Browsing by Author "Mutlugun, Evren"

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    High-quality white light generation using dually hybridized nanocrystals and conjugated polymers
    (IEEE, 2007) Nizamoğlu, Sedat; Özel, Tuncay; Mutlugun, Evren; Huyal, Ilkem Ozge; Sarı, Emre; Tian, N.; Holder, E.; Demir, Hilmi Volkan
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    Light-harvesting semiconductor quantum dot nanocrystals integrated on photovoltaic radial junction nanopillars
    (IEEE, 2010) Güzeltürk, Burak; Mutlugun, Evren; Wang X.; Pey, K.L.; Demir, Hilmi Volkan
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    Nanowire-shaped MoS2@MoO3 nanocomposites as a hole injection layer for quantum dot light-emitting diodes
    (American Chemical Society, 2022-08-23) Bastami, N.; Soheyli, E.; Arslan, A.; Sahrae, R.; Yazici, A. F.; Mutlugun, Evren
    Molybdenum disulfides and molybdenum trioxides are structures that possess the potential to work as efficient charge transport layers in optoelectronic devices. In the present study, as opposed to the existing Mo-based nanostructures in flake, sheet, or spherical forms, an extremely simple and low-cost hydrothermal method is used to prepare nanowires (NWs) of MoS2@MoO3 (MSO) composites. The synthesis method includes several advantages including easy handling and processing of inexpensive precursors to reach stable MSO NWs without the need for an oxygen-free medium, which would facilitate the possibility of mass production of these nanostructures. The structural analysis confirmed the formation of MSO nanocomposites with different Mo valence states, as well as NWs of average length and diameter of 70 nm and 5 nm, respectively. In order to demonstrate their potential for optoelectronic applications, MSO NWs were blended into hole injection layers (HILs) in quantum dot-based light-emitting diodes (QLEDs). Electroluminescence measurements show a substantial enhancement in both luminance (from 44,330 to 68,630 cd.m–2) and external quantum efficiency (from 1.6 to 2.3%), based on the increase in the ratio of MSO NWs from 3 to 10%. Interestingly, the addition of 10% volume of MSO NWs resulted in a remarkably smoother HIL with improved current efficiency and stability in green-emitting QLEDs. The simplicity and cost-effective features of the synthesis method along with outstanding favorable morphology demonstrated their ability to enhance the QLED performance and mark them as promising agents for optoelectronics.
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    Observation of anisotropic emission from semiconductor quantum dots in nanocomposites of metal nanoparticles
    (IEEE, 2010) Özel, Tuncay; Nizamoglu, Sedat; Sefunc, Mustafa A.; Samarskaya, Olga; Özel, İlkem O.; Mutlugun, Evren; Lesnyak V.; Gaponik, N.; Eychmuller, A.; Gaponenko, S.V.; Demir, Hilmi Volkan
    [No abstract available]
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    Superior CdSe/ZnS@Fe2O3 Yolk-Shell Nanoparticles as Optically Active MRI** Contrast Agents
    (Wiley, 2022-07-07) Ekici, D. D.; Mutlugun, Evren
    We have developed a robust synthesis methodology for quantum dots (QDs) nanoparticles with magnetic properties designed for biomodal imaging. These nanocrsytlas consists of a semiconductor quantum dot core with engineered fluorescence, which is located in a paramagnetic iron oxide shell that acts as a magnetic resonance imaging (MRI) contrast agent. Yolk-shell CdSe/ZnS@Fe2O3 nanoparticles (NPs) are synthesized via sonochemical decomposition of iron pentacarbonyl (Fe(CO)5) using the oleylamine (OAm) as the ligand. The sonochemical synthesis method of magnetic fluorescent NPs that can be used as MRI contrast agents provided advantages such as improved quantum efficiency and homogeneous size distributions. It has been determined that the luminescence efficiency of quantum dots decreases in coatings that can be made at high temperatures by thermal decomposition. In order to eliminate the disadvantage of elevated temperatures, the sonochemical decomposition method, which allows coating at low temperatures, has been used. With this method, yolk-shell (CdSe/ZnS@Fe2O3) nanoparticles were produced with high photoluminescence quantum efficiency and homogeneous size distributions. The synthesis magnetic fluorescent NPs optimized was determined to have the injection temperature of Fe(CO)5 at 60 ° C, Fe(CO)5/CdSe@ZnS ratio 0.7, OAm/Fe(CO)5 volume ratio 1.43 with an oxidation time 5 min. Under these conditions, the quantum efficiency was found to be 78 %, nanoparticle sizes between 11–14 nm and r1 value was 0.199, r2 value was 0.518 in MRI analysis. These optically active magnetic fluorescent nanoparticles as positive contrast agents (T1 weighted) are predicted to pave the way for the future of advanced bio-imaging systems. © 2022 Wiley-VCH GmbH.