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Publication Metadata only Binary CuPt alloy nanoparticles assembled on reduced graphene oxide-carbon black hybrid as efficient and cost-effective electrocatalyst for PEMFC(Pergamon-Elsevier Science Ltd, 2019) Yılmaz, Melike Sevim; Kaplan, Begüm Yarar; Gürsel, Selmiye Alkan; Department of Chemistry; Metin, Önder; Faculty Member; Department of Chemistry; College of Sciences; 46962Addressed herein is the synthesis of binary CuPt alloy nanoparticles (NPs), their assembly on reduced graphene oxide (rGO), Vulcan XC72 (VC) and their hybrid (rGO-VC) to be utilized as electrocatalysts for fuel cell reactions (HOR and ORR) in acidic medium and PEMFC tests. The synthesis of nearly-monodisperse Cu45Pt55 alloy NPs was achieved by using a chemical reduction route comprising the reduction of commercially available metal precursors in a hot surfactant solution. As-synthesized Cu45Pt55 alloy NPs were then assembled on three support materials, namely rGO, VC and rGO-VC) via liquid phase self-assembly method. After the characterization, the electrocatalysts were prepared by mixing the yielded materials with Nafion and their electrocatalysis performance was investigated by studying CV and LSV for HOR and ORR in acidic medium. Among the three electrocatalysts tested, Cu45Pt55/rGO-VC hybrid showed the highest catalytic activity with ECSA of 119 m(2) g(-1) and mass activity of 165 mA mg(pt)(-1). After the evaluation of electrochemical performance of the three prepared electrocatalysts, their performance was then evaluated in fuel cell conditions. In similar to electrochemical activities, the Cu45Pt55/rGO-VC hybrid electrocatalyst showed a superior fuel cell performance and power output by providing a maximum power of 480 mW cm(-2) with a relatively low Pt loading (0.28 mg cm(-2)). Additionally, the Cu45Pt55/rGO-VC hybrid electrocatalyst exhibited substantially better activity as compared to Pt/rGO-VC electrocatalyst. Therefore, the present study confirmed that alloying Pt with Cu enhances the catalytic activity of Pt metal along with the help of beneficial features of rGO-VC hybrid support material. It should be noted that this is the first example of studying PEMFC performance of CuPt alloy NPs supported on rGO, VC and rGO-VC hybrid.Publication Metadata only Binary CuPt alloy nanoparticles assembled on reduced graphene oxide-carbon black hybrid as efficient and cost-effective electrocatalyst for PEMFC [Int J Hydrogen Energy 44 (2019) 14184–14192](Pergamon-Elsevier Science Ltd, 2021) Sevim, Melike; Kaplan, Begüm Yarar; Gürsel, Selmiye Alkan; Department of Chemistry; Metin, Önder; Faculty Member; Department of Chemistry; College of Sciences; 46962N/APublication Metadata only Boosting electrocatalysis of oxygen reduction and evolution reactions with cost-effective cobalt and nitrogen-doped carbons prepared by simple carbonization of ionic liquids(Pergamon-Elsevier Science Ltd, 2022) Zdolsek, Nikola; Vujkovic, Milica; Brkovic, Snezana; Jocic, Ana; Dimitrijevic, Aleksandra; Trtic-Petrovic, Tatjana; Sljukic, Biljana; Department of Chemistry; Metin, Önder; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; 46962Development of cost-effective, bi-functional carbon electrocatalysts via direct carbonization of ionic liquids (bis(cholinium) tetrachlorocobaltate(II) ([Ch](2)[CoCl4]) and bis(1-butyl-3methylimidazolium) tetrachlorocobaltate(II) ([Bmim](2)[CoCl4])) is reported herein for the first time. Carbon electrocatalysts, dual-doped with cobalt and nitrogen, were tested for oxygen reduction (ORR) and oxygen evolution (OER) reactions. Both materials show high bifunctional catalytic activity and excellent stability due to synergistic effects arising from the presence of nitrogen and cobalt. Electrocatalyst prepared by carbonization of [Ch](2)[-CoCl4] show exceptional activity and selectivity toward ORR. Conversely, electrocatalyst prepared from [Bmim](2)[CoCl4] showed a slightly better OER performance indicating that different catalytic sites are responsible for O-2 reduction and H2O oxidation. Parent CoO particles with graphitic nitrogen boost activity for ORR, while elemental Co supported by nitrogen atoms is responsible for OER activity. Finally, energy consumption during electrolytic oxygen production was calculated revealing energy saving when using two materials as anode electrocatalysts.Publication Metadata only Charge storage characteristics of layer-by-layer assembled nickel hydroxide and graphene oxide nanosheets(Springer, 2019) N/A; Department of Chemistry; Department of Chemistry; Öztuna, Feriha Eylül Saraç; Ünal, Uğur; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 42079In this study, layer-by-layer assembled thin films composed of nickel hydroxide and graphene oxide nanosheets were produced via simple dip coating process. The surface topography of the thin films was investigated by atomic force microscopy measurements. Electrical conductivity of the thin films was enhanced by chemical reduction with hydrazine vapor. The effect of chemical reduction on the surface chemical structure was analyzed by X-ray photoelectron spectroscopy. To utilize the produced thin films as possible electrodes for electrochemical energy storage devices, cyclic voltammetric measurements were performed. The areal capacitance of a reduced 9-bilayer [Ni(OH)(2)/graphene oxide] thin film reached 5.2mFcm(-2) at a scan rate of 2mVs(-1), outperforming similar layer-by-layer assembled metal hydroxide/graphene thin films. Lastly, charge storage characteristics of as-deposited and reduced films were investigated by performing cyclic voltammetry at different scan rates and electrochemical impedance spectroscopy.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 Open Access Effect of cerium doping on morphology and physical properties of alpha-Fe2O3 films prepared by hydrothermal electrodeposition(Electrochemical Society (ECS), 2014) Department of Chemistry; Akkaya, Ceren Yılmaz; Ünal, Uğur; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and EngineeringIn this study, electrochemical growth of Ce-doped alpha-Fe2O3 films is reported. Electrodeposition at 75 degrees C and also a combined hydrothermal-electrochemical method to obtain hematite are presented. Both acidic and neutral plating solutions were used for the depositions. Ferric oxyhydroxide is produced by electrodeposition at 75 degrees C and converted to hematite phase after annealing. Hydrothermal-electrodeposition at 130 degrees C results in formation of hematite phase directly. The effect of temperature, deposition solution and cerium ion amount on the morphology and physical properties of hematite films are characterized.Publication Metadata only Electrochemical CO2 reduction to gaseous methane and carbon monoxide using plasma-synthesized copper nanowires(Springer, 2023) Butt, Faaz Ahmed; Alshahrani, Thamraa; Awan, Zahoor Ul Hussain; Christy, Maria; Khan, Firoz; Alanazi, Abdulaziz M.; Department of Chemistry; Ünal, Uğur; Department of Chemistry; College of SciencesThere is a growing interest among environmental researchers to synthesize a sustainable catalyst for CO2 conversion process. Copper and modified copper offer a wide window for such catalysts. In this study, we report the use of plasma-treated copper/copper oxide nanowires for electrochemical CO2 reduction for the first time. Plasma-treated Cu nanowires (CuO-P NWs) were comparatively evaluated with bulk copper surface in CO2 saturated test solutions, namely, KHCO3, KCl, and NaCl, with 0.1 and 1 M concentrations. CuO-P NWs demonstrate 50% increase in selectivity towards CO2 reduced gaseous products (CO and CH4) at a higher applied potential of - 1.1 V vs reversible hydrogen electrode. This increased selectivity is associated with decreased binding energy of the intermediate species on plasma-treated nanowires compared to bulk surface. Both CO and CH4 were the main products detected in the gaseous state, and CO is suggested as the main intermediate species. The effects of different cations and anions and their concentrations in the solutions were also analyzed. It was observed that dilute solutions in 0.1 M are optimal for electrochemical CO2 reduction (ECO2R) and that hydration energy of cations plays a significant role in ECO2R selectivity, while hydrogen evolution reaction was the competing reaction.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.