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    Benign Preparation of Metal-Organic Frameworks of Trimesic Acid and Cu, Co or Ni for Potential Sensor Applications
    (Springer, 2015) Sel, Kivanc; Demirci, Şahin; Meydan, Engin; Yildiz, Sema; Ozturk, Omer Faruk; Al-Lohedan, Hamad; Şahiner, Nurettin
    Metal-organic frameworks (MOFs) have been constructed using trimesic acid (TMA) as organic linker and Co(II), Ni(II) or Cu(II) metal ions from their corresponding aqueous chloride salts at room temperature. The prepared TMA-M (M: Co, Ni, and Cu) MOFs have been characterized in terms of their porosity and optical, thermal, electrical, and structural properties. The prepared MOFs were characterized in terms of their porosity through Brunauer-Emmett-Teller measurements, yielding a value of 330 m(2)/g for the TMA-Cu MOF. Structural analysis and thermal characterization of the prepared MOFs were done by using Fourier-transform infrared (FT-IR) spectroscopy, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), respectively. The optical properties were analyzed by fluorescence spectroscopy. Additionally, TMA-M MOF disks were prepared and their conductivities determined by room-temperature I-V measurements. The conductivity of the TMA-M MOFs was calculated to be between 7.97 x 10(-7) S/cm and 5.39 x 10(-9) S/cm.
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    Ionic liquid hydrogel templates: Bulkgel, cryogel, and microgel to be used for metal nanoparticle preparation and catalysis
    (Pergamon-Elsevier Science Ltd, 2015) Yildiz, Sema; Şahiner, Mehtap; Şahiner, Nurettin
    Here, we report the preparation of various crosslinked polymeric matrices from 3-acrylami dopropyl)-trimethylammonium chloride as p(APTMACl) ionic liquid hydrogels in the forms of bulk gel, cryogel, and microgel. Their utilization for in situ metal nanoparticle synthesis of Co and Ni, and then the comparison of catalytic performances of these materials in the reduction of 4-nitrophenol (4-NP), 4-nitroaniline (4-NA), and 4-nitrobenzaldehyde (4-NBA) to the corresponding amine forms of 4-AP, 4-AA, and 4-ABA, respectively, are investigated. As the polymeric hydrogel matrices are inherently positively charged, the metal salts of CoCl2 and NiCl2 were loaded into hydrogel matrices from the corresponding metal salt solution in ethanol. It was found that morphology and sizes of p(APTMACl) ionic liquid hydrogel materials played a great role in catalytic performances for the nitro compounds. The effect of temperature and kinetic parameters of different polymeric matrices for the reduction of 4-NP to 4-AP was investigated. The activation energies for bulk gel, cryogel, and microgel were calculated as 44.74, 34.02, and 40.7 kJ mol(-1), respectively. (C) 2015 Elsevier Ltd. All rights reserved.
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    Magnetic colloidal polymeric ionic liquid synthesis and use in hydrogen production
    (Elsevier Science Bv, 2014) Şahiner, Nurettin; Demir, Sahin; Yildiz, Sema
    Cationic microparticles were synthesized from (3-Acrylamidopropyl)-trimethylammonium chloride (p[APTMACl]) via an inverse suspension polymerization technique. These polymeric microparticles were treated with chloride salt of metals such as CoCl2, NiCl2, CuCl2, FeCl2, and FeCl3 in ethanol. This manuscript reports the ionic liquid (IL) microparticle as templates for in situ metal nanoparticle preparation, and their use as an environmentally benign catalyst system for energy applications. The p(APTMACl) microgels laden with these metal compounds were reduced to their corresponding metallic form with sodium borohydride. Interestingly, Co nanoparticles demonstrated intrinsic magnetic behavior and superior catalytic performance in hydrogen generation from hydrolysis of sodium borohydride (NaBH4) and ammonia borane (NH3BH3). Magnetic properties, zeta potential, particle sizes, and capacity for metal absorption of the p(APTMACl) microparticles were characterized. (C) 2014 Elsevier B.V. All rights reserved.
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    Metal nanoparticle-embedded super porous poly(3-sulfopropyl methacrylate) cryogel for H2 production from chemical hydride hydrolysis
    (Pergamon-Elsevier Science Ltd, 2014) Yildiz, Sema; Aktas, Nahit; Şahiner, Nurettin
    Poly(3-sulfopropyl methacrylate) (p(SPM)) cryogel was prepared under cryogenic conditions (T = 18 degrees C) and used as template for in situ metal nanoparticle preparation of Co, Ni and Cu. These metal nanoparticle-containing super macroporous cryogel composites were tested for H2 production from hydrolysis of sodium borohydride (NaBH4) and ammonia borane (AB). It was found that amongst p(SPM)-M (M: Co, Ni, and Cu) composite catalyst systems, the catalytic performances of Co- and Ni-containing p(SPM) cryogel composite catalyst systems were the same, however in hydrolysis of NH3BH3, the order of performance of the catalysts was Co > Ni > Cu. Interestingly, p(SPM)-Co cryogel composite demonstrated better catalytic performances in salt environments e.g., faster H2 production rate in sea and tap water compared to DI water, and almost no effect of ionic strength of the solution medium was observed, but the salt types were found to affect the H2 generation rate. Other parameters that affect H2 production rate such as metal type, temperature, water source, salt concentration, amount of metal nanocatalyst and reusability were investigated. It was found that the hydrogen generation rate (HGR) was increased to 2836 +/- 90 from 1000 +/- 53 (ml H-2)(g of Co min)l by multiple loading and reduction cycles of Co catalyst. Also, it was found that TOF values are highly temperature dependent, and increased to 15.1 0.8 from 2.4 0.1 (mol H-2)(mol catalyst min)l by increasing the temperature from 30 to 70 degrees C. The activation energy, activation enthalpy and activation entropy were determined as 40.8 kJ (mol)(-1), 37.23 kJ (mol K)(-1), and 170.87 J (mol respectively, for the hydrolysis reaction of NaBH4 with p(SPM)-Co catalyst system, and 25.03 kJ (mol)(-1), 22.41 kJ (mol K)(-1), and 182.8 J (mol K)(-1), respectively, for AB hydrolysis catalyzed by p(SPM)-Co composite system. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Preparation of superporous poly(4-vinyl pyridine) cryogel and their templated metal nanoparticle composites for H2 production via hydrolysis reactions
    (Elsevier, 2014) Şahiner, Nurettin; Yildiz, Sema
    The superporous cryogels of poly(4-vinylpyridine) p(4-VP) were prepared via free radical polymerization technique under cryogenic conditions (T = -18 degrees C). The prepared p(4-VP) cryogel was used as template for in situ metal nanoparticle preparation using Co, Ni and Cu by loading these ions into the p(4-VP) network from their corresponding metal (II) ion aqueous solutions, and then treating with a reducing agent, sodium borohydride (NaBH4). The prepared cryogel p(4-VP)-M (M: Co, Ni, Cu) composite catalysts were successfully used in hydrogen (H-2) generation from the hydrolysis of NaBH4 and ammonia borane (AB). The physicochemical structure and the thermal behavior of the prepared superporous p(4-VP) cryogels were analyzed via optical microscopy, FT-IR spectroscopy and thermogravimetric analyzer (TGA). The amounts of metal nanoparticles within superporous p(4-VP)-M cryogel composites were determined by atomic absorption spectroscopy (AAS) and TGA measurements. Multiple metal ion loading-reduction cycles were completed for superporous p(4-VP) cryogels to increase the amount of Co content. The activation energies for NaBH4 and AB hydrolysis catalyzed by superporous p(4-VP)-Co cryogel composites were calculated as 28.75 and 34.98 kJ/mol, respectively. (C) 2014 Elsevier B.V. All rights reserved.
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    The resourcefulness of p(4-VP) cryogels as template for in situ nanoparticle preparation of various metals and their use in H2 production, nitro compound reduction and dye degradation
    (Elsevier, 2015) Şahiner, Nurettin; Yildiz, Sema; Al-Lohedan, Hamad
    Poly(4-vinylpyridine) (p(4-VP)) cryogels were synthesized under cryogenic conditions (T=-18 degrees C) and were converted to positively charged forms by modifying with different alkyl dihalides of variable chain lengths such as 1,2-dibromoethane (1,2 BE), 1,4-dibromobutane (1,4 BB), 1,6-dibromohexane (1,6 BH), and 1,8-dibromooctane (1,8 BO). The chemical structure of synthesized supermacroporous 1,4 BB-p(4-VP) cryogels were confirmed by FT-IR spectroscopy. The 1,4 BB modified-poly(4-vinylpyridine) (1,4 BB-p(4-VP)) cryogels were used as template for in situ metal nanoparticle preparation as 1,4 BB-p(4-VP)-M (M: Co, Ni, Cu, and Fe) using chloride salts of Co, Ni, Cu, and Fe in ethanol. These metal-nanoparticle macroporous cryogel composites were employed in H-2 generation from hydrolysis of sodium borohydride (NaBH4). Metal nanoparticles embedded 1,4 BB-p(4-VP)-M were visualized by TEM, and thermal behavior of 1,4 BB-p(4-VP) cryogels were done by thermogravimetric analyzer (TGA). The metal content of 1,4 BB-p(4-VP)-M was estimated via atomic absorption spectroscopy (AAS). Multiple metal salt loading and reduction cycles were performed for 1,4 BB-p(4-VP) cryogels to increase the amount of contained Co. The activation energies, enthalpy, and entropy for NaBH4 hydrolysis catalyzed by 1,4 BB-p(4-VP)-Co cryogel composites were determined as 47.6 kJ (mol)(-1), 46.2 kJ (mol K)(-1), and 146.91 (mol K)(-1), respectively. The cryogel network embedded with Co, Ni, Cu, and Fe nanoparticles was also used as a catalyst in the reduction of 4-nitrophenol (4-NP) in an aqueous solution in excess amount of NaBH4. Furthermore, the Cu metal nanoparticle-containing 1,4 BB-p(4-VP) cryogel was utilized in the degradation of methylene blue (MB). (C) 2014 Elsevier B.V. All rights reserved.
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    Use of cryogels for in situ metal nanoparticle preparation and catalysis for hydrogen generation
    (Amer Chemical Soc, 2014) Şahiner, Nurettin; Seven, Fahriye; Yildiz, Sema; Aktas, Nahit
    [Anstract Not Available]