Chemical Engineering

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    Synthesis of Silver Nanoparticle-Immobilized Antibacterial Anion Exchange Membranes for Salinity Gradient Energy Production by Reverse Electrodialysis
    (ACS Sustainable Chemistry & Engineering, 2024-03-01) Eti, Mine ; Cihanoğlu, Aydın ; Hamaloğlu, Kadriye Özlem ; Altıok, Esra ; Güler, Enver ; Tuncel, Ali ; Kabay, Nalan
    Biofouling, stemming from the attachment of living microorganisms, such as bacteria, which form resilient biofilms on membrane surfaces, presents a significant challenge that hampers the efficiency of anion exchange membranes (AEMs) in reverse electrodialysis (RED) applications. This limitation curtails the generation of electrical power from salinity gradients, which, notably, is a sustainable form of energy known as osmotic energy. Reverse electrodialysis (RED) stands as a clean and promising process to harness this sustainable energy source. This study aimed to impart antibacterial activity to the synthesized AEMs using silver nanoparticles (AgNPs). For that purpose, AgNPs were synthesized at 30oC using two different pH (6.0 and pH 9.0) and immobilized into synthesized AEMs using the dip-coating technique. In nanoparticle synthesis, ascorbic acid (AA) and trisodium citrate (TSC) were used as a reductant and a stabilizer, respectively, to take under control of particle size and agglomeration behavior. The results indicated that AgNPs synthesized at pH 6.0 were dispersed on the AEMs surface without agglomeration. The stability of AgNPs immobilized on the membrane surface was tested under low and high-saline solutions. The antibacterial activities of AEMs were determined with the colony-counting method using Gram-negative (Escherichia coli) bacteria suspension. The viability of bacteria dramatically decreased after the immobilization of AgNPs to the AEMs. In the short and long-term RED tests, it has been observed that the AEMs having AgNPs have high energy-generating potentials, and power density up to 0.372 W/m2 can be obtained.
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    D-A-D type conjugated polymers in dual electrochromic devices tuning from green to blue colors
    (Synthetic Metals, 2023-07) İçli Özkurt, Merve ; Önal, Ahmet M. ; Cihaner, Atilla
    In this study, the electrochemical and electro-optical properties of four different dual electrochromic devices were unraveled. In all devices, soluble donor-acceptor-donor (D-A-D) type conjugated electrochromic polymers based on didecyl substituted 3,4-propylenedioxythiophene and heterodiazole analogues were used, and they were coated on ITO electrochemically for the construction of the electrochromic devices. Because all D-A-D polymers and PEDOT are colorful in their neutral states and colorless in their oxidized states, it is possible to observe one-to-one colors of pure two polymers in their electrochromic devices rather than a mixture of colors. It was observed that devices changed their colors from the tunes of green to blue under applied external voltage. Switching times, coloration efficiencies and stabilities of the electrochromic devices were calculated as ranging from 1.0 to 6.0 s, 133 to 544 cm2/C and 54% to 91%, respectively, after 5000 cycles. The P(PSeP-C10)-P(PNP-C10) device showed the highest coloration efficiency (544 cm2/C) as well as the best optical and electrochemical stabilities among the electrochromic devices after 5000 cycles (91% and 92%, respectively).
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    Side Chain effect on the electrochemical and optical properties of TPD based donor acceptor donor type monomers and polymers
    (Molecular Systems Design and Engineering, 2023) Çakal, Deniz ; Demir Arabacı, Elif ; Yıldırım, Erol ; Cihaner, Atilla ; Önal, Ahmet M.
    In organic π-conjugated materials, side chains play great roles that are far beyond solubility. In this work, we mainly focused on the synthesis of new donor-acceptor-donor (D-A-D) type conjugated monomers and their corresponding polymers appending TPD acceptor with a new side chain, fluorene, to investigate the side chain effect. In this context, to reveal the precise effect of the side chains on the optical and electrochemical properties of the monomers and polymers synthesized in this work, four series of D-A-D monomers, each containing a TPD core unit with a different side chain, have been discussed in comparison to each other. Notably, it was discovered that TPD acceptor unit can be modified by any functional group other than common alkyl chains to impart new functionalities by keeping their superior optoelectronic properties. New kind of side chains can be used to tune the physical characteristics such as solubility, absorption, emission and molecular packing. In this paper, fluorene-appended monomers as a new class of D-A-D type π-conjugated molecules were studied and it was found that E(Fl) and P(Fl) exhibited resonable quantum yields and their corresponding polymers revealed ambipolar character with slightly lower band gap as compared to the previous analougs containing other side chains. Observed experimental results were elucidated by first principle calculations. In this paper, we discussed that using side chain engineering is an effective strategy to improve next-generation organic π-conjugated materials with the desired properties.
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    Synthesis and Characterization of A Luminol Based Chemiluminescent Trimeric System
    (Journal of Fluorescence, 2023-07) Kesimal, Büşra ; Balcı, Burcu ; Çakal, Deniz ; Önal, Ahmet M. ; Cihaner, Atilla
    A luminol based chemiluminescent trimeric system, namely 2,3-dihydro-5,8-di(thiophen-2-yl)phthalazine-1,4-dione (T2B-Lum), bearing thiophene rings as donor units and 2,3-dihydrophthalazine-1,4-dione as an acceptor unit was synthesized in two steps via donor-acceptor-donor approach using two different methods. It was found that T2B-Lum emits chemiluminescent light when exposed to H2O2 in a basic medium, and the presence of substituents and the type of aromatic ring bearing chemiluminescent active group have a direct effect on the compound's sensitivity. Among the members of a large family of metal ions, fluorescent and chemiluminescent T2B-Lum exhibited high sensitivity to Cu2+ and Fe3+ ions. Except for other metal cations (silver(I), cadmium(II), cobalt(II), iron(III), lithium(I), magnesium(II), manganese(II), nickel(II), zinc(II)), it has been observed that T2B-Lum is mostly sensitive to copper(II) ions with a detection limit value of 2.2×10-3 M. On the other hand, T2B-Lum was also found to exhibit a high sensitivity to extremely dilute aqueous solutions (e.g., 1:50.000 dilution) of blood samples, making it a promising candidate for use in forensic applications.
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    Synthesis, Characterization and Application of High Sulfur Content Polymeric Materials from Fatty Acids
    (Reactive and Functional Polymers, 2023-06) Berk, Hasan ; Kaya, Murat ; Topçuoğlu, Mert ; Türkten, Nazlı ; Karataş, Yunus ; Cihaner, Atilla
    A new series of high sulfur content polymers containing various amounts of fatty acids (oleic acid (OA), linoleic acid (LA) and linolenic acid (LnA)) was synthesized via inverse vulcanization method and characterized successfully. In particular, the effect of double bonds and free alkyl chains on polysulfur copolymers has been investigated systematically by using OA with one double bond, LA with two double bonds and LnA with three double bonds. The copolymers with functional carboxylic acid groups are soluble in common organic solvents, processable and electroactive. Also, the usage of the copolymers was tested in the removal of methylene blue and as a cathode material in Li-S battery. Results showed that the polymers can be a potential material for use in dye removal.