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Sample records for monodispersed pd nanoparticles

  1. Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

    OpenAIRE

    Zhen Yin; Yining Zhang; Kai Chen; Jing Li; Wenjing Li; Pei Tang; Huabo Zhao; Qingjun Zhu; Xinhe Bao; Ding Ma

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the s...

  2. Monodispersed bimetallic PdAg nanoparticles with twinned structures: formation and enhancement for the methanol oxidation.

    Science.gov (United States)

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-03-10

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd₈₀Ag₂₀, Pd₆₅Ag₃₅ and Pd₄₆Ag₅₄ can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd₈₀Ag₂₀ nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system.

  3. One-pot synthesis of graphene-supported monodisperse Pd nanoparticles as catalyst for formic acid electro-oxidation.

    Science.gov (United States)

    Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

    2014-03-28

    To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

  4. One-Pot Synthesis of Graphene-Supported Monodisperse Pd Nanoparticles as Catalyst for Formic Acid Electro-oxidation

    Science.gov (United States)

    Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

    2014-03-01

    To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

  5. CO ppb sensors based on monodispersed SnOx:Pd mixed nanoparticle layers: Insight into dual conductance response

    Science.gov (United States)

    Aruna, I.; Kruis, F. E.; Kundu, S.; Muhler, M.; Theissmann, R.; Spasova, M.

    2009-03-01

    This study reports the modifications in CO sensing of SnOx nanoparticle layers by utilizing monodispersed Pd nanoparticles. The distinct advantage of monosized particles and contaminant-free samples with open porosity in addition to size effects resulted in improved CO sensing with decrease in Pd nanoparticle size to 5 nm, decreasing the lowest detection levels of CO using SnOx-based sensor technology down to 10 ppb (parts per billion) in dry synthetic air. The homogeneously mixed nanoparticle layers also exhibit discrimination capability between CO and ethanol in dry air as a manifestation of the dual conductance response. Detailed x-ray photoelectron spectroscopy studies clearly reveal "Mars-van Krevelen" as the key mechanism responsible for the observed sensing in mixed nanoparticle layers. The interfacial/surface PdO formed upon pretreatment in air is continuously "consumed" and "reformed" upon exposure, respectively, to CO and synthetic air. In contrast to the case of ethanol exposure with n-type response, the Pd aided reduction of tin oxide surface in CO ambient leads to p-type response. The sensors of the present study have a wide range of promising applications from air quality control to food and fuel industries.

  6. Aerosol fabrication methods for monodisperse nanoparticles

    Science.gov (United States)

    Jiang, Xingmao; Brinker, C Jeffrey

    2014-10-21

    Exemplary embodiments provide materials and methods for forming monodisperse particles. In one embodiment, the monodisperse particles can be formed by first spraying a nanoparticle-containing dispersion into aerosol droplets and then heating the aerosol droplets in the presence of a shell precursor to form core-shell particles. By removing either the shell layer or the nanoparticle core of the core-shell particles, monodisperse nanoparticles can be formed.

  7. Synthesis and antimicrobial activity of monodisperse copper nanoparticles.

    Science.gov (United States)

    Kruk, Tomasz; Szczepanowicz, Krzysztof; Stefańska, Joanna; Socha, Robert P; Warszyński, Piotr

    2015-04-01

    Metallic monodisperse copper nanoparticles at a relatively high concentration (300 ppm CuNPs) have been synthesized by the reduction of copper salt with hydrazine in the aqueous SDS solution. The average particles size and the distribution size were characterized by Dynamic Light Scattering (DLS), Nanosight-Nanoparticle Tracking Analysis (NTA). The morphology and structure of nanoparticles were investigated using Scanning Electron Microscopy (SEM). The chemical composition of the copper nanoparticles was determined by X-ray Photoelectron Spectroscopy (XPS). Monodisperse copper nanoparticles with average diameter 50 nm were received. UV/vis absorption spectra confirmed the formation of the nanoparticles with the characteristic peak 550 nm. The antimicrobial studies showed that the copper nanoparticles had high activity against Gram-positive bacteria, standard and clinical strains, including methicillin-resistant Staphylococcus aureus, comparable to silver nanoparticles and some antibiotics. They also exhibited antifungal activity against Candida species. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Preparation and Characterization of Monodisperse Nickel Nanoparticles by Polyol Process

    Institute of Scientific and Technical Information of China (English)

    LI Peng; GUAN Jianguo; ZHANG Qingjie; ZHAO Wenyu

    2005-01-01

    Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly ( N-vinyl- 2-pyrrolidone ). These nanoparticles were characterized by transmission electron microscopy (TEM), X- ray diffraction ( XRD ), selected area electron diffraction ( SAED ), as well as vibrating sample magnetometer (VSM). The experimental results show that the addition of PVP and the concentration of NaOH have strong influences on the size, agglomeration and uniformity of nanoparticles. In the presence of PVP and NaOH with low concentrations, monodisperse nickel nanoparticles with average diameters about 42 nm were obtained and characterized to be pure nickel crystalline with fcc structure. Secondary structures such as clusters, loops, and strings resulted from magnetic interactions between particles were observed. The chemical interaction between the PVP and nickel nanoparticles was found by FTIR. The saturation magnetization ( Ms ), remanent magnetization (Mr) and coercivity ( Hc ) of these nickel nanoparticles are lower than those of bulk nickel.

  9. Synthesis of Monodisperse Iron Oxide Nanoparticles without Surfactants

    Directory of Open Access Journals (Sweden)

    Xiao-Chen Yang

    2014-01-01

    Full Text Available Monodisperse iron oxide nanoparticles could be successfully synthesized with two kinds of precipitants through a precipitation method. As-prepared nanoparticles in the size around 10 nm with regular spherical-like shape were achieved by adjusting pH values. NaOH and NH3·H2O were used as two precipitants for comparison. The average size of nanoparticles with NH3·H2O precipitant got smaller and represented better dispersibility, while nanoparticles with NaOH precipitant represented better magnetic property. This work provided a simple method without using any organic solvents, organic metal salts, or surfactants which could easily obtain monodisperse nanoparticles with tunable morphology.

  10. Highly monodisperse bismuth nanoparticles and their three-dimensional superlattices.

    Science.gov (United States)

    Yarema, Maksym; Kovalenko, Maksym V; Hesser, Günter; Talapin, Dmitri V; Heiss, Wolfgang

    2010-11-01

    A simple and reproducible synthesis of highly monodisperse and ligand-protected bismuth nanoparticles (Bi NPs) is reported. The size of the single-crystalline and spherically shaped NPs is controlled between 11 and 22 nm mainly by the reaction temperature. The high uniformity of the NPs allows their self-assembly into long-range-ordered two- and three-dimensional superstructures.

  11. Monodispersive CoPt Nanoparticles Synthesized Using Chemical Reduction Method

    Institute of Scientific and Technical Information of China (English)

    SHEN Cheng-Min; HUI Chao; YANG Tian-Zhong; XIAO Cong-Wen; CHEN Shu-Tang; DING Hao; GAO Hong-Jun

    2008-01-01

    @@ Monodispersive CoPt nanoparticles in sizes of about 2.2 nm are synthesized by superhydride reduction of CoCl2 and PtCl2 in diphenyl ether. The as-prepared nanoparticles show a chemically disordered A1 structure and are superparamagnetic. Thermal annealing transforms the A1 structure into chemically ordered L1o structure and the particles are ferromagnetic at room temperature.

  12. Monodisperse magnesium hydride nanoparticles uniformly self-assembled on graphene.

    Science.gov (United States)

    Xia, Guanglin; Tan, Yingbin; Chen, Xiaowei; Sun, Dalin; Guo, Zaiping; Liu, Huakun; Ouyang, Liuzhang; Zhu, Min; Yu, Xuebin

    2015-10-21

    Monodisperse MgH2 nanoparticles with homogeneous distribution and a high loading percent are developed through hydrogenation-induced self-assembly under the structure-directing role of graphene. Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.

  13. Monodisperse Silver Nanoparticles Synthesized by a Microwave-Assisted Method

    Institute of Scientific and Technical Information of China (English)

    ZHU Shao-Peng; TANG Shao-Chun; MENG Xiang-Kang

    2009-01-01

    Silver nanoparticles with an average size of about 2Onto are synthesized in a colloidal solution with the aid of microwave irradiation. Neither additional reductant nor stabilizer is required in this microwave-assisted method.The color of the colloidal solution is found to be dark green, different from the characteristic yellow of silver colloidal solutions. The silver nanoparticles in the colloidal solution have a narrow size distribution and large yield quantity. UV-visible absorption spectroscopy analysis reveals that the as-synthesized monodisperse silver nanoparticles have exceptional optical properties. Raman spectroscopy measurements demonstrate that these silver nanoparticles exhibit a notable surface-enhanced Raman scattering ability.

  14. A Facile Solvothermal Synthesis of Monodisperse Ni Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    YU Peng-fei; CUI Bin; ZHANG Yan; SHI Qi-zhen

    2008-01-01

    A simple solvothermal approach was developed to synthesize uniform spherical monodisperse Ni nanoparticles, which can easily disperse in nonpolar solvents to form homogenous colloidal solution. The as-prepared sample was characterized by XRD, TEM, and FTIR. The results indicate that Ni nanoparticles have the structure of face-centered cube and a narrow distribution with a diameter of (3.5±0.5) nm. The FTIR spectrum reveals that the as a surfactant. The probable formation mechanism of the spherical nanoparticles was also discussed.

  15. A facile one-pot synthesis and enhanced formic acid oxidation of monodisperse Pd-Cu nanocatalysts.

    Science.gov (United States)

    Park, Kyu-Hwan; Lee, Young Wook; Kang, Shin Wook; Han, Sang Woo

    2011-06-06

    Highly monodisperse spherical 3 nm Pd-Cu alloy nanoparticles (NPs) were synthesized in high yield through the coreduction of [Pd(acac)(2)] (acac=acetylacetonate) and [Cu(acac)(2)] in nonhydrolytic solutions by using trioctylamine and oleic acid. The relative compositions of Pd and Cu could be tuned by controlling the molar ratios between the metal precursors in the raw solutions. The carbon-supported Pd-Cu NPs (Pd-Cu/C) were chemically dealloyed by acetic acid washing, which resulted in the formation of porous structures. The prepared Pd-Cu/C catalysts exhibited at least threefold enhancement of Pd mass activities compared with a commercial Pd/C catalyst toward formic acid oxidation in an acidic medium, and also showed outstanding electrocatalytic stabilities. The improved electrocatalytic properties of the Pd-Cu NPs are attributed to the presence of a large number of active sites on their surfaces owing to their small particle sizes and chemically dealloyed porous structures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles

    Science.gov (United States)

    Wang, Peng; Qi, Xuan; Zhang, Xuemin; Wang, Tieqiang; Li, Yunong; Zhang, Kai; Zhao, Shuang; Zhou, Jun; Fu, Yu

    2017-01-01

    This work has mainly investigated the influence of the solvent on the nanoparticles distribution in digestive ripening. The experiments suggested that the solvents played a key role in digestive ripening of Au nanoparticles (Au NPs). For the benzol solvents, the resulting size distribution of Au NPs was inversely related to the solvent polarity. It may be interpreted by the low Gibbs free energy of nanoparticles in the high polarity medium, which was supposedly in favor of reducing the nanoparticles distribution. Through digestive ripening in the highly polar benzol solvent of p-chlorotoluene, monodisperse Au NPs with relative standard deviation (RSD) of 4.8% were achieved. This indicated that digestive ripening was an effective and practical way to prepare high-quality nanoparticles, which holds great promise for the nanoscience and nanotechnology.

  17. Structure and Hydration of Highly Branched, Monodisperse Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Stanley, Christopher; Diallo, Souleymane; Katsaras, John; Dutcher, John

    Monodisperse phytoglycogen nanoparticles are a promising, new soft colloidal nanomaterial with many applications in the personal care, food, nutraceutical and pharmaceutical industries. These applications rely on exceptional properties that emerge from the highly branched structure of phytoglycogen and its interaction with water, such as extraordinarily high water retention, and low viscosity and exceptional stability in water. The structure and hydration of the nanoparticles was characterized using small angle neutron scattering (SANS) and quasielastic neutron scattering (QENS). SANS allowed us to determine the size of the nanoparticles, evaluate their radial density profile, quantify the particle-to-particle spacing, and determine their water content. The results show clearly that the nanoparticles are highly hydrated, with each nanoparticle containing 250% of its mass in water, and that aqueous dispersions approach a jamming transition at ~ 25% (w/w). QENS experiments provided an independent and consistent measure of the high level of hydration of the particles.

  18. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  19. A novel method for preparing monodispersed polystyrene nanoparticles

    Institute of Scientific and Technical Information of China (English)

    LIU Kaiyi; WANG Zhaoqun

    2007-01-01

    A preparation manner for monodispersed polystyrene(PS)nanoparticles polymerized by using a novel addition procedure of a monomer is suggested.In systems containing a smaller amount of surfactant compared with conventional microemulsion polymerization,the polymerization processes consists of three stages:adding dropwise the first part of the monomer for a few minutes at 80℃ and polymerizing for 1 h;adding collectively the residual part of the monomer and polymerizing at the same temperature for another 1 h;and then polymerizing at 85℃ for another 1 h.Based on discussions on the nucleation mechanism of particles in the polymerization system,the influences of monomer weight added dropwise,and amounts of initiator and emulsifier on the size and distribution of PS particles were investigated.PS nanoparticles with smaller diameter such as a number-average diameter of 18.7 nm and better monodispersity were obtained since the dropped styrene amount was suitable under 20wt-% emulsifier amount and 3wt-% initiator amount based on the monomer.

  20. Supported Pd-Cu bimetallic nanoparticles that have high activity for the electrochemical oxidation of methanol.

    Science.gov (United States)

    Yin, Zhen; Zhou, Wu; Gao, Yongjun; Ma, Ding; Kiely, Christopher J; Bao, Xinhe

    2012-04-16

    Monodisperse bimetallic Pd-Cu nanoparticles with controllable size and composition were synthesized by a one-step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd(85)-Cu(15), Pd(56)-Cu(44), and Pd(39)-Cu(61). The nanoparticles were separated from the solution mixture by extraction with non-polar solvents, such as n-hexane. Monodisperse bimetallic Pd-Cu nanoparticles with narrow size-distribution were obtained without the need for a size-selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as-prepared nanoparticles were loaded onto a Vulcan XC-72 carbon support. Supported bimetallic Pd-Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd-Cu catalyst that contained 15 % Cu, the activity was even comparable to the state-of-the-art commercially available Pt/C catalysts. A STEM-HAADF study indicated that the formation of random solid-solution alloy structures in the bimetallic Pd(85)-Cu(15)/C catalysts played a key role in improving the electrochemical activity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Oleylamine-mediated synthesis of Pd nanoparticles for catalytic formic acid oxidation.

    Science.gov (United States)

    Mazumder, Vismadeb; Sun, Shouheng

    2009-04-08

    We report a facile synthesis of monodisperse Pd nanoparticles by the reduction of Pd(acac)(2) with oleylamine and borane tributylamine complex. The oleylamine-coated Pd nanoparticles are readily "cleaned" with a 99% acetic acid wash, and the Pd particles supported on Ketjen carbon are catalytically active for formic acid oxidation in HClO(4) solution. The catalyst shows no obvious activity degradation after 1500 cyclic voltammetry cycles under ambient conditions. These Pd particles hold promise as a highly active non-Pt catalyst for fuel cell applications.

  2. Ultrasonically Aided Electrospray source for monodisperse, charged nanoparticles

    Science.gov (United States)

    Song, Weidong

    This dissertation presents a new method of producing nearly monodisperse electrospray using charged capillary standing waves. This method, based on the Ultrasonically Aided Electrospraying (UAE) technology concept invented by the author, includes the steps of dispensing a liquid on the top surface of a diaphragm so as to form a liquid film on the surface of the diaphragm, setting the diaphragm into vibration using piezoelectric transducers so as to induce capillary standing waves in the liquid film, applying electric charge to the capillary standing waves so that electrospray is extracted from the crests of the capillary standing waves. Theoretical analysis on the formation of charged particles from charged capillary standing waves at critically stable condition is performed. An experimental UAE system is designed, built, and tested and the performance of this new technology concept is assessed. Experimental results validate the capabilities of the UAE concept. The method has several applications including electric space propulsion, nano particulate technologies, nanoparticle spray coating and painting techniques, semiconductor fabrication and biomedical processes. Two example applications in electric space propulsion and nanoparticle spray coating are introduced.

  3. Solvothermal synthesis and characterization of monodisperse superparamagnetic iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shichuan; Zhang, Tonglai; Tang, Runze; Qiu, Hao [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); Wang, Caiqin [Shandong Special Industry Group Co., Ltd, Shandong 255201 (China); Zhou, Zunning [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

    2015-04-01

    A series of magnetic iron oxide nanoparticle clusters with different structure guide agents were synthesized by a modified solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analyses (TG), a vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR). It is found that the superparamagnetic nanoparticles guided by NaCit (sodium citrate) have high saturation magnetization (M{sub s}) of 69.641 emu/g and low retentivity (M{sub r}) of 0.8 emu/g. Guiding to form superparamagnetic clusters with size range of 80–110 nm, the adherent small-molecule citrate groups on the surface prevent the prefabricated ferrite crystals growing further. In contrast, the primary small crystal guided and stabilized by the PVP long-chain molecules assemble freely to larger ones and stop growing in size range of 100–150 nm, which has saturation magnetization (M{sub s}) of 97.979 emu/g and retentivity (M{sub r}) of 46.323 emu/g. The relevant formation mechanisms of the two types of samples are proposed at the end. The superparamagnetic ferrite clusters guided by sodium citrate are expected to be used for movement controlling of passive interference particles to avoid aggregation and the sample guided by PVP will be a candidate of nanometer wave absorbing material. - Highlights: • A facile synthesis of two kinds of monodisperse iron oxide nano-particle clusters was performed via a modified one-step solvothermal method in this work. • The NaCit and PVP as different guiding agents are used to control the formation and aggregation of nano-crystals during reacting and the ripening processes. • The superparamagnetic NaCit–Fe{sub 3}O{sub 4} samples have high saturation magnetization (M{sub s}) of 69.641 emu/g and low retentivity (M{sub r}) of 0.8 emu/g. • The relevant formation mechanisms of the two types of samples are proposed.

  4. Preparation of Monodisperse Nanoparticle of Layered Double Hydroxides and Polyoxyethylene Sulfate

    Institute of Scientific and Technical Information of China (English)

    XU Huizhong; QIN Lianjie; ZHANG Hong; YANG Qinzheng; YANG Jing

    2005-01-01

    In order to obtain the bio-molecule/ LDHs nanocomposites having regular crystal structure,three nanocomposites of layered double hydroxides and polyoxyethylene sulfates were prepared by ion-exchange method. TEM analysis reveals that the monodisperse rigid .sphere of approximately 200 nm in diameter could be gotten when the intergallery anion was PEGS-400. Such monodisperse nanoparticle could be used as a promising precursor for preparing bio-molecule/LDHs nanocomposites.

  5. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Sumeet Kumar

    2015-02-01

    Full Text Available In the present study, monodispersed CeO2 nanoparticles (NPs of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD, field emission scanning electron microscope (FE-SEM, high resolution transmission electron microscopy (HR-TEM, ultra-violet visible (UV-VIS spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms, coercivity (Hc and retentivity (Mr are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

  6. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sumeet; Ojha, Animesh K. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad-211004 (India); Srivastava, Manish, E-mail: 84.srivastava@gmail.com, E-mail: manish-mani84@rediffmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Singh, Jay [Department of Applied Chemistry and Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Layek, Samar [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Yashpal, Madhu [Electron Microscope Facility, Department of Anatomy Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005 (India); Materny, Arnulf [Center for Functional Materials and Nanomolecular Science, Jacobs University Bremen, Campus Ring, 28759 Bremen (Germany)

    2015-02-15

    In the present study, monodispersed CeO{sub 2} nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce{sup 4+} into Ce{sup 3+} at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm{sup -1} for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce{sup 3+} ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO{sub 2} samples.

  7. Formation mechanism of monodisperse, low molecular weight chitosan nanoparticles by ionic gelation technique.

    Science.gov (United States)

    Fan, Wen; Yan, Wei; Xu, Zushun; Ni, Hong

    2012-02-01

    Chitosan nanoparticles have been extensively studied for drug and gene delivery. In this paper, monodisperse, low molecular weight (LMW) chitosan nanoparticles were prepared by a novel method based on ionic gelation using sodium tripolyphosphate (TPP) as cross-linking agent. The objective of this study was to solve the problem of preparation of chitosan/TPP nanoparticles with high degree of monodispersity and stability, and investigate the effect of various parameters on the formation of LMW chitosan/TPP nanoparticles. It was found that the particle size distribution of the nanoparticles could be significantly narrowed by a combination of decreasing the concentration of acetic acid and reducing the ambient temperature during cross-linking process. The optimized nanoparticles exhibited a mean hydrodynamic diameter of 138 nm with a polydispersity index (PDI) of 0.026 and a zeta potential of +35 mV, the nanoparticles had good storage stability at room temperature up to at least 20 days.

  8. Effects of PVP on the preparation and growth mechanism of monodispersed Ni nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Monodispersed Ni nanoparticles were successfully prepared by chemical reduction with hydrazine hydrate in ethylene glycol.The effect of the amount of polyvinylpyrrolidone (PVP-K30) on the preparation of Ni nanoparticles was investigated.X-ray diffraction (XRD),transmission electron microscopy (TEM),and high resolution transmission electron microscopy (HRTEM) were employed to characterize the nickel particles are spherical in shape and are not agglomerated.A possible extensive mechanism of nickel nanoparticle formation has been suggested.

  9. An efficient photochemical route to Pd nanoparticles; application to the one-step synthesis of Pd@polymer nanocomposite films

    Science.gov (United States)

    Wolak, Séverine; Vidal, Loïc; Becht, Jean-Michel; Michelin, Laure; Balan, Lavinia

    2016-08-01

    We have developed a facile, efficient, low cost and ‘green’ photochemical approach to preparing surfactant-free Pd nanoparticles and Pd-immobilized@acrylate photo-polymer films at room temperature, under air and without any additional treatment. The reaction system only includes a photo-initiator used as a generator of free radicals and a Pd(II) salt. In ethanol solution, the photochemical reduction of Pd(II) to Pd(0) generates very small metal particles with a narrow size distribution (2-4 nm). Furthermore, we have shown that the formation of Pd nanoparticles from a Pd(II) salt can be reversible thus allowing easy handling and safe storage with the possibility of generating the nanoparticles just before use. In the presence of an acrylate bifunctional monomer, Pd@polymer film was obtained through a ‘one-pot, one-step’ process resulting from a simultaneous photo-reduction of Pd(II) and photo-polymerization of acrylate units. The simultaneous generation of a 3D polymer network and of metal particles leads to a homogeneous distribution of Pd nanoparticles in the photo-polymer matrix with an average diameter of approximately 3.7 ± 1.1 nm. Such as-prepared Pd@polymer films were found to efficiently catalyze the Mizoroki-Heck reaction in the presence of only 0.9 mequiv. of supported palladium. The major interest of this arrangement is its recoverability and reusability, which makes it very attractive both from a practical and economical viewpoint. Finally, it is worth noting that this innovation offers a great advantage over concurrent methods in that it is simply generated within minutes, it is highly stable, and there is sharp monodispersity in the size of the Pd nanoparticles that can be stored for months without alteration of their physico-chemical properties and catalytic activity.

  10. Conventional and microwave hydrothermal synthesis of monodispersed metal oxide nanoparticles at liquid-liquid interface

    Science.gov (United States)

    Monodispersed nanoparticles of metal oxide including ferrites MFe2O4 (M=, Ni, Co, Mn) and γ-Fe2O3, Ta2O5 etc. have been synthesized using a water-toluene interface under both conventional and microwave hydrothermal conditions. This general synthesis procedure uses readily availab...

  11. Preparation and Nonlinearity properties of Pd Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Pd nanoparticles less than 8 nm were photoinduced by a near-IR femtosecond laser. The sign of the refraction nonlinearity is negative for the Pd nanoparticles with TiO2, while it is positive for those without TiO2.

  12. Controlled Synthesis and Characterization of Monodisperse Fe3O4 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    SHI,Rongrong; GAO,Guanhua; YI,Ran; ZHOU,Kechao; QIU,Guanzhou; LIU,Xiaohe

    2009-01-01

    Monodisperse Fe3O4 nanoparticles were successfully synthesized through the thermal decomposition of iron acetylacetonate in octadecene solvent in the presence of oleic acid and oleylamine.The influences of experimental parameters,such as reacting temperature,amounts and kinds of surfactants,solvents,oleic acid and oleylamine,on the size and shape of monodisperse Fe3O4 nanoparticles were discussed.The phase structures,morphology,and size of the as-prepared products were investigated in detail by X-ray diffraction (XRD),transmission electron microscopy (TEM),selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM).Magnetic property was measured using a vibrating sample magnetometer (VSM) at room temperature,which revealed that Fe3O4 nanoparticles were of ferromagnetism with a saturation magnetization (Ms) of 74.0 emu/g and coercivity (Hc) of 72.6 Oe.

  13. Fabrication of monodisperse magnetic nanoparticles released in solution using a block copolymer template

    Science.gov (United States)

    Morcrette, Mélissa; Ortiz, Guillermo; Tallegas, Salomé; Joisten, Hélène; Tiron, Raluca; Baron, Thierry; Hou, Yanxia; Lequien, Stéphane; Bsiesy, Ahmad; Dieny, Bernard

    2017-07-01

    This paper describes a fabrication process of monodisperse magnetic nanoparticles released in solution, based on combined ‘top-down’ and ‘bottom-up’ approaches. The process involves the use of a self-assembled PS-PMMA block copolymer formed on a sacrificial layer. Such an approach was so far mostly explored for the preparation of patterned magnetic media for ultrahigh density magnetic storage. It is here extended to the preparation of released monodisperse nanoparticles for biomedical applications. A special sacrificial layer had to be developed compatible with the copolymer self-organization. The resulting nanoparticles exhibit very narrow size dispersion (≈7%) and can be good candidates as contrast agents for medical imaging i.e. magnetic resonance imaging or magnetic particle imaging. The approach provides a great freedom in the choice of the particles shapes and compositions. In particular, they can be made of biocompatible magnetic material.

  14. Synthesis and assembly of Pd nanoparticles on graphene for enhanced electrooxidation of formic acid

    Science.gov (United States)

    Jin, Tao; Guo, Shaojun; Zuo, Jing-Lin; Sun, Shouheng

    2012-12-01

    Monodisperse 4.5 nm Pd nanoparticles (NPs) were synthesized by solution phase reduction of palladium acetylacetonate with morpholine borane in a mixture of oleylamine and 1-octadecene. These NPs were assembled on graphene uniformly in the form of a monolayer, and showed much enhanced catalysis for electrooxidation of formic acid. The work demonstrates the great potential of graphene as a support to enhance NP catalysis and stability for important chemical oxidation reactions.Monodisperse 4.5 nm Pd nanoparticles (NPs) were synthesized by solution phase reduction of palladium acetylacetonate with morpholine borane in a mixture of oleylamine and 1-octadecene. These NPs were assembled on graphene uniformly in the form of a monolayer, and showed much enhanced catalysis for electrooxidation of formic acid. The work demonstrates the great potential of graphene as a support to enhance NP catalysis and stability for important chemical oxidation reactions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33060a

  15. Memory effects in metal-oxide-semiconductor capacitors incorporating dispensed highly monodisperse 1 nm silicon nanoparticles

    Science.gov (United States)

    Nayfeh, Osama M.; Antoniadis, Dimitri A.; Mantey, Kevin; Nayfeh, Munir H.

    2007-04-01

    Metal-oxide-semiconductor capacitors containing various densities of ex situ produced, colloidal, highly monodisperse, spherical, 1nm silicon nanoparticles were fabricated and evaluated for potential use as charge storage elements in future nonvolatile memory devices. The capacitance-voltage characteristics are well behaved and agree with similarly fabricated zero-nanoparticle control samples and with an ideal simulation. Unlike larger particle systems, the demonstrated memory effect exhibits effectively pure hole storage. The nature of charging, hole type versus electron type may be understood in terms of the characteristics of ultrasmall silicon nanoparticles: large energy gap, large charging energy, and consequently a small electron affinity.

  16. Development of ultrafine multichannel microfluidic mixer for synthesis of bimetallic nanoclusters: catalytic application of highly monodisperse AuPd nanoclusters stabilized by poly(N-vinylpyrrolidone).

    Science.gov (United States)

    Hayashi, Naoto; Sakai, Yuka; Tsunoyama, Hironori; Nakajima, Atsushi

    2014-09-02

    On account of their novel properties, bimetallic nanoparticles and nanoclusters (NCs) are strong potential candidates for optical, magnetic, and catalytic functional materials. These properties depend on the chemical composition and size (number of constituent atoms) of the NCs. Control of size, structure, and composition is particularly important for fabricating highly functional materials based on bimetallic NCs. Size- and structure-controlled synthesis of two-element alloys can reveal their intrinsic electronic synergistic effects. However, because synergistic enhancement of activity is strongly affected by composition as well as by size and structure, controlled synthesis is a challenging task, particularly in catalytic applications. To investigate catalytic synergistic effects, we have synthesized highly monodisperse, sub-2 nm, solid-solution AuPd NCs stabilized with poly(N-vinylpyrrolidone) (AuPd:PVP) using a newly developed ultrafine microfluidic mixing device with 15 μm wide multiple lamination channels. The synergistic enhancement for catalytic aerobic oxidation of benzyl alcohol exhibited a volcano-shaped trend, with a maximum at 20-65 at. % Pd. From X-ray photoelectron spectroscopic measurements, we confirmed that the enhanced activity originates from the enhanced electron density at the Au sites, donated by Pd sites.

  17. Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Zhiliang; Zhang Xingye; Xin Zhiqing; Deng Mengmeng; Wen Yongqiang; Song Yanlin, E-mail: zhangxy@iccas.ac.cn, E-mail: ylsong@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Lab of Organic Solids, Laboratory of New Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-21

    In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO{sub 3} mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 x 10{sup -8}-8.76 x 10{sup -8} {Omega} m after thermal treatment at 160 {sup 0}C for 30 min, which was about five times that of bulk silver (1.586 x 10{sup -8} {Omega} m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices.

  18. Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics.

    Science.gov (United States)

    Zhang, Zhiliang; Zhang, Xingye; Xin, Zhiqing; Deng, Mengmeng; Wen, Yongqiang; Song, Yanlin

    2011-10-21

    In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO(3) mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 × 10( - 8)-8.76 × 10( - 8) Ω m after thermal treatment at 160 °C for 30 min, which was about five times that of bulk silver (1.586 × 10( - 8) Ω m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices.

  19. Shape-controlled synthesis of highly monodisperse and small size gold nanoparticles

    Institute of Scientific and Technical Information of China (English)

    FU YunZhi; DU YuKou; YANG Ping; LI JinRu; JIANG Long

    2007-01-01

    We describe here that fine control of nanoparticle shape and size can be achieved by systematic variation of experimental parameters in the seeded growth procedure in aqueous solution. Cubic and spherical gold nanoparticles are obtained respectively. In particularly, the Au cubes are highly monodisperse in 33±2 nm diameter. The experimental methods involve the preparation of Au seed particles and the subsequent addition of an appropriate quantity of Au seed solution to the aqueous growth solutions containing desired quantities of CTAB and ascorbic acid (AA). Here, AA is a weak reducing agent and CTAB is not only a stable agent for nanoparticles but also an inductive agent for leading increase in the face of nanoparticle. Ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) are used to characterize the nanoparticles. The results show that the different size gold nanoparticles displayed high size homogenous distribution and formed mono-membrane at the air/solid interface.

  20. Synthesis of mono-dispersed Fe-Co nanoparticles with precise composition control

    Science.gov (United States)

    Wang, Yufeng; Zheng, Yi; Hu, Shuchun

    2017-01-01

    Monodispersed Fe-Co nanoparticles are synthesized by reducing FeCl2 and CoCl2 in diphenyl ether, with n-butyllithium as reducing agent and oleic acid as surfactant. The body centered cubic (BCC) crystal structure of Fe-Co nanoparticles is confirmed by both XRD patterns and TEM diffraction patterns. The average nanoparticle size is 10 nm at the reported experimental condition. The magnetization of the Fe-Co increases with increased cobalt atomic percentage. XPS technique is used to investigate the surface chemical states of Fe-Co nanoparticles. Finally, the composition of Fe-Co nanoparticles is investigated through EDX, confirming the molar ratio of Fe/Co in nanoparticles could be accurately controlled by changing the composition of the precursors.

  1. Microfluidic synthesis of monodisperse Cu nanoparticles in aqueous solution.

    Science.gov (United States)

    Ke, Te; Zeng, Xiao-Fei; Wang, Jie-Xin; Le, Yuan; Chu, Guang-Wen; Chen, Jian-Feng; Shao, Lei

    2011-06-01

    The continuous production of Cu nanoparticles with a particle size of 2-5 nm was conducted by sodium borohydride reduction of copper sulfate in aqueous solution in a tube-in-tube microchannel reactor (TMR), which consists of an inner tube and an outer tube with the reaction performed in the annular microchannel between these two tubes. The as-prepared Cu nanoparticles were compared with those obtained by a conventional batch synthesis process by using transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis spectroscopy. Due to the highly intensified micromixing effects in the TMR, Cu nanoparticles prepared by this route exhibits a smaller particle size, narrower size distribution and better stability in air. The TMR shows an excellent ability of preparing high-quality Cu nanoparticles in mild conditions. In addition, with the unique microchannel structure, the throughput capability of the TMR for the production of Cu nanoparticles is up to several liters per minute.

  2. Monodispersed Zinc Oxide Nanoparticle-Dye Dyads and Triads

    Energy Technology Data Exchange (ETDEWEB)

    Gladfelter, Wayne L. [Univ. of Minnesota, Minneapolis, MN (United States); Blank, David A. [Univ. of Minnesota, Minneapolis, MN (United States); Mann, Kent R. [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-06-22

    events at a fundamental level. This was combined with the synthesis of a broad range of sensitizers that provide systematic variation of the energetics, excited state dynamics, structure and interfacial bonding. The key is that the monodisperse nature and high dispersibility of the ZnO NCs made these experiments reproducible; in essence, the measurements were on discrete molecular species rather than on the complicated mixtures that resulted from the typical fabrication of functional photovoltaic cells. The monodispersed nature of the NCs also allowed the use of quantum confinement to investigate the role of donor/acceptor energetic alignment in chemically identical systems. The results added significantly to our basic understanding of energy and charge transfer events at molecule-semiconductor interfaces and will help the R&D community realize zinc oxide's full potential in solar cell applications.

  3. Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity

    Science.gov (United States)

    Bindhu, M. R.; Umadevi, M.

    2013-01-01

    Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri.

  4. Direct Dry-Grinding Synthesis of Monodisperse Lipophilic CuS Nanoparticles.

    Science.gov (United States)

    Li, Yajuan; Scott, Julie; Chen, Yi-Tzai; Guo, Liangran; Zhao, Mingyang; Wang, Xiaodong; Lu, Wei

    2015-07-15

    Copper sulfide nanoparticles, effective absorbers of near-infrared light, are recently attracting broad interest as a photothermal coupling agent for cancer therapy. Lipophilic copper sulfide nanoparticles are preferred for high performance biomedical applications due to high tissue affinity. Synthesis of lipophilic copper sulfide nanoparticles requires complicated multi-step processes under severe conditions. Here, we describe a new synthetic process, developed by direct dry-grinding of copper(II) acetylacetonate with sulfur under ambient environment at low temperature. The formed CuS nanoparticles are of uniform size, ~10 nm in diameter, and are monodispersed in chloroform. Each covellite CuS nanocrystal surface is modified with oleylamine through hydrogen bonding between sulfur atoms and amine groups of oleylamine. The nanoparticles demonstrate near-infrared light absorption for photothermal applications. The synthetic methodology described here is more convenient and less extreme than previous methods, and should thus greatly facilitate the preparation of photothermal lipophilic copper sulfide nanomaterials for cancer therapy.

  5. Cytotoxicity of monodispersed chitosan nanoparticles against the Caco-2 cells

    Energy Technology Data Exchange (ETDEWEB)

    Loh, Jing Wen [Laboratory for Drug Delivery, Pharmacy, Characterisation and Analysis, University of Western Australia (Australia); Saunders, Martin [Centre for Microscopy, Characterisation and Analysis, University of Western Australia (Australia); Lim, Lee-Yong, E-mail: lee.lim@uwa.edu.au [Laboratory for Drug Delivery, Pharmacy, Characterisation and Analysis, University of Western Australia (Australia); School of Biomedical, Biomolecular and Chemical Sciences, 35 Stirling Hwy, Crawley 6009 (Australia)

    2012-08-01

    Published toxicology data on chitosan nanoparticles (NP) often lack direct correlation to the in situ size and surface characteristics of the nanoparticles, and the repeated NP assaults as experienced in chronic use. The aim of this paper was to breach these gaps. Chitosan nanoparticles synthesized by spinning disc processing were characterised for size and zeta potential in HBSS and EMEM at pHs 6.0 and 7.4. Cytotoxicity against the Caco-2 cells was evaluated by measuring the changes in intracellular mitochondrial dehydrogenase activity, TEER and sodium fluorescein transport data and cell morphology. Cellular uptake of NP was observed under the confocal microscope. Contrary to established norms, the collective data suggest that the in vitro cytotoxicity of NP against the Caco-2 cells was less influenced by positive surface charges than by the particle size. Particle size was in turn determined by the pH of the medium in which the NP was dispersed, with the mean size ranging from 25 to 333 nm. At exposure concentration of 0.1%, NP of 25 ± 7 nm (zeta potential 5.3 ± 2.8 mV) was internalised by the Caco-2 cells, and the particles were observed to inflict extensive damage to the intracellular organelles. Concurrently, the transport of materials along the paracellular pathway was significantly facilitated. The Caco-2 cells were, however, capable of recovering from such assaults 5 days following NP removal, although a repeat NP exposure was observed to produce similar effects to the 1st exposure, with the cells exhibiting comparable resiliency to the 2nd assault. -- Highlights: ► Chitosan nanoparticles reduced mitochondrial dehydrogenase activity. ► Cellular uptake of chitosan nanoparticles was observed. ► Chitosan nanoparticles inflicted extensive damage to the cell morphology. ► The transport of materials along the paracellular pathway was facilitated.

  6. The Synthesis, Characterization and Catalytic Reaction Studies of Monodisperse Platinum Nanoparticles in Mesoporous Oxide Materials

    Energy Technology Data Exchange (ETDEWEB)

    Rioux, Robert M. [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    A catalyst design program was implemented in which Pt nanoparticles, either of monodisperse size and/or shape were synthesized, characterized and studied in a number of hydrocarbon conversion reactions. The novel preparation of these materials enables exquisite control over their physical and chemical properties that could be controlled (and therefore rationally tuned) during synthesis. The ability to synthesize rather than prepare catalysts followed by thorough characterization enable accurate structure-function relationships to be elucidated. This thesis emphasizes all three aspects of catalyst design: synthesis, characterization and reactivity studies. The precise control of metal nanoparticle size, surface structure and composition may enable the development of highly active and selective heterogeneous catalysts.

  7. Precisely Size-Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star-Like Block Copolymers.

    Science.gov (United States)

    Chen, Yihuang; Yoon, Young Jun; Pang, Xinchang; He, Yanjie; Jung, Jaehan; Feng, Chaowei; Zhang, Guangzhao; Lin, Zhiqun

    2016-12-01

    In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., "hairs") with even length. Interestingly, amphiphilic star-like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer "hairs" are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long-term stability. This amphiphilic star-like block copolymer nanoreactor-based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self-assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.

  8. Porous TiO2 Assembled from Monodispersed Nanoparticles.

    Science.gov (United States)

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-12-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

  9. Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone

    Science.gov (United States)

    Kumar, Dhiraj; Mutreja, Isha; Sykes, Peter

    2016-09-01

    Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ˜100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV-vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ˜100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering—volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

  10. Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone.

    Science.gov (United States)

    Kumar, Dhiraj; Mutreja, Isha; Sykes, Peter

    2016-09-02

    Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ∼100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV-vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ∼100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering-volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

  11. Porous TiO2 Assembled from Monodispersed Nanoparticles

    OpenAIRE

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-01-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending...

  12. Facile synthesis of monodisperse thermally immiscible Ag–Ni alloy nanoparticles at room temperature

    Indian Academy of Sciences (India)

    S Tabatabaei; S K Sadrnezhaad

    2014-10-01

    Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag–Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag–Ni ANPs was achieved. Stoichiometry of the Ag–Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand 100% Ag–Ni ANPs was observed in the system. Using Tetrakis hydroxymethyl phosphonium chloride resulted in construction of near-uniform ANPs in the easily controllable conditions of the present alloying procedure. Nanoparticles having up to 65% Ni were observed for the first time in this research.

  13. Coalescence of functional gold and monodisperse silver nanoparticles mediated by black Panax ginseng Meyer root extract

    Science.gov (United States)

    Wang, Dandan; Markus, Josua; Kim, Yeon-Ju; Wang, Chao; Jiménez Pérez, Zuly Elizabeth; Ahn, Sungeun; Aceituno, Verónica Castro; Mathiyalagan, Ramya; Yang, Deok Chun

    2016-01-01

    A rapid biological synthesis of multifunctional gold nanoparticle (AuNp) and monodisperse silver nanoparticle (AgNp) was achieved by an aqueous extract of black Panax ginseng Meyer root. The physicochemical transformation into black ginseng (BG) greatly enhanced the pharmacological activities of white ginseng and its minor ginsenoside content. The optimal temperature conditions and kinetics of bioreduction were investigated. Formation of BG-AuNps and BG-AgNps was verified by ultraviolet–visible spectrophotometry at 548 and 412 nm, respectively. The biosynthesized BG-AgNps were spherical and monodisperse with narrow distribution, while BG-AuNps were icosahedral-shaped and moderately polydisperse. Synthesized nanoparticles exhibited long-term stability in buffers of pH 7.0–8.0 and biological media (5% bovine serum albumin) at an ambient temperature and at 37°C. BG-AgNps showed effective antibacterial activity against Escherichia coli and Staphylococcus aureus. BG-AuNps and BG-AgNps demonstrated increased scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals. In addition, BG-AuNps and BG-AgNps were nontoxic to HaCaT and MCF-7 cells; the latter showed no cytotoxicity at concentrations lower than 10 µg/mL. At higher concentrations, BG-AgNps exhibited apparent apoptotic activity in MCF-7 breast cancer cell line through reactive oxygen species generation and nuclear fragmentation. PMID:28008248

  14. Size-Controlled and Optical Properties of Monodispersed Silver Nanoparticles Synthesized by the Radiolytic Reduction Method

    Directory of Open Access Journals (Sweden)

    Kazem Naghavi

    2013-04-01

    Full Text Available Size-controlled and monodispersed silver nanoparticles were synthesized from an aqueous solution containing silver nitrate as a metal precursor, polyvinyl alcohol as a capping agent, isopropyl alcohol as hydrogen and hydroxyl radical scavengers, and deionized water as a solvent with a simple radiolytic method. The average particle size decreased with an increase in dose due to the domination of nucleation over ion association in the formation of the nanoparticles by gamma reduction. The silver nanoparticles exhibit a very sharp and strong absorption spectrum with the absorption maximum λmax blue shifting with an increased dose, owing to a decrease in particle size. The absorption spectra of silver nanoparticles of various particle sizes were also calculated using a quantum physics treatment and an agreement was obtained with the experimental absorption data. The results suggest that the absorption spectrum of silver nanoparticles possibly derived from the intra-band excitations of conduction electrons from the lowest energy state (n = 5, l = 0 to higher energy states (n ≥ 6; Δl = 0, ±1; Δs = 0, ±1, allowed by the quantum numbers principle. This demonstrates that the absorption phenomenon of metal nanoparticles based on a quantum physics description could be exploited to be added into the fundamentals of metal nanoparticles and the related fields of nanoscience and nanotechnology.

  15. Direct dry-grinding synthesis of monodisperse lipophilic CuS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yajuan; Scott, Julie; Chen, Yi-Tzai; Guo, Liangran; Zhao, Mingyang; Wang, Xiaodong [Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, The University of Rhode Island, Kingston, RI 02881 (United States); Lu, Wei, E-mail: weilu@uri.edu [Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, The University of Rhode Island, Kingston, RI 02881 (United States); School of Pharmacy, Fudan University, Shanghai 201203 (China)

    2015-07-15

    Copper sulfide nanoparticles, effective absorbers of near-infrared light, are recently attracting broad interest as a photothermal coupling agent for cancer therapy. Lipophilic copper sulfide nanoparticles are preferred for high performance biomedical applications due to high tissue affinity. Synthesis of lipophilic copper sulfide nanoparticles requires complicated multi-step processes under severe conditions. Here, we describe a new synthetic process, developed by direct dry-grinding of copper(II) acetylacetonate with sulfur under ambient environment at low temperature. The formed CuS nanoparticles are of uniform size, ∼10 nm in diameter, and are monodispersed in chloroform. Each covellite CuS nanocrystal surface is modified with oleylamine through hydrogen bonding between sulfur atoms and amine groups of oleylamine. The nanoparticles demonstrate near-infrared light absorption for photothermal applications. The synthetic methodology described here is more convenient and less extreme than previous methods, and should thus greatly facilitate the preparation of photothermal lipophilic copper sulfide nanomaterials for cancer therapy. - Highlights: • We make lipophilic CuS nanoparticles by mechanical grinding method in large scale. • The reaction condition is studied to obtain high yield and uniform size. • The synthesis does not need nitrogen protection or high temperature. • Lipophilic CuS nanoparticles show significant near-infrared absorbance.

  16. Approximate Bayesian computation for estimating number concentrations of monodisperse nanoparticles in suspension by optical microscopy

    Science.gov (United States)

    Röding, Magnus; Zagato, Elisa; Remaut, Katrien; Braeckmans, Kevin

    2016-06-01

    We present an approximate Bayesian computation scheme for estimating number concentrations of monodisperse diffusing nanoparticles in suspension by optical particle tracking microscopy. The method is based on the probability distribution of the time spent by a particle inside a detection region. We validate the method on suspensions of well-controlled reference particles. We illustrate its usefulness with an application in gene therapy, applying the method to estimate number concentrations of plasmid DNA molecules and the average number of DNA molecules complexed with liposomal drug delivery particles.

  17. A Facile Synthesis of Monodisperse Au Nanoparticles and Their Catalysis of CO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng [ORNL; Peng, Sheng [Brown University; Lee, Youngmin [Brown University; Wang, Chao [Brown University; Yin, Hongfeng [ORNL; Sun, Shouheng [ORNL

    2008-01-01

    Monodisperse Au nanoparticles (NPs) have been synthesized at room temperature via a burst nucleation of Au upon injection of the reducing agent t-butylamine-borane complex into a 1, 2, 3, 4-tetrahydronaphthalene solution of HAuCl{sub 4} {center_dot} 3H{sub 2}O in the presence of oleylamine. The as-synthesized Au NPs show size-dependent surface plasmonic properties between 520 and 530 nm. They adopt an icosahedral shape and are polycrystalline with multiple-twinned structures. When deposited on a graphitized porous carbon support, the NPs are highly active for CO oxidation, showing 100% CO conversion at -45 C.

  18. Shape-controlled synthesis of highly monodisperse and small size gold nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We describe here that fine control of nanoparticle shape and size can be achieved by systematic varia-tion of experimental parameters in the seeded growth procedure in aqueous solution. Cubic and spherical gold nanoparticles are obtained respectively. In particularly, the Au cubes are highly mono-disperse in 33±2 nm diameter. The experimental methods involve the preparation of Au seed particles and the subsequent addition of an appropriate quantity of Au seed solution to the aqueous growth solutions containing desired quantities of CTAB and ascorbic acid (AA). Here, AA is a weak reducing agent and CTAB is not only a stable agent for nanoparticles but also an inductive agent for leading increase in the face of nanoparticle. Ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) are used to characterize the nanoparticles. The results show that the different size gold nanoparticles displayed high size homogenous distribution and formed mono-membrane at the air/solid interface.

  19. Monodisperse polyvinylpyrrolidone-coated CoFe2O4 nanoparticles: Synthesis, characterization and cytotoxicity study

    Science.gov (United States)

    Wang, Guangshuo; Ma, Yingying; Mu, Jingbo; Zhang, Zhixiao; Zhang, Xiaoliang; Zhang, Lina; Che, Hongwei; Bai, Yongmei; Hou, Junxian; Xie, Hailong

    2016-03-01

    In this study, monodisperse cobalt ferrite (CoFe2O4) nanoparticles were prepared successfully with various additions of polyvinylpyrrolidone (PVP) by sonochemical method, in which PVP served as a stabilizer and dispersant. The effects and roles of PVP on the morphology, microstructure and magnetic properties of the obtained CoFe2O4 were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). It was found that PVP-coated CoFe2O4 showed relatively well dispersion with narrow size distribution. The field-dependent magnetization curves indicated superparamagnetic behavior of PVP-coated CoFe2O4 with moderate saturation magnetization and hydrophilic character at room temperature. More importantly, the in vitro cytotoxicity testing exhibited negligible cytotoxicity of as-prepared PVP-CoFe2O4 even at the concentration as high as 150 μg/mL after 24 h treatment. Considering the superparamagnetic properties, hydrophilic character and negligible cytotoxicity, the monodisperse CoFe2O4 nanoparticles hold great potential in a variety of biomedical applications.

  20. DMSO as a solvent/ligand to monodisperse CdS spherical nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kaijun [China Pharmaceutical University, Physical Chemistry Lab, School of Science (China); Han, Qiaofeng, E-mail: hanqiaofeng@njust.edu.cn [Nanjing University of Science and Technology, Key Laboratory for Soft Chemistry and Functional Materials, Ministry of Education (China)

    2016-01-15

    Monodisperse CdS nanospheres assembled by small nanoparticles were prepared using dimethyl sulfoxide (DMSO) as a solvent through several routes including thermolysis of xanthate, the reaction of cadmium acetate (Cd(CH{sub 3}CO{sub 2}){sub 2}) with thiourea, and interfacial reaction of CS{sub 2} and Cd(CH{sub 3}CO{sub 2}){sub 2}/DMSO. The corresponding products possessed the particle sizes ranging from around 35 to 45 nm, 63 to 73 nm, and 240 to 280 nm, respectively. These products presented uniform spherical morphology, which provide insights into the effect of DMSO on CdS morphology. DMSO, as an aprotic and polar solvent, possesses unique properties. The oxygen and sulfur atoms in DMSO can coordinate to metal ions on nanoparticles surface, and the high polarity of DMSO is favorable to fast reaction, nucleation, growth, and Ostwald ripening, forming monodisperse nanospheres with narrow size distribution. The influence of CdS size on its photocatalytic activity was evaluated using Rhodamine B (RhB) as a model compound under visible light irradiation.

  1. Synthesis of monodisperse TiO2-paraffin core-shell nanoparticles for improved dielectric properties.

    Science.gov (United States)

    Balasubramanian, Balamurugan; Kraemer, Kristin L; Reding, Nicholas A; Skomski, Ralph; Ducharme, Stephen; Sellmyer, David J

    2010-04-27

    Core-shell structures of oxide nanoparticles having a high dielectric constant, and organic shells with large breakdown field are attractive candidates for large electrical energy storage applications. A high growth temperature, however, is required to obtain the dielectric oxide nanoparticles, which affects the process of core-shell formation and also leads to poor control of size, shape, and size-distribution. In this communication, we report a new synthetic process to grow core-shell nanoparticles by means of an experimental method that can be easily adapted to synthesize core-shell structures from a variety of inorganic-organic or inorganic-inorganic materials. Monodisperse and spherical TiO2 nanoparticles were produced at room temperature as a collimated cluster beam in the gas phase using a cluster-deposition source and subsequently coated with uniform paraffin nanoshells using in situ thermal evaporation, prior to deposition on substrates for further characterization and device processing. The paraffin nanoshells prevent the TiO2 nanoparticles from contacting each other and also act as a matrix in which the volume fraction of TiO2 nanoparticles was varied by controlling the thickness of the nanoshells. Parallel-plate capacitors were fabricated using dielectric core-shell nanoparticles having different shell thicknesses. With respect to the bulk paraffin, the effective dielectric constant of TiO2-paraffin core-shell nanoparticles is greatly enhanced with a decrease in the shell thickness. The capacitors show a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz-1 MHz, which are highly desirable for exploiting these core-shell nanoparticles for potential applications.

  2. Sonochemical synthesis of monodispersed magnetite nanoparticles by using an ethanol-water mixed solvent.

    Science.gov (United States)

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2009-06-01

    The magnetite nanoparticles were synthesized in an ethanol-water solution under ultrasonic irradiation from a Fe(OH)(2) precipitate. XRD, TEM, TG, IR, VSM and UV/vis absorption spectrum were used to characterize the magnetite nanoparticles. It was found that the formation of magnetite was accelerated in ethanol-water solution in the presence of ultrasonic irradiation, whereas, it was limited in ethanol-water solution under mechanical stirring. The monodispersibility of magnetite particles was improved significantly through the sonochemical synthesis in ethanol-water solution. The magnetic properties were improved for the samples synthesized under ultrasonic irradiation. This would be attributed to high Fe(2+) concentration in the magnetite cubic structure.

  3. Influence of Monodisperse Fe3O4 Nanoparticle Size on Electrical Properties of Vegetable Oil-Based Nanofluids

    Directory of Open Access Journals (Sweden)

    Bin Du

    2015-01-01

    Full Text Available Insulating oil modified by nanoparticles (often called nanofluids has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. In this paper, three sized monodisperse Fe3O4 nanoparticles were prepared and subsequently dispersed into insulating vegetable oil to achieve nanofluids. The dispersion stability of nanoparticles in nanofluids was examined by natural sedimentation and zeta potential measurement. The electrical breakdown strength, space charge distribution, and several dielectric characteristics, for example, permittivity, dielectric loss, and volume resistivity of these nanofluids, were comparatively investigated. Experimental results show that the monodisperse Fe3O4 nanoparticles not only enhance the dielectric strength but also uniform the electric field of the nanofluids. The depth of electrical potential well of insulating vegetable oils and nanofluids were analyzed to clarify the influence of nanoparticles on electron trapping and on insulation improvement of the vegetable oil.

  4. Hydrothermal growth of highly monodispersed TiO2 nanoparticles: Functional properties and dye-sensitized solar cell performance

    Science.gov (United States)

    Navaneethan, M.; Nithiananth, S.; Abinaya, R.; Harish, S.; Archana, J.; Sudha, L.; Ponnusamy, S.; Muthamizhchelvan, C.; Ikeda, H.; Hayakawa, Y.

    2017-10-01

    Monodispersed anatase TiO2 nanoparticles were synthesized by hydrothermal method using citric acid as a capping agent. The effect of citric acid and the growth time on the formation of TiO2, functional properties and dye-sensitized solar cell performances were investigated. X-ray diffraction pattern (XRD) and Raman spectroscopy results revealed that the TiO2 nanoparticles possess the anatase phase. Transmission electron microscopy (TEM) measurement revealed the formation of spherical nanoparticles with monodispersity in size and morphology. An average size of 14 nm was obtained for the growth period of 15 h. The maximum efficiency (η) of dye-sensitized solar cell was achieved for TiO2 nanoparticles grown for 15 h as 7.66% which was higher than that of commercial P25 TiO2 (5.23%) and uncapped nanoparticles (3.68%).

  5. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

    Science.gov (United States)

    Hufschmid, Ryan; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

    2015-06-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular

  6. Monodisperse embedded nanoparticles derived from an atomic metal-dispersed precursor of layered double hydroxide for architectured carbon nanotube formation

    DEFF Research Database (Denmark)

    Tian, Gui-Li; Zhao, Meng-Qiang; Zhang, Bingsen

    2014-01-01

    Monodisperse metal nanoparticles (NPs) with high activity and selectivity are among the most important catalytic materials. However, the intrinsic process to obtain well-dispersed metal NPs with tunable high density (ranging from 10(13) to 10(16) m(-2)) and thermal stability is not yet well under...

  7. A new method for preparing mono-dispersed nanoparticles using magnetized water

    Science.gov (United States)

    Nakhaei Pour, Ali; Gholizadeh, Mostafa; Housaindokht, Mohammadreza; Moosavi, Fatemeh; Monhemi, Hasan

    2017-04-01

    We studied the use of magnetized water on the size of the nanoparticles. Magnetized water found to reduce the diameter of the nanoparticles during a homogeneous precipitation process, which is a combination of nucleation and nuclei growth processes. We found that the modified water, which demonstrated different physical properties especially on the surface tension and viscosity, significantly influenced the both processes. Therefore, the nucleation process was initially prolonged in the homogeneous precipitation process due to the lower critical size of nucleus and higher rate of nucleation, and consequently formed smaller particles and a larger number of particles. Furthermore, the growth rate of nanoparticles was hindered owing to the higher viscosity of the water and restriction in the mass transport process. As a result, the precipitated particles with the magnetized water were eventually structured smaller particle diameter compared to the bulk. The presented method in here indicated a low cost, straightforward, and feasible technique for industrial application. In addition, this method could open a new promising perspective on nanomaterial synthesis in order to facilitate the production of monodispersed nanoparticles. Molecular dynamic confirmed that surface tension decreased as the external magnetic field was applied. Moreover, the density profile illustrated that the average number of hydrogen atoms is greater than oxygen atoms.

  8. Time Resolved Nucleation and Growth of Monodisperse FeOOH Nanoparticles Observed in situ

    Science.gov (United States)

    Legg, B. A.; Zhu, M.; Zhang, H.; Waychunas, G.; Banfield, J. F.

    2012-12-01

    The nucleation and growth of oxide minerals from aqueous solution is a poorly understood process. Complexities such as two-stage precipitation, phase transformation, and hydrolysis often inhibit simple interpretation. In this study, we track the thermally induced nucleation and growth of akaganeite (β-FeOOH) nanoparticles from FeCl3 solutions, using in situ time resolved small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM). Variations in reaction temperature (from 37 deg C to 80 deg C) and FeCl3 concentration (from 5 mM to 800 mM) produce systematic changes in nucleation rate, growth rate, particle size distribution, and aspect ratio. Low FeCl3 concentrations and high temperatures lead to formation of very small particles via rapid nucleation. (FeCl3 solutions are actually more supersaturated with respect to akaganeite when concentrations are low, due to the acid-base chemistry of ferric iron.) Increasing the FeCl3 concentration leads to large, highly monodisperse particles via size focused growth. Suspensions of highly monodisperse, elongated particles are found to self-organize into two dimensional colloidal crystals. The well-controlled growth processes in this system make it possible to conduct detailed kinetic modeling, and determine how both nucleation and growth rate respond to changes in the experimental conditions.

  9. Monodisperse Au nanoparticles for selective electrocatalytic reduction of CO2 to CO.

    Science.gov (United States)

    Zhu, Wenlei; Michalsky, Ronald; Metin, Önder; Lv, Haifeng; Guo, Shaojun; Wright, Christopher J; Sun, Xiaolian; Peterson, Andrew A; Sun, Shouheng

    2013-11-13

    We report selective electrocatalytic reduction of carbon dioxide to carbon monoxide on gold nanoparticles (NPs) in 0.5 M KHCO3 at 25 °C. Among monodisperse 4, 6, 8, and 10 nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at -0.67 V vs reversible hydrogen electrode, RHE). Density functional theory calculations suggest that more edge sites (active for CO evolution) than corner sites (active for the competitive H2 evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methylimidazolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at -0.52 V (vs RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO2 to CO.

  10. Synthesis and characterization of stable monodisperse silica nanoparticle sols for in vitro cytotoxicity testing.

    Science.gov (United States)

    Thomassen, Leen C J; Aerts, Alexander; Rabolli, Virginie; Lison, Dominique; Gonzalez, Laetitia; Kirsch-Volders, Micheline; Napierska, Dorota; Hoet, Peter H; Kirschhock, Christine E A; Martens, Johan A

    2010-01-05

    For the investigation of the interaction of nanoparticles with biomolecules, cells, organs, and animal models there is a need for well-characterized nanoparticle suspensions. In this paper we report the preparation of monodisperse dense amorphous silica nanoparticles (SNP) suspended in physiological media that are sterile and sufficiently stable against aggregation. SNP sols with various particle sizes (2-335 nm) were prepared via base-catalyzed hydrolysis and polymerization of tetraethyl orthosilicate under sterile conditions using either ammonia (Stober process (1) ) or lysine catalyst (Lys-Sil process (2) ). The series was complemented with commercial silica sols (Ludox). Silica nanoparticle suspensions were purified by dialysis and dispersed without using any dispersing agent into cell culture media (Dulbecco's Modified Eagle's medium) containing antibiotics. Particle sizes were determined by dynamic light scattering. SNP morphology, surface area, and porosity were characterized using electron microscopy and nitrogen adsorption. The SNP sols in cell culture medium were stable for several days. The catalytic activity of the SNP in the conversion of hydrogen peroxide into hydroxyl radicals was investigated using electron paramagnetic resonance. The catalytic activity per square meter of exposed silica surface area was found to be independent of particle size and preparation method. Using this unique series of nanoparticle suspensions, the relationship between cytotoxicity and particle size was investigated using human endothelial and mouse monocyte-macrophage cells. The cytotoxicity of the SNP was strongly dependent on particle size and cell type. This unique methodology and the collection of well-characterized SNP will be useful for further in vitro studies exploring the physicochemical determinants of nanoparticle toxicity.

  11. Size-controlled synthesis of monodispersed gold nanoparticles via carbon monoxide gas reduction

    Directory of Open Access Journals (Sweden)

    Lewinski Nastassja

    2011-01-01

    Full Text Available Abstract An in depth analysis of gold nanoparticle (AuNP synthesis and size tuning, utilizing carbon monoxide (CO gas as a reducing agent, is presented for the first time. The sizes of the AuNPs are tunable from ~4 to 100 nm by altering the concentration of HAuCl4 and inlet CO gas-injection flow rate. It is also found that speciation of aqueous HAuCl4, prior to reduction, influences the size, morphology, and properties of AuNPs when reduced with CO gas. Ensemble extinction spectra and TEM images provide clear evidence that CO reduction offers a high level of monodispersity with standard deviations as low as 3%. Upon synthesis, no excess reducing agent remains in solution eliminating the need for purification. The time necessary to synthesize AuNPs, using CO, is less than 2 min.

  12. Monodisperse sodium oleate coated magnetite high susceptibility nanoparticles for hyperthermia applications

    Science.gov (United States)

    Araújo-Neto, R. P.; Silva-Freitas, E. L.; Carvalho, J. F.; Pontes, T. R. F.; Silva, K. L.; Damasceno, I. H. M.; Egito, E. S. T.; Dantas, Ana L.; Morales, Marco A.; Carriço, Artur S.

    2014-09-01

    We report a simple and low cost methodology to synthesize sodium oleate coated magnetite nanoparticles for hyperthermia applications. The system consists of oleate coated magnetite nanoparticles with large susceptibility (1065 emu/gT), induced by the dipolar inter-particle interaction, with a magnetic core diameter in the 6 nm-12 nm size range. In aqueous medium, the nanoparticles agglomerate to form a monodisperse system, exhibiting a mean hydrodynamic diameter of 60.6 nm±4.1 nm, with a low average polydispersity index of 0.128±0.003, as required for intravenous applications. The system exhibits promising efficiency for magnetic hyperthermia, with a specific absorption rate of 14 W/g at a low field amplitude of 15.9 kA/m and frequency of 62 kHz. In a 50 mg/mL density in 1 mL, the temperature rises to 42.5 °C in 1.9 min.

  13. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Yan-yu [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Yang, Hui, E-mail: 549456369@qq.com [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Tao [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Chuang [Department of Highway & Bridge, Shaanxi Railway Institute, Weinan 714000 (China)

    2016-11-25

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag{sup +} (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO{sub 3}) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO{sub 3} concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV–vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10–16 nm. FTIR analysis revealed that biological macromolecules with groups of −NH{sub 2}, −OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications. - Highlights: • Monodisperse silver nanoparticles were first prepared by a green synthetical way through Ginkgo Biloba leaf extract. • The synthesized AgNPs is of high crystallinity, stable and good dispersion with smaller sizes between 10–16 nm. • The achieved AgNPs exhibits good antibacterial activities. • The biosynthesis method is advantageous for its cost effectiveness, availability, portability, nontoxic and environmentally benign.

  14. Synthesis and composition evolution of bimetallic Pd Pt alloy nanoparticles

    Science.gov (United States)

    Ren, Guoqiang; Shi, Honglan; Xing, Yangchuan

    2007-09-01

    This paper reports a study on the synthesis of Pd-Pt alloy nanoparticles and composition evolution of the alloys. The synthesis involves Pd and Pt acetylacetonate as the metal precursors and trioctylphosphine (TOP) as the solvent. Thermal decomposition of the Pd-TOP complex resulted in Pd nanoparticles, while substitution of Pt in the Pt-TOP complex by Pd allowed formation of the Pd-Pt alloys. It was observed that the Pd-Pt nanoparticles formed at the very beginning in the synthesis process are Pd rich with various nanoparticle sizes ranging from 1.5 to 25 nm in diameter. These nanoparticles averaged out through a digestive ripening process and reached a final size of 3.5 nm in about 10 min. The alloy compositions evolved throughout the synthesis process and only reached the preset Pd to Pt ratio of the precursors in 120 min. It was found that Pt acetylacetonate alone in TOP cannot produce Pt nanoparticles, which was attributed to the formation of a Pt-TOP complex and a strong coordination of Pt to the phosphine. This observation led us to propose an atomic exchange process between the Pt-TOP complex and the Pd atoms at the nanoparticle surface. As a result, the alloy formation process is limited by a substitution and diffusion rate of the Pt atoms at the surface of the alloy nanoparticles.

  15. Monodispersed calcium carbonate nanoparticles modulate local pH and inhibit tumor growth in vivo

    Science.gov (United States)

    Som, Avik; Raliya, Ramesh; Tian, Limei; Akers, Walter; Ippolito, Joseph E.; Singamaneni, Srikanth; Biswas, Pratim; Achilefu, Samuel

    2016-06-01

    The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits.The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3

  16. Synthesis of Monodispersed Gold Nanoparticles with Exceptional Colloidal Stability with Grafted Polyethylene Glycol-g-polyvinyl Alcohol

    Directory of Open Access Journals (Sweden)

    Alaaldin M. Alkilany

    2015-01-01

    Full Text Available Herein, we report the synthesis of spherical gold nanoparticles with tunable core size (23–79 nm in the presence of polyethylene glycol-g-polyvinyl alcohol (PEG-g-PVA grafted copolymer as a reducing, capping, and stabilizing agent in a one-step protocol. The resulted PEG-g-PVA-capped gold nanoparticles are monodispersed with an exceptional colloidal stability against salt addition, repeated centrifugation, and extensive dialysis. The effect of various synthesis parameters and the kinetic/mechanism of the nanoparticle formation are discussed.

  17. Controllable synthesis of gold nanoparticles with ultrasmall size and high monodispersity via continuous supplement of precursor.

    Science.gov (United States)

    Li, Yuanyuan; Liu, Shoujie; Yao, Tao; Sun, Zhihu; Jiang, Zheng; Huang, Yuying; Cheng, Hao; Huang, Yuanyuan; Jiang, Yong; Xie, Zhi; Pan, Guoqiang; Yan, Wensheng; Wei, Shiqiang

    2012-10-14

    Synthesis of monodisperse small Au nanoparticles in a controllable manner is of great importance for fundamental science and technical applications. Here, we report a "precursor continuous-supply" strategy for controllable synthesis of 0.9-3.3 nm Au nanoparticles with a narrow size distribution of 0.1-0.2 nm, using a weak reductant to slow-down the reducing rate of AuClPPh(3) precursor in ethanol. Time-dependent X-ray absorption and UV-Vis absorption measurements revealed that owing to the joint use of AuClPPh(3) and ethanol, the remnant AuClPPh(3) was self-supplied and the precursor concentration was maintained at a level near to its equilibrium solubility (ca. 1.65 mmol L(-1)) in ethanol. Hence the nucleation duration was extended that focused the initial size distribution of the Au clusters. With reaction going on for 58 min, most of AuClPPh(3) with a nominal Au concentration of 17.86 mmol L(-1) was converted to ethanol-soluble Au clusters with a size of about 1.0 nm, resulting in a high-yield synthesis.

  18. Synthesis of monodisperse nimesulide nanoparticles in microemulsions E170/isopropyl myristate/water/n-butanol (or isopropanol).

    Science.gov (United States)

    Debuigne, F; Cuisenaire, J; Jeunieau, L; Masereel, B; Nagy, J B

    2000-01-01

    Nanoparticles of nimesulide have been synthesized in two systems of microemulsion: E170/isopropyl myristate/water/n-butanol (or isopropanol). Nanoparticles are monodisperse. In the two microemulsions, the size of the nanoparticles is comprised between 45 and 60 A and also seems to be independent of the factor R ([water]/[E170]) and of the concentration of the nimesulide solubilized in chloroform. The constancy of the size suggests that the size is controlled by thermodynamic stabilization of the nanoparticles with the surfactant. The nature of the cosurfactant does not have an obvious influence on the nanoparticle size. The nanoparticles are instantaneously formed and stay stable during a long period of time (several months).

  19. Synthesis of monodispersed ZnAl{sub 2}O{sub 4} nanoparticles and their tribology properties as lubricant additives

    Energy Technology Data Exchange (ETDEWEB)

    Song, Xiaoyun; Zheng, Shaohua; Zhang, Jun; Li, Wei; Chen, Qiang [Key Laboratory of Inorganic Functional Materials in Universities of Shandong, School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Cao, Bingqiang, E-mail: mse_caobq@ujn.edu.cn [Key Laboratory of Inorganic Functional Materials in Universities of Shandong, School of Material Science and Engineering, University of Jinan, Jinan 250022 (China)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► The preparation of ZnAl{sub 2}O{sub 4} nanoparticles was realized by hydrothermal method. ► After surface modification, ZnAl{sub 2}O{sub 4} nanoparticles of narrow size distribution can disperse in lubricating oil stably. ► The modified ZnAl{sub 2}O{sub 4} nanoparticles as lubricating oil additives exhibit good tribology properties. -- Abstract: Monodispersed spherical zinc aluminate spinel (ZnAl{sub 2}O{sub 4}) nanoparticles were synthesized via a solvothermal method and modified by oleic acid in cyclohexanol solution. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and infrared spectrum (IR). The dispersion ability of nanoparticles in lubricant oil was measured with optical absorbance spectrum. The results show that the modified nanoparticles are nearly monodispersed and can stably disperse in lubricant oil. The tribological properties of the ZnAl{sub 2}O{sub 4} nanoparticles as an additive in lubricant oil were evaluated with four-ball test and thrust-ring test. For comparison, ZnO and Al{sub 2}O{sub 3} nanoparticles as additive in lubricant oil were also tested respectively. The results show that ZnAl{sub 2}O{sub 4} nanoparticles exhibit better tribology properties in terms of anti-wear and anti-friction than ZnO or Al{sub 2}O{sub 3} nanoparticles. The anti-friction and anti-wear mechanisms were discussed and the lubricating effect of ZnAl{sub 2}O{sub 4} nanoparticles can be attributed to nano-bearings effect and tribo-sintering mechanism.

  20. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.

    2009-09-14

    The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In

  1. Composite Electroplating to Obtain Ni-ZrO2 Nanocomposite Coatings Containing Monodispersed ZrO2 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; HOU Feng-yan; GUO He-tong

    2004-01-01

    The Zirconia nanoparticles are dispersed well in the plating bath using polyelectrolyte dispersant and NiZrO2 nanocomposite coatings containing monodispersed ZrO2 nanoparticles are successfully prepared under DC electrodeposition condition. The effects of the dispersant concentration on the dispersibility of Zirconia nanoparticles in the plating bath and the hardness of nanocomposite coatings have been investigated. The results shows that the hardness of nanocomposite coatings are strongly influenced by the dispersion state of ZrO2 nanoparticles in the composite coatings and only a very low volume percent of monodispered ZrO2 nanoparticles in Ni-ZrO2 composite coatings will result in higher hardness of the coating.

  2. Monodispersed magnetite nanoparticles optimized for magnetic fluid hyperthermia: Implications in biological systems

    Science.gov (United States)

    Khandhar, Amit P.; Ferguson, R. Matthew; Krishnan, Kannan M.

    2011-04-01

    Magnetite (Fe3O4) nanoparticles (MNPs) are suitable materials for Magnetic Fluid Hyperthermia (MFH), provided their size is carefully tailored to the applied alternating magnetic field (AMF) frequency. Since aqueous synthesis routes produce polydisperse MNPs that are not tailored for any specific AMF frequency, we have developed a comprehensive protocol for synthesizing highly monodispersed MNPs in organic solvents, specifically tailored for our field conditions (f = 376 kHz, H0 = 13.4 kA/m) and subsequently transferred them to water using a biocompatible amphiphilic polymer. These MNPs (σavg. = 0.175) show truly size-dependent heating rates, indicated by a sharp peak in the specific loss power (SLP, W/g Fe3O4) for 16 nm (diameter) particles. For broader size distributions (σavg. = 0.266), we observe a 30% drop in overall SLP. Furthermore, heating measurements in biological medium [Dulbecco's modified Eagle medium (DMEM) + 10% fetal bovine serum] show a significant drop for SLP (˜30% reduction in 16 nm MNPs). Dynamic Light Scattering (DLS) measurements show particle hydrodynamic size increases over time once dispersed in DMEM, indicating particle agglomeration. Since the effective magnetic relaxation time of MNPs is determined by fractional contribution of the Neel (independent of hydrodynamic size) and Brownian (dependent on hydrodynamic size) components, we conclude that agglomeration in biological medium modifies the Brownian contribution and thus the net heating capacity of MNPs.

  3. Magnetic Behaviour and Heating Effect of Fe3O4 Ferrofluids Composed of Monodisperse Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-Ying; DOU Yong-Hua; ZHANG Ling; GU Hong-Chen

    2007-01-01

    Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18 nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour,whereas the others display hysteresis properties and the coercivity increases with the increasing particle size.The spin glass-like behaviour and cusps near 190K are observed on all ferrofluids according to the temperature variation of field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements. The cusps are found to be associated with the freezing point of the solvent. As a comparison, the ferrofluids are dried and the FC and ZFC magnetization curves of powdery samples are also investigated. It is found that the blocking temperatures for the powdery samples are higher than those for their corresponding ferrofluids. Moreover, the size dependent heating effect of the ferrofluids is also investigated in ac magnetic field with a frequency of 55 kHz and amplitude of 200 Oe.

  4. Monodisperse Dual-Functional Upconversion Nanoparticles Enabled Near-Infrared Organolead Halide Perovskite Solar Cells.

    Science.gov (United States)

    He, Ming; Pang, Xinchang; Liu, Xueqin; Jiang, Beibei; He, Yanjie; Snaith, Henry; Lin, Zhiqun

    2016-03-18

    Extending the spectral absorption of organolead halide perovskite solar cells from visible into near-infrared (NIR) range renders the minimization of non-absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF4 :Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH3 NH3 PbI3 perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF4 :Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star-like poly(acrylic acid)-block-poly(ethylene oxide) (PAA-b-PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF4 :Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.

  5. Temperature and composition dependent structural evolution of AgPd bimetallic nanoparticle: phase diagram of (AgPd)151 nanoparticle.

    Science.gov (United States)

    Kim, Hyun You; Kim, Da Hye; Lee, Hyuck Mo

    2011-03-01

    We study the structural evolution of a 151 atom Ag-Pd bimetallic nanoparticle with composition and temperature. The solid-to-liquid transition region was investigated using molecular dynamics simulations with an improved collision method, and the solid-state structure of the nanoparticle was explored with a combination of molecular dynamics and density functional theory. Results show that an fcc-to-icosahedron transformation occurs at high temperature in all composition range and that a composition of nanoparticles concerns the atomic distribution of the (AgPd)151 nanoparticle. As a result, we constructed a phase diagram of the (AgPd)151 nanoparticle. Our phase diagram offers guidance on the application of Ag-Pd nanoparticles.

  6. Facile preparation of monodisperse, impurity-free, and antioxidation copper nanoparticles on a large scale for application in conductive ink.

    Science.gov (United States)

    Zhang, Yu; Zhu, Pengli; Li, Gang; Zhao, Tao; Fu, Xianzhu; Sun, Rong; Zhou, Feng; Wong, Ching-ping

    2014-01-08

    Monodisperse copper nanoparticles with high purity and antioxidation properties are synthesized quickly (only 5 min) on a large scale (multigram amounts) by a modified polyol process using slightly soluble Cu(OH)2 as the precursor, L-ascorbic acid as the reductant, and PEG-2000 as the protectant. The resulting copper nanoparticles have a size distribution of 135 ± 30 nm and do not suffer significant oxidation even after being stored for 30 days under ambient conditions. The copper nanoparticles can be well-dispersed in an oil-based ink, which can be silk-screen printed onto flexible substrates and then converted into conductive patterns after heat treatment. An optimal electrical resistivity of 15.8 μΩ cm is achieved, which is only 10 times larger than that of bulk copper. The synthesized copper nanoparticles could be considered as a cheap and effective material for printed electronics.

  7. Enhanced formic acid oxidation on Cu-Pd nanoparticles

    Science.gov (United States)

    Dai, Lin; Zou, Shouzhong

    Developing catalysts with high activity and high resistance to surface poisoning remains a challenge in direct formic acid fuel cell research. In this work, copper-palladium nanoparticles were formed through a galvanic replacement process. After electrochemically selective dissolution of surface Cu, Pd-enriched Cu-Pd nanoparticles were formed. These particles exhibit much higher formic acid oxidation activities than that on pure Pd nanoparticles, and they are much more resistant to the surface poisoning. Possible mechanisms of catalytic activity enhancement are briefly discussed.

  8. Monodisperse Ag@SiO2 core-shell nanoparticles as active inhibitors for marine anticorrosion applications.

    Science.gov (United States)

    Zhang, Xin-Sheng; Wang, Jie-Xin; Xu, Ke; Le, Yuan; Chen, Jian-Feng

    2011-04-01

    Monodisperse Ag@SiO2 core-shell structured nanoparticles were firstly utilized as a novel corrosion inhibitor for marine anticorrosion applications. The related marine anticorrosion properties were evaluated with an electrochemical noise (ECN) analysis during 2 weeks of accelerated immersion tests in natural seawater with the addition of various inorganic salts and nutriments. The experimental results indicate that the corrosion activity is markedly reduced by nearly 1-3 orders of magnitude owing to the introduction of Ag@SiO2 core-shell nanoparticles into coating. The inhibition efficiency of corrosion can reach as high as about 99%. More importantly, such a coating exhibits an excellent long-term sustained marine anticorrosion effect. So it could be reasonably inferred that silver cores as active inhibitors effectively prevent the corrosion damage from microorganisms, while silica shells act as a good protection for silver nanoparticles, delay the release of silver ions, and also function as the corrosion inhibiting action for inorganic salts. Therefore, this would make monodisperse Ag@SiO2 core-shell nanoparticles a potential and promising corrosion inhibitor for developing future advanced multifunctional coatings.

  9. Thermodynamics of hydrogen in Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Crespo, E.A. [Dpto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Claramonte, S. [Ing. de Materiales, Instituto Sabato, UNSAM/CNEA, Avda. Gral. Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Ruda, M. [Centro Atomico Bariloche, 8400 Bariloche (Argentina); Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Bariloche (Argentina); De Debiaggi, S. Ramos [Dpto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue - CONICET, Buenos Aires 1400, 8300, Neuquen (Argentina)

    2010-06-15

    From the atomistic simulation of pressure-composition isotherms of hydrogen absorption of Pd nanoparticles we calculated thermodynamic properties and evaluated them as a function of particle size. In the particle range studied both vertical stroke {delta}H vertical stroke and vertical stroke {delta}S vertical stroke decreased with particle size towards the corresponding bulk values. H atoms were segregated to the subsurface of the particles forming a shell structure that may explain an initial plateau shown in the particles isotherms that is not present in bulk simulations. We used potentials of the embedded-atom type (EAM) to describe the interaction between atoms and we performed Monte Carlo simulations to calculate the isotherms. (author)

  10. Preparation of Size-tunable, Highly Monodisperse PVP-Protected Pt-nanoparticles by Seed-mediated Growth

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, Matthias Michael; Jones, Louis C.; Somorjai, Gabor A.

    2008-04-02

    We demonstrate a preparative method which produces highly-monodisperse Pt-nanoparticles of tunable size without the external addition of seed particles. Hexachloroplatinic acid is dosed slowly to an ethylene glycol solution at 120 C and reduced in the presence of a stabilizing polymer poly-N-vinylpyrollidone (PVP). Slow addition of the Pt-salt first will first lead to the formation of nuclei (seeds) which then grow further to produce larger particles of any desired size between 3 and 8nm. The amount of added hexachloroplatinic acid precursor controls the size of the final nanoparticle product. TEM was used to determine size and morphology and to confirm the crystalline nature of the nanoparticles. Good reproducibility of the technique was demonstrated. Above 7nm, the particle shape and morphology changes suddenly indicating a change in the deposition selectivity of the Pt-precursor from (100) towards (111) crystal faces and breaking up of larger particles into smaller entities.

  11. Monodisperse polyvinylpyrrolidone-coated CoFe{sub 2}O{sub 4} nanoparticles: Synthesis, characterization and cytotoxicity study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guangshuo, E-mail: wgs8136@163.com; Ma, Yingying, E-mail: bzhjgcmyy@163.com; Mu, Jingbo; Zhang, Zhixiao; Zhang, Xiaoliang; Zhang, Lina; Che, Hongwei; Bai, Yongmei; Hou, Junxian; Xie, Hailong

    2016-03-01

    Graphical abstract: - Highlights: • Monodisperse cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles were prepared with various additions of polyvinylpyrrolidone (PVP) by a facile sonochemical method. • PVP-coated CoFe{sub 2}O{sub 4} showed relatively well dispersion and homogeneous shape with narrow size distribution. • PVP-coated CoFe{sub 2}O{sub 4} exhibited superparamagnetism with moderate saturation magnetization and hydrophilic character at room temperature. • Negligible cytotoxicity of PVP-coated CoFe{sub 2}O{sub 4} was observed even at high sample concentration after 24 h treatment. - Abstract: In this study, monodisperse cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles were prepared successfully with various additions of polyvinylpyrrolidone (PVP) by sonochemical method, in which PVP served as a stabilizer and dispersant. The effects and roles of PVP on the morphology, microstructure and magnetic properties of the obtained CoFe{sub 2}O{sub 4} were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). It was found that PVP-coated CoFe{sub 2}O{sub 4} showed relatively well dispersion with narrow size distribution. The field-dependent magnetization curves indicated superparamagnetic behavior of PVP-coated CoFe{sub 2}O{sub 4} with moderate saturation magnetization and hydrophilic character at room temperature. More importantly, the in vitro cytotoxicity testing exhibited negligible cytotoxicity of as-prepared PVP-CoFe{sub 2}O{sub 4} even at the concentration as high as 150 μg/mL after 24 h treatment. Considering the superparamagnetic properties, hydrophilic character and negligible cytotoxicity, the monodisperse CoFe{sub 2}O{sub 4} nanoparticles hold great potential in a variety of biomedical applications.

  12. Atomistic modeling of H absorption in Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ruda, M., E-mail: ruda@cab.cnea.gov.a [Centro Atomico Bariloche, 8400 Bariloche (Argentina); Centro Regional Universitario Bariloche, U.N. Comahue (Argentina); Crespo, E.A., E-mail: crespo@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Debiaggi, S. Ramos de, E-mail: ramos@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); CONICET (Argentina)

    2010-04-16

    Size affects the properties of absorption of H in Palladium nanoparticles. Because of their higher proportion of surface atoms compared to the bulk, the pressure-composition (P-C) isotherms of the nanoparticles are modified. We performed atomistic simulations for different-sized Pd nanoparticles and for the bulk at different H concentrations using the Monte Carlo technique in the TP{mu}N ensemble to calculate the P-C isotherms. The Pd-H interatomic potentials are of the Embedded Atom (EAM) type and have been recently developed by Zhou et al. . From the related van't Hoff equation we obtained |{Delta}H{sup o}| = (28 {+-} 7) kJ/0.5 mol of H{sub 2} and |{Delta}S{sup o}| = (71 {+-} 19) J/0.5 mol of H{sub 2}.K for the PdH formation in the bulk. For Pd nanoparticles previous simulations results based on a different set of EAM potentials showed that H was absorbed primarily in the surface before diffusing into the inside of small Pd clusters . Considering the better performance of Zhou's potentials for the bulk, in this work we analyzed the evolution of the equilibrium microstructure of Pd nanoparticles as a function of their size and H concentration. Our simulations predict enhanced hydrogen solubilities and vanishing plateaux when compared to the bulk and that H is absorbed in the subsurface of the nanoparticles.

  13. Direct incorporation of lipophilic nanoparticles into monodisperse perfluorocarbon nanodroplets via solvent dissolution from microfluidic-generated precursor microdroplets.

    Science.gov (United States)

    Seo, Minseok; Matsuura, Naomi

    2014-10-28

    Multifunctional medical agents based on imaging or therapy nanoparticles (NPs) incorporated into perfluorocarbon (PFC) droplets are promising new agents for cancer detection and treatment. For the first time, monodisperse PFC nanodroplets labeled with NPs have been produced. Lipophilic, as-synthesized, hydrocarbon-stabilized NPs are directly miscibilized into lipophobic PFCs using a removable cosolvent, diethyl ether (DEE), which eliminates the need of the typical time-consuming and expertise-specific NP surface modification steps previously required for NP incorporation into PFCs. This NP-DEE/PFC solution is then used to synthesize monodisperse, micrometer-scale, DEE-infused NP-PFC precursor droplets in water using microfluidics. After precursor microdroplet generation, the DEE cosolvent is removed by dissolution and evaporation, resulting in dramatically smaller, monodisperse, NP-labeled nanodroplets, with final droplet sizes far smaller than the minimum droplet size limit of the microfluidic system, and easily controlled by the amount of DEE mixed in the PFC phase prior to precursor droplet synthesis. Using this technique, unmodified lipophilic quantum dot (QD) NPs were integrated into monodisperse and PFC nanodroplets 165 times smaller in volume than the precursor microdroplets, with dimensions down to 470 nm. The final droplet sizes scaled with the PFC concentrations in the precursor microdroplets, and the QDs remain localized within the droplets after DEE is removed from the system. This method is robust and versatile, and it comprises a platform technology for other unmodified lipophilic NPs and molecules to be incorporated into different types of PFC droplets for the production of new NP-PFC hybrid agents for medical imaging and therapy applications.

  14. Formation of Au/Pd Alloy Nanoparticles on TMV

    Directory of Open Access Journals (Sweden)

    Jung-Sun Lim

    2010-01-01

    Full Text Available A gold-palladium (AuPd solid solution alloy was successfully deposited on the genetically engineered tobacco mosaic virus (TMV1Cys by the biosorption of Au(III and Pd(II precursors and the reduction of the Au(III and Pd(II to their respective metals or metal alloy. The resulting morphologies of alloy nanoparticles deposited on the TMV1Cys were observed with transmission electron microscopy (TEM, and the AuPd alloy formation was supported with surface plasmon resonance (SPR and selected area electron diffraction (SAED. In addition, selected alloy nanoparticles on the TMV1Cys were analyzed further with electron energy loss spectroscopy (EELS to confirm the presence of gold and palladium. Our result implies that biotemplated metal mineralization is a potentially useful methodology to prepare alloy nanoparticles.

  15. Final Report for Fractionation and Separation of Polydisperse Nanoparticles into Distinct Monodisperse Fractions Using CO2 Expanded Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Chistopher Roberts

    2007-08-31

    The overall objective of this project was to facilitate efficient fractionation and separation of polydisperse metal nanoparticle populations into distinct monodisperse fractions using the tunable solvent properties of gas expanded liquids. Specifically, the dispersibility of ligand-stabilized nanoparticles in an organic solution was controlled by altering the ligand-solvent interaction (solvation) by the addition of carbon dioxide (CO{sub 2}) gas as an antisolvent (thereby tailoring the bulk solvent strength) in a custom high pressure apparatus developed in our lab. This was accomplished by adjusting the CO{sub 2} pressure over the liquid dispersion, resulting in a simple means of tuning the nanoparticle precipitation by size. Overall, this work utilized the highly tunable solvent properties of organic/CO{sub 2} solvent mixtures to selectively size-separate dispersions of polydisperse nanoparticles (ranging from 1 to 20 nm in size) into monodisperse fractions ({+-}1nm). Specifically, three primary tasks were performed to meet the overall objective. Task 1 involved the investigation of the effects of various operating parameters (such as temperature, pressure, ligand length and ligand type) on the efficiency of separation and fractionation of Ag nanoparticles. In addition, a thermodynamic interaction energy model was developed to predict the dispersibility of different sized nanoparticles in the gas expanded liquids at various conditions. Task 2 involved the extension of the experimental procedures identified in task 1 to the separation of other metal particles used in catalysis such as Au as well as other materials such as semiconductor particles (e.g. CdSe). Task 3 involved using the optimal conditions identified in tasks 1 and 2 to scale up the process to handle sample sizes of greater than 1 g. An experimental system was designed to allow nanoparticles of increasingly smaller sizes to be precipitated sequentially in a vertical series of high pressure vessels by

  16. Ternary Pd-Ni-P hybrid electrocatalysts derived from Pd-Ni core-shell nanoparticles with enhanced formic acid oxidation activity.

    Science.gov (United States)

    Liang, Xin; Liu, Bo; Zhang, Juntao; Lu, Siqi; Zhuang, Zhongbin

    2016-09-25

    Ternary Pd-Ni-P hybrid electrocatalysts were synthesized through low temperature phosphidation of Pd-Ni core-shell nanoparticles. They show enhanced formic acid electro-oxidation activity compared to Pd, Pd-Ni and Pd-P nanoparticles, which is ascribed to the synergistic effect of the Ni and P components with Pd.

  17. Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sengar, Saurabh K.; Mehta, B. R., E-mail: brmehta@physics.iitd.ac.in [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Govind [Surface Physics Group, National Physical Laboratory (CSIR), New Delhi 110012 (India)

    2014-03-28

    In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity.

  18. Rapid Synthesis of Highly Monodisperse Au x Ag 1− x Alloy Nanoparticles via a Half-Seeding Approach

    KAUST Repository

    Chng, Ting Ting

    2011-05-03

    Gold-silver alloy AuxAg1-x is an important class of functional materials promising new applications across a wide array of technological fields. In this paper, we report a fast and facile synthetic protocol for preparation of highly monodisperse AuxAg1-x alloy nanoparticles in the size range of 3-6 nm. The precursors employed in this work are M(I)-alkanethiolates (M = Au and Ag), which can be easily prepared by mixing common chemicals such as HAuCl4 or AgNO3 with alkanethiols at room temperature. In this half-seeding approach, one of the M(I)-alkanethiolates is first heated and reduced in oleylamine solvent, and freshly formed metal clusters will then act as premature seeds on which both the first and second metals (from M(I)-alkanethiolates, M = Au and Ag) can grow accordingly without additional nucleation and thus achieve high monodispersity for product alloy nanoparticles. Unlike in other prevailing methods, both Au and Ag elements present in these solid precursors are in the same monovalent state and have identical supramolecular structures, which may lead to a more homogeneous reduction and complete interdiffusion at elevated reaction temperatures. When the M(I)-alkanethiolates are reduced to metallic forms, the detached alkanethiolate ligands will serve as capping agent to control the growth. More importantly, composition, particle size, and optical properties of AuxAg1-x alloy nanoparticles can be conveniently tuned with this approach. The optical limiting properties of the prepared particles have also been investigated at 532 and 1064 nm using 7 ns laser pulses, which reveals that the as-prepared alloy nanoparticles exhibit outstanding broadband optical limiting properties with low thresholds. © 2011 American Chemical Society.

  19. A facile route to monodisperse MPd (M = Co or Cu) alloy nanoparticles and their catalysis for electrooxidation of formic acid

    Science.gov (United States)

    Ho, Sally Fae; Mendoza-Garcia, Adriana; Guo, Shaojun; He, Kai; Su, Dong; Liu, Sheng; Metin, Önder; Sun, Shouheng

    2014-05-01

    MPd (M = Co, or Cu) nanoparticles (NPs) were synthesized by borane-amine reduction of metal acetylacetonates. The size of the MPd NPs was controlled at 3.5 nm and their compositions were tuned by the molar ratios of the metal precursors. These MPd NPs were active catalysts for electrochemical oxidation of formic acid and the Cu30Pd70 NPs showed the highest mass activity at 1192.9 A gPd-1, much higher than 552.6 A gPd-1 obtained from the 3.5 nm Pd NPs. Our synthesis provides a facile route to MPd NPs, allowing further investigation of MPd NP catalysts for electrochemical oxidation and many other chemical reactions.MPd (M = Co, or Cu) nanoparticles (NPs) were synthesized by borane-amine reduction of metal acetylacetonates. The size of the MPd NPs was controlled at 3.5 nm and their compositions were tuned by the molar ratios of the metal precursors. These MPd NPs were active catalysts for electrochemical oxidation of formic acid and the Cu30Pd70 NPs showed the highest mass activity at 1192.9 A gPd-1, much higher than 552.6 A gPd-1 obtained from the 3.5 nm Pd NPs. Our synthesis provides a facile route to MPd NPs, allowing further investigation of MPd NP catalysts for electrochemical oxidation and many other chemical reactions. Electronic supplementary information (ESI) available: Detailed synthetic and electrochemical analysis procedures, and XRD of the NPs. See DOI: 10.1039/c4nr01107d

  20. Atomic Structure of Au−Pd Bimetallic Alloyed Nanoparticles

    KAUST Repository

    Ding, Yong

    2010-09-08

    Using a two-step seed-mediated growth method, we synthesized bimetallic nanoparticles (NPs) having a gold octahedron core and a palladium epitaxial shell with controlled Pd-shell thickness. The mismatch-release mechanism between the Au core and Pd shell of the NPs was systematically investigated by high-resolution transmission electron microscopy. In the NPs coated with a single atomic layer of Pd, the strain between the surface Pd layer and the Au core is released by Shockley partial dislocations (SPDs) accompanied by the formation of stacking faults. For NPs coated with more Pd (>2 nm), the stacking faults still exist, but no SPDs are found. This may be due to the diffusion of Au atoms into the Pd shell layers to eliminate the SPDs. At the same time, a long-range ordered L11 AuPd alloy phase has been identified in the interface area, supporting the assumption of the diffusion of Au into Pd to release the interface mismatch. With increasing numbers of Pd shell layers, the shape of the Au-Pd NP changes, step by step, from truncated-octahedral to cubic. After the bimetallic NPs were annealed at 523 K for 10 min, the SPDs at the surface of the NPs coated with a single atomic layer of Pd disappeared due to diffusion of the Au atoms into the surface layer, while the stacking faults and the L11 Au-Pd alloyed structure remained. When the annealing temperature was increased to 800 K, electron diffraction patterns and diffraction contrast images revealed that the NPs became a uniform Au-Pd alloy, and most of the stacking faults disappeared as a result of the annealing. Even so, some clues still support the existence of the L11 phase, which suggests that the L11 phase is a stable, long-range ordered structure in Au-Pd bimetallic NPs. © 2010 American Chemical Society.

  1. Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

    Science.gov (United States)

    Semaltianos, N. G.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Assoul, M.; Monteil, G.

    2017-04-01

    Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

  2. Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying.

    Science.gov (United States)

    Semaltianos, N G; Chassagnon, R; Moutarlier, V; Blondeau-Patissier, V; Assoul, M; Monteil, G

    2017-04-18

    Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

  3. Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

    KAUST Repository

    Song, Hyon Min

    2015-01-13

    The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P42/mmc) with cell parameters of a = 3.050 Å and c = 5.344 Å, which are slightly larger than in the bulk phase (a = 3.03 Å, c = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs.

  4. In-site synthesis of monodisperse, oleylamine-capped Ag nanoparticles through microemulsion approach

    Science.gov (United States)

    Chen, Shun; Ju, Yanyun; Guo, Yi; Xiong, Chuanxi; Dong, Lijie

    2017-03-01

    Ag NPs were in-site synthesized through microemulsion method by reducing silver acetate with oleylamine-mediated at 70 °C with highly monodisperse and narrow size from 10 to 20 nm. The synthesis of Ag NPs was aided by oleylamine and the role of oleylamine was researched. This in-site synthesis approach to Ag NPs was reproducibility and high yield more than 80% with stable store about 6 months.

  5. High surface area monodispersed Fe3O4 nanoparticles alone and on physical exfoliated graphite for improved supercapacitors

    Science.gov (United States)

    Sarno, Maria; Ponticorvo, Eleonora; Cirillo, Claudia

    2016-12-01

    Highly conductive, unsophisticated and easy to be obtained physical exfoliated graphite (PHG) supporting well dispersed magnetite, Fe3O4/PHG nanocomposite, has been prepared by a one-step chemical strategy and physico-chemical characterized. The nanocomposite, favoured by the a-polar nanoparticles (NPs) capping, results in a self-assembled monolayer of monodispersed Fe3O4, covering perfectly the hydrophobic surfaces of PHG. The nanocomposite as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. It shows, after a suitable annealing, significant electrochemical properties (capacitance value of 787 F/g at 0.5 A g-1 and a Fe3O4/PHG weight ratio of 0.31) and good cycling stability (retention 91% after 30,000 cycles). Highly monodispersed very fine Fe3O4 NPs, covered by organic chains, have been also synthesized. The high surface area Fe3O4 NPs, after washing to leave a low content of organic chains able to avoid aggregation without excessively affecting the electrical properties of the material, exhibit remarkable pseudocapacitive activities, including the highest specific capacitance over reported for Fe3O4 (300 F/g at 0.5 A g-1).

  6. Light-induced growth of monodisperse silver nanoparticles with tunable SPR properties and wavelength self-limiting effect

    Science.gov (United States)

    Zheng, Xianliang; Lombardi, John R.

    2008-08-01

    We present a technique for the tunable synthesis of a variety of monodisperse silver nanoparticles. Utilizing different optical wavelengths to irradiate initially grown seed crystals, the size and shape of the products can be controlled. Monitoring the absorption spectrum during growth, we observe that initially the absorption maximum shifts to longer wavelengths and broadens, indicating increasing particle size and dispersion. Remarkably, this effect gradually comes to a halt and reverses, displaying a shift to shorter wavelengths and simultaneously narrower bandwidths, until on completion, a final size and relatively narrow distribution is reached. The final morphology is found to depend on control of the laser wavelength and power. Discs, triangular prisms as well as pyramidal and pentagonal prisms may be produced. A process based on a wavelength dependent self-limiting mechanism governed by the surface plasmon resonance controlling the photochemical reduction of particles is suggested. By a similar mechanism, we show that by using a sodium lamp instead of a laser as an excitation source, a monodisperse sample of nanotetrahedra can be produced.

  7. Pd-nanoparticles cause increased toxicity to kiwifruit pollen compared to soluble Pd(II)

    Energy Technology Data Exchange (ETDEWEB)

    Speranza, Anna, E-mail: anna.speranza@unibo.i [Dipartimento di Biologia, Universita di Bologna, via Irnerio 42, 40126 Bologna (Italy); Leopold, Kerstin, E-mail: kerstin.leopold@lrz.tu-muenchen.d [Arbeitsgruppe fuer Analytische Chemie, Technische Universitaet Muenchen, Garching (Germany); Maier, Marina, E-mail: marina.maier@ch.tum.d [Arbeitsgruppe fuer Analytische Chemie, Technische Universitaet Muenchen, Garching (Germany); Taddei, Anna Rita, E-mail: artaddei@unitus.i [CIME, Universita della Tuscia, Viterbo (Italy); Scoccianti, Valeria, E-mail: valeria.scoccianti@uniurb.i [Dipartimento di Scienze dell' Uomo, dell' Ambiente e della Natura, Universita di Urbino ' Carlo Bo' , Urbino (Italy)

    2010-03-15

    In the present study, endpoints including in vitro pollen performance (i.e., germination and tube growth) and lethality were used as assessments of nanotoxicity. Pollen was treated with 5-10 nm-sized Pd particles, similar to those released into the environment by catalytic car exhaust converters. Results showed Pd-nanoparticles altered kiwifruit pollen morphology and entered the grains more rapidly and to a greater extent than soluble Pd(II). At particulate Pd concentrations well below those of soluble Pd(II), pollen grains experienced rapid losses in endogenous calcium and pollen plasma membrane damage was induced. This resulted in severe inhibition and subsequent cessation of pollen tube emergence and elongation at particulate Pd concentrations as low as 0.4 mg L{sup -1}. Particulate Pd emissions related to automobile traffic have been increasing and are accumulating in the environment. This could seriously jeopardize in vivo pollen function, with impacts at an ecosystem level. - Nanoparticulate Pd - which resembles emissions from automobile catalysts - affects pollen to a higher extent than soluble Pd.

  8. Nearly Monodispersion CoSm Alloy Nanoparticles Formed by an In-situ Rapid Cooling and Passivating Microfluidic Process

    Directory of Open Access Journals (Sweden)

    Henry Laurence

    2009-01-01

    Full Text Available Abstract An in siturapid cooling and passivating microfluidic processhas been developed for the synthesis of nearly monodispersed cobalt samarium nanoparticles (NPs with tunable crystal structures and surface properties. This process involves promoting the nucleation and growth of NPs at an elevated temperature and rapidly quenching the NP colloids in a solution containing a passivating reagent at a reduced temperature. We have shown that Cobalt samarium NPs having amorphous crystal structures and a thin passivating layer can be synthesized with uniform nonspherical shapes and size of about 4.8 nm. The amorphous CoSm NPs in our study have blocking temperature near 40 K and average coercivity of 225 Oe at 10 K. The NPs also exhibit high anisotropic magnetic properties with a wasp-waist hysteresis loop and a bias shift of coercivity due to the shape anisotropy and the exchange coupling between the core and the thin oxidized surface layer.

  9. Synthesis and Magnetic Properties of Nearly Monodisperse CoFe2O4Nanoparticles Through a Simple Hydrothermal Condition

    Directory of Open Access Journals (Sweden)

    Li Xing-Hua

    2010-01-01

    Full Text Available Abstract Nearly monodisperse cobalt ferrite (CoFe2O4 nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid–solid-solution (LSS process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds.

  10. Electroreduction of oxygen on Vulcan carbon supported Pd nanoparticles and Pd-M nanoalloys in acid and alkaline solutions

    Energy Technology Data Exchange (ETDEWEB)

    Alexeyeva, N. [Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu (Estonia); Sarapuu, A., E-mail: ave.sarapuu@ut.ee [Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu (Estonia); Tammeveski, K. [Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu (Estonia); Vidal-Iglesias, F.J.; Solla-Gullon, J.; Feliu, J.M. [Instituto de Electroquimica, Universidad de Alicante, Apartado 99, 03080 Alicante (Spain)

    2011-07-30

    Highlights: > Electroreduction of O{sub 2} on carbon-supported Pd, PdCo and PdFe nanoparticles is studied. > Pd-based catalysts were prepared by reduction in the presence of citrate and in microemulsion. > Four-electron reduction of O{sub 2} proceeds in both acid and alkaline media. > Specific activity of PdCo and PdFe nanocatalysts was similar to that of Pd nanoparticles. - Abstract: The kinetics of O{sub 2} reduction on novel electrocatalyst materials deposited on carbon substrates were studied using the rotating disk electrode (RDE) technique. Palladium nanoparticles and Pd-M (PdCo and PdFe) nanoalloys supported on Vulcan XC-72R were prepared using two different synthetic routes. The catalyst samples were examined by transmission electron microscopy (TEM) and the average size of metal nanoparticles was determined. Electrochemical measurements were performed in 0.5 M H{sub 2}SO{sub 4} and in 0.1 M NaOH solutions. The influence of different synthetic conditions on the values of specific activity and other kinetic parameters was investigated. These parameters were determined from the Tafel plots taking into account the real electroactive area for each electrode. Pd nanoparticles and Pd-M nanoalloys exhibit significantly high electrocatalytic activity for the four-electron reduction of oxygen to water.

  11. CO adsorption over Pd nanoparticles: A general framework for IR simulations on nanoparticles

    Science.gov (United States)

    Zeinalipour-Yazdi, Constantinos D.; Willock, David J.; Thomas, Liam; Wilson, Karen; Lee, Adam F.

    2016-04-01

    CO vibrational spectra over catalytic nanoparticles under high coverages/pressures are discussed from a DFT perspective. Hybrid B3LYP and PBE DFT calculations of CO chemisorbed over Pd4 and Pd13 nanoclusters, and a 1.1 nm Pd38 nanoparticle, have been performed in order to simulate the corresponding coverage dependent infrared (IR) absorption spectra, and hence provide a quantitative foundation for the interpretation of experimental IR spectra of CO over Pd nanocatalysts. B3LYP simulated IR intensities are used to quantify site occupation numbers through comparison with experimental DRIFTS spectra, allowing an atomistic model of CO surface coverage to be created. DFT adsorption energetics for low CO coverage (θ → 0) suggest the CO binding strength follows the order hollow > bridge > linear, even for dispersion-corrected functionals for sub-nanometre Pd nanoclusters. For a Pd38 nanoparticle, hollow and bridge-bound are energetically similar (hollow ≈ bridge > atop). It is well known that this ordering has not been found at the high coverages used experimentally, wherein atop CO has a much higher population than observed over Pd(111), confirmed by our DRIFTS spectra for Pd nanoparticles supported on a KIT-6 silica, and hence site populations were calculated through a comparison of DFT and spectroscopic data. At high CO coverage (θ = 1), all three adsorbed CO species co-exist on Pd38, and their interdiffusion is thermally feasible at STP. Under such high surface coverages, DFT predicts that bridge-bound CO chains are thermodynamically stable and isoenergetic to an entirely hollow bound Pd/CO system. The Pd38 nanoparticle undergoes a linear (3.5%), isotropic expansion with increasing CO coverage, accompanied by 63 and 30 cm- 1 blue-shifts of hollow and linear bound CO respectively.

  12. Separation of Gases Using Ultra-Thin Porous Layers of Monodisperse Nanoparticles

    Directory of Open Access Journals (Sweden)

    Bubenchikov Mikhail A

    2016-01-01

    Full Text Available The present paper deals with a numerical solution of the two-dimensional problem of helium and methane molecules motion through an ultra-thin layer of a porous material composed of spherical nanoparticles of the same size. The interaction potential “nanoparticle-molecule” is obtained by integrating paired molecular interactions over the nanoparticle volume. Using the method of classical molecular dynamics, permeability of a layer having the size of about 10−8 m is studied.

  13. Monodispersed biocompatible Ag2S nanoparticles: Facile extracellular bio-fabrication using the gamma-proteobacterium, S. oneidensis

    Energy Technology Data Exchange (ETDEWEB)

    Suresh, Anil K [ORNL; Doktycz, Mitchel John [ORNL; Wang, Wei [ORNL; Moon, Ji Won [ORNL; Gu, Baohua [ORNL; Meyer III, Harry M [ORNL; Hensley, Dale K [ORNL; Retterer, Scott T [ORNL; Allison, David P [ORNL; Phelps, Tommy Joe [ORNL; Pelletier, Dale A [ORNL

    2011-01-01

    Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size and or shape dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs have become a priority. In the present illustration we report for the first time the efficient generation of extracellular Ag2S nanoparticles by the metal reducing bacterium, Shewanella oneidensis. The particles are nearly monodispersed with homogeneous shape distributions and are produced under ambient temperatures and pressures at high yield, 85 % theoretical maximum. UV-vis and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical properties, purity, and crystallinity of the as-synthesized particles. Further characterization revealed that the particles consist of spheres in the size range of 1-22 nm, with an average size of 9 3 nm and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these silver sulfide nanoparticles on Gram-negative Escherichia coli and Shewanella oneidensis and Gram-positive Bacillus subtilis bacterial systems as well as eukaryotic; mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells showed that the particles were non-inhibitory or non-cytotoxic to both these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag2S nanoparticles which are dispersible and biocompatible; thus providing excellent potential for their uses in optical imaging and electronic devices, and solar cell applications.

  14. Converting Homogeneous to Heterogeneous in Electrophilic Catalysis using Monodisperse Metal Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Witham, Cole A.; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N.; Somorjai, Gabor A.; Toste, F. Dean

    2009-10-15

    A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl{sub 2}, and catalyze a range of {pi}-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues.

  15. Continuous synthesis of monodispersed silver nanoparticles using a homogeneous heating microwave reactor system.

    Science.gov (United States)

    Nishioka, Masateru; Miyakawa, Masato; Kataoka, Haruki; Koda, Hidekazu; Sato, Koichi; Suzuki, Toshishige M

    2011-06-01

    Continuous synthesis of silver nanoparticles based on a polyol process was conducted using a microwave-assisted flow reactor installed in a cylindrical resonance cavity. Silver nitrate (AgNO(3)) and poly(N-vinylpyrrolidone) (PVP) dissolved in ethylene glycol were used respectively as a silver metal precursor and as a capping agent of nanoparticles. Ethylene glycol worked as the solvent and simultaneously as the reductant. Silver nanoparticles of narrow size distributions were synthesized steadily for 5 h, maintaining almost constant yield (>93%) and quality. The reaction was achieved within 2.8 s of residence time, although nanoparticles were not formed under this flow rate by conventional heating. A narrower particle size distribution was realized by the increased flow rate of the reaction solution. Nanoparticles of 9.8 nm average size with a standard deviation of 0.9 nm were synthesized at the rate of 100 ml h(-l).

  16. Green synthesis of monodisperse silver nanoparticles using hydroxy propyl methyl cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Chunfa; Zhang, Xianglin, E-mail: hust_zxl@mail.hust.edu.cn; Cai, Hao

    2014-01-15

    Graphical abstract: -- Highlights: • Synthesis of silver nanoparticles using hydroxy propyl methyl cellulose is reported. • HPMC and glucose are used as capping agent and reducing agent respectively. • It is the first time to use HPMC for synthesis of silver nanoparticles. • The small, spherical and well-dispersed particle is observed in the range of 3–17 nm. • The green method can be extended to other noble metals. -- Abstract: A simple and environmentally friendly method for the synthesis of highly stable and small sized silver nanoparticles with narrow distribution from 3 nm to 17 nm is reported. Silver nitrate, hydroxy propyl methyl cellulose (HPMC) and glucose, were used as silver precursor, capping agents and reducing agents respectively. The formation of silver nanoparticles was observed by change of color from colorless to wine red. The silver nanoparticles were characterized by transmission electron microscopy (TEM), UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that the obtained metallic nanoparticles were single crystalline silver nanoparticles capped with HPMC. The effects of the reaction time, reaction temperature and the concentration of silver ion and reducing agents on the particle size were investigated. A possible formation mechanism was proposed. The method may be extended to other noble metal for other technological applications such as additional medicinal, industrial applications.

  17. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    K C Barick; D Bahadur

    2006-11-01

    The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 spheres have been prepared by an in situ reaction using different molar ratios of Fe3+/Fe2+ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO2 as core and Fe3O4 nanoparticles as shell depend on the molar ratio of Fe3+/Fe2+.

  18. Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles.

    Science.gov (United States)

    Witham, Cole A; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N; Somorjai, Gabor A; Toste, F Dean

    2010-01-01

    A continuing goal in catalysis is to unite the advantages of homogeneous and heterogeneous catalytic processes. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this unification can also be supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl(2), and catalyse a range of π-bond activation reactions previously only catalysed through homogeneous processes. Multiple experimental methods are used to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, a size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared with larger, polymer-capped analogues.

  19. Comparison of bacterial cells and amine-functionalized abiotic surfaces as support for Pd nanoparticle synthesis

    DEFF Research Database (Denmark)

    De Corte, Simon; Bechstein, Stefanie; Lokanathan, Arcot R.

    2013-01-01

    An increasing demand for catalytic Pd nanoparticles has motivated the search for sustainable production methods. An innovative approach uses bacterial cells as support material for synthesizing Pd nanoparticles by reduction of Pd(II) with e.g. hydrogen or formate. Nevertheless, drawbacks...... nanoparticles, and that abiotic surfaces could support the Pd particle synthesis as efficiently as bacteria. In this study, we explore the possibility of replacing bacteria with amine-functionalized materials, and we compare different functionalization strategies. Pd nanoparticles formed on the support...... of microbially supported Pd catalysts are the low catalytic activity compared to conventional Pd nanocatalysts and the possible poisoning of the catalyst surface by sulfur originating from bacterial proteins. A recent study showed that amine groups were a key component in surface-supported synthesis of Pd...

  20. Monodisperse gold nanoparticles formed on bacterial crystalline surface layers (S-layers) by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dieluweit, S. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Pum, D. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Sleytr, U.B. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Kautek, W. [Department for Physical Chemistry, University of Vienna, Waehringer Strasse 42, A-1090 Vienna (Austria)]. E-mail: wolfgang.kautek@univie.ac.at

    2005-12-15

    The fabrication of patterned arrays of nanoparticles whose electronic, optical and magnetic properties will find technological applications, such as ultra-high-density memories, is currently one of the most important objectives of inorganic material research. In this study, the in situ electroless nucleation of ordered two-dimensional arrays of gold nanoparticles (5 nm in size) by using bacterial S-layers as molecular templates and their characterization by small spot X-ray photoelectron emission spectroscopy (XPS) is presented. This yielded the elemental composition of the nanoclusters, which consisted of almost entirely elemental gold, and possible side reactions on the cluster and protein surface. The preferential deposition of the gold nanoparticles on the S-layer suggests that topography and functional groups are important for superlattice formation.

  1. Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods.

    Science.gov (United States)

    Hu, Gaoshuang; Sheng, Wei; Zhang, Yan; Wang, Junping; Wu, Xuening; Wang, Shuo

    2016-05-18

    A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

  2. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Science.gov (United States)

    Ren, Yan-yu; Yang, Hui; Wang, Tao; Wang, Chuang

    2016-11-01

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag+ (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO3) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO3 concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV-vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10-16 nm. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications.

  3. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Chao [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Yang, Hui; Huang, Peiyan; Song, Huiyu [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China)

    2014-10-01

    Graphical abstract: The addition of Ru could significantly improve the performance of the mesoporous silica nanoparticles supported PdRu/MSN catalyst, which showed over 5 times higher mass activity than the mono-Pd/MSN towards the liquid-phase hydrogenation of phenol. The improved dispersion and the electronic interaction contributed to the enhanced catalytic activity for the catalyst towards phenol hydrogenation. - Highlights: • PdRu bimetal catalyst supported on mesoporous silica nanoparticles was prepared. • The average sizeof PdRu alloy is smaller than that of mono-Pd. • The addition of Ru to Pd modulates the electronic properties between Pd and Ru. • PdRu/MSN catalyst shows superior activity on phenol hydrogenation than Pd/MSN. • PdRu/MSN catalyst shows good selectivity for cyclohexanol to some extent. - Abstract: A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation–hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  4. Fabrication of monodisperse FePt rate at Au core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wei, D.H. [Institute of Physics, Academia Sinica, Taipei 115 (China); Hung, D.S. [Department of Information and Telecommunications Engineering, Ming Chuan University, Taipei 111 (China); Ho, C.S.; Wang, J.W. [Department of Chemical Engineering, Tunghai University, Taichung 407 (China); Yao, Y.D. [Department of Materials Engineering, Tatung University, Taipei 104 (China)

    2007-12-15

    Hydrophobic FePt rate at Au core-shell nanoparticles were chemically synthesized and with controllable surface-function properties. The enhanced optical property is due to the contribution of Au shell. The surface modification of FePt rate at Au nanoiparticles by using 11-mercaptoundecanoic acid (MUA) was hydrophilic through ligand exchange and with good biocompatibility for future multi-functional applications. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Two-stage melting of Au-Pd nanoparticles.

    Science.gov (United States)

    Mejía-Rosales, Sergio J; Fernandez-Navarro, Carlos; Pérez-Tijerina, Eduardo; Montejano-Carrizales, Juan Martín; José-Yacamán, Miguel

    2006-07-06

    Several series of molecular dynamics runs were performed to simulate the melting transition of bimetallic cuboctahedral nanoparticles of gold-palladium at different relative concentrations to study their structural properties before, in, and after the transition. The simulations were made in the canonical ensemble, each series covering a range of temperatures from 300 to 980 K, using the Rafii-Tabar version of the Sutton and Chen interatomic potential for metallic alloys. We found that the melting transition temperature has a strong dependence on the relative concentrations of the atomic species. We also found that, previous to the melting transition, the outer layer of the nanoparticle gets disordered in what can be thought as a premelting stage, where Au atoms near the surface migrate to the surface and remain there after the particle melts as a whole. The melting of the surface below Tm is consistent with studies of the interaction of a TEM electron beam with Au and Au-Pd nanoparticles.

  6. Fast, microwave-assisted synthesis of monodisperse HfO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Roo, Jonathan De; Keukeleere, Katrien De; Feys, Jonas; Lommens, Petra [Ghent University, Sol-Gel Centre for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS) (Belgium); Hens, Zeger [Ghent University, Physics and Chemistry of Nanostructures (PCN) (Belgium); Driessche, Isabel Van, E-mail: Isabel.VanDriessche@ugent.be [Ghent University, Sol-Gel Centre for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS) (Belgium)

    2013-07-15

    A conventional solvothermal synthesis was compared to a microwave-assisted method for the synthesis of HfO{sub 2} nanoparticles. In a microwave, the reaction could be completed in 3 h, compared to 3 days in an autoclave. In the microwave synthesis, the ensemble of particles was found to have a better size dispersion and a smaller average size (4 nm). The reaction mechanism was investigated and proof for an ether elimination process was provided. Post-synthetic modification with dopamine or dodecanoic acid permitted the suspension of the synthesized particles in both polar and apolar solvents, which is an advantage for further processing.

  7. Study of PtPd Bimetallic Nanoparticles for Fuel Cell Applications

    OpenAIRE

    Esparza, Rodrigo; Santoveña,Alan; Ruíz-Baltazar, Alvaro; Angeles-Pascual,Alvaro; Bahena,Daniel; Maya-Cornejo,Jose; Ledesma-García, Janet; Pérez,Ramiro

    2017-01-01

    Bimetallic nanoparticles are of special interest for their potential applications for fuel cells, mainly for portable power applications. Among the bimetallic systems, Pt-Pd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. In this work, Pt-Pd alloy bimetallic nanoparticles were synthesized through a chemical reduction method. The nanoparticles were characterized using aberration-corrected scanning/tr...

  8. A highly active Pd-P nanoparticle electrocatalyst for enhanced formic acid oxidation synthesized via stepwise electroless deposition.

    Science.gov (United States)

    Poon, Kee Chun; Khezri, Bahareh; Li, Yao; Webster, Richard D; Su, Haibin; Sato, Hirotaka

    2016-02-28

    A highly active Pd-P nanoparticle electrocatalyst for formic acid oxidation was synthesized using NaH2PO2 as the reducing agent. The Pd-P nanoparticles were amorphous and exhibited higher specific and mass activity values compared to commercial Pd/C electrocatalyts and reported literature values. Furthermore, the Pd-P nanoparticles were found to be more durable than Pd/C electrocatalyts.

  9. Electrodeposition of Pd Nanowires and Nanorods on Carbon Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bliznakov, S.; Vukmirovic, M.; Sutter, E.; Adzic, R.

    2011-06-01

    We report on the method for synthesizing palladium nanowires and nanorods involving the electrodeposition on oxidized amorphous carbon nanoparticles from chloride containing solutions. The effect of the deposition overpotential and the concentration of palladium ions on the morphology of the Pd electrodeposits have been established. Palladium grows predominately in the shape of nanowires if electrodeposited at potentials in the H underpotential deposition potential (UPD) range, where chloride ions are adsorbed only at the edges of nucleated monolayer-thick clusters on the carbon surface. The effect of the concentration of palladium ions on deposits morphology is also discussed. The mechanism of electrodeposition of Pd nanowires and nanorods in the H UPD potential range has been proposed.

  10. Monodisperse Pt Nanoparticles Assembled on Reduced Graphene Oxide: Highly Efficient and Reusable Catalyst for Methanol Oxidation and Dehydrocoupling of Dimethylamine-Borane (DMAB).

    Science.gov (United States)

    Yildiz, Yunus; Erken, Esma; Pamuk, Handan; Sert, Hakan; Sen, Fatih

    2016-06-01

    Herein, monodisperse platinum (0) nanocatalyst assembled on reduced graphene oxide (Pt(0)@RGO) was easily and reproducibly prepared by the double solvent reduction method at room temperature. Pt(0)@RGO was characterized by X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS) and transmission electron microscopy (TEM) measurements that verify the formation of monodisperse Pt (0) nanoparticles on RGO. The catalytic and electrocatalytic performances of Pt(0) @ RGO in terms of activity, isolability and reusability were investigated for both methanol oxidation and the dehydrocoupling of dimethylamine-borane (DMAB) in which Pt(0)@RGO was found to be highly active and reusable heterogeneous catalyst even at room temperature. The prepared nanoparticles can also electrocatalyze methanol oxidation with very high electrochemical activities (5.64 A/cm2 at 0.58 V for methanol). The activation energy (Ea), activation enthalpy (ΔH#), and activation entropy (ΔS#) for DMAB dehydrogenation were calculated to be 59.33 kJ mol(-1), 56.79 kJ mol(-1) and -151.68 J mol(-1) K(-1), respectively. The exceptional stability of new Pt(0) @ RGO nanoparticles towards agglomeration, leaching and CO poisoning allow these particles to be recycled and reused in the catalysis of DMAB dehydrogenation and methanol oxidation. After four subsequent reaction and recovery cycles, Pt(0) @ RGO retained ≥ 75% activity towards the complete dehydrogenation of DMAB.

  11. Synthesis of Pt, Pd, Pt/Ag and Pd/Ag nanoparticles by microwave-polyol method

    Indian Academy of Sciences (India)

    Kirti Patel; Sudhir Kapoor; Devilal Purshottam Dave; Tulsi Mukherjee

    2005-07-01

    Pt, Pd, Pt-Ag and Pd-Ag bimetallic nanoparticles were synthesized in ethylene glycol and glycerol using the microwave technique in the presence of a stabilizer poly(N-vinylpyrrolidone) (PVP). It has been observed that PVP is capable of complexing and stabilizing nanoparticles. Mixed clusters were formed by simultaneous reduction of the metal ions. The clusters were characterized using UV-Vis spectra, XRD and dynamic light scattering. To understand the mechanism of formation of mixed nanoparticles, several experimental parameters such as in situ irradiation of mixed metal salts and mixing of individual sols were attempted.

  12. Factors influencing the charge distribution on Pd x Pt y bimetallic nanoparticles

    Directory of Open Access Journals (Sweden)

    Carlos M. Celis-Cornejo

    2013-12-01

    Full Text Available We performed quantum mechanics calculations to elucidate the electronic behavior of Pd-Pt bimetallic nanoparticles, using density functional theory, in response to particle size and stoichiometric composition. Using neutrally charged nanoparticles and the Bader charge analysis, we found that external Pd atoms were positively charged, which agrees with previous XPS observations of supported Pd-Pt nanoparticles. From the calculations, unsupported nanoparticles exhibit an electron transfer from Pd to Pt. This result supports the idea that Pd electron-deficient species are possibly responsible of the hydrogenating function of these catalysts, in the hydrodesulfurization of dibenzothiophene. Additionally, it was found that the particle size does not affect the electronic charge distribution and the stoichiometric composition is the factor that greatly influences this property in nanoparticles.

  13. Microbial synthesis of bimetallic PdPt nanoparticles for catalytic reduction of 4-nitrophenol.

    Science.gov (United States)

    Tuo, Ya; Liu, Guangfei; Dong, Bin; Yu, Huali; Zhou, Jiti; Wang, Jing; Jin, Ruofei

    2017-02-01

    Bimetallic nanoparticles are generally believed to have improved catalytic activity and stability due to geometric and electronic changes. In this work, biogenic-Pd (bio-Pd), biogenic-Pt (bio-Pt), and biogenic-PdPt (bio-PdPt) nanoparticles were synthesized by Shewanella oneidensis MR-1 in the absence or presence of quinone. Compared with direct microbial reduction process, the addition of anthraquinone-2,6-disulfonate (AQDS) could promote the reduction efficiency of Pd(II) or/and Pt(IV) and result in decrease of particles size. All kinds of nanoparticles could catalyze 4-nitrophenol reduction by NaBH4 and their catalytic activities took the following order: bio-PdPt (AQDS) ∼ bio-PdPt > bio-Pd (AQDS) > bio-Pd > bio-Pt (AQDS) ∼ bio-Pt. Moreover, the bio-PdPt (AQDS) nanoparticles could be reused for 6 cycles. We believe that this simple and efficient biosynthesis approach for synthesizing bimetallic bio-PdPt nanocatalysts is important for preparing active and stable catalysts.

  14. Heterostructured Au/Pd-M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

    Science.gov (United States)

    Lutz, Patrick S.; Bae, In-Tae; Maye, Mathew M.

    2015-09-01

    The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had

  15. Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host.

    Science.gov (United States)

    Kim, Taeho; Fu, Xin; Warther, David; Sailor, Michael J

    2017-02-21

    Porous silicon nanoparticles containing both Pd and iron oxide nanoparticles are prepared and studied as magnetically recoverable catalysts for organic reductions. The Pd nanoparticles are generated in situ by electroless deposition of Pd(NH3)4(2+), where the porous Si skeleton acts as both a template and as a reducing agent and the released ammonia ligands raise the local pH to exert control over the size of the Pd nanoparticles. The nanocomposites are characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption, X-ray diffraction, superconducting quantum interference device magnetization, and dynamic light scattering. The nanocomposite consists of a porous Si nanoparticle (150 nm mean diameter) containing ∼20 nm pores, uniformly decorated with a high loading of surfactant-free Pd nanoparticles (12 nm mean diameter) and superparamagnetic γ-Fe2O3 nanoparticles (∼7 nm mean diameter). The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride is catalyzed by the nanocomposite, which is stable through the course of the reaction. Catalytic reduction of the organic dyes methylene blue and rhodamine B is also demonstrated. The conversion efficiency and catalytic activity are found to be superior to a commercial Pd/C catalyst compared under comparable reaction conditions. The composite catalyst can be recovered from the reaction mixture by applying an external magnetic field due to the existence of the superparamagnetic iron oxide nanoparticles in the construct. The recovered particles retain their catalytic activity.

  16. Synthesis of monodisperse MFe{sub 2}O{sub 4} (M = Fe and Zn) nanoparticles for polydiethylsiloxane-based ferrofluid with a solvothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Laboratory of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic Materials and Technology, South China Normal University, Guangzhou 510631 (China); Zhuang, Lin, E-mail: stszhl@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Zhang, Yong [Laboratory of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic Materials and Technology, South China Normal University, Guangzhou 510631 (China); Shen, Hui [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-09-15

    Highlights: • MFe{sub 2}O{sub 4} nanoparticles were synthesized through a facile solvothermal method. • The relationship between viscosity and temperature of the polydiethylsiloxane-based ferrofluid is discussed. • Fe{sub 3}O{sub 4} nanoparticles have a saturation magnetization of 73.06 emu/g at room temperature. - Abstract: Monodisperse MFe{sub 2}O{sub 4} (M = Fe, Zn) nanoparticles were successfully synthesized for the application of polydiethylsiloxane-based (PDES) ferrofluids (FFs) via a novel solvothermal method, with which 1-octanol and 1-octanamine act as binary solvent, oleic acid (OA) as the surfactant and metal acetylacetonate [M(acac){sub 3}](M = Fe and Zn) as the metal source. X-ray diffractometer confirms that the resultant nanoparticles are pure MFe{sub 2}O{sub 4} with a spinel structure. Infrared spectroscopy indicates that oleic acid is bound to the surface of MFe{sub 2}O{sub 4} through a covalent bond between carboxylate (COO{sup −}) and metal cations. The ratio of 1-octanol and 1-octanamine plays a key role in the formation of the sphere-shaped morphology. Transmission electron microscopy (TEM) images confirm that the Fe{sub 3}O{sub 4} particles are of 4–11 nm with good monodispersity and a narrow size distribution. The saturation magnetization of Fe{sub 3}O{sub 4} nanoparticles with sizes of 7 nm can reach up to 73.06 emu/g. Polydiethylsiloxane-based (PDES) FFs show relatively smaller changes of the viscosity with low temperatures (from −7 to 20 °C) than the polydimethylsiloxane-based (PDMS) FFs. For FFs applications, the relationship between viscosity and temperature is also discussed.

  17. Large-scale synthesis of monodisperse SiC nanoparticles with adjustable size, stoichiometric ratio and properties by fluidized bed chemical vapor deposition

    Science.gov (United States)

    Liu, Rongzheng; Liu, Malin; Chang, Jiaxing

    2017-02-01

    A facile fluidized bed chemical vapor deposition method was proposed for the synthesis of monodisperse SiC nanoparticles by using the single precursor of hexamethyldisilane (HMDS). SiC nanoparticles with average particle size from 10 to 200 nm were obtained by controlling the temperature and the gas ratio. An experimental chemical vapor deposition phase diagram of SiC in the HMDS-Ar-H2 system was obtained and three regions of SiC-Si, SiC and SiC-C can be distinguished. The BET surface area and the photoluminescence properties of the SiC nanoparticles can be adjusted by changing the nanoparticle size. For the SiC nanospheres with free carbon, a novel hierarchical structure with 5 8 nm SiC nanoparticles embedded into the graphite matrix was obtained. The advantages of fluidized bed technology for the preparation of SiC nanoparticles were proposed based on the features of homogenous reaction zone, narrow temperature distribution, ultra-short reactant residence time and mass production.

  18. Production of nearly monodisperse Fe3O4 and Fe@Fe3O4 nanoparticles in aqueous medium and their surface modification for biomedical applications

    Science.gov (United States)

    Tegafaw, Tirusew; Xu, Wenlong; Lee, Sang Hyup; Chae, Kwon Seok; Chang, Yongmin; Lee, Gang Ho

    2017-02-01

    Iron (Fe)-based nanoparticles are extremely valuable in biomedical applications owing to their low toxicity and high magnetization values at room temperature. In this study, we synthesized nearly monodisperse iron oxide (Fe3O4) and Fe@Fe3O4 (core: Fe, shell: Fe3O4) nanoparticles in aqueous medium under argon flow and then, coated them with various biocompatible ligands and silica. In this study, eight types of surface-modified nanoparticles were investigated, namely, Fe3O4@PAA (PAA = polyacrylic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PAA-FA (FA = folic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PEI-fluorescein (PEI = polyethylenimine; Mw of PEI = 1300 amu), Fe@Fe3O4@PEI (Mw of PEI = 10,000 amu), Fe3O4@SiO2 and Fe@Fe3O4@SiO2 nanoparticles. We characterized the prepared surface-modified nanoparticles using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) absorption spectroscopy, a superconducting quantum interference device (SQUID), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and confocal microscopy. Finally, we measured the cytotoxicity of the samples. The results indicate that the surface-modified nanoparticles are biocompatible and are potential candidates for various biomedical applications.

  19. Transmetallation as an effective strategy for the preparation of bimetallic CoPd and CuPd nanoparticles

    Science.gov (United States)

    Bersani, Marco; Conte, Luca; Martucci, Alessandro; Guglielmi, Massimo; Mattei, Giovanni; Bello, Valentina; Rosei, Renzo; Centazzo, Massimo

    2014-01-01

    The preparation of palladium alloy nanoparticles is of great interest for many applications, especially in catalysis. Starting from presynthesized nanoparticles of a less noble metal, a transmetallation reaction involving a redox process at the nanoparticle surface can be exploited to modify the nanoparticle composition and crystalline phase. As an example, monodispersed ε-cobalt and face-centered cubic copper nanoparticles were synthesized in organic solvents at high temperature and the as-formed nanoparticles were reacted with palladium(ii) hexafluoroacetylacetonate resulting in the formation of alloyed nanoparticles whose composition closely follows the reactant ratio. The oxidative state of the nanoparticle surface greatly affects the success of the transmetallation reaction and a reduction treatment was necessary to achieve the desired final product. Electron microscopy and X-ray diffraction showed that for cobalt a limiting palladium content for the ε-phase alloy is found, above which an fcc alloy nucleates, while for copper the fcc crystalline phase is preserved throughout the whole composition range.

  20. One-step facile synthesis of carbon-supported PdAu nanoparticles and their electrochemical property and stability

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiulan, E-mail: whoxiulan@163.com [College of Materials Science and Engineering, Nanjing Tech University (China); Shi, Junjun; Zhang, Jianbo [College of Materials Science and Engineering, Nanjing Tech University (China); Tang, Weiping [Shanghai Institute of Space Power Sources, Shanghai (China); Zhu, Haikui; Shen, Xiaodong [College of Materials Science and Engineering, Nanjing Tech University (China); Saito, Nagahiro [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University (Japan)

    2015-01-15

    Graphical abstract: Well-crystallized PdAu alloy nanoparticles with the average size of 2–5 nm supported on Ketjen Black (KB) were successfully fabricated from the metal wire electrodes via a one-step solution plasma process in water at atmospheric pressure. Multi-scan cyclic voltammetry showed they have better electrochemical stability in alkaline than in acidic solution. - Highlights: • Carbon-supported PdAu nanoparticles were fabricated by a solution plasma technique. • As-obtained PdAu nanoparticles were confirmed to be alloy. • PdAu nanoparticles have good electrochemical activities and stabilities. • PdAu nanoparticles in alkaline have better stability than that in acidic solution. - Abstract: Well-crystallized PdAu nanoparticles supported on Ketjen Black (KB) were successfully fabricated when both Pd and Au wires were served as the electrode pair by a solution plasma technique at atmospheric pressure. The synthesis of PdAu nanoparticles was almost simultaneous with their dispersion on KB. As-obtained PdAu nanoparticles were confirmed to be alloy by ultraviolet–visible spectrophotometer, transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX) of each particle. PdAu nanoparticles with the average diameter of 2–5 nm were equably distributed on KB. PdAu nanoparticles showed good electrocatalytic activity both in acidic and alkaline solution corresponding to their obvious oxidation and reduction features. PdAu nanoparticles have improved electrochemical stability compared with the electrochemical properties of Pd and Au nanoparticles mixture after long time multi-scan cyclic voltammetry. Multi-scan cyclic voltammetry also presented the PdAu nanoparticles in alkaline solution have better stability than that in acidic solution. Thus as-obtained PdAu alloy nanoparticles would become a promising electrocatalysts for fuel cells or Li-air batteries. This novel process showed its potential applications in designing optimization of

  1. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions.

    Science.gov (United States)

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-07-06

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd(2+) precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal.

  2. Carbon nanofiber supported bimetallic PdAu nanoparticles for formic acid electrooxidation

    Science.gov (United States)

    Qin, Yuan-Hang; Jiang, Yue; Niu, Dong-Fang; Zhang, Xin-Sheng; Zhou, Xing-Gui; Niu, Li; Yuan, Wei-Kang

    2012-10-01

    Carbon nanofiber (CNF) supported PdAu nanoparticles are synthesized with sodium citrate as the stabilizing agent and sodium borohydride as the reducing agent. High resolution transmission electron microscopy (HRTEM) characterization indicates that the synthesized PdAu particles are well dispersed on the CNF surface and X-ray diffraction (XRD) characterization indicates that the alloying degree of the synthesized PdAu nanoparticles can be improved by adding tetrahydrofuran to the synthesis solution. The results of electrochemical characterization indicate that the addition of Au can promote the electrocatalytic activity of Pd/C catalyst for formic acid oxidation and the CNF supported high-alloying PdAu catalyst possesses better electrocatalytic activity and stability for formic acid oxidation than either the CNF supported low-alloying PdAu catalyst or the CNF supported Pd catalyst.

  3. Synthesis of magnetic cobalt ferrite nanoparticles with controlled morphology, monodispersity and composition: the influence of solvent, surfactant, reductant and synthetic conditions

    Science.gov (United States)

    Lu, Le T.; Dung, Ngo T.; Tung, Le D.; Thanh, Cao T.; Quy, Ong K.; Chuc, Nguyen V.; Maenosono, Shinya; Thanh, Nguyen T. K.

    2015-11-01

    In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications.In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications. Electronic

  4. Microbially supported synthesis of catalytically active bimetallic Pd-Au nanoparticles.

    Science.gov (United States)

    Hosseinkhani, Baharak; Søbjerg, Lina Sveidal; Rotaru, Amelia-Elena; Emtiazi, Giti; Skrydstrup, Troels; Meyer, Rikke Louise

    2012-01-01

    Bimetallic nanoparticles are considered the next generation of nanocatalysts with increased stability and catalytic activity. Bio-supported synthesis of monometallic nanoparticles has been proposed as an environmentally friendly alternative to the conventional chemical and physical protocols. In this study we synthesize bimetallic bio-supported Pd-Au nanoparticles for the first time using microorganisms as support material. The synthesis involved two steps: (1) Formation of monometallic bio-supported Pd(0) and Au(0) nanoparticles on the surface of Cupriavidus necator cells, and (2) formation of bimetallic bio-supported nanoparticles by reduction of either Au(III) or Pd(II) on to the nanoparticles prepared in step one. Bio-supported monometallic Pd(0) or Au(0) nanoparticles were formed on the surface of C. necator by reduction of Pd(II) or Au(III) with formate. Addition of Au(III) or Pd(II) to the bio-supported particles resulted in increased particle size. UV-Vis spectrophotometry and HR-TEM analyses indicated that the previously monometallic nanoparticles had become fully or partially covered by Au(0) or Pd(0), respectively. Furthermore, Energy Dispersive Spectrometry (EDS) and Fast Fourier Transformation (FFT) analyses confirmed that the nanoparticles indeed were bimetallic. The bimetallic nanoparticles did not have a core-shell structure, but were superior to monometallic particles at reducing p-nitrophenol to p-aminophenol. Hence, formation of microbially supported nanoparticles may be a cheap and environmentally friendly approach for production of bimetallic nanocatalysts. Copyright © 2011 Wiley Periodicals, Inc.

  5. Partially crystallized Pd nanoparticles decorated TiO2 prepared by atmospheric-pressure cold plasma and its enhanced photocatalytic performance

    Institute of Scientific and Technical Information of China (English)

    Zhijian Xu; Bin Qi; Lanbo Di; Xiuling Zhang

    2014-01-01

    TiO2 decorated with partially crystallized Pd nanoparticles (Pd/TiO2-P) was successfully prepared by atmospheric-pressure dielectric barrier discharge cold plasma. The XRD and XPS analyses proved that Pd ions were reduced to partially crystallized metallic Pd nanoparticles in Pd/TiO2-P. The XPS spectra also indicated that an enhanced metal-support interaction was formed due to the existence of partially crystallized Pd nanoparticles with lower coordination number in Pd/TiO2-P. Photocatalytic activity of Pd/TiO2-P was much higher than that of TiO2 samples decorated with well crystallized Pd nanoparticles.

  6. TPO characterization of ethanol reduced Pd nanoparticles supported on SiO$_{2}$

    CERN Document Server

    Horváth, A; Sarkany, A; Guczi, L

    2002-01-01

    Silica-supported Pd catalysts were prepared at 298-353 K from Pd(II) chloride or Pd(II) acetate in suspension of SiO/sub 2/ and ethanol- water or ethanol-toluene mixtures, respectively. Reduction of Pd ions diffusing from liquid phase was ensured in an ethanol-rich adsorption layer covering the SiO/sub 2/ particles. Temperature-programmed oxidation (TPO) measurements were performed to characterize the organic impurities retained by solid phase. Vapour phase reduction /adsorption experiments with ethanol confirmed that under the reported reduction conditions, the Pd nanoparticles decompose ethanol and the CO formed remains chemisorbed on the Pd sites. Upon contacting the samples with air during the drying process to eliminate the solvent, the CO molecules are immediately removed from Pd sites by O/sub 2/, and thereby, a significant fraction (22-34%) of Pd sites becomes accessible for catalytic reactions. (33 refs).

  7. Solid phase metallurgy strategy to sub-5 nm Au-Pd and Ni-Pd bimetallic nanoparticles with controlled redox properties.

    Science.gov (United States)

    Tang, Yu; Xu, Shaodan; Dai, Yihu; Yan, Xiaoqing; Li, Renhong; Xiao, Liping; Fan, Jie

    2014-01-07

    A solid phase metallurgy strategy is applied to synthesize Au-Pd and Ni-Pd bimetallic nanoparticles (BMNPs) with a tight sub-5 nm particle size distribution. The near-surface elemental composition and redox properties of Au-Pd BMNPs can be well tailored, which leads to an optimized catalytic performance in n-hexane combustion.

  8. Self-organization of bimetallic PdAu nanoparticles on SiO{sub 2} surface

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Grimaldi, M. G. [Universita di Catania, Dipartimento di Fisica e Astronomia (Italy)

    2011-06-15

    Bimetallic PdAu nanoparticles on SiO{sub 2} substrate were produced by a sequential room-temperature sputtering deposition method. By the atomic force microscopy technique we studied the nanoparticles self-organization mechanisms in various conditions. First, Pd nucleation and growth proceeds at the substrate defects and the Pd nanoparticles density increase rapidly. During the second sputtering deposition, Au atoms adsorb on the SiO{sub 2} and diffuse toward Pd nanoparticles without forming new nuclei. The Au atoms are trapped by the preformed Pd nanoparticles, forming PdAu bimetallic nanoparticles which size increases. Furthermore, fixing the amount of deposited Pd and increasing the amount of deposited Au, we analyzed the evolution of the PdAu film surface morphology: we observe that the PdAu grows initially as three-dimensional islands; then the PdAu film morphology evolves from compact three-dimensional islands to partially coalesced worm-like structures, followed by a percolation morphology and finally to a continuous and rough film. The application of the interrupted coalescence model allowed us to evaluate the critical mean island diameter R{sub c} Almost-Equal-To 2.8 nm for the partial coalescence process. The application of the dynamic scaling theory of growing interfaces allowed us to evaluate the dynamic growth exponent {beta} = 0.21 {+-} 0.01 from the evolution of the film surface roughness. Finally, fixing the amount of deposited Pd and Au we studied the self-organization mechanism of the PdAu nanoparticles induced by thermal processes performed in the 973-1173 K temperature range. The observed kinetic growth mechanism is consistent with a surface diffusion-limited ripening of the nanoparticles with a temperature-dependent growth exponent. The dependence of the growth exponent on the temperature is supposed to be linked to the variation with the temperature of the characteristics of the PdAu alloy. The activation energy for the surface diffusion

  9. Aggregation mechanism of Pd nanoparticles in L-cysteine aqueous solution studied by NEXAFS and AFM

    Energy Technology Data Exchange (ETDEWEB)

    Tsukada, C., E-mail: tsukada.chie@e.mbox.nagoya-u.ac.jp [Department of Quantum Engineering, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ogawa, S.; Mizutani, T. [Department of Quantum Engineering, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kutluk, G.; Namatame, H.; Taniguchi, M. [Synchrotron Radiation Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Yagi, S. [Department of Quantum Engineering, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Synchrotron Radiation Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-0046 (Japan)

    2012-12-01

    Highlight: Black-Right-Pointing-Pointer We focus on the biocompatibility of Pd nanoparticles (NPs) for L-cysteine under water environment. Black-Right-Pointing-Pointer The Pd NPs have been fabricated and deposited on Si wafer by gas evaporation method. Black-Right-Pointing-Pointer When the Pd NPs/Si has been dipped into L-cysteine aqueous solution, the L-cysteine has selectively adsorbed on Pd NPs surface and existed as the L-cysteine thiolate, atomic S and L-cystine. Black-Right-Pointing-Pointer Moreover, the aggregation of Pd NPs occurs by the migration of Pd NPs on Si and the cross-linked reaction between L-cysteine thiolate molecules adsorbed on Pd NPs. - Abstract: We focus on the biocompatibility of Pd nanoparticles (NPs) from the point of microscopic view. Thus, as the basic research for the biocompatibility, we have investigated the adsorbates on the Pd NPs surface and the aggregation mechanism for the Pd NPs on Si substrate after dipping into L-cysteine aqueous solution by means of NEXAFS measurement and AFM observation. The Pd NPs have been fabricated and deposited on the Si wafer by the gas evaporation method. Judging from the results of NEXAFS measurement, it is clear that the L-cysteine thiolate and atomic S exist on the Pd NPs surface. The results of AFM observation show that the Pd NPs aggregate. It is thought that the aggregation of the Pd NPs occurs by both the migration of the Pd NPs on Si wafer and the cross-linked reaction.

  10. Fabrication of Au–Pd nanoparticles/graphene oxide and their excellent catalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    He, Yongqiang, E-mail: heyongqiang@126.com [Department of Applied Chemistry, Yuncheng University, Yuncheng 044000 (China); Zhang, Nana; Zhang, Lei [School of Science, Tianjin University, Tianjin 300072 (China); Gong, Qiaojuan [Department of Applied Chemistry, Yuncheng University, Yuncheng 044000 (China); Yi, Maocong [School of Science, Tianjin University, Tianjin 300072 (China); Wang, Wei [School of Chemical Engineering, Tianjin University, Tianjin 300072 (China); Qiu, Haixia, E-mail: qhx@tju.edu.cn [School of Science, Tianjin University, Tianjin 300072 (China); Gao, Jianping [School of Science, Tianjin University, Tianjin 300072 (China)

    2014-03-01

    Graphical abstract: - Highlights: • Au and Pd nanoparticles loaded on GO were fabricated without adding any reducing agents. • The Au–Pd NPs/GO were excellent catalysts for the reduction of 4-nitrophenol. • The Au–Pd NPs/GO showed superior catalytic activity for the Suzuki reaction. • The Au–Pd NPs/GO exhibit good reusability. - Abstract: A simple method to fabricate clean Au–Pd nanoparticles on graphene oxide (Au–Pd NPs/GO) without using any reducing agent or surfactant has been developed. GO simultaneously reduced the Au and Pd precursors to form a stable suspension of the Au–Pd NPs/GO. The nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and inductively coupled plasma. The Au–Pd NPs/GO exhibited catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol and for the Suzuki–Miyaura coupling reaction of chlorobenzene and phenylboronic acid in aqueous media.

  11. Gas Phase Fabrication of Pd-Ni Nanoparticle Arrays for Hydrogen Sensor Applications

    Directory of Open Access Journals (Sweden)

    Peng Xing

    2015-01-01

    Full Text Available Pd-Ni nanoparticles have been fabricated by gas aggregation process. The formation of Pd-Ni nano-alloys was confirmed by X-ray photoelectron spectroscopy measurements. By depositing Pd-Ni nanoparticles on the interdigital electrodes, quantum conductance-based hydrogen sensors were fabricated. The Ni content in the nanoparticle showed an obvious effect on the hydrogen response behavior corresponding to the conductance change of the nanoparticle film. Three typical response regions with different conductance-hydrogen pressure correlations were observed. It was found that the α-β phase transition region of palladium hydride moves to significant higher hydrogen pressure with the addition of nickel element, which greatly enhance the hydrogen sensing performance of the nanoparticle film.

  12. Monodispersed Silica Nanospheres Encapsulating Fe3O4 and LaF3:Eu3+ Nanoparticles for MRI Contrast Agent and Luminescent Imaging

    Science.gov (United States)

    Tian, Yang; Yu, Binbin; Yang, Hong-Yu; Liao, Ji

    2013-03-01

    Bifunctional nanospheres of silica encapsulating Fe3O4 and LaF3:Eu nanoparticles were synthesized in a reverse microemulsion solution. The nanospheres were perfectly monodispersed with a small diameter of 20 nm. The composition of the bifunctional nanospheres was confirmed by powder X-ray diffraction. Their magnetic and luminescent properties were measured at room temperature. The relaxation efficiency and T2-weighted images showed the high-performance for the product as a resonance imaging contrast agent. In addition, a qualitative cell uptake in human cervical cancer HeLa cells demonstrated that the SFLE nanospheres were efficiently up-taken into cytosol. Taken together, these findings suggest that the SiO2/Fe3O4-LaF3:Eu3+ nanospheres are good luminescence probes for bio-imaging.

  13. Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

    Science.gov (United States)

    Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

    2016-05-01

    Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

  14. Promotion of Phenol Photodecomposition over TiO2 Using Au, Pd, and AuPd Nanoparticles

    DEFF Research Database (Denmark)

    Su, Ren; Tiruvalam, Ramchandra; He, Qian

    2012-01-01

    Noble metal nanoparticles (Au, Pd, AuPd alloys) with a narrow size distribution supported on nanocrystalline TiO2 (M/TiO2) have been synthesized via a sol-immobilization route. The effect of metal identity and size on the photocatalytic performance of M/TiO2 has been systematically investigated...... using phenol as a probe molecule. A different phenol degradation pathway was observed when using M/TiO2 catalysts as compared to pristine TiO2.We propose a mechanism to illustrate how the noble metal nanoparticles enhance the efficiency of phenol decomposition based on photoreduction of p......-benzoquinone under anaerobic conditions. Our results suggest that the metal nanoparticles not only play a role in capturing photogenerated electrons, but are strongly involved in the photocatalytic reaction mechanism. The analysis of the reaction intermediates allows us to conclude that on M/TiO2 undesired redox...

  15. Effect of metal support interaction on surface segregation in Pd Pt nanoparticles

    Science.gov (United States)

    De Sarkar, A.; Menon, Mahesh; Khanra, Badal C.

    2001-10-01

    In this work, we present the results of our Monte Carlo (MC) simulation studies for the segregation behavior of supported, clean and gas-covered Pd-Pt nanoparticles as a function of the metal-support interaction. For preferential Pd-support interaction, the base of the nanoparticle is found to get enriched with Pd atoms; while for preferential interaction of Pt atoms with the support the base gets enriched in Pt. The composition of the rest of the particle changes slightly with the metal-support interaction. The presence of oxygen and hydrogen atoms does not influence the role of the metal-support interaction on the surface composition of Pd-Pt nanoparticles. The simulation results are found to be in total agreement with the known experimental results.

  16. Fast response and recovery of hydrogen sensing in Pd-Pt nanoparticle-graphene composite layers

    Science.gov (United States)

    Kumar, Rakesh; Varandani, Deepak; Mehta, B. R.; Singh, V. N.; Wen, Zhenhai; Feng, Xinliang; Müllen, Klaus

    2011-07-01

    This study reports the fast response and recovery of hydrogen sensing in nanoparticle-graphene composite layers fabricated using chemical methods and comprising of isolated Pd alloy nanoparticles dispersed onto graphene layers. For 2% hydrogen at 40 °C and 1 atm pressure, a response time of Pd-Pt nanoparticle-graphene composite material are important for understanding the effect of gas adsorption on electronic conduction in graphene layers and for developing a new type of gas sensor based on changes in the electronic properties of the interface.

  17. Effect of nanoparticle (Pd, Pd/Pt, Ni deposition on high temperature hydrogenation of Ti-V alloys in gaseous flow containing CO

    Directory of Open Access Journals (Sweden)

    S. Suwarno

    2017-02-01

    Full Text Available The hydrogenation properties of Ti-V hydrides coated with nanoparticles have been studied in gaseous mixtures of argon and hydrogen with and without additions of 1% CO. Nanoparticles of Pd, Ni, and co-deposited Pd/Pt with particle sizes of ~30–60 nm were formed by electroless deposition on the hydride surfaces. The alloy resistance to CO could be significantly improved by particle deposition. Large amounts of hydrogen were absorbed in a CO-containing gas when Ni and Pd/Pt deposition had been applied, while pure Pd deposition had no positive effect. Ni was found to have a stronger effect than those of Pd/Pt and Pd, possibly because of the size effect of Ni nanoparticles.

  18. Large faceted Pd nanocrystals supported small Pt nanoparticles as highly durable electrocatalysts for oxygen reduction

    Science.gov (United States)

    Zhang, Geng; Lu, Wangting; Cao, Longsheng; Qin, Xiaoping; Ding, Fei; Tang, Shun; Shao, Zhi-Gang; Yi, Baolian

    2016-09-01

    The reduction of Pt content together with the improvement of the durability of the catalyst for oxygen reduction reaction (ORR) is required to the large-scale commercialization of proton exchange membrane fuel cells. In this work, a novel ORR catalyst consisting of large Pd nanocrystal as the core with small Pt nanoparticles supported on the Pd core is prepared by a facile one-step synthesis method. The Pd substrate is presented in the form of well-defined cuboctahedrons and icosahedrons. The type of metal precursors and Pt/Pd molar ratio are important factors to obtain this Pd-supporting-Pt structure. The Pd2-s-Pt1 catalyst with a nominal Pt/Pd atomic ratio at 1/2 shows improved ORR activity: its mass specific activity and area specific activity is 2.5 and 3.5 times that of commercial Pt/C, respectively. More importantly, the Pd2-s-Pt1 catalyst demonstrates outstanding durability against potential cycling which can be ascribed to the slow dissolution of Pd core and the structure transformation from Pd@Pt to hollow PdPt alloyed nanocages. This exciting result provides a new pathway to the design of ORR catalyst with excellent durability.

  19. Influence of shell thickness on thermal stability of bimetallic Al-Pd nanoparticles

    Science.gov (United States)

    Wen, John Z.; Nguyen, Ngoc Ha; Rawlins, John; Petre, Catalin F.; Ringuette, Sophie

    2014-07-01

    Aluminum-based bimetallic core-shell nanoparticles have shown promising applications in civil and defense industries. This study addresses the thermal stability of aluminum-palladium (Al-Pd) core/shell nanoparticles with a varying shell thickness of 5, 6, and 7 Å, respectively. The classic molecular dynamics (MD) simulations are performed in order to investigate the effects of the shell thickness on the ignition mechanism and subsequent energetic processes of these nanoparticles. The histograms of temperature change and structural evolution clearly show the inhibition role of the Pd shell during ignition. While the nanoparticle with a thicker shell is more thermally stable and hence requires more excess energy, stored as the potential energy of the nanoparticle and provided through numerically heating, to initiate the thermite reaction, a higher adiabatic temperature can be produced from this nanoparticle, thanks to its greater content of Pd. The two-stage thermite reactions are discussed with their activation energy based on the energy balance processes during MD heating and production. Analyses of the simulation results reveal that the inner pressure of the core-shell nanoparticle increases with both temperature and the absorbed thermal energy during heating, which may result in a breakup of the Pd shell.

  20. Atomic-scale insights into structural and thermodynamic stability of Pd-Ni bimetallic nanoparticles.

    Science.gov (United States)

    Huang, Rao; Wen, Yu-Hua; Zhu, Zi-Zhong; Sun, Shi-Gang

    2016-04-14

    Atomic-scale understanding of structures and thermodynamic stability of core-shell nanoparticles is important for both their synthesis and application. In this study, we systematically investigated the structural stability and thermodynamic evolution of core-shell structured Pd-Ni nanoparticles by molecular dynamics simulations. It has been revealed that dislocations and stacking faults occur in the shell and their amounts are strongly dependent on the core/shell ratio. The presence of these defects lowers the structural and thermal stability of these nanoparticles, resulting in even lower melting points than both Pd and Ni monometallic nanoparticles. Furthermore, different melting behaviors have been disclosed in Pd-core/Ni-shell and Ni-core/Pd-shell nanoparticles. These diverse behaviors cause different relationships between the melting temperature and the amount of stacking faults. Our results display direct evidence for the tunable stability of bimetallic nanoparticles. This study provides a fundamental perspective on core-shell structured nanoparticles and has important implications for further tailoring their structural and thermodynamic stability by core/shell ratio or composition controlling.

  1. Self-assembly and graft polymerization route to Monodispersed Fe3O4@SiO2--polyaniline core-shell composite nanoparticles: physical properties.

    Science.gov (United States)

    Reddy, Kakarla Raghava; Lee, Kwang-Pill; Kim, Ju Young; Lee, Youngil

    2008-11-01

    This study describes the synthesis of monodispersed core-shell composites of silica-modified magnetic nanoparticles and conducting polyaniline by self-assembly and graft polymerization. Magnetic ferrite nanoparticles (Fe3O4) were prepared by coprecipitation of Fe+2 and Fe+3 ions in alkaline solution, and then silananized. The silanation of magnetic particles (Fe3O4@SiO2) was carried out using 3-bromopropyltrichlorosilane (BPTS) as the coupling agent. FT-IR spectra indicated the presence of Fe--O--Si chemical bonds in Fe3O4@SiO2. Core-shell type nanocomposites (Fe3O4@SiO2/PANI) were prepared by grafting polyaniline (PANI) on the surface of silanized magnetic particles through surface initiated in-situ chemical oxidative graft polymerization. The nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared (FTIR) spectra, UV-visible spectroscopy, photoluminescence (PL) spectra, electrical conductivity and magnetic characteristics. HRTEM images of the nanocomposites revealed that the silica-modified magnetic particles made up the core while PANI made up the shell. The XPS spectrum revealed the presence of silica in the composites, and the XRD results showed that the composites were more crystalline than pure PANI. PL spectra show that composites exhibit photoluminescent property. Conductivity of the composites (6.2 to 9.4 x 10(-2) S/cm) was higher than that of pristine PANI (3.7 x 10(-3) S/cm). The nanocomposites exhibited superparamagnetism. Formation mechanism of the core-shell structured nanocomposites and the effect of modified magnetic nanoparticles on the electro-magnetic properties of the Fe3O4@SiO2/PANI nanocomposites are also investigated. This method provides a new strategy for the generation of multi-functional nanocomposites that composed of other conducting polymers and metal nanoparticles.

  2. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    Science.gov (United States)

    Huang, Chao; Yang, Xu; Yang, Hui; Huang, Peiyan; Song, Huiyu; Liao, Shijun

    2014-10-01

    A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation-hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  3. Laser-induced in situ synthesis of Pd and Pt nanoparticles on polymer films

    Science.gov (United States)

    Mehrabanian, Mehran; Morselli, Davide; Caputo, Gianvito; Scarpellini, Alice; Palazon, Francisco; Athanassiou, Athanassia; Fragouli, Despina

    2016-12-01

    We present the localized in situ formation of Pd and Pt nanoparticles embedded in chitosan solid films. This is achieved by the photo-induced reduction of metallic precursors, previously incorporated in chitosan films, through controlled UV pulsed laser irradiation. Interestingly, at high number of laser pulses, Pd and Pt follow different formation pathways, contrary to their common photoreduction mechanism occurring at low irradiation pulses. Specifically, in the case of the Pd, a photofragmentation process takes place fracturing the previously formed nanoparticles into smaller ones; whereas in the case of Pt, the prolonged irradiation promotes the nanoparticles agglomeration. The combination of both precursors in a binary solid system results in the combined formation of both Pd and Pt nanoparticles in the polymer film upon laser irradiation. The herein reported approach is an efficient and precise tool to generate size- and density-controlled Pd and Pt nanoparticles in desired areas of polymeric films, rendering this method a potential candidate for the fabrication of flexible polymeric devices for gas-sensing or electro-catalysis applications.

  4. Study of coordination environments around Pd and Pt in a Pd-core Pt-shell nanoparticle during heating

    Science.gov (United States)

    Nishimura, Y. F.; Hamaguchi, T.; Yamaguchi, S.; Takagi, H.; Dohmae, K.; Nonaka, T.; Nagai, Y.

    2016-05-01

    Local coordination environments around Pd and Pt in a Pd-core Pt-shell nanoparticle (NP) at temperatures ranging from 473 to 873 K was evaluated by utilizing in situ XAFS measurement technique to investigate the temperature range in which a core-shell structure is preserved. The core-shell structure was considered to be kept up to 673 K and start to change at about 773 K. Heating to 873 K accelerated atomic mixing in the core-shell NPs. Catalytic properties of the present Pd-core Pt-shell NP are available in the stoichiometric C3H6-O2 atmosphere at temperatures less than 773 K at most.

  5. Hydrodechlorination Catalysis of Pd-on-Au Nanoparticles Varies with Particle Size

    Energy Technology Data Exchange (ETDEWEB)

    Pretzer, Lori A.; Song, Hyun J.; Fang, Yu-Lun; Zhao, Zhun; Guo, Neng; Wu, Tianpin; Arslan, Ilke; Miller, Jeffrey T.; Wong, Michael S.

    2013-02-01

    The dependence of bimetallic PdAu catalytic activity on the relative ratios of Pd and Au has been theoretically predicted and experimentally observed for a number of reactions. Trichloroethene (TCE), a common carcinogenic solvent that is difficult to remove from contaminated groundwater in many industrialized nations, can be chemically degraded especially rapidly with Au nanoparticles partially coated with Pd ("Pd-on-Au NPs"). These NPs catalyze the room-temperature water-phase TCE hydrodechlorination (HDC) reaction with activities that follow a volcano-shape dependence on Pd surface coverage. The effect of particle size is not known, though. Pd-on-Au NPs synthesized with 3, 7, and 10 nm Au NPs and Pd surface coverages between 0 and 150% were studied in detail. Volcano-shape dependence on Au particle size and Pd surface coverage was observed, with 7 nm Au NPs with a Pd coverage of 60-70% having the highest TCE HDC activity. Extended x-ray absorption fine-structure spectroscopy (EXAFS) revealed the correlation was strongest between catalytic activity and the presence of non-oxidized Pd ensembles of ~2-3 atoms in contact with ~8-10 Au atoms. Isolated Pd atoms and Pd ensembles were visualized for the first time through aberration-corrected scanning transmission electron microscopy (STEM). This study provides the most direct evidence yet for Pd-on-Au NPs containing 2-dimensional Pd ensembles as the active sites for TCE HDC and likely for other chemical reactions. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. This research was supported by the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  6. A simple plasma reduction for synthesis of Au and Pd nanoparticles at room temperature☆

    Institute of Scientific and Technical Information of China (English)

    Zhao Wang; Yu Zhu

    2015-01-01

    A simple and fast plasma reduction method is developed for synthesis of Au and Pd metal nanoparticles. The scanning electron microscopy (SEM) analysis indicates a formation of aggregates of Au and Pd nanoparticles with branched structure. The transmission electron microscopy (TEM) image shows that the inclusive nanopar-ticles are al about 5 nm in size. Compared to conventional hydrogen reduction method, plasma method inhibits the agglomeration of metal particles. The room temperature operation is very helpful to limit the nanoparticle size. Most interestingly, plasma reduction produces more flattened metal particles. This plasma reduction does not require the use of any hazardous reducing chemicals, showing the great potential for the fabrication of noble metal nanoparticles.

  7. DNA-Mediated Morphological Control of Pd-Au Bimetallic Nanoparticles.

    Science.gov (United States)

    Satyavolu, Nitya Sai Reddy; Tan, Li Huey; Lu, Yi

    2016-12-21

    Recent reports have shown that different DNA sequences can mediate the control of shapes and surface properties of nanoparticles. However, all previous studies have involved only monometallic particles, most of which were gold nanoparticles. Controlling the shape of bimetallic nanoparticles is more challenging, and there is little research into the use of DNA-based ligands for their morphological control. We report the DNA-templated synthesis of Pd-Au bimetallic nanoparticles starting from palladium nanocube seeds. The presence of different homo-oligomer DNA sequences containing 10 deoxy-ribonucleotides of thymine, adenine, cytosine, or guanine results in the growth of four distinct morphologies. Through detailed kinetic studies by absorption spectroscopy, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), we have determined the role of DNA in controlling Pd-Au nanoparticle growth morphologies. One major function of DNA is affecting various properties of the incoming metal atoms, including their diffusion and deposition on the Pd nanocube seed. Interestingly, nanoparticle growth in the presence of A10 follows an aggregative growth mechanism that is unique when compared to the other base oligomers. These findings demonstrate that DNA can allow for programmable control of bimetallic nanoparticle morphologies, resulting in more complex hybrid materials with different plasmonic properties. The capability to finely tune multimetallic nanoparticle morphology stems from the versatile structure that is unique to DNA in comparison to conventionally used capping agents in colloidal nanomaterial synthesis.

  8. Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

    Directory of Open Access Journals (Sweden)

    Vineetha Mukundan

    2014-03-01

    Full Text Available Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2 alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C. The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.

  9. Synthesis and Microstructural Investigations of Organometallic Pd(II Thiol-Gold Nanoparticles Hybrids

    Directory of Open Access Journals (Sweden)

    Cervellino Antonio

    2008-01-01

    Full Text Available Abstract In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II centers is presented. Pd(II thiol,trans, trans-[dithiolate-dibis(tributylphosphinedipalladium(II-4,4′-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm was achieved by choosing the suitable AuCl4 −/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NO x with the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction.

  10. Energetic and structural analysis of 102-atom Pd-Pt nanoparticles

    Science.gov (United States)

    Pacheco-Contreras, Rafael; Arteaga-Guerrero, Alvaro; Borbon-Gonzalez, Dora Julia; Posada-Amarillas, Alvaro; Schoen, J. Christian; Johnston, Roy L.

    2009-03-01

    We present an extensive study of the structural and energetic changes of 102-atom PdmPt102-m nanoparticles as a function of composition m, where the interatomic interactions are modeled with the many-body Gupta potential. The minimum energy structures are obtained through a genetic algorithm. The excess energy is calculated, as well as the pair distribution function g(r). The radial distribution of the atoms is computed for each composition; the result indicates a multi-layer segregation for some compositions, with a shell growth sequence as follows: a core with a small number of Pd atoms is followed by an intermediate shell of Pt atoms and the external shell consists of Pd atoms. A region where Pd and Pt atoms are mixed is observed between the outermost and intermediate shells. Furthermore, the pure Pd102 and Pt102 nanoparticles have the same structure, while a variety of different structures are observed for the bimetallic clusters.

  11. Particle size dependent heat of adsorption for CO on supported Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fischer-Wolfarth, Jan-Henrik; Flores-Camacho, Jose Manuel; Hartmann, Jens; Schauermann, Swetlana; Freund, Hans-Joachim [Fritz-Haber-Institute, Max-Planck-Society, Faradayweg 4-6, 14195 Berlin (Germany); Farmer, Jason; Campbell, Charles [Department of Chemistry, University of Washington, Seattle (United States)

    2010-07-01

    The particle size dependence of the heat of adsorption for carbon monoxide on supported Pd nanoparticles has been investigated at 300 K with a new single crystal microcalorimeter and compared to the heat of adsorption on Pd(111). The average Pd particle size was varied systematically in the range of 100 to 4900 Pd atoms, i.e. 2 to 8 nm diameter. All nanoparticles were supported on Fe{sub 3}O{sub 4}(111)/Pt(111). The initial heat of adsorption was found to decrease monotonically with decreasing particle size below 4 nm. The correlation of the heat of adsorption with a particle size dependent reduction of the particle lattice constant is discussed. Further, the microcalorimetry technique used to determine the adsorption energies and its performance is presented.

  12. Synthesis of cubic PtPd alloy nanoparticles as anode electrocatalysts for methanol and formic acid oxidation reactions.

    Science.gov (United States)

    Lee, Jin-Yeon; Kwak, Da-Hee; Lee, Young-Woo; Lee, Seul; Park, Kyung-Won

    2015-04-14

    The electrocatalytic properties for electro-oxidation reactions of shape-controlled Pt-based catalysts have been improved by alloying with 2nd elements. In this study, we demonstrate cubic PtPd alloy nanoparticles synthesized using a thermal decomposition method. The cubic PtPd nanoparticles exhibit a homogeneous distribution of alloy nanostructures in the presence of Pt and Pd metallic phases. The improved electrocatalytic activity for the electro-oxidation reactions of methanol and formic acid as chemical fuels might be attributed to the cubic alloy nanostructures. Furthermore, the cubic PtPd alloy nanoparticles as electrocatalysts exhibit excellent stability for electro-oxidation reactions.

  13. A general strategy for the preparation of carbon nanotubes and graphene oxide decorated with PdO nanoparticles in water.

    Science.gov (United States)

    He, Hongkun; Gao, Chao

    2010-07-02

    The preparation of carbon nanotube (CNT)/PdO nanoparticles and graphene oxide (GO)/PdO nanoparticle hybrids via a general aqueous solution strategy is reported. The PdO nanoparticles are generated in situ on the CNTs and GO by a one-step "green" synthetic approach in aqueous Pd(NO(3))(2) solution under ambient conditions without adding any additional chemicals. The production of PdO is confirmed by energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. The morphologies of the resulting CNT/PdO and GO/PdO nanohybrids are characterized by transmission and/or scanning transmission electron microscopy. PdO nanoparticles with an average size of 2-3 nm in diameter are decorated evenly along the surfaces of CNTs and GO. This synthesis strategy is demonstrated to be compatible for 1) CNTs with different modifications, including pristine, oxidized, and polymer-functionalized CNTs; 2) different types of CNTs, including single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multiwalled carbon nanotubes (MWCNTs); and 3) different shapes of carbon materials, including tubular CNTs and planar GO. The as-prepared CNT/PdO and GO/PdO nanohybrids can be transformed into CNT/Pd and GO/Pd nanohybrids by reduction with NaBH(4), and can then be used as a heterogeneous catalyst in the catalytic reduction of 4-nitrophenol.

  14. Controlled synthesis and synergistic effects of graphene-supported PdAu bimetallic nanoparticles with tunable catalytic properties.

    Science.gov (United States)

    Liu, Chang-Hai; Liu, Rui-Hua; Sun, Qi-Jun; Chang, Jian-Bing; Gao, Xu; Liu, Yang; Lee, Shuit-Tong; Kang, Zhen-Hui; Wang, Sui-Dong

    2015-04-14

    Graphene-supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Herein room-temperature-ionic-liquid-assisted metal sputtering is utilized to synthesize PdAu bimetallic nanoparticles on graphene with bare surface, small size, high surface density and controlled Pd-to-Au ratio. This controllable synthetic approach is green-chemistry compatible and totally free of additives and byproducts. The supported PdAu nanoparticles show excellent catalytic capabilities for both oxidation and reduction reactions, strongly dependent on the Pd-to-Au ratio. A strong correlation among catalytic performance, bimetallic composition and charge redistribution in the PdAu nanoparticles has been demonstrated. The results suggest that sufficient Au d-holes appear to be significant to the catalysis of oxidation reaction, and a metallic Pd surface is critical to the catalysis of reduction reaction. By the present method, the bimetallic combination can be tailored for distinct types of catalytic reactions.

  15. PdNi hollow nanoparticles for improved electrocatalytic oxygen reduction in alkaline environments.

    Science.gov (United States)

    Wang, Meng; Zhang, Weimin; Wang, Jiazhao; Wexler, David; Poynton, Simon D; Slade, Robert C T; Liu, Huakun; Winther-Jensen, Bjorn; Kerr, Robert; Shi, Dongqi; Chen, Jun

    2013-12-11

    Palladium-nickel (PdNi) hollow nanoparticles were synthesized via a modified galvanic replacement method using Ni nanoparticles as sacrificial templates in an aqueous medium. X-ray diffraction and transmission electron microscopy show that the as-synthesized nanoparticles are alloyed nanostructures and have hollow interiors with an average particle size of 30 nm and shell thickness of 5 nm. Compared with the commercially available Pt/C or Pd/C catalysts, the synthesized PdNi/C has superior electrocatalytic performance towards the oxygen reduction reaction, which makes it a promising electrocatalyst for alkaline anion exchange membrane fuel cells and alkali-based air-batteries. The electrocatalyst is finally examined in a H2/O2 alkaline anion exchange membrane fuel cell; the results show that such electrocatalysts could work in a real fuel cell application as a more efficient catalyst than state-of-the-art commercially available Pt/C.

  16. Solvent and stabilizer free growth of Ag and Pd nanoparticles using metallic salts/cyclotriphosphazenes mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Díaz Valenzuela, C. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); Valenzuela, M.L., E-mail: mlvalenzuela@unab.cl [Universidad Andres Bello, Departamento de Ciencias Química, Facultad de Ciencias Exactas, Av. Republica 275, Santiago (Chile); Caceres, S.; Diaz, R. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); O' Dwyer, C. [Applied Nanoscience Group, Department of Chemistry, University College Cork, Cork (Ireland); Micro and Nanoelectronics Centre, Tyndall National Institute, Lee Maltings, Cork (Ireland)

    2013-12-16

    Cyclotriphosphazene is used as a sacrificial solid-state template to synthesize a range of Ag and Pd nanoparticles with diverse geometries by thermal treatment using MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures. The Pd and Ag nanoparticles are synthesized by solid-state pyrolysis of AgPPh{sub 3}[CF{sub 3}SO{sub 3}]/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} and PdCl{sub 2}/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures with molar relationships of 1:1, 1:5 and 1:10 respectively, in air and at 800 °C. The morphology of the as-prepared nanoparticles is found to depend on the molar ratio of the precursor mixture, the preparation method and of the nature of the metal. Ag and Pd, microcrystals were thermally grown on Si from the respective 1:1 precursors while that metal foams were grown from 1:5 ratios precursors on SiO{sub 2} wafers. High resolution transmission electron microscopy investigations reveal in most cases small crystals of Pd. HRSTEM measurements indicate that the formation of the Pd and Ag nanoparticles occurs through a phase demixing and dewetting mechanism. This approach has potential to be a useful and facile method to prepare metallic nanoparticles without requiring solutions or surfactants for application in electronic, catalytic and sensor materials and devices. - Highlights: • Pyrolysis MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures under air, give Pd and Ag nanoparticles. • AgPPh{sub 3}[CF{sub 3}SO{sub 3}] and PdCl{sub 2} in molar ratios 1:1 and 1:5 were used. • Metal foams were obtained from 1:5 ratios when deposited on SiO{sub 2.} • Using crucible supporting in 1:1 metal/trimer <2 nm Pd nanoparticles were obtained. • The probable mechanism involves a dewetting, nucleation and ripening crystallization.

  17. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    Science.gov (United States)

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-01-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m−3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells. PMID:27734945

  18. Kinetics of 2-chlorobiphenyl Reductive Dechlorination by Pd-fe0 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jiang Junrong

    2016-01-01

    Full Text Available Kinetics of 2-chlorobiphenyl (2-Cl BP catalytic reductive dechlorination by Pd-Fe0 nanoparticles were investigated. Experimental results showed that ultrafine bimetallic Pd-Fe0e nanoparticles were synthesized in the presence of 40 kHz ultrasound in order to enhance disparity and avoid agglomeration. The application of ultrasonic irradiation during the synthesis of Pd-Fe0 nanoparticles further accelerated the dechlorinated removal ratio of 2-Cl BP. Up to 95.0% of 2-Cl BP was removed after 300 min reaction with the following experimental conditions: initial 2-Cl BP concentration 10 mg L-1, Pd content 0.8 wt. %, bimetallic Pd-Fe0 nanoparticles prepared in the presence of ultrasound available dosage 7g L-1, initial pH value in aqueous solution 3.0, and reaction temperature 25°C. The catalytic reductive dechlorination of 2-Cl BP followed pseudo-first-order kinetics and the apparent pseudo-first-order kinetics constant was 0.0143 min-1.

  19. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    Science.gov (United States)

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-10-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m‑3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells.

  20. Structural Rearrangement of Au-Pd Nanoparticles under Reaction Conditions: An ab Initio Molecular Dynamics Study.

    Science.gov (United States)

    Xu, Cong-Qiao; Lee, Mal-Soon; Wang, Yang-Gang; Cantu, David C; Li, Jun; Glezakou, Vassiliki-Alexandra; Rousseau, Roger

    2017-02-28

    The structure, composition, and atomic distribution of nanoalloys under operating conditions are of significant importance for their catalytic activity. In the present work, we use ab initio molecular dynamics simulations to understand the structural behavior of Au-Pd nanoalloys supported on rutile TiO2 under different conditions. We find that the Au-Pd structure is strongly dependent on the redox properties of the support, originating from strong metal-support interactions. Under reducing conditions, Pd atoms are inclined to move toward the metal/oxide interface, as indicated by a significant increase of Pd-Ti bonds. This could be attributed to the charge localization at the interface that leads to Coulomb attractions to positively charged Pd atoms. In contrast, under oxidizing conditions, Pd atoms would rather stay inside or on the exterior of the nanoparticle. Moreover, Pd atoms on the alloy surface can be stabilized by hydrogen adsorption, forming Pd-H bonds, which are stronger than Au-H bonds. Our work offers critical insights into the structure and redox properties of Au-Pd nanoalloy catalysts under working conditions.

  1. Pd nanoparticles formation inside porous polymeric scaffolds followed by in situ XANES/SAXS

    Science.gov (United States)

    Longo, A.; Lamberti, C.; Agostini, G.; Borfecchia, E.; Lazzarini, A.; Liu, W.; Giannici, F.; Portale, G.; Groppo, E.

    2016-05-01

    Simultaneous time-resolved SAXS and XANES techniques were employed to follow in situ the formation of Pd nanoparticles from palladium acetate precursor in two porous polymeric supports: polystyrene (PS) and poly(4-vinyl-pyridine) (P4VP). In this study we have investigated the effect of the use of different reducing agents (H2 and CO) from the gas phase. These results, in conjunction with data obtained by diffuse reflectance IR (DRIFT) spectroscopy and TEM measurements, allowed us to unravel the different roles played by gaseous H2 and CO in the formation of the Pd nanoparticles for both PS and P4VP hosting scaffolds.

  2. Synthesis, characterization, and electrochemical behavior of Au@Pd core shell nanoparticles

    Science.gov (United States)

    Wicaksono, W. P.; Ivandini, T. A.

    2017-04-01

    Au@Pd core shell nanoparticles (Au@Pd CSNPs) were successfully synthesized using a seed-mediated growth method. Firstly, a pale pink gold seed solution was used to produce a pale purple gold nanoparticles (AuNPs) core solution. Then, three series of Pd shell thickness using 20μ, 100 μL, and 500 μL of PdCl2 produced purple, brown, and deep brown of Au@Pd CSNPs respectively. A strong absorbance UV-Visible spectrum with peaks at 285 nm and 535 nm was identified for AuNPs formation. The disappearance of the peak at 535 nm was indicated the Au@Pd CSNPs formation. The electrochemical properties were examined in phosphate buffer pH 7 using cyclic voltammetry technique with boron-doped diamond (BDD) as working electrode showed a couple oxidation and reduction peak of gold at 0.67 V and at 0.33 V, respectively. The Au@Pd CNPs will be used for modification of BDD electrodes.

  3. Facile preparation of ZIF-8@Pd-CSS sandwich-type microspheres via in situ growth of ZIF-8 shells over Pd-loaded colloidal carbon spheres with aggregation-resistant and leach-proof properties for the Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tong; Lin, Lu [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Zhang, Xiongfu, E-mail: xfzhang@dlut.edu.cn [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Haiou; Yan, Xinjuan [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Zhang; Yeung, King Lun [Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR (China)

    2015-10-01

    Graphical abstract: - Highlights: • Uniform-sized colloidal carbon spheres were synthesized from low-cost glucose. • Pd nanoparticles were loaded onto the carbon spheres via self-reduction method. • A layer of ZIF-8 shell was in situ grown over the Pd-loaded carbon spheres. • The ZIF-8@Pd-CCS showed leach-proof and aggregation-resistant properties of Pd. - Abstract: Aiming to enhance the stability of noble metal nanoparticles that are anchored on the surface of colloidal carbon spheres (CCSs), we designed and prepared a new kind of sandwich-structured ZIF-8@Pd-CCS microsphere. Typically, uniform CCSs were first synthesized by the aromatization and carbonization of glucose under hydrothermal conditions. Subsequently, noble metal nanoparticles, herein Pd nanoparticles, were attached to the surface of CCSs via self-reduction route, followed by in situ assembly of a thin layer of ZIF-8 over the Pd nanoparticles to form the sandwich-type ZIF-8@Pd-CCS microspheres. X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of crystalline ZIF-8, while TEM analysis revealed that the ZIF-8 shells were closely bound to the Pd-loaded CCSs. The shell thickness could be tuned by varying the ZIF-8 assembly cycles. Further, liquid-phase hydrogenation of 1-hexene as the probe reaction was carried out over the ZIF-8@Pd-CCS microspheres and results showed that the prepared microspheres exhibited excellent agglomeration-resistant and leach-proof properties for the Pd nanoparticles, thus leading to the good reusability of the ZIF-8@Pd-CCS microspheres.

  4. Structural studies of Au-Pd bimetallic nanoparticles by a genetic algorithm method

    Science.gov (United States)

    Shao, Gui-Fang; Tu, Na-Na; Liu, Tun-Dong; Xu, Liang-You; Wen, Yu-Hua

    2015-06-01

    Metallic nanoparticles have attracted particular interests due to their excellent electronic, catalytic and optical properties over the past decades. Atomic-level understanding of structural characteristics of metallic nanoparticles is of great importance for their syntheses and applications because the structural characteristics strongly determine their chemical and physical properties. In this article, we systematically investigated the structural stability and structural features of Au-Pd nanoparticles by using the genetic algorithm with the quantum correction Sutton-Chen potentials. Layered coordinate ranking method and an effective fitness function have been introduced into the genetic algorithm to enhance its searching ability of low-energy configurations. Here were addressed eight representative nanoshapes including single-crystalline and multiple-twinned structures. The results reveal that the developed genetic algorithm exhibits superior searching ability. In all polyhedra, the truncated octahedron possessed the best stability, while the icosahedron did the worst. Moreover, segregation of Au to the surface and that of Pd to the core were disclosed in these polyhedral Au-Pd nanoparticles. Particularly, for Au composition of 50%, the optimized structures of Au-Pd nanoparticles were predicted to exhibit core-shell structures.

  5. Structural characterization of Pt-Pd core-shell nanoparticles by Cs-corrected STEM

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, R., E-mail: resparza@fata.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Garcia-Ruiz, Amado F. [UPIICSA-COFAA, Instituto Politecnico Nacional (Mexico); Velazquez Salazar, J. J. [University of Texas at San Antonio, Department of Physics and Astronomy (United States); Perez, R. [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Jose-Yacaman, M. [The University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-01-15

    Pt-Pd core-shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 Degree-Sign C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core-shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM-EDS and STEM-EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.

  6. One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fang; Yang, Die; Chen, Zuliang, E-mail: zuliang.chen@newcastle.edu.au; Megharaj, Mallavarapu; Naidu, Ravendra

    2016-02-13

    Highlights: • Green synthesis of bimetallic Fe/Pd NPs was firstly reported using the one-step method. • 98.0% of Orange II was removed by Fe/Pd NPs, but only 16.0% by Fe NPs. • Fe/Pd NPs with a diameter ranging from 10 to 100 nm were observed. • Removing Orange II using Fe/Pd NPs involved both adsorption and catalytic degradation. - Abstract: To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12 h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe{sup 2+} and Pd{sup 2+}, had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography–Mass Spectrum (HPLC–MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation.

  7. Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose

    at elevated temperatures. The time-resolved TEM images are presented and these offer direct insight into the fundamental dynamics of the sintering process at the nano-scale. For Pt, Pd and bimetallic Pt-Pd nanoparticles it is shown that the sintering process is governed by the Ostwald ripening mechanism...... correlations between neighbouring nanoparticles in the atom-exchange process. The sintering process was also presented statistically by particle size distributions extracted from the TEM images. The statistical data agreed only partly with the mean-field kinetic models for ripening, but the deviations could......This thesis presents a fundamental study of the sintering of supported nanoparticles in relation to diesel oxidation catalysts. The sintering of supported nanoparticles is an important challenge in relation to this catalyst, as well as many other catalyst systems, and a fundamental understanding...

  8. Shape-controlled synthesis of Pt-Pd core-shell nanoparticles exhibiting polyhedral morphologies by modified polyol method

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenviet_long@yahoo.com [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, Nguyen Trai, Hanoi (Viet Nam); Asaka, Toru; Matsubara, Takashi [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-04-15

    Pt-Pd core-shell nanoparticles were synthesized by a simple synthetic method. First, Pt nanoparticles were synthesized in a controlled manner via the reduction of chloroplantinic acid hexahydrate in ethylene glycol (EG) at 160 deg. C in the presence of silver nitrate and the stabilization of polyvinylpyrrolidon. AgNO{sub 3} used acts as a structure-modifying agent to the morphology of the Pt nanoparticles. These Pt nanoparticles function as the seeds for the successive reduction of sodium tetrachloropalladate (II) hydrate in EG under stirring for 15 min at 160 deg. C in order to synthesize Pt-Pd core-shell nanoparticles. To characterize the as-prepared Pt-Pd nanoparticles, transmission electron microscopy (TEM) and high-resolution TEM are used. The high-resolution elemental mappings were carried out using the combination of scanning TEM and X-ray energy-dispersive spectroscopy. The results also demonstrate the homogeneous nucleation and growth of the Pd metal shell on the definite Pt core. The synthesized Pt-Pd core-shell nanoparticles exhibit a sharp and polyhedral morphology. The epitaxial growth of the controlled Pd shells on the Pt cores via a polyol method was observed. It is suggested that Frank-van der Merwe and Stranski-Krastanov growth modes coexisted in the nucleation and growth of Pt-Pd core-shell nanoparticles.

  9. Dispersed-nanoparticle loading synthesis for monodisperse Au-titania composite particles and their crystallization for highly active UV and visible photocatalysts.

    Science.gov (United States)

    Sakamoto, Takeshi; Nagao, Daisuke; Noba, Masahiro; Ishii, Haruyuki; Konno, Mikio

    2014-06-24

    Submicrometer-sized amorphous titania spheres incorporating Au nanoparticles (NPs) were prepared in a one-pot synthesis consisting of a sol-gel reaction of titanium(IV) isopropoxide in the presence of chloroauric acid and a successive reduction with sodium borohydride in a mixed solvent of ethanol/acetonitrile. The synthesis was allowed to prepare monodisperse titania spheres that homogeneously incorporated Au NPs with sizes of ca. 7 nm. The Au NP-loaded titania spheres underwent different crystallization processes, including 500 °C calcination in air, high-temperature hydrothermal treatment (HHT), and/or low-temperature hydrothermal treatment (LHT). Photocatalytic experiments were conducted with the Au NP-loaded crystalline titania spheres under irradiation of UV and visible light. A combined process of LHT at 80 °C followed by calcination at 500 °C could effectively crystallize titania spheres maintaining the dispersion state of Au NPs, which led to photocatalytic activity higher than that of commercial P25 under UV irradiation. Under visible light irradiation, the Au NP-titania spheres prepared with a crystallization process of LHT at 80 °C for 6 h showed photocatalytic activity much higher than a commercial product of visible light photocatalyst. Structure analysis of the visible light photocatalysts indicates the importance of prevention of the Au NPs aggregation in the crystallization processes for enhancement of photocatalytic activity.

  10. Cross-linked branching nanohybrid polymer electrolyte with monodispersed TiO2 nanoparticles for high performance lithium-ion batteries

    Science.gov (United States)

    Ma, Cheng; Zhang, Jinfang; Xu, Mingquan; Xia, Qingbing; Liu, Jiatu; Zhao, Shuai; Chen, Libao; Pan, Anqiang; Ivey, Douglas G.; Wei, Weifeng

    2016-06-01

    Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO2-grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO2-grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10-4 S cm-1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO2-grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g-1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C).

  11. Preparation of mono-dispersed silver nanoparticles assisted by chitosan-g-poly(ε-caprolactone) micelles and their antimicrobial application

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Chunhua [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhang, Huan [State Key Laboratory of Bioreactor Engineering, New World Biotechnology Institute, East China University of Science and Technology, Shanghai 200237 (China); Lang, Meidong, E-mail: mdlang@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2014-05-01

    Graphical abstract: - Highlights: • Chemical modification of chitosan were conducted after phthaloyl protection of amino groups. • Silver nanoparticles were prepared in the presence of chitosan-based copolymer micelles. • The optimal time scale and weight ratios of silver to micelles were monitored by UV–vis spectrometer. - Abstract: Amphiphilic chitosan-graft-poly(ε-caprolactone) (CS-g-PCLs) copolymers were synthesized by a homogeneous coupling method and characterized by {sup 1}H NMR, FTIR and ninhydrin assay. The graft copolymers were subsequently self-assembled into micelles, which were measured by DLS and TEM. The particle size of the micelles decreased as the segment grafting fraction was increased. Thereafter, silver nanoparticles were prepared in the presence of chitosan-based micelles under UV irradiation. The molar ratio and radiation time of silver to micelles were optimized with process monitored via UV–vis spectrophotometer. DLS and TEM were used to illustrate the particle structure and size while XRD patterns were applied to characterize the crystal structures of polymer-assisted silver nanoparticles. Films impregnated with silver nanoparticles were conducted with results of strong antimicrobial activities against Escherichia coli and Staphylococcus aureus as model Gram-negative and positive bacteria.

  12. Supercritical fluid chemical deposition of Pd nanoparticles on magnesium–scandium alloy for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Couillaud, Samuel; Kirikova, Marina [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Zaïdi, Warda; Bonnet, Jean-Pierre [LRCS, UMR CNRS 6007, 33 rue Saint-Leu, 80039-Amiens (France); Marre, Samuel; Aymonier, Cyril [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Zhang, Junxian; Cuevas, Fermin; Latroche, Michel [ICMPE, CNRS-UPEC, UMR 7182, 2-8 rue Henri Dunant, 94320-Thiais (France); Aymard, Luc [LRCS, UMR CNRS 6007, 33 rue Saint-Leu, 80039-Amiens (France); Bobet, Jean-Louis, E-mail: bobet@icmcb-bordeaux.cnrs.fr [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France)

    2013-10-15

    Highlights: •Nanoparticles of Pd were deposed on the binary compound Mg{sub 0.65}Sc{sub 0.35} using the Supercritical Fluid Chemical Deposition (SFCD) method. •Numerous parameters were tested and optimized in order to obtain a homogeneous deposition. •At the first step, Pd@Mg0.65Sc0.35 decomposes into ScH{sub 2} and MgH{sub 2} under hydrogen pressure (1 MPa) at 330 °C. •The mixture, after decomposition absorbs hydrogen reversibly on Mg/MgH{sub 2} couple with good kinetics. -- Abstract: The deposition of Pd nanoparticles on the binary compound Mg{sub 0.65}Sc{sub 0.35} using the Supercritical Fluid Chemical Deposition (SFCD) method was performed. There, the SFCD operating parameters (co-solvent, temperature, CO{sub 2} and hydrogen pressure, reaction time) have been optimized to obtain homogeneous deposition of Pd nanoparticles (around 10 nm). The hydrogenation properties of the optimized Pd@Mg{sub 0.65}Sc{sub 0.35} material were determined and compared to those of Mg{sub 0.65}Sc{sub 0.35}Pd{sub 0.024}. The latter compound forms at 300 °C and 1 MPa of H{sub 2} a hydride that crystallizes in the fluorite structure, absorbs reversibly 1.5 wt.% hydrogen and exhibits fast kinetics. In contrast, Pd@Mg{sub 0.65}Sc{sub 0.35} compound decomposes into ScH{sub 2} and MgH{sub 2} during hydrogen absorption under the same conditions. However, reversible sorption reaches 3.3 wt.% of hydrogen while keeping good kinetics. The possible roles of Pd on the hydrogen-induced alloy decomposition are discussed.

  13. Aerobic dehydrogenation of cyclohexanone to phenol catalyzed by Pd(TFA)2/2-dimethylaminopyridine: evidence for the role of Pd nanoparticles.

    Science.gov (United States)

    Pun, Doris; Diao, Tianning; Stahl, Shannon S

    2013-06-05

    We have carried out a mechanistic investigation of aerobic dehydrogenation of cyclohexanones and cyclohexenones to phenols with a Pd(TFA)2/2-dimethylaminopyridine catalyst system. Numerous experimental methods, including kinetic studies, filtration tests, Hg poisoning experiments, transmission electron microscopy, and dynamic light scattering, provide compelling evidence that the initial Pd(II) catalyst mediates the first dehydrogenation of cyclohexanone to cyclohexenone, after which it evolves into soluble Pd nanoparticles that retain catalytic activity. This nanoparticle formation and stabilization is facilitated by each of the components in the catalytic reaction, including the ligand, TsOH, DMSO, substrate, and cyclohexenone intermediate.

  14. Photodeposited Pd Nanoparticles with Disordered Structure for Phenylacetylene Semihydrogenation

    Science.gov (United States)

    Fan, Qining; He, Sha; Hao, Lin; Liu, Xin; Zhu, Yue; Xu, Sailong; Zhang, Fazhi

    2017-01-01

    Developing effective heterogeneous metal catalysts with high selectivity and satisfactory activity for chemoselective hydrogenation of alkyne to alkene is of great importance in the chemical industry. Herein, we report our efforts to fabricate TiO2-supported Pd catalysts by a photodeposition method at room temperature for phenylacetylene semihydrogenation to styrene. The resulting Pd/TiO2 catalyst, possessing smaller Pd ensembles with ambiguous lattice fringes and more low coordination Pd sites, exhibits higher styrene selectivity compared to two contrastive Pd/TiO2 samples with larger ensembles and well-organized crystal structure fabricated by deposition-precipitation or photodeposition with subsequent thermal treatment at 300 °C. The sample derived from photodeposition exhibits greatly slow styrene hydrogenation in kinetic evaluation because the disordered structure of Pd particles in photodeposited Pd/TiO2 may prevent the formation of β-hydride phases and probably produce more surface H atoms, which may favor high styrene selectivity. PMID:28176843

  15. One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II.

    Science.gov (United States)

    Luo, Fang; Yang, Die; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2016-02-13

    To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe(2+) and Pd(2+), had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography-Mass Spectrum (HPLC-MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Ordered PdCu-Based Nanoparticles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalysts.

    Science.gov (United States)

    Jiang, Kezhu; Wang, Pengtang; Guo, Shaojun; Zhang, Xu; Shen, Xuan; Lu, Gang; Su, Dong; Huang, Xiaoqing

    2016-07-25

    The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Electrocatalytic reduction of bromate based on Pd nanoparticles uniformly anchored on polyaniline/SBA-15.

    Science.gov (United States)

    Sun, Chencheng; Deng, Ning; An, Hao; Cui, Hao; Zhai, Jianping

    2015-12-01

    A nano-composite electrocatalyst of Pd nanoparticles (Pd-NPs) anchored on polyaniline (PANI) supported by mesoporous SBA-15 (Pd-NPs/PANI/SBA-15), was synthesized using an in situ chemical method. Transmission electron microscopy showed that the Pd-NPs were homogeneously dispersed. Fourier-transform infrared and X-ray photoelectron spectroscopies confirmed that the Pd-NPs in the metallic state (Pd(0)) were predominantly immobilized on nitrogen sites in the PANI chains. The electrochemical performance of Pd-NPs/PANI/SBA-15 for electrocatalytic reduction of bromate (BrO3(-)) in an acidic medium was investigated by cyclic voltammetry (CV) and amperometric measurement. The reduction peak in the CV curves in the region 0.12 to -0.22V (vs. SCE) corresponded to response of BrO3(-) electroreduction, and the reduction peak current was well fitted linearly to the BrO3(-) concentration. It is proposed that the bromate ions diffuse to the Pd-NPs active sites and then the electrocatalytic reduction occurred with the H(+) doped in PANI. Furthermore, by amperometric measurement, Pd-NPs/PANI/SBA-15 showed relatively high sensitivity with respect to BrO3(-) concentration in the range of 8μmolL(-1) to 40mmolL(-1). Continuous CV for 200 cycles proved that Pd-NPs/PANI/SBA-15 had excellent electrocatalytic stability. These results show that Pd-NPs/PANI/SBA-15 is effective for electrocatalytic reduction of BrO3(-) and has great potential for the fabrication of BrO3(-) electrochemical sensor.

  18. Shape-dependent electrocatalysis: formic acid electrooxidation on cubic Pd nanoparticles.

    Science.gov (United States)

    Vidal-Iglesias, Francisco J; Arán-Ais, Rosa M; Solla-Gullón, José; Garnier, Emmanuel; Herrero, Enrique; Aldaz, Antonio; Feliu, Juan M

    2012-08-07

    The electrocatalytic properties of palladium nanocubes towards the electrochemical oxidation of formic acid were studied in H(2)SO(4) and HClO(4) solutions and compared with those of spherical Pd nanoparticles. The spherical and cubic Pd nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The intrinsic electrocatalytic properties of both nanoparticles were shown to be strongly dependent on the amount of metal deposited on the gold substrate. Thus, to properly compare the activity of both systems (spheres and nanocubes), the amount of sample has to be optimized to avoid problems due to a lower diffusion flux of reactants in the internal parts of the catalyst layer resulting in a lower apparent activity. Under the optimized conditions, the activity of the spheres and nanocubes was very similar between 0.1 and 0.35 V. From this potential value, the activity of the Pd nanocubes was remarkably higher. This enhanced electrocatalytic activity was attributed to the prevalence of Pd(100) facets in agreement with previous studies with Pd single crystal electrodes. The effect of HSO(4)(-)/SO(4)(2-) desorption-adsorption was also evaluated. The activity found in HClO(4) was significantly higher than that obtained in H(2)SO(4) in the whole potential range.

  19. Influence of α-amylase template concentration on systematic entrapment of highly stable and monodispersed colloidal gold nanoparticles

    Science.gov (United States)

    Ananth, A. Nitthin; Ananth, A. Nimrodh; Jose, Sujin P.; Umapathy, S.; Mathavan, T.

    2016-01-01

    Nano gold / α-amylase colloidal dispersions of profound stability were made using simple procedure with a conventional reducing agent. The surface plasmon resonance of the gold nanocrystals was used to quantify the extent of the dispersion stability and functionalization. It is found that the reduced gold nanoparticles were trapped into the protein network without denaturation the structure of α-amylase protein. This kind of entrapment of particles into the protein network prevents clustering of individual gold nanoparticles (6.42 nm ± 0.92 nm) by acting as a natural spacer. Systematic entrapment was facilitated by the affinity of gold to the sulfur moieties (Au-S) in the protein structure.

  20. Monodisperse nanoparticles from self-assembling amphiphilic cyclodextrins: modulable tools for the encapsulation and controlled release of pharmaceuticals.

    Science.gov (United States)

    Mendez-Ardoy, Alejandro; Gómez-García, Marta; Gèze, Annabelle; Putaux, Jean-Luc; Wouessidjewe, Denis; Ortiz Mellet, Carmen; Defaye, Jacques; García Fernández, José M; Benito, Juan M

    2012-07-01

    Selective chemical functionalization of cyclodextrins (CDs) is a readily amenable methodology to produce amphiphilic macromolecules endowed with modulable self-organizing capabilities. Herein, the synthesis of well-defined amphiphilic CD derivatives, with a "skirt-type" architecture, that incorporate long-chain fatty esters at the secondary hydroxyl rim and a variety of chemical functionalities (e. g. iodo, bromo, azido, cysteaminyl or isothiocyanato) at the primary hydroxyls rim is reported. Nanoprecipitation of the new CD facial amphiphiles, or binary mixtures of them, resulted in nanoparticles with average hydrodynamic diameters ranging from 100 to 240 nm that were stable in suspension for several months. The precise size, zeta potential and topology of the nanoparticles are intimately dependent on the functionalization pattern at the CD scaffold. Highly efficient molecular encapsulation capabilities of poorly bioavailable drugs such as diazepam (DZ) were demonstrated for certain derivatives, the drug release profile being dependent on the type of formulation (nanospheres or nanocapsules). The efficiency and versatility of the synthetic strategy, together with the possibility of exploiting the reactivity of the functional groups at the nanoparticle surface, offer excellent opportunities to further manipulate the carrier capabilities of this series of amphiphilic CDs from a bottom-up approach.

  1. Microbially supported synthesis of catalytically active bimetallic Pd-Au nanoparticles

    DEFF Research Database (Denmark)

    Hosseinkhani, Baharak; Søbjerg, Lina Sveidal; Rotaru, Amelia-Elena

    2012-01-01

    (II) to the bio-supported particles resulted in increased particle size. UV-Vis spectrophotometry and HR-TEM analyses indicated that the previously monometallic nanoparticles had become fully or partially covered by Au(0) or Pd(0), respectively. Furthermore, Energy Dispersive Spectrometry (EDS) and Fast Fourier...

  2. Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene: A highly efficient anodic catalyst for direct formic acid fuel cells

    Science.gov (United States)

    Hosseini, Hadi; Mahyari, Mojtaba; Bagheri, Akbar; Shaabani, Ahmad

    2014-02-01

    For the first time, Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene (Pd and PdCo/PPI-g-G) are prepared and characterized with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The electrocatalytic activity of Pd and PdCo/PPI-g-G are investigated in terms of formic acid electrooxidation in H2SO4 aqueous solution. The PdCo/PPI-g-G shows much higher formic acid oxidation activities in comparison with Pd/PPI-g-G, and it is more resistant to the surface poisoning. This improved electrocatalytic performance may be due to the fine dispersion of PdCo alloy nanoparticles and bi-functional effect. The kinetic parameters such as charge transfer coefficient and the diffusion coefficient of formic acid are estimated under the quasi steady-state conditions.

  3. Hydrogen-induced electrical and optical switching in Pd capped Pr nanoparticle layers

    Indian Academy of Sciences (India)

    Shubhra Kala; B R Mehta

    2008-06-01

    In this study, modification in the properties of hydrogen-induced switchable mirror based on Pr nanoparticle layers is reported. The reversible changes in hydrogen-induced electrical and optical properties of Pd capped Pr nanoparticle layers have been studied as a function of hydrogenation time and compared with the conventional device based on Pd capped Pr thin films. Faster electrical and optical response, higher optical contrast and presence of single absorption edge corresponding to Pr trihydride state in hydrogen loaded state have been observed in the case of nanoparticle layers. The improvement in the electrical and optical properties have been explained in terms of blue shift in the absorption edge due to quantum confinement effect, larger number of interparticle boundaries, presence of defects, loose adhesion to the substrate and enhanced surface to volume atom ratio at nanodimension.

  4. Synergistic Effects in CNTs-PdAu/Pt Trimetallic Nanoparticles with High Electrocatalytic Activity and Stability

    Science.gov (United States)

    Cai, Xin-Lei; Liu, Chang-Hai; Liu, Jie; Lu, Ying; Zhong, Ya-Nan; Nie, Kai-Qi; Xu, Jian-Long; Gao, Xu; Sun, Xu-Hui; Wang, Sui-Dong

    2017-10-01

    We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes (CNTs)-PdAu/Pt trimetallic nanoparticles (NPs), which allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions. The small-sized CNTs-PdAu/Pt NPs ( 3 nm, Pd/Au/Pt ratio of 3:1:2) act as nanocatalysts for the methanol oxidation reaction (MOR), showing excellent performance with electrocatalytic peak current of 4.4 A mg Pt -1 and high stability over 7000 s. The electrocatalytic activity and stability of the PdAu/Pt trimetallic NPs are much superior to those of the corresponding Pd/Pt and Au/Pt bimetallic NPs, as well as a commercial Pt/C catalyst. Systematic investigation of the microscopic, crystalline, and electronic structure of the PdAu/Pt NPs reveals alloying and charge redistribution in the PdAu/Pt NPs, which are responsible for the promotion of the electrocatalytic performance.

  5. Porous Pd nanoparticles with high photothermal conversion efficiency for efficient ablation of cancer cells.

    Science.gov (United States)

    Xiao, Jia-Wen; Fan, Shi-Xuan; Wang, Feng; Sun, Ling-Dong; Zheng, Xiao-Yu; Yan, Chun-Hua

    2014-04-21

    Nanoparticle (NP) mediated photothermal effect shows great potential as a noninvasive method for cancer therapy treatment, but the development of photothermal agents with high photothermal conversion efficiency, small size and good biocompatibility is still a big challenge. Herein, we report Pd NPs with a porous structure exhibiting enhanced near infrared (NIR) absorption as compared to Pd nanocubes with a similar size (almost two-fold enhancement with a molar extinction coefficient of 6.3 × 10(7) M(-1) cm(-1)), and the porous Pd NPs display monotonically rising absorbance from NIR to UV-Vis region. When dispersed in water and illuminated with an 808 nm laser, the porous Pd NPs give a photothermal conversion efficiency as high as 93.4%, which is comparable to the efficiency of Au nanorods we synthesized (98.6%). As the porous Pd NPs show broadband NIR absorption (650-1200 nm), this allows us to choose multiple laser wavelengths for photothermal therapy. In vitro photothermal heating of HeLa cells in the presence of porous Pd NPs leads to 100% cell death under 808 nm laser irradiation (8 W cm(-2), 4 min). For photothermal heating using 730 nm laser, 70% of HeLa cells were killed after 4 min irradiation at a relative low power density of 6 W cm(-2). These results demonstrated that the porous Pd nanostructure is an attractive photothermal agent for cancer therapy.

  6. Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation.

    Science.gov (United States)

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-03-01

    A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies.

  7. Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation

    Science.gov (United States)

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-03-01

    A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies.

  8. Alloy ratio effect of Pd/Pt nanoparticles on carbon nanotubes for catalysing methanol-tolerant oxygen reduction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chien-Liang, E-mail: cl_lee@url.com.t [Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Chiou, Hsueh-Ping; Wu, Shi-Chi; Wu, Chen-Chung [Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China)

    2010-12-30

    Pd{sub 1}Pt{sub 3}, Pd{sub 1}Pt{sub 1}, and Pd{sub 3}Pt{sub 1} nanoparticles supported on multi-wall carbon nanotubes (CNTs) were prepared by the self-regulation reduction of sodium n-dodecyl sulphate and used as catalysts in oxygen reduction reactions (ORRs). The crystal properties of these alloy nanoparticles on the CNT were measured by X-ray diffraction spectroscopy (XRD) and high-resolution transmission electron microscopy (HRTEM). The angle shifting of the XRD peak and the lattice spacing of the nanoparticles measured by HRTEM increased with an increase in Pd amount, indicating a regulable Pd-Pt ratio for the alloy nanoparticle composition. Rotating ring-disk electrode (RRDE) measurements indicate that the number of electrons catalysed by the Pd{sub 1}Pt{sub 3}/CNT, Pd{sub 1}Pt{sub 1}/CNT, and Pd{sub 3}Pt{sub 1}/CNT nanocatalysts in the ORRs were 3.98, 3.97, and 3.93, respectively. These results show that these ORRs occur via a 4-electron pathway. Linearly scanned voltammetry in the electrolyte with methanol revealed that Pd{sub 3}Pt{sub 1}/CNT has high methanol tolerance during ORRs.

  9. Structure Sensitivity Study of Waterborne Contaminant Hydrogenation Using Shape- and Size-Controlled Pd Nanoparticles

    KAUST Repository

    Shuai, Danmeng

    2013-03-01

    Catalytic reduction with Pd has emerged as a promising technology to remove a suite of contaminants from drinking water, such as oxyanions, disinfection byproducts, and halogenated pollutants, but low activity is a major challenge for application. To address this challenge, we synthesized a set of shape- and size-controlled Pd nanoparticles and evaluated the activity of three probe contaminants (i.e., nitrite, N-nitrosodimethylamine (NDMA), and diatrizoate) as a function of facet type (e.g., (100), (110), (111)), ratios of low- to high-coordination sites, and ratios of surface sites to total Pd (i.e., dispersion). Reduction results for an initial contaminant concentration of 100 μM show that initial turnover frequency (TOF0) for nitrite increases 4.7-fold with increasing percent of (100) surface Pd sites (from 0% to 95.3%), whereas the TOF0 for NDMA and for diatrizoate increases 4.5- and 3.6-fold, respectively, with an increasing percent of terrace surface Pd sites (from 79.8% to 95.3%). Results for an initial nitrite concentration of 2 mM show that TOF0 is the same for all shape- and size-controlled Pd nanoparticles. Trends for TOF0 were supported by results showing that all catalysts but one were stable in shape and size up to 12 days; for the exception, iodide liberation in diatrizoate reduction appeared to be responsible for a shape change of 4 nm octahedral Pd nanoparticles. Density functional theory (DFT) simulations for the free energy change of hydrogen (H2), nitrite, and nitric oxide (NO) adsorption and a two-site model based on the Langmuir-Hinshelwood mechanism suggest that competition of adsorbates for different Pd sites can explain the TOF0 results. Our study shows for the first time that catalytic reduction activity for waterborne contaminant removal varies with the Pd shape and size, and it suggests that Pd catalysts can be tailored for optimal performance to treat a variety of contaminants for drinking water. © 2013 American Chemical Society.

  10. Probing hydrodesulfurization over bimetallic phosphides using monodisperse Ni2-xMxP nanoparticles encapsulated in mesoporous silica

    Science.gov (United States)

    Danforth, Samuel J.; Liyanage, D. Ruchira; Hitihami-Mudiyanselage, Asha; Ilic, Boris; Brock, Stephanie L.; Bussell, Mark E.

    2016-06-01

    Metal phosphide nanoparticles encapsulated in mesoporous silica provide a well-defined system for probing the fundamental chemistry of the hydrodesulfurization (HDS) reaction over this new class of hydrotreating catalysts. To investigate composition effects in bimetallic phosphides, the HDS of dibenzothiophene (DBT) was carried out over a series of Ni-rich Ni2-xMxP@mSiO2 (M = Co, Fe) nanocatalysts (x ≤ 0.50). The Ni2-xMxP nanoparticles (average diameters: 11-13 nm) were prepared by solution-phase arrested precipitation and encapsulated in mesoporous silica, characterized by a range of techniques (XRD, TEM, IR spectroscopy, BET surface area, CO chemisorption) and tested for DBT HDS activity and selectivity. The highest activity was observed for a Ni1.92Co0.08P@mSiO2 nanocatalyst, but the overall trend was a decrease in HDS activity with increasing Co or Fe content. In contrast, the highest turnover frequency (TOF) was observed for the most Co- and Fe-rich compositions based on sites titrated by CO chemisorption. IR spectral studies of adsorbed CO on the Ni2-xMxP@mSiO2 catalysts indicate that an increase in electron density occurs on Ni sites as the Co or Fe content is increased, which may be responsible for the increased TOFs of the catalytic sites. The Ni2-xMxP@mSiO2 nanocatalysts exhibit a strong preference for the direct desulfurization pathway (DDS) for DBT HDS that changes only slightly with increasing Co or Fe content.

  11. Pd Nanoparticles Coupled to WO 2.72 Nanorods for Enhanced Electrochemical Oxidation of Formic Acid

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Zheng; Erdosy, Daniel P.; Mendoza-Garcia, Adriana; Duchesne, Paul N.; Li, Junrui; Muzzio, Michelle; Li, Qing; Zhang, Peng; Sun, Shouheng (Brown); (Dalhousie U.); (Huazhong)

    2017-03-02

    We synthesize a new type of hybrid Pd/WO2.72 structure with 5 nm Pd nanoparticles (NPs) anchored on 50 × 5 nm WO2.72 nanorods. The strong Pd/WO2.72 coupling results in the lattice expansion of Pd from 0.23 to 0.27 nm and the decrease of Pd surface electron density. As a result, the Pd/WO2.72 shows much enhanced catalysis toward electrochemical oxidation of formic acid in 0.1 M HClO4; it has a mass activity of ~1600 mA/mgPd in a broad potential range of 0.4–0.85 V (vs RHE) and shows no obvious activity loss after a 12 h chronoamperometry test at 0.4 V. Our work demonstrates an important strategy to enhance Pd NP catalyst efficiency for energy conversion reactions.

  12. Characterization and electrocatalytic properties of sonochemical synthesized PdAg nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Godinez-Garcia, Andres, E-mail: agodinez@qro.cinvestav.mx [Depto. Materiales, Centro de Investigacion y de Estudios Avanzados del IPN, Libramiento norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230 Santiago de Queretaro, Qro. (Mexico); Perez-Robles, Juan Francisco [Depto. Materiales, Centro de Investigacion y de Estudios Avanzados del IPN, Libramiento norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230 Santiago de Queretaro, Qro. (Mexico); Martinez-Tejada, Hader Vladimir [Grupo de Energia y Termodinamica, Universidad Pontificia Bolivariana, Medellin, Antioquia C.P. 050031 (Colombia); Solorza-Feria, Omar [Depto. Quimica, CINVESTAV-IPN, Av. IPN 2508, A. P. 14-740, 07360 D.F. Mexico (Mexico)

    2012-06-15

    High intensity ultrasound was used in the synthesis of PdAg nanoparticles. PdAg nanoparticles were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), scanning transmission electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM). Catalytic properties for oxygen reduction reaction (ORR) were determined by electrochemical techniques of cyclic voltammetry (CV) and thin-film rotating disk electrode (TF-RDE). Finally the electrocatalyst was tested as a cathode in a single polymer electrolyte membrane fuel cell (PEMFC). Sonochemical synthesis (SS) decreased the overpotential required for the ORR and increased the double-layer capacitance (DLC) respect to the sodium borohydride reduction method due to a better distribution on vulcan carbon support. The electrocatalytic activity of the nanometric bimetallic electrocatalyst for the ORR in acid media showed a favorable multielectron charge transfer process (n = 4e{sup -}) to water formation. The performance of the membrane electrode assembly (MEA) prepared with dispersed PdAg/C as a cathode catalyst in a single PEMFC is lower in comparison to platinum. - Highlights: Black-Right-Pointing-Pointer Sonochemical synthesized PdAg nanoparticles supported on carbon were produced. Black-Right-Pointing-Pointer The material showed catalytic properties for the oxygen reduction reaction (ORR). Black-Right-Pointing-Pointer The ORR favored the pathway to water formation.

  13. Highly dispersed Pd nanoparticles on chemically modified graphene with aminophenyl groups for formic acid oxidation

    Science.gov (United States)

    Yang, Su-Dong; Shen, Cheng-Min; Tong, Hao; He, Wei; Zhang, Xiao-Gang; Gao, Hong-Jun

    2011-11-01

    A novel electrode material based on chemically modified graphene (CMG) with aminophenyl groups is covalently functionalized by a nucleophilic ring-opening reaction between the epoxy groups of graphene oxide and the aminophenyl groups of p-phenylenediamine. Palladium nanoparticles with an average diameter of 4.2 nm are deposited on the CMG by a liquid-phase borohydride reduction. The electrocatalytic activity and stability of the Pd/CMG composite towards formic acid oxidation are found to be higher than those of reduced graphene oxide and commercial carbon materials such as Vulcan XC-72 supported Pd electrocatalysts.

  14. Rapid activation of MmNi{sub 5-x}M{sub x} based MH alloy through Pd nanoparticle impregnation

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, M.A. [Posgrado en Ingenieria y Ciencias Aplicadas, UAEM-CIICAp, Av Universidad 1001, Col. Chamilpa, 62210-Cuernavaca, Mor. (Mexico); Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apdo. Postal J-48, Puebla, Pue. 72570 (Mexico); Wang, Xianyou [Chemistry College, Xiangtan University, Hunan 411105 (China); Gonzalez-Rodriguez, J.G. [UAEM-CIICAp, Av. Universidad 1001, Col. Chamilpa, 62210-Cuernavaca, Mor. (Mexico); Gamboa, S.A. [Centro de Investigacion en Energia, Xochicalco S/N, Centro, 62580 Temixco, Morelos (Mexico)

    2006-04-21

    Faster activation of a multi-component AB{sub 5} based alloy metal hydride electrode through Pd nanoparticle (NP) impregnation is demonstrated. Pd nanoparticle impregnated MmNi{sub 5-x}M{sub x} based alloy was prepared and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and elemental mapping techniques. Electro-catalytic activity of laminar metal hydride electrodes containing Pd nanoparticles and micrometer size Ni particles was studied. Hydrogen absorption efficiency of the nanocomposite electrodes was compared with the metal hydride electrodes without Pd nanoparticles. The incorporation of nanostructured materials in the metal hydride alloy increased its hydrogen absorption capacity at the initial stage and activated much faster, indicating its good prospect for energy storage applications. (author)

  15. Effect of Organic Capping Layers over Monodisperse Platinum Nanoparticles upon Activity for Ethylene Hydrogenation and Carbon Monoxide Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, John N.; Tsung, Chia-Kuang; Huang, Wenyu; Somorjai, Gabor A.

    2009-03-24

    The influence of oleylamine (OA), trimethyl tetradecyl ammonium bromide (TTAB), and polyvinlypyrrolidone (PVP) capping agents upon the catalytic properties of Pt/silica catalysts was evaluated. Pt nanoparticles that were 1.5 nm in size were synthesized by the same procedure (ethylene glycol reduction under basic conditions) with the various capping agents added afterward for stabilization. Before examining catalytic properties for ethylene hydrogenation and CO oxidation, the Pt NPs were deposited onto mesoporous silica (SBA-15) supports and characterized by transmission electron microscopy (TEM), H{sub 2} chemisorption, and elemental analysis (ICP-MS). PVP- and TTAB-capped Pt yielded mass-normalized reaction rates that decreased with increasing pretreatment temperature, and this trend was attributed to the partial coverage of the Pt surface with decomposition products from the organic capping agent. Once normalized to the Pt surface area, similar intrinsic activities were obtained regardless of the pretreatment temperature, which indicated no influence on the nature of the active sites. Consequently, a chemical probe technique using intrinsic activity for ethylene hydrogenation was demonstrated as an acceptable method for estimating the metallic surface areas of Pt. Amine (OA) capping exhibited a detrimental influence on the catalytic properties as severe deactivation and low activity were observed for ethylene hydrogenation and CO oxidation, respectively. These results were consistent with amine groups being strong poisons for Pt surfaces, and revealed the need to consider the effects of capping agents on the catalytic properties.

  16. A General Strategy for the Preparation of Carbon Nanotubes and Graphene Oxide Decorated with PdO Nanoparticles in Water

    Directory of Open Access Journals (Sweden)

    Hongkun He

    2010-07-01

    Full Text Available The preparation of carbon nanotube (CNT/PdO nanoparticles and graphene oxide (GO/PdO nanoparticle hybrids via a general aqueous solution strategy is reported. The PdO nanoparticles are generated in situ on the CNTs and GO by a one-step “green” synthetic approach in aqueous Pd(NO32 solution under ambient conditions without adding any additional chemicals. The production of PdO is confirmed by energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. The morphologies of the resulting CNT/PdO and GO/PdO nanohybrids are characterized by transmission and/or scanning transmission electron microscopy. PdO nanoparticles with an average size of 2–3 nm in diameter are decorated evenly along the surfaces of CNTs and GO. This synthesis strategy is demonstrated to be compatible for 1 CNTs with different modifications, including pristine, oxidized, and polymer-functionalized CNTs; 2 different types of CNTs, including single-walled carbon nanotubes (SWCNTs, double-walled carbon nanotubes (DWCNTs, and multiwalled carbon nanotubes (MWCNTs; and 3 different shapes of carbon materials, including tubular CNTs and planar GO. The as-prepared CNT/PdO and GO/PdO nanohybrids can be transformed into CNT/Pd and GO/Pd nanohybrids by reduction with NaBH4, and can then be used as a heterogeneous catalyst in the catalytic reduction of 4-nitrophenol.

  17. PdPt bimetallic nanoparticles enabled by shape control with halide ions and their enhanced catalytic activities.

    Science.gov (United States)

    Zhang, Jinfeng; Wan, Lei; Liu, Lei; Deng, Yida; Zhong, Cheng; Hu, Wenbin

    2016-02-21

    In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl(-) ions, whereas the introduction of Br(-) ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth mode of Pt atoms on the exterior surface of the central Pd core. Moreover, the stronger adsorption function of I(-) ions and the resulting fast atomic diffusion promoted the generation of mesoporous core-shell PdPt bimetallic nanoparticles with many pore channels. In addition, the size of these synthesized PdPt nanoparticles exhibited a significant dependence on the concentration of the halide ions involved. Due to their specific structural features and synergistic effects, these PdPt catalysts exhibited shape-dependent catalytic performance and drastically enhanced electrocatalytic activities relative to that of commercial Pt black and Pt/C toward methanol oxidation.

  18. One-step synthesis of PtPdAu ternary alloy nanoparticles on graphene with superior methanol electrooxidation activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yuzhen; Gu Yonge; Lin Shaoxiong; Wei Jinping; Wang Zaihua [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Wang Chunming, E-mail: wangcm@lzu.edu.cn [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Du Yongling; Ye Weichun [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-10-01

    Highlights: > PtPdAu nanoparticles were synthesized on graphene sheets via chemical reduction method. > The prepared PtPdAu nanoparticles were ternary alloy with fcc structure. > The catalyst exhibited superior catalytic activity and stability for MOR in alkaline. - Abstract: Well-dispersed PtPdAu ternary alloy nanoparticles were synthesized on graphene sheets via a simple one-step chemical reduction method in ethylene glycol (EG) and water system, in which EG served as both reductive and dispersing agent. The electrocatalytic activity of PtPdAu/G was tested by methanol oxidation reaction (MOR). The catalyst was further characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which indicated that the as-synthesized PtPdAu nanoparticles with alloy structures were successfully dispersed on the graphene sheets. Electrocatalytic properties of the catalyst for MOR in alkaline have been investigated by cyclic voltammetry (CV), chronoamperometry and Tafel curves. The electrocatalytic activity and stability of PtPdAu/G were superior to PtPd/G, PtAu/G and Pt/G. In addition, the anodic peak current on PtPdAu/G catalyst was proportional to the concentration of methanol in the range of 0.05-1.00 M. This study implies that the prepared catalyst have great potential applications in fuel cells.

  19. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    Science.gov (United States)

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  20. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    Science.gov (United States)

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  1. Volcano-like behavior of Au-Pd core-shell nanoparticles in the selective oxidation of alcohols.

    Science.gov (United States)

    Silva, Tiago A G; Teixeira-Neto, Erico; López, Núria; Rossi, Liane M

    2014-07-21

    Gold-palladium (AuPd) nanoparticles have shown significantly enhanced activity relative to monometallic Au and Pd catalysts. Knowledge of composition and metal domain distributions is crucial to understanding activity and selectivity, but these parameters are difficult to ascertain in catalytic experiments that have primarily been devoted to equimolar nanoparticles. Here, we report AuPd nanoparticles of varying Au:Pd molar ratios that were prepared by a seed growth method. The selective oxidation of benzyl alcohol was used as a model reaction to study catalytic activity and selectivity changes that occurred after varying the composition of Pd in bimetallic catalysts. We observed a remarkable increase in catalytic conversion when using a 10:1 Au:Pd molar ratio. This composition corresponds to the amount of Pd necessary to cover the existing Au cores with a monolayer of Pd as a full-shell cluster. The key to increased catalytic activity derives from the balance between the number of active sites and the ease of product desorption. According to density functional theory calculations, both parameters are extremely sensitive to the Pd content resulting in the volcano-like activity observed.

  2. Room-temperature Fast Synthesis of Composition-adjustable Pt–Pd Alloy Sub-10-nm Nanoparticle Networks with Improved Electrocatalytic Activities

    National Research Council Canada - National Science Library

    Hou, Shuangxia; Xu, You; Liu, Yang; Xu, Rui; Zhang, Bin

    2012-01-01

    Pt–Pd alloy nanoparticle networks (Pt–Pd NN) with adjustable composition have been fast synthesized through a one-step room-temperature coreduction method in a water/ethylene glycol (EG) system...

  3. Transformation of Sodium Bicarbonate and CO2 into Sodium Formate over NiPd Nanoparticle Catalyst

    Directory of Open Access Journals (Sweden)

    Mengnan eWang

    2013-09-01

    Full Text Available The present research systematically investigated, for the first time, the transformation of sodium bicarbonate and CO2 into sodium formate over a series of Ni based metal nanoparticles (NPs. Ni NPs and eight NiM (M stands for a second metal NPs were prepared by a facile wet chemical process and then their catalytic performance were evaluated in sodium bicarbonate hydrogenation. Bimetallic NiPd NPs with a composition of 7:3 were found to be superior for this reaction, which are more active than both pure Ni and Pd NPs. Hot filtration experiment suggested the NPs to be the truly catalytic active species and kinetic analysis indicated the reaction mechanism to be different than most homogeneous catalysts. The enhanced activity of the bimetallic nanoparticles may be attributed to their smaller size and improved stability.

  4. Transformation of Sodium Bicarbonate and CO2 into Sodium Formate over NiPd Nanoparticle Catalyst

    Science.gov (United States)

    Wang, Mengnan; Zhang, Jiaguang; Yan, Ning

    2013-09-01

    The present research systematically investigated, for the first time, the transformation of sodium bicarbonate and CO2 into sodium formate over a series of Ni based metal nanoparticles (NPs). Ni NPs and eight NiM (M stands for a second metal) NPs were prepared by a facile wet chemical process and then their catalytic performance were evaluated in sodium bicarbonate hydrogenation. Bimetallic NiPd NPs with a composition of 7:3 were found to be superior for this reaction, which are more active than both pure Ni and Pd NPs. Hot filtration experiment suggested the NPs to be the truly catalytic active species and kinetic analysis indicated the reaction mechanism to be different than most homogeneous catalysts. The enhanced activity of the bimetallic nanoparticles may be attributed to their smaller size and improved stability.

  5. Exchange-coupled fct-FePd/α-Fe nanocomposite magnets converted from Pd/Fe3O4 core/shell nanoparticles.

    Science.gov (United States)

    Liu, Fei; Dong, Yunhe; Yang, Wenlong; Yu, Jing; Xu, Zhichuan; Hou, Yanglong

    2014-11-10

    We report the controlled synthesis of exchange-coupled face-centered tetragonal (fct) FePd/α-Fe nanocomposite magnets with variable Fe concentration. The composite was converted from Pd/Fe3O4 core/shell nanoparticles through a high-temperature annealing process in a reducing atmosphere. The shell thickness of core/shell Pd/Fe3O4 nanoparticles could be readily tuned, and subsequently the concentration of Fe in nanocomposite magnets was controlled. Upon annealing reduction, the hard magnetic fct-FePd phase was formed by the interdiffusion between reduced α-Fe and face-centered cubic (fcc) Pd, whereas the excessive α-Fe remained around the fct-FePd grains, realizing exchange coupling between the soft magnetic α-Fe and hard magnetic fct-FePd phases. Magnetic measurements showed variation in the magnetic properties of the nanocomposite magnets with different compositions, indicating distinct exchange coupling at the interfaces. The coercivity of the exchange-coupled nanocomposites could be tuned from 0.7 to 2.8 kOe and the saturation magnetization could be controlled from 93 to 160 emu g(-1). This work provides a bottom-up approach using exchange-coupled nanocomposites for engineering advanced permanent magnets with controllable magnetic properties.

  6. Sensitive voltammetric determination of vanillin with an AuPd nanoparticles-graphene composite modified electrode.

    Science.gov (United States)

    Shang, Lei; Zhao, Faqiong; Zeng, Baizhao

    2014-05-15

    In this work, graphene oxide was reduced to graphene with an endogenous reducing agent from dimethylformamide, and then AuPd alloy nanoparticles were electrodeposited on the graphene film. The obtained AuPd-graphene hybrid film was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and voltammetry. The electrochemical behavior of vanillin was studied using the AuPd-graphene hybrid based electrode. It presented high electrocatalytic activity and vanillin could produce a sensitive oxidation peak at it. Under the optimal conditions, the peak current was linear to the concentration of vanillin in the ranges of 0.1-7 and 10-40 μM. The sensitivities were 1.60 and 0.170 mA mM(-1) cm(-2), respectively; the detection limit was 20 nM. The electrode was successfully applied to the detection of vanillin in vanilla bean, vanilla tea and biscuit samples.

  7. Factors determining the stability, size distribution, and cellular accumulation of small, monodisperse chitosan nanoparticles as candidate vectors for anticancer drug delivery: application to the passive encapsulation of [14C]-doxorubicin

    Directory of Open Access Journals (Sweden)

    Masarudin MJ

    2015-12-01

    Full Text Available Mas Jaffri Masarudin,1 Suzanne M Cutts,2 Benny J Evison,3 Don R Phillips,2 Paul J Pigram4 1Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Malaysia; 2Department of Biochemistry, La Trobe University, Melbourne, Victoria, Australia; 3Department of Chemical Biology and Therapeutics, St Jude Children's Hospital, Memphis, TN, USA; 4Department of Physics, La Trobe University, Melbourne, Victoria, Australia Abstract: Development of parameters for the fabrication of nanosized vectors is pivotal for its successful administration in therapeutic applications. In this study, homogeneously distributed chitosan nanoparticles (CNPs with diameters as small as 62 nm and a polydispersity index (PDI of 0.15 were synthesized and purified using a simple, robust method that was highly reproducible. Nanoparticles were synthesized using modified ionic gelation of the chitosan polymer with sodium tripolyphosphate. Using this method, larger aggregates were mechanically isolated from single particles in the nanoparticle population by selective efficient centrifugation. The presence of disaggregated monodisperse nanoparticles was confirmed using atomic force microscopy. Factors such as anions, pH, and concentration were found to affect the size and stability of nanoparticles directly. The smallest nanoparticle population was ~62 nm in hydrodynamic size, with a low PDI of 0.15, indicating high particle homogeneity. CNPs were highly stable and retained their monodisperse morphology in serum-supplemented media in cell culture conditions for up to 72 hours, before slowly degrading over 6 days. Cell viability assays demonstrated that cells remained viable following a 72-hour exposure to 1 mg/mL CNPs, suggesting that the nanoparticles are well tolerated and highly suited for biomedical applications. Cellular uptake studies using fluorescein isothiocyanate-labeled CNPs showed that cancer cells

  8. The effect of microemulsion composition on the morphology of Pd nanoparticles deposited at the surface of TiO2 and photoactivity of Pd-TiO2

    Science.gov (United States)

    Długokęcka, Marta; Łuczak, Justyna; Polkowska, Żaneta; Zaleska-Medynska, Adriana

    2017-05-01

    A series of microemulsion (ME) system, constituted by different water to surfactant molar ratios (Wo) and oil to surfactant mass ratios (S), have been applied for Pd-TiO2 preparation. The effect of ME properties on the morphology of Pd nanoparticles formed at TiO2 surface and an effect of Pd size and distribution on the surface and photocatalytic properties of Pd-TiO2 were investigated. Microemulsion systems were characterized by means of viscosity, density, dynamic light scattering as well as surface tension measurements to find a correlation between the conditions of Pd nanoparticles formation, their morphology and photocatalyst features. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), UV-vis diffuse-reflectance spectroscopy (DRS), BET surface area and elemental analysis. The photocatalytic properties of Pd-modified TiO2 particles were studied in a model reaction of phenol photodegradation under Vis irradiation, as well as active species involved in the photocatalytic reaction were determined. Microemulsion composition was found to be a crucial parameter in determining the features of the TiO2-based photocatalysts covered by metallic nanoparticles. The highest photocatalytic activity under Vis radiation was observed for the Pd-TiO2 sample (average diameter 2.4 nm) obtained using 0.1 mol% Pd in the ME system containing 1.5 wt% of water and 82.8 wt% of cyclohexane with average droplet size of 2.83 ± 0.18 nm. In this regard, synthesis of such metal-semiconductor composites through the microemulsion route should always be preceded by investigation of ME properties in order to the eliminate the inhibitory effect of ME internal structure.

  9. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    Science.gov (United States)

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  10. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    Science.gov (United States)

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  11. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Villa, Alberto [Universita di Milano, Italy; Prati, Laura [Universita di Milano, Italy; Su, Dangshen [Fritz Haber Institute of the Max Planck Society, Berlin, Germany; Wang, Di [Fritz Haber Institute of the Max Planck Society, Berlin, Germany; Veith, Gabriel M [ORNL

    2010-01-01

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd{at}Au{sub PVA}/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  12. Enhanced formic acid electro-oxidation on PdIr nanoparticles prepared by ethylene glycol-assisted NaBH4 reduction process.

    Science.gov (United States)

    Chen, Jinwei; Wang, Gang; Wang, Xueqin; Tian, Jing; Zhu, Shifu; Wang, Ruilin

    2013-10-01

    The carbon supported PdIr nanoparticles were synthesized by an ethylene glycol-assisted NaBH4 reduction method, and the mass ratio of Pd to Ir was optimized. Then, their performances for formic acid electro-oxidation (FAEO) were investigated. The XRD and TEM characterizations show that the prepared PdIr/C catalysts have small mean size and good dispersion of PdIr nanoparticles. The electrochemical measurements demonstrate that the PdIr/C catalysts have greatly enhanced performance for FAEO compared with the Pd/C catalyst. The PdIr/C catalysts show higher current density and more than 50 mV negative shift of onset and peak potential than that of the Pd/C catalyst. With the optimal mass ratio of Pd to Ir, the PdIr/C-5 catalyst presents the highest catalytic activity for FAEO.

  13. A remarkable difference in CO2 hydrogenation to methanol on Pd nanoparticles supported inside and outside of carbon nanotubes.

    Science.gov (United States)

    Wang, Jijie; Lu, Sheng-mei; Li, Jun; Li, Can

    2015-12-25

    An obvious difference was found in CO2 hydrogenation to methanol on Pd nanoparticles (NPs) supported inside and outside of carbon nanotubes (CNTs). The turnover frequency of methanol synthesis on the Pd NPs supported inside of CNTs was 3.7 times those supported outside of CNTs. It was found that the amount of Pd(δ+) species inside of CNTs was much higher than that outside of CNTs. We proposed that one of the major reasons for the difference in CO2 hydrogenation to methanol might be relative to the concentration of the Pd(δ+) species.

  14. Dendrimer-templated Pd nanoparticles and Pd nanoparticles synthesized by reverse microemulsions as efficient nanocatalysts for the Heck reaction: A comparative study.

    Science.gov (United States)

    Noh, Ji-Hyang; Meijboom, Reinout

    2014-02-01

    Palladium nanoparticles (NPs) were prepared using a dendrimer-templated method using G4, G5 and G6 PAMAM-OH dendrimers as well as a reverse microemulsion method using the water/dioctyl sulfosuccinate sodium salt (aerosol-OT, AOT) surfactant/isooctane system with water to surfactant ratios (ω0) of 5, 10 and 13. These 6 catalysts were characterized by UV-Vis spectroscopy, TEM, EDX, and XRD. TEM micrographs showed that the average sizes of 2.74-3.32nm with narrower size distribution were achieved by using dendrimer-templated synthetic methods, whereas the reverse microemulsion method resulted in broad size distribution with an average size of 3.87-5.06nm. The influence of various reaction parameters such as base, catalyst dosing, alkene, aryl halide and temperature on the Heck C-C coupling reaction was evaluated. The activation parameters were derived from the reaction rate of each catalyst obtained at various temperatures. A correlation of catalytic activity, enthalpy of activation and particle size is discussed. Particle size changes of each catalyst were investigated after the catalytic reaction. Overall results indicated that dendrimer-templated Pd NP catalysts showed superior activity as compared to the Pd NPs synthesized by reverse microemulsions, with the dendrimer-templated G5-OH(Pd80) showing the best activity. These catalysts were also reusable for 3 cycles, retaining high yield and showing excellent yields under mild conditions. Therefore, the dendrimer-templated Pd NPs are efficient catalyst systems for the ligand-free Heck C-C coupling reaction.

  15. Synthesis of Monometallic (Au and Pd) and Bimetallic (AuPd) Nanoparticles Using Carbon Nitride (C3N4) Quantum Dots via the Photochemical Route for Nitrophenol Reduction.

    Science.gov (United States)

    Fageria, Pragati; Uppala, Shravan; Nazir, Roshan; Gangopadhyay, Subhashis; Chang, Chien-Hsiang; Basu, Mrinmoyee; Pande, Surojit

    2016-10-04

    In this study, we report the synthesis of monometallic (Au and Pd) and bimetallic (AuPd) nanoparticles (NPs) using graphitic carbon nitride (g-C3N4) quantum dots (QDs) and photochemical routes. Eliminating the necessity of any extra stabilizer or reducing agent, the photochemical reactions have been carried out using a UV light source of 365 nm where C3N4 QD itself functions as a suitable stabilizer as well as a reducing agent. The g-C3N4 QDs are excited upon irradiation with UV light and produce photogenerated electrons, which further facilitate the reduction of metal ions. The successful formation of Au, Pd, and AuPd alloy nanoparticles is evidenced by UV-vis, powder X-ray diffraction, X-ray photon spectroscopy, and energy-dispersive spectroscopy techniques. The morphology and distribution of metal nanoparticles over the C3N4 QD surface has been systematically investigated by high-resolution transmission electron microscopy (HRTEM) and SAED analysis. To explore the catalytic activity of the as-prepared samples, the reduction reaction of 4-nitrophenol with excellent performance is also investigated. It is noteworthy that the synthesis of both monometallic and bimetallic NPs can be accomplished by using a very small amount of g-C3N4, which can be used as a promising photoreducing material as well as a stabilizer for the synthesis of various metal nanoparticles.

  16. An ordered bcc CuPd nanoalloy synthesised via the thermal decomposition of Pd nanoparticles covered with a metal-organic framework under hydrogen gas.

    Science.gov (United States)

    Li, Guangqin; Kobayashi, Hirokazu; Kusada, Kohei; Taylor, Jared M; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Matsumura, Syo; Kitagawa, Hiroshi

    2014-11-18

    Presented here is the synthesis of an ordered bcc copper-palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal-organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal-organic framework decomposition.

  17. Newly developed stepwise electroless deposition enables a remarkably facile synthesis of highly active and stable amorphous Pd nanoparticle electrocatalysts for oxygen reduction reaction.

    Science.gov (United States)

    Poon, Kee Chun; Tan, Desmond C L; Vo, Thang D T; Khezri, Bahareh; Su, Haibin; Webster, Richard D; Sato, Hirotaka

    2014-04-09

    This paper reports on highly active and stable amorphous Pd nanoparticle electrocatalysts for the oxygen reduction reaction. The amorphous catalysts were synthesized by a remarkably facile and quick electroless deposition process newly developed in this study (process time <5 min). An electrode substrate (glassy carbon, carbon cloth) was sequentially dipped for 10 s into two separate solutions of a reducing agent (sodium hypophosphite (NaH2PO2)) and Pd ions to deposit amorphous Pd nanoparticles containing phosphorus (Pd-P). By repeating the deposition cycles, the specific and mass activities of the Pd nanoparticles can be actively tuned. Owing to the nanoscale amorphous nature, the obtained Pd-P nanoparticle electrocatalysts exhibited superior specific and mass activities compared with crystalline Pd nanoparticles synthesized by another reducing agent (N2H4) and commercial Pt-loaded carbon (Pt/C) and Pd-loaded carbon (Pd/C). The specific and mass activities of the amorphous Pd-P nanoparticles were over 4.5 times and 2.6 times higher than previously reported values of Pd and Pt catalysts.

  18. Synthesis of cubic and spherical Pd nanoparticles on graphene and their electrocatalytic performance in the oxidation of formic acid.

    Science.gov (United States)

    Yang, Sudong; Shen, Chengmin; Tian, Yuan; Zhang, Xiaogang; Gao, Hong-Jun

    2014-11-07

    Single-crystal palladium nanoparticles (NPs) with controllable morphology were synthesized on the surface of reduced graphene oxide (RGO) by a novel procedure, namely reducing palladium acetylacetonate [Pd(acac)2] with the N-methylpyrrolidone (NMP) solvent in the presence of poly(vinylpyrrolidone) (PVP). The resulting Pd nanocrystals (8 nm in diameter) were uniformly distributed on the RGO. A possible formation mechanism is discussed. The electrocatalytic performance of Pd nanocrystal/RGO catalysts during formic acid oxidation was investigated, which revealed that the cubic Pd/RGO catalyst performed significantly better than the spherical Pd/RGO catalyst. The shape of Pd nanocrystals on the surface of graphene nanosheets can be easily controlled via tuning the synthesis parameters, resulting in tunable catalytic properties. Moreover, this method can be easily extended to fabricate other noble metal nanostructures.

  19. Synthesis of cubic and spherical Pd nanoparticles on graphene and their electrocatalytic performance in the oxidation of formic acid

    Science.gov (United States)

    Yang, Sudong; Shen, Chengmin; Tian, Yuan; Zhang, Xiaogang; Gao, Hong-Jun

    2014-10-01

    Single-crystal palladium nanoparticles (NPs) with controllable morphology were synthesized on the surface of reduced graphene oxide (RGO) by a novel procedure, namely reducing palladium acetylacetonate [Pd(acac)2] with the N-methylpyrrolidone (NMP) solvent in the presence of poly(vinylpyrrolidone) (PVP). The resulting Pd nanocrystals (8 nm in diameter) were uniformly distributed on the RGO. A possible formation mechanism is discussed. The electrocatalytic performance of Pd nanocrystal/RGO catalysts during formic acid oxidation was investigated, which revealed that the cubic Pd/RGO catalyst performed significantly better than the spherical Pd/RGO catalyst. The shape of Pd nanocrystals on the surface of graphene nanosheets can be easily controlled via tuning the synthesis parameters, resulting in tunable catalytic properties. Moreover, this method can be easily extended to fabricate other noble metal nanostructures.

  20. Plasmonic Pd Nanoparticle- and Plasmonic Pd Nanorod-Decorated BiVO4 Electrodes with Enhanced Photoelectrochemical Water Splitting Efficiency Across Visible-NIR Region.

    Science.gov (United States)

    Yang, Weiwei; Xiong, Yunjie; Zou, Liangliang; Zou, Zhiqing; Li, Dongdong; Mi, Qixi; Wang, Yanshan; Yang, Hui

    2016-12-01

    The photoelectrochemical (PEC) water splitting performance of BiVO4 is partially hindered by insufficient photoresponse in the spectral region with energy below the band gap. Here, we demonstrate that the PEC water splitting efficiency of BiVO4 electrodes can be effectively enhanced by decorating Pd nanoparticles (NPs) and nanorods (NRs). The results indicate that the Pd NPs and NRs with different surface plasmon resonance (SPR) features delivered an enhanced PEC water splitting performance in the visible and near-infrared (NIR) regions, respectively. Considering that there is barely no absorption overlap between Pd nanostructures and BiVO4 and the finite-difference time domain (FDTD) simulation indicating there are substantial energetic hot electrons in the vicinity of Pd nanostructures, the enhanced PEC performance of Pd NP-decorated BiVO4 and Pd NR-decorated BiVO4 could both benefit from the hot electron injection mechanism instead of the plasmon resonance energy transfer process. Moreover, a combination of Pd NPs and NRs decorated on the BiVO4 electrodes leads to a broad-band enhancement across visible-NIR region.

  1. Synthesis and characterization of Pt-Pd nanoparticles with core-shell morphology: Nucleation and overgrowth of the Pd shells on the as-prepared and defined Pt seeds

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenvietlong@yahoo.com [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, km 10 Nguyen Trai, Hanoi (Viet Nam); Laboratory for Nanotechnology, Vietnam National University at Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, 6-1 Kasugakouen, Kasuga, Fukuoka 861-8580 (Japan); Hien, Tong Duy [Laboratory for Nanotechnology, Vietnam National University at Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Asaka, Toru [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Ohtaki, Michitaka [Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, 6-1 Kasugakouen, Kasuga, Fukuoka 861-8580 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-07-21

    Highlights: > The Pt-Pd core-shell nanoparticles based on the as-prepared Pt cores are synthesized. > Not only the Pt-Pd core-shell nanoparticles are formed, but also the separate formation of Pd nanoparticles as well. > The Pt cores without the morphological changes are protected by the Pd-shell overgrowths. > There are the co-existence of the layer-by-layer and island-on-wetting-layer growth modes of the Pd shells and the latter becomes the favorable overgrowth in the formation of core-shell structures. - Abstract: In the present research, Pt-Pd core-shell nanoparticles based on the as-prepared and defined Pt-seed cores with well-controlled size and morphology were synthesized. Their characterizations were investigated by using UV-vis spectroscopy, transmission electron microscopy (TEM), and high resolution (HR)TEM measurements. The high resolution elemental mappings were performed in the operation of high angle annular dark field (HAADF) in conjunction with scanning (S)TEM mode and X-ray energy dispersive spectroscopy (XEDS). It is found that not only the Pt-Pd core-shell nanoparticles were formed, but also the nucleation, growth, and the separate formation of single Pd nanoparticles as well. Interestingly, the as-prepared Pt cores without the morphological changes were protected by the overgrowths of the Pd shells during the successive reduction of sodium tetrachloropalladate (II) hydrate. There were the co-existence of the Frank-van der Merwe (FM) layer-by-layer and Stranski-Krastanov (SK) island-on-wetting-layer growth modes of the Pd shells on the as-prepared Pt cores. It is predicted that the SK growth became the favorable growth mode in the formation of the Pd shells in the formation Pt-Pd core-shell nanoparticles.

  2. Electrochemical promotion of catalysis over Pd nanoparticles for CO2 reduction.

    Science.gov (United States)

    Cai, Fan; Gao, Dunfeng; Zhou, Hu; Wang, Guoxiong; He, Ting; Gong, Huimin; Miao, Shu; Yang, Fan; Wang, Jianguo; Bao, Xinhe

    2017-04-01

    Electrochemical promotion of catalysis (EPOC) has been shown to accelerate the rate of many heterogeneous catalytic reactions; however, it has rarely been reported in low-temperature aqueous electrochemical reactions. Herein, we report a significant EPOC effect for the CO2 reduction to generate formate over Pd nanoparticles (NPs) in a 1 M KHCO3 aqueous solution. By applying a negative potential over differently-sized Pd NPs, the rate of formate production is greatly improved as compared to that at an open-circuit voltage, with a rate enhancement ratio ranging from 10 to 143. The thermocatalytic and electrocatalytic reduction of CO2 compete with each other and are promoted by the applied negative potential and H2 in the feeds, respectively. Inspired by the EPOC effect, a composite electrode containing Pd/C and Pt/C catalysts on different sides of a carbon paper was constructed for catalyzing the CO2 reduction without adding H2 to the feeds. Water electrolysis over Pt NPs generates H2, which then effectively promotes formate production over Pd NPs.

  3. Green and Facile Synthesis of Pd-Pt Alloy Nanoparticles by Laser Irradiation of Aqueous Solution.

    Science.gov (United States)

    Nakamura, Takahiro; Sato, Shunichi

    2015-01-01

    Solid-solution palladium-platinum (Pd-Pt) alloy nanoparticles (NPs) with fully tunable compositions were directly fabricated through high-intensity laser irradiation of an aqueous solution of palladium and platinum ions without using any reducing agents or thermal processes. Transmission electron microscopy (TEM) observations showed that nanometer-sized particles were fabricated by laser irradiation of mixed aqueous solutions of palladium and platinum ions with different feeding ratios. The crystalline nature of the NPs was precisely characterized by X-ray diffraction (XRD). Despite the fact that, for the bulk systems, a pair of XRD peak was detected between the palladium and platinum peaks because of the large miscibility gap in the Pd-Pt binary phase diagram, only a single XRD peak was seen for the Pd-Pt NPs fabricated in the present study. Moreover, the peak position shifted from that of pure palladium towards platinum with increasing fraction of platinum ions in solution. Consequently, the interplanar spacings of the alloy NPs agreed well with the estimated values obtained from Vegard's law. These observations strongly indicate the formation of solid-solution Pd-Pt alloy NPs with fully tunable compositions. This technique is not only a "green" (environmentally-friendly) and facile process, but is also widely applicable to other binary and ternary systems.

  4. Pd Nanoparticles and MOFs Synergistically Hybridized Halloysite Nanotubes for Hydrogen Storage

    Science.gov (United States)

    Jin, Jiao; Ouyang, Jing; Yang, Huaming

    2017-03-01

    Natural halloysite nanotubes (HNTs) were hybridized with metal-organic frameworks (MOFs) to prepare novel composites. MOFs were transformed into carbon by carbonization calcination, and palladium (Pd) nanoparticles were introduced to build an emerging ternary compound system for hydrogen adsorption. The hydrogen adsorption capacities of HNT-MOF composites were 0.23 and 0.24 wt%, while those of carbonized products were 0.24 and 0.27 wt% at 25 °C and 2.65 MPa, respectively. Al-based samples showed higher hydrogen adsorption capacities than Zn-based samples on account of different selectivity between metal and hydrogen and approximate porous characteristics. More pore structures are generated by the carbonization reaction from metal-organic frameworks into carbon; high specific surface area, uniform pore size, and large pore volume benefited the hydrogen adsorption ability of composites. Moreover, it was also possible to promote hydrogen adsorption capacity by incorporating Pd. The hydrogen adsorption capacity of ternary compound, Pd-C-H3-MOFs(Al), reached 0.32 wt% at 25 °C and 2.65 MPa. Dissociation was assumed to take place on the Pd particles, then atomic and molecule hydrogen spilled over to the structure of carboxylated HNTs, MOFs, and the carbon products for enhancing the hydrogen adsorption capacity.

  5. Spatial scanning spectroelectrochemistry. Study of the electrodeposition of Pd nanoparticles at the liquid/liquid interface.

    Science.gov (United States)

    Izquierdo, Daniel; Martinez, Alberto; Heras, Aranzazu; Lopez-Palacios, Jesus; Ruiz, Virginia; Dryfe, Robert A W; Colina, Alvaro

    2012-07-03

    Spatial scanning spectroelectrochemistry is a new analytical technique that provides spectral information at different distances from an electrified liquid/liquid interface where an electrochemical process takes place. As a proof of concept, we have studied two different electrochemical processes at the electrified liquid/liquid interface: (1) Ru(bpy)(3)(2+) transfer through the water/1,2-dichloroethane interface and (2) electrodeposition of Pd nanoparticles at the water/1,2-dichloroethane interface. The instrumental setup developed consists of a movable slit for the light beam to sample at well-defined positions on both sides of the interface, providing important information about the chemical process occurring. If the slit is scanned at different distances from the interface during an electrochemical experiment, a complete picture of the reactions and equilibria in the diffusion layer can be obtained. For example, in the case of the Ru(bpy)(3)(2+), the experiments show clearly how the complex is transferred from one phase to the other. In the case of electrosynthesis of Pd nanoparticles, it is demonstrated that nanoparticles are not only deposited at the interface but diffuse to the aqueous bulk solution. These in situ observations were confirmed by ex situ experiments using transmission electron microscopy.

  6. Size-tunable and monodisperse Tm³⁺/Gd³⁺-doped hexagonal NaYbF₄ nanoparticles with engineered efficient near infrared-to-near infrared upconversion for in vivo imaging.

    Science.gov (United States)

    Damasco, Jossana A; Chen, Guanying; Shao, Wei; Ågren, Hans; Huang, Haoyuan; Song, Wentao; Lovell, Jonathan F; Prasad, Paras N

    2014-08-27

    Hexagonal NaYbF4:Tm(3+) upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm(3+) nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd(3+)) can convert NaYbF4:Tm(3+) 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm(3+) 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ∼2 nm on the ∼22 nm core of hexagonal NaYbF4:Gd(3+) 30%/Tm(3+) 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline.

  7. Synthesis of highly dispersed Pd nanoparticles supported on multi-walled carbon nanotubes and their excellent catalytic performance for oxidation of benzyl alcohol

    NARCIS (Netherlands)

    Shinde, V.M.; Skupien, E.; Makkee, M.

    2015-01-01

    Narrow sized and highly homogeneous dispersed Pd nanoparticles have been synthesized on nitric acid-functionalized multi-walled carbon nanotubes (CNTs) without a capping agent. The TEM images show that the extremely small Pd nanoparticles with an average size of about 1.5 nm were homogeneously dispe

  8. Mixed-PtPd-shell PtPdCu nanoparticle nanotubes templated from copper nanowires as efficient and highly durable electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hui-Hui; Cui, Chun-Hua; Zhao, Shuo; Yao, Hong-Bin; Gao, Min-Rui; Fan, Feng-Jia; Yu, Shu-Hong [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026 (China); Div. of Nanomaterials and Chemistry, Heifei National Lab. for Physical, Sciences at Microscale (China)

    2012-10-15

    The controlled synthesis of mixed-PtPd-shell PtPdCu-alloy nanoparticle nanotubes (ANNTs) is demonstrated by galvanic displacement with partially sacrificial copper-nanowire templates, and following the electrochemical leaching of the non-noble metal Cu in the acidic electrolyte. These core-shell catalysts significantly reduce the amount of expensive Pt and highly improve the electrocatalytic activity and durability through their modified electronic structure, atomic distribution, and 1D structure property. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

    CSIR Research Space (South Africa)

    Ramulifho, T

    2012-01-01

    Full Text Available M. Modibedi, Charl J. Jafta, Mkhulu K. Mathe PII: S0013-4686(11)01623-9 DOI: doi:10.1016/j.electacta.2011.10.071 Reference: EA 17813 To appear in: Electrochimica Acta Received date: 25-6-2011 Revised date: 21-10-2011 Accepted date: 23...-10-2011 Please cite this article as: T. Ramulifho, K.I. Ozoemena, R.M. Modibedi, C.J. Jafta, M.K. Mathe, Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts...

  10. Electrocatalytic Oxidation of Formic Acid in an Alkaline Solution with Graphene-Oxide- Supported Ag and Pd Alloy Nanoparticles.

    Science.gov (United States)

    Han, Hyoung Soon; Yun, Mira; Jeong, Haesang; Jeon, Seungwon

    2015-08-01

    The electrocatalytic activities of metal-decorated graphene oxide (GO) catalysts were investigated. Electrochemically reduced GO-S-(CH2)4-S-Pd [ERGO-S-(CH2)4-S-Pd] and GO-S-(CH2)4-S-PdAg alloy [ERGO-S-(CH2)4-S-PdAg] were obtained through the electrochemical reduction of GO-S-(CH2)4-S-Pd and GO-S-(CH2)4-S-PdAg in a pH 5 PBS solution. It was demonstrated that the application of ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg used in a modified GCE improves the electrocatalytic oxidation of formic acid. The addition of an Ag nanoparticle with a carbon chain-Pd in the electrode provides an electrode with very interesting properties for the electrocatalytic oxidation of formic acid. The ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg were characterized via X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg can be employed for the electrocatalytic oxidation of formic acid. The electrochemical behaviors of this electrode were investigated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS).

  11. Electrocatalytic synthesis of hydrogen peroxide on Au-Pd nanoparticles: From fundamentals to continuous production

    Science.gov (United States)

    Pizzutilo, Enrico; Kasian, Olga; Choi, Chang Hyuck; Cherevko, Serhiy; Hutchings, Graham J.; Mayrhofer, Karl J. J.; Freakley, Simon J.

    2017-09-01

    The electrochemical synthesis of hydrogen peroxide (H2O2) represents a promising alternative to the anthraquinone process, as it combines on-site chemical and electrical production. The design of selective electrocatalysts is challenging and is commonly based on the alloying of elements to generate a synergistic effect and increase activity. In the present work, we report the electrochemical activity of Au-Pd nanoparticles immobilized directly onto an electrode as a model to study H2O2 electrochemical synthesis from fundamentals to continuous production. The impact of composition on the oxygen reduction reaction (ORR), the selectivity, as well as the peroxide reduction and oxidation reactions (PROR) are studied.

  12. Third-order optical nonlinearities of PVP/Pd nanohybrids

    Science.gov (United States)

    Papagiannouli, I.; Potamianos, D.; Krasia-Christoforou, T.; Couris, S.

    2017-10-01

    Pd nanoparticles stabilized by polyvinylpyrrolidone were synthesized following mild reduction of palladium ion complexes. Their morphology and optical properties were characterized using Transmission Electron Microscopy, Dynamic Light Scattering and UV-Vis absorption spectroscopy to confirm the existence of monodispersed, low-dimensional single nanoparticles. Furthermore, their third-order nonlinear optical properties were investigated by means of the Z-scan technique, using 35 ps and 4 ns laser pulses, both in the visible (532 nm) and in the infrared (1064 nm). These results denote that the surface plasmon resonance is not significantly contributing to the nonlinear optical response of Pd nanoparticles. In contrast, a two photon absorption process was found to contribute to the observed response. The present results are discussed and compared with previous literature findings.

  13. Ni-Supported Pd Nanoparticles with Ca Promoter: A New Catalyst for Low-Temperature Ammonia Cracking

    Science.gov (United States)

    Polanski, Jaroslaw; Bartczak, Piotr; Ambrozkiewicz, Weronika; Sitko, Rafal; Siudyga, Tomasz; Mianowski, Andrzej; Szade, Jacek; Balin, Katarzyna; Lelątko, Józef

    2015-01-01

    In this paper we report a new nanometallic, self-activating catalyst, namely, Ni-supported Pd nanoparticles (PdNPs/Ni) for low temperature ammonia cracking, which was prepared using a novel approach involving the transfer of nanoparticles from the intermediate carrier, i.e. nano-spherical SiO2, to the target carrier technical grade Ni (t-Ni) or high purity Ni (p-Ni) grains. The method that was developed allows a uniform nanoparticle size distribution (4,4±0.8 nm) to be obtained. Unexpectedly, the t-Ni-supported Pd NPs, which seemed to have a surface Ca impurity, appeared to be more active than the Ca-free (p-Ni) system. A comparison of the novel PdNPs/Ni catalyst with these reported in the literature clearly indicates the much better hydrogen productivity of the new system, which seems to be a highly efficient, flexible and durable catalyst for gas-phase heterogeneous ammonia cracking in which the TOF reaches a value of 2615 mmolH2/gPd min (10,570 molNH3/molPd(NP) h) at 600°C under a flow of 12 dm3/h (t-Ni). PMID:26308929

  14. Mixed Phytochemicals Mediated Synthesis of Multifunctional Ag-Au-Pd Nanoparticles for Glucose Oxidation and Antimicrobial Applications.

    Science.gov (United States)

    Rao, K Jagajjanani; Paria, Santanu

    2015-07-01

    The growing awareness toward the environment is increasing commercial demand for nanoparticles by green route syntheses. In this study, alloy-like Ag-Au-Pd trimetallic nanoparticles have been prepared by two plants extracts Aegle marmelos leaf (LE) and Syzygium aromaticum bud extracts (CE). Compositionally different Ag-Au-Pd nanoparticles with an atomic ratio of 5.26:2.16:1.0 (by LE) and 11.36:13.14:1.0 (by LE + CE) of Ag:Au:Pd were easily synthesized within 10 min at ambient conditions by changing the composition of phytochemicals. The average diameters of the nanoparticles by LE and LE + CE are ∼8 and ∼11 nm. The catalytic activity of the trimetallic nanoparticles was studied, and they were found to be efficient catalysts for the glucose oxidation process. The prepared nanoparticles also exhibited efficient antibacterial activity against a model Gram-negative bacteria Escherichia coli. The catalytic and antimicrobial properties of these readymade trimetallic nanoparticles have high possibility to be utilized in diverse fields of applications such as health care to environmental.

  15. Understanding the atomic-level process of CO-adsorption-driven surface segregation of Pd in (AuPd)147 bimetallic nanoparticles.

    Science.gov (United States)

    An, Hyesung; Ha, Hyunwoo; Yoo, Mi; Kim, Hyun You

    2017-08-24

    When the elements that compose bimetallic catalysts interact asymmetrically with reaction feedstock, the surface concentration of the bimetallic catalysts and the morphology of the reaction center evolve dynamically as a function of environmental factors such as the partial pressure of the triggering molecule. Relevant experimental and theoretical findings of the dynamic structural evolution of bimetallic catalysts under the reaction conditions are emerging, thus enabling the design of more consistent, reliable, and efficient bimetallic catalysts. In an initial attempt to provide an atomic-level understanding of the adsorption-induced structural evolution of bimetallic nanoparticles (NPs) under CO oxidation conditions, we used density functional theory to study the details of CO-adsorption-driven Pd surface segregation in (AuPd)147 bimetallic NPs. The strong CO affinity of Pd provides a driving force for Pd surface segregation. We found that the vertex site of the NP becomes a gateway for the initial Pd-Au swapping and the subsequent formation of an internal vacancy. This self-generated internal vacancy easily diffuses inside the NP and activates Pd-Au swapping pathways in the (100) NP facet. Our results reveal how the surface and internal concentrations of bimetallic NPs respond immediately to changes in the reaction conditions. Our findings should aid in the rational design of highly active and versatile bimetallic catalysts by considering the environmental factors that systematically affect the structure of bimetallic catalysts under the reaction conditions.

  16. Functional clay supported bimetallic nZVI/Pd nanoparticles used for removal of methyl orange from aqueous solution.

    Science.gov (United States)

    Wang, Ting; Su, Jin; Jin, Xiaoying; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2013-11-15

    Bentonite supported Fe/Pd nanoparticles (B/nZVI/Pd) were synthesized as composites that exhibit functionalities assisting in the removal of methyl orange (MO) from aqueous solution. The results showed that 91.87% of MO was removed using B/nZVI/Pd, while only 85% and 1.41% of MO were removed using nZVI/Pd and bentonite after 10 min, respectively. The new findings include that the presence of bentonite decreased the aggregation of nZVI/Pd and nZVI in the composite played its role as a reductant, while Pd(0) acted as the catalyst to enhance the degradation of MO, which were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis analysis and the batch experiments. The increase in B/nZVI/Pd loading led to greater removal efficiency, while decolorization efficiency declined in the presence of anions such as nitrate, sulfite and carbonate, especially nitrate, which decreased the apparent rate constant k(obs) almost 17.06-fold. The kinetics study indicated that the degradation of MO fitted well to the pseudo-first-order model, where the k(obs) was 0.0721 min(-1). Finally, the reactivity of aged B/nZVI/Pd was investigated, and the application of B/nZVI/Pd in wastewater indicated a removal efficiency higher than 93.75%. This provided a new environmental pollution management option for dyes-contaminated sites.

  17. Synthesis and characterization of metallic Pd embedded TiO2 nanoparticles by reverse micelle and sol-gel processing

    Institute of Scientific and Technical Information of China (English)

    Jeoung-Ho JIN; Min-Cheol CHU; Seong-Jai CHO; Dong-Sik BAE

    2009-01-01

    Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of titanium tetra-isopropoxide within the micro-emulsion. The spherical equivalent size for the Pd clusters formed in TiO2 matrix was estimated to be around (3±1) nm. The presence of Pd in the matrix was demonstrated by EDS spectroscopy. The effects of synthesis parameters, such as the concentration of Pd solution, the molar ratio of water to TIP, and the molar ratio of water to surfactant, were discussed.%This research was financially supported by the Ministry of Education, Science Technology(MEST) and Korea Industrial Technology Foundation(KOTEF) through the Human Resource Training Project for Regional Innovation.

  18. Effects of palladium on the optical and hydrogen sensing characteristics of Pd-doped ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    Anh-Thu Thi Do

    2014-08-01

    Full Text Available The effect of palladium doping of zinc oxide nanoparticles on the photoluminescence (PL properties and hydrogen sensing characteristics of gas sensors is investigated. The PL intensity shows that the carrier dynamics coincides with the buildup of the Pd-related green emission. The comparison between the deep level emission and the gas sensing response characteristics allows us to suggest that the dissociation of hydrogen takes place at PdZn-vacancies ([Pd 2+(4d9]. The design of this sensor allows for a continuous monitoring in the range of 0–100% LEL H2 concentration with high sensitivity and selectivity.

  19. Facile synthesis of Pt–Pd bimetallic nanoparticles by plasma discharge in liquid and their electrocatalytic activity toward methanol oxidation in alkaline media

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung-Min; Lee, Yu-Jin [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Kim, Jung-Wan [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Division of Bioengineering, InCheon National University, Incheon, 406-772 (Korea, Republic of); Lee, Sang-Yul, E-mail: sylee@kau.ac.kr [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of)

    2014-12-01

    The Pt–Pd bimetallic nanoparticles for direct methanol fuel cell applications were successfully prepared by plasma discharge in aqueous solution. The obtained nanoparticles were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. During plasma discharge, the nanoparticles were produced from the erosion of electrodes. It was noted that the erosion amount of anode electrodes was much greater than that of cathode electrodes so that the composition of Pt–Pd bimetallic nanoparticles could be changed with different power types and electrode configurations. Diffraction patterns fitted from Gaussian devolution indicated that the crystalline phase of Pt{sub 40}Pd{sub 60} products was composed of pure Pt, pure Pd and Pt–Pd alloy phases. The morphology of synthesized nanoparticles showed that nanowires connected with quasi-spherical nanoparticles with 2–3 nm in diameter were observed and large spherical particles with > 50 nm in diameter were also detected intermittently. The cyclic voltammetric measurement and continuous potential scan demonstrated that Pt{sub 40}Pd{sub 60} had much higher catalytic activity and better resistance to CO poisoning than Pt{sub 94}Pd{sub 6} and Pt{sub 1}Pd{sub 99} for methanol oxidation. These results indicate that the Pt{sub 40}Pd{sub 60} could be an excellent candidate for the direct methanol fuel cell applications.

  20. Engineered monodisperse mesoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, R.S.; Small, J.H.; Lagasse, R.R.; Schroeder, J.L.; Jamison, G.M.

    1997-08-01

    Porous materials technology has developed products with a wide variety of pore sizes ranging from 1 angstrom to 100`s of microns and beyond. Beyond 15{angstrom} it becomes difficult to obtain well ordered, monodisperse pores. In this report the authors describe efforts in making novel porous material having monodisperse, controllable pore sizes spanning the mesoporous range (20--500 {angstrom}). They set forth to achieve this by using unique properties associated with block copolymers--two linear homopolymers attached at their ends. Block copolymers phase separate into monodisperse mesophases. They desired to selectively remove one of the phases and leave the other behind, giving the uniform monodisperse pores. To try to achieve this the authors used ring-opening metathesis polymerization to make the block copolymers. They synthesized a wide variety of monomers and surveyed their polymers by TGA, with the idea that one phase could be made thermally labile while the other phase would be thermally stable. In the precipitated and sol-gel processed materials, they determined by porosimetry measurements that micropores, mesopores, and macropores were created. In the film processed sample there was not much porosity present. They moved to a new system that required much lower thermal treatments to thermally remove over 90% of the labile phase. Film casting followed by thermal treatment and solvent extraction produced the desired monodisperse materials (based solely on SEM results). Modeling using Density Functional Theory was also incorporated into this project. The modeling was able to predict accurately the domain size and spacing vs. molecular weight for a model system, as well as accurate interfacial thicknesses.

  1. Mesoporous silica nanoparticle supported PdIr bimetal catalyst for selective hydrogenation, and the significant promotional effect of Ir

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hui; Huang, Chao; Yang, Fan [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Du, Li [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China)

    2015-12-01

    Graphical abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction caused by the addition of Ir. - Highlights: • Mesoporous nanoparticles were synthesized and used as support for metal catalyst. • PdIr bimetallic catalyst exhibited significantly improved hydrogenation activity. • The strong promotion of Ir was recognized firstly and investigated intensively. • PdIr exhibits 18 times higher activity than Pd to the hydrogenation of nitrobenzene. - Abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction

  2. Correlation between palladium chemical state and photocatalytic performance of TiO{sub 2}–Pd based nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ming-Chung, E-mail: mingchungwu@mail.cgu.edu.tw [Department of Chemical and Materials Engineering, College of Engineering, Chang Gung University, Taoyuan 33302, Taiwan (China); Chang, I-Chun; Huang, Wei-Kang [Department of Chemical and Materials Engineering, College of Engineering, Chang Gung University, Taoyuan 33302, Taiwan (China); Tu, Yu-Chieh; Hsu, Che-Pu; Su, Wei-Fang [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2014-11-03

    Photocatalytic processes can be used to illustrate both solar energy conversion and environmental friendly applications. In this study, we synthesize several titanium dioxide–palladium (TiO{sub 2}–Pd) based catalysts by wet impregnation method plus hydrogen-thermal reduction process in order to develop high-effective photocatalysts that can be easily produced even in industrial quantities. Moreover, we examine the effects of hydrogen-thermal reduction process on the photocatalytic performance of TiO{sub 2}–Pd based catalysts. From X-ray photoelectron spectroscopy analysis, increasing the hydrogen reduction process time results in the decreasing of palladium ion (Pd{sup 2+}) and palladium oxide (PdO), but it causes the increasing of palladium (Pd) metal. The hydrogen reduction process is helpful for the preparation of TiO{sub 2}–Pd based catalysts with high photocatalytic decomposition of organic dyes (the apparent reaction rate constant ∼ 0.124 min{sup −1} under solar simulator irradiation) and excellent photocatalytic hydrogen production rate (∼ 26,000 μmol/g·h under UV-B irradiation). The TiO{sub 2}–Pd based catalysts prepared in this study exhibit high photocatalytic performance. They are also industrially relevant especially when the low cost of Pd metal is taken into consideration. - Highlights: • Increasing the hydrogen reduction time causes the decreasing of Pd{sup 2+} ion and PdO. • Increasing the hydrogen reduction time results in the increasing of Pd metal. • The optimal TiO{sub 2}–Pd240 nanoparticle exhibits the highest photocatalytic activity.

  3. Pt-Pd bimetallic nanoparticles on MWCNTs: catalyst for hydrogen peroxide electrosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Felix-Navarro, R. M., E-mail: moi6salazar@hotmail.com; Beltran-Gastelum, M.; Salazar-Gastelum, M. I.; Silva-Carrillo, C.; Reynoso-Soto, E. A.; Perez-Sicairos, S.; Lin, S. W. [Centro de Graduados e Investigacion, Instituto Tecnologico de Tijuana (Mexico); Paraguay-Delgado, F. [Centro de Investigacion en Materiales Avanzados (Mexico); Alonso-Nunez, G. [Centro de Nanociencias y Nanotecnologia (Mexico)

    2013-08-15

    Bimetallic nanoparticles of Pt-Pd were deposited by the microemulsion method on a multiwall carbon nanotube (MWCNTs) to obtain a Pt-Pd/MWCNTs for electrocatalytic reduction of O{sub 2} to H{sub 2}O{sub 2}. The activity and selectivity of the catalyst was determined qualitatively by the rotating disk electrode method in acidic medium. The catalyst was spray-coated onto a reticulated vitreous carbon substrate and quantitatively was tested in bulk electrolysis for 20 min under potentiostatic conditions (0.5 V vs Ag/AgCl) in a 0.5 M H{sub 2}SO{sub 4} electrolyte using dissolved O{sub 2}. The bulk electrolysis experiments show that the Pt-Pd/MWCNTs catalyst is more efficient for H{sub 2}O{sub 2} electrogeneration than a MWCNTs catalyst. Nitrobenzene degradation by electrogenerated H{sub 2}O{sub 2} alone and Electro-Fenton process were also tested. Our results show that both processes decompose nitrobenzene, but the Electro-Fenton process does it more efficiently. The prepared nanoparticulated catalyst shows a great potential in environmental applications.

  4. Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles.

    Science.gov (United States)

    Dilonardo, Elena; Penza, Michele; Alvisi, Marco; Rossi, Riccardo; Cassano, Gennaro; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa; Cioffi, Nicola

    2017-01-01

    Multiwalled carbon nanotube (MWCNT)-based chemiresistors were electrochemically decorated with Au and Pd nanoparticles (NPs), resulting in an improvement in the detection of gaseous pollutants as compared to sensors based on pristine MWCNTs. Electrophoresis was used to decorate MWCNTs with preformed Au or Pd NPs, thus preserving their nanometer-sized dimensions and allowing the metal content to be tuned by simply varying the deposition time. The sensing response of unmodified and metal-decorated MWCNTs was evaluated towards different gaseous pollutants (e.g., NO2, H2S, NH3 and C4H10) at a wide range of concentrations in the operating temperature range of 45-200 °C. The gas sensing results were related to the presence, type and loading of metal NPs used in the MWCNT functionalization. Compared to pristine MWCNTs, metal-decorated MWCNTs revealed a higher gas sensitivity, a faster response, a better stability, reversibility and repeatability, and a low detection limit, where all of these sensing properties were controlled by the type and loading of the deposited metal catalytic NPs. Specifically, in the NO2 gas sensing experiments, MWCNTs decorated with the lowest Au content revealed the highest sensitivity at 150 °C, while MWCNTs with the highest Pd loading showed the highest sensitivity when operated at 100 °C. Finally, considering the reported gas sensing results, sensing mechanisms have been proposed, correlating the chemical composition and gas sensing responses.

  5. Poly(sodium-p-styrenesulfonate) assisted microwave synthesis of ordered mesoporous carbon supported Pd nanoparticles for formic acid electro-oxidation

    Science.gov (United States)

    Sun, Zhi-Peng; Zhang, Xiao-Gang; Tong, Hao; Xue, Rui-Li; Liang, Yan-Yu; Li, Hu-Lin

    2009-10-01

    Pd nanoparticles highly dispersed onto the surface of ordered mesoporous carbons (OMCs) were synthesized successfully by poly(sodium-p-styrenesulfonate) (PSS) assisted microwave synthesis. Here, PSS served as a bifunctional molecule both for solubilizing and dispersing OMCs into aqueous solution and for jointing Pd 2+ to facilitate the subsequent uniform formation of Pd nanoparticles on their surfaces. The effects of PSS on structural and electrochemical properties of Pd/OMCs were investigated. It was found that the addition of PSS facilitated Pd nanoparticles to disperse on the carbon surface. Electrochemical properties showed that Pd catalysts prepared with addition of PSS displayed better electrochemical activity and stability for formic acid electro-oxidation than those without PSS.

  6. Formic acid electro-oxidation on carbon supported Pd{sub x}Pt{sub 1-x} (0 {>=} x {>=} 1) nanoparticles synthesized via modified polyol method

    Energy Technology Data Exchange (ETDEWEB)

    Baranova, Elena A., E-mail: elena.baranova@uottawa.c [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur St., Ottawa, ON, K1N 6N5 (Canada); Miles, Neil [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur St., Ottawa, ON, K1N 6N5 (Canada); Mercier, Patrick H.J.; Le Page, Yvon; Patarachao, Bussaraporn [Institute for Chemical Process and Environmental Technology, National Research Council Canada, 1200 Montreal Rd., Ottawa, ON, K1A 0R6 (Canada)

    2010-11-30

    Carbon supported nanoparticle catalysts of Pd{sub x}Pt{sub 1-x} (0 {>=} x {>=} 1) were synthesized using a modified polyol method and poly(N-vinyl-2-pyrrolidone) (PVP) as a stabilizer. Resulting nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperommetry (CA) study for formic acid electro-oxidation. Surface composition of the synthesized nanoparticles found from XPS revealed the Pt surface segregation even for the Pd-rich compositions. It is suggested that the surface segregation behavior in PdPt nanoparticles supported on carbon may be influenced, in addition to the difference in Pd and Pt surface energies, by particle size and particle interaction with the support. According to CA, the carbon supported Pd nanoparticles show the highest initial activity towards formic acid electro-oxidation at the potential of 0.3 V (RHE), due to the promotion of the direct dehydrogenation mechanism. However its stability is quite poor resulting in the fast deactivation of the Pd surface. Addition of Pt considerably improves the steady-state activity of Pd in 12 h CA experiment. CA measurements show that the most active catalyst is Pd{sub 0.5}Pt{sub 0.5} of 4 nm size, which displays narrow size distribution and Pd to Pt surface atomic ratio of 27-73.

  7. Solid solution alloy nanoparticles of immiscible Pd and Ru elements neighboring on Rh: changeover of the thermodynamic behavior for hydrogen storage and enhanced CO-oxidizing ability.

    Science.gov (United States)

    Kusada, Kohei; Kobayashi, Hirokazu; Ikeda, Ryuichi; Kubota, Yoshiki; Takata, Masaki; Toh, Shoichi; Yamamoto, Tomokazu; Matsumura, Syo; Sumi, Naoya; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kitagawa, Hiroshi

    2014-02-05

    Pd(x)Ru(1-x) solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of Pd(x)Ru(1-x) changes from fcc to hcp with increasing Ru content. The structures of Pd(x)Ru(1-x) nanoparticles in the Pd composition range of 30-70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the Pd(x)Ru(1-x) nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared Pd(x)Ru(1-x) nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd.

  8. Photochemical Synthesis of Au@Pd Core-Shell Nanoparticles for Methanol Oxidation Reaction: the Promotional Effect of the Au Core

    Directory of Open Access Journals (Sweden)

    Dong Yingnan

    2016-01-01

    Full Text Available A novel method for synthesizing Au@Pd core-shell nanoparticles was proposed based on photochemistry. By irradiating the mixture of Au (III and Pd (II ions using ultraviolet light, the Au@Pd core-shell nanoparticles were prepared. The size of the nanoparticles and the thickness of the Pd shell could be efficiently adjusted by changing the molar ratio of Au (III to Pd (II ion. In this way, nanoparticles with diameter in the range of 5.6~4.6 nm were obtained. The core-shell structure of the synthesized nanoparticles was showed by the characterization using UV-Vis, TEM/HR-TEM and XPS. The paper investigated the electrocatalysis performance of Au@Pd nanoparticles in the methanol catalytic oxidation reaction, as well as the electron donating effect of Au core to Pd shell and the promotion of this effect on the catalytic activity of Pd shell. The experimental results provided reference for the development of non-platinum catalysts of low-temperature fuel cell anode.

  9. Effect of Pd ion doping in the band gap of SnO{sub 2} nanoparticles: structural and optical studies

    Energy Technology Data Exchange (ETDEWEB)

    Nandan, Brajesh; Venugopal, B. [Pondicherry University, Centre for Nanoscience and Technology (India); Amirthapandian, S.; Panigrahi, B. K. [Indira Gandhi Centre for Atomic Research, Ion Beam and Computer Simulation Section, Materials Science Group (India); Thangadurai, P., E-mail: thangadurai.p@gmail.com [Pondicherry University, Centre for Nanoscience and Technology (India)

    2013-10-15

    Pd ion doping has influenced the band gap of SnO{sub 2} nanoparticles. Undoped and Pd ion-doped SnO{sub 2} nanoparticles were synthesized by chemical co-precipitation method. A tetragonal phase of SnO{sub 2} with a grain size range of 7-13 nm was obtained (studied by X-ray diffraction and transmission electron microscopy). A decreasing trend in the particle size with increasing doping concentration was observed. The presence of Pd in doped SnO{sub 2} was confirmed by chemical analysis carried out by energy-dispersive spectroscopy in the transmission electron microscope. Diffuse reflectance spectra showed a blue shift in absorption with increasing palladium concentration. Band gap of SnO{sub 2} nanoparticles was estimated from the diffuse reflectance spectra using Kubelka-Munk function and it was increasing with the increase of Pd ion concentration from 3.73 to 4.21 eV. The variation in band gap is attributed predominantly to the lattice strain and particle size. All the samples showed a broad photoluminescence emission centered at 375 nm when excited at 270 nm. A systematic study on the structural and optical properties of SnO{sub 2} nanoparticles is presented.

  10. Dendrimer-encapsulated Pd nanoparticles as catalysts for C-C cross-couplings in flow microreactors

    NARCIS (Netherlands)

    Ricciardi, R.; Huskens, Jurriaan; Verboom, Willem

    2015-01-01

    The inner walls of glass microreactors were functionalized with dendrimer-encapsulated Pd nanoparticles. The catalysts were efficient for the Heck–Cassar (copper-free Sonogashira) and Suzuki–Miyaura (SMC) cross-coupling reactions. For the Heck–Cassar reaction between iodobenzene and phenylacetylene,

  11. Triphasic liquid systems: generation and segregation of catalytically active Pd nanoparticles in an ammonium-based catalyst-philic phase.

    Science.gov (United States)

    Perosa, Alvise; Tundo, Pietro; Selva, Maurizio; Canton, Patrizia

    2006-11-21

    A triphasic liquid system fabricated from isooctane, aqueous base, and trioctylmethylammonium chloride/decanol promoted the formation of Pd-nanoparticles in the size range of 2-4 nm which remained immobilised in the onium phase, catalysed organic reactions, and could be recycled.

  12. Dendrimer-encapsulated Pd nanoparticles as catalysts for C-C cross-couplings in flow microreactors

    NARCIS (Netherlands)

    Ricciardi, R.; Huskens, J.; Verboom, W.

    2015-01-01

    The inner walls of glass microreactors were functionalized with dendrimer-encapsulated Pd nanoparticles. The catalysts were efficient for the Heck–Cassar (copper-free Sonogashira) and Suzuki–Miyaura (SMC) cross-coupling reactions. For the Heck–Cassar reaction between iodobenzene and phenylacetylene,

  13. Green Synthesis of Fe and Fe/Pd Bimetallic Nanoparticles in Membranes for Reductive Degradation of Chlorinated Organics

    Science.gov (United States)

    Membranes containing reactive nanoparticles (Fe and Fe/Pd) immobilized in a polymer film (polyacrylic acid, PAA-coated polyvinylidene fluoride, PVDF membrane) are prepared by a new method. In the present work a biodegradable, non-toxic -“green” reducing agent, green tea extract ...

  14. Preparation of Au-Pd bimetallic nanoparticles in porous germania nanospheres: A study of their morphology and catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Regan, Maureen R. [Department of Chemistry, Fordham University, 441, East Fordham Road, Bronx, NY 10458 (United States); Banerjee, Ipsita A. [Department of Chemistry, Fordham University, 441, East Fordham Road, Bronx, NY 10458 (United States)]. E-mail: banerjee@fordham.edu

    2006-03-15

    Size controlled Au-Pd bimetallic nanoparticles with an average size of 7-10 nm were grown in porous germania nanospheres. The properties of the resulting nanocomposites were characterized by electron microscopy, energy dispersive spectroscopy, and ultraviolet-visible spectroscopy. The catalytic activity of the nanocomposites was also examined by studying the degradation of p-nitroaniline.

  15. Shape-controlled synthesis of Au@Pd core-shell nanoparticles and their corresponding electrochemical properties

    KAUST Repository

    Song, Hyon Min

    2012-01-01

    The shape-controlled synthesis of Au@Pd core-shell nanoparticles (NPs) was successfully achieved through the emulsion phase generated during the phase transfer from organic to aqueous medium. Contrary to conventional epitaxial growth for obtaining core-shell structures, this method does not require high temperatures and does not have shape restrictions. © 2012 The Royal Society of Chemistry.

  16. Amphiphilic hollow porous shell encapsulated Au@Pd bimetal nanoparticles for aerobic oxidation of alcohols in water

    KAUST Repository

    Zou, Houbing

    2015-01-01

    © The Royal Society of Chemistry 2015. This work describes the design, synthesis and analysis of an amphiphilic hollow mesoporous shell encapsulating catalytically active Au@Pd bimetal nanoparticles. The particles exhibited excellent catalytic activity and stability in the aerobic oxidation of primary and secondary alcohols to their corresponding aldehydes or ketones in water when using air as an oxidizing agent under atmospheric pressure.

  17. Preparation of Bimetallic Pd-Co Nanoparticles on Graphene Support for Use as Methanol Tolerant Oxygen Reduction Electrocatalysts

    Directory of Open Access Journals (Sweden)

    R. N. Singh

    2012-12-01

    Full Text Available Graphene-supported (40-x wt% Pd x wt% Co (0≤x≤13.33 alloys/composites have been prepared by a microwave-assisted polyol reduction method and been investigated for their structural and electrocatalytic properties for the oxygen reduction reaction (ORR in 0.5 M H2SO4 at 298 K. The study demonstrated that the bimetallic Pd-Co composite nanoparticles are, in fact, alloy nanoparticles with fcc crystalline structure. Partial substitution of Pd by Co (from 3.64 to 13.33 wt% in 40 wt% Pd/graphene decreases the lattice parameter as well as the crystallite size and increases the apparent catalytic activity, the latter, however, being the greatest with 8 wt% Co. The ORR activity of the active 32 wt% Pd 8wt% Co is found to be considerably low when it was deposited on the support multiwall carbon nanotubes under similar conditions. The rotating disk electrode study indicated that the ORR on 32 wt% Pd 8 wt% Co/GNS in 0.5 M H2SO4 follows approximately the four-electron pathway.

  18. Atomic Layer Deposition of Pd Nanoparticles on TiO₂ Nanotubes for Ethanol Electrooxidation: Synthesis and Electrochemical Properties.

    Science.gov (United States)

    Assaud, Loïc; Brazeau, Nicolas; Barr, Maïssa K S; Hanbücken, Margrit; Ntais, Spyridon; Baranova, Elena A; Santinacci, Lionel

    2015-11-11

    Palladium nanoparticles are grown on TiO2 nanotubes by atomic layer deposition (ALD), and the resulting three-dimensional nanostructured catalysts are studied for ethanol electrooxidation in alkaline media. The morphology, the crystal structure, and the chemical composition of the Pd particles are fully characterized using scanning and transmission electron microscopies, X-ray diffraction, and X-ray photoelectron spectroscopy. The characterization revealed that the deposition proceeds onto the entire surface of the TiO2 nanotubes leading to the formation of well-defined and highly dispersed Pd nanoparticles. The electrooxidation of ethanol on Pd clusters deposited on TiO2 nanotubes shows not only a direct correlation between the catalytic activity and the particle size but also a steep increase of the response due to the enhancement of the metal-support interaction when the crystal structure of the TiO2 nanotubes is modified by annealing at 450 °C in air.

  19. Selective hydrogenation of 2-methyl-3-butyn-2-ol catalyzed by embedded polymer-protected PdZn nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Okhlopkova, Lyudmila B., E-mail: mila65@catalysis.ru; Matus, Ekaterina V.; Prosvirin, Igor P.; Kerzhentsev, Michail A.; Ismagilov, Zinfer R. [Boreskov Institute of Catalysis (Russian Federation)

    2015-12-15

    PdZn/TiO{sub 2} catalysts were synthesized by sol–gel method using a template Pluronic F127. PdZn nanoparticles with the size ranging from 1.7 to 2 nm were prepared by ethylene glycol reduction of ZnCl{sub 2} and Pd(CH{sub 3}COO){sub 2} in the presence of stabilizer and introduced into the matrix by addition into TiO{sub 2} sol, followed by different activation procedures. The structure, particles size, and chemical composition of nanoparticles and catalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy, and energy dispersive spectroscopy. The prepared catalysts have been tested in the selective hydrogenation of 2-methyl-3-butyn-2-ol, and the results have been compared with catalysts prepared by conventional impregnation. The results indicate that bimetallic PdZn nanoparticles-based catalysts show higher selectivity than corresponding monometallic Pd/TiO{sub 2}. Embedded on titania, bimetallic nanoparticles stabilized with polyvinylpyrrolidone exhibit good activity (1.1–1.8 mol MBY/mol Pd/s{sup −1}) and high selectivity to 2-methyl-3-buten-2-ol (81.5–88.9 % at 95 % conversion). The influence of the nature of the stabilizer, the stabilizer/metal molar ratio, and activation conditions on the catalytic behavior of the samples was analyzed. It is shown that the particle size does not significantly affect the catalytic properties in the range of 4.4–6.5 nm. The nature and amount of stabilizer seem to be crucial to prepare efficient catalyst.

  20. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    Science.gov (United States)

    2016-05-23

    synthesized by controlling Tetraethyl orthosilicate (TEOS) and ammonia solution concentration. The composites were used as nanoparticles fillers in...important to synthesize the uniform and monodisperse magnetic nanoparticles. So, we, as a team of this collaboration project, focused on synthesizing ...uniform and monodisperse magnetic nanoparticles. First, we synthesized silica-coated monodisperse iron oxide nanoparticles (≈ 30 nm) sent to

  1. Mg-AI Mixed Oxides Supported Bimetallic Au-Pd Nanoparticles with Superior Catalytic Properties in Aerobic Oxidation of Benzyl Alcohol and Glycerol

    Institute of Scientific and Technical Information of China (English)

    王亮; 张伟; 曾尚景; 苏党生; 孟祥举; 肖丰收

    2012-01-01

    Nano-sized Au and Pd catalysts are favorable for oxidations with molecular oxygen, and the preparation of this kind of nanoparticles with high catalytic activities is strongly desirable. We report a successful synthesis of bimetal- lic Au-Pd nanoparticles with rich edge and comer sites on unique support of Mg-AI mixed oxides (Au-Pd/MAO), which are favorable for producing metal nanoparticles with high degree of coordinative unsaturation of metal atoms The systematic microscopic characterizations confirm the bimetallic Au-Pd nanoparticles are present as Au-Pd alloy The irregular shape of the bimetallic nanoparticles are directly observed in HRTEM images. As we expected, Au-Pd/MAO gives very excellent catalytic performances in the aerobic oxidation of benzyl alcohol and glycerol. For example, Au-Pd/MAO shows very high TOF of 91000 h i at 433 K with molecular oxygen at air pressure in solvent-free oxidation of benzyl alcohol; this catalyst also shows relatively high selectivity for tartronic acid (TA- RAC, 36.6%) at high conversion (98.5%) in aerobic oxidation of glycerol. The superior catalytic properties of Au-Pd/MAO would be potentially important tbr production of fine chemicals.

  2. Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles for C1 to C3 Alcohol Oxidation and Dehydrogenation of Dimethylamine-borane (DMAB).

    Science.gov (United States)

    Erken, Esma; Yildiz, Yunus; Kilbaş, Benan; Sen, Fatih

    2016-06-01

    Highly efficient nearly monodisperse Pt NPs catalyze C1 to C3 alcohol oxidation with very high electrochemical activities and provides one of the highest catalytic activities (TOF = 21.50 h(-1)) in the dehydrogenation of DMAB at room temperature. The exceptional stability towards agglomeration, leaching and CO poisoning for the prepared catalyst allow these particles to be recycled and reused in the catalysis of both DMAB dehydrogenation and C1 to C3 alcohol oxidation. After four subsequent reaction and recovery cycles, catalyst retained ≥ 80% activity towards the complete dehydrogenation of DMAB. The prepared catalyst structures were determined by the X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) respectively.

  3. Monodisperse magnetite (Fe3O4) nanoparticles modified with water soluble polymers for the diagnosis of breast cancer by MRI method

    Science.gov (United States)

    Rezayan, Ali Hossein; Mousavi, Majid; Kheirjou, Somayyeh; Amoabediny, Ghasem; Ardestani, Mehdi Shafiee; Mohammadnejad, Javad

    2016-12-01

    In this study, magnetic nanoparticles (MNPs) were synthesized via co-precipitation method. To enhance the biocompatibility and colloidal stability of the synthesized nanoparticles, they were modified with carboxyl functionalized PEG via dopamine (DPA) linker. Both modified and unmodified Fe3O4 nanoparticles exhibited super paramagnetic behavior (particle size below 20 nm). The saturation magnetization (Ms) of PEGdiacid-modified Fe3O4 was 45 emu/g, which was less than the unmodified Fe3O4 nanoparticles (70 emu/g). This difference indicated that PEGdiacid polymer was immobilized on the surface of Fe3O4 nanoparticles successfully. To evaluate the efficiency of the resulting nanoparticles as contrast agents for magnetic resonance imaging (MRI), different concentration of MNPs and different value of echo time TE were investigated. The results showed that by increasing the concentration of the nanoparticles, transverse relaxation time (T2) decreased, which subsequently resulted in MR signal enhancement. T2-weighted MR images of the different concentration of MNPs in different value of echo time TE indicated that MR signal intensity increased with increase in TE value up to 66 and then remained constant. The cytotoxicity effect of the modified and unmodified nanoparticles was evaluated in three different concentrations (12, 60 and 312 mg l-1) on MDA-MB-231 cancer cells for 24 and 48 h. In both tested time (24 and 48 h) for all three samples, the modified nanoparticles had long life time than unmodified nanoparticles. Cellular uptake of modified MNPs was 80% and reduced to 9% by the unmodified MNPs.

  4. Developing electrochemical sensor for point-of-care diagnostics of oxidative stress marker using imprinted bimetallic Fe/Pd nanoparticle.

    Science.gov (United States)

    Roy, Ekta; Patra, Santanu; Madhuri, Rashmi; Sharma, Prashant K

    2015-01-01

    A novel electrochemical-sensing platform based on imprinted bimetallic Fe/Pd (BI-Fe/Pd) nanoparticle has been fabricated for point-of-care diagnostics of oxidative stress marker (3-nitrotyrosine) in biological fluids. Herein, BI-Fe/Pd nanoparticles are used as a platform on which 3-nitrotyrosine imprinted cavities are created using acrylamide as monomer and N-N'-methylene bisacrylamide as cross-linker. The performance of the obtained imprinted sensor is investigated by cyclic, differential pulse, and square wave voltammetry in stripping mode. The imprinted sensor exhibits high recognition ability and affinity for 3-nitrotyrosine in comparison with the non-imprinted one. In addition, the proposed sensor is capable of measuring 3-nitrotyrosine in aqueous as well as in human blood serum, plasma, and urine samples within the range of 4.90-867.57 µg L(-1) and 9.90-867.57 µg L(-1) with detection limit of 1.20 µg L(-1) and 3.25 µg L(-1) by square wave and differential pulse stripping voltammetry, respectively. Imprinted BI-Fe/Pd nanoparticle modified sensor shows high affinity and no interference from blood or urine components. Modified sensor was stored for 45 days at room temperature without any detrimental effects to their binding properties. The high affinity of proposed sensor and the lack of requirement for cold chain logistics make them an attractive alternative to the enzyme-linked immunosorbent assay (ELISA) technique. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Catalytic dechlorination of 2,4-dichlorophenol by Pd/Fe bimetallic nanoparticles in the presence of humic acid.

    Science.gov (United States)

    Zhang, Zhen; Shen, Qiaohui; Cissoko, Naman; Wo, Jingjing; Xu, Xinhua

    2010-10-15

    Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products--phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82-91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10 wt.%, 0.15 wt.% to 0.20 wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300 min, respectively, the nitrate (NO(3)(-)) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl(-), o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP. 2010 Elsevier B.V. All rights reserved.

  6. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  7. Hydrothermal synthesis of platinum-group-metal nanoparticles by using HEPES as a reductant and stabilizer.

    Science.gov (United States)

    So, Man-Ho; Ho, Chi-Ming; Chen, Rong; Che, Chi-Ming

    2010-06-01

    Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 degrees C). Monodispersed (monodispersity: 11-15%) metal nanoparticles were obtained with an average particle size of less than 5 nm (Ru: 1.8+/-0.2, Os: 1.6+/-0.2, Rh: 4.5+/-0.5, Ir: 2.0+/-0.3, Pd: 3.8+/-0.4, Pt: 1.9+/-0.2 nm). The size, monodispersity, and stability of the as-obtained metal nanoparticles were affected by the HEPES concentration, pH of the HEPES buffer solution, and reaction temperature. HEPES with two tertiary amines (piperazine groups) and terminal hydroxyl groups can act as a reductant and stabilizer. The HEPES molecules can bind to the surface of metal nanoparticles to prevent metal nanoparticles from aggregation. These platinum-group-metal nanoparticles could be deposited onto the surface of graphite, which catalyzed the aerobic oxidation of alcohols to aldehydes.

  8. Impact of bio-palladium nanoparticles (bio-Pd NPs) on the activity and structure of a marine microbial community.

    Science.gov (United States)

    Nuzzo, Andrea; Hosseinkhani, Baharak; Boon, Nico; Zanaroli, Giulio; Fava, Fabio

    2017-01-01

    Biogenic palladium nanoparticles (bio-Pd NPs) represent a promising catalyst for organohalide remediation in water and sediments. However, the available information regarding their possible impact in case of release into the environment, particularly on the environmental microbiota, is limited. In this study the toxicity of bio-Pd NPs on the model marine bacterium V. fischeri was assessed. The impacts of different concentrations of bio-Pd NPs on the respiratory metabolisms (i.e. organohalide respiration, sulfate reduction and methanogenesis) and the structure of a PCB-dechlorinating microbial community enriched form a marine sediment were also investigated in microcosms mimicking the actual sampling site conditions. Bio-Pd NPs had no toxic effect on V. fischeri. In addition, they had no significant effects on PCB-dehalogenating activity, while showing a partial, dose-dependent inhibitory effect on sulfate reduction as well as on methanogenesis. No toxic effects by bio-Pd NPs could be also observed on the total bacterial community structure, as its biodiversity was increased compared to the not exposed community. In addition, resilience of the microbial community to bio-Pd NPs exposure was observed, being the final community organization (Gini coefficient) of samples exposed to bio-Pd NPs similar to that of the not exposed one. Considering all the factors evaluated, bio-Pd NPs could be deemed as non-toxic to the marine microbiota in the conditions tested. This is the first study in which the impact of bio-Pd NPs is extensively evaluated over a microbial community in relevant environmental conditions, providing important information for the assessment of their environmental safety.

  9. Synthesis of palladium nanoparticles using poly aniline reduction as Pd Cl{sub 2}; Sintese de nanoparticulas de paladio utilizando polianilina como redutor de PdCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Everton Carlos; Oliveira, Maria Auxiliadora Silva de, E-mail: evertonquimica@gmail.com [Instituto Tecnologico da Aeronautica - ITA, Divisao de Engenharia Mecanica e Aeronautica, Centro de Referencia em Turbinas a Gas, Sao Jose dos Campos, SP (Brazil)

    2011-07-01

    The development of hybrid composites has grown in recent years due to their wide potential range of application. This paper describes the formation of palladium nanoparticles by reducing Pd (II) ions to Pd (0) with polyaniline emeraldine base (EB). The reduction of Pd{sup 2+} on the surface of polyaniline was examined by X-ray diffraction (XRD) and the morphology of the Pd particles was studied by scanning electron microscopy (SEM). Through the results of XRD and using the Scherrer's formula, it was possible to get the diameter of Pd particles that was close to 13 nm. SEM results showed white inclusions which were ascribed to cluster formation of palladium nanoparticles in polyaniline. (author)

  10. Facile synthesis of near-monodisperse Ag@Ni core-shell nanoparticles and their application for catalytic generation of hydrogen.

    Science.gov (United States)

    Guo, Huizhang; Chen, Yuanzhi; Chen, Xiaozhen; Wen, Ruitao; Yue, Guang-Hui; Peng, Dong-Liang

    2011-05-13

    Magnetically recyclable Ag-Ni core-shell nanoparticles have been fabricated via a simple one-pot synthetic route using oleylamine both as solvent and reducing agent and triphenylphosphine as a surfactant. As characterized by transmission electron microscopy (TEM), the as-synthesized Ag-Ni core-shell nanoparticles exhibit a very narrow size distribution with a typical size of 14.9 ± 1.2 nm and a tunable shell thickness. UV-vis absorption spectroscopy study shows that the formation of a Ni shell on Ag core can damp the surface plasmon resonance (SPR) of the Ag core and lead to a red-shifted SPR absorption peak. Magnetic measurement indicates that all the as-synthesized Ag-Ni core-shell nanoparticles are superparamagnetic at room temperature, and their blocking temperatures can be controlled by modulating the shell thickness. The as-synthesized Ag-Ni core-shell nanoparticles exhibit excellent catalytic properties for the generation of H(2) from dehydrogenation of sodium borohydride in aqueous solutions. The hydrogen generation rate of Ag-Ni core-shell nanoparticles is found to be much higher than that of Ag and Ni nanoparticles of a similar size, and the calculated activation energy for hydrogen generation is lower than that of many bimetallic catalysts. The strategy employed here can also be extended to other noble-magnetic metal systems.

  11. Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

    KAUST Repository

    Yin, Dongdong

    2017-01-05

    Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101(Cr) as a support. The prepared Pd@MIL-101(Cr) hetero-catalysts characterized with various analytical techniques, exhibited highly monodispersed immobilized Pd nanoparticles in the MIL-101(Cr) cavities, while retaining the pristine crystallinity and porosity. The intact hybrid Pd@MIL-101(Cr) has been demonstrated to be an efficient catalyst for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity (2-butene-1,4-diol (>94%)).

  12. Carbon-Nanotubes-Supported Pd Nanoparticles for Alcohol Oxidations in Fuel Cells: Effect of Number of Nanotube Walls on Activity.

    Science.gov (United States)

    Zhang, Jin; Lu, Shanfu; Xiang, Yan; Shen, Pei Kang; Liu, Jian; Jiang, San Ping

    2015-09-07

    Carbon nanotubes (CNTs) are well known electrocatalyst supports due to their high electrical conductivity, structural stability, and high surface area. Here, we demonstrate that the number of inner tubes or walls of CNTs also have a significant promotion effect on the activity of supported Pd nanoparticles (NPs) for alcohol oxidation reactions of direct alcohol fuel cells (DAFCs). Pd NPs with similar particle size (2.1-2.8 nm) were uniformly assembled on CNTs with different number of walls. The results indicate that Pd NPs supported on triple-walled CNTs (TWNTs) have the highest mass activity and stability for methanol, ethanol, and ethylene glycol oxidation reactions, as compared to Pd NPs supported on single-walled and multi-walled CNTs. Such a specific promotion effect of TWNTs on the electrocatalytic activity of Pd NPs is not related to the contribution of metal impurities in CNTs, oxygen-functional groups of CNTs or surface area of CNTs and Pd NPs. A facile charge transfer mechanism via electron tunneling between the outer wall and inner tubes of CNTs under electrochemical driving force is proposed for the significant promotion effect of TWNTs for the alcohol oxidation reactions in alkaline solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Remarkable activity of PdIr nanoparticles supported on the surface of carbon nanotubes pretreated via a sonochemical process for formic acid electro-oxidation

    Science.gov (United States)

    Chen, Jinwei; Li, Yuanjie; Liu, Shuangren; Wang, Gang; Tian, Jing; Jiang, Chunping; Zhu, Shifu; Wang, Ruilin

    2013-12-01

    It was reported for the first time that the surface treated multi-walled carbon nanotubes supported PdIr (PdIr/CNT-SCP) catalyst presents remarkable electrocatalytic activity and stability for formic acid electro-oxidation (FAEO). The surface of CNTs was functionalized by a sonochemical process for the deposition of PdIr nanoparticles (NPs). The XRD and TEM characterizations show that the prepared PdIr/CNT-SCP catalyst has small mean size and good dispersion of PdIr NPs on CNTs. The electrochemical measurements show that the onset and anodic peak potentials of FAEO on PdIr/CNT-SCP catalyst are 60 and 50 mV more negative than that on the commercial Pd/C catalyst. The mass-normalized peak current density of PdIr/CNT-SCP is 3365 mA mg-1Pd, which is 4.5, 1.4 and 2.7 times higher than that of PdIr/CNT-Untreated, PdIr/C-SCP and commercial Pd/C, respectively. It demonstrates the promotion of Ir and functionalized CNTs to Pd for FAEO.

  14. Impact of surface roughness of Au core in Au/Pd core-shell nanoparticles toward formic acid oxidation - Experiment and simulation

    Science.gov (United States)

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-12-01

    The Au/Pd core-shell nanoparticles (NPs) were synthesized via galvanic replacement of Cu by Pd on hollow Au cores by adding different concentrations of Na2SO3 solution. It was found that the higher concentration of Na2SO3 that was used, the rougher the Au nanospheres became. However, the rougher Au surface may cause more defects in the Pd layers and decrease the catalytic abilities. The Au/Pd NPs synthesized using 0 M Na2SO3 (denoted as 0 M-Au/Pd NPs) have the smoothest Pd surface and demonstrate higher formic acid oxidation (FAO) activity (0.714 mA cm-2, normalized to the surface area of Pd) than other Au/Pd NPs and commercial Pd black (0.47 mA cm-2). Additional electrochemical characterization of the 0 M-Au/Pd NPs also demonstrated lower CO-stripping onset and peak potentials, higher stability (8× improvement in stabilized oxidation current), and superior durability (by 1.6×) than the Pd black. In addition, a simple simulation of FAO was adopted to predict the anodic curve by including reaction intermediates of formate and hydroxyl. The 0 M-Au/Pd NPs were found to show higher formate and lower hydroxyl coverage than the Pd black.

  15. Cyanogel-derived N-doped C nanosheets immobilizing Pd-P nanoparticles: One-pot synthesis and enhanced hydrogenation catalytic performance

    Science.gov (United States)

    Zhang, Hao; Yan, Xiaohong; Huang, Yundi; Zhang, Mengru; Tang, Yawen; Sun, Dongmei; Xu, Lin; Wei, Shaohua

    2017-02-01

    For Pd-based nanocatalysts, stabilization of Pd nanoparticles on carbon support could not only effectively avoid particle aggregation and maintain catalytic stability during catalytic processes, but also facilitate enhancing the catalytic activity due to the synergy between Pd nanoparticles and carbon support. Furthermore, the incorporation of non-metal of phosphorus (P) into Pd could effectively modulate the electronic structure of Pd and thus help to boost the catalytic properties. However, one-pot synthesis of such nanohybrids remains a great challenge due to the distinct physiochemical properties of Pd, P and C components. Herein, we demonstrate a one-pot and scalable synthesis of highly dispersed PdP alloy nanoparticle-immobilized on N-doped graphitic carbon nanosheets (abbreviated as Pd-P@N-C nanosheets) by using inorganic-organic hybrid cyanogel as a reaction precursor. In virtue of both compositional and structural advantages, the as-synthesized Pd-P@N-C nanosheets manifest a superior catalytic activity and stability toward the hydrogenation of 4-nitrophenol (4-NP). We believe that the present work will provide a feasible and versatile strategy for the development of efficient catalysts for environmental remediation and can also be extendable to other carbon-based nanohybrids with desirable functionalities.

  16. Enhanced activity of Pd nanoparticles supported on Vulcan XC72R carbon pretreated via a modified Hummers method for formic acid electrooxidation

    Science.gov (United States)

    Cao, Jianyu; Song, Lingzheng; Tang, Jiali; Xu, Juan; Wang, Wenchang; Chen, Zhidong

    2013-06-01

    Vulcan XC72R carbons were pretreated using a modified Hummers method and adopted as the support of palladium nanoparticles for formic acid electrooxidation. XPS analysis was used to investigate the surface species of the pretreated XC72R (XC72R-O), indicating a significant increase in the content of surface carboxyl groups. The structural properties of Pd nanoparticles deposited on the XC72R-O (Pd/XC72R-O) were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their electrochemical performance was evaluated by cyclic voltammetry (CV) and chronoamperometry. Pd nanoparticles in the Pd/XC72R-O display an average size of ~6.7 nm with narrow size distribution. Electrochemical studies for formic acid oxidation reveal that the Pd/XC72R-O presents much higher electrocatalytic activity than that of the Pd/XC72R and commercial Pd/C, which may be due to the formation of carboxyl groups enhanced the interaction between the Pd particles and the carbon support, facilitating the dispersion of Pd particles and the formation of preferred plane orientation available for electrocatalytic reaction.

  17. Synthetically Tuned Atomic Ordering in PdCu Nanoparticles with Enhanced Catalytic Activity toward Solvent-Free Benzylamine Oxidation.

    Science.gov (United States)

    Marakatti, Vijaykumar S; Sarma, Saurav Ch; Joseph, Boby; Banerjee, Dipanjan; Peter, Sebastian C

    2017-02-01

    Synthesis of ordered compounds with nano size is of particular interest for tuning the surface properties with enhanced activity and selectivity toward various important industrial catalytic processes. In this work, we synthesized ordered PdCu nanoparticles as highly efficient catalyst for the solvent-free aerobic oxidation of benzylamine. The PdxCu1-x catalysts with different chemical compositions (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) were prepared by polyol method using NaBH4 as a reducing agent and were well-characterized by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) energy-dispersive analysis of X-rays, and X-ray absorption fine structure. The effect of different metal concentrations of Pd and Cu on the formation of PdxCu1-x nanoparticles was investigated. The XRD and TEM confirmed the formation of ordered PdCu intermetallic phase with body-centered cubic (BCC) structure for the synthetic composition of Pd/Cu = 1:1. For compositions x = 0, 0.25, 0.75, and 1, PdxCu1-x alloy with face-centered cubic (FCC) structure was observed, whereas mixed phase of BCC and FCC was observed for x = 0.4 and 0.6. The use of strong reducing agent (NaBH4) was essential to synthesize PdCu ordered phase compared to weak reducing agents such as oleylamine and ascorbic acid. The PdCu nanocatalyst with ordered structure (BCC) showed excellent catalytic activity compared to PdxCu1-x alloy nanoparticles with FCC structure. The atomic ordering in the PdCu intermetallic was the driving force for the enhancement in the catalytic activity with high benzylamine conversion of 94.0% and dibenzylimine selectivity of 92.2% compared to its monometallic and alloy counterparts. Moreover, ordered PdCu alloy showed good recyclability and activity toward the oxidation of different amines.

  18. Fabrication of Pd Nanoparticles Embedded C@Fe3O4 Core-Shell Hybrid Nanospheres: An Efficient Catalyst for Cyanation in Aryl Halides.

    Science.gov (United States)

    Suresh Kumar, Basuvaraj; Amali, Arlin Jose; Pitchumani, Kasi

    2015-10-21

    Isolated chemical reactors were fabricated by integrating catalytically active sites (Pd) with magnetic functionality (Fe3O4) along with carbon while preserving the constituents functional properties to realize the structure-property relationship of Pd by comparing the catalytic activity of spherical Pd NPs with cubical Pd NPs for cyanation in aryl halides using K4[Fe(CN)6] as a green cyanating agent to yield corresponding nitriles. The superior catalytic reactivity of the cubical Pd NPs is attributed to the larger number of {100} surface facets. The TEM images of reused catalyst shows the change in structure from cubical to spherical nanoparticles, attributed to the efficient leaching susceptibility of Pd {100} surface facets. The cubical Pd NPs on carbon@Fe3O4 is attractive in view of its high catalytic efficiency, easy synthesis, magnetic separability, environmental friendliness, high stability, gram scale applicability, and reusability.

  19. Facile and Rapid Synthesis of Ultrafine PtPd Bimetallic Nanoparticles and Their High Performance toward Methanol Electrooxidation

    Directory of Open Access Journals (Sweden)

    Tiantian Xia

    2014-01-01

    Full Text Available Uniform and sub-10 nm size bimetallic PtPd nanoparticles (NPs have been synthesized via a simple and facile method without using any surfactants at an ambient temperature. As a green and clean reductive agent, ascorbic acid (AA was employed for the coreduction of K2PtCl4 and K2PdCl4 in aqueous solution. The morphology, composition, and structure of PtPd NPs had been characterized by transmission electron microscopy (TEM, field emission high resolution transmission electron microscopy (FE-HRTEM, energy dispersive spectroscopy (EDS, X-ray diffraction (XRD, and X-ray photoelectron spectroscope (XPS. Comparing with both the monometallic Pt and Pd, the as-prepared alloy nanoparticles show superior electrocatalytic activity and better tolerance against poisoning by intermediates generated during methanol electrooxidation, which makes them a promising electrocatalysts for direct methanol fuel cells (DMFCs. Meanwhile, the green and simple approach could be easily extended to the manufacture of bimetallic or trimetallic alloy nanomaterials.

  20. Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution.

    Science.gov (United States)

    Salem, Mohamed A; Bakr, Eman A; El-Attar, Heba G

    2018-01-05

    Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17nm for Pt@Ag and 8.8nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH4) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes. Copyright © 2017. Published by Elsevier B.V.

  1. Synthesis of highly monodispersed teardrop-shaped core–shell SiO{sub 2}/TiO{sub 2} nanoparticles and their photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lihong; Zhou, Yifeng, E-mail: yifengzhou@126.com; Nie, Wangyan; Song, Linyong; Chen, Pengpeng, E-mail: chenpp@ahu.edu.cn

    2015-10-01

    Graphical abstract: - Highlights: • Uniform chitosan coated magnetic mesoporous silica nanoparticles (CMMSNs) were successfully synthesized. • The CMMSNs were applied to highly efficient methylene blue (MB) dyes removal, and the saturated adsorption capacity of MB was 43.03 mg/g. • The MB adsorption kinetic and adsorption isotherm analysis were studied. • The CMMSNs had a saturation magnetization of 12.6 emu/g and could be easily separated by a magnet after dye adsorption. - Abstract: In this study, teardrop-shaped SiO{sub 2}/TiO{sub 2} nanoparticles (TST-NPs) with core–shell structure were fabricated from tetraethoxysilane (TEOS) and tetrabutyl titanate (TBT) by sol–gel method. And these nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy. Photocatalytic activity of teardrop-shaped SiO{sub 2}/TiO{sub 2} nanoparticles after calcination (CST-NPs) was studied towards degradation of methylene blue under sunlight irradiation. The result showed that CST-NPs possessed good photocatalytic activity. The photocatalytic mechanism was also studied by adding different capture agent. Results showed that addition of 0.003 M of I{sup −} decreased the degradation of MB more than same amount of Ag{sup +}, indicating that the photogenerated holes may play a more essential role than photoinjected electrons in the oxidation of MB.

  2. Characterization and reactivity of iron nanoparticles prepared with added Cu, Pd, and Ni.

    Science.gov (United States)

    Chun, Chan Lan; Baer, Donald R; Matson, Dean W; Amonette, James E; Penn, R Lee

    2010-07-01

    The association of a secondary metal with iron particles affects redox reactivity in engineered remediation systems. However, the structural characteristics of the metal additives and mechanism responsible for changes in reactivity have not been fully elucidated. Here, we synthesized iron nanoparticles with Cu, Pd, and Ni content ranging from 0-2 mol % via a solution deposition process (SDP), hydrogen reduction process (HRP), or hydrogen reduction of ferrihydrite coprecipitated with the metal cations (HRCO). Results from solid-state characterization show that the synthesis methods produced similar iron core/magnetite shell particles but produced substantial differences in terms of the distribution of the metal additives. In SDP, the metal additives were heterogeneously distributed on the surface of the particles. The metal additives were clearly discernible in TEM images as spherical nanoparticles (5-20 nm) on the HRP and HRCO particles. Because the metals were integral to the synthesis process, we hypothesize that the metal additive is present as solute within the iron core of the HRCO particles. Kinetic batch experiments of carbon tetrachloride (CT) degradation were performed to quantitatively compare the redox reactivity of the particles. Overall, metal additives resulted in enhanced pseudo-first-order rate constants of CT degradation (k(O,CT)) compared to that of the iron nanoparticles. For the bimetallic iron nanoparticles prepared by SDP and HRP, k(O,CT) increased with the concentration of metal additives. The values of chloroform yield (Y(CF)) were independent of the identity and amount of metal additives. However, both k(O,CT) and Y(CF) of the HRCO iron particles were significantly increased. Results suggest that it is the distribution of the metal additives that most strongly impacts reactivity and product distribution. For example, for materials with ca. 0.9 mol % Ni, reactivity and Y(CF) varied substantially (HRCO > SDP > HRP), and HRCO-NiFe resulted in

  3. Green Synthesis and Characterization of Monodispersed Gold Nanoparticles: Toxicity Study, Delivery of Doxorubicin and Its Bio-Distribution in Mouse Model.

    Science.gov (United States)

    Mukherjee, Sudip; Sau, Samaresh; Madhuri, Durga; Bollu, Vishnu Sravan; Madhusudana, Kuncha; Sreedhar, Bojja; Banerjee, Rajkumar; Patra, Chitta Ranjan

    2016-01-01

    In the present article, we report the in vitro and in vivo delivery of doxorubicin using biosynthesized gold nanoparticles (b-Au-PP). Gold nanoparticles were synthesized by a simple, fast, efficient, environmentally friendly and economical green chemistry approach using an extract of Peltophorum pterocarpum (PP) leaves. Because the biosynthesized b-Au-PP was highly stable in various physiological buffers for several weeks and biocompatible in both in vitro and in vivo systems, we designed and developed a biosynthesized gold nanoparticle (b-Au-PP)-based drug-delivery system (DDS) using doxorubicin (Dox) (b-Au-PP-Dox). Both b-Au-PP and b-Au-PP-Dox were thoroughly characterized using several analytical tools. Administration of doxorubicin-loaded DDS (b-Au-PP-Dox) resulted in a significant inhibition of the proliferation of cancer cells (A549, B16F10) in vitro and of tumor growth in an in vivo model compared to doxorubicin alone. Furthermore, we found that the cellular uptake and release of Dox in the nanoconjugated form (b-Au-PP-Dox) were faster than the uptake and release of unconjugated Dox. The in vivo toxicity study did not show any significant changes in the hematology, serum clinical biochemistry or histopathology in the C57BL6/J female mice after consecutive intraperitoneal (IP) injections over a period of seven days. To the best of our knowledge, our study is the first to report the application of a biosynthesized gold nanoparticle-based DDS for cancer therapy in an animal model, in addition to a detailed in vivo toxicity study. Together, the results demonstrate that a biosynthesized gold nanoparticle-based drug-delivery system (b-Au-PP-Dox) could be used in the near future as an alternative cost-effective treatment strategy for cancer therapy.

  4. Highly dispersed Pd nanoparticles supported on 1,10-phenanthroline-functionalized multi-walled carbon nanotubes for electrooxidation of formic acid

    Science.gov (United States)

    Bai, Zhengyu; Guo, Yuming; Yang, Lin; Li, Lei; Li, Wujv; Xu, Pengle; Hu, Chuangang; Wang, Kui

    2011-08-01

    Functionalization step is generally prerequisite to immobilize metal nanoparticles on multi-walled carbon nanotubes (MWCNTs) for production of a high efficient electrocatalyst. We herein report a novel method to functionalize MWCNTs with 1,10-phenanthroline (phen-MWCNTs) as a catalyst support for Pd nanoparticles. Raman spectroscopic analysis results reveal that this phen functionalization method can preserve the integrity and electronic structure of MWCNTs and provide the highly effective functional groups on the surface for Pd nanoparticles. According to the transmission electron microscopy (TEM) measurements, the as-prepared Pd nanop articles are evenly deposited on the surface of the phen-MWCNTs without obvious agglomeration, and the average particle size of the Pd nanoparticles is 2.3 nm. Electrochemical measurements demonstrate that the as-prepared Pd/phen-MWCNTs catalyst has a better electrocatalytic activity and stability for the oxidation of formic acid than Pd catalyst on acid-treated MWCNTs. It is concluded that the as-prepared Pd/phen-MWCNTs would be a potential candidate as an anode electrocatalyst in direct formic acid fuel cell (DFAFC).

  5. Synthesis of PVP stabilized Cu/Pd nanoparticles with citrate complexing agent and its application as an activator for electroless copper deposition.

    Science.gov (United States)

    Lo, Sylvia H Y; Wang, Yung-Yun; Wan, Chi-Chao

    2007-06-01

    A simple method has been developed to synthesize Cu/Pd nanoparticles in aqueous solution in ambient condition with the addition of complexing agent, trisodium citrate. UV-vis spectra confirmed the complexing behavior of trisodium citrate and metal ions. The particles synthesized with trisodium citrate were well dispersed with particle size ranging between 3-4 nm while the particles without trisodium citrate were larger and aggregated, as demonstrated by transmission electron microscopy (TEM). X-ray diffraction patterns (XRD) indicated the formation of bimetallic nanoparticles without impurities in the complexing agent-supplemented system. In contrast, large amounts of PdO and Cu(OH)(2) were precipitated along with the formation of particles in the complexing agent-free system. X-ray photoelectron spectroscopy (XPS) revealed small amounts of oxidized Pd on the surface of particles and the existence of zerovalent Cu and oxidized Cu in particles with trisodium citrate. With a simpler process for electroless copper deposition, the Cu/Pd nanoparticle activator with less Pd metal used exhibited comparable catalytic activity to conventional Pd/Sn colloidal activator. In summary, application of Cu/Pd nanoparticles synthesized with the complexing agent as an activator suggested a novel, simpler and inexpensive process in PCB industry.

  6. Electrochemical Dealloying of PdCu3 Nanoparticles to Achieve Pt-like Activity for the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Jana, Rajkumar; Bhim, Anupam; Bothra, Pallavi; Pati, Swapan K; Peter, Sebastian C

    2016-10-20

    Manipulating the d-band center of the metal surface and hence optimizing the free energy of hydrogen adsorption (ΔGH ) close to the optimal adsorption energy (ΔGH =0) for hydrogen evolution reaction (HER), is an efficient strategy to enhance the activity for HER. Herein, we report a oleylamine-mediated (acting as the solvent, stabilizer, and reducing agent) strategy to synthesize intermetallic PdCu3 nanoparticles (NPs) without using any external reducing agent. Upon electrochemical cycling, PdCu3 transforms into Pd-rich PdCu (ΔGH =0.05 eV), exhibiting remarkably enhanced activity (with a current density of 25 mA cm(-2) at ∼69 mV overpotential) as an alternative to Pt for HER. The first-principle calculation suggests that formation of low coordination number Pd active sites alters the d-band center and hence optimal adsorption of hydrogen, leading to enhanced activity. This finding may provide guidelines towards the design and development of Pt-free highly active and robust electrocatalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A Synthetic Pseudo-Rh: NOx Reduction Activity and Electronic Structure of Pd-Ru Solid-solution Alloy Nanoparticles.

    Science.gov (United States)

    Sato, Katsutoshi; Tomonaga, Hiroyuki; Yamamoto, Tomokazu; Matsumura, Syo; Zulkifli, Nor Diana Binti; Ishimoto, Takayoshi; Koyama, Michihisa; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Nagaoka, Katsutoshi

    2016-06-24

    Rh is one of the most important noble metals for industrial applications. A major fraction of Rh is used as a catalyst for emission control in automotive catalytic converters because of its unparalleled activity toward NOx reduction. However, Rh is a rare and extremely expensive element; thus, the development of Rh alternative composed of abundant elements is desirable. Pd and Ru are located at the right and left of Rh in the periodic table, respectively, nevertheless this combination of elements is immiscible in the bulk state. Here, we report a Pd-Ru solid-solution-alloy nanoparticle (PdxRu1-x NP) catalyst exhibiting better NOx reduction activity than Rh. Theoretical calculations show that the electronic structure of Pd0.5Ru0.5 is similar to that of Rh, indicating that Pd0.5Ru0.5 can be regarded as a pseudo-Rh. Pd0.5Ru0.5 exhibits better activity than natural Rh, which implies promising applications not only for exhaust-gas cleaning but also for various chemical reactions.

  8. Synthesis, characterization, and debromination reactivity of cellulose-stabilized Pd/Fe nanoparticles for 2,2',4,4'-tretrabromodiphenyl ether

    Science.gov (United States)

    Huang, Guofu; Wang, Mianmian; Hu, Yongyou; Lv, Sihao; Li, Changfang

    2017-01-01

    In this study, two kinds of cellulose derivatives (polyanionic cellulose (PAC) and hydroxypropylmethyl cellulose (HPMC)) were selected as stabilizers of Pd/Fe nanoparticles (NPs) to investigate their influences on the debromination performances of 2,2',4,4'-tretrabromodiphenyl ether (BDE47). Field emission scanning electron microscope (FE-SEM) images revealed that the cellulose-stabilized Pd/Fe NPs were smaller and more uniform than the bare-Pd/Fe NPs. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) results suggested that cellulose coatings found on Pd/Fe NPs surfaces featured some antioxidation abilities, which followed the order of HPMC soils. PMID:28355273

  9. Controllable synthesis of monodisperse MnO nanoparticles%单分散MnO纳米粒子的可控制备

    Institute of Scientific and Technical Information of China (English)

    刘新杰; 张智军; 杨祖培

    2013-01-01

    研究了不同实验条件对MnO纳米粒子尺寸和形貌调控的影响.采用高温分解法以油酸锰为前驱体成功可控制备了3 nm、6 nm、10 nm、20 nm等多种粒径的MnO纳米粒子,并通过透射电子显微镜对其进行了表征.结果表明:反应温度、表面活性剂用量、溶剂用量等对纳米粒子的大小都有一定的影响.随着反应温度的升高,MnO纳米粒子的尺寸逐渐增加,而表面活性剂的用量增大则导致MnO纳米粒子的尺寸变小,增加溶剂用量有利于合成较大尺寸的MnO纳米粒子.此外,还分别用CTAB、DMSA、多巴胺等对MnO纳米粒子进行修饰,结果显示表面经亲水性处理后纳米粒子增加了水溶性,使其更好地用于生物成像和载药.%The morphology of manganese oxide (MnO) nanoparticles significantly affects their properties and various applications.In this paper,we report controllable synthesis and characterization of MnO nanoparticles (3 nm,6 nm,10 nm,20 nm) through the hightemperature decomposition approach.Our results showed that the reaction temperature,the amount of surfactants and solvent affect the size of the nanoparticles.MnO nanoparticles size increases with temperature and solvent content.However,increase of surfactants leads to decrease in the particle size.Finally,we modified the MnO nanoparticles with CTAB,DMSA and dopamine to render their aqueous solubility,which is essential for their biological applications.

  10. Structure and Hydrogen Adsorption Properties of SBA-15 Doped with Pd Nanoparticles.

    Science.gov (United States)

    Lee, Sang-Hwa; Park, Taehee; Yi, Whikun; Kim, Jaeyong

    2015-11-01

    Hydrogen adsorption properties of Pd-doped Santa Barbara amorphous No. 15 (Pd-SBA-15) were investigated and the results were compared with pure SBA-15 ones in terms of change of its structure and Pd concentration. Pd-SBA-15 samples were prepared by a hydrothermal reaction, using mixture of PEO20PPO70PEO20 (P123) and tetraethyl orthosilicate (TEOS). For the doping of Pd on SBA-15, PdC2 solution was added into the mixture of P123 and TEOS, and the solution was annealed at 80 degrees C for 2 hours under 800 Torr of hydrogen atmosphere. According to the X-ray diffraction and transmission electron microscope data, Pd-doped SBA-15 samples form a hexagonal array of mesoporous structure with 20-30 nm size of Pd particles. Values of specific surface area decreased from 630 to 414 m2/g as increasing the Pd doping level due to the increasing of the volume density. In fact, the volume density increased from 0.103 to 0.276 g/cc as increasing the mass ratio of PdCl2 to TEOS from 0 to 0.5. For the Pd-doped SBA-15, the amount of adsorbed hydrogen significantly increased from 0.49 to 0.99 wt% as increasing the Pd doping level from 0 to 0.5 demonstrating that Pd doping is an effect method for SBA-1 5 as a potential use of hydrogen storage application.

  11. Preparation of large monodisperse vesicles.

    Directory of Open Access Journals (Sweden)

    Ting F Zhu

    Full Text Available Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (approximately 100 nm in diameter results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-microm-diameter pores eliminates vesicles larger than 5 microm in diameter. Dialysis of extruded vesicles against 3-microm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 microm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of approximately 4 microm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery.

  12. Structuring Pd Nanoparticles on 2H-WS2 Nanosheets Induces Excellent Photocatalytic Activity for Cross-Coupling Reactions under Visible Light.

    Science.gov (United States)

    Raza, Faizan; Yim, DaBin; Park, Jung Hyun; Kim, Hye-In; Jeon, Su-Ji; Kim, Jong-Ho

    2017-10-05

    Effective photocatalysts and their surface engineering are essential for the efficient conversion of solar energy into chemical energy in photocatalyzed organic transformations. Herein, we report an effective approach for structuring Pd nanoparticles (NPs) on exfoliated 2H-WS2 nanosheets (WS2/PdNPs), resulting in hybrids with extraordinary photocatalytic activity in Suzuki reactions under visible light. Pd NPs of different sizes and densities, which can modulate the photocatalytic activity of the as-prepared WS2/PdNPs, were effectively structured on the basal plane of 2H-WS2 nanosheets via a sonic wave-assisted nucleation method without any reductants at room temperature. As the size of Pd NPs on WS2/PdNPs increased, their photocatalytic activity in Suzuki reactions at room temperature increased substantially. In addition, it was found that protic organic solvents play a crucial role in activating WS2/PdNPs catalysts in photocatalyzed Suzuki reactions, although these solvents are generally considered much less effective than polar aprotic ones in the conventional Suzuki reactions promoted by heterogeneous Pd catalysts. A mechanistic investigation suggested that photogenerated holes are transferred to protic organic solvents, whereas photogenerated electrons are transferred to Pd NPs. This transfer makes the Pd NPs electron-rich and accelerates the rate-determining step, i.e., the oxidative addition of aryl halides under visible light. WS2/PdNPs showed the highest turnover frequency (1244 h(-1)) for photocatalyzed Suzuki reactions among previously reported photocatalysts.

  13. Metal nanostructures with complex surface morphology: The case of supported lumpy Pd and Pt nanoparticles produced by laser processing of metal films

    Science.gov (United States)

    Ruffino, F.; Maugeri, P.; Cacciato, G.; Zimbone, M.; Grimaldi, M. G.

    2016-09-01

    In this work we report on the formation of lumpy Pd and Pt nanoparticles on fluorine-doped tin oxide/glass (FTO/glass) substrate by a laser-based approach. In general, complex-surface morphology metal nanoparticles can be used in several technological applications exploiting the peculiarities of their physical properties as modulated by nanoscale morphology. For example plasmonic metal nanoparticles presenting a lumpy morphology (i.e. larger particles coated on the surface by smaller particles) can be used in plasmonic solar cell devices providing broadband scattering enhancement over the smooth nanoparticles leading, so, to the increase of the device efficiency. However, the use of plasmonic lumpy nanoparticles remains largely unexplored due to the lack of simply, versatile, low-cost and high-throughput methods for the controllable production of such nanostructures. Starting from these considerations, we report on the observation that nanoscale-thick Pd and Pt films (17.6 and 27.9 nm, 12.1 and 19.5 nm, respectively) deposited on FTO/glass surface irradiated by nanosecond pulsed laser at fluences E in the 0.5-1.5 J/cm2 range, produce Pd and Pt lumpy nanoparticles on the FTO surface. In addition, using scanning electron microscopy analyses, we report on the observation that starting from each metal film of fixed thickness h, the fraction F of lumpy nanoparticles increases with the laser fluence E and saturates at the higher fluences. For each fixed fluence, F was found higher starting from the Pt films (at each starting film thickness h) with respect to the Pd films. For each fixed metal and fluence, F was found to be higher decreasing the starting thickness of the deposited film. To explain the formation of the lumpy Pd and Pt nanoparticles and the behavior of F as a function of E and h both for Pd and Pt, the thermodynamic behavior of the Pd and Pt films and nanoparticles due to the interaction with the nanosecond laser is discussed. In particular, the

  14. Synthesis of carbon-supported PdSn-SnO2 nanoparticles with different degrees of interfacial contact and enhanced catalytic activities for formic acid oxidation.

    Science.gov (United States)

    Wang, Hui; Liu, Ziyue; Ma, Yanjiao; Julian, Key; Ji, Shan; Linkov, Vladimir; Wang, Rongfang

    2013-09-07

    The conjunction of the PdSn alloy and SnO2 is of interest for improving catalytic activity in formic acid oxidation (FAO). Here, we report the synthesis of PdSn-SnO2 nanoparticles and a study of their catalytic FAO activity. Different degrees of interfacial contact between SnO2 and PdSn were obtained using two different stabilizers (sodium citrate and EDTA) during the reduction process in catalyst preparation. Compared to the PdSn alloy, PdSn-SnO2 supported on carbon black showed enhanced FAO catalytic activity due to the presence of SnO2 species. It was also found that interfacial contact between the PdSn alloy and the SnO2 phase has an impact on the activity towards CO oxidation and FAO.

  15. Fabrication of Au-Pd Core-shell Nanoparticles using Au Thin-Film Dewetting at High Temperature and Chemical Synthesis Methods

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Gyu; Lee, Hye-Jung; Oh, Yong-Jun [Hanbat National Univ., Daejeon (Korea, Republic of)

    2016-07-15

    Au-Pd bimetallic nanoparticles (NPs) have received a lot of attention in the fields of catalysts and hydrogen sensors. In this study, Au-Pd core-shell NP arrays were successfully fabricated using two steps: formation of the ordered array of Au NPs cores via solid-state dewetting of a Au thin film on a topographic silica substrate, and Pd shell formation via chemical synthesis using two different surfactants (CTAB and CTAC). Using the CTAB surfactant in particular, a 2-D composite structure comprised of an ordered array of Au-Pd NPs, with smaller Pd NPs on the nanoscopic gaps between the Au-Pd NPs, could be formed. This structure is expected to have potential application in resistance-base hydrogen sensors.

  16. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    Science.gov (United States)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  17. Nonenzymatic glucose sensor based on flower-shaped Au-Pd core-shell nanoparticles-ionic liquids composite film modified glassy carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xianlan [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Pan Hiabo, E-mail: hbpan@fzu.edu.c [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); State Key Laboratory Breeding Base of Photocatalysis, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Liu Hongfang [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Du Min [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2010-12-30

    A novel nonenzymatic glucose sensor based on flower-shaped (FS) Au -Pd core-shell nanoparticles-ionic liquids (ILs i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide, [P(C{sub 6}){sub 3}C{sub 14}][Tf{sub 2}N]) composite film modified glassy carbon electrodes (GCE) was reported. The Au-Pd nanocatalysts were prepared by seed-mediated growth method, forming the three-dimensional FS nanoparticles, where tens of small Pd nanoparticles ({approx}3 nm) aggregated on gold seeds ({approx}20 nm). The FS Au-Pd nanoparticle was a good candidate for the catalytic efficiency of nanometallic surfaces because of its flower-shaped nature, which has greater adsorption capacity. XPS analysis and zeta potential indicated that the surface of Pd atoms is positively charged, profiting the oxidation process of glucose. And ILs acted as bridge connecting Au-Pd one another and bucky gel as platform within the whole nanocomposite. So the modified electrode has higher sensitivity and selectivity owing to intrinsic synergistic effects of this nanocomposite. Amperometric measurements allow observation of the electrochemical oxidation of glucose at 0.0 V (vs. Ag/AgCl), the glucose oxidation current is linear to its concentration in the range of 5 nM-0.5 {mu}M, and the detection limit was found to be 1.0 nM (S/N = 3). The as-prepared nonenzyme glucose sensor exhibited excellent stability, repeatability, and selectivity.

  18. The pH-sensitive Pd nanoparticles as ink for ink-jet printing technology and electroless Cu metallic patterns on indium-doped tin oxide substrate

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Chun-Chieh; Lin, Yi [Medical Device Section, Medical Devices and Opto-Electronics Equipment Department, Metal Industries Research and Development Centre, Kaohsiung 802, Taiwan (China); Liu, Tsai-Yun [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan (China); Nian, Yan-Yu [Graduate School of Defense Science, Chung Cheng Institute of Technology, National Defense University, 335 Taiwan (China); Wang, Min-Wen, E-mail: mwwang@cc.kuas.edu.tw [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan (China); Ger, Ming-Der, E-mail: mingderger@gmail.com [Department of Chemical and Materials Engineering, Chung Cheng Institute of Technology, National Defense University, 335 Taiwan (China)

    2013-06-01

    In this work, a method to fabricate copper pattern on an indium-doped tin oxide (ITO) glass substrate is described. This method involves ink-jet printing of a pH-sensitive chitosan-g-polyvinyl acetate/Pd nanoparticle (CTS-g-PVAc-Pd) based ink on an untreated ITO plate to create the catalytic sites, onto which copper is subsequently deposited by an electroless plating method. To prepare the CTS-g-PVAc-Pd nanoparticles, a pH-sensitive chitosan-g-polyvinyl acetate (CTS-g-PVAc) copolymer is utilized to self-reduce Pd nanoparticles. The pH-sensitive CTS chains function as stabilizing agent for noble metal nanoparticles in acidic ink solution. On the other hand, CTS-g-PVAc copolymers convert to hydrophilic CTS-g-poly(vinyl alcohol) via alkali hydrolysis during the electroless copper plating. Therefore, the copper film with dramatically enhanced adhesion is formed on the surface of ITO glass without special pretreatment step before electroless deposition of copper film. Our results show that this process yields copper line with width down to 60 μm and ITO plated with the copper coating has good electrical conductivity, with an electrical resistivity of about 5.4 μΩ cm. - Highlights: • Chitosan-g-polyvinyl acetate copolymer provides reducing environment for Pd nanoparticles. • pH-sensitive Pd nanoparticles as ink for ink-jet printing. • Patterning Pd catalyst for the electroless deposition of copper patterns. • Method to fabricate copper patterns on In-doped tin oxide substrates. • Ink-jet printing can be directly and easily applied to fabricate metal patterns.

  19. A facile synthesis of MPd (M = Co, Cu) nanoparticles and their catalysis for formic acid oxidation.

    Science.gov (United States)

    Mazumder, Vismadeb; Chi, Miaofang; Mankin, Max N; Liu, Yi; Metin, Önder; Sun, Daohua; More, Karren L; Sun, Shouheng

    2012-02-08

    Monodisperse CoPd nanoparticles (NPs) were synthesized and studied for catalytic formic acid (HCOOH) oxidation (FAO). The NPs were prepared by coreduction of Co(acac)(2) (acac = acetylacetonate) and PdBr(2) at 260 °C in oleylamine and trioctylphosphine, and their sizes (5-12 nm) and compositions (Co(10)Pd(90) to Co(60)Pd(40)) were controlled by heating ramp rate, metal salt concentration, or metal molar ratios. The 8 nm CoPd NPs were activated for HCOOH oxidation by a simple ethanol wash. In 0.1 M HClO(4) and 2 M HCOOH solution, their catalytic activities followed the trend of Co(50)Pd(50) > Co(60)Pd(40) > Co(10)Pd(90) > Pd. The Co(50)Pd(50) NPs had an oxidation peak at 0.4 V with a peak current density of 774 A/g(Pd). As a comparison, commercial Pd catalysts showed an oxidation peak at 0.75 V with peak current density of only 254 A/g(Pd). The synthesis procedure could also be extended to prepare CuPd NPs when Co(acac)(2) was replaced by Cu(ac)(2) (ac = acetate) in an otherwise identical condition. The CuPd NPs were less active catalysts than CoPd or even Pd for FAO in HClO(4) solution. The synthesis provides a general approach to Pd-based bimetallic NPs and will enable further investigation of Pd-based alloy NPs for electro-oxidation and other catalytic reactions. © 2012 American Chemical Society

  20. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization

    Science.gov (United States)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-08-01

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of HE was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (TN) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus

  1. Hydrothermal synthesis of superparamagnetic and red luminescent bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er core@shell monodisperse nanoparticles and their subsequent ligand exchange in water

    Science.gov (United States)

    Qin, Zhenli; Du, Sinan; Luo, Yang; Liao, Zhijian; Zuo, Fang; Luo, Jianbin; Liu, Dong

    2016-08-01

    We report the use of an efficient hydrothermal method to synthesize superparamagnetic and red luminescent bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er nanoparticles (NPs) with core@shell structures via a seed-growth procedure. Oleic acid coated Fe3O4 (OA-Fe3O4) NPs were initially synthesized using a coprecipitation method. The as-synthesized OA-Fe3O4 NPs were then used as seeds, on which the red upconversion luminescent shell (Mn2+-doped NaYF4:Yb/Er) was formed. Furthermore, hydrophobic to hydrophilic surface modification of the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs was achieved via a ligand exchange method where oleic acid was displaced by a PEG phosphate ligand [PEG = poly(ethylene glycol)]. These materials were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). The Fe3O4 cores were uniformly coated with a Mn2+-doped NaYF4:Yb/Er shell, and the bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs were monodispersed. Furthermore, the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs exhibited a saturated magnetization value of 6.2 emu/g and emitted red luminescence under a 980 nm laser. The obtained bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs may find potential applications in drug targeting, bioseparation, and diagnostic analysis. The synthetic method may be employed for the preparation of other bifunctional nanomaterials.

  2. Effective decoration of Pd nanoparticles on the surface of SnO{sub 2} nanowires for enhancement of CO gas-sensing performance

    Energy Technology Data Exchange (ETDEWEB)

    Trung, Do Dang [International Training Institute for Materials Science, Hanoi University of Science and Technology, No. 1 Dai Co Viet Road, Hanoi (Viet Nam); Hoa, Nguyen Duc, E-mail: ndhoa@itims.edu.vn [International Training Institute for Materials Science, Hanoi University of Science and Technology, No. 1 Dai Co Viet Road, Hanoi (Viet Nam); Tong, Pham Van; Duy, Nguyen Van [International Training Institute for Materials Science, Hanoi University of Science and Technology, No. 1 Dai Co Viet Road, Hanoi (Viet Nam); Dao, T.D.; Chung, H.V.; Nagao, T. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Hieu, Nguyen Van, E-mail: hieu@itims.edu.vn [International Training Institute for Materials Science, Hanoi University of Science and Technology, No. 1 Dai Co Viet Road, Hanoi (Viet Nam)

    2014-01-30

    Highlights: • Pd nanoparticles decoration on nanowire's surface was done via a simple route. • The size and distribution of Pd nanoparticles was controlled by in situ reduction of the Pd complex. • The coating Pd enhanced capable detection of hazardous CO gas of on-chip growth SnO{sub 2} nanowires. • Pd-decorated SnO{sub 2} nanowires sensors have good stability to hazardous CO gas. -- Abstract: Decoration of noble metal nanoparticles (NPs) on the surface of semiconducting metal oxide nanowires (NWs) to enhance material characteristics, functionalization, and sensing abilities has attracted increasing interests from researchers worldwide. In this study, we introduce an effective method for the decoration of Pd NPs on the surface of SnO{sub 2} NWs to enhance CO gas-sensing performance. Single-crystal SnO{sub 2} NWs were fabricated by chemical vapor deposition, whereas Pd NPs were decorated on the surface of SnO{sub 2} NWs by in situ reduction of the Pd complex at room temperature without using any linker or reduction agent excepting the copolymer P123. The materials were characterized by advanced techniques, such as high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pd NPs were effectively decorated on the surface of SnO{sub 2} NWs. As an example, the CO sensing characteristics of SnO{sub 2} NWs decorated with Pd NPs were investigated at different temperatures. Results revealed that the gas sensor exhibited excellent sensing performance to CO at low concentration (1–25 ppm) with ultrafast response-recovery time (in seconds), high responsivity, good stability, and reproducibility.

  3. Natural DNA-modified graphene/Pd nanoparticles as highly active catalyst for formic acid electro-oxidation and for the Suzuki reaction.

    Science.gov (United States)

    Qu, Konggang; Wu, Li; Ren, Jinsong; Qu, Xiaogang

    2012-09-26

    Natural DNA has been considered as a building block for developing novel functional materials. It is abundant, renewable, and biodegradable and has a well-defined structure and conformation with many unique features, which are difficult to find in other polymers. Herein, calf thymus DNA modified graphene/Pd nanoparticle (DNA-G-Pd) hybrid materials are constructed for the first time using DNA as a mediator, and the prepared DNA-G-Pd hybrid shows high catalytic activity for fuel cell formic acid electro-oxidation and for organic Suzuki reaction. The main advantages of using DNA are not only because the aromatic nucleobases in DNA can interact through π-π stacking with graphene basal surface but also because they can chelate Pd via dative bonding in such defined sites along the DNA lattice. Our results indicate that isolated, homogeneous, and ultrafine spherical Pd nanoparticles are densely in situ decorated on DNA-modified graphene surfaces with high stability and dispersibility. The prepared DNA-G-Pd hybrid has much greater activity and durability for formic acid electro-oxidation than the commercial Pd/C catalyst and polyvinylpyrrolidone-mediated graphene/Pd nanoparticle (PVP-G-Pd) hybrid used for direct formic acid fuel cells (DFAFCs). Besides, the DNA-G-Pd hybrid can also be an efficient and recyclable catalyst for the organic Suzuki reaction in aqueous solution under aerobic conditions without any preactivation. Since DNA can chelate various transition metal cations, this proof-of-concept protocol provides the possibility for the tailored design of other novel catalytic materials based on graphene with full exploitation of their properties.

  4. PdM nanoparticles (M = Ni, Co, Fe, Mn) with high activity and stability in formic acid oxidation synthesized by sonochemical reactions

    Science.gov (United States)

    Matin, Md. Abdul; Jang, Ji-Hoon; Kwon, Young-Uk

    2014-09-01

    Bimetallic alloy PdnM (n = 1 for M = Mn, Fe, and Co; n = 1, 2, and 3 for M = Ni) nanoparticles (NPs) are synthesized on carbon supports by sonochemical reactions of Pd(acac)2 (acac = acetylacetonate) with M(acac)2 (M = Ni, Co, Mn) or Fe(acac)3 in ethylene glycol. The NPs are characterized by powder X-ray diffractometry, transmission electron microscopy (TEM), and inductively coupled plasma-atomic emission spectroscopy to determine their crystal structures, particle sizes, morphology, and elemental compositions. Alloy formation of the NPs is proven by energy dispersive X-ray spectroscopy line profiles using scanning TEM. The electronic structures and the surface compositions of NPs are analyzed using X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, respectively. PdnM NPs are applied as electrocatalysts for formic acid oxidation. The incorporation of M in Pd reduces the poisoning by surface hydroxyl groups. Activities based on the current densities are in the order of PdNi > PdFe > PdCo > PdMn. Within the PdnNi series, the activity is in the order of PdNi > Pd2Ni > Pd3Ni. The PdnM NP electrocatalysts show higher activity by a factor of 2-3.5 and improved durability than similarly prepared Pd NP electrocatalyst.

  5. Using RTILs of EMIBF4 as 'water' to prepare palladium nanoparticles onto MWCNTs by pyrolysis of PdCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ding Keqiang, E-mail: dkeqiang@263.ne [College of Chemistry and Materials Science, Hebei Normal University, Yuhua East Road No: 113, Shijiazhuang 050016 (China); Yang Guokai [College of Chemistry and Materials Science, Hebei Normal University, Yuhua East Road No: 113, Shijiazhuang 050016 (China)

    2010-02-28

    For the first time, palladium nanoparticles supported on MWCNTs (multi-walled carbon nanotubes), denoted as Pd/MWCNTs, were prepared by a simple pyrolysis process of PdCl{sub 2} dissolved in room temperature ionic liquids (RTILs) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF{sub 4}) rather than water. X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to characterize the structure of Pd/MWCNTs, and the results showed that Pd nanoparticles with highly crystalline structure and a diameter of around 4 nm were prepared, and more importantly, except for carbon and palladium no other elements were detected. The results obtained from a pyrolysis process only containing PdCl{sub 2} and EMIBF4 testified that in our developed pyrolysis process, EMIBF4 was used not only as ligands, to form a novel complex, but also as a reducing agent, to reduce Pd{sup 2+}. The electrocatalytic performance of Pd/MWCNTs-modified glassy carbon electrode towards ethanol oxidation reaction (EOR) was also probed by cycle voltammetry (CV), demonstrating that it was possible to utilize the obtained Pd/MWCNTs as anode materials in fuel cell. Initiating the application of RTILs in the pyrolysis process and finding that EMIBF4 could be employed as ligands and reducing agents are the main contributions of this preliminary work.

  6. Fabrication a new modified electrochemical sensor based on Au-Pd bimetallic nanoparticle decorated graphene for citalopram determination.

    Science.gov (United States)

    Daneshvar, Leili; Rounaghi, Gholam Hossein; Es'haghi, Zarrin; Chamsaz, Mahmoud; Tarahomi, Somayeh

    2016-12-01

    This paper proposes a simple approach for sensing of citalopram (CTL) using gold-palladium bimetallic nanoparticles (Au-PdNPs) decorated graphene modified gold electrode. Au-PdNPs were deposited at the surface of a graphene modified gold electrode with simple electrodeposition method. The morphology and the electrochemical properties of the modified electrode were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy dispersion spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave voltammetry (SWV). The novel sensor exhibited an excellent catalytic activity towards the oxidation of CTL. The oxidation peak current of CTL, was linear in the range of 0.5-50μM with a detection limit 0.049μM with respect to concentration of citalopram. The proposed sensor was successfully applied for determination of CTL tablet and human plasma samples with satisfactory results.

  7. Pd-Au bimetallic catalysts: understanding alloy effects from planar models and (supported) nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Goodman, Wayne D.

    2012-12-21

    Pd-Au bimetallic catalysts often display enhanced catalytic activities and selectivities compared with Pd-alone catalysts. This enhancement is often caused by two alloy effects, i.e., ensemble and ligand effects. The ensemble effect is dilution of surface Pd by Au. With increasing surface Au coverages, contiguous Pd ensembles disappear and isolated Pd ensembles form. For certain reactions, for example vinyl acetate synthesis, this effect is responsible for reaction rate enhancement via the formation of highly active surface sites, e.g., isolated Pd pairs. The disappearance of contiguous Pd ensembles also switches off side reactions catalyzed by these sites. This explains selectivity increase of certain reactions, for example direct H2O2 synthesis. The ligand effect is electronic perturbation of Au to Pd. By direct charge transfer or affecting bond length, the ligand effect causes the Pd d band to be more filled and the d-band center away from the Fermi level. Both changes make Pd more "atomic like" therefore binding reactants and products weaker. For certain reactions, this eliminates the so-called "self poisoning" and enhances activity/selectivity.

  8. Immobilized Pd nanoparticles on Tris-modified SiO2:Synthesis, characterization, and catalytic activity in Heck cross-coupling reactions

    Institute of Scientific and Technical Information of China (English)

    Abdol R.Hajipour; Ghobad Azizi

    2014-01-01

    The preparation of supported Pd nanoparticles on Tris (tris(hydroxymethyl)aminomethane)-modi-fied SiO2 gel and their catalytic application in Heck coupling are investigated. The catalyst was char-acterized using a combination of X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and scanning electron microscopy/energy-dispersive X-ray spec-troscopy. The supported Pd nanoparticles were found to be a highly active and reusable catalyst for the Heck reaction at a low Pd loading (0.02 mol%) because of stabilization by the Tris moieties. Several reaction parameters, including the type and amount of solvent, base, and temperature, were evaluated. The heterogeneity of the catalytic system was investigated using different approaches, and showed that slight Pd leaching into the reaction solution occurred under the reaction condi-tions. Despite this metal leaching, the catalyst can be reused seven times without significant loss of its activity.

  9. Electro-hydrodynamic generation of monodisperse nanoparticles in the sub-10 nm size range from strongly electrolytic salt solutions: governing parameters of scaling laws

    Energy Technology Data Exchange (ETDEWEB)

    Maisser, Anne, E-mail: a.maisser@tudelft.nl [Delft University of Technology (Netherlands); Attoui, Michel B. [LISA, UMR CNRS University Paris Est Creteil, University Paris-Diderot (France); Ganan-Calvo, Alfonso M. [Universidad de Sevilla, ESI (Spain); Szymanski, Wladyslaw W. [University of Vienna, Faculty of Physics (Austria)

    2013-01-15

    A charge reduced electro-hydrodynamic atomization (EHDA) device has been used to generate airborne salt clusters in the sub 10 nm size range. The focus of this study on that specific sub-micron range of electrospray droplets with relatively high electrical conductivities and permittivities aims to address the still existing controversy on the scaling laws of electrosprayed droplet diameters. In this study different concentrations of sodium chloride and potassium chloride-both show strong electrolytic behavior-have been electrosprayed from solutions in pure water, or from aqueous ammonium acetate buffer liquids of varying concentrations. The dry residue salt cluster diameter generated by the EHDA process have been measured using a differential mobility analyzer. The initial droplet diameter has been determined indirectly from the measured particle size following the steps of Chen et al. (J Aerosol Sci 26:963-977, 1995). Results have been compared to existing scaling laws valid for direct droplet measurements. They can be interpreted concisely on the basis of a realistic hypothesis on possible electrochemical effects taking place and affecting the droplet and thus nanoparticle formation in EHDA. The hypothesis developed in this work and the comparison with the experimental results are shown and discussed in the manuscript.

  10. Simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid based on graphene anchored with Pd-Pt nanoparticles.

    Science.gov (United States)

    Yan, Jun; Liu, Shi; Zhang, Zhenqin; He, Guangwu; Zhou, Ping; Liang, Haiying; Tian, Lulu; Zhou, Xuemin; Jiang, Huijun

    2013-11-01

    Pd-Pt bimetallic nanoparticles anchored on functionalized reduced graphene oxide (RGO) nanomaterials were synthesized via a one-step in situ reduction process, in which Pt and Pd ions were first attached to poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene oxide (GO) sheets, and then the encased metal ions and GO were subjected to simultaneous reduction by ethylene glycol. The as-prepared Pd3Pt1/PDDA-RGO nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electrochemical methods. In addition, an electrochemical sensor based on the graphene nanocomposites was fabricated for the simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in their ternary mixture. Three well-separated voltammetric peaks along with remarkable increasing electro-oxidation currents were obtained in differential pulse voltammetry (DPV) measurements. Under the optimized conditions, there were linear relationships between the peak currents and the concentrations in the range of 40-1200 μM for AA, 4-200 μM for DA and 4-400 μM for UA, with the limit of detection (LOD) (based on S/N=3) of 0.61, 0.04 and 0.10 μM for AA, DA and UA, respectively. This improved electrochemical performance can be attributed to the synergistic effect of metallic nanoparticles and RGO and the combination of the bimetallic nanoparticles. Furthermore, the practical electroanalytical utility of the sensor was demonstrated by the determination of AA, DA and together with UA in human urine and blood serum samples with satisfactory results. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Atomic-level Pd-Pt alloying and largely enhanced hydrogen-storage capacity in bimetallic nanoparticles reconstructed from core/shell structure by a process of hydrogen absorption/desorption.

    Science.gov (United States)

    Kobayashi, Hirokazu; Yamauchi, Miho; Kitagawa, Hiroshi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki

    2010-04-28

    We have achieved the creation of a solid-solution alloy where Pd and Pt are homogeneously mixed at the atomic level, by a process of hydrogen absorption/desorption as a trigger for core (Pd)/shell (Pt) nanoparticles. The structural change from core/shell to solid solution has been confirmed by in situ powder X-ray diffraction, energy dispersive spectra, solid-state (2)H NMR measurement, and hydrogen pressure-composition isotherms. The successfully obtained Pd-Pt solid-solution nanoparticles with a Pt content of 8-21 atom % had a higher hydrogen-storage capacity than Pd nanoparticles. Moreover, the hydrogen-storage capacity of Pd-Pt solid-solution nanoparticles can be tuned by changing the composition of Pd and Pt.

  12. Pd nanoparticles encapsulated in magnetic carbon nanocages: an efficient nanoenzyme for the selective detection and multicolor imaging of cancer cells

    Science.gov (United States)

    Chen, Gaosong; Song, Jingjing; Zhang, Haoli; Jiang, Yuntian; Liu, Weisheng; Zhang, Wei; Wang, Baodui

    2015-08-01

    Rapid and simple molecular recognition based techniques for the identification of the subtypes of cancer cells are essential in molecular medicine. However, improving the sensitivity and accuracy of the early diagnosis of this disease remains a major challenge. Herein, we develop a novel approach for the in situ growth of palladium nanoparticles in magnetic carbon nanocages (PdNPs/MCNCs). The confined Pd NPs, which have excellent dispersion in magnetic carbon nanocages, show superior catalytic performance for the cleavage reaction of N-butyl-4-NHAlloc-1,8-naphthalimide (NNPH), thereby producing significant changes in both color (from colorless to jade-green) and fluorescence (from blue to green) through the ICT process. Based on the abovementioned results, a novel sensing platform utilizing the PdNPs/MCNC nanocatalyst as an artificial enzyme and NNPH as a fluorescent and color change reporter molecule for the multicolor imaging and colorimetric detection of cancer cells was developed. We envision that this nanomaterial can be used as a power tool for a wide range of potential applications in biotechnology and medicine.Rapid and simple molecular recognition based techniques for the identification of the subtypes of cancer cells are essential in molecular medicine. However, improving the sensitivity and accuracy of the early diagnosis of this disease remains a major challenge. Herein, we develop a novel approach for the in situ growth of palladium nanoparticles in magnetic carbon nanocages (PdNPs/MCNCs). The confined Pd NPs, which have excellent dispersion in magnetic carbon nanocages, show superior catalytic performance for the cleavage reaction of N-butyl-4-NHAlloc-1,8-naphthalimide (NNPH), thereby producing significant changes in both color (from colorless to jade-green) and fluorescence (from blue to green) through the ICT process. Based on the abovementioned results, a novel sensing platform utilizing the PdNPs/MCNC nanocatalyst as an artificial enzyme and NNPH

  13. Controllable assembly of well-defined monodisperse Au nanoparticles on hierarchical ZnO microspheres for enhanced visible-light-driven photocatalytic and antibacterial activity

    Science.gov (United States)

    Wang, Yuan; Fang, Hua-Bin; Zheng, Yan-Zhen; Ye, Rongqin; Tao, Xia; Chen, Jian-Feng

    2015-11-01

    A high-efficiency visible-light-driven photocatalyst composed of homogeneously distributed Au nanoparticles (AuNPs) well-defined on hierarchical ZnO microspheres (ZMS) via a controllable layer-by-layer self-assembly technique is demonstrated. The gradual growth of the characteristic absorption bands of Au loaded on ZnO in the visible light region with an increasing number of assemblies indicates the enhancement of the light harvesting ability of the ZMS/Au composites as well as the reproducibility and controllability of the entire assembly process. Results on the photoelectrochemical performance characterized by EIS and transient photocurrent response spectra indicate that the ZMS/Au composites possess increased photoinduced charge separation and transfer efficiency compared to the pure ZMS film. As a result, the hybrid composites exhibited enhanced decomposition activity for methylene blue and salicylic acid as well as antibacterial activity in killing S. aureus and E. coli under visible light irradiation. It can be noted that well-distributed Au components even at a rather low Au/ZnO weight ratio of ~1.2% also exhibited extraordinary photocatalysis. Such a facile and controllable self-assembly approach may be viable for preparing high-performance visible-light-driven ZMS/Au photocatalysts in a simple and controllable way, and consequently, the technology may extend to other plasmon-enhanced heterostructures made of nanostructured semiconductors and noble metals for great potential application in environmental protection.A high-efficiency visible-light-driven photocatalyst composed of homogeneously distributed Au nanoparticles (AuNPs) well-defined on hierarchical ZnO microspheres (ZMS) via a controllable layer-by-layer self-assembly technique is demonstrated. The gradual growth of the characteristic absorption bands of Au loaded on ZnO in the visible light region with an increasing number of assemblies indicates the enhancement of the light harvesting ability of

  14. Enhancing the cyclability of Li-O2 batteries using PdM alloy nanoparticles anchored on nitrogen-doped reduced graphene as the cathode catalyst

    Science.gov (United States)

    Leng, Limin; Li, Jing; Zeng, Xiaoyuan; Song, Huiyu; Shu, Ting; Wang, Haishui; Liao, Shijun

    2017-01-01

    An efficient ORR/OER catalyst was developed by anchoring highly dispersed bimetallic PdM (M = Fe, Co, Ni) alloy nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO). This new type of catalyst exhibited excellent ORR/OER activity, and the addition of transition metals also significantly improved catalytic stability, with the catalyst containing Fe (PdFe/N-rGO) exhibiting the best stability. A battery using this PdFe/N-rGO catalyst was capable of long-term stable cycling for 400 cycles (2000 h) with a limited capacity of 1000 mAh g-1 at 400 mA g-1, which was much longer than a battery with Pd/N-rGO as the catalyst (only 80 cycles, 400 h). We attribute the high performance of these catalysts to the high surface area of N-rGO, the anchoring of highly dispersed Pd alloy nanoparticles, and the prevention of Pd alloy nanoparticle aggregation and dissolution by the presence of the transition metals.

  15. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  16. Size-controlled Pd Nanoparticles Supported onα-Al2O3 as Heterogeneous Catalyst for Selective Hydrogenation of Acetylene

    Institute of Scientific and Technical Information of China (English)

    张火利; 杨元一; 戴伟; 鲁树亮; 于海波; 吉媛媛

    2014-01-01

    Size-controlled Pd nanoparticles (PdNPs) were synthesized in aqueous solution, using sodium car-boxymethyl cellulose as the stabilizer. Size-controlled PdNPs were supported onα-Al2O3 by the incipient wetness impregnation method. The PdNPs onα-Al2O3 support were in a narrow particle size distribution in the range of 1-6 nm. A series of PdNPs/α-Al2O3 catalysts were used for the selective hydrogenation of acetylene in ethylene-rich stream. The results show that PdNPs/α-Al2O3 catalyst with 0.03%(by mass) Pd loading is a very effective and sta-ble catalyst. With promoter Ag added, ethylene selectivity is increased from 41.0%to 63.8%at 100 °C. Comparing with conventional Pd-Ag/α-Al2O3 catalyst, PdNPs-Ag/α-Al2O3 catalyst has better catalytic performance in acety-lene hydrogenation and shows good prospects for industrial application.

  17. Switching-off toluene formation in the solvent-free oxidation of benzyl alcohol using supported trimetallic Au-Pd-Pt nanoparticles.

    Science.gov (United States)

    He, Qian; Miedziak, Peter J; Kesavan, Lokesh; Dimitratos, Nikolaos; Sankar, Meenakshisundaram; Lopez-Sanchez, Jose Antonio; Forde, Michael M; Edwards, Jennifer K; Knight, David W; Taylor, Stuart H; Kiely, Christopher J; Hutchings, Graham J

    2013-01-01

    Trimetallic Au-Pd-Pt nanoparticles have been supported on activated carbon by the sol-immobilisation method. They are found to be highly active and selective catalysts for the solvent-free aerobic oxidation of benzyl alcohol. The addition of Pt promotes the selectivity to the desired product benzaldehyde at the expense of toluene formation. Detailed aberration corrected STEM-XEDS analysis confirmed that the supported particles are indeed Au-Pd-Pt ternary alloys, but also identified composition fluctuations from particle-to-particle which vary systematically with nanoparticle size.

  18. Synergistic catalysis of metal-organic framework-immobilized Au-Pd nanoparticles in dehydrogenation of formic acid for chemical hydrogen storage.

    Science.gov (United States)

    Gu, Xiaojun; Lu, Zhang-Hui; Jiang, Hai-Long; Akita, Tomoki; Xu, Qiang

    2011-08-10

    Bimetallic Au-Pd nanoparticles (NPs) were successfully immobilized in the metal-organic frameworks (MOFs) MIL-101 and ethylenediamine (ED)-grafted MIL-101 (ED-MIL-101) using a simple liquid impregnation method. The resulting composites, Au-Pd/MIL-101 and Au-Pd/ED-MIL-101, represent the first highly active MOF-immobilized metal catalysts for the complete conversion of formic acid to high-quality hydrogen at a convenient temperature for chemical hydrogen storage. Au-Pd NPs with strong bimetallic synergistic effects have a much higher catalytic activity and a higher tolerance with respect to CO poisoning than monometallic Au and Pd counterparts. © 2011 American Chemical Society

  19. A Facile Synthesis of MPd (M=Co, Cu) Nanoparticles and Their Catalysis for Formic Acid Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, Vismadeb [Brown University; Chi, Miaofang [ORNL; Mankin, Max [Brown University; Liu, Yi [Brown University; Metin, Onder [Ataturk University; Sun, Daohua [Xiamen University, China; More, Karren Leslie [ORNL; Sun, Shouheng [Brown University

    2012-01-01

    Monodisperse CoPd nanoparticles (NPs) were synthesized and studied for catalytic formic acid (HCOOH) oxidation (FAO). The NPs were prepared by coreduction of Co(acac)2 (acac = acetylacetonate) and PdBr2 at 260 C in oleylamine and trioctylphosphine, and their sizes (5-12 nm) and compositions (Co10Pd90 to Co60Pd40) were controlled by heating ramp rate, metal salt concentration, or metal molar ratios. The 8 nm CoPd NPs were activated for HCOOH oxidation by a simple ethanol wash. In 0.1 M HClO4 and 2 M HCOOH solution, their catalytic activities followed the trend of Co50Pd50 > Co60Pd40 > Co10Pd90 > Pd. The Co50Pd50 NPs had an oxidation peak at 0.4 V with a peak current density of 774 A/gPd. As a comparison, commercial Pd catalysts showed an oxidation peak at 0.75 V with peak current density of only 254 A/gPd. The synthesis procedure could also be extended to prepare CuPd NPs when Co(acac)2 was replaced by Cu(ac)2 (ac = acetate) in an otherwise identical condition. The CuPd NPs were less active catalysts than CoPd or even Pd for FAO in HClO4 solution. The synthesis provides a general approach to Pd-based bimetallic NPs and will enable further investigation of Pd-based alloy NPs for electro-oxidation and other catalytic reactions.

  20. Order-disorder transformation in Fe-Pd alloy nanoparticles studied by in situ transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Kazuhisa, E-mail: ksato@imr.tohoku.ac.j [Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047 (Japan); Kovacs, Andras; Hirotsu, Yoshihiko [Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047 (Japan)

    2011-03-01

    We have studied order-disorder transformation in Fe-Pd alloy nanoparticles by in situ transmission electron microscopy (TEM) and electron diffraction. The transformation is size-dependent, and the transformation temperatures are lower than those of the bulk alloys. The transformation proceeds continuously but rather steeply as the temperature increases, which differs from the first-order transformation observed in a bulk alloy or gradual transformation predicted by simulations for nanoparticles. Experimental results indicated that the continuous nature can be attributed to the distribution of the transformation temperature due to the distributions of both particle size and alloy composition. Quantitative intensity analyses of nanobeam electron diffraction (NBD) patterns indicated the existence of short-range order (SRO) inside disordered nanoparticles. The SRO as well as particle size distribution are responsible for the remaining weak superlattice reflections above the transformation temperature. In situ high-resolution TEM (HRTEM) observation revealed the existence of the SRO, which was consistent with the results obtained by NBD. We show that the disorder may not necessarily proceed continuously from the surface toward the center of the nanoparticle. Ordering from the disordered phase upon cooling was also observed by in situ HRTEM, which can be attributed to growth of the SRO.

  1. Electrochemical oxidation of ammonia on carbon-supported bi-metallic PtM (M = Ir, Pd, SnO{sub x}) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lomocso, Thegy L. [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

    2011-10-01

    Highlights: > Oxidation of NH{sub 3} is investigated on carbon-supported Pt and PtM (M = Pd, Ir, SnO{sub x}) nanoparticles. > Carbon supported PtPd and PtIr nanoparticles show higher catalytic activity if compared to Pt nanocatalyst. > Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity and enhanced stability for NH{sub 3} oxidation. > Electronic effect between two metals in PtIr is responsible for increase in the catalytic activity. - Abstract: Ammonia electro-oxidation was studied in alkaline solution on carbon-supported Pt and bimetallic Pt{sub y}M{sub 1-y} (M = Pd, Ir, SnO{sub x} and y = 70, 50 at.%) nanoparticles. Catalysts were synthesized using the modified polyol method and deposited on carbon, resulting in 20 wt.% of metal loading. Particle size, structure and surface composition of the particles were investigated using TEM, XRD and XPS. Mean size of PtM bi-metallic nanoparticles varied between 2.0 and 4.7 nm, depending on the second metal (M). XRD revealed the structure of all bi-metallic particles to be face-centered cubic and confirmed alloy formation for Pt{sub y}Pd{sub 1-y} (y = 70, 50 at.%) and Pt{sub 7}Ir{sub 3}nanoparticles, as well as partial alloying between Pt and SnO{sub x}. Electrochemical behaviour of ammonia on Pt and PtM nanoparticles is comparable to that expected for bulk Pt and PtM alloys. Addition of Pd to Pt at the nanoscale decreased the onset potential of ammonia oxidation if compared to pure platinum nanoparticles; however stability of the catalyst was poor. For Pt{sub 7}(SnO{sub x}){sub 3}, current densities were similar to Pt, whereas catalyst stability against deactivation was improved. It is found that carbon supported Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity with enhanced stability for ammonia electro-oxidation. Electronic effect generated between two metals in the bimetallic nanoparticles might be responsible for increase in the catalytic activity of Pd- and Ir-containing catalysts, causing

  2. 单分散磁性纳米粒子固定化猪胰脂肪酶的研究%STUDY ON LIPASE IMMOBILIZATION ON MONODISPERSE MAGNETIC NANOPARTICLES

    Institute of Scientific and Technical Information of China (English)

    朱浩; 侯晨; 李彦锋

    2011-01-01

    A simple, effective, green and economic approach of lipase immobilization is provided in this article. Single-crystal,hydrophilic, biocompatible Fe3O4magnetic nanoparticles as good carriers were prepared via a solvothermal reduction method. Microsphere diameters were observed to be about 200 nm by transmission electron microscopy ( TEM ). Superior monodispersity was demonstrated, and saturation magnetization was found to be 83.7 emug-1 . The resulting products were modified directly with γ-aminopropyltriethoxysilane (APTS). Porcine pancreas lipase ( PPL) was covalently immobilized on the obtained particles using glutaraldehyde as a coupling reagent. The enzymatic activities of free and immobilized PPL were measured by titration of fatty acid which came from the hydrolysis of olive oil and the amount of protein was determined by the Bradford method using bovine serum albumin ( BSA) as a standard. The factors related with the activity of the immobilized lipase on prior carriers, such as the pH value of the immobilized reaction, the concentration of glutaraldehyde and the amount of enzyme were investigated. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with free enzyme. High activity recovery (54. 8% ) of the immobilized lipase was achieved and the amount of protein was up to 120 mg/g. This immobilized lipase can be reused 10 times with the enzymatic activity remained above 90% .%借助溶热法制备了一种亲水及生物相容良好的Fe3O4磁性纳米粒子,用γ-氨丙基三乙氧基硅烷直接对所得磁性粒子表面改性,然后用戊二醛偶联法制得了固定化猪胰脂肪酶.表征研究显示,所得磁性粒子粒径约200 nm,具有良好的单分散性和磁响应性.考察了戊二醛浓度、给酶量和反应时间对脂肪酶固定化过程的影响,并通过游离酶与固定化酶的比较研究了所得固定化酶的性质.所得固定化猪胰脂肪酶呈现出优异的热稳定性

  3. Green synthesis of Pd nanoparticles at Apricot kernel shell substrate using Salvia hydrangea extract: Catalytic activity for reduction of organic dyes.

    Science.gov (United States)

    Khodadadi, Bahar; Bordbar, Maryam; Nasrollahzadeh, Mahmoud

    2017-03-15

    For the first time the extract of the plant of Salvia hydrangea was used to green synthesis of Pd nanoparticles (NPs) supported on Apricot kernel shell as an environmentally benign support. The Pd NPs/Apricot kernel shell as an effective catalyst was prepared through reduction of Pd(2+) ions using Salvia hydrangea extract as the reducing and capping agent and Pd NPs immobilization on Apricot kernel shell surface in the absence of any stabilizer or surfactant. According to FT-IR analysis, the hydroxyl groups of phenolics in Salvia hydrangea extract as bioreductant agents are directly responsible for the reduction of Pd(2+) ions and formation of Pd NPs. The as-prepared catalyst was characterized by Fourier transform infrared (FT-IR) and UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive X-ray spectroscopy (EDS), Elemental mapping, X-ray diffraction analysis (XRD) and transmittance electron microscopy (TEM). The synthesized catalyst was used in the reduction of 4-nitrophenol (4-NP), Methyl Orange (MO), Methylene Blue (MB), Rhodamine B (RhB), and Congo Red (CR) at room temperature. The Pd NPs/Apricot kernel shell showed excellent catalytic activity in the reduction of these organic dyes. In addition, it was found that Pd NPs/Apricot kernel shell can be recovered and reused several times without significant loss of catalytic activity. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Water-dispersable hybrid Au-Pd nanoparticles as catalysts in ethanol oxidation, aqueous phase Suzuki-Miyaura and Heck reactions

    KAUST Repository

    Song, Hyon Min

    2012-01-01

    The catalytic activities of water-dispersable Au@Pd core-shell nanoparticles (NPs) and Au-Pd alloy NPs were examined. There is growing interest in Au-Pd hybridized NPs in a supported matrix or non-supported forms as catalysts in various reactions that are not limited to conventional Pd-related reactions. Four different Au@Pd core-shell NPs in this study were prepared at room temperature with help from the emulsion phase surrounding the Au core NPs. Au-Pd alloy NPs were prepared over 90 °C, and underwent phase transfer to aqueous medium for their catalytic use. Au@Pd core-shell NPs show catalytic activity in ethanol oxidation reactions as electrocatalysts, and both core-shell and alloy NPs are good to excellent catalysts in various Suzuki-Miyaura and Heck reactions as heterogeneous catalysts. Specifically, Au@Pd core-shell NPs with sharp branched arms show the highest yield in the reactions tested in this study. A relatively small amount (0.25 mol%) was used throughout the catalytic reactions. © 2012 The Royal Society of Chemistry.

  5. Electro-oxidation of methanol in alkaline conditions using Pd-Ni nanoparticles prepared from organometallic precursors and supported on carbon vulcan

    Science.gov (United States)

    Manzo-Robledo, A.; Costa, Natália J. S.; Philippot, K.; Rossi, Liane M.; Ramírez-Meneses, E.; Guerrero-Ortega, L. P. A.; Ezquerra-Quiroga, S.

    2015-12-01

    Oxidation of low-molecular weight alcohols as energy sources using metal nanoparticles has attracted considerable interest for use as a power source in portable electronic devices. In this work, a series of mono- and bimetallic nanoparticles based on palladium and nickel (Pd, Pd90Ni10, Pd50Ni50, Pd10Ni90, and Ni) have been synthesized from organometallic precursors, namely tris(dibenzylideneacetone) dipalladium(0), Pd2(dba)3, and bis(1,5-cyclooctadiene)nickel(0), Ni(cod)2. Well-defined metal particles in the nanometric scale from 4.2 to 6.3 nm were observed by transmission electron microscopy. The as-prepared nanoparticles were mixed with a carbon Vulcan matrix (10 % wt. of the catalyst in turn) for investigation as electrocatalysts in methanol oxidation reaction (MOR) in alkaline conditions. The i- E profiles from cyclic voltammetry for the monometallic systems indicated a redox process attributed only to palladium or nickel, as expected. With the bimetallic nanomaterials, the redox process and the i- E characteristics are functions of the amount of nickel associated to palladium. From a fundamental point of view, it has been established that the OH ions' interfacial interaction and the MOR kinetics are affected by the presence of nickel (decreasing the faradic current) as supported by the current versus potential profiles obtained as a function of methanol concentration and with temperature variation.

  6. Scalable Synthesis of Ag Networks with Optimized Sub-monolayer Au-Pd Nanoparticle Covering for Highly Enhanced SERS Detection and Catalysis

    Science.gov (United States)

    Li, Tianyu; Vongehr, Sascha; Tang, Shaochun; Dai, Yuming; Huang, Xiao; Meng, Xiangkang

    2016-11-01

    Highly porous tri-metallic AgxAuyPdz networks with a sub-monolayer bimetallic Au-Pd nanoparticle coating were synthesized via a designed galvanic replacement reaction of Ag nanosponges suspended in mixed solutions of HAuCl4 and K2PdCl4. The resulting networks’ ligaments have a rough surface with bimetallic nanoparticles and nanopores due to removal of Ag. The surface morphology and composition are adjustable by the temperature and mixed solutions’ concentration. Very low combined Au and Pd atomic percentage (1-x) where x is atomic percentage of Ag leads to sub-monolayer nanoparticle coverings allowing a large number of active boundaries, nanopores, and metal-metal interfaces to be accessible. Optimization of the Au/Pd atomic ratio y/z obtains large surface-enhanced Raman scattering detection sensitivity (at y/z = 5.06) and a higher catalytic activity (at y/z = 3.55) toward reduction reactions as benchmarked with 4-nitrophenol than for most bimetallic catalysts. Subsequent optimization of x (at fixed y/z) further increases the catalytic activity to obtain a superior tri-metallic catalyst, which is mainly attributed to the synergy of several aspects including the large porosity, increased surface roughness, accessible interfaces, and hydrogen absorption capacity of nanosized Pd. This work provides a new concept for scalable synthesis and performance optimization of tri-metallic nanostructures.

  7. In Situ Generation of Pd-Pt Core-Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins.

    Science.gov (United States)

    Goswami, Anandarup; Rathi, Anuj K; Aparicio, Claudia; Tomanec, Ondrej; Petr, Martin; Pocklanova, Radka; Gawande, Manoj B; Varma, Rajender S; Zboril, Radek

    2017-01-25

    Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (>98%), excellent selectivity (>98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core-shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions.

  8. Synthesis of Pd nanoparticles decorated with graphene and their application in electrocatalytic degradation of 4-chlorophenol.

    Science.gov (United States)

    Bian, Zhao-Yong; Bian, Yu; Wang, Hui; Ding, Ai-Zhong

    2014-09-01

    Pd/graphene catalysts were prepared in situ from graphite oxide and palladium salts by the hydrogen-reduction method and were then used for the construction of Pd/graphene gas-diffusion electrodes (GDE). The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential pulse voltammetry (DPV) techniques. In the Pd/graphene catalysts, Pd particles, with an average size of 3.6 nm and an amorphous structure, were highly dispersed in the graphene. The Pd/graphene catalysts accelerated the two-electron reduction of O2 to H2O2 by feeding air, which favors the production of hydroxyl radicals (HO*). In the electrolytic system, HO* was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The dechlorination degree of 4-chlorophenol reached approximately 90.5% after 80 min, and the removal efficiency and the average removal efficiency of 4-chlorophenol, in terms of total organic carbon (TOC) after 120 min, reached approximately 93.3% and 85.1%, respectively. Furthermore, based on the analysis of electrolysis intermediates by high performance liquid chromatography (HPLC) and ion chromatography (IC), a reaction scheme was proposed for the Pd/grapheme GDE catalytic degradation of 4-chlorophenol.

  9. Assembling formation of highly dispersed Pd nanoparticles supported 1D carbon fiber electrospun with excellent catalytic active and recyclable performance for Suzuki reaction

    Science.gov (United States)

    Yu, Dongdong; Bai, Jie; Wang, Junzhong; Liang, Haiou; Li, Chunping

    2017-03-01

    In this work, the preparation of the palladium nanoparticles with carbon nanofibers (Pd NPs/CNFs) catalyst for the Suzuki reaction was described. In the process, palladium nanoparticles were formed in the reaction of palladium chloride and glucose. The Pd NPs/CNFs complex catalyst was prepared in subsequent calcination processes, a series of characterization revealed that the Pd NPs were well-dispersed on the surfaces of the carbon nanofibers or embedded in the carbon nanofibers. This catalyst showed high catalytic activity for the Suzuki reaction of aryl halide and aryl boronic acid in the ethanol/water (v/v = 4/3) solution, and the catalyst still had good stability after 10 cycles.

  10. Advanced electron microscopy characterization of multimetallic nanoparticles

    Science.gov (United States)

    Khanal, Subarna Raj

    Research in noble metal nanoparticles has led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: PtPd, Au-Au3Cu, Cu-Pt, AgPd/Pt and AuCu/Pt nanoparticles. The objective of this work is to understand the physical and chemical properties of nanomaterials and describe synthesis, characterization, surface properties and growth mechanism of various bimetallic and multimetallic nanoparticles. The findings have provided us with novel and significant insights into the physical and chemical properties of noble metal nanoparticles. Different synthesis routes allowed us to synthesize bimetallic: Pt-Pd, Au-Au3Cu, Cu-Pt and trimetallic: AgPd/Pt, AuCu/Pt, core-shell and alloyed nanoparticles with monodispersed sizes, controlled shapes and tunable surface properties. For example, we have synthesized the polyhedral PtPd core-shell nanoparticles with octahedral, decahedral, and triangular plates. Decahedral PtPd core-shell structures are novel morphologies for this system. For the first time we fabricated that the Au core and Au3Cu alloyed shell nanoparticles passivated with CuS2 surface layers and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu ordered superlattice alloyed shell surrounded by CuS 2 surface layer. Additionally, we have described both experimental and theoretical methods of

  11. Characterization of bimetallic Fe/Pd nanoparticles by grape leaf aqueous extract and identification of active biomolecules involved in the synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fang; Yang, Die; Chen, Zuliang, E-mail: Zuliang.chen@newcastle.edu.au; Megharaj, Mallavarapu; Naidu, Ravi

    2016-08-15

    This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20 nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC–MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs. - Graphical abstract: TEM image for the Fe/Pd NPs synthesized by grape leaf aqueous extract. - Highlights: • The one-step green synthesis of Fe/Pd nanoparticles has been systematically characterized. • TEM showed that the Fe/Pd NPs were polydispersed with a diameter ranging from 2 to 20 nm. • Active biomolecules in the grape extract were identified.

  12. Bifunctional nanocatalyst based on three-dimensional carbon nanotube-graphene hydrogel supported Pd nanoparticles: one-pot synthesis and its catalytic properties.

    Science.gov (United States)

    Zhang, Zheye; Sun, Tai; Chen, Chen; Xiao, Fei; Gong, Zheng; Wang, Shuai

    2014-12-10

    We reported the development of a new type of bifunctional nanocatalyst based on three-dimensional (3D) macroscopic carbon nanotube (CNT)-graphene hydrogel (GH) supported Pd nanoparticles (i.e., Pd-CNT-GH) and explored its practical application in catalytic reduction of p-nitrophenol to p-aminophenol. The 3D Pd-CNT-GH was synthesized by a facile one-pot self-assembled approach through hydrothermal treatment of a mixed aqueous precursor solution of PdCl4(2-), CNT, and graphene oxide (GO). Under the appropriate condition, the spontaneous redox reaction between precursor PdCl4(2-) and CNT-GO as well as the self-assembly of macroscopic CNT-GH occurs simultaneously, leading to the formation of 3D Pd-CNT-GH. Because of the unique structural and functional properties of different components in the nanocatalyst and the synergistic effect between them, the as-prepared Pd-CNT-GH exhibits superior catalytic performance toward the reduction of p-nitrophenol to p-aminophenol, with 100% conversion within 30 s, even when the content of Pd in it is as low as 2.98 wt %. Moreover, after 20 successive cycles of reactions, the reaction time still keeps within 46 s. Therefore, the rational design of 3D macroscopic graphene-based nanohybrid material supported highly catalytically active nanoparticles, combined with the facile one-pot self-assembled strategy, provide a universal platform to fabricate desired 3D multifunctional nanomaterials that can be used in a broad range of catalysis, environmental protection, energy storage and conversation, drug delivery, chemical and biological sensing, and so forth.

  13. Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film.

    Science.gov (United States)

    Sobota, Marek; Schmid, Martin; Happel, Markus; Amende, Max; Maier, Florian; Steinrück, Hans-Peter; Paape, Natalia; Wasserscheid, Peter; Laurin, Mathias; Gottfried, J Michael; Libuda, Jörg

    2010-09-21

    Towards a better understanding of novel catalytic materials consisting of supported noble metal catalysts modified by an ionic liquid (IL) film, we have performed a study under ultrahigh-vacuum (UHV) conditions. The model surface consists of Pd nanoparticles grown in UHV on an ordered alumina film on NiAl(110). Thin films of the room temperature IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf(2)N] are deposited onto this surface by means of physical vapor deposition (PVD). The interaction of the IL with clean and CO-covered Pd/Al(2)O(3)/NiAl(110) at 300 K and the thermal behavior of the deposited IL films on Pd/Al(2)O(3)/NiAl(110) are investigated by time-resolved infrared reflection absorption spectroscopy (TR-IRAS) and X-ray photoelectron spectroscopy (XPS). At 300 K, the IL adsorbs molecularly both onto the Pd particles and onto the alumina. The IR spectra suggest that the [Tf(2)N](-) anions interact with Pd sites preferentially via the sulfonyl groups. CO pre-adsorbed on the Pd particles is partially displaced by the IL, even at 300 K, and only the part of CO adsorbed onto hollow sites on (111) facets of the Pd particles remains in place. Upon heating to temperatures higher than the desorption temperature of the IL (>400 K), molecular desorption of the IL competes with decomposition. The decomposition products, atomic species and small fragments, remain preferentially adsorbed onto the Pd nanoparticles and strongly modify their surface properties. Most of the decomposition products originate from the [BMIM](+) cations, whereas the [Tf(2)N](-) anions desorb for the most part.

  14. Pd nanoparticles supported on functionalized multi-walled carbon nanotubes (MWCNTs) and electrooxidation for formic acid

    Science.gov (United States)

    Yang, Sudong; Zhang, Xiaogang; Mi, Hongyu; Ye, Xiangguo

    To improve the utilization and activity of anodic catalysts for formic acid electrooxidation, palladium (Pd) particles were loaded on the MWCNTs, which were functionalized in a mixture of 96% sulfuric acid and 4-aminobenzenesulfonic acid, using sodium nitrite to produce intermediate diazonium salts from substituted anilines. The composition, particle size, and crystallinity of the Pd/f-MWCNTs catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) measurements. The electrocatalytic properties of the Pd/f-MWCNTs catalysts for formic acid oxidation were investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 0.5 mol L -1 H 2SO 4 solution. The results demonstrated that the catalytic activity was greatly enhanced due to the improved water-solubility and dispersion of the f-MWCNTs, which were facile to make the small particle size (3.8 nm) and uniform dispersion of Pd particles loading on the surface of the MWCNTs. In addition, the functionalized MWCNTs with benzenesulfonic group can provide benzenesulfonic anions in aqueous solution, which may combine with hydrogen cation and then promote the oxidation of formic acid reactive intermediates. So the Pd/f-MWCNTs composites showed excellent electrocatalytic activity for formic acid oxidation.

  15. Single-phase aqueous approach toward Pd sub-10 nm nanocubes and Pd-Pt heterostructured ultrathin nanowires.

    Science.gov (United States)

    Yuan, Qiang; Zhuang, Jing; Wang, Xun

    2009-11-21

    Monodisperse, highly-selective sub-10 nm Pd and Rh nanocubes have been successfully synthesized and, for the first time, bimetallic Pd-Pt heterostructured ultrathin nanowires have been achieved through using Pd nanocubes as seeds by a one-pot, single-phase aqueous method.

  16. Improved battery performance using Pd nanoparticles synthesized on the surface of LiFePO4/C by ultrasound irradiation

    Science.gov (United States)

    Saliman, Muhammad Ali; Okawa, Hirokazu; Takai, Misaki; Ono, Yuki; Kato, Takahiro; Sugawara, Katsuyasu; Sato, Mineo

    2016-07-01

    LiFePO4 has been attracting interest as a cathode material for Li-ion batteries due to its high energy density, low cost, and eco-friendliness. The electrochemical performance of LiFePO4 is limited because it exhibits low Li-ion diffusivity and low electronic conductivity. Numerous solutions have been considered, such as carbon coating, which is widely known to improve the electronic conductivity of LiFePO4. The deposition of metal nanoparticles (NPs) on the surface of carbon-coated LiFePO4 further enhances the electronic conductivity. In this study, we deposited Pd NPs onto the surface of LiFePO4/C and investigated the resulting electrochemical performance. Sonochemical synthesis was used to prepare the metal NPs; the procedure did not require any surfactants and the reaction was rapid.

  17. Hydrodechlorination of polychlorinated biphenyls in contaminated soil from an e-waste recycling area, using nanoscale zerovalent iron and Pd/Fe bimetallic nanoparticles.

    Science.gov (United States)

    Chen, Xi; Yao, Xiaoyan; Yu, Chunna; Su, Xiaomei; Shen, Chaofeng; Chen, Chen; Huang, Ronglang; Xu, Xinhua

    2014-04-01

    Soil pollution by polychlorinated biphenyls (PCBs) arising from the crude disposal and recycling of electronic and electrical waste (e-waste) is a serious issue, and effective remediation technologies are urgently needed. Nanoscale zerovalent iron (nZVI) and bimetallic systems have been shown to promote successfully the destruction of halogenated organic compounds. In the present study, nZVI and Pd/Fe bimetallic nanoparticles synthesized by chemical deposition were used to remove 2,2',4,4',5,5'-hexachlorobiphenyl from deionized water, and then applied to PCBs contaminated soil collected from an e-waste recycling area. The results indicated that the hydrodechlorination of 2,2',4,4',5,5'-hexachlorobiphenyl by nZVI and Pd/Fe bimetallic nanoparticles followed pseudo-first-order kinetics and Pd loading was beneficial to the hydrodechlorination process. It was also found that the removal efficiencies of PCBs from soil achieved using Pd/Fe bimetallic nanoparticles were higher than that achieved using nZVI and that PCBs degradation might be affected by the soil properties. Finally, the potential challenges of nZVI application to in situ remediation were explored.

  18. Hierarchical top-porous/bottom-tubular TiO 2 nanostructures decorated with Pd nanoparticles for efficient photoelectrocatalytic decomposition of synergistic pollutants

    KAUST Repository

    Zhang, Zhonghai

    2012-02-22

    In this paper, top-porous and bottom-tubular TiO 2 nanotubes (TiO 2 NTs) loaded with palladium nanoparticles (Pd/TiO 2 NTs) were fabricated as an electrode for an enhanced photoelectrocatalytic (PEC) activity toward organic dye decomposition. TiO 2 NTs with a unique hierarchical top-porous and bottom-tubular structure were prepared by a facile two-step anodization method and Pd nanoparticles were decorated onto the TiO 2 NTs via a photoreduction process. The PEC activity of Pd/TiO 2 NTs was investigated by decomposition of methylene blue (MB) and Rhodamine B (RhB). Because of formation Schottky junctions between TiO 2 and Pd, which significantly promoted the electron transfer and reduced the recombination of photogenerated electrons and holes, the Pd/TiO 2 NT electrode showed significantly higher PEC activities than TiO 2 NTs. Interestingly, an obvious synergy between two dyes was observed and corresponding mechanism based on facilitated transfer of electrons and holes as a result of a suitable energy level alignment was suggested. The findings of this work provide a fundamental insight not only into the fabrication but also utility of Schottky junctions for enhanced environmental remediation processes. © 2012 American Chemical Society.

  19. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vidal-Iglesias, F.J.; Solla-Gullon, J.; Montiel, V.; Feliu, J.M.; Aldaz, A. [Instituto de Electroquimica, Universidad de Alicante, Apartado 99, 03080 Alicante (Spain)

    2007-09-27

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3-4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt{sub 75}Ir{sub 25} and Pt{sub 75}Rh{sub 25} nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes. (author)

  20. Unsupported PVA- and PVP-stabilized Pd nanoparticles as catalyst for nitrite hydrogenation in aqueous phase

    NARCIS (Netherlands)

    Zhao, Y.; Baeza, J.A.; Koteswara Rao, N.; Calvo, L.; Gilarranz, M.A.; Li, Y.D.; Lefferts, L.

    2014-01-01

    Pd colloids stabilized with polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) have been prepared, characterized with TEM, zeta potential measurements, CO chemisorption in aqueous phase, and ATR-IR spectroscopy using CO as a probe molecule, and finally tested for performance in nitrite hydrogena

  1. Efficient Sonogashira and Suzuki-Miyaura coupling reaction catalyzed by Pd-Nanoparticles

    Indian Academy of Sciences (India)

    Kishor E Balsane; Suresh S Shendage; Jayashree M Nagarkar

    2015-03-01

    The Pd nano particles were electrochemically deposited on nafion-graphene. They showed excellent catalytic activity towards Sonogashira and Suzuki-Miyaura cross-coupling reaction. Benzenediazonium salts were used as alternative to aromatic halide. The developed protocol offers recyclability, easy workups with short reaction time and good-to-excellent product yield.

  2. Pd-Pt random alloy nanocubes with tunable compositions and their enhanced electrocatalytic activities.

    Science.gov (United States)

    Yuan, Qiang; Zhou, Zhiyou; Zhuang, Jing; Wang, Xun

    2010-03-07

    Monodisperse, highly-selective sub-10 nm Pd-Pt random alloy nanocubes have been successfully synthesized in aqueous solution, and the electrocatalytic activity of these Pd-Pt alloys towards formic acid oxidation was investigated and compared with the activity of Pd sub-10 nm nanocubes, and the commercial Pd and Pt black.

  3. Origin and shape evolution of core-shell nanoparticles in Au-Pd: from few atoms to high Miller index facets

    Energy Technology Data Exchange (ETDEWEB)

    Bhattarai, Nabraj; Casillas, Gilberto; Khanal, Subarna; Velazquez Salazar, J. Jesus; Ponce, Arturo; Jose-Yacaman, Miguel, E-mail: miguel.yacaman@utsa.edu [University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-06-15

    Au-Pd core-shell nanocubes and triangular nanoparticles were systematically synthesized from a few Pd layers up to fully grown morphologies by a modified seed-mediated growth method. The shape evolution of Au-Pd core-shell nanoparticles from single crystal and singly twinned seed to final concave nanocube and triangular plates are presented at atomic level by Cs-corrected scanning transmission electron microscopy (STEM). The growth mechanism of both morphologies was studied throughout different sizes. It was found that the concave nanocubes grew from octahedral Au seeds due to fast growth along Left-Pointing-Angle-Bracket 111 Right-Pointing-Angle-Bracket directions; while the triangular nanoparticles grew from singly twinned Au seeds, growing twice as fast in Left-Pointing-Angle-Bracket 110 Right-Pointing-Angle-Bracket directions along the twin boundary; compared to the Left-Pointing-Angle-Bracket 111 Right-Pointing-Angle-Bracket direction perpendicular to the twin boundary. Both the concave nanocubes and triangular nanoparticles presented high index facet (HIF) surfaces that will increase the catalytic activity of different reactions.

  4. Montmorillonite-supported Pd0, Fe0, Cu0 and Ag0 nanoparticles: Properties and affinity towards CO2

    Science.gov (United States)

    Bouazizi, Nabil; Barrimo, Diana; Nousir, Saadia; Ben Slama, Romdhane; Roy, René; Azzouz, Abdelkrim

    2017-04-01

    This study reports the carbon dioxide (CO2) adsorption on montmorillonite (NaMt) incorporating Cu0, Fe0, Pd0 and Ag0 as metallic nanoparticles (MNPs). The changes in structural, textural, morphological and adsorption properties of the resulting materials (NaMt-MNPs) were investigated. Electron microscopy and X-ray diffraction showed that dispersion of fine MNPs occurs mainly within the interlayer space of NaMt, producing a slight structure expansion. This was accompanied by a visible enhancement of the affinity towards CO2, as supported by thermal programmed desorption measurements. NaMt-MNPs displayed high CO2 retention capacity (CRC) of ca. 657 μmol/g for NaMt-Cu as compared to NaMt. This was explained in terms of increased number of available adsorption sites due to enlarged interlayer spaces caused by MNP insertion. The differences in CO2 adsorption capacities clearly demonstrate the key role of MNPs in improving the surface properties and adsorption capacity. The results reported herein open new prospects for clay supported metal nanoparticles as efficient adsorbents for CO2.

  5. Ocular Brachytherapy Dosimetry for 103Pd and 125I in The Presence of Gold Nanoparticles: Monte Carlo Study

    CERN Document Server

    Asadi, S; Vahidian, M; Marghchouei, M; Masoudi, S Farhad

    2015-01-01

    The aim of the present Monte Carlo study is to evaluate the variation of energy deposition in healthy tissues in the human eye which is irradiated by brachytherapy sources in comparison with the resultant dose increase in the gold nanoparticle(GNP)-loaded choroidal melanoma. The effects of these nanoparticles on normal tissues are compared between 103Pd and 125I as two ophthalmic brachytherapy sources. Dose distribution in the tumor and healthy tissues have been taken into account for both mentioned brachytherapy sources. Also, in a certain point of the eye, the ratio of the absorbed dose by the normal tissue in the presence of GNPs to the absorbed dose by the same point in the absence of GNPs has been calculated. In addition, differences observed in the comparison of simple water phantom and actual simulated human eye in presence of GNPs are also a matter of interest that have been considered in the present work. The results show that the calculated dose enhancement factor in the tumor for 125I is higher tha...

  6. Application of aluminum-supported Pd, Rh, and Rh-Pd nanoparticles in supercritical carbon dioxide system for hydrodebromination of polybrominated diphenyl ethers.

    Science.gov (United States)

    Wu, Ben-Zen; Sun, Yu-Jie; Chen, Yan-Hua; Yak, Hwa Kwang; Yu, Jya-Jyun; Liao, Weisheng; Chiu, KongHwa; Peng, Shie-Ming

    2016-08-01

    Al-powder-supported Pd, Rh, and Rh-Pd catalysts were synthesized through a spontaneous redox reaction in aqueous solutions. These catalysts hydrodebrominated 4- and 4,4'-bromodiphenyl ethers in supercritical carbon dioxide at 200 atm CO2 containing 10 atm H2 and 80 °C in 1 h. Diphenyl ether was the major product of Pd/Al. Rh/Al and Rh-Pd/Al further hydrogenated two benzene rings of diphenyl ether to form dicyclohexyl ether. The hydrogenolysis of CO bonds on diphenyl ether over Rh/Al and Rh-Pd/Al was observed to generate cyclohexanol and cyclohexane (Rh-Pd/Al among three catalysts is suggested to be used for ex situ degradation of polybrominated diphenyl ethers in supercritical carbon dioxide. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Au-Pd/石墨烯和 Au-Pd/碳纳米管催化电化学氧化甲酸%Effect of graphene and carbon nanotubes supported Au-Pd nanoparticles for electrocatalytic oxidation of formic acid

    Institute of Scientific and Technical Information of China (English)

    高丽; 吕逍雨; 杨海堂; 杨敬贺; 毛立群

    2015-01-01

    利用化学还原法合成了石墨烯和碳纳米管负载的 Au‐Pd 纳米粒子.石墨烯负载的 Au‐Pd 纳米粒子(Au‐Pd/G)的粒径远小于碳纳米管负载的 Au‐Pd 纳米粒子(Au‐Pd/CNTs)的粒径,且 Au‐Pd 纳米粒子在复合材料上分布均匀.与碳纳米管负载的 Au‐Pd 纳米粒子催化剂相比,石墨烯负载的 Au‐Pd 催化剂对甲酸的催化显示出更好的电催化活性,结果表明作为 Au‐Pd 纳米粒子的基底,石墨烯可以明显提高 Au‐Pd 纳米粒子的电催化活性.在0.1 mol/L H2 SO4中,该纳米修饰电极对甲酸有良好的电催化作用,甲酸在电极上的氧化动力学过程为扩散控制过程.%Graphene and carbon nanotubes supported Au‐Pd nanoparticles are synthesized by a chemical reduction method .The particle size of graphene supported Au‐Pd nanoparticles (Au‐Pd/G) is much smaller than that of carbon nanotubes supported Au‐Pd nanoparticles (Au‐Pd/CNTs) .There is a relatively high degree of nanoparticles dispersion on Au‐Pd/G .The Au‐Pd/G catalyst shows a higher electrocatalytic activity for the formic acid electrooxidation compared to the Au‐Pd/CNTs catalyst indicating the substrate graphene can obviously enhance the cata‐lytic activity of Au‐Pd nanoparticles .In 0 .1 mol/L H2 SO4 solution ,the modified electrode ex‐hibited good electrocatalytic activity on the oxidation of formic acid ,and the electrode reaction of formic acid was a diffusion control process .

  8. Synthesis of novel AuPd nanoparticles decorated one-dimensional ZnO nanorod arrays with enhanced photoelectrochemical water splitting activity.

    Science.gov (United States)

    Lu, Yan; Zhang, Junlong; Ge, Lei; Han, Changcun; Qiu, Ping; Fang, Siman

    2016-12-01

    The vertically aligned one-dimensional (1D) ZnO nanorod arrays decorated with AuPd alloy nanoparticles have been synthesized with ZnO nanorod arrays as template via a mild hydrothermal method. In this work, the as-prepared AuPd/ZnO nanorod arrays demonstrated high light-harvesting efficiency. The microstructures, morphologies and chemical properties of the obtained AuPd/ZnO composite photocatalyst were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The photoelectrochemical (PEC) performances of as-obtained AuPd/ZnO nanorod arrays were examined, and the photocurrent density was up to 0.98mAcm(-2) at 0.787V versus Ag/AgCl, which was about 2.4 times higher than the pure ZnO sample. A possible photocatalytic mechanism of the AuPd/ZnO hybrid nanostructures under the simulated sunlight irradiation was proposed to guide further improvement of other desirable materials. According to the above experiment results, it can be clearly found that AuPd/ZnO composite nanorod arrays showed excellent PEC performance and had promising applications in the utilization of solar energy.

  9. Green-chemistry Compatible Approach to TiO2-supported PdAu Bimetallic Nanoparticles for Solvent-free 1-Phenylethanol Oxidation under Mild Conditions

    Institute of Scientific and Technical Information of China (English)

    Jian-Bing Chang; Chang-Hai Liu; Jie Liu; Yu-Yan Zhou; Xu Gao; Sui-Dong Wang

    2015-01-01

    TiO2-supported PdAu bimetallic nanoparticles (NPs) with small size and good dispersity were prepared by the room-temperature ionic liquid-assisted bimetal sputtering, which is simple, environmentally friendly, and free of additives and byproducts. Pd/Au atomic ratio can be tuned by controlling the sputtering conditions simply. High catalytic activity was found in PdAu–NPs–TiO2 hybrids for solvent-free selective oxidation of 1-phenylethanol using O2 as the oxidant at the low temperature of 50 °C and low pressure of 1 atm. It was found that Pd/Au ratio strongly affected the catalytical activity, and the highest conversion of about 35%and turnover frequency of about 421 h-1 were achieved at 1:1 of Pd/Au atomic ratio. The synergistic effect in PdAu NPs was also discussed based on the comprehensive characterization results. The present approach may offer an alternative platform for future development of green-chemistry compatible bimetallic nanocatalysts.

  10. Photoelectron diffraction of Rh nanoparticles growth on Fe{sub 3}O{sub 4}/Pd(111) ultra thin film

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, G.J.P.; Pancotti, A.; Lima, L.H.; Siervo, A. de; Landers, R. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

    2012-07-01

    Full text: Heterogeneous catalysis is a highly complex process. Usually, a catalyst is formed by transition metal nanoparticles (for example, Pd, Pt, Rh, Ni, Au) supported by an oxide such as alumina, silica, titania among others [1-4]. The performance of the catalyst in terms of macroscopic chemical parameters such as the temperature for reaction activation, selectivity and efficiency can be strongly influenced by different characteristics of the catalyst at the atomic level, for instance, its electronic and atomic structure, particle size and shape, crystallographic structure [5-6] and support material effects[1]. Metal-oxide-based catalysts are used for many important synthesis reactions in the chemical industry, such as selective oxidation, dehydrogenation, isomerization and other chemical processes [7]. Rhodium nanoparticles have been used, for example, in the studies of propionaldehyde decomposition under ultra-high vacuum (UHV) conditions. The aim of this work is to prepare rhodium nanoparticles on magnetite (Fe{sub 3}O{sub 4}) (111) growth on Pd(111). The rhodium clusters and iron oxide ultra-thin films (thickness <10ML) were prepared in UHV conditions by Molecular Beam Epitaxy (MBE) and keeping the substrate at 450 deg C. The system was characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and photoelectron diffraction (PED) performed at the SGM beam line at the Brazilian Synchrotron Light Source (LNLS). Our results shows the formation of small Rh an island with the same atomic structure of fcc Rh at bulk, and thickness lower then 5MLs. The islands cover approximately 15% of the iron surface. These findings were determined mainly with the PED experiments supported by a comprehensive simulation approach based on multiple scattering calculations. References: [1] J. Libuda, H.-J. Freund, Surf. Sci. Rep. 57, 157 (2005). [2] C. R. Henry, Surf. Sci. Rep. 31, 231 (1998). [3] N. Nilius, A. Corper, G. Bozdech, N. Ernst , H

  11. Studying the Structure and the Optical Properties of Pd Nanoparticles Affected by Precursor Concentration

    Directory of Open Access Journals (Sweden)

    Munaf. S. Majeed

    2016-01-01

    Full Text Available In this paper, Palladium (Pd nanoparticales (NPs at different concentrations (150 and 500 capped with poly (vinylpyrrolidone (PVP were Synthesized by a polyol reduction method in an ethylene glycol solution at temperature of 45C˚. The structural and optical properties of Pd NPs has been investigated, all thin films were tested using X-ray diffraction (XRD, all XRD peaks can be indexed as face centered cubic (FCC Structure, with strong crystalline orientation at (111 plane. The morphology properties of the prepared films were study by Atomic Force Microscopy (AFM the results indicated that all films have nanoscale grain size around 80 nm and Scan Electron Microscopy (SEM images show spherical nanoscale particles with clusters shape. The size of the particles decreased with increasing of concentrations

  12. Plasmon enhanced visible light photocatalysis for TiO2 supported Pd nanoparticles.

    Science.gov (United States)

    Lacerda, A M; Larrosa, I; Dunn, S

    2015-08-07

    A photocatalyst consisting of nanostructured Pd photochemically deposited on 20 nm TiO2 displays a reaction half-life for rhodamine b decolourisation of 0.5 minute compared to the 9.4 minutes for unmodified P25 under identical reaction conditions. We associate this increased decolourisation rate to the increase in solar light harvesting which we have measured at 8% due to a significant red shift in the absorption profile of the catalyst. We relate the increased absorption of light with a visible active plasmon effect that is associated with the Pd nanostructures on the TiO2. This overall red-shift in the light harvesting for the catalyst leads to photocatalytic activity for excitations up to 600 nm.

  13. Facile Synthesis of Monodisperse Gold Nanocrystals Using Virola oleifera

    Science.gov (United States)

    Milaneze, Bárbara A.; Oliveira, Jairo P.; Augusto, Ingrid; Keijok, Wanderson J.; Côrrea, Andressa S.; Ferreira, Débora M.; Nunes, Otalíbio C.; Gonçalves, Rita de Cássia R.; Kitagawa, Rodrigo R.; Celante, Vinícius G.; da Silva, André Romero; Pereira, Ana Claudia H.; Endringer, Denise C.; Schuenck, Ricardo P.; Guimarães, Marco C. C.

    2016-10-01

    The development of new routes and strategies for nanotechnology applications that only employ green synthesis has inspired investigators to devise natural systems. Among these systems, the synthesis of gold nanoparticles using plant extracts has been actively developed as an alternative, efficient, cost-effective, and environmentally safe method for producing nanoparticles, and this approach is also suitable for large-scale synthesis. This study reports reproducible and completely natural gold nanocrystals that were synthesized using Virola oleifera extract. V. oleifera resin is rich in epicatechin, ferulic acid, gallic acid, and flavonoids (i.e., quercetin and eriodictyol). These gold nanoparticles play three roles. First, these nanoparticles exhibit remarkable stability based on their zeta potential. Second, these nanoparticles are functionalized with flavonoids, and third, an efficient, economical, and environmentally friendly mechanism can be employed to produce green nanoparticles with organic compounds on the surface. Our model is capable of reducing the resin of V. oleifera, which creates stability and opens a new avenue for biological applications. This method does not require painstaking conditions or hazardous agents and is a rapid, efficient, and green approach for the fabrication of monodisperse gold nanoparticles.

  14. Structural disorder versus spin canting in monodisperse maghemite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Kubickova, S.; Vejpravova, J., E-mail: vejpravo@fzu.cz [Department of Magnetic Nanosystems, Institute of Physics of the ASCR, v.v.i., Na Slovance 2, 182 21 Prague (Czech Republic); Niznansky, D. [Faculty of Science, Department of Inorganic Chemistry, Charles University in Prague, Albertov 2030, 128 40 Prague (Czech Republic); Morales Herrero, M. P. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Salas, G. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Madrileno de Estudios Avanzados en Nanociencia, Campus Universitario de Cantoblanco, 28049 Madrid (Spain)

    2014-06-02

    Monodisperse maghemite nanoparticles with diameter ranging from 7 to 20 nm were examined by the In-field Mössbauer Spectroscopy (IFMS) in varying external magnetic field up to 6 T. Surprisingly, the small-sized particles (7 nm) exhibit nearly no spin canting in contrast to the larger particles with lower surface-to-volume ratio. We demonstrate that the observed phenomenon is originated by lower relative crystallinity of the larger particles with different internal structure. Hence, the persistence of the 2nd and 5th absorption lines in the IFMS cannot be unambiguously assigned to the surface spins.

  15. Room temperature biogenic synthesis of multiple nanoparticles (Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li) by Pseudomonas aeruginosa SM1

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Sarvesh Kumar; Constanti, Magda, E-mail: magdalena.constanti@urv.cat [Universitat Rovira i Virgili, Departament d' Enginyeria Quimica (Spain)

    2012-03-15

    Room temperature biosynthesis of Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li nanoparticles was achieved using Pseudomonas aeruginosa SM1 without the addition of growth media, electron donors, stabilizing agents, preparation of cell/cell-free extract or temperature, and pH adjustments. The resulting nanoparticles were characterized by Transmission electron microscopy and X-ray diffraction. It was observed that P. aeruginosa SM1 is capable of producing both intracellular (Co and Li) and extracellular (Ag, Pd, Fe, Rh, Ni, Ru, and Pt) nanoparticles in both crystalline and amorphous state. The FT-IR spectra clearly showed the presence of primary and secondary amines which may be responsible for the reduction and subsequent stabilization of the resulting extracellular nanoparticles which were obtained as a one-step process. This suggests toward an unknown 'selection mechanism' that reduces certain metal ions and allows others to enter the cell membrane. Finally, in this first of its kind study, single strain of bacteria was used to produce several different mono-metallic nanoparticles.

  16. Room temperature biogenic synthesis of multiple nanoparticles (Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li) by Pseudomonas aeruginosa SM1

    Science.gov (United States)

    Srivastava, Sarvesh Kumar; Constanti, Magda

    2012-03-01

    Room temperature biosynthesis of Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li nanoparticles was achieved using Pseudomonas aeruginosa SM1 without the addition of growth media, electron donors, stabilizing agents, preparation of cell/cell-free extract or temperature, and pH adjustments. The resulting nanoparticles were characterized by Transmission electron microscopy and X-ray diffraction. It was observed that P. aeruginosa SM1 is capable of producing both intracellular (Co and Li) and extracellular (Ag, Pd, Fe, Rh, Ni, Ru, and Pt) nanoparticles in both crystalline and amorphous state. The FT-IR spectra clearly showed the presence of primary and secondary amines which may be responsible for the reduction and subsequent stabilization of the resulting extracellular nanoparticles which were obtained as a one-step process. This suggests toward an unknown "selection mechanism" that reduces certain metal ions and allows others to enter the cell membrane. Finally, in this first of its kind study, single strain of bacteria was used to produce several different mono-metallic nanoparticles.

  17. Intermetallic GaPd2 Nanoparticles on SiO2 for Low-Pressure CO2 Hydrogenation to Methanol

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria; Sharafutdinov, Irek; Carvalho, Hudson W. P.

    2015-01-01

    A nanodispersed intermetallic GaPd2/SiO2 catalyst is prepared by simple impregnation of industrially relevant high-surface-area SiO2 with Pd and Ga nitrates, followed by drying, calcination, and reduction in hydrogen. The catalyst is tested for CO2 hydrogenation to methanol at ambient pressure...... and in situ extended X-ray absorption fine structure spectroscopy show that the GaPd2 intermetallic phase is formed upon activation of the catalyst via reduction and remains stable during CO2 hydrogenation. Identical location-transmission electron microscopy images acquired ex situ (i.e., micrographs...... of exactly the same catalyst area recorded at the different steps of activation and reaction procedure) show that nanoparticle size and dispersion are defined upon calcination with no significant changes observed after reduction and methanol synthesis. Similar conclusions can be drawn from electron...

  18. Green synthesis, characterization and catalytic activity of the Pd/TiO2 nanoparticles for the ligand-free Suzuki-Miyaura coupling reaction.

    Science.gov (United States)

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad

    2016-03-01

    A green synthesis process was developed for production of the Pd/TiO2 nanoparticles (NPs) without using toxic, hazardous and dangerous materials. Myrtus communis L. leaf extract serves as a mild, renewable and non-toxic reducing agent. The advantages of this biosynthesis method include use of cheap, clean, nontoxic and environmentally benign precursors and simple procedures without time-consuming polymerization and problems with treatment of a highly viscous polymeric resin. More importantly, the synthesized Pd/TiO2 NPs presented excellent catalytic activity for ligand-free Suzuki-Miyaura coupling which could be easily separated from the reaction mixture and reused many times with no loss of activity. Therefore, these properties indicate demonstrative benefits of the catalyst. The Pd/TiO2 NPs was characterized by FESEM, TEM, FT-IR, UV-vis spectroscopy and EDS. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Sensitive determination of dopamine in the presence of uric acid and ascorbic acid using TiO2 nanotubes modified with Pd, Pt and Au nanoparticles.

    Science.gov (United States)

    Mahshid, Sara; Li, Chengcheng; Mahshid, Sahar Sadat; Askari, Masoud; Dolati, Abolghasem; Yang, Lixia; Luo, Shenglian; Cai, Qingyun

    2011-06-07

    A simple modified TiO(2) nanotubes electrode was fabricated by electrodeposition of Pd, Pt and Au nanoparticles. The TiO(2) nanotubes electrode was prepared using the anodizing method, followed by modifying Pd nanoparticles onto the tubes surface, offering a uniform conductive surface for electrodeposition of Pt and Au. The performance of the modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The Au/Pt/Pd/TiO(2) NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. In both case, electro-oxidation peak currents of dopamine were linearly related to accumulated concentration over a wide concentration range of 5.0 × 10(-8) to 3.0 × 10(-5) M. However in the same range of dopamine concentration, the sensitivity had a significant loss at Pt/Pd/TiO(2) NTs electrode, suggesting the necessity for Au nanoparticles in modified electrode. The limit of the detection was determined as 3 × 10(-8) M for dopamine at signal-to-noise ratio equal to 3. Furthermore, the Au/Pt/Pd/TiO(2) NTs modified electrode was able to distinguish the oxidation response of dopamine, uric acid and ascorbic acid in mixture solution of different acidity. It was shown that the modified electrode possessed a very good reproducibility and long-term stability. The method was also successfully applied for determination of DA in human urine samples with satisfactory results.

  20. Electrochemical sensor for detection of hydrazine based on Au@Pd core–shell nanoparticles supported on amino-functionalized TiO{sub 2} nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xianlan [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Liu, Wei [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); Tang, Lele [College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Wang, Jian [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Du, Min [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2014-01-01

    In this paper, we reported a simple strategy for synthesizing well-defined TiO{sub 2}NTs–Au@Pd hybrid nanostructures with prior TiO{sub 2} nanotube functionalization (F-TiO{sub 2}NTs). TiO{sub 2}NTs with larger surface area (BET surface area is 184.9 m{sup 2} g{sup −1}) were synthesized by hydrothermal method, and the NTs are anatase phase with a range of 2–3 μm in length and 30–50 nm in diameter after calcined at 400 °C for 3 h. 3-Aminopropyl-trimethoxysilane (APTMS) as a coupling agent was reacted with the surface hydroxyl groups as anchoring sites for flower-shaped bimetallic Au@Pd nanostructures, self-assembling amine functionality on the surface of TiO{sub 2}NTs. Note that two faces at the interface between F-TiO{sub 2}NTs with (004) plane and Au@Pd nanostructures with (111) one of cubic Au and Pd nanoparticles are compatible, benefiting to the charge transfer between two components due to their crystalline coordination. The results showed that as-prepared F-TiO{sub 2}NTs–Au@Pd hybrid nanostructures modified glassy carbon electrode (GCE) exhibits high electrocatalytic activity toward hydrazine (N{sub 2}H{sub 4}) at low potential and a linear response from 0.06 to 700 μM with the detection limit for N{sub 2}H{sub 4} was found to be 1.2 × 10{sup −8} M (S/N = 3). Based on scan rate effect during the hydrazine oxidation, it indicates that the number of electrons transferred in the rate-limiting step is 1, and a transfer coefficient (α) is estimated as 0.73. The self-assembled F-TiO{sub 2}NTs–Au@Pd hybrid nanostructures as enhanced materials present excellent electrocatalytic activity, fast response, highly sensitive and have a promising application potential in nonenzymatic sensing. - Highlights: • Flower Au@Pd nanoparticles -TiO{sub 2} nanotubes (NTs) hybrid nanostructures were prepared by a self-assembled technique. • (004) plane of TiO{sub 2}NTs and (111) one of Au@Pd nanoparticles at the interface are compatible. • The electrochemical

  1. Density functional theory study on the adsorption and decomposition of the formic acid catalyzed by highly active mushroom-like Au@Pd@Pt tri-metallic nanoparticles.

    Science.gov (United States)

    Duan, Sai; Ji, Yong-Fei; Fang, Ping-Ping; Chen, Yan-Xia; Xu, Xin; Luo, Yi; Tian, Zhong-Qun

    2013-04-07

    Local structures and adsorption energies of a formic acid molecule and its decomposed intermediates (H, O, OH, CO, HCOO, and COOH) on highly electrocatalytically active mushroom-like Au-core@Pd-shell@Pt-cluster nanoparticles with two atomic layers of the Pd shell and stoichiometric Pt coverage of around half-monolayer (Au@2 ML Pd@0.5 ML Pt) have been investigated by first principles calculations. The adsorption sites at the center (far away from the Pt cluster) and the edge (close to the Pt cluster) are considered and compared. Significant repulsive interaction between the edge sites and CO is observed. The calculated potential energy surfaces demonstrate that, with respect to the center sites, the CO2 pathway is considerably promoted in the edge area. Our results reveal that the unique edge structure of the Pt cluster is responsible for the experimentally observed high electrocatalytic activity of the Au@Pd@Pt nanoparticles toward formic acid oxidation. Such microscopic understanding should be useful for the design of new electrochemical catalysts.

  2. Label-Free LSPR Detection of Trace Lead(II) Ions in Drinking Water by Synthetic Poly(mPD-co-ASA) Nanoparticles on Gold Nanoislands.

    Science.gov (United States)

    Qiu, Guangyu; Ng, Siu Pang; Liang, Xiongyi; Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

    2017-02-07

    Using self-assembly gold nanoislands (SAM-AuNIs) functionalized by poly(m-phenylenediamine-co-aniline-2-sulfonic acid) (poly(mPD-co-ASA)) copolymer nanoparticles as specific receptors, a highly sensitive localized surface plasmon resonance (LSPR) optochemical sensor is demonstrated for detection of trace lead cation (Pb(II)) in drinking water. The copolymer receptor is optimized in three aspects: (1) mole ratio of mPD:ASA monomers, (2) size of copolymer nanoparticles, and (3) surface density of the copolymer. It is shown that the 95:5 (mPD:ASA mole ratio) copolymer with size less than 100 nm exhibits the best Pb(II)-sensing performance, and the 200 times diluted standard copolymer solution contributes to the most effective functionalization protocol. The resulting poly(mPD-co-ASA)-functionalized LSPR sensor attains the detection limit to 0.011 ppb toward Pb(II) in drinking water, and the linear dynamic range covers 0.011 to 5000 ppb (i.e., 6 orders of magnitude). In addition, the sensing system exhibits robust selectivity to Pb(II) in the presence of other metallic cations as well as common anions. The proposed functional copolymer functionalized on AuNIs is found to provide excellent Pb(II)-sensing performance using simple LSPR instrumentation for rapid drinking-water inspection.

  3. Pd nanoparticles on ZnO-passivated porous carbon by atomic layer deposition: an effective electrochemical catalyst for Li-O2 battery.

    Science.gov (United States)

    Luo, Xiangyi; Piernavieja-Hermida, Mar; Lu, Jun; Wu, Tianpin; Wen, Jianguo; Ren, Yang; Miller, Dean; Zak Fang, Zhigang; Lei, Yu; Amine, Khalil

    2015-04-24

    Uniformly dispersed Pd nanoparticles on ZnO-passivated porous carbon were synthesized via an atomic layer deposition (ALD) technique, which was tested as a cathode material in a rechargeable Li-O2 battery, showing a highly active catalytic effect toward the electrochemical reactions-in particular, the oxygen evolution reaction. Transmission electron microscopy (TEM) showed discrete crystalline nanoparticles decorating the surface of the ZnO-passivated porous carbon support in which the size could be controlled in the range of 3-6 nm, depending on the number of Pd ALD cycles performed. X-ray absorption spectroscopy (XAS) at the Pd K-edge revealed that the carbon-supported Pd existed in a mixed phase of metallic palladium and palladium oxide. The ZnO-passivated layer effectively blocks the defect sites on the carbon surface, minimizing the electrolyte decomposition. Our results suggest that ALD is a promising technique for tailoring the surface composition and structure of nanoporous supports for Li-O2 batteries.

  4. Highly sensitive electrochemical immunosensor for the detection of alpha fetoprotein based on PdNi nanoparticles and N-doped graphene nanoribbons.

    Science.gov (United States)

    Li, Na; Ma, Hongmin; Cao, Wei; Wu, Dan; Yan, Tao; Du, Bin; Wei, Qin

    2015-12-15

    An ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of alpha fetoprotein (AFP). The β-cyclodextrins functionalized graphene sheets (CD-GS) were used as the sensing matrix for immobilizing adamantine-1-carboxylic acid functionalized primary anti-AFP (ADA-Ab1) and enhanced the electron transfer. PdNi alloy nanoparticles decorated N-doped graphene nanoribbons (PdNi/N-GNRs) were used as labels of secondary anti-AFP (Ab2), and PdNi alloy nanoparticles (PdNi NPs) exhibited high catalytic performance towards the reduction of H2O2. Meanwhile, with good dispersion, large specific surface area and good catalytic performance, N-doped graphene nanoribbons (N-GNRs) significantly amplified the electrochemical signal. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.0001-16 ng/mL with a low detection limit of 0.03 pg/mL. Additionally, the proposed immunosensor showed high specificity, good reproducibility and long-term stability, which have promising application in bioassay analysis.

  5. Monodisperse silica nanoparticles coated with gold nanoparticles as a sorbent for the extraction of phenol and dihydroxybenzenes from water samples based on dispersive micro-solid-phase extraction: Response surface methodology.

    Science.gov (United States)

    Khezeli, Tahere; Daneshfar, Ali

    2015-08-01

    A selective and sensitive method was developed based on dispersive micro-solid-phase extraction for the extraction of hydroquinone, resorcinol, pyrocatechol and phenol from water samples prior to high-performance liquid chromatography with UV detection. SiO2 , SiO2 @MPTES, and SiO2 @MPTES@Au nanoparticles (MPTES = 3-mercaptopropyltriethoxysilane) were synthesized and characterized by scanning electronic microscopy, thermogravimetric analysis, differential thermogravimetric analysis, and infrared spectroscopy. Variables such as the amount of sorbent (mg), pH and ionic strength of sample the solution, the volume of eluent solvent (μL), vortex and ultrasonic times (min) were investigated by Plackett-Burman design. The significant variables optimized by a Box-Behnken design were combined by a desirability function. Under optimized conditions, the calibration graphs of phenol and dihydroxybenzenes were linear in a concentration range of 1-500 μg/L, and with correlation coefficients more than 0.995. The limits of detection for hydroquinone, resorcinol, pyrocatechol, and phenol were 0.54, 0.58, 0.46, and 1.24 μg/L, and the limits of quantification were 1.81, 1.93, 1.54, and 4.23 μg/L, respectively. This procedure was successfully employed to determine target analytes in spiked water samples; the relative mean recoveries ranged from 93.5 to 98.9%.

  6. Selective Oxidation of Raw Glycerol Using Supported AuPd Nanoparticles

    Directory of Open Access Journals (Sweden)

    Carine E. Chan-Thaw

    2015-02-01

    Full Text Available Bimetallic AuPd supported on different carbonaceous materials and TiO2 was tested in the liquid phase oxidation of commercial grade and raw glycerol. The latter was directly obtained from the base-catalyzed transesterification of edible rapeseed oil using KOH. The best catalytic results were obtained using activated carbon and nitrogen-functionalized carbon nanofibers as supports. In fact, the catalysts were more active using pure glycerol instead of the one obtained from rapeseed, where strong deactivation phenomena were present. Fourier transform infrared (FT-IR and TEM were utilized to investigate the possible reasons for the observed loss of activity.

  7. Effective decoration of Pd nanoparticles on the surface of SnO2 nanowires for enhancement of CO gas-sensing performance.

    Science.gov (United States)

    Trung, Do Dang; Hoa, Nguyen Duc; Tong, Pham Van; Duy, Nguyen Van; Dao, T D; Chung, H V; Nagao, T; Hieu, Nguyen Van

    2014-01-30

    Decoration of noble metal nanoparticles (NPs) on the surface of semiconducting metal oxide nanowires (NWs) to enhance material characteristics, functionalization, and sensing abilities has attracted increasing interests from researchers worldwide. In this study, we introduce an effective method for the decoration of Pd NPs on the surface of SnO2 NWs to enhance CO gas-sensing performance. Single-crystal SnO2 NWs were fabricated by chemical vapor deposition, whereas Pd NPs were decorated on the surface of SnO2 NWs by in situ reduction of the Pd complex at room temperature without using any linker or reduction agent excepting the copolymer P123. The materials were characterized by advanced techniques, such as high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pd NPs were effectively decorated on the surface of SnO2 NWs. As an example, the CO sensing characteristics of SnO2 NWs decorated with Pd NPs were investigated at different temperatures. Results revealed that the gas sensor exhibited excellent sensing performance to CO at low concentration (1-25ppm) with ultrafast response-recovery time (in seconds), high responsivity, good stability, and reproducibility.

  8. Characterization of bimetallic Fe/Pd nanoparticles by grape leaf aqueous extract and identification of active biomolecules involved in the synthesis.

    Science.gov (United States)

    Luo, Fang; Yang, Die; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

    2016-08-15

    This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC-MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs.

  9. Fabrication of PdCo Bimetallic Nanoparticles Anchored on Three-Dimensional Ordered N-Doped Porous Carbon as an Efficient Catalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Xue, Hairong; Tang, Jing; Gong, Hao; Guo, Hu; Fan, Xiaoli; Wang, Tao; He, Jianping; Yamauchi, Yusuke

    2016-08-17

    PdCo bimetallic nanoparticles (NPs) anchored on three-dimensional (3D) ordered N-doped porous carbon (PdCo/NPC) were fabricated by an in situ synthesis. Within this composite, N-doped porous carbon (NPC) with an ordered mesoporous structure possesses a high surface area (659.6 m(2) g(-1)), which can facilitate electrolyte infiltration. NPC also acts as a perfect 3D conductive network, guaranteeing fast electron transport. In addition, homogeneously distributed PdCo alloy NPs (∼15 nm) combined with the doping of the N element can significantly improve the electrocatalytic activity for the oxygen reduction reaction (ORR). Due to the structural and material superiority, although the weight percentage of PdCo NPs (∼8 wt%) is much smaller than that of commercial Pt/C (20 wt%), the PdCo/NPC catalyst exhibits similar excellent electrocatalytic activity; however, its superior durability and methanol-tolerance ability of the ORR are as great as those of commercial Pt/C in alkaline media.

  10. Direct hydrogenation and one-pot reductive amidation of nitro compounds over Pd/ZnO nanoparticles as a recyclable and heterogeneous catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini-Sarvari, Mona, E-mail: hossaini@shirazu.ac.ir; Razmi, Zahra

    2015-01-01

    Graphical abstract: - Highlights: • Palladium supported on zinc oxide. • Nano crystalline Pd/ZnO as highly efficient heterogeneous catalyst. • Synthesis, chracterization, and application of nano-Pd/ZnO. • Ligand-free and air atmosphere conditions. - Abstract: A novel Pd supported on ZnO nanoparticles was readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% which was determined by ICP analysis and atomic absorption spectroscopy (AAS). Percentage of accessible Pd as active catalyst is also estimated to 2.72% based on the thermogravimetric (TG) analysis. This nano-sized Pd/ZnO with an average particle size of 20–25 nm and specific surface area 40.61 m{sup 2} g{sup −1} was used as a new reusable heterogeneous catalyst for direct hydrogenation and one-pot reductive amidation of nitro compounds without the use of any ligands under atmospheric pressure. The catalyst can be recovered and recycled several times without marked loss of activity.

  11. The impact of the chemical synthesis on the magnetic properties of intermetallic PdFe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos-Rubio, I.; Insausti, M.; Muro, I. Gil de [Universidad del País Vasco, UPV/EHU, Dpto. de Química Inorgánica (Spain); Arias-Duque, D. Carolina; Hernández-Garrido, Juan Carlos [Universidad de Cadiz, Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias (Spain); Rojo, T.; Lezama, L., E-mail: luis.lezama@ehu.es [Universidad del País Vasco, UPV/EHU, Dpto. de Química Inorgánica (Spain)

    2015-05-15

    Palladium-rich Iron nanoparticles in the 4–8 nm range have been produced by a combination of two methods: the thermal decomposition of organometallic precursors and the reduction of metallic salts by a polyol. Herein, it is shown how the details of the synthesis have a striking impact on the magnetic and morphological properties of the final products. In the synthesis of these bimetallic nanoparticles, the use of high reaction temperatures plays an essential role in attaining good chemical homogeneity, which has proved to have a key influence on the magnetic properties. Magnetic characterization has been performed by electron magnetic resonance and magnetization measurements, which have confirmed the superparamagnetic-like behavior at room temperature. No clear traces of magnetic polarization in palladium atoms have been detected. The combination of long-term stability and homogeneous chemical and magnetic properties makes these particles very suitable for a wide range of applications in nanotechnology.

  12. Novel platinum–palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

    Science.gov (United States)

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum–palladium bimetallic nanoparticles (Pt–PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2–5 nm, while PdNPs and Pt–PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88%±1.73% elemental Pt and 68.96%±1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm−1, attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm−1, associated with C–H stretching, N–H bending in primary amines, N–O stretching in nitro group, and C–C stretch, respectively. Anticancer activity against HeLa cells showed that Pt–PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt–PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. PMID:26719690

  13. Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

    Science.gov (United States)

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals.

  14. Defective graphene supported MPd12 (M = Fe, Co, Ni, Cu, Zn, Pd) nanoparticles as potential oxygen reduction electrocatalysts: A first-principles study

    KAUST Repository

    Liu, Xin

    2013-01-24

    We studied the electronic structure of MPd12 (M = Fe, Co, Ni, Cu, Zn, Pd) nanoparticles deposited on graphene substrates and their reactivity toward O adsorption, which are directly related to the catalytic performance of these composites in oxygen reduction reaction, by first-principles-based calculations. We found that the alloying between M and Pd can enhance the stability of nanoparticles and promote their oxygen reduction activity to be comparable with that of Pt(111). The defective graphene substrate can provide anchoring sites for these nanoparticles by forming strong metal-substrate interaction. The interfacial interaction can contribute to additional stability and further tune the averaged d-band center of the deposited alloy nanoparticles, resulting in strong interference on the O adsorption. As the O adsorption on these composites is weakened, the oxygen reduction reaction kinetics over these composites will also be promoted. These composites are thus expected to exhibit both high stability and superior catalytic performance in oxygen reduction reaction. © 2013 American Chemical Society.

  15. Degradation of {gamma}-HCH spiked soil using stabilized Pd/Fe{sup 0} bimetallic nanoparticles: Pathways, kinetics and effect of reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ritu [Ecotoxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Raebareli Road, Lucknow 226 025, UP (India); Misra, Virendra, E-mail: virendra_misra2001@yahoo.co.in [Ecotoxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Mudiam, Mohana Krishna Reddy [Analytical Chemistry Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Chauhan, Lalit Kumar Singh [Petroleum Toxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Singh, Rana Pratap [Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Raebareli Road, Lucknow 226 025, UP (India)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer This study explores the potential of CMC-Pd/nFe{sup 0} to degrade {gamma}-HCH in spiked soil. Black-Right-Pointing-Pointer Sorption-desorption characteristics and partitioning of {gamma}-HCH is investigated. Black-Right-Pointing-Pointer Three degradation pathways has been proposed and discussed. Black-Right-Pointing-Pointer {gamma}-HCH degradation mechanism and kinetics is elucidated. Black-Right-Pointing-Pointer Activation energy reveals that {gamma}-HCH degradation is a surface mediated reaction. - Abstract: This study investigates the degradation pathway of gamma-hexachlorocyclohexane ({gamma}-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe{sup 0} bimetallic nanoparticles (CMC-Pd/nFe{sup 0}). GC-MS analysis of {gamma}-HCH degradation products showed the formation of pentachlorocyclohexene, tri- and di-chlorobenzene as intermediate products while benzene was formed as the most stable end product. On the basis of identified intermediates and final products, degradation pathway of {gamma}-HCH has been proposed. Batch studies showed complete {gamma}-HCH degradation at a loading of 0.20 g/L CMC-Pd/nFe{sup 0} within 6 h of incubation. The surface area normalized rate constant (k{sub SA}) was found to be 7.6 Multiplication-Sign 10{sup -2} L min{sup -1} m{sup -2}. CMC-Pd/nFe{sup 0} displayed {approx}7-fold greater efficiency for {gamma}-HCH degradation in comparison to Fe{sup 0} nanoparticles (nFe{sup 0}), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe{sup 0} loading and reaction temperature facilitates {gamma}-HCH degradation, whereas a declining trend in degradation was noticed with the increase in pH, initial {gamma}-HCH concentration and in the presence of cations. The data on activation energy (33.7 kJ/mol) suggests that {gamma}-HCH degradation is a surface mediated reaction. The significance of the study with respect to remediation of {gamma}-HCH contaminated soil using

  16. Facile synthesis of bacitracin-templated palladium nanoparticles with superior electrocatalytic activity

    Science.gov (United States)

    Li, Yanji; Wang, Zi; Li, Xiaoling; Yin, Tian; Bian, Kexin; Gao, Faming; Gao, Dawei

    2017-02-01

    Palladium nanomaterials have attracted great attention on the development of electrocatalysts for fuel cells. Herein, we depicted a novel strategy in the synthesis of palladium nanoparticles with superior electrocatalytic activity. The new approach, based on the self-assembly of bacitracin biotemplate and palladium salt for the preparation of bacitracin-palladium nanoparticles (Bac-PdNPs), was simple, low-cost, and green. The complex, composed by a series of spherical Bac-PdNPs with a diameter of 70 nm, exhibited a chain-liked morphology in TEM and a face-centered cubic crystal structure in X-Ray diffraction and selected area electron diffraction. The palladium nanoparticles were mono-dispersed and stable in aqueous solution as shown in TEM and zeta potential. Most importantly, compared to the commercial palladium on carbon (Pd/C) catalyst (8.02 m2 g-1), the Bac-PdNPs showed a larger electrochemically active surface area (47.57 m2 g-1), which endowed the products an excellent electrocatalytic activity for ethanol oxidation in alkaline medium. The strategy in synthesis of Bac-PdNPs via biotemplate approach might light up new ideas in anode catalysts for direct ethanol fuel cells.

  17. Ultrasonic-electrodeposition of PtPd alloy nanoparticles on ionic liquid-functionalized graphene paper: towards a flexible and versatile nanohybrid electrode

    Science.gov (United States)

    Sun, Yimin; Zheng, Huaming; Wang, Chenxu; Yang, Mengmeng; Zhou, Aijun; Duan, Hongwei

    2016-01-01

    Here we fabricate a new type of flexible and versatile nanohybrid paper electrode by ultrasonic-electrodeposition of PtPd alloy nanoparticles on freestanding ionic liquid (IL)-functionalized graphene paper, and explore its multifunctional applications in electrochemical catalysis and sensing systems. The graphene-based paper materials demonstrate intrinsic flexibility, exceptional mechanical strength and high electrical conductivity, and therefore can serve as an ideal freestanding flexible electrode for electrochemical devices. Furthermore, the functionalization of graphene with IL (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate) not only increases the electroactive surface area of a graphene-based nanohybrid paper electrode, but also improves the adhesion and dispersion of metal nanoparticles on the paper surface. These unique attributes, combined with the merits of an ultrasonic-electrodeposition method, lead to the formation of PtPd alloy nanoparticles on IL-graphene paper with high loading, uniform distribution, controlled morphology and favourable size. Consequently, the resultant nanohybrid paper electrode exhibits remarkable catalytic activity as well as excellent cycle stability and improved anti-poisoning ability towards electrooxidation of fuel molecules such as methanol and ethanol. Furthermore, for nonenzymatic electrochemical sensing of some specific biomarkers such as glucose and reactive oxygen species, the nanohybrid paper electrode shows high selectivity, sensitivity and biocompatibility in these bio-catalytic processes, and can be used for real-time tracking hydrogen peroxide secretion by living human cells. All these features demonstrate its promising application as a versatile nanohybrid electrode material in flexible and lightweight electrochemical energy conversion and biosensing systems such as bendable on-chip power sources, wearable/implantable detectors and in vivo micro-biosensors.Here we fabricate a new type of flexible and

  18. Electrospun Pd nanoparticles loaded on Vulcan carbon/ conductive polymeric ionic liquid nanofibers for selective and sensitive determination of tramadol.

    Science.gov (United States)

    Fathirad, Fariba; Mostafavi, Ali; Afzali, Daryoush

    2016-10-12

    In the present work a sensitive and selective electrochemical sensor was fabricated based on a glassy carbon electrode which has been modified with Pd nanoparticles loaded on Vulcan carbon/conductive polymeric ionic liquid composite nanofibers. The nanostructures were characterized by UV-Vis, FT-IR, FESEM, EDX and XRD techniques. The electrochemical study of the modified electrode, as well as its efficiency for the electrooxidation of tramadol was described in 0.1 M phosphate buffered solution (PBS) (pH 7.0) using cyclic voltammetry, linear sweep voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. It has been found that application of the composite nanofibers result in a sensitivity enhancement and a considerable decrease in the anodic overpotential, leading to negative shifts about 200 mV in peak potential. The results exhibit a linear dynamic range from 0.05 μM to 200 μM and a detection limit of 0.015 μM for tramadol. Finally, the modified electrode was used for the determination of tramadol in pharmaceutical and biological samples.

  19. The Electrochemical Atomic Layer Deposition of Pt and Pd nanoparticles on Ni foam for the electrooxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2012-10-01

    Full Text Available Electrodeposition of Pt and Pd metal by surface limited redox replacement reactions was performed using the electrochemical atomic layer deposition. Carbon paper and Ni foam were used as substrates for metal deposition. Supported Pt and Pd...

  20. Monodisperse Ru Nanoparticles in [Bmim]BF4:Preparation and Application in Benzene Selective Hydrogenation%离子液体[Bmim]BF4中单分散Ru纳米粒子的制备及选择加氢性能

    Institute of Scientific and Technical Information of China (English)

    魏珺芳; 王延吉; 励娟; 薛伟

    2011-01-01

    The monodisperse Ru nanoparticles were prepared by chemical reduction method in 1-butyl-3-methyl limidizaolium tetrafluoroborate ([BMim]BF4). The prepared Ru nanoparticles were characterized by XRD as hexagonal close packed structure and no diffraction peak from oxidation products. TEM analysis of these nanoparticles shows that the monodisperse Ru nanoparticles prepared by positive dripping method disperse in the ionic liquids with diameter less than 5 nm. The Ru nanoparticles prepared by reverse dripping method agglomerate with diameter more than 10 nm. FTIR results indicate that a physically absorbed layer of ionic liquid is evident on the surface of Ru nanoparticles. TG results indicate that the ionic liquid serves not only as a protective agent or stabilizing agent to inhibit the aggregation of Ru nanoparticles, but also a modification agent adsorbed on the Ru nanoparticles. Results of benzene selective hydrogenation show that benzene conversion is relatively high in the reaction system with water, however the selectivity of cyclohexene is low, only 14.5% at 27.3% benzene conversion in the same system.%采用化学还原法在离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMim]BF4)中制备了单分散纳米金属Ru粒子.采用X射线衍射(XRD)、透射电镜(TEM)、傅里叶红外光谱(FTTR)及热重(TG)对所制备样品的形貌和结构进行了表征.XRD表征结果显示:在[BMim]BF4中制备的Ru具有六方紧密堆积结构,无氧化物峰出现;TEM结果显示:采用正滴法制备的Ru纳米粒子为球形颗粒,呈现良好的单分散状态,粒径分布窄,为2~5 nm,而采用反滴法制备的Ru纳米粒子则发生了严重的团聚,团聚体粒径大于10 nm;FTIR表征表明:Ru纳米粒子表面存在[BMjm]BF4液体层,分析二者之间存在较强的物理吸附作用,[BMim]BF4在Ru纳米粒子的制备中起到了修饰剂和保护剂的双重作用,这一推论通过TG分析得到了进一步验证.将分散于[BMim]BF4的Ru纳

  1. 单分散、规则球形Au@SiO_2核-壳纳米粒的制备及光谱研究%Preparation and Spectrum Study of Monodispersed Regular Spherical Au@SiO_2 Core-Shell Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    姚祖福; 黄可龙; 于金刚; 郭军; 李艳华; 方东

    2009-01-01

    Using 3-mercaptopropyhrimethoxysilane as linker,single gold nanoparticle was successfully encapsulated by silicon oxide shell,and Au@SiO_2 core-sheU nanoparticles were prepared.The nanocomposites were spherical and monodispersal.The gold nanoparticle located at the center of silica nano-sphere.No congregating gold nanoparticles were embedded in one silica sphere.The morphologies of the samples were characterized by transmission electron microscopy(TEM).The chemical contents of the samples were analyzed using energy diffraction X-ray(EDX)spectroscopy.And their optical properties were studied.%采用3-巯基丙基三甲氧基硅烷作为联结剂,成功将单个金纳米粒子包在氧化硅壳中,制得Au@SiO_2核壳纳米粒子;该复合纳米粒子形貌呈球形、单分散性较好,金纳米粒子位于氧化硅球的中心.无团聚的金纳米粒子包覆在氧化硅壳中.采用透射电镜(TEM)对样品的形貌进行了表征,通过能量散射X-射线能谱(EDX)分析了目标物的化学成分,并对所得核壳纳米粒子的光谱性质进行了研究.

  2. Immobilization of Ni–Pd/core–shell nanoparticles through thermal polymerization of acrylamide on glassy carbon electrode for highly stable and sensitive glutamate detection

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Huicheng, E-mail: doyhc@126.com [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082 (China); School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530008 (China); School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530008 (China); Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi University for Nationalities, Nanning, 530008 (China); Key Laboratory of Guangxi Colleges and Universities for Food Safety and Pharmaceutical Analytical Chemistry, Guangxi University for Nationalities, Nanning, 530008 (China); Ma, Zhenzhen [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082 (China); Wu, Zhaoyang, E-mail: zywu@hnu.edu.cn [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082 (China)

    2015-10-08

    The preparation of a persistently stable and sensitive biosensor is highly important for practical applications. To improve the stability and sensitivity of glutamate sensors, an electrode modified with glutamate dehydrogenase (GDH)/Ni–Pd/core–shell nanoparticles was developed using the thermal polymerization of acrylamide (AM) to immobilize the synthesized Ni–Pd/core–shell nanoparticles onto a glassy carbon electrode (GCE). The modified electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Electrochemical data showed that the prepared biosensor had remarkably enhanced electrocatalytic activity toward glutamate. Moreover, superior reproducibility and excellent stability were observed (relative average deviation was 2.96% after continuous use of the same sensor for 60 times, and current responses remained at 94.85% of the initial value after 60 d). The sensor also demonstrated highly sensitive amperometric detection of glutamate with a low limit of detection (0.052 μM, S/N = 3), high sensitivity (4.768 μA μM{sup −1} cm{sup −2}), and a wide, useful linear range (0.1–500 μM). No interference from potential interfering species such as L-cysteine, ascorbic acid, and L-aspartate were noted. The determination of glutamate levels in actual samples achieved good recovery percentages. - Highlights: • Ni–Pd/core–shell nanoparticles were synthesized. • Nanoparticles were immobilized onto electrodes through thermal polymerization. • The modified sensor exhibited excellent stability and sensitivity for glutamate detection. • The biosensor exhibited remarkable electrocatalytic activity toward glutamate. • The sensor successfully detected glutamate in tomato soup samples.

  3. The electrochemical atomic layer deposition of Pt and Pd nanoparticles on Ni foam for the electro oxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2013-01-01

    Full Text Available of the electrocatalytic activity of the prepared catalysts. TABLE I. Electrochemical Activity of Pt and Pd Towards the Oxidation of Methanol. Catalyst Onset potential (V vs Ag/AgCl) If/Ib Pt/Carbon paper 0.41 4.30 Pt/Ni foam 0.38 2.16 Pd/Carbon paper* Pd.../Ni foam* -0.456 -0.429 2.86 1.30 *: methanol oxidation performed in alkaline medium TABLE II. Electrochemical Activity of Pd Towards the Oxidation of Ethanol in alkaline electrolyte. Catalyst Onset potential (V vs Ag/AgCl) If/Ib Pd...

  4. Pd-Au nanoparticle decorated carbon nanotube as a sensing layer on the surface of glassy carbon electrode for electrochemical determination of ceftazidime.

    Science.gov (United States)

    Shahrokhian, Saeed; Salimian, Razieh; Rastgar, Shokoufeh

    2014-01-01

    A simple electrodeposition method is employed to construct a thin film modifier of palladium-gold nanoparticles (Pd-AuNPs) decorated multi-walled carbon nanotube (MWCNT) on the surface of glassy carbon electrode (GCE). Morphology and property of Pd-AuNPs-MWCNT have been examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical performance of Pd-AuNPs-MWCNT/GCE for detection of ceftazidime (CFZ) has been investigated by cyclic voltammetry (CV). This nanostructured film modified electrode effectively exhibited enhanced properties for detection of ceftazidime (CFZ). The effects of various experimental variables such as, the amount of casted MWCNT, time and potential of deposition of metal nanoparticles and the pH of the buffered solution on the electrode response are optimized. The proposed electrode showed a linear dynamic range of 0.05-50μM and the detection limit of 1nM for the CFZ. The modified electrode successfully supports the sensitive detection of trace amounts of the CFZ in pharmaceutical and clinical preparations.

  5. Mesoporous silica nanoparticles applied as a support for Pd and Au nanocatalysts in cycloisomerization reactions

    Directory of Open Access Journals (Sweden)

    Oscar Verho

    2014-11-01

    Full Text Available Ultra-small mesoporous silica nanoparticles (MSNs have been synthesized at room temperature with particle sizes ranging from 28 to 45 nm. These MSNs have been employed as heterogeneous supports for palladium and gold nanocatalysts. The colloidal nature of the MSNs is highly useful for catalytic applications as it allows for better mass transfer properties and a more uniform distribution of the nanocatalysts in solution. The two nanocatalysts were evaluated in the cycloisomerization of alkynoic acids and demonstrated to produce the corresponding alkylidene lactones in good to excellent yields under mild conditions. In addition to their high activity, the catalysts exhibit low degree of metal leaching and straight-forward recycling, which highlight the practical utility of MSNs as supports for nanocatalysts.

  6. Novel yolk-shell-structured Fe3O4@γ-AlOOH nanocomposite modified with Pd nanoparticles as a recyclable catalyst with excellent catalytic activity

    Science.gov (United States)

    Cui, Xueliang; Zheng, Yunfeng; Tian, Meng; Dong, Zhengping

    2017-09-01

    A novel yolk-shell-structured material (Fe3O4@γ-AlOOH-YSMs) with hierarchical γ-AlOOH flakes as the mesoporous shell and Fe3O4 nanoparticles (NPs) in the hollow core was prepared by using Fe3O4@SiO2 NPs as the seeds as well as NaAlO2 and urea as the precursor. The prepared Fe3O4@γ-AlOOH-YSMs were used as a catalyst support for fabricating a Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst with no obvious aggregation of the Pd NPs. The Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst was utilized for the catalytic reduction of the widely used and highly toxic 4-nitrophenol, rhodamine B, methylene blue, and methyl orange; and showed excellent catalytic activity as compared with other noble-metal-based catalysts. Furthermore, the Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst also can be easily separated from the reaction mixture and reused for at least ten times without any obvious decrease in the catalytic activity, indicating its reusability and stability.

  7. Laser synthesis of bimetallic nanoalloys in the vapor and liquid phases and the magnetic properties of PdM and PtM nanoparticles (M = Fe, Co and Ni).

    Science.gov (United States)

    Abdelsayed, Victor; Glaspell, Garry; Nguyen, Minh; Howe, James M; El-Shall, M Samy

    2008-01-01

    In this work, we present several examples of the synthesis and characterization of bimetallic nanoparticle alloys using the Laser Vaporization Controlled Condensation (LVCC) method. In the first example, the vapor phase synthesis of Au-Ag, Au-Pd, and Au-Pt nanoparticle alloys are presented. The formation of nanoalloys is concluded from the observation of one plasmon absorption band at a wavelength that varies linearly with the gold mole fraction in the nanoalloy. Both XRD data and HRTEM-EDX data confirm the formation of nanoparticle alloys and not simply mixtures of the two metal nanoparticles. Irradiation of a mixture of Au/Ag nanoparticles dispersed in water with the 532 nm unfocused laser results in efficient alloying while the 1064 nm laser radiation results only in evaporation and size reduction of the unalloyed nanoparticles. Selective absorption of the femtosecond 780 nm radiation by large Au aggregates results in the formation of smaller aggregates with fractal structures, and no evidence for the Au-Ag alloy formation. The synthesis of palladium and platinum nanoparticles alloyed with transition metals such as iron and nickel using the LVCC method is also presented. The alloyed nanoparticles (FePd, FePt, NiPd, NiPt, and FeNi) are found to be superparamagnetic.

  8. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, D.; Barman, P. B.; Hazra, S. K., E-mail: surajithazra@yahoo.co.in [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh-173234 (India); Dutta, D. [IC Design and Fabrication Centre, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata-700032 (India); Kumar, M.; Som, T. [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India)

    2015-10-28

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  9. Structures and energetics of 98 atom Pd-Pt nanoalloys: potential stability of the Leary tetrahedron for bimetallic nanoparticles.

    Science.gov (United States)

    Paz-Borbón, Lauro Oliver; Mortimer-Jones, Thomas V; Johnston, Roy L; Posada-Amarillas, Alvaro; Barcaro, Giovanni; Fortunelli, Alessandro

    2007-10-14

    The energetics of 98 atom bimetallic Pd-Pt clusters are studied using a combination of: a genetic algorithm technique (to explore vast areas of the configurational space); a basin-hopping atom-exchange routine (to search for lowest-energy homotops at fixed composition); and a shell optimisation approach (to search for high symmetry isomers). The interatomic interactions between Pd and Pt are modelled by the Gupta many-body empirical potential. For most compositions, the putative global minima are found to have structures based on defective Marks decahedra, but in the composition range from Pd46Pt52 to Pd63Pt35, the Leary tetrahedron (LT)--a structure previously identified for 98 atom Lennard-Jones clusters--is consistently found as the most stable structure. Based on the excess energy stability criterion, Pd56Pt42 represents the most stable cluster across the entire composition range. This structure, a Td-symmetry LT, exhibits multi-layer segregation with an innermost core of Pd atoms, an intermediate layer of Pt atoms and an outermost Pd surface shell (Pd-Pt-Pd). The stability of the Leary tetrahedron is compared against other low-energy competing structural motifs: the Marks decahedron (Dh-M), a "quasi" tetrahedron (a closed-packed structure) and two other closed-packed structures. The stability of LT structures is rationalized in terms of their spherical shape and the large number of nearest neighbours.

  10. Synthesis of a Novel Surfactant with Two Alkyl Tail-Chains (DDOBA) and Fabrication of Hydrophobic Gold Nanoparticles with High Monodispersity%新型双链表面活性剂DDOBA的合成与高单分散性憎水纳米金的制备

    Institute of Scientific and Technical Information of China (English)

    韩莹; 朱露; 沈明; 李恒恒

    2013-01-01

    3,4-Didodecyloxybenzylamine (DDOBA), a novel surfactant with two alkyl tail-chains, was designed and synthesized. DDOBA-capped hydrophobic gold nanoparticles were successful y fabricated using formic acid as a reducing agent in a DDOBA/n-butanol/n-heptane/formic acid/HAuCl4·4H2O water/oil (W/O) microemulsion system under microwave irradiation. DDOBA-stabilized gold nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). The experimental results showed that DDOBA not only participated in the formation of a stable W/O microemulsion system, but also became a good protecting agent for gold nanoparticles. Within an appropriate concentration range of components in the W/O microemulsion system, hydrophobic gold nanoparticles with high monodispersity can be obtained using this experimental method and automatical y form large areas of ordered monolayer built with DDOBA-capped gold nanoparticles at the air/water interface.%  自行设计合成了新颖的苄胺型双链表面活性剂3,4-双十二烷氧基苄胺(DDOBA)。利用DDOBA/正丁醇/正庚烷/甲酸/HAuCl4·4H2O自发形成的水/油(W/O)型微乳液作为微反应器,通过微波辐射下的甲酸还原法成功制备了DDOBA保护的憎水性金纳米粒子,并通过紫外-可见(UV-Vis)光谱、透射电镜(TEM)、高分辨透射电镜(HR-TEM)和X射线衍射(XRD)等方法进行了表征和分析。结果显示, DDOBA既可参与形成稳定的W/O型(油包水型)微乳液,又可作为金纳米粒子的良好保护剂。在合适的微乳液体系组成范围内,用本实验方法可以获得高单分散性的憎水性金纳米粒子,并能在空气/水界面上自动形成大面积短程有序的纳米金二维自组装膜。

  11. 室温合成团聚AuPd纳米粒子及其电催化性质%Room Temperature Synthesis and Characterization of Agglomerates of AuPd Bimetallic Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    冯苍松; 梁新义; 崔兰

    2011-01-01

    室温下以水合肼为还原剂,在N,N-二甲基甲酰胺中合成了团聚态的AuPd双金属纳米粒子.X射线衍射(XRD)表征结果证明,所合成的AuPd纳米粒子具有面心立方结构.高分辨透射电子显微镜表征表明,AuPd纳米粒子表面存在大量孪晶结构和晶面层错等表面缺陷.活性评价结果表明,具有高密度晶面缺陷的双团聚态AuPd纳米粒子对甲醇氧化表现出较好的催化活性.%A facile synthesis of the agglomerates of AuPd bimetallic nanoparticles with hydrazine hydrate as a reductant is presented. The structures and morphologies of the agglomerates of AuPd bimetallic nanoparticles were investigated by high-resolution transmission electron microscopy(HRTEM) and X-ray diffraction(XRD). The composition and catalytic property of the AuPd bimetallic nanoparticles were studied by energy dispersive X-ray spectroscopy (EDS) and cyclic voltammetry(CV). The as-synthesized AuPd nanoparticles display agglomerates with face central cubic(fcc) structure enclosed by flat {100} and {111} facets. The details of HRTEM image reveal that unstable small nanoparticles aggregate into the agglomerates of structures. And the surface structure of nanoparticles yields various types of surface defects. Meanwhile, the agglomerates of structure and high density surface defects of AuPd bimetallic nanoparticle are found to dramatically improve the electrocatalytic activities.

  12. Immobilized Pd on magnetic nanoparticles bearing proline as a highly efficient and retrievable Suzuki-Miyaura catalyst in aqueous media.

    Science.gov (United States)

    Nehlig, E; Waggeh, B; Millot, N; Lalatonne, Y; Motte, L; Guénin, E

    2015-01-14

    A magnetically retrievable nanocatalyst was evaluated for a microwave assisted Suzuki-Miyaura reaction in aqueous media. Excellent yields and conversions were obtained with low Pd loadings (down to 0.01 mol% Pd). It was stable up to 6 months in water under aerobic conditions and efficiency remained unaltered even after 7 repeated cycles.

  13. Enhanced catalytic performance for methane combustion of 3DOM CoFe2O4 by co-loading MnOx and Pd-Pt alloy nanoparticles

    Science.gov (United States)

    Li, Xiangyu; Liu, Yuxi; Deng, Jiguang; Xie, Shaohua; Zhao, Xingtian; Zhang, Yang; Zhang, Kunfeng; Arandiyan, Hamidreza; Guo, Guangsheng; Dai, Hongxing

    2017-05-01

    Three-dimensionally ordered macroporous (3DOM) CoFe2O4, zMnOx/3DOM CoFe2O4 (z = 4.99-12.30 wt%), and yPd-Pt/6.70 wt% MnOx/3DOM CoFe2O4 (y = 0.44-1.81 wt%; Pd/Pt molar ratio = 2.1-2.2) have been prepared using the polymethyl methacrylate microspheres-templating, incipient wetness impregnation, and bubble-assisted polyvinyl alcohol-protected reduction strategies, respectively. All of the samples were characterized by means of various techniques. Catalytic performance of the samples was measured for methane combustion. It is shown that the as-prepared samples exhibited a high-quality 3DOM structure (103 ± 20 nm in pore size) and a surface area of 19-28 m2/g, and the noble metal or alloy nanoparticles (NPs) with a size of 2.2-3.0 nm were uniformly dispersed on the macropore wall surface of 3DOM CoFe2O4. The loading of MnOx on CoFe2O4 gave rise to a slight increase in activity, however, the dispersion of Pd-Pt NPs on 6.70MnOx/3DOM CoFe2O4 significantly enhanced the catalytic performance, with the 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 sample showing the highest activity (T10% = 255 °C, T50% = 301 °C, and T90% = 372 °C at a space velocity of 20,000 mL/(g h)). We believe that the excellent catalytic activity of 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 was related to its well-dispersed Pd-Pt alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between MnOx or Pd-Pt NPs and 3DOM CoFe2O4.

  14. Characterization of intracellular palladium nanoparticles synthesized by Desulfovibrio desulfuricans and Bacillus benzeovorans

    Science.gov (United States)

    Omajali, Jacob B.; Mikheenko, Iryna P.; Merroun, Mohamed L.; Wood, Joseph; Macaskie, Lynne E.

    2015-06-01

    Early studies have focused on the synthesis of palladium nanoparticles within the periplasmic layer or on the outer membrane of Desulfovibrio desulfuricans and on the S-layer protein of Bacillus sphaericus. However, it has remained unclear whether the synthesis of palladium nanoparticles also takes place in the bacterial cell cytoplasm. This study reports the use of high-resolution scanning transmission electron microscopy with a high-angle annular dark field detector and energy dispersive X-ray spectrometry attachment to investigate the intracellular synthesis of palladium nanoparticles (Pd NPs). We show the intracellular synthesis of Pd NPs within cells of two anaerobic strains of D. desulfuricans and an aerobic strain of B. benzeovorans using hydrogen and formate as electron donors. The Pd nanoparticles were small and largely monodispersed, between 0.2 and 8 nm, occasionally from 9 to 12 nm with occasional larger nanoparticles. With D. desulfuricans NCIMB 8307 (but not D. desulfuricans NCIMB 8326) and with B. benzeovorans NCIMB 12555, the NPs were larger when made at the expense of formate, co-localizing with phosphate in the latter, and were crystalline, but were amorphous when made with H2, with no phosphorus association. The intracellular Pd nanoparticles were mainly icosahedrons with surfaces comprising {111} facets and about 5 % distortion when compared with that of bulk palladium. The particles were more concentrated in the cell cytoplasm than the cell wall, outer membrane, or periplasm. We provide new evidence for synthesis of palladium nanoparticles within the cytoplasm of bacteria, which were confirmed to maintain cellular integrity during this synthesis.

  15. Characterization of intracellular palladium nanoparticles synthesized by Desulfovibrio desulfuricans and Bacillus benzeovorans

    Energy Technology Data Exchange (ETDEWEB)

    Omajali, Jacob B., E-mail: JBO037@bham.ac.uk, E-mail: jbomajali@gmail.com; Mikheenko, Iryna P. [University of Birmingham, Unit of Functional Bionanomaterials, School of Biosciences, Institute of Microbiology and Infection (United Kingdom); Merroun, Mohamed L. [University of Granada, Department of Microbiology, Faculty of Sciences (Spain); Wood, Joseph [University of Birmingham, School of Chemical Engineering (United Kingdom); Macaskie, Lynne E. [University of Birmingham, Unit of Functional Bionanomaterials, School of Biosciences, Institute of Microbiology and Infection (United Kingdom)

    2015-06-15

    Early studies have focused on the synthesis of palladium nanoparticles within the periplasmic layer or on the outer membrane of Desulfovibrio desulfuricans and on the S-layer protein of Bacillus sphaericus. However, it has remained unclear whether the synthesis of palladium nanoparticles also takes place in the bacterial cell cytoplasm. This study reports the use of high-resolution scanning transmission electron microscopy with a high-angle annular dark field detector and energy dispersive X-ray spectrometry attachment to investigate the intracellular synthesis of palladium nanoparticles (Pd NPs). We show the intracellular synthesis of Pd NPs within cells of two anaerobic strains of D. desulfuricans and an aerobic strain of B. benzeovorans using hydrogen and formate as electron donors. The Pd nanoparticles were small and largely monodispersed, between 0.2 and 8 nm, occasionally from 9 to 12 nm with occasional larger nanoparticles. With D. desulfuricans NCIMB 8307 (but not D. desulfuricans NCIMB 8326) and with B. benzeovorans NCIMB 12555, the NPs were larger when made at the expense of formate, co-localizing with phosphate in the latter, and were crystalline, but were amorphous when made with H{sub 2,} with no phosphorus association. The intracellular Pd nanoparticles were mainly icosahedrons with surfaces comprising {111} facets and about 5 % distortion when compared with that of bulk palladium. The particles were more concentrated in the cell cytoplasm than the cell wall, outer membrane, or periplasm. We provide new evidence for synthesis of palladium nanoparticles within the cytoplasm of bacteria, which were confirmed to maintain cellular integrity during this synthesis.

  16. Size-Tunable and Monodisperse Tm3+/Gd3+-Doped Hexagonal NaYbF4 Nanoparticles with Engineered Efficient Near Infrared-to-Near Infrared Upconversion for In Vivo Imaging

    OpenAIRE

    Damasco, Jossana A.; Chen, Guanying; Shao, Wei; Ågren, Hans; Huang, Haoyuan; Song, Wentao; Lovell, Jonathan F; Prasad, Paras N.

    2014-01-01

    Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentr...

  17. Aerosol-Assisted Synthesis of Monodisperse Single-Crystalline α-Cristobalite Nanospheres

    OpenAIRE

    Jiang, Xingmao; Bao, Lihong; Cheng, Yung-Sung; Dunphy, Darren R.; Li, Xiaodong; Brinker, C. Jeffrey

    2011-01-01

    Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity nanocrystalline α-cristobalite is important for catalysis, nanocomposites, advanced polishing, and und...

  18. Aqueous dispersion of monodisperse magnetic iron oxide nanocrystals through phase transfer

    Energy Technology Data Exchange (ETDEWEB)

    Yu, William W [Department of Chemistry, Rice University, Houston, TX 77005 (United States); Chang, Emmanuel [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Sayes, Christie M [Department of Chemistry, Rice University, Houston, TX 77005 (United States); Drezek, Rebekah [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Colvin, Vicki L [Department of Chemistry, Rice University, Houston, TX 77005 (United States)

    2006-09-14

    A facile method was developed for completely transferring high quality monodisperse iron oxide nanocrystals from organic solvents to water. The as-prepared aqueous dispersions of iron oxide nanocrystals were extremely stable and could be functionalized for bioconjugation with biomolecules. These iron oxide nanocrystals showed negligible cytotoxicity to human breast cancer cells (SK-BR-3) and human dermal fibroblast cells. This method is general and versatile for many organic solvent-synthesized nanoparticles, including fluorescent semiconductor nanocrystals.

  19. 3D porous graphene-porous PdCu alloy nanoparticles-molecularly imprinted poly(para-aminobenzoic acid) composite for the electrocatalytic assay of melamine.

    Science.gov (United States)

    Shang, Lei; Zhao, Faqiong; Zeng, Baizhao

    2014-01-01

    In this work, a three-dimensional hybrid film with in- and out-of-plane pores was fabricated by using porous graphene as framework structure and porous PdCu alloy nanoparticles as building blocks. The porous PdCu alloy nanoparticles were prepared by chemical dealloying with acetic acid. The hierarchical pores had abundant active catalytic sites, and the material exhibited remarkable catalytic activity toward the oxidation of hydrazine. Based on this hybrid film, an electrochemical sensor of melamine was developed by further introducing melamine imprinted electro-polymer of para-aminobenzoic acid. Melamine was detected by differential pulse voltammetry using hydrazine as electrochemical probe. The detection signal was amplified due to the catalytic oxidation of hydrazine at this hybrid film. The linear determination range was 0.01-1 μM and the detection limit was 2 nM (S/N = 3). The sensor displayed high recognition capacity toward melamine and also showed good reproducibility and stability. It is promising in the determination of melamine in real samples.

  20. Water-dispersible Hollow Microporous Organic Network Spheres as Substrate for Electroless Deposition of Ultrafine Pd Nanoparticles with High Catalytic Activity and Recyclability.

    Science.gov (United States)

    Wang, Zhifang; Chang, Jing; Hu, Yuchen; Yu, Yifu; Guo, Yamei; Zhang, Bin

    2016-11-22

    Microporous organic networks (MONs) have been considered as an ideal substrate to stabilize active metal nanoparticles. However, the development of highly water-dispersible hollow MONs nanostructures which can serve as both the reducing agent and stabilizer is highly desirable but still challenging. Here we report a template-assisted method to synthesize hollow microporous organic network (H-MON) spheres using silica spheres as hard template and 1,3,5-triethynylbenzene as the building blocks through a Glaser coupling reaction. The obtained water-dispersible H-MON spheres bearing sp- and sp(2) -hybridized carbon atoms possess a highly conjugated electronic structure and show low reduction potential; thus, they can serve as a reducing agent and stabilizer for electroless deposition of highly dispersed Pd clusters to form a Pd/H-MON spherical hollow nanocomposite. Benefitting from their high porosity, large surface area, and excellent solution dispersibility, the as-prepared Pd/H-MON hollow nanocomposite exhibits a high catalytic performance and recyclability toward the reduction of 4-nitrophenol.

  1. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    Directory of Open Access Journals (Sweden)

    Zdansky Karel

    2011-01-01

    Full Text Available Abstract Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd nanoparticles (NPs in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures.

  2. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    Science.gov (United States)

    Zdansky, Karel

    2011-08-01

    Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd) nanoparticles (NPs) in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures.

  3. Fabrication of monodispersive nanoscale alginate–chitosan core–shell particulate systems for controlled release studies

    Energy Technology Data Exchange (ETDEWEB)

    Körpe, Didem Aksoy; Malekghasemi, Soheil; Aydın, Uğur; Duman, Memed, E-mail: memedduman@gmail.com [Hacettepe University, Institute of Science, Nanotechnology and Nanomedicine Division (Turkey)

    2014-12-15

    Biopolymers such as chitosan and alginate are widely used for controlled drug delivery systems. The present work aimed to develop a new protocol for preparation of monodisperse alginate-coated chitosan nanoparticles at nanoscale. Modifications of preparation protocol contain changing the pH of polymer solutions and adding extra centrifugation steps into the procedure. While chitosan nanoparticles were synthesized by ionic gelation method, they were coated with alginate by electrostatic interaction. The size, morphology, charge, and structural characterization of prepared core–shell nanoparticulated system were performed by AFM, Zeta sizer, and FTIR. BSA and DOX were loaded as test biomolecules to core and shell part of the nanoparticle, respectively. Release profiles of BSA and DOX were determined by spectrophotometry. The sizes of both chitosan and alginate-coated chitosan nanoparticles which were prepared by modified protocol were measured to be 50 ± 10 and 60 ± 3 nm, respectively. After loading BSA and DOX, the average size of the particles increased to 80 ± 7 nm. Moreover, while the zeta potential of chitosan nanoparticles was positive value, the value was inverted to negative after alginate coating. Release profile measurements of BSA and DOX were determined during 57 and 2 days, respectively. Our results demonstrated that monodisperse alginate-coated nanoparticles were synthesized and loaded successfully using our modified protocol.

  4. Fabrication of monodispersive nanoscale alginate-chitosan core-shell particulate systems for controlled release studies

    Science.gov (United States)

    Körpe, Didem Aksoy; Malekghasemi, Soheil; Aydın, Uğur; Duman, Memed

    2014-12-01

    Biopolymers such as chitosan and alginate are widely used for controlled drug delivery systems. The present work aimed to develop a new protocol for preparation of monodisperse alginate-coated chitosan nanoparticles at nanoscale. Modifications of preparation protocol contain changing the pH of polymer solutions and adding extra centrifugation steps into the procedure. While chitosan nanoparticles were synthesized by ionic gelation method, they were coated with alginate by electrostatic interaction. The size, morphology, charge, and structural characterization of prepared core-shell nanoparticulated system were performed by AFM, Zeta sizer, and FTIR. BSA and DOX were loaded as test biomolecules to core and shell part of the nanoparticle, respectively. Release profiles of BSA and DOX were determined by spectrophotometry. The sizes of both chitosan and alginate-coated chitosan nanoparticles which were prepared by modified protocol were measured to be 50 ± 10 and 60 ± 3 nm, respectively. After loading BSA and DOX, the average size of the particles increased to 80 ± 7 nm. Moreover, while the zeta potential of chitosan nanoparticles was positive value, the value was inverted to negative after alginate coating. Release profile measurements of BSA and DOX were determined during 57 and 2 days, respectively. Our results demonstrated that monodisperse alginate-coated nanoparticles were synthesized and loaded successfully using our modified protocol.

  5. Hierarchical Bi2WO6 architectures decorated with Pd nanoparticles for enhanced visible-light-driven photocatalytic activities

    Science.gov (United States)

    Zhang, Jinniu; Chen, Tianhua; Lu, Hongbing; Yang, Zhibo; Yin, Feng; Gao, Jianzhi; Liu, Qianru; Tu, Yafang

    2017-05-01

    A new kind of hierarchical Pd-Bi2WO6 architecture decorated with different molar ratios of Pd to Bi, has been fabricated by a hydrothermal process, followed by a chemical deposition method. The photocatalytic activities of the pure Bi2WO6 and Pd-Bi2WO6 nanocatalyst were examined in the degradation of Rhodamine B (RhB) dyes and phenol under visible light. The photocatalytic results showed that the Pd-Bi2WO6 nanocomposites possessed observably enhanced photocatalytic activities. Particularly, the 2.0% Pd loaded Bi2WO6 had the highest photocatalytic activity, exhibiting a nearly complete degradation of 30 mg/L RhB and 10 mg/L phenol within only 50 and 60 min, respectively. In addition, the trapping experiment results indicated that the photo-generated holes (h+) and rad O2- played a crucial role in the degradation of RhB. According to the experimental results, the photocatalytic degradation mechanism of Pd-Bi2WO6 was also proposed. The enhanced photocatalytic activities were ascribed to the combined effects of the highly efficient separation of electrons and holes, improved visible light utilization and increased BET specific surface areas of the Pd-Bi2WO6 nanocomposites.

  6. Optimal level of Au nanoparticles on Pd nanostructures providing remarkable electro-catalysis in direct ethanol fuel cell

    Science.gov (United States)

    Dutta, Abhijit; Mondal, Achintya; Broekmann, Peter; Datta, Jayati

    2017-09-01

    The designing and fabrication of economically viable electro-catalysts for ethanol oxidation reaction (EOR) in direct ethanol fuel cell (DEFC) has been one of the challenging issues over the decades. The present work deals with controlled synthesis of Pd coupled Au nano structure, as the non Pt group of catalysts for DEFC. The catalytic proficiency of bimetallic NPs (2-10 nm) are found to be strongly dependent on the Pd:Au ratio. The over voltage of EOR is considerably reduced by ∼260 mV with 33% of Au content in PdAu composition compared to Pd alone, demonstrating the beneficial role of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pd. The catalysts are further subjected to electrochemical analysis through voltammetry along with the temperature study on activation parameters. The quantitative determination of EOR products during the electrolysis is carried out by ion chromatographic analysis; vis-a-vis the coulombic efficiency of the product yield were derived from each of the compositions. Furthermore, a strong correlation among catalytic performances and bimetallic composition is established by screening the catalysts in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC. The performance testing demonstrates outstanding increase of peak power density (∼40 mWcm-2, 93%) for the best accomplishment Au (33%) covered Pd (67%) catalyst in comparison with the monometallic Pd.

  7. Palladium Recovery in a H2-Based Membrane Biofilm Reactor: Formation of Pd(0) Nanoparticles through Enzymatic and Autocatalytic Reductions.

    Science.gov (United States)

    Zhou, Chen; Ontiveros-Valencia, Aura; Wang, Zhaocheng; Maldonado, Juan; Zhao, He-Ping; Krajmalnik-Brown, Rosa; Rittmann, Bruce E

    2016-03-01

    Recovering palladium (Pd) from waste streams opens up the possibility of augmenting the supply of this important catalyst. We evaluated Pd reduction and recovery as a novel application of a H2-based membrane biofilm reactor (MBfR). At steady states, over 99% of the input soluble Pd(II) was reduced through concomitant enzymatic and autocatalytic processes at acidic or near neutral pHs. Nanoparticulate Pd(0), at an average crystallite size of 10 nm, was recovered with minimal leaching and heterogeneously associated with microbial cells and extracellular polymeric substances in the biofilm. The dominant phylotypes potentially responsible for Pd(II) reduction at circumneutral pH were denitrifying β-proteobacteria mainly consisting of the family Rhodocyclaceae. Though greatly shifted by acidic pH, the biofilm microbial community largely bounced back when the pH was returned to 7 within 2 weeks. These discoveries infer that the biofilm was capable of rapid adaptive evolution to stressed environmental change, and facilitated Pd recovery in versatile ways. This study demonstrates the promise of effective microbially driven Pd recovery in a single MBfR system that could be applied for the treatment of the waste streams, and it documents the role of biofilms in this reduction and recovery process.

  8. Electrochemical impedance study and performance of PdNi nanoparticles as cathode catalyst in a polymer electrolyte membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Sanchez, G.; Santana-Salinas, A.; Vazquez-Huerta, G.; Solorza-Feria, O. [Inst. Politenico Nacional, Centro de Investigacion y de Estudios Avanzados, Mexico City (Mexico). Dept. de Quimica

    2010-07-15

    Polymer electrolyte membrane fuel cells (PEMFC) convert the energy stored in hydrogen and oxygen molecules directly into electricity. However, technical and economic challenges must be overcome to address cost, performance and stability issues associated with membrane electrode assemblies (MEA). The oxygen reduction reaction (ORR) which takes place in the cathode is the limiting reaction due to the slow kinetics of ORR on metals, including platinum (Pt). For that reason, much research has gone into finding catalyst materials with a similar or greater performance than Pt. Bimetallic palladium (Pd) based catalysts have been considered as alternative materials for ORR. In this study, a carbon-dispersed bimetallic PdNi was prepared by borohydride reduction using PdCl{sub 2} and NiCl{sub 2} as precursors in a tetrahydrofuran (THF) solution. The PdNi loading and weight percentage were optimized using the Simplex method. The MEA performance was evaluated at optimum conditions using the PdNi electrocatalyst as the cathode and a Pt-Etek carbon cloth as the anode. The maximum power density of 122 mW per cm{sup 2} was reached with 45 percent of PdNi wt percent at 30 psi and 80 degrees C. The catalytic activity and the mechanism of the ORR on PdNi, in 0.5M H{sub 2}SO{sub 4} was investigated using electrochemical impedance spectroscopy. The Tafel slope and the charge transfer coefficient were obtained from the impedance spectra at optimum condition of PdNi loading and PdNi wt percent. 24 refs., 2 tabs., 5 figs.

  9. Ultrasmall PdmMn1-mOx binary alloyed nanoparticles on graphene catalysts for ethanol oxidation in alkaline media

    Science.gov (United States)

    Ahmed, Mohammad Shamsuddin; Park, Dongchul; Jeon, Seungwon

    2016-03-01

    A rare combination of graphene (G)-supported palladium and manganese in mixed-oxides binary alloyed catalysts (BACs) have been synthesized with the addition of Pd and Mn metals in various ratios (G/PdmMn1-mOx) through a facile wet-chemical method and employed as an efficient anode catalyst for ethanol oxidation reaction (EOR) in alkaline fuel cells. The as prepared G/PdmMn1-mOx BACs have been characterized by several instrumental techniques; the transmission electron microscopy images show that the ultrafine alloyed nanoparticles (NPs) are excellently monodispersed onto the G. The Pd and Mn in G/PdmMn1-mOx BACs have been alloyed homogeneously, and Mn presents in mixed-oxidized form that resulted by X-ray diffraction. The electrochemical performances, kinetics and stability of these catalysts toward EOR have been evaluated using cyclic voltammetry in 1 M KOH electrolyte. Among all G/PdmMn1-mOx BACs, the G/Pd0.5Mn0.5Ox catalyst has shown much superior mass activity and incredible stability than that of pure Pd catalysts (G/Pd1Mn0Ox, Pd/C and Pt/C). The well dispersion, ultrafine size of NPs and higher degree of alloying are the key factor for enhanced and stable EOR electrocatalysis on G/Pd0.5Mn0.5Ox.

  10. Pd Nanoparticles Decorated N-Doped Graphene Quantum Dots@N-Doped Carbon Hollow Nanospheres with High Electrochemical Sensing Performance in Cancer Detection.

    Science.gov (United States)

    Xi, Jiangbo; Xie, Chuyi; Zhang, Yan; Wang, Lu; Xiao, Jian; Duan, Xianming; Ren, Jinghua; Xiao, Fei; Wang, Shuai

    2016-08-31

    The development of carbon based hollow-structured nanospheres (HNSs) materials has stimulated growing interest due to their controllable structure, high specific surface area, large void space, enhanced mass transport, and good biocompatibility. The incorporation of functional nanomaterials into their core and/or shell opens new horizons in designing functionalized HNSs for a wider spectrum of promising applications. In this work, we report a new type of functionalized HNSs based on Pd nanoparticles (NPs) decorated double shell structured N-doped graphene quantum dots (NGQDs)@N-doped carbon (NC) HNSs, with ultrafine Pd NPs and "nanozyme" NGQDs as dual signal-amplifying nanoprobes, and explore their promising application as a highly efficient electrocatalyst in electrochemical sensing of a newly emerging biomarker, i.e., hydrogen peroxide (H2O2), for cancer detection. Due to the synergistic effect of the robust and conductive HNS supports and catalytically active Pd NPs and NGQD in facilitating electron transfer, the NGQD@NC@Pd HNS hybrid material exhibits high electrocatalytic activity toward the direct reduction of H2O2 and can promote the electrochemical reduction reaction of H2O2 at a favorable potential of 0 V, which effectively restrains the redox of most electroactive species in physiological samples and eliminates interference signals. The resultant electrochemical H2O2 biosensor based hybrid HNSs materials demonstrates attractive performance, including low detection limit down to nanomole level, short response time within 2 s, as well as high sensitivity, reproducibility, selectivity, and stability, and have been used in real-time tracking of trace amounts of H2O2 secreted from different living cancer cells in a normal state and treated with chemotherapy and radiotherapy.

  11. PdCu alloy nanoparticle-decorated copper nanotubes as enhanced electrocatalysts: DFT prediction validated by experiment

    Science.gov (United States)

    Wu, Dengfeng; Xu, Haoxiang; Cao, Dapeng; Fisher, Adrian; Gao, Yi; Cheng, Daojian

    2016-12-01

    In order to combine the advantages of both 0D and 1D nanostructured materials into a single catalyst, density functional theory (DFT) calculations have been used to study the PdCu alloy NP-decorated Cu nanotubes (PdCu@CuNTs). These present a significant improvement of the electrocatalytic activity of formic acid oxidation (FAO). Motivated by our theoretical work, we adopted the seed-mediated growth method to successfully synthesize the nanostructured PdCu@CuNTs. The new catalysts triple the catalytic activity for FAO, compared with commercial Pd/C. In summary, our work provides a new strategy for the DFT prediction and experimental synthesis of novel metal NP-decorated 1D nanostructures as electrocatalysts for fuel cells.

  12. Novel platinum–palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

    Directory of Open Access Journals (Sweden)

    Ghosh S

    2015-12-01

    Full Text Available Sougata Ghosh,1 Rahul Nitnavare,1 Ankush Dewle,1 Geetanjali B Tomar,1 Rohan Chippalkatti,1 Piyush More,1 Rohini Kitture,2 Sangeeta Kale,2 Jayesh Bellare,3 Balu A Chopade4 1Institute of Bioinformatics and Biotechnology, University of Pune, 2Department of Applied Physics, Defense Institute of Advanced Technology, Pune, 3Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, 4Department of Microbiology, University of Pune, Pune, India Abstract: Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum–palladium bimetallic nanoparticles (Pt–PdNPs along with individual platinum (PtNPs and palladium (PdNPs nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE. High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2–5 nm, while PdNPs and Pt–PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88%±1.73% elemental Pt and 68.96%±1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm-1, attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm-1, associated with C–H stretching, N–H bending in primary amines, N–O stretching in nitro group, and C–C stretch, respectively. Anticancer activity against HeLa cells showed that Pt–PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6% or PdNPs (33.15%. Further, Pt–PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. Keywords: Dioscorea bulbifera, platinum nanoparticles

  13. Spontaneous Breakup of Extended Monodisperse Polymer Melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Yu, Kaijia

    2011-01-01

    We apply continuum mechanical based, numerical modeling to study the dynamics of extended monodisperse polymer melts during the relaxation. The computations are within the ideas of the microstructural ‘‘interchain pressure’’ theory. The computations show a delayed necking resulting in a rupture...

  14. 高度单分散聚乙烯基倍半硅氧烷球形纳米粒子的制备及性能%Preparation and Properties of Highly Monodisperse Spherical Poly (vinylsilsesquioxane) Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    陈连喜; 李洁; 李曦; 翟鹏程; 张江涛; 张中明

    2013-01-01

    在水溶液中,以乙烯基三乙氧基硅烷(VTES)为前驱体,氨水(NH3·H2O)为催化剂,在表面活性剂十二烷基苯磺酸钠(SDBS)存在下,通过溶胶一凝胶法成功合成了具有不同粒径、高度单分散的聚乙烯基倍半硅氧烷(PVSQ)球形纳米粒子.研究结果表明,催化剂NH3·H2O与表面活性剂SDBS的用量对PVSQ的粒径和粒径分布影响很大,而前驱体VTES的用量对PVSQ的粒径无明显影响.通过场发射扫描电子显微镜(FESEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)及热重(TG)分析对产物的形貌、粒径和粒径分布、结构及热性能进行了表征.%In aqueous solution,highly monodisperse spherical poly (vinylsilsesquioxane) (PVSQ) particles with various sizes have been prepared successfully in the presence of surfactant sodium dodecyl benzene sulfonate(SDBS) using vinyl triethoxysilane (VTES) as precursor and ammonia hydroxide as catalyst by sol-gel method.The research results show that the amounts of catalyst(NH3· H2O) and surfactant(SDBS) have great effects on size and size distribution of PVSQ.However,the amount of precursor(VTES) has unobvious effect on size and size distribution of PVSQ.The shape,size and size distribution,structure,surface property and thermal behavior of the resulting products were analyzed and characterized by field emission scanning electron microscope(FESEM),Fourier transform infrared spectroscopy (FTIR),X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis(TGA),respectively.

  15. Simultaneous removal of co-contaminants: acid brilliant violet and Cu2+ by functional bimetallic Fe/Pd nanoparticles

    Science.gov (United States)

    Jin, Xiaoying; Chen, Zhengxian; Wang, Ting; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2014-10-01

    Effluents from the textile industry often contain dyes and metals that are a serious environmental concern. It is a challenge to develop a method for simultaneous removal of mixed contaminants. In this study, kaolinite supported bimetallic Fe/Pd (K-Fe/Pd) is firstly reported to be used for simultaneous catalytic removal of acid brilliant violet (ABV) and Cu2+ in aqueous solution, where the presence of kaolinite as a stable supporter and disperser maintains the reactivity of Fe0 as a reductant, while Pd0 as a catalyst accelerates the reaction. This was confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and batch experiments. 96.23 % of ABV and 100 % of Cu2+ was removed using K-Fe/Pd within 60 min, while only 77.50 % of ABV and 99.45 % of Cu2+ using K-Fe, and 19.75 % of ABV and 4.00 % of Cu2+ using kaolinite was removed, respectively. However, both efficiency and rate of removal in the mixed solution were higher than that of the single one regarding both ABV and Cu2+, which is attributable to the formation of in situ trimetallic Cu/Fe/Pd in the mixed solution. Different factors impacting on the removal of ABV-Cu2+ using K-Fe/Pd showed that the catalytic reduction decreased when pH, initial concentration, and temperature increased. Finally, the reuse and application of K-Fe/Pd in dyeing wastewater led to a removal efficiency of 96.35 % for ABV and 100 % for Cu2+, respectively.

  16. Green synthesis of the Pd nanoparticles supported on reduced graphene oxide using barberry fruit extract and its application as a recyclable and heterogeneous catalyst for the reduction of nitroarenes.

    Science.gov (United States)

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar; Alizadeh, Mohammad; Bagherzadeh, Mojtaba

    2016-03-15

    Through this manuscript the green synthesis of palladium nanoparticles supported on reduced graphene oxide (Pd NPs/RGO) under the mild conditions through reduction of the graphene oxide and Pd(2+) ions using barberry fruit extract as reducing and stabilizing agent is reported. The as-prepared Pd NPs/RGO was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The Pd NPs/RGO could be used as an efficient and heterogeneous catalyst for reduction of nitroarenes using sodium borohydride in an environmental friendly medium. Excellent yields of products were obtained with a wide range of substrates and the catalyst was recycled multiple times without any significant loss of its catalytic activity. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Shape-dependent electrocatalytic activity of monodispersed palladium nanocrystals toward formic acid oxidation.

    Science.gov (United States)

    Zhang, Xuwei; Yin, Huajie; Wang, Jinfeng; Chang, Lin; Gao, Yan; Liu, Wei; Tang, Zhiyong

    2013-09-21

    The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO4(2-) ions and formic acid on the surface of Pd nanocrystals.

  18. Facile synthesis of Pd-based bimetallic nanocrystals and their application as catalysts for methanol oxidation reaction

    Science.gov (United States)

    Xi, Pinxian; Cao, Yang; Yang, Fengchun; Ma, Cai; Chen, Fengjuan; Yu, Sha; Wang, Shuai; Zeng, Zhengzhi; Zhang, Xin

    2013-06-01

    We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations.We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00912b

  19. Synthesis of polystyrene microspheres and functionalization with Pd(0) nanoparticles to perform bioorthogonal organometallic chemistry in living cells.

    Science.gov (United States)

    Unciti-Broceta, Asier; Johansson, Emma M V; Yusop, Rahimi M; Sánchez-Martín, Rosario M; Bradley, Mark

    2012-05-31

    We have developed miniaturized heterogeneous Pd(0)-catalysts (Pd(0)-microspheres) with the ability to enter cells, stay harmlessly within the cytosol and mediate efficient bioorthogonal organometallic chemistries (e.g., allylcarbamate cleavage and Suzuki-Miyaura cross-coupling). This approach is a major addition to the toolbox available for performing chemical reactions within cells. Here we describe a full protocol for the synthesis of the Pd(0)-microspheres from readily available starting materials (by the synthesis of size-controlled amino-functionalized polystyrene microspheres), as well as for their characterization (electron microscopy and palladium quantitation) and functional validation ('in solution' and 'in cytoplasm' conversions). From the beginning of the synthesis to functional evaluation of the catalytic device requires 5 d of work.

  20. Reduced graphene oxide nanosheets decorated with Au-Pd bimetallic alloy nanoparticles towards efficient photocatalytic degradation of phenolic compounds in water.

    Science.gov (United States)

    Darabdhara, Gitashree; Boruah, Purna K; Borthakur, Priyakshree; Hussain, Najrul; Das, Manash R; Ahamad, Tansir; Alshehri, Saad M; Malgras, Victor; Wu, Kevin C-W; Yamauchi, Yusuke

    2016-04-21

    Reduced graphene oxide nanosheets decorated with Au-Pd bimetallic alloy nanoparticles are successfully prepared via a chemical approach consisting of reducing the metal precursors using ascorbic acid as reductant at an elevated temperature. The prepared nanocomposite is employed as a photocatalyst for the degradation of organic contaminants such as phenol, 2-chlorophenol (2-CP), and 2-nitrophenol (2-NP). The complete degradation of phenol is achieved after 300 min under natural sunlight irradiation whereas the degradation of 2-CP and 2-NP is completed after 180 min. The activity of the photocatalyst is evaluated considering several parameters such as the initial phenol concentration, the photocatalyst loading, and the pH of the solution. The degradation kinetics of all the compounds is carefully studied and found to follow a linear Langmuir-Hinshelwood model. Furthermore, the reusability of the photocatalyst is successfully achieved up to five cycles and the catalyst exhibits an excellent stability.

  1. Tungsten carbide promoted Pd and Pd-Co electrocatalysts for formic acid electrooxidation

    Science.gov (United States)

    Yin, Min; Li, Qingfeng; Jensen, Jens Oluf; Huang, Yunjie; Cleemann, Lars N.; Bjerrum, Niels J.; Xing, Wei

    2012-12-01

    Tungsten carbide (WC) promoted palladium (Pd) and palladium-cobalt (Pd-Co) nanocatalysts are prepared and characterized for formic acid electrooxidation. The WC as the dopant to carbon supports is found to enhance the CO tolerance and promote the activity of the Pd-based catalysts for formic acid oxidation. Alloying of Pd with Co further improves the electrocatalytic activity and stability of the WC supported catalysts, attributable to a synergistic effect of the carbide support and PdCo alloy nanoparticles.

  2. Titania Supported Pt and Pt/Pd Nano-particle Catalysts for the Oxidation of Sulfur Dioxide

    DEFF Research Database (Denmark)

    Koutsopoulos, Sotiris; Johannessen, Tue; Eriksen, Kim Michael

    2006-01-01

    Several types of titania (anatase) were used as supports for pure platinum and Pt–Pd bimetallic alloy catalysts. The preparation methods, normal wet impregnation technique and flame aerosol synthesis, obtained metal loadings of 2% by weight. The prepared catalysts were tested for SO2 oxidation...... activity at atmospheric pressure in the temperature range 250–600 °C. The SO2 to SO3 conversion efficiency of the Pt–Pd alloy was significantly higher than that of the individual metals. The effects of the preparation method and the titania type used on the properties and activity of the resulting catalyst...

  3. Beneficial effects of microwave-assisted heating versus conventional heating in noble metal nanoparticle synthesis.

    Science.gov (United States)

    Dahal, Naween; García, Stephany; Zhou, Jiping; Humphrey, Simon M

    2012-11-27

    An extensive comparative study of the effects of microwave versus conventional heating on the nucleation and growth of near-monodisperse Rh, Pd, and Pt nanoparticles has revealed distinct and preferential effects of the microwave heating method. A one-pot synthetic method has been investigated, which combines nucleation and growth in a single reaction via precise control over the precursor addition rate. Using this method, microwave-assisted heating enables the convenient preparation of polymer-capped nanoparticles with improved monodispersity, morphological control, and higher crystallinity, compared with samples heated conventionally under otherwise identical conditions. Extensive studies of Rh nanoparticle formation reveal fundamental differences during the nucleation phase that is directly dependent on the heating method; microwave irradiation was found to provide more uniform seeds for the subsequent growth of larger nanostructures of desired size and surface structure. Nanoparticle growth kinetics are also markedly different under microwave heating. While conventional heating generally yields particles with mixed morphologies, microwave synthesis consistently provides a majority of tetrahedral particles at intermediate sizes (5-7 nm) or larger cubes (8+ nm) upon further growth. High-resolution transmission electron microscopy indicates that Rh seeds and larger nanoparticles obtained from microwave-assisted synthesis are more highly crystalline and faceted versus their conventionally prepared counterparts. Microwave-prepared Rh nanoparticles also show approximately twice the catalytic activity of similar-sized conventionally prepared particles, as demonstrated in the vapor-phase hydrogenation of cyclohexene. Ligand exchange reactions to replace polymer capping agents with molecular stabilizing agents are also easily facilitated under microwave heating, due to the excitation of polar organic moieties; the ligand exchange proceeds with excellent retention of

  4. Reduced graphene oxide nanosheets decorated with Au-Pd bimetallic alloy nanoparticles towards efficient photocatalytic degradation of phenolic compounds in water

    Science.gov (United States)

    Darabdhara, Gitashree; Boruah, Purna K.; Borthakur, Priyakshree; Hussain, Najrul; Das, Manash R.; Ahamad, Tansir; Alshehri, Saad M.; Malgras, Victor; Wu, Kevin C.-W.; Yamauchi, Yusuke

    2016-04-01

    Reduced graphene oxide nanosheets decorated with Au-Pd bimetallic alloy nanoparticles are successfully prepared via a chemical approach consisting of reducing the metal precursors using ascorbic acid as reductant at an elevated temperature. The prepared nanocomposite is employed as a photocatalyst for the degradation of organic contaminants such as phenol, 2-chlorophenol (2-CP), and 2-nitrophenol (2-NP). The complete degradation of phenol is achieved after 300 min under natural sunlight irradiation whereas the degradation of 2-CP and 2-NP is completed after 180 min. The activity of the photocatalyst is evaluated considering several parameters such as the initial phenol concentration, the photocatalyst loading, and the pH of the solution. The degradation kinetics of all the compounds is carefully studied and found to follow a linear Langmuir-Hinshelwood model. Furthermore, the reusability of the photocatalyst is successfully achieved up to five cycles and the catalyst exhibits an excellent stability.Reduced graphene oxide nanosheets decorated with Au-Pd bimetallic alloy nanoparticles are successfully prepared via a chemical approach consisting of reducing the metal precursors using ascorbic acid as reductant at an elevated temperature. The prepared nanocomposite is employed as a photocatalyst for the degradation of organic contaminants such as phenol, 2-chlorophenol (2-CP), and 2-nitrophenol (2-NP). The complete degradation of phenol is achieved after 300 min under natural sunlight irradiation whereas the degradation of 2-CP and 2-NP is completed after 180 min. The activity of the photocatalyst is evaluated considering several parameters such as the initial phenol concentration, the photocatalyst loading, and the pH of the solution. The degradation kinetics of all the compounds is carefully studied and found to follow a linear Langmuir-Hinshelwood model. Furthermore, the reusability of the photocatalyst is successfully achieved up to five cycles and the catalyst

  5. Catalytic Intervention of MoO3 toward Ethanol Oxidation on PtPd Nanoparticles Decorated MoO3-Polypyrrole Composite Support.

    Science.gov (United States)

    De, Abhishek; Datta, Jayati; Haldar, Ipsita; Biswas, Mukul

    2016-10-14

    Ethanol oxidation reaction has been studied in acidic environment over PtPd nanoparticles (NPs) grown on the molybdenum oxide-polypyrrole composite (MOPC) support. The attempt was focused on using reduced Pt loading on non-carbon support for direct ethanol fuel cell (DEFC) operated with proton exchange membrane (PEM). As revealed in SEM study, a molybdenum oxide network exists in polypyrrole caging and the presence of metal NPs over the composite matrix is confirmed by TEM analysis. Further physicochemical characterizations such as XRD, EDAX, and XPS are followed in order to understand the surface morphology and composition of the hybrid structure. Electrochemical techniques such as voltammetry, choroamperometry, and impedance spectroscopy along with performance testing of an in-house-fabricated fuel cell are carried out to evaluate the catalytic activity of the materials for DEFC. The reaction products are estimated by ion chromatographic analysis. Considering the results obtained from the above characterization procedures, the best catalytic performance is exhibited by the Pt-Pd (1:1) on MOPC support. A clear intervention of the molybdenum oxide network is strongly advocated in the EOR sequence which increases the propensity of the reaction by making the metallites more energy efficient in terms of harnessing sufficient numbers of electrons than with the carbon support.

  6. Preparation and characterization of platinum (Pt) and palladium (Pd) nanoparticle decorated graphene sheets and their utilization for the elimination of basic fuchsin and indigo carmine dyes

    Science.gov (United States)

    Kurt, Belma Zengin; Durmus, Zehra; Durmus, Ali

    2016-01-01

    In this study, graphene nano sheets, prepared with chemical oxidation and reduction routes via modified-Hummer method, were successfully decorated with platinum (Pt) and palladium (Pd) nanoparticles. Structural and morphological features of resulted graphene-metal nanocomposites were characterized with FT-IR, XRD, SEM and TEM methods. Anti-oxidant activity (AOA) values of nanocomposites were determined. The IC50 values of Pt-graphene and Pd-graphene nanocomposites were found to be 46.1 and 90.2 μg/mL, respectively based on the ABTS method and 80.2 and 143.7 μg/mL according to the DPPH method. It was found that the graphene-metal nanocomposites exhibited superior free radical scavenging activity compared to several types of noble metal nano particles although the nanocomposites consist of much lower amount of active metal sites than the nano-crystalline metal powders. It was consequently reported that the graphene-metal nanocomposites could be successfully used for the photocatalytic elimination of fuchsin and indigo carmine dyes under light irradiation.

  7. Template synthesis of monodisperse carbon nanodots

    Science.gov (United States)

    Kurdyukov, D. A.; Eurov, D. A.; Stovpiaga, E. Yu.; Kirilenko, D. A.; Konyakhin, S. V.; Shvidchenko, A. V.; Golubev, V. G.

    2016-12-01

    Monodisperse carbon nanodots in pores of mesoporous silica particles are obtained by template synthesis. This method is based on introducing a precursor (organosilane) into pores, its thermal decomposition with formation of carbon nanodots, and the template removal. Structural analysis of the nanomaterial has been performed, which showed that carbon nanodots have an approximately spherical form and a graphite-like structure. According to dynamic light scattering data, the size of carbon nanodots is 3.3 ± 0.9 nm.

  8. Nanoparticle-supported and magnetically recoverable palladium (Pd) catalyst: a selective and sustainable oxidation protocol with high turnover number

    Science.gov (United States)

    A magnetic nanoparticle-supported ruthenium hydroxide catalyst was readily prepared from inexpensive starting materials and shown to catalyze hydration of nitriles with excellent yield in benign aqueous medium. Catalyst recovery using an external magnetic field, superior activity...

  9. A Systematic Investigation of p-Nitrophenol Reduction by Bimetallic Dendrimer Encapsulated Nanoparticles

    Science.gov (United States)

    2013-01-01

    We demonstrate that the reduction of p-nitrophenol to p-aminophenol by NaBH4 is catalyzed by both monometallic and bimetallic nanoparticles (NPs). We also demonstrate a straightforward and precise method for the synthesis of bimetallic nanoparticles using poly(amido)amine dendrimers. The resulting dendrimer encapsulated nanoparticles (DENs) are monodisperse, and the size distribution does not vary with different elemental combinations. Random alloys of Pt/Cu, Pd/Cu, Pd/Au, Pt/Au, and Au/Cu DENs were synthesized and evaluated as catalysts for p-nitrophenol reduction. These combinations are chosen in order to selectively tune the binding energy of the p-nitrophenol adsorbate to the nanoparticle surface. Following the Brønsted–Evans–Polanyi (BEP) relation, we show that the binding energy can reasonably predict the reaction rates of p-nitrophenol reduction. We demonstrate that the measured reaction rate constants of the bimetallic DENs is not always a simple average of the properties of the constituent metals. In particular, DENs containing metals with similar lattice constants produce a binding energy close to the average of the two constituents, whereas DENs containing metals with a lattice mismatch show a bimodal distribution of binding energies. Overall, in this work we present a uniform method for synthesizing pure and bimetallic DENs and demonstrate that their catalytic properties are dependent on the adsorbate’s binding energy. PMID:23616909

  10. Shape-dependent electrocatalytic activity of monodispersed palladium nanocrystals toward formic acid oxidation

    Science.gov (United States)

    Zhang, Xuwei; Yin, Huajie; Wang, Jinfeng; Chang, Lin; Gao, Yan; Liu, Wei; Tang, Zhiyong

    2013-08-01

    The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO42- ions and formic acid on the surface of Pd nanocrystals.The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO42- ions and formic acid on the surface of Pd nanocrystals. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03100d

  11. Facile Synthesis of Mono-Dispersed Polystyrene (PS/Ag Composite Microspheres via Modified Chemical Reduction

    Directory of Open Access Journals (Sweden)

    Wen Zhu

    2013-12-01

    Full Text Available A modified method based on in situ chemical reduction was developed to prepare mono-dispersed polystyrene/silver (PS/Ag composite microspheres. In this approach; mono-dispersed PS microspheres were synthesized through dispersion polymerization using poly-vinylpyrrolidone (PVP as a dispersant at first. Then, poly-dopamine (PDA was fabricated to functionally modify the surfaces of PS microspheres. With the addition of [Ag(NH32]+ to the PS dispersion, [Ag(NH32]+ complex ions were absorbed and reduced to silver nanoparticles on the surfaces of PS-PDA microspheres to form PS/Ag composite microspheres. PVP acted both as a solvent of the metallic precursor and as a reducing agent. PDA also acted both as a chemical protocol to immobilize the silver nanoparticles at the PS surface and as a reducing agent. Therefore, no additional reducing agents were needed. The resulting composite microspheres were characterized by TEM, field emission scanning electron microscopy (FESEM, energy-dispersive X-ray spectroscopy (EDS, XRD, UV-Vis and surface-enhanced Raman spectroscopy (SERS. The results showed that Ag nanoparticles (NPs were homogeneously immobilized onto the PS microspheres’ surface in the presence of PDA and PVP. PS/Ag composite microspheres were well formed with a uniform and compact shell layer and were adjustable in terms of their optical property.

  12. Development of monodispersed and functional magnetic polymeric liposomes via simple liposome method

    Energy Technology Data Exchange (ETDEWEB)

    Liang Xiaofei; Wang Hanjie [Tianjin University and Tianjin Key Laboratory of Composites and Functional Materials, Institute of Nanobiotechnology, School of Materials Science and Engineering (China); Jiang Xinguo [Fudan University, School of Pharmacy (China); Chang Jin, E-mail: jinchang@tju.edu.c [Tianjin University and Tianjin Key Laboratory of Composites and Functional Materials, Institute of Nanobiotechnology, School of Materials Science and Engineering (China)

    2010-06-15

    We are reporting a simple and rapid method to prepare superparamagnetic, controlled size, and monodispersed magnetic cationic polymeric liposomes (MCPL) by octadecyl quaternized carboxymethyl chitosan (OQCMC) and cholesterol. The whole process is only about 25 min with simple thin-film dispersion and solvent evaporation method. Hydrophilic magnetic nanoparticles (LM) and hydrophobic magnetic nanoparticles (BM) can be encapsulated into these cationic polymeric liposomes, simultaneously or respectively. A model hydrophobic drug indomethacin can be successfully filled in MCPL with high drug loading capacity 22%. MCPL encapsulating BM also showed strong DNA (pEGFP) binding ability. Drug-loaded MCPL have a long and controlled sustained release profile by changing the number of polymeric lipid layer. These functional MCPL nanospheres can be allowed to serve as ideal candidates for many biomedical applications.Graphical AbstractA simple and rapid liposome method was reported to prepare superparamagnetic, controlled size, and monodispersed magnetic cationic polymeric liposomes (MCPL) by polymeric surfactant, octadecyl quaternized carboxymethyl chitosan (OQCMC), and cholesterol. Hydrophilic Fe{sub 3}O{sub 4} ferrofluid and hydrophobic magnetic nanoparticles can be encapsulated into these cationic polymeric liposomes, simultaneously or respectively. Hydrophobic drug indomethacin can be encapsulated into this MCPL with high encapsulating efficiency and with controlled release profile by changing the number of polymeric lipid layer.

  13. Hydrothermal synthesis of superparamagnetic and red luminescent bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er core@shell monodisperse nanoparticles and their subsequent ligand exchange in water

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Zhenli; Du, Sinan; Luo, Yang; Liao, Zhijian; Zuo, Fang, E-mail: polymerzf@swun.cn; Luo, Jianbin; Liu, Dong

    2016-08-15

    Graphical abstract: An efficient hydrothermal method was used to fabricate the superparamagnetic and red luminescent bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2(*)+}-doped NaYF{sub 4}:Yb/Er nanoparticles (NPs) with core@shell structures through a seed-growth procedure. Then using PEG phosphate ligand to displace oleate from the as-synthesized NPs, hydrophilic Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er NPs with good water solubility are obtained. - Highlights: • Homogeneous size distribution of magnetic-upconversion core@shell structured nanoparticles (NPs) were synthesized. • The core@shell nanostructures were obtained by seed-growth method. • The oleic acid coated Fe{sub 3}O{sub 4} NPs were used as seeds and cores. • The magnetic-upconversion NPs emitted red luminescence under a 980 nm laser. • Synthesized magnetic-upconversion NPs were phase transferred using ligand exchange process. - Abstract: We report the use of an efficient hydrothermal method to synthesize superparamagnetic and red luminescent bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er nanoparticles (NPs) with core@shell structures via a seed-growth procedure. Oleic acid coated Fe{sub 3}O{sub 4} (OA-Fe{sub 3}O{sub 4}) NPs were initially synthesized using a coprecipitation method. The as-synthesized OA-Fe{sub 3}O{sub 4} NPs were then used as seeds, on which the red upconversion luminescent shell (Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er) was formed. Furthermore, hydrophobic to hydrophilic surface modification of the Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er NPs was achieved via a ligand exchange method where oleic acid was displaced by a PEG phosphate ligand [PEG = poly(ethylene glycol)]. These materials were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). The Fe{sub 3}O{sub 4} cores were uniformly coated with a Mn{sup 2+}-doped NaYF{sub 4}:Yb

  14. Biotemplate synthesis of monodispersed iron phosphate hollow microspheres.

    Science.gov (United States)

    Cao, Feng; Li, Dongxu

    2010-03-01

    Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe(3+), which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 degrees C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

  15. Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Cao Feng; Li Dongxu, E-mail: dongxuli@njut.edu.c [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China)

    2010-03-15

    Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe{sup 3+}, which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

  16. Microfluidic Production of Monodisperse Perfluorocarbon Microdroplets

    Science.gov (United States)

    Li, David; Schalte, Kevin; Fowlkes, J. Brian; Bull, Joseph

    2010-11-01

    Acoustic droplet vaporization (ADV) is process in which liquid perfluorocarbon (PFC) microdroplets are vaporized using focused ultrasound to form gas bubbles that are approximately 125 times larger in volume. Gas embolotherapy is a novel cancer treatment that uses ADV in vivo to strategically form gas emoboli, which can lodge in the microcirculation and starve tumors. Current methods to produce PFC microdroplets, such has high speed shaking or sonication, result in polydisperse droplet distributions where a fraction of droplets fall within the 2-10 microns range. In the clinical application with such a droplet distribution, large droplets are filtered by the lungs and small droplets result in bubbles that are too small to lodge in the tumor vasculature. Consequently, there is a need for a monodisperse droplet distribution. A microfluidic based device has been developed in order to produce such monodisperse PFC microdroplets. The device used hydrodynamic flow focusing to create droplets with a mean diameter less than 10 microns in diameter. This work is supported by NIH grant R01EB006476.

  17. Elongational viscosity of monodisperse and bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The start-up and steady uniaxial elongational viscosity have been measured for two monodisperse polystyrene melts with molecular weights of 52 and 103 kg/mole, and for three bidisperse polystyrene melts. The monodisperse melts show a maximum in the steady elongational viscosity vs. the elongation...

  18. The Pd(0) nanoparticles stabilized by collagen fibres as a recyclable heterogeneous catalyst for the Stille reaction under aerobic condition

    Indian Academy of Sciences (India)

    Babak Mohammadi-Aghdam; Siavash Bahari; Rahim Molaei

    2013-07-01

    The stabilized palladium(0) nanoparticles by collagen fibres was a highly active, air-stable and recyclable heterogeneous catalyst that could be used for the Stille coupling reactions between aryl iodides and organostannanes under aerobic conditions. This method offered the several advantages: high yield under facile reaction condition and easy work-up procedure. The catalyst was easily recovered from the reaction mixture by filtration and reused multiple times without significant reduction or decrease in the activity.

  19. Three-dimensional shapes and distribution of FePd nanoparticles observed by electron tomography using high-angle annular dark-field scanning transmission electron microscopy

    Science.gov (United States)

    Sato, Kazuhisa; Aoyagi, Kenta; Konno, Toyohiko J.

    2010-01-01

    We have studied three-dimensional shapes and distribution of FePd nanoparticles, prepared by electron beam deposition and postdeposition annealing, by means of single-axis tilt tomography using atomic number contrasts obtained by high-angle annular dark-field scanning transmission electron microscopy. Particle size, shape, and locations were reconstructed by weighted backprojection (WBP), as well as by simultaneous iterative reconstruction technique (SIRT). We have also estimated the particle size by simple extrapolation of tilt-series original data sets, which proved to be quite powerful. The results of the two algorithms for reconstruction have been compared quantitatively with those obtained by the extrapolation method and those independently reported by electron holography. It was found that the reconstructed intensity map by WBP contains a small amount of dotlike artifacts, which do not exist in the results by SIRT, and that the particle surface obtained by WBP is rougher than that by SIRT. We demonstrate, on the other hand, that WBP yields a better estimation of the particle size in the z direction than SIRT does, most likely due to the presence of a "missing wedge" in the original data set.

  20. Theoretical insights into the energetics and electronic properties of MPt12 (M = Fe, Co, Ni, Cu, and Pd) nanoparticles supported by N-doped defective graphene

    Science.gov (United States)

    Wang, Qing; Tian, Yu; Chen, Guangju; Zhao, Jingxiang

    2017-03-01

    Enhancing the catalytic activity and decreasing the usage of Pt catalysts has been a major target in widening their applications for developing proton-exchange membrane fuel cells. In this work, the adsorption energetics, structural features, and electronic properties of several MPt12 (M = Fe, Co, Ni, Cu, and Pd) nanoparticles (NPs) deposited on N-doped defective graphene were systemically explored by means of comprehensive density functional theory (DFT) computations. The computations revealed that the defective N-doped graphene substrate can provide anchoring site for these Pt-based alloying NPs due to their strong hybridization with the sp2 dangling bonds at the defect sites of substrate. Especially, these deposited MPt12 NPs exhibit reduced magnetic moment and their average d-band centers are shifted away from the Fermi level, as compared with the freestanding NPs, leading to the reduction of the adsorption energies of the O species. Thus, the defective N-doped graphene substrate not only enhances the stability of the deposited MPt12 NPs, but also endows them higher catalytic performance for the oxygen reduction reaction.

  1. From Polymeric Nanoparticles to Dye-containing Photonic Crystals:Synthesis,Self-assembling,Optical Features, Possible Applications

    Institute of Scientific and Technical Information of China (English)

    A.V.Yakimansky; A.Yu.Menshikova; N.N.Shevchenko; A.G.Bazhenova; S.K.Sazonov; A.I.Vedernikov; S.P.Gromov; V.A.Sazhnikov; M.V.Alfimov

    2007-01-01

    1 Results Self-assembling of monodisperse polymeric nanoparticles is a perspective method of obtaining photonic crystalline materials for optoelectronics,telecommunication industry and optosensorics.For tuning optical characteristics of photonic crystals it is advisable to functionalize nanoparticles by dyes absorbing or emitting light in the vicinity of the photonic band gap,which position depends on the nanoparticle diameter.To prepare monodisperse nanoparticles with the dye-functionalyzed surface emu...

  2. Synthesis of monodisperse crosslinked polystyrene microspheres

    Institute of Scientific and Technical Information of China (English)

    Jiang Kai; Chen Sheng-Li; Dong Peng; Liu Renxiao

    2008-01-01

    Monodisperse crosslinked polystyrene (CPS) particles were prepared through the normal emulsion polymerization method by adding crosslinker-divinylbenzene (DVB) into the reaction system after polystyrene (PS) particles grew to ~80% of the final size. When the amount of crosslinker DVB added was less than 6.17 wt% based on styrene, the prepared CPS particles were spherical and uniform and the size of the CPS particles could be predicted through the normal emulsion method. The glass transition temperature (Tg) of the prepared CPS particles was higher than that of un-crosslinked PS particles and, the more crosslinker that was added, the higher the Tg of CPS Particles. The prepared CPS particles had strong resistance to organic solvents.

  3. Monodisperse microdroplet generation and stopping without coalescence

    Energy Technology Data Exchange (ETDEWEB)

    Beer, Neil Reginald

    2016-02-23

    A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.

  4. On-demand one-step synthesis of monodisperse functional polymeric microspheres with droplet microfluidics.

    Science.gov (United States)

    Yu, Xu; Cheng, Gong; Zhou, Ming-Da; Zheng, Si-Yang

    2015-04-07

    A simple and robust method for one-step synthesis of monodisperse functional polymeric microspheres was established by generation of reversed microemulsion droplets in aqueous phase inside microfluidic chips and controlled evaporation of the organic solvent. Using this method, water-soluble nanomaterials can be easily encapsulated into biodegradable Poly(D,L-lactic-co-glycolic acid) (PLGA) to form functional microspheres. By controlling the flow rate of microemulsion phase, PLGA polymeric microspheres with narrow size distribution and diameters in the range of ∼50-100 μm were obtained. As a demonstration of the versatility of the approach, high-quality fluorescent CdTe:Zn(2+) quantum dots (QDs) of various emission spectra, superparamagnetic Fe3O4 nanoparticles, and water-soluble carbon nanotubes (CNTs) were used to synthesize fluorescent PLGA@QDs, magnetic PLGA@Fe3O4, and PLGA@CNTs polymeric microspheres, respectively. In order to show specific applications, the PLGA@Fe3O4 were modified with polydopamine (PDA), and then the silver nanoparticles grew on the surfaces of the PLGA@Fe3O4@PDA polymeric microspheres by reducting the Ag(+) to Ag(0). The as-prepared PLGA@Fe3O4@PDA-Ag microspheres showed a highly efficient catalytic reduction of the 4-nitrophenol, a highly toxic substance. The monodisperse uniform functional PLGA polymeric microspheres can potentially be critically important for multiple biomedical applications.

  5. Microwave Synthesized Monodisperse CdS Spheres of Different Size and Color for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Carlos A. Rodríguez-Castañeda

    2015-01-01

    Full Text Available Monodisperse CdS spheres of size of 40 to 140 nm were obtained by microwave heating from basic solutions. It is observed that larger CdS spheres were formed at lower solution pH (8.4–8.8 and smaller ones at higher solution pH (10.8–11.3. The color of CdS products changed with solution pH and reaction temperature; those synthesized at lower pH and temperature were of green-yellow color, whereas those formed at higher pH and temperature were of orange-yellow color. A good photovoltage was observed in CdS:poly(3-hexylthiophene solar cells with spherical CdS particles. This is due to the good dispersion of CdS nanoparticles in P3HT solution that led to a large interface area between the organic and inorganic semiconductors. Higher photocurrent density was obtained in green-yellow CdS particles of lower defect density. The efficient microwave chemistry accelerated the hydrolysis of thiourea in pH lower than 9 and produced monodisperse spherical CdS nanoparticles suitable for solar cell applications.

  6. Preparation of monodisperse magnetic polymer microspheres by swelling and thermolysis technique.

    Science.gov (United States)

    Yang, Chengli; Shao, Qian; He, Jie; Jiang, Biwang

    2010-04-06

    A novel process for the preparation of monodisperse magnetic polymer microspheres by uniquely combining swelling and thermolysis technique was reported. The monodisperse polystyrene microspheres were first prepared by dispersion polymerization and swelled in chloroform. Then, ferric oleate was dispersed in chloroform as a precursor and impregnated into the swoll