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Sample records for monodisperse fe-pt nanoparticles

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

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    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.)

  2. Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles

    Science.gov (United States)

    Seetala, Naidu V.; Harrell, J. W.; Lawson, Jeremy; Nikles, David E.; Williams, John R.; Isaacs-Smith, Tamara

    2005-12-01

    We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 × 1016 ions/cm2 at 43 °C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 °C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 × 107 erg/cc, and thermal stability factor of 130. A much higher 375 °C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.

  3. Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles

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    Seetala, Naidu V. [Department of Physics, Grambling State University, RWE Jones Drive, Carver Hall 81, Grambling, LA 71245 (United States)]. E-mail: naidusv@gram.edu; Harrell, J.W. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Lawson, Jeremy [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Nikles, David E. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Williams, John R. [Department of Physics, Auburn University, Auburn, AL 36849 (United States); Isaacs-Smith, Tamara [Department of Physics, Auburn University, Auburn, AL 36849 (United States)

    2005-12-15

    We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 x 10{sup 16} ions/cm{sup 2} at 43 {sup o}C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 {sup o}C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 x 10{sup 7} erg/cc, and thermal stability factor of 130. A much higher 375 {sup o}C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.

  4. Recent Advances in FePt Nanoparticles for Biomedicine

    Directory of Open Access Journals (Sweden)

    Yujuan Shi

    2015-01-01

    Full Text Available FePt nanoparticles have great potential for biomedical applications due to their superior characteristics, including superparamagnetism, resistance to oxidation, and high chemical stability. The present paper reviews the methods used to prepare FePt nanoparticles, surface modifications, and their applications in the biomedical field, such as biosensing, magnetic resonance imaging (MRI, targeted drug delivery, and therapy.

  5. Characterization of FePt nanoparticles in FePt/C multilayers

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    Barradas, N.P. E-mail: nunoni@itn.mces.pt; Alves, E.; Babonneau, D

    2004-06-01

    The areal density growth of recording media is expected to reach 100 Gbit/in.{sup 2} within a few years. Such high densities require magnetic grain sizes of 10 nm or less, which is close to the superparamagnetic limit of current media. Therefore, in order to retain thermal stability, it is essential to use a magnetic material with high anisotropy energy. Ordered metallic phases such as FePt and CoPt, which have very large magnetocrystalline anisotropy, are regarded as attractive candidates. We have deposited at different temperatures by ion beam sputtering C/(FePt/C){sub x20} multilayers, with nominal thickness t{sub C}=4 nm and t{sub FePt}=1 nm. The FePt consists of nanoparticles embedded in the C matrix. Using Rutherford backscattering at grazing angles of incidence, we determined the stoichiometry of the nanoparticles, the multilayer periodicity and the nanoparticle height. We compare the results with X-ray reflectivity, grazing incidence small-angle X-ray scattering, and transmission electron microscopy results.

  6. Formation of FePt Nanoparticles Having High Coercivity

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    Rutledge, R.D. [Vanderbilt University; MorrisIII, William H [Vanderbilt University; Wellons, M.S. [Vanderbilt University; Gai, Zheng [ORNL; Shen, Jian [ORNL; Bentley, James [ORNL; Wittig, J. E. [Vanderbilt University; Lukehart, C.M. [Vanderbilt University

    2006-01-01

    Ultrasonication of toluene solutions of the heteropolynuclear cluster complex, Pt{sub 3}Fe{sub 3}(CO){sub 15}, in the presence of oleic acid and oleylamine affords surface-capped fcc FePt nanoparticles having an average diameter of ca. 2 nm. Self-assembled arrays of these nanoparticles on oxidized Si wafers undergo a fcc-to-fct phase transition at 775 C to form ferromagnetic FePt nanocrystals ca. 5.8 nm in diameter well dispersed on the Si wafer surface. Room-temperature coercivity measurements of these annealed FePt nanoparticles confirm a high coercivity of ca. 22.3 kOe. Such high coercivity for fct FePt nanoparticles might result from use of a heterpolynuclear complex as a single-source precursor of Fe and Pt neutral atoms or from use of ultrasonication to form fcc FePt nanoparticles under conditions of exceptionally rapid heating. Experiments to determine the critical experimental conditions required to achieve such high room-temperature coercivities in ferromagnetic nanoparticles are underway.

  7. Novel Nanohybrids Derived from the Attachment of FePt Nanoparticles on Carbon Nanotubes

    NARCIS (Netherlands)

    Tsoufis, Theodoros; Tomou, Aphrodite; Gournis, Dimitrios; Douvalis, Alexios P.; Panagiotopoulos, Ioannis; Kooi, Bart; Georgakilas, Vasilios; Arfaoui, Imad; Bakas, Thomas

    2008-01-01

    Multiwalled carbon nanotubes (MWCNTs) were used as nanotemplates for the dispersion and stabilization of FePt nanoparticles (NPs). Pre-formed capped FePt NPs were connected to the MWCNTs external surface via covalent binding through organic linkers. Free FePt NPs and MWCNTs-FePt hybrids were anneale

  8. Large coercivity FePt nanoparticles prepared via a one-step method without post-annealing

    Science.gov (United States)

    Zhang, Xinwei; Xiong, Fang; Jiang, Xiaohong; Hua, Zhenghe; Wang, Chunlei; Yang, Shaoguang

    2016-12-01

    L10 FePt nanoparticles were synthesized by a one-step sol-gel autocombustion method, using nontoxic ferric nitrate, hexachloroplatinic acid, and glycine as starting materials. In contrast to common syntheses, high-temperature post-annealing was not required to form the L10 FePt phase. The entire ignition and combustion process lasted no more than one minute. The L10 FePt phase could form in the presence of the high temperature caused by the exothermic combustion reaction. Adjusting the glycine-to-metal ion molar ratio from 0.5 to 6.0 allowed its effects on the phase transformation and magnetic properties of the products to be investigated. X-ray diffraction indicated that pure phase L10 FePt was obtained at a glycine-to-metal ion molar ratio of 1.5. Transmission electron microscopy indicated that the monodisperse L10 FePt nanoparticles had an average particle size of about 20 nm. The reasons why the as-synthesized L10 FePt nanoparticles were not aggregated and sintered could be attributed to the large amount, a gas is being released and the short duration of heat treatment during this combustion. This finding constituted a significant improvement in the synthesis of L10 FePt nanoparticles. Magnetic measurements showed that the L10 FePt nanoparticles had a coercivity of 15.8 kOe at 300 K, and 23.2 kOe at 5 K. Thus, the L10 FePt nanoparticles had a very large coercivity.

  9. Z-STEM of L1o Ordering in FePt Magnetic Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, J. E. [Vanderbilt University; Bentley, James [ORNL; Lupini, Andrew R [ORNL; Lukehart, C.M. [Vanderbilt University

    2007-01-01

    The L1{sub o} (CuAuI) ordered FePt structure exhibits exceptional magnetic properties with uniaxial-magnetocrystalline anisotropy (K{sub u}) greater than 10{sup 6} ergs/cm3. Chemical synthesis methods can produce monodispersed FePt nanoparticles that have diameters ranging from 3 to 10 nm with a standard deviation of less than 5%. As-synthesized, the FePt nanoparticles are face-centered cubic (FCC) and require annealing at temperatures greater than 550 C for chemical ordering into the L1{sub o} structure. X-ray diffraction (XRD) methods typically characterize the ordering phase transformation by measuring the superlattice peaks. However, since the FePt nanoparticles coarsen during annealing, the larger particles may dominate the XRD data while the smallest particles correspondingly may contribute little to the diffracted intensity. Since recent data suggest that the FePt L1{sub o} ordering transformation is particle-size dependent, the current study employs high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), also known as atomic-number contrast or Z-STEM, methods to investigate the presence of L1{sub o} order in individual FePt nanoparticles.

  10. Enhanced magnetic properties of FePt nanoparticles codeposited on Ag nanoislands

    Science.gov (United States)

    Castaldi, L.; Giannakopoulos, K.; Travlos, A.; Boukos, N.; Niarchos, D.; Boukari, S.; Beaurepaire, E.

    2009-05-01

    Ag nanoislands have been used as nucleation sites for FePt nanoparticles when deposited on SiO2 surfaces by electron beam evaporation. We demonstrate that it is possible to nucleate FePt nanoparticles on predeposited Ag clusters and that this results in a significant improvement of the hard magnetic Ag/FePt nanoparticles' properties. We find that, besides the usual annealing treatments, a simple predeposition of Ag nanoclusters promotes the formation of the FePt L10 phase at larger FePt nominal thicknesses (fFePt). All the nanoparticles studied are ferromagnetic, except for those FePt samples deposited with lower nominal thicknesses (fFePt˜1.8 nm), which are superparamagnetic. The presence of Ag seeds promotes the A1/L10 transition, which results in a remarkable enhancement of the coercivity (Hc) for both the as-deposited and the annealed samples. Maximum Hc of 8.9 and 9.4 kOe are obtained for the Ag/FePt nanoparticles with fFePt˜1.8 and 3.5 nm, respectively. Our results are a strong indication that the nucleation of the FePt nanoparticles on Ag nanoclusters can promote significant magnetic hardening of the FePt nanoparticles by easing the transition from the disordered to the ordered phase.

  11. Explorations on size limit of L10-FePt nanoparticles for practical magnetic storage

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    Tao Huang

    2016-11-01

    Full Text Available With the advance of HAMR technology, the storage potential of L10-FePt nanoparticles with practical considerations are of great significance. We present an L10-FePt nanoparticle model based on atomistic spin model with Langevin thermodynamics to simulate the magnetic behaviors of L10-FePt nanoparticles at Curie temperature and room temperature to explore their practical design margins. Given specific composites, the Curie temperatures of L10-FePt nanoparticles decrease with their volume sizes decrease starting from 8 nm, meaning no more laser power increment needed for smaller L10-FePt nanoparticles. However, L10-FePt nanoparticles get unstable more easily while their volume sizes decrease at room temperature within 10 years. Above all, a reasonable size of L10-FePt nanoparticles for stable information retaining should not be less than 8 nm at a certain aspect ratio.

  12. Exchange-Coupled FePt Nanoparticle Assembly

    Science.gov (United States)

    Zeng, Hao; Vedantam, T.; Dai, Z. R.; Wang, Z. L.; Liu, J. P.; Sun, Shouheng

    2002-03-01

    High-performance permanent magnetic materials for energy-related applications need large energy-products. A permanent magnet with large (BH) products should exhibit both a high saturation magnetization , M_s, and a large coercive field, H_c. L10 ordered FePt has high Ms ( ~ 1100 emu/cm^3) and large magnetocrystalline anisotropy constant Ku (> 5e10^7 erg/cm^3), therefore may be a suitable candidates for permanent magnetic materials. We report synthesis of exchange-coupled FePt nanoparticle assemblies via solution phase deposition and controlled thermal annealing. FePt nanoparticles are prepared by high temperature solution phase decomposition of Fe(CO)_5and reduction of Pt(acac)2 in the presence of oleic acid and oleyl amine. The Fe and Pt composition of the nanoparticles is tuned by adjusting the molar ratio of Fe(CO)5 to Pt(acac)_2. The nanoparticles are easily dispersed into alkane solvent. Depositing particle dispersion on a solid substrate and controlling solvent evaporation yield self-organized magnetic nanoparticle assemblies. Magnetic hysteresis loops, remanence curves, and δM measurements show that annealing for short time under nitrogen yields isolated particle assemblies with random crystalline orientations. Prolonged annealing under reducing atmosphere leads to the evaporation of the organic surfactants, and results in grain agglomeration and inter grain exchange coupling. The degree of coupling can be readily controlled by annealing conditions. Changes in the magnetization reversal behavior have also been observed.This work is supported by DARPA No. DAAD 19-01-1-0546.

  13. Synthesis and characterization of magnetically hard Fe-Pt alloy nanoparticles and nano-islands

    Science.gov (United States)

    Hu, Xiaocao

    In this dissertation, we explored the fabrication of FePt nanoparticles and nano-islands with the face-centered tetragonal (fct, L10) phase prepared by both chemical synthesis routes and physical vapor deposition. Microstructure and magnetic properties characterizations were used to gain a fundamental understanding of the nano-structure formation and atomic ordering behavior and determine the possible applications in the next generation ultra-high density magnetic storage media. FePt nanoparticles prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] have been widely investigated and by tuning the processing procedure monodispersed FePt nanoparticles with good assembly can be obtained. The as-made FePt nanoparticles are usually in the magnetically soft face-centered cubic (fcc) phase. To transformation to the fct phase, post-annealing at above 600°C is needed which, however, introduces undesirable agglomeration and sintering. To address this problem, we used three different fabrication processes which are discussed below. In the first fabrication experiment, the FePt nanoparticles were fabricated by a novel environmental friendly method involving crystalline saline complex hexaaquairon (II) hexachloroplatinate ([Fe(H2O)6]PtCl 6) with a special layered structure. Then the precursor was ball milled with NaCl and annealed at temperatures above 400°C under a reducing atmosphere of forming gas (95% Ar and 5% H2) FePt nanoparticles were obtained after washing away NaCl with deionized water. This method avoids the use of the very poisonous Fe(CO)5 and other organic solvents such as oleylamine and oleic acid. Instead, environmentally friendly NaCl and water were used. The size of FePt nanoparticles was controlled by varying the proportion of precursor and NaCl (from 10mg/20g to 50mg/20g). Particles with size in the range of 6.2--13.2 nm were obtained. All the nanoparticles annealed above 400°C are in the highly ordered fct phase with a coercivity range of 4

  14. Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wellons, M.S. [Vanderbilt University; MorrisIII, William H [Vanderbilt University; Gai, Zheng [ORNL; Shen, Jian [ORNL; Bentley, James [ORNL; Wittig, J. E. [Vanderbilt University; Lukehart, C.M. [Vanderbilt University

    2007-01-01

    A one-step synthesis of L10 FePt nanoparticles ca. 17.0 nm in diameter by reductive decomposition of the single-source precursor, FePt(CO)4dppmBr2, on a water-soluble support (Na2CO3) is demonstrated. Direct conversion of a FePt(CO)4dppmBr2/Na2CO3 composite to a L10 FePt/Na2CO3 nanocomposite occurs at 600 C under getter gas with metal-ion reduction and minimal nanoparticle coalescence. Triturating the resulting nanocomposite with water simultaneously dissolves the sodium carbonate solid support and precipitates the formed fct FePt nanoparticles. As-prepared FePt nanoparticles are ferromagnetic and exhibit coercivities of 14.5 kOe at 300 K and 21.8 kOe at 5 K. When capped by functionalized methoxypoly(ethylene glycol) surfactant molecules, as-prepared, polydisperse ferromagnetic FePt nanoparticles can be dispersed and size-selected by fractional precipitation.

  15. Structural and Magnetic model of self-assembled FePt nanoparticle arrays

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, T

    2004-05-13

    Chemically ordered, self-assembled FePt nanoparticle arrays with high magnetic anisotropy are considered a candidate medium for data storage beyond 1 Tbit/in{sup 2}. We report comprehensive structural and magnetic studies on thin (3 layer) assemblies of polyethylenimine (PEI) and 4 nm Fe{sub 58}Pt{sub 42} nanoparticles using X-ray diffraction, small angle neutron scattering and magnetometry. We show that prior to annealing FePt nanoparticles in the PEI-FePt assembly consist of a metallic, magnetic core surrounded by a weakly magnetic or non-magnetic shell. High temperature annealing creates the desired L1{sub 0} chemical ordering and results in high coercivity FePt nanoparticles. However, we find that the high temperatures necessary to establish full chemical ordering leads to particle sintering and agglomeration. Understanding the magnetic and physical properties of these assemblies allows future research directions to be clarified for nanoparticle arrays as data storage media.

  16. Direct synthesis of water dispersible superparamagnetic TGA capped FePt nanoparticles: One pot, one shot

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Deepak K. [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India); Varadarajan, Komanduri S.; Patel, Anant B. [Center for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007 (India); Deb, Pritam, E-mail: pdeb@tezu.ernet.in [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India)

    2015-04-15

    Thioglycolic acid (TGA) capped hydrophilic fcc-FePt magnetic nanoparticles (MNPs) were directly synthesized by a facile one pot polyol method. Thioglycolic acid (TGA) was used to functionalize the nanoparticles by incorporating thiol group onto the surface. It helped in the preparation of highly stable dispersions of nanoparticles with spherical morphology. A possible formation mechanism for these FePt MNPs, depending on the role of TGA, was proposed. The as-prepared FePt MNPs possessed a face centered cubic structure with an average size of 6 ± 1 nm and superparamagnetic property at room temperature. MRI study showed that these MNPs exhibited a transverse relaxivity of ∼600 mg{sup −1} ml s{sup −1}, superior to that of reported iron oxide nanoparticles. - Highlights: • One pot synthesis of TGA capped hydrophilic FePt superparamagnetic nanoparticles. • Role of TGA molecules in the formation of FePt nanoparticles. • EDX reveals the equiatomic ratio of Fe and Pt atoms in FePt nanoparticles. • The HR-TEM exhibits spherical nanoparticles with a narrow size distribution. • High transverse relaxivity suggesting as potential MRI contrast agent.

  17. Biomimetic Synthesis of FePt Nanoparticles on Multi-Walled Carbon Nanotubes for Functional Nanomaterials

    Science.gov (United States)

    Wang, Li; Wang, Jiku; Li, Zhuang

    2013-02-01

    We present a facile green biomimetic synthesis of FePt nanoparticles (NPs) on the sidewalls of multi-walled carbon nanotubes (CNTs). A core-shell globular protein, ferritin (Fr), was bound onto Z-glycine N-succinimidyl ester (Z-Gly-OSu) modified CNTs and served as precursor to create FePt NPs at the core part of Fr. Biomimetic synthesis of FePt NPs was carried out by chemical reducing of Fe2+ and PtCl_{6}^{2-} ions that transferred into the core part of Fr molecules. The created one-dimensional CNT-FePt nanohybrids were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized CNT-FePt nanohybrids show multi-properties of high water-solubility, ferromagnetism, and electrocatalytic activity.

  18. Atomistic computer simulations of FePt nanoparticles. Thermodynamic and kinetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M.

    2007-12-20

    In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion. (orig.)

  19. Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

    Directory of Open Access Journals (Sweden)

    Gao Y

    2009-01-01

    Full Text Available Abstract FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO2 overlayer. A nearly complete transformation of L10 FePt was achieved for samples annealed at temperatures above 700 °C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM and dc-demagnetization (DCD remanence curves and Kelly–Henkel plots (ΔM measurement. The ΔM measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.

  20. Pure magnetic hard fct FePt nanoparticles: Chemical synthesis, structural and magnetic properties correlations

    Energy Technology Data Exchange (ETDEWEB)

    Suber, L., E-mail: lorenza.suber@ism.cnr.it [ISM-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Marchegiani, G. [ISM-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Olivetti, E.S.; Celegato, F.; Coïsson, M.; Tiberto, P. [INRIM, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy); Allia, P. [DISAT Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Barrera, G. [Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 7, 10125 Torino (Italy); Pilloni, L. [UTTMAT-CHI, Via Anguillarese 10, 00123 S. Maria di Galeria, Roma (Italy); Barba, L. [IC-CNR, Area Science Park, SS 14 Km 163.5 Basovizza, 34149 Trieste (Italy); Padella, F. [UTTMAT-CHI, Via Anguillarese 10, 00123 S. Maria di Galeria, Roma (Italy); Cossari, P. [IGAG-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Chiolerio, A. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy)

    2014-03-01

    FePt nanoparticles, containing a near-equal atomic percentage of Fe and Pt, with a face centered tetragonal structure (fct), are challenging for potential applications in high performance permanent magnets and high density data storage. In this study, we report on the chemical synthesis, carried out both solvothermally and hydrothermally in autoclave reacting iron (III) acetylacetonate and platinum (II) acetylacetonate with tri- or tetra-ethylene glycol, these employed as solvents, reducers and particle surface protecting agents as well. In both methods, a subsequent thermal treatment at high temperatures is necessary to transform the magnetic soft face centered cubic (fcc) phase to the hard fct one. Organic low-weight molecules, generally used to protect the nanoparticle surface and avoid particle aggregation, are decomposed by the thermal treatment resulting in particle aggregation and coalescence phenomena; on the contrary, in this case, a polymer matrix is formed as particle protecting agent and, by thermally treating the hydrothermally prepared nanoparticles up to 750 °C for 1 h, the pure magnetic hard fct phase is obtained while preserving the nanostructure. A detailed study is carried out on FePt nanoparticle structure (fcc and fct phases) and correlated to the magnetic properties of the system. - Highlights: • fct FePt nanoparticles for hard magnetic nanotechnology applications. • Influence of synthesis parameters on the precursor fcc FePt nanoparticle structure. • Easy hydrothermal method for preparing pure fct FePt nanoparticles. • Monitoring the role of temperature and time on the FePt fcc–fct phase transformation. • Correlation between FePt nanoparticle structural and magnetic properties.

  1. (001) textured FePt thin films on spherical SiO{sub 2} nanoparticle template

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph; Schubert, Christian; Teichgraeber, Andreas; Hietschold, Michael; Albrecht, Manfred [Institute of Physics, TU Chemnitz, Chemnitz (Germany); Romer-Urban, Sara [Nanoscale Materials Science, Empa, Duebendorf (Switzerland); Maret, Mireille [Laboratoire de Thermodynamique et Physico-Chimie Metallurgiques, ENSEEG, Saint Martin d' Heres (France); Makarov, Denys [Department of Physics, University of Konstanz, Konstanz (Germany)

    2009-07-01

    Due to its high magnetocrystalline anisotropy and excellent corrosion resistance, FePt is considered one of the most promising candidates for future magnetic data storage devices. In this study, densely-packed arrays of SiO{sub 2} nanoparticles have been used as a template to create regular FePt nanostructures suitable for application as patterned media. The sputter deposited FePt film displays a chemically disordered fcc phase. Postannealing in a commercial RTA setup yields both a high ordering parameter and the desired (001) texture as shown by XRD and TEM. The heating rate, heating time and heating temperature have been optimized on planar SiO{sub 2} substrates, obtaining perpendicular magnetic anisotropy and coercivities of up to 2 T. Furthermore, the FePt films exhibit a strong dewetting behavior on both planar substrates and spherical nanoparticles. By tuning the thickness of the FePt layer, the characteristic length scales of the dewetting process can be controlled. This was used to create isolated FePt nanostructures on SiO{sub 2} particle arrays with periodicities down to 50 nm.

  2. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    OpenAIRE

    Guus Rijnders; Jurriaan Huskens; van der Wiel, Wilfred G.; Blank, Dave H. A.; Reinhoudt, David N.; Sachin Kinge; Tian Gang; Oktay Yildirim

    2010-01-01

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assem...

  3. Monolayer-directed assembly and magnetic properties of FePt nanoparticles on patterned aluminum oxide.

    Science.gov (United States)

    Yildirim, Oktay; Gang, Tian; Kinge, Sachin; Reinhoudt, David N; Blank, Dave H; van der Wiel, Wilfred G; Rijnders, Guus; Huskens, Jurriaan

    2010-03-19

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al(2)O(3) substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al(2)O(3), which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al(2)O(3) surface and controlling the immersion time of the modified Al(2)O(3) substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N(2)/4%H(2)) led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices.

  4. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    Directory of Open Access Journals (Sweden)

    Guus Rijnders

    2010-03-01

    Full Text Available FePt nanoparticles (NPs were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(onates were used as an adsorbate to form self-assembled monolayers (SAMs on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP or phosphonoundecanoic acid (PNDA SAMs or with poly(ethyleneimine (PEI as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2 led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices.

  5. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    NARCIS (Netherlands)

    Yildirim, Oktay; Gang, Tian; Kinge, Sachin; Reinhoudt, David N.; Blank, Dave H.; Wiel, van der Wilfred G.; Rijnders, Guus; Huskens, Jurriaan

    2010-01-01

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs ont

  6. Tailoring nucleation and growth conditions for narrow compositional distributions in colloidal synthesized FePt nanoparticles

    Science.gov (United States)

    Srivastava, Chandan; Nikles, David E.; Thompson, Gregory B.

    2008-11-01

    To eliminate compositional and size variabilities between individual binary nanoparticles, it is essential to control the mechanistic steps involved in nanoparticle synthesis. A common method for synthesizing FePt nanoparticles involves the simultaneous decomposition and reduction in iron and platinum precursors, respectively. This simultaneous nucleation and growth method yields wide composition and size distributions. This paper describes and experimentally validates a methodology needed to tighten composition and size distributions for this process. By engineering the surfactant chemistry with tertiary phosphines to tightly bind the iron atoms in the iron precursor, uniform platinum rich seeds form during the initial stages of the synthesis. A thermodynamically preferred heterogeneous nucleation of iron atoms into these uniform platinum seeds in the subsequent stages produces a final dispersion with uniform particle-to-particle compositions. The paper addresses the understanding for optimizing the nucleation and growth sequences for compositional control in FePt nanoparticles.

  7. Effect of Cu doping on the structure and phase transition of directly synthesized FePt nanoparticles

    Science.gov (United States)

    Wang, Hanbin; Li, Yang; Chen, Xu; Shu, Dan; Liu, Xiang; Wang, Xina; Zhang, Jun; Wang, Hao; Wang, Yi; Ruterana, Pierre

    2017-01-01

    In this work, ternary Cu doped FePt nanoparticles were prepared in hexadecylamine at 320 °C by choosing FeCl2 as the Fe source. The experimental results showed that without Cu doping the as-prepared FePt nanoparticles possessed fcc structure and gradually exhibited typical fct diffraction peaks after increasing the Cu doping concentration. TEM images showed that the FePt nanoparticles had larger size and wider size distribution after introducing Cu additive. Magnetic property measurement showed that a coercivity of 4800 Oe was obtained when the composition of the ternary nanoparticles reached Fe35Pt45Cu20, in which the content of Fe+Cu was higher than Pt. The research indicates that Cu doping promotes the phase transition of FePt nanoparticles at temperature as low as 320 °C.

  8. The origin of enhanced L1 0 chemical ordering in Ag-doped FePt nanoparticles

    Science.gov (United States)

    Sung, Yun-Mo; Lee, Myung-Ki; Kim, Ki-Eun; Kim, Tae Geun

    2007-08-01

    FePt and Ag-doped FePt nanoparticles were synthesized by the thermolysis and polyol reductions. The A1-to-L1 0 transformation of the nanoparticles was investigated by differential scanning calorimetry (DSC) at different scanning rates, and the DSC endothermic peak shifts were monitored and used for the Kissinger analyses. The activation energy for the phase transformation was determined to be ˜251 and ˜219 kJ/mol for the pure and doped FePt nanoparticles, respectively. The decrease in the activation energy is the evidence of increased number of vacancies, which turned out to be the origin for the reduced L1 0 chemical ordering temperature in doped FePt.

  9. Controlling core/shell Au/FePt nanoparticle electrocatalysis via changing the core size and shell thickness.

    Science.gov (United States)

    Sun, Xiaolian; Li, Dongguo; Guo, Shaojun; Zhu, Wenlei; Sun, Shouheng

    2016-02-01

    Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm(-2) at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions.

  10. Array Formation and Size Effects in Chemically Synthesized FePt Nanoparticles

    Science.gov (United States)

    Colak, Levent; Hadjipanayis, George

    2007-03-01

    FePt nanoparticles with controlled size have been synthesized following a route given by Shukla et. al.[1] The effect of particle size on the magnetic properties has been investigated for nanoparticles with sizes of 3.0 and 6.0 nm. With the addition of the surfactants at a later stage of preparation, a long range self-assembled array of particles was obtained as evidenced by transmission electron microscope (TEM). By comparing bright field images of the samples with projected potential image simulations^ [2], the packing structures and stacking sequences of the arrays were identified. Well-aligned mono and multi layered hcp to bcc nanostructures are formed from 5 nm FePt nanoparticles. Subjecting the NP's to thermal processing at 800 ^oC results in a transformation of the nanoparticles from the disordered fcc phase to the ordered L10 phase. HRTEM studies have been carried out to investigate the development of particle morphology and microstructure during the synthesis and subsequent annealing of nanoparticles. 1. N. Shukla, C. Liu, A. G. Roy, Matt. Lett. 60, 2006, 995-998. 2. S. Yamamuro, D. F. Farrell and S. A. Majetich, Phys. Rev. B 65, 224431 (2002).

  11. Influences of surface coatings and components of FePt nanoparticles on the suppression of glioma cell proliferation

    Directory of Open Access Journals (Sweden)

    Sun H

    2012-07-01

    Full Text Available Haiming Sun,1,* Xiaohui Chen,2,* Dan Chen,1 Mingyan Dong,1 Xinning Fu,1 Qian Li,1 Xi Liu,1 Qingzhi Wu,1 Tong Qiu,1 Tao Wan,1 Shipu Li11State Key Laboratory of Advanced Technology for Materials Synthesis and Processing and Biomedical Materials and Engineering Center, Wuhan University of Technology, Wuhan, China; 2Department of Prosthetics, School of Stomatology, Wuhan University, Wuhan, China*Both authors contributed equally to this workAbstract: Malignant gliomas are primary brain tumors with high rates of morbidity and mortality; they are the fourth most common cause of cancer death. Novel diagnostic and therapeutic techniques based on nanomaterials provide promising options in the treatment of malignant gliomas. In order to evaluate the potential of FePt nanoparticles (NPs for malignant glioma therapy, FePt NPs with different surface coatings and components were tunably synthesized using oleic acid/oleylamine (OA/OA and cysteines (Cys as the capping agents, respectively. The samples were characterized using X-ray diffraction, transmission electron microscopy (TEM, X-ray photon spectroscopy, Fourier transform infrared spectroscopy, atomic absorption spectrum, and zeta potential. The influence of the surface coatings and components of the FePt NPs on the proliferation of glioma cells was assessed through MTT assay and TEM observation using three typical glioma cell lines (glioma U251 cells, astrocytoma U87 cells, and neuroglioma H4 cells as in vitro models. The results showed that the proliferation of glioma cells was significantly suppressed by lipophilic FePt-OA/OA NPs in a time- and/or dose-dependent manner, while no or low cytotoxic effects were detected in the case of hydrophilic FePt-Cys NPs. The IC50 value of FePt-OA/OA NPs on the three glioma cell lines was approximately 5–10 µg mL-1 after 24 hours’ incubation. Although the cellular uptake of FePt NPs was confirmed regardless of the surface coatings and components of the FePt NPs

  12. Structural and magnetic properties of FePt nanoparticles from the gas phase; Strukturelle und magnetische Eigenschaften von FePt-Nanopartikeln aus der Gasphase

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.

    2007-09-21

    In this work, we present the structural and magnetic characterization of FePt nanoparticles. The nanoparticles with mean size of about 6 nm were prepared by sputtering in the gas and subsequent inert gas condensation. The particles are annealed in the furnace during their flight prior to deposition on a substrate. The aim of this work is to prepare magnetically hard FePt nanoparticles in the L1{sub 0}-ordered phase. The structure of the particles was investigated by high-resolution transmission electron microscopy, and the investigations were supported by contrast simulations. The morphology of the particles varies with the sputter-gas pressure and with the annealing temperature. At a pressure of 0.5 mbar, the FePt-nanoparticles are multiply-twinned with an icosahedral structure and exhibit no formation of the L1{sub 0}-ordered phase. At a higher pressure of 1 mbar and an annealing temperature of 1000 C, the particles are partially single-crystalline. About 36 % of the particles are found to be in the L1{sub 0}-ordered state as was estimated by statistical counting supported by simulations. In order to activate the volume diffusion in the particles and to stabilize the formation of the L1{sub 0}-ordered state, the addition of nitrogen was used during the sputtering phase. In this phase, atomic nitrogen is incorporated interstitially into the structure of the primary particles. After annealing nitrogen effuses out of the particles and, thereby, increases the volume diffusion of the Fe and Pt atoms. The incorporation of nitrogen atoms during nucleation and their effusion at an annealing temperature of 1000 C was verified by electron energy loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS). Structural investigations on particles prepared in the presence of nitrogen shows that most of the particles are single-crystalline and about 70 % of them are L1{sub 0}-ordered. Detailed structural analysis of the nanoparticles was done by the exit wave

  13. Comparing and Optimizing Nitrate Adsorption from Aqueous Solution Using Fe/Pt Bimetallic Nanoparticles and Anion Exchange Resins

    Directory of Open Access Journals (Sweden)

    Muhammad Daud

    2015-01-01

    Full Text Available This research work was carried out for the removal of nitrate from raw water for a drinking water supply. Nitrate is a widespread ground water contaminant. Methodology employed in this study included adsorption on metal based nanoparticles and ion exchange using anionic resins. Fe/Pt bimetallic nanoparticles were prepared in the laboratory, by the reduction of their respective salts using sodium borohydride. Scanning electron microscope, X-ray diffraction, energy dispersive spectrometry, and X-ray florescence techniques were utilized for characterization of bimetallic Fe/Pt nanoparticles. Optimum dose, pH, temperature, and contact time were determined for NO3- removal through batch tests, both for metal based nanoparticles and anionic exchange resin. Adsorption data fitted well the Langmuir isotherm and conformed to the pseudofirst-order kinetic model. Results indicated 97% reduction in nitrate by 0.25 mg/L of Fe/Pt nanoparticles at pH 7 and 83% reduction in nitrate was observed using 0.50 mg/L anionic exchange resins at pH 4 and contact time of one hour. Overall, Fe/Pt bimetallic nanoparticles demonstrated greater NO3- removal efficiency due to the small particle size, extremely large surface area (627 m2/g, and high adsorption capacity.

  14. Preparation of Ultrafine Fe-Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis.

    Science.gov (United States)

    Watanabe, Masato; Takamura, Hitoshi; Sugai, Hiroshi

    2009-03-10

    We prepared ultrafine Fe-Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe-Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5-3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe-Pt nanoparticles and UV-visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe-Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.

  15. In situ investigation of ordering phase transformations in FePt magnetic nanoparticles.

    Science.gov (United States)

    Wittig, James E; Bentley, James; Allard, Lawrence F

    2016-12-11

    In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L10 ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments. However, during continuous high-magnification imaging the electron beam influenced the kinetics of the transformation so annealing had to be performed with the electron beam blanked. At 500°C where the reaction rate was relatively slow, observation of the transformation mechanisms using this sequential imaging protocol revealed that ordering proceeded from (002) surface facets but was incomplete and multiple-domain particles were formed that contained anti-phase domain boundaries and anti-site defects. At 600 and 700°C, the limitations of sequential imaging were revealed as a consequence of increased transformation kinetics. Annealing for only 5min at 700°C produced complete single-domain L10 order; such single-domain particles were more spherical in shape with (002) facets. The in situ experiments also provided information concerning nanoparticle sintering, coalescence, and consolidation. Although there was resistance to complete sintering due to the crystallography of L10 order, the driving force from the large surface-area-to-volume ratio resulted in considerable nanoparticle coalescence, which would render such FePt nanoparticles unsuitable for use as magnetic recording media. Comparison of the in situ data acquired using the protocol described above with parallel ex situ annealing experiments showed that identical behavior resulted in all cases.

  16. Defect Kinetics and Magnetic Studies of Ion-Irradiated FePt Nanoparticles

    Science.gov (United States)

    Seetala, Naidu V.

    2009-03-01

    We have used 300 keV Al+-irradiation and 1 MeV proton-irradiation to obtain vacancy-migration enhanced phase transformation of FePt nanoparticles at lower temperatures (˜200° C). SRIM-2006 computer code was used to estimate the irradiation parameters and the defect concentrations. Low temperature annealing showed promising results, but further annealing at higher temperatures gave detrimental effects due to lattice strain produced by larger defect clusters. These effects are more prominent in proton-irradiation and the effects of vacancy clusters seem to remain stronger even at higher temperatures. The magnetization results indicate dissociation of vacancy clusters above 600° C. The magnetization studies of 700° C and 800° C annealed particles aged for one year at room temperature showed defect strain release over time.

  17. Size effect on order-disorder transition kinetics of FePt nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuaidi [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Qi, Weihong, E-mail: qiwh216@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Key Laboratory of Non-ferrous Materials Science and Engineering, Ministry of Education, Changsha 410083 (China); Huang, Baiyun [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China)

    2014-01-28

    The kinetics of order-disorder transition of FePt nanoparticles during high temperature annealing is theoretically investigated. A model is developed to address the influence of large surface to volume ratio of nanoparticles on both the thermodynamic and kinetic aspect of the ordering process; specifically, the nucleation and growth of L1{sub 0} ordered domain within disordered nanoparticles. The size- and shape-dependence of transition kinetics are quantitatively addressed by a revised Johnson-Mehl-Avrami equation that included corrections for deviations caused by the domination of surface nucleation in nanoscale systems and the non-negligible size of the ordered nuclei. Calculation results based on the model suggested that smaller nanoparticles are kinetically more active but thermodynamically less transformable. The major obstacle in obtaining completely ordered nanoparticles is the elimination of antiphase boundaries. The results also quantitatively confirmed the existence of a size-limit in ordering, beyond which, inducing order-disorder transitions through annealing is impossible. A good agreement is observed between theory, experiment, and computer simulation results.

  18. “Single-” and “multi-core” FePt nanoparticles: from controlled synthesis via zwitterionic and silica bio-functionalization to MRI applications

    Energy Technology Data Exchange (ETDEWEB)

    Kostevšek, Nina, E-mail: nina.kostevsek@ijs.si; Šturm, Sašo [Jožef Stefan Institute, Department for Nanostructured Materials (Slovenia); Serša, Igor; Sepe, Ana [Jožef Stefan Institute, Department for Condensed Matter Physics (Slovenia); Bloemen, Maarten; Verbiest, Thierry [KU Leuven, Department of Chemistry (Belgium); Kobe, Spomenka; Žužek Rožman, Kristina [Jožef Stefan Institute, Department for Nanostructured Materials (Slovenia)

    2015-12-15

    The value of the magnetization has a strong influence on the performance of nanoparticles that act as the contrast agent material for MRI. In this article, we describe processing routes for the synthesis of FePt nanoparticles of different sizes, which, as a result, exhibit different magnetization values. “Single-core” FePt nanoparticles of different sizes (3–15 nm) were prepared via one-step or two-step synthesis, with the latter exhibiting twice the magnetization (m{sub (1.5T)} = 14.5 emu/g) of the nanoparticles formed via the one-step synthesis (m{sub (1.5T)} < 8 emu/g). Furthermore, we propose the synthesis of “multi-core” FePt nanoparticles by changing the ratio between the two surfactants (oleylamine and oleic acid). The step from smaller “single-core” FePt nanoparticles towards the larger, “multi-core” FePt nanoparticles (>20 nm) leads to an increase in the magnetization m{sub (1.5T)} from 8 to 19.5 emu/g, without exceeding the superparamagnetic limit. Stable water suspensions were prepared using two different approaches: (a) functionalization with a biocompatible, zwitterionic, catechol ligand, which was used on the FePt nanoparticles for the first time, and (b) coating with SiO{sub 2} shells of various thicknesses. These FePt-based nanostructures, the catechol- and SiO{sub 2}-coated “single-core” and “multi-core” FePt nanoparticles, were investigated in terms of the relaxation rates. The higher r{sub 2} values obtained for the “multi-core” FePt nanoparticles compared to that for the “single-core” ones indicate the superiority of the “multi-core” FePt nanoparticles as T{sub 2} contrast agents. Furthermore, it was shown that the SiO{sub 2} coating reduces the r{sub 1} and r{sub 2} relaxation values for both the “single-core” and “multi-core” FePt nanoparticles. The high r{sub 2}/r{sub 1} ratios obtained in our study put FePt nanoparticles near the top of the list of candidate materials for use in MRI

  19. Hexagonal-to-cubic phase transformation in composite thin films induced by FePt nanoparticles located at PS/PEO interfaces.

    Science.gov (United States)

    Aissou, Karim; Fleury, Guillaume; Pecastaings, Gilles; Alnasser, Thomas; Mornet, Stéphane; Goglio, Graziella; Hadziioannou, Georges

    2011-12-06

    The organization process of asymmetric poly(styrene-block-ethylene oxide) (PS-b-PEO) copolymer thin films blended with FePt nanoparticles is studied. In a first step, it is shown that FePt nanoparticles stabilized by oleic acid ligands are distributed within the PS matrix phase, whereas the same particles partially covered with short dopamine-terminated-methoxy poly(ethylene oxide) (mPEO-Dopa) are located at PS/PEO interfaces. The swelling of PS domains, induced by FePt_oleic acid nanoparticles during the solvent annealing process, results in formation of a disordered microstructure in comparison to the well-organized hexagonally close-packed (HCP) cylinder phase formed in the neat PS-b-PEO copolymer. The evolution of the microstructure of PS-b-PEO/FePt_mPEO-Dopa composite has been investigated for different solvent annealing treatments. Under high-humidity conditions during the vapor annealing process, the addition of FePt nanoparticles results in formation of spheres in the film split into terraces. The upper and lower terraces are occupied by spheres organized in an unusual square and HCP phases, respectively. Under low-humidity conditions, undulated PEO cylinders oriented parallel to substrate are formed in the presence of FePt nanoparticles. In this case, we observe that most of the nanoparticles accumulate within the core of topological defects, which induces a low nanoparticle concentration at the PS/PEO interfaces and so stabilizes an intermediate undulated cylinder phase.

  20. Sulfonate group-modified FePtCu nanoparticles as a selective probe for LDI-MS analysis of oligopeptides from a peptide mixture and human serum proteins.

    Science.gov (United States)

    Kawasaki, Hideya; Akira, Tarui; Watanabe, Takehiro; Nozaki, Kazuyoshi; Yonezawa, Tetsu; Arakawa, Ryuichi

    2009-11-01

    Bare FePtCu nanoparticles (NPs) are first prepared for laser desorption/ionization mass spectroscopy (LDI-MS) analysis as affinity probes to selectively trap oppositely charged analytes from a sample solution. Our present results demonstrate bare FePtCu NPs to be a potentially useful matrix for surface-assisted laser desorption/ionization mass spectroscopy (SALDI-MS), for the analysis of small proteins and peptides. The upper detectable mass range of peptides was approximately 5 kDa, and the detection limit for peptides approximately 5 fmol. Sulfonate group-modified FePtCu nanoparticles (FePtCu-SO(3)(-) NPs), with ionization being independent of the solution pH, can interact with a positively charged analyte, and the analyte-bound NPs can be separated from the reaction supernatant by centrifugation or an external magnetic field. An oligopeptide, Gly-Gly-Tyr-Arg (GGYR) from an oligopeptide mixture containing Asp-Asp-Asp-Asp (DDDD), Gly-Gly-Gly-Gly (GGGG) and GGYR, was detected using SALDI-MS with FePtCu-SO(3)(-) NPs employing electrostatic interaction. Furthermore, FePtCu-SO(3)(-) NPs can detect lysozyme (Lyz) in human serum through the electrostatic attraction between positively charged Lyz and FePtCu-SO(3)(-) NPs at pH 8, while detection of negatively charged albumin in human serum is not possible.

  1. FePt nanoparticle formation with lower phase transition temperature by single shot plasma focus ion irradiation

    Science.gov (United States)

    Lin, J. J.; Roshan, M. V.; Pan, Z. Y.; Verma, R.; Lee, P.; Springham, S. V.; Tan, T. L.; Rawat, R. S.

    2008-07-01

    Uniform FePt nanoparticles were synthesized through nanostructuring of pulsed laser deposited FePt thin films by single shot H+ ion irradiation using a plasma focus device. The annealing temperature required for phase transition from low Ku face-centred cubic to high Ku face-centred tetragonal, for ion irradiated samples, is simultaneously lowered down to 400 °C. The energetic H+ ion irradiation significantly reduces the activation energy for atomic ordering by increasing the number of vacancies. The advantage of using a plasma focus device is that it can achieve nanostructuring in much shorter time, in single shot ion exposure with pulse duration of typically about a few hundreds of nanoseconds, as compared with much longer duration required by continuous ion sources.

  2. 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.

  3. Synthesis and characterization of FePt nanoparticles by high energy ball milling with and without surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Velasco, V., E-mail: vvjimeno@fis.ucm.es [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Martinez, A.; Recio, J. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Hernando, A.; Crespo, P. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Dpto. de Fisica de Materiales, UCM, 28040 Madrid (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Fe and Pt powders in the presence of surfactants don't alloyed by HEBM technique. Black-Right-Pointing-Pointer FePt alloys obtained by dry milling exhibit particle sizes of around 10 {mu}m. Black-Right-Pointing-Pointer FePt alloys obtained by dry milling exhibit soft magnetic behavior. Black-Right-Pointing-Pointer A thermal treatment induces a phase transformation from FCC to FCT. - Abstract: FePt nanoparticles were prepared by high energy ball milling (HEBM) in two different ways. In the first one, elemental powders were mixed and milled whereas in the second one the milling was performed in the presence of oleyl amine and oleic acid as surfactants and hexane as a solvent. X-ray diffraction shows that when the milling is performed in dry conditions, Fe and Pt are alloyed after 5 h, whereas in the wet milling procedure alloying does not take place. In the first case, the diffraction pattern corresponds to the disordered FCC phase. This behavior is also corroborated by the evolution of the magnetic characteristics. In the case of the alloy obtained in dry conditions, the powder was heat treated in order to induce the transformation to the ordered phase. Coercivities of 2.5 kOe are obtained after 650 Degree-Sign C for 2 h.

  4. Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shu; Lee, Stephen L. [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); André, Pascal, E-mail: pjpandre@riken.jp [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); RIKEN, Wako 351-0198 (Japan); Department of Physics, CNRS-Ewha International Research Center (CERC), Ewha W. University, Seoul 120-750 (Korea, Republic of)

    2016-11-01

    Magnetic nanoparticles (MnPs) are relevant to a wide range of applications including high density information storage and magnetic resonance imaging to name but a few. Among the materials available to prepare MnPs, FePt is attracting growing attention. However, to harvest the strongest magnetic properties of FePt MnPs, a thermal annealing is often required to convert face-centered cubic as synthesized nPs into its tetragonal phase. Rarely addressed are the potential side effects of such treatments on the magnetic properties. In this study, we focus on the impact of silica shells often used in strategies aiming at overcoming MnP coalescence during the thermal annealing. While we show that this shell does prevent sintering, and that fcc-to-fct conversion does occur, we also reveal the formation of silicide, which can prevent the stronger magnetic properties of fct-FePt MnPs from being fully realised. This report therefore sheds lights on poorly investigated and understood interfacial phenomena occurring during the thermal annealing of MnPs and, by doing so, also highlights the benefits of developing new strategies to avoid silicide formation.

  5. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties

    Science.gov (United States)

    D'Addato, S.; Grillo, V.; di Bona, A.; Luches, P.; Frabboni, S.; Valeri, S.; Lupo, P.; Casoli, F.; Albertini, F.

    2013-12-01

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a ‘wasp-waist’ shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  6. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties.

    Science.gov (United States)

    D'Addato, S; Grillo, V; di Bona, A; Luches, P; Frabboni, S; Valeri, S; Lupo, P; Casoli, F; Albertini, F

    2013-12-13

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter (d) = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a 'wasp-waist' shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  7. Magnetic heating properties and neutron activation of tungsten-oxide coated biocompatible FePt core-shell nanoparticles.

    Science.gov (United States)

    Seemann, K M; Luysberg, M; Révay, Z; Kudejova, P; Sanz, B; Cassinelli, N; Loidl, A; Ilicic, K; Multhoff, G; Schmid, T E

    2015-01-10

    Magnetic nanoparticles are highly desirable for biomedical research and treatment of cancer especially when combined with hyperthermia. The efficacy of nanoparticle-based therapies could be improved by generating radioactive nanoparticles with a convenient decay time and which simultaneously have the capability to be used for locally confined heating. The core-shell morphology of such novel nanoparticles presented in this work involves a polysilico-tungstate molecule of the polyoxometalate family as a precursor coating material, which transforms into an amorphous tungsten oxide coating upon annealing of the FePt core-shell nanoparticles. The content of tungsten atoms in the nanoparticle shell is neutron activated using cold neutrons at the Heinz Maier-Leibnitz (FRMII) neutron facility and thereby transformed into the radioisotope W-187. The sizeable natural abundance of 28% for the W-186 precursor isotope, a radiopharmaceutically advantageous gamma-beta ratio of γβ≈30% and a range of approximately 1mm in biological tissue for the 1.3MeV β-radiation are promising features of the nanoparticles' potential for cancer therapy. Moreover, a high temperature annealing treatment enhances the magnetic moment of nanoparticles in such a way that a magnetic heating effect of several degrees Celsius in liquid suspension - a prerequisite for hyperthermia treatment of cancer - was observed. A rise in temperature of approximately 3°C in aqueous suspension is shown for a moderate nanoparticle concentration of 0.5mg/ml after 15min in an 831kHz high-frequency alternating magnetic field of 250Gauss field strength (25mT). The biocompatibility based on a low cytotoxicity in the non-neutron-activated state in combination with the hydrophilic nature of the tungsten oxide shell makes the coated magnetic FePt nanoparticles ideal candidates for advanced radiopharmaceutical applications.

  8. Water-soluble L-cysteine-coated FePt nanoparticles as dual MRI/CT imaging contrast agent for glioma.

    Science.gov (United States)

    Liang, Shuyan; Zhou, Qing; Wang, Min; Zhu, Yanhong; Wu, Qingzhi; Yang, Xiangliang

    2015-01-01

    Nanoparticles (NPs) are advantageous for the delivery of diagnosis agents to brain tumors. In this study, we attempted to develop an L-cysteine coated FePt (FePt-Cys) NP as MRI/CT imaging contrast agent for the diagnosis of malignant gliomas. FePt-Cys NPs were synthesized through a co-reduction route, which was characterized by transmission electron microscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and dynamic light scattering. The MRI and CT imaging ability of FePt-Cys NPs was evaluated using different gliomas cells (C6, SGH44, U251) as the model. Furthermore, the biocompatibility of the as-synthesized FePt-Cys NPs was evaluated using three different cell lines (ECV304, L929, and HEK293) as the model. The results showed that FePt-Cys NPs displayed excellent biocompatibility and good MRI/CT imaging ability, thereby indicating promising potential as a dual MRI/CT contrast agent for the diagnosis of brain malignant gliomas.

  9. Direct synthesis of L1{sub 0} FePt nanoparticles within carbon nanotubes by wet chemical procedure

    Energy Technology Data Exchange (ETDEWEB)

    Capobianchi, A; Laureti, S; Fiorani, D [Consiglio Nazionale delle Ricerche (CNR), Istituto di Struttura della Materia (ISM), Rome (Italy); Foglia, S [Consiglio Nazionale delle Ricerche (CNR), Istituto di Fotonica e Nanotecnologie, Rome (Italy); Palange, E, E-mail: aldo.capobianchi@ism.cnr.i [Universita degli Studi dell' Aquila, Dipartimento di Ingegneria Elettrica e dell' Informazione, L' Aquila (Italy)

    2010-12-01

    This paper reports on the low temperature synthesis of L1{sub 0} iron-platinum (FePt) particles within multiwall carbon nanotubes using a novel wet chemical method that allows the filling of the nanotube cavity keeping clean its external wall. In the proposed procedure, nanotubes are filled with a precursor salt of hexaaquairon(II) hexachloroplatinate, ([Fe(H{sub 2}O){sub 6}][PtCl{sub 6}]) and nanoparticles of the magnetically hard phase are directly obtained by heating at 400 {sup 0}C in a reductive atmosphere. The advantage of such a precursor, allowing one to obtain at low temperature the L1{sub 0} phase without passing through the soft fcc phase, is due to its structure, where the Fe and Pt atoms are arranged in alternating planes, as in the fct FePt structure. Morphological, structural and magnetic properties of the filled nanotubes have been investigated by transmission electron microscopy, x-ray diffraction and magnetization measurements. The results show the coexistence of nanoparticles in the superparamagnetic and blocked state, depending on the temperature, due to the particle size distribution.

  10. Water-soluble l-cysteine-coated FePt nanoparticles as dual MRI/CT imaging contrast agent for glioma

    Directory of Open Access Journals (Sweden)

    Liang SY

    2015-03-01

    Full Text Available Shuyan Liang,1 Qing Zhou,1 Min Wang,2,3 Yanhong Zhu,1 Qingzhi Wu,2,3 Xiangliang Yang1 1College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, People’s Republic of China; 2State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, People’s Republic of China; 3Biomedical Material and Engineering Center of Hubei Province, Wuhan University of Technology, Wuhan, People’s Republic of China Abstract: Nanoparticles (NPs are advantageous for the delivery of diagnosis agents to brain tumors. In this study, we attempted to develop an l-cysteine coated FePt (FePt-Cys NP as MRI/CT imaging contrast agent for the diagnosis of malignant gliomas. FePt-Cys NPs were synthesized through a co-reduction route, which was characterized by transmission electron microscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and dynamic light scattering. The MRI and CT imaging ability of FePt-Cys NPs was evaluated using different gliomas cells (C6, SGH44, U251 as the model. Furthermore, the biocompatibility of the as-synthesized FePt-Cys NPs was evaluated using three different cell lines (ECV304, L929, and HEK293 as the model. The results showed that FePt-Cys NPs displayed excellent biocompatibility and good MRI/CT imaging ability, thereby indicating promising potential as a dual MRI/CT contrast agent for the diagnosis of brain malignant gliomas. Keywords: CT, glioma, MRI

  11. Synthesis, structural characterization and magnetic properties of Fe/Pt core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pisane, K. L.; Singh, Sobhit; Seehra, M. S., E-mail: mseehra@wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    2015-05-07

    Structural and magnetic properties of Fe/Pt core-shell nanostructure prepared by a sequential reduction process are reported. Transmission electron microscopy shows nearly spherical particles fitting a lognormal size distribution with D{sub o} = 3.0 nm and distribution width λ{sub D} = 0.31. In x-ray diffraction, Bragg lines only from the Pt shell are clearly identified with line-widths yielding crystallite size = 3.1 nm. Measurements of magnetization M vs. T (2 K–350 K) in magnetic fields up to 90 kOe show a blocking temperature T{sub B} = 13 K below which hysteresis loops are observed with coercivity H{sub C} increasing with decreasing T reaching H{sub C} = 750 Oe at 2 K. Temperature dependence of the ac susceptibilities at frequencies f{sub m} = 10 Hz–5 kHz is measured to determine the change in T{sub B} with f{sub m} using the Vogel-Fulcher law. This analysis shows the presence of significant interparticle interaction, the Neel-Brown relaxation frequency f{sub o} = 5.3 × 10{sup 10 }Hz and anisotropy constant K{sub a} = 3.6 × 10{sup 6 }ergs/cm{sup 3}. A fit of the M vs. H data up to H = 90 kOe for T > T{sub B} to the modified Langevin function taking particle size distribution into account yields magnetic moment per particle consistent with the proposed core-shell structure; Fe core of 2.2 nm diameter and Pt shell of 0.4 nm thickness.

  12. FePt and CoPt nanoparticles prepared by micellar method. Effects of A1{yields}L1{sub 0} transition on oxidation resistance and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Han, Luyang

    2011-02-15

    In this thesis FePt and CoPt alloy nanoparticles are prepared with reverse micelles. The metallic nanoparticles with diameters of 2-12 nm and interparticle distances of 20-140 nm are obtained on Si substrates. The magnetic properties of FePt and CoPt nanoparticles as well as oxidation behavior of FePt nanoparticles are investigated. X-ray magnetic circular dichroism (XMCD) measurements on 5.8 nm FePt nanoparticles after hydrogen plasma reduction at 300 C reveals that the magnetic moment per Fe atom and magnetic anisotropy energy match chemically disordered FePt in A1 phase. Annealing at 650 C transform portion of FePt particles to chemically ordered L1{sub 0} phase. The presense of nanoparticles in L1{sub 0} phase is identified by high-resolution transmission electronmicroscopy (HRTEM) investigation, where it is also observed that large fraction of the particles contain defects such as twin boundaries and stacking faults. By increasing the annealing temperature or prolonging annealing time, ratio of transformed particles increases. The average magnetic anisotropy energy of the transformed particles is below 30% of the value of bulk FePt in L1{sub 0} phase. Annealing at above 750 C, however, decreases the average magnetic anisotropy in the sample. Similar A1 {yields} L1{sub 0} transition is observed in FePt nanoparticles with different diameters as well as in CoPt nanoparticles. The spin moment of Fe in FePt nanoparticles decreases with smaller particle diameter, while the orbital moment stays almost constant. Magnetic moments at room temperature are significantly reduced compared to those at low temperature, suggesting the Curie temperatures in FePt and CoPt nanoparticles are significantly lower than in the bulk. The annealing also induces Pt segregation towards the surface in FePt nanoparticles, which is identified by the decreased apparent Fe content measured by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The segregation of Pt

  13. Magnetic properties of the alloy system Fe-Pt. Bulk materials and nanoparticles; Magnetische Eigenschaften des Legierungssystems Fe-Pt. Volumenmaterialien und Nanopartikel

    Energy Technology Data Exchange (ETDEWEB)

    Antoniak, C.

    2007-12-14

    Besides the determination of magnetic properties of epitaxial grown Fe{sub x}Pt{sub 1-x} films like e.g. the magnetic anisotropy, effective magnetisation, exchange length and damping as reference data, wet-chemically synthesised spherical Fe{sub x}Pt{sub 1-x} nanoparticles with different sizes, compositions and crystal structures were examined systematically after the reduction of Fe oxides by a hydrogen plasma treatment. Organic ligands surrounding the particles after the synthesis, were removed as well during this procedure. These ligands prevent the agglomeration of the nanoparticles when deposited onto a substrate, but do not have any measurable effect on the oxide formation under air exposure and do not change the magnetic properties of oxidised nanoparticles within experimental error bars. Static and dynamic magnetic properties were determined using the ferromagnetic resonance technique and themeasurement of the x-ray absorption, especially the analysis of the X-ray circular dichroism. The analysis of the element-specific magnetic moments shows that the effective magnetic spin moment ({mu}{sup eff}{sub s}) of the Fe{sub x}Pt{sub 1-x} nanoparticles is reduced by 20.30% with respect to the one of the corresponding Fe{sub x}Pt{sub 1-x} film due to the inhomogeneous composition within the nanoparticles which was found by the analysis of the extended X-ray absorption fine structure. With decreasing particle size, {mu}{sup eff}{sub s} is further decreasing while the ratio of orbital-to-effective-spin magnetic moment ({mu}{sub l}/{mu}{sup eff}{sub s}) increases. Annealing at 600 C of a sample consisting of Fe{sub 0.50}Pt{sub 0.50} nanoparticles with a mean diameter around 6 nm yields a strong increase of the {mu}{sub l}/{mu}{sup eff}{sub s} ratio at the Fe sites: it reaches a value of about 9% and is as large as the value at the Pt sites. This is accompanied by an enhancement of the coercive field from (36{+-}5) mT to (292{+-}8) mT after annealing that can be

  14. First-principles prediction of the morphology of L 10 FePt nanoparticles supported on Mg(Ti)O for heat-assisted magnetic recording applications

    Science.gov (United States)

    Hung, Shih-Hsuan; McKenna, Keith

    2017-07-01

    We perform first-principles calculations to predict the morphology of L 10 ordered FePt nanoparticles grown on Mg(Ti)O substrates with relevance to application in heat-assisted magnetic recording (HAMR) media. We show how incorporation of Ti into MgO substrates reduces the FePt adhesion energy from -1.29 (pure MgO) to -2.35 J /m2 (pure TiO). This effect is due to the formation of strong Fe-Ti bonds at the interface. Consistent with experimental observations, the predicted equilibrium morphology of supported FePt nanoparticles is significantly changed, corresponding to increased wetting. This behavior is undesirable for HAMR media since it promotes grain growth which limits the storage density. We show how passivation of surface Ti atoms (e.g., with MgO) is sufficient to restore the wetting observed for pure MgO substrates offering a viable strategy for optimization of next generation recording media.

  15. Pt- and FePt- nanoparticles on the basis of emulsion techniques

    Energy Technology Data Exchange (ETDEWEB)

    Manzke, Achim; Wiedemann, Stefan; Enderle, Fabian; Plettl, Alfred; Ziemann, Paul [Institut fuer Festkoerperphysik, Universitaet Ulm (Germany); Schreiber, Eyk; Ziener, Ulrich [Institut fuer Organische Chemie III, Universitaet Ulm (Germany); Vogel, Nicolas; Landfester, Katharina [MPI fuer Polymerforschung, Mainz (Germany); Biskupek, Johannes; Kaiser, Ute [Materialwissenschaftliche Elektronenmikroskopie, Universitaet Ulm (Germany)

    2010-07-01

    Metal-precursor loaded colloidal polystyrene (PS) particles in aqueous solution are produced by an emulsion and miniemulsion technique, respectively. We report on colloids loaded with Pt- as well as with Fe- and Pt-complexes. After deposition of a hexagonally ordered monolayer of PS spheres on top of a silicon substrate, optimized plasma and temper sequences are applied to obtain metallic nanoparticles which still exhibit the original lateral order. The metal content within a colloid defines the size of the final particle, which could be varied between 6 and 14 nm, so far. The interparticle distance is determined by the diameter of the starting PS-particles and was varied between 80 and 250 nm. Different process steps are investigated by HRSEM, HRTEM and XPS giving insight in the plasma- and annealing process and demonstrating e.g. the crystalline structure of the Pt- nanoparticles.

  16. Magnetism of FePt Nanoclusters in Polyimide

    Directory of Open Access Journals (Sweden)

    Mircea Chipara

    2015-01-01

    Full Text Available FePt nanoclusters have been implanted onto polyimide films and subjected to thermal annealing in order to obtain a special magnetic phase (L10 dispersed within the polymer. SQUID measurements quantified the magnetic features of the as-prepared and annealed hybrid films. As-implanted FePt nanoparticles in polyimide films exhibited a blocking temperature of 70 ± 5 K. Thermal annealing in zero and 10 kOe applied magnetic field increased the magnetic anisotropy and coercivity of the samples. Wide Angle X-Ray Scattering confirmed the presence of FePt and L10 phase. All samples (as deposited and annealed exhibited electron spin resonance spectra consisting of two overlapping lines. The broad line was a ferromagnetic resonance originating from FePt nanoparticles. Its angular dependence indicated the magnetic anisotropy of FePt nanoparticles. SEM micrographs suggest a negligible coalescence of FePt nanoparticles, supporting that the enhancement of the magnetic properties is a consequence of the improvement of the L10 structure. The narrow ESR line was assigned to nonmagnetic (paramagnetic impurities within the samples consistent with graphite-like structures generated by the local degradation of the polymer during implantation and annealing. Raman spectroscopy confirmed the formation of graphitic structures in annealed KHN and in KHN-FePt.

  17. Orientation of FePt nanoparticles on top of a-SiO2/Si(001), MgO(001) and sapphire(0001): effect of thermal treatments and influence of substrate and particle size.

    Science.gov (United States)

    Schilling, Martin; Ziemann, Paul; Zhang, Zaoli; Biskupek, Johannes; Kaiser, Ute; Wiedwald, Ulf

    2016-01-01

    Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs) on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct) L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001), i.e., Si(001) with an amorphous (a-) native oxide layer on top, on MgO(001), and on sapphire(0001) substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: "small" NPs with diameters in the range of 2-3 nm and "large" ones in the range of 5-8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD), served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED) and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM) after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001) supports, however, FePt nanoparticles exhibit a clearly preferred (111) orientation even in the as-prepared state, which can be slightly improved by annealing at 600-650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111) orientation. On top of MgO(001) the effect of annealing on

  18. Reduced-temperature ordering of FePt nanoparticle assembled films by Fe30Pt70/Fe3O4 core/shell structure

    Institute of Scientific and Technical Information of China (English)

    He Shu-Li; Peng Yin; Liu Li-Li; Jiang Hong-Wei; Liu Li-Feng; Zheng Wu; Wang Ai-Ling

    2007-01-01

    In this paper, Fe3oPt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polycthylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2%%30%H2) for 1h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rich core, which leaded to the formation of L10 phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the coercivity of 4 KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.

  19. 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.

  20. Device for Controlled Distribution of FePt Nanoparticles Formations in a Stream of Liquid Medium under Influence of Magnetic Field

    Directory of Open Access Journals (Sweden)

    Karolis ŠILEIKA

    2014-04-01

    Full Text Available In this research paper a design of magnetic device comprising Halbach arrays which maximizes the magnetic forces acting on magnetic nanoparticles and which can be used for successful steering of said particles to a zone of interest and captured thereat while exhibiting a certain flow and accumulation pattern after injection into a stream of a liquid medium is presented. The aim was to investigate efficiency of such design of a magnetic device for application in magnetic targeting techniques. The presented construction was assembled from 10 magnetic elements having the same dimensions and residual magnetic field, and casing of Plexiglas material. Aggregating of clusters of FePt nanoparticles was evidently successful at preferable region located between two opposing parts of a magnetic device, which was tested for flow rates of (1 – 10 mL/min of main stream medium. To simulate the viscosity of blood a 1.5 % PVP 90 solution was used as the flowing medium. The shallow depth of targeting was chosen for practical reason: to ensure a maximum visibility of particle "steering" pattern obtainable by the magnetic device consisting of two adjacent parts comprising Halbach arrays. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.3371

  1. 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.

  2. Graphene nanoribbon/FePt bimetallic nanoparticles/uric acid as a novel magnetic sensing layer of screen printed electrode for sensitive determination of ampyra.

    Science.gov (United States)

    Hashemi, Pegah; Bagheri, Hasan; Afkhami, Abbas; Amidi, Salimeh; Madrakian, Tayyebeh

    2018-01-01

    A novel electrochemical sensor for sensitive determination of ampyra (Am) based on graphene nanoribbons modified by iron-platinum bimetallic nanoparticles and uric acid (SPCE/FePtGNR/UA) dropped on the screen-printed carbon electrode (SPCE) surface and magnetically captured onto an SPCE working electrode surface is reported in the present work. The modified nanocomposite and sensing layer was characterized by different techniques, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray powdered diffraction (XRD). Am determination by conventional electrochemical methods is not possible, because of its high redox overpotential. Therefore, the differential pulse voltammetry (DPV) signals of UA were used as a redox probe for indirect electrochemical determination of Am. The limit of detection (LOD) and linear concentration range were obtained as 0.028 and 0.08-9.0µmolL(-1) (3Sb/m = 3), respectively. The feasibility of the proposed method was examined by the detection of Am in biological and pharmaceutical samples with satisfactory results. The constructed electrochemical sensor was applied for fast, simple and sensitive detection of Am in real environments. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. 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.

  4. Facile synthesis of flower like FePt@ZnO core–shell structure and its bifunctional properties

    Energy Technology Data Exchange (ETDEWEB)

    Majeed, Jerina [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Jayakumar, O.D., E-mail: ddjaya@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Mandal, B.P. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Salunke, H.G. [Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Naik, R. [Department of Physics, Wayne State University, Detroit, MI 48202 (United States); Tyagi, A.K., E-mail: aktyagi@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2014-06-01

    Graphical abstract: Flower shaped FePt and ZnO coated FePt with core–shell nanostructures are synthesized by a facile solvothermal procedure. Shell thickness of ZnO over FePt core was tuned by varying FePt concentration with respect to ZnO. Hybrid structure with lower FePt concentration exhibited bifunctionality such as near room temperature ferromagnetism and photoluminescence. Pristine FePt crystallize in the fct (L1{sub 0}) phase whereas it converts into fcc phase in presence of ZnO. - Highlights: • FePt@ZnO hybrid core–shell particles, with unique flower shape morphology have been prepared by solvothermal method. • Phase transition of fct-FePt to fcc-FePt has been found in presence of ZnO nanoparticles. • Plausible mechanism for growth of flowershaped nanoparticle is in accordance with energy minimization principle. • The core shell structure (FePt@ZnO) exhibits bi-functional properties. - Abstract: Flower shaped FePt and ZnO coated FePt (FePt@ZnO) core–shell nanostructures are synthesized by a facile solvothermal procedure. Two different compositions (molar ratio) of FePt and ZnO (FePt:ZnO = 1:3 and FePt:ZnO = 1:6) core–shells with different thicknesses of ZnO shells were synthesized. Hybrid FePt@ZnO core–shell flower structure with lower FePt concentration (FePt:ZnO = 1:6) exhibited bifunctionality including near room temperature ferromagnetism and photoluminescence at ambient conditions. X-ray diffraction patterns of pristine FePt showed partially ordered face centred tetragonal (fct) L1{sub 0} phase whereas ZnO coated FePt (FePt@ZnO) nanostructures showed hexagonal ZnO and disordered phase of FePt with fcc structure. The phase transition of fct FePt to fcc phase occurring in presence of ZnO is further confirmed by transmission electron microscopy and magnetic measurement studies. The formation of the nanoflowers was possibly due to growth along the [0 1 1] or [0 0 1] direction, keeping the core nearly spherical in accordance with the

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Kinetic lattice Monte-Carlo simulations on the ordering kinetics of free and supported FePt L10-nanoparticles

    OpenAIRE

    Müller, Michael; Albe, Karsten

    2011-01-01

    The ordering kinetics in free and supported L10 nanoparticles was studied by means of lattice-based kinetic Monte-Carlo simulations. Starting from a fully disordered particle of Wulff shape, the simulations show that the nucleation of ordered domains is starting quickly on various (100) facets but is retarded in the particle volume due to the lack of vacancies compared with a thin film geometry. If a substrate is present, we do not find significant differences in the ordering behavior. This h...

  10. Orientation of FePt nanoparticles on top of a-SiO2/Si(001, MgO(001 and sapphire(0001: effect of thermal treatments and influence of substrate and particle size

    Directory of Open Access Journals (Sweden)

    Martin Schilling

    2016-04-01

    Full Text Available Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001, i.e., Si(001 with an amorphous (a- native oxide layer on top, on MgO(001, and on sapphire(0001 substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: “small” NPs with diameters in the range of 2–3 nm and “large” ones in the range of 5–8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD, served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001 supports, however, FePt nanoparticles exhibit a clearly preferred (111 orientation even in the as-prepared state, which can be slightly improved by annealing at 600–650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111 orientation. On top of MgO(001 the

  11. Kinetic lattice Monte-Carlo simulations on the ordering kinetics of free and supported FePt L10-nanoparticles

    Science.gov (United States)

    Müller, Michael

    2011-01-01

    Summary The ordering kinetics in free and supported L10 nanoparticles was studied by means of lattice-based kinetic Monte-Carlo simulations. Starting from a fully disordered particle of Wulff shape, the simulations show that the nucleation of ordered domains is starting quickly on various (100) facets but is retarded in the particle volume due to the lack of vacancies compared with a thin film geometry. If a substrate is present, we do not find significant differences in the ordering behavior. This holds true, even if we impose a massively increased thermodynamic driving force for interface segregation, because the nucleation of ordered domains on free facets is significantly faster than the bulk diffusion of the segregating species to the interface. In cases where wetting of the substrate or surface facetting occurs, we find that diffusional atomic motion on the surface goes along with an enhanced long-range order. PMID:21977414

  12. Agglomeration and Sintering in Annealed FePt Nanoparticle Assemblies Studied by Small Angle Neutron Scattering and X-Ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, T.

    2005-01-03

    In this work we give a detailed account of the use of small angle neutron scattering to study the properties of polymer mediated, self assembled nanoparticle arrays as a function of annealing temperature. The results from neutron scattering are compared with those obtained from x-ray diffraction. Both techniques show that particle size increases with annealing temperatures of 580 C and above. They also show that the distribution of particle diameters is significant and increases with annealing temperature. The complementary nature of the two measurements allows a comprehensive structural model of the assemblies to be developed in terms of particle sintering and agglomeration. To realize the potential of nanoparticle assemblies as a monodispersed data storage medium the problem of particle separation necessary to avoid sintering and agglomeration during annealing must be addressed.

  13. 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.

  14. Observation and elimination of broken symmetry in L1{sub 0} FePt nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Quarterman, P.; Wang, Hao; Qiu, Jiao-Ming; Ma, Bin; Liu, Xiaoqi; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering and the Center for Micromagnetics and Information Technologies (MINT), University of Minnesota, Minnesota 55455 (United States); Guo, Honghua [Department of Optical Science and Engineering, Fudan University, Shanghai (China)

    2015-12-07

    An unexplained surface anisotropy effect was observed and confirmed in the magnetization reversal process of both L1{sub 0} phase FePt nanoparticles with octahedral shape and (001) textured L1{sub 0} FePt thin films with island nanostructures. We suggest that the nature of the observed surface effect is caused by broken symmetry on the FePt surface, which results in weakened exchange coupling for surface atoms. Furthermore, we propose, and experimentally demonstrate, a method to repair the broken symmetry by capping the FePt islands with a Pt layer, which could prove invaluable in understanding fundamental limitations of magnetic nanostructures.

  15. 新型 FePt 石墨纳米囊的合成及其燃料电池催化剂的应用%Synthesis of novel graphene encapsulated FePt nanoparticle and its application in fuel cell catalyst

    Institute of Scientific and Technical Information of China (English)

    丁玎; 宋志灵; 陈卓

    2015-01-01

    铂基燃料电池催化剂的效率及性能对于燃料电池这一新兴能源的发展起着决定性作用。为了提高催化剂性能并降低成本,本文采用化学气相沉积(CVD)法一步合成了石墨烯(graphene)包裹的 FePt 纳米囊,并将该颗粒(G-FePt)作为直接甲醇燃料电池的电极催化剂。采用 TEM、XRD 等对其进行表征后,考察了其在甲醇氧化模型中的循环伏安电化学催化性能及稳定性。结果表明,该纳米囊表现出了良好的催化性能,电化学活性表面积 ECSA 达到了47.48 m2/g,相比于传统催化剂有了很大提高,同时在多次循环测试之后仍能保持较高的催化活性。该方法合成的纳米囊稳定、尺寸可控并具有贵金属的优良催化效果及石墨烯良好的电学性能,为未来燃料电池催化剂的发展提供了新的选择。%The efficiency and performance of platinum-based fuel cell catalyst play a critical role in the fuel cell development.To improve the performance and reduce the cost,we synthesized a graphene encapsulated FePt nanoparticle (G-FePt)through a sim-ple one-step CVD method and used it as a methanol oxidization fuel cell catalyst.After characterizing by TEM,XRD etc.its elec-trocatalytic performance and stability were investigated in the methanol oxidation model using cyclic voltammetry.The results show that this nanoparticle has a really good catalyst performance,the ECSA value is 47.48 m2/g,which is higher than those of conventional catalysts.Meanwhile,this nanoparticle can maintain its catalysis performance after long term cycling.G-FePt can integrate the excellent catalysis ability of noble metal with the superior electronic properties of graphene,which makes it to be a promising candidate for the future fuel cell catalyst development.

  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. Self-suspended permanent magnetic FePt ferrofluids

    KAUST Repository

    Dallas, Panagiotis

    2013-10-01

    We present the synthesis and characterization of a new class of self-suspended ferrofluids that exhibit remanent magnetization at room temperature. Our system relies on the chemisorption of a thiol-terminated ionic liquid with very low melting point on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic component. The ferrofluids do not show any sign of flocculation or phase separation, despite the strong interactions between the magnetic nanoparticles due to the strong chemisorption of the ionic liquid as evidenced by Raman spectroscopy and thermal analysis. Composites with high FePt loading (40 and 70. wt%) exhibit a pseudo solid-like rheological behavior and high remanent magnetization values (10.1 and 12.8. emu/g respectively). At lower FePt loading (12. wt%) a liquid like behavior is observed and the remanent and saturation magnetization values are 3.5 and 6.2. emu/g, respectively. The magnetic and flow properties of the materials can be easily fine tuned by controlling the type and amount of FePt nanoparticles used. © 2013 Elsevier Inc.

  20. One-pot synthesis of FePt/CNTs nanocomposites for efficient cellular imaging and cancer therapy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weihong; Zheng, Xiuwen, E-mail: xwzheng1976@163.com [Linyi University, School of Chemistry & Chemical Engineering, Shandong Provincial Key Laboratory of Detection Technology for Tumor Makers (China); Li, Shulian [Linyi Tumor Hospital (China); Zhang, Wei; Wen, Xin [Linyi University, School of Chemistry & Chemical Engineering, Shandong Provincial Key Laboratory of Detection Technology for Tumor Makers (China); Yue, Ludan [Shandong Normal University (China); Wang, Jinlong [Shandong University of Technology (China)

    2015-11-15

    Here, we developed a facile route to synthesize carbon nanotube-based FePt nanocomposites (FePt/CNTs) as a potential theranostic platform in the cancer treatment. FePt/CNTs were firstly synthesized via one-pot polyol route, and then functionalized with 6-arm-polyethylene glycol-amine polymer. The average size of FePt nanoparticles (NPs) is 3–4 nm, which is dispersed on the CNT surface (ca.50–150 nm). The as-prepared FePt NPs display high cytotoxicity by highly reactive oxygen species in cancer cells. Folic acid and fluorescein isothiocyanate are assembled onto the surface of FePt/CNTs for effective targeting of folate receptor-positive cancer cells and simultaneously for the visualization of cellular uptake. Therefore, the FePt/CNTs NPs capability of simultaneously performing diagnosis, therapy, and targeting is, therefore, promising for future potential widespread application in biomedicine.

  1. Size control of L12-FePt3 nanocrystals by spin-coating method

    Science.gov (United States)

    Bamshad, Zahra; Sebt, Seyed Ali; Abolhassani, Mohammad Reza

    2016-09-01

    Annealing is one of the stages of FePt nanoparticles preparation, during which the transition to a compositionally ordered phase occurs. In order to size and shape control of the nanoparticles in the mentioned stage, it is needed that they be distributed on a suitable surface. In the present work, the spin-coating method is suggested for preparing monolayer from L12-FePt3 nanoparticles colloidal solution on SiO2/Si substrates. FePt3 nanoparticles were gradually deposited as droplets on the center of a 500 rpm rotating substrate. This step was performed in hexane vapor atmosphere without any stopping time. The analyses revealed that a uniform surface distribution was formed so that, after annealing at 600 °C for 1 h the 6.1 nm L12-FePt3 nanoparticles were spherical in shape with standard deviation of 1.5 nm.

  2. 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.

  3. Dense-plasma-driven ultrafast formation of FePt organization on silicon substrate

    Indian Academy of Sciences (India)

    ROHIT MEDWAL; NEERU SEHDEV; WANG YING; R S RAWAT; S ANNAPOORNI

    2017-02-01

    This article demonstrates the removal of organic capping and promotion of long-range 2D organization of chemically synthesized FePt nanoparticles dispersed on Si$\\langle 100\\rangle$ substrate by means of pulsed H+ energetic ion irradiation using a dense plasma focus (DPF) device. The irradiation of energetic H$^+$ ions on FePt nanoparticles clearly resulted in enhanced structural and magnetic behaviour of the FePt nanoparticles as a function ofplasma focused irradiation shots. Transmission electron microscopy (TEM)/scanning electron microscopy (SEM) images of the FePt nanoparticles clearly show a marked enhancement in average particle size from 2.5 nm for nonirradiated sample to about 28nm for four plasma focus shots irradiation. The gradual removal of organic capping over chemically synthesized FePt nanoparticles with increasing plasma focus shots exposure is confirmed usingRaman spectroscopy. A uniform 2D organization of bimetallic FePt nanoparticles over 1 cm $\\times$ 1 cm silicon substrate is obtained with three plasma focus shots with better magnetic properties as compared with plasma-untreated FePtnanoparticles.

  4. 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.

  5. Cluster Monte Carlo methods for the FePt Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Lyberatos, A., E-mail: lyb@materials.uoc.gr [Materials Science and Technology Department, P.O. Box 2208, 71003 Heraklion (Greece); Parker, G.J. [HGST, A Western Digital Company, 3403 Yerba Buena Road, San Jose, CA 95135 (United States)

    2016-02-15

    Cluster Monte Carlo methods for the classical spin Hamiltonian of FePt with long range exchange interactions are presented. We use a combination of the Swendsen–Wang (or Wolff) and Metropolis algorithms that satisfies the detailed balance condition and ergodicity. The algorithms are tested by calculating the temperature dependence of the magnetization, susceptibility and heat capacity of L1{sub 0}-FePt nanoparticles in a range including the critical region. The cluster models yield numerical results in good agreement within statistical error with the standard single-spin flipping Monte Carlo method. The variation of the spin autocorrelation time with grain size is used to deduce the dynamic exponent of the algorithms. Our cluster models do not provide a more accurate estimate of the magnetic properties at equilibrium. - Highlights: • A new cluster Monte Carlo algorithm was applied to FePt nanoparticles. • Magnetic anisotropy imposes a restriction on cluster moves. • Inclusion of Metropolis steps is required to satisfy ergodicity. • In the critical region a percolating cluster occurs for any grain size. • Critical slowing down is not solved by the new cluster algorithms.

  6. Cluster Monte Carlo methods for the FePt Hamiltonian

    Science.gov (United States)

    Lyberatos, A.; Parker, G. J.

    2016-02-01

    Cluster Monte Carlo methods for the classical spin Hamiltonian of FePt with long range exchange interactions are presented. We use a combination of the Swendsen-Wang (or Wolff) and Metropolis algorithms that satisfies the detailed balance condition and ergodicity. The algorithms are tested by calculating the temperature dependence of the magnetization, susceptibility and heat capacity of L10-FePt nanoparticles in a range including the critical region. The cluster models yield numerical results in good agreement within statistical error with the standard single-spin flipping Monte Carlo method. The variation of the spin autocorrelation time with grain size is used to deduce the dynamic exponent of the algorithms. Our cluster models do not provide a more accurate estimate of the magnetic properties at equilibrium.

  7. 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.

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Observation of high coercive fields in chemically synthesized coated Fe-Pt nanostructures

    Science.gov (United States)

    Dalavi, Shankar B.; Panda, Rabi N.

    2017-04-01

    Nanocrystalline Fe-Pt alloys have been synthesized via chemical reduction route using various capping agents; such as: oleic acid/oleylamine (route-1) and oleic acid/CTAB (route-2). We could able to synthesize Fe50Pt and Fe54Pt alloys via route 1 and 2, respectively. As-prepared Fe-Pt alloys crystallize in disordered fcc phase with crystallite sizes of 2.3 nm and 6 nm for route-1 and route-2, respectively. Disordered Fe-Pt alloys were transformed to ordered fct phase after annealing at 600 °C. SEM studies confirm the spherical shape morphologies of annealed Fe-Pt nanoparticles with SEM particle sizes of 24.4 nm and 21.2 nm for route-1 and route-2, respectively. TEM study confirms the presence of 4.6 nm particles for annealed Fe50Pt alloys with several agglomerating clusters of bigger size and appropriately agrees well with the XRD study. Room temperature magnetization studies of as-prepared Fe-Pt alloys (fcc) show ferromagnetism with negligible coercivities. Average magnetic moments per particle for as-prepared Fe-Pt alloys were estimated to be 753 μB and 814 μB, for route 1 and 2, respectively. Ordered fct Fe-Pt alloys show high values of coercivities of 10,000 Oe and 10,792 Oe for route-1 and route-2, respectively. Observed magnetic properties of the fct Fe-Pt alloys nps were interpreted with the basis of order parameters, size, surface, and composition effects.

  14. 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.

  15. Rapid thermal annealing of FePt and FePt/Cu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph

    2011-01-10

    Chemically ordered FePt is one of the most promising materials to reach the ultimate limitations in storage density of future magnetic recording devices due to its high uniaxial magnetocrystalline anisotropy and a corrosion resistance superior to rare-earth based magnets. In this study, FePt and FePt/Cu bilayers have been sputter deposited at room temperature onto thermally oxidized silicon wafers, glass substrates and self-assembled arrays of spherical SiO{sub 2} particles with diameters down to 10 nm. Millisecond flash lamp annealing, as well as conventional rapid thermal annealing was employed to induce the phase transformation from the chemically disordered A1 phase into the chemically ordered L1{sub 0} phase. The influence of the annealing temperature, annealing time and the film thickness on the ordering transformation and (001) texture evolution of FePt films with near equiatomic composition was studied. Whereas flash lamp annealed FePt films exhibit a polycrystalline morphology with high chemical L1{sub 0} order, rapid thermal annealing can lead to the formation of chemically ordered FePt films with (001) texture on amorphous SiO{sub 2}/Si substrates. The resultant high perpendicular magnetic anisotropy and large coercivities up to 40 kOe are demonstrated. Simultaneously to the ordering transformation, rapid thermal annealing to temperatures exceeding 600 C leads to a break up of the continuous FePt film into separated islands. This dewetting behavior was utilized to create regular arrays of FePt nanostructures on SiO{sub 2} particle templates with periods down to 50 nm. The addition of Cu improves the (001) texture formation and chemical ordering for annealing temperatures T{sub a} {<=}600 C. In addition, the magnetic anisotropy and the coercivity of the ternary FePtCu alloy can be effectively tailored by adjusting the Cu content. The prospects of FePtCu based exchange spring media, as well as the magnetic properties of FePtCu nanostructures fabricated

  16. Magnetic Properties and Nanostructures of FePtCu:C Thin Films with FePt Underlayers

    Institute of Scientific and Technical Information of China (English)

    JIN Ling-Fang; YAN Ming-Lang

    2007-01-01

    Magnetic properties and nanostructures of FePtCu:C thin films with FePt underlayers (ULs) are studied. The effect of FePt ULs on the orientation and magnetic properties of the thin films are investigated by adjusting FePt UL thicknesses from 2nm to 14nm. X-ray diffraction (XRD) scans reveal that the orientation of the films is dependent on FePt UL thickness. For a 5-nm FePtCu:C nanocomposite thin film with a 2-nm FePt UL, the coercivity is 6.5 KOe, the correlation length is 59nm, the desired face-centred-tetragonal (fct) ordered structure [L10 phase] is formed and the c axis normal to the film plane [(001) texture] is obtained. These results indicate that the better orientation and magnetic properties of the films can be tuned by decreasing the thickness of the FePt UL.

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. Oriented-assembly of hollow FePt nanochains with tunable catalytic and magnetic properties

    Science.gov (United States)

    Liu, Jialong; Xia, Tianyu; Wang, Shouguo; Yang, Guang; Dong, Bowen; Wang, Chao; Ma, Qidi; Sun, Young; Wang, Rongming

    2016-06-01

    Hollow nanoparticles with large surface areas exhibit a lot of advantages for applications such as catalysis and energy storage. Furthermore, their performance can be manipulated by their deliberate assemblies. Dispersive hollow FePt nanospheres have been assembled into one-dimensional hollow FePt nanochains under the magnetic fields at room temperature. Based on the activation of galvanic replacement at different reaction stages, the size of hollow FePt nanochains can be deliberately manipulated varying from 20 nm to 300 nm, together with the length changing from 200 nm to 10 μm. The competition between movement of paramagnetic Fe3+ ions and shape recovering due to thermal fluctuations plays a critical effect on the structure of contact area between hollow nanospheres, leading to perforative structures. Compared with commercial Pt/C, well aligned hollow FePt nanochains show greatly enhanced catalytic activities in the methanol oxidation reaction (MOR) due to more favorable mass flow. Magnetic measurements indicate that the magnetic properties including Curie temperature and saturation magnetization can be tuned by the control of the size and shape of hollow nanochains.Hollow nanoparticles with large surface areas exhibit a lot of advantages for applications such as catalysis and energy storage. Furthermore, their performance can be manipulated by their deliberate assemblies. Dispersive hollow FePt nanospheres have been assembled into one-dimensional hollow FePt nanochains under the magnetic fields at room temperature. Based on the activation of galvanic replacement at different reaction stages, the size of hollow FePt nanochains can be deliberately manipulated varying from 20 nm to 300 nm, together with the length changing from 200 nm to 10 μm. The competition between movement of paramagnetic Fe3+ ions and shape recovering due to thermal fluctuations plays a critical effect on the structure of contact area between hollow nanospheres, leading to perforative

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Magnetic Properties and Microstructure of FeOx/Fe/FePt and FeOx/FePt Films

    Directory of Open Access Journals (Sweden)

    Jai-Lin Tsai

    2013-01-01

    Full Text Available The Fe(6 nm/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5~7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeOx(3 nm/Fe(3 nm/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeOx and Fe/FePt layers was decoupled. The moments in FeOx layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500°C and 800°C for 3 minutes. When the FeOx(3 nm/Fe(3 nm/FePt trilayer was annealed at 500°C, the layers structure was changed to FeOx(6 nm/FePt bilayer due to oxygen diffusion. The hard-magnetic FeOx(6 nm/FePt film was coupled with single switching field. The FeOx/(disordered FePt layer structure was observed with further annealing at 800°C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeOx layer, and hard-magnetic L10 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L10 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800°C.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Microwave-assisted chemical reduction routes for direct synthesis of (fct) L1 phase of Fe-Pt.

    Science.gov (United States)

    Acharya, Smita; Singh, Kamal

    2011-01-01

    Microwave-assisted chemical reduction route has been explored for the direct synthesis of fct L1(0) - phase of Fe-Pt nanoparticles in the present work. Effects of microwave power and irradiation time on the growth process are systematically studied. Using this facile and high yield technique we could tune particle size from 7 to 17 nm. Prepared Fe-Pt NPs exhibited ordered face centered tetragonal (fct) L1(0) phase without any post-synthesis treatment. The particle size and magnetic properties of the prepared Fe-Pt were found to be very sensitive to the microwave irradiation power, while influence of exposure time was insignificant. The hysteresis measurements were performed at 300 K to study magnetic properties of the synthesized Fe-Pt as a function of crystallite size. Coercivity and saturation magnetization were observed to be decreasing with diminishing particle size. The microwave-assisted route is found to be a simple technique for direct synthesis of metal alloys and may prove to be a potential tool of high density data storage materials such as Fe-Pt.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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%).

  12. 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

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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).

  6. 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.

  7. 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

  8. 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.

  9. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Takeshi, E-mail: go-sai@imr.tohoku.ac.jp; Takanashi, Koki [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Uchida, Ken-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Kikkawa, Takashi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Qiu, Zhiyong [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Saitoh, Eiji [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195 (Japan)

    2015-08-31

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (J{sub s}) in the FePt|Y{sub 3}Fe{sub 5}O{sub 12} (YIG) structure, and J{sub s} was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  10. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    Science.gov (United States)

    Seki, Takeshi; Uchida, Ken-ichi; Kikkawa, Takashi; Qiu, Zhiyong; Saitoh, Eiji; Takanashi, Koki

    2015-08-01

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  11. The system Fe-Pt-S at 1100°C

    DEFF Research Database (Denmark)

    Makovicky, Milota; Makovicky, Emil; Rose-Hansen, John

    2002-01-01

    geology, system Fe-Pt-S, iron-platinum alloys, isoferroplatinum, monosulfide solid-solution, cooperite......geology, system Fe-Pt-S, iron-platinum alloys, isoferroplatinum, monosulfide solid-solution, cooperite...

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Nanocrystalline Fe-Pt alloys. Phase transformations, structure and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Lyubina, J.V.

    2006-12-21

    This work has been devoted to the study of phase transformations involving chemical ordering and magnetic properties evolution in bulk Fe-Pt alloys composed of nanometersized grains. Nanocrystalline Fe{sub 100-x}Pt{sub x} (x=40-60) alloys have been prepared by mechanical ball milling of elemental Fe and Pt powders at liquid nitrogen temperature. The as-milled Fe-Pt alloys consist of {proportional_to} 100 {mu}m sized particles constituted by randomly oriented grains having an average size in the range of 10-40 nm. Depending on the milling time, three major microstructure types have been obtained: samples with a multilayer-type structure of Fe and Pt with a thickness of 20-300 nm and a very thin (several nanometers) A1 layer at their interfaces (2 h milled), an intermediate structure, consisting of finer lamellae of Fe and Pt (below approximately 100 nm) with the A1 layer thickness reaching several tens of nanometers (4 h milled) and alloys containing a homogeneous A1 phase (7 h milled). Subsequent heat treatment at elevated temperatures is required for the formation of the L1{sub 0} FePt phase. The ordering develops via so-called combined solid state reactions. It is accompanied by grain growth and thermally assisted removal of defects introduced by milling and proceeds rapidly at moderate temperatures by nucleation and growth of the ordered phases with a high degree of the long-range order. In a two-particle interaction model elaborated in the present work, the existence of hysteresis in recoil loops has been shown to arise from insufficient coupling between the low- and the high-anisotropy particles. The model reveals the main features of magnetisation reversal processes observed experimentally in exchange-coupled systems. Neutron diffraction has been used for the investigation of the magnetic structure of ordered and partially ordered nanocrystalline Fe-Pt alloys. (orig.)

  18. Annealing effects of chemically synthesized FePt nanocrystal films

    Science.gov (United States)

    Hyun, Changbae; Lee, Doh C.

    2005-03-01

    Chemically synthesized FePt nanocrystals can exhibit room temperature ferromagnetism after being annealed at temperatures above ˜500^oC[1]. The thermal annealing changes the crystal structure from face-centered cubic to the hard magnetic face-centered tetragonal phase. In thick nanocrystal films, the coercivity can be quite large, however, the coercivity of thin films has been found to decrease significantly with decreasing thickness, even losing the room temperature ferromagnetism in some cases[2]. In order to help determine how the microscopic magnetic structure in these thin films evolves with film thickness, we studied using magnetic force microscopy (MFM), under external applied fields, films consisting of 4 to 15 nanocrystal monolayers. We cast smooth films of 4 nm diameter FePt nanocrystals and annealed them at temperatures ranging from 400 to 650^oC, acquiring MFM images as a function of annealing temperature. Thin FePt films showed lower coercivity than thick films. To help interpret the MFM images, complementary magnetic and structural data was obtained using SQUID magnetometry, x-ray diffraction, and transmission electron microscopy (TEM). [1] S. Sun et al., Science 287, 1989 (2000). [2] G. A. Held et al., Journal of Applied Physics 95, 1481 (2004)

  19. 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.

  20. 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.

  1. Effects of Ag addition on FePt L10 ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

    Science.gov (United States)

    Wang, Lei; Gao, Tenghua; Yu, Youxing

    2015-12-01

    FePt and (FePt)91.2Ag8.8 alloy films were deposited by magnetron sputtering. The average coercivity of (FePt)91.2Ag8.8 films reaches 8.51 × 105 A/m, which is 0.63 × 105 A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L10 ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution reveals more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L10 ordering transition.

  2. 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.

  3. 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

  4. On the advantages of spring magnets compared to pure FePt: Strategy for rare-earth free permanent magnets following a bottom-up approach

    Science.gov (United States)

    Pousthomis, M.; Garnero, C.; Marcelot, C. G.; Blon, T.; Cayez, S.; Cassignol, C.; Du, V. A.; Krispin, M.; Arenal, R.; Soulantica, K.; Viau, G.; Lacroix, L.-M.

    2017-02-01

    Nanostructured magnets benefiting from efficient exchange-coupling between hard and soft grains represent an appealing approach for integrated miniaturized magnetic power sources. Using a bottom-up approach, nanostructured materials were prepared from binary assemblies of bcc FeCo and fcc FePt nanoparticles and compared with pure L10-FePt materials. The use of a bifunctional mercapto benzoic acid yields homogeneous assemblies of the two types of particles while reducing the organic matter amount. The 650 °C thermal annealing, mandatory to allow the L10-FePt phase transition, led to an important interdiffusion and thus decreased drastically the amount of soft phase present in the final composites. The analysis of recoil curves however evidenced the presence of an efficient interphase exchange coupling, which allows obtaining better magnetic performances than pure L10 FePt materials, energy product above 100 kJ m-3 being estimated for a Pt content of only 33%. These results clearly evidenced the interest of chemically grown nanoparticles for the preparation of performant spring-magnets, opening promising perspective for integrated subcentimetric magnets with optimized properties.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer

    Science.gov (United States)

    Dong, K. F.; Deng, J. Y.; Peng, Y. G.; Ju, G.; Chow, G. M.; Chen, J. S.

    2016-09-01

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) //ZrN (001) //TiN (001) among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained.

  10. Perpendicular magnetic anisotropy of Au/FePt thin films grown on Si substrates

    CERN Document Server

    Lee, Y W; Kim, C O

    1999-01-01

    FePt thin films show in plane magnetism with a very large coercive force when they are deposited on lattice-mismatched substrates, such as glass or Si In our research, FePt alloy thin films were deposited, using the coevaporation method, on a Au buffer layer which was evaporated onto a Si substrate at 500 .deg. C. The magnetic easy axis of the FePt film changed from the in-plane direction to the normal direction of the film. Therefore, it can be said that a Au buffer layer can enhance the perpendicular magnetic anisotropy of a FePt thin film on a lattice-mismatched substrate.

  11. Electrodeposited CoPt and FePt alloys nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Cagnon, L. [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France)]. E-mail: laurent.cagnon@grenoble.cnrs.fr; Dahmane, Y. [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Laboratoire de Materiaux, Electrochimie et Corrosion, BP 17, 15000 Tizi-Ouzou (Algeria); Voiron, J. [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Pairis, S. [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Bacia, M. [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Ortega, L. [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Benbrahim, N. [Laboratoire de Materiaux, Electrochimie et Corrosion, BP 17, 15000 Tizi-Ouzou (Algeria); Kadri, A. [Laboratoire de Materiaux, Electrochimie et Corrosion, BP 17, 15000 Tizi-Ouzou (Algeria)

    2007-03-15

    We have investigated CoPt and FePt alloys with the face centered tetragonal phase L10, which present very large magnetocrystalline anisotropy. Equiatomic CoPt nanowires exhibiting large coercive fields up to 1.1 T have been successfully prepared by electrodeposition into nanopores of commercial and home-made alumina membranes from a very simple electrolyte. The as-deposited material has the FCC structure with soft magnetic properties. An annealing treatment at 700 deg. C is crucial to transform this phase into the L1{sub 0} phase, which presents hard magnetic properties. Nanowires of annealed samples consist of small grains around 20 nm, with their c axes randomly distributed. The coercivity does not depend on the morphology and porosity of the two types of membranes but only on the deposited material elaborated with the appropriate thermal annealing process. Our preliminary results with FePt alloy indicate a more complicated system since the as-deposited material shows no magnetization. Magnetism appears only after annealing at 700-750 deg. C. Coercivity up to 0.85 T has been obtained at room temperature but with inhomogeneous phase composition. To achieve a single hard phase L1{sub 0}, it is essential to get for the as-deposited sample the equiatomic composition and then to employ the suitable annealing parameters (temperature and time) to change the whole FCC phase into the FCT ordered L1{sub 0} phase.

  12. 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.

  13. 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).

  14. 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.

  15. Effect of interfacial structures on spin dependent tunneling in epitaxial L1{sub 0}-FePt/MgO/FePt perpendicular magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Yang, G.; Li, D. L.; Wang, S. G., E-mail: Sgwang@iphy.ac.cn; Ma, Q. L.; Liang, S. H.; Wei, H. X.; Han, X. F. [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Hesjedal, T.; Ward, R. C. C. [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Kohn, A.; Elkayam, A.; Tal, N. [Department of Materials Engineering and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Zhang, X.-G. [Department of Physics and Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States); Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6493 (United States)

    2015-02-28

    Epitaxial FePt(001)/MgO/FePt magnetic tunnel junctions with L1{sub 0}-FePt electrodes showing perpendicular magnetic anisotropy were fabricated by molecular beam epitaxial growth. Tunnel magnetoresistance ratios of 21% and 53% were obtained at 300 K and 10 K, respectively. Our previous work, based on transmission electron microscopy, confirmed a semi-coherent interfacial structure with atomic steps (Kohn et al., APL 102, 062403 (2013)). Here, we show by x-ray photoemission spectroscopy and first-principles calculation that the bottom FePt/MgO interface is either Pt-terminated for regular growth or when an Fe layer is inserted at the interface, it is chemically bonded to O. Both these structures have a dominant role in spin dependent tunneling across the MgO barrier resulting in a decrease of the tunneling magnetoresistance ratio compared with previous predictions.

  16. 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.

  17. 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.

  18. Measurement of FePt thermal properties relevant to heat-assisted magnetic recording

    Science.gov (United States)

    Chernyshov, Alex; Treves, David; Le, Thanh; Zong, Fenghua; Ajan, Antony; Acharya, Ramamurthy

    2014-05-01

    Heat-assisted magnetic recording (HAMR) is the likely successor of the conventional perpendicular magnetic recording. Due to its high anisotropy, graded L10 ordered FePt is widely used as a HAMR recording layer. Electrically insulating MgO under-layer is essential for growing FePt in HAMR media. Experimentally, we observe very low thermal conductivity of FePt and significant thermal boundary resistance between FePt and MgO, whose magnitudes affect the HAMR thermal gradient. Realistic granular FePt media has >30% segregation, and, experimentally, we observe that FePt thermal properties are affected by segregation. We utilized time domain thermo-reflectance (TDTR) technique for studying FePt thermal conductivity and boundary resistance in realistic HAMR media stack. 1D finite element heat transport model was used for fitting experimental TDTR data and extracting thermal conductivities and related thermal boundary resistances. We found best fit thermal conductivity value for non-segregated FePt is as low as 13 W/mK. When reasonable amount of segregation (30%) is added, thermal conductivity reduces from 13 W/mK to 6 W/mK, and thermal boundary resistance to MgO reduces from 3.5 × 10-9 m2K/W to 0.7 × 10-9 m2K/W.

  19. NiO spacer mediated magnetic anisotropy in L 10-FePt /NiO /A 1 -FePt trilayer structures

    Science.gov (United States)

    Gao, Tenghua; Harumoto, Takashi; Zhang, Song; Tu, Rong; Zhang, Lianmeng; Nakamura, Yoshio; Shi, Ji

    2017-04-01

    L 10-FePt /NiO /A 1 -FePt trilayers have been grown on MgO(001) substrate, in which the top FePt layer is of A 1 structure, and the bottom FePt layer is of L 10 structure with 001 preferred orientation and strong perpendicular anisotropy. This structure gives rise to a 90∘ spin alignment configuration of the two ferromagnetic layers across the NiO spacer. To further manipulate the spin configurations of the trilayer structure, we performed an in-plane field cooling (FC). The subsequent hysteresis measurements for the top FePt layer show unambiguous angular dependence of remanent magnetization relative to the direction of the field during FC; i.e., in-plane anisotropy is induced. Taking into account the spin-flop configuration predicted in previous theoretical study, the coupling at the lower interface makes the Ni spins cant out of the (1 ¯1 ¯1 ) easy plane, and difficult to rotate around the axis perpendicular to the film plane. Correspondingly, the induced anisotropy after FC is considered to result from the realignment of Ni spins and enhancement of the coupling at the upper interface. The magnetic domain imaging results for the bottom perpendicular magnetized FePt layer strongly support this consideration; some of the stripe domains tend to be along the direction of the applied field during FC with reduced stripe width.

  20. Thermal-vacancy-assisted phase transition in FePt thin films

    Science.gov (United States)

    Li, X. H.; Wang, F. Q.; Liu, B. T.; Guo, D. F.; Zhang, X. Y.

    2011-04-01

    Understanding the ordering transition from A1 to L10 structure in FePt thin films is of great significance for developing L10-FePt films as ultrahigh density magnetic recording media. Here, the L10-ordering transition of FePt films has been investigated based on activation volume measurements. A large activation volume ΔV ∗=10-11 Å3=(0.75-0.8) Ω, where Ω is average atomic volume of FePt, is determined for atomic diffusions in the L10-ordering transition, indicating a thermal-vacancy-assisted phase transition. This transition is suggested to be predominantly dependent on the diffusion of Fe atoms. These findings have direct implications for yielding L10-FePt films at low temperatures and optimizing their microstructures.

  1. Effects of Ru and Ag cap layers on microstructure and magnetic properties of FePt ultrathin films.

    Science.gov (United States)

    Liu, Mingfeng; Jin, Tianli; Hao, Liang; Cao, Jiangwei; Wang, Ying; Wu, Dongping; Bai, Jianmin; Wei, Fulin

    2015-01-01

    The effects of Ru and Ag cap layers on the microstructure and magnetic properties of the FePt ultrathin films have been investigated. The results indicate that i) The Ag cap layer segregates from the FePt/Ag bilayer, lowers the FePt ordering temperature, promotes the FePt thin films to form island structure, and enhances the coercivity; ii) The Ru cap layer increases the FePt ordering temperature, helps to maintain smooth continuous structure film, and restrains the FePt (001) orientation and perpendicular magnetic anisotropy (PMA). The effects become more pronounced for the 3-nm-thick FePt thin films. The effects can be mainly attributed to the different melting point and thermal expansion stress between the cap layer and FePt thin films.

  2. Effects of Ru and Ag cap layers on microstructure and magnetic properties of FePt ultrathin films

    Science.gov (United States)

    Liu, Mingfeng; Jin, Tianli; Hao, Liang; Cao, Jiangwei; Wang, Ying; Wu, Dongping; Bai, Jianmin; Wei, Fulin

    2015-04-01

    The effects of Ru and Ag cap layers on the microstructure and magnetic properties of the FePt ultrathin films have been investigated. The results indicate that i) The Ag cap layer segregates from the FePt/Ag bilayer, lowers the FePt ordering temperature, promotes the FePt thin films to form island structure, and enhances the coercivity; ii) The Ru cap layer increases the FePt ordering temperature, helps to maintain smooth continuous structure film, and restrains the FePt (001) orientation and perpendicular magnetic anisotropy (PMA). The effects become more pronounced for the 3-nm-thick FePt thin films. The effects can be mainly attributed to the different melting point and thermal expansion stress between the cap layer and FePt thin films.

  3. 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.

  4. The structural transition from epitaxial Fe/Pt multilayers to an ordered FePt film using low energy ion beam sputtering deposition with no buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chih-Hao, E-mail: chlee@mx.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Yu-Sheng [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Liu, Li-Jung [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Huang, J.C.A. [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-11-03

    An epitaxial L1{sub 0} FePt thin film grown from an [Fe(10 Å)/Pt(10 Å)]{sub 15} multilayer with the orientation of (001) was prepared by an ion beam sputtering deposition method without buffer layer. From the measurement data of X-ray diffraction and X-ray reflectivity, the multilayer structure was totally disappeared and a uniform FePt alloy thin film was formed at temperatures higher than 600 °C. For the as-deposited thin film grown at 100 °C, the multilayer already possesses an epitaxial structure. The epitaxial relation is FePt(001)[100]//MgO(001)[100] and this epitaxial relation persists after sequential high temperature annealing. An epitaxial L1{sub 0} ordered FePt(001) film with order parameter of 0.95 was obtained when the annealing temperature reached 650 °C. The ordered FePt(001) thin film has a perpendicular magnetic anisotropy with a squareness of 0.95 ± 0.03 on the magnetic hysteresis loop. This experiment demonstrates that the low energy ion beam sputtering deposition will preserve the epitaxial relation with no buffer layer between multilayer and substrate. - Highlights: • The Fe/Pt films using ion sputtering deposition with no buffer layer is epitaxial. • Multilayer structure was totally disappeared at temperatures higher than 600 °C. • Order parameter reach 0.95 after annealing at 650 °C. • Interfacial epitaxial FePt alloy already formed at 100 °C.

  5. 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.

  6. Chemical ordering phenomena in nanostructured FePt: Monte Carlo simulations.

    Science.gov (United States)

    Brodacka, S; Kozlowski, M; Kozubski, R; Goyhenex, Ch; Murch, G E

    2015-11-14

    Free-surface-induced L10 chemical long-range ordering phenomena in a nanolayer, a nanowire and a cubic nanoparticle of FePt were studied by means of Monte Carlo simulations. The system was modeled with nearest-neighbor and next-nearest-neighbor interatomic pair interactions deduced from ab initio calculations. The generated samples, the dimensionality of which was determined by appropriate periodic boundary conditions imposed upon the generated supercells, were initially either perfectly ordered in the c-variant L10 superstructure ((001)-oriented monatomic planes), or completely disordered in the fcc crystalline structure. Vacancy-mediated creation of equilibrium atomic configurations was modelled by relaxing the systems at temperatures below the 'order-disorder' transition point using the Glauber algorithm implemented with the vacancy mechanism of atomic migration. The (100)-type-surface-induced heterogeneous nucleation of L10-order domains was observed and quantified by means of an original parameterization enabling selective determination of volume fractions of particular L10-variants. Due to the specific competition between the three kinds of (100)-type free surfaces, the initial c-L10 variant long-range order appeared to be the most stable in the cubic nanoparticle. The initially disordered samples were transformed by the creation of a specific L10 domain structure with a mosaic of particular L10-variant domains at the surfaces and almost homogeneous long-range order in the inner volume. The analysis of correlation effects revealed that chemical ordering was initiated at the free surfaces.

  7. 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.

  8. 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).

  9. Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    Xiaoli Li; Fang Wang; Fengxian Jiang; Xiaohong Xu; Haishun Wu

    2008-01-01

    FePt (50 rim) and [FePt(a nm)/MgO(b nm)]5/glass (a=1, 2, 3; b=1, 2, 3)films Were prepared by radio frequency (RF) magnetron sputtering technique, and then were annealed at 600℃ for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of (001) texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak inter- grain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanos- tructured films are promising candidates for future high-density perpendicular recording media. C 2008 University of Science and Technology Beijing. All fights reserved.

  10. Perpendicular Magnetization Behavior of Low- Temperature Ordered FePt Films with Insertion of Ag Nanolayers

    Directory of Open Access Journals (Sweden)

    Da-Hua Wei

    2016-03-01

    Full Text Available FePt-Ag nanocomposite films with large perpendicular magnetic anisotropy have been fabricated by alternate-atomic-layer electron beam evaporation onto MgO(100 substrates at the low temperature of 300 °C. Their magnetization behavior and microstructure have been studied. The surface topography was observed and varied from continuous to nanogranular microstructures with insertion of Ag nanolayers into Fe/Pt bilayer films. The measurement of angular-dependent coercivity showed a tendency of the domain-wall motion as a typical peak behavior shift toward more like a coherent Stoner-Wohlfarth rotation type with the insertion of Ag nanolayers into the FePt films. On the other hand, the inter-grain interaction was determined from a Kelly-Henkel plot. The FePt film without insertion of Ag nanolayers has a positive δM, indicating strong exchange coupling between neighboring grains, whereas the FePt film with insertion of Ag nanolayers has a negative δM, indicating that inter-grain exchange coupling is weaker, thus leading to the presence of dipole interaction in the FePt–Ag nanogranular films. The magnetic characteristic measurements confirmed that the perpendicular magnetization reversal behavior and related surface morphology of low-temperature-ordered FePt(001 nanogranular films can be systematically controlled by the insertion of Ag nanolayers into the FePt system for next generation magnetic storage medium applications.

  11. Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

    Institute of Scientific and Technical Information of China (English)

    Javad Hosseini; Mehdi Abdolmaleki; Hamid Reza Pouretedal; Mohammad Hossein Keshavarz

    2015-01-01

    An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.

  12. Magnetic properties and microstructure of FePt/MoC/CrRu films

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Jai-Lin, E-mail: tsaijl@dragon.nchu.edu.tw; Luo, Qi-Shao; Chen, Po-Ran; Tseng, Yun-Ting

    2015-05-15

    The FePt films with thickness of 4−10 nm were deposited on MoC/CrRu/glass at substrate temperature ranged from 260 to 410 °C by using magnetron sputtering and strong (001) textured FePt films were obtained at 380 °C and 410 °C. The multi-functional MoC conductive intermediate layer was used to resist the Cr diffusion and promote the epitaxial growth of the (001) textured FePt film which shows perpendicular magnetization and a linear-like in-plane magnetic loop. The out-of plane coercivity and shape of demagnetization curve were dominated by the ordering degree and perpendicular magnetic anisotropy which were increased with deposited temperature. The FePt film deposited at 290 °C shows continuous morphology and change to interconnected structure at 350 °C and finally form the island like structure at 380 °C and 410 °C. Each island contains many FePt grains and the smaller grains size was 12.2 nm which obtained at 5 nm thick FePt film. Perpendicular anisotropy of 1.1×10{sup 7} erg/cm{sup 3} and coercivity of 8.2 kOe have been demonstrated in 7 nm thick FePt film. - Highlights: • The MoC conductive intermediate layer was resisted the Cr diffusion. • The MoC layer promote the epitaxial growth of (001) textured FePt film. • The FePt film shows perpendicular magnetization on MoC layer.

  13. 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.

  14. Study on micro-structure and morphological evolution of Fe/Pt nano-magnetic film.

    Science.gov (United States)

    Ishiguro, S; Ju, D Y; Ogatsu, R; Nakano, T

    2011-10-01

    One of the vertical magnetic recordings medium materials of the hard disk drive (HDD) is a Fe/Pt thin film. The development of ultra-high density magnetic recording medium in next generation is expected the magnetic disks such as HDD with capacity enlargement of the data. In order to study effectiveness of the proposed sputtering method, we evaluated micro structure, magnetic and the mechanical properties of a Fe/Pt thin film by some sputtering process conditions. From research results, effect sputtering conditions on micro-structure and mechanical properties of Fe/Pt nano film are verified.

  15. 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+.

  16. 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.

  17. 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.

  18. Tuning morphology and magnetism in epitaxial L10 -FePt films

    Directory of Open Access Journals (Sweden)

    Morellón L.

    2013-01-01

    Full Text Available In this work, well-ordered epitaxial FePt thin films have been grown by RF sputtering on two different substrates (MgO (100 and SrTiO3 (100 and the effect of different lattice parameters between the substrate and FePt film on morphology and magnetic behavior has been considered. Growth conditions have been optimized to obtain different morphologies and magnetic behaviors.

  19. Tuning morphology and magnetism in epitaxial L10 -FePt films

    Science.gov (United States)

    Lupo, P.; Orna, J.; Casoli, F.; Nasi, L.; Ranzieri, P.; Calestani, D.; Algarabel, P.; Morellón, L.; Albertini, F.

    2013-01-01

    In this work, well-ordered epitaxial FePt thin films have been grown by RF sputtering on two different substrates (MgO (100) and SrTiO3 (100)) and the effect of different lattice parameters between the substrate and FePt film on morphology and magnetic behavior has been considered. Growth conditions have been optimized to obtain different morphologies and magnetic behaviors.

  20. 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.

  1. 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.

  2. Microstructures and magnetic properties of [SiO2/FePt]5/Ag thin films

    Institute of Scientific and Technical Information of China (English)

    FAN Jiu-ping; XU Xiao-hong; JIANG Feng-xian; TIAN Bao-qiang; WU Hai-shun

    2008-01-01

    [SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied to study the magnetic properties and microstructures of the films. The results show that without Ag underlayer [SiO2/FePt]5 films deposited onto the glass are FCC disordered; with the addition of Ag underlayer [SiO2/FePt]5/Ag films are changed into L10 and (111) mixed texture. The variation of the SiO2 nonmagnetic layer thickness in [SiO2/FePt]5/Ag films indicates that SiO2-doping plays an important role in improving the order parameter and the perpendicular magnetic anisotropy, and reducing the grain size and intergrain interactions. By controllingSiO2 thickness the highly perpendicular magnetic anisotropy can be obtained in the [SiO2 (0. 6nm)/FePt (3 nm)]5/Ag (50 nm) films and highly (001)-oriented films can be obtained in the [SiO2 (2 nm)/FePt (3 nm)]5/Ag (50 nm) films.

  3. 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.

  4. Thickness limit in perpendicular magnetic anisotropy L1{sub 0} FePt(0 0 1) thin film

    Energy Technology Data Exchange (ETDEWEB)

    Sun, A.-C. [Department of Physics and Center for Nanostorage Research, National Taiwan University, Taipei 106, Taiwan (China); Hsu, J.-H. [Department of Physics and Center for Nanostorage Research, National Taiwan University, Taipei 106, Taiwan (China)]. E-mail: jhhsu@phys.ntu.edu.tw; Kuo, P.C. [Institute of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China); Huang, H.L. [Department of Physics and Center for Nanostorage Research, National Taiwan University, Taipei 106, Taiwan (China); Lu, H.C. [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Wang, S.F. [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China)

    2007-03-15

    Perpendicular magnetic anisotropy L1{sub 0} FePt (0 0 1) films with various thicknesses were prepared onto Pt(0 0 1)/Cr(0 0 2) bilayers. When the thickness of FePt layer was smaller than 30 nm, a single orientation of L1{sub 0} FePt(0 0 1) texture was present, confirming that the easy axis was perpendicular to the film plane. But as the thickness increased over 30 nm along with the L1{sub 0} FePt(0 0 1) orientation, the peak corresponding to L1{sub 0} FePt (1 1 1) orientation was also observed, which indicated the quality degradation of perpendicular magnetic anisotropy. From our study, the critical thickness for growing perfect L1{sub 0} FePt(0 0 1) single orientation is around 30 nm.

  5. Growth, structure and magnetic properties of magnetron sputtered FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Cantelli, Valentina

    2010-07-01

    The L1{sub 0} FePt phase belongs to the most promising hard ferromagnetic materials for high density recording media. The main challenges for thin FePt films are: (i) to lower the process temperature for the transition from the soft magnetic A1 to the hard magnetic L1{sub 0} phase, (ii) to realize c-axes preferential oriented layers independently from the substrate nature and (iii) to control layer morphology supporting the formation of FePt-L1{sub 0} selforganized isolated nanoislands towards an increase of the signal-to-noise ratio. In this study, dc magnetron sputtered FePt thin films on amorphous substrates were investigated. The work is focused on the correlation between structural and magnetic properties with respect to the influence of deposition parameters like growth mode (cosputtering vs. layer - by - layer) and the variation of the deposition gas (Ar, Xe) or pressure (0.3-3 Pa). In low-pressure Ar discharges, high energetic particle impacts support vacancies formation during layer growth lowering the phase transition temperature to (320{+-}20) C. By reducing the particle kinetic energy in Xe discharges, highly (001) preferential oriented L1{sub 0}-FePt films were obtained on a-SiO{sub 2} after vacuum annealing. L1{sub 0}-FePt nano-island formation was supported by the introduction of an Ag matrix, or by random ballistic aggregation and atomic self shadowing realized by FePt depositions at very high pressure (3 Pa). The high coercivity (1.5 T) of granular, magnetic isotropic FePt layers, deposited in Ar discharges, was measured with SQUID magnetometer hysteresis loops. For non-granular films with (001) preferential orientation the coercivity decreased (0.6 T) together with an enhancement of the out-of- plane anisotropy. Nanoislands show a coercive field close to the values obtained for granular layers but exhibit an in-plane easy axis due to shape anisotropy effects. An extensive study with different synchrotron X-ray scattering techniques, mainly

  6. Laser-assisted atom probe tomography investigation of magnetic FePt nanoclusters: First experiments

    Energy Technology Data Exchange (ETDEWEB)

    Folcke, E.; Larde, R. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Le Breton, J.M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Gruber, M.; Vurpillot, F. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Shield, J.E.; Rui, X. [Department of Mechanical and Materials Engineering, Nebraska Center for Materials and Nanoscience, University of Nebraska, N104 WSEC, Lincoln, NE 68588 (United States); Patterson, M.M. [Department of Physics, University of Wisconsin-Stout, Menomonie, WI 54751 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer FePt nanoclusters dispersed in a Cr matrix were studied by atom probe tomography. Black-Right-Pointing-Pointer Simulated experiments were conducted to study the artefacts of the analysis. Black-Right-Pointing-Pointer In FePt nanoclusters, Fe and Pt are present in equiatomic proportions. Black-Right-Pointing-Pointer FePt nanoclusters are homogeneous, no core-shell structure is observed. - Abstract: FePt nanoclusters dispersed in a Cr matrix have been investigated by laser-assisted atom probe tomography. The results were analysed according to simulated evaporation experiments. Three-dimensional (3D) reconstructions reveal the presence of nanoclusters roughly spherical in shape, with a size in good agreement with previous transmission electron microscopy observations. Some clusters appear to be broken up after the evaporation process due to the fact that the Cr matrix has a lower evaporation field than Fe and Pt. It is thus shown that the observed FePt nanoclusters are chemically homogeneous. They contain Fe and Pt in equiatomic proportions, with no core-shell structure observed.

  7. Ledge-type Co/L10-FePt exchange-coupled composites

    Science.gov (United States)

    Speliotis, Th.; Giannopoulos, G.; Niarchos, D.; Li, W. F.; Hadjipanayis, G.; Barucca, G.; Agostinelli, E.; Laureti, S.; Peddis, D.; Testa, A. M.; Varvaro, G.

    2016-06-01

    FePt-based exchange-coupled composites consisting of a magnetically hard L10-FePt phase exchange-coupled with a soft ferromagnetic material are promising candidates for future ultra-high density (>1 Tbit/in2) perpendicular magnetic recording media, also being of interest for other applications including spin torque oscillators and micro-electro-mechanical systems, among others. In this paper, the effect of the thickness of a soft Co layer (3 composites deposited on an MgO (100) substrate is systematically studied by combining morpho-structural analyses and angular magnetization measurements. Starting from a film consisting of isolated L10(001)-FePt islands, the ledge-type structure was obtained by depositing a Co layer that either covered the FePt islands or filled-up the inter-island region, gradually forming a continuous layer with increasing Co thickness. A perpendicular anisotropy was maintained up to thCo ˜ 9.5 nm and a significant reduction in the coercivity (about 50% for thCo ˜ 3 nm) with the increase in thCo was observed, indicating that, by coupling hard FePt and soft Co phases in a ledge-type configuration, the writability can be greatly improved. Recoil loops' measurements confirmed the exchange-coupled behavior, reinforcing a potential interest in these systems for future magnetic recording media.

  8. Microstructure and magnetic properties of sputtered Fe-Pt thin films

    CERN Document Server

    Mahalingam, T; Chen, J H; Wang, S F; Inoue, K

    2003-01-01

    The characterization of rf magnetron-sputtered Fe-Pt thin films at various compositions (Pt = 15, 24, 46 and 78 at%) is reported. X-ray diffraction studies on annealed Fe-46%Pt thin films at 600 deg C revealed an ordered L1 sub 0 gamma sub 2 -FePt phase with fct structure whereas annealed Fe-24%Pt and Fe-78%Pt films exhibited ordered gamma sub 1 -Fe sub 3 Pt and gamma sub 3 -FePt sub 3 phases, respectively. The effects of argon quenching and rapid thermal annealing (RTA) on the structural and magnetic properties are investigated. When the films are annealed at 600 deg C for 1 h and then quenched to room temperature in argon gas, ordered gamma sub 2 -FePt with L1 sub 0 phase is obtained. Argon-quenched and rapid thermal annealed films exhibit microtwins in scanning electron microscopy analysis. The appearance of microtwins may be attributed to the planar defects developed in the FePt films due to the release of elastic strain during annealing. The saturation magnetization is found to increase with ferrous cont...

  9. High Temperature Magnetic Properties of Indirect Exchange Spring FePt/M(Cu,C/Fe Trilayer Thin Films

    Directory of Open Access Journals (Sweden)

    Anabil Gayen

    2013-01-01

    Full Text Available We report the investigation of temperature dependent magnetic properties of FePt and FePt(30/M(Cu,C/Fe(5 trilayer thin films prepared by using magnetron sputtering technique at ambient temperature and postannealed at different temperatures. L10 ordering, hard magnetic properties, and thermal stability of FePt films are improved with increasing postannealing temperature. In FePt/M/Fe trilayer, the formation of interlayer exchange coupling between magnetic layers depends on interlayer materials and interface morphology. In FePt/C/Fe trilayer, when the C interlayer thickness was about 0.5 nm, a strong interlayer exchange coupling between hard and soft layers was achieved, and saturation magnetization was enhanced considerably after using interlayer exchange coupling with Fe. In addition, incoherent magnetization reversal process observed in FePt/Fe films changes into coherent switching process in FePt/C/Fe films giving rise to a single hysteresis loop. High temperature magnetic studies up to 573 K reveal that the effective reduction in the coercivity decreases largely from 34 Oe/K for FePt/Fe film to 13 Oe/K for FePt/C(0.5/Fe film demonstrating that the interlayer exchange coupling seems to be a promising approach to improve the stability of hard magnetic properties at high temperatures, which is suitable for high-performance magnets and thermally assisted magnetic recording media.

  10. Nonepitaxial growth of a (001) textured L10 Fe-Pt film in H2 and N2 annealing atmospheres

    Institute of Scientific and Technical Information of China (English)

    WU Peiwen; HU Xuerang; QIAN Jun; YUAN Jun

    2006-01-01

    A nonepitaxial (001) textured Fe-Pt alloyed film was obtained by annealing Fe/Pt multilayers in H2. No such nonepitaxial (001) texture was observed for similar multilayers annealed in N2 atmosphere. Sensitive electron energy loss spectroscopy and the left shift of the L10 FePt (111) diffraction peak indicate oxidation in the N2 annealed samples. The oxidation dramatically degrades the (001) texture of the Fe-Pt film and induces the composition change in the alloyed layer.The relation between the texture formation and oxidation was discussed.

  11. 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.

  12. Structural transformation of FePt nanocomposite films during annealing and its effects on magnetic properties

    Institute of Scientific and Technical Information of China (English)

    ZHAN Xiaoyuan; ZHANG Yue; GU Yousong; LI Jianmin

    2006-01-01

    Fe100-xPtx(x=30at.%-60at.% ) nanocomposite films were deposited on natural-oxidized Si(100) substrates by magnetron sputtering. The as-deposited films were annealed between 373 and 1073 K. In situ X-ray diffraction shows that the FePt nanocomposite films undergo a phase transformation from a disordered FCC phase to an ordered L10 phase between 673 and 773 K. The coercivity is 306 kA·m-1 whiles the average grain sizes is about 10 nm in the optimized FePt alloy film sample annealed at 673K. The adjustable coercivity and fine grain size suggest that this FePt nanocomposites system is suitable as recording media at extremely high areal density.

  13. The influence of interface exchange coupling on the demagnetization process for perpendicularly oriented FePt/α-Fe/FePt trilayers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The influence of the interface exchange coupling on the magnetization reversal process for a FePt/α-Fe/FePt tri-layer structure has been studied through a micromagnetic approach.The analytical formula of the nucleation field has been derived.It is found that the nucleation field increases as the interface coupling constant rises.Especially when the thickness of the soft layer is small,the influence of the exchange coupling on the nucleation field is significant.The angular distributions of the magnetization for various exchange coupling constants have been obtained by numerical calculation.It is found that the angular distribution of the magnetization is discontinuous at the interface of the hard and soft layers.In the meantime,the pinning field decreases with the increase of the thickness of the soft layer and the exchange coupling constant.

  14. FePt magnetic particles prepared by surfactant-assisted ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Velasco, V., E-mail: vvjimeno@fis.ucm.es [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, P.O. Box 155, Las Rozas 28230 (Spain); Departamento de Física de Materiales, Universidad Complutense de Madrid, Madrid 28040 (Spain); Hernando, A.; Crespo, P. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, P.O. Box 155, Las Rozas 28230 (Spain); Departamento de Física de Materiales, Universidad Complutense de Madrid, Madrid 28040 (Spain)

    2013-10-15

    High-energy ball milling of Fe and Pt elemental powders has been carried out under dry and wet (in presence of solvent and surfactants) conditions. Dry milling leads to the formation of the disordered FCC-FePt alloy whereas by the wet milling procedure the main process is the decrease of Fe and Pt particle size, although some dissolution of Pt into Fe grains cannot be ruled out, and no hint of the formation of the FCC-FePt phase is observed even to milling times up to 20 h, as X-ray diffraction, electron microscopy and Mössbauer spectroscopy indicates. The as-milled particles were annealed at 600 °C for 2 h under Ar atmosphere. It is noticed that the disordered fcc-FePt phase observed in particles milled under dry conditions transform to ordered fct phase characterized by a hard magnetic behavior with a coercive field up to 10,000 Oe. However, those particles milled in the surfactant/solvent medium exhibit a soft magnetic behavior with a coercive field of 600 Oe. These results indicate that wet high-energy ball milling is not an adequate technique for obtaining single-phase FePt particles. - Highlights: • FePt particles have been obtained by high-energy ball milling. • In the presence of surfactants and solvents, almost no alloying process takes place. • After annealing, the coercive field of the FePt alloy particles increases from 150 Oe to 10,000 Oe.

  15. 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.

  16. Magnetic properties of soft layer/FePt-MgO exchange coupled composite Perpendicular recording media

    Institute of Scientific and Technical Information of China (English)

    Yin Jin-Hua; Takao Suzuki; Pan Li-Qing

    2008-01-01

    The magnetic properties of exchange coupled composite(ECC)media that are composed of perpendicular magnetic recording media FePt-MgO and two kinds of soft layers have been studied by using an x-ray diffractometer,a polar Kerr magneto-optical system(PMOKE)and a vibrating sample magnetometer(VSM).The results show that ECC media can reduce the coercivities of perpendicular magnetic recording media FePt-MgO.The ECC media with granular-type soft layers have weaker exchange couplings between magnetic grains and the magnetization process,for ECC media of this kind mainly follow the Stoner-Wohlfarth model.

  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. Effects of Ag addition on FePt L1{sub 0} ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lei; Yu, Youxing, E-mail: yuyouxing@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Gao, Tenghua [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, Oh-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2015-12-21

    FePt and (FePt){sub 91.2}Ag{sub 8.8} alloy films were deposited by magnetron sputtering. The average coercivity of (FePt){sub 91.2}Ag{sub 8.8} films reaches 8.51 × 10{sup 5} A/m, which is 0.63 × 10{sup 5} A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L1{sub 0} ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution reveals more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L1{sub 0} ordering transition.

  20. 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

  1. Reduction of Ordering Temperature of FePt Al2O3 Thin Films by N2 Addition During Sputtering

    Science.gov (United States)

    Cao, Jiang-Wei; Katayama, N.; Yang, Zheng; Wei, Fu-Lin; Matsumoto, M.; Morisako, A.; Liu, Xiao-Xi; Takei, S.

    2005-11-01

    We investigate the effect of N2 addition during sputtering on the microstructure and magnetic properties of FePt-Al2O3 thin films. The texture of FePt phase in FePt-Al2O3 thin films changes from (111) to a more random orientation by N2 addition during sputtering. The ordering temperature of FePt phase reduces about 100°C with appropriate N2 partial pressure. A larger coercivity of 6.0×105 A/m is obtained with N2 partial pressure about 15%. Structural analysis reveals that a small quantity of Fe3N phase forms during sputtering and the release of N atoms during the post annealing induces a large number of vacancies in the films, which benefits to the transformation of FePt phase from fcc to fct.

  2. Study of perpendicular anisotropy L1{sub 0}-FePt pseudo spin valves using a micromagnetic trilayer model

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Pin, E-mail: hopin@mit.edu [Department of Materials Science and Engineering, National University of Singapore, 117576 Singapore (Singapore); Data Storage Institute, Agency of Science, Technology and Research - A*STAR, 117608 Singapore (Singapore); Evans, Richard F. L.; Chantrell, Roy W. [Department of Physics, University of York, York YO10 5DD (United Kingdom); Han, Guchang [Data Storage Institute, Agency of Science, Technology and Research - A*STAR, 117608 Singapore (Singapore); Chow, Gan-Moog; Chen, Jingsheng [Department of Materials Science and Engineering, National University of Singapore, 117576 Singapore (Singapore)

    2015-06-07

    A trilayer micromagnetic model based on the Landau-Lifshitz-Bloch equation of motion is utilized to study the properties of L1{sub 0}-FePt/TiN/L1{sub 0}-FePt pseudo spin valves (PSVs) in direct comparison with experiment. Theoretical studies give an insight on the crystallographic texture, magnetic properties, reversal behavior, interlayer coupling effects, and magneto-transport properties of the PSVs, in particular, with varying thickness of the top L1{sub 0}-FePt and TiN spacer. We show that morphological changes in the FePt layers, induced by varying the FePt layer thickness, lead to different hysteresis behaviors of the samples, caused by changes in the interlayer and intralayer exchange couplings. Such effects are important for the optimization of the PSVs due to the relationship between the magnetic properties, domain structures, and the magnetoresistance of the device.

  3. Effect of a Boron Underlayer on the Ordering and Orientation of Sputtered FePt Film

    Institute of Scientific and Technical Information of China (English)

    LI Yong-Le; HUANG An-Ping; FENG Tang-Fu; CHEN Qiang; SHU Xiao-Lin; CHEN Jun-Yang; CHEN Zi-Yu

    2011-01-01

    @@ FePt multilayer films with a boron underlayer are prepared on Si (100) substrates using magnetron sputtering and vacuum annealing is carried out to obtain the hard magnetic Llo phase.According to the microstructural and magnetic measurement results, the ordering of the FePt films is facilitated at low annealing temperatures while it is blocked at high ones by introducing boron.Moreover, (001) orientation of the samples is obviously improved by inserting a boron underlayer, which is further confirmed by the MFM analysis.The relevant mechanism is discussed by considering the diffusion of boron atoms and the consequential in-plane tensile stress.%FePt multilayer Sims with a boron underlayer are prepared on Si (100) substrates using magnetron sputtering and vacuum annealing is carried out to obtain the hard magnetic Llo phase. According to the microstructural and magnetic measurement results, the ordering of the FePt 61ms is facilitated at low annealing temperatures while it is blocked at high ones by introducing boron. Moreover, (001) orientation of the samples is obviously improved by inserting a boron underlayer, which is further confirmed by the MFM analysis. The relevant mechanism is discussed by considering the diffusion of boron atoms and the consequential in-plane tensile stress.

  4. Nitriding-induced texture, ordering and coercivity enhancement in FePtAgB nanocomposite magnets

    Science.gov (United States)

    Crisan, O.; Vasiliu, F.; Palade, P.; Mercioniu, I.

    2016-03-01

    FePt system attracts currently a great deal of interest for applications as future RE free permanent magnets. Among the key issues to be solved one may count the decreasing of the ordering temperature and improvement of magnetic behavior. For that purpose we have studied the effect of a nitriding post-synthesis procedure on the FePtAgB melt spun ribbons, aimed at refining the microstructure and enhancing the magnetic performances. Deep structural characterization by transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction allowed us to observe the morphology and to correctly assign and identify the nature of the main granular phases observed. Nitriding procedure is shown to strongly enhance the (001) texturing and the degree of ordering of the L10 FePt phase, as well as largely increase of coercivity, compared to the as-cast state. These changes are interpreted in terms of Ag segregation towards intergranular region associated to N diffusion and creation of vacancies that favor consistently the process of ordering the FePt grains into the L10 tetragonal phase.

  5. Magnetron sputtering deposition of [FePt/Ag]n multilayers for perpendicular recording

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    [FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions (n) on the structure and magnetic properties of the multilayers were investigated. It was found that the difference between in-plane and out-of-plane coercivities varied with an increase of inserted Ag layer thickness in the [FePt 2 nm/Ag x nm]10 multilayers. The ratio of out-of-plane coercivity to in-plane coercivity reached the maximum value with the Ag layer thickness of 5 nm, indicating that the Ag layer thickness plays an important role in obtaining perpendicular orientation. For the [FePt 2 nm/Ag 5 nm]n multilayers, perpendicular orientation is also influenced by n. The maximum value of the ratio of out-of-plane coercivity to in-plane coercivity appeared when n was given as 8. It was found that the [FePt 2 nm/Ag 5 nm]8 had a high perpendicular coercivity of 520 kA/m and a low in-plane one of 88 kA/m, which shows a strong perpendicular anisotropy.

  6. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

    Directory of Open Access Journals (Sweden)

    Chun Dong

    2011-01-01

    Full Text Available Abstract A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe and high magnetization (900–1,000 emu/cm3 characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  7. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer.

    Science.gov (United States)

    Kim, Hyunsu; Noh, Jin-Seo; Roh, Jong Wook; Chun, Dong Won; Kim, Sungman; Jung, Sang Hyun; Kang, Ho Kwan; Jeong, Won Yong; Lee, Wooyoung

    2011-12-01

    A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900-1,000 emu/cm(3)) characteristic of L 10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  8. Perpendicular magnetic anisotropy of FePt film on Si substrate with SiO{sub 2} underlayer and B{sub 4}C interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H. [Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China)], E-mail: nanoguy@126.com; Yang, F.J. [Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China)], E-mail: yangfujun77@sina.com; Mo, Q.; Zhang, J.; Wang, H.B.; Wang, Y. [Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China)

    2009-09-15

    FePt multilayer composite films with and without B{sub 4}C interlayer have been prepared by magnetron sputtering, respectively, and subsequent annealing in vacuum. It was found that the B{sub 4}C layers effectively serve as spacers to separate the FePt layers, enhancing (0 0 1) orientation of FePt alloy. Our results show that highly (0 0 1) oriented FePt/B{sub 4}C films have significant potential as perpendicular recording media.

  9. Exchange coupled composite FePt/TbCo/[Co/Ni]N films with an TbCo interlayer

    Directory of Open Access Journals (Sweden)

    Bin Ma

    2017-05-01

    Full Text Available The exchange coupled composite FePt/TbCo/[Co/Ni]N films have been prepared by DC magnetron sputtering. The net magnetization of ferromagnetic TbCo changes with the temperature variation, and then the magnetic configuration of FePt/TbCo/[Co/Ni]N changes. When a RE-dominated Tb32Co68 is inserted, FePt/Tb32Co68/[Co/Ni]5 has high coercivity at room temperature because of its synthesis ferrimagnetic sandwich structure, but small coercivity is obtained when the temperature is higher than 200 °C because of its graded ECC structure.

  10. 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.

  11. Dependence of grain sizes and microstrains on annealing temperature in Fe/Pt multilayers and L1{sub 0} FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zotov, Nikolay [Institute for Materials, Ruhr-University Bochum, 44780 Bochum (Germany)], E-mail: Nikolay.Zotov@ruhr-uni-bochum.de; Feydt, Juergen [Forschungszentrum Caesar, Ludwig-Erhard-Allee 2, 53175 Bonn (Germany); Ludwig, Alfred [Institute for Materials, Ruhr-University Bochum, 44780 Bochum (Germany)

    2008-11-28

    Fe/Pt multilayers (MLs) with an overall composition Fe{sub 52}Pt{sub 48}, deposited by magnetron sputtering on thermally oxidized Si wafer substrates, were post annealed in vacuum at various temperatures (T{sub A}) in the range 573-973 K. The MLs transform directly and completely into polycrystalline hard-magnetic FePt thin films with ordered L1{sub 0} structure above T{sub A} = 573 K. The evolution of the microstructure, the order parameter and the stacking fault density with annealing temperature was investigated by ex-situ X-ray diffraction and line-broadening analysis. The average microstrains of the thin films are relatively small ( {approx} 0.2%) and remain practically constant as a function of T{sub A}. The thin films show anisotropic size-broadening and grain growth: fast growth rate along the [221] direction and a slow growth rate along the [001] direction. The annealing temperature dependence of the average grain size could be described by a grain growth model with grain growth exponent n = 3 {+-} 0.5 and activation energy 0.51 {+-} 0.07 eV.

  12. Structural and Magnetic Properties of FePt-C Nanocomposite Films

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; YANG Fu-Jun; CHEN Kan-Song; ZHOU Bin; ZHANG Yuan-Wei; GU Hao-Shuang; CHIAH M. F.; CHEUNG W. Y.; WONG S. P.

    2004-01-01

    @@ Nanocomposite FePt-C thin films were prepared by a pulsed filtered vacuum arc deposition technique. The films were characterized by non-Rutherford backscattering spectrometry, x-ray diffraction, and magnetic force microscopy. The dependence of magnetic properties against annealing temperature was studied by using a vibrating sample magnetometer. Both x-ray diffraction and magnetic force microscopy analyses confirmed the formation of nano-crystallites of face-centred-tetragonal phase of FePt in the carbon matrix after annealing at a sufficiently high temperature. For the film with a composition of (Fe0.55Pt0.45)0.78C0.22, the coercivity and the grain size were observed to increase with increasing annealing temperature, up to a value of 3.5 kOe at an annealing temperature of 650℃, and with a grain size about 10. 5 nm.

  13. Magnetic moments in chemically ordered mass-selected CoPt and FePt clusters

    Energy Technology Data Exchange (ETDEWEB)

    Dupuis, V., E-mail: Veronique.Dupuis@univ-lyon1.fr [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex (France); Khadra, G.; Linas, S.; Hillion, A. [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex (France); Gragnaniello, L. [Institute of Condensed Matter Physics, EPFL, CH-1015 Lausanne (Switzerland); Tamion, A.; Tuaillon-Combes, J.; Bardotti, L.; Tournus, F. [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex (France); Otero, E.; Ohresser, P. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, F-91192 Gif-sur-Yvette Cedex (France); Rogalev, A.; Wilhelm, F. [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex (France)

    2015-06-01

    By combining high photon flux and chemical selectivity, X-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) have been used to study the magnetism of CoPt and FePt clusters before and after their transition to the chemically ordered L1{sub 0}-like phase. Compared to the bulk, we find larger magnetic spin and orbital moments of Fe, Co and Pt atoms in nanoalloys. - Highlights: • Study of magnetism on well-defined CoPt and FePt clusters embedded in carbon matrix • X-ray magnetic circular dichroism (XMCD) at each specific Fe, Co and Pt edges, before and after annealing to induce transition to the chemically L1{sub 0}-like phase. • Quantitative values of the spin and orbital magnetic moments of Co (resp. Fe) and Pt after the chemical ordering transition. • Specific nanoalloy effects.

  14. FePt films on self-assembled SiO2 particle arrays

    Science.gov (United States)

    Makarov, D.; Brombacher, C.; Liscio, F.; Maret, M.; Parlinska, M.; Meier, S.; Kappenberger, P.; Albrecht, M.

    2008-03-01

    Chemically L10 ordered (001) textured FePt thin films with perpendicular magnetic anisotropy can be grown on amorphous planar SiO2 substrate with an underlayer stack of [Pt (3nm )/Cr (50nm)] adopting a [002] orientation when deposited at 350°C. This knowledge of optimum layer stack was transferred to self-assembled SiO2 particle arrays. While 330nm SiO2 particle arrays reveal perpendicular magnetic anisotropy with a remanence of almost one and a coercivity of 370mT, on 160nm particles, the FePt caps show a (111) texturing, leading to the random orientation of the easy axis of the magnetization.

  15. Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Attane, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigne, C.

    2001-08-06

    Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (K{sub u}=5 x 10{sup 6}Jm{sup -3}) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 <112> partial dislocations along {l_brace}111{r_brace} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation. {copyright} 2001 American Institute of Physics.

  16. Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films

    Science.gov (United States)

    Attané, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigné, C.

    2001-08-01

    Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (Ku=5×106J m-3) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 partial dislocations along {111} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation.

  17. Structure and magnetic properties of vacuum an-nealed FePt/Ag nano-multilayers

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    (FePt/Ag)n nano-multilayers were deposited on MgO(100) single crystal with laser ablation and then subjected to annealing. FePt L10 grains with (001) texture and a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for improving the (111) preferential orientation and decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to an activation volume as small as 6×10?25 m3, showing the promising perspective of being the recording medium for future high density perpendicular recording.

  18. Composition and size dependence of magnetic properties of FePt/Fe exchange-spring films

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yu; Zhang, Zhe; Duan, Nian; Wang, Jiawei; Chen, Yuang; Tong, Bei; Yang, Xiaofei; Zhang, Yue, E-mail: yue-zhang@mail.hust.edu.cn

    2014-12-15

    The composition and size dependence of the magnetic properties of FePt/Fe exchange-spring bilayer films was studied using micromagnetic simulation. Based on the simulated hysteresis loops for composite layers with an identical thickness of 20 nm and different composition ratios, it can be observed that when the thickness ratio of Fe is 10%, an exchange-spring effect with a negative nucleation field appears; the switching field is greatly reduced compared to the rigid magnetic FePt, and the squareness ratio reaches its maximum value. When the thickness ratio of Fe is 25% and more, the nucleation fields become positive; meanwhile, the coercivity is smaller than the switching field, and the squareness ratio decreases because of the increase in the thickness of the Fe film. In addition, at a fixed thickness ratio and total volume, the switching field of the FePt/Fe bilayer films is further reduced, accompanied by a decrease in the squareness ratio due to an increase in the thickness of the Fe layer. - Highlights: • Exchange-spring behavior of FePt/Fe multi-layers was studied via micro-magnetic simulation. • As total thickness is 20 nm, optimal magnetic property is shown when the thickness ratio of Fe is 10%. • As total thickness is 20 nm, nucleation fields are positive when the thickness ratio of Fe is 25% and larger. • As total thickness is 20 nm, coercivity is greatly reduced when the thickness ratio of Fe is 25% and larger. • Under fixed volume and the thickness ratio of Fe (10%), switching field can be reduced by reducing the bottom size.

  19. MOKE spectroscopy of FePtCu thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Fronk, Michael; Smykalla, Lars; Brombacher, Christoph; Schubert, Christian; Albrecht, Manfred; Salvan, Georgeta [Chemnitz University of Technology (Germany)

    2010-07-01

    Since the uniaxial magnetic anisotropy of FePt in its chemically ordered L1{sub 0} phase can reach 10 MJ/m{sup 3} FePt is considered to be a promising material for future magnetic storage devices. In this work Fe{sub 52}Pt{sub 48}(5 nm-x)/Cu(x) bilayers have been sputter deposited at room temperature onto thermally oxidized Si wafers and afterwards annealed to various temperatures between 450 C and 800 C under N{sub 2} atmosphere using a commercial rapid thermal annealing (RTA) setup. The RTA procedure leads to the formation of a ternary FePtCu alloy with pronounced perpendicular magnetic anisotropy. The dependence of both the coercivity and remanence extracted from polar MOKE hysteresis loops at 1.96 eV on the annealing temperature will be discussed with respect to the initial Cu thicknesses of 0.5 nm and 0.9 nm. In addition, MOKE-spectroscopy in the energy range between 1.7 eV and 5.5 eV was performed and a clear dependence on the initial Cu thickness and the annealing temperature is found. In some of the spectra the main spectral feature at around 2 eV exhibits a fine structure, which could be caused by the coexistence of the two crystalline phases and/or by the presence of defect sites.

  20. Formation of hard magnetic L1{sub 0}-FePt/FePd monolayers from elemental multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Nam Hoon

    2007-06-18

    In this thesis, ordered L1{sub 0}-FePt and FePd films of different nominal compositions are prepared from Fe/Pt and Fe/Pd multilayers by annealing. In case of the L1{sub 0}-FePt films the composition of the films is modified by changing the individual elemental layer thicknesses in the multilayer precursors. This simple variation of the composition is the great advantage of the multilayer approach compared to sputtering single alloy layer from an alloy target. The formation mechanism of the fct phase from the multilayers and the microstructural properties are investigated. The characteristics of the hysteresis loop (coercivity {mu}{sub 0}H{sub c}, remanence J{sub r}) and of the intrinsic magnetic properties (anisotropy constant K{sub l}, spontaneous polarization J{sub s}, exchange constant A) of the ordered L1{sub 0}-FePt and FePd films are studied. The effects of the composition of the L1{sub 0}-FePt films on the microstructural and magnetic properties are investigated. The microstructure of these ordered L1{sub 0}-FePt films are then correlated to the magnetic properties with microstructural parameters by investigating the temperature dependence of the coercivity. (orig.)

  1. Growth, structure and magnetic properties of FePt nanostructures on NaCl(001) and MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Liscio, F; Maret, M; Doisneau-Cottignies, B [Science et Ingenierie des Materiaux et Procedes (SIMaP), INP-Grenoble/CNRS/UJF, BP 75, 38402 Saint-Martin d' Heres (France); Makarov, D; Albrecht, M [Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany); Roussel, H, E-mail: mireille.maret@simap.grenoble-inp.fr [Consortium des Moyens Technologiques Communs, INP-Grenoble, BP 75, 38402 Saint-Martin d' Heres (France)

    2010-02-10

    A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl(001) and MgO(001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a 'cube-over-cube' growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl(001) is not preceded by the formation of a wetting layer as observed on MgO(001). The higher degree of L1{sub 0} chemical ordering in FePt nanostructures grown on MgO(001) accompanied by the absence of L1{sub 0} variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L1{sub 0} phase with an out-of-plane c-axis. Superparamagnetic behavior is revealed for the FePt nanostructures grown on NaCl(001) due to their small size and relatively poor chemical order.

  2. Structural and magnetic characterization of FePt films deposited onto SiO{sub 2} spherical particle arrays

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph; Makarov, Denys; Schatz, Guenter; Albrecht, Manfred [University of Konstanz, Department of Physics, D-78457 Konstanz (Germany); Maret, Mireille; Liscio, Fabiola [Laboratoire de Thermodynamique et Physico-Chimie Metallurgiques, ENSEEG, Saint Martin d' Heres (France)

    2007-07-01

    The growth of FePt films at 450 C on a Pt/Cr buffer layer deposited onto SiO{sub 2} spherical particle arrays and for comparison on flat thermally oxidized Si(001) substrates has been studied. The structural properties of the FePt films, such as the orientation and size of the crystalline grains and the degree of L1{sub 0}-type chemical ordering, were investigated by in-situ RHEED and ex-situ XRD. Magnetic characterization was performed by MFM, polar MOKE and SQUID. Increasing the Cr buffer underlayer thickness favors the formation of the FePt chemically ordered L1{sub 0} phase. An out-of-plane coercivity of the FePt alloy about 4 kOe was thus obtained for a Cr thickness of 50 nm. While the continuous films on oxidized Si(001) substrates show magnetic domain patterns with domain sizes in the range of 50-100 nm, multi-domain states are observed for the FePt alloy grown on the particle arrays. The influence of the Cr underlayer thickness and Pt buffer layer on the magnetic properties of FePt are discussed for various particle arrays and compared to micromagnetic simulations, providing a description of magnetization reversal.

  3. Growth, structure and magnetic properties of FePt nanostructures on NaCl(001) and MgO(001)

    Science.gov (United States)

    Liscio, F.; Makarov, D.; Maret, M.; Doisneau-Cottignies, B.; Roussel, H.; Albrecht, M.

    2010-02-01

    A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl(001) and MgO(001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a 'cube-over-cube' growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl(001) is not preceded by the formation of a wetting layer as observed on MgO(001). The higher degree of L10 chemical ordering in FePt nanostructures grown on MgO(001) accompanied by the absence of L10 variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L10 phase with an out-of-plane c-axis. Superparamagnetic behavior is revealed for the FePt nanostructures grown on NaCl(001) due to their small size and relatively poor chemical order.

  4. 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.

  5. Multimetallic nanoparticle catalysts with enhanced electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shouheng; Zhang, Sen; Zhu, Huiyuan; Guo, Shaojun

    2015-07-28

    A new structure-control strategy to optimize nanoparticle catalysis is provided. The presence of Au in FePtAu facilitates FePt structure transformation from chemically disordered face centered cubic (fcc) structure to chemically ordered face centered tetragonal (fct) structure, and further promotes formic acid oxidation reaction (FAOR). The fct-FePtAu nanoparticles show high CO poisoning resistance, achieve mass activity as high as about 2810 mA/mg Pt, and retain greater than 90% activity after a 13 hour stability test.

  6. Multimetallic nanoparticle catalysts with enhanced electrooxidation

    Science.gov (United States)

    Sun, Shouheng; Zhang, Sen; Zhu, Huiyuan; Guo, Shaojun

    2015-07-28

    A new structure-control strategy to optimize nanoparticle catalysis is provided. The presence of Au in FePtAu facilitates FePt structure transformation from chemically disordered face centered cubic (fcc) structure to chemically ordered face centered tetragonal (fct) structure, and further promotes formic acid oxidation reaction (FAOR). The fct-FePtAu nanoparticles show high CO poisoning resistance, achieve mass activity as high as about 2810 mA/mg Pt, and retain greater than 90% activity after a 13 hour stability test.

  7. Influence of MgO underlayers on the structure and magnetic properties of FePt-C nanogranular films for heat-assisted magnetic recording media

    Directory of Open Access Journals (Sweden)

    T. Shiroyama

    2016-10-01

    Full Text Available In order to optimize the nanogranular structure of FePt-C for heat-assisted magnetic recording media, we investigated the influence of MgO underlayers on the growth of FePt grains in the FePt-C layer. The FePt-C layer was deposited by using the alternating sputtering method, by which FePt and FePt-C layers were alternately deposited. To understand the growth mechanism of the FePt-C layer on the MgO underlayers deposited under various conditions, detailed plan-view and cross sectional transmission electron microscopy observations were made for different film thicknesses. We found that columnar FePt grains grow only when the deposition conditions of the MgO underlayer are optimal. Direct TEM observation of the growth process of the FePt-C layer revealed that the number density of nuclei is sufficient in the initial stage of the film deposition; however, coarsening of the grains after grain impingement causes a substantial decrease in the number density of the FePt grains.

  8. Influence of carbon chain length on the synthesis and yield of fatty amine-coated iron-platinum nanoparticles

    Science.gov (United States)

    Taylor, Robert M.; Monson, Todd C.; Gullapalli, Rama R.

    2014-06-01

    Iron oxide nanoparticles are among the most widely used and characterized magnetic nanoparticles. However, metal alloys such as superparamagnetic iron-platinum particles (SIPPs), which have better magnetic properties, are receiving increased attention. Scalable techniques to routinely synthesize SIPPs in bulk need further study. Here, we focus on the role played by the fatty amine ligand in the formation of the bimetallic FePt nanocrystal. More specifically, we compare the effect of varying lengths of fatty amine ligands on the shape, structure, uniformity, composition, and magnetic properties of the SIPPs. We synthesized SIPPs by employing a `green' thermal decomposition reaction using fatty amine ligands containing 12 to 18 carbons in length. Greater fatty amine chain length increased the polydispersity, particle concentration, iron concentration, and the stability of the SIPPs. Additionally, longer reflux times increased the diameter of the particles, but decreased the iron concentration, suggesting that shorter reaction times are preferable. Fourier transform infrared spectroscopy of the SIPPs indicates that the ligands are successfully bound to the FePt cores through the amine group. Superconducting quantum interference device magnetometry measurements suggest that all of the SIPPs were superparamagnetic at room temperature and that SIPPs synthesized using tetradecylamine had the highest saturation magnetization. Our findings indicate that the octadecylamine ligand, which is currently used for the routine synthesis of SIPPs, may not be optimal. Overall, we found that using tetradecylamine and a 30-min reflux reaction resulted in optimal particles with the highest degree of monodispersity, iron content, stability, and saturation magnetization.

  9. Nano spin-diodes using FePt-NDs with huge on/off current ratio at room temperature

    Science.gov (United States)

    Makihara, Katsunori; Kato, Takeshi; Kabeya, Yuuki; Mitsuyuki, Yusuke; Ohta, Akio; Oshima, Daiki; Iwata, Satoshi; Darma, Yudi; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2016-09-01

    Spin transistors have attracted tremendous interest as new functional devices. However, few studies have investigated enhancements of the ON/OFF current ratio as a function of the electron spin behavior. Here, we found a significantly high spin-dependent current ratio—more than 102 at 1.5 V—when changing the relative direction of the magnetizations between FePt nanodots (NDs) and the CoPtCr-coated atomic force microscope (AFM) probe at room temperature. This means that ON and OFF states were achieved by switching the magnetization of the FePt NDs, which can be regarded as spin-diodes. The FePt magnetic NDs were fabricated by exposing a bi-layer metal stack to a remote H2 plasma (H2-RP) on ~1.7 nm SiO2/Si(100) substrates. The ultrathin bi-layers with a uniform surface coverage are changed drastically to NDs with an areal density as high as ~5 × 1011 cm‑2. The FePt NDs exhibit a large perpendicular anisotropy with an out-of-plane coercivity of ~4.8 kOe, reflecting the magneto-crystalline anisotropy of (001) oriented L10 phase FePt. We also designed and fabricated double-stacked FePt-NDs with low and high coercivities sandwiched between an ultra-thin Si-oxide interlayer, and confirmed a high ON/OFF current ratio when switching the relative magnetization directions of the low and high coercivity FePt NDs.

  10. Nano spin-diodes using FePt-NDs with huge on/off current ratio at room temperature

    Science.gov (United States)

    Makihara, Katsunori; Kato, Takeshi; Kabeya, Yuuki; Mitsuyuki, Yusuke; Ohta, Akio; Oshima, Daiki; Iwata, Satoshi; Darma, Yudi; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2016-01-01

    Spin transistors have attracted tremendous interest as new functional devices. However, few studies have investigated enhancements of the ON/OFF current ratio as a function of the electron spin behavior. Here, we found a significantly high spin-dependent current ratio—more than 102 at 1.5 V—when changing the relative direction of the magnetizations between FePt nanodots (NDs) and the CoPtCr-coated atomic force microscope (AFM) probe at room temperature. This means that ON and OFF states were achieved by switching the magnetization of the FePt NDs, which can be regarded as spin-diodes. The FePt magnetic NDs were fabricated by exposing a bi-layer metal stack to a remote H2 plasma (H2-RP) on ~1.7 nm SiO2/Si(100) substrates. The ultrathin bi-layers with a uniform surface coverage are changed drastically to NDs with an areal density as high as ~5 × 1011 cm−2. The FePt NDs exhibit a large perpendicular anisotropy with an out-of-plane coercivity of ~4.8 kOe, reflecting the magneto-crystalline anisotropy of (001) oriented L10 phase FePt. We also designed and fabricated double-stacked FePt-NDs with low and high coercivities sandwiched between an ultra-thin Si-oxide interlayer, and confirmed a high ON/OFF current ratio when switching the relative magnetization directions of the low and high coercivity FePt NDs. PMID:27615374

  11. Abnormal temperature dependence of the coercive field in FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán, J.M. [Facultad de Ciencias Químicas – Universidad Nacional de Córdoba – 5000 Córdoba (Argentina); Álvarez, N.; Salva, H.R.; Vásquez Mansilla, M.; Gómez, J. [Centro Atómico Bariloche (CNEA), Instituto Balseiro (U. N. Cuyo) and Conicet, 8400 Bariloche, Río Negro (Argentina); Butera, A., E-mail: butera@cab.cnea.gov.ar [Centro Atómico Bariloche (CNEA), Instituto Balseiro (U. N. Cuyo) and Conicet, 8400 Bariloche, Río Negro (Argentina)

    2013-12-15

    We have observed notable changes in the magnetic response of FePt thin films that we have attributed to a transition in the magnetic domain structure when the film thickness or the temperature is varied. The critical thickness for this transition depends on the Q-factor, Q=K{sub ⊥}/2πM{sub s}{sup 2}, so that a change in the domain structure is expected when changes in the perpendicular anisotropy, K{sub ⊥}, or the saturation magnetization, M{sub s}, occur. At room temperature these samples have Q∼0.3, and a transition between planar to stripe-like domains occurs for a film thickness d∼30nm. Due to the different thermal expansion of the FePt alloy and the Si substrate a reduction in Q is predicted when the temperature is lowered. From magnetization vs. field loops measured at different temperatures below T=300 K, we have effectively observed a change in the coercive field which can be associated to a transition from stripe-like to in-plane domains. The transition temperature range is broad, indicating a gradual variation between the two magnetic configurations, but changes systematically with film thickness, consistent with an interfacial induced stress. A model that includes the temperature dependence of the strain and the magnetization, predicts correctly the observation of a larger critical thickness at lower temperatures. - Highlights: • The magnetic domain configuration of disordered FePt films can be thermally switched between in-plane domains and stripe domains. • Results are explained by considering the full temperature dependence of the induced stress which produces an out-of-plane anisotropy axis. • The transition temperature changes systematically with film thickness, consistent with an interfacial induced stress.

  12. Composition influence on the microstructures and magnetic properties of FePt thin films

    Institute of Scientific and Technical Information of China (English)

    Liu Li-Wang; Dang Hong-Gang; Sheng Wei; Wang Ying; Cao Jiang-Wei; Bai Jian-Min; Wei Fu-Lin

    2013-01-01

    The FexPt100-x (10 nm) (x =31-51) thin films are fabricated on Si (100) substrates by using magnetron sputtering.The highly ordered L10 FePt phase is obtained after post-annealing at 700 ℃C in Fe47Pt53 thin film.The sample shows good perpendicular anisotropy with a square loop and a linear loop in the out-of-plane and the in-plane direction,respectively.The variations of the magnetic domains are investigated in the films when the content value of Fe changes from 31% to 51%.

  13. Tailoring exchange bias through chemical order in epitaxial FePt3 films

    Science.gov (United States)

    Saerbeck, T.; Zhu, H.; Lott, D.; Lee, H.; LeClair, P. R.; Mankey, G. J.; Stampfl, A. P. J.; Klose, F.

    2013-07-01

    Intentional introduction of chemical disorder into mono-stoichiometric epitaxial FePt3 films allows to create a ferro-/antiferromagnetic two-phase system, which shows a pronounced and controllable exchange bias effect. In contrast to conventional exchange bias systems, granular magnetic interfaces are created within the same crystallographic structure by local variation of chemical order. The amount of the exchange bias can be controlled by the relative amount and size of ferromagnetic and antiferromagnetic volume fractions and the interface between them. The tailoring of the magnetic composition alone, without affecting the chemical and structural compositions, opens the way to study granular magnetic exchange bias concepts separated from structural artifacts.

  14. Exploring the potential of remote plasma sputtering for the production of L10 ordered FePt thin films

    Science.gov (United States)

    Zygridou, S.; Barton, C. W.; Nutter, P. W.; Thomson, T.

    2017-07-01

    Lowering the temperature at which the desirable L10 phase forms in FePt thin films is a key requirement in the development of next generation high-density data storage media and spintronic devices. Remote plasma sputtering offers a higher degree of control over the sputtering parameters, allowing the properties of films to be tailored, and potentially can affect the ordering kinetics of the L10 phase of FePt. Here, we report a comprehensive study of FePt thin films deposited under a range of temperatures and sputtering conditions. X-ray diffraction and magnetometry investigations show that whilst FePt thin films ordered in the L10 phase with high perpendicular anisotropy can be produced using this technique, there is no significant reduction in the required ordering temperature compared with films produced using conventional DC sputtering. Optimally ordered L10 FePt films were fabricated when the film was deposited at a substrate temperature of 200 °C, followed by post annealing at 750 °C.

  15. Off-easy-plane antiferromagnetic spin canting in coupled FePt/NiO bilayer structure with perpendicular exchange bias

    Science.gov (United States)

    Gao, Tenghua; Itokawa, Nobuhide; Wang, Jian; Yu, Youxing; Harumoto, Takashi; Nakamura, Yoshio; Shi, Ji

    2016-08-01

    We report on the investigation of perpendicular exchange bias in FePt (001 ) /NiO (1 ¯1 ¯1 ) orthogonal exchange couple with FePt partially L 10 ordered. From initial magnetization curve measurement and magnetic domain imaging, we find that, for the as-grown bilayer structure, the FePt layer experiences a small-angle magnetization rotation when it is magnetized near to saturation in film normal direction. After field cooling, the bilayer structure shows a significant enhancement of perpendicular magnetic anisotropy, indicating the field mediated coupling between the spins across the FePt/NiO interface. According to Koon's theoretical calculation on the basis of lowest energy ferromagnetic/antiferromagnetic coupling configuration for compensated spins at antiferromagnetic side, we consider slightly slanted Ni spins at the interface off the (1 ¯1 ¯1 ) easy plane can stabilize the spin coupling between FePt and NiO and result in the observed exchange bias in this paper. This consideration was further confirmed by stripe domain width calculation.

  16. Effects of Ag layers on the SiO2/FePt thin films deposited by magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    FAN Jiuping; XU Xiaohong; WANG Fang; JIANG Fengxian; TIAN Baoqiang; JIN Tao

    2008-01-01

    The effects of Ag Iayers with different locations and thicknesses on the structural and magnetic property of SiO2/FePt multilayer films were investigated.The non-magnetic Ag layer plays an important role in inducing(001)orientation and ordering of FePt grains,as well as the SiO2-doping reducing the grin size and the magnetic exchange coupling between grains.When the 10 nm Ag layer is moved from the bottom to the top of the SiO2/FePt multilayer film,the coercivity gradually decreases;the largest difference betwogn the out-of-plane coercivity and the in-plane one is obtained in the sample of[SiO2(2 nm)/FePt(3 nm)]3/Ag(10 nm)/[SiO2(2 nm)//FePt(3 nm)]2.Furthermore,the location of Ag layers was fixed and the thickness was changed.The XRD curves suggest that the intensity of the(001)peak becomes the strongest with the addition of 10 nm Ag layers.

  17. Study of microstructure and magnetic properties of L10 FePt/SiO2 thin films

    Directory of Open Access Journals (Sweden)

    Giannopoulos G.

    2014-07-01

    Full Text Available Achieving magnetic recording densities in excess of 1Tbit/in2 requires not only perpendicular media with anisotropies larger than 7 MJ/m3, making FePt alloys an ideal choice, but also a narrow distribution below 10 nm for a reduced S/N ratio. Such grain size reduction and shape control are crucial parameters for high density magnetic recording, along with high thermal stability. Previous work has shown that the L10 FePt grain size can be controlled by alloying FePt with materials such as C, Ag, and insulators such as AlOx, MgO. Au and Al2O3 also act to segregate and magnetically decouple the FePt grains. Better results were obtained with C with respect to the uniformity of grains and SiO2 with respect to the shape. We present our results on co-sputtering FePt with C or SiO2 (up to 30 vol % on MgO (001 single crystal substrates at 350 and 500 oC. With C or SiO2 addition we achieved grain size reduction, shape control and isolated structure formation, producing continuous films with high uniformity and a narrow grain size distribution. These additions thus allow us to simultaneously control the coercivity and the S/N ratio. We also will report structural and microstructural properties.

  18. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu-substitution in single-crystalline FePt thin films

    Directory of Open Access Journals (Sweden)

    Takuya Ono

    2016-05-01

    Full Text Available In L10 (fct-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu thin films grown epitaxially on MgO(001 substrates at a substrate temperature of 350  °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m of FePt-X films as a function of the effective number of valence electrons (neff in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( K u comp of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the K u comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  19. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    Science.gov (United States)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  20. 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.

  1. 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).

  2. Magnet-in-the-Semiconductor Nanomaterials: High Electron Mobility in All-Inorganic Arrays of FePt/CdSe and FePt/CdS Core-Shell Heterostructures.

    Science.gov (United States)

    Son, Jae Sung; Lee, Jong-Soo; Shevchenko, Elena V; Talapin, Dmitri V

    2013-06-06

    We report a colloidal synthesis and electrical and magnetotransport properties of multifunctional "magnet-in-the-semiconductor" nanostructures composed of FePt core and CdSe or CdS shell. Thin films of all-inorganic FePt/CdSe and FePt/CdS core-shell nanostructures capped with In2Se4(2-) molecular chalcogenide (MCC) ligands exhibited n-type charge transport with high field-effect electron mobility of 3.4 and 0.02 cm(2)/V·s, respectively. These nanostructures also showed a negative magnetoresistance characteristic for spin-dependent tunneling. We discuss the mechanism of charge transport and gating in the arrays of metal/semiconductor core-shell nanostructures.

  3. 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.

  4. Influence of phase transformation on the permanent-magnetic properties of Fe-Pt based alloys

    Science.gov (United States)

    Brück, E.; Xiao, Q. F.; Thang, P. D.; Toonen, M. J.; de Boer, F. R.; Buschow, K. H. J.

    2001-07-01

    We have studied the effect of the atomic disorder-order transformation on remanence enhancement and coercivity in Fe-Pt-based materials by isothermal annealing at temperatures well below the transformation point. We also investigated the effect of the annealing temperature and the effect of various types of additives. The relative amount of the low-temperature hard-magnetic face-centered-tetragonal (FCT) phase precipitated in the high-temperature magnetically soft face-centered-cubic (FCC) phase was determined by means of X-ray diffraction. As a function of annealing time and annealing temperature, particle size and relative amount of the FCT phase increased at the cost of the FCC phase. These changes were followed by means of magnetic measurements. We observed a continuous increase in coercivity with increasing annealing time, eventually reaching a maximum. The Kneller-Hawig model was used to explain the occurrence of remanence enhancement and the continuously changing degree of exchange coupling between the magnetically soft and hard phase. The suitability of Fe-Pt based alloys in dental applications is discussed.

  5. 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.

  6. 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.

  7. Edge-modulated perpendicular magnetic anisotropy in [Co/Pd]n and L10-FePt thin film wires

    Science.gov (United States)

    Zhang, Jinshuo; Ho, Pin; Currivan-Incorvia, Jean Anne; Siddiqui, Saima A.; Baldo, Marc A.; Ross, Caroline A.

    2015-11-01

    Thickness modulation at the edges of nanostructured magnetic thin films is shown to have important effects on their perpendicular magnetic anisotropy. Thin film wires with tapered edges were made from [Co/Pd]20 multilayers or L10-FePt films using liftoff with a double-layer resist. The effect of edge taper on the reversal process was studied using magnetic force microscopy and micromagnetic modeling. In [Co/Pd]20, the anisotropy was lower in the tapered edge regions which switched at a lower reverse field compared to the center of the wire. The L10-FePt wires showed opposite behavior with the tapered regions exhibiting higher anisotropy.

  8. 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

  9. 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.

  10. Angular dependence of demagnetization processes in Fe-FePt perpendicular exchange-spring bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Solzi, M. [Dipartimento di Fisica, Universita di Parma and CNISM, V.le G.P. Usberti 7/A, 43100 Parma (Italy)]. E-mail: solzi@fis.unipr.it; Pernechele, C. [Dipartimento di Fisica, Universita di Parma and CNISM, V.le G.P. Usberti 7/A, 43100 Parma (Italy); Pellicelli, R. [Dipartimento di Fisica, Universita di Parma and CNISM, V.le G.P. Usberti 7/A, 43100 Parma (Italy); Ghidini, M. [Dipartimento di Fisica, Universita di Parma and CNISM, V.le G.P. Usberti 7/A, 43100 Parma (Italy); Albertini, F. [IMEM-CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy); Casoli, F. [IMEM-CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy)

    2007-09-15

    The angular dependence of hysteresis loops of exchange-spring (ES) bilayers constituted by a Fe layer as the soft phase and a hard layer of L1{sub 0} Fe{sub 53}Pt{sub 47} is presented. FePt thin films of nominal thickness 10 nm have been prepared by RF sputtering on MgO (1 0 0) substrates in order to achieve the epitaxial growth with the c-axis perpendicular to the film plane. The Fe soft layers have been deposited at RT with various thicknesses (from 2 to 10 nm). The angular dependence of the bilayers' magnetic properties is studied by SQUID magnetometry varying the angle between the easy axis of the hard phase and the direction of the applied field from 0 to {pi}/2. The magnetic behavior at different angles is analyzed by a one-dimensional micromagnetic model specifically extended to the case of perpendicular magnetic anisotropy (PMA)

  11. The effect of vacancy created by ion irradiation on the ordering of FePt: A first-principle study

    Energy Technology Data Exchange (ETDEWEB)

    Shu, X.L. [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)], E-mail: shuxlin@buaa.edu.cn; Chen, Z.Y.; Chen, Q. [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China); Hu, W.Y. [Department of Applied Physics, Hunan University, Changsha, Hunan 410082 (China)

    2009-09-15

    Ion irradiation has been used to promote ordering processes and to modify the magnetic properties of magnetic thin films. The major reason for ion irradiation reducing the ordering temperature is the introduction of a number of vacancies. The vacancy and its influence on the ordering temperature and magnetic properties in L1{sub 0} ordered FePt are investigated by first-principle simulation. The vacancy formation energy for Fe and Pt in FePt alloy are 1.45 and 2.25 eV respectively. The calculated order-disorder transition temperature of Fe{sub 50}Pt{sub 50} is 1680 K. The order-disorder transition temperatures for Fe vacancy and Pt vacancy models are about 50 K and 200 K lower than that of the stoichiometric Fe{sub 50}Pt{sub 50} alloy respectively. The results suggested that the vacancy in FePt alloy favors the ordering process. The saturation magnetization of stoichiometric L1{sub 0} FePt is 1070 emu/cc and these of Fe and Pt vacancy are 1027 and 1075 emu/cc, respectively.

  12. The effect of vacancy created by ion irradiation on the ordering of FePt: A first-principle study

    Science.gov (United States)

    Shu, X. L.; Chen, Z. Y.; Chen, Q.; Hu, W. Y.

    2009-09-01

    Ion irradiation has been used to promote ordering processes and to modify the magnetic properties of magnetic thin films. The major reason for ion irradiation reducing the ordering temperature is the introduction of a number of vacancies. The vacancy and its influence on the ordering temperature and magnetic properties in L10 ordered FePt are investigated by first-principle simulation. The vacancy formation energy for Fe and Pt in FePt alloy are 1.45 and 2.25 eV respectively. The calculated order-disorder transition temperature of Fe50Pt50 is 1680 K. The order-disorder transition temperatures for Fe vacancy and Pt vacancy models are about 50 K and 200 K lower than that of the stoichiometric Fe50Pt50 alloy respectively. The results suggested that the vacancy in FePt alloy favors the ordering process. The saturation magnetization of stoichiometric L10 FePt is 1070 emu/cc and these of Fe and Pt vacancy are 1027 and 1075 emu/cc, respectively.

  13. Exchange interaction in L10-ordered FePt and CoPt from first-principles

    Science.gov (United States)

    Liu, X. B.; Altounian, Z.

    2011-04-01

    The exchange interactions have been studied from a first-principles density functional calculation in FePt and CoPt with the tetragonal L10-type structure. For FePt, the effective exchange parameters of Fe at the sites 1a and 1c, JFe1a and JFe1c, have the same negative value (-1.40 mRy) while that between Fe (1a) and Fe (1c), JFe1a -1c, have a large positive value (8.29 mRy) and JFe-Pt also has a positive value (1.20 mRy). Similarly, for CoPt, the exchange parameters are JCo1a = JCo1c = -0.86 mRy, JCo1a -1c = 8.47 mRy and JCo-Pt = 1.30 mRy. The estimated mean fields TC are about 802 K and 870 K for FePt and CoPt, respectively, in good agreement with the experiments. TC shows peak value at c/a = 1 in FePt and CoPt, respectively, resulting from the interplay between negative and positive exchange interactions.

  14. Magnetic Properties of Nanoparticle Matrix Composites

    Science.gov (United States)

    2015-06-02

    Vijay Kumar Foundation 1969 Sector 4 Gurgaon, Harayana 122001 India 8. PERFORMING ORGANIZATION REPORT NUMBER N/A 9. SPONSORING... media . Some of these nanoparticles (such as Fe-Pt) can also be very interesting for catalysis. Fe-Pt is one of the most promising materials due to its...Foundation; Mailing Address: 1969 Sector 4, Gurgaon 122001, Haryana, India ; Phone/Fax: +91-124-4079369 Period of Performance: 04/03/2013 – 04/02

  15. Fabrication of iron-platinum ferromagnetic nanoparticles

    Science.gov (United States)

    Elkins, Kevin Eugene

    Fabrication of chemically disordered FePt particles ranging from 2--9 nm with a precision of 1 nm has been achieved through modification of key process variables including surfactant concentration, heating rates and the type of iron precursor. In addition, the shape evolution of the FePt nanoparticles during particle growth can be manipulated to give cubic or rod geometries through changes to the surfactant injection sequence and solvent system. The primary method for synthesis of the disordered FePt nanoparticles is the polyol reduction reported by Fievet et al., which has been modified and used extensively for synthesis of differing nanoparticle systems. Our procedures use platinum acetylacetonate, iron pentacarbonyl or ferric acetylacetonate as precursors for the FePt alloy, oleic acid and oleyl amine for the surfactants, 1,2-hexadecanediol to assist with the reduction of the precursors and either dioctyl ether or phenyl ether for the solvent system. For iron pentacarbonyl based reactions, adjustment of heating rates to reflux temperatures from 1--15°C per minute allows control of FePt particle diameters from 3--8 nm. Substitution of iron pentacarbonyl with ferric acetylacetonate as the iron source results in 2 nm particles. A high platinum to surfactant ratio of 10 to 1 will yield 9 nm FePt particles when iron pentacarbonyl is used as the precursor. For use of these particles in advanced applications, the synthesized particles must be transformed to the L1o phase through annealing at temperatures above 500°C. Inhibition of particle sintering can be avoided through dispersion in a NaCl matrix at a weight ratio of 400 to 1 salt to fcc FePt particles. Production of L1o FePt nanoparticles with high magnetic anisotropy with this process has been successful, allowing the original size and size distribution of the particles.

  16. 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.

  17. Microstructures and magnetic properties of L1{sub 0} FePt films deposited on NaCl-type films

    Energy Technology Data Exchange (ETDEWEB)

    Sun, T.H., E-mail: s9931829@m99.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, S.C.; Su, W.H. [Department of Materials Engineering and Center for Thin Film Technologies and Applications, Ming Chi University of Technology, Taipei 24301, Taiwan (China); Chen, J.R. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2013-10-01

    A single-layered FePt film of 30 nm thickness with perpendicular magnetic anisotropy is achieved by depositing the film onto a heated Si(100) substrate at 620 °C. Its perpendicular coercivity (Hc{sub ⊥}), saturation magnetization (M{sub s}) and perpendicular squareness (S{sub ⊥}) are as high as 1113 kA/m, 0.594 Wb/m{sup 2} and 0.96, respectively. The perpendicular magnetic anisotropy degrades when a 5-nm NiO film is introduced under this single-layered film. Upon further increasing the thickness of the NiO film to 10 nm, the Hc{sub ⊥} of the single-layered film decreases greatly to around 330 kA/m. Compared to a NiO underlayer, the Hc{sub ⊥} of the FePt film remains above 1000 kA/m when a 10-nm MgO underlayer is introduced. Furthermore, when the thickness of the MgO underlayer is decreased to 5 nm, the perpendicular magnetic anisotropy of the single-layered FePt film is further enhanced. Its Hc{sub ⊥} stays high at 1081 kA/m; however, S{sub ⊥} increases significantly to 1. - Highlights: ► A thin MgO underlayer enhances the perpendicular magnetic anisotropy of FePt film. ► A NiO underlayer degrades the perpendicular magnetic anisotropy of the film. ► Ni atoms diffuse from NiO underlayer into FePt layer forming NiFe compounds.

  18. 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

  19. Room temperature FePt nanoparticles formation kinetics by laser solution photolysis

    CSIR Research Space (South Africa)

    Nkosi, S

    2012-04-01

    Full Text Available Formation Kinetics by Laser solution photolysis S. Nkosi1, B.W. Mwakikunga2, E. Sideras-Haddad1 1University of the Witwatersrand 2 DST/NCNSM, Pretoria The 4th International Conference on Nanoscience and Nanotechnology 1 – 4 April 2012, University... emission during photolysis, � the produced either positive or negative metallic ions (liquid form). Theoretical consideration transabsreflLASER IIII ++= Energy conservation (Kirchoff’s law) lossestransferheat dt dNVH dt dTV V NCII ptransabs __+∆∆+∆== Slide...

  20. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy

    Science.gov (United States)

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M.; Ross, Caroline A.

    2016-02-01

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the

  1. Direct observation of dendritic domain growth in perpendicular magnetic anisotropy CoFe/Pt multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Liu Haoliang [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); He Wei, E-mail: hewei@aphy.iphy.ac.cn [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Du Haifeng; Wu Qiong; Fang Yapeng [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhu Yun [College of Physics and Electronic Information Science, Tianjin Normal University, Tianjin 300387 (China); Cai Jianwang [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Cheng Zhaohua, E-mail: zhcheng@aphy.iphy.ac.cn [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-09-15

    We present the experimental results on thermally activated magnetization reversal for [Co{sub 0.9}Fe{sub 0.1}(5.0 A)/Pt(20 A)]{sub 4} multilayer. Direct domain observations show that magnetization reversal is initiated with rare nucleation and followed by dendritic growth of domain walls. Based on macroscopic magnetic parameters from experimental data, the dendritic domain growth mode is qualitatively interpreted by Monte Carlo simulations in terms of a simple uniaxial magnetic anisotropy model. Moreover, both time evolution of domain growth observation and magnetic relaxation measurements reveal that CoFe/Pt multilayer has a relatively large activation volume compared with Co/Pt multilayers. - Highlights: > We investigate magnetization reversal of [Co{sub 0.9}Fe{sub 0.1}(5.0 A)/Pt(20 A)]{sub 4} multilayer. > Magnetization reversal is governed by thermally activated mechanism. > Magnetic domains evolve in dendritic domain growth mode. > Relatively large activation volume is obtained for the multilayer. > Monte Carlo simulation reproduces the domain growth mode well.

  2. Thermal Decay and Reversal of Exchange Bias Field of CoFe/PtMn Bilayer after Ga+ Irradiation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Guang-Hong; ZHU Yu-Fu; LIN Yue-Bin

    2011-01-01

    @@ An applied field is used to perform Ga+ ion irradiation on a CoFe/PtMn bilayer.Effects of the applied field and energy transfer between Ga+ ions and antiferromagnetic(AFM) atoms on the exchange bias field Hex are investigated.A partially reversed Hex is found in CoFe/PtMn specimens irradiated at a dose of 1 × 1014 ions/cm2 with an applied field anti-parallel to the original exchange bias direction.We believe that the rapid energy transfer and local temperature increase originating from the interaction between Ga+ ions and AFM atoms result in spin reversal and the formation of reversed AFM domains when specimens are irradiated with anti-parallel fields.The decrease in Hex when annealing the film in a negative saturation field indicates a thermal decay process.The AFM moments are reversed by thermal activation over an energy barrier distribution,which may change in some way as the temperature increases.%An applied field is used to perform Ga+ ion irradiation on a CoFe/PtMn bilayer. Effects of the applied field and energy transfer between Ga+ ions and antiferromagnetic (AFM) atoms on the exchange bias field Hex are investigated. A partially reversed Hex is found in CoFe/PtMn specimens irradiated at a dose of 1 × 1014 ions/cm2 with an applied field anti-parallel to the original exchange bias direction. We believe that the rapid energy transfer and local temperature increase originating from the interaction between Ga+ ions and AFM atoms result in spin reversal and the formation of reversed AFM domains when specimens are irradiated with anti-parallel fields. The decrease in Hex when annealing the film in a negative saturation field indicates a thermal decay process. The AFM moments are reversed by thermal activation over an energy barrier distribution, which may change in some way as the temperature increases.

  3. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy.

    Science.gov (United States)

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M; Ross, Caroline A

    2016-03-07

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ∼75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.

  4. Origin of open recoil curves in L1{sub 0}-A1 FePt exchange coupled nanocomposite thin film

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, Rajan [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Kapoor, Akanksha [M. Tech Nanoscience and Nanotechnology, University of Delhi, Delhi 110007 (India); Lamba, S. [School of Sciences, Indira Gandhi National Open University, New Delhi 110068 (India); Annapoorni, S., E-mail: annapoornis@yahoo.co.in [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2016-11-15

    Mixed phase FePt systems with intergranular coupling may be looked upon as natural exchange spring systems. The coupling strength between the soft and hard phase in these systems can be analyzed using recoil curves. However, the origin of open recoil curves depicting the breakdown of exchange coupling or anisotropy variation in hard phase is still an ambiguity and requires an in-depth analysis. In order to investigate this, an analysis of the recoil curves for L1{sub 0}–A1 FePt nanocomposite thin films of varying thickness have been performed. The switching field distribution reveals that the maximum of openness of recoil curve is directly proportional to the amount of uncoupled soft phase present in the system. The coupling between the hard and soft phase is also found to increase with the thickness of the film. Monte Carlo simulations on a model three dimensional array of interacting nanomagnetic grains provide further insight into the effect of inter granular exchange interactions between the soft and hard phases. - Highlights: • L1{sub 0}-A1 FePt nanocomposites thin films of different thickness have been fabricated by DC sputtering. • Hysteresis curve measurements exhibit perfect single phase (L1{sub 0}) like behavior for thicker films. • SFD reveals that the openness of recoil curves is directly linked with the amount of uncoupled soft (A1) phase. • Monte Carlo simulation predicts that the extent of exchange interaction increases with thickness of the film.

  5. Magnetization reorientation induced by interfacial structures in ultrathin disordered FePt film sandwiched by SiO{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Guang; Zhang, Jing-Yan [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, Shou-Guo, E-mail: sgwang@iphy.ac.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Jiang, Shao-Long; Zhao, Yun-Chi [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ma, Qi-Di; Wang, Chao; Dong, Bo-Wen; Liu, Jia-Long; Zhang, Ying; Sun, Young [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-10-30

    In general, ultrathin disordered FePt film exhibits in-plane magnetic anisotropy due to large demagnetization fields and negligible volume anisotropy. Here, we demonstrated that magnetization reorientation from in-plane to out-of-plane takes place when ultrathin disordered FePt film is sandwiched by amorphous SiO{sub 2} layers and annealed at 350 °C. Based on the interfacial and structural analysis from X-ray photoelectron spectroscopy and high resolution transmission electron microscopy, the reorientation originates from the electronic structural changes because of strong bonding between Fe and O atoms at the top FePt/SiO{sub 2} interface. This interface anisotropy plays a crucial role in the magnetic behaviour, resulting in magnetization reorientation of ultrathin disordered FePt film.

  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. 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.

  8. Microstructure and magnetic properties of FePt film with combined MoC/(Mg-X)O (X=Cu, Ni, Co) intermediate layers

    Science.gov (United States)

    Tsai, Jai-Lin; Tzeng, Jie-Lin; Hu, Keng-Chun; Li, Hsu-Kang; Pan, Zu-Yu; Chang, Yuan-Shuo; Liao, Chang-Chun

    2017-01-01

    The magnetic properties and microstructure of FePt films grown on MoC layer and MoC/(Mg-X)O (X=Cu, Ni, Co) combined intermediate layers were studied. The (Mg-X)O (X=Cu, Ni, Co) layer with thickness of 5 nm was deposited on CrRu seed layer at 395 °C. The CrRu (200) texture was enhanced which may due to well grains growth in specific orientation and small lattice mismatch with (Mg-X)O (X=Cu, Ni, Co). Finally, the FePt/MoC layers were deposited on (Mg-X)O layer at 425 °C. Using MoC/MgCuO combined intermediate layers, the rocking width of FePt (001) and CrRu (200) diffraction peak were changed from 7.1° to 6.1°, and 5.7° to 3.8°, respectively. For MoC/MgCoO dual intermediate layers, the rocking width of FePt (001) and CrRu (200) diffraction peak were 6.7° and 4.1°. The FePt/MoC/MgCoO film illustrates perpendicular magnetic anisotropy with out-of plane coercivity of 9.3 kOe which is higher than FePt film deposited on MoC layer (8.5 kOe) and the in-plane loops is linear. From microstructure, the FePt grains were more separated on MoC/(Mg-X)O (X=Cu, Ni, Co) combined intermediate layers.

  9. Microstructure and magnetic properties of (001) textured L1(0) FePt films on amorphous glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Speliotis, T; Varvaro, G; Testa, AM; Giannopoulos, G; Agostinelli, E; Li, W; Hadjipanayis, G; Niarchos, D

    2015-05-15

    L1(0) FePt thin films with an island-like morphology and magnetic perpendicular anisotropy were grown at low temperature (300 < T-dep< 375 degrees C) by magnetron sputtering on Hoya glass substrates using a 30-nm thick Cr (2 0 0) underlayer. An MgO buffer layer with a thickness of 2 nm was used to inhibit the diffusion from the Cr underlayer and promote the growth of (0 0 1) oriented L1(0) FePt films by inducing an in-plane lattice distortion. By varying the substrate temperature and the Ar sputter pressure (3.5 < P-Ar< 15 mTorr) during the deposition, the degree of chemical order, the microstructure and the magnetic properties were tuned and the best properties in term of squareness ratio (M-r/M-s similar to 0.95) and coercive field (H-c similar to 14 kOe) were observed for films deposited at T-dep = 350 degrees C and P-Ar= 5 mTorr, due to the appearance of a tensile strain, which favors the perpendicular anisotropy. The analysis of the angular dependence of remanent magnetization curves on the optimized sample suggests that the magnetization reversal is highly incoherent due to the inter-island interactions. Our results provide useful information on the low temperature growth of FePt films with perpendicular anisotropy onto glass substrates, which are relevant for a variety of technological applications, such as magnetic recording and spintronic devices. (C) 2015 Elsevier B.V. All rights reserved.

  10. Molecular dynamic simulation study of plasma etching L10 FePt media in embedded mask patterning (EMP process

    Directory of Open Access Journals (Sweden)

    Jianxin Zhu

    2017-05-01

    Full Text Available Plasma etching process of single-crystal L10-FePt media [H. Wang et al., Appl. Phys. Lett. 102(5 (2013] is studied using molecular dynamic simulation. Embedded-Atom Method [M. S. Daw and M. I. Baskes, Phy. Rev. B 29, 6443 (1984; X. W. Zhou, R. A. Johnson and H. N. G. Wadley, Phy. Rev. B 69, 144113 (2004] is used to calculate the interatomic potential within atoms in FePt alloy, and ZBL potential [J.F. Ziegler, J. P. Biersack and U. Littmark, “The Stopping and Range of Ions in Matter,” Volume 1, Pergamon,1985] in comparison with conventional Lennard-Jones “12-6” potential is applied to interactions between etching gas ions and metal atoms. It is shown the post-etch structure defects can include amorphized surface layer and lattice interstitial point defects that caused by etchant ions passed through the surface layer. We show that the amorphized or damaged FePt lattice surface layer (or “magnetic dead-layer” thickness after etching increases with ion energy for Ar ion impacts, but significantly small for He ions at up to 250eV ion energy. However, we showed that He sputtering creates more interstitial defects at lower energy levels and defects are deeper below the surface compared to Ar sputtering. We also calculate the interstitial defect level and depth as dependence on ion energy for both Ar and He ions. Media magnetic property loss due to these defects is also discussed.

  11. Tuning anomalous Hall conductivity in L1[sub 0] FePt films by long range chemical ordering

    KAUST Repository

    Chen, M.

    2011-02-24

    For L10 FePt films, the anomalous Hall conductivity σ xy=-a σxx-b, where a=a0f(T), b=b 0f(T), and f (T) is the temperature dependence factor of the spontaneous magnetization. With increasing chemical long range ordering S, a0 changes its sign accompanied by a reduction of its magnitude and b0 increases monotonically. The spin-orbit coupling strength is suggested to increase with increasing S. As an approach, the long range chemical ordering can be used to control the anomalous Hall effect in ferromagnetic alloy films. © 2011 American Institute of Physics.

  12. Nano-structure formation of Fe-Pt perpendicular magnetic recording media co-deposited with MgO, Al{sub 2}O{sub 3} and SiO{sub 2} additives

    Energy Technology Data Exchange (ETDEWEB)

    Safran, G. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences 1121 Budapest, Konkoly-Thege ut 29-33 (Hungary)]. E-mail: safran@mfa.kfki.hu; Suzuki, T. [Akita Research Institute of Advanced Technology (AIT), 4-21 Sanuki, Araya, Akita 010-1623 (Japan); Ouchi, K. [Akita Research Institute of Advanced Technology (AIT), 4-21 Sanuki, Araya, Akita 010-1623 (Japan); Barna, P.B. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences 1121 Budapest, Konkoly-Thege ut 29-33 (Hungary); Radnoczi, G. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences 1121 Budapest, Konkoly-Thege ut 29-33 (Hungary)

    2006-02-21

    Perpendicular magnetic recording media samples were prepared by sputter deposition on sapphire with a layer sequence of MgO seed-layer/Cr under-layer/FeSi soft magnetic under-layer/MgO intermediate layer/FePt-oxide recording layer. The effects of MgO, Al{sub 2}O{sub 3} and SiO{sub 2} additives on the morphology and orientation of the FePt layer were investigated by transmission electron microscopy. The samples exhibited (001) orientation of the L1 FePt phase with the mutual orientations of sapphire substrate//MgO(100)[001]//Cr(100)[11-bar0]//FeSi(100)[11-bar0]//MgO(100) [001]//FePt(001)[100]. The morphology of the FePt films varied due to the co-deposited oxides: The FePt layers were continuous and segmented by stacking faults aligned at 54{sup o} to the surface. Films with SiO{sub 2} addition, beside the oriented columnar FePt grains, exhibited a fraction of misoriented crystallites due to random repeated nucleation. Al{sub 2}O{sub 3} addition resulted in a layered structure, i.e. an initial continuous epitaxial FePt layer covered by a secondary layer of FePt-Al{sub 2}O{sub 3} composite. Both components (FePt and MgO) of the MgO-added samples were grown epitaxially on the MgO intermediate layer, so that a nano-composite of intercalated (001) FePt and (001) MgO was formed. The revealed microstructures and formation mechanisms may facilitate the improvement of the structural and magnetic properties of the FePt-oxide composite perpendicular magnetic recording media.

  13. Structure and magnetic properties of FePt/Ag nano-granular films with perpendicular magnetic anisotropy%垂直取向FePt/Ag纳米颗粒薄膜的结构和磁性

    Institute of Scientific and Technical Information of China (English)

    李宝河; 黄阀; 杨涛; 冯春; 翟中海; 朱逢吾

    2005-01-01

    用磁控溅射法在单晶MgO(100)基片上制备了[FePt 2 nm/Ag dnm]10多层膜,经真空热处理后,得到具有高矫顽力的垂直取向L10-FePt/Ag颗粒膜.x射线衍射结果表明,在250℃的热基片上溅射,当Ag层厚度d=3-11nm时,FePt颗粒具有很好的[001]取向,随着Ag层厚度的增加,FePt颗粒尺寸减小.[FePr 2 nm/Ag9 nm]10经过600℃真空热处理15 min后,颗粒大小仅约8 nm,垂直矫顽力达到692kA/m.这种无磁耦合作用的颗粒膜,适合用作超高密度的垂直磁记录介质.

  14. Epitaxial Fe3Pt/FePt nanocomposites on MgO and SrTiO3

    Science.gov (United States)

    Casoli, F.; Lupo, P.; Nasi, L.; Cabassi, R.; Fabbrici, S.; Bolzoni, F.; Ranzieri, P.; Albertini, F.

    2015-02-01

    We have exploited the pseudomorphic growth of the magnetically soft Fe3Pt phase on top of L10-FePt to obtain fully epitaxial soft/hard nanocomposites on both MgO(100) and SrTiO3(100). The magnetic properties of this new nanocomposite system, driven by the soft/hard exchange-coupling, can be tailored by varying soft phase thickness, soft phase magnetic anisotropy and substrate. Coercivity is strongly reduced by the addition of the soft phase, a reduction which is definitely affected by the nominal composition of the soft phase and by the substrate choice; similarly is the magnetic phase diagram of the composite system. Coercive field decreases down to 21% of the hard layer value for Fe3Pt(5 nm)/FePt(3.55 nm) nanocomposites on SrTiO3; this maximum coercivity reduction was obtained with a nominal atomic content of Fe in the soft phase of 80%.

  15. Magnetic and structural properties of electrodeposited CoPt and FePt nanowires in nanoporous alumina templates

    Energy Technology Data Exchange (ETDEWEB)

    Dahmane, Y [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Cagnon, L [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Voiron, J [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Pairis, S [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Bacia, M [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Ortega, L [Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9 (France); Benbrahim, N [Laboratoire de Materiaux, Electrochimie et Corrosion, BP 17, 15000 Tizi-Ouzou (Algeria); Kadri, A [Laboratoire de Materiaux, Electrochimie et Corrosion, BP 17, 15000 Tizi-Ouzou (Algeria)

    2006-11-07

    CoPt and FePt nanowire arrays were successfully prepared by electrodeposition into nanochannels of porous alumina membranes. The as-deposited CoPt alloy has a face centred cubic structure and displays soft magnetic properties. Heat treatment at 700 {sup 0}C for different durations, under vacuum condition was carried out in order to obtain the ordered face centred tetragonal phase L1{sub 0}, exhibiting hard magnetic properties. After annealing, arrays of nanowires actually show hard magnetic properties with coercive fields up to 1.1 T at room temperature. Phase transformation, structural and magnetic properties were analysed and necessary conditions to obtain optimum magnetic properties are concluded. The first results obtained with FePt nanowires denote a more complicated system since the as-deposited material shows no magnetization. Magnetism appears only after annealing at 700 {sup 0}C minimum. Coercivity up to 1.1 T has been obtained at room temperature but with inhomogeneous phase composition.

  16. Development of Nanostructured Stress Free Pt-Rich FePt Films for Micro Electro Mechanical System Applications

    Directory of Open Access Journals (Sweden)

    T. M. Selvakumari

    2009-01-01

    Full Text Available Problem statement: The electroplating technique is especially interesting due to its low cost, high throughput and high quality of deposit. Magnetic thin films are extensively used in various electronic devices including high density recording media and Micro Electro Mechanical (MEMS devices. So we examined FePt films and give good magnetic properties. Approach: The Pt-rich FePt alloys were electrodeposited galvanostatically by various temperature baths. Results: The elemental percentage of Pt in the film was very high determined by X-ray spectroscopy. Surface characterization was carried out by using X-Ray Diffractometer (XRD and Scanning Electron Microscope (SEM.The magnetic properties determined by Vibrating sample magnetometer. Hardness and adhesion of the films were also discussed. Conclusion/Recommendation: The films were soft magnetic character of lower temperature bath and become a hard magnetic character of higher temperature bath. Therefore this magnetic films could be an important material for incorporate in Micro electro mechanical devices.

  17. Micromagnetic analysis of the hardening mechanisms of nanocrystalline MnBi and nanopatterned FePt intermetallic compounds.

    Science.gov (United States)

    Kronmüller, H; Yang, J B; Goll, D

    2014-02-12

    The uniaxial intermetallic compounds of L10-FePt and the low temperature NiAs structure of MnBi are suitable alloys for application as high-density recording materials or as high-coercivity permanent magnets. Single domain particles of these materials are characterized by coercive fields above 1 T over a large temperature range. In particular MnBi shows a coercive field of 2 T at 450 K. Its extraordinary magnetic properties in the temperature range up to 600 K are due to an increase of the magnetocrystalline anisotropy constant from 1.2 MJ m(-3) at 300 K to 2.4 MJ m(-3) at 450 K. In spite of the large coercivities obtained for both type of materials their experimental values deviate considerably from the theoretical values Hc = 2K1/Js valid for a homogeneous rotation process in spherical particles. As is well known these discrepancies are due to the deteriorating effects of the microstructure. For an analysis of the coercive fields the Stoner-Wohlfarth theory has to be expanded with respect to higher anisotropy constants and to microstructural effects such as misaligned grains and grain surfaces with reduced anisotropy constants. It is shown that the temperature dependence and the angular dependence of Hc for FePt as well as MnBi can be quantitatively interpreted by taking into account the above mentioned intrinsic and microstructural effects.

  18. Effects of annealing time on the structural and magnetic properties of L1{sub 0} FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zotov, N., E-mail: Nikolay.Zotov@ruhr-uni-bochum.d [Institut fuer Werkstoffe, Fakultaet fuer Maschinenbau, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Hiergeist, R.; Savan, A.; Ludwig, A. [Institut fuer Werkstoffe, Fakultaet fuer Maschinenbau, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2010-06-30

    Thermal annealing of [Fe 1.65 nm/Pt 1.84 nm]{sub 50} multilayers at 673 K for various annealing times between 60 and 12000 s leads to the direct formation of the fully ordered L1{sub 0} FePt phase with (111) texture. The average grain sizes, determined from X-ray diffraction size-strain analysis, are smaller than the critical size for multi-domain FePt particles, suggesting the presence of single-domain (SD) grains. The coercivity increases with annealing time and increasing grain size and reaches values of about 955 kA/m. The remanence values are typical for randomly oriented weakly-interacting particles. A decrease of the remanence with annealing time suggests a decrease of the intergrain exchange interactions with annealing time. Analysis of minor loops and the initial magnetization curves shows the presence of a broad distribution of critical fields, which the individual SD particles have to overcome for the magnetization reversal.

  19. Origin of open recoil curves in L10-A1 FePt exchange coupled nanocomposite thin film

    Science.gov (United States)

    Goyal, Rajan; Kapoor, Akanksha; Lamba, S.; Annapoorni, S.

    2016-11-01

    Mixed phase FePt systems with intergranular coupling may be looked upon as natural exchange spring systems. The coupling strength between the soft and hard phase in these systems can be analyzed using recoil curves. However, the origin of open recoil curves depicting the breakdown of exchange coupling or anisotropy variation in hard phase is still an ambiguity and requires an in-depth analysis. In order to investigate this, an analysis of the recoil curves for L10-A1 FePt nanocomposite thin films of varying thickness have been performed. The switching field distribution reveals that the maximum of openness of recoil curve is directly proportional to the amount of uncoupled soft phase present in the system. The coupling between the hard and soft phase is also found to increase with the thickness of the film. Monte Carlo simulations on a model three dimensional array of interacting nanomagnetic grains provide further insight into the effect of inter granular exchange interactions between the soft and hard phases.

  20. Order and phase nucleation in non-equilibrium nanocomposite Fe-Pt thin films with perpendicular magnetic anisotropy.

    Energy Technology Data Exchange (ETDEWEB)

    Clavero, C.; Skuza, J. R.; Garcia-Martin, J. M.; Cebollada, A.; Walko, D. A.; Lukaszew, R. A.; Coll. of William and Mary; Inst. de Microelectronica de Madrid

    2009-03-01

    We report on the time evolution of mass transport upon annealing nonequilibrium Fe-Pt nanocomposite films, leading to nucleation of L1{sub 0} chemically ordered phase. The nonequilibrium nanocomposite films were fabricated by applying Fe{sup +} ion implantation to epitaxial Pt films grown on (001) MgO substrates, yielding Fe nanoclusters embedded in a Pt matrix at a tailored penetration depth. Time-resolved x-ray diffraction studies were carried out using synchrotron radiation, allowing determination of the activation energy for nucleation of the FePt L1{sub 0} phase within the segregated nanoclusters during annealing. The growth of the segregated L1{sub 0} ordered phase was modeled using ideal grain-size law and found to be dominated by strain-driven surface nucleation. The activation energies were found to correlate with the nanocluster size. Magnetic characterization of selected annealed samples indicates perpendicular magnetic anisotropy with high coercive field coincident with high value of the chemical order parameter of the ordered phase within the magnetic nanoclusters.

  1. CoPt and FePt magnetic alloys grown on van der Waals WSe{sub 2}(0001) surfaces and on arrays of SiO{sub 2} spherical particles

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, Denys

    2008-06-06

    regard an interesting approach, which combines non-magnetic spherical nanoparticle self-assembly with defined magnetic properties provided by a magnetic film, deposited onto the particles, was recently proposed. This enables an elegant possibility of creating magnetic nanostructure arrays with high perpendicular magnetic anisotropy provided by FePt and CoPt alloys, which is required for high thermal stability. The investigation of the magnetic and structural properties of these alloys grown on arrays of amorphous SiO{sub 2} nanospheres is thereafter discussed. (orig.)

  2. Point defects in L10 FePt studied by molecular dynamics simulations based on an analytic bond-order potential

    Science.gov (United States)

    Dong, Hao; Shu, Xiaolin; Wang, Rongming

    2011-08-01

    The point defects and their related physical properties in L10 FePt are investigated by molecular dynamics simulations based on an analytic bond-order potential. The calculated results agree well with the experimental value, indicating that the analytic bond-order potential is suitable to describe the structural properties and surface energies of the FePt alloy in the L10 phase. However, the calculated vacancy formation energy of an Fe atom is higher than that of a Pt atom, which disagrees with some other previously calculated results. This result indicates that the analytic bond-order potential is unable to describe the related point defect properties. The analytic bond-order potential needs to be modified in order to study these defect properties of an FePt alloy.

  3. Optimum thickness of soft magnetic phase in FePt/FeCo permanent magnet superlattices with high energy product and large magnetic anisotropy energy

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar Jain

    2016-02-01

    Full Text Available Ab initio calculations on hard/soft (FePtm/(FeCon, (m = 4, 6, 8 and n = 2-2m magnetic superlattices show that the B2 type FeCo layers become anisotropic with varying interlayer spacing and enhanced magnetic moments. The average magnetic moment in superlattices is higher than in bulk FePt, resulting in high maximum energy product for (FePt4/(FeCo8 which is nearly double the calculated value for bulk FePt. The calculation of the magnetic anisotropy energy shows that the optimal thickness of the soft magnetic phase for good permanent magnet behaviour of the superlattice is less than ∼2 nm.

  4. 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

  5. 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.

  6. 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.

  7. Enhancement of L10 ordering with the c-axis perpendicular to the substrate in FePt alloy film by using an epitaxial cap-layer

    Science.gov (United States)

    Ohtake, Mitsuru; Nakamura, Masahiro; Futamoto, Masaaki; Kirino, Fumiyoshi; Inaba, Nobuyuki

    2017-05-01

    FePt alloy thin films with cap-layers of MgO or C are prepared on MgO(001) single-crystal substrates by using a two-step method consisting of low-temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. The FePt film thickness is fixed at 10 nm, whereas the cap-layer thickness is varied from 1 to 10 nm. The influences of cap-layer material and cap-layer thickness on the variant structure and the L10 ordering are investigated. Single-crystal FePt(001) films with disordered fcc structure (A1) grow epitaxially on the substrates at 200 °C. Single-crystal MgO(001) cap-layers grow epitaxially on the FePt films, whereas the structure of C cap-layers is amorphous. The phase transformation from A1 to L10 occurs when the films are annealed at 600 °C. The FePt films with MgO cap-layers thicker than 2 nm consist of L10(001) variant with the c-axis perpendicular to the substrate surface, whereas those with C cap-layers involve small volumes of L10(100) and (010) variants with the c-axis lying in the film plane. The in-plane and the out-of-plane lattices are respectively more expanded and contracted in the continuous-lattice MgO/FePt/MgO structure due to accommodations of misfits of FePt film with respect to not only the MgO substrate but also the MgO cap-layer. The lattice deformation promotes phase transformation along the perpendicular direction and L10 ordering. The FePt films consisting of only L10(001) variant show strong perpendicular magnetic anisotropies and low in-plane coercivities. The present study shows that an introduction of epitaxial cap-layer is effective in controlling the c-axis perpendicular to the substrate surface.

  8. In-plane anisotropic effect of magnetoelectric coupled PMN-PT/FePt multiferroic heterostructure: Static and microwave properties

    Directory of Open Access Journals (Sweden)

    Jose M. Vargas

    2014-10-01

    Full Text Available The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT. The sample was a (011-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1, a microwave magnetoelectric (ME coupling of 28 Oe cm kV −1 was estimated, whereas a value of 42 Oe cm kV −1 was obtained through the hard magnetization axis (100. Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1, a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz, we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.

  9. Structure and magnetization reversal mechanism in L1{sub 0} FePt films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.J. [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Zheng Jianguo [Laboratory for Electron and X-ray Instrumentation, Calit2, University of California-Irvine, Irvine, CA 92697 (United States); Shi, Z., E-mail: shizhong@tongji.edu.cn [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Department of Physics, Tongji University, Shanghai 200092 (China); Zhou, S.M. [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Department of Physics, Tongji University, Shanghai 200092 (China); Sun, L. [Department of Mechanical Engineering and Texas Center for Superconductivity (TcSUH), University of Houston, Houston, Texas 77204 (United States); Du, J. [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2012-06-30

    A series of L1{sub 0} Fe{sub 63}Pt{sub 37} films with controlled thickness (t{sub FM}) were deposited on MgO(100) substrates for microstructure and magnetization reversal mechanism study. X-ray diffraction measurements show that face-centered tetragonal (200) peak also exists in addition to face-centered tetragonal (002) one, and becomes weak for thick films. High resolution electron microscopy study reveals the existence of periodic misfit dislocations at the FePt/MgO interface and other types of defects such as twins and antiphase boundary inside the film. Out-of-plane initial magnetization shows a slow increase responding to the external magnetic field and then follows a steep increase. The out-of-plane coercivity H{sub C} at room temperature decreases with increasing t{sub FM} and increases when the angle {theta}{sub H} between the external magnetic field and the film normal direction increases. H{sub C} at {theta}{sub H} = 0 changes as a linear function of temperature for individual samples and the slope decreases with increasing t{sub FM}. In addition, magnetic viscosity measurements show that the fluctuation field at room temperature decreases with increasing t{sub FM}. These phenomena indicate that the magnetization reversal in the L1{sub 0} FePt films should be realized by the motion of weakly pinned domain wall and thus governed by the thermal activation model. The magnetization reversal thermal activation volume and corresponding energy increase with increasing t{sub FM}, as a result of the interactions between domain walls and structural defects can be attributed to the sample microstructural characteristic evolution with t{sub FM}. - Highlights: Black-Right-Pointing-Pointer A series of L1{sub 0} Fe{sub 63}Pt{sub 37} films with controlled thickness (t{sub FM}) were prepared. Black-Right-Pointing-Pointer Periodic misfit dislocations are observed at the FePt/MgO interface. Black-Right-Pointing-Pointer The dependence of H{sub C} on t{sub FM} and T is

  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. Large-area patterning of sub-100 nm epitaxial L10 FePt dots array via nanoimprint lithography

    Directory of Open Access Journals (Sweden)

    Zheng Li

    2015-08-01

    Full Text Available Bit-patterned media, a promising candidate for next generation high density magnetic recording, requires sub-100 nm dots array on a wafer scale, a high degree of patterning control of the size distribution, and a material with high perpendicular anisotropy. In this work, large area (0.75 cm × 0.75 cm dots array was achieved by nanoimprint lithography and ion milling from L10 FePt thin films that are pre-sputtered at 450 °C with both high crystalline quality and good chemical order. The sub-100 nm dots are decoupled from each other and show both narrow size distributions and high coercivity values on the order of 11 kOe. Our work would cast light for the application of bit-patterned media.

  12. Ballistic and diffusive current spin polarization in L1{sub o}-ordered FePt and FePd

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, Klaus M.; Baltz, Vincent; Hickey, Mark C.; Marrows, Christopher H.; Hickey, Bryan J. [E.C. Stoner Laboratory, School of Physics and Astronomy, University of Leeds, Leeds (United Kingdom); MacKenzie, Maureen; Chapman, John N. [Department of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom); Miguel, Jorge; Kuch, Wolfgang [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Berlin (Germany); Kronast, Florian [BESSY, Albert-Einstein-Strasse 15, Berlin (Germany)

    2008-07-01

    We report on the discrepancy of the current spin polarization in the ballistic and diffusive electron transport regime in L1{sub o}-ordered epitaxial FePt and FePd layers. The films studied displayed a chemical long range order parameter of 0.4

  13. (001)-textured growth of L1{sub 0}-FePt thin films on MgO and Cr seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Matthes, Patrick; Brombacher, Christoph; Daniel, Marcus; Beddies, Gunther; Albrecht, Manfred [Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz (Germany)

    2011-07-01

    Chemically ordered FePt has a high uniaxial anisotropy with the easy axis in (001)-direction. It has been shown that (001)-textured MgO and Cr [2] seed layers can be used to stabilize the (001)-texture of L1{sub 0}-chemically ordered FePt on amorphous substrates. In this study the growth of MgO and Cr seed layers was optimized by varying the process parameters (deposition temperature and rate as well as Ar pressure) and their influence on the magnetic properties of epitaxially grown FePt films have been analyzed. In addition, reference samples on MgO(100) single crystals were prepared. XRD measurements revealed a high degree of chemical order leading to a K{sub eff} of (8.5{+-}1.3) x 10{sup 6}erg/cm{sup 3} after FePt deposition at 350 C. The low deposition temperature results in a smooth film morphology and a reversal behaviour which is dominated by domain wall propagation.

  14. 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.

  15. 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.

  16. Chemically Functional Alkanethiol Derivitized Magnetic Nanoparticles

    Science.gov (United States)

    2003-01-01

    agents in medical imaging technologies7, and ’spintronics’ 8 (i.e., spin-based data transfer and storage). For example, Co and FePt nanoparticles have been...with a personal computer. Pt microelectrodes (25pin diameter) were created by flame-sealing Pt microwire (Alfa Aesar) in glass capillaries. The sealed

  17. 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.

  18. 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.

  19. 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.

  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. Tunable spin-wave frequency gap in anisotropy-graded FePt films obtained by ion irradiation

    Science.gov (United States)

    Tacchi, S.; Pini, M. G.; Rettori, A.; Varvaro, G.; di Bona, A.; Valeri, S.; Albertini, F.; Lupo, P.; Casoli, F.

    2016-07-01

    The effect of graded anisotropy on static and dynamic magnetic properties of Ar+-irradiated FePt films has been investigated by static magnetometry, magnetic force microscopy, and Brillouin light scattering from thermally excited spin waves. A gradual variation of magnetic anisotropy with film thickness was obtained by Ar+ irradiation. The irradiation incidence angle influences the anisotropy profile: on decreasing α , a decreasing thickness of the hard L 10 phase and an increasing thickness of the soft A1 phase were obtained. Accordingly, the zero-field spin-wave frequency gap was found to decrease. In the sample with the highest soft-phase thickness the spin-wave frequency gap takes a substantial value (ν0≈6 GHz), which could be reproduced assuming the presence of a nonzero "rotatable" anisotropy (i.e., any direction in the film plane can be established as the easy axis by the application of a saturating magnetic field along this direction). The hypothesis is supported by both magnetometry and magnetic force microscopy data.

  3. Influence of energetic ions and neutral atoms on the L1 0 ordering of FePt films

    Science.gov (United States)

    Cantelli, V.; von Borany, J.; Mücklich, A.; Zhou, Shengqiang; Grenzer, J.

    2007-04-01

    The A1 → L10 phase transition of Fe50Pt50 films, deposited at room-temperature on amorphous SiO2 by dc magnetron co-sputtering at 0.3 Pa, was studied with in-situ X-ray diffraction. An almost complete transition characterized by a long-range order parameter S > 0.8 is obtained already after a heat treatment at (320 ± 20) °C. A post-deposition He ion irradiation (50 keV, 1 × 1015 - 3 × 1016 cm-2) does not further reduce the transition temperature. Theoretical calculations reveal that, due to the negligible thermalization of the sputtered atoms and reflected ions in the plasma, a considerable fraction of energetic ions and atoms meet the substrate surface. The low transition temperature is explained by the impact of energetic ions and atoms which provoke significant adatom mobility and a decrease of the activation energy for atomic reordering by vacancies. Consequently, using deposition parameters leading to a strong thermalized plasma, the FePt films showed an increase of the transition temperature up to 400 °C, a lower S-value (S ≅ 0.6) and a reduced coercivity.

  4. Atomically flat surface of (0 0 1) textured FePt thin films by residual stress control

    Science.gov (United States)

    Liu, S. H.; Hsiao, S. N.; Chou, C. L.; Chen, S. K.; Lee, H. Y.

    2015-11-01

    Single-layered Fe52Pt48 films with thickness of 10 nm were sputter-deposited on glass substrates. Rapid thermal annealing with different heating rates (10-110 K/s) was applied to transform as-deposited fcc phase into L10 phase and meanwhile to align [0 0 1]-axis of L10 crystal along plane normal direction. Based on X-ray diffractometry using synchrotron radiation source, the texture coefficient of (0 0 1)-plane increases with increasing heating rate from 10 to 40 K/s, which is correlated with perpendicular magnetic anisotropy and in-plane tensile stress analyzed by asymmetric sin2 ψ method. Furthermore, it was revealed by atomic force microscopy that the dewetting process occurred as heating rate was raised up to 80 K/s and higher. The change in the microstructure due to stress relaxation leads to the degradation of (0 0 1) orientation and magnetic properties. Surface roughness is closely related to the in-plane tensile stress. Enhanced perpendicular magnetic anisotropy and atomically flat surface were achieved for the samples annealed at 40 K/s, which may be suitable for further practical applications. This work also suggests a feasible way for surface engineering by controlling internal stress of the FePt without introducing cap layer.

  5. Perpendicular Magnetic Anisotropy and Induced Magnetic Structures of Pt Layers in the Fe/Pt Multilayers Investigated by Resonant X-ray Magnetic Scattering

    Science.gov (United States)

    Lee, Mihee; Takechi, Ryota; Hosoito, Nobuyoshi

    2017-02-01

    Depth distribution of the magnetization induced in the paramagnetic Pt layers of Fe/Pt multilayers was investigated by resonant X-ray magnetic scattering (RXMS) near the Pt L3 absorption edge. Two samples with different perpendicular magnetic anisotropy (PMA) were chosen for RXMS measurements. The magnetic depth profile of the Pt layer was determined in the magnetic saturation state of the Fe magnetization with the sample of weak PMA. The magnetization process of the Pt layer was investigated with the sample of moderate PMA. It is found that the Pt atoms near the interface region have a perpendicular component of the induced magnetization even in the saturation state of the Fe magnetization, suggesting that the PMA of Fe/Pt multilayers originates from the Pt atoms near the interface region. Concerning the magnetization process, the induced Pt magnetization is not proportional to the Fe magnetization. This implies a complicated magnetizing mechanism of the Pt layer by the Fe magnetization.

  6. 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.

  7. Design and Micromagnetic Simulation of Fe/L10-FePt/Fe Trilayer for Exchange Coupled Composite Bit Patterned Media at Ultrahigh Areal Density

    Directory of Open Access Journals (Sweden)

    Warunee Tipcharoen

    2015-01-01

    Full Text Available Exchange coupled composite bit patterned media (ECC-BPM are one candidate to solve the trilemma issues, overcome superparamagnetic limitations, and obtain ultrahigh areal density. In this work, the ECC continuous media and ECC-BPM of Fe/L10-FePt/Fe trilayer schemes are proposed and investigated based on the Landau-Lifshitz-Gilbert equation. The switching field, Hsw, of the hard phase in the proposed continuous ECC trilayer media structure is reduced below the maximum write head field at interlayer exchange coupling between hard and soft phases, Aex, higher than 20 pJ/m and its value is lower than that for continuous L10-FePt single layer media and L10-FePt/Fe bilayer. Furthermore, the Hsw of the proposed ECC-BPM is lower than the maximum write head field with exchange coupling coefficient between neighboring dots of 5 pJ/m and Aex over 10 pJ/m. Therefore, the proposed ECC-BPM trilayer has the highest potential and is suitable for ultrahigh areal density magnetic recording technology at ultrahigh areal density. The results of this work may be gainful idea for nanopatterning in magnetic media nanotechnology.

  8. Tailoring out-of-plane magnetic properties of pulsed laser deposited FePt thin films by changing laser energy fluence

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Tan, T.L.; Tan, K.S.; Lee, P. [NSSE, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Liu, Hai; Yadian, Boluo; Hu, Ge; Huang, Yizhong; Ramanujan, R.V. [School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Rawat, R.S., E-mail: rajdeep.rawat@nie.edu.sg [NSSE, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore)

    2014-10-01

    Highlights: • Laser energy fluence (LEF) effect on composition, microstructure and magnetism. • Enhancing out-of-plane magnetic properties by tailoring LEF on target surface. • Higher LEF results in more energetic plasma species causing vacancy defects. • Formation of vacancy defect in FePt thin films leads to improved magnetic properties. • Best out-of-plane magnetic properties are achieved with medium LEF. - Abstract: Magnetic properties of pulsed laser deposited (PLD) FePt thin films are investigated at three different laser energy fluences of 51, 136 and 182 J/cm{sup 2}. Deposition at lower laser energy fluence (51 J/cm{sup 2}) yields softer out-of-plane coercivity (≤0.4 kG), whereas deposition at higher laser energy fluence (136 and 182 J/cm{sup 2}) results in harder out-of-plane coercivity (≥5.0 kG). The improved coercivity is found to be attributed to the formation of vacancy defects in thin films, which is indicated by stress change from tensile to compressive form with increasing laser energy fluence. Maximum out-of-plane saturated magnetization of 615 emu/cm{sup 3} and remanent squareness ratio of 0.88 are achieved for 16 nm thick FePt thin films deposited at moderate laser energy fluence of 136 J/cm{sup 2}, making them suitable for high density perpendicular data storage applications.

  9. Disentangling the physical contributions to the anomalous Hall effect and domain wall resistance in isoelectronic L10-FePd and L10-FePt alloys

    Science.gov (United States)

    Seemann, Klaus; Garcia-Sanchez, Felipe; Kakay, Attila; Schneider, Claus; Freimuth, Frank; Mokrousov, Yuriy; Bluegel, Stefan; Hertel, Riccardo

    2012-02-01

    We analyze the origin of the electrical resistance arising in domain walls of perpendicularly magnetized materials by considering a superposition of anisotropic magnetoresistance and the resistance implied by the magnetization chirality. The domain wall profiles of L10-FePd and L10-FePt are determined by micromagnetic simulations based on which we perform first principles calculations to quantify electron transport through the core and closure region of the walls. The wall resistance, being twice as high in L10-FePd than in L10-FePt, is found to be clearly dominated in both cases by a high gradient of magnetization rotation, and not by the spin-orbit interaction driven anisotropic magnetoresistance effect. Concerning the anomalous Hall effect on the other hand, we show that difference in spin-orbit interaction strength of Pt and Pd atoms leads to a pronounced cross-over from an extrinsic side jump mechanism in L10-FePd to an intrinsic Berry-phase anomalous Hall effect in L10-FePt.

  10. Spin-orbit torques and spin accumulation in FePt/Pt and Co/Cu thin films from first principles: The role of impurities

    Science.gov (United States)

    Géranton, Guillaume; Zimmermann, Bernd; Long, Nguyen H.; Mavropoulos, Phivos; Blügel, Stefan; Freimuth, Frank; Mokrousov, Yuriy

    2016-06-01

    Using the Boltzmann formalism based on the first principles electronic structure and scattering rates, we investigate the current-induced spin accumulation and spin-orbit torques in FePt/Pt and Co/Cu bilayers in the presence of substitutional impurities. In FePt/Pt bilayers we consider the effect of intermixing of Fe and Pt atoms in the FePt layer and find a crucial dependence of spin accumulation and spin-orbit torques on the details of the distribution of these defects. In Co/Cu bilayers we predict that the magnitude and sign of the spin-orbit torque and spin accumulation depend very sensitively on the type of the impurities used to dope the Cu substrate. Moreover, simultaneously with impurity-driven scattering, we consider the effect of an additional constant quasiparticle broadening of the states at the Fermi surface to simulate phonon scattering at room temperature and discover that even a small broadening of the order of 25 meV can drastically influence the magnitude of the considered effects. We explain our findings based on the analysis of the complex interplay of several competing Fermi surface contributions to the spin accumulation and spin-orbit torques in these structurally and chemically nonuniform systems.

  11. Electric-field manipulation of coercivity in FePt/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructures investigated by anomalous Hall effect measurement

    Science.gov (United States)

    Liu, Mingfeng; Hao, Liang; Jin, Tianli; Cao, Jiangwei; Bai, Jianmin; Wu, Dongping; Wang, Ying; Wei, Fulin

    2015-06-01

    The effect of electric field (E-field) on the magnetism of FePt thin films in FePt/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) heterostructures was investigated by anomalous Hall effect measurement. For FePt films of different thicknesses, the coercivity vs E-field curves show a typical butterfly-like loop behavior. Further results indicate that the coercivity variation is composed of the volatile symmetrical butterfly-like loop and nonvolatile hysteresis loop-like parts, which originate from the volatile and nonvolatile strains induced by the E-field in the PMN-PT(001) substrate, respectively. No significant difference has been observed after inserting a 2 nm W interlayer, suggesting that the charge-mediated coercivity variation is negligible in FePt/PMN-PT heterostructures.

  12. 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

  13. 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

  14. Property comparison of a CoSiB/Pt multilayer to Co/Pt and CoFe/Pt with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, S.; Yim, H. I. [Sookmyung Women' s University, Seoul (Korea, Republic of)

    2011-07-15

    We have investigated the perpendicular magnetic anisotropy of a [CoSiB t{sub CoSiB}/Pt 14 A]{sub 5} multilayer as a function of the CoSiB thickness. We have studied the perpendicular magnetic anisotropy of [Co t{sub Co}/Pt 15 A]{sub 5} and [CoFe t{sub CoFe}/Pt 10 A]{sub 5} multilayers for various thicknesses of Co and CoFe. Furthermore, we have measured and compared the coercivities and the saturation magnetizations of all samples. In this study, samples were [Co t{sub Co} /Pt 15 A]{sub 5}, [CoFe t{sub CoFe}/Pt 10 A]{sub 5} and [CoSiB t{sub CoSiB} /Pt 14 A]{sub 5} with t = 2, 3, 4, and 5 A. The coercivities and the saturation magnetizations were obtained 223.76 Oe and 341.25 emu/cm{sup 3}, 395.86 Oe and 286.79 emu/cm{sup 3} and 155.13 Oe and 429.98 emu/cm{sup 3} in CoSiB/Pt, Co/Pt and CoFe/Pt mutilayers, respectively. The maximum coercivity was obtained 395.86 Oe in the [Co 3 A /Pt 15 A]{sub 5} multilayer, and the minimum saturation magnetization was 286.79 emu/cm{sup 3} in the [Co 2 A /Pt 15 A]{sub 5} multilayer.

  15. Finite electric field effects in the large perpendicular magnetic anisotropy surface Pt/Fe/Pt(001): a first-principles study.

    Science.gov (United States)

    Tsujikawa, Masahito; Oda, Tatsuki

    2009-06-19

    We investigate crystalline magnetic anisotropy in the electric field (EF) for the FePt surface which has a large perpendicular anisotropy, by means of the first-principles approach. Anisotropy is reduced linearly with respect to the inward EF, associated with the induced spin density around the Fe layer. Although the magnetic anisotropy energy (MAE) density reveals large variation around the atoms, the intrinsic contribution to the MAE is found to mainly come from the Fe layer. The surface without the capping Pt layer also shows similar linear dependence.

  16. Structure, magnetism, and interface properties of epitactical thin Fe and FePt films on GaAs(001) substrates; Struktur, Magnetismus und Grenzflaecheneigenschaften epitaktischer duenner Fe- und FePt-Filme auf GaAs(001)-Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Schuster, Ellen Ursula

    2007-12-17

    The research in this thesis is focused on the study of the Fe spin structure and interface magnetism of thin epitaxial Fe layers or epitaxial FePt alloy films with chemical L1{sub 0} order on GaAs(001) surfaces. The main method of investigation was isotope-specific conversion electron Moessbauer spectroscopy (CEMS) combined with the {sup 57}Fe probe-layer technique in the temperature range of 4.2-300 K. The film structure was studied using electron diffraction (RHEED) and X-ray diffraction (XRD). The chemical order parameter S determined by XRD was found to increase with rising growth temperature, T{sub S}, to a maximum value of 0.71, until long range order is destroyed at T{sub S}>350 C by alloying with the substrate. As an important result a linear correlation between short-range order (revealed by the relative spectral area of the L1{sub 0} phase) and long-range order S was observed. The observed perpendicular Fe spin texture, characterized by the mean tilting angle left angle {theta} right angle of the Fe spins (relative to the film normal direction), was found to correlate with the L1{sub 0} phase content and with S. Furthermore, epitaxial Fe(001) films on GaAs(001)-(4 x 6) and on GaAs(001)-LED surfaces were grown successfully. In the initial stage of Fe film growth non-monotonous behavior of the in-plane lattice parameter was observed by RHEED. The magnetic hyperfine field distributions P(B{sub hf}) at the Fe/GaAs interface extracted from CEMS spectra for T{sub S}=-140 C or room temperature (RT) were found to be very similar. The observed large mean hyperfine fields of left angle B{sub hf} right angle {approx}25-27 T at the interface indicate the presence of high average Fe moments of 1.7-1.8 {mu}{sub B}. Nonmagnetic interface layers either can be excluded (Fe/GaAs) or are very thin (0.5 ML,Fe/GaAs-LED). Owing to its island structure an ultrathin (1.9 ML thick) uncoated Fe(001) film on GaAs(001)-(4 x 6) shows superparamagnetism with a blocking temperature of

  17. Micromagnetic simulation with three models of FeCo/L10 FePt exchange-coupled particles for bit-patterned media

    Institute of Scientific and Technical Information of China (English)

    Wang Ying; Wang Rui; Xie Hai-Long; Bai Jian-Min; Wei Fu-Lin

    2013-01-01

    Compositing soft and hard materials is a promising method to decrease the coercivity of L10 FePt,which is considered to be a suitable material for bit-patterned media.This paper reports the simulation of three models of FeCo/L10 FePt exchange-coupled composite particles for bit patterned media by the OOMMF micromagnetic simulation software:the enclosed model,the side-enclosed model,and the top-covered model.All of them have the same volumes of the soft and hard parts but different shapes.Simulation results show that the switching fields for the three models can be reduced to about 10 kOe (1Oe =79.5775 A/m) and the factor gain can be improved to 1.4 when the interface exchange coefficient has a proper value.Compared to the other models,the enclosed model has a wider range of interface exchange coefficient values,in which a low switching field and high gain can be obtained.The dependence of the switching fields on the angle of the applied field shows that none of the three models are easily affected by the stray field of a magnetic head.

  18. Tuning the Curie temperature of L1{sub 0} ordered FePt thin films through site-specific substitution of Rh

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Dongbin, E-mail: dongbin.xu@seagate.com [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore); Sun, Cheng-Jun, E-mail: cjsun@aps.anl.gov, E-mail: msecgm@nus.edu.sg; Heald, Steve M. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chen, Jing-Sheng; Chow, Gan Moog, E-mail: cjsun@aps.anl.gov, E-mail: msecgm@nus.edu.sg [Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore); Zhou, Tie-Jun [Data Storage Institute, Agency for Science, Technology and Research (A-STAR), Singapore 117608 (Singapore); Bergman, Anders; Sanyal, Biplab [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden)

    2014-10-14

    In structurally ordered magnetic thin films, the Curie temperature (T{sub C}) of ferromagnetic films depends on the exchange integral of the short range ordered neighboring atoms. The exchange integral may be adjusted by controlling the elemental substitutional concentration at the lattice site of interest. We show how to control the T{sub C} in high anisotropy L1{sub 0} Fe{sub 50}Pt{sub 50} magnetic thin films by substituting Rh into the Pt site. Rh substitution in L1{sub 0} FePt modified the local atomic environment and the corresponding electronic properties, while retaining the ordered L1{sub 0} phase. The analysis of extended x-ray Absorption Fine Structure spectra shows that Rh uniformly substitutes for Pt in L1{sub 0} FePt. A model of antiferromagnetic defects caused by controlled Rh substitution of the Pt site, reducing the T{sub C,} is proposed to interpret this phenomenon and its validity is further examined by ab initio density functional calculations.

  19. Epitaxial Fe{sub 3}Pt/FePt nanocomposites on MgO and SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Casoli, F., E-mail: casoli@imem.cnr.it; Nasi, L.; Cabassi, R.; Fabbrici, S.; Bolzoni, F.; Ranzieri, P.; Albertini, F. [IMEM-CNR, Parco Area delle Scienze 37/A, Parma, I-43124 (Italy); Lupo, P. [Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2015-02-28

    We have exploited the pseudomorphic growth of the magnetically soft Fe{sub 3}Pt phase on top of L1{sub 0}-FePt to obtain fully epitaxial soft/hard nanocomposites on both MgO(100) and SrTiO{sub 3}(100). The magnetic properties of this new nanocomposite system, driven by the soft/hard exchange-coupling, can be tailored by varying soft phase thickness, soft phase magnetic anisotropy and substrate. Coercivity is strongly reduced by the addition of the soft phase, a reduction which is definitely affected by the nominal composition of the soft phase and by the substrate choice; similarly is the magnetic phase diagram of the composite system. Coercive field decreases down to 21% of the hard layer value for Fe{sub 3}Pt(5 nm)/FePt(3.55 nm) nanocomposites on SrTiO{sub 3}; this maximum coercivity reduction was obtained with a nominal atomic content of Fe in the soft phase of 80%.

  20. Tailoring out-of-plane magnetic properties of pulsed laser deposited FePt thin films by changing laser energy fluence

    Science.gov (United States)

    Wang, Ying; Tan, T. L.; Tan, K. S.; Lee, P.; Liu, Hai; Yadian, Boluo; Hu, Ge; Huang, Yizhong; Ramanujan, R. V.; Rawat, R. S.

    2014-10-01

    Magnetic properties of pulsed laser deposited (PLD) FePt thin films are investigated at three different laser energy fluences of 51, 136 and 182 J/cm2. Deposition at lower laser energy fluence (51 J/cm2) yields softer out-of-plane coercivity (≤0.4 kG), whereas deposition at higher laser energy fluence (136 and 182 J/cm2) results in harder out-of-plane coercivity (≥5.0 kG). The improved coercivity is found to be attributed to the formation of vacancy defects in thin films, which is indicated by stress change from tensile to compressive form with increasing laser energy fluence. Maximum out-of-plane saturated magnetization of 615 emu/cm3 and remanent squareness ratio of 0.88 are achieved for 16 nm thick FePt thin films deposited at moderate laser energy fluence of 136 J/cm2, making them suitable for high density perpendicular data storage applications.

  1. In-plane electric field controlled perpendicular magnetic anisotropy in an FePt/[Pb(Mg1/3Nb2/3)O3]0.7-(PbTiO3)0.3 heterostructure

    Science.gov (United States)

    Guo, Qi; Xu, Xiaoguang; Feng, Julong; Liu, Pengfei; Wu, Yong; Ma, Li; Zhou, Shiming; Miao, Jun; Jiang, Yong

    2016-06-01

    We report the in-plane electric field controlled perpendicular magnetic anisotropy of L10-FePt films deposited on polarized [Pb(Mg1/3Nb2/3)O3]0.7-(PbTiO3)0.3 single crystal substrates. The out-of-plane coercivity (H c⊥) of FePt films exhibits a regular response to the in-plane electric field applied on substrates. The experimental change of H c⊥ is approximately 21.3% with the electric field varying from -10 to 10 kV/cm. The magnetization direction can be controlled by switching the electric field. The remanence of FePt films can also be manipulated by the electric field, so that a “W”-shaped sawtooth magnetic signal can be generated by a sawtooth electric field.

  2. 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.

  3. 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.

  4. 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%.

  5. L10 ordered phase formation in FePt, FePd, CoPt, and CoPd alloy thin films epitaxially grown on MgO(001) single-crystal substrates

    Science.gov (United States)

    Ohtake, Mitsuru; Ouchi, Shouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2012-04-01

    The FePt, FePd, CoPt, and CoPd epitaxial thin films are prepared on MgO(001) single-crystal substrates by ultrahigh vacuum RF magnetron sputtering. The effects of the magnetic material and the substrate temperature on the film growth, the film structure, and the magnetic properties are investigated. The L10 ordered phase formation is observed for FePt, FePd, and CoPt films prepared at temperatures higher than 200, 400, and 600 °C, respectively, whereas that is not recognized for CoPd films. The L10-FePd(001) single-crystal films with the c-axis normal to the substrate surface are formed, whereas the FePt and CoPt epitaxial films include L10(100) crystals whose c-axis is parallel to the substrate surface, in addition to the L10(001) crystals. Upon increasing the substrate temperature, the ordering degree increases. A higher ordering parameter is observed in the order of FePd > FePt > CoPt. The magnetic properties are influenced by the crystal structure, the crystallographic orientation of the L10 crystal, and the ordering degree.

  6. Bimetallic nanoparticles for arsenic detection.

    Science.gov (United States)

    Moghimi, Nafiseh; Mohapatra, Mamata; Leung, Kam Tong

    2015-06-02

    Effective and sensitive monitoring of heavy metal ions, particularly arsenic, in drinking water is very important to risk management of public health. Arsenic is one of the most serious natural pollutants in soil and water in more than 70 countries in the world. The need for very sensitive sensors to detect ultralow amounts of arsenic has attracted great research interest. Here, bimetallic FePt, FeAu, FePd, and AuPt nanoparticles (NPs) are electrochemically deposited on the Si(100) substrate, and their electrochemical properties are studied for As(III) detection. We show that trace amounts of As(III) in neutral pH could be determined by using anodic stripping voltammetry. The synergistic effect of alloying with Fe leads to better performance for Fe-noble metal NPs (Au, Pt, and Pd) than pristine noble metal NPs (without Fe alloying). Limit of detection and linear range are obtained for FePt, FeAu, and FePd NPs. The best performance is found for FePt NPs with a limit of detection of 0.8 ppb and a sensitivity of 0.42 μA ppb(-1). The selectivity of the sensor has also been tested in the presence of a large amount of Cu(II), as the most detrimental interferer ion for As detection. The bimetallic NPs therefore promise to be an effective, high-performance electrochemical sensor for the detection of ultratrace quantities of arsenic.

  7. Demagnetization dynamics of C-dop ed FePt film%C掺杂FePt铁磁薄膜光诱导超快退磁动力学研究∗

    Institute of Scientific and Technical Information of China (English)

    潘群峰; 张泽宇; 王会真; 林贤; 金钻明; 程振祥; 马国宏

    2016-01-01

    Magneto-optical information storage has been a hot research subject for several years. FePt exhibits abundant physical properties and has received much attention as a candidate material. Its alloy film with perpendicular anisotropy and small grain size has important applications in magnetic recordings due to the large intrinsic magnetic anisotropy which ensures long-time thermal stability of nanometer sized bits. However, the large coercive field of FePt is a significant factor that hinders its application. As is well known, the magnetic anisotropy in FePt alloy can be precisely modulated by carbon-doping, and as a result, the coercive field of FePt film can be modified effectively with the carbon dopant. On the other hand, the microscopic mechanism of magnetic storage relies on the motion of spin system. Ultrashort femtosecond laser has been demonstrated to be a very effective tool to investigate the dynamical coupling among different degrees of freedom, such as electron, spin and lattice in a ferromagnetic film. The research on spin dynamics has become a new frontier of condensed matter physics, which is crucial for ultrafast magnetic recording materials. In this work, by using the time-resolved magneto-optical Kerr effect spectroscopy, we study the ultrafast spin dynamics of two FePt alloy films with different carbon dopants under the applied magnetic field along the film surface. The FePt alloy films with different carbon dopants are fabricated on silicon substrates by the sputtering method. The main experimental findings in this work are as follows. (i) The transient Kerr signal is linearly proportional to the magnetization with the magnetic field up to 0.8 T, while the transient reflectivity of the film is independent of the applied magnetic field. (ii) For FePt alloy films with different coercive fields, it is found that the demagnetization time of the film with smaller coercive field is significantly faster than that of the larger counterpart: the former

  8. 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

  9. 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.

  10. Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles

    Directory of Open Access Journals (Sweden)

    Ulf Wiedwald

    2010-11-01

    Full Text Available Monatomic (Fe, Co and bimetallic (FePt and CoPt nanoparticles were prepared by exploiting the self-organization of precursor loaded reverse micelles. Achievements and limitations of the preparation approach are critically discussed. We show that self-assembled metallic nanoparticles can be prepared with diameters d = 2–12 nm and interparticle distances D = 20–140 nm on various substrates. Structural, electronic and magnetic properties of the particle arrays were characterized by several techniques to give a comprehensive view of the high quality of the method. For Co nanoparticles, it is demonstrated that magnetostatic interactions can be neglected for distances which are at least 6 times larger than the particle diameter. Focus is placed on FePt alloy nanoparticles which show a huge magnetic anisotropy in the L10 phase, however, this is still less by a factor of 3–4 when compared to the anisotropy of the bulk counterpart. A similar observation was also found for CoPt nanoparticles (NPs. These results are related to imperfect crystal structures as revealed by HRTEM as well as to compositional distributions of the prepared particles. Interestingly, the results demonstrate that the averaged effective magnetic anisotropy of FePt nanoparticles does not strongly depend on size. Consequently, magnetization stability should scale linearly with the volume of the NPs and give rise to a critical value for stability at ambient temperature. Indeed, for diameters above 6 nm such stability is observed for the current FePt and CoPt NPs. Finally, the long-term conservation of nanoparticles by Au photoseeding is presented.

  11. PEGylated FePt-Fe3O4 composite nanoassemblies (CNAs): in vitro hyperthermia, drug delivery and generation of reactive oxygen species (ROS).

    Science.gov (United States)

    Sahu, Niroj Kumar; Gupta, Jagriti; Bahadur, Dhirendra

    2015-05-21

    Chemothermal therapy is widely used in clinical applications for the treatment of tumors. However, the major challenge is the use of a multifunctional nano platform for significant regression of the tumor. In this study, a simple synthesis of highly aqueous stable, carboxyl enriched, PEGylated mesoporous iron platinum-iron(ii,iii) oxide (FePt-Fe3O4) composite nanoassemblies (CNAs) by a simple hydrothermal approach is reported. CNAs exhibit a high loading capacity ∼90 wt% of the anticancer therapeutic drug, doxorubicin (DOX) because of its porous nature and the availability of abundant negatively charged carboxylic groups on its surface. DOX loaded CNAs (CNAs + DOX) showed a pH responsive drug release in a cell-mimicking environment. Furthermore, the release was enhanced by the application of a alternating current magnetic field. CNAs show no appreciable cytotoxicity in mouse fibroblast (L929) cells but show toxic effects in cervical cancer (HeLa) cells at a concentration of ∼1 mg mL(-1). A suitable composition of CNAs with a concentration of 2 mg mL(-1) can generate a hyperthermic temperature of ∼43 °C. Also, CNAs, because of their Fe and Pt contents, have an ability to generate reactive oxygen species (ROS) in the presence of hydrogen peroxide inside the cancer cells which helps to enhance its therapeutic effects. The synergistic combination of chemotherapy and ROS is very efficient for killing cancer cells.

  12. Applications of an energy-dispersive pnCCD for X-ray reflectivity: Investigation of interdiffusion in Fe-Pt multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Abboud, Ali; Send, Sebastian; Pietsch, Ullrich [Universitaet Siegen, FB Physik, Walter-Flex-Strasse 3, 57072 Siegen (Germany); Hartmann, Robert [PNSensor GmbH, Muenchen (Germany); Strueder, Lothar [Universitaet Siegen, FB Physik, Walter-Flex-Strasse 3, 57072 Siegen (Germany); Planck-Institut fuer extraterrestrische Physik (MPE), Muenchen (Germany); MPI Halbleiterlabor, Muenchen (Germany); Savan, Alan; Ludwig, Alfred [Ruhr-Universitaet Bochum, Bochum (Germany); Zotov, Nikolay [Forschungszentrum Juelich, Juelich (Germany)

    2011-11-15

    A frame store pn-junction CCD (pnCCD) detector was applied to study thermally induced interdiffusion in Fe/Pt thin film multilayers (MLs) in a temperature range between 300 and 585 K. Based on the energy resolution of the detector the reflectivity was measured simultaneously in a spectral range between 8 keV < E < 20 keV including the Pt L-edge energies close to 11.5 keV. Above T = 533 K we find a strong drop of intensities at 1st and 2nd order ML Bragg peak interpreted by mutual interdiffusion. Considering a simulated model of interdiffusion it has been found that the concentration of iron that diffuses into the platinum sub layers is higher than that of platinum into iron. The time dependence of inter diffusion was also calculated in the range of 533-568 K and was described by the Arrhenius equation D(T) = D{sub 0} exp(-H{sub a}/k{sub B}T). The activation energy for the MLs used [Fe 1.7 nm/Pt 2 nm]{sub 50} was found to be 0.94 {+-} 0.22 eV. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. 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。

  14. 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...

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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...

  20. 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.

  1. Ionic Functionalization of Hydrophobic Colloidal Nanoparticles To Form Ionic Nanoparticles with Enzymelike Properties.

    Science.gov (United States)

    Liu, Yuan; Purich, Daniel L; Wu, Cuichen; Wu, Yuan; Chen, Tao; Cui, Cheng; Zhang, Liqin; Cansiz, Sena; Hou, Weijia; Wang, Yanyue; Yang, Shengyuan; Tan, Weihong

    2015-12-01

    Inorganic colloidal nanoparticles (NPs) stabilized by a layer of hydrophobic surfactant on their surfaces have poor solubility in the aqueous phase, thus limiting their application as biosensors under physiological conditions. Here we report a simple model to ionize various types of hydrophobic colloidal NPs, including FePt, cubic Fe3O4, Pd, CdSe, and NaYF4 (Yb 30%, Er 2%, Nd 1%) NPs, to multicharged (positive and negative) NPs via ligand exchange. Surfaces of neutral hydrophobic NPs were converted to multicharged ions, thus making them soluble in water. Furthermore, peroxidase-like activity was observed for ionic FePt, Fe3O4, Pd, and CdSe NPs, of which FePt and CdSe catalyzed the oxidation of the colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) to the blue-colored product in the absence of H2O2, while Pd and Fe3O4 catalyzed the oxidization of TMB in the presence of H2O2. With the benefit of the ionic functionalization protocols described herein, colloidal NPs should gain wider use as biomarkers, nanozymes, and biosensors.

  2. Enhancement of order degree and perpendicular magnetic anisotropy of L10 ordered Fe(Pt,Pd) alloy film by introducing a thin MgO cap-layer

    Science.gov (United States)

    Noguchi, Youhei; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi; Inaba, Nobuyuki

    2016-07-01

    Fe50PtxPd50-x (at%, x=0-50) alloy films of 10 nm thickness with and without 2-nm-thick MgO cap-layers are prepared on MgO(001) single-crystal substrates by employing a two-step method consisting of low-temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. The influences of MgO cap-layer on the structure and the magnetic properties are investigated. Fe50PtxPd50-x films epitaxially grow on the substrates at 200 °C. The Fe50Pd50 and the Fe50Pt12.5Pd37.5 films are respectively composed of (001) single-crystals with disordered fcc-based (A1) and bcc-based (A2) structures. The films with x>25 consist of mixtures of A1 and A2 crystals. The volume ratio of A2 to A1 crystal decreases with increasing the x value from 25 to 50. The in-plane and out-of-plane lattices are respectively expanded and shrunk due to accommodation of lattice mismatch between film and substrate. When the films are annealed at 600 °C, phase transformation to L10 ordered phase takes place. L10 phase transformation of Fe50PtxPd50-x film is promoted for a sample with MgO cap-layer and the order degree is higher than that without cap-layer. Furthermore, L10 ordering with the c-axis perpendicular to the substrate surface is enhanced for the film with cap-layer. The cap-layer is considered to be giving a tension stress to the magnetic film in lateral direction which promotes L10 ordering with the c-axis perpendicular to the substrate. Deposition of cap-layer is shown effective in achieving higher order degree and in enhancing perpendicular magnetic anisotropy with Fe(Pt,Pd) films.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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...

  11. 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...

  12. 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.

  13. 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.

  14. A high sensitive biosensor based on FePt/CNTs nanocomposite/N-(4-hydroxyphenyl)-3,5-dinitrobenzamide modified carbon paste electrode for simultaneous determination of glutathione and piroxicam.

    Science.gov (United States)

    Karimi-Maleh, Hassan; Tahernejad-Javazmi, Fahimeh; Ensafi, Ali A; Moradi, Reza; Mallakpour, Shadpour; Beitollahi, Hadi

    2014-10-15

    This study describes the development, electrochemical characterization and utilization of novel modified N-(4-hydroxyphenyl)-3,5-dinitrobenzamide-FePt/CNTs carbon paste electrode for the electrocatalytic determination of glutathione (GSH) in the presence of piroxicam (PXM) for the first time. The synthesized nanocomposite was characterized with different methods such as TEM and XRD. The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of GSH and PXM. The peak currents were linearly dependent on GSH and PXM concentrations in the range of 0.004-340 and 0.5-550 µmol L(-1), with detection limits of 1.0 nmol L(-1) and 0.1 µmolL(-1), respectively. The modified electrode was successfully used for the determination of the analytes in real samples with satisfactory results.

  15. 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.

  16. 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.

  17. 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 swollen polymer microspheres. Subsequently, the iron oxide nanoparticles were formed within the polymer matrix by thermal decomposition of ferric oleate. The morphology, inner structure, and magnetic properties of the magnetic polymer microspheres were studied with a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), and superconducting quantum interference device (SQUID) magnetometer. The results showed that the average diameter of the magnetic polymer microspheres was 5.1 microm with a standard deviation of 0.106, and the magnetic polymer microspheres with saturation magnetization of 12.6 emu/g exhibited distinct superparamagnetic characteristics at room temperature. More interestingly, the magnetite nanoparticles with a spinel structure are evenly distributed over the whole area of the polymer microspheres. These magnetic polymer microspheres have potential applications in biotechnology.

  18. Small silicon, big opportunities: the development and future of colloidally-stable monodisperse silicon nanocrystals.

    Science.gov (United States)

    Mastronardi, Melanie L; Henderson, Eric J; Puzzo, Daniel P; Ozin, Geoffrey A

    2012-11-14

    Nanomaterials are becoming increasingly widespread in consumer technologies, but there is global concern about the toxicity of nanomaterials to humans and the environment as they move rapidly from the research laboratory to the market place. With this in mind, it makes sense to intensify the nanochemistry community's global research effort on the synthesis and study of nanoparticles that are purportedly "green". One potentially green nanoparticle that seems to be a most promising candidate in this context is silicon, whose appealing optical, optoelectronic, photonic, and biomedical attributes are recently gaining much attention. In this paper, we outline some of our recent contributions to the development of the growing field of silicon nanocrystals (ncSi) in order to stress the importance of continued study of ncSi as a green alternative to the archetypal semiconductor nanocrystals like CdSe, InAs, and PbS. While a variety of developments in synthetic methods, characterization techniques, and applications have been reported in recent years, the ability to prepare colloidally-stable monodisperse ncSi samples may prove to have the largest impact on the field, as it opens the door to study and access the tunable size-dependent properties of ncSi. Here, we summarize our recent contributions in size-separation methods to achieve monodisperse samples, the characterization of size-dependant property trends, the development of ncSi applications, and their potential impact on the promising future of ncSi.

  19. Purification of Nanoparticles by Size and Shape

    Science.gov (United States)

    Robertson, James D.; Rizzello, Loris; Avila-Olias, Milagros; Gaitzsch, Jens; Contini, Claudia; Magoń, Monika S.; Renshaw, Stephen A.; Battaglia, Giuseppe

    2016-06-01

    Producing monodisperse nanoparticles is essential to ensure consistency in biological experiments and to enable a smooth translation into the clinic. Purification of samples into discrete sizes and shapes may not only improve sample quality, but also provide us with the tools to understand which physical properties of nanoparticles are beneficial for a drug delivery vector. In this study, using polymersomes as a model system, we explore four techniques for purifying pre-formed nanoparticles into discrete fractions based on their size, shape or density. We show that these techniques can successfully separate polymersomes into monodisperse fractions.

  20. Synthesis of single-walled carbon nanotube networks using monodisperse metallic nanocatalysts encapsulated in reverse micelles

    Directory of Open Access Journals (Sweden)

    Gayduchenko Igor A.

    2016-01-01

    Full Text Available We report on a method of synthesis of single-walled carbon nanotubes percolated networks on silicon dioxide substrates using monodisperse Co and Ni catalyst. The catalytic nanoparticles were obtained by modified method of reverse micelles of bis-(2-ethylhexyl sulfosuccinate sodium in isooctane solution that provides the nanoparticle size control in range of 1 to 5 nm. The metallic nanoparticles of Ni and Co were characterized using transmission electron microscopy (TEM and atomic-force microscopy (AFM. Carbon nanotubes were synthesized by chemical vapor deposition of CH4/H2 composition at temperature 1000 °С on catalysts pre-deposited on silicon dioxide substrate. Before temperature treatment during the carbon nanotube synthesis most of the catalyst material agglomerates due to magnetic forces while during the nanotube growth disintegrates into the separate nanoparticles with narrow diameter distribution. The formed nanotube networks were characterized using AFM, scanning electron microscopy (SEM and Raman spectroscopy. We find that the nanotubes are mainly single-walled carbon nanotubes with high structural perfection up to 200 μm long with diameters from 1.3 to 1.7 nm consistent with catalyst nanoparticles diameter distribution and independent of its material.

  1. Facile Method for Preparation of Silica Coated Monodisperse Superparamagnetic Microspheres

    Directory of Open Access Journals (Sweden)

    Xuan-Hung Pham

    2016-01-01

    Full Text Available This paper presents a facile method for preparation of silica coated monodisperse superparamagnetic microsphere. Herein, monodisperse porous polystyrene-divinylbenzene microbeads were prepared by seeded emulsion polymerization and subsequently sulfonated with acetic acid/H2SO4. The as-prepared sulfonated macroporous beads were magnetized in presence of Fe2+/Fe3+ under alkaline condition and were subjected to silica coating by sol-gel process, providing water compatibility, easily modifiable surface form, and chemical stability. FE-SEM, TEM, FT-IR, and TGA were employed to characterize the silica coated monodisperse magnetic beads (~7.5 μm. The proposed monodisperse magnetic beads can be used as mobile solid phase particles candidate for protein and DNA separation.

  2. Metal Fe{sup 3+} ions assisted synthesis of highly monodisperse Ag/SiO{sub 2} nanohybrids and their antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Nianchun; Xue, Feng [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Yu, Xiang [Analytical and Testing Center, Jinan University, Guangzhou 510632 (China); Zhou, Huihua [Guangdong East Sunshine Pharmaceutical Co., Ltd., Dongguan 523871 (China); Ding, Enyong, E-mail: eyding@scut.edu.cn [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China)

    2013-02-15

    Graphical abstract: TEM images of the Ag/SiO{sub 2}-2 nanohybrids. The homogeneous and more mono-disperse Ag nanoparticles deposit on SiO{sub 2} spheres. Through this method, Ag nanoparticles are easily formed on the surface of SiO{sub 2} compared to other methods. Highlights: Black-Right-Pointing-Pointer We prepared homogeneous and mono-dispersed Ag/SiO{sub 2}-2 nanohybrids by adding Fe{sup 3+} ions. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids had core(SiO{sub 2})-shell(Ag) structure. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids exhibited excellent antibacterial activity against bacteria. Black-Right-Pointing-Pointer The reaction temperature was lower and the yield of Ag/SiO{sub 2}-2 nanohybrids were higher. - Abstract: Highly monodispersed Ag/SiO{sub 2} nanohybrids with excellent antibacterial property were synthesized by using DMF as a reducing agent and employing an additional redox potential of metal Fe{sup 3+} ion as a catalytic agent. The obtained Ag/SiO{sub 2}-2 nanohybrids of about 240 nm were highly monodispersity and uniformity by adding trace Fe{sup 3+} ions into the reaction which Ag{sup +} reacted with N,N-dimethyl formamide (DMF) at 70 Degree-Sign C. Compared to the conventional techniques, which need long time and high temperature for silica coating of Ag nanoparticles, this new method was capable of synthesizing monodispersed, uniform, high yield Ag/SiO{sub 2} nanohybrids. The electron was transferred from the Fe{sup 2+} ion to the Ag{sup +} ion to accelerate the nucleation of silver nanoparticles. The chemical structures, morphologies and properties of the Ag/SiO{sub 2} nanohybrids were characterized by X-ray diffraction (XRD), (High-resolution, Scanning transmission) transmission electron microscopy (TEM, HRTEM and STEM), and X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy (UV-vis) and test of antibacterial. The results demonstrated that the silver nanoparticles supported on the surface of Si

  3. Rapid enumeration of phage in monodisperse emulsions.

    Science.gov (United States)

    Tjhung, Katrina F; Burnham, Sean; Anany, Hany; Griffiths, Mansel W; Derda, Ratmir

    2014-06-17

    Phage-based detection assays have been developed for the detection of viable bacteria for applications in clinical diagnosis, monitoring of water quality, and food safety. The majority of these assays deliver a positive readout in the form of newly generated progeny phages by the bacterial host of interest. Progeny phages are often visualized as plaques, or holes, in a lawn of bacteria on an agar-filled Petri dish; however, this rate-limiting step requires up to 12 h of incubation time. We have previously described an amplification of bacteriophages M13 inside droplets of media suspended in perfluorinated oil; a single phage M13 in a droplet yields 10(7) copies in 3-4 h. Here, we describe that encapsulation of reporter phages, both lytic T4-LacZ and nonlytic M13, in monodisperse droplets can also be used for rapid enumeration of phage. Compartmentalization in droplets accelerated the development of the signal from the reporter enzyme; counting of "positive" droplets yields accurate enumeration of phage particles ranging from 10(2) to 10(6) pfu/mL. For enumeration of T4-LacZ phage, the fluorescent signal appeared in as little as 90 min. Unlike bulk assays, quantification in emulsion is robust and insensitive to fluctuations in environmental conditions (e.g., temperature). Power-free emulsification using gravity-driven flow in the absence of syringe pumps and portable fluorescence imaging solutions makes this technology promising for use at the point of care in low-resource environments. This droplet-based phage enumeration method could accelerate and simplify point-of-care detection of the pathogens for which reporter bacteriophages have been developed.

  4. nanoparticles

    Science.gov (United States)

    Zhao, Yu; Li, Hui; Liu, Xu-Jun; Guan, Lei-Lei; Li, Yan-Li; Sun, Jian; Ying, Zhi-Feng; Wu, Jia-Da; Xu, Ning

    2014-06-01

    Evenly separated crystalline CuIn0.8Ga0.2Se2 (CIGS) nanoparticles are deposited on ITO-glass substrate by pulsed laser deposition. Such CIGS layers are introduced between conjugated polymer layers and ITO-glass substrates for enhancing light absorbance of polymer solar cells. The P3HT:PCBM absorbance between 300 and 650 nm is enhanced obviously due to the introduction of CIGS nanoparticles. The current density-voltage curves of a P3HT:PCBM/CIGS solar cell demonstrate that the short-circuit current density is improved from 0.77 to 1.20 mA/cm2. The photoluminescence spectra show that the excitons in the polymer are obviously quenched, suggesting that the charge transfer between the P3HT:PCBM and CIGS occurred. The results reveal that the CIGS nanoparticles may exhibit the localized surface plasmon resonance effect just as metallic nanostructures.

  5. Preparation of monodisperse, superparamagnetic, luminescent, and multifunctional PGMA microspheres with amino-groups

    Institute of Scientific and Technical Information of China (English)

    WANG WeiCai; ZHANG Qi; ZHANG BingBo; LI DeNa; DONG XiaoQing; ZHANG Lei; CHANG Jin

    2008-01-01

    Micron-sized, monodisperse, superparamagnetic, luminescent composite poly(glycidyl methacrylate) (PGMA) microspheres with functional amino-groups were successfully synthesized in this study. The process of preparation was as follows: preparation of monodisperse poly(glycidyl methacrylate) mi-crospheres by dispersion polymerization method; modification of poly(glycidyl methacrylate) micro-spheres with ethylene diamine to form amino-groups; impregnation of iron ions (Fe2+ and Fe3+) inside the microspheres and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe3O,4>) nanoparticles within the polymer microspheres; infusion of CdSe/CdS core-shell quantum dots (QDs) into magnetic polymer microspheres. Scanning electron microscopy (SEM) was used to char-acterize surface morphology and size distribution of composite microspheres. The average size of mi-crospheres was 1.42μm with a size variation of 3.8%, The composite microspheres were bright enough and easily observed using a conventional fluorescence microscope, The composite microspheres were easily separated from solution by magnetic decantation using a permanent magnet. The new multi-functional composite microspheres are promising to be used in a variety of bioanalytical assays in-volving luminescence detection and magnetic separation.

  6. Extended X-ray absorption fine structure of bimetallic nanoparticles

    Directory of Open Access Journals (Sweden)

    Carolin Antoniak

    2011-05-01

    Full Text Available Electronic and magnetic properties strongly depend on the structure of the material, especially on the crystal symmetry and chemical environment. In nanoparticles, the break of symmetry at the surface may yield different physical properties with respect to the corresponding bulk material. A useful tool to investigate the electronic structure, magnetic behaviour and local crystallographic structure is X-ray absorption spectroscopy. In this review, recent developments in the field of extended X-ray absorption fine structure measurements and in the analysis methods for structural investigations of bimetallic nanoparticles are highlighted. The standard analysis based on Fourier transforms is compared to the relatively new field of wavelet transforms that have the potential to outperform traditional analysis, especially in bimetallic alloys. As an example, the lattice expansion and inhomogeneous alloying found in FePt nanoparticles is presented, and this is discussed below in terms of the influence of employed density functional theory calculations on the magnetic properties.

  7. Ternary alloy systems. Phase diagrams, crystallographic and thermodynamic data critically evaluated by MSIT {sup registered}. Subvol. D. Iron systems. Pt. 3: Selected systems from Co-Fe-Si to Cu-Fe-Pt

    Energy Technology Data Exchange (ETDEWEB)

    Effenberg, Guenter; Ilyenko, Svitlana (eds.) [MSI, Materials Science International Services GmbH, Stuttgart (Germany); Bochvar, Nataliya; Bondar, Anatoliy; Cornish, Lesley (and others)

    2008-07-01

    Volume 11 of group IV presents phase diagrams, crystallographic and thermodynamic data of ternary alloy systems. The subvolume D deals with iron systems, with part 3 considering selected systems from Co-Fe-Si to Cu-Fe-Pt. At ambient pressure the equilibria of each individual ternary system are discussed as functions of temperature yielding spatial diagrams whose sections and projections are displayed. The phase equilibria are described in terms of liquidus, solidus and solvus projections, isothermal, vertical and quasibinary sections. Data on invariant equilibria are generally given in the form of tables and reaction schemes. The volume forms a comprehensive review and rigorous systematization of the presently available data. For each system the often conflicting literature and contradictory information has been thoroughly evaluated by a team of experts, MSIT, and can thus be presented in a standard format. Back to the year 1900 the literature has been reviewed, implying possible reinterpretations from today's state of knowledge, and incorporated in the volume. The tables and diagrams are preceded by descriptive commenting texts. (orig.)

  8. Growth Kinetics of Monodisperse Polystyrene Microspheres Prepared by Dispersion Polymerization

    Directory of Open Access Journals (Sweden)

    Fan Li

    2013-01-01

    Full Text Available Dispersion polymerization has been widely applied to the synthesis of monodisperse micron-sized polymer colloidal spheres. Many efforts have been devoted to studying the influence of initial conditions on the size and uniformity of the resultant microspheres, aiming to synthesize micron-size monodisperse colloidal spheres. However, the inner contradiction between the size and the size distribution of colloidal spheres hinders the realization of this goal. In this work, we drew our attention from the initial conditions to the growth stage of dispersion polymerization. We tracked the size evolution of colloidal sphere during the dispersion polymerization, through which we established a kinetic model that described the relationship between the monomer concentration and the reaction time. The model may provide a guideline to prepare large polymer colloidal spheres with good monodispersity by continuous monomer feeding during the growth stage to maintain the concentration of monomer at a constant value in a dispersion polymerization process.

  9. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Directory of Open Access Journals (Sweden)

    Silvia Varela-Aramburu

    2016-09-01

    Full Text Available Gold nanoclusters are small (1–3 nm nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery.

  10. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Science.gov (United States)

    Varela-Aramburu, Silvia; Wirth, Richard; Lai, Chian-Hui; Orts-Gil, Guillermo

    2016-01-01

    Summary Gold nanoclusters are small (1–3 nm) nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery. PMID:27826501

  11. nanoparticles

    Science.gov (United States)

    Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J. Enrique

    2014-10-01

    Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.

  12. Production of monodisperse epigallocatechin gallate (EGCG) microparticles by spray drying for high antioxidant activity retention.

    Science.gov (United States)

    Fu, Nan; Zhou, Zihao; Jones, Tyson Byrne; Tan, Timothy T Y; Wu, Winston Duo; Lin, Sean Xuqi; Chen, Xiao Dong; Chan, Peggy P Y

    2011-07-15

    Epigallocatechin gallate (EGCG) originated from green tea is well-known for its pharmaceutical potential and antiproliferating effect on carcinoma cells. For drug delivery, EGCG in a micro-/nanoparticle form is desirable for their optimized chemopreventive effect. In this study, first time reports that EGCG microparticles produced by low temperature spray drying can maintain high antioxidant activity. A monodisperse droplet generation system was used to realize the production of EGCG microparticles. EGCG microparticles were obtained with narrow size distribution and diameter of 30.24 ± 1.88 μM and 43.39 ± 0.69 μM for pure EGCG and lactose-added EGCG, respectively. The EC50 value (the amount of EGCG necessary to scavenge 50% of free radical in the medium) of spray dried pure EGCG particles obtained from different temperature is in the range of 3.029-3.075 μM compared to untreated EGCG with EC50 value of 3.028 μM. Varying the drying temperatures from 70°C and 130°C showed little detrimental effect on EGCG antioxidant activity. NMR spectrum demonstrated the EGCG did not undergo chemical structural change after spray drying. The major protective mechanism was considered to be: (1) the use of low temperature and (2) the heat loss from water evaporation that kept the particle temperature at low level. With further drier optimization, this monodisperse spray drying technique can be used as an efficient and economic approach to produce EGCG micro-/nanoparticles.

  13. Spontaneous droplet formation techniques for monodisperse emulsions preparation – Perspectives for food applications

    NARCIS (Netherlands)

    Maan, A.A.; Schroën, C.G.P.H.; Boom, R.M.

    2011-01-01

    Spontaneous droplet formation through Laplace pressure differences is a simple method for making monodisperse emulsions and is claimed to be suited for shear and temperature sensitive products, and those requiring high monodispersity. Techniques belonging to this category include (grooved) microchan

  14. Bulk synthesis of monodisperse magnetic FeNi3 nanopowders by flow levitation method.

    Science.gov (United States)

    Chen, Shanjun; Chen, Yan; Kang, Xiaoli; Li, Song; Tian, Yonghong; Wu, Weidong; Tang, Yongjian

    2013-10-01

    In this work, a novel bulk synthesis method for monodisperse FeNi3 nanoparticles was developed by flow levitation method (FL). The Fe and Ni vapours ascending from the high temperature levitated droplet was condensed by cryogenic Ar gas under atmospheric pressure. X-ray diffraction was used to identify and characterize the crystal phase of prepared powders exhibiting a FeNi3 phase. The morphology and size of nanopowders were observed by transmission electron microscopy (TEM). The chemical composition of the nanoparticles was determined with energy dispersive spectrometer (EDS). The results indicated that the FeNi3 permalloy powders are nearly spherical-shaped with diameter about 50-200 nm. Measurement of the magnetic property of nanopowders by a superconducting quantum interference device (SQUID, Quantum Design MPMS-7) showed a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 220 Oe and saturation magnetization of 107.17 emu/g, at 293 K. At 5 K, the obtained saturation magnetization of the sample was 102.16 emu/g. The production rate of FeNi3 nanoparticles was estimated to be about 6 g/h. This method has great potential in mass production of FeNi3 nannoparticles.

  15. Thermoplastic polyurethanes with TDI-based monodisperse hard segments

    NARCIS (Netherlands)

    De, D.; Araichimani, A.; ten Hoopen, Hermina W.M.; Gaymans, R.J.

    2009-01-01

    Polyurethanes with PTMO soft segments and toluene diisocyanate diamide as urethane segment were studied. The toluene diisocyanate diamide urethane segment was monodisperse in length. The soft segment length was changed by extending PTMO with TDI units to a soft segment length varying from 2 250 to

  16. A general approach for monodisperse colloidal perovskites, Chemistry of Materials

    NARCIS (Netherlands)

    Demirors, A.F.; Imhof, A.

    2009-01-01

    We describe a novel general method for synthesizing monodisperse colloidal perovskite particles at room temperature by postsynthesis addition of metal hydroxides to amorphous titania colloids. In previous work, we used titania particles to synthesize homogenously mixed silica-titania composite parti

  17. Alkyl-Functionalized Oxide-Free Silicon Nanoparticles: Synthesis and Optical Properties

    NARCIS (Netherlands)

    Rosso-Vasic, M.; Spruijt, E.; Lagen, van B.; Cola, de L.; Zuilhof, H.

    2008-01-01

    Highly monodisperse silicon nanoparticles (1.57 ± 0.21 nm) are synthesized with a covalently attached alkyl monolayer on a gram scale. Infrared spectroscopy shows that these silicon nanoparticles contain only a few oxygen atoms per nanoparticle. XPS spectra clearly show the presence of unoxidized Si

  18. Dispersion behavior of core-shell silica-polymer nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Core-shell silica nanoparticles are superior in modifying surface wetting behavior, enhancing nucleation and growth in crystallization, improving dispersion of naked nanoparticles, and thus upgrading the overall properties of organic polymers. The dispersion behavior and morphology of monodisperse core-shell silica particles in several polymers including polyesters are reviewed and their potential applications are discussed.

  19. Alliages magnétiques FePd et FePt en couches minces sous contrainte épitaxiale : mise en ordre en température et propriétés magnétiques

    Science.gov (United States)

    Arenal de La Concha, R.; Schuster, I.; Halley, D.; Marty, A.; Bayle-Guillemaud, P.

    2002-07-01

    In order to increase the storage capacities of the media of magnetic recording one seeks to decrease the size of the magnetic fields which carry information. The growth of thin layers of magnetic alloys in ordered phases makes it possible to plan structures with very strong perpendicular magnetic anisotropy, necessary to obtain stable fields in spite of their reduced size. We studied, thanks to an original device of in temperature X-rays diffraction, the ordering of FePd layers or FePt deposited by MBE in different states of initial order and constraint, then submitted to heat treatment. The ordering occured along the growth axis. The structure of the layers is very inhomogeneous: not ordered and ordered domains coexist, with or without defect in the stacking of the L10 phase, even domains of other phases. The small zones, which have been ordered during the growth, do not seem to take part in the development of the long range order during the treatment. The evolution of the ordered fraction is identical whatever the imposed state of epitaxial stress. Modifications of the experimental conditions make it possible from now to plan more systematic measurements with a temperature history more rigorous in order to confirm these observations. Afin d'augmenter les capacités de stockage des media d'enregistre ment magnétique, on cherche à diminuer la taille des domaines magnétiques qui portent l'information. L'élaboration de couches minces d'alliages magnétiques dans des phases ordonnées permet d'envisager des structures à très forte anisotropie magnétique perpendiculaire, nécessaire pour obtenir des domaines stables malgré leur taille réduite. Nous avons étudié, grâce à un dispositif original de diffraction X en température, la mise en ordre de couches FePd ou FePt déposées par MBE dans des états différents d'ordre initial et de contrainte. La mise en ordre se fait selon l'axe de croissance. La structure des couches est très inhomogène : coexistent

  20. Structural and magnetic features of heterogeneously nucleated Fe-oxide nanoparticles

    Science.gov (United States)

    Simeonidis, K.; Mourdikoudis, S.; Tsiaoussis, I.; Angelakeris, M.; Dendrinou-Samara, C.; Kalogirou, O.

    Iron oxide nanoparticles of diameter 14 nm were synthesized by applying Pt seed-assisted heterogeneous thermal decomposition of Fe(CO) 5 in a two-stage procedure. The intense heating treatment resulted in a remarkable mean volume increment compared to previous studies. This method is able to control the nanoparticle mean diameter, keeping the demand for thermal energy at low levels. High-resolution electron microscopy images and the corresponding electron diffraction patterns revealed the appearance of a FePt 3 core in each nanoparticle, surrounded by highly crystallized inverse spinel Fe 3O 4 formed after atmospheric oxidation, as shown by a combination of X-ray diffraction and chemical analysis. Magnetic measurements indicated that the presence of Pt-rich core does not cause any visible modification to the values of saturation magnetization and anisotropy constant of nanoparticles, compared to homogeneously nucleated iron oxide particles of the same size.

  1. Newly designed silver coated-magnetic, monodisperse polymeric microbeads as SERS substrate for low-level detection of amoxicillin

    Science.gov (United States)

    Kibar, Güneş; Topal, Ahmet Emin; Dana, Aykutlu; Tuncel, Ali

    2016-09-01

    We report the preparation of silver-coated magnetic polymethacrylate core-shell nanoparticles for use in surface-enhanced Raman scattering based drug detection. Monodisperse porous poly (mono-2-(methacryloyloxy)ethyl succinate-co-glycerol dimethacrylate), poly (MMES-co-GDMA) microbeads of ca. 5 μm diameter were first synthesized through a multistage microsuspension polymerization technique to serve as a carboxyl-bearing core region. Microspheres were subsequently magnetized by the co-precipitation of ferric ions, aminated through the surface hydroxyl groups and decorated with Au nanoparticles via electrostatic attraction. An Ag shell was then formed on top of the Au layer through a seed-mediated growth process, resulting in micron-sized monodisperse microbeads that exhibit Raman enhancement effects due to the roughness of the Ag surface layer. The core-shell microspheres were used as a new substrate for the detection of amoxicillin at trace concentrations up to 10-8 M by SERS. The proposed SERS platform can be evaluated as a useful tool for the follow-up amoxicillin pollution and low-level detection of amoxicillin in aqueous media.

  2. Enhanced bio-compatibility of ferrofluids of self-assembled superparamagnetic iron oxide-silica core-shell nanoparticles

    Digital Repository Service at National Institute of Oceanography (India)

    Narayanan, T.N.; Mary, A; Swalih, P.K.A; Kumar, D.S.; Makarov, D.; Albrecht, M.; Puthumana, J.; Anas, A; Anantharaman, A

    -interacting, monodispersed and hence the synthesis of such nanostructures has great relevance in the realm of nanoscience. Silica-coated superparamagnetic iron oxide nanoparticles based ferrofluids were prepared using polyethylene glycol as carrier fluid by employing a...

  3. Method of synthesizing tungsten nanoparticles

    Science.gov (United States)

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  4. Tribological characteristics of monodispersed cerium borate nanospheres in biodegradable rapeseed oil lubricant

    Energy Technology Data Exchange (ETDEWEB)

    Boshui, Chen, E-mail: boshuichen@163.com; Kecheng, Gu; Jianhua, Fang; Jiang, Wu; Jiu, Wang; Nan, Zhang

    2015-10-30

    Graphical abstract: - Highlights: • Monodispersed stearic acid-capped cerium borate composite nanoparticles were prepared by hydrothermal method. Their morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics were also characterized. • The surface-capped cerium borate nanoparticles exhibited excellent dispersing stability in rapeseed oil. As new lubricating additives, they were also outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil in biodegradable rapeseed oil. The results presented in this paper would be of important significance for developing green lubricants and lubricant additives. • The prominent tribological performances of SA/CeBO{sub 3} in rapeseed oil were investigated and attributed to the formation of a composite boundary lubrication film mainly composed of lubricous tribochemical species on the tribo-surfaces. - Abstract: Stearic acid-capped cerium borate composite nanoparticles, abbreviated as SA/CeBO{sub 3}, were prepared by hydrothermal method. The morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics, of SA/CeBO{sub 3} were characterized by scanning electron microscope, energy dispersive X-ray spectrometer, dynamic laser particle size analyzer, X-ray diffraction, and Fourier transform infrared spectrometer, respectively. The friction and wear performances of SA/CeBO{sub 3} as a lubricating additive in a rapeseed oil were evaluated on a four-ball tribo-tester. The tribochemical characteristics of the worn surfaces were investigated by X-ray photoelectron spectroscopy. The results showed that the hydrophobic SA/CeBO{sub 3} were monodispersed nanospheres with an average diameter of 8 nm, and exhibited excellent dispersing stability in rapeseed oil. Meanwhile, SA/CeBO{sub 3} nanospheres were outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil. The prominent

  5. Facile synthesis of monodisperse superparamagnetic Fe3O4/PMMA composite nanospheres with high magnetization

    Science.gov (United States)

    Lan, Fang; Liu, Ke-Xia; Jiang, Wen; Zeng, Xiao-Bo; Wu, Yao; Gu, Zhong-Wei

    2011-06-01

    Monodisperse superparamagnetic Fe3O4/polymethyl methacrylate (PMMA) composite nanospheres with high saturation magnetization were successfully prepared by a facile novel miniemulsion polymerization method. The ferrofluid, MMA monomer and surfactants were co-sonicated and emulsified to form stable miniemulsion for polymerization. The samples were characterized by DLS, TEM, FTIR, XRD, TGA and VSM. The diameter of the Fe3O4/PMMA composite nanospheres by DLS was close to 90 nm with corresponding polydispersity index (PDI) as small as 0.099, which indicated that the nanospheres have excellent homogeneity in aqueous medium. The TEM results implied that the Fe3O4/PMMA composite nanospheres had a perfect core-shell structure with about 3 nm thin PMMA shells, and the core was composed of many homogeneous and closely packed Fe3O4 nanoparticles. VSM and TGA showed that the Fe3O4/PMMA composite nanospheres with at least 65% high magnetite content were superparamagnetic, and the saturation magnetization was as high as around 39 emu g - 1 (total mass), which was only decreased by 17% compared with the initial bare Fe3O4 nanoparticles.

  6. A co-flow-focusing monodisperse microbubble generator

    KAUST Repository

    Zhang, Jiaming

    2014-02-14

    We use a simple and inexpensive microfluidic device, which is based on microscope glass slides and two tapered glass capillaries, to produce monodisperse microbubbles. The innermost capillary used for transporting the gas is inserted into the second capillary, with its 2 μm sharp tip aligned with the center of the converging-diverging throat of the second capillary. This configuration provides a small and smooth gas flow rate, and a high velocity gradient at the tube outlet. Highly monodisperse microbubbles with diameters ranging from 3.5 to 60 microns have been successfully produced at a rate of up to 40 kHz. A simple scaling law, which is based on the capillary number and liquid-to-gas flow rate ratio, successfully predicts the bubble size. © 2014 IOP Publishing Ltd.

  7. Facile synthesis of monodisperse functional magnetic dialdehyde starch nano-composite and used for highly effective recovery of Hg(II).

    Science.gov (United States)

    Wang, Yang; Zhang, Yun; Hou, Chen; Qi, Zhigang; He, Xinghua; Li, Yanfeng

    2015-12-01

    By covalently linking dialdehyde starch and amine functionalized Fe3O4 nanoparticle, and modifying with aminothiourea functional group, the novel monodisperse nano-composite has been successfully synthesized without any toxic crosslinking agent. The resulting nano-composite was characterized by means of the Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), elemental analysis and vibrating sample magnetometer (VSM). As the new kind of low-cost and environmentally friendly adsorbent with the excellent monodispersity in aqueous phase, the obtained nano-composite has shown not only the good adsorption capacity for Hg(II) on high initial concentration, but also the strong removal ability on low concentration. Moreover, the unique selectivity for Hg(II) among the mixed metal ions solution and good regeneration performance of nano-composite has also been demonstrated by batch experiments.

  8. Facile Synthesis of Monodisperse CdS Nanocrystals via Microreaction

    Directory of Open Access Journals (Sweden)

    Zhou Xinggui

    2009-01-01

    Full Text Available Abstract CdS-based nanocrystals (NCs have attracted extensive interest due to their potential application as key luminescent materials for blue and white LEDs. In this research, the continuous synthesis of monodisperse CdS NCs was demonstrated utilizing a capillary microreactor. The enhanced heat and mass transfer in the microreactor was useful to reduce the reaction temperature and residence time to synthesize monodisperse CdS NCs. The superior stability of the microreactor and its continuous operation allowed the investigation of synthesis parameters with high efficiency. Reaction temperature was found to be a key parameter for balancing the reactivity of CdS precursors, while residence time was shown to be an important factor that governs the size and size distribution of the CdS NCs. Furthermore, variation of OA concentration was demonstrated to be a facile tuning mechanism for controlling the size of the CdS NCs. The variation of the volume percentage of OA from 10.5 to 51.2% and the variation of the residence time from 17 to 136 s facilitated the synthesis of monodisperse CdS NCs in the size range of 3.0–5.4 nm, and the NCs produced photoluminescent emissions in the range of 391–463 nm.

  9. Synthesis and characterization of gold-deposited red, green and blue fluorescent silica nanoparticles for biosensor application.

    Science.gov (United States)

    Lee, Kyoung G; Wi, Rinbok; Park, Tae Jung; Yoon, Sun Hong; Lee, Jaebeom; Lee, Seok Jae; Kim, Do Hyun

    2010-09-14

    Fluorescent silica nanoparticles deposited with highly monodisperse gold nanoparticles (1-2 nm) were synthesized via the W/O method and intensive ultrasound irradiation. A large surface area of gold-doped fluorescent silica nanoparticle serves as a platform to immobilize a specific binding protein for biomolecules interaction in bioimaging applications.

  10. Progress in the preparation of magnetic nanoparticles for applications in biomedicine

    Energy Technology Data Exchange (ETDEWEB)

    Roca, A G; Costo, R; Rebolledo, A F; Veintemillas-Verdaguer, S; Tartaj, P; Gonzalez-Carreno, T; Morales, M P; Serna, C J, E-mail: puerto@icmm.csic.e [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain)

    2009-11-21

    This review summarizes recent advances in synthesis routes for quickly and reliably making and functionalizing magnetic nanoparticles for applications in biomedicine. We put special emphasis on describing synthetic strategies that result in the production of nanosized materials with well-defined physical and crystallochemical characteristics as well as colloidal and magnetic properties. Rather than grouping the information according to the synthetic route, we have described methods to prepare water-dispersible equiaxial magnetic nanoparticles with sizes below about 10 nm, sizes between 10 and 30 nm and sizes around the monodomain-multidomain magnetic transition. We have also described some recent examples reporting the preparation of anisometric nanoparticles as well as methods to prepare magnetic nanosized materials other than iron oxide ferrites, for example Co and Mn ferrite, FePt and manganites. Finally, we have described examples of the preparation of multicomponent systems with purely inorganic or organic-inorganic characteristics. (topical review)

  11. Templated synthesis of monodisperse mesoporous maghemite/silica microspheres for magnetic separation of genomic DNA

    Science.gov (United States)

    Chen, Feng; Shi, Ruobing; Xue, Yun; Chen, Lei; Wan, Qian-Hong

    2010-08-01

    A novel method is described for the preparation of superparamagnetic mesoporous maghemite (γ-Fe 2O 3)/silica (SiO 2) composite microspheres to allow rapid magnetic separation of DNA from biological samples. With magnetite (Fe 3O 4) and silica nanoparticles as starting materials, such microspheres were synthesized by the following two consecutive steps: (1) formation of monodispersed organic/inorganic hybrid microspheres through urea-formaldedyde (UF) polymerization and (2) removal of the organic template and phase transformation of Fe 3O 4 to γ-Fe 2O 3 by calcination at elevated temperatures. The as-synthesized particles obtained by heating at temperature 300 °C feature spherical shape and uniform particle size ( dparticle=1.72 μm), high saturation magnetization ( Ms=17.22 emu/g), superparamagnetism ( Mr/ Ms=0.023), high surface area ( SBET=240 m 2/g), and mesoporosity ( dpore=6.62 nm). The composite microsphere consists of interlocked amorphous SiO 2 nanoparticles, in which cubic γ-Fe 2O 3 nanocrystals are homogeneously dispersed and thermally stable against γ- to α-phase transformation at temperatures up to 600 °C. With the exposed iron oxide nanoparticles coated with a thin layer of silica shell, the magnetic microspheres were used as a solid-phase adsorbent for rapid extraction of genomic DNA from plant samples. The results show that the DNA templates isolated from pea and green pepper displayed single bands with molecular weights greater than 8 kb and A260/ A280 values of 1.60-1.72. The PCR amplification of a fragment encoding the endogenous chloroplast ndhB gene confirmed that the DNA templates obtained were inhibitor-free and amenable to sensitive amplification-based DNA technologies.

  12. Facile method to synthesize oleic acid-capped magnetite nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We described a simple one-step process for the synthesis of oleic acid-capped magnetite nanoparticles using the dimethyl sulfoxide(DMSO) to oxidize the precursor Fe~(2+) at 140℃.By adjusting the alkalinity of the reaction system,magnetite nanoparticles with two sizes of 4 and 7 nm could be easily achieved.And the magnetite nanoparticles coated by oleate were well-monodispersed in organic solvent.

  13. Highly monodisperse low-magnetization magnetite nanocubes as simultaneous T1-T2 MRI contrast agents

    Science.gov (United States)

    Sharma, V. K.; Alipour, A.; Soran-Erdem, Z.; Aykut, Z. G.; Demir, H. V.

    2015-06-01

    We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin canting effect. As a proof-of-concept demonstration, we showed their potential as dual contrast agents for both T1- and T2-weighted MRI via phantom studies, in vivo imaging and relaxivity measurements. Therefore, these low-magnetization magnetite nanocubes, while being non-toxic and bio-compatible, hold great promise as excellent dual-mode T1 and T2 contrast agents for MRI.We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin

  14. Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

    Science.gov (United States)

    Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

    2015-11-17

    Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

  15. Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

    2017-09-12

    Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

  16. Highly monodispersed tin oxide/mesoporous starbust carbon composite as high-performance Li-ion battery anode.

    Science.gov (United States)

    Chen, Jiajun; Yano, Kazuhisa

    2013-08-28

    The widespread commercialization of today's plug-in hybrid and all electric vehicles will rely on improved lithium batteries with higher energy density, greater power, and durability.To take advantage of the high density of SnO2 anodes for Li ion batteries, we achieved a smart design of monodispersed SnO2/MSCS composite with very high content of SnO2 by a simple infiltration procedure. The synergistic effects of the unique nanoarchitecture of MSCS and the ultrafine size of SnO2 nanoparticle endowed the composite with superior electrochemical performance. Because of the high density of the composite resulting from its monodispersed submicrometer spherical morphology, an exceptionally high reversible lithium storage capacity (both gravimetric and volumetric), very close to the theoretical capacity (1491 mA h/g), can be achieved with good cyclability (capacity retention of 92.5% after 15 cycles). The SnO2/MSCS composite anode exhibited a high reversible average capacity of about 1200 mAh/g over 30 cycles at a current of 80 mAh/g, which corresponds to about 1440 mAh/cm(3) (practical volumetric capacity). In addition, a Coulombic efficiency close to 100% was achieved, and less than 25% first irreversible capacity loss was observed.

  17. MONODISPERSE MICRON-SIZED POLYACRYLAMIDE PARTICLES SYNTHESIZED BY DISPERSION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Xin Hou; Bo Gao; Zhe-guo Zhang; Kang-de Yao

    2007-01-01

    Monodisperse micron-sized polyacrylamide (PAM) particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic results demonstrated the formation of PAM. POM and TEM observations revealed that PAM particles had a regular shape and good dispersity. A thick layer of surfactant (PVP) still existed on PAM particles after multiple centrifugation and ultrasonic re-dispersion in ethanol, which indicates a strong interaction between PVP and PAM. The effects of various polymerization factors on the average size of PAM particles have also been studied.

  18. Tribological characteristics of monodispersed cerium borate nanospheres in biodegradable rapeseed oil lubricant

    Science.gov (United States)

    Boshui, Chen; Kecheng, Gu; Jianhua, Fang; Jiang, Wu; Jiu, Wang; Nan, Zhang

    2015-10-01

    Stearic acid-capped cerium borate composite nanoparticles, abbreviated as SA/CeBO3, were prepared by hydrothermal method. The morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics, of SA/CeBO3 were characterized by scanning electron microscope, energy dispersive X-ray spectrometer, dynamic laser particle size analyzer, X-ray diffraction, and Fourier transform infrared spectrometer, respectively. The friction and wear performances of SA/CeBO3 as a lubricating additive in a rapeseed oil were evaluated on a four-ball tribo-tester. The tribochemical characteristics of the worn surfaces were investigated by X-ray photoelectron spectroscopy. The results showed that the hydrophobic SA/CeBO3 were monodispersed nanospheres with an average diameter of 8 nm, and exhibited excellent dispersing stability in rapeseed oil. Meanwhile, SA/CeBO3 nanospheres were outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil. The prominent tribological performances of SA/CeBO3 in rapeseed oil were attributed to the formation of a composite boundary lubrication film mainly composed of lubricous tribochemical species of B2O3, CeO2 and Fe2O3, and the adsorbates of SA/CeBO3 and rapeseed oil, on the tribo-surfaces.

  19. HIGH IMMOBILIZATION OF ANTIBACTERIAL MOIETIES ONTO MONODISPERSE MICROSPHERES BY DISPERSION POLYMERIZATION USING BICATIONIC VIOLOGEN SURFMER

    Institute of Scientific and Technical Information of China (English)

    Sheng-liu Wang; Xiao-fang Yang; Lian-ying Liu; Wan-tai Yang

    2012-01-01

    In order to achieve monodisperse particles with high content of antibacterial groups covalently bonded on surface,a bicationic viologen,N-hexyl-N'-(4-vinylbenzyl)-4,4'-bipyridinium bromide chloride (HVV) was devised as a surfmer in dispersion polymerization of styrene (St) using a mixture of methanol (or ethylene glycol) and water as media.Effects of content of HVV,its addition profile and composition of reaction media on particles size and incorporation of HVV moieties were mainly investigated.The attachment of silver and gold nanoparticles on particle surface under UV irradiation ascertained the surface-bonded HVV segments.SEM,TEM observations and XPS,zata potential measurements indicated that increase of initial HVV contents and addition of HVV (when polymerization had been performed for 3 h) led to grown particles and enhanced immobilization of HVV moieties.Using a mixture of ethylene glycol and water as reaction media,small particles (520-142 nm) with highly attached HVV moieties were prepared.Furthermore,antibacterial efficacy of the resultant particles against S.aureus was assayed,and particles with more HVV moieties anchored on surface demonstrated greater efficiency of antibacterial activity.

  20. Size Controlled Synthesis of Starch Nanoparticles by a Microemulsion Method

    Directory of Open Access Journals (Sweden)

    Suk Fun Chin

    2014-01-01

    Full Text Available Controllable particles sizes of starch nanoparticles were synthesized via a precipitation in water-in-oil microemulsion approach. Microemulsion method offers the advantages of ultralow interfacial tension, large interfacial area, and being thermodynamically stable and affords monodispersed nanoparticles. The synthesis parameters such as stirring rates, ratios of oil/cosurfactant, oil phases, cosurfactants, and ratios of water/oil were found to affect the mean particle size of starch nanoparticles. Starch nanoparticles with mean particles sizes of 109 nm were synthesized by direct nanoprecipitation method, whereas by using precipitation in microemulsion approach, starch nanoparticles with smaller mean particles sizes of 83 nm were obtained.

  1. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    NARCIS (Netherlands)

    Bhattacharjee, S.; Opstal, van E.J.; Alink, G.M.; Marcelis, A.T.M.; Zuilhof, H.; Rietjens, I.M.C.M.

    2013-01-01

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/s

  2. Surface charge-specific cytotoxicity and cellular uptake of tri-block copolymer nanoparticles

    NARCIS (Netherlands)

    Bhattacharjee, S.; Ershov, D.S.; Gucht, van der J.; Alink, G.M.; Rietjens, I.; Zuilhof, H.; Marcelis, A.T.M.

    2013-01-01

    A series of monodisperse (45 ± 5 nm) fluorescent nanoparticles from tri-block copolymers (polymeric nanoparticles (PNPs)) bearing different surface charges were synthesised and investigated for cytotoxicity in NR8383 and Caco-2 cells. The positive PNPs were more cytotoxic and induced a higher intrac

  3. Synthesis, photocatalytic activity, and photogenerated hydroxyl radicals of monodisperse colloidal ZnO nanospheres

    Science.gov (United States)

    Yang, Chong; Li, Qingsong; Tang, Limei; Xin, Kun; Bai, Ailing; Yu, Yingmin

    2015-12-01

    In the present study, monodisperse colloidal zinc oxide (ZnO) nanospheres were successfully synthesized via a newly developed two-stage solution method followed by facile calcination at various temperatures. The effects of calcination temperature on the structure, morphology, and optical properties as well as the photocatalytic activity of the as-made ZnO samples were investigated systematically by Fourier transform infrared spectrometry, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-visible spectroscopy (DRS), photoluminescence, and related photocatalytic activity tests. The thermal decomposition was analyzed by thermogravimetric analysis. The crystallinity was found to gradually increase with increasing calcination temperature, whereas the decrease in the Brunauer-Emmett-Teller specific surface area of the samples with calcination may be ascribed to the increased particle size. The DRS results provided clear evidence for the decrease in band gap energy of ZnO samples with an increase in calcination temperature. The photoluminescence spectra demonstrated the calcination-dependent emission features, especially the UV emission intensity. In particular, the ZnO product calcined at 400 °C exhibited the highest photocatalytic activity, degrading methylene blue by almost 99.1% in 70 min, which is ascribed to the large specific surface area and pore volume, high electron-hole pair separation efficient, and great redox potential of the obtained ZnO nanoparticles. In addition, the production of photogenerated hydroxyl radicals (•OH) was consistent with the methylene blue degradation efficiency over the as-made ZnO nanoparticles. Using isopropanol as a hydroxyl radical scavenger, •OH was determined to be the main active oxygen species in the photocatalytic process. A possible mechanism of photodegradation under UV light irradiation also is proposed.

  4. Interchain tube pressure effect in extensional flows of oligomer diluted nearly monodisperse polystyrene melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Huang, Qian

    2014-01-01

    We have derived a constitutive equation to explain the extensional dynamics of oligomer-diluted monodisperse polymers, if the length of the diluent has at least two Kuhn steps. These polymer systems have a flow dynamics which distinguish from pure monodisperse melts and solutions thereof, if the ...

  5. Monodisperse Femto- to Atto-liter Droplet Formation Using a Nano-Microchannel Interface

    NARCIS (Netherlands)

    Shui, Lingling; Berg, van den Albert; Eijkel, Jan C.T.; Kim, Tae Song; Lee, Yoon-Sik; Chung, Taek-Dong; Jeon, Noo Li; Suh, Kahp-Yang; Choo, Jaebum; Kim, Yong-Kweon

    2009-01-01

    We demonstrate the production of sub-micrometer diameter monodisperse droplets by using a nano-micro channel interface. A perfectly steady nanoscopic liquid filament can be formed by a geometric confinement which eventually gives rise to a stable production of nearly perfectly monodisperse droplets.

  6. Surface properties of poly(ethylene oxide)-based segmented block copolymers with monodisperse hard segments

    NARCIS (Netherlands)

    Husken, D.; Feijen, Jan; Gaymans, R.J.

    2009-01-01

    The surface properties of segmented block copolymers based on poly(ethylene oxide) (PEO) segments and monodisperse crystallizable tetra-amide segments were studied. The monodisperse crystallizable segments (T6T6T) were based on terephthalate (T) and hexamethylenediamine (6). Due to the crystallinity

  7. Solvothermal synthesis and controlled self-assembly of monodisperse titanium-based perovskite colloidal nanocrystals

    Science.gov (United States)

    Caruntu, Daniela; Rostamzadeh, Taha; Costanzo, Tommaso; Salemizadeh Parizi, Saman; Caruntu, Gabriel

    2015-07-01

    The rational design of monodisperse ferroelectric nanocrystals with controlled size and shape and their organization into hierarchical structures has been a critical step for understanding the polar ordering in nanoscale ferroelectrics, as well as the design of nanocrystal-based functional materials which harness the properties of individual nanoparticles and the collective interactions between them. We report here on the synthesis and self-assembly of aggregate-free, single-crystalline titanium-based perovskite nanoparticles with controlled morphology and surface composition by using a simple, easily scalable and highly versatile colloidal route. Single-crystalline, non-aggregated BaTiO3 colloidal nanocrystals, used as a model system, have been prepared under solvothermal conditions at temperatures as low as 180 °C. The shape of the nanocrystals was tuned from spheroidal to cubic upon changing the polarity of the solvent, whereas their size was varied from 16 to 30 nm for spheres and 5 to 78 nm for cubes by changing the concentration of the precursors and the reaction time, respectively. The hydrophobic, oleic acid-passivated nanoparticles exhibit very good solubility in non-polar solvents and can be rendered dispersible in polar solvents by a simple process involving the oxidative cleavage of the double bond upon treating the nanopowders with the Lemieux-von Rudloff reagent. Lattice dynamic analysis indicated that regardless of their size, BaTiO3 nanocrystals present local disorder within the perovskite unit cell, associated with the existence of polar ordering. We also demonstrate for the first time that, in addition to being used for fabricating large area, crack-free, highly uniform films, BaTiO3 nanocubes can serve as building blocks for the design of 2D and 3D mesoscale structures, such as superlattices and superparticles. Interestingly, the type of superlattice structure (simple cubic or face centered cubic) appears to be determined by the type of solvent

  8. Monodisperse cobalt ferrite nanomagnets with uniform silica coatings.

    Science.gov (United States)

    Dai, Qiu; Lam, Michelle; Swanson, Sally; Yu, Rui-Hui Rachel; Milliron, Delia J; Topuria, Teya; Jubert, Pierre-Olivier; Nelson, Alshakim

    2010-11-16

    Ferro- and ferrimagnetic nanoparticles are difficult to manipulate in solution as a consequence of the formation of magnetically induced nanoparticle aggregates, which hamper the utility of these particles for applications ranging from data storage to bionanotechnology. Nonmagnetic shells that encapsulate these magnetic particles can reduce the interparticle magnetic interactions and improve the dispersibility of the nanoparticles in solution. A route to create uniform silica shells around individual cobalt ferrite nanoparticles--which uses poly(acrylic acid) to bind to the nanoparticle surface and inhibit nanoparticle aggregation prior to the addition of a silica precursor--was developed. In the absence of the poly(acrylic acid) the cobalt ferrite nanoparticles irreversibly aggregated during the silica shell formation. The thickness of the silica shell around the core-shell nanoparticles could be controlled in order to tune the interparticle magnetic coupling as well as inhibit magnetically induced nanoparticle aggregation. These ferrimagnetic core-silica shell structures form stable dispersion in polar solvents such as EtOH and water, which is critical for enabling technologies that require the assembly or derivatization of ferrimagnetic particles in solution.

  9. Intrinsic Magnetism and Collective Magnetic Properties of Size-Selected Nanoparticles

    Science.gov (United States)

    Antoniak, C.; Friedenberger, N.; Trunova, A.; Meckenstock, R.; Kronast, F.; Fauth, K.; Farle, M.; Wende, H.

    Using size-selected spherical FePt nanoparticles and cubic Fe/Fe-oxide nanoparticles as examples, we discuss the recent progress in the determination of static and dynamic properties of nanomagnets. Synchroton radiation-based characterisation techniques in combination with detailed structural, chemical and morphological investigations by transmission and scanning electron microscopy allow the quantitative correlation between element-specific magnetic response and spin structure on the one hand and shape, crystal and electronic structure of the particles on the other hand. Examples of measurements of element-specific hysteresis loops of single 18 nm sized nanocubes are discussed. Magnetic anisotropy of superparamagnetic ensembles and their dynamic magnetic response are investigated by ferromagnetic resonance as a function of temperature at different microwave frequencies. Such investigations allow the determination of the magnetic relaxation and the extraction of the average magnetic anisotropy energy density of the individual particles.

  10. Applications of Bacterial Magnetic Nanoparticles in Nanobiotechnology.

    Science.gov (United States)

    Chen, Chuanfang; Wang, Pingping; Li, Linlin

    2016-03-01

    The bacterial magnetic nanoparticle (BMP) has been well researched in nanobiotechnology as a new magnetic crystal. The BMPs are extracted from magnetotactic bacteria and under precise biological control. Compared with engineered magnetic nanoparticles synthesized by chemical approaches, BMPs have the properties of large production, monodispersity, high crystallinity, and close-to-bulk magnetization, which enable BMPs to be the highly promising magnetic nanoparticles for nanobiotechnology. In this paper, we review the biomedical applications of BMPs in magnetic hyperthermia, drug treatment with tumour and bioseparation. In addition, the biodistribution and toxicity are also reviewed.

  11. Gum arabic modified Fe3O4 nanoparticles cross linked with collagen for isolation of bacteria

    Directory of Open Access Journals (Sweden)

    Chittor Raghuraman

    2010-12-01

    Full Text Available Abstract Background Multifunctional magnetic nanoparticles are important class of materials in the field of nanobiotechnology, as it is an emerging area of research for material science and molecular biology researchers. One of the various methods to obtain multifunctional nanomaterials, molecular functionalization by attaching organic functional groups to nanomagnetic materials is an important technique. Recently, functionalized magnetic nanoparticles have been demonstrated to be useful in isolation/detection of dangerous pathogens (bacteria/viruses for human life. Iron (Fe based material especially FePt is used in the isolation of ultralow concentrations (2 cfu/ml of bacteria in less time and it has been demonstrated that van-FePt may be used as an alternative fast detection technique with respect to conventional polymerase chain reaction (PCR method. However, still further improved demonstrations are necessary with interest to biocompatibility and green chemistry. Herein, we report the synthesis of Fe3O4 nanoparticles by template medication and its application for the detection/isolation of S. aureus bacteria. Results The reduction of anhydrous Iron chloride (FeCl3 in presence of sodium borohydride and water soluble polyelectrolyte (polydiallyldimethyl ammonium chloride, PDADMAC produces black precipitates. The X-ray diffraction (XRD, XPS and TEM analysis of the precipitates dried at 373 K demonstrated the formation of nanocrystalline Fe3O4. Moreover, scanning electron microscopy (SEM showed isolated staphylococcous aureus (S. aureus bacteria at ultralow concentrations using collagen coated gum arabic modified iron oxide nanoparticles (CCGAMION. Conclusion We are able to synthesize nanocrystalline Fe3O4 and CCGAMION was able to isolate S. aureus bacteria at 8-10 cfu (colony forming units/ml within ~3 minutes.

  12. MONODISPERSED AND NANOSIZED DENDRIMER/POLYSTYRENE LATEX PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Changfeng Yi; Zushun Xu; Warren T. Ford

    2004-01-01

    Emulsion polymerization of styrene was carried out using dendrimer DAB-dendr-(NH2)64 as seed. The size and size distribution of the emulsion particles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the effects of emulsion polymerization conditions on the preparation of emulsion particle were investigated. It has been found that the nanosized dendrimer/polystyrene polymer emulsion particles obtained were in the range of 26~64 nm in diameter, and were monodisperse; the size and size distribution of emulsion particles were influenced by the contents of dendrimer DAB-dendr-(NH2)64, emulsifier and initiator, as well as the pH value.

  13. Selection of quasi-monodisperse super-micron aerosol particles

    Science.gov (United States)

    Rösch, Michael; Pfeifer, Sascha; Wiedensohler, Alfred; Stratmann, Frank

    2014-05-01

    Size-segregated quasi monodisperse particles are essential for e.g. fundamental research concerning cloud microphysical processes. Commonly a DMA (Differential Mobility Analyzer) is used to produce quasi-monodisperse submicron particles. Thereto first, polydisperse aerosol particles are bipolarly charged by a neutralizer, and then selected according to their electrical mobility with the DMA [Knutson et al. 1975]. Selecting a certain electrical mobility with a DMA results in a particle size distribution, which contains singly charged particles as well as undesired multiply charged larger particles. Often these larger particles need to either be removed from the generated aerosol or their signals have to be corrected for in the data inversion and interpretation process. This problem becomes even more serious when considering super-micron particles. Here we will present two different techniques for generating quasi-monodisperse super-micron aerosol particles with no or only an insignificant number of larger sized particles being present. First, we use a combination of a cyclone with adjustable aerodynamic cut-off diameter and our custom-built Maxi-DMA [Raddatz et al. 2013]. The cyclone removes particles larger than the desired ones prior to mobility selection with the DMA. This results in a reduction of the number of multiply charged particles of up to 99.8%. Second, we utilize a new combination of cyclone and PCVI (Pumped Counterflow Virtual Impactor), which is based on purely inertial separation and avoids particle charging. The PCVI instrument was previously described by Boulter et al. (2006) and Kulkarni et al. (2011). With our two setups we are able to produce quasi-monodisperse aerosol particles in the diameter range from 0.5 to 4.4 µm without a significant number of larger undesired particles being present. Acknowledgements: This work was done within the framework of the DFG funded Ice Nucleation research UnIT (INUIT, FOR 1525) under WE 4722/1-1. References

  14. Monodisperse Clusters in Charged Attractive Colloids: Linear Renormalization of Repulsion.

    Science.gov (United States)

    Růžička, Štěpán; Allen, Michael P

    2015-08-11

    Experiments done on polydisperse particles of cadmium selenide have recently shown that the particles form spherical isolated clusters with low polydispersity of cluster size. The computer simulation model of Xia et al. ( Nat. Nanotechnol. 2011 , 6 , 580 ) explaining this behavior used a short-range van der Waals attraction combined with a variable long-range screened electrostatic repulsion, depending linearly on the volume of the clusters. In this work, we term this dependence "linear renormalization" of the repulsive term, and we use advanced Monte Carlo simulations to investigate the kinetically slowed down phase separation in a similar but simpler model. We show that amorphous drops do not dissolve and crystallinity evolves very slowly under linear renormalization, and we confirm that low polydispersity of cluster size can also be achieved using this model. The results indicate that the linear renormalization generally leads to monodisperse clusters.

  15. Identification of Spinel Iron Oxide Nanoparticles by 57Fe NMR

    Directory of Open Access Journals (Sweden)

    SangGap Lee

    2011-12-01

    Full Text Available We have synthesized and studied monodisperse iron oxide nanoparticles of smaller than 10 nm to identify between the two spinel phases, magnetite and maghemite. It is shown that 57Fe NMR spectroscopy is a promising tool for distinguishing between the two phases.

  16. Templated synthesis of monodisperse mesoporous maghemite/silica microspheres for magnetic separation of genomic DNA

    Energy Technology Data Exchange (ETDEWEB)

    Chen Feng; Shi Ruobing; Xue Yun; Chen Lei [School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072 (China); Wan Qianhong, E-mail: qhwan@tju.edu.c [School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072 (China)

    2010-08-15

    A novel method is described for the preparation of superparamagnetic mesoporous maghemite (gamma-Fe{sub 2}O{sub 3})/silica (SiO{sub 2}) composite microspheres to allow rapid magnetic separation of DNA from biological samples. With magnetite (Fe{sub 3}O{sub 4}) and silica nanoparticles as starting materials, such microspheres were synthesized by the following two consecutive steps: (1) formation of monodispersed organic/inorganic hybrid microspheres through urea-formaldedyde (UF) polymerization and (2) removal of the organic template and phase transformation of Fe{sub 3}O{sub 4} to gamma-Fe{sub 2}O{sub 3} by calcination at elevated temperatures. The as-synthesized particles obtained by heating at temperature 300 deg. C feature spherical shape and uniform particle size (d{sub particle}=1.72 mum), high saturation magnetization (M{sub s}=17.22 emu/g), superparamagnetism (M{sub r}/M{sub s}=0.023), high surface area (S{sub BET}=240 m{sup 2}/g), and mesoporosity (d{sub pore}=6.62 nm). The composite microsphere consists of interlocked amorphous SiO{sub 2} nanoparticles, in which cubic gamma-Fe{sub 2}O{sub 3} nanocrystals are homogeneously dispersed and thermally stable against gamma- to alpha-phase transformation at temperatures up to 600 deg. C. With the exposed iron oxide nanoparticles coated with a thin layer of silica shell, the magnetic microspheres were used as a solid-phase adsorbent for rapid extraction of genomic DNA from plant samples. The results show that the DNA templates isolated from pea and green pepper displayed single bands with molecular weights greater than 8 kb and A{sub 260}/A{sub 280} values of 1.60-1.72. The PCR amplification of a fragment encoding the endogenous chloroplast ndhB gene confirmed that the DNA templates obtained were inhibitor-free and amenable to sensitive amplification-based DNA technologies.

  17. Synthetic Polymers at Interfaces: Monodisperse Emulsions Multiple Emulsions and Liquid Marbles

    Science.gov (United States)

    Sun, Guanqing

    discussion of emulsion stabilization and preparation. A historical review of multiple emulsions is presented subsequently and the stability mechanism is discussed in details with regard to the transportation kinetics of small molecules through the separating membrane of double emulsions. The principle, property and applications of liquid marbles are then summarized. Secondly, the preparation of monodisperse Pickering emulsions stabilized by soft PNIPAM-co-MAA microgels through SPG membrane emulsification is described. The influence of the membrane pore size, pH of the particle dispersion, particle size and the operating parameters of the membrane emulsification device on the size of the emulsion droplets was investigated systematically. The improvement in monodispersity of the emulsion droplets allows us to measure the release profiles of a small molecular dye and a larger nanoparticle through the colloidosomes. It is further demonstrated that the preparation of monodisperse emulsions stabilized by other types of soft particles allows us control the stability of the emulsion with a pH trigger and improved biocompatibility. Thirdly, the preparation of multiple emulsions stabilized by a special designed PEG-b-PS diblock copolymer with desired hydrophobicity by one-step method was presented. The ultra-stability of the as-obtained multiple emulsions was ascribed to the effective steric stabilization of the two interfaces with different polymer configurations at the interfaces. A series of diblock copolymer with increasing PS chain length was then synthesized to investigate the influence of asymmetry ratio on the type of emulsions prepared. It is found that the diblock copolymers with the asymmetry ratio of approximately 1 had the highest power to stabilize multiple emulsions. The multiple emulsions were demonstrated to be a promising platform for controlled release. In the end, particle-stabilized water-in-air liquid marbles were investigated. PSco-MAA nanoparticles synthesized

  18. Surface plasmon resonance optical sensor and antibacterial activities of biosynthesized silver nanoparticles

    Science.gov (United States)

    Bindhu, M. R.; Umadevi, M.

    2014-03-01

    Silver nanoparticles were prepared using aqueous fruit extract of Ananas comosus as reducing agent. These silver nanoparticles showed surface plasmon peak at 439 nm. They were monodispersed and spherical in shape with an average particle size of 10 nm. The crystallinity of these nanoparticles was evident from clear lattice fringes in the HRTEM images and bright circular spots in the SAED pattern. The antibacterial activities of prepared nanoparticles were found to be size-dependent, the smaller nanoparticles showing more bactericidal effect. Aqueous Zn2+ and Cu4+ selectivity and sensitivity study of this green synthesized nanoparticle was performed by optical sensor based surface plasmon resonance (SPR) at room temperature.

  19. Lysozyme Catalyzes the Formation of Antimicrobial Silver Nanoparticles (POSTPRINT)

    Science.gov (United States)

    2009-04-01

    aseptics and therapeutic use in the future. KEYWORDS: antimicrobial · lysozyme · silver · nanoparticle · biocompatibility · biomineralization A RT IC LE VOL...protein that will adsorb to ionic and hydro- phobic surfaces, including metal surfaces.2124 After synthesis in methanol, lysozyme-stabilized nanoparti- cle...the strong ionic interactions be- tween metal nanoparticles normally make it difficult to achieve high concentrations of monodispersed and stable

  20. Monodisperse mesoporous anatase beads as high performance and safer anodes for lithium ion batteries

    Science.gov (United States)

    Rodriguez, Erwin F.; Chen, Dehong; Hollenkamp, Anthony F.; Cao, Lu; Caruso, Rachel A.

    2015-10-01

    To achieve high efficiency lithium ion batteries (LIBs), an effective active material is important. In this regard, monodisperse mesoporous titania beads (MMTBs) featuring well interconnected nanoparticles were synthesised, and their mesoporous properties were tuned to study how these affect the electrochemical performance in LIBs. Two pore diameters of 15 and 25 nm, three bead diameters of 360, 800 and 2100 nm, and various annealing temperatures (from 300 to 650 °C) were investigated. The electrochemical results showed that while the pore size does not significantly influence the electrochemical behaviour, the specific surface area and the nanocrystal size affect the performance. Also, there is an optimum annealing temperature that enhances electron transfer across the titania bead structure. The carbon content employed in the electrode was varied, showing that the bead diameter strongly influences the minimal content of the conductive carbon required to fabricate the electrode. As a general rule, the smaller the bead diameter, the more carbon was required in the electrode. A large energy capacity and high current rate performance were achieved on the MMTBs featuring high surface area, nano-sized anatase crystals and well-sintered connections between the nanocrystals. The high stability of these mesoporous structures was demonstrated by charge/discharge cycling up to 500 cycles. Devices constructed with the MMTBs retained more than 80% of the initial capacity, indicating an excellent performance.To achieve high efficiency lithium ion batteries (LIBs), an effective active material is important. In this regard, monodisperse mesoporous titania beads (MMTBs) featuring well interconnected nanoparticles were synthesised, and their mesoporous properties were tuned to study how these affect the electrochemical performance in LIBs. Two pore diameters of 15 and 25 nm, three bead diameters of 360, 800 and 2100 nm, and various annealing temperatures (from 300 to 650

  1. Surface segregations in platinum-based alloy nanoparticles

    Science.gov (United States)

    Yamakawa, Shunsuke; Asahi, Ryoji; Koyama, Toshiyuki

    2014-04-01

    A phase-field model that describes the radial distributions of the ordered-disordered phase and surface segregation in a single-alloy nanoparticle is introduced to clarify the overall behavior of surface segregation of various Pt-based alloy nanoparticles. One of the obstacles to apply a platinum-transition metal alloy as a cathode electro-catalyst of a polymer electrolyte fuel cell is the need to ensure the retention of the designed surface composition in an alloy nanoparticle against the alloy combinations, a particle size, and heat treatment. From the results of calculations for CrPt, FePt, CoPt, NiPt, CuPt, PdPt, IrPt, and AuPt binary nanoparticles with diameters below 10 nm at 973.15 K, the compositional variation within a single particle was found to depend on the balance between the atomic interaction within particles and the surface free energy. In addition, the obtained specific steady-state composition of the surface varied significantly with alloy combination and particle diameter. Based on the general tendencies of a binary system to exhibit segregation, attempts to control the amount of platinum segregation on the surface using a ternary-alloy system were examined.

  2. Efficient thermolysis route to monodisperse Cu₂ZnSnS₄ nanocrystals with controlled shape and structure

    National Research Council Canada - National Science Library

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-01-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents...

  3. Cr/alpha-Cr2O3 monodispersed spherical core-shell particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-07-01

    Full Text Available Monodispersed spherical core-shell particles of Cr/alpha-Cr2O3 cermet ACG coatings investigated within this contribution could be successfully employed in thermal converters. Their selectivity depends on their chemical, physical and structural...

  4. Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell

    KAUST Repository

    Qi, Genggeng

    2010-05-11

    Monodispersed HMSs with tunable particle size and shell thickness were successfully synthesized using relatively concentrated polystyrene latex templates and a silica precursor in a weakly basic ethanol/water mixture. The particle size of the capsules can vary from 100 nm to micrometers. These highly engineered monodispersed capsules synthesized by a facile and scalable process may find applications in drug delivery, catalysis, separationm or as biological and chemical microreactors. © 2010 American Chemical Society.

  5. Periodic jetting and monodisperse jet drops from oblique gas injection

    Science.gov (United States)

    McRae, Oliver; Gaillard, Antoine; Bird, James C.

    2017-07-01

    When air is blown in a straw or tube near an air-liquid interface, typically one of two behaviors is observed: a dimple in the liquid's surface, or a frenzy of sputtering bubbles, waves, and spray. Here we report and characterize an intermediate regime that can develop when a confined air jet enters the interface at an angle. This regime is oscillatory with a distinct characteristic frequency and can develop periodic angled jets that can break up into monodisperse aerosols. The underlying mechanisms responsible for this highly periodic regime are not well understood. Here we flow a continuous stream of gas through a tube near a liquid surface, observing both optically and acoustically the deformation of the liquid-air interface as various parameters are systematically adjusted. We show that the Kelvin-Helmholtz instability is responsible for the inception of waves within a cavity formed by the gas. Inertia, gravity, and capillary forces both shape the cavity and govern the frequency and amplitude of these gas-induced cavity waves. The flapping cavity focuses the waves into a series of periodic jets that can break up into droplets following the Rayleigh-Plateau instability. We present scaling arguments to rationalize the fundamental frequencies driving this system, as well as the conditions that bound the periodic regime. These frequencies and conditions compare well with our experimental results.

  6. Jamming of Monodisperse Cylindrical Grains in Featureless Vertical Channels

    Science.gov (United States)

    Friedl, Nicholas; Baxter, G. William

    2014-03-01

    We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel under the influence of gravity. These grains have an aspect-ratio less than two (H/D aspirin tablets, 35mm film canisters, poker chips, or coins. Monodisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. No combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College.

  7. Spark Ignition of Monodisperse Fuel Sprays. Ph.D. Thesis

    Science.gov (United States)

    Danis, Allen M.; Cernansky, Nicholas P.; Namer, Izak

    1987-01-01

    A study of spark ignition energy requirements was conducted with a monodisperse spray system allowing independent control of droplet size, equivalent ratio, and fuel type. Minimum ignition energies were measured for n-heptane and methanol sprays characterized at the spark gap in terms of droplet diameter, equivalence ratio (number density) and extent of prevaporization. In addition to sprays, minimum ignition energies were measured for completely prevaporized mixtures of the same fuels over a range of equivalence ratios to provide data at the lower limit of droplet size. Results showed that spray ignition was enhanced with decreasing droplet size and increasing equivalence ratio over the ranges of the parameters studied. By comparing spray and prevaporized ignition results, the existence of an optimum droplet size for ignition was indicated for both fuels. Fuel volatility was seen to be a critical factor in spray ignition. The spray ignition results were analyzed using two different empirical ignition models for quiescent mixtures. Both models accurately predicted the experimental ignition energies for the majority of the spray conditions. Spray ignition was observed to be probabilistic in nature, and ignition was quantified in terms of an ignition frequency for a given spark energy. A model was developed to predict ignition frequencies based on the variation in spark energy and equivalence ratio in the spark gap. The resulting ignition frequency simulations were nearly identical to the experimentally observed values.

  8. Formation of monodisperse mesoporous silica microparticles via spray-drying.

    Science.gov (United States)

    Waldron, Kathryn; Wu, Winston Duo; Wu, Zhangxiong; Liu, Wenjie; Selomulya, Cordelia; Zhao, Dongyuan; Chen, Xiao Dong

    2014-03-15

    In this work, a protocol to synthesize monodisperse mesoporous silica microparticles via a unique microfluidic jet spray-drying route is reported for the first time. The microparticles demonstrated highly ordered hexagonal mesostructures with surface areas ranging from ~900 up to 1500 m(2)/g and pore volumes from ~0.6 to 0.8 cm(3)/g. The particle size could be easily controlled from ~50 to 100 μm from the same diameter nozzle via changing the initial solute content, or changing the drying temperature. The ratio of the surfactant (CTAB) and silica (TEOS), and the amount of water in the precursor were found to affect the degree of ordering of mesopores by promoting either the self-assembly of the surfactant-silica micelles or the condensation of the silica as two competing processes in evaporation induced self-assembly. The drying rate and the curvature of particles also affected the self-assembly of the mesostructure. The particle mesostructure is not influenced by the inlet drying temperature in the range of 92-160 °C, with even a relatively low temperature of 92 °C producing highly ordered mesoporous microparticles. The spray-drying derived mesoporous silica microparticles, while of larger sizes and more rapidly synthesized, showed a comparable performance with the conventional mesoporous silica MCM-41 in controlled release of a dye, Rhodamine B, indicating that these spray dried microparticles could be used for the immobilisation and controlled release of small molecules.

  9. Monodisperse droplet generation for microscale mass transfer studies

    Science.gov (United States)

    Roberts, Christine; Rao, Rekha; Grillet, Anne; Jove-Colon, Carlos; Brooks, Carlton; Nemer, Martin

    2011-11-01

    Understanding interfacial mass transport on a droplet scale is essential for modeling liquid-liquid extraction processes. A thin flow-focusing microfluidic channel is evaluated for generating monodisperse liquid droplets for microscale mass transport studies. Surface treatment of the microfluidic device allows creation of both oil in water and water in oil emulsions, facilitating a large parameter study of viscosity and flow rate ratios. The unusually thin channel height promotes a flow regime where no droplets form. Through confocal microscopy, this regime is shown to be highly influenced by the contact angle of the liquids with the channel. Drop sizes are found to scale with a modified capillary number. Liquid streamlines within the droplets are inferred by high speed imagery of microparticles dispersed in the droplet phase. Finally, species mass transfer to the droplet fluid is quantitatively measured using high speed imaging. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85.

  10. Methanobactin-mediated one-step synthesis of gold nanoparticles.

    Science.gov (United States)

    Xin, Jia-ying; Cheng, Dan-dan; Zhang, Lan-xuan; Lin, Kai; Fan, Hong-chen; Wang, Yan; Xia, Chun-gu

    2013-11-01

    Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.

  11. Methanobactin-Mediated One-Step Synthesis of Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2013-11-01

    Full Text Available Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III to Au (0. In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III to Mb in solution. X-ray photoelectron spectroscopy (XPS, fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR spectra suggest that Mb molecules catalytically reduce Au (III to Au (0 with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.

  12. An easy shortcut synthesis of size-controlled bismuth nanoparticles and their use in the SLS growth of high-quality colloidal cadmium selenide quantum wires.

    Science.gov (United States)

    Wang, Fudong; Buhro, William E

    2010-02-22

    An easy shortcut synthesis of thermally stable, near-monodisperse Bi nanoparticles from BiCl(3) and Na[N(SiMe(3))(2)] is described. The diameters of the Bi nanoparticles are controlled in the range of 4-29 nm by varying the amounts of BiCl(3) and Na[N(SiMe(3))(2)] employed. Standard deviations in their diameter distributions are 5-15% of the mean diameters, consistent with near monodispersity. These Bi nanoparticles are shown to be the best currently available catalysts for the solution-liquid-solid (SLS) growth of high-quality CdSe quantum wires.

  13. Large-scale, low-cost synthesis of monodispersed gold nanorods using a gemini surfactant

    Science.gov (United States)

    Xu, Yong; Zhao, Yang; Chen, Lei; Wang, Xuchun; Sun, Jianxia; Wu, Haihua; Bao, Feng; Fan, Jian; Zhang, Qiao

    2015-04-01

    In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the complex effect between bromide ions and gold ions. This work will not only help to achieve the industrial production of AuNRs, but also promote research into practical applications of various nanomaterials.In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the

  14. 单分散ZnO微球的合成及表征%Synthesis of monodispersed ZnO microspheres and characterizations

    Institute of Scientific and Technical Information of China (English)

    颜蔚; 安明; 王响; 董琪琪; 孙丽宁; 施利毅; 邓维

    2012-01-01

    采用简单的两步法合成了直径范围从50~200 nm的单分散的ZnO微球:在第一步反应中制备了ZnO纳米粒子的乙醇分散液;然后在第二步反应中加入适量的ZnO纳米粒子的乙醇分散液,从而合成出单分散的ZnO微球.通过改变第二步反应中所加入的ZnO纳米粒子的乙醇分散液的量,可以改变制备的单分散ZnO微球的直径.通过透射电子显微镜和X-射线衍射分析可以得知,ZnO微球是由ZnO纳米粒子聚集而成.不论ZnO微球的直径是多少,其多分散指数均小于1,并且当ZnO微球的直径为150 nm时,其多分散指数仅为0.16.%In this paper, monodispersed ZnO microspheres in sizes from 50 to 200 nm were synthesized with a developed two-step method. In the primary reaction, ethanol suspension of ZnO nanoparticles was prepared, and monodispersed ZnO microspheres were synthesized in the secondary reaction by adding the ZnO nanoparticles suspension into the reaction solution. Diameter of the ZnO microspheres could be controlled by varying the volume of QDs suspension added. The transmission microscopy images and X-ray diffraction patterns of the ZnO microspheres showed that no matter their diameters, the ZnO microspheres were formed by aggregation of well crystallized ZnO nanoparticles. The polydispersity indexes (PDI) of ZnO microspheres were detected. It is found that PDI values of the microspheres were all less than 1. 0, suggesting the monodispersi-ty of the ZnO microspheres. The PDI value was only 0. 16 when the diameter of the ZnO microspheres was 150 nm.

  15. Surface-Bound Ligands Modulate Chemoselectivity and Activity of a Bimetallic Nanoparticle Catalyst

    KAUST Repository

    Vu, Khanh B.

    2015-04-03

    "Naked" metal nanoparticles (NPs) are thermodynamically and kinetically unstable in solution. Ligands, surfactants, or polymers, which adsorb at a particle\\'s surface, can be used to stabilize NPs; however, such a mode of stabilization is undesirable for catalytic applications because the adsorbates block the surface active sites. The catalytic activity and the stability of NPs are usually inversely correlated. Here, we describe an example of a bimetallic (PtFe) NP catalyst stabilized by carboxylate surface ligands that bind preferentially to one of the metals (Fe). NPs stabilized by fluorous ligands were found to be remarkably competent in catalyzing the hydrogenation of cinnamaldehyde; NPs stabilized by hydrocarbon ligands were significantly less active. The chain length of the fluorous ligands played a key role in determining the chemoselectivity of the FePt NP catalysts. (Chemical Presented). © 2015 American Chemical Society.

  16. Chemically ordered face-centred tetragonal Fe–Pt nanoparticles embedded SiO2 films

    Indian Academy of Sciences (India)

    Sourav Pramanik; Goutam De

    2012-12-01

    Chemically ordered face-centred tetragonal (fct) Fe–Pt alloy nanoparticles (NPs) embedded SiO2 films were synthesized on glass substrate by in situ hybrid sol–gel approach followed by heating at 450–900 °C in air and reducing (10% H2–90% Ar) atmospheres. Heat treatment of Fe/Pt co-doped films in air caused generation of Pt NPs first. At this stage, Fe remained in ionic state covalently bonded with silica network. Further heat treatment at 800–900 °C in reducing atmosphere facilitated the formation of uniformly dispersed fct Fe–Pt alloy NPs in amorphous SiO2 film matrix. The generated alloy composition was estimated by grazing incidence X-ray diffraction and TEM analysis to be Fe0.42Pt0.58 which is close to the nominal value.

  17. Antifungal activity of gold nanoparticles prepared by solvothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Tokeer, E-mail: tahmad3@jmi.ac.in [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India); Wani, Irshad A.; Lone, Irfan H.; Ganguly, Aparna [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India); Manzoor, Nikhat; Ahmad, Aijaz [Department of Biosciences, Jamia Millia Islamia, New Delhi 110025 (India); Ahmed, Jahangeer [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Al-Shihri, Ayed S. [Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, P.O. Box 9004 (Saudi Arabia)

    2013-01-15

    Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m{sup 2}/g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m{sup 2/}g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract: Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl{sub 2} and NaBH{sub 4} as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl{sub 2}, however, NaBH{sub 4} produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m{sup 2}/g for 7 nm and 269 m{sup 2}/g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H{sup +} efflux of the Candida species than 15 nm sized gold nanoparticles.

  18. Biogenic green synthesis of monodispersed gum kondagogu (Cochlospermum gossypium) iron nanocomposite material and its application in germination and growth of mung bean (Vigna radiata) as a plant model.

    Science.gov (United States)

    Raju, Dugyala; Mehta, Urmil J; Beedu, Sashidhar Rao

    2016-06-01

    An eco-friendly green and one-pot synthesis of highly monodispersed iron (Fe) nanoparticles (NPs) by using a natural biopolymer, gum kondagogu (GK) as reducing and capping agent is proposed. The NPs synthesised were characterised by ultra-violet-visible spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray diffraction. As the concentration of gum and time increases, the intensity of NPs formation increased. The NPs were highly monodispersed with uniform circular shapes of 2-6 nm in size. The formed NPs were crystalline in nature which was confirmed by diffraction analysis. The conversion ratio of Fe ionic form to NPs was 21% which was quantified by inductively coupled plasma mass spectroscopy (ICP-MS). Fe is essential for plant growth and development. A study was conducted to examine the effect of these NPs on the growth of mung bean (Vigna radiata). The radical length and biomass was increased in seeds exposed to Fe NPs than the ions. The uptake of Fe NPs by the sprouts was also quantified by ICP-MS, in which Fe was more in mung bean seeds exposed to NPs. The α-amylase activity was increased in the seeds exposed to NPs. The observed increase in the biomass by Fe NPs and seed germination may facilitate its application in the agriculture as an important cost-effective method for plant growth.

  19. Inter-laboratory comparison on the size and stability of monodisperse and bimodal synthetic reference particles for standardization of extracellular vesicle measurements

    Science.gov (United States)

    Nicolet, Anaïs; Meli, Felix; van der Pol, Edwin; Yuana, Yuana; Gollwitzer, Christian; Krumrey, Michael; Cizmar, Petr; Buhr, Egbert; Pétry, Jasmine; Sebaihi, Noham; de Boeck, Bert; Fokkema, Vincent; Bergmans, Rob; Nieuwland, Rienk

    2016-03-01

    In future, measurements of extracellular vesicles in body fluids could become a standard diagnostic tool in medicine. For this purpose, reliable and traceable methods, which can be easily applied in hospitals, have to be established. Within the European Metrological Research Project (EMRP) ‘Metrological characterization of micro-vesicles from body fluids as non-invasive diagnostic biomarkers’ (www.metves.eu), various nanoparticle reference materials were developed and characterized. We present results of an international comparison among four national metrology institutes and a university hospital. The size distributions of five monodisperse and two bimodal spherical particle samples with diameters ranging from 50 nm to 315 nm made out of silica and polystyrene were compared. Furthermore, the stability of the samples was verified over a period of 18 months. While monodisperse reference particle samples above a certain size level lead to good agreements of the size measurements among the different methods, small and bimodal samples show the limitations of current ‘clinical’ methods. All samples proved to be stable within the uncertainty of the applied methods.

  20. Facile synthesis of Fe3O4 nanoparticles by reduction phase transformation from gamma-Fe2O3 nanoparticles in organic solvent.

    Science.gov (United States)

    Hai, Hoang Tri; Kura, Hiroaki; Takahashi, Migaku; Ogawa, Tomoyuki

    2010-01-01

    A phase transformation induced by the reduction of as-synthesized gamma-maghemite (gamma-Fe(2)O(3)) nanoparticles was performed in solution by exploiting the reservoir of reduction gas (CO) generated from the incomplete combustion reaction of organic substances in the reactor. Results from X-ray diffraction, color indicator, and magnetic analysis using a SQUID strongly support this phase transformation. Based on this route, monodisperse magnetite (Fe(3)O(4)) nanoparticles were simply produced in the range from 260 to 300 degrees C. Almost all aspects of the original gamma-Fe(2)O(3) nanoparticles, such as shape, size, and monodispersity, were maintained in the produced Fe(3)O(4) nanoparticles.

  1. Monodisperse Hollow Tricolor Pigment Particles for Electronic Paper

    Directory of Open Access Journals (Sweden)

    Meng Xianwei

    2009-01-01

    Full Text Available Abstract A general approach has been designed to blue, green, and red pigments by metal ions doping hollow TiO 2. The reaction involves initial formation of PS at TiO2 core–shell nanoparticles via a mixed-solvent method, and then mixing with metal ions solution containing PEG, followed calcining in the atmosphere. The as-prepared hollow pigments exhibit uniform size, bright color, and tunable density, which are fit for electronic paper display.

  2. Photochemical preparation and application research of Au nanoparticles

    Institute of Scientific and Technical Information of China (English)

    DONG; Shou-an; SUN; Jia-lin

    2005-01-01

    Gold nanoparticles protected by organic small molecular compounds or macromolecule have attracted considerable attention and their preparation is one of hotspots in the nano-chemical material field due to their ongoing and potential applications in optics, electronics, catalysts and biosensors. In recent years there are many liquid phase chemistry methods to prepare monodispersed gold particles. Among them, the photochemical method is quite attractive because of its some important advantages for size-controlled synthesis of gold nanoparticles. Therefore, in this paper the recert progress of the photochemical preparing Au nanoparticle materials was briefly introduced and mainly emphasized authors' own works of this area.

  3. 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.

  4. Controllable Synthesis and Magnetic Properties of Monodisperse Fe3O4 Nanoparticles

    Science.gov (United States)

    Wang, Zhu-Liang; Ma, Hui; Wang, Fang; Li, Min; Zhang, Li-Guo; Xu, Xiao-Hong

    2016-10-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 51571135, 11274214 and 61434002, the Special Funds of Shanxi Scholars Program under Grant No IRT1156, Collaborative Innovation Center for Shanxi Advanced Permanent Materials and Technology, and the Special Funds of the Ministry of Education of China under Grant No 20121404130001.

  5. Controlled Microwave-Assisted Growth of Monodisperse of Silica Nanoparticles under Acid Catalysis (Postprint)

    Science.gov (United States)

    2012-11-26

    over conventional heating techniques because they deliver large amounts of controlled power quickly to small volumes of absorbing media, promoting...transition states, such as pentacoordinate and hexacoordinate silanes .25,38,39 Recently, a DFT study has postulated that the formation of stable silica

  6. Monodisperse, submicrometer droplets via condensation of microfluidic-generated gas bubbles.

    Science.gov (United States)

    Seo, Minseok; Matsuura, Naomi

    2012-09-10

    Microfluidics (MFs) can produce monodisperse droplets with precise size control. However, the synthesis of monodisperse droplets much smaller than the minimum feature size of the microfluidic device (MFD) remains challenging, thus limiting the production of submicrometer droplets. To overcome the minimum micrometer-scale droplet sizes that can be generated using typical MFDs, the droplet material is heated above its boiling point (bp), and then MFs is used to produce monodisperse micrometer-scale bubbles (MBs) that are easily formed in the size regime where standard MFDs have excellent size control. After MBs are formed, they are cooled, condensing into dramatically smaller droplets that are beyond the size limit achievable using the original MFD, with a size decrease corresponding to the density difference between the gas and liquid phases of the droplet material. Herein, it is shown experimentally that monodisperse, submicrometer droplets of predictable sizes can be condensed from a monodisperse population of MBs as generated by MFs. Using perfluoropentane (PFP) as a representative solvent due to its low bp (29.2 °C), it is demonstrated that monodisperse PFP MBs can be produced at MFD temperatures >3.6 °C above the bp of PFP over a wide range of sizes (i.e., diameters from 2 to 200 μm). Independent of initial size, the generated MBs shrink rapidly in size from about 3 to 0 °C above the bp of PFP, corresponding to a phase change from gas to liquid, after which they shrink more slowly to form fully condensed droplets with diameters 5.0 ± 0.1 times smaller than the initial size of the MBs, even in the submicrometer size regime. This new method is versatile and flexible, and may be applied to any type of low-bp solvent for the manufacture of different submicrometer droplets for which precisely controlled dimensions are required.

  7. Synthesis of alpha-Fe nanoparticles by solventless thermal decomposition.

    Science.gov (United States)

    Cha, Hyun Gil; Kim, Young Hwan; Kim, Chang Woo; Lee, Don Keun; Moon, Sung Doo; Kwon, Hae Woong; Kang, Young Soo

    2006-11-01

    A new preparation for highly crystalline and monodisperse Fe3O4 nanoparticle is reported. This synthesis requires the use of rather complicated procedures including delicate control of surfactants ratios and inert reaction conditions due to the toxic and unstable nature of the precursors none the less because thermal decomposition methods were tried to synthesize monodispersed inorganic nanocrystallites until very recently. The synthesis of Fe3O4 nanocrystallites by using Fe(+2)-oleate2 complex was studied. The Fe(+2)-oleate2 complex was prepared from the reaction of iron chloride and sodium oleate in water. The thermal decomposition of the complex at the reduced pressure (0.3 torr) and about 300 degrees was done without any solvent. We demonstrated that a new solventless synthesis of size- and shape-monodisperse Fe3O4 nanoparticles depends on the amount of Na-oleate. And it is possible to remove the oleate ligand using reduction process. We confirmed that the nanoparticles changed from Fe3O4 to alpha-Fe phase obtained higher magnetic properties and crystallites by a vibrating sample magnetometer (VSM) and x-ray powder diffraction (XRD). Removal of the organic surfactant and other volatile components surrounding Fe3O4 nanoparticles was detected by fourier transform infrared spectroscopy (FT-IR).

  8. Acute toxicity of copper oxide nanoparticles to Daphnia magna under different test conditions

    DEFF Research Database (Denmark)

    Thit, Amalie; Huggins, Krista; Selck, Henriette

    2017-01-01

    The acute toxicity of monodispersed 6 nm and Daphnia magna was assessed using 48 h immobilization tests. CuSO4 was used as a reference. Four different exposure conditions were tested, to study whether the toxicity of the nanoparticle...

  9. PREPARATION OF MONODISPERSE CROSSLINKED POLYMER MICROSPHERES HAVING CHLOROMETHYL GROUP BY DISTILLATION-PRECIPITATION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Shu-Feng Li; Xin-Lin Yang; Wen-Qiang Huang

    2005-01-01

    Monodisperse crosslinked poly(chloromethylstyrene-co-divinylbenzene) (poly(CMSt-co-DVB)) microspheres were prepared by distillation-precipitation copolymerization of chloromethylstyrene (CMSt) and divinylbenzene (DVB) in neat acetonitrile. The polymer particles had clean surfaces due to the absence of any added stabilizer. The size of the particles ranges from 2.59 μm to 3.19 μm and with mono-dispersity around 1.002-1.014. The effects of monomer feed in copolymerization on the microsphere formation were described. The polymer microspheres were characterized by SEM and chlorinity elemental analysis.

  10. A facile method to produce highly monodispersed nanospheres of cystine aggregates

    Science.gov (United States)

    Han, Hongliang; Wang, Chungang; Ma, Zhanfang; Su, Zhongmin

    2006-10-01

    Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials.

  11. A facile method to produce highly monodispersed nanospheres of cystine aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Han Hongliang; Wang Chungang; Ma Zhanfang; Su Zhongmin [Chemistry Department, Northeast Normal University, Changchun 130024 (China)

    2006-10-28

    Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials.

  12. Ultra-pure, water-dispersed Au nanoparticles produced by femtosecond laser ablation and fragmentation

    Science.gov (United States)

    Kubiliūtė, Reda; Maximova, Ksenia A; Lajevardipour, Alireza; Yong, Jiawey; Hartley, Jennifer S; Mohsin, Abu SM; Blandin, Pierre; Chon, James WM; Sentis, Marc; Stoddart, Paul R; Kabashin, Andrei; Rotomskis, Ričardas; Clayton, Andrew HA; Juodkazis, Saulius

    2013-01-01

    Aqueous solutions of ultra-pure gold nanoparticles have been prepared by methods of femtosecond laser ablation from a solid target and fragmentation from already formed colloids. Despite the absence of protecting ligands, the solutions could be (1) fairly stable and poly size-dispersed; or (2) very stable and monodispersed, for the two fabrication modalities, respectively. Fluorescence quenching behavior and its intricacies were revealed by fluorescence lifetime imaging microscopy in rhodamine 6G water solution. We show that surface-enhanced Raman scattering of rhodamine 6G on gold nanoparticles can be detected with high fidelity down to micromolar concentrations using the nanoparticles. Application potential of pure gold nanoparticles with polydispersed and nearly monodispersed size distributions are discussed. PMID:23888114

  13. Malva parviflora extract assisted green synthesis of silver nanoparticles

    Science.gov (United States)

    Zayed, Mervat F.; Eisa, Wael H.; Shabaka, A. A.

    2012-12-01

    Five plant leaf extracts (Malva parviflora, Beta vulgaris subsp. Vulgaris, Anethum graveolens, Allium kurrat and Capsicum frutescens) were screened for their bioreduction behavior for synthesis of silver nanoparticles. M. parviflora (Malvaceae) was found to exhibit the best reducing and protecting action in terms of synthesis rate and monodispersity of the prepared silver nanoparticles. Our measurements indicate that biosynthesis of Ag nanoparticles by M. parviflora produces Ag nanoparticles with the diameters in the range of 19-25 nm. XRD studies reveal a high degree of crystallinity and monophasic Ag nanoparticles of face-centered cubic structure. FTIR analysis proved that particles are reduced and stabilized in solution by the capping agent that is likely to be proteins secreted by the biomass. The present process is an excellent candidate for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.

  14. Synthesis of high magnetization Fe and FeCo nanoparticles by high temperature chemical reduction

    Energy Technology Data Exchange (ETDEWEB)

    Kandapallil, B; Colborn, RE; Bonitatibus, PJ; Johnson, F

    2015-03-15

    Fe and FeCo ferromagnetic nanoparticles in the 5-10 nm size regimes featuring high magnetization were synthesized using a modified chemical reduction method. The structure and morphology of these nanoparticles were confirmed by XRD and TOM analysis. These small, monodisperse and phase pure nanoparticles exhibited magnetic saturation of 210 emu/g (Fe) and 220 emu/g (Fe+Co) for Fe and FeCo nanoparticles respectively. The magnetization was found to be dependent on the temperature at which the reducing agent was introduced. (C) 2014 Elsevier B.V. All rights reserved,

  15. Size-controlled bismuth nanoparticles physically grown by the support of cobalt atomic flux

    Science.gov (United States)

    Lee, Ho Seok; Noh, Jin-Seo

    2016-04-01

    Bi nanoparticle arrays with the almost monodispersity were synthesized using a magnetically assisted physical method. The average size and the overall morphology of Bi nanoparticles could be controlled by the adjustment of several parameters such as relative powers applied to Bi and Co targets, substrate temperature, and growth time. It was disclosed that Bi nanoparticles grow larger at a higher relative power to Bi, higher substrate temperature, and longer growth time, accompanying the deterioration of well-developed faceted structures. This physical method may provide a facile and fast route to achieving quality Bi nanoparticle arrays with a certain extent of size and morphology controllability.

  16. Composite nanoparticle of Au and quantum dots for X-ray computed tomography and fluorescence dual-mode imaging in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ji-Tao; Yang, Xiao-Quan; Zhang, Xiao-Shuai; Yan, Dong-Mei; Yao, Ming-Hao; Qin, Meng-Yao; Zhao, Yuan-Di, E-mail: zydi@mail.hust.edu.cn [Huazhong University of Science and Technology, Britton Chance Center for Biomedical Photonics at Wuhan National Laboratory for Optoelectronics - Hubei Bioinformatics & Molecular Imaging Key Laboratory, Department of Biomedical Engineering, College of Life Science and Technology (China)

    2015-12-15

    In this study, composite nanoparticles comprising Au nanoparticle and quantum dots were built and used for contrast-enhanced computed tomography imaging (CT) and fluorescence dual-mode imaging in vivo. The nanoparticle exhibited good monodispersity and good biocompatibility, and had excellent CT contrast-enhancement effect and fluorescence imaging capability. They were appropriate for being used as dual-mode imaging probe in vivo.

  17. 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.

  18. Green synthesis of well-dispersed gold nanoparticles using Macrotyloma uniflorum.

    Science.gov (United States)

    Aromal, S Aswathy; Vidhu, V K; Philip, Daizy

    2012-01-01

    The synthesis of metal nanoparticles of different sizes, shapes, chemical composition and controlled monodispersity is an important area of research in nanotechnology because of their interesting physical properties and technological applications. Present work describes an eco-friendly method for the synthesis of spherical gold nanoparticles using aqueous extract of Macrotyloma uniflorum. The effects of quantity of extract, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. The high crystallinity of nanoparticles with fcc phase is evident from HRTEM images, SAED and XRD patterns. Synthesized nanoparticles have size in the range 14-17nm. FTIR spectrum indicates the presence of different functional groups present in the bio-molecule capping the nanoparticles. The possible mechanism leading to the formation of gold nanoparticles is suggested.

  19. Characterization and catalytic activity of gold nanoparticles synthesized using ayurvedic arishtams.

    Science.gov (United States)

    Aromal, S Aswathy; Babu, K V Dinesh; Philip, Daizy

    2012-10-01

    The development of new synthesis methods for monodispersed nanocrystals using cheap and nontoxic chemicals, environmentally benign solvents and renewable materials remains a challenge to the scientific community. The present work reports a new green method for the synthesis of gold nanoparticles. Four different ayurvedic arishtams are used for the reduction of Au(3+) to Au nanoparticles. This method is simple, efficient, economic and nontoxic. Gold nanoparticles having different sizes in the range from 15 to 23 nm could be obtained. The nanoparticles have been characterized by UV-Visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. The high crystallinity of nanoparticles is evident from bright circular spots in the SAED pattern and peaks in the XRD pattern. The synthesized gold nanoparticles show good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol by excess NaBH(4). The synthesized nanoparticles are found to exhibit size dependent catalytic property, the smaller nanoparticles showing faster activity.

  20. Monodispersed water-in-oil emulsions prepared with semi-metal microfluidic EDGE systems

    NARCIS (Netherlands)

    Maan, A.A.; Schroën, C.G.P.H.; Boom, R.M.

    2013-01-01

    Monodispersed water-in-oil emulsions were prepared with EDGE (Edge based Droplet GEneration) systems, which generate many droplets simultaneously from one junction. The devices (with plateau height of 1.0 µm) were coated with Cu and CuNi having the same hydrophobicity but different surface

  1. Lock and key colloids through polymerization-induced buckling of monodisperse silicon oil droplets

    NARCIS (Netherlands)

    Sacanna, S.|info:eu-repo/dai/nl/311471676; Irvine, W.T.M.; Rossi, L.|info:eu-repo/dai/nl/314410376; Pine, D.J.

    2011-01-01

    We have developed a new simple method to fabricate bulk amounts of colloidal spheres with well defined cavities from monodisperse emulsions. Herein, we describe the formation mechanism of ‘‘reactive’’ silicon oil droplets that deform to reproducible shapes via a polymerization-induced buckling

  2. Effect of particle clustering of silver nanoparticles on ultrathin silicon solar cell

    Science.gov (United States)

    Shokeen, Poonam; Jain, Amit; Kapoor, Avinashi; Gupta, Vinay

    2016-07-01

    Particle clustering is a major concern for uniform dispersal of nanoparticles in various deposition procedures. Well separated uniform distribution of metal nanoparticles is essential for effective coupling of surface plasmons. This work experimentally and theoretically, discusses the effect of nanoparticle clustering on the light trapping efficiency of silver nanoparticles. Pulsed laser deposition system has been used for deposition of silver nanoparticles, and substrate heating has been used to promote uniform distribution of nanoparticles. Pre-heated substrate depositions are compared with corresponding post-annealed samples. XRD, FESEM, Photoluminescence and UV-visible spectroscopy have been used to study the variations in their structural and optical properties. Mono-dispersal of silver nanoparticles for pre-heated substrates results in sharper surface plasmon resonance in comparison to post-annealed samples. Mie theory is used to estimate the particle size of the nanoparticles and findings are in accordance with quantitative analysis of FESEM images. Finite-difference time domain technique is used to discuss the effect of particle distribution on an ultrathin film silicon solar cell. Device degradation is observed as a result of clustering of silver nanoparticles. Hence, mono-dispersal of plasmonic nanostructures is important for required results and pre-heated deposition of metal nanoparticles by pulsed laser deposition can effectively solve the problem of particle clustering.

  3. Sustainable steric stabilization of colloidal titania nanoparticles

    Science.gov (United States)

    Elbasuney, Sherif

    2017-07-01

    A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180-240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This

  4. 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.

  5. High stability and reactivity of defective graphene-supported Fe{sub n}Pt{sub 13−n} (n = 1, 2, and 3) nanoparticles for oxygen reduction reaction: a theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Duo [Harbin Normal University, Key Laboratory for Photo/Electro Bandgap Materials, Ministry of Education (China); Tian, Yu [Harbin Normal University, College of Chemistry and Chemical Engineering (China); Zhao, Jingxiang; Wang, Xuanzhang, E-mail: xzwang@126.com [Harbin Normal University, Key Laboratory for Photo/Electro Bandgap Materials, Ministry of Education (China)

    2015-01-15

    Recent experimental studies have shown that the FePt nanoparticles (NPs) assembled on graphene exhibit enhanced durability and catalytic activity for oxygen reduction reaction (ORR) than Pt—only catalysts. In this work, we have performed density functional theory calculations to investigate the stability and reactivity of several Fe{sub n}Pt{sub 13−n} NPs deposited on defective graphene for ORR, where n is adopted as 0, 1, 2, and 3, respectively. The results indicate that the alloying between Fe and Pt can enhance the stability of NPs and promote their oxygen reduction activity. Moreover, the monovacancy site in the graphene can provide anchoring sites for these bimetallic NPs by forming strong metal–substrate interaction, ensuring their high stability. Importantly, the O{sub 2} adsorption on these composites is weakened in various ways, which is ascribed to the change in their averaged d-band center. Thus, these composites exhibit superior catalytic performance in ORR by providing a balance in the O{sub 2} binding strength that allows for enhanced turnover. Our results may be useful to unravel the high stability and reactivity of defective graphene-FePt NPs for ORR from a theoretical perspective.

  6. Synthesis of mono-dispersed nanofluids using solution plasma

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Yong Kang, E-mail: yk@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Bratescu, Maria Antoaneta, E-mail: maria@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Ueno, Tomonaga, E-mail: tomo@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan); Saito, Nagahiro, E-mail: hiro@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan)

    2014-07-14

    Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface during and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.

  7. Synthesis of mono-dispersed nanofluids using solution plasma.

    Science.gov (United States)

    Heo, Yong Kang; Bratescu, Maria Antoaneta; Ueno, Tomonaga; Saito, Nagahiro

    2014-07-14

    Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface during and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.

  8. Synthesis of Stabilized Myrrh-Capped Hydrocolloidal Magnetite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ayman M. Atta

    2014-07-01

    Full Text Available Herein we report a new method for synthesizing stabilized magnetic nanoparticle (MNP colloids. A new class of monodisperse water-soluble magnetite nano-particles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The ferrous and ferric ions were hydrolyzed at low temperature at pH 9 in the presence of iodine to produce iron oxide nanoparticles. The natural product myrrh gum was used as capping agent to produce highly dispersed coated magnetite nanoparticles. The structure and morphology of the magnetic nanogel was characterized by Fourier transform infrared spectroscopy (FTIR and transmission electron microscopy (TEM, and X-ray diffraction (XRD was used to examine the crystal structure of the produced magnetite nanoparticles.

  9. Synthesis of stabilized myrrh-capped hydrocolloidal magnetite nanoparticles.

    Science.gov (United States)

    Atta, Ayman M; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2014-07-31

    Herein we report a new method for synthesizing stabilized magnetic nanoparticle (MNP) colloids. A new class of monodisperse water-soluble magnetite nano-particles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The ferrous and ferric ions were hydrolyzed at low temperature at pH 9 in the presence of iodine to produce iron oxide nanoparticles. The natural product myrrh gum was used as capping agent to produce highly dispersed coated magnetite nanoparticles. The structure and morphology of the magnetic nanogel was characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), and X-ray diffraction (XRD) was used to examine the crystal structure of the produced magnetite nanoparticles.

  10. International interlaboratory study for sizing and quatification of Ag nanoparticles in food simulants by single-particle ICPMS

    NARCIS (Netherlands)

    Linsinger, T.P.J.; Peters, R.J.B.; Weigel, S.

    2014-01-01

    This publication describes the first international intercomparison of particle-size determination by single-particle inductively coupled plasma mass spectrometry (sp-ICPMS). Concentrated monodisperse silver nanoparticle suspensions with particle diameters of 20, 40 and 100 nm and a blank solution we

  11. High coating of Ru(II) complexes on gold nanoparticles for single particle luminescence imaging in cells.

    Science.gov (United States)

    Rogers, Nicola J; Claire, Sunil; Harris, Robert M; Farabi, Shiva; Zikeli, Gerald; Styles, Iain B; Hodges, Nikolas J; Pikramenou, Zoe

    2014-01-18

    Gold nanoparticles are efficiently labelled with a luminescent ruthenium complex, producing 13 and 100 nm diameter, monodisperse red-emissive imaging probes with luminescence lifetimes prolonged over the molecular unit. Single, 100 nm particles are observed in whole cell luminescence imaging which reveals their biomolecular association with chromatin in the nucleus of cancer cells.

  12. Highly stable, protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Lori; Kora, Aruna Jyothi; Arunachalam, J., E-mail: aruncccm@gmail.com

    2012-08-01

    A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8 {+-} 1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected-area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics. - Highlights: Black-Right-Pointing-Pointer Method for NaBH{sub 4} reduced and BSA capped gold nanoparticle was standardized. Black-Right-Pointing-Pointer Nanoparticles were spherical and nearly monodispersed with a size of 7.8 nm. Black-Right-Pointing-Pointer Nanoparticles are extremely stable towards pH modification and electrolyte addition. Black

  13. Pore fabrication in various silica-based nanoparticles by controlled etching

    KAUST Repository

    Zhao, L. J.

    2010-07-20

    A novel method based on controlled etching was developed to fabricate nanopores on preformed silica nanoparticles (<100 nm in diameter). The obtained monodisperse nanoporous particles could form highly stable homogeneous colloidal solution. Fluorescent silica nanoparticles and magnetic silica-coated γ-Fe 2O 3 nanoparticles were investigated as examples to illustrate that this strategy could be generally applied to various silica-based functional nanoparticles. The results indicated that this method was effective for generating pores on these nanoparticles without altering their original functionalities. The obtained multifunctional nanoparticles would be useful for many biological and biomedical applications. These porous nanoparticles could also serve as building blocks to fabricate three-dimensionally periodic structures that have the potential to be used as photonic crystals. © 2010 American Chemical Society.

  14. The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds.

    Science.gov (United States)

    Kelsen, Vinciane; Wendt, Bianca; Werkmeister, Svenja; Junge, Kathrin; Beller, Matthias; Chaudret, Bruno

    2013-04-28

    The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C=X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C=O bond hydrogenation.

  15. Functionalization of gold nanoparticles as antidiabetic nanomaterial.

    Science.gov (United States)

    Venkatachalam, M; Govindaraju, K; Mohamed Sadiq, A; Tamilselvan, S; Ganesh Kumar, V; Singaravelu, G

    2013-12-01

    In the present investigation, functionalization of gold nanoparticles synthesized using propanoic acid 2-(3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl) (PAT) an active biocomponent isolated from Cassia auriculata is studied in detail. On reaction of PAT with aqueous HAuCl4, rapid formation of stable gold nanoparticles was achieved. Formation of gold nanoparticles was confirmed by UV-vis spectroscopy, XRD, GC-MS,FTIR, TEM and SEM with EDAX. Gold nanoparticles mostly were monodisperse, spherical in shape and ranged in size 12-41 nm. Gold nanoparticles