Mehmet Gulcan

Amylamine stabilized platinum(0) nanoparticles: active and reusable nanocatalyst in the room temperature dehydrogenation of dimethylamine-borane

Herein, we report the preparation and characterization of platinum(0) nanoparticles stabilized by amylamine (C5H11NH2) ligands plus their catalytic use in the room temperature dehydrocoupling of dimethylamine-borane ((CH3)2NHBH3), which has attracted recent attention as a promising solid hydrogen storage material. Amylamine stabilized platinum(0) nanoparticles were reproducibly generated by an ethanol–superhydride reduction method and their preliminary characterization was done by ICP-OES, XRD, ATR-IR, TEM, HRTEM, and XPS spectroscopies. The sum of their results shows the formation of highly crystalline and colloidally stable platinum(0) nanoparticles. The catalytic performance of these new platinum(0) nanoparticles in terms of activity, isolability and reusability was investigated in the catalytic dehydrocoupling of dimethylamine-borane, in which they were found to be active and reusable heterogeneous catalysts even at room temperature.

Determination of vanillin in commercial food product by adsorptive stripping voltammetry using a boron-doped diamond electrode

A method for the determination of food additive vanillin was developed by adsorptive stripping voltammetry. Its determination was carried out at the anodically pre-treated boron-doped diamond electrode in aqueous solutions. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in phosphate buffer, pH 2.5 at +1.14 V (vs. Ag/AgCl) (a pre-concentration step being carried out at open-circuit condition for 60s). A linear calibration graph was obtained in the concentration range of 0.5-15.0 μg mL(-1) (3.3×10(-6)-9.8×10(-5) mol L(-1)) with a detection limit of 0.024 μg mL(-1) (1.6×10(-7) mol L(-1)). As an example, the practical applicability of the proposed method was tested for the determination of this flavouring agent in commercial pudding powder of Keshkule (Turkish milk pudding with almond flour).

Hydroxyapatite-nanosphere supported ruthenium(0) nanoparticle catalyst for hydrogen generation from ammonia-borane solution: kinetic studies for nanoparticle formation and hydrogen evolution

The development of readily prepared effective heterogeneous catalysts for hydrogen generation from ammonia-borane (AB; NH3BH3) solution under mild conditions still remains a challenge in the field of “hydrogen economy”. In this study, we report our finding of an in situ generated, highly active ruthenium nanocatalyst for the dehydrogenation of ammonia-borane in water at room temperature. The new catalyst system consists of ruthenium(0) nanoparticles supported on nanohydroxyapatite (RuNPs@nano-HAp), and can be reproducibly prepared under in situ conditions from the ammonia-borane reduction of Ru3+ ions exchanged into nanohydroxyapatite (Ru3+@nano-HAp) during the hydrolytic dehydrogenation of ammonia-borane at 25 ± 0.1 °C. Nanohydroxyapatite-supported ruthenium(0) nanoparticles were characterized by a combination of advanced analytical techniques. The sum of their results shows the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 2.6 ± 0.6 nm on the surface of the nanospheres of hydroxyapatite by keeping the host matrix intact. The resulting RuNPs@nano-HAp are highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane with an initial TOF value of 205 min−1 by generating 3.0 equiv. of H2 per mole of ammonia-borane at 25 ± 0.1 °C. Moreover, they are sufficiently stable to be isolated and bottled as solid materials, which can be reused as active catalyst under the identical conditions of first run. The work reported here also includes the following results: (i) monitoring the formation kinetics of the in situ generated RuNPs@nano-HAp by hydrogen generation from the hydrolytic dehydrogenation of ammonia-borane as the reporter reaction. The sigmoidal kinetics of catalyst formation and concomitant dehydrogenation fits well to the two-step, slow nucleation, followed by autocatalytic surface growth mechanism, P → Q (rate constant k1) and P + Q → 2Q (rate constant k2), in which P is Ru3+@nano-HAp and Q is the growing, catalytically active RuNPs@nano-HAp; (ii) the compilation of kinetic data for the RuNPs@nano-HAp catalyzed hydrolytic dehydrogenation of ammonia-borane depending on the temperature and catalyst concentration to determine the dependency of reaction rate on catalyst concentration and activation parameters (Ea, ΔH#, and ΔS#) of the reaction.

Synthesis and Characterization of Cu(II), Ni(II), Co(II), Mn(II), and Cd(II) Transition Metal Complexes of Tridentate Schiff Base Derived from O-Vanillin and N-Aminopyrimidine-2-Thione

Abstract Monobasic tridentate Schiff base ligand having ONS donor sequence was prepared by condensing N-aminopyrimidine-2-thione with o-vanillin. The complexes were formed by reacting ligand and the metal acetates of Cu(II), Ni(II), Co(II), Mn(II), and Cd(II) in methanol to get a series of mononuclear and dinuclear complexes. The characterization of ligand and metal complexes were carried out by elemental analyses, conductivity measurements, magnetic susceptibility data, FTIR, UV-vis, NMR, and API-ES mass spectral data. The structure of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, API-ES mass spectral data and thermal gravitational analysis (TGA). GRAPHICAL ABSTRACT

In Situ Formed Ruthenium(0) Nanoparticles Supported on TiO2 Catalyzed Hydrogen Generation from Aqueous Ammonia-Borane Solution at Room Temperature Under Air

Herein, the authors report that TiO2 supported ruthenium nanoparticles (Ru(0)/TiO2) during hydrolysis starting with RuCl3/TiO2 precatalyst act as highly active, long-lived, and reusable nanocatalyst in the hydrogen generation from the hydrolysis of ammonia-borane (NH3BH3) at room temperature. The resulting Ru(0)/TiO2 catalyze hydrogen generation from the hydrolysis of ammonia-borane with an initial turnover frequency value of 200 min−1 at 25 ± 0.1°C. More importantly, Ru(0)/TiO2 are stable enough to be isolated and bottled as solid material, which can be reused as active catalyst under the identical conditions of the first run.

Synthesis, characterisation and antimicrobial activity 1-aminopyrimidine-2(1 H )-thione and its Co(II), Ni(II), Pd(II) and Pt(II) complexes

Metal complexes of 1-aminopyrimidine-2(1H)-thione were prepared from acetate salts of Co(II), Ni(II), Pd(II) and Pt(II) in methanol. Electronic spectral data and magnetic moment measurements suggest mononuclear square planar geometrical structures for the metal complexes. The ligand and all the metal complexes were evaluated for their antimicrobial activity. The newly synthesised ligand and the Co(II) complex showed moderate activity against all tested bacteria and yeast strains.

The novel pyridine based symmetrical Schiff base ligand and its transition metal complexes: synthesis, spectral definitions and application in dye sensitized solar cells (DSSCs)

The pyridine based azo-linked symmetrical Schiff base ligand, (E)-2,2′-((1E,1′E)-(pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))bis(4-((E)-phenyldiazenyl)phenol) (H2L), and its Co(II), Ni(II) and Pd(II) transition metal complexes were prepared, and defined by using elemental analysis, Fourier transform infrared, UV–visible, mass, nuclear magnetic resonance spectra, molar conductance, magnetic susceptibility and thermal analysis techniques. The conductivity results pointed out the non-electrolytic nature of all metal complexes. Elemental composition, ultraviolet spectra and magnetic susceptibility data showed that the synthesized complexes are in the binuclear structure and square plane geometry. When compared to the characteristic infrared bands for the functional groups of the ligand structure with complex molecules are reached, the ligand binds to the metal atom via phenolic OH and azomethine-nitrogen. Furthermore, the dye-sensitized solar cells (DSSCs) based on H2L and its metal complexes were fabricated, and photovoltaic properties of these devices were also investigated. The power conversion efficiency of fabricated devices based on ligand H2L can be improved with the incorporation of the transition metal complex.

Synthesis of bis(thiosemicarbazone) derivatives: Definition, crystal structure, biological potential and computational analysis

GRAPHICAL ABSTRACT ABSTRACT (2-(2-(2-methoxyphenyl)hydrazono)cyclohexane-1,3-diylidene) bis(hydrazine carbothioamide) (L1), 4-(2-(-2,-6-bis(2-carbamothioylhydrazono) cyclohexylidene) hydrazinyl)benzoic acid (L2), and (2-(2-(4-bromophenyl) hydrazono) cyclohexane-1,3-diylidene) bis(hydrazinecarbothioamide) (L3) bis(thiosemicarbazone) derivative compounds were synthesized by the condensation reaction of thiosemicarbazide and various ketone compounds. The structures of synthesized compounds were characterized by using FT-IR, 1H and 13C-NMR spectra, elemental analysis and mass spectra. Also, the structure of L1 has been determined by X-ray crystallographic analysis. Additionally, the antioxidant activities (free radical (DPPH) scavenging, iron chelating and reducing power) of compounds were evaluated. Especially, L3 displayed good DPPH activity (84.13%) at 100 mg/L. Moreover, pBR322 plasmid DNA cleavage activity was examined and all of the compounds were able to cleave the plasmid DNA. Finally, the ground state geometries of the thiosemicarbazone derivatives were optimized using Density Functional Theory applications at B3LYP/6-31G (d,p) level in order to obtain information about the 3D geometries and electronic structure.

Carbon-nanotube-based rhodium nanoparticles as highly-active catalyst for hydrolytic dehydrogenation of dimethylamineborane at room temperature

In this study, we present a carbon nanotube-based Rh nanomaterial as a highly active catalyst for the hydrolytic dehydrogenation of dimethylamine - borane (DMAB) at room temperature. The prepared multi-walled carbon nanotube based Rh nanoparticles, called Rh NPs@ MWCNT, was readily prepared, stabilized and effectively used for the hydrolytic dehydrogenation of DMAB under ambient conditions. Monodisperse Rh NPs@ MWCNT nanocatalyst was characterized by using advanced analytical methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) etc. These analytical methods revealed that Rh nanoparticles on the surface of MWCNT were well dispersed and the average particle size was found to be 1.44 ± 0.17 nm. The catalytic experiments revealed that the new Rh NPs@MWCNT nanocatalyst has a high catalytic effect to obtain hydrogen in 3.0 equation from DMAB, and the record catalytic TOF value for the catalytic reaction catalyzed by Rh NPs@MWCNT nanocatalyst was found to be 3010.47 h-1 at room temperature. The current study presents the detailed kinetic studies of the hydrolytic dehydrogenation of DMAB catalyzed by Rh NPs@MWCNT, the results of catalytic experiments were performed at different temperatures, substrate and catalyst concentrations, the Rh NPs@MWCNT nanocatalyst was effectively used in the completion of the hydrolytic dehydrogenation of DMAB, and activation energy, enthalpy and entropy parameters. The experimental results showed that monodisperse Rh NPs@MWCNT nanocatalyst have record catalytic activity with TOF value of 3010.47 h-1, and Rh(0) nanoparticles were well dispersed on the multi-walled carbon nanotubes.