Researcher:
Han, Mertcan

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Master Student

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Mertcan

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Han

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Han, Mertcan

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2020 - 202215

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Researcher Of Publications: search.filters.isAuthorOfPublication.071bb330-814d-4105-86cc-1493c9db01ef

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    Biocompatibility and neural stimulation capacity of aluminum antimonide nanocrystals biointerfaces for use in artificial vision
    (Association for Research in Vision and Ophthalmology (ARVO), 2021) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Kesim, Cem; Han, Mertcan; Yıldız, Erdost; Jalali, Houman Bahmani; Qureshi, Mohammad Haroon; Hasanreisoğlu, Murat; Nizamoğlu, Sedat; Şahin, Afsun; Doctor; Master Student; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); 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; School of Medicine; College of Engineering; School of Medicine; Koç University Hospital; N/A; N/A; N/A; N/A; N/A; N/A; N/A; 387367; N/A; N/A; N/A; N/A; 182001; 130295; 71267
    N/A
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    Silk protein sheet origami for directional random biolasers
    (Optica Publishing Group, 2022) Doğru-Yüksel, Itır Bakış; Jeong, Chanho; Park, Byeonghak; Lee, Ju Seung; Kim, Tae-Il; Department of Electrical and Electronics Engineering; N/A; Nizamoğlu, Sedat; Han, Mertcan; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 130295; N/A
    We demonstrate controlled random lasers via origami of dye-doped silk fibroin protein sheets. Folding the films generate nano-scale cracks that form spatially localized feedback and lead to low threshold laser emission.
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    Erratum to: exciton recycling via InP quantum dot funnels for luminescent solar concentrators
    (Tsinghua University) Ow-Yang, Cleva W.; N/A; N/A; N/A; N/A; Department of Physics; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Sadeghi, Sadra; Toker, Işınsu Baylam; Han, Mertcan; Sennaroğlu, Alphan; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Physics; 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 Sciences; N/A; N/A; N/A; N/A; 23851; 130295
    The article "Exciton recycling via InP quantum dot funnels for luminescent solar concentrators" written by Houman Bahmani Jalali(1),, Sadra Sadeghi(2),, Isinsu Baylam(3,4), Mertcan Han(5), Cleva W. Ow-Yang(6), Alphan Sennaroğlu(3,4), and Sedat Nizamoğlu(1,2,5) (x2709;), was originally published Online First without Open Access. After publication online first, the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to (c) The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The original article has been corrected.
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    Multiscale dynamics of lipid vesicles in polymeric microenvironment
    (Mdpi, 2022) N/A; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Karaz, Selcan; Han, Mertcan; Akay, Gizem; Önal, Asım; Nizamoğlu, Sedat; Kızılel, Seda; Şenses, Erkan; Master Student; Master Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; 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; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; 130295; 28376; 280298
    Understanding dynamic and complex interaction of biological membranes with extracellular matrices plays a crucial role in controlling a variety of cell behavior and functions, from cell adhesion and growth to signaling and differentiation. Tremendous interest in tissue engineering has made it possible to design polymeric scaffolds mimicking the topology and mechanical properties of the native extracellular microenvironment; however, A fundamental question remains unanswered: that is, how the viscoelastic extracellular environment modifies the hierarchical dynamics of lipid membranes. in this work, we used aqueous solutions of poly(ethylene glycol) (PEG) with different molecular weights to mimic the viscous medium of cells and nearly monodisperse unilamellar DMPC/DMPG liposomes as a membrane model. Using small-angle X-ray scattering (SaXS), dynamic light scattering, temperature-modulated differential scanning calorimetry, bulk rheology, and fluorescence lifetime spectroscopy, we investigated the structural phase map and multiscale dynamics of the liposome-polymer mixtures. the results suggest an unprecedented dynamic coupling between polymer chains and phospholipid bilayers at different length/time scales. the microviscosity of the lipid bilayers is directly influenced by the relaxation of the whole chain, resulting in accelerated dynamics of lipids within the bilayers in the case of short chains compared to the polymer-free liposome case. at the macroscopic level, the gel-to-fluid transition of the bilayers results in a remarkable thermal-stiffening behavior of polymer-liposome solutions that can be modified by the concentration of the liposomes and the polymer chain length.
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    Effect of polymer topology on microstructure, segmental dynamics, and ionic conductivity in PEO/PMMA-based solid polymer electrolytes
    (American Chemical Society (ACS), 2022) Bakar, Recep; Li, Tianyu; Hong, Kunlun; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Department of Chemical and Biological Engineering; N/A; N/A; Aydemir, Umut; Nizamoğlu, Sedat; Han, Mertcan; Şenses, Erkan; Darvishi, Saeid; Bakar, Recep; Faculty Member; Faculty Member; Master Student; Faculty Member; PhD Student; PhD Student; Department of Chemistry; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; College of Sciences; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 58403; 130295; N/A; 280298; N/A; N/A
    Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have attracted much interest due to their high ionic conductivity resulting from inherently fast segmental dynamics and high salt solubility, yet they lack mechanical stability in their neat form. Blending PEO with another rigid, or high glass transition temperature, polymer is a versatile way to improve the mechanical stability; however, the ionic conductivity is strongly reduced due to slower segmental dynamics of highly interpenetrating linear polymer chains. In this work, we used model PEO/PMMA blend systems prepared with various well-defined PEO architectures (linear, stars, hyperbranched, and bottlebrushes) doped with lithium bis(trifluoromethane-sulfonyl)-imide (LiTFSI) and investigated, for the first time, the role of macromolecular architecture of PEO on crystallization, segmental dynamics, and ionic conductivity in the blends and electrolytes. The results suggest that room-temperature miscibility of these polymers can be dramatically extended by using nonlinear PEO in the blends instead of linear chains, which crystallize above 35 wt %. The broadband dielectric spectroscopy results revealed enhanced decoupling of PMMA and PEO segmental dynamics in compact branched architectures, which helps to achieve faster segmental motion of star PEO in glassy PMMA. This manifests as nearly three-fold higher ionic conductivity in these nonlinear blends compared to the conventional linear PEO/PMMA system. Regardless of the PEO architectures, the temperature dependence of ionic conductivity blends with PMMA and LiTFSI is well defined using the Vogel-Fulcher-Tammann mechanism, suggesting that ion transport is mainly affected by the segmental motion. The activation energy values decrease with the increasing ionic conductivity. Overall, our results show that macromolecular architecture can be a tool to decouple segmental dynamics and ion mobility to rationally design SPEs with improved performance.
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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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    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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    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.
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    PublicationOpen Access
    Exciton recycling via InP quantum dot funnels for luminescent solar concentrators
    (Tsinghua University, 2021) Ow-Yang, Cleva W.; N/A; N/A; Department of Physics; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Sadeghi, Sadra; Toker, Işınsu Baylam; Han, Mertcan; Sennaroğlu, Alphan; Nizamoğlu, Sedat; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Physics; Department of Electrical and Electronics Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 23851; 130295
    Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum dot levels for LSCs. Here, we demonstrate cascaded energy transfer and exciton recycling at nanoassembly level for LSCs. The graded structure composed of different sized toxic-heavy-metal-free InP/ZnS core/shell QDs incorporated on copper doped InP QDs, facilitating exciton routing toward narrow band gap QDs at a high nonradiative energy transfer efficiency of 66%. At the final stage of non-radiative energy transfer, the photogenerated holes make ultrafast electronic transitions to copper-induced mid-gap states for radiative recombination in the near-infrared. The exciton recycling facilitates a photoluminescence quantum yield increase of 34% and 61% in comparison with semi-graded and ungraded energy profiles, respectively. Thanks to the suppressed reabsorption and enhanced photoluminescence quantum yield, the graded LSC achieved an optical quantum efficiency of 22.2%. Hence, engineering at nanoassembly level combined with nonradiative energy transfer and exciton funneling offer promise for efficient solar energy harvesting.
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    PublicationOpen Access
    Photovoltaic neurointerface based on aluminum antimonide nanocrystals
    (Springer Nature, 2021) Department of Electrical and Electronics Engineering; N/A; Han, Mertcan; Nizamoğlu, Sedat; Jalali, Houman Bahmani; Yıldız, Erdost; Qureshi, Mohammad Haroon; Şahin, Afsun; Master Student; Faculty Member; PhD Student; PhD Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; 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 Health Sciences; School of Medicine; N/A; 130295; N/A; N/A; N/A; 171267
    Light activated modulation of neural activity is an emerging field for the basic investigation of neural systems and development of new therapeutic methods such as artificial retina. Colloidal inorganic nanocrystals have great potential for neural interfaces due to their adjustable optoelectronic properties via high-level structural, compositional, and size control. However, toxic heavy metal content (e.g., cadmium, mercury), electrochemical coupling to the cells and low photon-to-current efficiency limit their effective use. Here, we introduce the use of aluminum antimonide (AlSb) nanocrystals as the cell interfacing layer for capacitive neural stimulation in the blue spectrum. We demonstrate successful photostimulation of primary hippocampal neurons below ocular safety limits. In addition, our device shows high biocompatibility in vitro and passive accelerated ageing tests indicate a functional lifetime over 3 years showing their feasible use for chronic implants. We demonstrate that nanocrystal biointerfaces hold high promise for future bioelectronics and protheses.