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    A Novel ruthenium(II) complex-based electrode for non-enzymatic glucose sensing applications
    (Springer, 2025) Kucukoflaz Korkmaz, Merve; Dayan, Serkan; Ozdemir, Namik; Erdener, Digdem; Dayan, Osman; Cetinkaya, Bekir
    Ruthenium-based complexes demonstrate high potential in the catalysation of the electrochemical oxidation of glucose, offering high sensitivity and stability in glucose detection. In this study, a ruthenium complex (Ru1) was synthesised using 2,2 '-bipyridine-4,4 '-dicarboxylic acid (DCBpy), potassium iodide (KI) and [RuCl2(p-cymene)](2). The structural properties of Ru1 were investigated using X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and UV-vis spectroscopy analyses, which revealed its structure. The electrochemical behaviour of the Ru1 complex was systematically investigated and found to be promising for application in a glucose biosensor. Cyclic voltammetry measurements revealed an increase in electrochemical activity on the electrode surface over time, showing a steady rise at a potential of 0.32 V. This indicates high sensitivity and reliability in glucose detection. Chronoamperometric analysis showed a linear response to glucose concentrations ranging from 0.1 to 0.8 mM, demonstrating the sensor's sensitivity. These properties make the Ru1 complex a promising candidate for use in glucose detection biosensors. In conclusion, the complex's electrocatalytic activity and stability could be key to advancing biosensor technologies by enhancing sensitivity.
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    Colorimetric probe and optical behaviours of new azomethine derivatives of sulfonamide
    (Elsevier, 2022) Tekin, Sezen; Karatay, Ahmet; Erdener, Digdem; Yildiz, Elif Akhuseyin; Boyacioglu, Bahadir; Unver, Huseyin; Yıldız, Mustafa
    Syntheses, colorimetric anion probe properties, density functional theory (DFT) studies, and optical properties of the Schiffbases; 4-fluoro-N-(2-hydroxy-5-methylbenzylidene) benzenesulfonamide (1), 4fluoro-N-(2-hydroxy-5-nitrobenzylidene)benzenesulfonamide (2) and 4-fluoro-N-[(2-hydroxynaphthalen1-yl)methylene]benzenesulfonamide (3) were reported. The structure of the compounds was elucidated using MS, FTIR, and UV-visible spectroscopic techniques. Their structures were examined by theoretical calculations using density functional theory (DFT). The colorimetric response of the Schiffbase receptors in DMSO was investigated before and after the addition of an equivalent amount of each anion to evaluate the anion recognition properties. The ultrafast transient absorption spectroscopy measurements were performed to investigate the energy transfer dynamics and decay kinetics of the compounds 1-3. The fluorescence and wavelength-dependent pump-probe measurements of the compounds showed that the excited state lifetime of compound 2 is shorter than compounds 1 and 3. The fluorescence properties of compounds 1-3 were compatible with the pump-probe spectroscopy measurements. The compounds with longer ESA lifetimes showed higher fluorescence. (c) 2021 Published by Elsevier B.V.
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    Colorimetric probing and fluorescent chemosensor features of functionalized sulphonamide-azomethine derivatives
    (Elsevier Science Sa, 2022) Yildiz, Elif Akhuseyin; Erdener, Digdem; Tekin, Sezen; Karatay, Ahmet; Boyacioglu, Bahadir; Unver, Huseyin; Yıldız, Mustafa
    In this work, we have experimentally synthesized bromosulfonamide-based azomethine compounds through the reaction of 4-bromobenzenesulfonamide with 2-hydroxy-5-iodobenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, and 2-hydroxy-l-naphthaldehyde. We have also characterized the molecular structure of the investigated compounds with MS, H-1 NMR, FTIR and UV-vis spectra. Theoretically, using DFT and TD-DFT methods, we computed frontier molecular orbitals (FMOs) energies and UV-vis spectra as well. We have also obtained the electron localization function (ELF) maps to identify electrophilic substitution sites in the molecules and density of states (DOS) diagrams to show the composition of the fragment orbitals that contribute to the molecular orbitals. We have investigated steady-state absorption, emission features, and excited state dynamics to better understand the photophysical process of bromosulfonamide-based azomethines. It has been demonstrated that by adding a naphthalene unit, the absorption properties of azomethine into two branches. Besides, azomethine, including heavy iodo atoms, presents a slight decrement in the fluorescence intensity. According to thorough calculations of charge transfer dynamics using femtosecond transient absorption spectra, the bromosulfonamidebased azomethines with iodo atoms and incorporating naphthalene units exhibit an intersystem crossing mechanism following photoexcitation. The colorimetric response of the compounds in DMSO to the addition of the equivalent amount of anions (F- , Br- , I-, CN-, SCN-, ClO4-, HSO4-, AcO-, H2PO4- , N-3(-) and OH-) was investigated. In this regard, while the addition of F- ,CN- ,AcO- , H2PO4- and OH(- )anions into the solution containing the compounds resulted in a significant color change, the addition of Br-, I-, SCN-, ClO4- HSO4- and N-3 anions resulted in no color change.
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    Design, Synthesis, and Optoelectronic Characterization of a Novel Cu(II) Complex-Based Photodiode with Prof. Dr. Yakuphanoglu's Advanced Fytronix Solar Simulator Characterization Techniques
    (Pergamon-Elsevier Science Ltd, 2026) Dere, Aysegul; Erdener, Digdem; Yalcin, Mesut; Ozdemir, Namik; Dayan, Osman; Mansour, Shehab; Yakuphanoglu, Fahrettin
    In this study, a Cu(II) complex, [CuLCl2], containing pyridine-2,6-dicarboxamide (L) and two chloro ligands was synthesized from the reaction of CuCl2 & sdot;.2H2O with pyridine-2,6-dicarboxamide in methanol and characterized for optoelectronic applications. X-ray crystallography confirmed the monoclinic structure of the complex and the presence of a square pyramidal geometry around the Cu(II) ion. Further characterization was performed using FT-IR spectroscopy, mass spectrometry, and electrochemical analysis. Additionally, the photonic device was fabricated by incorporating the Cu(II) complex as a layer on a p-type silicon substrate. The electrical and optical properties of the device were investigated at different illumination intensities. The current-voltage (I-V) characteristics indicate that the photodiode generates significant photocurrent under illumination. The device exhibited a stable and rapid photoresponse. The responsivity (R) and detectability (D*) values of the photodiode were measured as 2.9 mA/W and 1.95 x 1013 Jones, respectively, at an illumination intensity of 80 mW/cm2. Time-dependent photo-response and detection analyses demonstrated the stability of the diode under light on-off cycles.
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    Naked-eye colorimetric anion probing and fluorescent switching features of conjugated Schiff Bases derived from 4-(Trifluoromethyl) benzenesulfonamide
    (Elsevier, 2022) Yildiz, Elif Akhuseyin; Tekin, Sezen; Erdener, Digdem; Karatay, Ahmet; Boyacioglu, Bahadir; Unver, Huseyin; Yıldız, Mustafa
    In this work, synthesis, spectroscopic, density functional theory (DFT) and photophysical studies of the three conjugated benzenesulfonamide Schiff bases were reported. We also calculated the energies of the frontier molecular orbitals (FMOs) and UV-Vis spectra of Schiff bases theoretically using the DFT and TD-DFT methods. Additionally, photophysical properties were investigated by UV-Vis and fluorescence spectroscopy techniques. The ground state interactions show that the absorption band has been separated into two branches and bathochromatically tuned to the visible region, and fluorescence intensity decreased in the case of the Schiff base incorporated naphthalene unit. Furthermore, the charge transfer dynamics of the compounds were analyzed using femtosecond transient absorption spectroscopy measurements proving the triplet-triplet transitions via intersystem crossing mechanism. Based on the ultrafast pump-probe experimental results, as well as decay kinetics of the compounds, the Schiff base with naphthalene unit, showed a fast transition to the triplet state (1.2 ps) as compared to Schiff bases including methyl (4 ps) and chloro (2.7 ps) units. However, upon the addition of various anions, the molecule structure gains anion sensing and fluorescence switching capabilities under daylight and UV light. The obtained experimental results pointed out that the modification of Schiff base molecules with methyl, chlorine and naphthalene units affected its photophysical properties as well as excited-state dynamics significantly.
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    Spectroscopic Studies and Crystal Structure of 4-(2-Hydroxy-3-Methoxybenzylideneamino)-N-(5-Methylisoxazol-3-yl) Benzenesulfonamide
    (Springer/Plenum Publishers, 2010) Yıldız, Mustafa; Unver, Hueseyin; Erdener, Digdem; Iskeleli, Nazan Ocak
    Schiff base 4-[(2-hydroxy-3-methoxybenzylideneamino)-N-(5-methylisoxazol-3-yl)benzene-sulfonamidehas been synthesized from the reaction of 4-amino-N-(5-methylisoxazol-3-yl)benzenesulfonamide(sulfamethoxazole) with 2-hydroxy-3-methoxybenzaldehyde. It has been characterized by elemental analysis, MS, IR, H-1 NMR, C-13 NMR, HET-COR and UV-Visible techniques. The structure of it also has been examined crystallographically. For the compound exist as dominant form of enol-imines in both the solid state and the solutions. It crystallizes in the monoclinic space group P2(1)/c with a = 8.2694(7), b = 8.3453( 5), c = 26.260( 2) angstrom, beta = 97.142(7)degrees, V = 1798.1(2) angstrom(3) , D-x = 1.431 g cm(-3), R-1 = 0.0529 and wR(2) = 0.1370 [ I > 2 sigma(I)], respectively.
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    Synthesis and spectroscopic properties of geminal-bis(tert-butylamino)cyclotriphosphazenes obtained by the reaction of Spiro and ansa phenoxycyclotriphosphazenes with the tert-butylamine and the crystal structure of 4,4?-bis(tert-butylamino)-2,6?,6?,10-tetrachloro-4?,4?,6?,6?-tetrahydrospyro[12H-dibenzo[d,g]- (1,3,2]dioxaphosphocin-6,2??5-[1,3,5,2,4,6]-triazaphosphorine]
    (Serbian Chemical Soc, 2011) Erdener, Digdem; Yıldız, Mustafa; Unver, Huseyin; Iskeleli, Nazan Ocak; Durlu, Tahsin Nuri
    The condensation reactions of partly substituted spiro and ansa phcnoxycyclotriphosphazenes 1 and 2 with tert-butylamine produce disubstituted geminal-bis(tert-butylamino)phenoxycyclotriphosphazene derivatives (3 and 4). The structures of these compounds were characterized by elemental analysis, and IR, H-1-, C-13-, P-31-NMR and mass spectroscopic techniques. Compound 3 was also examined by X-ray crystallography and found to be crystallized in the monoclinic space group P2(1)/n with the unit cell parameters: a = = 10.842(4), b = 9.375(5), c = 29.104(11) angstrom, beta = 99.25(3), V= 2920(2) angstrom(3), D-x = 1.404 g cm(-3).
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    Synthesis and Spectroscopic Properties of Spiro, Ansa and Bino Phosphazenes
    (Asian Journal Of Chemistry, 2012) Erdener, Digdem; Yıldız, Mustafa
    The spiro (1, 2), ansa (3) and bino (4) phosphaza-lariat ethers have been synthesized. The structures of the compounds (1, 2, 3 and 4) are characterized by elemental analysis, mass spectrometry, IR, H-1, C-13 and P-31 NMR spectroscopy.
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    Synthesis, DFT computations and antimicrobial activity of a Schiff base derived from 2-hydroxynaphthaldehyde: Remarkable solvent effect
    (Elsevier, 2020) Tercan, Melek; Ozdemir, Namik; Ozdemir, Fethi Ahmet; Serbetci, Zafer; Erdener, Digdem; Cetinkaya, Bekir; Dayan, Osman
    A new Schiff base bearing sulfonamide group was synthesized and characterized by spectroscopic techniques. Its spectroscopic properties were investigated through density functional theory (DFT/B3LYP) method with the 6-311++G(d,p) basis set theoretically and the zwitterion reversible arrow enol tautomerization was studied using IEF-PCM approximation. The thermodynamic (entropy, enthalpy and Gibbs free energy changes) and energetic quantities of the zwitterion reversible arrow enol tautomerization indicate that the migration of single proton between zwitterion reversible arrow enol tautomer's is unfavored for both directions in all phases. During the change from the water phase to the gas phase, the tautomeric energy barrier increases for the proton transfer reaction from the zwitterion form to the enol form, while the barrier decreases from the enol form to the zwitterion form. On the other hand, experimental studies (UV-vis. and NMR spectroscopies) release that there are two tautomeric species which are the zwitterion form in polar and the enol form in apolar solvents for the soluted compound. Furthermore, the antibacterial effect of the compound was investigated in two different solvents (DMSO and THF) to demonstrate the effect of dominant tautomeric species. The results indicate that the solution in which the enol form is dominant than the zwitterionic form has more antimicrobial efficiency for all bacterial species. (C) 2020 Elsevier B.V. All rights reserved.
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    Synthesis, spectroscopic studies and crystal structure of (E)-2-(2,4-dihydroxybenzylidene)thiosemicarbazone and (E)-2-[(1H-indol-3-yl)methylene]thiosemicarbazone
    (Elsevier, 2009) Yıldız, Mustafa; Unver, Huseyin; Erdener, Digdem; Kiraz, Askin; Iskeleli, Nazan Ocak
    Thiosemicarbazone Schiff bases (1 and 2) derived from 2,4-dihydroxybenzaldehyde, indoline-3-carbaldehyde and thiosemicarbazone have been synthesized and their structures were elucidated by elemental analysis. FT-IR, H-1 NMR, C-13 NMR and UV-visible spectroscopic techniques. The structures of compounds 1 and 2 have also been examined cyrstallographically. The title compounds 1 and 2 crystallize in the monoclinic space group C-2/c and triclinic space group P (1) over bar, with unit cell parameters: a = 21.421 (1) and 7.233(1), b = 4.131(1) and 11.166(1), c = 24.942(2) and 13.648(1) angstrom, V = 1856.1(2) and 1019.5(1) angstrom(3), D-x = 1.512 and 1.422 g cm(-3) and Z = 8 and 4, respectively. (C) 2008 Elsevier B.V. All rights reserved.