Browsing by Author "Celebi, Metin"

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2,6-Bis((e) and Its Metal(Ii) Complexes: Synthesis, Spectroscopy, Biological Activity, and Photoluminescence Features
(Wiley-v C H verlag Gmbh, 2013) Gulcan, Mehmet; Zengin, Huseyin; Celebi, Metin; Sonmez, Mehmet; Berber, Ismet
The preparation, characterization, magnetic measurements, antimicrobial activity, and photoluminescence properties of a number of metal complexes with a Schiff base ligand derived from 2, 6-diformyl-4-methylphenol and 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-thione are reported herein. UV/Vis spectra and magnetic measurements infer square planar stereochemistry for Pd-II and Pt-II complexes, and octahedral arrangement for the other metal complexes. The compounds results in intense emission (where (max) = 402 nm) upon irradiation by UV light. The photoluminescence quantum yields and long excited-state lifetimes of the ligand and its complexes were calculated as 42% and 3.94 ns, respectively. The photoluminescence intensities and quantum yields of metal complexes changed upon complexation with various metal ions. The ligand and its complexes are of interest as organic emitting materials for electroluminescent devices. The complexes were additionally evaluated for in vitro the antimicrobial activity against bacterial and fungal strains. While Cu-II, Co-II, and Pt-II complexes have good antifungal efficiency against yeast (MICs, 80 gmL(-1)), only the complex [Cu(L)(AcO)]4H(2)O had effective and selective antimicrobial activity against all tested microorganisms with MIC values in the range of 40-80 gmL(-1), except for E. coli ATCC 4230. This study suggests that the complex [Cu(L)(AcO)]4H(2)O may be a new potential antimicrobial substance towards bacteria and fungi.
Amine Grafted Silica Supported Craupd Alloy Nanoparticles: Superb Heterogeneous Catalysts for the Room Temperature Dehydrogenation of Formic Acid
(Royal Soc Chemistry, 2015) Yurderi, Mehmet; Bulut, Ahmet; Caner, Nurdan; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet
Herein we show that a previously unappreciated combination of CrAuPd alloy nanoparticles and amine-grafted silica support facilitates the liberation of CO-free H-2 from dehydrogenation of formic acid with record activity in the absence of any additives at room temperature. Furthermore, their excellent catalytic stability makes them isolable and reusable heterogeneous catalysts in the formic acid dehydrogenation.
Carbon Dispersed Copper-Cobalt Alloy Nanoparticles: a Cost-Effective Heterogeneous Catalyst With Exceptional Performance in the Hydrolytic Dehydrogenation of Ammonia-Borane
(Elsevier, 2016) Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet
Herein, we report the development of a new and cost-effective nanocatalyst for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3), which is considered to be one of the most promising solid hydrogen carriers due to its high gravimetric hydrogen storage capacity (19.6 wt%) and low molecular weight. The new catalyst system consisting of bimetallic copper-cobalt alloy nanoparticles supported on activated carbon was simply and reproducibly prepared by surfactant-free deposition-reduction technique at room temperature. The characterization of this new catalytic material was done by the combination of multi-pronged techniques including ICP-MS, XRD, XPS, BFTEM, HR-TEM, STEM and HAADF-STEM-line analysis. The sum of their results revealed that the formation of copper-cobalt alloy nanoparticles (d(mean) =1.8 nm) on the surface of activated carbon (CuCo/C). These new carbon supported copper-cobalt alloy nanoparticles act as highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane, providing an initial turnover frequency of TOF = 2700 h(-1) at 298 K, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, easy recovery and high durability of these supported CuCo nanoparticles make CuCo/C recyclable heterogeneous catalyst for the hydrolytic dehydrogenation of ammonia-borane. They retain almost their inherent activity even at 10th catalytic reuse in the hydrolytic dehydrogenation of ammonia-borane at 298K. (C) 2015 Elsevier B.V. All rights reserved.
Cobalt Nanoparticles Supported on Alumina Nanofibers (co/Al2o3): Cost Effective Catalytic System for the Hydrolysis of Methylamine Borane
(Pergamon-elsevier Science Ltd, 2019) Baguc, Ismail Burak; Yurderi, Mehmet; Bulut, Ahmet; Celebi, Metin; Kanberoglu, Gulsah Saydan; Zahmakiran, Mehmet; Baysal, Akin
Amongst different amine-borane derivatives, methylamine-borane (CH3NH2BH3) seems to be one of the capable aspirants in the storing of hydrogen attributable to its high hydrogen capacity, stability and aptitude to generate hydrogen through its catalytic hydrolysis reaction under ambient conditions. In this research paper, we report that cobalt nano-particles supported on alumina nanofibers (Co/Al2O3) are acting as active nanocatalyst for catalytic hydrolysis of methylamine-borane. Co/Al2O3 nanocatalyst was fabricated by double-solvent method followed with wet-chemical reduction, and was characterized by utilizing various spectroscopic methods and imaging techniques. The results gathered from these analyses showed that the formation Al2O3 nanofibers supported cobalt(0) nanoparticles with a mean diameter of 3.9 +/- 1.2 nm. The catalytic feat of these cobalt nanoparticles was scrutinized in the catalytic hydrolysis of methylamine-borane by considering their activity and durability performances. They achieve releasing of 3.0 equivalent of H-2 via methylamine-borane hydrolysis at room temperature (initial TOF = 297 mol H-2/mol metal x h). Along with activity the catalytic durability of Co/Al2O3 was also studied by carrying out recyclability tests and it was found that these supported cobalt nanoparticles have good durability during the course of the catalytic recycles so that Co/Al2O3 preserves almost its innate activity at 5th catalytic recycle. The studies presented here also contains kinetic investigation of Co/Al2O3 catalyzed methylamine borane hydrolysis depending on the temperature, cobalt and methylamine borane concentrations, which were used to define rate expression and the activation energy of the catalytic reaction. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Effects of the R-Go Doping on the Structural, Optical and Electrical Properties of Cdo Nanostructured Films by Ultrasonic Spray Pyrolysis
(Springer, 2020) Imer, Arife Gencer; Gulcan, Mehmet; Celebi, Metin; Tombak, Ahmet; Ocak, Yusuf Selim
Undoped and reduced graphene oxide (r-GO)-doped CdO films were prepared via the ultrasonic spray pyrolysis method with weight ratios of 1, 3 and 5% onto substrates. The successfully prepared films were characterized to understand the influence of r-GO dopant content on the morphological, structural, electrical and optical properties of the films by several diagnostic techniques. XRD measurement confirms that all the films were polycrystalline in the cubic phase of CdO with the preferred orientation (111). The optical band gap of the films decreases with the increase in doping amount. The r-GO@CdO nanostructured films were used as an interfacial layer to fabricate the heterojunction device and to investigate their electrical properties using current-voltage and capacitance-voltage measurements in the dark. The rectification properties of the studied devices increase with the r-GO dopant amount. The obtained results indicate that the r-GO content in the CdO films is responsible for the modification of physical properties of electronic device.
A Graphene-Based Electrochemical Sensor for the Individual, Selective and Simultaneous Determination of Total Chlorogenic Acids, Vanillin and Caffeine in Food and Beverage Samples
(Wiley-v C H verlag Gmbh, 2018) Yigit, Aydin; Alpar, Nurcan; Yardim, Yavuz; Celebi, Metin; Senturk, Zuehre
An electrochemical sensor based on the electrocatalytic activity of graphene (GR) was prepared, and used for the individual, selective and simultaneous determination of 5-O-Caffeoylquinic acid (5-CQA) that is major compound of chlorogenic acids in coffee, vanillin (VAN) and caffeine (CAF). The electrochemical behaviors of these compounds on GR modified glassy carbon electrode (GR/GCE) were investigated by cyclic voltammetry and square-wave adsorptive stripping voltammetry. By using stripping conditions after 30s accumulation under open-circuit voltage, the electrochemical oxidation peaks appeared at +0.53, 0.83 and 1.39V in phosphate buffer pH2.5, and good linear current responses were obtained with detection limits of 4.4x10(-9), 5.0x10(-7), and 3.0x10(-7)M for 5-CQA, VAN and CAF, respectively. The potential applicability of the proposed method was illustrated in commercial food and beverage samples.
Graphene/Nafion Composite Film Modified Glassy Carbon Electrode for Simultaneous Determination of Paracetamol, Aspirin and Caffeine in Pharmaceutical Formulations
(Elsevier Science Bv, 2016) Yigit, Aydin; Yardim, Yavuz; Celebi, Metin; Levent, Abdulkadir; Senturk, Zuhre
A graphene-Nafion composite film was fabricated on the glassy carbon electrode (GR-NF/GCE), and used for simultaneous determination of paracetamol (PAR), aspirin (ASA) and caffeine (CAF). The electrochemical behaviors of PAR, ASA and CAF were investigated by cyclic voltammetry and square-wave adsorptive anodic stripping voltammetry. By using stripping one for simultaneous determination of PAR, ASA and CAF, their electrochemical oxidation peaks appeared at +0.64,1.04 and 1.44 V, and good linear current responses were obtained with the detection limits of 18 ng mL(-1) (1.2 x 10(-9) M), 11.7 ng mL(-1) (6.5 x 10(-8) M) and 7.3 ng mL(-1) (3.8 x 10(-8) M), respectively. Finally, the proposed electrochemical sensor was successfully applied for quantifying PAR, ASA and CAF in commercial tablet formulations. (C) 2016 Elsevier B.V. All rights reserved.
High-Efficiency Removal of Cationic Dye and Heavy Metal Ions From Aqueous Solution Using Amino-Functionalized Graphene Oxide, Adsorption Isotherms, Kinetics Studies, and Mechanism
(Tubitak Scientific & Technological Research Council Turkey, 2022) Celebi, Metin; Sogut, Eda Gokirmak
GO-NH2 (amino functionalized graphene oxide) was synthesized by grafting (3-aminopropyl) triethoxysilane onto the surface GO (graphene oxide). The GO-NH2 with a higher surface area and many active sites was characterized and its effectiveness in removing Rhod B dye and Ni(II) ions from wastewater by adsorption was observed. The effects of pH, time, and strange ions on the adsorption efficiency were investigated. The equilibrium isotherm data confirmed that it fits the Langmuir and Freundlich isotherm models. GO and GO-NH2 exhibited high adsorption capacity (QM); 2500 (mg L-1) and 3333 (mg L-1) for Rhod B dye, and 312.5 (mg L-1), and 714.28 (mg L-1) for Ni(II) ions, respectively. The kinetics of adsorption was studied using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and the Boyd model. It was found that the adsorption followed pseudo-second-order and film diffusion model are effective in this adsorption process. Adsorption mechanisms have been attributed to possible electrostatic attractions, hydrogen bonding, and interactions. In summary, the experimental results showed the synthesized GO and GO-NH2 would be promising adsorbents to remove aqueous solutions contaminated with Rhod B dye and Ni(II) ions.
Keggin Type-Polyoxometalate Decorated Ruthenium Nanoparticles: Highly Active and Selective Nanocatalyst for the Oxidation of Veratryl Alcohol as a Lignin Model Compound
(Wiley-v C H verlag Gmbh, 2017) Baguc, Ismail Burak; Saglam, Serif; Ertas, Ilknur Efecan; Keles, Muhammed Nuri; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet
Described herein is a new nanocatalyst system that efficiently works in the aerobic oxidation of veratryl alcohol (VA), which is formed by cleavage of beta-O-4 linkages in lignin, to veratraldehyde (VAL) under mild reaction conditions. The new nanocatalyst system comprised of ruthenium(0) nanoparticles supported on the Keggin type polyoxometalate (POM; K-3[PMo12O40]) network (Ru/POM) can simply and reproducibly be prepared by the dimethylamine-borane ((CH3)(2)NHBH3) reduction of ruthenium(III) chloride trihydrate (RuCl3.3H(2)O) in isopropanol solution of K-3[P Mo12O40] at room temperature. The characterization of Ru/POM by the combination of various analytical techniques reveals that the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 4.7 +/- 1.2nm on the surface of POM network structure. This new Ru/POM nanocatalyst displays remarkable activity (TOF=7.5mol VAld/mol Ru x h) at high selectivity (> 98%) and almost complete conversion (98%) in the aerobic oxidation of VA to VAld under mild conditions.
Manganese Oxide Octahedral Molecular Sieves Stabilized Rh Nanoparticles for the Hydrogen Production From the Ethylenediamine-Bisborane Hydrolysis
(Pergamon-elsevier Science Ltd, 2022) Celebi, Metin; Ruzgar, Adem; Karatas, Yasar; Gulcan, Mehmet
Ethylenediamine-bisborane (C2H14B2N2, BH3NH2CH2CH2NH2BH3, EDB), an important carbon derivative of ammonia-borane (AB), has come to the fore in recent years due to some disadvantages that limit the practical use of AB for the applications of hydrogen storage. EDB is a very promising chemical hydrogen storage material in the solid crystal form at room temperature, with a hydrogen content of 16.3% by weight, which decomposes rapidly at temperatures above 363 K. Despite all these superior features, studies on catalytic systems that catalyze the hydrogen production from the EDB are very few. In the present study, we report the synthesis, characterization, and application of manganese oxide octahedral molecular sieves (OMS-2) stabilized Rh nanoparticles (Rh@OMS-2) as highly efficient and reusable catalysts for the hydrogen production from the hydrolysis of EDB. The results of characterization using P-XRD, XPS, FT-IR, SEM, SEM-elemental mapping, TEM, HR-TEM, and ICP-OES disclose that Rh (0) nanoparticles were well spread on the surface of OMS-2 nanorods. Rh@OMS-2 showed a record catalytic activity in EDB hydrolysis with an initial turn-over frequency of 102.95 min(-1) (6177 h(-1)) at 25 +/- 0.1 degrees C, the highest value ever reported for the hydrolysis of EDB. In addition, the fact that the Rh@OMS-2 catalyst kept its initial activity at the end of the 7th cycle in the hydrolysis of EDB showed that the Rh@OMS-2 was reusable and stable heterogeneous catalyst in this catalytic transformation. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Metallo Phthalocyanines Bearing (2-((2 (p-Tolyl)amino)ethoxy) and (2-((2 (p-Tolyl)amino)ethoxy)phthalonitrile Substituents: Synthesis, Characterization, Aggregation Behavior, Antioxidant and Antibacterial Activity
(Elsevier Science Sa, 2014) Celebi, Metin; Agirtas, M. Salih; Okumus, Veysi; Ozdemir, Sadin
The novel phthalonitrile derivatives bearing (2-((2-hydroxyethyl)(p-tolyl)amino)ethoxy) and (2-((2-phenoxyethyl)(p-tolyl)amino)ethoxy)phthalonitrile substituents at peripheral position were prepared by a nucleophilic displacement reaction. Cyclotetramerization of these phthalonitrile derivatives in the presence of corresponding metal salts gave the new metallophthalocyanines. The novel compounds were characterized by using various spectroscopic data. The aggregation investigations carried out in different concentrations indicate that phthalocyanine compounds do not have any aggregation behavior for the concentration range of 10(-4)-10(-6) M in tetrahydrofuran. In vitro three antioxidant test methods, namely diphenylpicrylhydrazyl radical scavenging activity, metal chelating activity and reducing power were used to determine the antioxidant activity of compounds. Compounds were analyzed for their antibacterial activity against some bacteria by using the disk-diffusion method. (C) 2014 Elsevier B.V. All rights reserved.
Nanohydrotalcite Supported Ruthenium Nanoparticles: Highly Efficient Heterogeneous Catalyst for the Oxidative Valorization of Lignin Model Compounds
(Wiley-v C H verlag Gmbh, 2017) Baguc, Ismail Burak; Celebi, Metin; Karakas, Kadir; Ertas, Ilknur Efecan; Keles, Muhammed Nuri; Kaya, Murat; Zahmakiran, Mehmet
The catalytic transformation of lignocellulosic biomass derived chemicals into value-added chemicals under mild conditions remains a challenge in the fields of synthetic chemistry and catalysis. Herein, we describe a new heterogeneous catalyst system that efficiently works in the oxidative valorization of lignin model compounds. This new heterogeneous catalyst system comprised of nano-sized hydrotalcite (n-HT; Mg6Al2 (CO3)(OH)(16)) supported ruthenium(0) nanoparticles (Ru/ n-HT) was prepared by ion-exchange of [Ru(OH2)Cl-5](2-) anions with the extraframework CO32- anions of n-HT followed by their borohydride reduction (NaBH4) in water at room temperature. The characterization of Ru/n-HT was done by the combination of various spectroscopic and the sum of their results revealed that the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 3.2 +/- 0.9 nm on the surface of n-HT structure. The catalytic performance of Ru/n-HT in terms of activity, selectivity and stability was tested in the aerobic oxidation of cinnamyl, veratryl and vanillyl alcohols, which are important lignin model compounds used to mimic the propyl side chain, the phenolic and non-phenolic, respectively functional groups of lignin. We found that Ru/ n-HT nanocatalyst displays remarkable activity at high selectivity and almost complete conversion in these catalytic transformations under mild reaction conditions (at 373 K under 3 bar initial O-2 pressure).
A New Pyrimidine-Derived Ligand, N-Pyrimidine Oxalamic Acid, and Its Cu(Ii), Co(Ii), Mn(Ii), Ni(Ii), Zn(Ii), Cd(Ii), and Pd(Ii) Complexes: Synthesis, Characterization, Electrochemical Properties, and Biological Activity
(Taylor & Francis Ltd, 2010) Sonmez, Mehmet; Celebi, Metin; Levent, Abdulkadir; Berber, Ismet; Senturk, Zuehre
A new heterocyclic compound N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-oxalamic acid has been synthesized from N-amino pyrimidine-2-one and oxalylchloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, AAS, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and thermogravimetric analyses. An octahedral geometry has been suggested for all the complexes, except for Pd(II) complex, in which the metal center is square planar. Each ligand binds using C(2)=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes are also discussed. The new synthesized compounds were evaluated for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using the microdilution procedure. The Cu(II) complex displayed selective and effective antibacterial activity against one Gram-positive spore-forming bacterium (Bacillus cereus ATCC 7064), two Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) at 40-80 mu g mL-1, but poor activity against Candida species. The Cu(II) complex might be a new antibacterial agent against Gram-positive bacteria.
New Water Soluble Phenoxy Phenyl Diazenyl Benzoic Acid Substituted Phthalocyanine Derivatives: Synthesis, Antioxidant Activities, Atypical Aggregation Behavior and Electronic Properties
(Elsevier Sci Ltd, 2013) Agirtas, M. Salih; Celebi, Metin; Gumus, Selcuk; Ozdemir, Sadin; Okumus, Veysi
Novel substituted phthalonitrile derivatives were obtained by the reaction of 2-(4-hydroxyphenylazo) benzoic acid and 4,5-dichloro-1,2-dicyanobenzene, or 4-nitrophthalonitrile. Peripherally phenoxy phenyl diazenyl benzoic acid substituted zinc (II) phthalocyanine complexes, and their sodium salts were synthesized and characterized for the first time. The newly synthesized phthalocyanine complexes show excellent solubility in water. The aggregation investigations carried out in different concentrations indicate that phenoxy phenyl diazenyl benzoic acid-substituted phthalocyanine compounds do not have any aggregation behavior for the concentration range of 7.00 x 10(-5)-4.38 x 10(-6) M in DMF. The antioxidant activities of DMF solution of compounds were analyzed through radical scavenging, and chelating ability to Fe2+ cation. Additionally, new compounds did not show any antibacterial activity against some selected bacteria cultures. Moreover, the ground-state geometries of the complexes were optimized using density functional theory (DFT) methods at B3LYP/6-31G(d,p) level in order to obtain information about the 3D geometries and electronic structure. (C) 2013 Elsevier Ltd. All rights reserved.
Nickel Nanoparticles Decorated on Electrospun Polycaprolactone/Chitosan Nanofibers as Flexible, Highly Active and Reusable Nanocatalyst in the Reduction of Nitrophenols Under Mild Conditions
(Elsevier Science Bv, 2017) Karakas, Kadir; Celebioglu, Asli; Celebi, Metin; Uyar, Tamer; Zahmakiran, Mehmet
Today, the reduction of nitro aromatics stands a major challenge because of the pollutant and detrimental nature of these compounds. In the present study, we show that nickel(0) nanoparticles (Ni-NP) decorated on electrospun polymeric (polycaprolactone(PCL)/chitosan) nanofibers (Ni-NP/ENF) effectively catalyze the reduction of various nitrophenols (2-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol) under mild conditions. Ni-NP/ENF nanocatalyst was reproducibly prepared by deposition-reduction technique. The detailed characterization of these Ni-NP/ENF based nanocatalyst have been performed by using various spectroscopic tools including ICP-OES, P-XRD, XPS, SEM, BFTEM, HRTEM and BFTEM-EDX techniques. The results revealed the formation of well-dispersed nickel(0) NP (d(mean) = 2.71-2.93 nm) on the surface of electrospun polymeric nanofibers. The catalytic activity of the resulting Ni-NP/ENF was evaluated in the catalytic reduction of nitrophenols in aqueous solution in the presence of sodium borohydride (NaBH4) as reducing agent, in which Ni-NP/ENF nanocatalyst has shown high activity (TOF=46.2 mol 2-nitrophenol/mol Ni min; 48.2 mol 2,4-dinitrophenol/mol Ni min; 65.6 mol 2,4,6-trinitrophenol/mol Ni min). More importantly, due to the nanofibrous polymeric support, Ni-NP/ENF has shown a flexible characteristics along with reusability property. Testing the catalytic stability of Ni-NP/ENF revealed that this new catalytic material provides high reusability performance (at 3rd reuse 86% for 2-nitrophenol, 83% 2,4-dinitrophenol and 82% 2,4,6-trinitrophenol) for the reduction of nitrophenols even at room temperature and under air. The present study reported here also includes the compilation of wealthy kinetic data for Ni-NP/ENF catalyzed the reduction of nitrophenols in aqueous sodium borohydride solution depending on temperature and type of support material (Al2O3, C, SiO2) to understand the effect of the support material and determine the activation parameters. (C) 2016 Elsevier B.V. All rights reserved.
Palladium Nanoparticles Decorated Graphene Oxide: Active and Reusable Nanocatalyst for the Catalytic Reduction of Hexavalent Chromium(Vi)
(Wiley-v C H verlag Gmbh, 2017) Celebi, Metin; Karakas, Kadir; Ertas, Ilknur Efecan; Kaya, Murat; Zahmakiran, Mehmet
Today, the catalytic reduction of Cr(VI) to Cr(III) stands one of the most important challenges in the environmental chemistry and catalysis due to highly stable, contaminant and toxic nature of Cr(VI). In this study, we show that a new nanocatalyst system comprised of 3-aminopropyltriethoxysilane (APTS) stabilized palladium(0) nanoparticles grafted onto the surface of graphene oxide (Pd/GO) efficiently works in the catalytic reduction of Cr(VI) to Cr(III) under mild reaction conditions. Pd/GO nanocatalyst was reproducibly prepared through two-steps procedure: (i) H-2 reduction of Pd(dba)2(dba= dibenzylideneacetone) in the presence of APTS in THF to synthesize colloidal APTS stabilized palladium(0) nanoparticles and then (ii) the deposition of 3-aminopropyltriethoxysilane stabilized palladium 0) nanoparticles onto the surface of graphene oxide (GO) by impregnation. The characterization of Pd/GO was carried out by advanced analytical techniques. The summation of the results acquired from these analyses reveals that the formation of well-dispersed and highly crystalline palladium(0) nanoparticles on the surface of GO. The catalytic performance of the resulting Pd/GO in terms of activity and stability was assessed in the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid (HCOOH) as a reducing agent. We found that Pd/GO nanocatalyst exhibits high activity (TOF= 3.6 mol Cr2O72-/mol Pdxmin) and reusability (> 90% at 5th reuse) in this catalytic transformation at room temperature.
Palladium Nanoparticles Decorated on Amine Functionalized Graphene Nanosheets as Excellent Nanocatalyst for the Hydrogenation of Nitrophenols To Aminophenol Counterparts
(Elsevier Science Bv, 2019) Sogukomerogullari, Hatice Gamze; Karatas, Yasar; Celebi, Metin; Gulcan, Mehmet; Sonmez, Mehmet; Zahmakiran, Mehmet
We reported the improved catalytic property of Pd (0) nanoparticles decorated on amine-functionalized graphene nanosheets (Pd/GNS-NH2) for the hydrogenation of nitrophenol derivatives in the presence of NaBH4 at moderate conditions. Pd/GNS-NH2 nanocatalyst was synthesized by the deposition-reduction method. Sundry techniques such as ICP-OES, P-XRD, XPS, TEM, HR-TEM and EDX have been applied to explain the structure and morphology of the Pd/GNS-NH2 nanocatalyst. The results show that the Pd (0) nanoparticles are perfectly dispersed on the surface of the GNS-NH2 support material (d(mean) = 1.38-2.63 nm). The catalytic activity of the Pd/GNS-NH2 nanocatalyst was tested in the hydrogenation of nitrophenol derivatives in water in the presence of NaBH4 as reductant and the excellent activity of nanocatalyst have been detected against 2-nitrophenol, 4nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol derivatives with 116.8, 65.9, 42.8 and 11.4 min(-1) initial TOF values, respectively. Another important point is that the nanocatalyst has very high reusability performance (at 5th reuse between 71.5 and 91.5%) for the hydrogenation of nitrophenols. Finally, catalytic studies have been carried out at various temperatures to calculate the E-a, Delta H-not equal and Delta S-not equal.
Palladium Nanoparticles Supported on Amine-Functionalized Sio2 for the Catalytic Hexavalent Chromium Reduction
(Elsevier Science Bv, 2016) Celebi, Metin; Yurderi, Mehmet; Bulut, Ahrnet; Kaya, Murat; Zahmakiran, Mehmet
Hexavalent chromium (Cr(VI)) is commonly identified acutely toxic, a proven mutagen and carcinogen heavy metal pollutant in the aquatic environment, whereas Cr(III) is believed to be an essential element. In the present study, we show that palladium(0) nanoparticles supported on 3-aminopropyltriethoxysilane (APTS) functionalized silica (Pd@SiO2-NH2) effectively catalyze the reduction of Cr(VI) to Cr(III) by using formic acid (HCOOH) as reducing agent under mild conditions (at room temperature under air). Pd@SiO2-NH2 catalyst was reproducibly prepared by deposition-reduction technique and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-vis, XPS, BFTEM, HRTEM and TEM-EDX techniques. The sum of their results is indicative of the formation of well-dispersed palladium(0) nanoparticles (d(mean) = 3.7 nm) on the surface of APTS-functionalized SiO2. The catalytic performance of the resulting palladium(0) nanoparticles in terms of activity and stability was evaluated by the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid as a reducing agent. Our results reveal that Pd@SiO2-NH2 catalyst displays unprecedented activity (TOF = 258 mol Cr2O72-/mol Pd min) and reusability (<85% at 5th reuse) for the reduction of Cr(VI) to Cr(III) at room temperature. The present study reported here also includes the compilation of wealthy kinetic data for Pd@SiO2-NH2 catalyzed the reduction of Cr(VI) to Cr(III) in aqueous formic acid (HCOOH)-sodium formate (HCOONa) solution depending on substrate [Cr2O72-], catalyst [Pd@SiO2-NH2], surface grafted amine [APTS], formic acid [HCOOH], sodium formate [HCOONa] concentrations, temperature and type of support material (Al2O3, C, unmodified SiO2) to understand the nature of the catalytic reaction and determine the rate expression and activation parameters. (C) 2015 Elsevier B.V. All rights reserved.
Palladium(Ii) and Platinum(Ii) Complexes of a Symmetric Schiff Base Derived From 2,6,diformyl-4 With N-Aminopyrimidine: Synthesis, Characterization and Detection of Dna Interaction by Voltammetry
(Elsevier France-editions Scientifiques Medicales Elsevier, 2010) Sonmez, Mehmet; Celebi, Metin; Yardim, Yavuz; Senturk, Zuhre
The two new mononuclear complexes were prepared by reacting symmetric Schiff base, containing pyrimidine rings and the metal chlorides of Pd(II) and Pt(II) in methanol. The mononuclear structure of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, IR, UV-Vis, NMR, DTA/TGA and API-ES mass spectral data. The interaction of these metal complexes with fish sperm double-stranded DNA (dsDNA) was studied electrochemically based on the oxidation signals of guanine and adenine. Differential pulse (DP) voltammetry by using renewable pencil graphite electrode was employed to monitor the DNA interaction at the surface or in solution. The results indicate that Pd(II) and (Pt) complexes with Schiff base ligand having pyrimidine rings strongly interacted with DNA. (C) 2010 Elsevier Masson SAS. All rights reserved.
Pd(0) Nanoparticles Decorated on Graphene Nanosheets (Gns): Synthesis, Definition and Testing of the Catalytic Performance in the Methanolysis of Ammonia Borane at Room Conditions
(Wiley-v C H verlag Gmbh, 2017) Karatas, Yasar; Gulcan, Mehmet; Celebi, Metin; Zahmakiran, Mehmet
Pd(0) nanoparticles (NPs) decorated on graphene nanosheets (GNS), Pd/GNS, have been synthesized by classical wet-chemical method and reduced by using sodium borohydride. The definition of the Pd/GNS nanocatalyst by the combination methods reveals that the formation of well-dispersed highly crystalline 3.68 +/- 0.35 nm Pd(0) NPs on the surface of GNS. The Pd/GNS nanocatalyst was tested as a catalyst in the hydrogen production reaction via methanolysis of ammonia-borane. Compared with the heterogeneous catalyst systems used for this reaction up to now in the literature, it has been understood that this is one of the best catalysts in terms of high efficiency (TOF = 101.5 mol H-2 mol catalyst(-1) min(-1), 253.75 min(-1) corrected for the surface atoms), low activation energy (46 kJ mol(-1)) and total conversion (> 99%) at room conditions. The more important is the remarkable stability of Pd/GNS against to agglomeration make Pd/GNS recyclable catalyst for the methanolysis of AB. Pd/GNS nanocatalyst retains 74.6% of its initial activity with 95.8% of conversion even at 5(th) recycle in the methanolysis of AB. Finally, the methanolysis reaction was carried out at various temperatures with different catalyst and substrate concentrations to write the rate equation and determine other activation parameters (Delta H-# and Delta S-#).