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Sahiner N.,Canakkale Onsekiz Mart University | Sahiner N.,Nanoscience and Technology Research and Application Center | Seven F.,Nanoscience and Technology Research and Application Center
RSC Advances

Superporous and nonporous poly(2-acrylamido-2-methyl-1-propansulfonic acid) [p(AMPS)] cryogels and hydrogels were prepared under freezing conditions (-18 °C) and at room temperature (25 °C), respectively. The swelling equilibrium values of the p(AMPS) cryogels were extremely fast, 3600 fold faster than those of conventional hydrogels. The p(AMPS) cryogels were further employed as highly effective supports for the in situ preparation of metal nanoparticles within superporous networks, by loading Co(ii) and Ni(ii) ions into the cryogel network from aqueous environments and reducing with NaBH 4. The Co metal nanoparticle-containing cryogel composites demonstrated superior catalytic performances in comparison to nonporous p(AMPS) hydrogel composites for energy and environmental applications e.g., hydrogen production from the hydrolysis of sodium borohydride, and reduction of 4-nitrophenol to 4-aminophenol. The energy applications of cryogel-based p(AMPS)-Co metal composites, especially, were investigated in detail. The effect of various parameters on the rate of the hydrogen generation reaction, such as porosity, metal types, pH, the types of reaction water, temperature and reuse of catalyst, were examined for the p(AMPS)-Co cryogel composite materials. With the p(AMPS)-Co cryogel composite a very high hydrogen generation rate of 14 501 mL H2 per min per g of Co was attained. This value is one of the best recorded values in comparison to the values obtained for other similar catalysts reported in the literature. p(AMPS)-Co composite cryogels were repeatedly used without significant loss of catalytic activity (82%) even after five repetitive uses for catalytic hydrolysis reactions with NaBH4. Additionally, a very low activation energy for the p(AMPS)-Co cryogel composite systems was attained: Ea = 15.40 ± 0.3 kJ mol-1. © 2014 the Partner Organisations. Source

Sahiner N.,Canakkale Onsekiz Mart University | Sahiner N.,Nanoscience and Technology Research and Application Center | Ilgin P.,Canakkale Onsekiz Mart University
Journal of Polymer Science, Part A: Polymer Chemistry

Polymeric particles comprising acrylonitrile (AN)-based core and acrylamide derivative-based shell in the submicron range with positive and negative charges were synthesized via microemulsion polymerization. 2-Acrylamido-2- methylpropane sulfonic acid (AMPS) and 3-(acrylamidopropyl)-trimethyl ammonium chloride (APTMACl) were used as shell-forming charged monomers onto AN core for the synthesis of p(AN-co-AMPS) and p(AN-co-APTMACl), respectively, using an oil-in-water emulsion system. To tune the characteristics of the core-shell particles, AN moieties in the core were amidoximated to change the nature of the core from hydrophobic (nitrile) to hydrophilic (amidoxime) nature. Additionally, colloidal magnetite particles (Fe3O4) produced by chemical coprecipitation technique under alkaline and inert conditions were also included inside p(AN-co-AMPS) and p(AN-co-APTMACl) particles as dual-responsive nanocomposites against pH and magnetic field. With the magnetic properties, AN-based core with modifiable characteristics and acrylamide-based polyelectrolyte shells with variable charges and sizes were further used as drug carriers. For potential targeted drug delivery application of the synthesized soft particles and their composites Naproxen and Trimethoprim were used as model drugs, and he release studies were carried in phosphate buffer saline (pH = 7.4) at ambient temperature. © 2010 Wiley Periodicals, Inc. Source

Sahiner N.,Canakkale Onsekiz Mart University | Sahiner N.,Nanoscience and Technology Research and Application Center | Yasar A.O.,Canakkale Onsekiz Mart University
Fuel Processing Technology

Poly(vinyl imidazole) (p(VI)) and poly(VI)-silica (p(VI)-Si) composites were synthesized in an oil-in-water micro emulsion system. Additional pores were generated inside p(VI)-Si composites by removing the silica by HF treatment to obtain poly(VI)-porous (p(VI)-por) particles. The size of p(VI)-based particles ranged between 300 and 800 nm. Co and Ni metal nanoparticles were prepared inside p(VI)-based particles by the absorption of the corresponding metal ions from aqueous solution, and reduction with NaBH4 in situ. Different parameters such as temperature, metal nanoparticle types, NaOH concentration, and metal ion reloading for metal nanoparticle formation for hydrogen generation were investigated. The activation energy, the enthalpy, and the entropy for the NaBH4 hydrolysis reaction were calculated to be 37.578 kJ mol - 1, 34.146 kJ mol- 1, and - 191.22 kJ mol- 1 K- 1, respectively. It was found that the hydrogen production rate increased drastically by five times repetitive metal ion loading-reduction cycles that increased the amount of metal nanoparticle inside p(VI) particles. © 2013 Elsevier B.V. Source

Seven F.,Canakkale Onsekiz Mart University | Sahiner N.,Canakkale Onsekiz Mart University | Sahiner N.,Nanoscience and Technology Research and Application Center
International Journal of Hydrogen Energy

P(AAM-co-VSA) hydrogel was prepared at different mole ratios form the corresponding monomers and used in absorption of metal ions such as Co and Ni from aqueous environments. Then, these bound metal ions within the hydrogel matrices were reduced to their metal nanoparticles by aqueous NaBH4 treatment. Finally, p(AAm-co-VSA)-M (M: Co or Ni) composites were used as reactor in the hydrolysis of NaBH4 for hydrogen generation. The amounts of metal ions before and after metal nanoparticle formation were determined by Atomic Absorption Spectroscopy (AAS). P(AAm-VSA) hydrogel showed greater absorption tendency for Ni(II) ions than Co(II) ions, and the metal ion binding capacity of these hydrogels was increased with an increase in the amount of VSA in the copolymeric hydrogel. It was also found that although the amount of Ni ions loaded into the hydrogel matrices were more than Co ions, Co metal nanoparticle-containing hydrogel produced hydrogen faster than Ni metal nanoparticle-containing hydrogel composites. The activation energy for the Co nanoparticle-embedded p(AAm-co-VSA) was found as 34.505 kJ mol -1k-1, and other thermodynamic parameters were also calculated. The p(AAm-co-VSA)-Co hydrogel can be used up to 5 times repetitively without any loss of yield but with 55% of catalytic activity.Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights. Source

Seven F.,Canakkale Onsekiz Mart University | Sahiner N.,Canakkale Onsekiz Mart University | Sahiner N.,Nanoscience and Technology Research and Application Center
Journal of Power Sources

The neutral 3-D superporous cryogel is prepared from a poly(acrylamide) (p(AAm)) hydrogel network modified with an amidoximation reaction to induce chemical changes to produce superporous amidoximated-p(AAm) (amid-p(AAm)) cryogel. The newly-formed strongly ionizable matrices can readily absorb metal ions such as Co(II) and Ni(II) enabling in situ preparation of corresponding metal nanoparticles by NaBH4treatments. It is found that the superporous amid-p(AAm)-Co cryogel composite is very effective as a catalyst for H2generation from hydrolysis of NaBH4in alkaline medium. Furthermore, it is demonstrated that the metal ion loading capacity and catalytic activity of superporous amid-p(AAm)-Co cryogel composites increased with 2nd and 3rd Co(II) ion loading and reduction cycles. The hydrogen generation rate of p(AAm)-Co metal composites is increased to 1926.3 ± 1.1 from 1130.2 ± 1.5 (mL H2) (min)-1(g of M)-1. The effect of various parameters such as porosity, metal type, the number of reloading and reduction cycles of the metal ion, and temperature are investigated for the hydrolysis of NaBH4. The kinetic parameters such as energy, enthalpy and entropy are determined as Ea = 39.7 ± 0.2 kJ mol-1, ΔH = 37.2 ± 0.1 kJ mol-1and ΔS = -171.9 ± 0.5 J mol-1K-1, respectively. © 2014 Elsevier B.V. All rights reserved. Source

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