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Article Citation - WoS: 46Citation - Scopus: 51Ruthenium(0) Nanoparticles Supported on Magnetic Silica Coated Cobalt Ferrite: Reusable Catalyst in Hydrogen Generation From the Hydrolysis of Ammonia-Borane(Elsevier Science Bv, 2014) Akbayrak, Serdar; Kaya, Murat; Volkan, Murvet; Ozkar, SaimRuthenium(0) nanoparticles supported on magnetic silica-coated cobalt ferrite (Ru(0)/SiO2-CoFe2O4) were in situ generated from the reduction of Ru3+/SiO2-CoFe2O4 during the catalytic hydrolysis of ammonia-borane (AB). Ruthenium(III) ions were impregnated on SiO2-CoFe2O4 from the aqueous solution of ruthenium(III) chloride and then reduced by AB at room temperature yielding Ru(0)/SiO2-CoFe2O4 which were isolated from the reaction solution by using a permanent magnet and characterized by ICP-OES, XRD, TEM, TEM-EDX and XPS techniques. The resulting magnetically isolable Ru(0)/SiO2-CoFe2O4 were found to be highly reusable catalyst in hydrolysis of AB retaining 94% of their initial catalytic activity even after tenth run. Ru(0)/SiO2-CoFe2O4 provide the highest catalytic activity after the tenth use in hydrolysis of AB as compared to the other ruthenium catalysts. The work reported here also includes the formation kinetics of ruthenium(0) nanoparticles. The evaluation of rate constants for the nucleation and autocatalytic surface growth of ruthenium(0) nanoparticles at various temperatures provides the estimation of activation energy for both reactions; E-a = 116 +/- 7 kJ/mol for the nucleation and E-a = 51 +/- 2 kJ/mol for the autocatalytic surface growth of ruthenium(0) nanoparticles. The report also includes the activation energy of the catalytic hydrogen generation from the hydrolysis of AB (E-a = 45 +/- 2 kJ/mol) determined from the evaluation of temperature dependent kinetic data and the effect of catalyst concentration on the rate of hydrolysis of AB. (C) 2014 Elsevier B.V. All rights reserved.Article Citation - WoS: 35Citation - Scopus: 32Preparation of Silica Coated Cobalt Ferrite Magnetic Nanoparticles for the Purification of Histidine-Tagged Proteins(Pergamon-elsevier Science Ltd, 2015) Aygar, Gulfem; Kaya, Murat; Ozkan, Necati; Kocabiyik, Semra; Volkan, MurvetSurface modified cobalt ferrite (CoFe2O4) nanoparticles containing Ni-NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe2O4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe2O4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe2O4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO2-CoFe2O4) was modified by amine (NH2) groups in order to add further functional groups on the silica shell. Then, carboxyl (-COOH) functional groups were added to the SiO2-CoFe2O4 magnetic nanoparticles through the NH2 groups. After that N alpha,N alpha-Bis(carboxymethyl)-L-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO2-CoFe2O4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3. (C) 2015 Elsevier Ltd. All rights reserved.
