Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 4Soluble Cytotoxic Ruthenium(ii) Complexes With 2-Hydrazinopyridine(Pleiades Publishing, 2019) Soliman, A. A.; Attaby, F. A.; Alajrawy, O., I; Majeed, S. R.; Şahin, C.; Varlıklı, CananNew water soluble Ru(II) binary complex [Ru(C5H7N3)(X)(H2O)(2)] with 2-hydrazinopyridine and its ternary complexes with X = dichloride, oxalate, malonate or pyrophosphate ligands have been synthesized. The complexes have been characterized using elemental analyses, mass, IR, and UV-Vis. spectroscopies, cyclic voltammetry, magnetic susceptibility, and thermal analysis. The complexes are diamagnetic and the electronic spectral data showed that peaks are due to low spin octahedral Ru(II) complexes. The optimized structures of the complexes 1-4 indicate distorted octahedral geometry with bond angles around the ruthenium atom ranged from 80.44 degrees to 99.64 degrees. The values of the electronic energies (-635 to -1145 a.u.), the highest occupied molecular orbital energies (-0.181 to 0.073 a.u.) and lowest unoccupied molecular orbital energies (-0.056 to 0.167 a.u.) indicate the stability of the complexes. The complexes are polarized as indicated from the dipole moment values (9.39-14.27 Debye). The complexes have noticeable cytotoxicity with IC50 (mu M): 0.011-0.062 (HepG-2), 0.015-0.080 (MCF-7), 0.015-0.116 (HCT-116), and PC-3 (0.034-0.125).Article Citation - WoS: 28Citation - Scopus: 29Enhancing the Efficiency of Mixed Halide Mesoporous Perovskite Solar Cells by Introducing Amine Modified Graphene Oxide Buffer Layer(Elsevier, 2020) Şahin, Çiğdem; Diker, Halide; Sygkridou, Dimitra; Varlıklı, Canan; Stathatos, EliasIn this study, graphene oxide (GO) was synthesized via Tour method and then modified with two different amine sources that contained different branched alkyl chains. The GO and modified GOs (mGOs) with dihexylamine (DHA) and 2-ethylhexylamine (2EHA) as amine sources were used respectively as buffer layers in mixed halide mesoporous perovskite solar cells (PSCs) in order to examine whether they could improve their performance. GO and mGO samples were characterized by several techniques such as X-Ray Diffraction, X-Ray photoelectron spectroscopy (XPS), Raman analysis and thermal gravimetric analysis (TGA). The preparation of the CH3NH3PbI3-xClx perovskite solution was performed using standard Schlenk techniques under argon atmosphere to attain a homogeneous coverage of the perovskite film. The solar cells with the additional layer of mGO derivatives between perovskite and hole transporting layer showed an improved overall performance compared to the reference devices which was attributed to the enhanced charge carrier transport via the mGOs. In particular, 10% increase to the overall performance of the solar cells was monitored in devices where 2-ethylhexylamine (2EHA) modified GO was used, compared to standard cell without buffer layer. (C) 2019 Elsevier Ltd. All rights reserved.Article Citation - WoS: 30Citation - Scopus: 32Perylene-Embedded Electrospun Ps Fibers for White Light Generation(Elsevier Ltd., 2019) Güner, Tuğrul; Aksoy, Erkan; Demir, Mustafa Muammer; Varlıklı, CananPerylene dyes have been employed in the fabrication of white light due to their superior photophysical properties and relatively easy synthetic methods. However, their molecular aggregation in solid state is one of the main handicaps since it causes deviation in their optical properties and quenches photoluminescence quantum yields (Phi(f)). Investigation of the photophysical properties of a green (PTE), a yellow (PDI) and a new red (DiPhAPDI) emitting perylene derivative in solution, drop-casted films, polystyrene (PS) fibers and PS fibers embedded in poly (dimethyl siloxane) (PDMS) showed that PS:dye fibers prevent aggregation to some extend and allows high Of of dyes. The Of values of PTE, PDI and DiPhAPDI were all higher than 93.0% in solution and 84.8%, 94.3% and 73.6%, respectively in PS:dye fibers. Embedding the fibers in PDMS improved the photostabilities of the dyes two folds compared to their solution phases. The prepared dye containing fibers were combined together into a single PDMS film and utilized as a frequency conversion layer on a blue LED. Fabricated samples were found to show high color rendering index (>= 90), adjustable CCT (7500 K-5000 K), and power efficiency values exceeding 2001m/W depending on the used fiber amount in mass.Article Citation - WoS: 11Citation - Scopus: 11Structural Stability of Physisorbed Air-Oxidized Decanethiols on Au(111)(American Chemical Society, 2020) Kabanoy, Nikolai; Tsvetanova, Martina; Klaysyuk, Andrey L.; Zandvliet, Harold J. W.; Sotthewes, Kai; Kap, Özlem; Varlıklı, CananWe have studied the dynamic behavior of decanethiol and air-oxidized decanethiol self-assembled monolayers (SAMs) on Au(111) using time-resolved scanning tunneling microscopy at room temperature. The air-oxidized decanethiols arrange in a lamellae-like structure leaving the herringbone reconstruction of the Au(111) surface intact, indicating a rather weak interaction between the molecules and the surface. Successive STM images show that the air-oxidized molecules are structurally more stable as compared to the nonoxidized decanethiol molecules. This is further confirmed by performing current-time traces with the feedback loop disabled at different locations and at different molecular phases. Density function theory calculations reveal that the diffusion barrier of the physisorbed oxidized decanethiol molecule on Au(111) is about 100 meV higher than the diffusion barrier of a chemisorbed Au-decanethiol complex on Au(111). A two-dimensional activity map of individual current-time traces performed on the air-oxidized decanethiol phase reveals that all the dynamic events take place within the vacancy lines between the air-oxidized decanethiols. These results reveal that the oxidation of thiols provides a pathway to produce more robust and stable self-assembled monolayers at ambient conditions.Article Citation - WoS: 29Citation - Scopus: 32Enhanced Capacitive Behaviour of Graphene Based Electrochemical Double Layer Capacitors by Etheric Substitution on Ionic Liquids(Elsevier, 2020) Siyahjani, Shirin; Öner, Saliha; Diker, Halide; Gültekin, Burak; Varlıklı, CananIn this study, we report the effect of etheric substituents in imidazolium and ammonium based ionic liquids (IL) on the performance of electrochemical double layer capacitors (EDLC) consisted of gel polymer electrolyte (GPE) and reduced graphene oxide (RGO) electrode. GPEs contain poly (vinylidene fluoride-hexafluompropylene) (PVDF-HFP) and the ILs. Ammonium and imidazolium based ionic liquids (ILs) differ by their length of etheric groups and etheric group contents, respectively. According to the cyclic voltammetry, galvanostatic chargedischarge and electrochemical impedance spectroscopy measurements, longer etheric group substituted {N-methyl-2- (2-methoxyethoxy)-N,N-bis [2- (2-methoxyethoxy)ethyl] ethan-1-aminium bis(tri-fluoromethanesulfonyl)imide (AMEt-TFSI) and ether substituted (3-allyl-1-[2-(2-methoxyethoxy)ethyl]-1H-imidazole-3-ium bis(trifluommethanesulfonyeimide (AL3IL-TFSI), tender specific capacitances of 250 Fg(-1) and 238 Fg(-1) and energy density values of 61.36 wh kg(-1) and 61.56 wh kg(-1), respectively.Conference Object Citation - WoS: 3Citation - Scopus: 2Fabrication and Characterization of a Solution Processed Flexible Thermal Sensor by Using Chemically Synthesized Go and Rgo(Institute of Electrical and Electronics Engineers Inc., 2019) Bozkurt, Hakan; Diker, Halide; Varlıklı, CananGraphene oxide (GO) was reduced by ascorbic acid which is an environmental-friendly reductant and obtained sample was named as reduced GO (rGO). Stable dispersions of GO and rGO were prepared in N,N-Dimethylformamide (DMF). Compared to GO sample, rGO was determined to have more thermal stability, smaller sheet size and lower surface energy. GO and rGO dispersions were drop-casted on aluminum (Al) coated acetate substrate and used as thermal sensor. Fabricated sensors were tested from 25 °C to 150 °C. The sensors fabricated with GO, were not stabile against driven temperature changes. However, rGO ones, presented no thermal hysteresis effect after the first heating step. This sensor (Al/rGO/Al) acted like an NTC (Negative Temperature Coefficient) thermistor. The resistance of the rGO sensor was changed between 42 k? to 25 k? depending on the test temperature range (25 °C to 150 °C). Average beta value was calculated as 519.7649 K. © 2019 IEEE.Article Citation - WoS: 7Citation - Scopus: 7Synthesis, Photophysical and Electrochemical Properties of Novel Carbazole-Triazine Based High Triplet Energy, Solution-Processable Materials(Elsevier, 2018) Öner, Saliha; Aydemir, Murat; Yeşil, Fatih; Şahin, Çiğdem; Varlıklı, CananA series of molecules; tBuCz1SiTrz, tBuCz2SiTrz and tBuCz3SiTrz, which contain carbazole unit as hole-transporting group (donor-D) and triazine unit as electron transporting group (acceptor-A) were synthesized and characterized as high-triplet energy (>2.9 eV), solution-processable bipolar emitting materials. The conjugation between the D-A groups was interrupted by using bulky tetraphenylsilane groups as spacer aiming to obtain large bandgap and high-triplet energy. The photophysical behaviors of the molecules were investigated by UV-Vis absorption, photoluminescence, phosphorescence, photoluminescence quantum yield and lifetime measurements. Solvent polarity effects were investigated on the intramolecular charge transfer (ICT) behaviour and large solvatochromic effect was observed with the increasing solvent polarity. Electrochemical properties were determined by cyclic voltammetry. All molecules showed oxidation bands arise from the carbazole groups. Reduction bands were originated from the triazine groups and the intramolecular charge transfer between D-A groups. Photophysical, electrochemical and computational characterizations addressed that tBuCz2SiTrz has the weakest ICT character, highest photoluminescence quantum yield (PLQY) and charge balance.Article Citation - WoS: 31Citation - Scopus: 34Highly Efficient Supercapacitor Using Single-Walled Carbon Nanotube Electrodes and Ionic Liquid Incorporated Solid Gel Electrolyte(SAGE Publications, 2018) Siyahjani, Shirin; Öner, Saliha; Singh, Pramod K.; Varlıklı, CananGel polymer electrolyte (GPE) comprising a low viscosity ionic liquid, that is, 1-propyl-3-methyl imidazolium bis(trifluoromethyl sulfonyl)imide (PMI-TFSI, viscosity 38 cP at 20°C) and a polymer, that is, polyvinyl alcohol (PVA) have been prepared using solution cast technique and characterized by impedance spectroscopy, X-ray diffraction, differential scanning calorimetry, optical microscopy, and Fourier transform infrared spectroscopy. Blending PMI-TFSI with PVA matrix hindered the crystallinity of polymer matrix and presented remarkable enhancement in electrical conductivity with a conductivity maxima at 250 wt% PMI-TFSI. The prepared electric double-layer capacitor using single-walled carbon nanotube as symmetric electrodes and PVA:250 wt% PMI-TFSI as GPE presented a capacitance value of about 28 F g−Article Citation - WoS: 28Citation - Scopus: 30P3HT-graphene bilayer electrode for Schottky junction photodetectors(IOP Publishing Ltd., 2018) Aydın, Hasan; Kalkan, Sırrı Batuhan; Varlıklı, Canan; Çelebi, CemWe have investigated the effect of a poly (3-hexylthiophene-2.5-diyl)(P3HT)-graphene bilayer electrode on the photoresponsivity characteristics of Si-based Schottky photodetectors. P3HT, which is known to be an electron donor and absorb light in the visible spectrum, was placed on CVD grown graphene by dip-coating method. The results of the UV-vis and Raman spectroscopy measurements have been evaluated to confirm the optical and electronic modification of graphene by the P3HT thin film. Current-voltage measurements of graphene/Si and P3HT-graphene/Si revealed rectification behavior confirming a Schottky junction formation at the graphene/Si interface. Time-resolved photocurrent spectroscopy measurements showed the devices had excellent durability and a fast response speed. We found that the maximum spectral photoresponsivity of the P3HT-graphene/Si photodetector increased more than three orders of magnitude compared to that of the bare graphene/Si photodetector. The observed increment in the photoresponsivity of the P3HT-graphene/Si samples was attributed to the charge transfer doping from P3HT to graphene within the spectral range between near-ultraviolet and near-infrared. Furthermore, the P3HT-graphene electrode was found to improve the specific detectivity and noise equivalent power of graphene/Si photodetectors. The obtained results showed that the P3HT-graphene bilayer electrodes significantly improved the photoresponsivity characteristics of our samples and thus can be used as a functional component in Si-based optoelectronic device applications.Conference Object Citation - WoS: 9Citation - Scopus: 11White Led Light Production Using Dibromoperylene Derivatives in Down Conversion of Energy(Canadian Science Publishing, 2018) Aksoy, Erkan; Demir, Nuriye; Varlıklı, CananPerylene derivatives of N,N′-bis(2,6-diisopropylphenyl)-1,6(7)-dibromoperylene-3,4,9,10-tetracarboxylic diimide (DBrPDI) and 1,7-dibromo perylene-3,4,9,10-tetracarboxylic acid butyl ester (DBrPTE) were synthesized, and their structural and optical characterizations were explored. Both DBrPDI and DBrPTE, which were utilized as wavelength converters on a GaN/InGaN based blue LED, were singlet sensitizers and had molar absorptivity constants around 104 Lmol-1cm-1. The blue LED that was used had Commission internationale de l'eclairage (CIE) coordinates of x, y = 0.13, 0.06; power and luminous efficiencies of 2.7 lm/W and 6.6 cd/A @5 mA, respectively. Because the fluorescence quantum yield of DBrPDI was much higher than that of DBrPTE, a meaningful white light efficiency was obtained with the diimide derivative. The use of DBrPDI resulted in white light with CIE coordinates of x, y = 0.34, 0.29 and luminous efficiency of 6.35 cd/A @5 mA, respectively. Using DBrPDI in a resin matrix resulted in more than three orders of magnitude increase in the luminous efficiency value (23.0 cd/A @5 mA) while the CIE coordinates remained the same. Whenever the applied current reached 20 mA, a CRI value of Ra = 90 was obtained.