Scopus İndeksli Yayınlar Koleksiyonu

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Now showing 1 - 6 of 6
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Rec. 2100 Color Gamut Revelation Using Spectrally Ultranarrow Emitters
    (SPIE - Society of Photo-Optical Instrumentation Engineers, 2017-11-22) Genc, Sinan; Uguz, Mustafa; Yilmaz, Osman; Mutlugun, Evren
    We theoretically simulate the performance of ultranarrow emitters for the first time to achieve record high coverage for the International Telecommunication Union Radiocommunication Sector BT. 2100 (Rec. 2100) and National Television System Committee (NTSC) color gamut. Our results, employing more than 130-m parameter sets, include the investigation into peak emission wavelength and full width at half maximum (FWHM) values for three primaries that show ultranarrow emitters, i.e., nanoplatelets are potentially promising materials to fully cover the Rec. 2100 color gamut. Using ultranarrow emitters having FWHM as low as 6 nm can provide the ability to attain 99.7% coverage area of the Rec. 2100 color gamut as well as increasing the NTSC triangle to 133.7% with full coverage. The parameter set that provides possibility to fully reach Rec. 2100 also has been shown to match with D65 white light by making use of the correct combination of those three primaries. Furthermore, we investigate the effect of the fourth color component on the CIE 1931 color space without sacrificing the achieved coverage percentages. The investigation into the fourth color component, cyan, is shown for the first time to enhance the Rec. 2100 gamut area to 127.7% with 99.9% coverage. The fourth color component also provides an NTSC coverage ratio of 171.5%. The investigation into the potential of emitters with ultranarrow emission bandwidth holds great promise for future display applications. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
  • Article
    Citation - WoS: 6
    Citation - Scopus: 9
    Impact of Red Emissive Zncdtes Quantum Dots on the Electro-Optic Switching, Dielectric and Electrochemical Features of Nematic Liquid Crystal: Towards Tunable Optoelectronic Systems
    (Elsevier, 2023-06) Seidalilir, Zahra; Shishehbor, Sepideh; Soheyli, Ehsan; Sabaeian, Mohammad
    In the present study, the concentration-dependent dielectric, electro-optical, and electrochemical properties of ZnCdTeS quantum dots (QDs) doped E7 nematic liquid crystal (NLC) mixtures were investigated. The dielectric permittivity components (epsilon(parallel to) and epsilon(perpendicular to)) and dielectric anisotropy (Delta epsilon -epsilon(parallel to) - epsilon perpendicular to.) of NLC samples containing varied concentrations of ZnCdTeS QDs (i. e. 0.10, 0.25, 0.50, 0.75, and 1 wt%) were measured at various temperatures. In the nematic phase, the results demonstrated that e. increases much more than epsilon(perpendicular to) upon an increase in the concentration of ZnCdTeS QDs. Delta epsilon enhanced as the concentration of QDs increased, reaching a maximum at 0.50 wt%, then decreased with further addition. Dielectric measurements revealed the formation of self-aligned QD arrays along the nematic director, which act similarly to multiple parallel capacitors in the NLC system. Moreover, electro-optical studies illustrated the significant effect of QDs doping on lowering the threshold voltage and response time. Interestingly, the optical switching-off time of NLC containing 0.50 wt% of the QDs decreased by similar to 50% compared to that of the pure E7 sample. The reduced screening effect resulting from the QDs ioncapturing mechanism, enhanced effective intermolecular interactions, and increased dielectric anisotropy in the NLC system are the major factors responsible for the improved electro-optical characteristics. The impedance behavior of NLC cells was studied in the frequency range of 0.1 Hz-100 kHz. It indicated that the addition of ZnCdTeS QDs results in a remarkable increase of 96% in the electrical conductivity of the NLC system. Furthermore, the QDs doping significantly improved the NLC device's charge capacitance. Such studies would undoubtedly be beneficial for designing next-generation tunable optoelectronic systems since QDs can be utilized for tuning the dielectric anisotropy, electro-optical characteristics, charge capacitance, and conductivity of NLCs.
  • Article
    Citation - WoS: 63
    Citation - Scopus: 64
    Effective Neural Photostimulation Using Indium-Based Type-II Quantum Dots
    (Amer Chemical Soc, 2018-07-18) Jalali, Houman Bahmani; Aria, Mohammad Mohammadi; Dikbas, Ugur Meric; Sadeghi, Sadra; Kumar, Baskaran Ganesh; Sahin, Mehmet; Nizamoglu, Sedat; Ganesh Kumar, Baskaran; Bahmani Jalali, Houman; Mohammadi Aria, Mohammad
    Light-induced stimulation of neurons via photoactive surfaces offers rich opportunities for the development of therapeutic methods and high-resolution retinal prosthetic devices. Quantum dots serve as an attractive building block for such surfaces, as they can be easily functionalized to match the biocompatibility and charge transport requirements of cell stimulation. Although indium based colloidal quantum dots with type-I band alignment have attracted significant attention as a nontoxic alternative to cadmium-based ones, little attention has been paid to their photovoltaic potential as type-II heterostructures. Herein, we demonstrate type-II indium phosphide/zinc oxide core/shell quantum dots that are incorporated into a photoelectrode structure for neural photostimulation. This induces a hyperpolarizing bioelectrical current that triggers the firing of a single neural cell at 4 mu W mm(-2), 26-fold lower than the ocular safety limit for continuous exposure to visible light. These findings show that nanomaterials can induce a biocompatible and effective biological junction and can introduce a route in the use of quantum dots in photoelectrode architectures for artificial retinal prostheses.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Effect of a Buffer Layer Between the Shell and Ligand on the Optical Properties of an Exciton and Biexciton in Type-II Quantum Dot Nanocrystals
    (Taylor & Francis Ltd, 2016-11-09) Koc, Fatih; Koksal, Koray; Sahin, Mehmet
    In this study, we have investigated the effect of the buffer layers on the electronic and optical properties of an exciton (X) and a biexciton (XX) in a type-II CdTe/CdSe quantum dot nanocrystal. In an experimental study, it has been reported that when a CdTe/CdSe quantum dot nanocrystal is coated by a ZnTe material as a buffer layer, the photoluminescence quantum yield is growing from 4 to 20%. We have confirmed theoretically this improvement and extended the calculations to an XX structure. In the calculations, two different semiconductor materials, CdS and ZnTe, have been considered for the buffer layer. We have theoretically shown that the buffer layer causes an increase in the radiative oscillator strength of both X and XX. When the ZnTe is used as the buffer layer, the oscillator strength becomes stronger when compared to CdSe buffer material because of higher conduction band offset between CdSe and ZnTe.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 23
    Antibacterial Type-II InP/ZnO Quantum Dots Via Multimodal Reactive Oxygen Species
    (Elsevier Science SA, 2024-01) Khan, Saad Ullah; Eren, Guncem Ozgun; Atac, Nazli; Onal, Asim; Qureshi, Mohammad Haroon; Cooper, Francis Korshe; Nizamoglu, Sedat
    The emergence of multidrug-resistant bacteria as a global health threat has necessitated the exploration of alternative treatments to combat bacterial infections. Among these, photocatalytic nanomaterials such as quantum dots (QDs) have shown great promise and type-I QDs have been investigated thus far. In this study, we introduce type-II InP/ZnO core/shell QDs that are ligand-exchanged with a short-chain inorganic sulfide ion (S2-) for antibacterial activity. Interestingly, InP/ZnO QDs simultaneously generate reactive oxygen species (ROS) including hydroxyl (center dot OH) and superoxide (O-2(center dot-) ) radicals, while only O-2(center dot-) radicals can be released by the type-I sulfide-capped InP/ZnS QDs. The optimized nanostructure achieved effective inhibition of Pseudomonas aeruginosa and Escherichia coli bacteria growth to the level of 99.99% and 70.31% under low-intensity green light illumination of 5 mW.cm(-2). Our findings highlight the importance of type-II QDs as a new avenue for developing effective antibacterial agents against drug-resistant pathogens.
  • Article
    Citation - WoS: 56
    Citation - Scopus: 61
    A Detailed Investigation of the Electronic Properties of a Multi-Layer Spherical Quantum Dot With a Parabolic Confinement
    (Elsevier Science Bv, 2012-07) Akgul, Selcuk; Sahin, Mehmet; Koksal, Koray
    In this work, we aim a detailed investigation of the electronic properties of a spherical multi-layer quantum dot with and without a hydrogenic impurity. The structure is introduced in the form of core/shell/well/shell layers. The core and well layers are defined by the parabolic electronic potentials. We carry out the effect of the core radius and layer thickness on the energy levels, their wave functions, binding energies of the impurity and the probability distributions. In order to determine the sublevel eigenvalues and eigenfunctions, the Schrodinger equation is solved full numerically by shooting method in the frame of the effective mass approximation. The results are analyzed in detail as a function of the layer thicknesses and their probable physical reasons are tried to be explained. It is found that the electronic properties and impurity binding energies are strongly depending on the layer thicknesses. (C) 2012 Elsevier B.V. All rights reserved.