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Doğru-Yüksel, Itır Bakış

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PhD Student

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Itır Bakış

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Doğru-Yüksel

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Doğru-Yüksel, Itır Bakış

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2017 - 201972020 - 202211

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Now showing 1 - 10 of 18
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    Silk as a biodegradable resist for field-emission scanning probe lithography
    (Institute of Physics (IOP) Publishing, 2020) Sadeghi, Sadra; Rangelow, Ivo W.; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Alaca, Burhanettin Erdem; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Doğru-Yüksel, Itır Bakış; Nizamoğlu, Sedat; Faculty Member; Other; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); N/A; N/A; N/A; N/A; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 115108; N/A; N/A; N/A; 130295
    The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of similar to 50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.
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    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; 130295
    When 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.
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    Biomaterial disk lasers by suppressing the coffee ring effect
    (American Chemical Society (ACS), 2018) N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Melikov, Rustamzhon; Nizamoğlu, Sedat; PhD Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; N/A; N/A; 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; N/A; N/A; N/A; 130295
    Inspired by the suppression of the coffee ring effect, we developed self-assembled disk lasers that can be formed with a wide variety of biomaterials. For proof of concept, we formed the disks with the natural protein silk fibroin or the synthetic biopolymer polyvinylpyrrolidone, which created a whispering gallery mode resonator that we combined with organic dyes for laser light generation. The lasers were flexible enough to bend around surfaces, physically transient in aqueous environments, and could be directly placed on various substrates. Moreover, the characteristics of laser emission could be modified by altering the size of the disk. Our results therefore highlight a new combination of materials that can be used in the environmentally friendly production of waste-free photonic devices.
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    Eco-friendly silk-hydrogel lenses for LEDs
    (Optica Publishing Group (formerly OSA), 2018) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Melikov, Rustamzhon; Press, Daniel Aaron; Kumar, Baskaran Ganesh; Doğru-Yüksel, Itır Bakış; Sadeghi, Sadra; Chirea, Mariana; Yılgör, İskender; Nizamoğlu, Sedat; PhD Student; Researcher; Other; PhD Student; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of 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 Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 24181; 130295
    In this study, silk fibroin in hydrogel form is analyzed as an eco-friendly alternative to conventional polymers for lens applications in light-emitting diodes. The intensity profile was controlled via dome- and crater-type lenses.
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    Single transverse mode eGFP modified silk fibroin laser
    (Optica Publishing Group (formerly OSA), 2018) Min, Kyungtaek; Umar, Muhammad; Kim, Sunghwan; N/A; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Jalali, Houman Bahmani; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics 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 Sciences; College of Engineering; N/A; N/A; N/A; N/A; 206349; 130295
    A single transverse mode distributed feedback laser is reported where the gain medium is composed enhanced green fluorescent protein in silk fibroin matrix. Moreover, optical feedback is increased with a high refractive index TiO<inf>2</inf> layer.
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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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    Past, present and future of indium phosphide quantum dots
    (Tsinghua Univ Press, 2022) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Jalali, Houman Bahmani; Nizamoğlu, Sedat; Sadeghi, Sadra; Önal, Asım; Doğru-Yüksel, Itır Bakış; PhD Student; Faculty Member; PhD Student; PhD Student; Department of Electrical and Electronics 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; N/A; 130295; N/A; N/A; N/A
    Indium phosphide (InP) colloidal quantum dots (QDs) have been drawn significant attention as a potentially less toxic alternative to cadmium-based QDs over the past two decades. The advances in their colloidal synthesis methods have allowed for the synthesis of a wide variety of compositions, heterojunctions, dopants, and ligands that enabled spectral tunability from blue to near-infrared, narrow emission linewidths, and perfect quantum yields approaching unity. Furthermore, it has higher covalency compared to cadmium chalcogenides leading to improved optical stability. The state-of-the-art InP QDs with appealing optical and electronic properties have excelled in many applications such as light-emitting diodes, luminescent solar concentrators (LSCs), and solar cells with high potential for commercialization. This review focuses on the history, recent development, and future aspect of synthesis and application of colloidal InP QDs.
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    Organic photovoltaic pseudocapacitors for neurostimulation
    (Amer Chemical Soc, 2020) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Molecular Biology and Genetics; N/A; Department of Chemical and Biological Engineering; N/A; Department of Electrical and Electronics Engineering; Han, Mertcan; Srivastava, Shashi Bhushan; Yıldız, Erdost; Melikov, Rustamzhon; Sürme, Saliha; Doğru-Yüksel, Itır Bakış; Kavaklı, İbrahim Halil; Şahin, Afsun; Nizamoğlu, Sedat; Master Student; Researcher; PhD Student; PhD Student; Teaching Faculty; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; 389349; N/A; 40319; 171267; 130295
    Neural interfaces are the fundamental tools to understand the brain and cure many nervous-system diseases. For proper interfacing, seamless integration, efficient and safe digital-to-biological signal transduction, and long operational lifetime are required. Here, we devised a wireless optoelectronic pseudocapacitor converting the optical energy to safe capacitive currents by dissociating the photogenerated excitons in the photovoltaic unit and effectively routing the holes to the supercapacitor electrode and the pseudocapacitive electrode-electrolyte interfacial layer of PEDOT:PSS for reversible faradic reactions. The biointerface showed high peak capacitive currents of similar to 3 mA.cm(-2) with total charge injection of similar to 1 mu C.cm(-2) at responsivity of 30 mA.W-1, generating high photovoltages over 400 mV for the main eye photoreception colors of blue, green, and red. Moreover, modification of PEDOT:PSS controls the charging/discharging phases leading to rapid capacitive photoresponse of 50 mu s and effective membrane depolarization at the single-cell level. The neural interface has a device lifetime of over 1.5 years in the aqueous environment and showed stability without significant performance decrease after sterilization steps. Our results demonstrate that adopting the pseudocapacitance phenomenon on organic photovoltaics paves an ultraefficient, safe, and robust way toward communicating with biological systems.
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    All-protein 3D coffee stain lasers
    (Optica Publishing Group (formerly OSA), 2018) 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; 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; 130295
    The transition from a 2D to a 3D coffee stain that has a well-defined and hollow spherelike structure is demonstrated. Self-assembled all-protein lasers are constructed by 3D coffee stains.
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    Silk nanocrack origami for controllable random lasers
    (Wiley-V C H Verlag Gmbh, 2021) Jeong, Chanho; Park, Byeonghak; Lee, Ju Seung; Kim, Tae-il; N/A; N/A; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Han, Mertcan; Nizamoğlu, Sedat; PhD Student; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 130295
    The ancient art of Origami started to evolve as a contemporary technological method for the realization of morphologically induced and unconventional advanced functional structures. Here, directional random lasers (RLs) that are formed by folding (i.e., ori) dye-doped natural protein silk fibroin (SF) film as paper (i.e., kami) are demonstrated. The folding stress induces parallel nanocracks that simultaneously function as diffuse reflectors and laser light outcouplers at the boundaries of the optical gain medium. Random lasing is observed after a threshold energy level of 0.8 nJ mu m(-2) with an in-plane divergence-angle of 13 degrees. Moreover, the central laser emission wavelength is tuned from 588.7 to 602.1 nm by controlling the adjacent nanocracks distance and additional laser emission directions are introduced by further folding SF at different in-plane angles that induce rectangular and triangular geometries. More significantly, RL is fabricated via a quick, scalable, and environmentally friendly stress-induced nanocracking process maintaining its mechanical and optical properties even after 10,000 times of bending test. Hence, this study introduces a novel form of biocompatible, biodegradable, and large-area protein microlasers by using an unconventional laser fabrication approach.