N/A; 59917; 295531Innovative metal boride nanocatalysts containing crystalline Co-Ni based binary/ternary boride phases were synthesized and used in the hydrolysis of NaBH4. All the as-prepared catalysts were in high-purity with average particle sizes ranging between similar to 51 and 94 nm and consisting of different crystalline phases (e.g. CoB, Co2B, Co5B16, NiB, Ni4B3, Ni2Co0-67B0.33). The synergetic effect of the different binary/ternary boride phases in the composite catalysts had a positive role on the catalytic performances thus, while the binary boride containing phases of unstable cobalt borides or single Ni4B3 were not showing any catalytic activity. The Co-Ni-B based catalyst containing crystalline phases of CoB-Ni4B3 exhibited the highest H-2 production rate (500.0 mL H-2 min(-1) g(cat)(-1)), with an apparent activation energy of 32.7 kJ/mol. The recyclability evaluations showed that the catalyst provides stability even after the 5th cycle. The results suggested that the composite structures demonstrate favorable catalytic properties compared to those of their single components and they can be used as alternative and stable catalysts for efficient hydrogen production from sodium borohydride.