Scopus İndeksli Yayınlar Koleksiyonu

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Π-Conjugated Donor-Acceptor Small Molecule Thin-Films on Gold Electrodes for Reducing the Metal Work-Function
    (Elsevier Science SA, 2016-10) Azum, Naved; Taib, Layla Ahmad; Al Angari, Yasser Mohammed; Asiri, Abdullah M.; Denti, Mitchel; Zhao, Wei; Facchetti, Antonio
    This paper reports the design, facile synthesis and purification of four pi-conjugated donor-acceptor small molecules comprising heteroaromatic units, DA-1-DA-4, for surface and electronic structure modification of gold thin film. These molecules were characterized by H-1/C-13 nuclear magnetic resonance spectroscopy, cyclic voltammetry, UV-Vis spectroscopy, and single-crystal X-ray diffraction. Morphologically smooth thin-films (similar to 5 nm) of DA-1-DA-4 were deposited onto Au thin films via thermal evaporation and characterized by atomic force microscopy, theta-2 theta X-ray diffraction and ultraviolet photoelectron spectroscopy. The work functions of the small molecule coated Au electrodes are shifted to lower energies by similar to 0.1-03 eV, compared to that of the bare Au film measured as a reference. The vapor-deposition of structurally,simple small molecules developed here shows great promise as a facile approach to reduce gold work function for electron injection/extraction between organic semiconductors and Au contacts in various opto-electronic devices. (C) 2016 Elsevier B.V. All tights reserved.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 11
    Trans-Cis Isomerization Assisted Synthesis of Solution-Processable Yellow Fluorescent Maleic Anhydrides for White-Light Generation
    (Elsevier Science SA, 2015-12) Ozdemir, Mehmet; Genc, Sinan; Ozdemir, Resul; Altintas, Yemliha; Citir, Murat; Sen, Unal; Usta, Hakan
    Heterocyclic maleic anhydride derivatives have been extensively studied in natural products chemistry over the past few decades. However, their incorporation into optoelectronic devices has lagged behind that of other pi-conjugated systems, and they have never been studied in white light emitting diodes (WLEDs). The development of emissive pi-conjugated materials for (WLEDs) has been an emerging scientific and technological research area to replace phosphors used in LED-based solid-state lighting. Here, we demonstrate the design, synthesis and characterization of two new highly emissive alkyl-substituted bis(thienyl)maleic anhydrides (C6-Th2MA and C12-Th2MA) with favorable photophysical properties. The new core is synthesized via a novel trans-to-cis isomerization-assisted one-pot reaction, which is demonstrated for the first time in the literature for the synthesis of a bis(heteroaryl)maleic anhydride. Due to its favorable absorption and fluorescence properties in the blue and yellow region of the visible spectrum, respectively, C12-Th2MA is studied as a potential wavelength-upconverting material. A WLED fabricated by drop-casting a polymeric solution of C12-Th2MA on a blue LED (InGaN, 455 nm) yields promising CIE coordinates and color-rendering index (CRI) values of (0.24, 0.20) and 65.0, respectively. Considering the simplicity of the current molecular structure and facile synthesis, alkyl-substituted bis(thienyl)maleic anhydrides stand as ideal phosphor alternatives. Therefore, the current findings may open new perspectives for the development of maleic anhydride-based small molecules for low-cost, energy-efficient, and solution-processed lighting technologies. (C) 2015 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 14
    The Effect of Ligand Chain Length on the Optical Properties of Alloyed Core-Shell InPZnS/ZnS Quantum Dots
    (Elsevier Science SA, 2017-07) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, Evren
    In this work, we demonstrate the effect of organic ligands on the optical properties of alloyed core-shell InPZnS/ZnS quantum dots (QDs). We have systematically studied the synthesis and characterization of InPZnS/ZnS QDs using short and long chain length ligands i.e., butyric (C4), hexanoic (C6), octanoic (C8), dodecanoic (C12), myristic (C14), palmitic (C16) and stearic acids (C18), respectively. This study achieved more than 85% quantum yield with 43 nm full-width-half maximum value, using dodecanoic acid as the capping ligand. The properties of the QDs with short and long chain length ligands have been analyzed using UV Vis absorption spectrophotometer, steady state and time resolved photoluminescence spectrometer, X-ray diffraction, Zeta sizer, transmission electron microscopy and energy dispersive X-ray spectroscopy. (C) 2017 Published by Elsevier B.V.
  • Article
    Citation - WoS: 54
    Citation - Scopus: 61
    Synthesis, Cytotoxic and Antimicrobial Activities of Novel Cobalt and ZINC Complexes of Benzimidazole Derivatives
    (Elsevier Science SA, 2017-01) Apohan, Elif; Yilmaz, Ulku; Yilmaz, Ozgur; Serindag, Ayfer; Kucukbay, Hasan; Yesilada, Ozfer; Baran, Yusuf
    In this study fourteen novel cobalt (II) or zinc (II) complexes of benzimidazoles were synthesized from the 1-(4-substitutedbenzyl)-1H-benzimidazoles and CoCl2.6H(2)O or ZnCl2. Cytotoxic activities of novel complexes were investigated against lung cancer cells (A549) and BEAS-2B. Three of the examined compounds (1, 4 and 5) showed high cytotoxic activity against A549. While the IC50 of the cisplatin was 2.56 pg/mL for A549 cells at 72 h, the IC50 values of compounds 1, 4 and 5 were 1.97, 1.87 and 1.9 mu g/mL, respectively. IC50 values of these compounds for BEAS-2B cells were higher than the IC50 values for A549. While the IC50 values for BEAS-2B cells were 59.8, 24.5 and 32.67 mu g/mL, respectively, the IC50 of the cisplatin was determined as 2.53 pgimL in the present work. Three of the compounds have also high antimicrobial activity against all the microorganisms used. (C) 2016 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 9
    Citation - Scopus: 11
    Size, Material Type, and Concentration Estimation for Micro-Particles in Liquid Samples
    (Elsevier Science SA, 2024-05) Genc, Sinan; Erdem, Talha; Icoz, Kutay
    The on -site examination and characterization of microparticles are becoming crucial due to the significant rise in plastic pollution in natural resources. Hence, identifying the specific microplastic composition and quantity would enable the implementation of preventive measures. This paper presents a cost-effective setup that utilizes the Random Forest algorithm to detect the size and refractive index of micro particles, hence facilitating the identification of the material type. The system utilizes the scattering patterns of laser light from the dispersion of microparticles, namely within the concentration range of 0.05 fM to 3.00 fM. The refractive indices and particle sizes of melamine (Me8) spheres with a size of 8 mu m, as well as polystyrene (PS8) spheres with a size of 8 mu m and (PS10) 10 mu m, were estimated using the Random Forest algorithm and recorded scattering patterns. The proposed method may deliver findings with an average deviation of 0.23 mu m for particle size and 0.015 for particle refractive index. The statistical analysis indicated that there was no notable disparity between the experimental findings and the predictions derived from the machine learning system. The existing configuration can be readily converted into a point -of -use system that can be employed on -site for the purpose of monitoring and identifying microplastic contamination.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Robust Reactivity, Neutron Source, and Precursor Estimators for Nuclear Reactors
    (Elsevier Science SA, 2013-12) Ablay, Gunyaz
    Reactivity, precursor concentration, and external neutron source strength determine control, operation and performance of nuclear reactors. These main reactor quantities are not directly measurable and must be calculated or estimated using reactor kinetics. This study presents efficient and robust nonlinear estimation algorithms for predicting these fundamental reactor quantities. The effectiveness of the proposed estimators is assessed through chirp and step test signals in the presence of parameter uncertainties and measurement noise. (C) 2013 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 18
    Citation - Scopus: 20
    Respiration Monitoring Using a Paper-Based Wearable Humidity Sensor, a Step Forward to Clinical Tests
    (Elsevier Science SA, 2023-06) Solak, Irfan; Gencer, Serife; Yildirim, Beyza; Oznur, Emine; Hah, Dooyoung; Icoz, Kutay
    Monitoring respiratory variables can provide valuable information for clinical applications and sport activities. Paper-based wearable respiration monitoring systems have great advantages and potential, they are low-cost, easily disposable, non-invasive and can provide real-time, reliable data. Despite some examples presented for exhaled breath analysis using paper-based sensors exist, none of them have been validated yet in a study involving many patients. In this work, we present a novel paper-based platform for exhaled breath sensors and validate it on 101 subjects including 41 patients to demonstrate its clinical applicability. By using the paperbased wearable capacitive sensors, we collected respiration data from different groups of people, namely, smokers, non-smokers and patients diagnosed with pneumonia, or chronic obstructive pulmonary disease (COPD). The change in humidity during inhale and exhale was converted to capacitance change and thus an electrical signal was obtained. The electrical signal was transmitted to a nearby computer and capacitance versus time data was post-processed. Four ratio parameters were defined on the recorded data; area, rate, maximum amplitude, and average maximum-minimum difference, all of which were compared between deep breathing and normal breathing. The collected data was statistically analyzed, and the humidity changes were compared among different groups. The results show that the developed sensor and the proposed analysis method can be used to detect the humidity changes in breathing, and to differentiate between smokers and non-smokers, and between non-smokers and patients with pulmonary disease.
  • Article
    Citation - WoS: 29
    Citation - Scopus: 31
    Pressure-Induced Amorphization, Mechanical and Electronic Properties of Zeolitic Imidazolate Framework (ZIF-8)
    (Elsevier Science SA, 2020-01) Erkartal, Mustafa; Durandurdu, Murat
    Ab initio molecular dynamics (AIMD) simulations are carried out to probe the high-pressure behavior of ZIF-8 over wide pressure-range. Under compression, the enormous distortions in the ZnN4 tetrahedral units lead to a crystal-to-amorphous phase transition at around 3 GPa. During the amorphization process, the Zn-N coordination is retained. No other phase change but a possible fracture of the system is proposed above 10 GPa. Depending on released pressures, amorphous states with different densities are recovered. Yet when the applied pressure is released just before the amorphization, the rotations of imidazolate linkers (swing effect) cause an isostructural crystal-to-crystal phase transition, in agreement with experiments. In the tensile regime, no phase transition is perceived up to -2.75 GPa at which point the structural failure is observed. The crystal-amorphous phase transitions are also discovered at around 4 GPa under uniaxial compressions. The amorphous structures formed under uniaxial stress are about 20% denser than the one formed under the hydrostatic pressure. The average Young's modulus and Poisson's ratio of ZIF-8 are estimated to be around 5.6 GPa and 0.4, respectively. Interestingly, the tensile strength of ZIF-8 is found to be about 50% greater than its compressive strength. This paper shows that the experimentally observed phase transitions can be successfully reproduced with a clear explanation about the transition mechanism(s) at the atomistic level and all mechanical properties can be accurately calculated for a given ZIF structure by using AIMD simulations.
  • Article
    Citation - WoS: 23
    Citation - Scopus: 25
    Preparation of Highly Emissive and Reproducible Cu-In-S/ZnS Core/Shell Quantum Dots With a Mid-Gap Emission Character
    (Elsevier Science SA, 2020-05) Jawhar, Nawzad Nadhim; Soheyli, Ehsan; Yazici, Ahmet Faruk; Mutlugun, Evren; Sahraei, Reza
    Copper indium sulfide (CIS) quantum dots (QDs) are one of the newest types of luminescent semiconductors with low-toxicity and earth-abundant features. The present work reports the successful aqueous synthesis of CIS/ZnS core/shell QDs using dual-stabilizing agents of N-acetyl-L-cysteine and trisodium citrate. Off-stoichiometric QDs with In-rich compositions were found to be very small and highly emissive after coating by a shell of wide bandgap ZnS. The effect of various experimental parameters was evaluated to achieve highly reproducible QDs with bright reddish emission. Results showed a significant contribution of mid-gap defect states in the recombination processes (based on the gradual increase in absorbance recorded for samples, relatively high Urbach energy, large Stokes shift, large FWHM value in PL spectra, as well as the long-lived PL decay time). In addition, the chemical stability of samples was investigated using highly oxidant H2O2 agent and results demonstrate their superior stability. The combination of low-toxicity, intense and stable emission, along with synthetic advantages demonstrates that the present aqueous-soluble and emissive QDs can be considered as an excellent bio-photonic structure suitable for different fields of biological imaging and diagnostics. (C) 2020 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 51
    Citation - Scopus: 51
    Multiplexed Patterning of Cesium Lead Halide Perovskite Nanocrystals by Additive Jet Printing for Efficient White Light Generation
    (Elsevier Science SA, 2020-01) Altintas, Yemliha; Torun, Ilker; Yazici, Ahmet Faruk; Beskazak, Emre; Erdem, Talha; Onses, M. Serdar; Mutlugun, Evren; Serdar Onses, M.
    Inorganic perovskite nanocrystals (PNCs) offer the ability to precisely but also flexibly control the peak emission wavelength while also possessing narrow-band emission spectra and high quantum yields. Owing to these features, PNCs have been already employed as color converters on LEDs. Nevertheless, the anion exchange reactions that prevent the blending of perovskites of different colors remain as an important bottleneck. As a remedy to this issue, here we employ additive jet printing to form separated stripes of these nanocrystals. Within this framework, we first present the synthesis of CsPbBr3 and CsPbBrxI3-x nanocrystals spanning the whole visible regime and optimize the cleaning procedure to obtain PNCs possessing photoluminescence quantum yields as high as 91% and emission linewidths as narrow as 15 nm, making them suitable for high quality white light generation. Next, we employ electrohydrodynamic jet printing to form closely spaced stripes of PNCs of various colors and integrated these films with a blue LED to create a white LED. Our proof-of-concept LED achieves high photometric performance as it possesses a color rendering index of 91.3, luminous efficacy of optical radiation > 300 lm/W-opt, and correlated color temperature of ca. 7000 K. We believe that additive jet printing technique will pave the way for a ubiquitous use of these PNCs in light-emitting devices in the near future.