Browsing by Author "Gulcan, Mehmet"

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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.
Amylamine Stabilized Platinum(0) Nanoparticles: Active and Reusable Nanocatalyst in the Room Temperature Dehydrogenation of Dimethylamine-Borane
(Royal Soc Chemistry, 2014) Sen, Fatih; Karatas, Yasar; Gulcan, Mehmet; Zahmakiran, Mehmet
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)(2)NHBH3), 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.
Carbon-Nanotube Rhodium Nanoparticles as Highly-Active Catalyst for Hydrolytic Dehydrogenation of Dimethylamineborane at Room Temperature
(Academic Press inc Elsevier Science, 2018) Gunbatar, Serdar; Aygun, Aysenur; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
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. (C) 2018 Elsevier Inc. All rights reserved.
The Catalytic Activity of Halloysite-Supported Ru Nanoparticles in the Methanolysis of Sodium Borohydride for Hydrogen Production
(Pergamon-elsevier Science Ltd, 2023) Gozeten, Ibrahim; Karakas, Kadir; Karatas, Yasar; Tunc, Mehmet; Gulcan, Mehmet
Finding environmentally friendly new energy sources is very urgent for a sustainable and clean energy future. It is vital to reach clean energy sources such as hydrogen, which does not create a polluting by-product when burned with oxygen. In this study, for a livable clean universe, hydrogen production studies were carried out from sodium borohydride (NaBH4), which is a very good hydrogen storage material, in a methanolysis environment, over ruthenium nanoparticles (Ru (0) NPs) impregnated on halloysite (Hall) support ma-terial (Ru (0)@Hall) at room conditions. The catalytic performance of the newly synthesized Ru (0)@Hall nanocatalyst was tested in the NaBH4 methanolysis reaction for hydrogen production. It was determined that Ru (0)/Hall nanocatalyst showed excellent activity (initial turn-over frequency (TOFinitial) = 1882 h-1; 31.37 min-1) and reusability (at the end of the 5th cycle, it retained 90% of its initial activity) performance in the catalytic meth-anolysis of NaBH4. The analyzes of the Ru (0)@Hall nanocatalyst, both fresh and at the end of the 5th catalytic cycle, were made with advanced analytical methods (ICP-OES, XRD, XPS, SEM, HRTEM, TEM, TEM-EDX, BET) and the nature of the catalytic material was clarified. The results showed the homogeneous distribution of Ru (0) NPs on the Hall surface (mean size = 1.53 +/- 0.17 nm). Kinetic studies of hydrogen production from catalytic methanolysis reaction of NaBH4 were performed based on nanocatalyst [Ru (0)@Hall], substrate [NaBH4] concentrations, and temperature (298-318 K). From the kinetic data, the kinetic parameters (Ea, DH*, and DS*) were calculated and the rate equation was determined.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Catalytic Methanolysis and Hydrolysis of Hydrazine-Borane With Monodisperse Ru Nps@nano-Ceo2 Catalyst for Hydrogen Generation at Room Temperature
(Pergamon-elsevier Science Ltd, 2019) Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
Herein, we report metal catalyzed methanolysis and hydrolysis of hydrazine-borane as a fast hydrogen generation system under mild conditions. To the best of our knowledge, this is the first report that a monodisperse Ru NPs@nano-CeO2 catalyst can achieve a complete conversion of N2H4BH3 to H-2 with the assistance of both methanolysis and hydrolysis reactions. In order to achieve hydrolysis and methanolysis effectively, monodisperse Ru NPs@nano-CeO2 catalyst have been prepared by modifying the chemical reduction method which is a very simple and efficient method in room conditions. The synthesized Ru NPs@nano-CeO2 catalyst showed excellent catalytic activity, stability, and selectivity in the production of hydrogen by both hydrolysis and methanolysis of the hydrazine-borane. The results reported here also includes (i) identification of the prepared catalyst by using analytical techniques such as XRD, XPS, TEM, HR-TEM, (ii) determination of stoichiometry for methanolysis and hydrolysis reactions, (iii) determination of rate constants and laws for methanolysis and hydrolysis reactions, (iv) determination of kinetic parameters such as enthalpy, entropy and activation energy for methanolysis and hydrolysis reactions. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Comparative of Mil101(Cr) and Nano-Mil101(cr) Electrode as an Electrochemical Hydrogen Peroxide Sensor
(Wiley-v C H verlag Gmbh, 2022) Salman, Firat; Kazici, Hilal Celik; Gulcan, Mehmet
Herein, an electrochemical sensor for the detection of H2O2 based on nafion glassy carbon electrode modified with MIL101(Cr) and nano-MIL101(Cr) are developed and its electrochemical characterizations analyzed by CV and CA. In comparison with the NGCE, MIL101/NGCE and nano-MIL101/NGCE, the nano-MIL101/NGCE showed a sharp redox peak specific to H2O2 was obtained in the phosphate-calibrated solution. nano-MIL101/NGCE exhibited good linear response in terms of the relationship between peak currents and concentrations as from 0 to 650 mu M (R-2=0.99), with a low limit of detection 3.8 mu M, high sensitivity 986 mu A mM(-1) cm(-2) and nano-MIL101/NGCE exhibited ideal repeatability, reproducibility, stability and the interference-free perception of H2O2.
Determination of Vanillin in Commercial Food Product by Adsorptive Stripping Voltammetry Using a Boron-Doped Diamond Electrode
(Elsevier Sci Ltd, 2013) Yardim, Yavuz; Gulcan, Mehmet; Senturk, Zuhre
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 60 s). A linear calibration graph was obtained in the concentration range of 0.5-15.0 mu g mL(-1) (3.3 x 10(-6)-9.8 x 10(-6) mol L-1) with a detection limit of 0.024 mu g mL(-1) (1.6 x 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). (C) 2013 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.
Enhancement in the Photovoltaic Efficiency of Dye-Sensitized Solar Cell by Doping Tio2 With Mil-101 Mof Structure
(Elsevier Sci Ltd, 2022) Ugur, Ali; Imer, Arife Gencer; Gulcan, Mehmet
In this work, pure and MIL-101 doped TiO2 films on fluorine doped tinoxide (FTO) were prepared by sol-gel method for dye sensitized solar cell (DSSC) fabrication. MIL-101 metal-organic framework (MOF) structure was synthesized by hydrothermal method and it was used as dopant in TiO2 to enhance an efficiency of DSSC device for the first time. The surface morphology of pure and MIL-101 doped TiO2 films were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), the crystallite size and structural properties of these films were studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques, respectively. Ultraviolet-visible spectroscopy (UV-Vis) measurement presents the change in an optical characteristic and the band gap of the film with MIL-101 incorporation owing to its high surface area. The efficiency enhancement in DSSC device with MIL-101 doping was analyzed via current-voltage (I-V) measurement under various power of solar simulator. The results confirm that power conversion efficiency (PCE) can enhance with MIL-101 doping into TiO2. The power conversion efficiency of MIL101@DSSC is 8.687% under 100 mW/cm(2) illumination power, which is 1.85 times greater than PCE of undoped DSSC (4.689%). The enhancing efficiency of MIL-101@DSSC can be associated with the energy band alignment, improvement in photoelectron trapping, and increase in dye adsorption owing to pore structure of MIL-101.
Enhancement of Adsorption Capacity of Reduced Graphene Oxide by Sulfonic Acid Functionalization: Malachite Green and Zn (Ii) Uptake
(Elsevier Science Sa, 2020) Sogut, Eda Gokirmak; Karatas, Yasar; Gulcan, Mehmet; Kilic, Necla Caliskan
Graphene oxide (GO) was synthesized according to the Hummers' method developed to remove some impurities such as malachite green dye and Zn (II) metal ion from aqueous solutions. However, due to the problem of dispersion in water, graphene oxide surface is generally functionalized or composites are prepared with different materials. For this reason, the produced graphene oxide is functionalized with sulfanilic acid to obtain reduced sulfonated graphene oxide (rGO-SO3H). For the characterization of materials, DR/UV-vis, Raman, FT-IR, SEM and SEM-EDX mapping techniques were used. Also, reduced graphene oxide (rGO) was evaluated as a comparative example in adsorption. Effect of parameters such as pH, initial concentration and temperature on the removal of metal ions and dye was studied. Equilibrium was achieved in 90 min. The highest percentage removal of rGO and rSGO was observed at pH = 7. Equilibrium isotherms are defined using nonlinear Langmuir, Freundlich, Dubinin - Radushkevich (D - R) and Sips adsorption isotherm equations. Maximum adsorption capacities were determined as 588.23 mg g 1 and 1111.11 mg g(-1) for malachite green, 166.66 mg g(-1) and 322.58 mg g(-1) for Zn (II), respectively for rGO and rGO-SO3H. Kinetic experimental results fit well with the pseudo-second order model for both dye and metal ion; coefficients of determination were close to 1. Thermodynamic studies showed that the adsorption was spontaneous and the adsorption processes were controlled by a physical mechanism.
Enhancing the Catalytic Activity of Pd Nanoparticles in the Hydrolysis of Ethylenediamine-Bisborane Through Sulfonation of Graphene Oxide as a Solid Support
(Pergamon-elsevier Science Ltd, 2024) Karatas, Yasar; Gulcan, Mehmet
Ethylenediamine-bisborane (EDB), with its high hydrogen storage capacity, has been in the limelight among researchers. In this study, a new catalytic hybrid material (Pd@rGO-SO3H), comprising sulfonated reduced graphene oxide (rGO-SO3H) and palladium (Pd), was developed. This material serves as a highly efficient and reusable catalyst in the hydrogen production from EDB hydrolysis. The synthesized EDB, rGO-SO3H, and Pd@rGO-SO3H were characterized using ICP-OES, PXRD, XPS, SEM, TEM, and TEM/EDX tools. The initial TOF value of the Pd@rGO-SO3H catalyst in hydrogen production from EDB hydrolysis was calculated as 136 min- 1. This TOF value was found to be remarkably high compared to related studies in the literature. The reusability performance of Pd@rGO-SO3H was observed to be quite stable. Finally, activation parameters, such as activation energy (Ea), activation enthalpy (Delta H#), and activation entropy (Delta S#) for the hydrolysis reaction, were calculated by conducting catalytic reactions at different temperatures using relevant equations.
Ex Situ Synthesis and Characterization of a Polymer-Carbon Nanotube-Based Hybrid Nanocatalyst With One of the Highest Catalytic Activities and Stabilities for the Hydrolytic Dehydrogenation of Hydrazine-Borane at Room Temperature Conditions
(Academic Press inc Elsevier Science, 2019) Demirkan, Buse; Kuyuldar, Esra; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
In this study, a facile ex situ synthesis of a polyaniline-multiwalled carbon nanotube-based Pt nanocatalyst (Pt@PANI-MWCNT) with an average particle size of 3.18 +/- 0.12 nm was performed successfully. The obtained Pt@PANI-MWCNT nanocatalysts were isolated from the solution medium by centrifugation and then were characterized by spectroscopy and microscopy methods. The characterization studies showed that the prepared Pt nanoparticles were formed on PANI-MWCNT surface, and H-2 evolution was obtained by the dehydrogenation of hydrazine-borane in water as a model reaction under room temperature conditions, with the help of the synthesized nanocatalyst. It was observed that the Pt@PANI-MWCNT nanocatalyst had a very high catalytic activity for the hydrolytic dehydrogenation of hydrazine-borane and generated 2.95 mol of H-2 for 1 mol of hydrazine-borane. The initial turn-over frequency (TOFinitial) value of the prepared nanocatalyst for the model reaction at room temperature conditions was found to be 168.5 min(-1). The calculations for the kinetics of the hydrolytic dehydrogenation reaction showed that the hydrazine-borane catalytic reaction kinetics are first order, with respect to the catalyst concentration; several activation parameters, such as entropy (Delta S-#, (app) = -72.11 +/- 3 J/mol K), enthalpy (Delta S-#, (app) = 43.5 +/- 2 kJ/mol) and activation energy (E-a,E- app = 45.5 +/- 2 kJ/mol), of the catalytic reaction with the Pt@PANI-MWCNT nanocatalyst were calculated using these kinetic data. (C) 2019 Elsevier Inc. All rights reserved.
Fabrication and Characterization of Copper Nanoparticles Anchored on Sulfonated Reduced Graphene Oxide as Effective Catalyst for the Reduction of Thioflavine-T Cationic Dye in Aqueous Medium
(Elsevier Science Sa, 2022) Yildirim, Rahel; Karatas, Yasar; Demirci, Umit B.; Gulcan, Mehmet
The development of innovative methods for the effective removal of toxic organic pollutants from wastewater is of paramount importance. Removal of organic pollutants from aqueous media by chemical reduction using low cost metal-based nanocatalysts and in the presence of sodium borohydride (NaBH4), as a reducing agent, has become a very valuable approach in recent years. We report the advanced catalytic property of copper (0) nanoparticles (Cu NPs) supported on sulfonated reduced graphene oxide (Cu@rGO-SO3H) for the catalytic reduction of thioflavine-T (ThT) dye in the presence of NaBH4, at moderate conditions. Cu@rGO-SO3H catalyst was synthesized by the impregnation-reduction method and diverse characterization techniques were applied to explain the structure and morphology. The results show that the Cu NPs are perfectly dispersed on the surface of the rGO-SO3H support surface (d(mean) = 6.9 +/- 0.4 nm). The catalytic activity of the Cu@rGO-SO3H catalyst was tested in the reduction of ThT in water at 298 K in the presence of NaBH4 and the excellent activity of catalyst have been detected against ThT with 30.5 min(-1) initial turn-over frequency (TOFinitial) value. Another important point is that the catalyst has good reusability performance (at 5th reuse 68%) for the catalytic reduction of ThT. Our catalytic studies were also carried out at various temperatures in order to calculate the E-a, Delta H-not equal and Delta S-not equal.
The First Approach for the Simultaneous Quantification of Isoproturon, Carbendazim, and Carbofuran at the Surface of a Mil-101(cr) Metal-Organic Framework-Based Electrode
(Elsevier, 2023) Pinar, Pinar Talay; Yardim, Yavuz; Gulcan, Mehmet; Senturk, Zuhre
A novel approach has been proposed for the simultaneous detection of isoproturon (ISO), carbendazim (CAR), and carbofuran (CRF) pesticides. This is achieved by employing an electrochemical sensor modified with nano- MIL-101(Cr) on a glassy carbon electrode, providing high selectivity and sensitivity. Structural and morpho-logical analysis of the nanomaterial was conducted using SEM, SEM/EDX, SEM Elemental Mapping, P-XRD, and FT-IR techniques. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square wave voltammetry (SWV) techniques were utilized to characterize nano-MIL-101(Cr) and assess its suitability as an electrode material for sensing purposes. The electrochemical sensor demonstrated strong linearity in simultaneously determining ISO (+0.98 V, vs. Ag/AgCl), CAR (+1.19 V, vs. Ag/AgCl), and CRF (+1.34 V, vs. Ag/AgCl) across concentration ranges of 0.25-2.50 mu M, 0.1-2.0 mu M, and 1.0-20.0 mu M, respectively, under optimized conditions. Detection limits for ISO, CAR, and CRF were determined as 0.015 mu M, 0.02 mu M, and 0.32 mu M, respectively. The proposed electrochemical sensor was effectively employed for analyzing real samples, such as soil and river water, for pesticide detection.
Fluorescence Properties and Electrochemical Behavior of Some Schiff Bases Derived From N-Aminopyrimidine
(Springer/plenum Publishers, 2014) Gulcan, Mehmet; Dogru, Umit; Ozturk, Gulsiye; Levent, Abdulkadir; Akbas, Esvet
A series of Schiff bases (L (1) , L (2) and L (3) ) were prepared by refluxing aromatic aldehydes with N-Aminopyrimidine derivatives in methanol and ethanol. The structures of synthesized compounds were characterized by FTIR, H-1 NMR, C-13 NMR and microanalysis. The electrochemical behaviors of the Schiff base ligands were also discussed. Moreover, the evaluation of absorption and emission properties of the structures were carried out in five different solvents. The products show visible absorption maxima in the range of 304-576 nm, and emission maxima from 636 to 736 nm in all solvents tested.
Green and Efficient Oxidative Desulfurization of Refractory S-Compounds From Liquid Fuels Catalyzed by Chromium-Based Mil-101 Stabilized Moox Catalyst
(Elsevier, 2022) Gumus, Ilkay; Karatas, Yasar; Gulcan, Mehmet
In this work, MoOx/MIL-101(Cr) a new composite material, involving the collaboration of MoOx and MIL-101 (Cr) to remove the refractory S-compounds (RSCs) from fuels via oxidative desulfurization (ODS) process were successfully synthesized. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), powder X-ray diffraction (P-XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), fourier transform infrared spectroscopy (FT-IR), N-2 sorption measurement (BET) and X-ray photoelectron spectroscopy (XPS). The prepared MoOx/MIL-101(Cr) was applied for the ODS of model fuel oil and showed the remarkably catalytic activity for the removal of RSCs from model fuel oil via oxidation. In addition, the effect of Mo-loading amount, H2O2/sulfur (O/S) molar ratio, and reaction temperature on the ODS reactivity were investigated. To explore the specific reaction mechanism of ODS over the MoOx/MIL-101(Cr), the effect of radical scavengers on ODS activity was examined. The radical scavengers experiments showed that the present oxidation reaction occurred through a radical mechanism involving the formation of center dot OH and center dot O-2 species. In addition, it was found that the ODS efficiency is majorly related to the Mo5+ species forming with electron transfer to Mo6+ ion from Lewis acid sites of MIL-101(Cr). Furthermore, the MoOx/MIL-101(Cr) catalyst possesses recycling performance and remarkable stability, and even after five recycles, the removal of DBT was > 94.8%. Hence, it could be confirmed that MoOx/MIL-101(Cr) is very useful in the ODS to remove RSCs from fuels in the presence of H2O2.
Green Synthesis of Palladium Nanoparticles: Preparation, Characterization, and Investigation of Antioxidant, Antimicrobial, Anticancer, and Dna Cleavage Activities
(Wiley, 2021) Gulbagca, Fulya; Aygun, Aysenur; Gulcan, Mehmet; Ozdemir, Sadin; Gonca, Serpil; Sen, Fatih
Green synthesis is considered to be one of the most suitable method because it enhances the therapeutic effects of palladium nanoparticles (Pd NPs). In this study, various biological activities such as antimicrobial, anticancer, antioxidant, and DNA cleavage activities of Urtica-mediated green synthesizing Pd NPs were investigated. The synthesized Pd NPs were characterized by using UV-vis, XPS, FT-IR, TEM, and XRD analyses. As a result of the TEM analysis of Pd NPs, the mean particle size was found to be 7.44 +/- 1.94 nm, and this result was supported by XRD analysis. The maximum DPPH scavenging activity was determined as 79.6% at 500 mg/L. The newly green synthesized Pd NPs exhibited high antimicrobial activity to gram-negative bacteria than gram-positive bacteria. Urtica-mediated green synthesized Pd NPs also showed double strain DNA cleavage activity. For the cytotoxic effects of Pd NPs, the MDA-MB-231 breast cancer cell line, HT-29 colon cancer cell line, Mia Paca-2 human pancreatic cancer cell line, and healthy cell line L929-Murine fibroblast cell line were used. IC50 values of Pd NPs against MDA-MB-231, HT-29, and MIA PaCa-2 cancer cell lines were calculated as 31.175, 20.383, and 29.335 mu g/ml, respectively. No significant cytotoxic effect was observed in the healthy lines L929.
H2 Production From the Hydrolytic Dehydrogenation of Methylamine-Borane Catalyzed by Sulfonated Reduced Graphene Oxide-Aided Synthesis of Ruthenium Nanoparticles
(Pergamon-elsevier Science Ltd, 2021) Yildirim, Rahel; Gulcan, Mehmet
A new catalyst was prepared using sulfonated reduced graphene oxide support with a large surface area containing ruthenium nanoparticles (Ru@rGO-SO3H). The developed Ru@rGO-SO3H catalyst was used in the hydrogen production process from the hydrolytic dehydrogenation of methylamine-borane (MeAB). Sulfonated reduced graphene oxide and the developed catalyst were characterized by Raman and FT-IR spectroscopies, ICP-OES, XRD, XPS, TEM, TEM-EDX, SEM and SEM-EDX techniques. The average particle size of Ru nano particles, which were homogeneously distributed on the sulfonated reduced graphene oxide surface, was found as 2.2 +/- 0.2 nm. After analyzing the effect of nanocatalyst and substrate concentrations on the catalytic reaction, reactions were realized at different temperatures, the efficiency of the Ru@rGO-SO3H nanocatalyst in initial turnover frequency (TOFinitial) and the activation parameters (E-a, Delta H-# and Delta S-#) were calculated. According to the data obtained, the TOFinitial value was calculated as 5300.86 h(-1) (88.35 min(-1)). E-a, Delta H-# and Delta S-# values were also calculated as 53.83 kJ/mol, 50.73 kJ/mol and -51.55 J/mol.K, respectively. Finally, when the reusability performance results of the catalyst are evaluated, it is found that the catalyst is very stable and retains its initial effectiveness to a great extent (>95%) after the 5th reuse. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Highly Efficient and Selective One-Pot Tandem Imine Synthesis Via Amine-Alcohol Cross-Coupling Reaction Catalysed by Chromium-Based Mil-101 Supported Au Nanoparticles
(Elsevier, 2021) Gumus, Ilkay; Ruzgar, Adem; Karatas, Yasar; Gulcan, Mehmet
One-pot tandem synthesis of imines from alcohols and amines is regarded as an effective, economic and green approach under mild conditions. In this work, Au nanoparticles (NPs) dispersed on MIL-101 (Au/MIL-101) were demonstrated as highly active and selective bifunctional heterogeneous catalyst for production of various imine derivatives with excellent yields, via amine-alcohol cross-coupling reaction at 343 K in an open flask under an Ar atmosphere. Various physicochemical techniques, including inductively coupled plasma optical emission spectroscopy (ICP-OES), powder X-ray diffraction (P-XRD), X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) and N2 adsorption-desorption, were used to characterize of the Au/MIL-101 catalyst. The obtained bifunctional catalyst is highly active and selective towards one-pot imine formation and exhibited the highest TOF (30.15-51.47 h(-1)) among all the ever-reported MOF-supported Au catalysts. The reaction mechanism of the imine formation from alcohol and amine over Au/MIL-101 catalyst was proposed. Mechanism experiment results demonstrate that Au NPs highly effective in activating oxidation of benzyl alcohol to benzaldehyde while the Lewis acid sites on MIL-101 catalyzed the second condensation step without interfering with the oxidation step. As a result, the excellent catalytic performance of Au/MIL-101 can be ascribed to the synergistic effect between Au NPs with Lewis acid sites in MIL-101.
Hydroxyapatite-Nanosphere Supported Ruthenium(0) Nanoparticle Catalyst for Hydrogen Generation From Ammonia-Borane Solution: Kinetic Studies for Nanoparticle Formation and Hydrogen Evolution
(Royal Soc Chemistry, 2014) Durak, Halil; Gulcan, Mehmet; Zahmakiran, Mehmet; Ozkar, Saim; Kaya, Murat
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 degrees 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 H-2 per mole of ammonia-borane at 25 +/- 0.1 degrees 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 k(1)) and P + Q -> 2Q (rate constant k(2)), 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 (E-a, Delta H-#, and Delta S-#) of the reaction.