Researcher:
Özer, Melek Sermin

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Melek Sermin

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Özer

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Özer, Melek Sermin

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2022 - 20235

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    Catalytic dehydrogenation of natural terpenes via CuPd alloy nanoparticles generated on mesoporous graphitic carbon nitride
    (Wiley, 2023) Mekkaoui, Ayoub Abdelkader; El Houssame, Soufiane; N/A; N/A; N/A; Department of Chemistry; Yalın, Ahsen Sare; Sündü, Buse; Özer, Melek Sermin; Metin, Önder; PhD Student; PhD Student; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; College of Engineering; N/A; N/A; N/A; 46962
    A facile wet-chemical protocol for the synthesis of bimetallic CuPd alloy nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (m-gCN), serving as both stabilizer and support material, was presented herein. The presented protocol allowed to synthesize nearly monodisperse CuPd alloy NPs with an average particle size of 3.9 +/- 0.9 nm without use of any additional surfactants and to prepare CuPd/m-gCN nanocatalysts with different Cu/Pd compositions (Cu25Pd75/m-gCN, Cu35Pd65/m-gCN, Cu16Pd74/m-gCN, Cu32Pd68/m-gCN, Cu10Pd90/m-gCN, and Cu50Pd50/m-gCN). After the detailed characterization of CuPd/m-gCN nanocatalysts, they were utilized as catalysts in the dehydrogenation of terpenes. Among all tested nanocatalysts, Cu50Pd50/m-gCN showed the highest activity in terms of the product yields within the same reaction time. Various parameters influencing the catalytic activity of Cu50Pd50/m-gCN were studied using himachalene as a model substrate and the optimum conditions were determined. Under the optimized reaction conditions, the catalytic application of Cu50Pd50/m-gCN nanocatalysts was extended to nine different terpenes and the corresponding products were obtained in high conversion yields (>90%) under mild conditions. A reusability test showed that Cu50Pd50/m-gCN nanocatalysts can be re-used up to four cycles without significant loss in their initial activity.
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    Highly efficient white LEDs by using near unity emitting colloidal quantum dots in liquid medium
    (Optica Publishing Group, 2022) Department of Electrical and Electronics Engineering; Department of Chemistry; Department of Chemistry; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Nizamoğlu, Sedat; Yılgör, İskender; Metin, Önder; Özer, Melek Sermin; Önal, Asım; Eren, Güncem Özgün; Sadeghi, Sadra; Melikov, Rustamzhon; Jalali, Houman Bahmani; Doğru-Yüksel, Itır Bakış; Han, Mertcan; Karatüm, Onuralp; Faculty Member; Faculty Member; Faculty Member; Researcher; PhD Student; PhD Student; PhD Student; PhD Student; PhD Student; PhD Student; Master Student; Other; Department of Chemistry; Department of Electrical and Electronics Engineering; College of Engineering; College of Sciences; College of Sciences; N/A; Graduate School of Sciences and 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; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 130295; 24181; 46962; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A
    We developed quantum dot (QD) based color-conversion white LEDs that reach over 150 lumens per electrical Watt. For that we synthesized alloyed ZnCdSe/ZnSe QDs with 94% of quantum efficiency and injected QD-liquids on blue LEDs.
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    Synergism between few-layer black phosphorus and graphitic carbon nitride enhances the photoredox C-H arylation under visible light irradiation
    (Royal Soc Chemistry, 2022) Kılıç, Haydar; Department of Chemistry; Department of Chemistry; N/A; Department of Chemistry; Eroğlu, Zafer; Özer, Melek Sermin; Kubanaliev, Temirlan; Metin, Önder; Researcher; Researcher; Master Student; Faculty Member; 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); College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 46962
    The development of solar-driven chemical transformations is one of the most attractive research interests as they lay the groundwork for a more sustainable future. To reach this target, efficient photocatalysts, particularly metal-free photocatalysts, should be designed and fabricated. For the design of efficient photocatalysts in terms of optical, chemical/thermal properties, and long-term stability, constructing heterojunctions of two-dimensional (2D) materials consisting of earth-abundant elements is one of the most environmentally friendly options. In this study, a highly efficient photoredox catalyst was developed by combining few-layer black phosphorus (FLBP) and graphitic carbon nitride (g-CN) binary heterojunctions, which build up a synergistic effect at the heterojunction interfaces. As-prepared FLBP/g-CN heterojunctions were tested in photoredox C-H arylation of heteroarenes with diazonium salts under visible light irradiation and showed excellent activity, with the product yields reaching up to 94% under ambient conditions. The activity of FLBP/g-CN heterojunctions showed a volcano-shaped relation with respect to the BP loading ratios, where the FLBP/g-CN with 35 wt% FLBP provided the best performance. The substrate scope of FLBP/g-CN heterojunctions was investigated over a variety of heteroarenes (furan, thiophene, and N-Boc pyrrole) with diazonium salts bearing electron-donating (ED) and electron-withdrawing (EWD) groups (29 examples in total). Moreover, a suitable band diagram showing a unique electron-hole migration between g-CN and FLBP, which is different from anticipated type-I heterojunction in the heterojunction structure, was proposed by the mechanistic studies and charge migration experiments.
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    Bismuthene as a versatile photocatalyst operating under variable conditions for the photoredox C-H bond functionalization
    (Elsevier, 2022) Kilic, Murat; Rothlisberger, Ursula; N/A; N/A; N/A; Department of Chemistry; Özer, Melek Sermin; Eroğlu, Zafer; Yalın, Ahsen Sare; Metin, Önder; Researcher; Researcher; PhD Student; Faculty Member; 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); N/A; N/A; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 46962
    Recently, layered two-dimensional (2D) semiconductor materials composed of group 15 elements (pnictogens) are demonstrated as efficient photocatalysts in various applications. However, only little attention is given to the investigation of their catalytic properties, and even there is no example of the photocatalytic application of bismuthene so far. Here we report for the first time on the use of 2D bismuthene as a photocatalyst in a liquidphase organic transformation. 2D bismuthene is proven to be an efficient photocatalyst that can be operated under various reaction conditions including indoor light illumination, darkness, outdoors and low temperature for the photoredox C-H arylation of (hetero)arenes with high product yields. The presented bismuthene catalyzed photoredox C-H arylation protocol works efficiently on a broad substrate scope of (hetero)arenes with aryl diazonium salts bearing electron-withdrawing and electron-donating groups. Moreover, a density functional theory (DFT) study reveals mechanistic details that lie behind the catalytic activity of bismuthene.
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    PublicationOpen Access
    High performance white light-emitting diodes over 150 lm/W using near-unity-emitting quantum dots in a liquid matrix
    (American Chemical Society (ACS), 2022) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Chemistry; Önal, Asım; Eren, Güncem Özgün; Sadeghi, Sadra; Melikov, Rustamzhon; Han, Mertcan; Karatüm, Onuralp; Özer, Melek Sermin; Jalali, Houman Bahmani; Doğru-Yüksel, Itır Bakış; Yılgör, İskender; Metin, Önder; Nizamoğlu, Sedat; PhD Student; PhD Student; Master Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; 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; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; 24181; 46962; 130295
    In the next decade, we will witness the replacement of a majority of conventional light sources with light-emitting diodes (LEDs). Efficient LEDs other than phosphors can enhance their functionality and meet different lighting needs. Quantum dots (QDs) have high potential for future LED technology due to their sensitive band-gap tuning via the quantum confinement effect and compositional control, high photoluminescence quantum yield (PLQY), and mass-production capacity. Herein, we demonstrate white LEDs using QDs that reach over 150 lumens per electrical Watt. For that we synthesized green-and red-emitting ZnCdSe/ZnSe core/shell QDs by low-temperature nucleation, high-temperature shell formation, and postsynthetic trap-state removal. Their cadmium concentration is lower than 100 ppm, satisfying the current EU RoHS regulations, and their PLQY reaches a high level of 94%. The PLQY of QDs is maintained within the device on blue LED via liquid injection, and their integration at optimized optical densities leads to 129.6 and 170.4 lm/W for red-green-blue (RGB)-and green-blue (GB)-based white LEDs, respectively. Our simulations further showed that an efficiency level of over 230 lm/W is achievable using ultraefficient blue LED pumps. The simple fabrication and high performance of white LEDs using QD liquids show high promise for next-generation lighting devices.