Researcher: Melikov, Rustamzhon
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Melikov, Rustamzhon
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Publication Metadata only 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; 130295The 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.Publication Metadata only 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; 130295When 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.Publication Metadata only Light-emitting devices based on Type-II InP/ZnO quantum dots(American Chemical Society (ACS), 2019) N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Karatüm, Onuralp; Jalali, Houman Bahmani; Sadeghi, Sadra; Melikov, Rustamzhon; Srivastava, Shashi Bhushan; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; PhD Student; Researcher; Faculty Member; 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; N/A; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 130295One of the major challenges for present-day quantum dot light-emitting diode (QLED) technology is the transition from toxic heavy metal to "green" material-based devices. This report proposes an alternative cadmium-free material of type-II InP/ZnO core/shell quantum dots (QDs) for QLEDs. In this study, InP/ZnO core/shell QDs are nanoengineered by adjusting the shell coverage for optimum in-film quantum efficiency, and device parameters are investigated to reach a maximum QLED performance. The fully solution processed QLEDs made of biocompatible and environmentally benign QDs presented in this study exhibit low turn on voltage of 2.8 V, external quantum efficiency of 0.53%, and current efficiency of 1 cd/A, with a saturated color emission in the yellow-orange spectral region. This study paves the way towards nontoxic and efficient LEDs using type-II QDs.Publication Metadata only Radiative energy transfer in color-conversion 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; Department of Electrical and Electronics Engineering; Melikov, Rustamzhon; Press, Daniel Aaron; Kumar, Baskaran Ganesh; Sadeghi, Sadra; Nizamoğlu, Sedat; PhD Student; Researcher; Other; PhD Student; 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; College of Engineering; N/A; N/A; N/A; N/A; 130295We developed a matrix method that calculates and reveals all the radiative energy transfer processes of absorption, reabsorption, inter-absorption and their iterative and combinatorial interactions in down-conversion layer of a light-emitting diode.Publication Metadata only Protein integrated white LEDs for lighting(Optica Publishing Group (formerly OSA), 2014) N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Press, Daniel Aaron; Melikov, Rustamzhon; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; Researcher; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; College of 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; 206349; 130295We demonstrated a new class of white LEDs based on biologically-derived fluorescent proteins. For this we expressed eGFP and mCherry proteins, and integrated them over blue LED chips for cool-, daylight- and warm-white light generation.Publication Metadata only Efficient nanocrystal-based white LEDs with suppressed absorption losses(Optica Publishing Group, 2022) Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Nizamoğlu, Sedat; Önal, Asım; Sadeghi, Sadra; Melikov, Rustamzhon; Faculty Member; PhD Student; PhD Student; PhD Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 130295; N/A; N/A; N/AWe demonstrate efficient white LEDs by using the combination of green-emitting near-unity quantum dots with red-emitting nanorods. Stokes-shift in red via dot-to-rod transition reduced absorption losses and led to a high quantum efficiency of 42.9%.Publication Metadata only 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; 130295Inspired 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.Publication Metadata only Ultra-efficient and high-quality white light-emitting devices using fluorescent proteins in aqueous medium(Wiley, 2020) N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Sadeghi, Sadra; Melikov, Rustamzhon; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; 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; College of Sciences; College of Engineering; N/A; N/A; N/A; 206349; 130295The transformation of electronics toward “green” and efficient devices is critical for the environmental sustainability and energy future. So far, majority of efficient lighting devices have been realized by artificial optical materials such as rare-earth-elements-doped phosphors, colloidal quantum dots (QDs) and dyes. In this study, red-emitting mScarlet and green-emitting eGFP fluorescent proteins are determined for high-performance white LEDs, expressed in living Escherichia coli and the purified proteins are integrated in their natural aqueous environment onto blue LED chips. The aqueous integration preserved quantum yield levels of the proteins above 70% in the device architecture and facilitated a high luminous efficiency (LE) of 81 lm W−1 with a color rendering index (CRI) of 83, which is the most efficient eco-friendly white LED reported to date. Moreover, the concentration ratio are also optimized of red- and green-emitting proteins and white protein-based LEDs with a maximum CRI of 92 are demonstrated. This study shows that fluorescent proteins hold great promise for the next generation eco-friendly, efficient and high-quality white light sources.Publication Metadata only Excitonic energy transfer within inp/zns quantum dot langmuir-blodgett assemblies(Amer Chemical Soc, 2018) N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Melikov, Rustamzhon; Sadeghi, Sadra; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 130295Interparticle energy transfer offers great promise to a diverse range of applications ranging from artificial solar energy harvesting to nanoscale rulers in biology. Here, we assembled InP/ZnS core/shell quantum dot monolayers via the Langmuir-Blodgett technique and studied the effect of ZnS shell thickness on the excitonic energy transfer within these core/shell quantum dots. Three types of InP-based core/shell quantum dot Langmuir-Blodgett assemblies with different ZnS shell thicknesses were assembled. The structural and optical properties of colloidal quantum dots reveal the successful multiple ZnS shell growth, and atomic force microscopy studies show the smoothness of the assembled monolayers. Time-resolved photoluminescence (PL) and fluorescence lifetime imaging microscopy (FLIM) studies of the thick-shell QD monolayer reveal narrower lifetime distribution in comparison with the thin-shell QD monolayer. The interparticle excitonic energy transfer was studied by spectrally resolved traces, and higher energy transfer was observed for the thin-shell InP/1ZnS QD monolayer. Finally, we calculated the average exciton energy and indicated that the energy transfer induced exciton energy shift decreased significantly from 95 to 27 meV after multiple ZnS shell growth.Publication Metadata only Stokes-shift-engineered indium phosphide quantum dots for efficient luminescent solar concentrators(American Chemical Society (ACS), 2018) Ow-Yang, Cleva W.; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Sadeghi, Sadra; Jalali, Houman Bahmani; Melikov, Rustamzhon; Kumar, Baskaran Ganesh; Aria, Mohammad Mohammadi; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Other; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 130295Luminescent solar concentrators (LSCs) show promise because of their potential for low-cost, large-area, and high-efficiency energy harvesting. Stokes shift engineering of luminescent quantum dots (QDs) is a favorable approach to suppress reabsorption losses in LSCs; however, the use of highly toxic heavy metals in QDs constitutes a serious concern for environmental sustainability. Here, we report LSCs based on cadmium-free InP/ZnO core/shell QDs with type-II band alignment that allow for the suppression of reabsorption by Stokes shift engineering. The spectral emission and absorption overlap was controlled by the growth of a ZnO shell on an InP core. At the same time, the ZnO layer also facilitates the photostability of the QDs within the host matrix. We analyzed the optical performance of indium-based LSCs and identified the optical efficiency as 1.45%. The transparency, flexibility, and cadmium-free content of the LSCs hold promise for solar window applications.