Browsing by Author "Eroglu, Deniz"

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A benzimidazole-based turn-off fluorescent sensor for selective detection of mercury (II)
(2020) Ergun, Emine Gul Cansu; Ertas, Gulay; Eroglu, Deniz; 0000-0002-3941-4345; I-7385-2017
In this study, potential fluorescent sensing ability of a donor-acceptor-donor type conjugated molecule over various metal ions (Ni(II), Zn(II), Cu(II), Cd(II), Pb(II), Fe(II), Fe(III), As(III), Se(IV), Hg(I) and Hg(II)) was investigated. The sensor basically includes benzimidazole and 3,4-propylenedioxythiophene as the acceptor and donor units, respectively. Solution of the sensor in tetrahydrofuran exhibits an emission with having a maximum at 632 nm. Since having insolubility of some ions in tetrahydrofuran, ion solutions were prepared in deionized water and titrations were performed by stepwise additions of ions into sensor solution in tetrahydrofuran. The control experiment including only deionized water resulted in 7 nm red-shift and 71 % quenching in the emission band. On the other hand, upon 1.07 eq. addition of Hg(II), 25 nm red-shift and 88 % fluorescent quenching were observed, exhibiting a difference among other ions. The corresponding spectral-shift and quenching amounts in the emission were found to be time-dependent and reach to equilibrium after 10 min. Studies showed that Hg(II) in aqueous solutions can be selectively detected even in the presence of other ions. Moreover, presence of Hg(II) (0.36 eq or beyond) changed the color of the sensor solution from pink to pale violet, which can be followed by the naked eye. In the light of these results, the reported sensor can be assigned as a fluorescent and a chromogenic sensor for Hg(II) detection. Limit of quantification was found to be 39.2 nM, which is comparable to the most of the fluorescent Hg(II) sensors in the literature.
Cross-exchange of donor units in donor-acceptor-donor type conjugated molecules: Effect of symmetrical and unsymmetrical linkage on the electrochemical and optical properties
(2020) Eroglu, Deniz; Ergun, Emine Gul Cansu; Onal, Ahmet M.; 0000-0002-3941-4345; I-7385-2017
A series of donor-acceptor-donor type molecules were synthesized using carbazole (C) and thiophene (T) as donor units. The donors were connected symmetrically and unsymmetrically to the acceptor unit of benzothiadiazole (B). With having four combinations, CBC, CBT, TBT and CTBTC, changes in the electrochemical and optical behaviors of the monomers were investigated using cyclic voltammetry, differential pulse voltammetry, UV-Vis and Fluorescence spectrometry techniques. Replacing one of the symmetrical C units in CBC with T unit caused a slight red shift in lower energy absorption band. On the other hand, having both C and T units symmetrically in the monomer structure exhibited about 70 nm red shift in the optical absorption. Electrochemical polymerization of the monomers was studied via potential cycling. In the case of formation of polymer films, the effect of exchange and combination of the donors on the electrochemical and optical properties was investigated. (C) 2020 Elsevier Ltd. All rights reserved.
An electrochemically and optically stable electrochromic polymer film based on EDOT and 1,2,3,4-tetrahydrophenazine
(2019) Ergun, Emine Gul Cansu; Eroglu, Deniz
In this work, 3,4-ethylenedioxythiophene (EDOT) and 1,2,3,4-tetrahydrophenazine based donor-acceptor-donor type monomer (EBE) was synthesized, electropolymerized and the resulting polymer film (P(EBE)) was investigated in terms of its electrochemical and spectroelectrochemical properties. The polymer film showed excellent electrochemical stability upon 1000 switchings by saving almost full of its electroactivity. Moreover, 95% of the optical contrast was maintained after 500 switchings. The optical band gap value was calculated using Tauc Plot method and found as 1.5 eV. P(EBE) film revealed multichromic behaviour between its fully neutral and oxidized states; dark cyanish-green at - 0.8 V, more green at - 0.5 V and transmissive green beyond 0.6 V potentials. Finally, a dual type electrochromic device (ECD) was constructed with P(EBE) and poly(3,4-ethylenedioxythiophene) (PEDOT) films and the spectroelectrochemical behaviour of ECD was depicted.