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Sample records for ir oxide nanocluster

  1. Enhanced electrochemical water oxidation: the impact of nanoclusters and nanocavities

    NARCIS (Netherlands)

    Zhang, X.; Cao, C.; Bieberle, A.

    2017-01-01

    The structures of transition metal surfaces and metal oxides are commonly believed to have a significant effect on the catalytic reactions. Density functional theory calculations are therefore used in this study to investigate the oxygen evolution reaction (OER) over nanostructured, i.e. nanocluster

  2. Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

    Energy Technology Data Exchange (ETDEWEB)

    Ribis, J., E-mail: joel.ribis@cea.fr [CEA, DEN, SRMA, F-91191 Gif sur Yvette (France); Bordas, E.; Trocellier, P.; Serruys, Y. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, 91191 Gif sur Yvette (France); Carlan, Y. de [CEA, DEN, SRMA, F-91191 Gif sur Yvette (France); Legris, A. [UMET, CNRS/UMR 8207, Bât. C6, Univ. Lille 1, 59655 Villeneuve d’Ascq (France)

    2015-12-15

    ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe–Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

  3. Silver electrodeposition over an Ir/Ir oxide electrode

    International Nuclear Information System (INIS)

    Lezna, R.O.; Tacconi, N.R. de; Arvia, A.J.

    1984-01-01

    Changes in electrochemical response brought about by the electrodeposition of small amounts of silver on oxide covered iridium electrodes are examined in relation to the semiconducting properties of the oxide. The charge involved in both silver and hydrogen atoms was found to remain practically constant and independent of the oxide thickness which was gradually increased by potentiodynamic cycling up to greater anodic switching potentials. This result suggests that the charge transfer for both processes takes place at the bare metal. The considerable increase in the film conductivity when the potential is above ductivity when the potential is above oV (MSE) is shown by the fact that under certain controlled conditions the silver electroreduction/ electroxidation reactions are shifted to a more anodic potential region where the oxide becomes conductor and participates in the charge transfer process. Silver loading increases the electrical conductivity of the oxide providing a large cross section for the electroxidation of Ir, particularly in a region where the oxide conductivity is poor (E [pt

  4. Platinum nano-cluster thin film formed on glassy carbon and the application for methanol oxidation

    International Nuclear Information System (INIS)

    Chang, Gang; Oyama, Munetaka; Hirao, Kazuyuki

    2007-01-01

    As an interesting platinum nanostructured material, a Pt nano-cluster film (PtNCF) attached on glassy carbon (GC) is reported. Through the reduction of PtCl 4 2- by ascorbic acid in the presence of GC substrate, a Pt thin continuous film composed of small nano-clusters which had a further agglomerated nanostructure of small grains could be attached on the GC surface. It was found that the electrocatalytic ability of PtNCF for the methanol oxidation was apparently higher than those of the Pt nano-clusters dispersedly attached on GC or indium in oxides. In addition, the electrocatalytic performance of PtNCF per Pt amount was superior to that of Pt black on GC. These results indicate that, in spite of the continuous nanostructures, nano-grains of PtNCF worked effectively for the catalytic electrolysis. The present PtNCF can be regarded as an interesting thin film material, which can be easily prepared by one-step chemical reduction

  5. Correlation of photobleaching, oxidation and metal induced fluorescence quenching of DNA-templated silver nanoclusters.

    Science.gov (United States)

    Morishita, Kiyoshi; MacLean, James L; Liu, Biwu; Jiang, Hui; Liu, Juewen

    2013-04-07

    Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg(2+), where d(10)-d(10) metallophilic interaction has often been proposed for associating Hg(2+) with nanoclusters. However, it cannot explain the lack of response to other d(10) ions such as Zn(2+) and Cd(2+). In our effort to elucidate the quenching mechanism, we studied a total of eight AgNCs prepared by different hairpin DNA sequences; they showed different sensitivity to Hg(2+), and DNA with a larger cytosine loop size produced more sensitive AgNCs. In all the cases, samples strongly quenched by Hg(2+) were also more easily photobleached. Light of shorter wavelengths bleached AgNCs more potently, and photobleached samples can be recovered by NaBH4. Strong fluorescence quenching was also observed with high redox potential metal ions such as Ag(+), Au(3+), Cu(2+) and Hg(2+), but not with low redox potential ions. Such metal induced quenching cannot be recovered by NaBH4. Electronic absorption and mass spectrometry studies offered further insights into the oxidation reaction. Our results correlate many important experimental observations and will fuel the further growth of this field.

  6. Reductive Deprotection of Monolayer Protected Nanoclusters: An Efficient Route to Supported Ultrasmall Au Nanocatalysts for Selective Oxidation

    Czech Academy of Sciences Publication Activity Database

    Das, S.; Goswami, A.; Hesari, M.; Al-Sharab, J. F.; Mikmeková, Eliška; Maran, F.; Asefa, T.

    2014-01-01

    Roč. 10, č. 8 (2014), s. 1473-1478 ISSN 1613-6810 R&D Projects: GA MŠk(CZ) LO1212 Keywords : gold nanoclusters * selective oxidation * heterogeneous nanocatalysis * styrene oxidation * borohydride reduction Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 8.368, year: 2014

  7. Atomic structure and special reactivity toward methanol oxidation of vanadia nanoclusters on TiO2(110).

    Science.gov (United States)

    Artiglia, Luca; Agnoli, Stefano; Vittadini, Andrea; Verdini, Alberto; Cossaro, Albano; Floreano, Luca; Granozzi, Gaetano

    2013-11-20

    We have grown highly controlled VOx nanoclusters on rutile TiO2(110). The combination of photoemission and photoelectron diffraction techniques based on synchrotron radiation with DFT calculations has allowed identifying these nanostructures as exotic V4O6 nanoclusters, which hold vanadyl groups, even if vanadium oxidation state is formally +3. Our theoretical investigation also indicates that on the surface of titania, vanadia mononuclear species, with oxidation states ranging from +2 to +4, can be strongly stabilized by aggregation into tetramers that are characterized by a charge transfer to the titania substrate and a consequent decrease of the electron density in the vanadium 3d levels. We then performed temperature programmed desorption experiments using methanol as probe molecule to understand the impact of these unusual electronic and structural properties on the chemical reactivity, obtaining that the V4O6 nanoclusters can selectively convert methanol to formaldehyde at an unprecedented low temperature (300 K).

  8. Photoconductivity, photoluminescence and optical Kerr nonlinear effects in zinc oxide films containing chromium nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Torres, C., E-mail: crstorres@yahoo.com.mx [Seccion de Estudios de Posgrado e Investigacion, ESIME-Z, Instituto Politecnico Nacional, Mexico, DF 07738 (Mexico); Garcia-Cruz, M.L. [Centro de Investigacion en Dispositivos Semiconductores, Benemerita Universidad Autonoma de Puebla, A. P. J-48, Puebla 72570, Mexico (Mexico); Castaneda, L., E-mail: luisca@sirio.ifuap.buap.mx [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, A. P. J-48, Puebla 72570, Mexico (Mexico); Rangel Rojo, R. [CICESE/Depto. de Optica, A. P. 360, Ensenada, BC 22860 (Mexico); Tamayo-Rivera, L. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, DF 01000 (Mexico); Maldonado, A. [Depto. de Ing. Electrica, CINVESTAV IPN-SEES, A. P. 14740, Mexico DF 07000 (Mexico); Avendano-Alejo, M., E-mail: imax_aa@yahoo.com.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, A. P. 70-186, 04510, DF (Mexico); and others

    2012-04-15

    Chromium doped zinc oxide thin solid films were deposited on soda-lime glass substrates. The photoconductivity of the material and its influence on the optical behavior was evaluated. A non-alkoxide sol-gel synthesis approach was used for the preparation of the samples. An enhancement of the photoluminescence response exhibited by the resulting photoconductive films with embedded chromium nanoclusters is presented. The modification in the photoconduction induced by a 445 nm wavelength was measured and then associated with the participation of the optical absorptive response. In order to investigate the third order optical nonlinearities of the samples, a standard time-resolved Optical Kerr Gate configuration with 80 fs pulses at 830 nm was used and a quasi-instantaneous pure electronic nonlinearity without the contribution of nonlinear optical absorption was observed. We estimate that from the inclusion of Cr nanoclusters into the sample results a strong optical Kerr effect originated by quantum confinement. The large photoluminescence response and the important refractive nonlinearity of the photoconductive samples seem to promise potential applications for the development of multifunctional all-optical nanodevices. - Highlights: Black-Right-Pointing-Pointer Enhancement in photoluminescence for chromium doped zinc oxide films is presented. Black-Right-Pointing-Pointer A strong and ultrafast optical Kerr effect seems to result from quantum confinement. Black-Right-Pointing-Pointer Photoconductive properties for optical and optoelectronic functions were observed.

  9. In vivo target bio-imaging of Alzheimer's disease by fluorescent zinc oxide nanoclusters.

    Science.gov (United States)

    Lai, Lanmei; Zhao, Chunqiu; Su, Meina; Li, Xiaoqi; Liu, Xiaoli; Jiang, Hui; Amatore, Christian; Wang, Xuemei

    2016-07-21

    Alzheimer's disease (AD) is an irreversible neurodegenerative disease which is difficult to cure. When Alzheimer's disease occurs, the level of zinc ions in the brain changes, and the relevant amount of zinc ions continue decreasing in the cerebrospinal fluid and plasma of Alzheimer's patients with disease exacerbation. In view of these considerations, we have explored a new strategy for the in vivo rapid fluorescence imaging of Alzheimer's disease through target bio-labeling of zinc oxide nanoclusters which were biosynthesized in vivo in the Alzheimer's brain via intravenous injection of zinc gluconate solution. By using three-month-old and six-month-old Alzheimer's model mice as models, our observations demonstrate that biocompatible zinc ions could pass through the blood-brain barrier of the Alzheimer's disease mice and generate fluorescent zinc oxide nanoclusters (ZnO NCs) through biosynthesis, and then the bio-synthesized ZnO NCs could readily accumulate in situ on the hippocampus specific region for the in vivo fluorescent labeling of the affected sites. This study provides a new way for the rapid diagnosis of Alzheimer's disease and may have promising prospects in the effective diagnosis of Alzheimer's disease.

  10. Electronic structures and adsorption configurations of gold nanoclusters on cerium oxide defect surfaces

    Science.gov (United States)

    Wang, Lu; Mei, Wai-Ning; Lawrence, Neil; Brewer, Joseph R.; Wells-Kingsbury, James; Ihrig, Marcella; Wang, Gonghua; Cheung, Chin Li; Soo, Yun-Liang

    2012-02-01

    Fluorite-structured cerium oxide (or ceria, CeO2-x, 0 fluorite-structured slab model of defective ceria with a chemical formula corresponding to CeO1.5. The optimized surface structure of this model was found to contain both surface and sub-surface OVDs, similar to those observed in our HRTEM data for low pressure activated nanoceria. Significantly, the model captures comparable reduction in the average Ce-O bond distance and also atomic coordination numbers observed in our EXAFS data. To explore the roles of Au nanoclusters, we adsorbed flat clusters of 3, 4, 9, 10, and 19 Au atoms on ceria slabs, optimized their configurations, and computed the corresponding electronic structures applying first-principle approach. Consequently, we present the density of states results to elucidate the experimentally observed optical property change and s-d hybridization.

  11. Fabrication of highly catalytic silver nanoclusters/graphene oxide nanocomposite as nanotag for sensitive electrochemical immunoassay

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiamian; Wang, Xiuyun; Wu, Shuo, E-mail: wushuo@dlut.edu.cn; Song, Jie; Zhao, Yanqiu; Ge, Yanqiu; Meng, Changgong

    2016-02-04

    Silver nanoclusters and graphene oxide nanocomposite (AgNCs/GRO) is synthesized and functionalized with detection antibody for highly sensitive electrochemical sensing of carcinoembryonic antigen (CEA), a model tumor marker involved in many cancers. AgNCs with large surface area and abundant amount of low-coordinated sites are synthesized with DNA as template and exhibit high catalytic activity towards the electrochemical reduction of H{sub 2}O{sub 2}. GRO is employed to assemble with AgNCs because it has large specific surface area, super electronic conductivity and strong π-π stacking interaction with the hydrophobic bases of DNA, which can further improve the catalytic ability of the AgNCs. Using AgNCs/GRO as signal amplification tag, an enzyme-free electrochemical immunosensing protocol is designed for the highly sensitive detection of CEA on the capture antibody functionalized immunosensing interface. Under optimal conditions, the designed immunosensor exhibits a wide linear range from 0.1 pg mL{sup −1} to 100 ng mL{sup −1} and a low limit of detection of 0.037 pg mL{sup −1}. Practical sample analysis reveals the sensor has good accuracy and reproducibility, indicating the great application prospective of the AgNCs/GRO in fabricating highly sensitive immunosensors, which can be extended to the detection of various kinds of low abundance disease related proteins. - Highlights: • An enzyme-free electrochemical immunosensor is reported for detecting proteins. • A silver nanocluster/graphene oxide composite is synthesized as nanotag. • The nanotags exhibit highly catalytic activity to the electro-reduction of H{sub 2}O{sub 2}. • The as-fabricated immunosensor could detect protein in serum samples.

  12. Enhancement in electro-oxidation of methanol over PtRu black catalyst through strong interaction with iron oxide nanocluster.

    Science.gov (United States)

    Jeon, Min Ku; Lee, Ki Rak; Woo, Seong Ihl

    2010-11-02

    One of the major issues in direct methanol fuel cell research is to develop a new catalyst for methanol electro-oxidation reaction (MOR) with high activity and low cost. In this study, a new, simple, and economic way was introduced to improve the catalytic activity of commercial PtRu black catalyst for the MOR. A nanocomposite electrode was fabricated by mixing the PtRu catalyst with Fe(2)O(3) nanoclusters. When 10 wt % of the PtRu catalyst was replaced by the Fe(2)O(3) nanoclusters, mass activity (A/g(Pt)) increased by 80% compared to that of the pure PtRu catalyst. Specific activity of the mixed catalyst was 100% higher than that of the pure PtRu catalyst. The nanocomposite catalysts were also applied to single cells. Although the amount of the PtRu catalyst was reduced by 10 wt %, 10% higher potential was observed in the nanocomposite catalysts at a current density of 100 mA/cm(2).

  13. Study on IR Properties of Reduced Graphene Oxide

    Science.gov (United States)

    Ma, Deyue; Li, Xiaoxia; Guo, Yuxiang; Zeng, Yurun

    2018-01-01

    Firstly, the reduced graphene oxide was prepared by modified hummer method and characterized. Then, the complex refractive index of reduced graphene oxide in IR band was tested and its IR absorption and radiation properties were researched by correlated calculation. The results show that reduced graphene oxide prepared by hummer method are multilayered graphene with defects and functional groups on its surface. Its absorption in near and far IR bands is strong, but it’s weaker in middle IR band. At the IR atmosphere Window, its normal spectral emissivity decreases with wavelength increasing, and its total normal spectral emissivity in 3 ∼ 5μm and 8 ∼ 14μm are 0.75 and 0.625, respectively. Therefore, reduced graphene oxide can be used as IR absorption and coating materials and have a great potential in microwave and infrared compatible materials.

  14. New Ir Bis-Carbonyl Precursor for Water Oxidation Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Daria L. [Department of Chemistry, Yale University, 225; Beltrán-Suito, Rodrigo [Department of Chemistry, Yale University, 225; Thomsen, Julianne M. [Department of Chemistry, Yale University, 225; Hashmi, Sara M. [Department of Chemical and Environmental; Materna, Kelly L. [Department of Chemistry, Yale University, 225; Sheehan, Stafford W. [Catalytic Innovations LLC, 70 Crandall; Mercado, Brandon Q. [Department of Chemistry, Yale University, 225; Brudvig, Gary W. [Department of Chemistry, Yale University, 225; Crabtree, Robert H. [Department of Chemistry, Yale University, 225

    2016-02-05

    This paper introduces IrI(CO)2(pyalc) (pyalc = (2-pyridyl)-2-propanoate) as an atom-efficient precursor for Ir-based homogeneous oxidation catalysis. This compound was chosen to simplify analysis of the water oxidation catalyst species formed by the previously reported Cp*IrIII(pyalc)OH water oxidation precatalyst. Here, we present a comparative study on the chemical and catalytic properties of these two precursors. Previous studies show that oxidative activation of Cp*Ir-based precursors with NaIO4 results in formation of a blue IrIV species. This activation is concomitant with the loss of the placeholder Cp* ligand which oxidatively degrades to form acetic acid, iodate, and other obligatory byproducts. The activation process requires substantial amounts of primary oxidant, and the degradation products complicate analysis of the resulting IrIV species. The species formed from oxidation of the Ir(CO)2(pyalc) precursor, on the other hand, lacks these degradation products (the CO ligands are easily lost upon oxidation) which allows for more detailed examination of the resulting Ir(pyalc) active species both catalytically and spectroscopically, although complete structural analysis is still elusive. Once Ir(CO)2(pyalc) is activated, the system requires acetic acid or acetate to prevent the formation of nanoparticles. Investigation of the activated bis-carbonyl complex also suggests several Ir(pyalc) isomers may exist in solution. By 1H NMR, activated Ir(CO)2(pyalc) has fewer isomers than activated Cp*Ir complexes, allowing for advanced characterization. Future research in this direction is expected to contribute to a better structural understanding of the active species. A diol crystallization agent was needed for the structure determination of 3.

  15. Influence of ball-milling and annealing conditions on nanocluster characteristics in oxide dispersion strengthened steels

    International Nuclear Information System (INIS)

    Laurent-Brocq, M.; Legendre, F.; Mathon, M.-H.; Mascaro, A.; Poissonnet, S.; Radiguet, B.; Pareige, P.; Loyer, M.; Leseigneur, O.

    2012-01-01

    The characteristics of strengthening nanoclusters (NCs) have a major influence on the mechanical properties of oxide dispersion strengthened (ODS) steels. To determine how to control NC formation, ODS powders are synthesized in different ball-milling and annealing conditions, then characterized by electron probe micro-analysis and small angle neutron scattering. During ball-milling, reactants are dissolved into the metallic matrix until a Ti, Y and O solid solution is formed and then NC nucleation begins. Nucleation is greatly enhanced during the first minutes of annealing at 800 °C without any coarsening afterwards. The intensity and temperature of ball-milling influence this mechanism and thus the characteristics of the formed NC, whereas the nature of reactants, for a given composition, has no impact on NC size and volume fraction. Consequently, to promote the formation of fine and dense dispersion of NC, two main modifications to the usual process are proposed: (i) perform a long and/or intense ball-milling with a limited overheating, and (ii) anneal the as-milled powder at 800 °C before performing the thermo-mechanical treatment.

  16. Fabrication of highly catalytic silver nanoclusters/graphene oxide nanocomposite as nanotag for sensitive electrochemical immunoassay.

    Science.gov (United States)

    Wang, Jiamian; Wang, Xiuyun; Wu, Shuo; Song, Jie; Zhao, Yanqiu; Ge, Yanqiu; Meng, Changgong

    2016-02-04

    Silver nanoclusters and graphene oxide nanocomposite (AgNCs/GRO) is synthesized and functionalized with detection antibody for highly sensitive electrochemical sensing of carcinoembryonic antigen (CEA), a model tumor marker involved in many cancers. AgNCs with large surface area and abundant amount of low-coordinated sites are synthesized with DNA as template and exhibit high catalytic activity towards the electrochemical reduction of H2O2. GRO is employed to assemble with AgNCs because it has large specific surface area, super electronic conductivity and strong π-π stacking interaction with the hydrophobic bases of DNA, which can further improve the catalytic ability of the AgNCs. Using AgNCs/GRO as signal amplification tag, an enzyme-free electrochemical immunosensing protocol is designed for the highly sensitive detection of CEA on the capture antibody functionalized immunosensing interface. Under optimal conditions, the designed immunosensor exhibits a wide linear range from 0.1 pg mL(-1) to 100 ng mL(-1) and a low limit of detection of 0.037 pg mL(-1). Practical sample analysis reveals the sensor has good accuracy and reproducibility, indicating the great application prospective of the AgNCs/GRO in fabricating highly sensitive immunosensors, which can be extended to the detection of various kinds of low abundance disease related proteins. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Atomically Monodisperse Nickel Nanoclusters as Highly Active Electrocatalysts for Water Oxidation

    KAUST Repository

    Joya, Khurram

    2016-04-08

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 and initiate the oxygen evolution at an amazingly low overpotential of ~1.51 V (vs RHE; η ≈ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm–2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec–1 is observed using Ni4(PET)8. These results are comparable to the state-of-the art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm–2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

  18. Atomic structure of Pt nanoclusters supported by graphene/Ir(111) and reversible transformation under CO exposure

    Science.gov (United States)

    Franz, Dirk; Blanc, Nils; Coraux, Johann; Renaud, Gilles; Runte, Sven; Gerber, Timm; Busse, Carsten; Michely, Thomas; Feibelman, Peter J.; Hejral, Uta; Stierle, Andreas

    2016-01-01

    We have investigated the atomic structure of graphene/Ir(111) supported platinum clusters with on average fewer than 40 atoms by means of surface x-ray diffraction (SXRD), grazing incidence small angle x-ray scattering (GISAXS), and normal incidence x-ray standing waves (NIXSW) measurements, in comparison with density functional theory calculations (DFT). GISAXS revealed that the clusters with 1.3 nm diameter form a regular array with domain sizes of 90 nm. SXRD shows that the 1-2 monolayer high, (111) oriented Pt nanoparticles grow epitaxially on the graphene support. From the combined analysis of the SXRD and NIXSW data, a three-dimensional (3D) structural model of the clusters and the graphene support can be deduced which is in line with the DFT results. For the clusters grown in ultrahigh vacuum the lattice parameter is reduced by (4.6 ±0.1 )% compared to bulk platinum. The graphene layer undergoes a strong Pt adsorption induced buckling, caused by a rehybridization of the carbon atoms below the cluster. In situ observation of the Pt clusters in CO and O2 environments revealed a reversible change of the clusters' strain state while successively dosing CO at room temperature and O2 at 575 K, pointing to a CO oxidation activity of the Pt clusters.

  19. Fabrication of peptide stabilized fluorescent gold nanocluster/graphene oxide nanocomplex and its application in turn-on detection of metalloproteinase-9.

    Science.gov (United States)

    Nguyen, Phuong-Diem; Cong, Vu Thanh; Baek, Changyoon; Min, Junhong

    2017-03-15

    This study introduces the double-ligands stabilizing gold nanoclusters and the fabrication of gold nanocluster/graphene nanocomplex as a "turn-on" fluorescent probe for the detection of cancer-related enzyme matrix metalloproteinase-9. A facile, one-step approach was developed for the synthesis of fluorescent gold nanoclusters using peptides and mercaptoundecanoic acid as co-templating ligands. The peptide was designed to possess a metalloproteinase-9 cleavage site and to act not only as a stabilizer but also as a targeting ligand for the enzyme detection. The prepared gold nanoclusters show an intense red fluorescence with a broad adsorption spectrum. In the presence of the enzyme, due to the excellent quenching properties and the negligible background of graphene oxide, the developed peptide-gold nanocluster/graphene nanocomplex yielded an intense "turn-on" fluorescent response, which strongly correlated with the enzyme concentration. The limit of detection of the nanocomplex was 0.15nM. The sensor was successfully applied for "turn-on" detection of metalloproteinase-9 secreted from human breast adenocarcinoma MCF-7 cells with high sensitivity, selectivity, significant improvement in terms of detection time and simplicity. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    Science.gov (United States)

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  1. Catalysis by Nanostructures: Methane, Ethylene Oxide, and Propylene Oxide Synthesis on Ag, Cu or Au Nanoclusters

    Science.gov (United States)

    2008-02-07

    properties 46-54. One of the most significant findings is that one can control the activity of SnO2 to CO oxidation by placing a SnO 2 nanowire above...on semiconductor surfaces: An experimental setup. Intl J Mass Spectrometry 254, 202-209 (2006) 12. G. Mills, M. S. Gordon, and H. Metiu, Oxygen

  2. Dissociation of CO2 on rhodium nanoclusters (Rh13) in various structures supported on unzipped graphene oxide--a DFT study.

    Science.gov (United States)

    Chang, Chun-Chih; Ho, Jia-Jen

    2015-04-28

    The catalytic activity of rhodium nanoclusters (Rh13) on unzipped graphene oxide (Rh13/UGO) has been investigated for comparison with Rh13 nanoclusters and Rh(111) surfaces. The binding energy of Rh atoms on UGO is less than the cohesive energy (-5.75 eV) of bulk Rh, indicating that the Rh atoms adsorbed on UGO tend to collect into clusters. We systematically calculated the adsorption energies of CO2 on Rh13 nanoclusters in various stable shapes on unzipped graphene oxide; Rh13-Ih/UGO had the highest energy (where the Ih represents icosahedral shape), -1.18 eV, with the C-O bond being elongated from 1.17 to 1.29 Å; the barrier to dissociation of CO2 on Rh13-Ih/UGO is, accordingly, the smallest (Ea = 0.45 eV), indicating that Rh13-Ih/UGO might act as an effective material to adsorb and activate the scission of the C-O bond of CO2. The calculated data required to support all evidence of this result, including the electronic distribution and the density of states, are provided.

  3. Comparative Analysis of Particle Swarm and Differential Evolution via Tuning on Ultrasmall Titanium Oxide Nanoclusters

    Science.gov (United States)

    Inclan, Eric; Lassester, Jack; Geohegan, David; Yoon, Mina

    Optimization algorithms (OA) coupled with numerical methods enable researchers to identify and study (meta) stable nanoclusters without the control restrictions of empirical methods. An algorithm's performance is governed by two factors: (1) its compatibility with an objective function, (2) the dimension of a design space, which increases with cluster size. Although researchers often tune an algorithm's user-defined parameters (UDP), tuning is not guaranteed to improve performance. In this research, Particle Swarm (PSO) and Differential Evolution (DE), are compared by tuning their UDP in a multi-objective optimization environment (MOE). Combined with a Kolmogorov Smirnov test for statistical significance, the MOE enables the study of the Pareto Front (PF), made of the UDP settings that trade-off between best performance in energy minimization (``effectiveness'') based on force-field potential energy, and best convergence rate (``efficiency''). By studying the PF, this research finds that UDP values frequently suggested in the literature do not provide best effectiveness for these methods. Additionally, monotonic convergence is found to significantly improve efficiency without sacrificing effectiveness for very small systems, suggesting better compatibility. Work is supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  4. Ultra-sensitive determination of epinephrine based on TiO{sub 2}-Au nanoclusters supported on reduced graphene oxide and carbon nanotube hybrid nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jianbo, E-mail: chm_lijianbo@yeah.net; Wang, Xiaojiao; Duan, Huimin; Wang, Yanhui; Luo, Chuannan, E-mail: chm_lijianbo@yeah.net

    2016-07-01

    A highly efficient and sensitive electrochemical sensor for EP based on reduced graphene and multi-walled carbon nanotube hybrid nanocomposites loaded TiO{sub 2}-Au nano-clusters modified glassy carbon electrode was developed. The surface nature and morphology of the nanocomposite film and the electrochemical properties of the sensor were characterized by Raman spectra, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectra (EDX), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. Carbon nanomaterials were widely used in sensing due to its large electroactive surface area, fast electron transport and strong adsorption capacity. Meanwhile, TiO{sub 2}-Au nano-clusters could accelerate the electron transfer, increase reactive site and extend electrochemical response window. The nanocomposite film could greatly enhance the response sensitivity and decrease the overpotential. The resulting sensor showed an excellent electrocatalytic activity toward EP. Under the optimum conditions (i.e. pH 6.0, 0.1 M PBS, preconcentration for 110 s), Differential pulse voltammetry was employed to detect ultra-trace amounts of EP. The result of a wide linear range of 1.0–300 nM and limited of detection 0.34 nM (S/N = 3) were obtained. The constructed sensor exhibited excellent accuracy and precision, the relative standard deviation (RSD) was less than 5%. The nanocomposite film sensor was successfully used to accurately detect the content of EP in practical samples, and the recoveries for the standards added are 97%–105%. - Highlights: • The three dimensional composite materials rGO/CNTs were successful synthesized. • High conductivity and catalytic activity of TiO{sub 2}-Au nanoclusters were synthesized. • The sensor displays a wide linear range, low detection limit and good stability.

  5. Benchmark Calculations of Energetic Properties of Groups 4 and 6 Transition Metal Oxide Nanoclusters Including Comparison to Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zongtang; Both, Johan; Li, Shenggang; Yue, Shuwen; Aprà, Edoardo; Keçeli, Murat; Wagner, Albert F.; Dixon, David A.

    2016-08-09

    The heats of formation and the normalized clustering energies (NCEs) for the group 4 and group 6 transition metal oxide (TMO) trimers and tetramers have been calculated by the Feller-Peterson-Dixon (FPD) method. The heats of formation predicted by the FPD method do not differ much from those previously derived from the NCEs at the CCSD(T)/aT level except for the CrO3 nanoclusters. New and improved heats of formation for Cr3O9 and Cr4O12 were obtained using PW91 orbitals instead of Hartree-Fock (HF) orbitals. Diffuse functions are necessary to predict accurate heats of formation. The fluoride affinities (FAs) are calculated with the CCSD(T) method. The relative energies (REs) of different isomers, NCEs, electron affinities (EAs), and FAs of (MO2)n ( M = Ti, Zr, Hf, n = 1 – 4 ) and (MO3)n ( M = Cr, Mo, W, n = 1 – 3) clusters have been benchmarked with 55 exchange-correlation DFT functionals including both pure and hybrid types. The absolute errors of the DFT results are mostly less than ±10 kcal/mol for the NCEs and the EAs, and less than ±15 kcal/mol for the FAs. Hybrid functionals usually perform better than the pure functionals for the REs and NCEs. The performance of the two types of functionals in predicting EAs and FAs is comparable. The B1B95 and PBE1PBE functionals provide reliable energetic properties for most isomers. Long range corrected pure functionals usually give poor FAs. The standard deviation of the absolute error is always close to the mean errors and the probability distributions of the DFT errors are often not Gaussian (normal). The breadth of the distribution of errors and the maximum probability are dependent on the energy property and the isomer.

  6. A reactive molecular dynamic simulation of oxidation of a silicon nanocluster

    International Nuclear Information System (INIS)

    Song Pengxiang; Ding Yulong; Wen Dongsheng

    2013-01-01

    This study presents an atomic level of molecular dynamic simulation of oxidation of silicon nanoparticle in use of a reactive force field (ReaxFF). The oxidation dynamics is revealed through the energy release, bond evolution and oxygen exchange processes. The oxidation is found to proceed in the manner of evolution of silicon–oxygen bond configuration, accompanied by the oxygen exchange process. The heat of reaction and the activation energy of the bond transformation process are also estimated, which indicates the capability of ReaxFF in the simulation of energetic materials.

  7. Metallic oxide nano-clusters synthesis by ion implantation in high purity Fe10Cr alloy

    International Nuclear Information System (INIS)

    Zheng, Ce

    2015-01-01

    ODS (Oxide Dispersed Strengthened) steels, which are reinforced with metal dispersions of nano-oxides (based on Y, Ti and O elements), are promising materials for future nuclear reactors. The detailed understanding of the mechanisms involved in the precipitation of these nano-oxides would improve manufacturing and mechanical properties of these ODS steels, with a strong economic impact for their industrialization. To experimentally study these mechanisms, an analytical approach by ion implantation is used, to control various parameters of synthesis of these precipitates as the temperature and concentration. This study demonstrated the feasibility of this method and concerned the behaviour of alloys models (based on aluminium oxide) under thermal annealing. High purity Fe-10Cr alloys were implanted with Al and O ions at room temperature. Transmission electron microscopy observations showed that the nano-oxides appear in the Fe-10Cr matrix upon ion implantation at room temperature without subsequent annealing. The mobility of implanted elements is caused by the defects created during ion implantation, allowing the nucleation of these nanoparticles, of a few nm in diameter. These nanoparticles are composed of aluminium and oxygen, and also chromium. The high-resolution experiments show that their crystallographic structure is that of a non-equilibrium compound of aluminium oxide (cubic γ-Al 2 O 3 type). The heat treatment performed after implantation induces the growth of the nano-sized oxides, and a phase change that tends to balance to the equilibrium structure (hexagonal α-Al 2 O 3 type). These results on model alloys are fully applicable to industrial materials: indeed ion implantation reproduces the conditions of milling and heat treatments are at equivalent temperatures to those of thermo-mechanical treatments. A mechanism involving the precipitation of nano-oxide dispersed in ODS alloys is proposed in this manuscript based on the obtained experimental results

  8. Structure-property relationships in NO x sensor materials composed of arrays of vanadium oxide nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Putrevu, Naga Ravikanth; Darling, Seth B.; Segre, Carlo U.; Ganegoda, Hasitha; Khan, M. Ishaque

    2017-12-01

    The mixed‐valent vanadium oxide based three‐dimensional framework structure species [Cd3(H2O)12V16IVV2VO36(OH)6(AO4)]∙24H2O, (A=V,S) (Cd3(VO)o) represents a rare example of an interesting sensor material which exhibits NOx {NO+NO2} semiconducting gas sensor properties under ambient conditions. The electrical resistance of the sensor material Cd3(VO)o decreases in air. Combined characterization studies revealed that the building block, {V18O42(AO4)} cluster, of 3‐D framework undergoes oxidation and remains intact for at least 2 months. The decrease in resistance is attributable to the reactivity of molecular oxygen towards vanadium which results in an increase in the oxidation state as well as the coordination number of vanadium center and decrease in band gap of Cd3(VO)o. Based on these results we propose that the changes in semiconducting properties of Cd3(VO)o under ambient conditions are due to the greater overlap between the O 2p and V 3d orbitals occurring during the oxidation.

  9. Tuning size and catalytic activity of nano-clusters of cobalt oxide

    Indian Academy of Sciences (India)

    Cobalt oxides were prepared by three different methods: (1) by reacting cobalt nitrate with oxalic acid, (2) co-precipitating cobalt nitrate with sodium carbonate, and (3) using sodium dodecyl sulphate as organic surfactant. All three samples were characterized before and after calcination by solvent extraction and the ...

  10. Structure-property relationships in NOx sensor materials composed of arrays of vanadium oxide nanoclusters

    Science.gov (United States)

    Putrevu, Naga Ravikanth; Darling, Seth B.; Segre, Carlo U.; Ganegoda, Hasitha; Khan, M. Ishaque

    2017-12-01

    The mixed-valent vanadium oxide based three-dimensional framework structure species [Cd3(H2O)12V16IVV2VO36(OH)6 (AO4)]·24H2O, (A = V,S) (Cd3(VO)o) represents a rare example of an interesting sensor material which exhibits NOx {NO + NO2} semiconducting gas sensor properties under ambient conditions. The electrical resistance of the sensor material Cd3(VO)o decreases in air. Combined characterization studies revealed that the building block, {V18O42(AO4)} cluster, of 3-D framework undergoes oxidation and remains intact for at least 2 months. The decrease in resistance is attributable to the reactivity of molecular oxygen towards vanadium which results in an increase in the oxidation state as well as the coordination number of vanadium center and decrease in band gap of Cd3(VO)o. Based on these results we propose that the changes in semiconducting properties of Cd3(VO)o under ambient conditions are due to the greater overlap between the O 2p and V 3d orbitals occurring during the oxidation.

  11. Chemisorption of CO and mechanism of CO oxidation on supported platinum nanoclusters

    KAUST Repository

    Allian, Ayman Daoud

    2011-03-30

    Kinetic, isotopic, and infrared studies on well-defined dispersed Pt clusters are combined here with first-principle theoretical methods on model cluster surfaces to probe the mechanism and structural requirements for CO oxidation catalysis at conditions typical of its industrial practice. CO oxidation turnover rates and the dynamics and thermodynamics of adsorption-desorption processes on cluster surfaces saturated with chemisorbed CO were measured on 1-20 nm Pt clusters under conditions of strict kinetic control. Turnover rates are proportional to O2 pressure and inversely proportional to CO pressure, consistent with kinetically relevant irreversible O2 activation steps on vacant sites present within saturated CO monolayers. These conclusions are consistent with the lack of isotopic scrambling in C16O-18O2-16O 2 reactions, and with infrared bands for chemisorbed CO that did not change within a CO pressure range that strongly influenced CO oxidation turnover rates. Density functional theory estimates of rate and equilibrium constants show that the kinetically relevant O2 activation steps involve direct O2* (or O2) reactions with CO* to form reactive O*-O-C*=O intermediates that decompose to form CO 2 and chemisorbed O*, instead of unassisted activation steps involving molecular adsorption and subsequent dissociation of O2. These CO-assisted O2 dissociation pathways avoid the higher barriers imposed by the spin-forbidden transitions required for unassisted O2 dissociation on surfaces saturated with chemisorbed CO. Measured rate parameters for CO oxidation were independent of Pt cluster size; these parameters depend on the ratio of rate constants for O2 reactions with CO* and CO adsorption equilibrium constants, which reflect the respective activation barriers and reaction enthalpies for these two steps. Infrared spectra during isotopic displacement and thermal desorption with 12CO- 13CO mixtures showed that the binding, dynamics, and thermodynamics of CO

  12. Ir-Ni oxide as a promising material for nerve and brain stimulating electrodes

    Directory of Open Access Journals (Sweden)

    Joan Stilling

    2014-09-01

    Full Text Available Tremendous potential for successful medical device development lies in both electrical stimulation therapies and neuronal prosthetic devices, which can be utilized in an extensive number of neurological disorders. These technologies rely on the successful electrical stimulation of biological tissue (i.e. neurons through the use of electrodes. However, this technology faces the principal problem of poor stimulus selectivity due to the currently available electrode’s large size relative to its targeted population of neurons. Irreversible damage to both the stimulated tissue and electrode are limiting factors in miniaturization of this technology, as charge density increases with decreasing electrode size. In an attempt to find an equilibrium between these two opposing constraints (electrode size and charge density, the objective of this work was to develop a novel iridium-nickel oxide (Ir0.2-Ni0.8-oxide coating that could intrinsically offer high charge storage capacity. Thermal decomposition was used to fabricate titanium oxide, iridium oxide, nickel oxide, and bimetallic iridium-nickel oxide coatings on titanium electrode substrates. The Ir0.2-Ni0.8-oxide coating yielded the highest intrinsic (material property and extrinsic (material property + surface area charge storage capacity (CSC among the investigated materials, exceeding the performance of the current state-of-the-art neural stimulating electrode, Ir-oxide. This indicates that the Ir0.2-Ni0.8-oxide material is a promising alternative to currently used Ir-oxide, Pt, Au and carbon-based stimulating electrodes.

  13. Biocompatibility of Ir/Ti-oxide coatings: Interaction with platelets, endothelial and smooth muscle cells

    Energy Technology Data Exchange (ETDEWEB)

    Habibzadeh, Sajjad [Department of Chemical Engineering, McGill University, Montreal, QC (Canada); Li, Ling [Department of Anatomy and Cell Biology, McGill University, Montreal, QC (Canada); Omanovic, Sasha [Department of Chemical Engineering, McGill University, Montreal, QC (Canada); Shum-Tim, Dominique [Divisions of Cardiac Surgery and Surgical Research, Department of Surgery, McGill University, Montreal, QC (Canada); Davis, Elaine C., E-mail: elaine.davis@mcgill.ca [Department of Anatomy and Cell Biology, McGill University, Montreal, QC (Canada)

    2014-05-01

    Graphical abstract: - Highlights: • Ir/Ti-oxide coated surfaces are characterized by the so-called “cracked-mud” morphology. • 40% Ir in the coating material results in a morphologically uniform coating. • ECs and SMCs showed a desirable response to the Ir/Ti-oxide coated surfaces. • Ir/Ti-oxide coated surfaces are more bio/hemocompatible than the untreated 316L stainless steel. - Abstract: Applying surface coatings on a biomedical implant is a promising modification technique which can enhance the implant's biocompatibility via controlling blood constituents- or/and cell-surface interaction. In this study, the influence of composition of Ir{sub x}Ti{sub 1−x}-oxide coatings (x = 0, 0.2, 0.4, 0.6, 0.8, 1) formed on a titanium (Ti) substrate on the responses of platelets, endothelial cells (ECs) and smooth muscle cells (SMCs) was investigated. The results showed that a significant decrease in platelet adhesion and activation was obtained on Ir{sub 0.2}Ti{sub 0.8}-oxide and Ir{sub 0.4}Ti{sub 0.6}-oxide coatings, rendering the surfaces more blood compatible, in comparison to the control (316L stainless steel, 316L-SS) and other coating compositions. Further, a substantial increase in the EC/SMC surface count ratio after 4 h of cell attachment to the Ir{sub 0.2}Ti{sub 0.8}-oxide and Ir{sub 0.4}Ti{sub 0.6}-oxide coatings, relative to the 316L-SS control and the other coating compositions, indicated high potential of these coatings for the enhancement of surface endothelialization. This indicates the capability of the corresponding coating compositions to promote EC proliferation on the surface, while inhibiting that of SMCs, which is important in cardiovascular stents applications.

  14. IrPdRu/C as H2Oxidation Catalysts for Alkaline Fuel Cells.

    Science.gov (United States)

    Wang, Hongsen; Abruña, Héctor D

    2017-05-24

    H 2 oxidation kinetics on Pt in alkaline media are very sluggish, being over 100 times slower than in acidic media, and thus, new and more active H 2 oxidation electrocatalysts must be developed in order to enable alkaline exchange membrane fuel cells (AEMFCs). In this Communication, we present a new type of catalysts-carbon-supported IrPdRu nanoparticles-as H 2 oxidation catalysts in alkaline media. These catalysts exhibit higher activity than Pt/C and Ir/C catalysts and are also quite stable. In particular, Ir 3 Ru 7 /C and Ir 3 Pd 1 Ru 6 /C catalysts are significantly more active and less expensive than Pt/C and Ir/C, and are thus promising new anode catalysts for alkaline fuel cell applications.

  15. Impaired oxidative balance and association of blood glucose, insulin and HOMA-IR index in migraine.

    Science.gov (United States)

    Yilmaz, Necat; Aydin, Ozgur; Yegin, Aysenur; Tiltak, Aysun; Eren, Esin; Aykal, Guzin

    2011-01-01

    The nature of the relationship between glucose metabolism and occurrence of migraine has not been elucidated precisely. This study investigated the status of oxidative/antioxidative balance and its relationship with the glucose metabolism in migraineurs to get new points of view for the underlying oxidative mechanisms. Sixty migraineurs and 46 control subjects were included in the study. Oxidative stress index, total oxidant and antioxidant status of both groups were examined in addition to the insulin and HOMA-IR index levels. HOMA-IR index was significantly enhanced in migraineurs (P = 0.038); similarly oxidative stress index and total oxidant status were higher in patients compared to the controls (P HOMA-IR index might play a role in the potential early pathogenesis for migraine.

  16. Size, shape, and crystallinity of luminescent structures in oxidized Si nanoclusters and H-passivated porous Si

    Science.gov (United States)

    Schuppler, S.; Marcus, M. A.; Xie, Y. H.; Harris, T. D.; Brown, W. L.; Chabal, Y. J.; Szajowski, P. J.; Friedman, S. L.; Adler, D. L.; Ross, F. M.

    1994-11-01

    Near-edge and extended x-ray absorption fine structure measurements from a wide variety of H-passivated porous Si samples and oxidized Si nanocrystals, combined with electron microscopy, ir-absorption, alpha-recoil, and luminescence emission data, provide a consistent structural picture of the species responsible for the luminescence observed in these systems. For luminescent porous Si samples peaking in the visible region, i. e., less than or equal 700nm, their mass-weighted-average structures are determined here to be particles - not wires, whose short-range character is crystalline - not amorphous, and whose dimensions - typically less than 15 angstrom - are significantly smaller than previously reported or proposed. These results depend only on sample luminescence behavior, not on sample preparation details, and thus have general implications in describing the mechanism responsible for visible luminescence in porous silicon. New results are also presented which demonstrate that the observed luminescence is unrelated to either the photo-oxidized Si species in porous Si or the interfacial suboxide species in the Si nanocrystals.

  17. Variable charge molecular dynamics studies of oxygen diffusion processes in nickel leading to the formation of internal oxide nano-clusters

    International Nuclear Information System (INIS)

    Garruchet, S.; Politano, O.; Vignal, V.; Arnoux, P.

    2009-01-01

    Full text of publication follows: New materials are under development for numerous applications in 4. generation reactor (Supercritical water reactor for example) and will have to operate at high temperature and in corrosive environments. Nickel and nickel based alloys are one of the most important candidate because of their good mechanical properties on a wide variety of severe environments (corrosive, irradiative, high temperatures,...). In this work, we simulated a model system of nickel to study the diffusivity of atomic oxygen and the formation of internal oxide nano-clusters by variable charge molecular dynamics techniques. Oxidation of nickel surfaces proceeds by cationic diffusion. In that sense, the governing parameter is the diffusion of Nickel in the oxide scale. However, it is also experimentally observed that some oxygen atoms are trapped within the metal. At high temperature, those atoms can diffuse and form internal oxide clusters in nano-voids within the metallic bulk. To characterize such processes, many experimental approaches have determined the O diffusion coefficient in Ni. However recent experimental studies expressed doubts about these values as the role played by impurities and/or vacancies during the diffusion processes was not addressed. Recently, some authors showed that O couldn't diffuse in Ni in absence of defects. As a consequence, new O diffusion coefficient has to be determined and correlated to the defects concentration in the system. To our knowledge, only a few numbers of theoretical investigations are dedicated to this topic. In particular all the numerical studies were performed by using the density functional theory (DFT)]. These approaches permitted to calculate migration energy and diffusion path at 0 K. However, a complete study of O diffusion at high temperature is still missing. This last leads us to develop variable charge molecular dynamics (MD) simulations on the diffusion of atomic O in Ni in the range 950 K to 1600 K

  18. IR-doped ruthenium oxide catalyst for oxygen evolution

    Science.gov (United States)

    Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

    2012-01-01

    A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

  19. Oxide Protective Coats for Ir/Re Rocket Combustion Chambers

    Science.gov (United States)

    Fortini, Arthur; Tuffias, Robert H.

    2003-01-01

    An improved material system has been developed for rocket engine combustion chambers for burning oxygen/ hydrogen mixtures or novel monopropellants, which are highly oxidizing at operating temperatures. The baseline for developing the improved material system is a prior iridium/rhenium system for chambers burning nitrogen tetroxide/monomethyl hydrazine mixtures, which are less oxidizing. The baseline combustion chamber comprises an outer layer of rhenium that provides structural support, plus an inner layer of iridium that acts as a barrier to oxidation of the rhenium. In the improved material system, the layer of iridium is thin and is coated with a thermal fatigue-resistant refractory oxide (specifically, hafnium oxide) that serves partly as a thermal barrier to decrease the temperature and thus the rate of oxidation of the rhenium. The oxide layer also acts as a barrier against the transport of oxidizing species to the surface of the iridium. Tests in which various oxygen/hydrogen mixtures were burned in iridium/rhenium combustion chambers lined with hafnium oxide showed that the operational lifetimes of combustion chambers of the improved material system are an order of magnitude greater than those of the baseline combustion chambers.

  20. Atomically Precise Metal Nanoclusters for Catalytic Application

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Rongchao [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-11-18

    The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily high selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au25(SR)18, Au28(SR)20, Au38(SR)24, Au99(SR)42, Au144(SR)60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our

  1. Toward an Understanding of Catalysis by Supported Metal Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    D. W. Goodman; J. Wang; B. K. Min; E. Ozensoy; F. Yang

    2002-01-01

    OAK (B204) The goal of this program is an atomic-level understanding of catalysis by supported metal nanoclusters, especially the surface intermediates in selective oxidation by noble metal nanocatalysts.

  2. Metal oxide-coating PMMA or Talc as a new IR blocker inhibits IR-induced decrease of collagens in human dermal fibroblasts.

    Science.gov (United States)

    Nam, J-J; Lee, K-E; Kim, Y J

    2015-08-01

    The purpose of this study was whether P/M or T/M inhibits IR-induced decrease of collagens in human dermal fibroblasts, using P/M or T/M blocked near-IR (NIR) transmittance significantly in spectrophotometer measurement. As metal oxides are effective inorganic molecules for intercepting IR radiation, we have developed metal oxide-coating PMMA (P/M) or Talc (T/M) as a new IR blocker. Inhibitory effect of the new IR blocker on collagen degradation was measured by gene and protein expressions of procollagens and MMPs, respectively, in IR-irradiated Hs68 cell line. Using P/M or T/M inhibited IR-induced increases of MMP-1, MMP-3 and MMP-9, and IR-induced decreases of type 1 and 4 procollagen in a dose-dependent manner in dermal fibroblasts. In addition, using both P/M and T/M blocked the increase of cell media temperature induced by IR lamp. The results suggest that P/M or T/M can inhibit decrease of collagens by blocking IR-induced heat transmission in human dermal fibroblasts. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  3. Synthesis and oxidation of CpIrIII compounds: functionalization of a Cp methyl group.

    Science.gov (United States)

    Park-Gehrke, Lisa S; Freudenthal, John; Kaminsky, Werner; Dipasquale, Antonio G; Mayer, James M

    2009-03-21

    [CpIrCl(2)](2) () and new CpIr(III)(L-L)X complexes (L-L = N-O or C-N chelating ligands; X = Cl, I, Me) have been prepared and their reactivity with two-electron chemical oxidants explored. Reaction of with PhI(OAc)(2) in wet solvents yields a new chloro-bridged dimer in which each of the Cp ligands has been singly acetoxylated to form [Cp(OAc)Ir(III)Cl(2)](2) () (Cp(OAc) = eta(5)-C(5)Me(4)CH(2)OAc). Complex and related carboxy- and alkoxy-functionalized Cp(OR) complexes can also be prepared from plus (PhIO)(n) and ROH. [Cp(OAc)Ir(III)Cl(2)](2) () and the methoxy analogue [Cp(OMe)Ir(III)Cl(2)](2) () have been structurally characterized. Treatment of [CpIrCl(2)](2) () with 2-phenylpyridine yields CpIr(III)(ppy)Cl () (ppy = cyclometallated 2-phenylpyridyl) which is readily converted to its iodide and methyl analogues CpIr(III)(ppy)I and CpIr(III)(ppy)Me (). CpIr(III) complexes were also prepared with N-O chelating ligands derived from anthranilic acid (2-aminobenzoic acid) and alpha-aminoisobutyric acid (H(2)NCMe(2)COOH), ligands chosen to be relatively oxidation resistant. These complexes and were reacted with potential two-electron oxidants including PhI(OAc)(2), hexachlorocyclohexadienone (C(6)Cl(6)O), N-fluoro-2,4,6-trimethylpyridinium (Me(3)pyF(+)), [Me(3)O]BF(4) and MeOTf (OTf = triflate, CF(3)SO(3)). Iridium(V) complexes were not observed or implicated in these reactions, despite the similarity of the potential products to known CpIr(V) species. The carbon electrophiles [Me(3)O]BF(4) and MeOTf appear to react preferentially at the N-O ligands, to give methyl esters in some cases. Overall, the results indicate that Cp is not inert under oxidizing conditions and is therefore not a good supporting ligand for oxidizing organometallic complexes.

  4. The Effect of PtRuIr Nanoparticle Crystallinity in Electrocatalytic Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Vladimir Linkov

    2013-04-01

    Full Text Available Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate.

  5. The Effect of PtRuIr Nanoparticle Crystallinity in Electrocatalytic Methanol Oxidation

    Science.gov (United States)

    Ma, Yanjiao; Wang, Rongfang; Wang, Hui; Liao, Shijun; Key, Julian; Linkov, Vladimir; Ji, Shan

    2013-01-01

    Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate. PMID:28809233

  6. Biocompatibility of Ir/Ti-oxide coatings: Interaction with platelets, endothelial and smooth muscle cells

    Science.gov (United States)

    Habibzadeh, Sajjad; Li, Ling; Omanovic, Sasha; Shum-Tim, Dominique; Davis, Elaine C.

    2014-05-01

    Applying surface coatings on a biomedical implant is a promising modification technique which can enhance the implant's biocompatibility via controlling blood constituents- or/and cell-surface interaction. In this study, the influence of composition of IrxTi1-x-oxide coatings (x = 0, 0.2, 0.4, 0.6, 0.8, 1) formed on a titanium (Ti) substrate on the responses of platelets, endothelial cells (ECs) and smooth muscle cells (SMCs) was investigated. The results showed that a significant decrease in platelet adhesion and activation was obtained on Ir0.2Ti0.8-oxide and Ir0.4Ti0.6-oxide coatings, rendering the surfaces more blood compatible, in comparison to the control (316L stainless steel, 316L-SS) and other coating compositions. Further, a substantial increase in the EC/SMC surface count ratio after 4 h of cell attachment to the Ir0.2Ti0.8-oxide and Ir0.4Ti0.6-oxide coatings, relative to the 316L-SS control and the other coating compositions, indicated high potential of these coatings for the enhancement of surface endothelialization. This indicates the capability of the corresponding coating compositions to promote EC proliferation on the surface, while inhibiting that of SMCs, which is important in cardiovascular stents applications.

  7. Catalytic hydrolysis of ammonia borane for hydrogen generation using cobalt nanocluster catalyst supported on polydopamine functionalized multiwalled carbon nanotube

    International Nuclear Information System (INIS)

    Arthur, Ernest Evans; Li, Fang; Momade, Francis W.Y.; Kim, Hern

    2014-01-01

    Hydrogen was generated from ammonia borane complex by hydrolysis using cobalt nanocluster catalyst supported on polydopamine functionalized MWCNTs (multi-walled carbon nanotubes). The impregnation-chemical reduction method was used for the preparation of the supported catalyst. The nanocluster catalyst support was formed by in-situ oxidative polymerization of dopamine on the MWCNTs in alkaline solution at room temperature. The structural and physical–chemical properties of the nanocluster catalyst were characterized by FT-IR (Fourier transform infrared spectroscopy), EDX (energy-dispersive X-ray spectroscopy), SEM (scanning electron microscope), XRD (X-ray diffraction) and TEM (transmission electron microscopy). The nanocluster catalyst showed good catalytic activity for the hydrogen generation from aqueous ammonia borane complex. A reusability test to determine the practical usage of the catalyst was also investigated. The result revealed that the catalyst maintained an appreciable catalytic performance and stability in terms of its reusability after three cycle of reuse for the hydrolysis reaction. Also, the activation energy for the hydrolysis of ammonia borane complex was estimated to be 50.41 kJmol −1 , which is lower than the values of some of the reported catalyst. The catalyst can be considered as a promising candidate in developing highly efficient portable hydrogen generation systems such as PEMFC (proton exchange membrane fuel cells). - Highlights: • Co/Pdop-o-MWCNT (Pdop functionalized MWCNT supported cobalt nanocluster) catalyst was synthesized for hydrogen generation. • It is an active catalyst for hydrogen generation via hydrolysis of ammonia borane. • It showed good stability in terms of reusability for the hydrogen generation

  8. Vitamin C affects the antioxidative/oxidative status in rats irradiated with ultraviolet (UV) and infrared (IR) light

    DEFF Research Database (Denmark)

    Niemiec, T.; Sawosz, E.; Chwalibog, André

    2006-01-01

    Four grups of twenty growing Wistar rats were irradiated with either UV, IR, UV+IR light or were not irradiated (control). Ten rats from each group received a diet supplemented with 0.6% of L-ascorbic acid. The effects of the mega-dose of vitamin C were evaluated by changes in the antioxidative....../oxidative status. UV and IR radiation promoted oxidative DNA degradation in rat livers and supplementation with ascorbic acid strengthened the prooxidative effects on DNA oxidation in rats irradiated with UV or IR light. Vitamin C also increased the tiobarbituric acid reactive substances (TBARS) concentration...

  9. Fingerprinting DNA oxidation processes: IR characterization of the 5-methyl-2'-deoxycytidine radical cation.

    Science.gov (United States)

    Bucher, Dominik B; Pilles, Bert M; Pfaffeneder, Toni; Carell, Thomas; Zinth, Wolfgang

    2014-02-24

    Methylated cytidine plays an important role as an epigenetic signal in gene regulation. Its oxidation products are assumed to be involved in active demethylation processes but also in damaging DNA. Here, we report the photochemical production of the 5-methyl-2'-deoxycytidine radical cation via a two-photon ionization process. The radical cation is detected by time-resolved IR spectroscopy and identified by band assignment using density functional theory calculations. Two final oxidation products are characterized with liquid chromatography coupled to mass spectrometry. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Fundamental Study of Facile and Stable Hydrogen Evolution Reaction at Electrospun Ir and Ru Mixed Oxide Nanofibers.

    Science.gov (United States)

    Cho, Yun-Bin; Yu, Areum; Lee, Chongmok; Kim, Myung Hwa; Lee, Youngmi

    2018-01-10

    Electrochemical hydrogen evolution reaction (HER) has been an interesting research topic in terms of the increasing need of renewable and alternative energy conversion devices. In this article, Ir x Ru 1-x O y (y = 0 or 2) nanofibers with diverse compositions of Ir/IrO 2 and RuO 2 are synthesized by electrospinning and calcination procedures. Their HER activities are measured in 1.0 M NaOH. Interestingly, the HER activities of Ir x Ru 1-x O y nanofibers improve gradually during repetitive cathodic potential scans for HER, and then eventually reach the steady-state consistencies. This cathodic activation is attributed to the transformation of the nanofiber surface oxides to the metallic alloy. Among a series of Ir x Ru 1-x O y nanofibers, the cathodically activated Ir 0.80 Ru 0.20 O y shows the best HER activity and stability even compared with IrO y and RuO y , commercial Pt and commercial Ir (20 wt % each metal loading on Vulcan carbon), where a superior stability is possibly ascribed to the instant generation of active Ir and Ru metals on the catalyst surface upon HER. Density functional theory calculation results for hydrogen adsorption show that the energy and adsorbate-catalyst distance at metallic Ir 0.80 Ru 0.20 are close to those at Pt. This suggests that mixed metallic Ir and Ru are significant contributors to the improved HER activity of Ir 0.80 Ru 0.20 O y after the cathodic activation. The present findings clearly demonstrate that the mixed oxide of Ir and Ru is a very effective electrocatalytic system for HER.

  11. Substoichiometric cobalt oxide monolayer on Ir(100)-(1 x 1)

    International Nuclear Information System (INIS)

    Gubo, M; Ebensperger, C; Meyer, W; Hammer, L; Heinz, K

    2009-01-01

    A substoichiometric monolayer of cobalt oxide has been prepared by deposition and oxidation of slightly less than one monolayer of cobalt on the unreconstructed surface of Ir(100). The ultrathin film was investigated by scanning tunnelling microscopy (STM) and quantitative low-energy electron diffraction (LEED). The cobalt species of the film reside in or near hollow positions of the substrate with, however, unoccupied sites (vacancies) in a 3 x 3 arrangement. In the so-formed 3 x 3 supercell the oxide's oxygen species are both threefold and fourfold coordinated to cobalt, forming pyramids with a triangular and square cobalt basis, respectively. These pyramids are the building blocks of the oxide. Due to the reduced coordination as compared to the sixfold one in the bulk of rock-salt-type CoO, the Co-O bond lengths are smaller than in the latter. For the threefold coordination they compare very well with the bond length in oxygen terminated CoO(111) films investigated recently. The substoichiometric 3 x 3 oxide monolayer phase transforms to a stoichiometric c(10 x 2)-periodic oxide monolayer under oxygen exposure, in which, however, cobalt and oxygen species are in (111) orientation and so form a CoO(111) layer.

  12. Silver sub-nanoclusters electrocatalyze ethanol oxidation and provide protection against ethanol toxicity in cultured mammalian cells.

    Science.gov (United States)

    Selva, Javier; Martínez, Susana E; Buceta, David; Rodríguez-Vázquez, María J; Blanco, M Carmen; López-Quintela, M Arturo; Egea, Gustavo

    2010-05-26

    Silver atomic quantum clusters (AgAQCs), with two or three silver atoms, show electrocatalytic activities that are not found in nanoparticles or in bulk silver. AgAQCs supported on glassy carbon electrodes oxidize ethanol and other alcohols in macroscopic electrochemical cells in acidic and basic media. This electrocatalysis occurs at very low potentials (from approximately +200 mV vs RHE), at physiological pH, and at ethanol concentrations that are found in alcoholic patients. When mammalian cells are co-exposed to ethanol and AgAQCs, alcohol-induced alterations such as rounded cell morphology, disorganization of the actin cytoskeleton, and activation of caspase-3 are all prevented. This cytoprotective effect of AgAQCs is also observed in primary cultures of newborn rat astrocytes exposed to ethanol, which is a cellular model of fetal alcohol syndrome. AgAQCs oxidize ethanol from the culture medium only when ethanol and AgAQCs are added to cells simultaneously, which suggests that cytoprotection by AgAQCs is provided by the ethanol electro-oxidation mediated by the combined action of AgAQCs and cells. Overall, these findings not only show that AgAQCs are efficient electrocatalysts at physiological pH and prevent ethanol toxicity in cultured mammalian cells, but also suggest that AgAQCs could be used to modify redox reactions and in this way promote or inhibit biological reactions.

  13. Optical properties of reduced graphene oxide and CuFe2O4 composites in the IR region

    Science.gov (United States)

    Ma, De-yue; Li, Xiao-xia; Guo, Yu-xiang; Zeng, Yu-run

    2018-01-01

    The complex refractive index of reduced graphene oxide and CuFe2O4 composites prepared by hydrothermal method was calculated using infrared Micro-reflective spectra and K-K relation, and the calculation errors were analyzed according to its IR transmission and spectral reflectivity calculated by Fresnel formula. And then normal emissivity of the composite in IR atmospheric window was calculated by means of Fresnel formula and modified refraction angle formula. The calculation accuracy was verified by comparing measured normal total emissivity with the calculated one. The results show that complex refractive index and normal emissivity calculated by the formulas have a high accuracy. It has been found that the composite has a good absorption and radiation characteristics in IR atmospheric window and a strong scattering ability in middle IR region by analyzing its extinction, absorption and radiation properties in IR region. Therefore, it may be used as IR absorption, extinction and radiation materials in some special fields.

  14. IL-23 Promotes Myocardial I/R Injury by Increasing the Inflammatory Responses and Oxidative Stress Reactions

    Directory of Open Access Journals (Sweden)

    Xiaorong Hu

    2016-05-01

    Full Text Available Background/Aims: Inflammation and oxidative stress play an important role in myocardial ischemia and reperfusion (I/R injury. We hypothesized that IL-23, a pro-inflammatory cytokine, could promote myocardial I/R injury by increasing the inflammatory response and oxidative stress. Methods: Male Sprague-Dawley rats were randomly assigned into sham operated control (SO group, ischemia and reperfusion (I/R group, (IL-23 + I/R group and (anti-IL-23 + I/R group. At 4 h after reperfusion, the serum concentration of lactate dehydrogenase (LDH, creatine kinase (CK and the tissue MDA concentration and SOD activity were measured. The infarcte size was measured by TTC staining. Apoptosis in heart sections were measured by TUNEL staining. The expression of HMGB1 and IL-17A were detected by Western Blotting and the expression of TNF-α and IL-6 were detected by Elisa. Results: After 4 h reperfusion, compared with the I/R group, IL-23 significantly increased the infarct size, the apoptosis of cardiomyocytes and the levels of LDH and CK (all P 0.05. All these effects were abolished by anti-IL-23 administration. Conclusion: The present study suggested that IL-23 may promote myocardial I/R injury by increasing the inflammatory responses and oxidative stress reaction.

  15. IrO2-SiO2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

    International Nuclear Information System (INIS)

    Wang Xiaomei; Hu Jiming; Zhang Jianqing

    2010-01-01

    Mixed IrO 2 -SiO 2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H 2 IrCl 6 ) and tetraethoxysilane (TEOS) mixed precursors in organic solvents. The solution chemistry and thermal decomposition kinetics of the mixed precursors were investigated by ultra violet/visible (UV/vis) spectroscopy and thermogravimetry (TGA) and differential thermal analysis (DTA), respectively. The physiochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is shown from the UV/vis spectra that the electronic absorption intensity of IrCl 6 2- complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H 2 IrCl 6 is inhibited by TEOS in the low temperature range, but the further oxidation reaction at high temperatures of formed intermediates is independent of the presence of silane component. Physical measurements show a restriction effect of silica on the crystallization and crystal growth processes of IrO 2 , leading to the formation of finer oxide particles and the porous morphology of the binary oxide films. The porous composite films exhibit high apparent electrocatalytic activity toward the oxygen evolution reaction. In addition, the long-term stability of Ti-supported IrO 2 electrodes is found to apparently improve with appropriate amount of SiO 2 incorporation, as tested under galvanostatic electrolysis.

  16. The formation of Cr2O3 nanoclusters over graphene sheet and carbon nanotubes

    Science.gov (United States)

    Dabaghmanesh, Samira; Neek-Amal, Mehdi; Partoens, Bart; Neyts, Erik C.

    2017-11-01

    Carbon supported metal oxide nanoparticles hold promise for various future applications in diverse areas including spintronics, catalysis and biomedicine. These applications, however, typically depend on the structure and morphology of the nanoparticles. In this contribution, we employ classical molecular dynamic simulations based on a recently developed force field to study the structural properties of Cr2O3 nanoclusters over graphene and carbon nanotubes. We observe that Cr2O3 nanoclusters tend to aggregate over both freestanding graphene and carbon nanotubes and form larger nanoclusters. These large nanoclusters are characterized by their worm-like shape with a lattice constant similar to that of bulk Cr2O3. We also investigate the structural deformation induced in graphene due to the presence of Cr2O3 nanoclusters.

  17. Graphene oxide/carbon nanoparticle thin film based IR detector: Surface properties and device characterization

    Directory of Open Access Journals (Sweden)

    Farzana Aktar Chowdhury

    2015-10-01

    Full Text Available This work deals with the synthesis, characterization, and application of carbon nanoparticles (CNP adorned graphene oxide (GO nanocomposite materials. Here we mainly focus on an emerging topic in modern research field presenting GO-CNP nanocomposite as a infrared (IR radiation detector device. GO-CNP thin film devices were fabricated from liquid phase at ambient condition where no modifying treatments were necessary. It works with no cooling treatment and also for stationary objects. A sharp response of human body IR radiation was detected with time constants of 3 and 36 sec and radiation responsivity was 3 mAW−1. The current also rises for quite a long time before saturation. This work discusses state-of-the-art material developing technique based on near-infrared photon absorption and their use in field deployable instrument for real-world applications. GO-CNP-based thin solid composite films also offer its potentiality to be utilized as p-type absorber material in thin film solar cell, as well.

  18. Graphene oxide/carbon nanoparticle thin film based IR detector: Surface properties and device characterization

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Farzana Aktar [Experimental Physics Division, Atomic Energy Centre, 4, Kazi Nazrul Islam Avenue, Dhaka-1000 (Bangladesh); Hossain, Mohammad Abul [Department of Chemistry, Faculty of Science, University of Dhaka, Dhaka-1000 (Bangladesh); Uchida, Koji; Tamura, Takahiro; Sugawa, Kosuke; Mochida, Tomoaki; Otsuki, Joe [College of Science and Technology, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Mohiuddin, Tariq [Department of Physics, College of Science, Sultan Qaboos University, Muscat (Oman); Boby, Monny Akter [Department of Physics, Faculty of Science, University of Dhaka, Dhaka-1000 (Bangladesh); Alam, Mohammad Sahabul, E-mail: msalam@ksu.edu.sa [Department of Physics, Faculty of Science, University of Dhaka, Dhaka-1000 (Bangladesh); Department of Chemical Engineering, College of Engineering & King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2015-10-15

    This work deals with the synthesis, characterization, and application of carbon nanoparticles (CNP) adorned graphene oxide (GO) nanocomposite materials. Here we mainly focus on an emerging topic in modern research field presenting GO-CNP nanocomposite as a infrared (IR) radiation detector device. GO-CNP thin film devices were fabricated from liquid phase at ambient condition where no modifying treatments were necessary. It works with no cooling treatment and also for stationary objects. A sharp response of human body IR radiation was detected with time constants of 3 and 36 sec and radiation responsivity was 3 mAW{sup −1}. The current also rises for quite a long time before saturation. This work discusses state-of-the-art material developing technique based on near-infrared photon absorption and their use in field deployable instrument for real-world applications. GO-CNP-based thin solid composite films also offer its potentiality to be utilized as p-type absorber material in thin film solar cell, as well.

  19. Supported Pd nanoclusters with enhanced hydrogen spillover for NOxremoval via H2-SCR: the elimination of "volcano-type" behaviour.

    Science.gov (United States)

    Peng, Zhezhe; Li, Zongyuan; Liu, Yun-Quan; Yan, Shuai; Tong, Jianing; Wang, Duo; Ye, Yueyuan; Li, Shuirong

    2017-05-30

    A rational design of a Pd catalyst with highly dispersed Pd nanoclusters on an Al doped ceria-based oxide for low temperature selective catalytic reduction of NO x by hydrogen with excess O 2 was achieved. The supported Pd nanocluster shows a high hydrogen spillover ability and a NO x conversion of >84% within 100-300 °C.

  20. Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

    Directory of Open Access Journals (Sweden)

    Jiji Antony

    2006-01-01

    Full Text Available Nanoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7∘C. Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM. The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET process are size-dependent and compared with the calculated data.

  1. Pressurized polyol synthesis of Al-doped ZnO nanoclusters with high electrical conductivity and low near-infrared transmittance

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho-Nyun; Shin, Chi-Ho [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of); Hwang, Duck Kun [Department of Corporate Diagnosis, Small and Medium Business Corporation, Seoul 150-718 (Korea, Republic of); Kim, Haekyoung [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Oh, Kyeongseok [Department of Chemical and Environmental Technology, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Hyun-Jong, E-mail: hjkim23@kitech.re.kr [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of)

    2015-09-25

    Highlights: • Low-temperature pressurized polyol method synthesized Al-doped ZnO nanoclusters. • Reaction time affected the doping efficiency, resistivity, and NIR transmittance. • The near-IR blocking efficiency of Al-doped ZnO (AZO) nanoclusters reached 85%. • AZO nanocluster coatings could be used for heat reflectors or artificial glasses. - Abstract: In this study, a novel pressurized polyol method is proposed to synthesize aluminum-doped ZnO (AZO) nanoclusters without utilizing additional thermal treatment to avoid the merging of nanoclusters. The size of the AZO nanoclusters range from 100 to 150 nm with a resistivity of 204 Ω cm. The AZO nanoclusters primarily consist of approximately 10-nm nanocrystals that form a spherically clustered morphology. A two-stage growth model has been proposed based on the results of scanning electron microscopy and transmission electron microscopy images, nanocluster sizes, and X-ray diffraction patterns. The primary AZO nanocrystals first nucleate under pressurized conditions and then spontaneously aggregate into larger nanoclusters. Optically, the AZO nanoclusters exhibit a significant decrease in the near-infrared (NIR) transmittance compared to pure ZnO nanoparticles. The NIR blocking efficiency of AZO nanoclusters reached 85%. Moreover, the doping efficiency, resistivity, and NIR transmittance of AZO nanoclusters are influenced by the reaction time in the pressurized polyol solution. On the other hand, the reaction time has no effect on the particle size and crystallinity. An optically transparent coating for the AZO nanoclusters, which consisted of iso-propanol solvent and ultraviolet-curable acrylic binder, was also demonstrated.

  2. Enhanced pulsed magneto-motive ultrasound imaging using superparamagnetic nanoclusters

    International Nuclear Information System (INIS)

    Mehrmohammadi, M; Qu, M; Emelianov, S Y; Yoon, K Y; Johnston, K P

    2011-01-01

    Recently, pulsed magneto-motive ultrasound (pMMUS) imaging augmented with ultra-small magnetic nanoparticles has been introduced as a tool capable of imaging events at molecular and cellular levels. The sensitivity of a pMMUS system depends on several parameters, including the size, geometry and magnetic properties of the nanoparticles. Under the same magnetic field, larger magnetic nanostructures experience a stronger magnetic force and produce larger displacement, thus improving the sensitivity and signal-to-noise ratio (SNR) of pMMUS imaging. Unfortunately, large magnetic iron-oxide nanoparticles are typically ferromagnetic and thus are very difficult to stabilize against colloidal aggregation. In the current study we demonstrate improvement of pMMUS image quality by using large size superparamagnetic nanoclusters characterized by strong magnetization per particle. Water-soluble magnetic nanoclusters of two sizes (15 and 55 nm average size) were synthesized from 3 nm iron precursors in the presence of citrate capping ligand. The size distribution of synthesized nanoclusters and individual nanoparticles was characterized using dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM). Tissue mimicking phantoms containing single nanoparticles and two sizes of nanoclusters were imaged using a custom-built pMMUS imaging system. While the magnetic properties of citrate-coated nanoclusters are identical to those of superparamagnetic nanoparticles, the magneto-motive signal detected from nanoclusters is larger, i.e. the same magnetic field produced larger magnetically induced displacement. Therefore, our study demonstrates that clusters of superparamagnetic nanoparticles result in pMMUS images with higher contrast and SNR.

  3. Oxide-supported IrNiO(x) core-shell particles as efficient, cost-effective, and stable catalysts for electrochemical water splitting.

    Science.gov (United States)

    Nong, Hong Nhan; Oh, Hyung-Suk; Reier, Tobias; Willinger, Elena; Willinger, Marc-Georg; Petkov, Valeri; Teschner, Detre; Strasser, Peter

    2015-03-02

    Active and highly stable oxide-supported IrNiO(x) core-shell catalysts for electrochemical water splitting are presented. IrNi(x)@IrO(x) nanoparticles supported on high-surface-area mesoporous antimony-doped tin oxide (IrNiO(x)/Meso-ATO) were synthesized from bimetallic IrNi(x) precursor alloys (PA-IrNi(x) /Meso-ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNi(x)/Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core-shell particles. The core-shell IrNiO(x)/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl 2 O 4 spinel in oxidizing atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weizhen; Nie, Lei; Chen, Ying; Kovarik, Libor; Liu, Jun; Wang, Yong

    2017-04-01

    With the capability of MgAl2O4 spinel {111} nano-facets in stabilizing small Rh, Ir and Pt particles, bimetallic Ir-Pt catalysts on the same support were investigated, aiming at further lowering the catalyst cost by substituting expensive Pt with cheaper Ir in the bulk. Small Pt-Ir nano-alloy particles (< 2nm) were successfully stabilized on the spinel {111} nano-facets as expected. Interestingly, methanol oxidative dehydrogenation (ODH) rate on the surface Pt atoms increases with oxidizing aging but decreases upon reducing treatment, where Ir is almost inactive under the same reaction conditions. Up to three times enhancement in Pt exposure was achieved when the sample was oxidized at 800 °C in air for 1 week and subsequently reduced by H2 for 2 h, demonstrating successful surface enrichment of Pt on Pt-Ir nano-alloy particles. A dynamic stabilization mechanism involving wetting\

  5. Nanocrystals and Nanoclusters as Cocatalysts for Photocatalytic Water Splitting

    KAUST Repository

    Sinatra, Lutfan

    2016-12-04

    studied for the photocatalytic H2 production in order to explore the synergistic effect of the plasmonic resonance from the Au nanoparticles and pn-junction between Cu2O and TiO2. Additionally, the plasmonic effect of the Au films was also studied and utilized in order to improve the PWS. Secondly, the nanoscaling of cocatalysts was studied in order to improve the efficiency thereof and to reduce the cost of the cocatalyst materials. Moreover, it is sought to explore the quantum size effect on the properties of the cocatalyst and their effect on the photocatalytic reaction. Atomically precise Au and Ni nanoclusters were employed in these studies. Au nanoclusters were studied in relation to the cocatalysts in the photocatalytic water splitting, and Ni nanoclusters were studied in relation to the cocatalysts in the electrocatalytic water oxidation. The results of these studies will provide new insights in relation to the strategy used in order to develop efficient cocatalysts for the purpose of photocatalytic water splitting.

  6. Formation and vibrational structure of Si nano-clusters in ZnO matrix

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Serrano, J. [Universidad Autonoma del Estado de Hidalgo, Hidalgo (Mexico); Pal, U. [Universidad Autonoma de Puebla, Puebla (Mexico); Koshizaki, N.; Sasaki, T. [National Institute of Materials and Chemical Research, Ibaraki (Japan)

    2001-02-01

    We have studied the formation and vibrational structure of Si nano-clusters in ZnO matrix prepared by radio-frequency (r.f.) co-sputtering, and characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) spectroscopy techniques. The composite films of Si/ZnO were grown o quartz substrates by co-sputtering of Si and ZnO targets. TEM images show a homogeneous distribution of clusters in the matrix with average size varied from 3.7 nm to 34 nm depending on the temperature of annealing. IR absorption measurements revealed the bands correspond to the modes of vibrations of Si{sub 3} in its triangular geometrical structure. By analysing the IR absorption and XPS spectra we found that the nano-clusters consist of a Si{sub 3} core and a SiO{sub x} cap layer. With the increase of annealing temperature, the vibrational states of Si changed from the triplet {sup 3}B1(C2{sub v}) and {sup 3}A'{sub 2}(D{sub 3h}) states to its singlet ground state {sup 1}A{sub 1}(C2{sub v}) and the oxidation state of Si in SiO{sub x} increased. The evolution of the local atomic structure of the Si nano-clusters with the variation of Si content in the film and with the variation of the temperature of annealing are discussed. [Spanish] Se estudia la formacion y estructura vibracional de nano-cumulos de Si en matriz de ZnO preparados por la tecnica de radio-frecuencia (r.f.) co-sputtering, y caracterizados por Microscopia Electronica de Transmision (TEM), Espectroscopia Fotoelectronica de rayos X (XPS) y Espectroscopia de Infrarrojo (IR). Las peliculas compositas de Si/ZnO fueron crecidas sobre sustratos de cuarzo mediante el co-sputtering de blancos de Si y ZnO. Las imagenes de TEM mostraron una distribucion homogenea de cumulos en la matriz con un tamano promedio de 3.7 nm a 34 nm dependiendo de la temperatura de tratamiento. Las mediciones de IR relevaron las bandas correspondientes a los modos de vibracion de Si{sub 3} en su estructura

  7. Tunable antenna-coupled metal-oxide-metal (MOM) uncooled IR detector (Invited Paper)

    Science.gov (United States)

    Esfandiari, Pashang; Bernstein, G.; Fay, P.; Porod, W.; Rakos, B.; Zarandy, A.; Berland, B.; Boloni, L.; Boreman, G.; Lail, B.; Monacelli, B.; Weeks, A.

    2005-05-01

    Missile Defense Agency/Advanced Systems, in partnership with both EUTECUS/University of Notre Dame (UND) and ITN Energy Systems/University of Central Florida (UCF) has embarked on developing a multispectral imaging IR sensor. This technology, when matured, could revolutionize IR sensor technology by reducing the need for cooling, eliminating lattice matching and avoiding epitaxial fabrication processes. This paper describes the approaches employed by both EUTECUS/UND and ITN/UCF teams to integrate nano-antenna technology with the existing cellular neural network (CNN) processor to produce multispectral IR sensors. This effort is a leap into the performance realm where biological systems operate.

  8. Sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer platform using the BSA-stabilized Au nanoclusters/amino-functionalized graphene oxide hybrids.

    Science.gov (United States)

    Lan, Jing; Zou, Hong Yan; Wang, Qiang; Zeng, Ping; Li, Yuan Fang; Huang, Cheng Zhi

    2016-12-01

    An ultra-sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer in the BSA-stabilized gold nanoclusters/amino-functionalized graphene oxide (BSA-AuNCs/NH 2 -GO) hybrids was successfully realized. The BSA-AuNCs containing amounts of carboxyl groups could be absorbed on the surface of NH 2 -GO through the electrostatic interaction, which resulted in the fluorescence quenching of BSA-AuNCs with high efficiency. However, heparin, possessing high density of negative charge, could compete with BSA-AuNCs to bind NH 2 -GO and block the energy transfer from BSA-AuNCs to NH 2 -GO. The fluorescence recovery of BSA-AuNCs was closely related to the amount of heparin and there was a good linear relationship between fluorescence recovery of BSA-AuNCs and heparin over the range of 100ng/mL to 30μg/mL with a detection limit of 40ng/mL. What's more, the fluorescence assay was successfully applied for heparin sensing in human serums and intracellular imaging. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Possibility of superradiance by magnetic nanoclusters

    International Nuclear Information System (INIS)

    Yukalov, V I; Yukalova, E P

    2011-01-01

    The possibility of realizing spin superradiance by an assembly of magnetic nanoclusters is analyzed. The known obstacles for realizing such a coherent radiation by magnetic nanoclusters are their large magnetic anisotropy, strong dephasing dipole interactions, and an essential nonuniformity of their sizes. In order to give a persuasive conclusion, a microscopic theory is developed, providing an accurate description of nanocluster spin dynamics. It is shown that, despite the obstacles, it is feasible to organize such a setup that magnetic nanoclusters would produce strong superradiant emission

  10. DqsIR quorum sensing-mediated gene regulation of the extremophilic bacterium Deinococcus radiodurans in response to oxidative stress.

    Science.gov (United States)

    Lin, Lin; Dai, Shang; Tian, Bing; Li, Tao; Yu, Jiangliu; Liu, Chengzhi; Wang, Liangyan; Xu, Hong; Zhao, Ye; Hua, Yuejin

    2016-05-01

    Here, we show that AHLs can be employed by Deinococcus radiodurans, which belongs to the unique phylum Deinococcus-Thermus and is known for its cellular resistance to environmental stresses. An AHL-mediated quorum-sensing system (DqsI/DqsR) was identified in D. radiodurans. We found that under non-stress conditions, the AHL level was "shielded" by quorum quenching enzymes, whereas AHLs accumulated when D. radiodurans was exposed to oxidative stress. Upon exposure to H2 O2 , AHL synthetic enzymes (DqsI) were immediately induced, while the expression of quorum-quenching enzymes began to increase approximately 30 min after exposure to H2 O2 , as shown by time-course analyses of gene expression. Both dqsI mutant (DMDqsI) and dqsR mutant (MDqsR) were more sensitive to oxidative stress compared with the wild-type strain. Exogenous AHLs (5 μM) could completely restore the survival fraction of DMDqsI under oxidative stress. RNA-seq analysis showed that a number of genes involved in stress-response, cellular cleansing, and DNA repair had altered transcriptional levels in MDqsR. The DqsR, acting as a regulator of quorum sensing, controls gene expression along with AHLs. Hence, the DqsIR-mediated quorum sensing that mediates gene regulation is an adaptive strategy for D. radiodurans in response to oxidative stresses and is conserved in the extremophilic Deinococcus bacteria. © 2016 John Wiley & Sons Ltd.

  11. Catalytic photooxidation of pentachlorophenol using semiconductor nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    WILCOXON,JESS P.

    2000-04-17

    Pentachlorophenol (PCP) is a toxic chlorinated aromatic molecule widely used as fungicide, a bactericide and a wood preservation, and thus ubiquitous in the environment. The authors report photo-oxidation of PCP using a variety of nanosize semiconductor metal oxides and sulfides in both aqueous and polar organic solvents and compare the photo-oxidation kinetics of these nanoclusters to widely studied bulk powders like Degussa P-25 TiO{sub 2} and CdS. They study both the light intensity dependence of PCP photooxidation for nanosize SnO{sub 2} and the size dependence of PCP photooxidation for both nanosize SnO{sub 2} and MoS{sub 2}. They find an extremely strong size dependence for the latter which they attribute to its size-dependent band gap and the associated change in redox potentials due to quantum confinement of the hole-electron pair. The authors show that nanosize MoS{sub 2} with a diameter of d=3.0 nm and an absorbance edge of {approximately}450 nm is a very effective photooxidation catalyst for complete PCP mineralization, even when using only visible light irradiation.

  12. Interaction of nitrogen oxides with sublimed layers of (meso-tetraphenylporphyrinato)cobalt(II); IR evidence of oxo-transfer from (nitro)porphyrinatocobalt(III) to free nitric oxide.

    Science.gov (United States)

    Kurtikyan, Tigran S; Mardyukov, Arthur N; Goodwin, John A

    2003-12-15

    Interaction of a low-pressure NO2 with sublimed layers of (meso-tetraphenylporphyrinato)cobalt(II) (Co(TPP)) leads to formation of 5-coordinate nitro complex Co(III)(TPP)(NO2). Upon exposure of these layers to pyridine vapors, the fast reaction with formation of 6-coordinate nitro-pyridine porphyrins (Py)Co(III)(TPP)(NO2) occurs. By means of IR spectroscopy and use of nitrogen oxide isotopomers, it is shown that an oxo-transfer reaction occurs from 5-coordinate species to free nitric oxide (NO) while the 6-coordinate complex is rather inert. It is also demonstrated that the stepwise addition of low-pressure NO2 to nitrosyl complex Co(TPP)(NO) leads to formation of the nitro complex most likely by an exchange reaction.

  13. Solution Structures of Highly Active Molecular Ir Water-Oxidation Catalysts from Density Functional Theory Combined with High-Energy X-ray Scattering and EXAFS Spectroscopy.

    Science.gov (United States)

    Yang, Ke R; Matula, Adam J; Kwon, Gihan; Hong, Jiyun; Sheehan, Stafford W; Thomsen, Julianne M; Brudvig, Gary W; Crabtree, Robert H; Tiede, David M; Chen, Lin X; Batista, Victor S

    2016-05-04

    The solution structures of highly active Ir water-oxidation catalysts are elucidated by combining density functional theory, high-energy X-ray scattering (HEXS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. We find that the catalysts are Ir dimers with mono-μ-O cores and terminal anionic ligands, generated in situ through partial oxidation of a common catalyst precursor. The proposed structures are supported by (1)H and (17)O NMR, EPR, resonance Raman and UV-vis spectra, electrophoresis, etc. Our findings are particularly valuable to understand the mechanism of water oxidation by highly reactive Ir catalysts. Importantly, our DFT-EXAFS-HEXS methodology provides a new in situ technique for characterization of active species in catalytic systems.

  14. Arsenate uptake by Al nanoclusters and other Al-based sorbents during water treatment.

    Science.gov (United States)

    Mertens, Jasmin; Rose, Jérôme; Wehrli, Bernhard; Furrer, Gerhard

    2016-01-01

    In many parts of the world, arsenic from geogenic and anthropogenic sources deteriorates the quality of drinking water resources. Effective methods of arsenic removal include adsorption and coagulation with iron- and aluminum-based materials, of which polyaluminum chloride is widely employed as coagulant in water treatment due to its low cost and high efficiency. We compared the arsenic uptake capacity and the arsenic bonding sites of different Al-based sorbents, including Al nanoclusters, polyaluminum chloride, polyaluminum granulate, and gibbsite. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that As(V) forms bidentate-binuclear complexes in interaction with all Al-based removal agents. The octahedral configuration of nanoclusters and the distribution of sorption sites remain the same in all types of removal agents consisting of nano-scale Al oxyhydroxide particles. The obtained distances for As(V)-O and As(V)-Al agreed with previously published data and were found to be 1.69 ± 0.02 Å and 3.17-3.21 Å, respectively. Our study suggests that As(V) binds to Al nanoclusters as strongly as to Al oxide surfaces. The As sorption capacity of Al nanoclusters was found to be very similar to that of Al clusters in a polyaluminum chloride. The most efficient Al-based sorbents for arsenic removal were Al nanoclusters, followed by polyaluminum granulate. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. {Fe6O2}-Based Assembly of a Tetradecanuclear Iron Nanocluster

    Directory of Open Access Journals (Sweden)

    Svetlana G. Baca

    2011-01-01

    Full Text Available The tetradecanuclear FeIII pivalate nanocluster [Fe14O10(OH4(Piv18], comprising a new type of metal oxide framework, has been solvothermally synthesized from a hexanuclear iron pivalate precursor in dichlormethane/acetonitrile solution. Magnetic measurements indicate the presence of very strong antiferromagnetic interactions in the cluster core.

  16. Propane selective oxidation on alkaline earth exchanged zeolite Y: room temperature in situ IR study

    NARCIS (Netherlands)

    Xu, J.; Mojet, Barbara; van Ommen, J.G.; Lefferts, Leonardus

    2003-01-01

    The effect of zeolite Y ion-exchanged with a series of alkaline-earth cations on selective propane oxidation at room temperature was studied with in situ infrared spectroscopy. Isopropylhydroperoxide was observed as a reaction intermediate and can be decomposed into acetone and water. Contrary to

  17. Dexmedetomidine (DEX) protects against hepatic ischemia/reperfusion (I/R) injury by suppressing inflammation and oxidative stress in NLRC5 deficient mice.

    Science.gov (United States)

    Chen, Zong; Ding, Tao; Ma, Chuan-Gen

    2017-11-18

    Hepatic ischemia/reperfusion (I/R) injury could arise as a complication of liver surgery and transplantation. No specific therapeutic strategies are available to attenuate I/R injury. NOD-, LRR-and CARD-containing 5 (NLRC5), a member of the NOD-like protein family, has been suggested to negatively regulate nuclear factor kappa B (NF-κB) through interacting with IKKα and blocking their phosphorylation. Dexmedetomidine (DEX) has been shown to attenuate liver injury. In the current study, we investigated the pre-treatment of DEX on hepatic I/R injury in wild type (WT) and NLRC5 knockout (NLRC5 -/- ) mice. Our results indicated that NLRC5 -/- showed significantly stronger histologic damage, inflammatory response, oxidative stress and apoptosis after I/R compared to the WT group of mice, indicating the protective role of NLRC5 against liver I/R injury. Importantly, I/R-induced increase of NLRC5 was reduced by DEX pre-treatment. After hepatic I/R injury, WT and NLRC5 -/- mice pre-treated with DEX exhibited attenuated histological disruption, and reduced pro-inflammatory mediators, including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-1β and inducible nitric oxide synthase (iNOS), which was associated with the inactivated NF-κB pathway. Moreover, suppression of oxidative stress and apoptosis was observed in DEX-treated mice with I/R injury, probably through enhancing nuclear factor erythroid 2-related factor 2 (Nrf2), reducing mitogen-activated protein kinases (MAPKs) and Caspase-3/poly (ADP-ribose) polymerase (PARP) pathways. In vitro, the results were further confirmed in WT and NLRC5 -/- hepatocytes pre-treated with or without DEX. Together, the findings illustrated that lack of NLRC5 resulted in severer liver I/R injury, which could be alleviated by DEX pre-treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Catalytic activity of gold nanoclusters supported by cerium oxide: interplay between cluster reactivity, size, and interface charge transfer revealed by DFT calculations

    Science.gov (United States)

    Fabris, Stefano; Farnesi Camellone, Matteo

    2010-03-01

    The parameters controlling the catalytic activity of oxide-supported Au atoms and clusters are studied by means of density functional theory calculations. CeO2(111) surfaces containing positively charged Au ions, either as supported Au^+ or as substitutional Au^3+ ions, are shown to activate molecular CO and to catalyze its oxidation to CO2 via participation of lattice O. For the Au^+ adatoms, the limiting rate is determined by the adsorbate spillover. The reaction proceeds with CO oxidation via O vacancy formation. These vacancies readily attract the Au^+ adatoms, turn them into negatively charged Au^δ- adspecies that prevent further CO adsorption, thus deactivating the catalyst. The reactivity of gold nanoparticles nucleated at O vacancies can be recovered for cluster sizes as small as Au2. Substitutional Au3+ ions dispersed into the ceria lattice can instead sustain a full catalytic cycle maintaining their charge state and activity along the reaction process. The interplay between the reversible Ce^4+/Ce^3+ and Au^3+/Au^+ redox couples underpins the high catalytic activity of dispersed Au atoms into the ceria substrate. Ab-initio surface thermodynamics is used to investigate the stability of different solid solutions and to predict more reactive catalysts.

  19. Nanoclusters a bridge across disciplines

    CERN Document Server

    Jena, Purusottam

    2010-01-01

    This comprehensive book on Nanoclusters comprises sixteen authoritative chapters written by leading researchers in the field. It provides insight into topics that are currently at the cutting edge of cluster science, with the main focus on metal and metal compound systems that are of particular interest in materials science, and also on aspects related to biology and medicine. While there are numerous books on clusters, the focus on clusters as a bridge across disciplines sets this book apart from others. Delivers cutting edge coverage of cluster science Covers a broad range of topics in

  20. Operando XAS Study of the Surface Oxidation State on a Monolayer IrOx on RuOx and Ru Oxide Based Nanoparticles for Oxygen Evolution in Acidic Media

    DEFF Research Database (Denmark)

    Pedersen, Anders Filsøe; Escribano, Maria Escudero; Sebok, Bela

    2017-01-01

    that the average Ir oxidation state change is strongly affected by the coverage of atomic O. The observed shifts in oxidation state suggest that the surface has a high coverage of O at potentials just below the potential where oxygen evolution is exergonic in free energy. This observation is consistent...

  1. Atomic scale investigation of silicon nanowires and nanoclusters

    Directory of Open Access Journals (Sweden)

    Gourbilleau Fabrice

    2011-01-01

    Full Text Available Abstract In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold and dopant (boron in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers.

  2. Characterization of silicon-oxide interfaces and organic monolayers by IR-UV ellipsometry and FTIR spectroscopy

    Science.gov (United States)

    Hess, P.; Patzner, P.; Osipov, A. V.; Hu, Z. G.; Lingenfelser, D.; Prunici, P.; Schmohl, A.

    2006-08-01

    VUV-laser-induced oxidation of Si(111)-(1×1):H, Si(100):H, and a-Si:H at 157 nm (F II laser) in pure O II and pure H IIO atmospheres was studied between 30°C and 250°C. The oxidation process was monitored in real time by spectroscopic ellipsometry (NIR-UV) and FTIR spectroscopy. The ellipsometric measurements could be simulated with a three-layer model, providing detailed information on the variation of the suboxide interface with the nature of the silicon substrate surface. Besides the silicon-dioxide and suboxide layer, a dense, disordered, roughly monolayer thick silicon layer was included, as found previously by molecular dynamics calculations. The deviations from the classical Deal-Grove mechanism and the self-limited growth of the ultrathin dioxide layers (TMS) groups and n-alkylthiol monolayers on gold-coated silicon. The C-H stretching vibrations of the methylene and methyl groups could be identified by FTIR spectroscopy and IR ellipsometry.

  3. Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

    NARCIS (Netherlands)

    Keller, D.E.; Visser, T.; Soulimani, F.; Koningsberger, D.C.; Weckhuysen, B.M.

    2007-01-01

    The effect of hydration on the molecular structure of silica-supported vanadium oxide catalysts with loadings of 1–16 wt.% V has been systematically investigated by infrared, Raman, UV–vis and EXAFS spectroscopy. IR and Raman spectra recorded during hydration revealed the formation of V–OH groups,

  4. Poly (dopamine) coated superparamagnetic iron oxide nanocluster for noninvasive labeling, tracking, and targeted delivery of adipose tissue-derived stem cells

    Science.gov (United States)

    Liao, Naishun; Wu, Ming; Pan, Fan; Lin, Jiumao; Li, Zuanfang; Zhang, Da; Wang, Yingchao; Zheng, Youshi; Peng, Jun; Liu, Xiaolong; Liu, Jingfeng

    2016-01-01

    Tracking and monitoring of cells in vivo after transplantation can provide crucial information for stem cell therapy. Magnetic resonance imaging (MRI) combined with contrast agents is believed to be an effective and non-invasive technique for cell tracking in living bodies. However, commercial superparamagnetic iron oxide nanoparticles (SPIONs) applied to label cells suffer from shortages such as potential toxicity, low labeling efficiency, and low contrast enhancing. Herein, the adipose tissue-derived stem cells (ADSCs) were efficiently labeled with SPIONs coated with poly (dopamine) (SPIONs cluster@PDA), without affecting their viability, proliferation, apoptosis, surface marker expression, as well as their self-renew ability and multi-differentiation potential. The labeled cells transplanted into the mice through tail intravenous injection exhibited a negative enhancement of the MRI signal in the damaged liver-induced by carbon tetrachloride, and subsequently these homed ADSCs with SPIONs cluster@PDA labeling exhibited excellent repair effects to the damaged liver. Moreover, the enhanced target-homing to tissue of interest and repair effects of SPIONs cluster@PDA-labeled ADSCs could be achieved by use of external magnetic field in the excisional skin wound mice model. Therefore, we provide a facile, safe, noninvasive and sensitive method for external magnetic field targeted delivery and MRI based tracking of transplanted cells in vivo.

  5. Phosphorescent Nanocluster Light-Emitting Diodes.

    Science.gov (United States)

    Kuttipillai, Padmanaban S; Zhao, Yimu; Traverse, Christopher J; Staples, Richard J; Levine, Benjamin G; Lunt, Richard R

    2016-01-13

    Devices utilizing an entirely new class of earth abundant, inexpensive phosphorescent emitters based on metal-halide nanoclusters are reported. Light-emitting diodes with tunable performance are demonstrated by varying cation substitution to these nanoclusters. Theoretical calculations provide insight about the nature of the phosphorescent emitting states, which involves a strong pseudo-Jahn-Teller distortion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

    Science.gov (United States)

    Liu, Lichen; Corma, Avelino

    2018-04-16

    Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

  7. Role of Bi promotion and solvent in platinum-catalyzed alcohol oxidation probed by in situ X-ray absorption and ATR-IR spectroscopy

    DEFF Research Database (Denmark)

    Mondelli, C.; Grunwaldt, Jan-Dierk; Ferri, D.

    2010-01-01

    the catalysts under working conditions using in situ X-ray absorption spectroscopy (XAS) and attenuated total reflection infrared spectroscopy (ATR-IR), aiming at uncovering the roles of the metal promoter and the reaction medium. XAS confirms that Bi is oxidized more easily than Pt, maintaining the catalytic....... This behaviour is not observed in the presence of Bi, whose geometric effect (site blocking) is interpreted as additionally limiting the adsorption of toluene and the premature deactivation of Pt. ATR-IR spectroscopy during CO adsorption on Pt and during reaction indicates that Bi is located rather on extended...

  8. Direct ethanol fuel cell, CO and ethanol oxidation on core-shell C/Ni-Au-[Pt and (Pt- Ir)] catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, C.A.D.; Tremiliosi-Filho, G. [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica], Email: cesaraug@sc.usp.br; Kokoh, K.B.; Coutanceau, C.; Baranton, S. [Universite de Poitiers (France). Lab. de Catalyse en Chimie Organique (LACCO). Equipe Electrocatalyse

    2010-07-01

    In this paper presents to study of the Pt and Pt-Ir monolayer that were deposited on core-shell Ni-Au nanoparticles supported on carbon. Catalysts with the following molar ratios were prepared: Pt and Pt{sub 65}Ir{sub 35}, Pt{sub 75}Ir{sub 2}5, Pt{sub 80}Ir{sub 20} and Pt{sub 85}Ir{sub 15}. The means particle sizes were in the range of 2 - 6 nm for all catalysts. The electrochemical properties examined in the ethanol and CO oxidation by cyclic voltammetry, and In situ IR spectroscopy measurements (SPAIRS) enabled to determine intermediates and reaction products as a function of the metallic compositions of catalysts. All of the catalysts were tested as anodes of a single direct ethanol fuel cell (DEFC) tests in 1.0 M ethanol solution. As a result, higher power densities were obtained with the core-shell particles in comparison to those issued from the commercial catalyst (Pt-ETEK). Thus, the maximum power densities at 90 deg C for the different systems are: (i) commercial C/Pt catalyst (E-TEK): ca. 0.010 W cm{sup -2}, C/Ni-Au-(Pt{sub 85}Ir{sub 15}): ca. 0.013 W cm{sup -2} and C/Ni-Au-Pt: ca. 0.018 W cm{sup -2} (all core-shell systems were normalization by Pt load). As a result, the performance of the core-shell nanoparticles is much better than that produced for the commercial catalyst and the C/Ni-Au-Pt system showed the best performance. (author)

  9. Fluorescence enhancement of DNA-silver nanoclusters from guanine proximity

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Hsin-chih [Los Alamos National Laboratory; Sharma, Jaswinder [Los Alamos National Laboratory; Yoo, Hyojong [Los Alamos National Laboratory; Martinez, Jennifer S [Los Alamos National Laboratory

    2010-01-01

    Oligonucleotide-templated, silver nanoclusters (DNA/Ag NCs) are a versatile set of fluorophores and have already been used for live cell imaging, detection of specific metal ions, and single-nucleotide variation identification. Compared to commonly used organic dyes, these fluorescent nanoclusters have much better photostability and are often a few times brighter. Owing to their small size, simple preparation, and biocompatibility (i.e. made of nontoxic metals), DNA/Ag NCs should find more applications in biological imaging and chemical detection in the years to come. While clearly promising as new fluorophores, DNA/Ag NCs possess a unique and poorly understood dynamic process not shared by organic dyes or photoluminescent nanocrystals - the conversion among different NC species due to silver oxidation/reduction or NC regrouping. While this environmental sensitivity can be viewed as a drawback, in the appropriate context, it can be used as a sensor or reporter. Often reversible, conversions among different NC species have been found to depend upon a number of factors, including time, temperature, oxygen and salt content. In this communication, we report significant fluorescence enhancement of DNA/Ag NCs via interactions with guanine-rich DNA sequences. Moreover, we demonstrated this property can be used for sensitive detection of specific target DNA from a human oncogene (i.e. Braf gene).

  10. Efficient and clean synthesis of graphene supported platinum nanoclusters and its application in direct methanol fuel cell

    International Nuclear Information System (INIS)

    Ji Kai; Chang Gang; Oyama, Munetaka; Shang Xunzhong; Liu Xiong; He Yunbin

    2012-01-01

    Highlights: ► Pt nanoclusters/graphene (PtNCs/graphene) was synthesized within one-step process. ► Environment friendly ascorbic acid was chosen as the reductant. ► The synthesized PtNCs/graphene show superior electrocatalytic activity to methanol. ► PtNCs/graphene show superior electrocatalytic stability in methanol electrooxidation. - Abstract: The graphene supported platinum nanoclusters was synthesized by an efficient and clean method, in which graphene oxide and Pt ion precursor were reduced by ascorbic acid within one-step process. The obtained Pt nanoclusters attached graphene composite (PtNCs/graphene) was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), which can directly show that Pt nanoclusters successfully formed on graphene and well distributed on the edges and wrinkles of graphene sheets. The further electrochemical characterizations including cyclic voltammograms (CV), current–time methods indicated that PtNCs/graphene has significantly higher electrocatalytic activity and stability for methanol electrooxidation compared to the normal Vulcan XC-72 and graphite supported Pt nanoclusters, which will lead a further application as a new electrode material in direct methanol fuel cell (DMFC).

  11. Au Nanoclusters and Photosensitizer Dual Loaded Spatiotemporal Controllable Liposomal Nanocomposites Enhance Tumor Photodynamic Therapy Effect by Inhibiting Thioredoxin Reductase.

    Science.gov (United States)

    Gao, Fuping; Zheng, Weiping; Gao, Liang; Cai, Pengju; Liu, Ru; Wang, Yaling; Yuan, Qing; Zhao, Yuliang; Gao, Xueyun

    2017-04-01

    Photodynamic therapy (PDT) is a minimally invasive therapeutic procedure of tumors with high selectivity and low side effect. However, it is usually not efficient in long-lasting tumor control. One of the main reasons is tumor cells develop some protective mechanisms that help them to deal with oxidative stress in the environment. The thioredoxin system in cancer is an important antioxidant defense system. Au nanoclusters could effectively inhibit thioredoxin reductase (TrxR) in tumor cell cytoplasm. Herein, Au nanoclusters and photosensitizer Chlorine 6 (Ce6) are co-loaded in spatiotemporal controllable liposomal nanocomposites. pH responsive molecule inserted in lipid bilayer greatly contributes to the instability of the lipid membrane in lysosomal at low pH environment. Then the payloads can rapidly release into cytoplasm. Au nanoclusters effectively inhibit TrxR in cytoplasm and enhance the photodynamic-induced intracellular reactive oxygen-free radical concentration, improving the effect of PDT. Breast cancer is chosen as a tumor model and the Au nanoclusters and photosensitizer co-loaded liposomal nanocomposites are studied to improve the effect of PDT both in vitro and in vivo, and its corresponding mechanism is investigated. This study develops a new application of gold nanoclusters and provides a new train of thoughts for enhancing the effect of PDT. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Fluorescent DNA Stabilized Silver Nanoclusters as Biosensors

    Directory of Open Access Journals (Sweden)

    Alfonso Latorre

    2013-01-01

    Full Text Available DNA stabilized fluorescent silver nanoclusters are promising materials, of which fluorescent properties can be exploited to develop sensors. Particularly, the presence of a DNA strand in the structure has promoted the development of gene sensors where one part of the sensor is able to recognize the target gene sequence. Moreover, since oligonucleotides can be designed to have binding properties (aptamers a variety of sensors for proteins and cells have been developed using silver nanoclusters. In this review the applications of this material as sensors of different biomolecules are summarized.

  13. Plasmon tsunamis on metallic nanoclusters.

    Science.gov (United States)

    Lucas, A A; Sunjic, M

    2012-03-14

    A model is constructed to describe inelastic scattering events accompanying electron capture by a highly charged ion flying by a metallic nanosphere. The electronic energy liberated by an electron leaving the Fermi level of the metal and dropping into a deep Rydberg state of the ion is used to increase the ion kinetic energy and, simultaneously, to excite multiple surface plasmons around the positively charged hole left behind on the metal sphere. This tsunami-like phenomenon manifests itself as periodic oscillations in the kinetic energy gain spectrum of the ion. The theory developed here extends our previous treatment (Lucas et al 2011 New J. Phys. 13 013034) of the Ar(q+)/C(60) charge exchange system. We provide an analysis of how the individual multipolar surface plasmons of the metallic sphere contribute to the formation of the oscillatory gain spectrum. Gain spectra showing characteristic, tsunami-like oscillations are simulated for Ar(15+) ions capturing one electron in distant collisions with Al and Na nanoclusters.

  14. IR intensity

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2015-01-01

    Definitions, formulas, and code for producing epsilon values (molar absorption coefficients) and IR spectral curve from 'Gaussian' FREQ output.......Definitions, formulas, and code for producing epsilon values (molar absorption coefficients) and IR spectral curve from 'Gaussian' FREQ output....

  15. Deposition of non-stoichiometric tungsten oxides+MO2 composites (M=Ru or Ir) and study of their catalytic properties in hydrogen or oxygen evolution reactions

    International Nuclear Information System (INIS)

    Baruffaldi, Claudia; Cattarin, Sandro; Musiani, Marco

    2003-01-01

    The electrodeposition of composites consisting of a non-stoichiometric tungsten oxide matrix and either RuO 2 or IrO 2 dispersed particles was investigated. These materials were then tested as electrodes for both reduction (hydrogen evolution) and oxidation (oxygen evolution) reactions in acid medium. The composite deposition was carried out by cyclic voltammetry, potentiostatic or galvanostatic electrolysis of suspensions of the RuO 2 or IrO 2 particles in two different media described as appropriate for WO 3 deposition: (i) a colloidal suspension obtained from Na 2 WO 4 and H 2 SO 4 or (ii) a solution obtained by dissolving W powder in aqueous H 2 O 2 . All the deposited composites were found to catalyse the hydrogen evolution reaction but none was active in oxygen evolution, presumably due to an inadequate electronic conductivity of the matrix. Such a behaviour differs from that of Pt-containing tungsten oxide electrodes which have been described as suitable anodes for the oxidation of organics

  16. Bifunctional electrodes with ir and Ru oxide mixtures and pt for unified regenerative cells; Electrodos bifuncionales basados en mezclas de oxidos de Ir y Ru con Pt para celdas regenerativas unificadas

    Energy Technology Data Exchange (ETDEWEB)

    Duron-Torres, S.M.; Escalante-Garcia, I.L. [Universidad Autonoma de Zacatecas, Zacatecas (Mexico); Cruz, J. C.; Arriaga-Hurtado; L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico)]. E-mail: duronsm@prodigy.net.mx

    2009-09-15

    Unified regenerative fuel cells (URFC) represent an attractive option to obtain hydrogen and generate energy using a compact device. Nevertheless, the fusion of a fuel cell (PEMFC) and a water electrolyzer continue to be a challenge because of the wide range of conditions to which this type of device is subject. Because of its kinetic characteristics, oxygen reduction reaction (ORR) in PEMFC and oxygen evolution reaction (OER) in PEMWE are the limiting stages of the URFC depending on the mode of operation. The primary focus of research related to URFC is the obtainment of bifunctional electrocatalysts that satisfactorily perform in both oxygen reactions and support the different working conditions found in a fuel cell and an electrolyzer. The present work contributes to the research on bifunctional electrocatalysts and shows some preliminary results from the electrochemical study of different Pt gcc, IrO{sub 2} and RuO{sub 2} mixtures supported in Ebonex® as oxygen electrodes. The electrochemical characterization with cyclic voltamperometry (CV), linear voltamperometry (LV) and electrochemical impedance spectroscopy (EIS) in H{sub 2}SO{sub 4} 0.5 M, in the absence and present of oxygen shows that Ebonex®-supported bifunctional electrodes IrO{sub 2}-Pt and RuO{sub 2}-Pt present reasonable electrocatalytic properties for oxygen evolution and reduction reactions and present the possibility of their use in an URFC. The Ir- based oxide electrodes show greater stability than ruthenium-oxide electrodes. [Spanish] Las celdas de combustible regenerativas unificadas (URFC) representan una atractiva opcion para la obtencion de hidrogeno y generacion de energia en un dispositivo compacto. Sin embargo, la fusion de una celda de combustible (PEMFC) y un electrolizador de agua (PEMWE) sigue siendo un reto por la amplia gama de condiciones a que se sujeta un dispositivo de este tipo. Por sus caracteristicas cineticas, la reaccion de reduccion de oxigeno (ORR) en la PEMFC y la

  17. Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Abolghasemi, Mir Mahdi; Yousefi, Vahid; Rafiee, Ezzat

    2014-01-01

    A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL −1 and a dynamic range as wide as from 0.001 to 100 ng mL −1 . Under optimum conditions, the repeatability for one fiber (n = 3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction. (author)

  18. Peptide-stabilized, fluorescent silver nanoclusters

    DEFF Research Database (Denmark)

    Gregersen, Simon; Vosch, Tom André Jos; Jensen, Knud Jørgen

    2016-01-01

    Few-atom silver nanoclusters (AgNCs) can exhibit strong fluorescence; however, they require ligands to prevent aggregation into larger nanoparticles. Fluorescent AgNCs in biopolymer scaffolds have so far mainly been synthesized in solution, and peptides have only found limited use compared to DNA...

  19. The fcc structure isomerization in gold nanoclusters.

    Science.gov (United States)

    Zhuang, Shengli; Liao, Lingwen; Li, Man-Bo; Yao, Chuanhao; Zhao, Yan; Dong, Hongwei; Li, Jin; Deng, Haiteng; Li, Lingling; Wu, Zhikun

    2017-10-12

    Structural isomerization is an important concept in organic chemistry and it is recently found to be applicable to thiolated gold nanoparticles. However, to the best of our knowledge, the isomerization with the kernel structure of the cluster changed while maintaining fcc packing was not previously found. Here, we report such a structural isomerization by synthesizing a novel gold nanocluster and solving its atomic structure. The as-obtained novel gold nanocluster Au 52 (PET) 32 (PET = phenylethanethiolate) has completely the same Au/S molar ratio as a well-known gold nanocluster Au 52 (TBBT) 32 (TBBT = 4-tert-butyl-benzenethiolate) but an essentially different fcc structure. As a result of fcc structure isomerization, Au 52 (PET) 32 has remarkably different UV/vis/NIR absorption from Au 52 (TBBT) 32 . Another interesting finding in this work is that the kernel of Au 52 (PET) 32 has high-indexed (311)-like facets, which is not previously reported in the structures of gold nanoclusters to the best of our knowledge.

  20. Mechanism of oxalate ion adsorption on chromium oxide-hydroxide from pH dependence and time evolution of ATR-IR spectra

    Science.gov (United States)

    Degenhardt, Jens; McQuillan, A. James

    1999-09-01

    A chromium (III) oxide-hydroxide colloid film has been used to model the passive surface of stainless steel in in situ ATR-IR studies of oxalate ion adsorption from aqueous oxalate solutions over a wide pH range. Studies of time and pH dependence of adsorption have been used to reveal a mechanism of adsorption proceeding through ionic, hydrogen bonded and coordinated oxalate species. A Langmuir adsorption constant of 4.5×10 4 M -1 was determined for the surface coordinated oxalate from an adsorption isotherm at pH=3.

  1. The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden; Vegge, Tejs

    2014-01-01

    The presence of water often gives rise to oxygen adsorption on catalyst surfaces through decomposition of water and the adsorbed oxygen or hydroxide species often occupy important surfaces sites, resulting in a decrease or a total hindrance of other chemical reactions taking place at that site...... are -0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface....... In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density...

  2. First-principles calculations on Fe-Pt nanoclusters of various morphologies.

    Science.gov (United States)

    Platonenko, Alexander; Piskunov, Sergei; Bocharov, Dmitry; Zhukovskii, Yuri F; Evarestov, Robert A; Bellucci, Stefano

    2017-09-05

    Bimetallic FePt nanoparticles with L1 0 structure are attracting a lot of attention due to their high magnetocrystalline anisotropy and high coercivity what makes them potential material for storage of ultra-high density magnetic data. FePt nanoclusters are considered also as nanocatalysts for growth of carbon nanotubes of different chiralities. Using the DFT-LCAO CRYSTAL14 code, we have performed large-scale spin-polarized calculations on 19 different polyhedral structures of FePt nanoparticles in order to estimate which icosahedral or hcp-structured morphology is the energetically more preferable. Surface energy calculations of all aforementioned nanoparticles indicate that the global minimum corresponds to the nanocluster possessing the icosahedron "onion-like" structure and Fe 43 Pt 104 morphology where the outer layer consists of Pt atoms. The presence of the Pt-enriched layer around FePt core explains high oxidation resistance and environmental stability, both observed experimentally.

  3. Effects of trimethylaluminium and tetrakis(ethylmethylamino) hafnium in the early stages of the atomic-layer-deposition of aluminum oxide and hafnium oxide on hydroxylated GaN nanoclusters.

    Science.gov (United States)

    León-Plata, Paola A; Coan, Mary R; Seminario, Jorge M

    2013-10-01

    We calculate the interactions of two atomic layer deposition (ALD) reactants, trimethylaluminium (TMA) and tetrakis(ethylmethylamino) hafnium (TEMAH) with the hydroxylated Ga-face of GaN clusters when aluminum oxide and hafnium oxide, respectively, are being deposited. The GaN clusters are suitable as testbeds for the actual Ga-face on practical GaN nanocrystals of importance not only in electronics but for several other applications in nanotechnology. We find that TMA spontaneously interacts with hydroxylated GaN; however it does not follow the atomic layer deposition reaction path unless there is an excess in potential energy introduced in the clusters at the beginning of the optimization, for instance, using larger bond lengths of various bonds in the initial structures. TEMAH also does not interact with hydroxylated GaN, unless there is an excess in potential energy. The formation of a Ga-N(CH3)(CH2CH3) bond during the ALD of HfO2 using TEMAH as the reactant without breaking the Hf-N bond could be the key part of the mechanism behind the formation of an interface layer at the HfO2/GaN interface.

  4. Theoretical Investigation of the Structural Stabilities of Ceria Surfaces and Supported Metal Nanocluster in Vapor and Aqueous Phases

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhibo [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Liu, Ning [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Chen, Biaohua [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Li, Jianwei [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Mei, Donghai [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

    2018-01-25

    Understanding the structural stability and dynamics at the interface between the solid metal oxide and aqueous phase is significant in a variety of industrial applications including heterogeneous catalysis and environmental remediation. In the present work, the stabilities of three low-index ceria (CeO2) surfaces, i.e., (111), (110) and (100) in vapor and aqueous phases were studied using ab initio molecular dynamics simulations and density functional theory (DFT) calculations. Gibbs surface free energies as a function of temperature, water partial pressure, and water coverages were calculated using DFT based atomistic thermodynamic approach. On the basis of surface free energies, the morphology and exposed surface structures of the CeO2 nanoparticle were predicted using Wulff construction principle. It is found that the partially hydroxylated (111) and (100) are two major surface structures of CeO2 nanoparticles in vapor phase at ambient temperature (300 K). As the temperature increases, the fully dehydrated (111) surface gradually becomes the most dominant surface structure. While in aqueous phase, the exposed surface of the CeO2 nanoparticle is dominated by the hydroxylated (110) structure at 393 K. Finally, the morphology and stability of a cuboctahedron Pt13 nanocluster supported on CeO2 surfaces in both gas and aqueous phases were investigated. In gas phase, the supported Pt13 nanocluster has the tendency to wetting the CeO2 surface due to the strong metal-support interaction. The calculated interaction energies suggest the CeO2(110) surface provides the best stability for the Pt13 nanocluster. The CeO2 supported Pt13 nanoclusters are oxidized. Compared to the gas phase, the morphology of the CeO2 supported Pt13 nanocluster is less distorted due to the solvation effect provided by surrounding water molecules in aqueous phase. More electrons are transferred from the Pt13 nanocluster to the CeO2 support, implying the supported Pt13 nanocluster is further

  5. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    International Nuclear Information System (INIS)

    Kaur, Maninder; Qiang, You; Dai, Qilin; Tang, Jinke; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao

    2013-01-01

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr ( 2 O 3 and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (∼25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of σ-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs

  6. Ras acylation, compartmentalization and signaling nanoclusters (Review)

    OpenAIRE

    HENIS, YOAV I.; HANCOCK, JOHN F.; PRIOR, IAN A.

    2008-01-01

    Ras proteins have become paradigms for isoform- and compartment-specific signaling. Recent work has shown that Ras isoforms are differentially distributed within cell surface signaling nanoclusters and on endomembranous compartments. The critical feature regulating Ras protein localization and isoform-specific functions is the C-terminal hypervariable region (HVR). In this review we discuss the differential post-translational modifications and reversible targeting functions of Ras isoform HVR...

  7. Fluorescent Pressure Response of Protein-Nanocluster Polymer Composites

    Science.gov (United States)

    2016-05-01

    nanoclusters exhibit fluorescent effects similarly to semiconductor-based quantum dots and are not nearly as toxic due to their lack of heavy metals .7...Strongly emissive individual DNA -encapsulated Ag nanoclusters as single molecule fluorophores. PNAS 31. 2007:12616–12621. 5. Wang F, Tan WB

  8. Passivation of cobalt nanocluster assembled thin films with hydrogen

    DEFF Research Database (Denmark)

    Romero, C.P.; Volodin, A.; Di Vece, M.

    2012-01-01

    The effect of hydrogen passivation on bare and Pd capped cobalt nanocluster assembled thin films was studied with Rutherford backscattering spectrometry (RBS) and magnetic force microscopy (MFM) after exposure to ambient conditions. The nanoclusters are produced in a laser vaporization cluster...

  9. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.

    2016-06-22

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  10. Electrochemical oxidation of trace organic contaminants in reverse osmosis concentrate using RuO2/IrO2-coated titanium anodes.

    Science.gov (United States)

    Radjenovic, Jelena; Bagastyo, Arseto; Rozendal, René A; Mu, Yang; Keller, Jürg; Rabaey, Korneel

    2011-02-01

    During membrane treatment of secondary effluent from wastewater treatment plants, a reverse osmosis concentrate (ROC) containing trace organic contaminants is generated. As the latter are of concern, effective and economic treatment methods are required. Here, we investigated electrochemical oxidation of ROC using Ti/Ru(0.7)Ir(0.3)O(2) electrodes, focussing on the removal of dissolved organic carbon (DOC), specific ultra-violet absorbance at 254 nm (SUVA(254)), and 28 pharmaceuticals and pesticides frequently encountered in secondary treated effluents. The experiments were conducted in a continuously fed reactor at current densities (J) ranging from 1 to 250 A m(-2) anode, and a batch reactor at J = 250 A m(-2). Higher mineralization efficiency was observed during batch oxidation (e.g. 25.1 ± 2.7% DOC removal vs 0% removal in the continuous reactor after applying specific electrical charge, Q = 437.0 A h m(-3) ROC), indicating that DOC removal is depending on indirect oxidation by electrogenerated oxidants that accumulate in the bulk liquid. An initial increase and subsequent slow decrease in SUVA(254) during batch mode suggests the introduction of auxochrome substituents (e.g. -Cl, NH(2)Cl, -Br, and -OH) into the aromatic compounds. Contrarily, in the continuous reactor ring-cleaving oxidation products were generated, and SUVA(254) removal correlated with applied charge. Furthermore, 20 of the target pharmaceuticals and pesticides completely disappeared in both the continuous and batch experiments when applying J ≥ 150 A m(-2) (i.e. Q ≥ 461.5 A h m(-3)) and 437.0 A h m(-3) (J = 250 A m(-2)), respectively. Compounds that were more persistent during continuous oxidation were characterized by the presence of electrophilic groups on the aromatic ring (e.g. triclopyr) or by the absence of stronger nucleophilic substituents (e.g. ibuprofen). These pollutants were oxidized when applying higher specific electrical charge in batch mode (i.e. 1.45 kA h m(-3) ROC

  11. Nanostructured transition metal oxides useful for water oxidation catalysis

    Science.gov (United States)

    Frei, Heinz M; Jiao, Feng

    2013-12-24

    The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

  12. [Electrochemical oxidation of ammonia nitrogen wastewater using Ti/RuO2-TiO2-IrO2-SnO2 electrode].

    Science.gov (United States)

    Xu, Li-li; Shi, Han-chang; Chen, Jin-luan

    2007-09-01

    Electrochemical oxidation ammonia is a new method of ammonia nitrogen wastewater treatment. A study was undertaken of electrochemical oxidation ammonia wastewater in cycle mobil-electrobath. The anode was Ti/RuO2-TiO2-IrO2-SnO2 expanded metal sheet electrode. The cathode was expanded metal sheet electrode. The parameters investigated were the optimal available time for the measurement of ammonia nitrogen, flowrate and current density. The energy consumption, anode efficiency and current efficiency were analysed in different current densities. Experimental results show that when the concentration of the chlorine ion was 400 mg/L and the initial ammoniac nitrogen concentration was 40 mg/L, the flowrate had little impact on ammonia nitrogen removal, but current density had greater impact. Under the condition with flowrate 600 mL/min, current density 20 mA/cm2, electrolytic time 90 min, ammonia nitrogen removal ratio was 99.37%. The energy consumption was 500 kW x h and the anode efficiency was 2.68 h x m2 x A per kg NH4+ -N removed, and instantaneous current efficiency (ICE) was 0.28. Research has shown that electrochemical oxidation ammonia wastewater has better prospects.

  13. Spectroscopic (NMR, UV, FT-IR and FT-Raman) analysis and theoretical investigation of nicotinamide N-oxide with density functional theory.

    Science.gov (United States)

    Atac, Ahmet; Karabacak, Mehmet; Kose, Etem; Karaca, Caglar

    2011-12-01

    The spectroscopic properties of the nicotinamide N-oxide (abbreviated as NANO, C(6)H(6)N(2)O(2)) were examined by FT-IR, FT-Raman, NMR and UV techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The (1)H and (13)C NMR spectra were recorded in DMSO. The UV absorption spectrum of the compound that dissolved in water was recorded in the range of 200-800 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using Density Functional Theory (DFT) employing B3LYP methods with the 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The optimized structure of compound was interpreted and compared with the reported experimental values. The observed vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values. As a result, the optimized geometry and calculated spectroscopic data show a good agreement with the experimental results. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Nanoclusters and Microparticles in Gases and Vapors

    CERN Document Server

    Smirnov, Boris M

    2012-01-01

    Research of processes involving Nanoclusters and Microparticleshas been developing fastin many fields of rescent research, in particular in materials science. To stay at the cutting edge of this development, a sound understanding of the processes is needed. In this work, several processes involving small particles are described, such as transport processes in gases, charging of small particles in gases, chemical processes, atom attachment and quenching of excited atomic particles on surfaces, nucleation, coagulation, coalescence and growth processes for particles and aggregates. This work pres

  15. Stable isomers and electronic, vibrational, and optical properties of WS2 nano-clusters: A first-principles study.

    Science.gov (United States)

    Hafizi, Roohollah; Hashemifar, S Javad; Alaei, Mojtaba; Jangrouei, MohammadReza; Akbarzadeh, Hadi

    2016-12-07

    In this paper, we employ an evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS 2 ) n nano-clusters (n = 1 - 9), within three different exchange-correlation functionals. Our results suggest that n = 5 and 8 are possible candidates for the low temperature magic sizes of WS 2 nano-clusters while at temperatures above 500 Kelvin, n = 7 exhibits a comparable relative stability with n = 8. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal Perdew-Burke-Ernzerhof and Becke-Lee-Yang-Parr functionals, hybrid B3LYP functional, many body based DFT+GW approach, ΔSCF method, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in a real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS 2 nano-clusters.

  16. Inyang, IR

    African Journals Online (AJOL)

    Inyang, IR. Vol 5, No 4 (2009) - Articles Changes in Total Protein and Transaminase Activities in Clarias Gariepinus Exposed to Diazinon Abstract. ISSN: 0794-4721. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and ...

  17. Flourescent Peptide-Stabilized Silver-Nanoclusters

    DEFF Research Database (Denmark)

    Gregersen, Simon

    Fluorescent probes are widely used in the fields of imaging, detection, and diagnostics, and in order to achieve methodical progress, the search for new tools is an on-going quest. Within the last few decades, few-atom noble metal nanoclusters (NCs) have gathered increasing attention due to their......Fluorescent probes are widely used in the fields of imaging, detection, and diagnostics, and in order to achieve methodical progress, the search for new tools is an on-going quest. Within the last few decades, few-atom noble metal nanoclusters (NCs) have gathered increasing attention due...... to their physical and optoelectronic properties. These include great photostability, low toxicity, small size, and tunable spectral properties. Chemical stability of noble metal NCs is, however, very low, and they only exist transiently without a stabilizing scaffold. This has to date been done in solution using....../reorganization of the peptide to facilitate NC formation. Following an initial chelation involving the thiol-functionality of cysteine side-chains, the coordination of silver into a defined NC is expected to be the driving force of the folding process. This work also illustrates the shortcomings of MALDI-TOF mass spectrometry...

  18. Waveguiding properties of Er-implanted silicon-rich oxides

    International Nuclear Information System (INIS)

    Elliman, R.G.; Forcales, M.; Wilkinson, A.R.; Smith, N.J.

    2007-01-01

    The optical properties of erbium-doped silicon-rich silicon-oxide waveguides containing amorphous silicon nanoclusters and/or silicon nanocrystals are reported. Both amorphous nanoclusters and nanocrystals are shown to act as effective sensitizers for Er, with nanocrystals being more effective at low pump powers and nanoclusters being more effective at higher pump powers. All samples are shown to exhibit photo-induced absorption, as measured for a guided 1.5 μm probe beam while the waveguide was illuminated from above with a 477 nm pump beam. At a given pump power samples containing silicon nanocrystals exhibited greater attenuation than samples containing amorphous nanoclusters. The absorption is shown to be consistent with confined-carrier absorption due to photoexcited carriers in the nanocrystals and/or nanoclusters

  19. Supported lipid bilayers as templates to design manganese oxide ...

    Indian Academy of Sciences (India)

    Abstract. This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and.

  20. DNA/RNA Detection Using DNA-Templated Few-Atom Silver Nanoclusters

    Directory of Open Access Journals (Sweden)

    Hsin-Chih Yeh

    2013-04-01

    Full Text Available DNA-templated few-atom silver nanoclusters (DNA/Ag NCs are a new class of organic/inorganic composite nanomaterials whose fluorescence emission can be tuned throughout the visible and near-IR range by simply programming the template sequences. Compared to organic dyes, DNA/Ag NCs can be brighter and more photostable. Compared to quantum dots, DNA/Ag NCs are smaller, less prone to blinking on long timescales, and do not have a toxic core. The preparation of DNA/Ag NCs is simple and there is no need to remove excess precursors as these precursors are non-fluorescent. Our recent discovery of the fluorogenic and color switching properties of DNA/Ag NCs have led to the invention of new molecular probes, termed NanoCluster Beacons (NCBs, for DNA detection, with the capability to differentiate single-nucleotide polymorphisms by emission colors. NCBs are inexpensive, easy to prepare, and compatible with commercial DNA synthesizers. Many other groups have also explored and taken advantage of the environment sensitivities of DNA/Ag NCs in creating new tools for DNA/RNA detection and single-nucleotide polymorphism identification. In this review, we summarize the recent trends in the use of DNA/Ag NCs for developing DNA/RNA sensors.

  1. Crystallization of silicon nanoclusters with inert gas temperature control

    Science.gov (United States)

    Zhao, Junlei; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Cassidy, Cathal; Aranishi, Kengo; Sowwan, Mukhles; Nordlund, Kai; Djurabekova, Flyura

    2015-01-01

    We analyze the fundamental process of crystallization of silicon nanoclusters by means of molecular dynamics simulations, complemented by magnetron-sputter inert gas condensation, which was used to synthesize polycrystalline silicon nanoclusters with good size control. We utilize two well-established Si interatomic potentials: the Stillinger-Weber and the Tersoff III. Both the simulations and experiments show that upon cooling down by an Ar gas thermal bath, initially liquid, free-standing Si nanocluster can grow multiple crystal nuclei, which drive their transition into polycrystalline solid nanoclusters. The simulations allow detailed analysis of the mechanism, and show that the crystallization temperature is size-dependent and that the probability of crystalline phase nucleation depends on the highest temperature the cluster reaches during the initial condensation and the cooling rate after it.

  2. Adsorption of small gas molecules on B36 nanocluster

    Indian Academy of Sciences (India)

    Supplementary Information. Journal of Chemical Sciences. Adsorption of small gas molecules on B36 nanocluster. YOUNES VALADBEIGI. *. , HOSSEIN FARROKHPOUR and MAHMOUD TABRIZCHI. Department of chemistry, Isfahan University of Technology, Isfahan, 84156-83111, Iran. *. Corresponding Author: Younes ...

  3. Understanding the mechanism of enhanced charge separation and visible light photocatalytic activity of modified wurtzite ZnO with nanoclusters of ZnS and graphene oxide: from a hybrid density functional study

    CSIR Research Space (South Africa)

    Opoku, F

    2017-01-01

    Full Text Available Van Sitter CGCE Govender PP ABSTRACT: Recently, semiconductor photocatalysts have received significant interest in addressing the global energy and environmental crisis. Despite the great potential application of zinc oxide (Zn...

  4. Charge transfer interactions in oligomer coated gold nanoclusters

    International Nuclear Information System (INIS)

    Newmai, M. Boazbou; Kumar, Pandian Senthil

    2016-01-01

    Gold nanoclusters were synthesized by a bottom-up synergistic approach of in-situ oligomerization of the monomer, N-vinyl pyrrolidone (NVP) and simultaneous weak reduction of Au-NVP complexes in the absence of any other external energy sources, thereby making these tiny gold clusters as the most elemental building blocks to construct further novel nano/microstructures with application potentials. It is well-known that metal clusters with less than 2 nm size do not show the usual surface plasmon band, because of the presence of a band-gap at the fermi level. Nevertheless, our present oligomer coated gold clusters show a discrete intense band at around 630 nm, which could very well be attributed to the charge transfer between the oligomer chain and the surface Au atoms. Such kind of sacrificial plasmon induced charge transfer interaction, observed for the very first time to the best of our knowledge, were also strongly corroborated through the enhancement / shifting of specific vibrational / rotational peaks as observed from the FTIR and Raman measurements as a function of the metal oxidation states, thus representing a new prototype for an efficient solar energy conversion probe.

  5. "light-on" sensing of antioxidants using gold nanoclusters

    KAUST Repository

    Hu, Lianzhe

    2014-05-20

    Depletion of intracellular antioxidants is linked to major cytotoxic events and cellular disorders, such as oxidative stress and multiple sclerosis. In addition to medical diagnosis, determining the concentration of antioxidants in foodstuffs, food preservatives, and cosmetics has proved to be very vital. Gold nanoclusters (Au-NCs) have a core size below 2 nm and contain several metal atoms. They have interesting photophysical properties, are readily functionalized, and are safe to use in various biomedical applications. Herein, a simple and quantitative spectroscopic method based on Au-NCs is developed to detect and image antioxidants such as ascorbic acid. The sensing mechanism is based on the fact that antioxidants can protect the fluorescence of Au-NCs against quenching by highly reactive oxygen species. Our method shows great accuracy when employed to detect the total antioxidant capacity in commercial fruit juice. Moreover, confocal fluorescence microscopy images of HeLa cells show that this approach can be successfully used to image antioxidant levels in living cells. Finally, the potential application of this "light-on" detection method in multiple logic gate fabrication was discussed using the fluorescence intensity of Au-NCs as output. © 2014 American Chemical Society.

  6. Development of budesonide nanocluster dry powder aerosols: preformulation.

    Science.gov (United States)

    El-Gendy, Nashwa; Selvam, Parthiban; Soni, Pravin; Berkland, Cory

    2012-09-01

    Wet milling was previously demonstrated as a simple process for producing agglomerates of budesonide nanoparticles (also known as NanoClusters) for use in dry powder aerosol formulation. The resulting budesonide NanoCluster powders exhibited a large emitted fraction and a high fine particle fraction (FPF) from a Monodose® dry powder inhaler. In this work, excipients were added premilling or postmilling and the performance of budesonide NanoCluster dry powders was investigated. Sodium chloride, Pluronic®, or ethanol was added prior to milling due to their ability to modify surface tension or ionic strength and thereby affect the attrition/agglomeration process. Lactose or l-leucine was added after milling because these are known to modify powder flow and dispersion. The chemical stability of budesonide was maintained in all cases, but the physical aerosol properties changed substantially with the addition of excipients. In all cases, the addition of excipients led to an increase in the size of the budesonide NanoClusters and tended to reduce the emitted fraction and FPF. Titrating excipients may provide a means to discretely modify the aerosol properties of budesonide NanoClusters but did not match the performance of excipient-free NanoCluster powder. Copyright © 2012 Wiley Periodicals, Inc.

  7. Controlled nanoclustering of magnetic nanoparticles using telechelic polysiloxane and disiloxane

    Science.gov (United States)

    Thong-On, Bandit; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha

    2015-06-01

    Diacrylate-terminated polydimethylsiloxane (PDMS) and disiloxane were synthesized and used for controlling degree of nanoclustering of magnetite nanoparticles (MNPs). PDMS was synthesized via a ring-opening polymerization of octamethylcyclotetrasiloxane (D4), followed by end functionalization with diacrylate groups. Diacrylate-terminated disiloxane was separately synthesized in a similar fashion without the use of D4 in the reaction. They were then reacted with amino-coated MNPs to obtain MNP-embedded siloxane nanoclusters. Transmission electron microscopy showed the formation of MNP-siloxane nanoclusters with the size of 70-200 nm. Degree of MNP nanoclustering can be adjusted by varying the MNP-to-siloxane ratio to obtain hydrodynamic size ranging from 200 to 2400 nm. Using the same ratio of MNPs to the siloxanes, PDMS resulted in the nanoclusters with smaller D h and more stable in toluene than those coated with disiloxane. These novel nanoclusters with controllable size might be ideal candidates for biomedical and other advanced applications after suitable surface modification.

  8. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    Science.gov (United States)

    de la Vega, A. Estrada; Garza-Navarro, M. A.; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V.

    2016-01-01

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  9. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Vega, A. Estrada de la; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2016-01-15

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  10. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Maninder; Qiang, You, E-mail: youqiang@uidaho.edu [Department of Physics, University of Idaho, Moscow, Idaho 83844 (United States); Dai, Qilin; Tang, Jinke [Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071 (United States); Bowden, Mark; Engelhard, Mark [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Wu, Yaqiao [Department of Materials Science and Engineering, Boise State University, Boise, Idaho 83725 (United States); Center for Advanced Energy Studies, Idaho Falls, Idaho 83401 (United States)

    2013-11-11

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr{sub 2}O{sub 3} and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (∼25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of σ-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs.

  11. Investigating the adsorption of H2O on ZnO nanoclusters by first principle calculations

    KAUST Repository

    Al-Sunaidi, Abdullah A.

    2011-04-01

    The interaction of a single H2O molecule on selected ZnO nanoclusters is investigated by carrying out calculations based on the density-functional theory at the hybrid-GGA (B97-2) level. These clusters have ring, drum, tube and bubble shapes and their physical properties like the binding energy and the band gap energy depend strongly on the shape and size of the cluster. Depending on the stability of the cluster, H2O show both chemisorption and dissociation on the surfaces of the clusters. We analyzed the effect of H2O adsorption on the properties of clusters of size n = 12 via the density of state, HOMO-LUMO orbitals and the changes in the IR frequencies. © 2011 Elsevier B.V. All rights reserved.

  12. Quantum chemical calculation (electronic and topologic) and experimental (FT-IR, FT-Raman and UV) analysis of isonicotinic acid N-oxide.

    Science.gov (United States)

    Karaca, Caglar; Atac, Ahmet; Karabacak, Mehmet

    2015-04-05

    In this work, the molecular conformation, vibrational and electronic analysis of isonicotinic acid N-oxide (iso-NANO) were presented in the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. The geometry optimization and energies associated possible two conformers (Rot-I and Rot-II) were computed. The vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The obtained structures were analyzed with the Atoms in Molecules (AIMs) methodology. The computational results diagnose the most stable conformer of iso-NANO as the Rot-I form. Total density of state (TDOS) and partial density of state (PDOS) and also overlap population density of state (OPDOS) diagrams analysis for the most stable conformer (Rot-I) were calculated using the same method. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated. As a result, the optimized geometry and calculated spectroscopic data show a good agreement with the experimental results. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Exchange bias and magnetic behaviour of iron nanoclusters prepared by the gas aggregation technique

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Marcos, J., E-mail: sanchej@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Laguna-Marco, M.A.; Martinez-Morillas, R. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Jimenez-Villacorta, F. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); SpLine Spanish CRG Beamline at the European Synchrotron Radiation Facilities, ESRF-BP 220-38043 Grenoble Cedex (France); Cespedes, E. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Menendez, N. [Dep. Quimica-Fisica Aplicada, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Gas aggregation phase technique allows obtaining {alpha}-Fe{sub 2}O{sub 3} nanoparticles. Black-Right-Pointing-Pointer We have reported exchange bias up to 3250 Oe at 2 K. Black-Right-Pointing-Pointer Exchange bias may be tuned by different stoichiometry of {alpha}-Fe{sub 2}O{sub 3} nanoparticles. - Abstract: Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias (H{sub E}) values up to H{sub E} = 3300 Oe at low temperatures. In order to explain the observed magnetic properties, composition and crystallographic phase have been determined by X-ray absorption spectroscopy. A metal-oxide core-shell arrangement has to be discarded to explain the large obtained values of H{sub E} since structural results show nanoclusters formed by the antiferromagnetic {alpha}-Fe{sub 2}O{sub 3} oxide. Moreover, nanoparticles of few nanometers formed by substoichiometric {alpha}-Fe{sub 2}O{sub 3} explain the observed weak ferromagnetism and let to understand the origin of large exchange bias by the interaction between different spin sublattice configurations provided by the low iron coordination at surface.

  14. Observation of the long-lived triplet excited state of perylenebisimide (PBI) in C^N cyclometalated Ir(III) complexes and application in photocatalytic oxidation.

    Science.gov (United States)

    Sun, Jifu; Zhong, Fangfang; Zhao, Jianzhang

    2013-07-14

    Perylenebisimide (PBI) was used to prepare C^N cyclometalated Ir(III) complexes that show strong absorption of visible light and it is the first time the long-lived triplet excited state of PBI chromophore was observed in a transition metal complex (τT = 22.3 μs). Previously, the lifetime of the triplet state of PBI in transition metal complexes was usually shorter than 1.0 μs. Long-lived triplet excited states are useful for applications in photocatalysis or other photophysical processes concerning triplet-triplet-energy-transfer. PBI and amino-PBI were used for preparation of cyclometalated Ir(III) complexes (Ir-2 and Ir-3), in which the PBI chromophore was connected to the coordination center via C≡C π-conjugation bond. The new complexes show strong absorption in visible region (ε = 34,200 M(-1) cm(-1) at 541 nm for Ir-2, and ε = 19,000 at 669 nm for Ir-3), compared to the model complex Ir(ppy)(bpy)[PF6] Ir-1 (ε PBI-localized long-lived (3)IL states were populated for Ir-2 and Ir-3 upon photoexcitation. The complexes were used as triplet photosensitizers for (1)O2-mediated photooxidation of 1,5-dihydronaphthalene to produce juglone, an important intermediate for preparation of anti-cancer compounds. (1)O2 quantum yields (Φ(Δ)) up to 91% were observed for the new Ir(III) complexes and the overall photosensitizing ability is much higher than the conventional Ir(III) complex Ir-1, which shows the typical weak visible light absorption in visible region. Our results are useful for preparation of transition metal complexes that show strong absorption of visible light and long-lived triplet excited state and for the application of these complexes in photocatalysis.

  15. Flourescent Peptide-Stabilized Silver-Nanoclusters

    DEFF Research Database (Denmark)

    Gregersen, Simon

    throughput dramatically with regards to discovery of novel ligands. Our approach employs Fmoc solid-phase peptide synthesis on a PEGA resin which allows for on-resin screening of peptide ligands which, in turn, removes the tedious and labor-intensive work-up of synthesized peptides. The method allows for on......Fluorescent probes are widely used in the fields of imaging, detection, and diagnostics, and in order to achieve methodical progress, the search for new tools is an on-going quest. Within the last few decades, few-atom noble metal nanoclusters (NCs) have gathered increasing attention due....../reorganization of the peptide to facilitate NC formation. Following an initial chelation involving the thiol-functionality of cysteine side-chains, the coordination of silver into a defined NC is expected to be the driving force of the folding process. This work also illustrates the shortcomings of MALDI-TOF mass spectrometry...

  16. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  17. Silver Nanocluster Reparative Effect in Hernioplasty

    Directory of Open Access Journals (Sweden)

    Nikolay M. Anichkov

    2014-06-01

    Full Text Available Background: The acceleration of re-epithelialization and fibroblast differentiation were noted during the experiments with silver nanoclusters (SNs by interrupting the negative development of inflammation at the level of cytokines and promoting a positive course of reparative processes. The aim of this work was to elaborate the experimental model of prosthesis hernioplasty in subcutaneous and intraperitoneal locations of hernioprostheses with SNs, which allowed us to study the course of reparative reactions in all layers of the anterior abdominal wall. Material and Methods: We used a modified hernioprosthesis made from polyester fibers coated with a metal-polymer composition, including the stabilized SN in a concentration of 6.8 and 11.3 mg per 1 g of the hernioprosthesis mesh. During this research we used guinea pigs to study the in vivo tissue reactions. The clinical part of the study included the group of 212 patients who underwent removal of an inguinal hernia. We have identified various factors associated with infectious and toxic effects on the body by determining the level of the serum glutamate-pyruvate-transaminase (SGPT. Results: In implantation of the hernioprostheses, including the high concentration of SN in the laparotomy wound, the exudative component of the inflammation was weakly expressed. It was mostly the proliferative changes that took place. We did not find either CD8-positive type T lymphocytes or PAX5-positive type B activated cells in the exudate. Conclusion: Our research has shown that the use of hernioprostheses that include silver nanoclusters leads to the reduction of inflammation in the exudative phase and to a more favorable course of reparative processes.

  18. Self-organization of nanocluster δ-layers at ion-beam-mixed Si-SiO2 interfaces

    International Nuclear Information System (INIS)

    Roentzsch, L.

    2003-11-01

    This diploma thesis presents experimental evidence of a theoretical concept which predicts the self-organization of δ-layers of silicon nanoclusters in the buried oxide of a MOS-like structure. This approach of ''bottom-up'' structuring might be of eminent importance in view of future semiconductor memory devices. Unconventionally, a 15 nm thin SiO 2 layer, which is enclosed by a 50 nm poly-Si capping layer and the Si substrate, is irradiated with Si + ions. Ion impact drives the system to a state far from thermodynamic equilibrium, i.e. the local composition of the target is modified to a degree unattainable in common processes. A region of SiO x (x 2 matrix at a distance of ∼3 nm from the Si substrate. The physical mechanisms of ion mixing of the two Si-SiO 2 interfaces and subsequent phase separation, which result in the desired sample structure, are elucidated from the viewpoint of computer simulations. In addition, experimental evidence is presented based on various methods, including TEM, RBS, and SIMS. A novel method of Si nanocluster decoration is of particular importance which applies Ge as contrast enhancing element in TEM studies of tiny Si nanoclusters. (orig.)

  19. NanoClusters Enhance Drug Delivery in Mechanical Ventilation

    Science.gov (United States)

    Pornputtapitak, Warangkana

    The overall goal of this thesis was to develop a dry powder delivery system for patients on mechanical ventilation. The studies were divided into two parts: the formulation development and the device design. The pulmonary system is an attractive route for drug delivery since the lungs have a large accessible surface area for treatment or drug absorption. For ventilated patients, inhaled drugs have to successfully navigate ventilator tubing and an endotracheal tube. Agglomerates of drug nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. This Thesis systematically investigated formulations of NanoClusters and their aerosol performance in a conventional inhaler and a device designed for use during mechanical ventilation. These engineered powders of budesonide (NC-Bud) were delivered via a MonodoseRTM inhaler or a novel device through commercial endotracheal tubes, and analyzed by cascade impaction. NC-Bud had a higher efficiency of aerosol delivery compared to micronized stock budesonide. The delivery efficiency was independent of ventilator parameters such as inspiration patterns, inspiration volumes, and inspiration flow rates. A novel device designed to fit directly to the ventilator and endotracheal tubing connections and the MonodoseRTM inhaler showed the same efficiency of drug delivery. The new device combined with NanoCluster formulation technology, therefore, allowed convenient and efficient drug delivery through endotracheal tubes. Furthermore, itraconazole (ITZ), a triazole antifungal agent, was formulated as a NanoCluster powder via milling (top-down process) or precipitation (bottom-up process) without using any excipients. ITZ NanoClusters prepared by wet milling showed better aerosol performance compared to micronized stock ITZ and ITZ NanoClusters prepared by precipitation. ITZ NanoClusters prepared by precipitation methods also showed an amorphous state

  20. New Ablation-Resistant Material Candidate for Hypersonic Applications: Synthesis, Composition, and Oxidation Resistance of HfIr3-Based Solid Solution.

    Science.gov (United States)

    Lozanov, Victor V; Baklanova, Natalya I; Bulina, Natalia V; Titov, Anatoly T

    2018-04-18

    The peculiarities of the solid-state interaction in the HfC-Ir system have been studied within the 1000-1600 °C temperature range using a set of modern analytical techniques. It was stated that the interaction of HfC with iridium becomes noticeable at temperatures as low as 1000-1100 °C and results in the formation of HfIr 3 -based substitutional solid solution. The homogeneity range of the HfIr 3± x phase was evaluated and refined as HfIr 2.43 -HfIr 3.36 . The durability of the HfIr 3 -based system under extreme environmental conditions was studied. It was shown that the HfIr 3 -based material displays excellent ablation resistance under extreme environmental conditions. The benefits of the new designed material result from its relative oxygen impermeability and special microstructure similar to superalloys. The results obtained in this work allow us to consider HfIr 3 as a very promising candidate for extreme applications.

  1. Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.

    Science.gov (United States)

    Chakraborty, Amrita; Fernandez, Ann Candice; Som, Anirban; Mondal, Biswajit; Natarajan, Ganapati; Paramasivam, Ganesan; Lahtinen, Tanja; Häkkinen, Hannu; Nonappa, Nonappa; Pradeep, Thalappil

    2018-04-01

    We present the self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs). Unlike highly sophisticated DNA nanotechnology, our approach demonstrates a strategically simple hydrogen bonding-directed self-assembly of nanoclusters leading to octahedral nanocrystals encapsulating GNRs. Specifically, we use the p-mercaptobenzoic acid (pMBA) protected atomically precise nanocluster, Na4[Ag44(pMBA)30] and pMBA functionalized GNRs. High resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H-bonding leading to octahedral symmetry. Further, use of water dispersible gold nanoclusters, Au~250(pMBA)n and Au102(pMBA)44 also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles present a new category of precision hybrids with diverse possibilities. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Oxidation of substituted alkyl radicals by IrCl62-, Fe(CN)63-, and MnO4- in aqueous solution. Electron transfer versus chlorine transfer from IrCl62-

    International Nuclear Information System (INIS)

    Steenken, S.; Neta, P.

    1982-01-01

    Alkyl radicals substituted at C/sub α/ by alkyl, carboxyl, hydroxyl, alkoxyl, and chlorine react in aqueous solutions with Ir/sup IV/Cl 6 2- to yield Ir(III) species. In the case of substitution by hydroxyl and alkoxyl, the rate constants are in the diffusion-controlled range ((4-6) x 10 9 M -1 s -1 ) and the reaction proceeds by electron transfer. In the case of ethyl, methyl, carboxymethyl, and chloromethyl radicals the rate constants range from 3.1 x 10 9 for ethyl to 2.8 x 10 7 M -1 s -1 for trichloromethyl and the reaction proceeds by chlorine transfer from IrCl 6 2- to the alkyl radical. With isopropyl and tert-butyll radicals the reaction proceeds by both electron and chlorine transfer. Alkyl radicals also react with Fe(CN) 6 3- . The rate constants increase strongly with increasing alkylation at C/sub α/ from 5 x 10 6 for methyl to 3.6 x 10 9 M -1 s -1 for tert-butyl, indicating that the transition state for the reaction is highly polar. Rate constants for reaction of MnO 4 - with alkyl radicals are of the order 10 9 M -1 s -1 . 4 figures, 1 table

  3. 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.

  4. Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?

    Energy Technology Data Exchange (ETDEWEB)

    Podhorodecki, A., E-mail: artur.p.podhorodecki@pwr.wroc.pl; Golacki, L. W.; Zatryb, G.; Misiewicz, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Wang, J.; Jadwisienczak, W. [School of EECS, Ohio University, Stocker Center 363, Athens, Ohio 45701 (United States); Fedus, K. [Institute of Physics, Nicholas Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland); Wojcik, J.; Wilson, P. R. J.; Mascher, P. [Department of Engineering Physics and Centre for Emerging Device Technologies, McMaster University, 1280 Main St. W, Hamilton, Ontario L8S4L7 (Canada)

    2014-04-14

    In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

  5. Gold nanoclusters with bright near-infrared photoluminescence.

    Science.gov (United States)

    Pramanik, Goutam; Humpolickova, Jana; Valenta, Jan; Kundu, Paromita; Bals, Sara; Bour, Petr; Dracinsky, Martin; Cigler, Petr

    2018-02-22

    The increase in nonradiative pathways with decreasing emission energy reduces the luminescence quantum yield (QY) of near-infrared photoluminescent (NIR PL) metal nanoclusters. Efficient surface ligand chemistry can significantly improve the luminescence QY of NIR PL metal nanoclusters. In contrast to the widely reported but modestly effective thiolate ligand-to-metal core charge transfer, we show that metal-to-ligand charge transfer (MLCT) can be used to greatly enhance the luminescence QY of NIR PL gold nanoclusters (AuNCs). We synthesized water-soluble and colloidally stable NIR PL AuNCs with unprecedentedly high QY (∼25%) upon introduction of triphenylphosphonium moieties into the surface capping layer. By using a combination of spectroscopic and theoretical methods, we provide evidence for gold core-to-ligand charge transfer occurring in AuNCs. We envision that this work can stimulate the development of these unusually bright AuNCs for promising optoelectronic, bioimaging, and other applications.

  6. DFT study of the structure, chemical ordering and molecular adsorption of Pd-Ir nanoalloys.

    Science.gov (United States)

    Fan, Tian-E; Demiroglu, Ilker; Hussein, Heider A; Liu, Tun-Dong; Johnston, Roy L

    2017-10-11

    The structures and surface adsorption sites of Pd-Ir nanoalloys are crucial to the understanding of their catalytic performance because they can affect the activity and selectivity of nanocatalysts. In this article, density functional theory (DFT) calculations are performed on bare Pd-Ir nanoalloys to systematically explore their stability and chemical ordering properties, before studying the adsorption of CO on the nanoalloys. First, the structural stability of 38-atom and 79-atom truncated octahedral (TO) Pd-Ir nanoalloys are investigated. Then the adsorption properties and preferred adsorption sites of CO on 38-atom Pd-Ir nanoalloys are considered. The Pd shell Ir core structure, which has the lowest energy of all the considered isomers, exhibits the highest structural stability, while the Pd core Ir shell configuration is the least stable. In addition, the adsorption strength of CO on Ir atoms is found to be greater than on Pd for Pd-Ir nanoclusters. The preferred adsorption sites of CO on pure Pd and Ir clusters are in agreement with calculations and experiments on extended Pd and Ir surfaces. In addition, d-band center and charge effects on CO adsorption strength on Pd-Ir nanoalloys are analyzed by comparison with pure clusters. The study provides a valuable theoretical insight into catalytically active Pd-Ir nanoalloys.

  7. GE NANOCLUSTERS IN PLANAR GLASS WAVEGUIDES DEPOSITED BY PECVD

    DEFF Research Database (Denmark)

    Haiyan, Ou; Olsen, Johnny H.; Rottwitt, Karsten

    2004-01-01

    . In this work we study the size and distribution of the nanoclusters by transmission electron microscopy (TEM) and Raman spectroscopy. The formation of the clusters is investigated by varying the Ge concentration in the glass and changing the annealing conditions such as temperature, atmosphere and time....... The combined effect of a strong nonlinear glass material and a material platform that is well known from standard planar lightwave components makes this Ge nanoclusters material very promising for optical nonlinear waveguide components that are readily fabricated by using the same processing as standard...

  8. Luminescent Metal Nanoclusters for Potential Chemosensor Applications

    Directory of Open Access Journals (Sweden)

    Muthaiah Shellaiah

    2017-12-01

    Full Text Available Studies of metal nanocluster (M-NCs-based sensors for specific analyte detection have achieved significant progress in recent decades. Ultra-small-size (<2 nm M-NCs consist of several to a few hundred metal atoms and exhibit extraordinary physical and chemical properties. Similar to organic molecules, M-NCs display absorption and emission properties via electronic transitions between energy levels upon interaction with light. As such, researchers tend to apply M-NCs in diverse fields, such as in chemosensors, biological imaging, catalysis, and environmental and electronic devices. Chemo- and bio-sensory uses have been extensively explored with luminescent NCs of Au, Ag, Cu, and Pt as potential sensory materials. Luminescent bi-metallic NCs, such as Au-Ag, Au-Cu, Au-Pd, and Au-Pt have also been used as probes in chemosensory investigations. Both metallic and bi-metallic NCs have been utilized to detect various analytes, such as metal ions, anions, biomolecules, proteins, acidity or alkalinity of a solution (pH, and nucleic acids, at diverse detection ranges and limits. In this review, we have summarized the chemosensory applications of luminescent M-NCs and bi-metallic NCs.

  9. H2 adsorption on free and graphene-supported Ni nanoclusters: A theoretical study

    Science.gov (United States)

    Farmanzadeh, Davood; Abdollahi, Tahereh

    2018-02-01

    Density functional theory (DFT) was used to investigate the applicability of the graphene-supported Nin nanoclusters as catalysts for the hydrogenation reaction. The adsorption and complete dissociation of the H2 on the Nin nanoclusters were investigated at the PBE-G/DNP level of theory. Accordingly, molecularly and dissociatively adsorbed hydrogens were seen on the Nin (n = 2-3) and Nin (n = 4-10) nanoclusters, respectively. The hydrogen adsorption on the Ni6 and Ni4 nanoclusters were more effective than other nanoclusters. Therefore, we investigated the hydrogen adsorption on the graphene-supported Ni2, Ni4 and Ni6 nanoclusters. The nanocluster adsorption energy on the graphene increased with the number of atoms in the nanocluster, whereas the adsorption energy per atom decreased. Hence, due to the stronger interactions of Ni-Ni than those of Ni-C, it seemed that the formation of nanoclusters on the graphene surface was favorable over the dispersion of the separate atoms. The results confirmed that the H2 was dissociatively adsorbed on the graphene-supported Ni4 and Ni6 nanoclusters, which can make them good candidates as catalysts.

  10. Fluxible nanoclusters of Fe3O4 nanocrystal-embedded polyaniline by macromolecule-induced self-assembly.

    Science.gov (United States)

    Huang, Jing; Li, Qi; Li, Denian; Wang, Yue; Dong, Lijie; Xie, Haian; Wang, Jun; Xiong, Chuanxi

    2013-08-13

    We have prepared Fe3O4 nanocrystal-embedded polyaniline hybrids with well-defined cluster-like morphology through macromolecule-induced self-assembly. These magnetic and electrically conductive composite nanoclusters show flowability at room temperature in the absence of any solvent, which offers great potential in applications such as microwave absorbents and electromagnetic shielding coatings. This macromolecule-induced self-assembly strategy can be readily applied on the fabrication of other ion oxide/conjugated polymer composites to achieve robust multifunctional materials.

  11. Ultrafast coherence transfer in DNA-templated silver nanoclusters

    DEFF Research Database (Denmark)

    Thyrhaug, Erling; Bogh, Sidsel Ammitzbøll; Carro, Miguel

    2017-01-01

    DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure...

  12. Pinning of size-selected Pd nanoclusters on graphite

    NARCIS (Netherlands)

    Gibilisco, S.; Di Vece, M.; Palomba, S.; Faraci, G.; Palmer, R.E.

    2006-01-01

    The production of stable cluster arrays on smooth surfaces has several potential technological applications. We report a study of the pinning of size-selected palladium nanoclusters on the graphite surface. The clusters formed during gas aggregation in vacuum are projected with sufficient kinetic

  13. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    Stable nanoclusters of Cu were synthesized using Langmuir–Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas.

  14. An oscillator based on a single Au nanocluster

    Science.gov (United States)

    Gorshkov, O. N.; Filatov, D. O.; Antonov, D. A.; Antonov, I. N.; Shenina, M. E.; Pavlov, D. A.

    2017-01-01

    Metal nanoclusters embedded into the ultrathin dielectric films attracted much attention in recent years due to their unusual electronic, optical, etc., properties differing from those of the bulk metals essentially and, hence, to the prospects of their applications in novel nanoelectronic, single electronic, non-volatile memory, etc., devices. Here, we report on the experimental observation of the electrical oscillations in an oscillating loop connected to a contact of a conductive probe of an Atomic Force Microscope to a tunnel-transparent ( ˜6.5 nm thick) yttria stabilized zirconia film with embedded Au nanoclusters on the Si substrate. The oscillations were attributed to the negative differential resistance of the probe-to-sample contact originating from the resonant electron tunnelling between the probe and the Si substrate via the quantum confined electron energy levels in small ( ≈2.5 nm in diameter) Au nanoclusters. This observation demonstrates the prospects of building an oscillator nanoelectronic device based on an individual nanometer-sized metal nanocluster.

  15. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    Unknown

    Organization of copper nanoclusters in Langmuir–Blodgett films ... A number of methods have been employed for preparing metallic nano- .... Work is pre- sently underway to investigate such films. Acknowledgement. The authors would like to thank the Department of. Science and Technology, New Delhi, for a project grant.

  16. Platinum-gold nanoclusters as catalyst for direct methanol fuel cells.

    Science.gov (United States)

    Giorgi, L; Giorgi, R; Gagliardi, S; Serra, E; Alvisi, M; Signore, M A; Piscopiello, E

    2011-10-01

    Nanosized platinum-gold alloys clusters have been deposited on gas diffusion electrode by sputter deposition. The deposits were characterized by FE-SEM, TEM and XPS in order to verify the formation of alloy nanoparticles and to study the influence of deposition technique on the nanomorphology. The deposition by sputtering process allowed a uniform distribution of metal particles on porous surface of carbon supports. Typical island growth mode was observed with the formation of a dispersed metal nanoclusters (mean size about 5 nm). Cyclic voltammetry was used to determine the electrochemical active surface and the electrocatalytic performance of the PtAu electrocatalysts for methanol oxidation reaction. The data were re-calculated in the form of mass specific activity (MSA). The sputter-catalyzed electrodes showed higher performance and stability compared to commercial catalysts.

  17. Laminated Copper Nanocluster Incorporated Antioxidative Paper Device with RGB System-Assisted Signal Improvement

    Directory of Open Access Journals (Sweden)

    Chong-You Chen

    2018-02-01

    Full Text Available Paper-based analytical devices are an emerging class of lightweight and simple-to-use analytical platform. However, challenges such as instrumental requirements and chemical reagents durability, represent a barrier for less-developed countries and markets. Herein, we report an advanced laminated device using red emitting copper nanocluster and RGB digital analysis for signal improvement. Upon RGB system assistance, the device signal-to-background ratio and the calibration sensitivity are highly enhanced under a filter-free setup. In addition, the calibration sensitivity, limit of detection, and coefficient of determination are on par with those determined by instrumental fluorescence analysis. Moreover, the limitation of using oxidation-susceptible fluorescent nanomaterials is overcome by the introduction of protecting tape barriers, antioxidative sheets, and lamination enclosing. The robustness of device is highly advanced, and the durability is prolonged to more than tenfold.

  18. Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Halder, A.; Chattopadhyay, R.; Majumder, S.; Paul, M. C.; Das, S.; Bhadra, S. K., E-mail: skbhadra@cgcri.res.in [Fiber Optics and Photonics Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India); Bysakh, S.; Unnikrishnan, M. [Material Characterization Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India)

    2015-01-05

    An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

  19. Microscopic Fuel Particles Produced by Self-Assembly of Actinide Nanoclusters on Carbon Nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Na, Chongzheng [Univ. of Notre Dame, IN (United States)

    2016-10-17

    Many consider further development of nuclear power to be essential for sustained development of society; however, the fuel forms currently used are expensive to recycle. In this project, we sought to create the knowledge and knowhow that are needed to produce nanocomposite materials by directly depositing uranium nanoclusters on networks of carbon-­ based nanomaterials. The objectives of the proposed work were to (1) determine the control of uranium nanocluster surface chemistry on nanocomposite formation, (2) determine the control of carbon nanomaterial surface chemistry on nanocomposite formation, and (3) develop protocols for synthesizing uranium-­carbon nanomaterials. After examining a wide variety of synthetic methods, we show that synthesizing graphene-­supported UO2 nanocrystals in polar ethylene glycol compounds by polyol reduction under boiling reflux can enable the use of an inexpensive graphene precursor graphene oxide in the production of uranium-carbon nanocomposites in a one-­pot process. We further show that triethylene glycol is the most suitable solvent for producing nanometer-­sized UO2 crystals compared to monoethylene glycol, diethylene glycol, and polyethylene glycol. Graphene-­supported UO2 nanocrystals synthesized with triethylene glycol show evidence of heteroepitaxy, which can be beneficial for facilitating heat transfer in nuclear fuel particles. Furthermore, we show that graphene-supported UO2 nanocrystals synthesized by polyol reduction can be readily stored in alcohols, preventing oxidation from the prevalent oxygen in air. Together, these methods provide a facile approach for preparing and storing graphene-supported UO nanocrystals for further investigation and development under ambient conditions.

  20. Hydrophilic magnetic nanoclusters with thermo-responsive properties and their drug controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Meerod, Siraprapa [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Rutnakornpituk, Boonjira; Wichai, Uthai [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Center of Excellence in Biomaterials, Faculty of Science, Naresuan University, Phitsanulok 65000 Thailand (Thailand); Rutnakornpituk, Metha, E-mail: methar@nu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Center of Excellence in Biomaterials, Faculty of Science, Naresuan University, Phitsanulok 65000 Thailand (Thailand)

    2015-10-15

    Synthesis and drug controlled release properties of thermo-responsive magnetic nanoclusters grafted with poly(N-isopropylacrylamide) (poly(NIPAAm)) and poly(NIPAAm-co-poly(ethylene glycol) methyl ether methacrylate) (PEGMA) copolymers were described. These magnetic nanoclusters were synthesized via an in situ radical polymerization in the presence of acrylamide-grafted magnetic nanoparticles (MNPs). Poly(NIPAAm) provided thermo-responsive properties, while PEGMA played a role in good water dispersibility to the nanoclusters. The ratios of PEGMA to NIPAAm in the (co)polymerization in the presence of the MNPs were fine-tuned such that the nanoclusters with good water dispersibility, good magnetic sensitivity and thermo responsiveness were obtained. The size of the nanoclusters was in the range of 50–100 nm in diameter with about 100–200 particles/cluster. The nanoclusters were well dispersible in water at room temperature and can be suddenly agglomerated when temperature was increased beyond the lower critical solution temperature (LCST) (32 °C). The release behavior of an indomethacin model drug from the nanoclusters was also investigated. These novel magnetic nanoclusters with good dispersibility in water and reversible thermo-responsive properties might be good candidates for the targeting drug controlled release applications. - Highlights: • Nanoclusters with good water dispersibility and magnetic response were prepared. • They were grafted with thermo-responsive poly(NIPAAm) and/or poly(PEGMA). • Poly(NIPAAm) provided thermo-responsive properties to the nanoclusters. • Poly(PEGMA) provided good water dispersibilityto the nanoclusters. • Accelerated and controllable releases of a drug from the nanoclusters were shown.

  1. Formation of bimetallic Ag-Pd nanoclusters via the reaction between Ag nanoclusters and Pd2+ ions.

    Science.gov (United States)

    Chen, Ching-Hsiang; Sarma, Loka Subramanyam; Wang, Guo-Rung; Chen, Jiun-Ming; Shih, Shou-Chu; Tang, Mau-Tsu; Liu, Ding-Goa; Lee, Jyh-Fu; Chen, Jing-Ming; Hwang, Bing-Joe

    2006-06-01

    We have investigated systematically the mechanistic aspects of the Ag-Pd bimetallic cluster formation within sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles by using in-situ X-ray absorption spectroscopy (XAS). A two-step sequential reduction method is employed for the synthesis of Ag-Pd bimetallic clusters. The first step involves preparation of Ag nanoclusters, by mixing the Ag+ ions containing the AOT microemulsion system with a reducing agent hydrazine (N2H4) containing the AOT microemulsion system. In the second step, the addition of Pd2+ ions to Ag nanoclusters led to the formation of Ag-Pd bimetallic clusters via the reaction between Ag nanoclusters and Pd2+ ions in AOT reverse micelles. The reduction of silver ions and the formation of corresponding Ag nanoclusters are monitored as a function of the dosage of the reducing agent, hydrazine. In-situ XAS allowed probing of the reaction between Ag nanoclusters and Pd2+ ions during the formation of Ag-Pd bimetallic clusters. Analysis of Ag and Pd K-edge XAS spectra reveals that in the final stage Ag-Pd clusters, in which "Ag" atoms prefer to be surrounded by "Pd" and "Pd" atoms prefer to be surrounded by "Pd", were formed. On the basis of XAS results presented here, we are able to propose a structural model for each step so that this work provides a detailed insight into the mechanism of nucleation and growth of Ag-Pd bimetallic clusters. We also discussed the atomic distribution of Ag and Pd atoms in Ag-Pd bimetallic clusters based on the calculated XAS structural parameters.

  2. Size-dependent structure of CdSe nanoclusters formed after ion implantation in MgO

    NARCIS (Netherlands)

    van Huis, MA; van Veen, A; Schut, H; Eijt, SWH; Kooi, BJ; De Hosson, JTM

    The band gap as well as the optical and structural properties of semiconductor CdSe nanoclusters change as a function of the nanocluster size. Embedded CdSe nanoclusters in MgO were created by means of sequential Cd and Se ion implantation followed by thermal annealing. Changes during annealing were

  3. Size Dependence of Atomically Precise Gold Nanoclusters in Chemoselective Hydrogenation and Active Site Structure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gao [Carnegie Mellon University (CMU); Jiang, Deen [ORNL; Kumar, Santosh [Carnegie Mellon University (CMU); Chen, Yuxiang [Carnegie Mellon University (CMU); Jin, Rongchao [Carnegie Mellon University (CMU)

    2014-01-01

    We here investigate the catalytic properties of water-soluble Aun(SG)m nanocluster catalysts (H-SG = glutathione) of different sizes, including Au15(SG)13, Au18(SG)14, Au25(SG)18, Au38(SG)24, and captopril-capped Au25(Capt)18 nanoclusters. These Aun(SR)m nanoclusters (-SR represents thiolate generally) are used as homogeneous catalysts (i.e., without supports) in the chemoselective hydrogenation of 4-nitrobenzaldehyde (4-NO2PhCHO) to 4-nitrobenzyl alcohol (4-NO2PhCH2OH) in water with H2 gas (20 bar) as the hydrogen source. These nanocluster catalysts, except Au18(SG)14, remain intact after the catalytic reaction, evidenced by UV-vis spectra which are characteristic of each sized nanoclusters and thus serve as spectroscopic fingerprints . We observe a drastic size-dependence and steric effect of protecting ligands on the gold nanocluster catalysts in the hydrogenation reaction. Density functional theory (DFT) modeling of the 4-nitrobenzaldehyde adsorption shows that both the CHO and NO2 groups are in close interact with the S-Au-S staples on the gold nanocluster surface; the adsorption of the 4-nitrobenzaldehyde molecule on the four different sized Aun(SR)m nanoclusters are moderately strong and similar in strength. The DFT results suggest that the catalytic activity of the Aun(SR)m nanoclusters is primarily determined by the surface area of the Au nanocluster, consistent with the observed trend of the conversion of 4-nitrobenzaldehyde versus the cluster size. Overall, this work offers the molecular insight into the hydrogenation of 4-nitrobenzaldehyde and the catalytically active site structure on gold nanocluster catalysts.

  4. Size effect on the adsorption and dissociation of CO{sub 2} on Co nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haiyan; Cao, Dapeng; Fisher, Adrian [International Research Center for Soft Matter, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Johnston, Roy L. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Cheng, Daojian, E-mail: chengdj@mail.buct.edu.cn [International Research Center for Soft Matter, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China)

    2017-02-28

    Highlights: • Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters were predicted as the high-symmetry structures. • CO{sub 2} dissociation on the size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters was studied. • Co{sub 55} nanocluster possesses the highest activity relevant to CO{sub 2} dissociation. • A non-monotonous behavior of the dissociation barrier of CO{sub 2} with the size was found. - Abstract: Spin-polarized density functional theory calculations were carried out to study the adsorption and dissociation properties of CO{sub 2} on size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters. Based on genetic algorithm method, Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters were predicted as the most stable high-symmetry structures among these Co{sub n} (n = 2–58) nanoclusters from the Gupta potential. For the adsorption of CO{sub 2}, CO and O on size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters, the lowest adsorption strength is found for all the different adsorbates on Co{sub 55} nanocluster. For the dissociation of CO{sub 2} on these size-selected Co nanoclusters, the largest Co{sub 55} nanocluster possesses the greatest catalytic activity for the dissociation of CO{sub 2}, with the smallest reaction barrier of 0.38 eV. Our results reveal a non-monotonous behavior of the catalytic activities of Co nanoclusters on size, which is of fundamental interest for the design of new Co catalysts for the conversion of CO{sub 2}.

  5. The expanding universe of thiolated gold nanoclusters and beyond.

    Science.gov (United States)

    Jiang, De-en

    2013-08-21

    Thiolated gold nanoclusters form a universe of their own. Researchers in this field are constantly pushing the boundary of this universe by identifying new compositions and in a few "lucky" cases, solving their structures. Such solved structures, even if there are only few, provide important hints for predicting the many identified compositions that are yet to be crystallized or structure determined. Structure prediction is the most pressing issue for a computational chemist in this field. The success of the density functional theory method in gauging the energetic ordering of isomers for thiolated gold clusters has been truly remarkable, but to predict the most stable structure for a given composition remains a great challenge. In this feature article from a computational chemist's point of view, the author shows how one understands and predicts structures for thiolated gold nanoclusters based on his old and new results. To further entertain the reader, the author also offers several "imaginative" structures, claims, and challenges for this field.

  6. Luminescent metal nanoclusters: controlled synthesis and functional applications

    Directory of Open Access Journals (Sweden)

    Hong-Tao Sun

    2014-04-01

    Full Text Available Luminescent metal nanoclusters that consist of only several, to tens of, metal atoms and which possess sizes comparable to the Fermi wavelength of electrons have recently attracted significant attention. This new class of luminescent materials not only provides the missing link between atomic and nanoparticle behaviors in metals but also they present abundant novel information for the development of new applicable material systems to meet urgent needs in many areas (such as ultrasensitive sensors for heavy metals, bioimaging, as well as information technology mainly because of their attractive characteristics, including ultra-small size, good dispersibility, excellent biocompatibility and photostability. In this review, we summarize recent advances in the controlled synthesis and application of luminescent metal nanoclusters, with a particular emphasis on Pt, Mo, Bi and alloy clusters. We also speculate on their future and discuss potential developments for their use in sensors, bioimaging and energy harvesting and conversion.

  7. Luminescent metal nanoclusters: controlled synthesis and functional applications

    Science.gov (United States)

    Sun, Hong-Tao; Sakka, Yoshio

    2014-02-01

    Luminescent metal nanoclusters that consist of only several, to tens of, metal atoms and which possess sizes comparable to the Fermi wavelength of electrons have recently attracted significant attention. This new class of luminescent materials not only provides the missing link between atomic and nanoparticle behaviors in metals but also they present abundant novel information for the development of new applicable material systems to meet urgent needs in many areas (such as ultrasensitive sensors for heavy metals, bioimaging, as well as information technology) mainly because of their attractive characteristics, including ultra-small size, good dispersibility, excellent biocompatibility and photostability. In this review, we summarize recent advances in the controlled synthesis and application of luminescent metal nanoclusters, with a particular emphasis on Pt, Mo, Bi and alloy clusters. We also speculate on their future and discuss potential developments for their use in sensors, bioimaging and energy harvesting and conversion.

  8. Luminescent metal nanoclusters: controlled synthesis and functional applications

    OpenAIRE

    Sun, Hong-Tao; Sakka, Yoshio

    2013-01-01

    Luminescent metal nanoclusters that consist of only several, to tens of, metal atoms and which possess sizes comparable to the Fermi wavelength of electrons have recently attracted significant attention. This new class of luminescent materials not only provides the missing link between atomic and nanoparticle behaviors in metals but also they present abundant novel information for the development of new applicable material systems to meet urgent needs in many areas (such as ultrasensitive sen...

  9. Theory of Nanocluster Size Distributions from Ion Beam Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-06-13

    Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.

  10. Ruthenium(0) nanoclusters stabilized by a Nanozeolite framework: isolable, reusable, and green catalyst for the hydrogenation of neat aromatics under mild conditions with the unprecedented catalytic activity and lifetime.

    Science.gov (United States)

    Zahmakiran, Mehmet; Tonbul, Yalçin; Ozkar, Saim

    2010-05-12

    The hydrogenation of aromatics is a ubiquitous chemical transformation used in both the petrochemical and specialty industry and is important for the generation of clean diesel fuels. Reported herein is the discovery of a superior heterogeneous catalyst, superior in terms of catalytic activity, selectivity, and lifetime in the hydrogenation of aromatics in the solvent-free system under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure). Ruthenium(0) nanoclusters stabilized by a nanozeolite framework as a new catalytic material is reproducibly prepared from the borohydride reduction of a colloidal solution of ruthenium(III)-exchanged nanozeolites at room temperature and characterized by using ICP-OES, XRD, XPS, DLS, TEM, HRTEM, TEM/EDX, mid-IR, far-IR, and Raman spectroscopy. The resultant ruthenium(0) nanoclusters hydrogenate neat benzene to cyclohexane with 100% conversion under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure) with record catalytic activity (initial TOF = 5430 h(-1)) and lifetime (TTO = 177 200). They provide exceptional catalytic activity not only in the hydrogenation of neat benzene but also in the solvent-free hydrogenation of methyl substituted aromatics such as toluene, o-xylene, and mesitylene under otherwise identical conditions. Moreover, they are an isolable, bottleable, and reusable catalyst in the hydrogenation of neat aromatics. When the isolated ruthenium(0) nanoclusters are reused, they retain 92% of their initial catalytic activity even for the third run in the hydrogenation of neat benzene under the same conditions as those of the first run. The work reported here also includes (i) far-infrared spectroscopic investigation of nanozeolite, ruthenium(III)-exchanged-nanozeolite, and ruthenium(0) nanoclusters stabilized by a nanozeolite framework, indicating that the host framework remains intact after the formation of a nanozeolite framework stabilized ruthenium(0) nanoclusters; (ii) the

  11. Synthesis and catalytic properties of metal and semiconductor nanoclusters

    Science.gov (United States)

    Wilcoxon, J. P.; Martino, T.; Klavetter, E.; Sylwester, A. P.

    Synthesis of metal or semiconductor nanoclusters in microheterogeneous oil-continuous inverse micelle systems is discussed. We focus on synthesis and catalytic properties of palladium, iron, and iron sulfide nanoclusters. Cluster size-control is achieved by changing the micelle size which is determined by small angle neutron scattering (SANS) and chosen to produce cluster in size range of 1-20 nm. Cluster sizes were determined by either transmission electron microscopy (TEM) or small-angle x-ray scattering (SAXS). Cluster structure was determined by either x-ray or electron diffraction. In the case of Fe nanoclusters, the crystal structure depended on the chemical nature of the surfactant micelle used in the synthesis, illustrating the important role of the surfactant during the growth process. Results of in-situ pyrene hydrogenation using size-selected Pd clusters show a significant increase in activity/total surface area as the size decreases. These clusters also proved effective as unsupported catalysts for direct coal hydropyrolysis, even at very low metal concentrations. Synthesis and optical features of a new semiconductor cluster material, FeS2, are discussed with regard to its use in photocatalysis. Application of FeS2 in coal hydrogenolysis reactions has improved yields of short chain hydrocarbons significantly compared to conventional FeS2 powders.

  12. Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities.

    Science.gov (United States)

    Jin, Rongchao; Zeng, Chenjie; Zhou, Meng; Chen, Yuxiang

    2016-09-28

    Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1-3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the stability, metal-ligand interfacial bonding, ligand assembly on particle surfaces, aesthetic structural patterns, periodicities, and emergence of the metallic state) and to develop a range of potential applications such as in catalysis, biomedicine, sensing, imaging, optics, and energy conversion. Although most of the research activity currently focuses on thiolate-protected gold nanoclusters, important progress has also been achieved in other ligand-protected gold, silver, and bimetal (or alloy) nanoclusters. All of these types of unique nanoparticles will bring unprecedented opportunities, not only in understanding the fundamental questions of nanoparticles but also in opening up new horizons for scientific studies of nanoparticles.

  13. Ge nanoclusters in PECVD-deposited glass after heat treating and electron irradiation

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rørdam, Troels Peter; Rottwitt, Karsten

    2007-01-01

    This paper reports the formation of Ge nanoclusters in silica glass thin films deposited by plasma-enhanced chemical vapor deposition (PECVD). We studied the samples by transmission electron microscopy (TEM) and Raman spectroscopy after annealing. TEM investigation shows that the Ge nanoclusters...

  14. Size and Structure of Cytochrome-c bound to Gold nano-clusters ...

    Indian Academy of Sciences (India)

    CATHERINE GHOSH

    Protein-protected fluorescent metal nano-clusters have been widely used for cell imaging,13,17 and intra- cellular drug and protein delivery.14,18 20 Recently, we have used cytochrome c-protected gold nano-cluster. (AuNC) to deliver cytochrome c (Cyt C) inside live cells.19 Also, we have used lysozyme-protected AuNC.

  15. Evidence of Energy Transfer from Tryptophan to BSA/HSA Protected Gold Nanoclusters.

    Science.gov (United States)

    Raut, Sangram; Chib, Rahul; Butler, Susan; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2014-09-01

    This work reports on the chromophores interactions within protein-protected gold nanoclusters. We conducted spectroscopic studies of fluorescence emissions originated from gold nanoclusters and intrinsic tryptophan (Trp) in BSA or HSA proteins. Both, steady state fluorescence and lifetime measurements show a significant Forster resonance energy transfer (FRET) from Trp to the gold nanocluster. Tryptophan lifetimes in the case of protein-protected gold nanoclusters are 2.6ns and 2.3ns for BSA and HSA Au clusters while 5.8ns for native BSA and 5.6 for native HSA. The apparent distances from Trp to gold nanocluster emission center, we estimated as 24.75A 0 for BSA and 23.80A 0 for HSA. We also studied a potassium iodide (KI) quenching of protein-protected gold nanoclusters and compared with the quenching of BSA and HAS alone. The rates of Trp quenching were smaller in BSA-Au and HSA-Au nanoclusters than in the case of free proteins, which is consistent with shorter lifetime of quenched Trp(s) and lower accessibility for KI. While Trp residues were quenched by KI, the emissions originated from nanoclusters were practically unquenched. In summary, for BSA and HSA Au clusters, we found 55% and 59% energy transfer efficiency respectively from tryoptophan to gold clusters. We believe this interaction can be used to our advantage in terms of developing resonance energy transfer based sensing applications.

  16. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Maninder; Dai, Qilin; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao; Tang, Jinke; Qiang, You

    2013-01-01

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr2O3 and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (rv25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of r-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs. The giant magnetoresistance (GMR) effect,1,2 where an antiferromagnetic (AFM) exchange coupling exists between two ferromagnetic (FM) layers separated by a certain type of magnetic or non-magnetic spacer,3 has significant potential for application in the magnetic recording industry. Soon after the discovery of the GMR, the magnetic properties of multilayer systems (FeCr) became a subject of intensive study. The application of bulk iron-chromium (Fe-Cr) alloys has been of great interest, as these alloys exhibit favorable prop- erties including corrosion resistance, high strength, hardness, low oxidation rate, and strength retention at elevated temper- ature. However, the structural and magnetic properties of Cr-doped Fe nanoclusters (NCs) have not been investigated in-depth. Of all NCs, Fe-based clusters have unique magnetic properties as well as favorable catalytic characteristics in reactivity, selectivity, and durability.4 The incorporation of dopant of varied type and concentration in Fe can modify its chemical ordering, thereby optimizing its electrical, optical, and magnetic properties and opening up many new applications. The substitution of an Fe atom (1.24 A°) by a Cr atom (1.25 A° ) can easily modify the magnetic properties, since (i) the curie temperature (Tc ) of Fe is 1043 K, while Cr is an itinerant AFM with a bulk Neel temperature TN =311 K, and (ii) Fe

  17. Magnetic and electrical properties of quadruple perovskites with 12 layer structures Ba4LnM3O12 (Ln=rare earths; M=Ru, Ir): The role of metal-metal bonding in perovskite-related oxides

    International Nuclear Information System (INIS)

    Shimoda, Yuki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio

    2010-01-01

    Structures and magnetic and electrical properties of quadruple perovskites containing rare earths Ba 4 LnM 3 O 12 (Ln=rare earths; M=Ru, Ir) were investigated. They crystallize in the 12L-perovskite-type structure. Three MO 6 octahedra are connected to each other by face-sharing and form a M 3 O 12 trimer. The M 3 O 12 trimers and LnO 6 octahedra are alternately linked by corner-sharing, forming the perovskite-type structure with 12 layers. For Ln=Ce, Pr, and Tb, both the Ln and M ions are in the tetravalent state (Ba 4 Ln 4+ M 4+ 3 O 12 ), and for other Ln ions, Ln ions are in the trivalent state and the mean oxidation state of M ions is +4.33 (Ba 4 Ln 3+ M 4.33+ 3 O 12 ). All the Ba 4 Ln 3+ Ru 4.33+ 3 O 12 compounds show magnetic ordering at low temperatures, while any of the corresponding iridium-containing compounds Ba 4 Ln 3+ Ir 4.33+ 3 O 12 is paramagnetic down to 1.8 K. Ba 4 Ce 4+ Ir 4+ 3 O 12 orders antiferromagnetically at 10.5 K, while the corresponding ruthenium-containing compound Ba 4 Ce 4+ Ru 4+ 3 O 12 is paramagnetic. These magnetic results were well understood by the magnetic behavior of M 3 O 12 . The effective magnetic moments and the entropy change for the magnetic ordering show that the trimers Ru 4.33+ 3 O 12 and Ir 4+ 3 O 12 have the S=1/2 ground state, and in other cases there is no magnetic contribution from the trimers Ru 4+ 3 O 12 or Ir 4.33+ 3 O 12 . Measurements of the electrical resistivity of Ba 4 LnM 3 O 12 and its analysis show that these compounds demonstrate two-dimensional Mott-variable range hopping behavior. - Graphical abstract: Structures and magnetic and electrical properties of quadruple perovskites containing rare earths Ba 4 LnM 3 O 12 (Ln=rare earths; M = Ru, Ir) were investigated. They crystallize in the 12L-perovskite-type structure. All the Ba 4 Ln 3+ Ru 4.33+ 3 O 12 compounds show magnetic ordering at low temperatures, while any of the corresponding iridium-containing compounds Ba 4 Ln 3+ Ir 4.33+ 3 O 12 is

  18. Synthesis and Doping of Ligand-Protected Atomically-Precise Metal Nanoclusters

    KAUST Repository

    Aljuhani, Maha A.

    2016-05-01

    Rapidly expanding research in nanotechnology has led to exciting progress in a versatile array of applications from medical diagnostics to catalysis. This success resulted from the manipulation of the desired properties of nanomaterials by controlling their size, shape, and composition. Among the most thriving areas of research about nanoparticle is the synthesis and doping of the ligand-protected atomically-precise metal nanoclusters. In this thesis, we developed three different novel metal nanoclusters, such as doped Ag29 with five gold (Au) atoms leading to enhance its quantum yield with remarkable stability. We also developed half-doped (alloyed) cluster of Ni6 nanocluster with molybdenum (Mo). This enabled enhanced stability and better catalytic activity. The third metal nanocluster that we synthesized was Au28 nanocluster by using di-thiolate as the ligand stabilizer instead of mono-thiolate. The new metal clusters obtained have been characterized by spectroscopic, electrochemical and crystallographic methods.

  19. Pt, Co–Pt and Fe–Pt alloy nanoclusters encapsulated in virus capsids

    International Nuclear Information System (INIS)

    Okuda, M; Eloi, J-C; Jones, S E Ward; Schwarzacher, W; Verwegen, M; Cornelissen, J J L M

    2016-01-01

    Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl 4 ] − by NaBH 4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co–Pt and Fe–Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid. (paper)

  20. A Comparative XAFS Study of Gold-thiolate Nanoparticles and Nanoclusters

    International Nuclear Information System (INIS)

    Chevrier, D M; Chatt, A; Zhang, P; Sham, T K

    2013-01-01

    Tiopronin-capped gold nanoparticles and gold nanoclusters of sizes 3.0 and 1.5 nm, respectively, were investigated with XAFS at the gold L 3 -edge. The specific EXAFS fitting procedure is discussed for obtaining reliable fit parameters for each system. The difficulties and challenges faced when analysing EXAFS data for gold nanoparticles and nanoclusters are also mentioned. Fitting results for gold nanoparticles reveal a small amount of surface Au-thiolate interactions with a large Au-Au metal core. For gold nanoclusters, only a one-shell fit was obtainable. Instead of Au-Au metal core, long-range interactions are expected for gold nanoclusters. Tiopronin-capped gold nanoclusters are proposed to be polymeric in nature, which helps explain the observed red luminescence.

  1. Two-Way Transformation between fcc- and Nonfcc-Structured Gold Nanoclusters.

    Science.gov (United States)

    Dong, Hongwei; Liao, Lingwen; Wu, Zhikun

    2017-11-02

    Precisely tuning the structure of nanomaterials, especially in a two-way style, is challenging but of great importance for regulating properties and for practical applications. The structural transformation from nonfcc to fcc (face center cubic) in gold nanoclusters has been recently reported; however, the reverse process, that is, the structural transformation from fcc to nonfcc, not to mention the two-way structural transformation between fcc and nonfcc, remains unknown. We developed a novel synthesis method, successfully fulfilled the two-way structure transformation, and studied the stability of gold nanoclusters with different structures. Additionally, a novel gold nanocluster was synthesized and structurally resolved by single-crystal X-ray crystallography. This work has important implications for structure and property tuning of gold nanoclusters and might open up some new potential applications for gold nanoclusters.

  2. Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

    International Nuclear Information System (INIS)

    Kenyon, A. J.; Wojdak, M.; Ahmad, I.; Loh, W. H.; Oton, C. J.

    2008-01-01

    We discuss the use of rate equations to analyze the sensitization of erbium luminescence by silicon nanoclusters. In applying the general form of second-order coupled rate-equations to the Si nanocluster-erbium system, we find that the photoluminescence dynamics cannot be described using a simple rate equation model. Both rise and fall times exhibit a stretched exponential behavior, which we propose arises from a combination of a strongly distance-dependent nanocluster-erbium interaction, along with the finite size distribution and indirect band gap of the silicon nanoclusters. Furthermore, the low fraction of erbium ions that can be excited nonresonantly is a result of the small number of ions coupled to nanoclusters

  3. Colloidal Gold Nanoclusters Spiked Silica Fillers in Mixed Matrix Coatings: Simultaneous Detection and Inhibition of Healthcare-Associated Infections.

    Science.gov (United States)

    Alsaiari, Shahad K; Hammami, Mohammed A; Croissant, Jonas G; Omar, Haneen W; Neelakanda, Pradeep; Yapici, Tahir; Peinemann, Klaus-Viktor; Khashab, Niveen M

    2017-03-01

    Healthcare-associated infections (HAIs) are the infections that patients get while receiving medical treatment in a medical facility with bacterial HAIs being the most common. Silver and gold nanoparticles (NPs) have been successfully employed as antibacterial motifs; however, NPs leaching in addition to poor dispersion and overall reproducibility are major hurdles to further product development. In this study, the authors design and fabricate a smart antibacterial mixed-matrix membrane coating comprising colloidal lysozyme-templated gold nanoclusters as nanofillers in poly(ethylene oxide)/poly(butylene terephthalate) amphiphilic polymer matrix. Mesoporous silica nanoparticles-lysozyme functionalized gold nanoclusters disperse homogenously within the polymer matrix with no phase separation and zero NPs leaching. This mixed-matrix coating can successfully sense and inhibit bacterial contamination via a controlled release mechanism that is only triggered by bacteria. The system is coated on a common radiographic dental imaging device (photostimulable phosphor plate) that is prone to oral bacteria contamination. Variation and eventually disappearance of the red fluorescence surface under UV light signals bacterial infection. Kanamycin, an antimicrobial agent, is controllably released to instantly inhibit bacterial growth. Interestingly, the quality of the images obtained with these coated surfaces is the same as uncoated surfaces and thus the safe application of such smart coatings can be expanded to include other medical devices without compromising their utility. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Colloidal Gold Nanoclusters Spiked Silica Fillers in Mixed Matrix Coatings: Simultaneous Detection and Inhibition of Healthcare-Associated Infections

    KAUST Repository

    Alsaiari, Shahad K.

    2017-01-25

    Healthcare-associated infections (HAIs) are the infections that patients get while receiving medical treatment in a medical facility with bacterial HAIs being the most common. Silver and gold nanoparticles (NPs) have been successfully employed as antibacterial motifs; however, NPs leaching in addition to poor dispersion and overall reproducibility are major hurdles to further product development. In this study, the authors design and fabricate a smart antibacterial mixed-matrix membrane coating comprising colloidal lysozyme-templated gold nanoclusters as nanofillers in poly(ethylene oxide)/poly(butylene terephthalate) amphiphilic polymer matrix. Mesoporous silica nanoparticles-lysozyme functionalized gold nanoclusters disperse homogenously within the polymer matrix with no phase separation and zero NPs leaching. This mixed-matrix coating can successfully sense and inhibit bacterial contamination via a controlled release mechanism that is only triggered by bacteria. The system is coated on a common radiographic dental imaging device (photostimulable phosphor plate) that is prone to oral bacteria contamination. Variation and eventually disappearance of the red fluorescence surface under UV light signals bacterial infection. Kanamycin, an antimicrobial agent, is controllably released to instantly inhibit bacterial growth. Interestingly, the quality of the images obtained with these coated surfaces is the same as uncoated surfaces and thus the safe application of such smart coatings can be expanded to include other medical devices without compromising their utility.

  5. Preparation of Cu Nanoclusters within Dendrimer Templates

    National Research Council Canada - National Science Library

    Zhao, M

    1998-01-01

    ... (16-atom Cu cluster in G4 and 64-atom Cu cluster in G6 dendrimers). The clusters remain trapped within the dendrimers for extended periods of time, do not agglomerate, and do not precipitate. The clusters can also be oxidized to yield dendrimer-encapsulated Cu(2+).

  6. TiO₂ Films Modified with Au Nanoclusters as Self-Cleaning Surfaces under Visible Light.

    Science.gov (United States)

    Liao, Ting-Wei; Verbruggen, Sammy W; Claes, Nathalie; Yadav, Anupam; Grandjean, Didier; Bals, Sara; Lievens, Peter

    2018-01-08

    In this study, we applied cluster beam deposition (CBD) as a new approach for fabricating efficient plasmon-based photocatalytic materials. Au nanoclusters (AuNCs) produced in the gas phase were deposited on TiO₂ P25-coated silicon wafers with coverage ranging from 2 to 8 atomic monolayer (ML) equivalents. Scanning Electron Microscopy (SEM) images of the AuNCs modified TiO₂ P25 films show that the surface is uniformly covered by the AuNCs that remain isolated at low coverage (2 ML, 4 ML) and aggregate at higher coverage (8 ML). A clear relationship between AuNCs coverage and photocatalytic activity towards stearic acid photo-oxidation was measured, both under ultraviolet and green light illumination. TiO₂ P25 covered with 4 ML AuNCs showed the best stearic acid photo-oxidation performance under green light illumination (Formal Quantum Efficiency 1.6 × 10 -6 over a period of 93 h). These results demonstrate the large potential of gas-phase AuNCs beam deposition technology for the fabrication of visible light active plasmonic photocatalysts.

  7. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, L.; Mandal, A.R. [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India); Mandal, S.K., E-mail: sk_mandal@hotmail.co [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India)

    2010-04-15

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni{sup 2+} clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni{sup 2+} clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  8. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Science.gov (United States)

    Kabir, L.; Mandal, A. R.; Mandal, S. K.

    2010-04-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  9. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    International Nuclear Information System (INIS)

    Kabir, L.; Mandal, A.R.; Mandal, S.K.

    2010-01-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  10. High yield synthesis of Au25 nanoclusters by controlling the reduction process.

    Science.gov (United States)

    Jin, Shenshen; Meng, Xiangming; Jin, Shan; Zhu, Manzhou

    2013-02-01

    The syntheses of gold nanoclusters, namely, the 25-gold-atom nanocluster (Au25(SR)18) and 38-gold-atom nanocluster (Au38(SR)24), with SR representing the thiol ligand, were described in previously reported studies. The synthesis was via a fast reduction process using sodium borohydride. The ratio of Au:HSR:NaBH4 was 1:3:10. Herein we report that the Au25 nanocluster can also be synthesized via a slow reduction process through a dropwise addition of an aqueous solution of sodium borohydride. The ratio of Au:S:NaBH4 is also changed to 1:3:5. This method synthesized Au25 nanoclusters at a high yield (47%). Pure Au25 nanoclusters were obtained after extraction, and the product was fully characterized by UV-vis spectroscopy, thermogravimetric analysis (TGA) and Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry. The possible formation mechanism is discussed in this paper. This work contributes to a better understanding of the mechanism of Au25 formation and provides a basis for further study of gold nanoclusters.

  11. Growth of gold nanoclusters and nanocrystals induced by lysozyme protein in thin film conformation

    Energy Technology Data Exchange (ETDEWEB)

    Bhowal, Ashim Chandra; Kundu, Sarathi, E-mail: sarathi.kundu@gmail.com

    2016-08-22

    Highlights: • Gold nanoclusters and nanocrystals form on thin film of lysozyme protein. • Nanocrystals formation is possible from mM concentration of HAuCl{sub 4}. • Both nanoclusters and nanocrystals follow Langmuir-like growth on protein surface. • Growth rate of nanocrystal is slower than nanocluster. • On protein surface nanocrystals take triangular, hexagonal and disc as shape. - Abstract: Structures and growth behavior of gold nanoclusters and nanocrystals have been explored on thin films of globular protein lysozyme by using UV–vis and photoluminescence spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). A simple and one-step environment friendly method has been used to grow nanocrystals on protein surface from HAuCl{sub 4} solution. It has been found that if different interaction times are provided between lysozyme films and HAuCl{sub 4} solution, then initially formed tiny gold nanoclusters on protein surface transform into nanocrystals with the passage of time. XRD analysis shows the formation of faced-centered cubic lattice along (1 1 1) crystalline direction and AFM images confirm the presence of circular, rod-like, triangular and hexagonal crystal structures. Langmuir-like growth behavior has been identified for both the gold nanoclusters and nanocrystals formation induced by the lysozyme films, however, nanocrystal growth is relatively slower than nanocluster.

  12. Growth of gold nanoclusters and nanocrystals induced by lysozyme protein in thin film conformation

    International Nuclear Information System (INIS)

    Bhowal, Ashim Chandra; Kundu, Sarathi

    2016-01-01

    Highlights: • Gold nanoclusters and nanocrystals form on thin film of lysozyme protein. • Nanocrystals formation is possible from mM concentration of HAuCl 4 . • Both nanoclusters and nanocrystals follow Langmuir-like growth on protein surface. • Growth rate of nanocrystal is slower than nanocluster. • On protein surface nanocrystals take triangular, hexagonal and disc as shape. - Abstract: Structures and growth behavior of gold nanoclusters and nanocrystals have been explored on thin films of globular protein lysozyme by using UV–vis and photoluminescence spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). A simple and one-step environment friendly method has been used to grow nanocrystals on protein surface from HAuCl 4 solution. It has been found that if different interaction times are provided between lysozyme films and HAuCl 4 solution, then initially formed tiny gold nanoclusters on protein surface transform into nanocrystals with the passage of time. XRD analysis shows the formation of faced-centered cubic lattice along (1 1 1) crystalline direction and AFM images confirm the presence of circular, rod-like, triangular and hexagonal crystal structures. Langmuir-like growth behavior has been identified for both the gold nanoclusters and nanocrystals formation induced by the lysozyme films, however, nanocrystal growth is relatively slower than nanocluster.

  13. Establishing the NO Oxidation State in Complexes [Cl5(NO)M]n-, M = Ru or Ir, trough Experiments and DFT Calculations

    Czech Academy of Sciences Publication Activity Database

    Sieger, M.; Sarkar, B.; Záliš, Stanislav; Fiedler, Jan; Escola, N.; Doctorovich, F.; Olabe, J. A.; Kaim, W.

    -, č. 12 (2004), s. 1797-1800 ISSN 1477-9226 R&D Projects: GA ČR GA203/03/0821; GA MŠk OC D14.20; GA MŠk OC D15.10 Institutional research plan: CEZ:AV0Z4040901 Keywords : NO oxidation * DFT calculations * spectroelectrochemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.926, year: 2004

  14. Importance of configurational contributions to the free energy of nanoclusters

    Directory of Open Access Journals (Sweden)

    M. Posselt

    2013-07-01

    Full Text Available An effective simulation method based on the Wang-Landau Monte Carlo algorithm is used in order to demonstrate the significance of the configurational contributions to the free energy of embedded nanoclusters. Starting from the most stable cluster configuration the simulation provides all geometrically different, but simply connected and sufficiently compact configurations of a nanocluster of a given size and the respective formation energies. The knowledge of these data allows the calculation of the free formation and free binding energy of the cluster at T ≠ 0. The method is applied to coherent Cu clusters in bcc-Fe. It is shown that even at moderate temperatures the configurational contributions to the free formation and binding energy must not be neglected. The dependence of the monomer free binding energy on clusters size is found to change significantly with increasing temperature which has a considerable effect on the pathway of cluster evolution. Therefore, present investigations provide an essential contribution to the improvement of the input parameters for object kinetic Monte Carlo simulations and rate theory used in multi-scale simulations of the nanostructure evolution. The calculation scheme developed in this work is rather general and applicable to many types of embedded nanoclusters. Compared to the method of overlapping distributions hitherto used in some cases to determine the configurational part of the free energy the new method has major advantages. Various tests are performed in order verify the presented approach and to compare with the results of the other calculation procedure. A roadmap is proposed to include the vibrational contributions to the free energy of the clusters within the framework of the method employed in this work.

  15. Intriguing structures and magic sizes of heavy noble metal nanoclusters around size 55 governed by relativistic effect and covalent bonding

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X. J.; Xue, X. L.; Jia, Yu [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Guo, Z. X. [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Department of Chemistry and London Centre for Nanotechnology, University College London, London WC1H (United Kingdom); Li, S. F., E-mail: sflizzu@zzu.edu.cn [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); ICQD, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zhang, Zhenyu, E-mail: zhangzy@ustc.edu.cn [ICQD, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Gao, Y. F., E-mail: ygao7@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-11-07

    Nanoclusters usually display exotic physical and chemical properties due to their intriguing geometric structures in contrast to their bulk counterparts. By means of first-principles calculations within density functional theory, we find that heavy noble metal Pt{sub N} nanoclusters around the size N = 55 begin to prefer an open configuration, rather than previously reported close-packed icosahedron or core-shell structures. Particularly, for Pt{sub N}, the widely supposed icosahedronal magic cluster is changed to a three-atomic-layered structure with D{sub 6h} symmetry, which can be well addressed by our recently established generalized Wulff construction principle (GWCP). However, the magic number of Pt{sub N} clusters around 55 is shifted to a new odd number of 57. The high symmetric three-layered Pt{sub 57} motif is mainly stabilized by the enhanced covalent bonding contributed by both spin-orbital coupling effect and the open d orbital (5d{sup 9}6s{sup 1}) of Pt, which result in a delicate balance between the enhanced Pt–Pt covalent bonding of the interlayers and negligible d dangling bonds on the cluster edges. These findings about Pt{sub N} clusters are also applicable to Ir{sub N} clusters, but qualitatively different from their earlier neighboring element Os and their later neighboring element Au. The magic numbers for Os and Au are even, being 56 and 58, respectively. The findings of the new odd magic number 57 are the important supplementary of the recently established GWCP.

  16. Morphological and magnetic properties of cobalt nanoclusters electrodeposited onto HOPG

    International Nuclear Information System (INIS)

    Rivera, M.; Rios-Reyes, C.H.; Mendoza-Huizar, L.H.

    2008-01-01

    In this work, the morphological and magnetic properties of cobalt nanoclusters obtained from two different sulphate electrolyte solutions were studied. The aggregates were electrodeposited onto highly oriented pyrolytic graphite electrodes in overpotential conditions, in order to investigate the cationic influence on the final properties of the aggregates. In both cases, scanning electron microscopy and atomic force microscopy showed random isolated clusters on the electrode surface, where size variations were determined by the electrolyte solution. By using magnetic force microscopy, the distribution of the electrodeposited magnetic material was more clearly observed which gave some insights on the growth mechanism of these aggregates.

  17. Gold nanocluster distribution on faceted and kinked Si nanowires

    International Nuclear Information System (INIS)

    Boukhicha, Rym; Vincent, Laetitia; Renard, Charles; Gardès, Cyrille; Yam, Vy; Fossard, Frédéric; Patriarche, Gilles; Jabeen, Fauzia; Bouchier, Daniel

    2012-01-01

    Si nanowires were grown on (111) substrates by ultra high vacuum chemical vapor deposition using the Au-catalyzed vapor–liquid–solid (VLS) technique. Depending on the growth temperature, the nanowires can be straight in the direction or kinked towards . We present a transmission electron microscopy investigation of the Si nanowires. Results exhibit the relationship between the morphology of nanowires and the distribution of gold on sidewalls bounding the nanowires. The distribution of Au nanoclusters is used as a probe to investigate the growth mechanisms of the VLS process. Our observations are consistent with the model of nucleation and step flow related to the oscillatory behavior of the catalyst droplet.

  18. Theory of nanocluster size distributions from ion beam synthesis.

    Science.gov (United States)

    Yuan, C W; Yi, D O; Sharp, I D; Shin, S J; Liao, C Y; Guzman, J; Ager, J W; Haller, E E; Chrzan, D C

    2009-04-10

    Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady-state shape for the cluster-size distribution that depends only on a characteristic length determined by the effective diffusion coefficient, the ion solubility, and the volumetric ion flux. The average cluster size in the steady-state regime is determined by the implanted species or matrix interface energy.

  19. Effect of quencher, denaturants, temperature and pH on the fluorescent properties of BSA protected gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Chib, Rahul, E-mail: Rahul.chib@live.unthsc.edu [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Butler, Susan [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Raut, Sangram [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129 (United States); Shah, Sunil; Borejdo, Julian [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Gryczynski, Zygmunt [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129 (United States); Gryczynski, Ignacy, E-mail: ignacy.gryczynski@unthsc.edu [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States)

    2015-12-15

    In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The photophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties. - Highlights: • Tryptophan is easily accessible in native BSA compared to BSA Au nanoclusters. • Guanidine HCL denatures native BSA more compared to BSA Au nanoclusters. • High temperature decreases the quantum yield of tryptophan and BSA Au nanocluster. • Emission wavelength of BSA Au nanoclusters remains constant with increasing pH. • BSA Au nanoclusters are robust to the changes in their environments.

  20. Effect of quencher, denaturants, temperature and pH on the fluorescent properties of BSA protected gold nanoclusters

    International Nuclear Information System (INIS)

    Chib, Rahul; Butler, Susan; Raut, Sangram; Shah, Sunil; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-01-01

    In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The photophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties. - Highlights: • Tryptophan is easily accessible in native BSA compared to BSA Au nanoclusters. • Guanidine HCL denatures native BSA more compared to BSA Au nanoclusters. • High temperature decreases the quantum yield of tryptophan and BSA Au nanocluster. • Emission wavelength of BSA Au nanoclusters remains constant with increasing pH. • BSA Au nanoclusters are robust to the changes in their environments.

  1. Ge nanoclusters in PECVD-deposited glass caused only by heat treatment

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rørdam, Troels Peter; Rottwitt, Karsten

    2008-01-01

    This paper reports the formation of Ge nanoclusters in a multi-layer structure consisting of alternating thin films of Ge-doped silica glass and SiGe, deposited by plasma-enhanced chemical vapor deposition (PECVD) and post annealed at 1100 °C in N2 atmosphere. We studied the annealed samples...... embedded with Ge nanoclusters after annealing. These nanoclusters are crystalline and varied in size. There were no clusters in the Ge-doped glass layer. Raman spectra verified the existence of crystalline Ge clusters. The positional shift of the Ge vibrational peak with the change of the focus depth...

  2. Growth of cluster assembled ZnO film by nanocluster beam deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Nilanjan [Department of Physics, Manipal University Jaipur, Jaipur-303007 (India)

    2015-06-24

    ZnO is considered as one of the most promising material for optoelectronic devices. The present work emphasizes production of cluster assembled ZnO films by a UHV nanocluster beam deposition technique where the nanoclusters were produced in a laser vaporization cluster source. The microstructural and the optical properties of the ZnO nanocluster film deposited were investigated. As the wet chemical processes are not compatible with current solid state methods of device fabrication, therefore alternative UHV technique described in the paper is the need of the hour.

  3. An IR study of the adsorption of ethylhydroxyethylcellulose on the surface of titanium and iron oxides under the action of mechanoactivation

    Science.gov (United States)

    Bulychev, N. A.; Fomin, V. N.; Malyukova, E. B.; Ur'ev, N. B.

    2010-12-01

    The adsorption of hydrophilic ethylhydroxyethylcellulose (EHEC) polymer on the surface of TiO2 and Fe2O3 inorganic pigments under the action of intense mechanical actions was studied by infrared spectroscopy. Mechanoactivation methods included ultrasonic action and mechanical treatment at sonic frequencies. Intense action on TiO2 and Fe2O3 aqueous disperse systems activated the surface of inorganic oxides and intensified the adsorption of the polymer. It also caused the formation of adsorption-solvation EHEC layers with increased densities, which determined the sedimentation stability of disperse systems.

  4. IOT Overview: IR Instruments

    Science.gov (United States)

    Mason, E.

    In this instrument review chapter the calibration plans of ESO IR instruments are presented and briefly reviewed focusing, in particular, on the case of ISAAC, which has been the first IR instrument at VLT and whose calibration plan served as prototype for the coming instruments.

  5. IR Hot Wave

    Energy Technology Data Exchange (ETDEWEB)

    Graham, T. B.

    2010-04-01

    The IR Hot Wave{trademark} furnace is a breakthrough heat treatment system for manufacturing metal components. Near-infrared (IR) radiant energy combines with IR convective heating for heat treating. Heat treatment is an essential process in the manufacture of most components. The controlled heating and cooling of a metal or metal alloy alters its physical, mechanical, and sometimes chemical properties without changing the object's shape. The IR Hot Wave{trademark} furnace offers the simplest, quickest, most efficient, and cost-effective heat treatment option for metals and metal alloys. Compared with other heat treatment alternatives, the IR Hot Wave{trademark} system: (1) is 3 to 15 times faster; (2) is 2 to 3 times more energy efficient; (3) is 20% to 50% more cost-effective; (4) has a {+-}1 C thermal profile compared to a {+-}10 C thermal profile for conventional gas furnaces; and (5) has a 25% to 50% smaller footprint.

  6. NaIrO3-A pentavalent post-perovskite

    International Nuclear Information System (INIS)

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-01-01

    Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

  7. A new formaldehyde sensor from silver nanoclusters modified Tollens' reagent.

    Science.gov (United States)

    Chaiendoo, Kanokwan; Sooksin, Sawarin; Kulchat, Sirinan; Promarak, Vinich; Tuntulani, Thawatchai; Ngeontae, Wittaya

    2018-07-30

    A selective colorimetric assay for detecting formaldehyde (FA) was proposed based on silver nanoclusters (AgNCs) templated by polymethacrylic acid (PMAA). The chemodosimeter was easily fabricated by the formation of Tollens' reagent in the presence of AgNCs (AgNCs@Tollens). The detection principle was based on the change in the color caused by the change in the particle size from nanoclusters (no LSPR) to nanoparticles (with LSPR) upon the reduction of Tollens' reagent by FA. In the presence of FA, the intensity of a new absorbance band with a maximum at a wavelength of 430 nm corresponding to the LSPR of the AgNPs linearly increased as a function of the FA concentration, exhibiting a color change that could be observed by the naked eye. This method provided a working range of 30-50 µM with lower detection limit (LOD) of 27.99 µM. The proposed method exhibited excellent selectivity towards FA over other aldehyde-containing compounds. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. Reversible aggregation and chemical resistance of magnetic nanoclusters for their recycling and repetitive use in industrial bioprocesses.

    Science.gov (United States)

    Caparrós, C; Benelmekki, M; Montràs, A; Lanceros-Méndez, S; Martínez, L I

    2012-08-01

    Magnetic nanoclusters are widely used as carriers for biomedical and bioindustrial applications. The chemical resistance of the nanoclusters is a key factor for the recycling the magnetic beads for a repetitive use in the industrial bioprocesses. In this work, a study of the chemical resistance of Fe2O3 silica-coated nanoclusters at different pH is presented. The use of Horizontal Low Gradient Magnetic Field (HLGMF) for the control and separation of the magnetic nanoclusters at diferent magnetic field gradients is also investigated. For these purposes Fe2O3 silica-coated nanoclusters are synthesised and characreized by SQUID, TEM, Zeta potential techniques. The magnetophoresis study was performed at 15 T/m and 30 T/m magnetic field gradients. Recycling aspects of the nanoclusters were estimated by evaluating their resistance to pH variation from acid to basic solutions of about pH 2.5 and 10.

  9. Hydrogen-Induced Ostwald Ripening at Room Temperature in a Pd Nanocluster Film

    NARCIS (Netherlands)

    Di Vece, M.|info:eu-repo/dai/nl/248753355; Grandjean, D.P.P.; van Bael, M.J.; Romero, C.P.; Wang, X; Decoster, S.; Vantomme, A.; Lievens, P.

    2008-01-01

    The structural and morphological changes occurring in an ensemble of vapor deposited palladium nanoclusters have been studied after several hydrogenation cycles with x-ray diffraction, extended x-rayabsorption fine structure spectroscopy, Rutherford backscattering spectrometry, and STM. Initial

  10. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires.

    Science.gov (United States)

    Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

    2013-09-09

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  11. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2013-09-01

    Full Text Available Cetyltrimethyl ammonium bromide cationic (CTAB surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD, scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS. This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  12. Synthesis of Co–Al layered double hydroxide nanoclusters as reduction nanocatalyst in aqueous media

    Directory of Open Access Journals (Sweden)

    Daisuke Kino

    2017-12-01

    Full Text Available Layered double hydroxides (LDHs have attracted attention as green materials due to their catalytic ability in benign aqueous solvents. We here demonstrate the synthesis of colloidal Co–Al LDH nanoclusters with an average size of <10 nm via a facile liquid-phase reaction for the enhancement of the catalytic activity. To the best of our knowledge, the present LDH is the smallest Co–Al LDH with an extremely large surface area and stability in an aqueous solvent, forming a stable and concentrated colloidal solution as high as 40 g/L. We investigated the formation mechanism, and the catalytic activity of Co–Al LDH nanoclusters. The Co–Al LDH nanoclusters showed 47 times higher rate of the reduction of dye molecules in the aqueous media than standard Co–Al LDH particles with a micrometer size. LDH nanoclusters demonstrated here are promising green nanocatalysts for the aqueous reaction processes.

  13. Electronic and dynamics properties of a molecular wire of graphane nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    León, A., E-mail: alejandro.leon@udp.cl [Facultad de Ingeniería, Universidad Diego Portales, Ejército 441, Santiago (Chile); Pacheco, M., E-mail: monica.pacheco@usm.cl [Departamento de Física, Universidad Santa María, Casilla 110-V, Valparaíso (Chile)

    2011-11-14

    In this work we study the electronics and dynamical properties of an array of graphane nanoclusters. The electronic properties are obtained from first principles calculations. The dynamical study is performed by solving the time-dependent Schrödinger equation, adopting the occupation number Hamiltonian and using parameters obtained with first principles calculations. The thermal behavior is simulated by a stochastic algorithm. Our results show that for a set of geometric parameters of the array of nanoclusters, the system exhibits bi-stability in the charge configuration, excitation energies that allow operation at room temperature, operation times below the picosecond and scalability. -- Highlights: ► Graphane nanoclusters can propagate binary information at room temperature. ► Molecular wire formed by graphane nanoclusters has characteristics of bistability. ► Graphane nanoribbon shows similar performance to the automaton of molecules.

  14. Multilayered nanoclusters of platinum and gold: insights on electrodeposition pathways, electrocatalysis, surface and bulk compositional properties

    CSIR Research Space (South Africa)

    Mkwizu, TS

    2013-06-01

    Full Text Available Electrochemical, surface and bulk compositional properties of multilayered nanoclusters of Pt and Au, electrochemically deposited on glassy carbon under conditions involving sequential surface–limited redox–replacement reactions (performed at open...

  15. Growth of gold nanoclusters and nanocrystals induced by lysozyme protein in thin film conformation

    Science.gov (United States)

    Bhowal, Ashim Chandra; Kundu, Sarathi

    2016-08-01

    Structures and growth behavior of gold nanoclusters and nanocrystals have been explored on thin films of globular protein lysozyme by using UV-vis and photoluminescence spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). A simple and one-step environment friendly method has been used to grow nanocrystals on protein surface from HAuCl4 solution. It has been found that if different interaction times are provided between lysozyme films and HAuCl4 solution, then initially formed tiny gold nanoclusters on protein surface transform into nanocrystals with the passage of time. XRD analysis shows the formation of faced-centered cubic lattice along (1 1 1) crystalline direction and AFM images confirm the presence of circular, rod-like, triangular and hexagonal crystal structures. Langmuir-like growth behavior has been identified for both the gold nanoclusters and nanocrystals formation induced by the lysozyme films, however, nanocrystal growth is relatively slower than nanocluster.

  16. Precise positioning and assembly of metallic nanoclusters as building blocks of nanostructures: A molecular dynamics study

    Science.gov (United States)

    Mahboobi, S. H.; Meghdari, A.; Jalili, N.; Amiri, F.

    2009-12-01

    Molecular dynamics simulations are used to study the manipulation of metallic nanoclusters. These particles are assumed as potential building blocks for bottom-up manufacturing of nanoscale structures. One of the key factors in the assembly of nanoclusters is the precise positioning of them by a manipulation system. Prediction of the corresponding behavior under the influence of working conditions is of crucial importance for planning of controlled positioning and assembly of nanoclusters. The focus of the present research is on ultra-fine metallic nanoclusters. The effects of material type and manipulation strategy on the success of the process have been investigated by molecular dynamics. Such qualitative simulation studies can evaluate the chance of success of a certain nanopositioning scenario regarding different working conditions before consuming high experimental expenses.

  17. Stable silver nanoclusters electrochemically deposited on nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Jin, Shi; Chen, Man; Dong, Haifeng; He, Bingyu; Lu, Huiting; Su, Lei; Dai, Wenhao; Zhang, Qiaochu; Zhang, Xueji

    2015-01-01

    Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter , which is vital in high performance fuel cells, batteries and nanodevices.

  18. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    OpenAIRE

    Magnus Willander; Xianjie Liu; Zafar Hussain Ibupoto; Kimleang Khun

    2013-01-01

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline co...

  19. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    Science.gov (United States)

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor.

  20. Iridium Ziegler-Type Hydrogenation Catalysts Made from [(1,5-COD)Ir( -O2C8H15)]2 and AlEt3: Spectroscopic and Kinetic Evidence for the Irn Species Present and for Nanoparticles as the Fastest Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Alley, W.; Hamdemir, I; Wang, Q; Frenkel, A; Li, L; Yang, J; Menard, L; Nuzzo, R; Ozkar, S; Finke, R

    2010-01-01

    Ziegler-type hydrogenation catalysts, those made from a group 8-10 transition metal precatalyst and an AlR{sub 3} cocatalyst, are often used for large scale industrial polymer hydrogenation; note that Ziegler-type hydrogenation catalysts are not the same as Ziegler-Natta polymerization catalysts. A review of prior studies of Ziegler-type hydrogenation catalysts (Alley et al. J. Mol. Catal. A: Chem. 2010, 315, 1-27) reveals that a {approx}50 year old problem is identifying the metal species present before, during, and after Ziegler-type hydrogenation catalysis, and which species are the kinetically best, fastest catalysts-that is, which species are the true hydrogenation catalysts. Also of significant interest is whether what we have termed 'Ziegler nanoclusters' are present and what their relative catalytic activity is. Reported herein is the characterization of an Ir Ziegler-type hydrogenation catalyst, a valuable model (vide infra) for the Co-based industrial Ziegler-type hydrogenation catalyst, made from the crystallographically characterized [(1,5-COD)Ir({mu}-O{sub 2}C{sub 8}H{sub 15})]{sub 2} precatalyst plus AlEt{sub 3}. Characterization of this Ir model system is accomplished before and after catalysis using a battery of physical methods including Z-contrast scanning transmission electron microscopy (STEM), high resolution (HR)TEM, and X-ray absorption fine structure (XAFS) spectroscopy. Kinetic studies plus Hg(0) poisoning experiments are then employed to probe which species are the fastest catalysts. The main findings herein are that (i) a combination of the catalyst precursors [(1,5-COD)Ir({mu}-O{sub 2}C{sub 8}H{sub 15})]{sub 2} and AlEt{sub 3} gives catalytically active solutions containing a broad distribution of Ir{sub n} species ranging from monometallic Ir complexes to nanometer scale, noncrystalline Ir{sub n} nanoclusters (up to Ir{sub {approx}100} by Z-contrast STEM) with the estimated mean Ir species being 0.5-0.7 nm, Ir{sub {approx}4

  1. Assembly, Structure and Properties of DNA Programmable Nanoclusters

    Science.gov (United States)

    Chi, Cheng

    Finite size nanoclusters can be viewed as a nanoscale analogue of molecules. Just as molecules, synthesized from atoms, give access to new properties, clusters composed of nanoparticles modulate of their functional properties of nanoparticles. In contrast to synthetic chemistry which is a mature field, the creation of nanoscale clusters with well-defined architectures is a new and challenging area of research. My work explores how to assemble model systems of nanoclusters using DNA-programmable interparticle linkages. The simplest clusters of two particles, dimers, allow one to investigate fundamental effects in these systems. Such clusters serve as a versatile platform to understand DNA-mediated interactions, especially in the non-trivial regime where the nanoparticle and DNA chains are comparable in size. I systematically studied a few fundamental questions as follows: Firstly, we examined the structure of nanoparticle dimers in detail by a combination of X-ray scattering experiments and molecular simulations. We found that, for a given DNA length, the interparticle separation within the dimer is controlled primarily by the number of linking DNA. We summarized our findings in a simple model that captures the interplay of the number of DNA bridges, their length, the particle's curvature and the excluded volume effects. We demonstrated the applicability of the model to our results, without any free parameters. As a consequence, the increase of dimer separation with increasing temperature can be understood as a result of changing the number of connecting DNA. Later, we investigated the self-assembly process of DNA-functionalized particles in the presence of various lengths of the DNA linkage strands using 3 different pathways. We observed a high yield of dimer formation when significantly long linkers were applied. Small Angle X-ray Scattering revealed two configurations of the small clusters by different pathways. In one case, the interparticle distance increases

  2. SnO2, IrO2, Ta2O5, Bi2O3, and TiO2 nanoparticle anodes: electrochemical oxidation coupled with the cathodic reduction of water to yield molecular H2

    International Nuclear Information System (INIS)

    Choi, Jina; Qu Yan; Hoffmann, Michael R.

    2012-01-01

    In recent years, the search for environmentally friendly alternative energy sources with reduced carbon footprints has increased. The coupling of photovoltaic power sources with advanced electrolysis systems for hydrogen production via water splitting using organic contaminants as sacrificial electron donors has been considered to a be viable alternative. In this report, we demonstrated the feasibility of a scaled-up rooftop prototype of the proposed hybrid photovoltaic-electrolysis system, which utilizes semiconductor nanoparticles coated on to metal substrates as electrodes for the generation of hydrogen coupled with the oxidation of wastewater. Application of an anodic bias of >2.0 V to bismuth-doped TiO 2 (BiO x –TiO 2 ) on Ti metal anodes with a sequential under-coatings of nanoparticulate SnO 2 , IrO 2 , Ta 2 O 5 , and Bi 2 O 3 results in the electrochemical degradation of a variety of organic chemical contaminants in water (i.e., rhodamine B (Rh.B), methylene blue (MB), salicylic acid, triclosan, and phenol) and actual wastewater from a chemical manufacturing plant, while at the same time, molecular hydrogen is produced at stainless steel (SS) cathodes. The kinetics of the anodic substrates oxidation is investigated as a function of the cell current (I cell ), substrate concentration, and background electrolyte composition (e.g., NaCl, Na 2 SO 4 , or seawater). Average current efficiencies were found to be in the range of 4–22 %, while the cathodic current and energy efficiencies for hydrogen production were found to be in the range of 50–70 % and 20–40 %, respectively.

  3. Protection of p+-n-Si Photoanodes by Sputter-Deposited Ir/IrOxThin Films

    DEFF Research Database (Denmark)

    Mei, Bastian Timo; Seger, Brian; Pedersen, Thomas

    2014-01-01

    Sputter deposition of Ir/IrOx on p+-n-Si without interfacial corrosion protection layers yielded photoanodes capable of efficient water oxidation (OER) in acidic media (1 M H2SO4). Stability of at least 18 h was shown by chronoamperomety at 1.23 V versus RHE (reversible hydrogen electrode) under 38...

  4. Ag29(BDT)12(TPP)4: A Tetravalent Nanocluster.

    Science.gov (United States)

    AbdulHalim, Lina G; Bootharaju, Megalamane S; Tang, Qing; Del Gobbo, Silvano; AbdulHalim, Rasha G; Eddaoudi, Mohamed; Jiang, De-en; Bakr, Osman M

    2015-09-23

    The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties, and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT, 1,3-benzenedithiol; TPP, triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT (wide footprint bidentate thiols) in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield, and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical band gap compared to that of the solution state, suggesting strong interparticle electronic coupling occurs in the solid state.

  5. Research Update: Interfacing ultrasmall metal nanoclusters with biological systems

    Science.gov (United States)

    Shang, Li; Nienhaus, G. Ulrich

    2017-05-01

    Metal nanoclusters (NCs), a new type of nanomaterial with unique physicochemical properties, show great potential in many biomedical applications. Understanding their behavior in the complex biological environment is critical not only for designing highly efficient NC-based nanomedicines but also for elucidating the biological impact (e.g., toxicity) of these emerging nanomaterials. In this review, we give an overview of recent progress in exploring interactions of metal NCs with biological systems, including protein adsorption onto NCs, NC interactions with cells, and also the in vivo behavior of NCs. We also discuss the biological responses to the interactions, key parameters defining the interactions, and current challenges in the exploration of NCs in the complex biological environment.

  6. Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

    International Nuclear Information System (INIS)

    Suzdalev, I.P.

    2005-01-01

    Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

  7. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    International Nuclear Information System (INIS)

    Hao, Jiannan; Shu, Xiaolin; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-01-01

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential’s best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  8. Gold Nanocluster-Mediated Cellular Death under Electromagnetic Radiation.

    Science.gov (United States)

    Cifuentes-Rius, Anna; Ivask, Angela; Das, Shreya; Penya-Auladell, Nuria; Fabregas, Laura; Fletcher, Nicholas L; Houston, Zachary H; Thurecht, Kristofer J; Voelcker, Nicolas H

    2017-11-29

    Gold nanoclusters (Au NCs) have become a promising nanomaterial for cancer therapy because of their biocompatibility and fluorescent properties. In this study, the effect of ultrasmall protein-stabilized 2 nm Au NCs on six types of mammalian cells (fibroblasts, B-lymphocytes, glioblastoma, neuroblastoma, and two types of prostate cancer cells) under electromagnetic radiation is investigated. Cellular association of Au NCs in vitro is concentration-dependent, and Au NCs have low intrinsic toxicity. However, when Au NC-incubated cells are exposed to a 1 GHz electromagnetic field (microwave radiation), cell viability significantly decreases, thus demonstrating that Au NCs exhibit specific microwave-dependent cytotoxicity, likely resulting from localized heating. Upon i.v. injection in mice, Au NCs are still present at 24 h post administration. Considering the specific microwave-dependent cytotoxicity and low intrinsic toxicity, our work suggests the potential of Au NCs as effective and safe nanomedicines for cancer therapy.

  9. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiannan; Shu, Xiaolin, E-mail: shuxlin@buaa.edu.cn; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-02-15

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential’s best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  10. Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

    KAUST Repository

    Pablo-Pedro, Ricardo

    2017-08-17

    High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we performed DFT calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the zigzag and armchair directions may permit the design of novel n-type electronic materials and spinctronics devices that incorporate both high electron affinities and very low internal reorganization energies.

  11. Connections Between Theory and Experiment for Gold and Silver Nanoclusters.

    Science.gov (United States)

    Weerawardene, K L Dimuthu M; Häkkinen, Hannu; Aikens, Christine M

    2018-02-28

    Ligand-stabilized gold and silver nanoparticles are of tremendous current interest in sensing, catalysis, and energy applications. Experimental and theoretical studies have closely interacted to elucidate properties such as the geometric and electronic structures of these fascinating systems. In this review, the interplay between theory and experiment is described; areas such as optical absorption and doping, where the theory-experiment connections are well established, are discussed in detail; and the current status of these connections in newer fields of study, such as luminescence, transient absorption, and the effects of solvent and the surrounding environment, are highlighted. Close communication between theory and experiment has been extremely valuable for developing an understanding of these nanocluster systems in the past decade and will undoubtedly continue to play a major role in future years. Expected final online publication date for the Annual Review of Physical Chemistry Volume 69 is April 20, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  12. Some positive effects of introducing Pt4+ and Fe3+ to the MnMo-oxide anode deposited on IrO2/Ti substrate for best oxygen evolution efficiency during electrolysis in 0.5M NaCl solution

    OpenAIRE

    Abou Shahba, R.M.; Attia, E.M.; Deiab, N.M.

    2013-01-01

    NaCl solution (0.5 M) of pH 2 was electrolyzed at 1000 Am−2 at room temperature. Addition of Pt4+ and Fe3+ to the prepared MnMo-oxide anode deposited on IrO2/Ti substrate, significantly improves the performance of anode for the oxygen evolution reaction (OER) during NaCl electrolysis. After 2000 h of electrolysis, the oxygen evolution efficiency (OEE) is in the order of MnMoPt-oxide > MnMoFe-oxide > MnMo-oxide anodes with 100%, 99%, and 93.2% OEE, respectively. The loss in weight of MnMo-oxid...

  13. A scalable synthesis of highly stable and water dispersible Ag 44(SR)30 nanoclusters

    KAUST Repository

    AbdulHalim, Lina G.

    2013-01-01

    We report the synthesis of atomically monodisperse thiol-protected silver nanoclusters [Ag44(SR)30] m, (SR = 5-mercapto-2-nitrobenzoic acid) in which the product nanocluster is highly stable in contrast to previous preparation methods. The method is one-pot, scalable, and produces nanoclusters that are stable in aqueous solution for at least 9 months at room temperature under ambient conditions, with very little degradation to their unique UV-Vis optical absorption spectrum. The composition, size, and monodispersity were determined by electrospray ionization mass spectrometry and analytical ultracentrifugation. The produced nanoclusters are likely to be in a superatom charge-state of m = 4-, due to the fact that their optical absorption spectrum shares most of the unique features of the intense and broadly absorbing nanoparticles identified as [Ag44(SR) 30]4- by Harkness et al. (Nanoscale, 2012, 4, 4269). A protocol to transfer the nanoclusters to organic solvents is also described. Using the disperse nanoclusters in organic media, we fabricated solid-state films of [Ag44(SR)30]m that retained all the distinct features of the optical absorption spectrum of the nanoclusters in solution. The films were studied by X-ray diffraction and photoelectron spectroscopy in order to investigate their crystallinity, atomic composition and valence band structure. The stability, scalability, and the film fabrication method demonstrated in this work pave the way towards the crystallization of [Ag44(SR)30]m and its full structural determination by single crystal X-ray diffraction. Moreover, due to their unique and attractive optical properties with multiple optical transitions, we anticipate these clusters to find practical applications in light-harvesting, such as photovoltaics and photocatalysis, which have been hindered so far by the instability of previous generations of the cluster. © 2013 The Royal Society of Chemistry.

  14. Electronic structure, local magnetism, and spin-orbit effects of Ir(IV)-, Ir(V)-, and Ir(VI)-based compounds

    Energy Technology Data Exchange (ETDEWEB)

    Laguna-Marco, M. A.; Kayser, P.; Alonso, J. A.; Martínez-Lope, M. J.; van Veenendaal, M.; Choi, Y.; Haskel, D.

    2015-06-01

    Element- and orbital-selective x-ray absorption and magnetic circular dichroism measurements are carried out to probe the electronic structure and magnetism of Ir 5d electronic states in double perovskite Sr2MIrO6 (M = Mg, Ca, Sc, Ti, Ni, Fe, Zn, In) and La2NiIrO6 compounds. All the studied systems present a significant influence of spin-orbit interactions in the electronic ground state. In addition, we find that the Ir 5d local magnetic moment shows different character depending on the oxidation state despite the net magnetization being similar for all the compounds. Ir carries an orbital contribution comparable to the spin contribution for Ir4+ (5d(5)) and Ir5+ (5d(4)) oxides, whereas the orbital contribution is quenched for Ir6+ (5d(3)) samples. Incorporation of a magnetic 3d atom allows getting insight into the magnetic coupling between 5d and 3d transition metals. Together with previous susceptibility and neutron diffractionmeasurements, the results indicate that Ir carries a significant local magnetic moment even in samples without a 3d metal. The size of the (small) net magnetization of these compounds is a result of predominant antiferromagnetic interactions between local moments coupled with structural details of each perovskite structure

  15. Synthesis of biocompatible AuAgS/Ag2S nanoclusters and their applications in photocatalysis and mercury detection

    International Nuclear Information System (INIS)

    Zhao, Qian; Chen, Shenna; Zhang, Lingyang; Huang, Haowen; Liu, Fengping; Liu, Xuanyong

    2014-01-01

    In this paper, a facile approach for preparation of AuAgS/Ag 2 S nanoclusters was developed. The unique AuAgS/Ag 2 S nanoclusters capped with biomolecules exhibit interesting excellent optical and catalytic properties. The fluorescent AuAgS/Ag 2 S nanoclusters show tunable luminescence depending on the nanocluster size. The apoptosis assay demonstrated that the AuAgS/Ag 2 S nanoclusters showed low cytotoxicity and good biocompatibility. Therefore, the nanoclusters can be used not only as a probe for labeling cells but also for their photocatalytic activity for photodegradation of organic dye. Moreover, a highly selective and sensitive assay for detection of mercury including Hg 2+ and undissociated mercury complexes was developed based on the quenching fluorescent AuAgS/Ag 2 S nanoclusters, which provides a promising approach for determining various forms of Hg in the mercury-based compounds in environment. These unique nanoclusters may have potential applications in biological labeling, sensing mercury, and photodegradation of various organic pollutants in waste water.Graphical Abstract

  16. Effect of Quencher, Denaturants, Temperature and pH on the Fluorescent Properties of BSA Protected Gold Nanoclusters.

    Science.gov (United States)

    Chib, Rahul; Butler, Susan; Raut, Sangram; Shah, Sunil; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-12-01

    In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The phtophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties.

  17. Self-trapping nature of Tl nanoclusters on the Si(111)-7x7 surface

    International Nuclear Information System (INIS)

    Hwang, C G; Kim, N D; Lee, G; Shin, S Y; Kim, J S; Chung, J W

    2008-01-01

    We have studied properties of thallium (Tl) nanoclusters formed on the Si(111)-7x7 surface at room temperature (RT) by utilizing photoemission spectroscopy (PES) and high-resolution electron-energy-loss spectroscopy (HREELS) combined with first principles calculations. Our PES data reveal that the surface states stemming from the Si substrate remain quite inert with Tl adsorption producing no Tl-induced state until saturation at Tl coverage θ=0.21 monolayers. Such a behavior, in sharp contrast with the extremely reactive surface states upon the formation of Na or Li nanoclusters, together with the presence of a unique Tl-induced loss peak in HREELS spectra suggests no strong Si-Tl bonding, and is well understood in terms of gradual filling of Si dangling bonds with increasing θ. Our calculation further indicates the presence of several metastable atomic structures of Tl nanoclusters at RT rapidly transforming from one to another faster than 10 10 flippings per second. We thus conclude that the highly mobile Tl atoms form self-trapped nanoclusters within the attractive basins of the Si substrate at RT with several metastable phases. The mobile and multi-phased nature of Tl nanoclusters not only accounts for all the existing experimental observations available at present, but also provides an example of self-trapping of atoms in a nanometre-scale region

  18. Real-time transmission electron microscope observation of gold nanoclusters diffusing into silicon at room temperature

    International Nuclear Information System (INIS)

    Ishida, Tadashi; Nakajima, Yuuki; Fujita, Hiroyuki; Endo, Junji; Collard, Dominique

    2009-01-01

    Gold diffusion into silicon at room temperature was observed in real time with atomic resolution. Gold nanoclusters were formed on a silicon surface by an electrical discharge between a silicon tip and a gold coated tip inside an ultrahigh-vacuum transmission electron microscope (TEM) specimen chamber. At the moment of the gold nanocluster deposition, the gold nanoclusters had a crystalline structure. The crystalline structure gradually disappeared due to the interdiffusion between silicon and gold as observed after the deposition of gold nanoclusters. The shape of the nanocluster gradually changed due to the gold diffusion into the damaged silicon. The diffusion front between silicon and gold moved toward the silicon side. From the observations of the diffusion front, the gold diffusivity at room temperature was extracted. The extracted activation energy, 0.21 eV, matched the activation energy in bulk diffusion between damaged silicon and gold. This information is useful for optimizing the hybridization between solid-state and biological nanodevices in which gold is used as an adhesive layer between the two devices.

  19. Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins.

    Science.gov (United States)

    Rodríguez, Henry A; Giraldo, Luis F; Casanova, Herley

    2015-07-01

    The aim of this work was to study the effect of silica nanoclusters (SiNC), obtained by a solvent evaporation method and functionalized by 3-methacryloxypropyltrimethoxysilane (MPS) and MPS+octyltrimethoxysilane (OTMS) (50/50wt/wt), on the rheological, mechanical and sorption properties of urethane dimethylacrylate (UDMA)/triethylenglycol dimethacrylate (TEGDMA) (80/20wt/wt) resins blend. Silica nanoparticles (SiNP) were silanized with MPS or MPS+OTMS (50/50wt/wt) and incorporated in an UDMA-isopropanol mix to produce functionalized silica nanoclusters after evaporating the isopropanol. The effect of functionalized SiNC on resins rheological properties was determined by large and small deformation tests. Mechanical, thermal, sorption and solubility properties were evaluated for composite materials. The UDMA/TEGDMA (80/20wt/wt) resins blend with added SiNC (ca. 350nm) and functionalized with MPS showed a Newtonian flow behavior associated to their spheroidal shape, whereas the resins blend with nanoclusters silanized with MPS+OTMS (50/50wt/wt) (ca. 400nm) showed a shear-thinning behavior due to nanoclusters irregular shape. Composite materials prepared with bare silica nanoclusters showed lower compressive strength than functionalized silica nanoclusters. MPS functionalized nanoclusters showed better mechanical properties but higher water sorption than functionalized nanoclusters with both silane coupling agents, MPS and OTMS. The solvent evaporation method applied to functionalized nanoparticles showed to be an alternative way to the sinterization method for producing nanoclusters, which improved some dental composite mechanical properties and reduced water sorption. The shape of functionalized silica nanoclusters showed to have influence on the rheological properties of SiNC resin suspensions and the mechanical and sorption properties of light cured composites. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Modification of erbium photoluminescence decay rate due to ITO layers on thin films of SiO{sub 2}:Er doped with Si-nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Wojdak, M., E-mail: m.wojdak@ucl.ac.uk [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Jayatilleka, H. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Department of Electrical and Computer Engineering, University of Toronto, 10 King' s College Road, Toronto, Ontario, Canada M5S 3G4 (Canada); Shah, M. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Kenyon, A.J., E-mail: t.kenyon@ucl.ac.uk [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Gourbilleau, F.; Rizk, R. [Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), ENSICAEN, CNRS, CEA/IRAMIS, Université de Caen, 14050 CAEN cedex (France)

    2013-04-15

    During the fabrication of MOS light emitting devices, the thin film of active material is usually characterized by photoluminescence measurements before electrical contacts are deposited. However, the presence of a conductive contact layer can alter the luminescent properties of the active material. The local optical density of states changes due to the proximity of luminescent species to the interface with the conductive medium (the top electrode), and this modifies the radiative rate of luminescent centers within the active layer. In this paper we report enhancement of the observed erbium photoluminescence rate after deposition of indium tin oxide contacts on thin films of SiO{sub 2}:Er containing silicon nanoclusters, and relate this to Purcell enhancement of the erbium radiative rate. -- Highlights: ► We studied photoluminescence of Er in SiO{sub 2} thin films doped with Si nanoclusters. ► Presence of ITO layer on the top enhances photoluminescence decay rate of Er. ► The effect depends on the thickness of active film. ► Radiative rate change in proximity of ITO layer was calculated theoretically. ► The calculation results are compared with the experiment and discussed.

  1. Charge Carrier Dynamics at Silver Nanocluster-Molecular Acceptor Interfaces

    KAUST Repository

    Almansaf, Abdulkhaleq

    2017-07-01

    A fundamental understanding of interfacial charge transfer at donor-acceptor interfaces is very crucial as it is considered among the most important dynamical processes for optimizing performance in many light harvesting systems, including photovoltaics and photo-catalysis. In general, the photo-generated singlet excitons in photoactive materials exhibit very short lifetimes because of their dipole-allowed spin radiative decay and short diffusion lengths. In contrast, the radiative decay of triplet excitons is dipole forbidden; therefore, their lifetimes are considerably longer. The discussion in this thesis primarily focuses on the relevant parameters that are involved in charge separation (CS), charge transfer (CT), intersystem crossing (ISC) rate, triplet state lifetime, and carrier recombination (CR) at silver nanocluster (NCs) molecular-acceptors interfaces. A combination of steady-state and femto- and nanosecond broadband transient absorption spectroscopies were used to investigate the charge carrier dynamics in various donor-acceptor systems. Additionally, this thesis was prolonged to investigate some important factors that influence the charge carrier dynamics in Ag29 silver NCs donor-acceptor systems, such as the metal doping and chemical structure of the nanocluster and molecular acceptors. Interestingly, clear correlations between the steady-state measurements and timeresolved spectroscopy results are found. In the first study, we have investigated the interfacial charge transfer dynamics in positively charged meso units of 5, 10, 15, 20-tetra (1- methyl-4-pyridino)-porphyrin tetra (p-toluene sulfonate) (TMPyP) and neutral charged 5, 10, 15, 20-tetra (4-pyridyl)-porphyrin (TPyP), with negatively charged undoped and gold (Au)- doped silver Ag29 NCs. Moreover, this study showed the impact of Au doping on the charge carrier dynamics of the system. In the second study, we have investigated the interfacial charge transfer dynamics in [Pt2 Ag23 Cl7 (PPh3

  2. A Collection of Topological Types of Nanoclusters and Its Application to Icosahedron-Based Intermetallics.

    Science.gov (United States)

    Pankova, Arina A; Akhmetshina, Tatiana G; Blatov, Vladislav A; Proserpio, Davide M

    2015-07-06

    In this study, we carried out a topological and geometrical analysis of more than 27 000 intermetallics. More than 2000 topologically different nanoclusters were determined and stored in an electronic database as the Topological Types of Nanoclusters (TTN) collection. Besides the topology of the nanoclusters, the TTN collection contains the information on their occurrence as well as on motifs of their assembly in intermetallics; it is included to the set of the ToposPro topological collections. With the TTN collection we analyzed the topology of local binding and overall topological motifs in the 1528 intermetallics assembled with icosahedron-based building units. Taking the TTN collection as a starting point, we present the concept of a knowledge database and an expert system that can be used to process a huge set of data to find general regularities in the crystal structures of intermetallics and to predict some of their features.

  3. Fabrication and modification of metal nanocluster composites using ion and laser beams

    International Nuclear Information System (INIS)

    Haglund, R.F. Jr.; Osborne, D.H. Jr.; Magruder, R.H. III; White, C.W.; Zuhr, R.A.; Townsend, P.D.; Hole, D.E.; Leuchtner, R.E.

    1994-12-01

    Metal nanocluster composites have attractive properties for applications in nonlinear optics. However, traditional fabrication techniques -- using melt-glass substrates -- are severely constrained by equilibrium thermodynamics and kinetics. This paper describes the fabrication of metal nanoclusters in both crystalline and glassy hosts by ion implantation and pulsed laser deposition. The size and size distribution of the metal nanoclusters can be modified by controlling substrate temperature during implantation, by subsequent thermal annealing, or by laser irradiation. The authors have characterized the optical response of the composites by absorption and third-order nonlinear-optical spectroscopies; electron and scanning-probe microscopies have been used to benchmark the physical characteristics of the composites. The outlook for controlling the structure and nonlinear optical response properties of these nanophase materials appears increasingly promising

  4. Nonlinear optical properties of Cu nanoclusters by ion implantation in silicate glass

    Science.gov (United States)

    Wang, Y. H.; Wang, Y. M.; Lu, J. D.; Ji, L. L.; Zang, R. G.; Wang, R. W.

    2010-02-01

    Metal nanocluster composite glass prepared by 180 keV Cu ions into silica with dose of 1 × 10 17 ions/cm 2 has been studied. The microstructural properties of the nanoclusters were analysed by optical absorption spectra and transmission electron microscopy (TEM). Third-order nonlinear optical properties of the nanoclusters were measured at 1064 nm and 532 nm excitations using Z-scan technique. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility were deduced. The mechanisms responsible for the nonlinear response were discussed. Absolute third-order nonlinear susceptibility χ of this kind of sample was determined to be 2.1 × 10 -7 esu at 532 nm and 1.2 × 10 -7 esu at 1064 nm, respectively.

  5. Nonlinear optical properties of Cu nanocluster composite fabricated by 180 keV ion implantation

    Science.gov (United States)

    Wang, Y. H.; Wang, Y. M.; Lu, J. D.; Ji, L. L.; Zang, R. G.; Wang, R. W.

    2009-11-01

    Metal nanocluster composite glass prepared by 180 keV Cu ions into silica with dose of 5×10 16 ions/cm 2 has been studied. The microstructural properties of the nanoclusters has been verified by optical absorption spectra and transmission electron microscopy (TEM). Third-order nonlinear optical properties of the nanoclusters were measured at 1064 and 532 nm excitations using Z-scan technique. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility were deduced. Results of the investigation of nonlinear refraction by the off-axis Z-scan configuration were presented and the mechanisms responsible for the nonlinear response were discussed. Third-order nonlinear susceptibility χ(3) of this kind of sample was determined to be 8.7×10 -8 esu at 532 nm and 6.0×10 -8 esu at 1064 nm, respectively.

  6. Some positive effects of introducing Pt4+ and Fe3+ to the MnMo-oxide anode deposited on IrO2/Ti substrate for best oxygen evolution efficiency during electrolysis in 0.5 M NaCl solution

    Directory of Open Access Journals (Sweden)

    R.M. Abou Shahba

    2013-06-01

    Full Text Available NaCl solution (0.5 M of pH 2 was electrolyzed at 1000 Am−2 at room temperature. Addition of Pt4+ and Fe3+ to the prepared MnMo-oxide anode deposited on IrO2/Ti substrate, significantly improves the performance of anode for the oxygen evolution reaction (OER during NaCl electrolysis. After 2000 h of electrolysis, the oxygen evolution efficiency (OEE is in the order of MnMoPt-oxide > MnMoFe-oxide > MnMo-oxide anodes with 100%, 99%, and 93.2% OEE, respectively. The loss in weight of MnMo-oxide is reduced from about 13% to 3.2% and 0.0% by addition of iron and platinum cations, to the deposition electrolyte. The mean average grain size of MnO2, MnMo-, MnMoFe- and MnMoPt-oxide deposits prepared in electrolytes of pH 0.0 are in the range of 25.5, 16.22, 13.5 ∼ 16.5 and 13 ∼ 17.5 nm, respectively. The physicochemical properties of the deposits were characterized using X-ray diffraction spectroscopy (XRD, energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM and electrochemical techniques. EDX analysis illustrates that IrO2/Ti is stable during the deposition process and behaves only as conductive substrate. SEM illustrates that, all elements constituting MnMoPt- and MnMoFe-oxide deposits are homogeneously distributed in the oxide surface.

  7. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2 n...... nanoparticles synthesized on Au(lll), and establishes a new picture of the active edge sires of the nanoclusters. The results demonstrate a way to get detailed atomic-scale information on catalysts in general....

  8. Polarization memory of white luminescence of Ag nanoclusters dispersed in glass host.

    Science.gov (United States)

    Kuznetsov, A S; Tikhomirov, V K; Moshchalkov, V V

    2012-09-10

    A mechanism for white luminescence of Ag nanoclusters dispersed in oxyfluoride glass host has been revealed by studying a temperature dependence of its polarization memory. The spectral dependence of the polarization memory indicates the presence of a variety of Ag nanoclusters, particularly emitting in the blue, green and red. Temperature activated intercluster energy transfer has been found responsible for white luminescence. The means for increasing luminescence quantum yield have been suggested. This efficient white luminescence may be used in highly demanded devices, such as luminescent lamps, displays, color phosphors for LEDs, photovoltaic devices based on down shifting of solar spectrum.

  9. Controlled formation of emissive silver nanoclusters using rationally designed metal-binding proteins.

    Science.gov (United States)

    Morozov, Vasily A; Ogawa, Michael Y

    2013-08-19

    The metal-binding properties of rationally designed, synthetic proteins were used to prepare a series of emissive silver nanoclusters having predictable sizes and emission energies. Metal-binding α-helical coiled coils were designed to exist as peptide trimers, tetramers, and hexamers and found to uniquely bind 6, 8, and 12 Ag(+) ions, respectively. Subsequent treatment with a chemical reducing agent produced a series of peptide-bound Ag(0) nanoclusters that display a strong visible fluorescence whose emission energies depend on the number of bound metal ions in excellent agreement with theory.

  10. An algorithm to use higher order invariants for modelling potential energy surface of nanoclusters

    Science.gov (United States)

    Jindal, Shweta; Bulusu, Satya S.

    2018-02-01

    In order to fit potential energy surface (PES) of gold nanoclusters, we have integrated bispectrum features with artificial neural network (ANN) learning technique in this work. We have also devised an algorithm for selecting the frequencies that need to be coupled for extracting the phase information between different frequency bands. We have found that higher order invariant like bispectrum is highly efficient in exploring the PES as compared to other invariants. The sensitivity of bispectrum can also be exploited in acting as an order parameter for calculating many thermodynamic properties of nanoclusters.

  11. Stabilizing Protein Effects on the Pressure Sensitivity of Fluorescent Gold Nanoclusters

    Science.gov (United States)

    2016-01-13

    Qi-Wei Li, Shui-Hong Li, Wei Ge, Xiao Chen, Hui Jiang, Xue-Mei Wang. Novel in situ biosynthesized fluorescent zinc nanoclusters for specific...nanoclusters: synthesis and recent biological application. J Nanomaterials. 2015;6:1–23. 15. Liu CL, Wu HT, Hsiao YH , Lai CW, Shih CW, Peng YK, Tang KC...synthesis and biological applications. Nano Today. 2011;6:401–418. 17. Wen F, Dong YH , Feng L, Wang S, Zhang SC, Zhang XR. Horseradish peroxidase

  12. Absorption Spectra of CuGaSe2 and CuInSe2 Semiconducting Nanoclusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2015-10-01

    The structural and optical properties of the chalcopyrite CunGanSe2n and CunInnSe2n nanoclusters (n = 2, 4, 6, and 8) are investigated as a function of the size using a combination of basin-hopping global optimization and time-dependent density functional theory. Although the lowest energy structures are found to show almost random geometries, the band gaps and absorption spectra still are subject to systematic blue shifts for decreasing cluster size in the case of CunGanSe2n, indicating strong electron confinement. The applicability of the nanoclusters in photovoltaics is discussed. © 2015 American Chemical Society.

  13. Quantum Analysis of Dispersion and Induction Energies in Organic van der Waals Nanoclusters

    Science.gov (United States)

    Popova, Anna M.; Komarov, Viacheslav V.; Schmidt, Lothar; Jungclas, Hartmut

    2017-11-01

    A new analytical method is presented, which describes the interactions of three neutral organic molecules forming an isolated nanocluster. We assume that one of the three molecules has a permanent dipole moment. The induction processes and Coulomb interactions inside the nanocluster are considered taking into account molecular charges and structure properties. The functions of the dispersion and induction energies are obtained in analytical form without any phenomenological representations. The method was applied to a specific cluster consisting of two pyrene molecules and one pentene molecule with a dipole moment equal to 0.6 D. The values of the intermolecular interaction energies for these molecules are calculated and presented versus intermolecular distances.

  14. 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.

  15. Ag29(BDT)12(TPP)4: A Tetravalent Nanocluster

    KAUST Repository

    AbdulHalim, Lina G.

    2015-06-24

    The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT: 1,3-benzenedithiols; TPP: triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT—wide footprint bidentate thiols—in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical bandgap compared to that of the solution state, suggesting strong inter-particle electronic coupling occurs in the solid state.

  16. Growth simulations of silver shells on copper and palladium nanoclusters

    Science.gov (United States)

    Baletto, F.; Mottet, C.; Ferrando, R.

    2002-10-01

    The growth of Ag-Pd and Ag-Cu core-shell nanoclusters is studied by molecular-dynamics simulations on realistic time scales. The metals are modeled by many-body potentials derived in the framework of the second-moment approximation to the tight-binding model. First, the energy barriers of the most relevant diffusion processes of Ag adatoms on Pd and Cu cores are calculated, and then growth simulations are performed for several values of the deposition flux and of the temperature. We find that well-defined Ag shells on both Pd and Cu cores are grown. In particular, single-layer shells with a few defects can be obtained in a wide range of temperatures. The main difference between the Ag-Pd and the Ag-Cu systems is that in the former better structures are obtained at low temperatures, while in the latter, the best shells are grown at high temperatures. These behaviors are explained in terms of the ability (inability) to incorporate Ag adatoms into the Pd or Cu cores.

  17. Efficient Radioisotope Energy Transfer by Gold Nanoclusters for Molecular Imaging.

    Science.gov (United States)

    Volotskova, Olga; Sun, Conroy; Stafford, Jason H; Koh, Ai Leen; Ma, Xiaowei; Cheng, Zhen; Cui, Bianxiao; Pratx, Guillem; Xing, Lei

    2015-08-26

    Beta-emitting isotopes Fluorine-18 and Yttrium-90 are tested for their potential to stimulate gold nanoclusters conjugated with blood serum proteins (AuNCs). AuNCs excited by either medical radioisotope are found to be highly effective ionizing radiation energy transfer mediators, suitable for in vivo optical imaging. AuNCs synthesized with protein templates convert beta-decaying radioisotope energy into tissue-penetrating optical signals between 620 and 800 nm. Optical signals are not detected from AuNCs incubated with Technetium-99m, a pure gamma emitter that is used as a control. Optical emission from AuNCs is not proportional to Cerenkov radiation, indicating that the energy transfer between the radionuclide and AuNC is only partially mediated by Cerenkov photons. A direct Coulombic interaction is proposed as a novel and significant mechanism of energy transfer between decaying radionuclides and AuNCs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Silver Nanoclusters: From Design Principles to Practical Applications

    KAUST Repository

    Abdulhalim, Lina G.

    2015-12-08

    A strategy based on reticulating metal ions and organic ligands into atomically precise gold and silver nanoclusters (NCs) with high monodispersity has been advanced to a point that allows the design of NCs with strict stoichiometries, functionalities and valence. Of the Ag NCs discovered, Ag44 is the most studied, not only due to its high absorption that transcends the visible spectrum suitable for photovoltaics but also because of its long excited state lifetime, as revealed by nanosecond transient absorption spectroscopy. A major principle discovered in this dissertation is the ability to produce Ag44 in scalable amounts and with high stability in addition to modulation of the functional groups of the organic ligands via a fast and complete ligand exchange process. This new discovery has led to the development of synthetic designs in which new sizes were obtained by varying the reaction parameters (e.g., ligands functionality, reaction temperature and time), namely, Ag29 using dithiols and phosphines. The synthesized NCs possess tetravalent functionalities that facilitate their crystallization and characterization. Furthermore, Ag29 glows red and is therefore a possible candidate for sensing and imaging applications.

  19. Exotic high activity surface patterns in PtAu nanoclusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2013-05-09

    The structure and chemical ordering of PtAu nanoclusters of 79, 135, and 201 atoms are studied via a combination of a basin hopping atom-exchange technique (to locate the lowest energy homotops at fixed composition), a symmetry orbit technique (to find the high symmetry isomers), and density functional theory local reoptimization (for determining the most stable homotop). The interatomic interactions between Pt and Au are derived from the empirical Gupta potential. The lowest energy structures show a marked tendency toward PtcoreAushell chemical ordering by enrichment of the more cohesive Pt in the core region and of Au in the shell region. We observe a preferential segregation of Pt atoms to (111) facets and Au atoms to (100) facets of the truncated octahedron cluster motif. Exotic surface patterns are obtained particularly for Pt-rich compositions, where Pt atoms are being surrounded by Au atoms. These surface arrangements boost the catalytic activity by creating a large number of active sites. © 2013 American Chemical Society.

  20. Synthesis and characterization of human transferrin-stabilized gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Le Guevel, Xavier; Schneider, Marc [Pharmaceutical Nanotechnology, Saarland University, Saarbruecken (Germany); Daum, Nicole, E-mail: Marc.Schneider@mx.uni-saarland.de [Drug Delivery, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarbruecken (Germany)

    2011-07-08

    Human transferrin has been biolabelled with gold nanoclusters (Au NCs) using a simple, fast and non-toxic method. These nanocrystals (<2 nm) are stabilized in the protein via sulfur groups and have a high fluorescence emission in the near infrared region (QY = 4.3%; {lambda}{sub em} = 695 nm). Structural investigation and photophysical measurements show a high population of clusters formed of 22-33 gold atoms covalently bound to the transferrin. In solutions with pH ranging from 5 to 10 and in buffer solutions (PBS, HEPES), those biolabelled proteins exhibit a good stability. No significant quenching effect of the fluorescent transferrin has been detected after iron loading of iron-free transferrin (apoTf) and in the presence of a specific polyclonal antibody. Additionally, antibody-induced agglomeration demonstrates no alteration in the protein activity and the receptor target ability. MTT and Vialight Plus tests show no cytotoxicity of these labelled proteins in cells (1 {mu}g ml{sup -1}-1 mg ml{sup -1}). Cell line experiments (A549) indicate also an uptake of the iron loaded fluorescent proteins inside cells. These remarkable data highlight the potential of a new type of non-toxic fluorescent transferrin for imaging and targeting.

  1. TiO2 Films Modified with Au Nanoclusters as Self-Cleaning Surfaces under Visible Light

    Directory of Open Access Journals (Sweden)

    Ting-Wei Liao

    2018-01-01

    Full Text Available In this study, we applied cluster beam deposition (CBD as a new approach for fabricating efficient plasmon-based photocatalytic materials. Au nanoclusters (AuNCs produced in the gas phase were deposited on TiO2 P25-coated silicon wafers with coverage ranging from 2 to 8 atomic monolayer (ML equivalents. Scanning Electron Microscopy (SEM images of the AuNCs modified TiO2 P25 films show that the surface is uniformly covered by the AuNCs that remain isolated at low coverage (2 ML, 4 ML and aggregate at higher coverage (8 ML. A clear relationship between AuNCs coverage and photocatalytic activity towards stearic acid photo-oxidation was measured, both under ultraviolet and green light illumination. TiO2 P25 covered with 4 ML AuNCs showed the best stearic acid photo-oxidation performance under green light illumination (Formal Quantum Efficiency 1.6 × 10−6 over a period of 93 h. These results demonstrate the large potential of gas-phase AuNCs beam deposition technology for the fabrication of visible light active plasmonic photocatalysts.

  2. TiO2 Films Modified with Au Nanoclusters as Self-Cleaning Surfaces under Visible Light

    Science.gov (United States)

    Claes, Nathalie; Yadav, Anupam; Bals, Sara

    2018-01-01

    In this study, we applied cluster beam deposition (CBD) as a new approach for fabricating efficient plasmon-based photocatalytic materials. Au nanoclusters (AuNCs) produced in the gas phase were deposited on TiO2 P25-coated silicon wafers with coverage ranging from 2 to 8 atomic monolayer (ML) equivalents. Scanning Electron Microscopy (SEM) images of the AuNCs modified TiO2 P25 films show that the surface is uniformly covered by the AuNCs that remain isolated at low coverage (2 ML, 4 ML) and aggregate at higher coverage (8 ML). A clear relationship between AuNCs coverage and photocatalytic activity towards stearic acid photo-oxidation was measured, both under ultraviolet and green light illumination. TiO2 P25 covered with 4 ML AuNCs showed the best stearic acid photo-oxidation performance under green light illumination (Formal Quantum Efficiency 1.6 × 10−6 over a period of 93 h). These results demonstrate the large potential of gas-phase AuNCs beam deposition technology for the fabrication of visible light active plasmonic photocatalysts. PMID:29316728

  3. Energy of the Isolated Metastable Iron-Nickel FCC Nanocluster with a Carbon Atom in the Tetragonal Interstice.

    Science.gov (United States)

    Bondarenko, Natalya V; Nedolya, Anatoliy V

    2017-12-01

    The energy of the isolated iron-nickel nanocluster was calculated by molecular mechanics method using Lennard-Jones potential. The cluster included a carbon atom that drifted from an inside octahedral interstice to a tetrahedral interstice in [Formula: see text] direction and after that in direction to the surface. In addition, one of 14 iron atoms was replaced by a nickel atom, the position of which was changing during simulation.The energy of the nanocluster was estimated at the different interatomic distances. As a result of simulation, the optimal interatomic distances of Fe-Ni-C nanocluster was chosen for the simulation, in which height of the potential barrier was maximal and face-centered cubic (FCC) nanocluster was the most stable.It is shown that there were three main positions of a nickel atom that significantly affected nanocluster's energy.The calculation results indicated that position of the carbon atom in the octahedral interstice was more energetically favorable than tetrahedral interstice in the case of FCC nanocluster. On the other side, the potential barrier was smaller in the direction [Formula: see text] than in the direction .This indicates that there are two ways for carbon atom to drift to the surface of the nanocluster.

  4. Unique atom hyper-kagome order in Na4Ir3O8 and in low-symmetry spinel modifications.

    Science.gov (United States)

    Talanov, V M; Shirokov, V B; Talanov, M V

    2015-05-01

    Group-theoretical and thermodynamic methods of the Landau theory of phase transitions are used to investigate the hyper-kagome atomic order in structures of ordered spinels and a spinel-like Na4Ir3O8 crystal. The formation of an atom hyper-kagome sublattice in Na4Ir3O8 is described theoretically on the basis of the archetype (hypothetical parent structure/phase) concept. The archetype structure of Na4Ir3O8 has a spinel-like structure (space group Fd\\bar 3m) and composition [Na1/2Ir3/2](16d)[Na3/2](16c)O(32e)4. The critical order parameter which induces hypothetical phase transition has been stated. It is shown that the derived structure of Na4Ir3O8 is formed as a result of the displacements of Na, Ir and O atoms, and ordering of Na, Ir and O atoms, ordering dxy, dxz, dyz orbitals as well. Ordering of all atoms takes place according to the type 1:3. Ir and Na atoms form an intriguing atom order: a network of corner-shared Ir triangles called a hyper-kagome lattice. The Ir atoms form nanoclusters which are named decagons. The existence of hyper-kagome lattices in six types of ordered spinel structures is predicted theoretically. The structure mechanisms of the formation of the predicted hyper-kagome atom order in some ordered spinel phases are established. For a number of cases typical diagrams of possible crystal phase states are built in the framework of the Landau theory of phase transitions. Thermodynamical conditions of hyper-kagome order formation are discussed by means of these diagrams. The proposed theory is in accordance with experimental data.

  5. CO oxidation on gold nanoparticles: Theoretical studies

    DEFF Research Database (Denmark)

    Remediakis, Ioannis; Lopez, Nuria; Nørskov, Jens Kehlet

    2005-01-01

    We present a summary of our theoretical results regarding CO oxidation on both oxide-supported and isolated gold nanoparticles. Using Density Functional Theory we have studied the adsorption of molecules and the oxidation reaction of CO on gold clusters. Low-coordinated sites on the gold...... nanoparticles can adsorb small inorganic molecules such as O2 and CO, and the presence of these sites is the key factor for the catalytic properties of supported gold nanoclusters. Other contributions, induced by the presence of the support, can provide parallel channels for the reaction and modulate the final...

  6. Compositional evolution of Pd-based nanoclusters under thermal annealing in ion implanted SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mattei, G. E-mail: mattei@padova.infm.it; Battaglin, G.; Bello, V.; Cattaruzza, E.; De Julian, C.; De Marchi, G.; Maurizio, C.; Mazzoldi, P.; Parolin, M.; Sada, C

    2004-06-01

    Sequential ion implantation has been used to synthesize Pd-based alloy nanoclusters in SiO{sub 2}. Three systems have been investigated (PdCu, PdAg and PdFe) in terms of nanocluster formation and stability under thermal annealing. In particular, we focused on the role played by the annealing atmosphere. A comparison is made with similar alloy-based systems obtained by sequential ion implantation in silica of Au-Ag or Au-Cu followed by annealing under similar conditions. Strong similarities have been found in the compositional evolution of Pd-based and Au-based nanoclusters.

  7. IR and the Earth

    DEFF Research Database (Denmark)

    Corry, Olaf; Stevenson, Hayley

    2017-01-01

    politics and offers an account of how this builds on older ways in which the natural world has made up part of the stuff of international politics. Second, it surveys the main traditions and approaches to studying International Relations of the environment, painting a picture of diversification in two......, ‘what has the environment ever done for IR?’, before the plan for the rest of the book sketches the content and direction of the ensuing chapters that explore the problematique of International Relations and the Earth....

  8. Enhanced Bonding of Silver Nanoparticles on Oxidized TiO2(110)

    DEFF Research Database (Denmark)

    Hansen, Jonas Ørbæk; Salazar, Estephania Lira; Galliker, Patrick

    2010-01-01

    The nucleation and growth of silver nanoclusters on TiO2(110) surfaces with on-top O adatoms (oxidized TiO2), surface O vacancies and H adatoms (reduced TiO2) have been studied. From the interplay of scanning tunneling microscopy/photoelectron spectroscopy experiments and density functional theor...

  9. Surface enhanced Raman scattering (SERS) study of L-arginine adsorbed on Ag nanoclusters on glass substrate by nanocluster deposition method

    Science.gov (United States)

    Botta, Raju; Bansal, C.

    2015-06-01

    Spheroidal shape Ag nanoclusters were prepared using inert gas phase condensation technique of cluster deposition system. Annealed the Ag nanocluster film at 300 °C to get proper size and also tune the surface plasmon resonance (SPR) with excitation wavelength. L- Arginine (L-Arg) amino acid was taken to study the quantitative nature of the Raman peaks with molar concentration. Wide range of aqueous solution of L-Arg amino acid was prepared by sequential dilution method (1 mM to 1 µM) and 40 µL of L-Arg was dropped on the Ag nanocluster film and allowed to dry in the ambient conditions. Further Raman measurements were carried out using 514 nm laser excitation sources. Guanidium fragment vibrational mode and COO- symmetric stretching mode peaks were taken for the quantitative measurement. All the SERS spectrums are in good agreement with earlier reports and are reproducible over the substrate. A good correlation between peak intensity and molar concentration was found. These results show promising applications in the protein analysis.

  10. Methionine-Capped Gold Nanoclusters as a Fluorescence-Enhanced Probe for Cadmium(II Sensing

    Directory of Open Access Journals (Sweden)

    Yan Peng

    2018-02-01

    Full Text Available Gold nanoclusters (Au NCs have been considered as novel heavy metal ions sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. In this study, a green and facile method was developed for the preparation of fluorescent water-soluble gold nanoclusters with methionine as a stabilizer. The nanoclusters emit orange fluorescence with excitation/emission peaks at 420/565 nm and a quantum yield of about 1.46%. The fluorescence of the Au NCs is selectively and sensitively enhanced by addition of Cd(II ions attributed to the Cd(II ion-induced aggregation of nanoclusters. This finding was further used to design a fluorometric method for the determination of Cd(II ions, which had a linear response in the concentration range from 50 nM to 35 μM and a detection limit of 12.25 nM. The practicality of the nanoprobe was validated in various environmental water samples and milk powder samples, with a fairly satisfactory recovery percent.

  11. Formation of optical properties of intermetallic nanoclusters formed by sequential ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Zuhr, R.A. [Oak Ridge National Lab., TN (United States). Solid State Div.; Magruder, R.H. III; Anderson, T.S. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Applied and Engineering Sciences

    1997-09-01

    Recent demonstrations that large third order nonlinear responses can be achieved in metal nanocluster glass composites are of significant interest because of their potential for use in all optical switching networks. These composite materials exhibit picosecond switching and relaxation times, thermal and chemical stability, high laser damage thresholds, and low two photon absorption. Ion implantation has been shown to be a useful fabrication method to form these nanoclusters in silica because of its ability to produce thin films in waveguide configurations containing a high volume fraction (> 1%) of metal colloids with well defined vertical and horizontal dimensional control. Using sequential ion implantation of more than one element the authors can modify the composition and microstructure of the composites by forming intermetallic metal colloids. In this work the authors report on the improved optical response of metallic nanocluster composites formed by sequential implantation of Cd and Ag and Sb and Ag. Characterization of the samples by transmission electron microscopy (TEM) reveals that approximately spherical metallic colloids are formed for all implanted species during the implantation process. Selected area diffraction patterns indicate that the colloids formed are intermetallic in composition. Linear optical absorption measurements made at room temperature in air from 900 to 200 nm show significant changes in both the magnitude and wavelength of the surface plasmon resonance. The formation of intermetallic nanoclusters results in changes in both the linear and nonlinear optical properties of the composite material that are not possible with single element colloids alone. The results are explained in terms of effective medium theory.

  12. Biophysical mechanism for ras-nanocluster formation and signaling in plasma membrane.

    Directory of Open Access Journals (Sweden)

    Thomas Gurry

    2009-07-01

    Full Text Available Ras GTPases are lipid-anchored G proteins, which play a fundamental role in cell signaling processes. Electron micrographs of immunogold-labeled Ras have shown that membrane-bound Ras molecules segregate into nanocluster domains. Several models have been developed in attempts to obtain quantitative descriptions of nanocluster formation, but all have relied on assumptions such as a constant, expression-level independent ratio of Ras in clusters to Ras monomers (cluster/monomer ratio. However, this assumption is inconsistent with the law of mass action. Here, we present a biophysical model of Ras clustering based on short-range attraction and long-range repulsion between Ras molecules in the membrane. To test this model, we performed Monte Carlo simulations and compared statistical clustering properties with experimental data. We find that we can recover the experimentally-observed clustering across a range of Ras expression levels, without assuming a constant cluster/monomer ratio or the existence of lipid rafts. In addition, our model makes predictions about the signaling properties of Ras nanoclusters in support of the idea that Ras nanoclusters act as an analog-digital-analog converter for high fidelity signaling.

  13. Nanomorphology of Polymer Frameworks and Their Role as Templates for Generating Size-Controlled Metal Nanoclusters

    Czech Academy of Sciences Publication Activity Database

    Artuso, F.; D'Archivio, A. A.; Lora, S.; Jeřábek, Karel; Králik, E.; Corain, B.

    2003-01-01

    Roč. 9, č. 21 (2003), s. 5292-5296 ISSN 0947-6539 Grant - others:GA-(IT) 2001038991; VEGA(SK) 1/9142/02 Institutional research plan: CEZ:AV0Z4072921 Keywords : nanoclusters * nano-structures * gel-type resins Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.353, year: 2003

  14. Mechanistic insights from atomically precise gold nanocluster-catalyzed reduction of 4-nitrophenol

    Directory of Open Access Journals (Sweden)

    Shuo Zhao

    2016-10-01

    Full Text Available A trio of thiolate-protected atomically precise gold nanoclusters, [Au23(S-c-C6H1116]–, Au24(SCH2pHtBu20 and [Au25(SCH2CH2pH18]–, are utilized as catalysts for 4-nitrophenol (4-NP reduction to 4-aminophenol (4-AP. Despite nearly identical sizes (~1 nm, the three nanoclusters possess distinctly different atomic packing structures and surface ligand binding modes, which contribute to different catalytic performance. The [Au23(S-c-C6H1116]– nanocluster shows the highest activity with a kinetic rate constant of 0.0370 s−1, which is higher than those of Au24(SCH2pHtBu20 (0.0090 s−1 and [Au25(SCH2CH2pH18]– (0.0242 s−1. Such a trio of gold nanoclusters indicate that the atomic packing mode and electronic structure play a crucial role in determining their catalytic performance.

  15. In situ transmission electron microscopy studies on structural dynamics of transition metal nanoclusters

    NARCIS (Netherlands)

    Vystavel, T.; Koch, S.A.; Palasantzas, G.; Hosson, J.Th.M. De

    The structural stability of transition metal nanoclusters has been scrutinized with in situ transmission electron microscopy as a function of temperature. In particular iron, cobalt, niobium, and molybdenum clusters with diameters around 5 nm have been investigated. During exposure to air, a thin

  16. Antibacterial silver nanocluster/silica composite coatings on stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ferraris, M.; Perero, S. [Politecnico di Torino, Department of Applied Science and Technology, Torino, C.so Duca degli Abruzzi 24, I-10129 (Italy); Ferraris, S., E-mail: sara.ferraris@polito.it [Politecnico di Torino, Department of Applied Science and Technology, Torino, C.so Duca degli Abruzzi 24, I-10129 (Italy); Miola, M.; Vernè, E. [Politecnico di Torino, Department of Applied Science and Technology, Torino, C.so Duca degli Abruzzi 24, I-10129 (Italy); Skoglund, S. [KTH Royal Institute of Technology, Div. Surface and Corrosion Science, Dr. Kristinas v. 51, SE-100 44 (Sweden); Blomberg, E. [KTH Royal Institute of Technology, Div. Surface and Corrosion Science, Dr. Kristinas v. 51, SE-100 44 (Sweden); SP Technical Research Institute of Sweden, Chemistry, Materials and Surfaces, P.O. Box 5607, SE-114 86 Stockholm (Sweden); Odnevall Wallinder, I. [KTH Royal Institute of Technology, Div. Surface and Corrosion Science, Dr. Kristinas v. 51, SE-100 44 (Sweden)

    2017-02-28

    Highlights: • A silver nanocluster-silica composite coating sputter-deposited onto stainless steel. • Good adhesion and resistance upon cleaning with NaOH, H{sub 2}SO{sub 4} and detergents. • Low release of silver ions and no release as silver nanoparticles. • Good antibacterial activity against S. aureus even after heating to 450 °C. • Good antibacterial activity shown during cheese production. - Abstract: A coating made of silver nanocluster/silica composites has been deposited, via a radio frequency (RF) co-sputtering technique, for the first time onto stainless steel (AISI 304L) with the aim to improve its antibacterial properties. Different thermal treatments after coating deposition have been applied in order to optimize the coating adhesion, cohesion and its antibacterial properties. Its applicability has been investigated at realistic conditions in a cheese production plant. The physico-chemical characteristics of the coatings have been analyzed by means of different bulk and surface analytical techniques. Field emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), contact angle measurements and atomic force microscopy (AFM) were employed to assess coating morphology, composition, surface roughness, wetting properties, size and local distribution of the nanoparticles within the coating. Tape tests were used to determine the adhesion/cohesion properties of the coating. The amount and time-dependence of released silver in solutions of acetic acid, artificial water, artificial tap water and artificial milk were determined by means of Atomic Absorption Spectroscopy (AAS). The antibacterial effect of the coating was evaluated at different experimental conditions using a standard bacterial strain of Staphylococcus aureus in compliance with National Committee for Clinical Laboratory Standards (NCCLS) and AATCC 147 standards. The Ahearn test was performed to measure the adhesion of bacteria to the coated stainless steel

  17. Antibacterial silver nanocluster/silica composite coatings on stainless steel

    International Nuclear Information System (INIS)

    Ferraris, M.; Perero, S.; Ferraris, S.; Miola, M.; Vernè, E.; Skoglund, S.; Blomberg, E.; Odnevall Wallinder, I.

    2017-01-01

    Highlights: • A silver nanocluster-silica composite coating sputter-deposited onto stainless steel. • Good adhesion and resistance upon cleaning with NaOH, H 2 SO 4 and detergents. • Low release of silver ions and no release as silver nanoparticles. • Good antibacterial activity against S. aureus even after heating to 450 °C. • Good antibacterial activity shown during cheese production. - Abstract: A coating made of silver nanocluster/silica composites has been deposited, via a radio frequency (RF) co-sputtering technique, for the first time onto stainless steel (AISI 304L) with the aim to improve its antibacterial properties. Different thermal treatments after coating deposition have been applied in order to optimize the coating adhesion, cohesion and its antibacterial properties. Its applicability has been investigated at realistic conditions in a cheese production plant. The physico-chemical characteristics of the coatings have been analyzed by means of different bulk and surface analytical techniques. Field emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), contact angle measurements and atomic force microscopy (AFM) were employed to assess coating morphology, composition, surface roughness, wetting properties, size and local distribution of the nanoparticles within the coating. Tape tests were used to determine the adhesion/cohesion properties of the coating. The amount and time-dependence of released silver in solutions of acetic acid, artificial water, artificial tap water and artificial milk were determined by means of Atomic Absorption Spectroscopy (AAS). The antibacterial effect of the coating was evaluated at different experimental conditions using a standard bacterial strain of Staphylococcus aureus in compliance with National Committee for Clinical Laboratory Standards (NCCLS) and AATCC 147 standards. The Ahearn test was performed to measure the adhesion of bacteria to the coated stainless steel surface

  18. Detailed IR aperture measurements

    CERN Document Server

    Bruce, Roderik; Garcia Morales, Hector; Giovannozzi, Massimo; Hermes, Pascal Dominik; Mirarchi, Daniele; Quaranta, Elena; Redaelli, Stefano; Rossi, Carlo; Skowronski, Piotr Krzysztof; Wretborn, Sven Joel; CERN. Geneva. ATS Department

    2016-01-01

    MD 1673 was carried out on October 5 2016, in order to investigate in more detail the available aperture in the LHC high-luminosity insertions at 6.5 TeV and β∗=40 cm. Previous aperture measurements in 2016 during commissioning had shown that the available aperture is at the edge of protection, and that the aperture bottleneck at β∗=40 cm in certain cases is found in the separation plane instead of in the crossing plane. Furthermore, the bottlenecks were consistently found in close to the upstream end of Q3 on the side of the incoming beam, and not in Q2 on the outgoing beam as expected from calculations. Therefore, this MD aimed at measuring IR1 and IR5 separately (at 6.5 TeV and β∗=40 cm, for 185 µrad half crossing angle), to further localize the bottlenecks longitudinally using newly installed BLMs, investigate the difference in aperture between Q2 and Q3, and to see if any aperture can be gained using special orbit bumps.

  19. Application of ionizing radiation for metal nanoclusters synthesis

    International Nuclear Information System (INIS)

    Smietanko-Chmielewska, D.K.; Chmielewski, A.G.; Warsaw University of Technology, Warsaw

    2011-01-01

    Complete text of publication follows. Possibility of ionizing radiation application in nanotechnology has been observed from very beginning when this field of science and technology was named. The lithography is based on electron and ion beam applications, and metal clusters synthesis by radiation induced radicals was reported many years ago. International Atomic Energy Agency was the first organization which has started coordinated programs on radiation applications in nanotechnology which are being continued in the frame of regional cooperation project RER8014. Some of applications led to patented technical solutions. Then review papers and chapters in the books have been published. The main applications beside of lithography deal with metal nanoclusters and nano-composites synthesis. Polymer composites containing metal nanoparticles have attracted a great interest due to their unique chemical and physical properties. 'Green' chemistry promotes application of natural fibers in such structures, among them cellulose is one of the most frequently used. However, cellulose fabric have ability to absorb moisture, so under certain conditions of humidity and temperature they can be subjected to microbial attack. One of the most popular and best known antibacterial agents is silver, which serves as a potential antibacterial material acting against an exceptionally broad spectrum of bacteria including activity against antibiotic-resistant bacteria. Silver nanoparticles (Ag NPs) were grown at the cellulose fibers surface by direct reduction of AgNO 3 with electron beam (EB) application. The big field of development concerns nano composites, possibility of e/X units application enlarge this possibility to industrial scale product manufacturing. Acknowledgement: This work was supported by the IAEA, regional project RER/8/014 and by the Ministry of Science and Higher Education, project DPN/W14/IAEA/2009.

  20. Switching a Nanocluster Core from Hollow to Non-hollow

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2016-03-24

    Modulating the structure-property relationship in atomically precise nanoclusters (NCs) is vital for developing novel NC materials and advancing their applications. While promising biphasic ligand-exchange (LE) strategies have been developed primarily to attain novel NCs, understanding the mechanistic aspects involved in tuning the core and the ligand-shell of NCs in such biphasic processes is challenging. Here, we design a single phase LE process that enabled us to elucidate the mechanism of how a hollow NC (e.g., [Ag44(SR)30]4-, -SR: thiolate) converts into a non-hollow NC (e.g., [Ag25(SR)18]-), and vice versa. Our study reveals that the complete LE of the hollow [Ag44(SPhF)30]4- NCs (–SPhF: 4-fluorobenzenethiolate) with incoming 2,4-dimethylbenzenethiol (HSPhMe2) induced distortions in the Ag44 structure forming the non-hollow [Ag25(SPhMe2)18]- by a disproportionation mechanism. While the reverse reaction of [Ag25(SPhMe2)18]- with HSPhF prompted an unusual dimerization of Ag25, followed by a rearrangement step that reproduces the original [Ag44(SPhF)30]4-. Remarkably, both the forward and the backward reactions proceed through similar size intermediates that seem to be governed by the boundary conditions set by the thermodynamic and electronic stability of the hollow and non-hollow metal cores. Furthermore, the resizing of NCs highlights the surprisingly long-range effect of the ligands which are felt by atoms far deep in the metal core, thus opening a new path for controlling the structural evolution of nanoparticles.

  1. Reversible Size Control of Silver Nanoclusters via Ligand-exchange

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2015-05-21

    The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

  2. Distinct metal-exchange pathways of doped Ag25 nanoclusters

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2016-09-09

    Atomically precise metal nanoclusters (NCs) containing more than one type of metal atom (i.e., doped or alloyed), due to synergistic effects, open new avenues for engineering the catalytic and optical properties of NCs in a manner that homometal NCs cannot. Unfortunately, it is still a major challenge to controllably introduce multimetallic dopants in NCs, understanding the dopants\\' positions, mechanism, and synergistic effects. To overcome these challenges, we designed a metal-exchange approach involving NCs as molecular templates and metal ions as the source of the incoming dopant. In particular, two structurally similar monodoped silver-rich NCs, [MAg24(SR)(18)](2-) (M = Pd/Pt and SR: thiolate), were synthesized as templates to study their mechanistic transformation in response to the introduction of gold atoms. The controllable incorporation of Au atoms into the MAg24 framework facilitated the elucidation of distinct doping pathways through high-resolution mass spectrometry, optical spectroscopy and elemental analysis. Interestingly, gold replaced the central Pd atom of [PdAg24(SR)(18)](2-) clusters to produce predominantly bimetallic [AuAg24(SR)(18)](-) clusters along with a minor product of an [Au2Ag23(SR)(18)](-) cluster. In contrast, the central Pt atom remained intact in [PtAg24(SR)(18)](2-) clusters, and gold replaced the noncentral Ag atoms to form trimetallic [AuxPtAg24-x(SR)(18)](2-) NCs, where x = 1-2, with a portion of the starting [PtAg24(SR)(18)](2-) NCs remaining. This study reveals some of the unusual metal-exchange pathways of doped NCs and the important role played by the initial metal dopant in directing the position of a second dopant in the final product.

  3. Accelerating the peroxidase-like activity of gold nanoclusters at neutral pH for colorimetric detection of heparin and heparinase activity.

    Science.gov (United States)

    Hu, Lianzhe; Liao, Hong; Feng, Lingyan; Wang, Min; Fu, Wensheng

    2018-04-26

    The peroxidase-like catalytic activity of gold nanoclusters (NCs) is quite low around physiological pH, which greatly limits their biological applications. Herein, we found heparin can greatly accelerate the peroxidase-like activity of Au-NCs at neutral pH. The catalytic activity of Au-NCs toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2 was 25-fold increased in the presence of heparin at pH 7. The addition of heparin not only accelerated the initial catalytic rate of Au-NCs, but also prevented the Au-NCs from catalyst deactivation. This allows the sensitive colorimetric detection of heparin at neutral pH. In the presence of heparinase, heparin was hydrolyzed into small fragments, weakening the enhancement effect of catalytic activity. Based on this phenomenon, the sensitive colorimetric determination of heparinase in biological samples was also developed.

  4. Matrix Sputtering Method: A Novel Physical Approach for Photoluminescent Noble Metal Nanoclusters.

    Science.gov (United States)

    Ishida, Yohei; Corpuz, Ryan D; Yonezawa, Tetsu

    2017-12-19

    Noble metal nanoclusters are believed to be the transition between single metal atoms, which show distinct optical properties, and metal nanoparticles, which show characteristic plasmon absorbance. The interesting properties of these materials emerge when the particle size is well below 2 nm, such as photoluminescence, which has potential application particularly in biomedical fields. These photoluminescent ultrasmall nanoclusters are typically produced by chemical reduction, which limits their practical application because of the inherent toxicity of the reagents used in this method. Thus, alternative strategies are sought, particularly in terms of physical approaches, which are known as "greener alternatives," to produce high-purity materials at high yields. Thus, a new approach using the sputtering technique was developed. This method was initially used to produce thin films using solid substrates; now it can be applied even with liquid substrates such as ionic liquids or polyethylene glycol as long as these liquids have a low vapor pressure. This revolutionary development has opened up new areas of research, particularly for the synthesis of colloidal nanoparticles with dimensions below 10 nm. We are among the first to apply the sputtering technique to the physical synthesis of photoluminescent noble metal nanoclusters. Although typical sputtering systems have relied on the effect of surface composition and viscosity of the liquid matrix on controlling particle diameters, which only resulted in diameters ca. 3-10 nm, that were all plasmonic, our new approach introduced thiol molecules as stabilizers inspired from chemical methods. In the chemical syntheses of metal nanoparticles, controlling the concentration ratio between metal ions and stabilizing reagents is a possible means of systematic size control. However, it was not clear whether this would be applicable in a sputtering system. Our latest results showed that we were able to generically produce a

  5. Heterostructure of Au nanocluster tipping on a ZnS quantum rod: controlled synthesis and novel luminescence.

    Science.gov (United States)

    Tian, Yang; Wang, Ligang; Yu, Shanshan; Zhou, Weiwei

    2015-08-14

    Heterostructures of metal nanoparticles and semiconductors are widely studied for their unique properties. However, few reports are available on the heterostructure of metal nanoclusters and semiconductors. In the present study, a heterostructure, in which gold nanoclusters selectively locate at ZnS quantum rod (QR) tips, was fabricated using a two-step solvothermal route. The composition, intrinsic crystallography, and junction of the prepared heterostructure were thoroughly investigated, and it was observed to exhibit novel luminescent behaviours. By comparison with the individual components of ZnS QRs and gold clusters, the resultant heterostructure shows an enhanced exciton emission and complete depression of defect emission for the ZnS component, and a pronounced red emission for the gold nanocluster component. The mechanism of these properties and the charge transfer between gold nanoclusters and ZnS QRs were also explored. The size and location of gold in the heterostructure were also controlled during synthesis to study their effects on the luminescence.

  6. Template-Free Supracolloidal Self-Assembly of Atomically Precise Gold Nanoclusters: From 2D Colloidal Crystals to Spherical Capsids.

    Science.gov (United States)

    Nonappa; Lahtinen, Tanja; Haataja, Johannes S; Tero, Tiia-Riikka; Häkkinen, Hannu; Ikkala, Olli

    2016-12-23

    We report supracolloidal self-assembly of atomically precise and strictly monodisperse gold nanoclusters involving p-mercaptobenzoic acid ligands (Au 102 -pMBA 44 ) under aqueous conditions into hexagonally packed monolayer-thick two-dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template-free manner by the spontaneous patchiness of the pMBA ligands around the Au 102 -pMBA 44 nanoclusters preferably towards equatorial plane, thus promoting inter-nanocluster hydrogen bonds and high packing to planar sheets. More generally, the findings encourage to explore atomically precise nanoclusters towards highly controlled colloidal self-assemblies. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Chiral ligand-protected gold nanoclusters: Considering the optical activity from a viewpoint of ligand dissymmetric field

    Directory of Open Access Journals (Sweden)

    Hiroshi Yao

    2016-10-01

    Full Text Available Chirality is a geometric property of a physical, chemical, or biological object, which is not superimposable on its mirror image. Its significant presence has led to a strong demand in the development of chiral drugs, sensors, catalysts, and photofunctional materials. In recent years, chirality of nanoscale organic/inorganic hybrids has received tremendous attention owing to potential applications in chiral nanotechnology. In particular, with the recent progress in the syntheses and characterizations of atomically precise gold nanoclusters protected by achiral thiolates, atomic level origins of their chirality have been unveiled. On the other hand, chirality or optical activity in metal nanoclusters can also be introduced via the surface chiral ligands, which should be universal for the nanosystems. This tutorial review presents some optically-active metal (gold nanoclusters protected by chiral thiolates or phosphines, and their chiroptical (or circular dichroism; CD properties are discussed mostly from a viewpoint of the ligand dissymmetric field scheme. The examples are the gold nanoclusters protected by (R-/(S-2-phenylpropane-1-thiol, (R-/(S-mercaptosuccinic acid, phenylboronate-D/L-fructose complexes, phosphine sulfonate-ephedrinium ion pairs, or glutathione. Some methodologies for versatile asymmetric transformation and chiroptical controls of the nanocluster compounds are also described. In the dissymmetric field model as the origin of optical activity, the chiroptical responses of the gold nanoclusters are strongly associated with coupled oscillator and/or CD stealing mechanisms based on the concept of induced CD (ICD derived from a perturbation theory, so on this basis, some characteristic features of the observed CD responses of chiral ligand-protected gold nanoclusters are presented in detail. We believe that various kinds of origins of chirality found in ligand-protected gold nanoclusters may provide models for understanding those of

  8. Consecutive C[subscript 60] Fullerene Dissociation from Ir([eta][superscript 2]-C[subscript 60])(CO)(Cl)(PPh[subscript 3])[subscript 2] and the Oxidative Addition of Benzene

    Science.gov (United States)

    Felix, Tamara; Cortes-Figueroa, Jose E.

    2010-01-01

    This laboratory activity is a mechanistic exploration of the interactions between electronically deficient organometallic compounds and solvent molecules. Simple kinetics experiments designed to explore the mechanism of C[subscript 60] fullerene-benzene exchange on Ir(([eta][superscript 2]-C[subscript 60])(CO)(Cl)(PPh[subscript 3])[subscript 2]…

  9. One-step microwave-assisted synthesis of water-dispersible Fe3O4 magnetic nanoclusters for hyperthermia applications

    Science.gov (United States)

    Sathya, Ayyappan; Kalyani, S.; Ranoo, Surojit; Philip, John

    2017-10-01

    To realize magnetic hyperthermia as an alternate stand-alone therapeutic procedure for cancer treatment, magnetic nanoparticles with optimal performance, within the biologically safe limits, are to be produced using simple, reproducible and scalable techniques. Herein, we present a simple, one-step approach for synthesis of water-dispersible magnetic nanoclusters (MNCs) of superparamagnetic iron oxide by reducing of Fe2(SO4)3 in sodium acetate (alkali), poly ethylene glycol (capping ligand), and ethylene glycol (solvent and reductant) in a microwave reactor. The average size and saturation magnetization of the MNC's are tuned from 27 to 52 nm and 32 to 58 emu/g by increasing the reaction time from 10 to 600 s. Transmission electron microscopy images reveal that each MNC composed of large number of primary Fe3O4 nanoparticles. The synthesised MNCs show excellent colloidal stability in aqueous phase due to the adsorbed PEG layer. The highest SAR value of 215 ± 10 W/gFe observed in 52 nm size MNC at a frequency of 126 kHz and field of 63 kA/m suggest the potential use of these MNC in hyperthermia applications. This study further opens up the possibilities to develop metal ion-doped MNCs with tunable sizes suitable for various biomedical applications using microwave assisted synthesis.

  10. Label-Free Fluorescent Detection of Trypsin Activity Based on DNA-Stabilized Silver Nanocluster-Peptide Conjugates

    Directory of Open Access Journals (Sweden)

    Cai-Xia Zhuo

    2016-11-01

    Full Text Available Trypsin is important during the regulation of pancreatic exocrine function. The detection of trypsin activity is currently limited because of the need for the substrate to be labeled with a fluorescent tag. A label-free fluorescent method has been developed to monitor trypsin activity. The designed peptide probe consists of six arginine molecules and a cysteine terminus and can be conjugated to DNA-stabilized silver nanoclusters (DNA-AgNCs by Ag-S bonding to enhance fluorescence. The peptide probe can also be adsorbed to the surface of graphene oxide (GO, thus resulting in the fluorescence quenching of DNA-AgNCs-peptide conjugate because of Förster resonance energy transfer. Once trypsin had degraded the peptide probe into amino acid residues, the DNA-AgNCs were released from the surface of GO, and the enhanced fluorescence of DNA-AgNCs was restored. Trypsin can be determined with a linear range of 0.0–50.0 ng/mL with a concentration as low as 1 ng/mL. This label-free method is simple and sensitive and has been successfully used for the determination of trypsin in serum. The method can also be modified to detect other proteases.

  11. A fluorometric biosensor based on functional Au/Ag nanoclusters for real-time monitoring of tyrosinase activity.

    Science.gov (United States)

    Ao, Hang; Qian, Zhaosheng; Zhu, Yuyu; Zhao, Meizhi; Tang, Cong; Huang, Yuanyuan; Feng, Hui; Wang, Aijun

    2016-12-15

    Due to the vital role of tyrosinase in melanin biosynthesis and its function as an important biomarker for melanoma cancer, highly sensitive detection of its activity using biocompatible materials is in urgent demand. Herein we report a convenient and highly sensitive fluorometric biosensor for tyrosinase activity detection based on biocompatible dopamine-functionalized Au/Ag nanoclusters (Dopa-Au/Ag NCs). Dopamine with redox property was covalently linked to Au/Ag NCs surface and formed a Dopa-Au/Ag NCs bioconjugate with strong blue fluorescence. Dopamine is readily oxidized by molecular oxygen under the catalysis of tyrosinase. After dopamine is transformed to o-dopaquinone, an intraparticle photoinduced election transfer (PET) process occurs between Au/Ag NCs and o-dopaquinone moiety, leading to the fluorescence quenching of the Dopa-Au/Ag NCs bioconjugate. Thus, this biosensor was utilized for sensitive and selective detection of tyrosinase in terms of the relationship between fluorescence quenching efficiency and tyrosinase activity. This study discovers that Au/Ag NCs and dopaquinone can serve as a good electron acceptor and donor pair which results in an efficient intraparticle photoinduced electron transfer process, and also provides another alternative way for tyrosinase activity monitoring. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. The IRS-1 signaling system.

    Science.gov (United States)

    Myers, M G; Sun, X J; White, M F

    1994-07-01

    Insulin-receptor substrate 1 (IRS-1) is a principal substrate of the receptor tyrosine kinase for insulin and insulin-like growth factor 1, and a substrate for a tyrosine kinase activated by interleukin 4. IRS-1 undergoes multisite tyrosine phosphorylation and mediates downstream signals by 'docking' various proteins that contain Src homology 2 domains. IRS-1 appears to be a unique molecule; however, 4PS, a protein found mainly in hemopoietic cells, may represent another member of this family.

  13. Covalently linked multimers of gold nanoclusters Au102(p-MBA)44 and Au∼250(p-MBA)n.

    Science.gov (United States)

    Lahtinen, Tanja; Hulkko, Eero; Sokołowska, Karolina; Tero, Tiia-Riikka; Saarnio, Ville; Lindgren, Johan; Pettersson, Mika; Häkkinen, Hannu; Lehtovaara, Lauri

    2016-11-10

    We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au 102 (p-MBA) 44 nanocluster with biphenyl-4,4'-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BPDT molecules. The linking chemistry is not specific to Au 102 (p-MBA) 44 . The same approach yields multimers also for a larger monodisperse p-MBA-protected cluster of approximately 250 gold atoms, Au ∼250 (p-MBA) n . While the Au 102 (p-MBA) 44 is not plasmonic, the Au ∼250 (p-MBA) n nanocluster supports localized surface plasmon resonance (LSPR) at 530 nm. Multimers of the Au ∼250 (p-MBA) n exhibit additional transitions in their UV-vis spectrum at 630 nm and 810 nm, indicating the presence of hybridized LSPR modes. Well-defined structures and relatively small sizes make these systems excellent candidates for connecting ab initio theoretical studies and experimental quantum plasmonics. Moreover, our work opens new possibilities in the controlled synthesis of advanced monodisperse nanocluster superstructures.

  14. Self-Assembly of Plasmonic Nanoclusters for Optical Metauids

    Science.gov (United States)

    Schade, Nicholas Benjamin

    90% yield with a nonequilibrium "random parking" model based on irreversible binding. Simulations based on this model reveal that 100% yield of tetrahedra is possible in principle. Finally, we combine these results and present methods for the self-assembly and purification of tetrahedral plasmonic nanoclusters, the simplest building blocks for isotropic metafluids.

  15. Ag nanocluster-based color converters for white organic light-emitting devices

    Science.gov (United States)

    Nishikitani, Yoshinori; Takizawa, Daisuke; Uchida, Soichi; Lu, Yue; Nishimura, Suzushi; Oyaizu, Kenichi; Nishide, Hiroyuki

    2017-11-01

    The authors present Ag nanocluster-based color converters (Ag NC color converters), which convert part of the blue light from a light source to yellow light so as to create white organic light-emitting devices that could be suitable for lighting systems. Ag NCs synthesized by poly(methacrylic acid) template methods have a statistical size distribution with a mean diameter of around 4.5 nm, which is larger than the Fermi wavelength of around 2 nm. Hence, like free electrons in metals, the Ag NC electrons are thought to form a continuous energy band, leading to the formation of surface plasmons by photoexcitation. As for the fluorescence emission mechanism, the fact that the photoluminescence is excitation wavelength dependent suggests that the fluorescence originates from surface plasmons in Ag NCs of different sizes. By using Ag NC color converters and suitable blue light sources, white organic light-emitting devices can be fabricated based on the concept of light-mixing. For our blue light sources, we used polymer light-emitting electrochemical cells (PLECs), which, like organic light-emitting diodes, are area light sources. The PLECs were fabricated with a blue fluorescent π-conjugated polymer, poly[(9,9-dihexylfluoren-2,7-diyl)-co-(anthracen-9,10-diyl)] (PDHFA), and a polymeric solid electrolyte composed of poly(ethylene oxide) and KCF3SO3. In this device structure, the Ag NC color converter absorbs blue light from the PDHFA-based PLEC (PDHFA-PLEC) and then emits yellow light. When the PDHFA-PLEC is turned on by applying an external voltage, pure white light emission can be produced with Commission Internationale de l'Eclairage coordinates of (x = 0.32, y = 0.33) and a color rendering index of 93.6. This study shows that utilization of Ag NC color converters and blue PLECs is a very promising and highly effective method for realizing white organic light-emitting devices.

  16. The emergence of nonbulk properties in supported metal clusters: negative thermal expansion and atomic disorder in Pt nanoclusters supported on gamma-Al2O3.

    Science.gov (United States)

    Sanchez, Sergio I; Menard, Laurent D; Bram, Ariella; Kang, Joo H; Small, Matthew W; Nuzzo, Ralph G; Frenkel, Anatoly I

    2009-05-27

    The structural dynamics-cluster size and adsorbate-dependent thermal behaviors of the metal-metal (M-M) bond distances and interatomic order-of Pt nanoclusters supported on a gamma-Al(2)O(3) are described. Data from scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) studies reveal that these materials possess a dramatically nonbulklike nature. Under an inert atmosphere small, subnanometer Pt/gamma-Al(2)O(3) clusters exhibit marked relaxations of the M-M bond distances, negative thermal expansion (NTE) with an average linear thermal expansion coefficient alpha = (-2.4 +/- 0.4) x 10(-5) K(-1), large static disorder and dynamical bond (interatomic) disorder that is poorly modeled within the constraints of classical theory. The data further demonstrate a significant temperature-dependence to the electronic structure of the Pt clusters, thereby suggesting the necessity of an active model to describe the cluster/support interactions mediating the cluster's dynamical structure. The quantitative dependences of these nonbulklike behaviors on cluster size (0.9 to 2.9 nm), ambient atmosphere (He, 4% H(2) in He or 20% O(2) in He) and support identity (gamma-Al(2)O(3) or carbon black) are systematically investigated. We show that the nonbulk structural, electronic and dynamical perturbations are most dramatically evidenced for the smallest clusters. The adsorption of hydrogen on the clusters leads to an increase of the Pt-Pt bondlengths (due to a lifting of the surface relaxation) and significant attenuation of the disorder present in the system. Oxidation of these same clusters has the opposite effect, leading to an increase in Pt-Pt bond strain and subsequent enhancement in nonbulklike thermal properties. The structural and electronic properties of Pt nanoclusters supported on carbon black contrast markedly with those of the Pt/gamma-Al(2)O(3) samples in that neither NTE nor comparable levels of atomic disorder are observed. The Pt

  17. Water clustering on nanostructured iron oxide films

    DEFF Research Database (Denmark)

    Merte, Lindsay Richard; Bechstein, Ralf; Peng, G.

    2014-01-01

    , but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moire-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer...... islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous...

  18. IMS-MS and IMS-IMS investigation of the structure and stability of dimethylamine-sulfuric acid nanoclusters.

    Science.gov (United States)

    Ouyang, Hui; He, Siqin; Larriba-Andaluz, Carlos; Hogan, Christopher J

    2015-03-12

    Recent studies of new particle formation events in the atmosphere suggest that nanoclusters (i.e, the species formed during the early stages of particle growth which are composed of 10(1)-10(3) molecules) may consist of amines and sulfuric acid. The physicochemical properties of sub-10 nm amine-sulfuric acid clusters are hence of interest. In this work, we measure the density, thermostability, and extent of water uptake of <8.5 nm effective diameter dimethylamine-sulfuric (DMAS) nanoclusters in the gas phase, produced via positive electrospray ionization. Specifically, we employ three systems to investigate DMAS properties: ion mobility spectrometry (IMS, with a parallel-plate differential mobility analyzer) is coupled with mass spectrometry to measure masses and collision cross sections for <100 kDa positively charged nanoclusters, two differential mobility analyzers in series (IMS-IMS) are used to examine thermostability, and finally a differential mobility analyzer coupled to an atmospheric pressure drift tube ion mobility spectrometer (also IMS-IMS) is used for water uptake measurements. IMS-MS measurements reveal that dry DMAS nanoclusters have densities of ∼1567 kg/m(3) near 300 K, independent of the ratio of dimethylamine to sulfuric acid originally present in the electrospray solution. IMS-IMS thermostability studies reveal that partial pressures of DMAS nanoclusters are dependent upon the electrospray solution concentration ratio, R = [H2SO4]/[(CH3)2NH]. Extrapolating measurements, we estimate that dry DMAS nanoclusters have surface vapor pressures of order 10(-4) Pa near 300 K, with the surface vapor pressure increasing with increasing values of R through most of the probed concentration range. This suggests that nanocluster surface vapor pressures are substantially enhanced by capillarity effects (the Kelvin effect). Meanwhile, IMS-IMS water uptake measurements show clearly that DMAS nanoclusters uptake water at relative humidities beyond 10% near 300

  19. NO Reactions Over Ir-Based Catalysts in the Presence of O2

    Directory of Open Access Journals (Sweden)

    Mingxin Guo

    2011-01-01

    Full Text Available The behaviour of a series of Ir-based catalysts supported on SiO2, ZSM-5 and γ-Al2O3 with various Ir loadings prepared by impregnation method was conducted by temperature programmed reaction (TPR technique. The result implies that NO is oxidized to NO2 while simultaneously being reduced to N2 or N2O in the NO reactions over iridium catalysts. The surface active phase over iridium catalysts that promote the NO reactions is IrO2. The catalytic activity increases with the increase of the Ir loading and support materials have a little effect on the catalytic activity. When the loading is less than 0.1%, the catalytic activity was found to be dependent on the nature of support materials and in order: Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2. When the loading is higher than 0.1%, the catalytic activity for NO oxidation is in order: Ir/ZSM-5>Ir/SiO2>Ir/γ -Al2O3, which is correlated with Ir dispersion on the surface of support materials and the catalytic activity for NO reduction is in sequence: Ir/γ -Al2O3>Ir/SiO2>Ir/ZSM-5, which is attributed to the adsorbed-dissociation of NO2. Compared to Pt/γ-Al2O3, Ir/γ-Al2O3 catalyst is more benefit for the NO reduction.

  20. Carbon surface diffusion and SiC nanocluster self-ordering

    International Nuclear Information System (INIS)

    Pezoldt, J.; Trushin, Yu.V.; Kharlamov, V.S.; Schmidt, A.A.; Cimalla, V.; Ambacher, O.

    2006-01-01

    The process of the spatial ordering of SiC nanoclusters on the step edges on Si surfaces was studied by means of multi-scale computer simulation. The evolution of cluster arrays on an ideal flat surface and surfaces with terraces of various widths was performed by kinetic Monte Carlo (KMC) simulations based on quantitative studies of potential energy surfaces (PES) by molecular dynamics (MD). PES analysis revealed that certain types of steps act as strong trapping centres for both Si and C adatoms stimulating clusters nucleation. Spatial ordering of the SiC nanoclusters at the terrace edges can be achieved if the parameters of the growth process (substrate temperature, carbon flux) and substrate (steps direction and terrace widths) are adjusted to the surface morphology. Temperature ranges for growth regimes with and without formation of cluster chains were determined. Cluster size distributions and the dependence of optimal terrace width for self ordering on the deposition parameters were obtained

  1. Investigation of a V15 magnetic molecular nanocluster by the Monte Carlo method

    International Nuclear Information System (INIS)

    Khizriev, K. Sh.; Dzhamalutdinova, I. S.; Taaev, T. A.

    2013-01-01

    Exchange interactions in a V 15 magnetic molecular nanocluster are considered, and the process of magnetization reversal for various values of the set of exchange constants is analyzed by the Monte Carlo method. It is shown that the best agreement between the field dependence of susceptibility and experimental results is observed for the following set of exchange interaction constants in a V 15 magnetic molecular nanocluster: J = 500 K, J′ = 150 K, J″ = 225 K, J 1 = 50 K, and J 2 = 50 K. It is observed for the first time that, in a strong magnetic field, for each of the three transitions from low-spin to high-spin states, the heat capacity exhibits two closely spaced maxima

  2. Synthesis, characterization, and growth simulations of Cu–Pt bimetallic nanoclusters

    Directory of Open Access Journals (Sweden)

    Subarna Khanal

    2014-08-01

    Full Text Available Highly monodispersed Cu–Pt bimetallic nanoclusters were synthesized by a facile synthesis approach. Analysis of transmission electron microscopy (TEM and spherical aberration (Cs-corrected scanning transmission electron microscopy (STEM images shows that the average diameter of the Cu–Pt nanoclusters is 3.0 ± 1.0 nm. The high angle annular dark field (HAADF-STEM images, intensity profiles, and energy dispersive X-ray spectroscopy (EDX line scans, allowed us to study the distribution of Cu and Pt with atomistic resolution, finding that Pt is embedded randomly in the Cu lattice. A novel simulation method is applied to study the growth mechanism, which shows the formation of alloy structures in good agreement with the experimental evidence. The findings give insight into the formation mechanism of the nanosized Cu–Pt bimetallic catalysts.

  3. Ab initio structural and electronic properties of hydrogenated silicon nanoclusters in the ground and excited state

    International Nuclear Information System (INIS)

    Degoli, Elena; Bisi, O.; Ossicini, Stefano; Cantele, G.; Ninno, D.; Luppi, Eleonora; Magri, Rita

    2004-01-01

    Electronic and structural properties of small hydrogenated silicon nanoclusters as a function of dimension are calculated from ab initio technique. The effects induced by the creation of an electron-hole pair are discussed in detail, showing the strong interplay between the structural and optical properties of the system. The distortion induced on the structure after an electronic excitation of the cluster is analyzed together with the role of the symmetry constraint during the relaxation. We point out how the overall effect is that of significantly changing the electronic spectrum if no symmetry constraint is imposed to the system. Such distortion can account for the Stokes shift and provides a possible structural model to be linked to the four-level scheme invoked in the literature to explain recent results for the optical gain in silicon nanoclusters. Finally, formation energies for clusters with increasing dimension are calculated and their relative stability discussed

  4. Interface-controlled thermal transport properties in nano-clustered phase change materials

    Science.gov (United States)

    Lee, Dongbok; Kang, Stephen Dongmin; Kim, Hyun-Mi; Kang, Dae-Hwan; Lyeo, Ho-Ki; Kim, Ki-Bum

    2012-04-01

    We measured the thermal conductivity of nano-clustered Ge2Sb2Te5(GST)-TiOx films in situ upon annealing from room temperature to 200 °C by the time-domain thermoreflectance method. The nano-clustered structure was found to significantly reduce the thermal conductivity of the crystallized GST-TiOx films. The reduction is attributed to the thermal resistance provided by the TiOx boundaries, of which the impact is identified by estimating the apparent interfacial thermal conductance of the embedded GST/TiOx interfaces. We suggest how to deal with the electronic contribution to thermal transport for this procedure. The apparent interfacial thermal conductance of the embedded GST/TiOx interfaces was found to tune closer to the intrinsic value 30 MW/m2 K as the microstructure of the films evolved into a distinctly clustered structure.

  5. Nanocluster ionization energies and work function of aluminum, and their temperature dependence

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Avik; Kresin, Vitaly V. [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484 (United States)

    2015-10-28

    Ionization threshold energies of Al{sub n} (n = 32-95) nanoclusters are determined by laser ionization of free neutral metal clusters thermalized to several temperatures in the range from 65 K to 230 K. The photoion yield curves of cold clusters follow a quadratic energy dependence above threshold, in agreement with the Fowler law of surface photoemission. Accurate data collection and analysis procedures make it possible to resolve very small (few parts in a thousand) temperature-induced shifts in the ionization energies. Extrapolation of the data to the bulk limit enables a determination of the thermal shift of the polycrystalline metal work function, found to be in excellent agreement with theoretical prediction based on the influence of thermal expansion. Small clusters display somewhat larger thermal shifts, reflecting their greater susceptibility to thermal expansion. Ionization studies of free size-resolved nanoclusters facilitate understanding of the interplay of surface, electronic, and lattice properties under contamination-free conditions.

  6. IR seeker simulator and IR scene generation to evaluate IR decoy effectiveness; 2005BU1-EO

    NARCIS (Netherlands)

    Jong, W. de; Dam, F.A.M.; Kunz, G.J.; Schleijpen, H.M.A.

    2005-01-01

    IR decoys can be an effective countermeasure against IR guided anti ship missiles. However, it's not so easy to determine how the decoys should be deployed to get maximum effectiveness. A limitation of trials is that results are obtained for the specific trial condition only. Software tools have

  7. Three-dimensional atom probe microscopy study of interphase precipitation and nanoclusters in thermomechanically treated titanium–molybdenum steels

    International Nuclear Information System (INIS)

    Mukherjee, S.; Timokhina, I.B.; Zhu, C.; Ringer, S.P.; Hodgson, P.D.

    2013-01-01

    Atom probe microscopy was used to generate tomographic analyses of solute clustering and precipitation reactions in a Ti–Mo added microalloyed steel under simulated strip-rolling conditions. It was observed that the interphase row spacing of precipitates was reduced with the application of a pre-strain. The atom probe data also revealed the coexistence of nanoclusters and precipitate particles, even after isothermal holding for 3600 s. These microstructural features occurred both within 3-D interphase precipitate sheets, and in randomly selected fields of view. A bimodal distribution of larger (∼8–10 nm) precipitates coexisted with smaller nanoclusters (∼3 nm) within the interphase sheets/rows. Both the nanoclusters and the precipitates possessed a disc morphology, although nanoclusters with less than ∼30 atoms were more irregular in shape. The size of the nanoclusters and the precipitates was expressed as a Guinier radius, and this varied between 0.5 and 8 nm for both strain conditions, with the average size ∼1.8 nm. The composition of the nanoclusters varied over a wide range, yet was mostly rich in C. All of the nanoclusters and precipitates consisted of a mixture of Ti, Mo and C and the average precipitate composition was close to that of MC carbide stoichiometry, where M represents a mixture of Ti and Mo. In the majority of cases, the Ti/Mo ratio in the MC carbides was > 1. As the Guinier radius increased above 2.5 nm, the composition range became narrower, towards the MC carbide stoichiometry, with a small amount of Fe (∼3–12 at.%)

  8. Size dependent structural and polymorphic transitions in ZnO: from nanocluster to bulk.

    Science.gov (United States)

    Viñes, Francesc; Lamiel-Garcia, Oriol; Illas, Francesc; Bromley, Stefan T

    2017-07-20

    We report on an extensive survey of (ZnO) N nanostructures ranging from bottom-up generated nanoclusters to top-down nanoparticles cuts from bulk polymorphs. The obtained results enable us to follow the energetic preferences of structure and polymorphism in (ZnO) N systems with N varying between 10-1026. This size range encompasses small nanoclusters with 10s of atoms and nanoparticles with 100s of atoms, which we also compare with appropriate bulk limits. In all cases the nanostructures and bulk systems are optimized using accurate all-electron, relativistic density functional theory based calculations with numeric atom centered orbital basis sets. Specifically, sets of five families of (ZnO) N species are considered: single-layered and multi-layered nanocages, and bulk cut nanoparticles from the sodalite (SOD), body centered tetragonal (BCT), and wurtzite (WZ) ZnO polymorphs. Using suitable fits to interpolate and extrapolate these data allows us to assess the size-dependent energetic stabilities of each family. With increasing size our results indicate a progressive change in energetic stability from single-layered to multi-layered cage-like nanoclusters. For nanoparticles of around 2.6 nm diameter we identify a transitional region where multi-layered cages, SOD, and BCT nanostructures are very similar in energetic stability. This transition size also marks the size regime at which bottom-up nanoclusters give way to top-down bulk-cut nanoparticles. Eventually, a final crossover is found where the most stable WZ-ZnO polymorph begins to energetically dominate at N ∼ 2200. This size corresponds to an approximate nanoparticle diameter of 4.7 nm, in line with experiments reporting the observation of wurtzite crystallinity in isolated ligand-free ZnO nanoparticles of 4-5 nm size or larger.

  9. Linear and Nonlinear Optical Response in Silver Nanoclusters: Insight from a Computational Investigation (Postprint)

    Science.gov (United States)

    2016-01-05

    dodecahedron, with each of these 20 atoms centered above one of the 20 triangular faces of the core icosahedron , maintaining the Ih symmetry. This structure is...extracted from the dodecahedron for each cap, and the remaining eight silver atoms in the dodecahedron form a cube that encases the core icosahedron ...PR′3)8 nanocluster structure is comprised of six silver atoms located at the vertices of an icosahedron . The remaining eight silver atoms are located

  10. Light-Emitting Diodes: Phosphorescent Nanocluster Light-Emitting Diodes (Adv. Mater. 2/2016).

    Science.gov (United States)

    Kuttipillai, Padmanaban S; Zhao, Yimu; Traverse, Christopher J; Staples, Richard J; Levine, Benjamin G; Lunt, Richard R

    2016-01-13

    On page 320, R. R. Lunt and co-workers demonstrate electroluminescence from earth-abundant phosphorescent metal halide nanoclusters. These inorganic emitters, which exhibit rich photophysics combined with a high phosphorescence quantum yield, are employed in red and near-infrared light-emitting diodes, providing a new platform of phosphorescent emitters for low-cost and high-performance light-emission applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. On the Evolution from Non-Plasmonic Metal Nanoclusters to Plasmonic Nanocrystals

    Science.gov (United States)

    2014-09-24

    figure shows the CO2 adsorption site on the nanocluster simulated by DFT . We also investigated the catalytic activity of the Pt1Au24 bimetallic...sensitive to an even small variation of particle size (e.g. a single-atom difference). Thus, a conventional level of synthetic control over particle...Fig. 5), with the Pt atom uniquely located in the center of the cluster . Large perturbations to the electronic structure and optical properties were

  12. Automated electrodeposition of bimetallic noble-metal nanoclusters via redox-replacement reactions for electrocatalysis

    CSIR Research Space (South Africa)

    Mkwizu, TS

    2009-01-01

    Full Text Available of Bimetallic Noble-Metal Nanoclusters via Redox- Replacement Reactions for Electrocatalysis T. S. Mkwizua,b, M. K. Matheb, and I. Cukrowskia aDepartment of Chemistry, University of Pretoria, NW-1 Building, Pretoria, 0002, South Africa b... strategies have utilized surface-limited redox-replacement reactions involving spontaneous replacement of less noble, sacrificial elements, such as Cu or Pb, used as templating layers in controlled synthesis of multilayers composed of noble metals...

  13. Gradients of Rac1 Nanoclusters Support Spatial Patterns of Rac1 Signaling.

    Science.gov (United States)

    Remorino, Amanda; De Beco, Simon; Cayrac, Fanny; Di Federico, Fahima; Cornilleau, Gaetan; Gautreau, Alexis; Parrini, Maria Carla; Masson, Jean-Baptiste; Dahan, Maxime; Coppey, Mathieu

    2017-11-14

    Rac1 is a small RhoGTPase switch that orchestrates actin branching in space and time and protrusion/retraction cycles of the lamellipodia at the cell front during mesenchymal migration. Biosensor imaging has revealed a graded concentration of active GTP-loaded Rac1 in protruding regions of the cell. Here, using single-molecule imaging and super-resolution microscopy, we show an additional supramolecular organization of Rac1. We find that Rac1 partitions and is immobilized into nanoclusters of 50-100 molecules each. These nanoclusters assemble because of the interaction of the polybasic tail of Rac1 with the phosphoinositide lipids PIP2 and PIP3. The additional interactions with GEFs and possibly GAPs, downstream effectors, and other partners are responsible for an enrichment of Rac1 nanoclusters in protruding regions of the cell. Our results show that subcellular patterns of Rac1 activity are supported by gradients of signaling nanodomains of heterogeneous molecular composition, which presumably act as discrete signaling platforms. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  14. Synthesis and analysis of gold nanoclusters on silicon substrates by ion beams

    International Nuclear Information System (INIS)

    Sood, D.K.; Venkatachalam, D.K.; Bhargava, S.K.; Evans, P.J.

    2005-01-01

    To facilitate the growth of silica nanowires on silicon substrates, two different seeding techniques: 1) ion implantation and 2) chemical deposition of as-synthesised gold colloids have been compared for the formation of catalysing gold nanoclusters. The prepared substrates of both types were analysed using Rutherford backscattering spectrometry at ANSTO to determine the amount of gold and its depth distribution. The topography of the substrates deposited with chemically synthesised gold nanoparticles were studied under SEM. The preliminary ion beam (RBS) analysis has shown ion implantation as a novel technique for seeding Au nanoclusters on silicon substrates facilitating growth of nanowires. This method holds a great potential for using any metal across the periodic table that can act as catalysing seed nanoclusters for nanowire growth. The use of chemical deposition as a seeding technique to deposit as-synthesised gold nanoparticles requires further investigations. RBS results show significant difference in the depth distribution of the gold nanoparticles on silicon substrates seeded by two different techniques. (author). 6 refs., 4 figs

  15. Rapid fluorescence assay for Sudan dyes using polyethyleneimine-coated copper nanoclusters

    International Nuclear Information System (INIS)

    Ling, Yu; Li, Jia Xing; Li, Nian Bing; Luo, Hong Qun; Qu, Fei

    2014-01-01

    We report that the intensity of the blue fluorescence of copper nanoclusters coated with polyethyleneimine (PEI) is strongly reduced in the presence of the food dyestuffs Sudan I-IV. This finding was exploited in a label-free fluorescence assay for these Sudan dyes both in ethanol and aqueous solutions. The PEI-capped nanoclusters have an average diameter of 1.8 nm and are displaying, under 355 nm excitation, a blue emission at 480 nm that matches the absorption bands of the Sudan dyes. The clusters are stable in solution for at least 1 month. Under optimum conditions, this assay can be applied to the quantification of the dyes Sudan I, II, III, and IV, respectively, in the 0.1−30, 0.1–30, 0.1–25, and 0.1–25 μM concentration ranges, and the detection limits (3σ/slope) are 65, 70, 45, and 50 nM, respectively. The capability of reducing the fluorescence of the PEI-capped copper nanoclusters is directly related to the number of the functional groups in that Sudan III and IV give lower detection limits. This analytical scheme exhibits a remarkably high selectivity for the Sudan dyes over potentially interfering substances. The method was successfully applied to determine Sudan I, II, III, and IV in hot chilli powder. (author)

  16. Electronic Properties of Metallic Nanoclusters on Semiconductor Surfaces: Implications for Nanoelectronic Device Applications

    International Nuclear Information System (INIS)

    Lee, Takhee; Liu Jia; Chen, N.-P.; Andres, R.P.; Janes, D.B.; Reifenberger, R.

    2000-01-01

    We review current research on the electronic properties of nanoscale metallic islands and clusters deposited on semiconductor substrates. Reported results for a number of nanoscale metal-semiconductor systems are summarized in terms of their fabrication and characterization. In addition to the issues faced in large-area metal-semiconductor systems, nano-systems present unique challenges in both the realization of well-controlled interfaces at the nanoscale and the ability to adequately characterize their electrical properties. Imaging by scanning tunneling microscopy as well as electrical characterization by current-voltage spectroscopy enable the study of the electrical properties of nanoclusters/semiconductor systems at the nanoscale. As an example of the low-resistance interfaces that can be realized, low-resistance nanocontacts consisting of metal nanoclusters deposited on specially designed ohmic contact structures are described. To illustrate a possible path to employing metal/semiconductor nanostructures in nanoelectronic applications, we also describe the fabrication and performance of uniform 2-D arrays of such metallic clusters on semiconductor substrates. Using self-assembly techniques involving conjugated organic tether molecules, arrays of nanoclusters have been formed in both unpatterned and patterned regions on semiconductor surfaces. Imaging and electrical characterization via scanning tunneling microscopy/spectroscopy indicate that high quality local ordering has been achieved within the arrays and that the clusters are electronically coupled to the semiconductor substrate via the low-resistance metal/semiconductor interface

  17. First-principles calculated decomposition pathways for LiBH4 nanoclusters

    Science.gov (United States)

    Huang, Zhi-Quan; Chen, Wei-Chih; Chuang, Feng-Chuan; Majzoub, Eric H.; Ozoliņš, Vidvuds

    2016-05-01

    We analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathways markedly differ from those in bulk LiBH4. While experiments have found that the bulk material decomposes into LiH and B, with Li2B12H12 as a kinetically inhibited intermediate phase, (LiBH4)n nanoclusters with n ≤ 12 are predicted to decompose into mixed LinBn clusters via a series of intermediate clusters of LinBnHm (m ≤ 4n). The calculated pressure-composition isotherms and temperature-pressure isobars exhibit sloping plateaus due to finite size effects on reaction thermodynamics. Generally, decomposition temperatures of free-standing clusters are found to increase with decreasing cluster size due to thermodynamic destabilization of reaction products.

  18. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger, E-mail: s.numazawa@hzdr.de [Helmholtz-Zentrum Dresden Rossendorf (HZDR), Institut fuer Ionenstrahlphysik und Materialforschung, PO Box 510119, 01314 Dresden (Germany)

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO{sub 2} surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and {approx}1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns. (fast track communication)

  19. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO2.

    Science.gov (United States)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

  20. Formation of gold nanoclusters in MgO by ion implantation at elevated temperatures

    International Nuclear Information System (INIS)

    Fedorov, A.V.; Huis, M.A. van; Veen, A. van; Schut, H.

    2000-01-01

    Gold nanoclusters were formed in (1 0 0) MgO containing nanosize cavities. Nanocavities were created by a combination of 30 keV 3 He implantation and subsequent annealing. Au was introduced inside the cavities by 30 keV Au ion implantation. The implantation dose varied from 10 16 to 3x10 16 cm -2 and the implantation temperature varied from room temperature (RT) to 1270 K. In the case of the RT implantations the samples were subsequently annealed stepwise in air up to 1370 K. The evolution of the implantation defects and the formation of nanoclusters was monitored by positron beam analysis (PBA), optical absorption spectrometry and Rutherford backscattering spectroscopy (RBS)/channeling. Optical absorption resonance peaks were observed at 570-610 nm for the RT implantations and at 525-550 nm for the implantations carried out at elevated temperatures. In the case of 1270 K implantation an extra absorption peak at 818 nm was observed. The influence of the implantation temperature on shape and position of the absorption band ascribed to nanoclusters is discussed

  1. Atomic characterization of Si nanoclusters embedded in SiO2 by atom probe tomography

    Science.gov (United States)

    2011-01-01

    Silicon nanoclusters are of prime interest for new generation of optoelectronic and microelectronics components. Physical properties (light emission, carrier storage...) of systems using such nanoclusters are strongly dependent on nanostructural characteristics. These characteristics (size, composition, distribution, and interface nature) are until now obtained using conventional high-resolution analytic methods, such as high-resolution transmission electron microscopy, EFTEM, or EELS. In this article, a complementary technique, the atom probe tomography, was used for studying a multilayer (ML) system containing silicon clusters. Such a technique and its analysis give information on the structure at the atomic level and allow obtaining complementary information with respect to other techniques. A description of the different steps for such analysis: sample preparation, atom probe analysis, and data treatment are detailed. An atomic scale description of the Si nanoclusters/SiO2 ML will be fully described. This system is composed of 3.8-nm-thick SiO layers and 4-nm-thick SiO2 layers annealed 1 h at 900°C. PMID:21711666

  2. Atomic characterization of Si nanoclusters embedded in SiO2 by atom probe tomography

    Directory of Open Access Journals (Sweden)

    Gourbilleau Fabrice

    2011-01-01

    Full Text Available Abstract Silicon nanoclusters are of prime interest for new generation of optoelectronic and microelectronics components. Physical properties (light emission, carrier storage... of systems using such nanoclusters are strongly dependent on nanostructural characteristics. These characteristics (size, composition, distribution, and interface nature are until now obtained using conventional high-resolution analytic methods, such as high-resolution transmission electron microscopy, EFTEM, or EELS. In this article, a complementary technique, the atom probe tomography, was used for studying a multilayer (ML system containing silicon clusters. Such a technique and its analysis give information on the structure at the atomic level and allow obtaining complementary information with respect to other techniques. A description of the different steps for such analysis: sample preparation, atom probe analysis, and data treatment are detailed. An atomic scale description of the Si nanoclusters/SiO2 ML will be fully described. This system is composed of 3.8-nm-thick SiO layers and 4-nm-thick SiO2 layers annealed 1 h at 900°C.

  3. In situ growth of luminescent silver nanoclusters inside bulk sol-gel silica glasses

    Science.gov (United States)

    El Hamzaoui, Hicham; Capoen, Bruno; Razdobreev, Igor; Bouazaoui, Mohamed

    2017-07-01

    Silver nanocluster-doped glasses are attractive materials for various photonic applications. In this paper, bulk silica glasses doped with luminescent silver nanoclusters have been prepared using the sol-gel technique. As a first step, dense silica glasses doped with ionic silver have been loaded with hydrogen. Thereafter, a heat-treatment in air atmosphere was performed to enable the growth of silver nanoclusters at different temperatures in the range 100-600 °C. The optical properties of the obtained nanocomposites have been studied, as a function of the post-annealing temperature, using optical absorption and photoluminescence spectroscopies. It has been shown that, under UV photoexcitation, the hydrogenated samples, heat-treated between 200 and 500 °C present visible luminescence due to cationic and neutral molecular-like silver clusters, consisting of a small number of Ag atoms or ions. After annealing at 600 °C, further Ag aggregation led to 2 nm-size silver nanoparticles, resulting in a quenching of the visible luminescence.

  4. In situ studies on controlling an atomically-accurate formation process of gold nanoclusters.

    Science.gov (United States)

    Yang, Lina; Cheng, Hao; Jiang, Yong; Huang, Ting; Bao, Jie; Sun, Zhihu; Jiang, Zheng; Ma, Jingyuan; Sun, Fanfei; Liu, Qinghua; Yao, Tao; Deng, Huijuan; Wang, Shuxin; Zhu, Manzhou; Wei, Shiqiang

    2015-09-14

    Knowledge of the molecular formation mechanism of metal nanoclusters is essential for developing chemistry for accurate control over their synthesis. Herein, the "top-down" synthetic process of monodisperse Au13 nanoclusters via HCl etching of polydisperse Aun clusters (15 ≤ n ≤ 65) is traced by a combination of in situ X-ray/UV-vis absorption spectroscopy and time-dependent mass spectrometry. It is revealed experimentally that the HCl-induced synthesis of Au13 is achieved by accurately controlling the etching process with two distinctive steps, in sharp contrast to the traditional thiol-etching mechanism through release of the Au(i) complex. The first step involves the direct fragmentation of the initial larger Aun clusters into metastable intermediate Au8-Au13 smaller clusters. This is a critical step, which allows for the secondary size-growth step of the intermediates toward the atomically monodisperse Au13 clusters via incorporating the reactive Au(i)-Cl species in the solution. Such a secondary-growth pathway is further confirmed by the successful growth of Au13 through reaction of isolated Au11 clusters with AuClPPh3 in the HCl environment. This work addresses the importance of reaction intermediates in guiding the way towards controllable synthesis of metal nanoclusters.

  5. High-rate synthesis of phosphine-stabilized undecagold nanoclusters using a multilayered micromixer

    International Nuclear Information System (INIS)

    Jin, Hyung Dae; Chang, Chih-Hung; Garrison, Anna; Tseng, T; Paul, Brian K

    2010-01-01

    Growth in the potential applications of nanomaterials has led to a focus on the development of new manufacturing approaches for these materials. In particular, an increased demand due to the unique properties of nanomaterials requires a substantial yield of high-performance materials and a simultaneous reduction in the environmental impact of these processes. In this paper, a high-rate production of phosphine-stabilized undecagold nanoclusters was achieved using a layer-up strategy which involves the use of microlamination architectures; the patterning and bonding of thin layers of material (laminae) to create a multilayered micromixer in the range of 25-250 μm thick was used to step up the production of phosphine-stabilized undecagold nanoclusters. The continuous production of highly monodispersed phosphine-stabilized undecagold nanoclusters at a rate of about 11.8 (mg s -1 ) was achieved using a microreactor with a size of 1.687 cm 3 . This result is about 500 times over conventional batch syntheses based on the production rate per reactor volume.

  6. DFT study of hydrogen production from formic acid decomposition on Pd-Au alloy nanoclusters

    Science.gov (United States)

    Liu, D.; Gao, Z. Y.; Wang, X. C.; Zeng, J.; Li, Y. M.

    2017-12-01

    Recently, it has been reported that the hydrogen production rate of formic acid decomposition can be significantly increased using Pd-Au binary alloy nano-catalysts [Wang et al. J. Mater. Chem. A 1 (2013) 12721-12725]. To explain the reaction mechanism of this alloy catalysis method, formic acid decomposition reactions on pure Pd and Pd-Au alloy nanoclusters are studied via density functional theory simulations. The simulation results indicate that the addition of inert element Au would not influence formic acid decomposition on Pd surface sites of Pd-Au alloy nanoclusters. On the other hand, the existence of Au surface sites brings relative weak hydrogen atom adsorption. On Pd-Au alloy nanoclusters, the dissociated hydrogen atoms from formic acid are easier to combine as hydrogen molecules than that on pure Pd clusters. Via the synergetic effect between Pd and Au, both formic acid decomposition and hydrogen production are events with large probability, which eventually results in high hydrogen production rate.

  7. Double surface plasmon enhanced organic light-emitting diodes by gold nanoparticles and silver nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Chia-Yuan; Chen, Ying-Chung [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-12-30

    Graphical abstract: - Highlights: • The buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated. • The silver nanoclusters will generate surface plasmon resonance effect, resulting that the localized electric field around the silver nanoclusters is enhanced. • When the recombination region of the excitons is too close to the nanoparticles of the hole-transport layer, the nonradiative quenching of excitons is generated. - Abstract: The influence of gold nanoparticles (GNPs) and silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The GNPs are doped into (poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)) (PEDOT: PSS) and the SNCs are introduced between the electron-injection layer and cathode alumina. The power efficiency of the device, at the maximum luminance, with double surface plasmon resonance and buffer layer is about 2.15 times higher than that of the device without GNPs and SNCs because the absorption peaks of GNPs and SNCs are as good as the photoluminescence peak of the emission layer, resulting in strong surface plasmon resonance effect in the device. In addition, the buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated.

  8. Ultrafast 2D IR microscopy.

    Science.gov (United States)

    Baiz, Carlos R; Schach, Denise; Tokmakoff, Andrei

    2014-07-28

    We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear "one beam" geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments.

  9. Redox Activity of Oxo-Bridged Iridium Dimers in an N,O-Donor Environment: Characterization of Remarkably Stable Ir(IV,V) Complexes.

    Science.gov (United States)

    Sinha, Shashi Bhushan; Shopov, Dimitar Y; Sharninghausen, Liam S; Stein, Christopher J; Mercado, Brandon Q; Balcells, David; Pedersen, Thomas Bondo; Reiher, Markus; Brudvig, Gary W; Crabtree, Robert H

    2017-07-19

    Chemical and electrochemical oxidation or reduction of our recently reported Ir(IV,IV) mono-μ-oxo dimers results in the formation of fully characterized Ir(IV,V) and Ir(III,III) complexes. The Ir(IV,V) dimers are unprecedented and exhibit remarkable stability under ambient conditions. This stability and modest reduction potential of 0.99 V vs NHE is in part attributed to complete charge delocalization across both Ir centers. Trends in crystallographic bond lengths and angles shed light on the structural changes accompanying oxidation and reduction. The similarity of these mono-μ-oxo dimers to our Ir "blue solution" water-oxidation catalyst gives insight into potential reactive intermediates of this structurally elusive catalyst. Additionally, a highly reactive material, proposed to be a Ir(V,V) μ-oxo species, is formed on electrochemical oxidation of the Ir(IV,V) complex in organic solvents at 1.9 V vs NHE. Spectroelectrochemistry shows reversible conversion between the Ir(IV,V) and proposed Ir(V,V) species without any degradation, highlighting the exceptional oxidation resistance of the 2-(2-pyridinyl)-2-propanolate (pyalk) ligand and robustness of these dimers. The Ir(III,III), Ir(IV,IV) and Ir(IV,V) redox states have been computationally studied both with DFT and multiconfigurational calculations. The calculations support the stability of these complexes and provide further insight into their electronic structures.

  10. Low-dose patterning of platinum nanoclusters on carbon nanotubes by focused-electron-beam-induced deposition as studied by TEM

    Directory of Open Access Journals (Sweden)

    Xiaoxing Ke

    2013-02-01

    Full Text Available Focused-electron-beam-induced deposition (FEBID is used as a direct-write approach to decorate ultrasmall Pt nanoclusters on carbon nanotubes at selected sites in a straightforward maskless manner. The as-deposited nanostructures are studied by transmission electron microscopy (TEM in 2D and 3D, demonstrating that the Pt nanoclusters are well-dispersed, covering the selected areas of the CNT surface completely. The ability of FEBID to graft nanoclusters on multiple sides, through an electron-transparent target within one step, is unique as a physical deposition method. Using high-resolution TEM we have shown that the CNT structure can be well preserved thanks to the low dose used in FEBID. By tuning the electron-beam parameters, the density and distribution of the nanoclusters can be controlled. The purity of as-deposited nanoclusters can be improved by low-energy electron irradiation at room temperature.

  11. Low-dose patterning of platinum nanoclusters on carbon nanotubes by focused-electron-beam-induced deposition as studied by TEM

    Science.gov (United States)

    Bittencourt, Carla; Bals, Sara; Van Tendeloo, Gustaaf

    2013-01-01

    Summary Focused-electron-beam-induced deposition (FEBID) is used as a direct-write approach to decorate ultrasmall Pt nanoclusters on carbon nanotubes at selected sites in a straightforward maskless manner. The as-deposited nanostructures are studied by transmission electron microscopy (TEM) in 2D and 3D, demonstrating that the Pt nanoclusters are well-dispersed, covering the selected areas of the CNT surface completely. The ability of FEBID to graft nanoclusters on multiple sides, through an electron-transparent target within one step, is unique as a physical deposition method. Using high-resolution TEM we have shown that the CNT structure can be well preserved thanks to the low dose used in FEBID. By tuning the electron-beam parameters, the density and distribution of the nanoclusters can be controlled. The purity of as-deposited nanoclusters can be improved by low-energy electron irradiation at room temperature. PMID:23399584

  12. Surface enhanced Raman scattering by organic and inorganic semiconductors formed on laterally ordered arrays of Au nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Milekhin, Alexander G., E-mail: milekhin@thermo.isp.nsc.ru [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentiev av. 13, 630090, Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov str. 2, 630090, Novosibirsk (Russian Federation); Yeryukov, Nikolay A., E-mail: yeryukov@isp.nsc.ru [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentiev av. 13, 630090, Novosibirsk (Russian Federation); Sveshnikova, Larisa L.; Duda, Tatyana A.; Rodyakina, Ekaterina E. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentiev av. 13, 630090, Novosibirsk (Russian Federation); Sheremet, Evgeniya S.; Ludemann, Michael; Gordan, Ovidiu D. [Semiconductor Physics, Chemnitz University of Technology, D-09107, Chemnitz (Germany); Latyshev, Alexander V. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentiev av. 13, 630090, Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov str. 2, 630090, Novosibirsk (Russian Federation); Zahn, Dietrich R.T. [Semiconductor Physics, Chemnitz University of Technology, D-09107, Chemnitz (Germany)

    2013-09-30

    This work is devoted to the investigation of surface-enhanced Raman scattering by vibrational modes of cobalt phthalocyanine ultrathin films and CuS nanocrystals prepared using by organic molecular beam vapor deposition and the Langmuir–Blodgett technique, respectively, on laterally ordered arrays of Au nanoclusters formed by electron beam lithography on Si and GaAs substrates. The surface-enhanced Raman scattering study of cobalt phthalocyanine films demonstrates the strong dependence of Raman intensity of vibrational modes in cobalt phthalocyanine on the laser excitation wavelength as well as on the size and period of Au nanoclusters. By tuning the optical resonance conditions a maximal enhancement factor of 2 × 10{sup 4} is achieved. The investigation of surface-enhanced Raman scattering by cobalt phthalocyanine deposited on laterally ordered arrays of paired Au nanoclusters (dimers) reveals anisotropic enhancement with respect to polarization of the scattered light parallel or perpendicular to the dimer axis. - Highlights: • Controllable and reproducible Au nanocluster and dimer arrays were fabricated. • Surface enhanced Raman scattering (SERS) by CuS nanocrystals was observed. • SERS by ultrathin cobalt phthalocyanine (CoPc) films was observed. • Dependence of SERS enhancement factor on the size of Au nanoclusters is resonant. • SERS by ultrathin CoPc films formed on Au dimer arrays is polarization dependent.

  13. CCD and IR array controllers

    Science.gov (United States)

    Leach, Robert W.; Low, Frank J.

    2000-08-01

    A family of controllers has bene developed that is powerful and flexible enough to operate a wide range of CCD and IR focal plane arrays in a variety of ground-based applications. These include fast readout of small CCD and IR arrays for adaptive optics applications, slow readout of large CCD and IR mosaics, and single CCD and IR array operation at low background/low noise regimes as well as high background/high speed regimes. The CCD and IR controllers have a common digital core based on user- programmable digital signal processors that are used to generate the array clocking and signal processing signals customized for each application. A fiber optic link passes image data and commands to VME or PCI interface boards resident in a host computer to the controller. CCD signal processing is done with a dual slope integrator operating at speeds of up to one Megapixel per second per channel. Signal processing of IR arrays is done either with a dual channel video processor or a four channel video processor that has built-in image memory and a coadder to 32-bit precision for operating high background arrays. Recent developments underway include the implementation of a fast fiber optic data link operating at a speed of 12.5 Megapixels per second for fast image transfer from the controller to the host computer, and supporting image acquisition software and device drivers for the PCI interface board for the Sun Solaris, Linux and Windows 2000 operating systems.

  14. Diacylhydrazone-assembled {Ln11} nanoclusters featuring a "double-boats conformation" topology: synthesis, structures and magnetism.

    Science.gov (United States)

    Wang, Kai; Chen, Zi-Lu; Zou, Hua-Hong; Zhang, Shu-Hua; Li, Yan; Zhang, Xiu-Qing; Sun, Wei-Yin; Liang, Fu-Pei

    2018-02-13

    A family of novel Ln nanoclusters, namely, [Ln 11 (ovpho) 4 (μ-CH 3 O) 2 (μ-H 2 O) 2 (μ 3 -OH) 6 (CH 3 OH) 4 (H 2 O) 2 (NO 3 ) 8 ](OH)·xH 2 O·yCH 3 OH [Ln = Gd (1), x = 1, y = 3; Ln = Tb (2), x = 1, y = 3; Ln = Dy (3), x = 0, y = 3], was obtained via solvothermal reactions of Ln(NO 3 ) 3 with a diacylhydrazone ligand N,N'-bis(o-vanillidene)pyridine-2,6-dicarbohydrazide N-oxide (H 4 ovpho). Their isostructural molecular structures are composed of two crystallographically symmetric {Ln 6 } rings sharing a Ln 3+ ion, and display an unprecedented "double boat conformation" topology that, to our knowledge, has not yet been reported. O phenol , O enol and O oxynitride from ovpho 4- ligands, as well as O methanol , O water and O hydroxyl help to bridge the Ln 3+ ions. The structural variation between these {Ln 11 } clusters and a previously reported {Gd 18 } nanowheel, both of which are assembled by H 4 ovpho under the same synthetic method and reaction conditions, is caused only by changing the anions of Ln salts. Magnetic investigations revealed a large magnetocaloric effect (MCE) of 1, whose maximum -ΔS m value reaches 30.1 J kg -1 K -1 for ΔH = 50 kOe at 2.0 K. Additionally, it was found that 3 shows single-molecule magnets (SMMs) behavior, with an approximated energy barrier U eff = 6.13 K and pre-exponential factor τ 0 = 1.70 × 10 -6 s.

  15. A novel colorimetric method based on copper nanoclusters with intrinsic peroxidase-like for detecting xanthine in serum samples

    Science.gov (United States)

    Yan, Zhengyu; Niu, Qianqian; Mou, Mingyao; Wu, Yi; Liu, Xiaoxuan; Liao, Shenghua

    2017-07-01

    A facile strategy for detecting xanthine in serum samples by copper nanocluster (CuNCs) with high intrinsic peroxidase-like activity was reported. Firstly, a simple, mild and time-saving method for preparing CuNCs was developed, in which dithiothreitol (DTT) and bovine serum albumin (BSA) were used as reductant and stabilizer, respectively. The as-prepared CuNCs exhibited a fluorescence emission at 590 nm with a quantum yield (QY) of approximately 5.29%, the fluorescence intensity of the as-prepared CuNCs exhibited no considerable change when stored under ambient condition with the lifetime is 1.75 μs. Moreover, the as-prepared CuNCs exhibited high intrinsic peroxidase-like activity with lower K m ( K m = 8.90 × 10-6 mol L-1) for H2O2, which indicated that CuNCs have a higher affinity for H2O2. Compared with natural enzyme, the as-synthesized CuNCs are more catalytic stable over a wide range of pH (4.0 13.0) and temperature (4 80 °C). Finally, an indirect method for sensing xanthine was established because xanthine oxidase can catalyse the oxidation of xanthine to produce H2O2. Xanthine could be detected as low as 3.8 × 10-7 mol L-1 with a linear range from 5.0 × 10-7 to 1.0 × 10-4 mol L-1. These results proved that the proposed method is sensitive and accurate and could be successfully applied to the determination of xanthine in the serum sample with satisfaction.

  16. Fabrication and in vitro characterization of gadolinium-based nanoclusters for simultaneous drug delivery and radiation enhancement

    Science.gov (United States)

    Yoo, Shannon S.; Guo, Linghong; Sun, Xuejun; Shaw, Andrew R.; Yuan, Zhipeng; Löbenberg, Raimar; Roa, Wilson H.

    2016-09-01

    We report the synthesis of a gadolinium hydroxide (Gd(OH)3) nanorod based doxorubicin (Dox) delivery system that can enhance both magnetic resonance imaging contrast and radiation sensitivity. A simple and cost effective wet-chemical method was utilized in the presence of manganese (Mn) ions and Dox to produce the Gd(OH)3:Mn·Dox nanocluster structure. The Gd(OH)3:Mn·Dox nanocluster was composed of Mn-doped Gd(OH)3 nanorods arranged in parallel with Dox as a linker molecule between the adjacent nanorods. No other studies have utilized Dox as both the linker and therapeutic molecule in a nanostructure to date. The Gd(OH)3 nanorod is reported to have no significant cellular or in vivo toxicity, which makes it an ideal base material for this biomedical application. The Gd(OH)3:Mn·Dox nanocluster exhibited paramagnetic behavior and was stable in a colloidal solution. The nanocluster also enabled high Dox loading capacity and specifically released Dox in a sustained and pH-dependent manner. The positively charged Gd(OH)3:Mn·Dox nanoclusters were readily internalized into MDA-MB-231 breast cancer cells via endocytosis, which resulted in intracellular release of Dox. The released Dox in cells was effective in conferring cytotoxicity and inhibiting proliferation of cancer cells. Furthermore, a synergistic anticancer effect could be observed with radiation treatment. Overall, the Gd(OH)3:Mn·Dox nanocluster drug delivery system described herein may have potential utility in clinics as a multifunctional theranostic nanoparticle with combined benefits in both diagnosis and therapy in the management of cancer.

  17. Effects of doping in 25-atom bimetallic nanocluster catalysts for carbon–carbon coupling reaction of iodoanisole and phenylacetylene

    Directory of Open Access Journals (Sweden)

    Zhimin Li

    2016-10-01

    Full Text Available We here report the catalytic effects of foreign atoms (Cu, Ag, and Pt doped into well-defined 25-gold-atom nanoclusters. Using the carbon-carbon coupling reaction of p-iodoanisole and phenylacetylene as a model reaction, the gold-based bimetallic MxAu25−x(SR18 (–SR=–SCH2CH2Ph nanoclusters (supported on titania were found to exhibit distinct effects on the conversion of p-iodoanisole as well as the selectivity for the Sonogashira cross-coupling product, 1-methoxy-4-(2-phenylethynylbenzene. Compared to Au25(SR18, the centrally doped Pt1Au24(SR18 causes a drop in catalytic activity but with the selectivity retained, while the AgxAu25−x(SR18 nanoclusters gave an overall performance comparable to Au25(SR18. Interestingly, CuxAu25−x(SR18 nanoclusters prefer the Ullmann homo-coupling pathway and give rise to product 4,4′-dimethoxy-1,1′-biphenyl, which is in opposite to the other three nanocluster catalysts. Our overall conclusion is that the conversion of p-iodoanisole is largely affected by the electronic effect in the bimetallic nanoclusters’ 13-atom core (i.e., Pt1Au12, CuxAu13−x, and Au13, with the exception of Ag doping, and that the selectivity is primarily determined by the type of atoms on the MxAu12−x shell (M=Ag, Cu, and Au in the nanocluster catalysts.

  18. Ag nanocluster functionalized glasses for efficient photonic conversion in light sources, solar cells and flexible screen monitors

    Science.gov (United States)

    Kuznetsov, A. S.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

    2013-10-01

    An ever growing demand for efficient energy conversion, for instance in luminescent lamps, flexible screens and solar cells, results in the current significant growth of research on functionalized nanomaterials for these applications. This paper reviews recent developments of a new class of optically active nanostructured materials based on glasses doped with luminescent Ag nanoclusters consisting of only a few Ag atoms, suitable for mercury-free white light generation and solar down-shifting. This new approach, based solely on Ag nanocluster doped glasses, is compared to other alternatives in the field of Ag and rare-earth ion co-doped materials.

  19. #Occupy IR: Exposing the Orthodoxy

    Directory of Open Access Journals (Sweden)

    Ivan Manokha

    2012-03-01

    Full Text Available The #occupy IR/IPE initiative was created in response to the #occupy movement, whose own roots can be traced backed to the latest crisis of global finance. In this contribution, we link #occupy and the crisis in a different way. We argue that we must occupy IR/IPE because of the discipline’s failure to apprehend and acknowledge the crisis itself, just as the Occupy movement is calling for their overarching authorities to notice and help address the social and economic inequalities produced by this crisis. More precisely, we argue that the dominant academic orthodoxy, via a series of continuously reproduced dichotomies, has rendered IR/IPE incapable of dealing with a phenomenon as complex as the financial crisis...

  20. Impaired Insulin Signaling is Associated with Hepatic Mitochondrial Dysfunction in IR+/−-IRS-1+/− Double Heterozygous (IR-IRS1dh Mice

    Directory of Open Access Journals (Sweden)

    Andras Franko

    2017-05-01

    Full Text Available Mitochondria play a pivotal role in energy metabolism, but whether insulin signaling per se could regulate mitochondrial function has not been identified yet. To investigate whether mitochondrial function is regulated by insulin signaling, we analyzed muscle and liver of insulin receptor (IR+/−-insulin receptor substrate-1 (IRS-1+/− double heterozygous (IR-IRS1dh mice, a well described model for insulin resistance. IR-IRS1dh mice were studied at the age of 6 and 12 months and glucose metabolism was determined by glucose and insulin tolerance tests. Mitochondrial enzyme activities, oxygen consumption, and membrane potential were assessed using spectrophotometric, respirometric, and proton motive force analysis, respectively. IR-IRS1dh mice showed elevated serum insulin levels. Hepatic mitochondrial oxygen consumption was reduced in IR-IRS1dh animals at 12 months of age. Furthermore, 6-month-old IR-IRS1dh mice demonstrated enhanced mitochondrial respiration in skeletal muscle, but a tendency of impaired glucose tolerance. On the other hand, 12-month-old IR-IRS1dh mice showed improved glucose tolerance, but normal muscle mitochondrial function. Our data revealed that deficiency in IR/IRS-1 resulted in normal or even elevated skeletal muscle, but impaired hepatic mitochondrial function, suggesting a direct cross-talk between insulin signaling and mitochondria in the liver.

  1. Impaired Insulin Signaling is Associated with Hepatic Mitochondrial Dysfunction in IR+/--IRS-1+/-Double Heterozygous (IR-IRS1dh) Mice.

    Science.gov (United States)

    Franko, Andras; Kunze, Alexander; Böse, Marlen; von Kleist-Retzow, Jürgen-Christoph; Paulsson, Mats; Hartmann, Ursula; Wiesner, Rudolf J

    2017-05-30

    Mitochondria play a pivotal role in energy metabolism, but whether insulin signaling per se could regulate mitochondrial function has not been identified yet. To investigate whether mitochondrial function is regulated by insulin signaling, we analyzed muscle and liver of insulin receptor (IR) +/- -insulin receptor substrate-1 (IRS-1) +/- double heterozygous (IR-IRS1dh) mice, a well described model for insulin resistance. IR-IRS1dh mice were studied at the age of 6 and 12 months and glucose metabolism was determined by glucose and insulin tolerance tests. Mitochondrial enzyme activities, oxygen consumption, and membrane potential were assessed using spectrophotometric, respirometric, and proton motive force analysis, respectively. IR-IRS1dh mice showed elevated serum insulin levels. Hepatic mitochondrial oxygen consumption was reduced in IR-IRS1dh animals at 12 months of age. Furthermore, 6-month-old IR-IRS1dh mice demonstrated enhanced mitochondrial respiration in skeletal muscle, but a tendency of impaired glucose tolerance. On the other hand, 12-month-old IR-IRS1dh mice showed improved glucose tolerance, but normal muscle mitochondrial function. Our data revealed that deficiency in IR/IRS-1 resulted in normal or even elevated skeletal muscle, but impaired hepatic mitochondrial function, suggesting a direct cross-talk between insulin signaling and mitochondria in the liver.

  2. Atmospheric chemistry of CH3O(CF2CF2O)(n)CH3 (n=1-3): Kinetics and mechanism of oxidation initiated by Cl atoms and OH radicals, IR spectra, and global warmin potentials

    DEFF Research Database (Denmark)

    Andersen, Mads Peter Sulbæk; Hurley, MD; Wallington, TJ

    2004-01-01

    Smog chambers equipped with FTIR spectrometers were used to study the Cl atom and OH radical initiated oxidation of CH3O(CF2CF2O)(n)CH3 (n = 1-3) in 720 +/- 20 Torr of air at 296 +/- 3 K. Relative rate techniques were used to measure k(Cl + CH3O(CF2CF2O)(n)CH3) (3.7 +/- 10.7) x 10(-13) and k...

  3. How Does Amino Acid Ligand Modulate Au Core Structure and Characteristics in Peptide Coated Au Nanocluster?

    Science.gov (United States)

    Li, Nan; Li, Xu; Zhao, Hongkang; Zhao, Lina

    2018-03-01

    The atomic structures and the corresponding physicochemical properties of peptide coated Au nanoclusters determine their distinctive biological targeting applications. To learn the modulation of amino acid ligand on the atomic structure and electronic characteristics of coated Au core is the fundamental knowledge for peptide coated Au nanocluster design and construction. Based on our recent coated Au nanocluster configuration study (Nanoscale, 2016, 8, 11454), we built the typically simplified Au13(Cys-Au-Cys) system to more clearly learn the basic modulation information of amino acid ligand on Au core by the density functional theory (DFT) calculations. There are two isomers as ligand adjacent bonding (Iso1) and diagonal bonding (Iso2) to Au13 cores. The geometry optimizations indicate the adjacent bonding Iso1 is more stable than Iso2. More important, the Au13 core of Iso1 distorts much more significantly than that of Iso2 by Cys-Au-Cys bonding through the root-mean-square deviation (RMSD) analysis, which modulate their electronic characteristics in different ways. In addition, the frontier molecular orbital results of Au13(Cys-Au-Cys) isomers confirm that the Au cores mainly determine the blue shifts of Au13(Cys-Au-Cys) systems versus the original Au13 core in their UV-visible absorption spectrum studies. The configuration of Au13 core performs deformation under Cys-Au-Cys ligand modulation to reach new stability with distinct atomic structure and electronic properties, which could be the theory basis for peptide coated AuNCs design and construction.

  4. Tuning size and catalytic activity of nano-clusters of cobalt oxide

    Indian Academy of Sciences (India)

    Unknown

    oxalic acid, (2) co-precipitating cobalt nitrate with sodium carbonate, and (3) using sodium dodecyl sul- .... Co(NO3)2 + Na2CO3 → CoCO3 + 2NaNO3,. CoCO3. ∆. → ∆ CoO + CO2,. CoO → (in air and heating) Co3O4. In method III, cobalt nitrate, sodium dodecyl sul- .... The conversion of cyclohexane on the current po-.

  5. Sputter deposition on gas diffusion electrodes of Pt-Au nanoclusters for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Giorgi, L.; Giorgi, R.; Gagliardi, S.; Serra, E. [ENEA Casaccia Research Center, Rome (Italy). Physics Technologies and New Materials; Alvisi, M.; Signore, M.A. [ENEA Brindisi Research Center, Brindisi (Italy). Physics Technologies and New Materials

    2008-07-01

    Polymer electrolyte fuel cells (PEFCs) are suited for use in commercial electrical vehicle and electric power applications. The gas diffusion electrodes of PEFCs are catalyzed by the deposition of platinum (Pt) nanoparticles on carbon powder. The particles must be localized on the electrode surface in order to achieve high electrocatalyst utilization. This study discussed a method of preparing PEFC electrodes using sputter deposition of a Pt-gold (Au) alloy nanoparticles on carbon powders. The method was designed to improve electrode performance and catalyst utilization. The nano-sized alloy clusters were deposited on a gas diffusion electrode at room temperature. The deposits were then characterized using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) in order to examine the effect of the deposition technique on the nano-morphology and electrocatalytic performance of the electrode. Results of the study showed that the technique can be used in the large-scale manufacture of fuel cell electrodes. 3 refs., 1 fig.

  6. The effect of silicon crystallographic orientation on the formation of silicon nanoclusters during anodic electrochemical etching

    International Nuclear Information System (INIS)

    Timokhov, D. F.; Timokhov, F. P.

    2009-01-01

    Possible ways for increasing the photoluminescence quantum yield of porous silicon layers have been investigated. The effect of the anodization parameters on the photoluminescence properties for porous silicon layers formed on silicon substrates with different crystallographic orientations was studied. The average diameters for silicon nanoclusters are calculated from the photoluminescence spectra of porous silicon. The influence of the substrate crystallographic orientation on the photoluminescence quantum yield of porous silicon is revealed. A model explaining the effect of the substrate orientation on the photoluminescence properties for the porous silicon layers formed by anode electrochemical etching is proposed.

  7. Probing DNA-stabilized fluorescent silver nanocluster spectral heterogeneity by time-correlated single photon counting

    DEFF Research Database (Denmark)

    Carro, Miguel; Paolucci, Valentina; Hooley, Emma Nicole

    2016-01-01

    the comparison of sample preparation and the judgment of reproducibility. Therefore, we propose the use of the average decay time spectra as a robust and easy tool to characterize and compare different as-synthesized DNA-AgNC samples. The average decay time spectra can in general also be used to characterize......DNA-stabilized silver nanoclusters (DNA-AgNCs) are promising fluorophores whose photophysical properties and synthesis procedures have received increased attention in the literature. However, depending on the preparation conditions and the DNA sequence, the DNA-AgNC samples can host a range...

  8. Pd-based alloy nanoclusters in ion-implanted silica: Formation and stability under thermal annealing

    Energy Technology Data Exchange (ETDEWEB)

    Battaglin, G.; Cattaruzza, E.; De Marchi, G.; Gonella, F.; Mattei, G. E-mail: mattei@padova.infm.it; Maurizio, C.; Mazzoldi, P.; Parolin, M.; Sada, C.; Calliari, I

    2002-05-01

    In this work we report on the formation and stability under thermal annealing of Pd-Cu and Pd-Ag alloy nanoclusters obtained by sequential ion implantation in silica. The role of the annealing atmosphere on the alloy cluster formation and stability is investigated. A comparison is made with similar alloy-based systems obtained by sequential ion implantation in silica of Au-Ag or Au-Cu followed by annealing under similar conditions, in order to evidence the peculiar effect of the various metals in controlling the alloy evolution and/or decomposition.

  9. Directed organization of gold nanoclusters on silver nanowires: A step forward in heterostructure assembly

    Science.gov (United States)

    Sharma, Jadab; Vivek, J. P.; Vijayamohanan, Kunjukrishna P.; Singh, Poonam; Dharmadhikari, C. V.

    2006-05-01

    We investigate the directed assembly of tridecylamine protected gold nanoclusters of 4-5nm size on functionalized silver nanowires of 55-60nm diameter and the electron transfer behavior of this integrated structure using transmission electron microscopy, non-contact atomic force microscopy, and scanning tunneling microscopy/spectroscopy. Linear I-V for bare silver nanowire suggests metallic behavior but high tunnel resistance indicates presence of insulating layer on the surface. Identical I-Vs obtained for isolated gold nanoparticle and heterostructure suggests that electron transport across nanowires in the latter is governed by gold nanoparticles in contrast to expected ballistic or diffusive transport along their length.

  10. Probing the Absorption and Emission Transition Dipole Moment of DNA Stabilized Silver Nanoclusters

    DEFF Research Database (Denmark)

    Hooley, Emma Nicole; Carro Temboury, Miguel R.; Vosch, Tom André Jos

    2017-01-01

    Using single molecule polarization measurements, we investigate the excitation and emission polarization characteristics of DNA stabilized silver nanoclusters (C24-AgNCs). Although small changes in the polarization generally accompany changes to the emission spectrum, the emission and excitation...... transition dipoles tend to be steady over time and aligned in a similar direction, when immobilized in PVA. The emission transition dipole patterns, observed for C24-AgNCs in defocused wide field imaging, match that of a single emitter. The small changes to the polarization and spectral shifting that were...

  11. Novel Sol-Gel Based Pt Nanocluster Catalysts for Propane Dehydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Boespflug, Elaine; Kawola, Jeffrey S.; Martino, Anthony; Sault, Allen G.

    1999-08-09

    We report propane dehydrogenation behavior of catalysts prepared using two novel synthesis strategies that combine inverse micelle Pt nanocluster technology with silica and alumina sol-gel processing. Unlike some other sol-gel catalyst preparations. Pt particles in these catalysts are not encapsulated in the support structure and the entire Pt particle surface is accessible for reaction. Turnover frequencies (TOF) for these catalysts are comparable to those obtained over Pt catalysts prepared by traditional techniques such as impregnation, yet the resistance to deactivation by carbon poisoning is much greater in our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.

  12. Ultrafast static and diffusion-controlled electron transfer at Ag 29 nanocluster/molecular acceptor interfaces

    KAUST Repository

    Aly, Shawkat Mohammede

    2015-10-29

    Efficient absorption of visible light and a long-lived excited state lifetime of silver nanoclusters (Ag29 NCs) are integral properties for these new clusters to serve as light-harvesting materials. Upon optical excitation, electron injection at Ag29 NC/methyl viologen (MV2+) interfaces is very efficient and ultrafast. Interestingly, our femto- and nanosecond time-resolved results demonstrate clearly that both dynamic and static electron transfer mechanisms are involved in photoluminescence quenching of Ag29 NCs. © 2016 The Royal Society of Chemistry.

  13. Enhanced Activity and Durability of Nanosized Pt-SnO2/IrO2/CNTs Catalyst for Methanol Electrooxidation.

    Science.gov (United States)

    Wang, Hongjuan; Wang, Xiaohui; Zheng, Jiadao; Peng, Feng; Yu, Hao

    2015-05-01

    Pt-SnO2/IrO2/CNTs anode catalyst for direct methanol fuel cell was designed and prepared with IrO2/CNTs as support for the subsequent immobilization of Pt and SnO2 at the same time. The structure of the catalysts and their catalytic performance in methanol electrooxidation were investigated and the roles of IrO2 and SnO2 in methanol electrooxidation were discussed as well. Results show that Pt-SnO2/IrO2/CNTs catalyst exhibits the best activity and durability for methanol electrooxidation when compared with Pt/CNTs, Pt/IrO2/CNTs and Pt-SnO2/CNTs. According to the results of electrochemical tests and physicochemical characterizations, the enhancements of Pt-SnO2/IrO2/CNTs were attributed to the special properties of IrO2 and SnO2, in which IrO2 mainly increases the methanol oxidation activity and SnO2 mainly improves the CO oxidation ability and durability. Therefore, Pt-SnO2/IrO2/CNTs exhibits excellent performance for methanol oxidation with higher electrocatalytic activity (I(f) of 1054 A g(Pt(-1)) and powerful anti-poisoning ability (the onset potential for CO oxidation of 0.3 V) and outstanding durability (the sustained time t in CP of 617 s), revealing a suitable anode catalyst for DMFCs.

  14. Spin orientations of the spin-half Ir{sup 4+} ions in Sr{sub 3}NiIrO{sub 6}, Sr{sub 2}IrO{sub 4}, and Na{sub 2}IrO{sub 3}: Density functional, perturbation theory, and Madelung potential analyses

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Elijah E.; Whangbo, Myung-Hwan, E-mail: mike-whangbo@ncsu.edu [Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204 (United States); Xiang, Hongjun [Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, Collaborative Innovation Center of Advanced Microstructures, and Department of Physics, Fudan University, Shanghai 200433 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China); Köhler, Jürgen [Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart (Germany)

    2016-03-21

    The spins of the low-spin Ir{sup 4+} (S = 1/2, d{sup 5}) ions at the octahedral sites of the oxides Sr{sub 3}NiIrO{sub 6}, Sr{sub 2}IrO{sub 4}, and Na{sub 2}IrO{sub 3} exhibit preferred orientations with respect to their IrO{sub 6} octahedra. We evaluated the magnetic anisotropies of these S = 1/2 ions on the basis of density functional theory (DFT) calculations including spin-orbit coupling (SOC), and probed their origin by performing perturbation theory analyses with SOC as perturbation within the LS coupling scheme. The observed spin orientations of Sr{sub 3}NiIrO{sub 6} and Sr{sub 2}IrO{sub 4} are correctly predicted by DFT calculations, and are accounted for by the perturbation theory analysis. As for the spin orientation of Na{sub 2}IrO{sub 3}, both experimental studies and DFT calculations have not been unequivocal. Our analysis reveals that the Ir{sup 4+} spin orientation of Na{sub 2}IrO{sub 3} should have nonzero components along the c- and a-axis directions. The spin orientations determined by DFT calculations are sensitive to the accuracy of the crystal structures employed, which is explained by perturbation theory analyses when interactions between adjacent Ir{sup 4+} ions are taken into consideration. There are indications implying that the 5d electrons of Na{sub 2}IrO{sub 3} are less strongly localized compared with those of Sr{sub 3}NiIrO{sub 6} and Sr{sub 2}IrO{sub 4}. This implication was confirmed by showing that the Madelung potentials of the Ir{sup 4+} ions are less negative in Na{sub 2}IrO{sub 3} than in Sr{sub 3}NiIrO{sub 6} and Sr{sub 2}IrO{sub 4}. Most transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC induces interactions among their crystal-field split d-states, and the associated mixing of the states modifies only the orbital parts of the states. This finding cannot be mimicked by a spin Hamiltonian because this model Hamiltonian lacks the orbital degree of freedom, thereby leading to the spin-half syndrome. The

  15. Electrochemical behavior of Azure A/gold nanoclusters modified electrode and its application as non-enzymatic hydrogen peroxide sensor.

    Science.gov (United States)

    Priya, C; Sivasankari, G; Narayanan, S Sriman

    2012-09-01

    A novel non-enzymatic hydrogen peroxide sensor was developed using Azure A/gold nanoclusters modified graphite electrode. The method of preparation of Azure A/gold nanoclusters was simple and it was characterized by UV-visible spectroscopy, field emission scanning electron microscopy (FESEM) and confocal Raman microscopy. The electrochemical properties of Azure A/gold nanoclusters modified graphite electrode was characterized by cyclic voltammetry. In 0.1M H(2)SO(4) the modified electrode showed redox peaks which correspond to the redox behavior of gold nanoparticle. In 0.1M PBS the modified electrode exhibited well defined redox peaks with the formal potential of -0.253 V which is analogous to the redox reaction of Azure A. The results have shown that the gold nanoclusters has reduced the formal potential of Azure A and enhanced the current due to the fast charge transfer kinetics. Also the modified electrode showed an enhanced electrocatalytic activity towards the reduction of H(2)O(2) in the concentration range of 3.26×10(-6)M to 3.2×10(-3)M with a detection limit of 1.08×10(-6)M (S/N=3). The proposed electrode exhibited good stability and reproducibility, and it has the potential application as a sensor for other biologically significant compounds. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Highly selective GaN-nanowire/TiO2-nanocluster hybrid sensors for detection of benzene and related environment pollutants.

    Science.gov (United States)

    Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Rao, Mulpuri V

    2011-07-22

    Nanowire-nanocluster hybrid chemical sensors were realized by functionalizing gallium nitride (GaN) nanowires (NWs) with titanium dioxide (TiO(2)) nanoclusters for selectively sensing benzene and other related aromatic compounds. Hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO(2) nanoclusters using RF magnetron sputtering. The sensor fabrication process employed standard microfabrication techniques. X-ray diffraction and high-resolution analytical transmission electron microscopy using energy-dispersive x-ray and electron energy-loss spectroscopies confirmed the presence of the anatase phase in TiO(2) clusters after post-deposition anneal at 700 °C. A change of current was observed for these hybrid sensors when exposed to the vapors of aromatic compounds (benzene, toluene, ethylbenzene, xylene and chlorobenzene mixed with air) under UV excitation, while they had no response to non-aromatic organic compounds such as methanol, ethanol, isopropanol, chloroform, acetone and 1,3-hexadiene. The sensitivity range for the noted aromatic compounds except chlorobenzene were from 1% down to 50 parts per billion (ppb) at room temperature. By combining the enhanced catalytic properties of the TiO(2) nanoclusters with the sensitive transduction capability of the nanowires, an ultra-sensitive and selective chemical sensing architecture is demonstrated. We have proposed a mechanism that could qualitatively explain the observed sensing behavior.

  17. Microwave-Assisted Synthesis of Red-Light Emitting Au Nanoclusters with the Use of Egg White

    Science.gov (United States)

    Tian, Jinghan; Yan, Lei; Sang, Aohua; Yuan, Hongyan; Zheng, Baozhan; Xiao, Dan

    2014-01-01

    We developed a simple, cost-effective, and eco-friendly method to synthesize gold nanoclusters (AuNCs) with red fluorescence. The experiment was performed using HAuCl[subscript 4], egg white, Na[subscript 2]CO[subscript 3] (known as soda ash or washing soda), and a microwave oven. In our experiment, fluorescent AuNCs were prepared within a…

  18. Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001.

    Directory of Open Access Journals (Sweden)

    Puran Pandey

    Full Text Available Au nano-clusters and nanoparticles (NPs have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001 by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

  19. Oxide dispersion strengthened ferritic steels: a basic research joint program in France

    Energy Technology Data Exchange (ETDEWEB)

    Boutard, J.-L., E-mail: jean-louis.boutard@cea.fr [Cabinet du Haut-Commissaire, CEA/Saclay, 91191 Gif sur Yvette Cedex (France); Badjeck, V. [LPS, UMR CNRS 8502, Building 510, Université Paris-Sud 11, 91405 Orsay Cedex (France); Barguet, L. [LAUM, UMR CNRS 6613, Building IAM – UFR Sciences, Avenue O. Messiaen, 72085 Le Mans Cedex 9 (France); Barouh, C. [DMN/SRMP, CEA/Saclay, Building 520, 91191 Gif sur Yvette Cedex (France); Bhattacharya, A. [DMN/SRMP, CEA/Saclay, Building 520, 91191 Gif sur Yvette Cedex (France); CSNSM, UMR CNRS 8609, Université Paris-Sud 11, Buildings 104 and 108, 91405 Orsay Campus (France); Colignon, Y. [IM2NP, UMR CNRS 7334, Case 142, Faculté des Sciences, Campus de Saint Jérôme, Aix Marseille Université, 13397 Marseille Cedex 20 (France); Hatzoglou, C. [GPM, UMR CNRS 6634, Technopôle du Madrillet, Avenue de l’Université, BP12, 76801 Saint Etienne du Rouvray Cedex (France); Loyer-Prost, M. [DMN/SRMP, CEA/Saclay, Building 520, 91191 Gif sur Yvette Cedex (France); Rouffié, A.L. [DMN/SRMA, CEA/Saclay, Building 455, 91191 Gif sur Yvette Cedex (France); Sallez, N. [SIMAP, UMR CNRS 5266, INPG, Domaine Universitaire, 1130 rue de la Piscine, BP75, 38402 Saint Martin d’Hères Cedex (France); Salmon-Legagneur, H. [DMN/SRMA, CEA/Saclay, Building 455, 91191 Gif sur Yvette Cedex (France); Schuler, T. [DMN/SRMP, CEA/Saclay, Building 520, 91191 Gif sur Yvette Cedex (France)

    2014-12-15

    AREVA, CEA, CNRS, EDF and Mécachrome are funding a joint program of basic research on Oxide Dispersion Strengthened Steels (ODISSEE), in support to the development of oxide dispersion strengthened 9–14% Cr ferritic–martensitic steels for the fuel element cladding of future Sodium-cooled fast neutron reactors. The selected objectives and the results obtained so far will be presented concerning (i) physical–chemical characterisation of the nano-clusters as a function of ball-milling process, metallurgical conditions and irradiation, (ii) meso-scale understanding of failure mechanisms under dynamic loading and creep, and, (iii) kinetic modelling of nano-clusters nucleation and α/α′ unmixing.

  20. Shaped Ir-Ni bimetallic nanoparticles for minimizing Ir utilization in oxygen evolution reaction.

    Science.gov (United States)

    Lim, Jinkyu; Yang, Sungeun; Kim, Chanyeon; Roh, Chi-Woo; Kwon, Yongwoo; Kim, Yong-Tae; Lee, Hyunjoo

    2016-04-25

    Shaped Ir-Ni bimetallic nanoparticles were synthesized and used for electrocatalytic oxygen evolution reaction (OER). The obtained bimetallic nanoparticles showed significantly enhanced Ir mass activity and durability compared with Ir nanoparticles.

  1. (VI) oxide in acetic acid

    African Journals Online (AJOL)

    The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media was studied. The reaction products were analysed using infra red (IR) and gas chromatography coupled with mass (GC/MS) spectroscopy. The major products of the oxidation reaction in acetic acid medium were cyclohexanol, ...

  2. Formation of Ni/C based polyacrylonitrile nanocomposites under IR-radiation

    Directory of Open Access Journals (Sweden)

    Dmitriy G. Muratov

    2016-09-01

    By calculating the total Gibbs energy of possible reduction reactions of nickel chloride and oxide pyrolysis PAN products we have shown the possibility of the formation of nanocomposites comprising nickel oxide nanoparticles which can be reduced to zero-valence state at higher temperature IR heating (more than 5000 °C.

  3. Optical and magnetic properties of Cu-doped 13-atom Ag nanoclusters

    International Nuclear Information System (INIS)

    Rao, Yi; Lei, Yimin; Cui, Xiangyuan; Liu, Zongwen; Chen, Fuyi

    2013-01-01

    Highlights: •Cu atom tends to occupy the core position in the Ag–Cu nanoclusters. •Global minimum of Ag 12 Cu 1 cluster is predicted to be cuboctahedral shape. •High symmetry clusters have high magnetic moment. •Icosahedral core–shell Ag 12 Cu 1 cluster has ferromagnetic properties. -- Abstract: The structural, optical and magnetic properties of Ag 13 , Ag 12 Cu 1 and Cu 13 clusters have been investigated using density functional theory calculations. The global minimum of the Ag 12 Cu 1 cluster is predicted to be cuboctahedral (COh) core–shell structure with O h point group symmetry while the icosahedral (Ih) core–shell isomer has a higher HOMO–LUMO gap and higher magnetic moment. The optical absorption spectrum of the Ih Ag 12 Cu 1 has three absorption peaks at 2.17, 2.41 and 2.65 eV, compared with that the COh Ag 12 Cu 1 has one main absorption peak at 2.51 eV. The characteristics in electronic density of states (DOSs) show that Ih core–shell Ag 12 Cu 1 has ferromagnetic properties like pure Au 13 , Ag 13 nanoclusters. The sizable split between spin up and spin down DOS of d states in the inner Cu atom and sp states in the outer Ag atoms bring in large magnetic moment to Ih Ag 12 Cu 1 cluster

  4. Quantification of NS1 dengue biomarker in serum via optomagnetic nanocluster detection

    Science.gov (United States)

    Antunes, Paula; Watterson, Daniel; Parmvi, Mattias; Burger, Robert; Boisen, Anja; Young, Paul; Cooper, Matthew A.; Hansen, Mikkel F.; Ranzoni, Andrea; Donolato, Marco

    2015-11-01

    Dengue is a tropical vector-borne disease without cure or vaccine that progressively spreads into regions with temperate climates. Diagnostic tools amenable to resource-limited settings would be highly valuable for epidemiologic control and containment during outbreaks. Here, we present a novel low-cost automated biosensing platform for detection of dengue fever biomarker NS1 and demonstrate it on NS1 spiked in human serum. Magnetic nanoparticles (MNPs) are coated with high-affinity monoclonal antibodies against NS1 via bio-orthogonal Cu-free ‘click’ chemistry on an anti-fouling surface molecular architecture. The presence of the target antigen NS1 triggers MNP agglutination and the formation of nanoclusters with rapid kinetics enhanced by external magnetic actuation. The amount and size of the nanoclusters correlate with the target concentration and can be quantified using an optomagnetic readout method. The resulting automated dengue fever assay takes just 8 minutes, requires 6 μL of serum sample and shows a limit of detection of 25 ng/mL with an upper detection range of 20000 ng/mL. The technology holds a great potential to be applied to NS1 detection in patient samples. As the assay is implemented on a low-cost microfluidic disc the platform is suited for further expansion to multiplexed detection of a wide panel of biomarkers.

  5. Luminescent golden silk and fabric through in situ chemically coating pristine-silk with gold nanoclusters.

    Science.gov (United States)

    Zhang, Pu; Lan, Jing; Wang, Yi; Xiong, Zu Hong; Huang, Cheng Zhi

    2015-01-01

    Silk is an excellent natural material and has been used for a variety of applications. Modification of the pristine silk is usually needed depending on the intended purpose. The technical treatments involved in the modification not only should be easy, rapid, environmentally friendly, and cheap but should also retain the features of the pristine silk. Herein, we demonstrate that luminescent silk and fabric can be produced through nanotechnology. The surface of the natural silk fiber is chemically coated with luminescent gold nanoclusters (AuNCs) composed of tens to hundreds of Au atoms through a redox reaction between the protein-based silk and an Au salt precursor. The luminescent silk coated with AuNCs (called golden silk) possesses good optical properties, including a relatively long wavelength emission, high quantum yields, a long fluorescent lifetime, and photostability. Moreover, golden silk prepared this way has better mechanical properties than pristine silk, is better able to inhibit UV, and has lower toxicity in vitro. This work not only provides an effective strategy for in situ preparation of luminescent metal nanoclusters on a solid substrate but also paves the way for large-scale and industrialized production of novel silk-based materials or fabrics through nanotechnology. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. In vivo self-bio-imaging of tumors through in situ biosynthesized fluorescent gold nanoclusters

    Science.gov (United States)

    Wang, Jianling; Zhang, Gen; Li, Qiwei; Jiang, Hui; Liu, Chongyang; Amatore, Christian; Wang, Xuemei

    2013-01-01

    Fluorescence imaging in vivo allows non-invasive tumor diagnostic thus permitting a direct monitoring of cancer therapies progresses. It is established herein that fluorescent gold nanoclusters are spontaneously biosynthesized by cancerous cell (i.e., HepG2, human hepatocarcinoma cell line; K562, leukemia cell line) incubated with micromolar chloroauric acid solutions, a biocompatible molecular Au(III) species. Gold nanoparticles form by Au(III) reduction inside cells cytoplasms and ultimately concentrate around their nucleoli, thus affording precise cell imaging. Importantly, this does not occur in non-cancerous cells, as evidenced with human embryo liver cells (L02) used as controls. This dichotomy is exploited for a new strategy for in vivo self-bio-imaging of tumors. Subcutaneous injections of millimolar chloroauric acid solution near xenograft tumors of the nude mouse model of hepatocellular carcinoma or chronic myeloid leukemia led to efficient biosynthesis of fluorescent gold nanoclusters without significant dissemination to the surrounding normal tissues, hence allowing specific fluorescent self-bio-marking of the tumors.

  7. Growth dynamics of copper thin film deposited by soft-landing of size selected nanoclusters

    Science.gov (United States)

    Mondal, Shyamal; Chowdhury, Debasree; Barman, Pintu; Bhattacharyya, Satya Ranjan

    2017-12-01

    We investigate surface kinetic roughening of copper films grown on Si(1 0 0) substrates at room temperature by means of atomic force microscopy study. Films were deposited at various durations by soft landing of size selected ( 3 nm) nanoclusters using a state of the art nanocluster deposition system. The film growth exhibits two growth regimes with a crossover time of 40 min. In the first regime, surface morphologies show bimodal distribution and surface roughness shows a linear increase with growth exponent β = 0.14 ± 0.02. In the second regime, the height distribution becomes Gaussian and surface roughness shows a steep rise with high β value 0.83 ± 0.45. On the other hand, the roughness exponent α ranges from 0.68 ± 0.03 to 0.84 ± 0.01 for low to high deposition regimes. Estimated scaling exponent suggests the diffusion of clusters on substrate surface and shadowing effect play dominant role in growth mechanism of the nanostructured thin film. Contribution to the Topical Issue: "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

  8. Sizing protein-templated gold nanoclusters by time resolved fluorescence anisotropy decay measurements

    Science.gov (United States)

    Soleilhac, Antonin; Bertorelle, Franck; Antoine, Rodolphe

    2018-03-01

    Protein-templated gold nanoclusters (AuNCs) are very attractive due to their unique fluorescence properties. A major problem however may arise due to protein structure changes upon the nucleation of an AuNC within the protein for any future use as in vivo probes, for instance. In this work, we propose a simple and reliable fluorescence based technique measuring the hydrodynamic size of protein-templated gold nanoclusters. This technique uses the relation between the time resolved fluorescence anisotropy decay and the hydrodynamic volume, through the rotational correlation time. We determine the molecular size of protein-directed AuNCs, with protein templates of increasing sizes, e.g. insulin, lysozyme, and bovine serum albumin (BSA). The comparison of sizes obtained by other techniques (e.g. dynamic light scattering and small-angle X-ray scattering) between bare and gold clusters containing proteins allows us to address the volume changes induced either by conformational changes (for BSA) or the formation of protein dimers (for insulin and lysozyme) during cluster formation and incorporation.

  9. Carbon-coated Zinc Sulfide nano-clusters: synthesis, photothermal conversion and adsorption properties.

    Science.gov (United States)

    Bao, Chunlin; Zhu, Guoxing; Shen, Mengqi; Yang, Jing

    2014-12-15

    Carbon-coated cluster-like ZnS nanospheres were synthesized by a facile solvothermal route. ZnCl2, thiourea, and glucose were selected as the raw materials. The formed ZnS with hexagonal phase has spherical cluster-like structure, which shows good monodispersity in size. A thin layer carbon is coated on the surface of ZnS cluster-like spheres. The thickness of carbon shell is dependent on the dosage of glucose. The carbon-coated ZnS nano-clusters show the same emission as that of pristine ZnS nano-clusters. Exposure of the aqueous dispersion of carbon-coated ZnS products to 980 nm laser can elevate its temperature by 5.1°C in 8 min. It was found that the photothermal conversion effect mainly comes from the carbon component and at the same time, the heterointerface between ZnS and carbon also provides a positive role for it. In addition, the carbon-coated ZnS products can absorb dye molecular with highest adsorption capacity of 36.8 mg/g toward Rhodamine B. The present finding demonstrates their potential applications in photothermal agents, adsorbents, and related fields. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Effect of thermal treatment on the growth, structure and luminescence of nitride-passivated silicon nanoclusters

    Directory of Open Access Journals (Sweden)

    Normand Elise

    2011-01-01

    Full Text Available Abstract Silicon nanoclusters (Si-ncs embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.

  11. The determination of copper ions based on sensitized chemiluminescence of silver nanoclusters

    International Nuclear Information System (INIS)

    Yu, X.; Wang, Q.

    2011-01-01

    We report on the first application of novel, water-soluble and fluorescent silver nanoclusters (Ag NCs) in a chemiluminescent (CL) detection system. A method has been developed for the determination of copper(II) ion that is based on the fact that the weak CL resulting from the redox reaction between Ce(IV) ion and sulfite ion is strongly enhanced by the Ag NCs and that the main CL signals now originate from Ag NCs. UV-visible spectra, CL spectra and fluorescent (FL) spectra were acquired to investigate the enhanced CL mechanism. It is proposed that the electronic energy of the excited state intermediate SO2* that originates from the CL reaction is transferred to Ag NCs to form an electronically excited NC whose emission is observed. In addition, it is found that copper(II) is capable of inhibiting the CL of the nanoclusters system, but not if other common metal ions are present. The detection of copper(II) is achieved indirectly by measuring the CL intensity of Ag NCs. Under the optimized experimental conditions, a linear relationship does exist between the intensity of CL and the concentrations of copper(II) in the range of 0.2 nM to 0.1 mM. The detection limit is 0.12 nM. The method is applied to the determination of copper(II) ion in tap water with satisfactory results. (author)

  12. Multi-facet implications of PEGylated lysozyme stabilized-silver nanoclusters loaded recombinant PTEN cargo in cancer theranostics.

    Science.gov (United States)

    Arora, Neha; Gavya S, Lalitha; Ghosh, Siddhartha S

    2018-05-01

    Amalgamation of delivery and tracking of therapeutically relevant moieties on a single platform is made possible by the application of metal nanoclusters, an innovative class of luminescent nanomaterials. Metal nanoclusters, possessing molecule-like attributes, display extraordinary size and shape tunable properties befitting theranostic applications. Herein, we report successful assembly of therapeutically significant phosphatase protein PTEN and fluorescent lysozyme-stabilized silver nanoclusters to accomplish delivery and tracking of the protein. Down-regulation of PTEN perturbs the cellular networking leading to copious pathological conditions. The integration of purified recombinant PTEN with silver nanoclusters was evaluated by fluorescence spectroscopy study. A key feature of this study is the use of polyethylene glycol coating that allows fabrication of the assembly into spherical nanocomposites as characterized by transmission electron microscope along with retention of both optical functionality of the cluster and biological activity of the protein. Prior to cellular application, the functional integrity of PTEN in the composite was determined in vitro, by enzymatic assay employing para-nitrophenylphosphate as substrate. Cellular internalization of the cargo was studied by confocal microscopy and flow cytometry analysis. The efficacy of the payload on modulation of cellular signaling was assessed on cell lines that expressed PTEN differentially. PTEN null U-87 MG and PTEN expressing MCF7 cell lines displayed successful alteration of AKT and FAK signaling proteins culminating in cell cycle arrest and reduced wound healing capacity. A dose dependent reduction in cell proliferation of MCF7 cells was achieved. For U-87 MG, treatment with the payload resulted in chemosensitization toward anti-cancer drug erlotinib. Thus, PEG coated GST-PTEN loaded silver nanoclusters serves as a comprehensive system encompassing cellular imaging and protein delivery with

  13. WFC3 IR subarray anomaly

    Science.gov (United States)

    Bushouse, Howard

    2009-07-01

    Certain combinations of WFC3 IR subarray size and sample sequence yield images that show a sharp change in background level that exactly bi-sects each detector amplifier quadrant. The change in level has an amplitude of a few DN per pixel. The cause of this anomaly and its apparent correlation with subarray size and sample sequence is not understood. Given the 4 available subarray sizes and 11 available readout sample sequences, there are a total of 44 possible subarray mode readout combinations. To date, 14 of those combinations have been used on-orbit in either calibration and GO programs. Of those, 3 combinations show the anomaly. This program will obtain IR dark exposures in the remaining 30 readout combinations that have not yet been explored. This will add to our knowledge of which combinations show the anomaly and will therefore help us to understand its origin.

  14. Oferta ir akceptas vartojimo sutartyse

    OpenAIRE

    Ežerskytė, Ramunė

    2011-01-01

    Sutarčiai sudaryti paprastai reikia, kad viena šalis pasiūlytų sudaryti sutartį (oferta), o kita šalis sutiktų su pasiūlymu (akceptas). Sutarčių įvairovėje išskiriamos vartojimo sutartys, kurios dėl silpnesnės šalies apsaugos principo įgyvendinimo pasižymi tam tikrais ypatumais. Vartojimo sutarčių sudarymas pateikiant ofertą ir akceptą yra šio magistro baigiamojo darbo objektas. Magistro baigiamąjį darbą sudaro trys dalys. Pirmojoje darbo dalyje analizuojama vartojimo sutarties sąvoka ir spec...

  15. Hidroenergijos panaudojimo raida ir perspektyvos

    OpenAIRE

    Vizbaras, Andrius

    2008-01-01

    Ilgą laiko tarpą hidroenergetika vertinta kaip sėkminga žmonijos vystimosi ir akivaizdžios naudos išraiška, pastaruoju metu siejama su reikšmingu poveikiu gamtinei aplinkai bei įtaka klimato kaitai. Lygumų šalyse, net ir mažos galios hidroelektrinių statyba pareikalauja didelių užliejamų žemės plotų. Šiame darbe atlikome aštuoniasdešimties iki 2007 metų pastatytų hidroelektrinių poveikio aplinkai analizę bei aptarėme galimą „Lietuvos hidroenergetinių išteklių schemoje„ numatytų statyti HE pov...

  16. Climate Prediction Center IR 4km Dataset

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CPC IR 4km dataset was created from all available individual geostationary satellite data which have been merged to form nearly seamless global (60N-60S) IR...

  17. Incorporating gold nanoclusters and target-directed liposomes as a synergistic amplified colorimetric sensor for HER2-positive breast cancer cell detection

    OpenAIRE

    Tao, Yu; Li, Mingqiang; Kim, Bumjun; Auguste, Debra T.

    2017-01-01

    Breast cancer is the second leading cause of cancer-related mortality in women. Successful development of sensitive nanoprobes for breast cancer cell detection is of great importance for breast cancer diagnosis and symptomatic treatment. Herein, inspired by the intrinsic peroxidase property of gold nanoclusters, high loading, and targeting ability of ErbB2/Her2 antibody functionalized liposomes, we report that gold nanoclusters-loaded, target-directed, functionalized liposomes can serve as a ...

  18. Au Sub-Nanoclusters on TiO2 toward Highly Efficient and Selective Electrocatalyst for N2 Conversion to NH3 at Ambient Conditions.

    Science.gov (United States)

    Shi, Miao-Miao; Bao, Di; Wulan, Ba-Ri; Li, Yong-He; Zhang, Yue-Fei; Yan, Jun-Min; Jiang, Qing

    2017-05-01

    As the NN bond in N 2 is one of the strongest bonds in chemistry, the fixation of N 2 to ammonia is a kinetically complex and energetically challenging reaction and, up to now, its synthesis is still heavily relying on energy and capital intensive Haber-Bosch process (150-350 atm, 350-550 °C), wherein the input of H 2 and energy are largely derived from fossil fuels and thus result in large amount of CO 2 emission. In this paper, it is demonstrated that by using Au sub-nanoclusters (≈0.5 nm ) embedded on TiO 2 (Au loading is 1.542 wt%), the electrocatalytic N 2 reduction reaction (NRR) is indeed possible at ambient condition. Unexpectedly, NRR with very high and stable production yield (NH 3 : 21.4 µg h -1 mg -1 cat. , Faradaic efficiency: 8.11%) and good selectivity is achieved at -0.2 V versus RHE, which is much higher than that of the best results for N 2 fixation under ambient conditions, and even comparable to the yield and activation energy under high temperatures and/or pressures. As isolated precious metal active centers dispersed onto oxide supports provide a well-defined system, the special structure of atomic Au cluster would promote other important reactions besides NRR for water splitting, fuel cells, and other electrochemical devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Immobilization of gold nanoclusters inside porous electrospun fibers for selective detection of Cu(II): A strategic approach to shielding pristine performance

    Science.gov (United States)

    Senthamizhan, Anitha; Celebioglu, Asli; Balusamy, Brabu; Uyar, Tamer

    2015-10-01

    Here, a distinct demonstration of highly sensitive and selective detection of copper (Cu2+) in a vastly porous cellulose acetate fibers (pCAF) has been carried out using dithiothreitol capped gold nanocluster (DTT.AuNC) as fluorescent probe. A careful optimization of all potential factors affecting the performance of the probe for effective detection of Cu2+ were studied and the resultant sensor strip exhibiting unique features including high stability, retained parent fluorescence nature and reproducibility. The visual colorimetric detection of Cu2+ in water, presenting the selective sensing performance towards Cu2+ ions over Zn2+, Cd2+ and Hg2+ under UV light in naked eye, contrast to other metal ions that didn’t significantly produce such a change. The comparative sensing performance of DTT.AuNC@pCAF, keeping the nonporous CA fiber (DTT.AuNC@nCAF) as a support matrix has been demonstrated. The resulting weak response of DTT.AuNC@nCAF denotes the lack of ligand protection leading to the poor coordination ability with Cu2+. The determined detection limit (50 ppb) is far lower than the maximum level of Cu2+ in drinking water (1.3 ppm) set by U.S. Environmental Protection Agency (EPA). An interesting find from this study has been the specific oxidation nature between Cu2+ and DTT.AuNC, offering solid evidence for selective sensors.

  20. 2D-COS of in situ μ-Raman and in situ IR spectra for structure evolution characterisation of NEP-deposited cobalt oxide catalyst during n-nonane combustion.

    Science.gov (United States)

    Chlebda, Damian K; Jodłowski, Przemysław J; Jędrzejczyk, Roman J; Łojewska, Joanna

    2017-11-05

    New catalytic systems are still in development to meet the challenge of regulations concerning the emission of volatile organic compounds (VOCs). This is because such compounds have a significant impact on air quality and some of them are toxic to the environment and human beings. The catalytic combustion process of VOCs over non-noble metal catalysts is of great interest to researchers. The high conversion parameters and cost effective preparation makes them a valuable alternative to monoliths and noble metal catalysts. In this study, the cobalt catalyst was prepared by non-equilibrium plasma deposition of organic precursor on calcined kanthal steel. Thus prepared, cobalt oxide based microstructural short-channel reactors were tested for n-nonane combustion and the catalyst surfaces were examined by in situ μ-Raman spectroscopy and in situ infrared spectroscopy. The spectra collected at various temperatures were used in generalised two-dimensional correlation analysis to establish the sequential order of spectral intensity changes and correlate the simultaneous changes in bands selectively coupled by different interaction mechanisms. The 2D synchronous and asynchronous contour maps were proved to be a valuable extension to the standard analysis of the temperature dependent 1D spectra. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. 2D-COS of in situ μ-Raman and in situ IR spectra for structure evolution characterisation of NEP-deposited cobalt oxide catalyst during n-nonane combustion

    Science.gov (United States)

    Chlebda, Damian K.; Jodłowski, Przemysław J.; Jędrzejczyk, Roman J.; Łojewska, Joanna

    2017-11-01

    New catalytic systems are still in development to meet the challenge of regulations concerning the emission of volatile organic compounds (VOCs). This is because such compounds have a significant impact on air quality and some of them are toxic to the environment and human beings. The catalytic combustion process of VOCs over non-noble metal catalysts is of great interest to researchers. The high conversion parameters and cost effective preparation makes them a valuable alternative to monoliths and noble metal catalysts. In this study, the cobalt catalyst was prepared by non-equilibrium plasma deposition of organic precursor on calcined kanthal steel. Thus prepared, cobalt oxide based microstructural short-channel reactors were tested for n-nonane combustion and the catalyst surfaces were examined by in situ μ-Raman spectroscopy and in situ infrared spectroscopy. The spectra collected at various temperatures were used in generalised two-dimensional correlation analysis to establish the sequential order of spectral intensity changes and correlate the simultaneous changes in bands selectively coupled by different interaction mechanisms. The 2D synchronous and asynchronous contour maps were proved to be a valuable extension to the standard analysis of the temperature dependent 1D spectra.

  2. Formation and structures of Au-Rh bimetallic nanoclusters supported on a thin film of Al2O3/NiAl(100).

    Science.gov (United States)

    Hsu, Po-Wei; Liao, Zhen-He; Hung, Ting-Chieh; Lee, Hsuan; Wu, Yu-Cheng; Lai, Yu-Ling; Hsu, Yao-Jane; Lin, Yuwei; Wang, Jeng-Han; Luo, Meng-Fan

    2017-06-07

    Self-organized alloying of Au with Rh in nanoclusters on an ordered thin film of Al 2 O 3 /NiAl(100) was investigated via various surface probe techniques under ultrahigh-vacuum conditions and calculations based on density-functional theory. The bimetallic clusters were formed on the sequential deposition of vapors of Au and Rh onto Al 2 O 3 /NiAl(100) at 300 K. The formation was more effective on the oxide seeded with Rh, since all post-deposited Au joined the pregrown Rh clusters; for metal deposition in the reverse order, some separate Rh clusters were formed. The contrasting behavior is rationalized through the easier nucleation of Rh on the oxide surface, due to the stronger Rh-oxide and Rh-Rh bonds. The alloying in the clusters proceeded, regardless of the order of metal deposition, toward a specific structure: an fcc phase, (100) orientation and Rh core-Au shell structure. The orientation, structural ordering and lattice parameters of the Au-Rh bimetallic clusters resembled Rh clusters, rather than Au clusters, on Al 2 O 3 /NiAl(100), even with Rh in a minor proportion. The Rh-predominated core-shell structuring corresponds to the binding energies in the order Rh-Rh > Rh-Au > Au-Au. The core-shell segregation, although active, was somewhat kinetically hindered, since elevating the sample temperature induced further encapsulation of Rh. The bimetallic clusters became thermally unstable above 500 K, for which both Rh and Au atoms began to diffuse into the substrate. Moreover, the electronic structures of surface elements on the bimetallic clusters, controlled by both structural and electronic effects, show a promising reactivity.

  3. Isolated Gramicidin Peptides Probed by IR Spectroscopy

    NARCIS (Netherlands)

    Rijs, A. M.; Kabelac, M.; Abo-Riziq, A.; Hobza, P.; de Vries, M. S.

    2011-01-01

    We report double-resonant IR/UV ion-dip spectroscopy of neutral gramicidin peptides in the gas phase. The IR spectra of gramicidin A and C, recorded in both the 1000 cm(-1) to 1800 cm(-1) and the 2700 to 3750 cm(-1) region, allow structural analysis. By studying this broad IR range, various local

  4. Diffraction-limited IR Microspectroscopy with IRENI

    Science.gov (United States)

    J. Sedlmair; B. Illman; M. Unger; C. Hirschmugl

    2012-01-01

    In a unique way, IRENI (Infrared environmental Imaging), operated at the Synchrotron Radiation Center in Madison, combines IR spectroscopy and IR imaging, revealing the chemical morphology of a sample. Most storage ring based IR confocal microscopes have to overcome a trade-off between spatial resolution versus...

  5. Ag50(Dppm)6(SR)30and Its Homologue AuxAg50-x(Dppm)6(SR)30Alloy Nanocluster: Seeded Growth, Structure Determination, and Differences in Properties.

    Science.gov (United States)

    Du, Wenjun; Jin, Shan; Xiong, Lin; Chen, Man; Zhang, Jun; Zou, Xuejuan; Pei, Yong; Wang, Shuxin; Zhu, Manzhou

    2017-02-01

    A large thiolate/phosphine coprotected Ag 50 (Dppm) 6 (SR) 30 nanocluster was synthesized through the further growth of Ag 44 (SR) 30 nanocluster and characterized by X-ray photoelectron spectroscopy (XPS), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray analysis. This new nanocluster comprised a 32-metal-atom dodecahedral kernel and two symmetrical Ag 9 (SR) 15 P 6 ring motifs. The 20 valence electrons correspond to shell closure in the Jellium model. Moreover, this nanocluster could be alloyed by templated/galvanic metal exchange to the homologue Au x Ag 50-x (Dppm) 6 (SR) 30 nanocluster; the latter showed much higher thermal stability than the Ag 50 (Dppm) 6 (SR) 30 nanocluster. Further experiments were conducted to study the optical, electrical, and photoluminescence properties of both nanoclusters. Our work not only reports two new larger size nanoclusters but also reveals a new way to synthesize larger size silver and alloy nanoclusters, that is, controlled growth/alloying.

  6. Biomedical applications of magneto-plasmonic nanoclusters (Conference Presentation)

    Science.gov (United States)

    Sokolov, Konstantin V.; Wu, Chun-Hsien; Cook, Jason; Zal, Tomasz; Emelianov, Stanislav

    2016-03-01

    Perhaps one of the most intriguing aspects of nanotechnology is the ability to create multimodal and multifunctional nanostructures that can open new venues in solving challenging biomedical problems. Here, we present multimodal magneto-plasmonic nanoparticles (MPNs) with a strong red-NIR absorbance, superparamagnetic properties and a high magnetic moment in an external magnetic field. Our design is based on self-assembly of 6 nm primary particles which consist of 5 nm diameter iron-oxide cores coated with a very thin ca. 0.5 nm gold shell. The assembly results in spherical highly uniform MPNs. We developed antibody targeted MPNs to address two highly challenging applications: (i) development of real-time assays for capture, enumeration and characterization of circulating tumor cells (CTCs), and (ii) enhancement of adoptive cell immunotherapy (ACT). Our results showed that MPNs can be used for simultaneous magnetic capture and photoacoustic (PA) detection of cancer cells in whole blood with no laborious processing steps. Furthermore, we demonstrated that MPNs conjugated with anti-CD8 antibodies, which are specific for cytotoxic T cells used in ATC, label CD8+ T cells with high specificity ex vivo and in vivo. Labeled T cells can be easily manipulated by a small magnet in suspension and under flow conditions. In addition, MPNs generate high contrast in MRI and PA imaging with the potential to detect just few cells per imaging voxel. These results show that immunotargeted MPNs can be explored for simultaneous visualization and magnetic guidance of T cell subsets in vivo for cancer treatment.

  7. IR spectral analysis for the diagnostics of crust earthquake precursors

    Science.gov (United States)

    Umarkhodgaev, R. M.; Liperovsky, V. A.; Mikhailin, V. V.; Meister, C.-V.; Naumov, D. Ju

    2012-04-01

    In regions of future earthquakes, a few days before the seismic shock, the emanation of radon and hydrogen is being observed, which causes clouds of increased ionisation in the atmosphere. In the present work the possible diagnostics of these clouds using infrared (IR) spectroscopy is considered, which may be important and useful for the general geophysical system of earthquake prediction and the observation of industrial emissions of radioactive materials into the atmosphere. Some possible physical processes are analysed, which cause, under the condition of additional ionisation in a pre-breakdown electrical field, emissions in the IR interval. In doing so, the transparency region of the IR spectrum at wavelengths of 7-15 μm is taken into account. This transparency region corresponds to spectral lines of small atmospheric constituents like CH4, CO2, N2O, NO2, NO, and O3. The possible intensities of the IR emissions observable in laboratories and in nature are estimated. The acceleration process of the electrons in the pre-breakdown electrical field before its adhesion to the molecules is analysed. The laboratory equipment for the investigation of the IR absorption spectrum is constructed for the cases of normal and decreased atmospheric pressures. The syntheses of ozone and nitrous oxides are performed in the barrier discharge. It is studied if the products of the syntheses may be used to model atmospheric processes where these components take part. Spectra of products of the syntheses in the wavelength region of 2-10 μm are observed and analysed. A device is created for the syntheses and accumulation of nitrous oxides. Experiments to observe the IR-spectra of ozone and nitrous oxides during the syntheses and during the further evolution of these molecules are performed. For the earthquake prediction, practically, the investigation of emission spectra is most important, but during the laboratory experiments, the radiation of the excited molecules is shifted by a

  8. SnO{sub 2}, IrO{sub 2}, Ta{sub 2}O{sub 5}, Bi{sub 2}O{sub 3}, and TiO{sub 2} nanoparticle anodes: electrochemical oxidation coupled with the cathodic reduction of water to yield molecular H{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jina [KRICT, Korea Research Institute of Chemical Technology (Korea, Republic of); Qu Yan; Hoffmann, Michael R., E-mail: mrh@caltech.edu [California Institute of Technology, Linde-Robinson Laboratories (United States)

    2012-08-15

    In recent years, the search for environmentally friendly alternative energy sources with reduced carbon footprints has increased. The coupling of photovoltaic power sources with advanced electrolysis systems for hydrogen production via water splitting using organic contaminants as sacrificial electron donors has been considered to a be viable alternative. In this report, we demonstrated the feasibility of a scaled-up rooftop prototype of the proposed hybrid photovoltaic-electrolysis system, which utilizes semiconductor nanoparticles coated on to metal substrates as electrodes for the generation of hydrogen coupled with the oxidation of wastewater. Application of an anodic bias of >2.0 V to bismuth-doped TiO{sub 2} (BiO{sub x}-TiO{sub 2}) on Ti metal anodes with a sequential under-coatings of nanoparticulate SnO{sub 2}, IrO{sub 2}, Ta{sub 2}O{sub 5}, and Bi{sub 2}O{sub 3} results in the electrochemical degradation of a variety of organic chemical contaminants in water (i.e., rhodamine B (Rh.B), methylene blue (MB), salicylic acid, triclosan, and phenol) and actual wastewater from a chemical manufacturing plant, while at the same time, molecular hydrogen is produced at stainless steel (SS) cathodes. The kinetics of the anodic substrates oxidation is investigated as a function of the cell current (I{sub cell}), substrate concentration, and background electrolyte composition (e.g., NaCl, Na{sub 2}SO{sub 4}, or seawater). Average current efficiencies were found to be in the range of 4-22 %, while the cathodic current and energy efficiencies for hydrogen production were found to be in the range of 50-70 % and 20-40 %, respectively.

  9. Anisotropic Magnetoresistance in Antiferromagnetic Sr_{2}IrO_{4}

    Directory of Open Access Journals (Sweden)

    C. Wang

    2014-11-01

    Full Text Available We report point-contact measurements of anisotropic magnetoresistance (AMR in a single crystal of antiferromagnetic Mott insulator Sr_{2}IrO_{4}. The point-contact technique is used here as a local probe of magnetotransport properties on the nanoscale. The measurements at liquid nitrogen temperature reveal negative magnetoresistances (up to 28% for modest magnetic fields (250 mT applied within the IrO_{2} a-b plane and electric currents flowing perpendicular to the plane. The angular dependence of magnetoresistance shows a crossover from fourfold to twofold symmetry in response to an increasing magnetic field with angular variations in resistance from 1% to 14%. We tentatively attribute the fourfold symmetry to the crystalline component of AMR and the field-induced transition to the effects of applied field on the canting of antiferromagnetic-coupled moments in Sr_{2}IrO_{4}. The observed AMR is very large compared to the crystalline AMRs in 3d transition metal alloys or oxides (0.1%–0.5% and can be associated with the large spin-orbit interactions in this 5d oxide while the transition provides evidence of correlations between electronic transport, magnetic order, and orbital states. The finding of this work opens an entirely new avenue to not only gain a new insight into physics associated with spin-orbit coupling but also to better harness the power of spintronics in a more technically favorable fashion.

  10. Coprates Chasma Landslides in IR

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] Today's daytime IR image is of a portion of Coprates Chasma, part of Valles Marineris. As with yesterday's image, this image shows multiple large landslides. Image information: IR instrument. Latitude -8.2, Longitude 300.2 East (59.8 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  11. Characterization of a fluorescence probe based on gold nanoclusters for cell and animal imaging

    International Nuclear Information System (INIS)

    Chen Haiyan; Zhang Xin; Cheng Zhengqi; Dai Xi; Zhu Rui; Gu Yueqing; Li Bowen; Wang Chuan

    2013-01-01

    A facile approach to synthesize gold nanoclusters (Au NCs) with bluish green fluorescence using histidine as both reductant and capping agent was reported. The UV–visible absorption and photoluminescence spectra measurement was performed to explore its optical properties under different circumstances (preparing condition, temperature, pH, storing time). Then, MPA, a NIR organic dye, was conjugated to Au NCs (Au-MPA) for in vivo fluorescence imaging application. Low cytotoxicity and high affinity to tumor of this nanoprobe was proved at the cellular level, and its bio-distribution in normal nude mice and MCF-7 tumor-bearing mice was also investigated. Consequently, the results demonstrated the promising potential of the green Au NCs conjugated with NIR dye as nanoprobes in bioimaging and related fields. (paper)

  12. Contribution of Metal Defects in the Assembly Induced Emission of Cu Nanoclusters

    KAUST Repository

    Wu, Zhennan

    2017-03-20

    Aggregation/assembly induced emission (AIE) has been observed for metal nanoclusters (NCs), but the origin of the enhanced emission is not fully understood, yet. In this work, the significant contribution of metal defects on AIE is revealed by engineering the self-assembly process of Cu NCs using ethanol. The presence of ethanol leads to a rapid assembly of NCs into ultrathin nanosheets, promoting the formation of metal defects-rich surface. Detailed studies and computer simulation confirm that the metal defects-rich nanosheets possess increased Cu(I)-to-Cu(0) ratio, which greatly influences ligand-to-metal-metal charge transfer and therewith facilitates the radiative relaxation of excitons. Consequently, the Cu NCs self-assembly nanosheets exhibit obvious emission enhancement.

  13. Fluorescent turn-on determination of the activity of peptidases using peptide templated gold nanoclusters

    International Nuclear Information System (INIS)

    Luo, Junjun; Wang, Liqiang; Zeng, Ke; Shen, Congcong; Qian, Pin; Yang, Minghui; Rasooly, Avraham; Qu, Fengli

    2016-01-01

    The fluorescence intensity of gold nanoclusters (AuNCs) is inversely related to the length of a peptide immobilized on its surface. This finding has been exploited to design a turn-on fluorescent method for the determination of the activity of peptidase. The β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) was chosen as a model peptidase. BACE1 cleaves the peptide substrates on AuNCs, and the fluorescence intensity of the AuNCs (at exCitation/emission wavelengths of 320/405 nm) carrying the rest of the cleaved peptide is significantly higher than that of the AuNCs with uncleaved peptide. Transmission electron microscopy revealed a decrease in the size of the AuNCs which is assumed cause fluorescence enhancement. The assay was applied to the determination of BACE1 activity in spiked cell lysates, and recoveries were between 96.9 and 104.0 %. (author)

  14. Gold Doping of Silver Nanoclusters: A 26-Fold Enhancement in the Luminescence Quantum Yield

    KAUST Repository

    Soldan, Giada

    2016-04-10

    A high quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for a wide range of applications. Unfortunately, the weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility. Herein, we accomplished a ≥26-fold PL QY enhancement of the Ag29(BDT)12(TPP)4 cluster (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) by doping with a discrete number of Au atoms, producing Ag29-xAux(BDT)12(TPP)4, x=1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660nm. Single-crystal XRD, mass spectrometry, optical, and NMR spectroscopy shed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.

  15. A New Class of Atomically Precise, Hydride-Rich Silver Nanoclusters Co-Protected by Phosphines

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2016-10-10

    Thiols and phosphines are the most widely used organic ligands to attain atomically precise metal nanoclusters (NCs). Here, we used simple hydrides (e.g., H–) as ligands along with phosphines, such as triphenylphosphine (TPP), 1,2-bis(diphenylphosphino)ethane [DPPE], and tris(4-fluorophenyl)phosphine [TFPP] to design and synthesize a new class of hydride-rich silver NCs. This class includes [Ag18H16(TPP)10]2+, [Ag25H22(DPPE)8]3+, and [Ag26H22(TFPP)13]2+. Our work reveals a new family of atomically precise NCs protected by H– ligands and labile phosphines, with potentially more accessible active metal sites for functionalization and provides a new set of stable NC sizes with simpler ligand–metal bonding for researchers to explore both experimentally and computationally.

  16. Silver nanocluster films for glucose sensing by Surface Enhanced Raman Scattering (SERS

    Directory of Open Access Journals (Sweden)

    Raju Botta

    2016-07-01

    Full Text Available The detection of glucose by Surface Enhanced Raman Scattering (SERS is a challenging problem because glucose molecules have a small Raman scattering cross-section and they have a low affinity for adsorption on metal nanoparticle surfaces. In this study we used 2-Thienylboronic acid (2-TBA as a bridge or linker molecule between the metal surface and the glucose molecule and observed an intense Raman line at 986 cm−1 that was used to quantify the glucose concentration in the molar concentration range 1 μM–500 μM. A good correlation was observed between the intensity of this line and molar concentration of glucose. These results would find applications in the development of a non-invasive glucose sensor for diabetic patients using saliva as the body fluid instead of blood serum. Keywords: SERS, Nanoclusters, Raman Spectroscopy, 2-Thienylboronic acid, d-Glucose

  17. Probing the photoluminescence properties of gold nanoclusters by fluorescence lifetime correlation spectroscopy

    International Nuclear Information System (INIS)

    Yuan, C. T.; Lin, T. N.; Shen, J. L.; Lin, C. A.; Chang, W. H.; Cheng, H. W.; Tang, J.

    2013-01-01

    Gold nanoclusters (Au NCs) have attracted much attention for promising applications in biological imaging owing to their tiny sizes and biocompatibility. So far, most efforts have been focused on the strategies for fabricating high-quality Au NCs and then characterized by conventional ensemble measurement. Here, a fusion single-molecule technique combining fluorescence correlation spectroscopy and time-correlated single-photon counting can be successfully applied to probe the photoluminescence (PL) properties for sparse Au NCs. In this case, the triplet-state dynamics and diffusion process can be observed simultaneously and the relevant time constants can be derived. This work provides a complementary insight into the PL mechanism at the molecular levels for Au NCs in solution

  18. Modeling of metal nanocluster growth on patterned substrates and surface pattern formation under ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, Satoshi

    2012-11-01

    This work addresses the metal nanocluster growth process on prepatterned substrates, the development of atomistic simulation method with respect to an acceleration of the atomistic transition states, and the continuum model of the ion-beam inducing semiconductor surface pattern formation mechanism. Experimentally, highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO{sub 2} surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well-separated. The first topic is the investigation of this growth process with a continuum theoretical approach to the surface gas condensation as well as an atomistic cluster growth model. The atomistic simulation model is a lattice-based kinetic Monte-Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag monomers and {approx}1 nm square surface migration ranges of Ag monomers. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns. The second topic specifies the acceleration scheme utilized in the metallic cluster growth model. Concerning the atomistic movements, a classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements

  19. Search Directions for Direct H2O2 Synthesis Catalysts Starting from Au-12 Nanoclusters

    DEFF Research Database (Denmark)

    Grabow, Lars; Larsen, Britt Hvolbæk; Falsig, Hanne

    2012-01-01

    We present density functional theory calculations on the direct synthesis of H2O2 from H-2 and O-2 over an Au-12 corner model of a gold nanoparticle. We first show a simple route for the direct formation of H2O2 over a gold nanocatalyst, by studying the energetics of 20 possible elementary...... that the rate of H2O2 and H2O formation can be determined from a single descriptor, namely, the binding energy of oxygen (E-O). Our model predicts the search direction starting from an Au-12 nanocluster for an optimal catalyst in terms of activity and selectivity for direct H2O2 synthesis. Taking also stability...

  20. Photocatalytic synthesis of intensely photoluminescent gold nanoclusters and application in cell imaging

    Science.gov (United States)

    Wei, Ming; Tian, Ye; Wang, Lijun; Hong, Yuankai; Sha, Yinlin

    2017-07-01

    In this article, a facile and rapid method was developed to synthesize intensely photoluminescent gold nanoclusters (AuNCs) based on photocatalytic reduction. Using (5-mercapto-1,3,4-thiadiazol-2-ylthio)acetic acid (TMT) that is a photosensitive material as the ligands, AuNC@TMT, with high photoluminescence quantum yield (19.7%), were prepared. The average diameter of gold core is 1.69 ± 0.22 nm. The maximum excitation and emission wavelengths of AuNC@TMT are at 422 and 516 nm, respectively. The mechanism of photocatalytic reduction is preliminarily understood. Under UV lamp with 365 nm irradiation, Au(Ι)-TMT complex occurred with electron transfer from TMT to Au(Ι), which was reduced to Au(0) as the gold core of AuNC. Thus, it indicates that the photosensitive and electron transport materials with a thiol group will be superior ligands for synthesis of intensely photoluminescent AuNCs.

  1. Protein coated gold nanoparticles as template for the directed synthesis of highly fluorescent gold nanoclusters

    Science.gov (United States)

    Zhang, Lingyan; Han, Fei

    2018-04-01

    Bovine serum albumin (BSA) modified gold nanoparticles (AuNPs) was selected as template for the synthesis of AuNPs@gold nanoclusters (AuNCs) core/shell nanoparticles, in which BSA not only acted as dual functions agent for both anchoring and reducing Au3+ ions, but also was employed as a bridge between the AuNPs and AuNCs. Optical properties of AuNPs@AuNCs core/shell nanoparticles were studied using UV-visible and fluorescence spectroscopy. The prepared AuNPs@AuNCs core/shell nanoparticles exhibited sphere size uniformity with improved monodispersity, excellent fluorescence and fluorescent stability. Compared with AuNCs, AuNPs@AuNCs core/shell nanoparticles possessed large size and strong fluorescence intensity due to the effect of AuNPs as core. Moreover, the mechanism of the AuNPs induced fluorescence changes of the core/shell nanoparticles was first explored.

  2. Calcium carbonate-gold nanocluster hybrid spheres: synthesis and versatile application in immunoassays.

    Science.gov (United States)

    Peng, Juan; Feng, Li-Na; Zhang, Kui; Li, Xing-Hua; Jiang, Li-Ping; Zhu, Jun-Jie

    2012-04-23

    Fluorescent gold nanoclusters (AuNCs) were incorporated into porous calcium carbonate spheres through electrostatic interaction. The resulting CaCO(3)/AuNCs hybrid material exhibited interesting properties, such as porous structure, excellent biocompatibility, good water solubility, and degradability. These properties make the CaCO(3)/AuNCs hybrid material a promising template to assemble horseradish peroxidase/antibody conjugates (HRP-Ab(2)). By using CaCO(3)/AuNCs/HRP-Ab(2) bioconjugates as probes, a versatile immunosensor was developed for fluorescent and electrochemical detection of the cancer biomarker neuron-specific enolase (NSE). The detection limits of the sensor were 2.0 and 0.1 pg mL(-1) for fluorescent and electrochemical detection, respectively. The immunosensor shows high sensitivity and offers an alternative strategy for the detection of other proteins and DNA. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. One-Step Synthesis of Zeolite Membranes Containing Catalytic Metal Nanoclusters.

    Science.gov (United States)

    Kim, Seok-Jhin; Tan, Shuai; Taborga Claure, Micaela; Briones Gil, Laura; More, Karren L; Liu, Yujun; Moore, Jason S; Dixit, Ravindra S; Pendergast, John G; Sholl, David S; Jones, Christopher W; Nair, Sankar

    2016-09-21

    Metal-loaded zeolitic membranes are promising candidates as catalytic membrane reactors. We report a one-step synthesis method to synthesize zeolite membranes containing metal nanoclusters, that has advantages in comparison to multistep methods such as impregnation and ion exchange. Pure-silica MFI zeolite-Pt hybrid membranes were prepared by hydrothermal synthesis with addition of 3-mercaptopropyl-trimethoxysilane (MPS) and a platinum precursor. Composition analysis and mapping by energy-dispersive X-ray spectroscopy (EDX) reveal that Pt ions/clusters are uniformly distributed along the membrane cross-section. High-magnification scanning transmission electron microscopy (STEM) analysis shows that Pt metal clusters in the hybrid zeolite membrane have a diameter distribution in the range of 0.5-2.0 nm. In contrast, a pure-silica MFI membrane synthesized from an MPS-free solution shows negligible incorporation of Pt metal clusters. To characterize the properties of the hybrid (zeolite/metal) membrane, it was used as a catalytic membrane reactor (CMR) for high-temperature propane dehydrogenation (PDH) at 600 °C and 1 atm. The results indicate that Pt metal clusters formed within the MFI zeolite membrane can serve as effective catalysts for high-temperature PDH reaction along with H2 removal via membrane permeation, thereby increasing both conversion and selectivity in relation to a conventional membrane reactor containing an equivalent amount of packed Pt catalyst in contact with an MFI membrane. The hybrid zeolite-Pt CMR also showed stable conversion and selectivity upon extended high-temperature operation (12 h), indicating that encapsulation in the zeolite allowed thermal stabilization of the Pt nanoclusters and reduced catalyst deactivation.

  4. Resonance energy transfer between fluorescent BSA protected Au nanoclusters and organic fluorophores.

    Science.gov (United States)

    Raut, Sangram; Rich, Ryan; Fudala, Rafal; Butler, Susan; Kokate, Rutika; Gryczynski, Zygmunt; Luchowski, Rafal; Gryczynski, Ignacy

    2014-01-07

    Bovine serum albumin (BSA) protected nanoclusters (Au and Ag) represent a group of nanomaterials that holds great promise in biophysical applications due to their unique fluorescence properties and lack of toxicity. These metal nanoclusters have utility in a variety of disciplines including catalysis, biosensing, photonics, imaging and molecular electronics. However, they suffer from several disadvantages such as low fluorescence quantum efficiency (typically near 6%) and broad emission spectrum (540 nm to 800 nm). We describe an approach to enhance the apparent brightness of BSA Au clusters by linking them with a high extinction donor organic dye pacific blue (PB). In this conjugate PB acts as a donor to BSA Au clusters and enhances its brightness by resonance energy transfer (RET). We found that the emission of BSA Au clusters can be enhanced by a magnitude of two-fold by resonance energy transfer (RET) from the high extinction donor PB, and BSA Au clusters can act as an acceptor to nanosecond lifetime organic dyes. By pumping the BSA Au clusters using a high extinction donor, one can increase the effective brightness of less bright fluorophores like BSA Au clusters. Moreover, we prepared another conjugate of BSA Au clusters with the near infrared (NIR) dye Dylight 750 (Dy750), where BSA Au clusters act as a donor to Dy750. We observed that BSA Au clusters can function as a donor, showing 46% transfer efficiency to the NIR dye Dy750 with a long lifetime component in the acceptor decay through RET. Such RET-based probes can be used to prevent the problems of a broad emission spectrum associated with the BSA Au clusters. Moreover, transferring energy from BSA Au clusters to Dy750 will result in a RET probe with a narrow emission spectrum and long lifetime component which can be utilized in imaging applications.

  5. Novel synthesis of gold nanoclusters templated with L-tyrosine for selective analyzing tyrosinase

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoming, E-mail: ming4444@swu.edu.cn; Luo, Yawen; Zhuo, Yan; Feng, Yuanjiao; Zhu, Shanshan

    2014-08-20

    Graphical abstract: One-pot and novel synthesized fluorescent gold nanoclusters templated with L-tyrosine (AuNCs@Tyr) were employed for investigating tyrosinase activity on the basis of aggregations of AuNCs@Tyr on its active sites during the catalysis reactions, thus leading to the fluorescence quenching of AuNCs@Tyr. - Highlights: • A novel, one-pot strategy for synthesizing fluorescent AuNCs@Tyr was proposed. • A selective and cost-effective assay for TR activity has been well established. • This AuNCs@Tyr here may broaden avenues for detecting TR in clinical applications. - Abstract: L-Tyrosine (Tyr), playing roles as both a reducing reagent and a protecting ligand, has been first employed for synthesizing fluorescent gold nanoclusters (AuNCs@Tyr) via a novel one-pot strategy. The as-prepared AuNCs@Tyr exhibited a fluorescence emission at 470 nm with a quantum yield of approximately 2.5%. Subsequently, the AuNCs@Tyr described here was applied for detections of tyrosinase (TR) activity, which was based on the mechanism of aggregations of AuNCs@Tyr occurring on the active sites of TR since TR was introduced, thus leading to the fluorescence quenching of AuNCs@Tyr. Accordingly, TR was analyzed in a linear range of 0.5–200 u mL{sup −1} with a detection limit of 0.08 u mL{sup −1} at a signal-to-noise ratio of 3. Significantly, TR has been considered as a critical marker for melanoma owing to its specifically expressing in melanoma cells. Therefore, this analytical method towards investigating TR activity may broaden avenues for meaningfully clinical applications.

  6. Time-reversal symmetry breaking hidden order in Sr2(Ir,Rh)O4

    Science.gov (United States)

    Jeong, Jaehong; Sidis, Yvan; Louat, Alex; Brouet, Véronique; Bourges, Philippe

    2017-04-01

    Layered 5d transition iridium oxides, Sr2(Ir,Rh)O4, are described as unconventional Mott insulators with strong spin-orbit coupling. The undoped compound, Sr2IrO4, is a nearly ideal two-dimensional pseudospin-1/2 Heisenberg antiferromagnet, similarly to the insulating parent compound of high-temperature superconducting copper oxides. Using polarized neutron diffraction, we here report a hidden magnetic order in pure and doped Sr2(Ir,Rh)O4, distinct from the usual antiferromagnetic pseudospin ordering. We find that time-reversal symmetry is broken while the lattice translation invariance is preserved in the hidden order phase. The onset temperature matches that of the odd-parity hidden order recently highlighted using optical second-harmonic generation experiments. The novel magnetic order and broken symmetries can be explained by the loop-current model, previously predicted for the copper oxide superconductors.

  7. Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, J; Dolgner, K; Greve, H; Zaporojtchenko, V; Faupel, F [Technische Fakultaet der Christian-Albrechts-Universitaet zu Kiel, Lehrstuhl fuer Materialverbunde, Kaiserstr. 2, D-24143 Kiel (Germany)

    2006-12-07

    Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

  8. Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

    Science.gov (United States)

    Kruse, J.; Dolgner, K.; Greve, H.; Zaporojtchenko, V.; Faupel, F.

    2006-12-01

    Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

  9. Absorption and fluorescence characteristics of photo-activated adenylate cyclase nano-clusters from the amoeboflagellate Naegleria gruberi NEG-M strain

    Energy Technology Data Exchange (ETDEWEB)

    Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Fakultaet fuer Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Stierl, M.; Hegemann, P. [Institut fuer Biologie/Experimentelle Biophysik, Humboldt Universitaet zu Berlin, Invalidenstrasse 42, D-10115 Berlin (Germany); Kateriya, S. [Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi 110021 (India)

    2012-01-02

    Graphical abstract: Protein color center emissions were observed in the wavelength range from 340 nm to 900 nm from nano-clusters of the photo-activated adenylate cyclase (nPAC) from the amoeboflagellate Naegleria gruberi. Highlights: Black-Right-Pointing-Pointer Adenylyl cyclase nPAC in aqueous pH 7.5 buffer dissolved only to nano-clusters. Black-Right-Pointing-Pointer Nano-cluster size was determined by light attenuation (scattering) measurements. Black-Right-Pointing-Pointer The size of the nano-clusters was growing by coalescing during observation period. Black-Right-Pointing-Pointer In nPAC nano-clusters color centers were present in emission range of 360-900 nm. Black-Right-Pointing-Pointer The nPAC color center emission is compared with fluorescent protein emission. - Abstract: The spectroscopic characteristics of BLUF (BLUF = sensor of blue light using flavin) domain containing soluble adenylate cyclase (nPAC = Naegleria photo-activated cyclase) samples from the amoeboflagellate Naegleria gruberi NEG-M strain is studied at room temperature. The absorption and fluorescence spectroscopic development in the dark was investigated over two weeks. Attenuation coefficient spectra, fluorescence quantum distributions, fluorescence quantum yields, and fluorescence excitation distributions were measured. Thawing of frozen nPAC samples gave solutions with varying protein nano-cluster size and varying flavin, tyrosine, tryptophan, and protein color-center emission. Protein color-center emission was observed in the wavelength range of 360-900 nm with narrow emission bands of small Stokes shift and broad emission bands of large Stokes shift. The emission spectra evolved in time with protein nano-cluster aging.

  10. Synthesis and magnetic properties of 12L-perovskites Ba4LnIr3O12 (Ln=lanthanides)

    International Nuclear Information System (INIS)

    Shimoda, Yuki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio

    2009-01-01

    New quadruple perovskite oxides Ba 4 LnIr 3 O 12 (Ln=lanthanides) were prepared and their magnetic properties were investigated. They crystallize in the monoclinic 12L-perovskite-type structure with space group C2/m. The Ir 3 O 12 trimers and LnO 6 octahedra are alternately linked by corner-sharing and form the perovskite-type structure with 12 layers. The Ln and Ir ions are both in the tetravalent state for Ln=Ce, Pr, and Tb compounds (Ba 4 Ln 4+ Ir 3 4+ O 12 ), and for other compounds (Ln=La, Nd, Sm-Gd, Dy-Lu), Ln ions are in the trivalent state and the mean oxidation state of Ir ions is +4.33(Ba 4 Ln 3+ Ir 3 4+.33 O 12 ). An antiferromagnetic transition has been observed for Ln=Ce, Pr, and Tb compounds at 10.5, 35, and 16 K, respectively, while the other compounds are paramagnetic down to 1.8 K. - Graphical abstract: New quadruple perovskite oxides Ba 4 LnIr 3 O 12 were prepared and they form the perovskite-type structure with 12 layers, in which Ir 3 O 12 trimers and LnO 6 octahedra are alternately linked by corner-sharing. For Ln=Ce, Pr, and Tb compounds, an antiferromagnetic transition was observed at 10.5, 35, and 16 K, respectively.

  11. Hydrothermal synthesis of polyethylenimine-protected high luminescent Pt-nanoclusters and their application to the detection of nitroimidazoles

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Na [State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012 (China); College of Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin, 132022 (China); Li, Hong-Wei, E-mail: lihongwei@jlu.edu.cn [State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012 (China); Wu, Yuqing, E-mail: yqwu@jlu.edu.cn [State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012 (China)

    2017-03-15

    A novel one-step hydrothermal synthesis of highly fluorescent platinum nanoclusters protected by polyethylenimine (Pt-NCs@PEI) is described. The products are characterized well by UV–vis absorption, fluorescence spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) imaging. The Pt-NCs@PEI possess high quantum yield at 28%, which is the relatively high one among the reported Pt-NCs; especially, the synthesis is in one-step and the reaction time is much shorter (<1 h) than the related methods. In addition, the Pt-NCs@PEI have large Stocks-shift (∼150 nm), high tolerability to the extreme pH and high ionic strengths, and excellent photo-stability under UV–vis irradiation, lay the foundation for the practical bio-applications. Finally, the obtained Pt-NCs@PEI are used to determine trace amount of metronidazole (MTZ) in buffer solution in showing a linear response over a concentration range of 0.25–300 μM and a low detection limit of 0.1 μM. Furthermore, the related investigation on response mechanism will be helpful to design and synthesize new metal nanoclusters as fluorescent probe to detect the trace amount of harmful medicine residuum as nitroimidazoles in human body. - Highlights: • This paper provides the first hydrothermal synthesis of platinum nanoclusters. • The prepared polyethylenimine-protected platinum nanoclusters possess high quantum yield of 28%. • A new method to detect trace amount of metronidazole in urine is proposed.

  12. Hydrothermal synthesis of polyethylenimine-protected high luminescent Pt-nanoclusters and their application to the detection of nitroimidazoles

    International Nuclear Information System (INIS)

    Xu, Na; Li, Hong-Wei; Wu, Yuqing

    2017-01-01

    A novel one-step hydrothermal synthesis of highly fluorescent platinum nanoclusters protected by polyethylenimine (Pt-NCs@PEI) is described. The products are characterized well by UV–vis absorption, fluorescence spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) imaging. The Pt-NCs@PEI possess high quantum yield at 28%, which is the relatively high one among the reported Pt-NCs; especially, the synthesis is in one-step and the reaction time is much shorter (<1 h) than the related methods. In addition, the Pt-NCs@PEI have large Stocks-shift (∼150 nm), high tolerability to the extreme pH and high ionic strengths, and excellent photo-stability under UV–vis irradiation, lay the foundation for the practical bio-applications. Finally, the obtained Pt-NCs@PEI are used to determine trace amount of metronidazole (MTZ) in buffer solution in showing a linear response over a concentration range of 0.25–300 μM and a low detection limit of 0.1 μM. Furthermore, the related investigation on response mechanism will be helpful to design and synthesize new metal nanoclusters as fluorescent probe to detect the trace amount of harmful medicine residuum as nitroimidazoles in human body. - Highlights: • This paper provides the first hydrothermal synthesis of platinum nanoclusters. • The prepared polyethylenimine-protected platinum nanoclusters possess high quantum yield of 28%. • A new method to detect trace amount of metronidazole in urine is proposed.

  13. One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution

    International Nuclear Information System (INIS)

    Yang, Xiaoming; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

    2014-01-01

    Graphical abstract: An innovative and simple strategy for synthesizing high-fluorescent Cu nanoclusters stabilized with L-cysteine has been successfully established in aqueous solution. Significantly, the Cu nanoclusters were employed for sensitive and selective detections of Hg 2+ , coding and fluorescent staining, suggesting their potential toward various applications. - Highlights: • A novel, one-step strategy for synthesizing water-soluble CuNCs was established. • A simple, selective, and cost-effective assay for Hg 2+ was developed. • CuNCs may broaden ways for fluorescent staining and coding. - Abstract: Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg 2+ on the basis of the interactions between Hg 2+ and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg 2+ in a linear range of 1.0 × 10 −7 mol L −1 × 10 −3 mol L −1 , with a detection limit of 2.4 × 10 −8 mol L −1 at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications

  14. Melting of core-shell Ag-Ni and Ag-Co nanoclusters studied via molecular dynamic simulations

    Czech Academy of Sciences Publication Activity Database

    Kuntová, Zdeňka; Rossi, G.; Ferrando, R.

    2008-01-01

    Roč. 77, č. 20 (2008), 205431/1-205431/8 ISSN 1098-0121 Grant - others:European Community Sixth Framework Programme(XE) GSOMEN NMP4-CT-2004-001594; CNR(IT) SSA-TMN Institutional research plan: CEZ:AV0Z10100521 Keywords : molecular dynamics * melting * nanocluster Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  15. Innovations in IR projector arrays

    Science.gov (United States)

    Cole, Barry E.; Higashi, B.; Ridley, Jeff A.; Holmen, J.; Newstrom, K.; Zins, C.; Nguyen, K.; Weeres, Steven R.; Johnson, Burgess R.; Stockbridge, Robert G.; Murrer, Robert Lee; Olson, Eric M.; Bergin, Thomas P.; Kircher, James R.; Flynn, David S.

    2000-07-01

    In the past year, Honeywell has developed a 512 X 512 snapshot scene projector containing pixels with very high radiance efficiency. The array can operate in both snapshot and raster mode. The array pixels have near black body characteristics, high radiance outputs, broad band performance, and high speed. IR measurements and performance of these pixels will be described. In addition, a vacuum probe station that makes it possible to select the best die for packaging and delivery based on wafer level radiance screening, has been developed and is in operation. This system, as well as other improvements, will be described. Finally, a review of the status of the present projectors and plans for future arrays is included.

  16. IR Thermography NDE of ISS Radiator Panels

    Science.gov (United States)

    Koshti, Ajay; Winfree, William; Morton, Richard; Wilson, Walter; Reynolds, Gary

    2010-01-01

    The presentation covers an active and a passive infrared (IR) thermography for detection of delaminations in the radiator panels used for the International Space Station (ISS) program. The passive radiator IR data was taken by a NASA astronaut in an extravehicular activity (EVA) using a modified FLIR EVA hand-held camera. The IR data could be successfully analyzed to detect gross facesheet disbonds. The technique used the internal hot fluid tube as the heat source in analyzing the IR data. Some non-flight ISS radiators were inspected using an active technique of IR flash thermography to detect disbond of face sheet with honeycomb core, and debonds in facesheet overlap areas. The surface temperature and radiated heat emission from flight radiators is stable during acquisition of the IR video data. This data was analyzed to detect locations of unexpected surface temperature gradients. The flash thermography data was analyzed using derivative analysis and contrast evolutions. Results of the inspection are provided.

  17. Electrophoretic deposition of ZnO nanostructures: Au nanoclusters on Si substrates induce self-assembled nanowire growth

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval, Claudia [Laboratorio de Nanomateriales y Propiedades Dieléctricas, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán (Argentina); Marin, Oscar [CONICET – LAFISO, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán (Argentina); Real, Silvina [Laboratorio de Nanomateriales y Propiedades Dieléctricas, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán (Argentina); Comedi, David [CONICET – LAFISO, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán (Argentina); Tirado, Mónica, E-mail: mtirado@herrera.unt.edu.ar [Laboratorio de Nanomateriales y Propiedades Dieléctricas, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán (Argentina)

    2014-09-15

    Highlights: • ZnO nanowires were grown on silicon substrate by electrophoretic deposition technique without use a porous template. • The growth was induced by Au nanoclusters and was performed at room temperature. • The photoluminescence spectrum for the nanowires obtained shows a broad UV-blue excitonic emission peak and a low emission in the green region. - Abstract: The present work reports the self-assembled growth of ZnO nanowires on silicon substrate with nanometer sized Au clusters using electrophoretic deposition technique at room temperature without a sacrificial template. A colloidal suspension of ≈5 nm sized ZnO nanoparticles dispersed in 2-propanol was used (nanoparticle bandgap of 3.47 eV as determined from absorbance measurements). The results show that the Au nanoclusters on the silicon substrate induce the self-assembly of the ZnO nanoparticles into vertically aligned ZnO nanowires. This effect is tentatively explained as being due to increased electric field intensities near the Au nanoclusters during the electrophoretic deposition. Photoluminescence measurements reveal the presence of quantum confined excitons and a relatively low concentration of deep defects in the nanowires. The electric field guided growth of semiconductor nanostructures at room temperature has great industrial potential as it minimizes production costs and enables the use of substrate materials not withstanding high temperatures.

  18. Modification of Deposited, Size-Selected MoS2 Nanoclusters by Sulphur Addition: An Aberration-Corrected STEM Study

    Directory of Open Access Journals (Sweden)

    Yubiao Niu

    2016-12-01

    Full Text Available Molybdenum disulphide (MoS2 is an earth-abundant material which has several industrial applications and is considered a candidate for platinum replacement in electrochemistry. Size-selected MoS2 nanoclusters were synthesised in the gas phase using a magnetron sputtering, gas condensation cluster beam source with a lateral time-of-flight mass selector. Most of the deposited MoS2 nanoclusters, analysed by an aberration-corrected scanning transmission electron microscope (STEM in high-angle annular dark field (HAADF mode, showed poorly ordered layer structures with an average diameter of 5.5 nm. By annealing and the addition of sulphur to the clusters (by sublimation in the cluster source, the clusters were transformed into larger, crystalline structures. Annealing alone did not lead to crystallization, only to a cluster size increase by decomposition and coalescence of the primary clusters. Sulphur addition alone led to a partially crystalline structure without a significant change in the size. Thus, both annealing and sulphur addition processes were needed to obtain highly crystalline MoS2 nanoclusters.

  19. Coated protein nanoclusters from influenza H7N9 HA are highly immunogenic and induce robust protective immunity.

    Science.gov (United States)

    Wang, Li; Chang, Timothy Z; He, Yuan; Kim, Jong R; Wang, Shelly; Mohan, Teena; Berman, Zachary; Tompkins, S Mark; Tripp, Ralph A; Compans, Richard W; Champion, Julie A; Wang, Bao-Zhong

    2017-01-01

    Recurring influenza viruses pose an annual threat to public health. A time-saving, cost-effective and egg-independent influenza vaccine approach is important particularly when responding to an emerging pandemic. We fabricated coated, two-layer protein nanoclusters from recombinant trimeric hemagglutinin from an avian-origin H7N9 influenza A virus as an approach for vaccine development in response to an emerging pandemic. Assessment of the virus-specific immune responses and protective efficacy in mice immunized with the nanoclusters demonstrated that the vaccine candidates were highly immunogenic, able to induce protective immunity and long-lasting humoral antibody responses to this virus without the use of adjuvants. Because the advantages of the highly immunogenic coated nanoclusters also include rapid productions in an egg-independent system, this approach has great potential for influenza vaccine production not only in response to an emerging pandemic, but also as a replacement for conventional seasonal influenza vaccines. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Polyelectrolyte-assisted preparation of gold nanocluster-doped silica particles with high incorporation efficiency and improved stability

    Science.gov (United States)

    Wang, Haonan; Huang, Zhenzhen; Guo, Zilong; Yang, Wensheng

    2017-07-01

    In this paper, we reported an approach for efficient incorporation of glutathione-capped gold nanoclusters (GSH-Au NCs) into silica particles with the assistance of a polyelectrolyte, poly-diallyldimethyl-ammoniumchloride (PDDA). In this approach, the negatively charged GSH-Au NCs were firstly mixed with the positively charged PDDA to form PDDA-Au NC complexes. Then, the complexes were added into a pre-hydrolyzed Stöber system to get the Au NCs-doped silica particles. With increased ratio of PDDA in the complexes, the negative charges on surface of the Au NCs were neutralized gradually and finally reversed to positive in presence of excess PDDA, which facilitated the incorporation of the Au NCs into the negatively charged silica matrix. Under the optimal amount of PDDA in the complexes, the incorporation efficiency of Au NCs could be as high as 88%. After being incorporated into the silica matrix, the Au NCs become much robust against pH and heavy metal ions attributed to the protection effect of silica and PDDA. This approach was also extendable to highly efficient incorporation of other negatively charged metal nanoclusters, such as bovine serum albumin-capped Cu nanoclusters, into silica matrix.

  1. Feminist Challenge to the Mainstream IR

    OpenAIRE

    Aydın, Gülşen

    2016-01-01

    This study deals with the Feminist challenge to the Mainstream International Relations Discipline (IR) - rationalist theories, especially Realism - and the mainstream's responses to this challenge. It addresses the issue in five steps. Firstly, it sheds light on how Feminism is related to International Relations. Secondly, it examines how Feminist IR theorists criticize the Mainstream IR due to its state-centric approach and argue that being obsessed with anarchic international system prevent...

  2. Measuring Collimator Infrared (IR) Spectral Transmission

    Science.gov (United States)

    2016-05-01

    TECHNICAL REPORT RDMR-WD-16-15 MEASURING COLLIMATOR INFRARED ( IR ) SPECTRAL TRANSMISSION Christopher L. Dobbins Weapons...AND DATES COVERED Final 4. TITLE AND SUBTITLE Measuring Collimator Infrared ( IR ) Spectral Transmission 5. FUNDING NUMBERS 6. AUTHOR(S) Christopher L...release; distribution is unlimited. 12b. DISTRIBUTION CODE A 13. ABSTRACT (Maximum 200 Words) Several Infrared ( IR ) imaging systems have been measured

  3. How to remedy Eurocentrism in IR?

    DEFF Research Database (Denmark)

    Bilgin, Pinar

    2016-01-01

    While IR's Eurocentric limits are usually acknowledged, what those limits mean for theorizing about the international is seldom clarified. In The Global Transformation, Buzan and Lawson offer a 'composite approach' that goes some way towards addressing IR's Eurocentrism, challenging existing myths...... helps us recognize what is missing from IR theorizing - conceptions of the international by 'others' who also constitute the international. I illustrate this point by focussing on a landmark text on Ottoman history, Ortayll's The Longest Century of the Empire....

  4. Production and analysis of ultradispersed uranium oxide powders

    Science.gov (United States)

    Zajogin, A. P.; Komyak, A. I.; Umreiko, D. S.; Umreiko, S. D.

    2010-05-01

    Spectroscopic studies are made of the laser plasma formed near the surface of a porous body containing nanoquantities of uranium compounds which is irradiated by two successive laser pulses. The feasibility of using laser chemical methods for obtaining nanoclusters of uranium oxide particles in the volume of a porous body and the simultaneous possibility of determining the uranium content with good sensitivity are demonstrated. The thermochemical and spectral characteristics of the analogs of their compounds with chlorine are determined and studied. The possibility of producing uranium dioxides under ordinary conditions and their analysis in the reaction products is demonstrated.

  5. Electrocatalytic properties of Ti/Pt–IrO2 anode for oxygen evolution in PEM water electrolysis

    DEFF Research Database (Denmark)

    Ye, Feng; Li, Jianling; Wang, Xindong

    2010-01-01

    A novel Pt–IrO2 electrocatalyst was prepared using the dip-coating/calcinations method on titanium substrates. Titanium electrodes coated with oxides were investigated for oxygen evolution. Experimental results showed that Ti/Pt–IrO2 electrode containing 30mol% Pt in the coating exhibited...... significantly higher electrocatalytic activity for oxygen evolution compared to Ti/IrO2 prepared by the same method, which is also supported by the electrochemical impedance data. Stability tests demonstrated Pt–IrO2 electrocatalyst had a service cycle of 10,000 times in 0.1M H2SO4 solution. And the anode...... surface had hardly discovered cracks and had compact structures, which contributed to stable nature of the electrode together with good conductivity and specific interaction between Pt and IrO2 formed during the calcination. Furthermore, the enhanced catalytic activity for O2 evolution at Ti/Pt–IrO2...

  6. Increasing Medical Student Exposure to IR through Integration of IR into the Gross Anatomy Course.

    Science.gov (United States)

    DePietro, Daniel M; Kiefer, Ryan M; Redmond, Jonas W; Workman, Alan D; Nadolski, Gregory J; Gade, Terence P; Trerotola, Scott O; Hunt, Stephen J

    2017-10-01

    To compare medical student knowledge of and interest in interventional radiology (IR) before and after the integration of an IR lecture series within the gross anatomy course. Four elective IR lectures were scheduled to coincide with the relevant anatomy dissection curriculum. Anonymous surveys were distributed to 146 students before and after the lectures regarding students' knowledge of and interest in IR, responsibilities of an IR physician, and IR training pathways. Those who did not attend served as controls. Response rates were 67% (n = 98) in the prelecture group, 55% (n = 22) in the group who attended the lecture, and 28% (n = 30) in the control group. A total of 73% of the prelecture group reported little knowledge of IR compared with other specialties. This decreased to 27% in those who attended the lecture (P IR than any other specialty, compared with 7% of controls (P value not significant) and 2% of the prelecture group (P IR procedures (mean, 1.82) than the prelecture group (mean, 0.57; P IR, compared with 24% in the prelecture group and 33% in the control group (P IR residency, compared with 5% in the prelecture group and 33% in the control group (P IR education into the gross anatomy course proved to be a highly effective way of teaching preclinical students about IR and generating interest in the field. Copyright © 2017 SIR. All rights reserved.

  7. Atmospheric Entry Experiments at IRS

    Science.gov (United States)

    Auweter-Kurtz, M.; Endlich, P.; Herdrich, G.; Kurtz, H.; Laux, T.; Löhle, S.; Nazina, N.; Pidan, S.

    2002-01-01

    Entering the atmosphere of celestial bodies, spacecrafts encounter gases at velocities of several km/s, thereby being subjected to great heat loads. The thermal protection systems and the environment (plasma) have to be investigated by means of computational and ground facility based simulations. For more than a decade, plasma wind tunnels at IRS have been used for the investigation of TPS materials. Nevertheless, ground tests and computer simulations cannot re- place space flights completely. Particularly, entry mission phases encounter challenging problems, such as hypersonic aerothermodynamics. Concerning the TPS, radiation-cooled materials used for reuseable spacecrafts and ablator tech- nologies are of importance. Besides the mentioned technologies, there is the goal to manage guidance navigation, con- trol, landing technology and inflatable technologies such as ballutes that aim to keep vehicles in the atmosphere without landing. The requirement to save mass and energy for planned interplanetary missions such as Mars Society Balloon Mission, Mars Sample Return Mission, Mars Express or Venus Sample Return mission led to the need for manoeuvres like aerocapture, aero-breaking and hyperbolic entries. All three are characterized by very high kinetic vehicle energies to be dissipated by the manoeuvre. In this field flight data are rare. The importance of these manoeuvres and the need to increase the knowledge of required TPS designs and behavior during such mission phases point out the need of flight experiments. As result of the experience within the plasma diagnostic tool development and the plasma wind tunnel data base, flight experiments like the PYrometric RE-entry EXperiment PYREX were developed, fully qualified and successfully flown. Flight experiments such as the entry spectrometer RESPECT and PYREX on HOPE-X are in the conceptual phase. To increase knowledge in the scope of atmospheric manoeuvres and entries, data bases have to be created combining both

  8. Synthesis and X-Ray Crystallographic Characterisation of Frustum-Shaped Ligated [Cu18 H16 (DPPE)6 ]2+ and [Cu16 H14 (DPPA)6 ]2+ Nanoclusters and Studies on Their H2 Evolution Reactions.

    Science.gov (United States)

    Li, Jiaye; Ma, Howard Z; Reid, Gavin E; Edwards, Alison J; Hong, Yuning; White, Jonathan M; Mulder, Roger J; O'Hair, Richard A J

    2018-02-09

    We report new structural motifs for Cu nanoclusters that conceptually represent seed crystals for large face-centred cubic (FCC) crystal growth. Kinetically controlled syntheses, high resolution mass spectrometry experiments for determination of the dication formulae and crystallographic characterisation were carried out for [Cu 18 H 16 (DPPE) 6 ][BF 4 ][Cl] (DPPE=bis(diphenylphosphino)ethane) and [Cu 16 H 14 (DPPA) 6 ][(BF 4 ) 2 ] (DPPA=bis(diphenylphosphino)amine) polyhydrido nanoclusters, which feature the unprecedented bifrustum and frustum metal-core architecture in metal nanoclusters. The Cu 18 nanocluster contains two Cu 9 frustum cupolae and the Cu 16 nanocluster has one Cu 9 frustum cupola and a Cu 7 distorted hexagonal-shape base. Gas-phase experiments revealed that both Cu 18 H 16 and Cu 16 H 14 cores can spontaneously release H 2 upon removal of one bisphosphine capping ligand. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. A cuboctahedral platinum (Pt79) nanocluster enclosed by well defined facets favours di-sigma adsorption and improves the reaction kinetics for methanol fuel cells.

    Science.gov (United States)

    Mahata, Arup; Choudhuri, Indrani; Pathak, Biswarup

    2015-08-28

    The methanol dehydrogenation steps are studied very systematically on the (111) facet of a cuboctahedral platinum (Pt79) nanocluster enclosed by well-defined facets. The various intermediates formed during the methanol decompositions are adsorbed at the edge and bridge site of the facet either vertically (through C- and O-centres) or in parallel. The di-sigma adsorption (in parallel) on the (111) facet of the nanocluster is the most stable structure for most of the intermediates and such binding improves the interaction between the substrate and the nanocluster and thus the catalytic activity. The reaction thermodynamics, activation barrier, and temperature dependent reaction rates are calculated for all the successive methanol dehydrogenation steps to understand the methanol decomposition mechanism, and these values are compared with previous studies to understand the catalytic activity of the nanocluster. We find the catalytic activity of the nanocluster is excellent while comparing with any previous reports and the methanol dehydrogenation thermodynamics and kinetics are best when the intermediates are adsorbed in a di-sigma manner.

  10. Teaching IR to Medical Students: A Call to Action.

    Science.gov (United States)

    Lee, Aoife M; Lee, Michael J

    2018-02-01

    Interventional radiology (IR) has grown rapidly over the last 20 years and is now an essential component of modern medicine. Despite IR's increasing penetration and reputation in healthcare systems, IR is poorly taught, if taught at all, in most medical schools. Medical students are the referrers of tomorrow and potential IR recruits and deserve to be taught IR by expert IRs. The lack of formal IR teaching curricula in many medical schools needs to be addressed urgently for the continued development and dissemination of, particularly acute, IR services throughout Europe. We call on IRs to take up the baton to teach IR to the next generation of doctors.

  11. Coatings of nanostructured pristine graphene-IrOx hybrids for neural electrodes: Layered stacking and the role of non-oxygenated graphene.

    Science.gov (United States)

    Pérez, E; Lichtenstein, M P; Suñol, C; Casañ-Pastor, N

    2015-10-01

    The need to enhance charge capacity in neural stimulation-electrodes is promoting the formation of new materials and coatings. Among all the possible types of graphene, pristine graphene prepared by graphite electrochemical exfoliation, is used in this work to form a new nanostructured IrOx-graphene hybrid (IrOx-eG). Graphene is stabilized in suspension by IrOx nanoparticles without surfactants. Anodic electrodeposition results in coatings with much smaller roughness than IrOx-graphene oxide. Exfoliated pristine graphene (eG), does not electrodeposit in absence of iridium, but IrOx-nanoparticle adhesion on graphene flakes drives the process. IrOx-eG has a significantly different electronic state than graphene oxide, and different coordination for carbon. Electron diffraction shows the reflection features expected for graphene. IrOx 1-2 nm cluster/nanoparticles are oxohydroxo-species and adhere to 10nm graphene platelets. eG induces charge storage capacity values five times larger than in pure IrOx, and if calculated per carbon atom, this enhancement is one order magnitude larger than the induced by graphene oxide. IrOx-eG coatings show optimal in vitro neural cell viability and function as cell culture substrates. The fully straightforward electrochemical exfoliation and electrodeposition constitutes a step towards the application of graphene in biomedical systems, expanding the knowledge of pristine graphene vs. graphene oxide, in bioelectrodes. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Premier's imaging IR limb sounder

    Science.gov (United States)

    Kraft, Stefan; Bézy, Jean-Loup; Meynart, Roland; Langen, Jörg; Carnicero Dominguez, Bernardo; Bensi, Paolo; Silvestrin, Pierluigi

    2017-11-01

    The Imaging IR Limb Sounder (IRLS) is one of the two instruments planned on board of the candidate Earth Explorer Core Mission PREMIER. PREMIER stands for PRocess Exploration through Measurements of Infrared and Millimetre-wave Emitted Radiation. PREMIER went recently through the process of a feasibility study (Phase A) within the Earth Observation Envelope Program. Emerging from recent advanced instrument technologies IRLS shall, next to a millimetre-wave limb sounder (called STEAMR), explore the benefits of three-dimensional limb sounding with embedded cloud imaging capability. Such 3D imaging technology is expected to open a new era of limb sounding that will allow detailed studies of the link between atmospheric composition and climate, since it will map simultaneously fields of temperature and many trace gases in the mid/upper troposphere and stratosphere across a large vertical and horizontal field of view and with high vertical and horizontal resolution. PREMIER shall fly in a tandem formation looking backwards to METOP's swath and thereby improve meteorological and environmental analyses.

  13. Atom condensation on an atomically smooth surface: Ir, Re, W, and Pd on Ir(111)

    International Nuclear Information System (INIS)

    Wang, S.C.; Ehrlich, G.

    1991-01-01

    The distribution of condensing metal atoms over the two types of sites present on an atomically smooth Ir(111) has been measured in a field ion microscope. For Ir, Re, W, and Pd from a thermal source, condensing on Ir(111) at ∼20 K, the atoms are randomly distributed, as expected if they condense at the first site struck

  14. Biochemical applications of FT-IR spectroscopy

    NARCIS (Netherlands)

    Pistorius, A.M.A.

    1996-01-01

    This thesis describes the use of (FT-)IR spectroscopy in general biochemical research. In chapter 3, IR spectroscopy is used in the quantitation of residual detergent after reconstitution of an integral membrane protein in a pre-defined lipid matrix. This chapter discusses the choice of the

  15. Status Of Sofradir IR-CCD Detectors

    Science.gov (United States)

    Tribolet, Philippe; Radisson, Patrick

    1988-05-01

    The topics of this paper deal with the IR-CCD detectors manufactured by SOFRADIR the new French joint venture. Description of the IRCCD technology and the advantages of this approach are given. In conclusion, some IR-CCD typical results are given.

  16. Gold nanocluster-based vaccines for dual-delivery of antigens and immunostimulatory oligonucleotides

    Science.gov (United States)

    Tao, Yu; Zhang, Yan; Ju, Enguo; Ren, Hui; Ren, Jinsong

    2015-07-01

    We here report a facile one-pot synthesis of fluorescent gold nanoclusters (AuNCs) via the peptide biomineralization method, which can elicit specific immunological responses. The as-prepared peptide-protected AuNCs (peptide-AuNCs) display strong red fluorescence, and more importantly, as compared to the peptide alone, the immune stimulatory ability of the resulting peptide-AuNCs can not only be retained, but can also be efficaciously enhanced. Moreover, through a dual-delivery of antigen peptides and cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), the as-prepared peptide-AuNC-CpG conjugates can also act as smart self-vaccines to assist in the generation of high immunostimulatory activity, and be applied as a probe for intracellular imaging. Both in vitro and in vivo studies provide strong evidence that the AuNC-based vaccines may be utilized as safe and efficient immunostimulatory agents that are able to prevent and/or treat a variety of ailments.We here report a facile one-pot synthesis of fluorescent gold nanoclusters (AuNCs) via the peptide biomineralization method, which can elicit specific immunological responses. The as-prepared peptide-protected AuNCs (peptide-AuNCs) display strong red fluorescence, and more importantly, as compared to the peptide alone, the immune stimulatory ability of the resulting peptide-AuNCs can not only be retained, but can also be efficaciously enhanced. Moreover, through a dual-delivery of antigen peptides and cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), the as-prepared peptide-AuNC-CpG conjugates can also act as smart self-vaccines to assist in the generation of high immunostimulatory activity, and be applied as a probe for intracellular imaging. Both in vitro and in vivo studies provide strong evidence that the AuNC-based vaccines may be utilized as safe and efficient immunostimulatory agents that are able to prevent and/or treat a variety of ailments. Electronic supplementary information (ESI

  17. Mechanistic aspects of fluorescent gold nanocluster internalization by live HeLa cells

    Science.gov (United States)

    Yang, Linxiao; Shang, Li; Nienhaus, G. Ulrich

    2013-01-01

    We have studied cellular uptake of ultrasmall fluorescent gold nanoclusters (AuNCs) by HeLa cells by confocal fluorescence microscopy in combination with quantitative image analysis. Water solubilized, lipoic acid-protected AuNCs, which had an overall hydrodynamic diameter of 3.3 nm and emitted fluorescence in the near-infrared region at ~700 nm, were observed to accumulate on the cell membrane prior to internalization. The internalization mechanisms were analyzed using inhibitors known to interfere with specific pathways. Cellular uptake of AuNCs is energy-dependent and involves multiple mechanisms: clathrin-mediated endocytosis and macropinocytosis appear to play a significant role, whereas the caveolin-mediated pathway contributes only to a lesser extent. Co-labeling of different cell organelles showed that intracellular trafficking of AuNCs mainly follows through endosomal pathways. The AuNCs were ultimately transferred to lysosomes; they were completely excluded from the nucleus even after 24 h.We have studied cellular uptake of ultrasmall fluorescent gold nanoclusters (AuNCs) by HeLa cells by confocal fluorescence microscopy in combination with quantitative image analysis. Water solubilized, lipoic acid-protected AuNCs, which had an overall hydrodynamic diameter of 3.3 nm and emitted fluorescence in the near-infrared region at ~700 nm, were observed to accumulate on the cell membrane prior to internalization. The internalization mechanisms were analyzed using inhibitors known to interfere with specific pathways. Cellular uptake of AuNCs is energy-dependent and involves multiple mechanisms: clathrin-mediated endocytosis and macropinocytosis appear to play a significant role, whereas the caveolin-mediated pathway contributes only to a lesser extent. Co-labeling of different cell organelles showed that intracellular trafficking of AuNCs mainly follows through endosomal pathways. The AuNCs were ultimately transferred to lysosomes; they were completely excluded

  18. Gold nanoclusters as switch-off fluorescent probe for detection of uric acid based on the inner filter effect of hydrogen peroxide-mediated enlargement of gold nanoparticles.

    Science.gov (United States)

    Liu, Yanyan; Li, Hongchang; Guo, Bin; Wei, Lijuan; Chen, Bo; Zhang, Youyu

    2017-05-15

    Herein we report a novel switch-off fluorescent probe for highly selective determination of uric acid (UA) based on the inner filter effect (IFE), by using poly-(vinylpyrrolidone)-protected gold nanoparticles (PVP-AuNPs) and chondroitin sulfate-stabilized gold nanoclusters (CS-AuNCs) as the IFE absorber/fluorophore pair. In this IFE-based fluorometric assay, the newly designed CS-AuNCs were explored as an original fluorophore and the hydrogen peroxide (H 2 O 2 ) -driven formed PVP-AuNPs can be a powerful absorber to influence the excitation of the fluorophore, due to the complementary overlap between the absorption band of PVP-AuNPs and the emission band of CS-AuNCs. Under the optimized conditions, the extent of the signal quenching depends linearly on the H 2 O 2 concentration in the range of 1-100μM (R 2 =0.995) with a detection limit down to 0.3μM. Based on the H 2 O 2 -dependent fluorescence IFE principle, we further developed a new assay strategy to enable selective sensing of UA by using a specific uricase-catalyzed UA oxidation as the in situ H 2 O 2 generator. The proposed uricase-linked IFE-based assay exhibited excellent analytical performance for measuring UA over the concentration ranging from 5 to 100μM (R 2 =0.991), and can be successfully applied to detection of UA as low as 1.7μM (3σ) in diluted human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Signal-on electrochemical assay for label-free detection of TdT and BamHI activity based on grown DNA nanowire-templated copper nanoclusters.

    Science.gov (United States)

    Hu, Yufang; Zhang, Qingqing; Xu, Lihua; Wang, Jiao; Rao, Jiajia; Guo, Zhiyong; Wang, Sui

    2017-11-01

    Electrochemical methods allow fast and inexpensive analysis of enzymatic activity. Here, a simple and yet efficient "signal-on" electrochemical assay for sensitive, label-free detection of DNA-related enzyme activity was established on the basis of terminal deoxynucleotidyl transferase (TdT)-mediated extension strategy. TdT, which is a template-independent DNA polymerase, can catalyze the sequential addition of deoxythymidine triphosphate (dTTP) at the 3'-OH terminus of single-stranded DNA (ssDNA); then, the TdT-yield T-rich DNA nanowires can be employed as the synthetic template of copper nanoclusters (CuNCs). Grown DNA nanowires-templated CuNCs (noted as DNA-CuNCs) were attached onto graphene oxide (GO) surface and exhibited unique electrocatalytic activity to H 2 O 2 reduction. Under optimal conditions, the proposed biosensor was utilized for quantitatively monitoring TdT activity, with the observed LOD of 0.1 U/mL. It also displayed high selectivity to TdT with excellent stability, and offered a facile, convenient electrochemical method for TdT-relevant inhibitors screening. Moreover, the proposed sensor was successfully used for BamHI activity detection, in which a new 3'-OH terminal was exposed by the digestion of a phosphate group. Ultimately, it has good prospects in DNA-related enzyme-based biochemical studies, disease diagnosis, and drug discovery. Graphical Abstract Extraordinary TdT-generated DNA-CuNCs are synthesized and act as a novel electrochemical sensing platform for sensitive detection of TdT and BamHI activity in biological environments.

  20. Resonant surface-enhanced Raman scattering by optical phonons in a monolayer of CdSe nanocrystals on Au nanocluster arrays

    Energy Technology Data Exchange (ETDEWEB)

    Milekhin, Alexander G., E-mail: milekhin@isp.nsc.ru [A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentjeva, 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov str. 2, 630090 Novosibirsk (Russian Federation); Sveshnikova, Larisa L.; Duda, Tatyana A. [A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentjeva, 13, 630090 Novosibirsk (Russian Federation); Rodyakina, Ekaterina E. [A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentjeva, 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov str. 2, 630090 Novosibirsk (Russian Federation); Dzhagan, Volodymyr M. [Semiconductor Physics, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Sheremet, Evgeniya [Solid Surfaces Analysis, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Gordan, Ovidiu D. [Semiconductor Physics, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Himcinschi, Cameliu [Institut für Theoretische Physik, TU Bergakademie Freiberg, 09596 Freiberg (Germany); Latyshev, Alexander V. [A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentjeva, 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov str. 2, 630090 Novosibirsk (Russian Federation); Zahn, Dietrich R.T. [Semiconductor Physics, Technische Universität Chemnitz, D-09107 Chemnitz (Germany)

    2016-05-01

    Highlights: • Regular Au nanocluster and dimer arrays as well as single Au dimers are fabricated. • Resonant SERS by monolayers of CdSe nanocrystals deposited on the Au nanostructures is observed. • LO energy change for CdSe NCs on different single Au dimers indicates SERS by single or a few NCs. - Abstract: Here we present the results on an investigation of resonant Stokes and anti- Stokes surface-enhanced Raman scattering (SERS) by optical phonons in colloidal CdSe nanocrystals (NCs) homogeneously deposited on arrays of Au nanoclusters using the Langmuir–Blodgett technology. The thickness of deposited NCs, determined by transmission and scanning electron microscopy, amounts to approximately 1 monolayer. Special attention is paid to the determination of the localized surface plasmon resonance (LSPR) energy in the arrays of Au nanoclusters as a function of the nanocluster size by means of micro-ellipsometry. SERS by optical phonons in CdSe NCs shows a significant enhancement factor with a maximal value of 2 × 10{sup 3} which depends resonantly on the Au nanocluster size and thus on the LSPR energy. The deposition of CdSe NCs on the arrays of Au nanocluster dimers enabled us to study the polarization dependence of SERS. It was found that a maximal SERS signal is observed for the light polarization along the dimer axis. Finally, SERS by optical phonons was observed for CdSe NCs deposited on the structures with a single Au dimer. A difference of the LO phonon energy is observed for CdSe NCs on different single dimers. This effect is explained as the confinement-induced shift which depends on the CdSe nanocrystal size and indicates quasi-single NC Raman spectra being obtained.

  1. Controllable 5-sulfosalicylic acid assisted solvothermal synthesis of monodispersed superparamagnetic Fe{sub 3}O{sub 4} nanoclusters with tunable size

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wentao [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Tang, Bingtao, E-mail: tangbt@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Wu, Suli; Gao, Zhanming; Ju, Benzhi [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Teng, Xiaoxu [School of Chemistry and Chemical Engineering, Yangtze Normal University, Chongqing 408100 (China); Zhang, Shufen [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

    2017-02-01

    Monodispersed Fe{sub 3}O{sub 4} nanoclusters were synthesized in a one-pot solvothermal route with 5-sulfosalicylic acid (SSA) as the functional ligand in a mixed-solvent system of diethylene glycol/ethylene glycol (DEG/EG). Nucleation and aggregation growth model was responsible for the formation of secondary structure of the clusters. In the process, the size of the clusters can be effectively controlled by varying the amounts of SSA and the volume ratio of DEG/EG. The nanoclusters exhibited superparamagnetic properties with high saturation magnetization value of about 68.7 emu g{sup −1} at room temperature. The water-soluble small-molecule SSA grafted on the surface of Fe{sub 3}O{sub 4} nanocrystals rendered the superparamagnetic clusters dispersible in water, which is crucial for potential applications in biomedical fields. - Graphical abstract: 5-sulfosalicylic acid assisted solvothermal synthesis of monodispersed superparamagnetic Fe{sub 3}O{sub 4} nanoclusters with tunable size by a mixed-solvent system of DEG/EG. - Highlights: • Monodispersed Fe{sub 3}O{sub 4} nanoclusters were synthesized in a one-pot 5-sulfosalicylic acid assisted solvothermal route. • The size of the clusters are tunable by varying the amounts of 5-sulfosalicylic acid and the volume ratio of DEG/EG. • The nanoclusters exhibited superparamagnetic properties with high saturation magnetization value. • The 5-sulfosalicylic acid grafted Fe{sub 3}O{sub 4} nanoclusters can be dispersed in water.

  2. Synthesis of magnetic orderly mesoporous α-Fe2O3nanocluster derived from MIL-100(Fe) for rapid and efficient arsenic(III,V) removal.

    Science.gov (United States)

    Liu, Zhongmin; Chen, Jitao; Wu, Yongchuan; Li, Yaru; Zhao, Jingyu; Na, Ping

    2018-02-05

    A calcination time regulation method has been unprecedentedly used to adjust the orderly meso-structure of novel α-Fe 2 O 3 nanoclusters derived from MIL-100(Fe) (MIL: Materials of Institute Lavoisier). The as-synthesized magnetic orderly mesoporous α-Fe 2 O 3 nanoclusters were characterized by XRD, SEM, TEM, TGA, N 2 adsorption-desorption isotherms, VSM, Zeta potential, FTIR and XPS. The 6h calcinated α-Fe 2 O 3 nanocluster exhibited the optimal properties, including the high specific surface area and the orderly mesoporous properties, which facilitate the arsenic(III,V) adsorption capacity. The maximum adsorption capacities of As(III) and As(V) were 109.89 and 181.82mgg -1 , respectively, and adsorption equilibrium can be reached just within 30min. The kinetics intra-particle diffusion model and adsorption isotherms reveal that the adsorption rate is controlled by pore diffusion and the adsorption process belongs to Langmuir monolayer adsorption. These results indicate that the orderly mesoporous structure of α-Fe 2 O 3 nanoclusters plays a key role in rapid and efficient adsorption for arsenic(III,V). Meanwhile, adsorption mechanism verifies that arsenic can react with active sites (Fe-OH) to form complexes by Fe-O-As bond. Moreover, α-Fe 2 O 3 nanocluster can be separated easily due to its excellent magnetism. Above all, the magnetism orderly mesoporous α-Fe 2 O 3 nanocluster is a promising adsorbent for emergent treatment of arsenic in practice. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Visualizing Infrared (IR) Spectroscopy with Computer Animation

    Science.gov (United States)

    Abrams, Charles B.; Fine, Leonard W.

    1996-01-01

    IR Tutor, an interactive, animated infrared (IR) spectroscopy tutorial has been developed for Macintosh and IBM-compatible computers. Using unique color animation, complicated vibrational modes can be introduced to beginning students. Rules governing the appearance of IR absorption bands become obvious because the vibrational modes can be visualized. Each peak in the IR spectrum is highlighted, and the animation of the corresponding normal mode can be shown. Students can study each spectrum stepwise, or click on any individual peak to see its assignment. Important regions of each spectrum can be expanded and spectra can be overlaid for comparison. An introduction to the theory of IR spectroscopy is included, making the program a complete instructional package. Our own success in using this software for teaching and research in both academic and industrial environments will be described. IR Tutor consists of three sections: (1) The 'Introduction' is a review of basic principles of spectroscopy. (2) 'Theory' begins with the classical model of a simple diatomic molecule and is expanded to include larger molecules by introducing normal modes and group frequencies. (3) 'Interpretation' is the heart of the tutorial. Thirteen IR spectra are analyzed in detail, covering the most important functional groups. This section features color animation of each normal mode, full interactivity, overlay of related spectra, and expansion of important regions. This section can also be used as a reference.

  4. Morphology and atomic-scale structure of single-layer WS2 nanoclusters.

    Science.gov (United States)

    Füchtbauer, Henrik G; Tuxen, Anders K; Moses, Poul G; Topsøe, Henrik; Besenbacher, Flemming; Lauritsen, Jeppe V

    2013-10-14

    Two-dimensional sheets of transition metal (Mo and W) sulfides are attracting strong attention due to the unique electronic and optical properties associated with the material in its single-layer form. The single-layer MoS2 and WS2 are already in widespread commercial use in catalytic applications as both hydrotreating and hydrocracking catalysts. Consequently, characterization of the morphology and atomic structure of such particles is of utmost importance for the understanding of the catalytic active phase. However, in comparison with the related MoS2 system only little is known about the fundamental properties of single-layer WS2 (tungstenite). Here, we use an interplay of atom-resolved Scanning Tunneling Microscopy (STM) studies of Au(111)-supported WS2 nanoparticles and calculated edge structures using Density Functional Theory (DFT) to reveal the equilibrium morphology and prevalent edge structures of single-layer WS2. The STM results reveal that the single layer S-W-S sheets adopt a triangular equilibrium shape under the sulfiding conditions of the synthesis, with fully sulfided edges. The predominant edge structures are determined to be the (101[combining macron]0) W-edge, but for the smallest nanoclusters also the (1[combining macron]010) S-edges become important. DFT calculations are used to construct phase diagrams of the WS2 edges, and describe their sulfur and hydrogen coordination under different conditions, and in this way shed light on the catalytic role of WS2 edges.

  5. Investigating solvent effects on aggregation behaviour, linear and nonlinear optical properties of silver nanoclusters

    Science.gov (United States)

    Bhavitha, K. B.; Nair, Anju K.; Perumbilavil, Sreekanth; Joseph, Saju; Kala, M. S.; Saha, Abhijit; Narayanan, R. Aravinda; Hameed, Nishar; Thomas, Sabu; Oluwafemi, Oluwatobi S.; Kalarikkal, Nandakumar

    2017-11-01

    We herein report the solvent effects on the aggregation, linear and nonlinear optical properties of silver nanoclusters synthesised using three solvents namely; ethanol, acetone and isopropanol. The Ag clusters were characterized using UV-Visible (UV-vis) and photoluminescence (PL) spectroscopy, Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and open aperture Z-Scan measurements. Density functional theory (DFT) calculations at the B3PW91 level of theory, were done to compute the electric dipole, quadrupole, octapole and hexadecapole moment of mercaptosuccinic acid and mercaptosuccinic acid-Ag9 cluster in three solvents. Linear optical properties show characteristic absorption profile with quantum confinement at different wavelengths for all the three clusters. The Open aperture Z-scan measurement in Ag clusters establishes the optical limiting properties which arise mostly from excited state absorption (ESA) and relatively weak saturable absorption (SA). The nonlinear optical behaviour varies within the three clusters with maximum optical limiting value obtained for the clusters synthesised using acetone. The theoretically computed hyperpolarizabilities together with z-scan measurements establish the solvent effect on the clusters and their potential applications in optical limiting devices.

  6. Synthesis, characterization, and cytotoxicity evaluation of high-magnetization multifunctional nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Petran, Anca; Radu, Teodora; Nan, Alexandrina [National Institute for Research and Development of Isotopic and Molecular Technologies (Romania); Olteanu, Diana; Filip, Adriana, E-mail: adrianafilip33@yahoo.com; Clichici, Simona; Baldea, Ioana [Iuliu Hatieganu University of Medicine and Pharmacy, Department of Physiology (Romania); Suciu, Maria; Turcu, Rodica, E-mail: rodica.turcu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies (Romania)

    2017-01-15

    The paper presents the synthesis, characterization, and in vitro cytotoxicity tests of Fe{sub 3}O{sub 4} magnetic nanoclusters coated with ethylenediaminetetraacetic acid disodium salt (EDTA). Electron microscopy analysis (SEM) evidences that magnetite nanoparticles are closely packed into the clusters stabilized with EDTA with well-defined near spherical shapes and sizes in the range 100–200 nm. From XRD measurements, we determined the mean size of the crystallites inside the magnetic cluster about 36 nm. The saturation magnetization determined for the magnetic clusters stabilized with EDTA has high value, about 81.7 emu/g at 300 K. X-ray photoelectron spectroscopy has been used to determine both the elemental and chemical structure of the magnetic cluster surface. In vitro studies have shown that the magnetic clusters at low doses did not induce toxicity on human umbilical vein endothelial cells or lesions of the cell membrane. In contrast, at high doses, the magnetic clusters increased the lipid peroxidation and reduced the leakage of a cytoplasmic enzyme, lactate dehydrogenase (LDH), in parallel with increasing the antioxidant defense.

  7. Preparation and Characterization of Chitosan/Soy Protein Isolate Nanocomposite Film Reinforced by Cu Nanoclusters

    Directory of Open Access Journals (Sweden)

    Kuang Li

    2017-06-01

    Full Text Available Soy protein isolate (SPI based films have received considerable attention for use in packaging materials. However, SPI-based films exhibit relatively poor mechanical properties and water resistance ability. To tackle these challenges, chitosan (CS and endogenous Cu nanoclusters (NCs capped with protein were proposed and designed to modify SPI-based films. Attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray diffraction patterns of composite films demonstrated that interactions, such as hydrogen bonds in the film forming process, promoted the cross-linking of composite films. The surface microstructure of CS/SPI films modified with Cu NCs was more uniform and transmission electron microscopy (TEM showed that uniform and discrete clusters were formed. Compared with untreated SPI films, the tensile strength and elongation at break of composite films were simultaneously improved by 118.78% and 74.93%, respectively. Moreover, these composite films also exhibited higher water contact angle and degradation temperature than that of pure SPI film. The water vapor permeation of the modified film also decreased. These improved properties of functional bio-polymers show great potential as food packaging materials.

  8. The role of the surfaces in the photon absorption in Ge nanoclusters embedded in silica

    Directory of Open Access Journals (Sweden)

    Nicotra Giuseppe

    2011-01-01

    Full Text Available Abstract The usage of semiconductor nanostructures is highly promising for boosting the energy conversion efficiency in photovoltaics technology, but still some of the underlying mechanisms are not well understood at the nanoscale length. Ge quantum dots (QDs should have a larger absorption and a more efficient quantum confinement effect than Si ones, thus they are good candidate for third-generation solar cells. In this work, Ge QDs embedded in silica matrix have been synthesized through magnetron sputtering deposition and annealing up to 800°C. The thermal evolution of the QD size (2 to 10 nm has been followed by transmission electron microscopy and X-ray diffraction techniques, evidencing an Ostwald ripening mechanism with a concomitant amorphous-crystalline transition. The optical absorption of Ge nanoclusters has been measured by spectrophotometry analyses, evidencing an optical bandgap of 1.6 eV, unexpectedly independent of the QDs size or of the solid phase (amorphous or crystalline. A simple modeling, based on the Tauc law, shows that the photon absorption has a much larger extent in smaller Ge QDs, being related to the surface extent rather than to the volume. These data are presented and discussed also considering the outcomes for application of Ge nanostructures in photovoltaics. PACS: 81.07.Ta; 78.67.Hc; 68.65.-k

  9. Imaging C. elegans with thiolated tryptophan-based NIR fluorescent gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Barman, Apurba Kr. [Indian Institute of Technology Kanpur, Department of Chemistry (India); Chaturbedi, Amaresh; Subramaniam, K. [Indian Institute of Technology Kanpur, Department of Biological Sciences and Bioengineering (India); Verma, Sandeep, E-mail: sverma@iitk.ac.in [Indian Institute of Technology Kanpur, Department of Chemistry (India)

    2013-11-15

    Multidentate, thiolated, tryptophan-containing peptide conjugates were synthesized for the preparation of gold nanoclusters (AuNCs). Precursor Au{sub 11}(PPh{sub 3}){sub 8}Cl{sub 3} was prepared by the reduction of HAuCl{sub 4}, followed by the use of tryptophan-containing peptide conjugates in ligand displacement reactions, to afford near-infrared fluorescent AuNCs. The emission maxima for these newly synthesized AuNCs were ∼715 nm. AuNCs were characterized with the help of UV–Vis, FTIR, fluorescence and MALDI analysis. FTIR spectra showed that the ligands bind to Au atoms through Au–S bonds, while MALDI mass spectra revealed that the clusters consisted of 20–23 Au atoms. Introduction of hydrophilic –COOH groups engendered water solubility to these AuNCs, enabling bioimaging applications. We demonstrate fluorescence imaging of the nematode C. elegans and confirm distribution of these AuNCs in nematode gut with the help of green fluorescent protein co-localization experiments.

  10. Unraveling the molecular mechanism of photosynthetic toxicity of highly fluorescent silver nanoclusters to Scenedesmus obliquus.

    Science.gov (United States)

    Zhang, Li; Goswami, Nirmal; Xie, Jianping; Zhang, Bo; He, Yiliang

    2017-11-27

    While the discovery of numerous attractive properties of silver at the nanoscale has increased their demand in many sectors including medicine, optics, sensing, painting and cosmetics, it has also raised wide public concerns about their effect on living organisms in aquatic environment. Despite the continuous effort to understand the various aspects of the toxicity of silver nanomaterials, the molecular level understanding on their cytotoxicity mechanism to biological organisms has remained unclear. Herein, we demonstrated the underlying mechanism of the photosynthetic toxicity against green algae namely, Scenedesmus obliquus by using an emerging silver nanomaterial, called silver nanoclusters (defined as r-Ag NCs). By exploiting the unique fluorescence properties of r-Ag NCs along with various other analytical/biological tools, we proposed that the photosynthetic toxicity of r-Ag NCs was largely attributed to the "joint-toxicity" effect of particulate form of r-Ag NCs and its released Ag + , which resulted in the disruption of the electron transport chain of light reaction and affected the content of key enzymes (RuBP carboxylase/ oxygenase) of Calvin cycle of algae cells. We believe that the present study can also be applied to the assessment of the ecological risk derived from other metal nanoparticles.

  11. Facile Fabrication of a Gold Nanocluster-Based Membrane for the Detection of Hydrogen Peroxide

    Directory of Open Access Journals (Sweden)

    Pu Zhang

    2016-07-01

    Full Text Available In this work, we present a simple and rapid method to synthesize red luminescent gold nanoclusters (AuNCs with high quantum yield (QY, ~16%, excellent photostability and biocompatibility. Next, we fabricated a solid membrane by loading the as-prepared AuNCs in an agar matrix. Different from nanomaterials dispersed in solution, the AuNCs-based solid membrane has distinct advantages including convenience of transportation, while still maintaining strong red luminescence, and relatively long duration storage without aggregation. Taking hydrogen peroxide (H2O2 as a typical example, we then employed the AuNCs as a luminescent probe and investigated their sensing performance, either in solution phase or on a solid substrate. The detection of H2O2 could be achieved in wide concentration ranges over 805 nM–1.61 mM and 161 μM–19.32 mM in solution and on a solid membrane, respectively, with limits of detection (LOD of 80 nM and 20 μM. Moreover, the AuNCs-based membrane could also be used for visual detection of H2O2 in the range of 0–3.22 mM. In view of the convenient synthesis route and attractive luminescent properties, the AuNCs-based membrane presented in this work is quite promising for applications such as optical sensing, fluorescent imaging, and photovoltaics.

  12. Cisplatin Prodrug-Conjugated Gold Nanocluster for Fluorescence Imaging and Targeted Therapy of the Breast Cancer.

    Science.gov (United States)

    Zhou, Fangyuan; Feng, Bing; Yu, Haijun; Wang, Dangge; Wang, Tingting; Liu, Jianping; Meng, Qingshuo; Wang, Siling; Zhang, Pengcheng; Zhang, Zhiwen; Li, Yaping

    2016-01-01

    Theranostic nanomedicine has emerged as a promising modality for cancer diagnosis and treatment. In this study, we report the fabrication of fluorescence gold nanoclusters (GNC) conjugated with a cisplatin prodrug and folic acid (FA) (FA-GNC-Pt) for fluorescence imaging and targeted chemotherapy of breast cancer. The physio-chemical properties of FA-GNC-Pt nanoparticles are thoroughly characterized by fluorescence/UV-Vis spectroscopic measurement, particle size and zeta-potential examination. We find that FA-modification significantly accelerated the cellular uptake and increased the cytotoxicity of GNC-Pt nanoparticles in murine 4T1 breast cancer cells. Fluorescence imaging in vivo using 4T1 tumor bearing nude mouse model shows that FA-GNC-Pt nanoparticles selectively accumulate in the orthotopic 4T1 tumor and generate strong fluorescence signal due to the tumor targeting effect of FA. Moreover, we demonstrate that FA-GNC-Pt nanoparticles significantly inhibit the growth and lung metastasis of the orthotopically implanted 4T1 breast tumors. All these data imply a good potential of the GNC-based theranostic nanoplatform for fluorescence tumor imaging and cancer therapy.

  13. Generation of nanoclusters by ultrafast laser ablation of Al: Molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Miloshevsky, Alexander; Phillips, Mark C.; Harilal, Sivanandan S.; Dressman, Phillip; Miloshevsky, Gennady

    2017-11-01

    The laser ablation of materials induced by an ultrashort femtosecond pulse is a complex phenomenon, which depends on both the material properties and the properties of the laser pulse. The unique capability of a combination of molecular dynamics (MD) and Momentum Scaling Model (MSM) methods is developed and applied to a large atomic system for studying the process of ultrafast laser-material interactions, behavior of matter in a highly non-equilibrium state, material disintegration, and formation of nanoparticles (NPs). Laser pulses with several fluences in the range from 500 J/m2 to 5000 J/m2 interacting with a large system of aluminum atoms are simulated. The response of Al material to the laser energy deposition is investigated within the finite-size laser spot. It is found that the shape of the plasma plume is dynamically changing during an expansion process. At several tens of picoseconds it can be characterized as a long hollow ellipsoid surrounded by atomized and nano-clustered particles. The time evolution of NP clusters in the plume is investigated. The collisions between the single Al atoms and generated NPs and fragmentation of large NPs determine the fractions of different-size NP clusters in the plume. The MD-MSM simulations show that laser fluence greatly affects the size distribution of NPs, their polar angles, magnitude and direction vectors of NP velocities. These results and predictions are supported by the experimental data and previous MD simulations.

  14. Sensitive detection of alkaline phosphatase by switching on gold nanoclusters fluorescence quenched by pyridoxal phosphate.

    Science.gov (United States)

    Halawa, Mohamed Ibrahim; Gao, Wenyue; Saqib, Muhammad; Kitte, Shimeles Addisu; Wu, Fengxia; Xu, Guobao

    2017-09-15

    In this work, we designed highly sensitive and selective luminescent detection method for alkaline phosphatase using bovine serum albumin functionalized gold nanoclusters (BSA-AuNCs) as the nanosensor probe and pyridoxal phosphate as the substrate of alkaline phosphatase. We found that pyridoxal phosphate can quench the fluorescence of BSA-AuNCs and pyridoxal has little effect on the fluorescence of BSA-AuNCs. The proposed mechanism of fluorescence quenching by PLP was explored on the basis of data obtained from high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), UV-vis spectrophotometry, fluorescence spectroscopy, fluorescence decay time measurements and circular dichroism (CD) spectroscopy. Alkaline phosphatase catalyzes the hydrolysis of pyridoxal phosphate to generate pyridoxal, restoring the fluorescence of BSA-AuNCs. Therefore, a recovery type approach has been developed for the sensitive detection of alkaline phosphatase in the range of 1.0-200.0U/L (R 2 =0.995) with a detection limit of 0.05U/L. The proposed sensor exhibit excellent selectivity among various enzymes, such as glucose oxidase, lysozyme, trypsin, papain, and pepsin. The present switch-on fluorescence sensing strategy for alkaline phosphatase was successfully applied in human serum plasma with good recoveries (100.60-104.46%), revealing that this nanosensor probe is a promising tool for ALP detection. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Experimental determination of the energy difference between competing isomers of deposited, size-selected gold nanoclusters.

    Science.gov (United States)

    Foster, D M; Ferrando, R; Palmer, R E

    2018-04-03

    The equilibrium structures and dynamics of a nanoscale system are regulated by a complex potential energy surface (PES). This is a key target of theoretical calculations but experimentally elusive. We report the measurement of a key PES parameter for a model nanosystem: size-selected Au nanoclusters, soft-landed on amorphous silicon nitride supports. We obtain the energy difference between the most abundant structural isomers of magic number Au 561 clusters, the decahedron and face-centred-cubic (fcc) structures, from the equilibrium proportions of the isomers. These are measured by atomic-resolution scanning transmission electron microscopy, with an ultra-stable heating stage, as a function of temperature (125-500 °C). At lower temperatures (20-125 °C) the behaviour is kinetic, exhibiting down conversion of metastable decahedra into fcc structures; the higher state is repopulated at higher temperatures in equilibrium. We find the decahedron is 0.040 ± 0.020 eV higher in energy than the fcc isomer, providing a benchmark for the theoretical treatment of nanoparticles.

  16. Eight-Electron Silver and Mixed Gold/Silver Nanoclusters Stabilized by Selenium Donor Ligands.

    Science.gov (United States)

    Chang, Wan-Ting; Lee, Po-Yi; Liao, Jian-Hong; Chakrahari, Kiran Kumarvarma; Kahlal, Samia; Liu, Yu-Chiao; Chiang, Ming-Hsi; Saillard, Jean-Yves; Liu, C W

    2017-08-14

    The first atomically and structurally precise silver-nanoclusters stabilized by Se-donor ligands, [Ag 20 {Se 2 P(O i Pr) 2 } 12 ] (3) and [Ag 21 {Se 2 P(OEt) 2 } 12 ] + (4), were isolated by ligand replacement reaction of [Ag 20 {S 2 P(O i Pr) 2 } 12 ] (1) and [Ag 21 {S 2 P(O i Pr) 2 } 12 ] + (2), respectively. Furthermore, doping reactions of 4 with Au(PPh 3 )Cl resulted in the formation of [AuAg 20 {Se 2 P(OEt) 2 } 12 ] + (5). Structures of 3, 4, and 5 were determined by single-crystal X-ray diffraction. The anatomy of cluster 3 with an Ag 20 core having C 3 symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag 21 and Au@Ag 20 core of O h symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag 13 and Au@Ag 12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen-passivated silver nanoparticles, which have been theoretically confirmed as 8-electron superatoms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Spherical harmonics based descriptor for neural network potentials: Structure and dynamics of Au147 nanocluster

    Science.gov (United States)

    Jindal, Shweta; Chiriki, Siva; Bulusu, Satya S.

    2017-05-01

    We propose a highly efficient method for fitting the potential energy surface of a nanocluster using a spherical harmonics based descriptor integrated with an artificial neural network. Our method achieves the accuracy of quantum mechanics and speed of empirical potentials. For large sized gold clusters (Au147), the computational time for accurate calculation of energy and forces is about 1.7 s, which is faster by several orders of magnitude compared to density functional theory (DFT). This method is used to perform the global minimum optimizations and molecular dynamics simulations for Au147, and it is found that its global minimum is not an icosahedron. The isomer that can be regarded as the global minimum is found to be 4 eV lower in energy than the icosahedron and is confirmed from DFT. The geometry of the obtained global minimum contains 105 atoms on the surface and 42 atoms in the core. A brief study on the fluxionality in Au147 is performed, and it is concluded that Au147 has a dynamic surface, thus opening a new window for studying its reaction dynamics.

  18. Oligonucleotide-stabilized fluorescent silver nanoclusters for the specific and sensitive detection of biotin.

    Science.gov (United States)

    Xiong, Xiaoli; Tang, Yan; Zhao, Jingjin; Zhao, Shulin

    2016-02-21

    A novel biotin fluorescent probe based on oligonucleotide-stabilized silver nanoclusters (DNA-AgNCs) was synthesized by employing a biotinylated cytosine-rich sequence as a synthesized template. The fluorescence properties of the DNA-AgNCs are related to the modified position of the DNA. When biotin is linked to the middle thymine base of the DNA sequence, the DNA-AgNCs emit the strongest fluorescence. Moreover, the stability of the DNA-AgNCs was affected by avidin through biotin-avidin binding, quenching the fluorescence of the DNA-AgNCs. In contrast, if free biotin is further introduced into this system, the quenching is apparently weakened by competition, leading to the restoration of fluorescence. This phenomenon can be utilized for the detection of biotin. Under the optimal conditions, the fluorescence recovery is linearly proportional to the concentration of biotin in the range of 10 nM-1.0 μM with a detection limit of 6.0 nM. This DNA-AgNCs probe with excellent fluorescent properties is sensitive and selective for the detection of biotin and has been applied for the determination of biotin in wheat flour.

  19. Engineering ultrasmall water-soluble gold and silver nanoclusters for biomedical applications.

    Science.gov (United States)

    Luo, Zhentao; Zheng, Kaiyuan; Xie, Jianping

    2014-05-25

    Gold and silver nanoclusters or Au/Ag NCs with core sizes smaller than 2 nm have been an attractive frontier of nanoparticle research because of their unique physicochemical properties such as well-defined molecular structure, discrete electronic transitions, quantized charging, and strong luminescence. As a result of these unique properties, ultrasmall size, and good biocompatibility, Au/Ag NCs have great potential for a variety of biomedical applications, such as bioimaging, biosensing, antimicrobial agents, and cancer therapy. In this feature article, we will first discuss some critical biological considerations, such as biocompatibility and renal clearance, of Au/Ag NCs that are applied for biomedical applications, leading to some design criteria for functional Au/Ag NCs in the biological settings. According to these biological considerations, we will then survey some efficient synthetic strategies for the preparation of protein- and peptide-protected Au/Ag NCs with an emphasis on our recent contributions in this fast-growing field. In the last part, we will highlight some potential biomedical applications of these protein- and peptide-protected Au/Ag NCs. It is believed that with continued efforts to understand the interactions of biomolecule-protected Au/Ag NCs with the biological systems, scientists can largely realize the great potential of Au/Ag NCs for biomedical applications, which could finally pave their way towards clinical use.

  20. Quantum effects on the structure of pure and binary metallic nanoclusters

    Science.gov (United States)

    Ferrando, R.; Fortunelli, A.; Rossi, G.

    2005-08-01

    A family of high-symmetry bimetallic clusters—recently shown to give rise to “magic” structures in the case of Ag-Cu and Ag-Ni nanoclusters—is investigated also in the case of Ag-Pd, Ag-Co, Au-Cu, Au-Ni, and Au-Co. Cluster structures obtained by global optimization within a semiempirical potential model are then reoptimized via density functional calculations. Sizes up to 45 atoms are considered. Ag-Cu, Ag-Ni, and Au-Ni clusters have some common characteristics. They present polyicosahedral character and achieve maximum stability at the Ag- and Au-rich compositions, when the structural arrangement is associated to a Ni(Cu)core-Ag(Au)shell chemical ordering. This is due both to the huge size mismatch between the components and a clear tendency of the larger atoms to segregate at the surface. In Au-Cu and Ag-Pd, clusters achieve their best stability at intermediate compositions, in agreement with the tendency of these metals to mix in the bulk phase. Finally, for Ag-Co and Au-Co, peculiar quantum effects favor intermediate compositions despite the fact that these metal phases separate in the bulk. These results are rationalized in terms of the interplay between electronic and volumetric effects on the structure of metallic nanoclusters.

  1. Transition metal doped ZnO nanoclusters for carbon monoxide detection: DFT studies.

    Science.gov (United States)

    Aslanzadeh, Saeed

    2016-07-01

    Metal doped ZnO nanomaterials have attracted considerable attention as a chemical sensor for toxic gases. Here, the electronic sensitivity of pristine and Sc-, Ti-, V-, Cr-, Mn-, and Fe-doped Zn12O12 nanoclusters toward CO gas is investigated using density functional theory calculations. It is found that replacing a Zn atom by a Sc or Ti atom does not change the sensitivity of cluster but doping V and Cr atoms significantly increase the sensitivity. Also, Mn, or Fe doping slightly improves the sensitivity. It is predicted that among all, the Cr-doped ZnO cluster may be the most favorable sensor for CO detection because its electrical conductivity considerably changes after the CO adsorption, thereby, generating an electrical signal. The calculated Gibbs free energy change for the adsorption of CO molecule on the Cr-doped cluster is about -51.2 kcal mol(-1) at 298.15 K and 1 atm, and the HOMO-LUMO gap of the adsorbent is changed by about 117.8 %.

  2. Spherical harmonics based descriptor for neural network potentials: Structure and dynamics of Au147nanocluster.

    Science.gov (United States)

    Jindal, Shweta; Chiriki, Siva; Bulusu, Satya S

    2017-05-28

    We propose a highly efficient method for fitting the potential energy surface of a nanocluster using a spherical harmonics based descriptor integrated with an artificial neural network. Our method achieves the accuracy of quantum mechanics and speed of empirical potentials. For large sized gold clusters (Au 147 ), the computational time for accurate calculation of energy and forces is about 1.7 s, which is faster by several orders of magnitude compared to density functional theory (DFT). This method is used to perform the global minimum optimizations and molecular dynamics simulations for Au 147 , and it is found that its global minimum is not an icosahedron. The isomer that can be regarded as the global minimum is found to be 4 eV lower in energy than the icosahedron and is confirmed from DFT. The geometry of the obtained global minimum contains 105 atoms on the surface and 42 atoms in the core. A brief study on the fluxionality in Au 147 is performed, and it is concluded that Au 147 has a dynamic surface, thus opening a new window for studying its reaction dynamics.

  3. Stimuli-disassembling gold nanoclusters for diagnosis of early stage oral cancer by optical coherence tomography

    Science.gov (United States)

    Kim, Chang Soo; Ingato, Dominique; Wilder-Smith, Petra; Chen, Zhongping; Kwon, Young Jik

    2018-01-01

    A key design consideration in developing contrast agents is obtaining distinct, multiple signal changes in diseased tissue. Plasmonic gold nanoparticles (Au NPs) have been developed as contrast agents due to their strong surface plasmon resonance (SPR). This study aims to demonstrate that stimuli-responsive plasmonic Au nanoclusters (Au NCs) can be used as a contrast agent for optical coherence tomography (OCT) in detecting early-stage cancer. Au NPs were clustered via acid-cleavable linkers to synthesize Au NCs that disassemble under mildly acidic conditions into individual Au NPs, simultaneously diminishing SPR effect (quantified by scattering intensity) and increasing Brownian motion (quantified by Doppler variance). The acid-triggered morphological and accompanying optico-physical property changes of the acid-disassembling Au NCs were confirmed by TEM, DLS, UV/Vis, and OCT. Stimuli-responsive Au NCs were applied in a hamster check pouch model carrying early-stage squamous carcinoma tissue. The tissue was visualized by OCT imaging, which showed reduced scattering intensity and increased Doppler variance in the dysplastic tissue. This study demonstrates the promise of diagnosing early-stage cancer using molecularly programmable, inorganic nanomaterial-based contrast agents that are capable of generating multiple, stimuli-triggered diagnostic signals in early-stage cancer.[Figure not available: see fulltext.

  4. Synthesis and Optical Properties of a Dithiolate/Phosphine-Protected Au28 Nanocluster

    KAUST Repository

    Aljuhani, Maha A.

    2016-12-17

    While monothiols and simple phosphines are commonly exploited for size-controlled synthesis of atomically precise gold nanoclusters (NCs), dithiols or dithiol-phosphine combinations are seldom applied. Herein, we used a dithiol (benzene-1,3-dithiol, BDT) and a phosphine (triphenylphosphine, TPP) together as ligands and synthesized an atomically precise gold NC with the formula [Au28(BDT)4(TPP)9]2+. This NC exhibited multiple absorption features and a charge of +2, which are distinctly different from the reported all-thiolated [Au28(SR)20]0 NC (SR: monothiolate). The composition of [Au28(BDT)4(TPP)9]2+ NC was deduced from high-resolution electrospray ionization mass spectrometry (ESI MS) and it was further corroborated by thermogravimetric analysis (TGA). Differential pulse voltammetry (DPV) revealed a HOMO–LUMO gap of 1.27 eV, which is in good agreement with the energy gap of 1.3 eV obtained from its UV–vis spectrum. The successful synthesis of atomically precise, dithiol-protected Au28 NC would stimulate theoretical and experimental research into bidentate ligands as a new path for expanding the library of different metal NCs, which have so far been dominated by monodentate thiols.

  5. Silver nanocluster based sensitivity amplification of a quartz crystal microbalance gene sensor

    International Nuclear Information System (INIS)

    Zhou, Lin; Lu, Peng; Zhu, Mingyao; Li, Baole; Yang, Peihui; Cai, Jiye

    2016-01-01

    The article describes a quartz crystal microbalance (QCM) biosensor for the determination of nucleic acids via a DNA-templated assembly of silver nanoclusters (AgNCs) which represents a novel way for efficient signal amplification. A QCM was modified with probe DNA to specifically capture target DNA. Then, DNA-templated AgNCs were assembled to enhance the sensitivity of the QCM sensor via Ag(I) ions attached to the DNA skeleton, this followed by hydroquinone-induced reductive formation of the AgNCs. TEM and AFM were used to further confirm the formation of DNA-templated AgNCs. The results showed that frequency response of QCM sensor is up to 87 times larger when using this mode of amplification. A linear relationship was obtained between the frequency response and DNA concentration over the 0.6 to 130 nM range, with a 0.1 nM detection limit. In our perception, this scheme for improved sensitivity provides a straightforward and widely applicable tool for sensing DNA. (author)

  6. Facile Synthesis of Gd-Functionalized Gold Nanoclusters as Potential MRI/CT Contrast Agents

    Directory of Open Access Journals (Sweden)

    Wenjun Le

    2016-04-01

    Full Text Available Multi-modal imaging plays a key role in the earlier detection of disease. In this work, a facile bioinspired method was developed to synthesize Gd-functionalized gold nanoclusters (Gd-Au NCs. The Gd-Au NCs exhibit a uniform size, with an average size of 5.6 nm in dynamic light scattering (DLS, which is a bit bigger than gold clusters (3.74 nm, DLS, while the fluorescent properties of Gd-Au NCs are almost the same as that of Au NCs. Moreover, the Gd-Au NCs exhibit a high longitudinal relaxivity value (r1 of 22.111 s−1 per mM of Gd in phosphate-buffered saline (PBS, which is six times higher than that of commercial Magnevist (A complex of gadolinium with a chelating agent, diethylenetriamine penta-acetic acid, Gd-DTPA, r1 = 3.56 mM−1·s−1. Besides, as evaluated by nano single photon emission computed tomography (SPECT and computed tomography (CT the Gd-Au NCs have a potential application as CT contrast agents because of the Au element. Finally, the Gd-Au NCs show little cytotoxicity, even when the Au concentration is up to 250 μM. Thus, the Gd-Au NCs can act as multi-modal imaging contrast agents.

  7. Functional gold nanoclusters as antimicrobial agents for antibiotic-resistant bacteria.

    Science.gov (United States)

    Chen, Wei-Yu; Lin, Ju-Yu; Chen, Wei-Jen; Luo, Liyang; Wei-Guang Diau, Eric; Chen, Yu-Chie

    2010-07-01

    Our aim was to demonstrate that lysozyme-directed generation of gold nanoclusters (Au NCs) are potential antimicrobial agents for antibiotic-resistant bacteria and broad labeling agents for pathogenic bacteria. Lysozyme is an enzyme that is capable of hydrolyzing the cell walls of bacteria. In this study, we demonstrated the generation of functional Au NCs by using lysozyme as the sequester and the reducing agent for Au precursors at 40 degrees C. In addition, to shorten the reaction time, the reaction was conducted under microwave irradiation within a short period of time for the first time. The bioactivity of the lysozyme on the Au NCs was retained. Therefore, the as-prepared lysozyme-Au NCs with desirable fluorescence feature were successfully employed to be broad-band labeling agents for pathogenic bacteria. Furthermore, we also demonstrated that the lysozyme-Au NCs can be used to effectively inhibit the cell growth of notorious antibiotic-resistant bacteria, including pan-drug-resistant Acinetobacter baumannii and vancomycin-resistant Enterococcus faecalis. The potential of employing the lysozyme-Au NCs for bacterial labeling and as antimicrobial agents is expected.

  8. A sensitive chemiluminescence method for the determination of cysteine based on silver nanoclusters

    International Nuclear Information System (INIS)

    Yu, X.; Wang, Q.; Liu, X.; Luo, X.

    2012-01-01

    We have developed a sensitive chemiluminescent (CL) assay for cysteine. It is based on the use of water-soluble and fluorescent silver nanoclusters (Ag NCs) which are found to be able to strongly enhance the weak CL signal resulting from the redox reaction between Ce(IV) ion and sulfite ion. This enhancement is inhibited by cysteine under appropriate conditions. Taking advantage of this specific CL inhibition, a novel CL method for the sensitive and selective detection of cysteine was developed. This effect is interpreted in terms of an electronic energy transfer from excited state intermediate sulfur dioxide (originating from the CL reaction between Ce(IV) and sulfite ions) to the Ag-NCs. The latter become electronically excited and thus can act as a new source of emission. The method was applied to the determination of cysteine in the range from 5.0 nM to 1.0 μM, with a detection limit at 2.5 nM (S/N=3). (author)

  9. An Organometallic Cu20Nanocluster: Synthesis, Characterization, Immobilization on Silica, and "Click" Chemistry.

    Science.gov (United States)

    Cook, Andrew W; Jones, Zachary R; Wu, Guang; Scott, Susannah L; Hayton, Trevor W

    2018-01-10

    The development of atomically precise nanoclusters (APNCs) protected by organometallic ligands, such as acetylides and hydrides, is an emerging area of nanoscience. In principle, these organometallic APNCs should not require harsh pretreatment for activation toward catalysis, such as calcination, which can lead to sintering. Herein, we report the synthesis of the mixed-valent organometallic copper APNC, [Cu 20 (CCPh) 12 (OAc) 6 )] (1), via reduction of Cu(OAc) with Ph 2 SiH 2 in the presence of phenylacetylene. This cluster is a rare example of a two-electron copper superatom, and the first to feature a tetrahedral [Cu 4 ] 2+ core, which is a unique "kernel" for a Cu-only superatom. Complex 1 can be readily immobilized on dry, partially dehydroxylated silica, a process that cleanly results in release of 1 equiv of phenylacetylene per Cu 20 cluster. Cu K-edge EXAFS confirms that the immobilized cluster 2 is structurally similar to 1. In addition, both 1 and 2 are effective catalysts for [3+2] cycloaddition reactions between alkynes and azides (i.e., "Click" reactions) at room temperature. Significantly, neither cluster requires any pretreatment for activation toward catalysis. Moreover, EXAFS analysis of 2 after catalysis demonstrates that the cluster undergoes no major structural or nuclearity changes during the reaction, consistent with our observation that supported cluster 2 is more stable than unsupported cluster 1 under "Click" reaction conditions.

  10. Bio-NCs - the marriage of ultrasmall metal nanoclusters with biomolecules

    Science.gov (United States)

    Goswami, Nirmal; Zheng, Kaiyuan; Xie, Jianping

    2014-10-01

    Ultrasmall metal nanoclusters (NCs) have attracted increasing attention due to their fascinating physicochemical properties. Today, functional metal NCs are finding growing acceptance in biomedical applications. To achieve a better performance in biomedical applications, metal NCs can be interfaced with biomolecules, such as proteins, peptides, and DNA, to form a new class of biomolecule-NC composites (or bio-NCs in short), which typically show synergistic or novel physicochemical and physiological properties. This feature article focuses on the recent studies emerging at the interface of metal NCs and biomolecules, where the interactions could impart unique physicochemical properties to the metal NCs, as well as mutually regulate biological functions of the bio-NCs. In this article, we first provide a broad overview of key concepts and developments in the novel biomolecule-directed synthesis of metal NCs. A special focus is placed on the key roles of biomolecules in metal NC synthesis. In the second part, we describe how the encapsulated metal NCs affect the structure and function of biomolecules. Followed by that, we discuss several unique synergistic effects observed in the bio-NCs, and illustrate them with examples highlighting their potential biomedical applications. Continued interdisciplinary efforts are required to build up in-depth knowledge about the interfacial chemistry and biology of bio-NCs, which could further pave their ways toward biomedical applications.

  11. Electrochemical properties of IrO2 active anode with TNTs interlayer for oxygen evolution

    Science.gov (United States)

    Cao, Huazhen; Chen, Mengjie; Wu, Liankui; Hou, Guangya; Tang, Yiping; Zheng, Guoqu

    2018-01-01

    A novel IrO2 coating titanium anode (IrO2/TNTs/Ti) without cracks in microstructure has been prepared via a thermal decomposition method using heat-treated TiO2 nanotube arrays (TNTs) as interlayer. This electrode shows a significantly higher activity for oxygen evolution reaction (OER) and longer lifetime than the IrO2/Ti electrodes without a TNTs layer. The influence of IrO2 amount and calcination temperatures on oxygen evolution as well as morphology and phase characteristics were studied by electrochemical measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations. The results show that the catalytic properties of oxide electrodes highly depended on the loading amount of IrO2 and calcination temperatures. The electrode fabricated at calcination temperature of 600 °C showed a weak electrocatalytic activity due to high degree of crystallinity, grain growth, accumulation of active component and the collapse of TNTs. On the contrary, the IrO2/TNTs/Ti electrode prepared at low calcination temperature (400 °C) possesses extremely more surface active sites and high activity for oxygen evolution in the initial stage, but its service life is very short. The IrO2/TNTs/Ti electrode was found to achieve the lowest film resistance and the charge transfer resistance at an optimal loading amount of 6 g/m2. By simply optimizing both calcination temperature and IrO2 loading amount, IrO2/TNTs/Ti electrode with high activity and long lifetime can be fabricated.

  12. Crumpled rGO-supported Pt-Ir bifunctional catalyst prepared by spray pyrolysis for unitized regenerative fuel cells

    Science.gov (United States)

    Kim, In Gyeom; Nah, In Wook; Oh, In-Hwan; Park, Sehkyu

    2017-10-01

    Three-dimensional (3D) crumpled reduced graphene oxide supported Pt-Ir alloys that served as bifunctional oxygen catalysts for use in untized regenerative fuel cells were synthesized by a facile spray pyrolysis method. Pt-Ir catalysts supported on rGO (Pt-Ir/rGOs) were physically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to observe change in composition by heat treatment, alloying, and morphological transition of the catalysts. Their catalytic activities and stabilities for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) conditions were electrochemically investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), potential cycling and hold tests on the rotating disk electrode (RDE). Pt-Ir/rGO with no post heat-treatment (Pt-Ir/rGO_NP) showed a lower activity for ORR and OER although metal nanoparticles decorated on the support are relatively small. However, Pt-Ir/rGO showed remarkably enhanced activity following heat treatment, depending on temperature. Pt-Ir/rGO heat-treated at 600 °C after spray pyrolysis (Pt-Ir/rGO_P600) exhibited a higher activity and stability than a commercially available Pt/C catalyst kept under the ORR condition, and it also revealed a comparable OER activity and durability versus the commercial unsupported Ir catalyst.

  13. Nanotubular Iridium-Cobalt Mixed Oxide Crystalline Architectures Inherited from Cobalt Oxide for Highly Efficient Oxygen Evolution Reaction Catalysis.

    Science.gov (United States)

    Yu, Areum; Lee, Chongmok; Kim, Myung Hwa; Lee, Youngmi

    2017-10-11

    Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as Ir x Co 1-x O y , where x is the relative Ir atomic content to the overall metal content. The formation of a variety of Ir x Co 1-x O y (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that Ir x Co 1-x O y polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO 2 and Co 3 O 4 , where Ir, Co, and O were homogeneously distributed throughout the entire nanostructures. The facile formation of Ir x Co 1-x O y nanotubes was mainly ascribed to the inclination of Co 3 O 4 to form the nanotubes during the calcination process, which could play a critical role in providing a template of tubular structure and facilitating the formation of IrO 2 by being incorporated with Ir precursors. Furthermore, the electroactivity of obtained Ir x Co 1-x O y nanotubes was characterized for oxygen evolution reaction (OER) with rotating disk electrode voltammetry in 1 M NaOH aqueous solution. Among diverse Ir x Co 1-x O y , Ir 0.46 Co 0.54 O y nanotubes showed the best OER activity (the least-positive onset potential, greatest current density, and low Tafel slope), which was even better than that of commercial Ir/C. The Ir 0.46 Co 0.54 O y nanotubes also exhibited a high stability in alkaline electrolyte. Expensive Ir mixed with cheap Co at an optimum ratio showed a greater OER catalytic activity than pure Ir oxide, one of the most efficient OER catalysts.

  14. PKCδ-mediated IRS-1 Ser24 phosphorylation negatively regulates IRS-1 function

    International Nuclear Information System (INIS)

    Greene, Michael W.; Ruhoff, Mary S.; Roth, Richard A.; Kim, Jeong-a; Quon, Michael J.; Krause, Jean A.

    2006-01-01

    The IRS-1 PH and PTB domains are essential for insulin-stimulated IRS-1 Tyr phosphorylation and insulin signaling, while Ser/Thr phosphorylation of IRS-1 disrupts these signaling events. To investigate consensus PKC phosphorylation sites in the PH-PTB domains of human IRS-1, we changed Ser24, Ser58, and Thr191 to Ala (3A) or Glu (3E), to block or mimic phosphorylation, respectively. The 3A mutant abrogated the inhibitory effect of PKCδ on insulin-stimulated IRS-1 Tyr phosphorylation, while reductions in insulin-stimulated IRS-1 Tyr phosphorylation, cellular proliferation, and Akt activation were observed with the 3E mutant. When single Glu mutants were tested, the Ser24 to Glu mutant had the greatest inhibitory effect on insulin-stimulated IRS-1 Tyr phosphorylation. PKCδ-mediated IRS-1 Ser24 phosphorylation was confirmed in cells with PKCδ catalytic domain mutants and by an RNAi method. Mechanistic studies revealed that IRS-1 with Ala and Glu point mutations at Ser24 impaired phosphatidylinositol-4,5-bisphosphate binding. In summary, our data are consistent with the hypothesis that Ser24 is a negative regulatory phosphorylation site in IRS-1

  15. Factors responsible for the stability and the existence of a clean energy gap of a silicon nanocluster

    International Nuclear Information System (INIS)

    Liu, Lei; Jayanthi, C. S.; Wu, Shi-Yu

    2001-01-01

    We present a critical theoretical study of electronic properties of silicon nanoclusters, in particular the roles played by symmetry, relaxation, and hydrogen passivation on the stability, the gap states and the energy gap of the system using the order N [O(N)] nonorthogonal tight-binding molecular dynamics and the local analysis of electronic structure. We find that for an unrelaxed cluster with its atoms occupying the regular tetrahedral network, the presence of undistorted local bonding configuration is sufficient for the appearance of a small clean energy gap. However, the energy gap of the unrelaxed cluster does not start at the highest occupied molecular orbital (HOMO). In fact, between the HOMO and the lower edge of the energy gap, localized dangling bond states are found. With hydrogen passivation, the localized dangling bond states are eliminated, resulting in a wider and clean energy gap. Relaxation of these hydrogen passivated clusters does not alter either the structure or the energy gap appreciably. However, if the silicon clusters are allowed to relax first, the majority of the dangling bonds are eliminated but additional defect states due to bond distortion appear, making the energy gap dirty. Hydrogen passivation of these relaxed clusters will further eliminate most of the remnant dangling bonds but no appreciable effect on the defect states associated with bond distortions will take place, thus still resulting in a dirty gap. For the hydrogen-passivated Si N nanoclusters with no bond distortion and no overall symmetry, we have studied the variation of the energy gap as a function of size of the cluster for N in the range of 80< N<6000. The dependence of the energy gap on the size shows similar behavior to that for silicon nanoclusters with no bond distortion but possessing overall symmetry

  16. Implementing GPS into Pave-IR.

    Science.gov (United States)

    2009-03-01

    To further enhance the capabilities of the Pave-IR thermal segregation detection system developed at the Texas Transportation Institute, researchers incorporated global positioning system (GPS) data collection into the thermal profiles. This GPS capa...

  17. Joint IAEA/NEA IRS guidelines

    International Nuclear Information System (INIS)

    1997-01-01

    The Incident Reporting System (IRS) is an international system jointly operated by the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD/NEA). The fundamental objective of the IRS is to contribute to improving the safety of commercial nuclear power plants (NPPs) which are operated worldwide. This objective can be achieved by providing timely and detailed information on both technical and human factors related to events of safety significance which occur at these plants. The purpose of these guidelines, which supersede the previous IAEA Safety Series No. 93 (Part II) and the NEA IRS guidelines, is to describe the system and to give users the necessary background and guidance to enable them to produce IRS reports meeting a high standard of quality while retaining the high efficiency of the system expected by all Member States operating nuclear power plants

  18. Novel Wavelength Standards in the Near IR

    National Research Council Canada - National Science Library

    Corwin, Kristan L

    2008-01-01

    .... This research has three major components, consisting of spectroscopy in hollow fiber, the development of a near-IR optical frequency comb with which to characterize the transitions inside the fiber...

  19. IR aperture measurement at β*=40 cm

    CERN Document Server

    Bruce, Roderik; Hermes, Pascal Dominik; Kwee-Hinzmann, Regina; Mereghetti, Alessio; Mirarchi, Daniele; Redaelli, Stefano; Salvachua Ferrando, Belen Maria; Skowronski, Piotr Krzysztof; Valentino, Gianluca; Valloni, Alessandra; CERN. Geneva. ATS Department

    2015-01-01

    This note summarizes MD 307, performed on August 27 2015, during which we measured with beam the global apertures at 6.5 TeV with IR1 and IR5 squeezed to β* =40 cm and a half crossing angle of 205 rad. The measurement technique involved opening collimators in steps, while inducing beam losses at each step, until the main loss location moved from the collimators to the global bottleneck in one of the triplets. Measurements were performed in both beams and planes, and each measurement gave the minimum triplet aperture over IR1 and IR5. The results are in very good agreement with theoretical predictions. At the end of the MD, an asynchronous beam dump test was performed with all collimators moved in to so-called 2-σ retraction settings. This MD is one in a series meant to address various open points for the reach in β* in Run II.

  20. Activity uniformity of Ir-192 seeds

    International Nuclear Information System (INIS)

    Ling, C.C.; Gromadzki, Z.C.

    1981-01-01

    A simple device that uses materials and apparatus commonly available in a radiotherapy department has been designed, fabricated and used in routine quality control relative to the activity uniformity of clinical Ir-192 seeds in ribbons. Detailed evaluation indicated that this system is easy to use and can yield relative activity measurements of individual Ir-192 seeds accurate to within 2%. With this device, activity uniformity of commercial Ir-192 seeds from two manufacturers has been assessed. For the seven shipments of Ir-192 seeds studied, the root mean square variations of individual seed strength from the average of each shipment ranged from 3.4 to 7.1%. Variation in seed activity by more than +- 10% from the average is not uncommon

  1. Infrared (IR) remote sensing of gases

    OpenAIRE

    López Martínez, Fernando

    2008-01-01

    The IR Imaging and Remote Sensing Laboratory – LIR-UC3M of Universidad Carlos III, has developed Multi and Hyper spectral Infrared (IR) analysis techniques for gas remote sensing. Design of specific sensors for the determination of gases and their concentration are proposed. Almost all gases (CO2, CO, NO2, O3, HC o NH, …) related to industrial, environmental or military safety can be detected. Companies or centres with interest in the use of specific application sensors are required.

  2. Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

    International Nuclear Information System (INIS)

    Mattei, G.; Maurizio, C.; Fernandez, C Julian de; Mazzoldi, P.; Battaglin, G.; Canton, P.; Cattaruzza, E.; Scian, C.

    2006-01-01

    In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 deg. C) when nanoclusters are considered. Starting from Co:SiO 2 composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 deg. C and 900 deg. C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented

  3. pH-Induced Surface Modification of Atomically Precise Silver Nanoclusters: An Approach for Tunable Optical and Electronic Properties

    KAUST Repository

    AbdulHalim, Lina G.

    2016-10-24

    Noble metal nanoclusters (NCs) play a pivotal role in bridging the gap between molecules and quantum dots. Fundamental understanding of the evolution of the structural, optical, and electronic properties of these materials in various environments is of paramount importance for many applications. Using state-of-the-art spectroscopy, we provide the first decisive experimental evidence that the structural, electronic, and optical properties of Ag-44(MNBA)(30) NCs can now be tailored by controlling the chemical environment. Infrared and photoelectron spectroscopies clearly indicate that there is a dimerization between two adjacent ligands capping the NCs that takes place upon lowering the pH from 13 to 7.

  4. The impact of Au doping on the charge carrier dynamics at the interfaces between cationic porphyrin and silver nanoclusters

    KAUST Repository

    Almansaf, Abdulkhaleq A.

    2017-02-04

    We explore the impact of Au doping on the charge transfer dynamics between the positively charged porphyrin (TMPyP) and negatively charged silver nanoclusters (Ag29 NCs). Our transient absorption (TA) spectroscopic results demonstrate that the interfacial charge transfer, the intersystem crossing and the triplet state lifetime of porphyrin can be tuned by the doping of Au atoms in Ag29 NCs. Additionally, we found that the electrostatic interaction between the negative charge of the cluster and the positive charge on the TMPyP is the driving force that brings them close to each other for complex formation and subsequently facilitates the transfer process.

  5. Thermodynamics of the melting process in Au nano-clusters: Phenomenology, energy, entropy and quasi-chemical modeling

    Science.gov (United States)

    Bertoldi, Dalía S.; Millán, Emmanuel N.; Guillermet, Armando Fernández

    2017-12-01

    The paper presents a thermodynamic study of the melting transition in Au nano-clusters with a number of atoms (N) in the range 103 means of a formalism involving an isomerization-type reaction between the atoms in the SPL and the LPL is explored. To this aim, an equilibrium constant (Keq) involving the concentration of such types of atoms is introduced. Finally, it is shown that a thermodynamic, van't Hoff analysis of the size-dependence of Keq yields values of the T0 temperature which are in very good agreement with those obtained from the energy and entropy values.

  6. A Fluorescence Light-Up Ag Nanocluster Probe that Discriminates Single-Nucleotide Variants by Emission Color

    OpenAIRE

    Yeh, Hsin-Chih; Sharma, Jaswinder; Shih, Ie-Ming; Vu, Dung M.; Martinez, Jennifer S.; Werner, James H.

    2012-01-01

    Rapid and precise screening of small genetic variations, such as single-nucleotide polymorphisms (SNPs), among an individual’s genome is still an unmet challenge at point-of-care settings. One crucial step towards this goal is the development of discrimination probes that require no enzymatic reaction and are easy to use. Here we report a new type of fluorescent molecular probe, termed a chameleon NanoCluster Beacon (cNCB), that lights up into different colors upon binding SNP targets. NanoCl...

  7. Atomic-layer deposited IrO2 nanodots for charge-trap flash-memory devices

    International Nuclear Information System (INIS)

    Choi, Sangmoo; Cha, Young-Kwan; Seo, Bum-Seok; Park, Sangjin; Park, Ju-Hee; Shin, Sangmin; Seol, Kwang Soo; Park, Jong-Bong; Jung, Young-Soo; Park, Youngsoo; Park, Yoondong; Yoo, In-Kyeong; Choi, Suk-Ho

    2007-01-01

    Charge-trap flash- (CTF) memory structures have been fabricated by employing IrO 2 nanodots (NDs) grown by atomic-layer deposition. A band of isolated IrO 2 NDs of about 3 nm lying almost parallel to Si/SiO 2 interface is confirmed by transmission electron microscopy and x-ray photoelectron spectroscopy. The memory device with IrO 2 NDs shows much larger capacitance-voltage (C-V) hysteresis and memory window compared with the control sample without IrO 2 NDs. After annealing at 800 deg. C for 20 min, the ND device shows almost no change in the width of C-V hysteresis and the ND distribution. These results indicate that the IrO 2 NDs embedded in SiO 2 can be utilized as thermally stable, discrete charge traps, promising for metal oxide-ND-based CTF memory devices

  8. Investigation of the electrochemical behaviour of thermally prepared Pt-IrO2 electrodes

    Directory of Open Access Journals (Sweden)

    Konan Honoré Kondro

    2008-04-01

    Full Text Available Different IrO2 electrodes in which the molar percentage of platinum (Pt varies from 0 %mol Pt to 100 %mol Pt were prepared on titanium (Ti substrate by thermal decomposition techniques. The electrodes were characterized physically (SEM, XPS and electrochemically and then applied to methanol oxidation. The SEM micrographs indicated that the electrodes present different morphologies depending on the amount of platinum in the deposit and the cracks observed on the 0 %mol Pt electrode diminish in size tending to a compact and rough surface for 70 %mol Pt electrode. XPS results indicate good quality of the coating layer deposited on the titanium substrate. The voltammetric investigations in the supporting electrolyte indicate that the electrodes with low amount of platinum (less than 10 %mol Pt behave as pure IrO2. But in the case of electrodes containing more than 40 %mol Pt, the voltammograms are like that of platinum. Electrocatalytic activity towards methanol oxidation was observed with the electrodes containing high amount of platinum. Its oxidation begins at a potential of about 210 mV lower on such electrodes than the pure platinum electrode (100 %mol Pt. But for electrode containing low quantity of Pt, the surface of the coating is essentially composed of IrO2 and methanol oxidation occurs in the domain of water decomposition solely. The increase of the electrocatalytic behaviour of the electrodes containing high amount of Pt towards methanol oxidation is due to the bifunctional behaviour of the electrodes.

  9. Selective IR reflective coatings development. Final report, 24 July 1978-24 October 1979

    Energy Technology Data Exchange (ETDEWEB)

    Lefkow, A R; Lee, J C

    1979-10-01

    The objective of this program is to develop selective infrared (IR) reflective solar transparent coatings for use on plastic glazing materials. The coating systems studied for this application were indium-tin oxide, tin oxide, and antimony-doped tin oxide. These semiconductor thin films were deposited by two plasma-assisted deposition techniques, ion plating and chemical vapor plasma deposition (CVPD), in which electron kinetic energy from the plasma mitigates the high substate temperature usually required to achieve sufficient thin film crystallinity. The best coating performance obtained in the program by these approaches was 80 to 85% solar transmission and 35% (at 10 microns) to 50% (at 40 microns) IR reflectance for Sb:SnO/sub 2/ films plasma-deposited from Sn(CH/sub 3/)/sub 4/ and SbCl/sub 5/ vapor sources. This is not thought to be the ultimate performance achievable for CVPD-grown Sb:SnO/sub 2/ films.

  10. Fabrication of flexible Ir and Ir-Rh wires and application for thermocouple

    Science.gov (United States)

    Murakami, Rikito; Kamada, Kei; Shoji, Yasuhiro; Yokota, Yuui; Yoshino, Masao; Kurosawa, Shunsuke; Ohashi, Yuji; Yamaji, Akihiro; Yoshikawa, Akira

    2018-04-01

    The fabrication and thermal electromotive force characteristics of Ir/Ir-Rh thermocouples capable of repeated bending deformation are described. Ir and Ir-Rh wires with a diameter of 0.5 mm were fabricated using the alloy-micro-pulling-down method. Scanning electron microscopy and electron backscattering diffraction of the radial cross section of the grown wires were performed to investigate the microstructure and orientation of the crystal grains. At the start of growth, the microstructure was polycrystalline with diameters of several hundred micrometers, while at the 8-m growth point it was found to be monocrystalline. The observed single crystals of pure Ir and Ir-Rh alloy were oriented in the 〈1 1 3〉 and 〈1 1 2〉 directions, respectively, whereas the polycrystalline Ir-Rh samples showed preferential growth in the 〈1 0 0〉 direction. The thermal electromotive force of the fabricated Ir/Ir-Rh thermocouple was measured by the comparison technique and the fixed-point technique, and the thermoelectric power was estimated to be 5.9 μV/°C in the range from 600°C to 1100°C.

  11. The Enzymatic Oxidation of Graphene Oxide

    Science.gov (United States)

    Kotchey, Gregg P.; Allen, Brett L.; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A.; Tyurina, Yulia Y.; Klein-Seetharaman, Judith; Kagan, Valerian E.; Star, Alexander

    2011-01-01

    Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon – the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (~40 µM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, UV-Vis, EPR and FT-IR spectroscopy, TEM, AFM, SDS-PAGE, and GC-MS. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Due to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors. PMID:21344859

  12. Oxidative damage in clinical ischemia/reperfusion injury: a reappraisal.

    Science.gov (United States)

    de Vries, Dorottya K; Kortekaas, Kirsten A; Tsikas, Dimitrios; Wijermars, Leonie G M; van Noorden, Cornelis J F; Suchy, Maria-Theresia; Cobbaert, Christa M; Klautz, Robert J M; Schaapherder, Alexander F M; Lindeman, Jan H N

    2013-08-20

    Ischemia/reperfusion (I/R) injury is a common clinical problem. Although the pathophysiological mechanisms underlying I/R injury are unclear, oxidative damage is considered a key factor in the initiation of I/R injury. Findings from preclinical studies consistently show that quenching reactive oxygen and nitrogen species (RONS), thus limiting oxidative damage, alleviates I/R injury. Results from clinical intervention studies on the other hand are largely inconclusive. In this study, we systematically evaluated the release of established biomarkers of oxidative and nitrosative damage during planned I/R of the kidney and heart in a wide range of clinical conditions. Sequential arteriovenous concentration differences allowed specific measurements over the reperfused organ in time. None of the biomarkers of oxidative and nitrosative damage (i.e., malondialdehyde, 15(S)-8-iso-prostaglandin F2α, nitrite, nitrate, and nitrotyrosine) were released upon reperfusion. Cumulative urinary measurements confirmed plasma findings. As of these negative findings, we tested for oxidative stress during I/R and found activation of the nuclear factor erythroid 2-related factor 2 (Nrf2), the master regulator of oxidative stress signaling. This comprehensive, clinical study evaluates the role of RONS in I/R injury in two different human organs (kidney and heart). Results show oxidative stress, but do not provide evidence for oxidative damage during early reperfusion, thereby challenging the prevailing paradigm on RONS-mediated I/R injury. Findings from this study suggest that the contribution of oxidative damage to human I/R may be less than commonly thought and propose a re-evaluation of the mechanism of I/R.

  13. The Size of Activating and Inhibitory Killer Ig-like Receptor Nanoclusters Is Controlled by the Transmembrane Sequence and Affects Signaling

    Directory of Open Access Journals (Sweden)

    Anna Oszmiana

    2016-05-01

    Full Text Available Super-resolution microscopy has revealed that immune cell receptors are organized in nanoscale clusters at cell surfaces and immune synapses. However, mechanisms and functions for this nanoscale organization remain unclear. Here, we used super-resolution microscopy to compare the surface organization of paired killer Ig-like receptors (KIR, KIR2DL1 and KIR2DS1, on human primary natural killer cells and cell lines. Activating KIR2DS1 assembled in clusters two-fold larger than its inhibitory counterpart KIR2DL1. Site-directed mutagenesis established that the size of nanoclusters is controlled by transmembrane amino acid 233, a lysine in KIR2DS1. Super-resolution microscopy also revealed two ways in which the nanoscale clustering of KIR affects signaling. First, KIR2DS1 and DAP12 nanoclusters are juxtaposed in the resting cell state but coalesce upon receptor ligation. Second, quantitative super-resolution microscopy revealed that phosphorylation of the kinase ZAP-70 or phosphatase SHP-1 is favored in larger KIR nanoclusters. Thus, the size of KIR nanoclusters depends on the transmembrane sequence and affects downstream signaling.

  14. Redox-Triggered Bonding-Induced Emission of Thiol-Functionalized Gold Nanoclusters for Luminescence Turn-On Detection of Molecular Oxygen.

    Science.gov (United States)

    Ao, Hang; Feng, Hui; Zhao, Mengting; Zhao, Meizhi; Chen, Jianrong; Qian, Zhaosheng

    2017-11-22

    Most optical sensors for molecular oxygen were developed based on the quenching effect of the luminescence of oxygen-sensitive probes; however, the signal turn-off mode of these probes is undesirable to quantify and visualize molecular oxygen. Herein, we report a novel luminescence turn-on detection strategy for molecular oxygen via the specific oxygen-triggered bonding-induced emission of thiol-functionalized gold nanoclusters. Thiol-functionalized gold nanoclusters were prepared by a facile one-step synthesis, and as-prepared gold nanoclusters possess significant aggregation-induced emission (AIE) property. It is the first time to discover the oxygen-triggered bonding-induced emission (BIE) behavior of gold nanoclusters, which results in disulfide-linked covalent bonding assemblies with intensely red luminescence. This specific redox-triggered BIE is capable of quantitatively detecting dissolved oxygen in aqueous solution in a light-up manner, and trace amount of dissolved oxygen at ppb level is achieved based on this detection method. A facile and convenient test strip for oxygen detection was also developed to monitor molecular oxygen in a gas matrix. Covalent bonding-induced emission is proven to be a more efficient way to attain high brightness of AIEgens than a physical aggregation-induced emission process, and provides a more convenient and desirable detection method for molecular oxygen than the previous sensors.

  15. Generating Palladium Nanoclusters Inside Very Lipophilic Gel-Type Functional Resins: Preliminary Catalytic Tests in the Hydrogenation of 2-Ethyl-Anthraquinone to 2-Ethylanthrahydroquinone

    Czech Academy of Sciences Publication Activity Database

    Bombi, G.; Lora, S.; Zancato, M.; D'Archivio, A. A.; Jeřábek, Karel; Corain, B.

    2003-01-01

    Roč. 194, 1-2 (2003), s. 273-281 ISSN 1381-1169 Institutional research plan: CEZ:AV0Z4072921 Keywords : palladium nanoclusters * gel-type resins * catalyst Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.264, year: 2003

  16. Disorder effect on heat capacity, self-diffusion coefficient, and choosing best potential model for melting temperature, in gold–copper bimetallic nanocluster with 55 atoms

    International Nuclear Information System (INIS)

    Taherkhani, Farid; Akbarzadeh, Hamed; Feyzi, Mostafa; Rafiee, Hamid Reza

    2015-01-01

    Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models

  17. Attenuated total reflection design for in situ FT-IR spectroelectrochemical studies

    International Nuclear Information System (INIS)

    Visser, Hendrik; Curtright, Aimee E.; McCusker, James K.; Sauer, Kenneth

    2000-01-01

    A versatile spectroelectrochemical apparatus is introduced to study the changes in IR spectra of organic and inorganic compounds upon oxidation or reduction. The design is based on an attenuated total reflection (ATR) device, which permits the study of a wide spectral range of 16,700 cm-1 (600 nm) - 250 cm-1 with a small opaque region of 2250 - 1900 cm-1. In addition, an IR data collection protocol is introduced to deal with electrochemically non-reversible background signals. This method is tested with ferrocene in acetonitrile, producing results that agree with those in the literature

  18. Simultaneous electrochemical detection of dopamine and uric acid over ceria supported three dimensional gold nanoclusters

    Science.gov (United States)

    Palanisamy, Sivakumar

    2014-12-01

    CeO2 is well known for being an active material to support the growth of Au nanoclusters (Au NCs). In this work, three dimensional (3D) Au NCs were deposited on three different shaped CeO2 nanostructures such as nanoparticles (NPs), nanorod arrays (NRAs) and nanoflowers (NFs) modified Ti substrate for electrochemical simultaneous detection of dopamine (DA) and uric acid (UA). The electrodeposition of 3D Au NCs were carried out via cyclic voltammetric (CV) method at over-potential, while CeO2 nanostructures were deposited by galvanostatic constant current method under the optimized conditions. The morphology and elemental composition analysis of 3D Au NCs with CeO2 nanostructures were characterized by SEM, XRD, XPS and EDAX measurements. The electrocatalytic activity of 3D Au NCs on different CeO2 supports were thoroughly investigated by using voltammetric and amperometric techniques. According to the obtained results, CeO2 NPs supported 3D Au NCs (3D Au NCs@CeO2 NPs) displayed strong signal for DA as compared to that of CeO2 NRAs (3D Au NCs@CeO2 NRAs) and CeO2 NFs supported 3D Au NCs (3D Au NCs@CeO2 NFs). In addition, the 3D Au NCs@CeO2 NPs electrode resulted in more sensitive and simultaneous detection of DA in the presence of excess UA. Thus, the 3D Au NCs@CeO2 NPs electrode can practically be applied for the detection of DA using biological samples.

  19. Features of exciton dynamics in molecular nanoclusters (J-aggregates): Exciton self-trapping (Review Article)

    Science.gov (United States)

    Malyukin, Yu. V.; Sorokin, A. V.; Semynozhenko, V. P.

    2016-06-01

    We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation of the exciton self-trapping effect, which is already well-known in bulk crystals, in ordered molecular nanoclusters called J-aggregates. Weakly-coupled one-dimensional (1D) molecular chains are the main structural feature of J-aggregates, wherein the electron excitations are manifested as 1D Frenkel excitons. According to the continuum theory of Rashba-Toyozawa, J-aggregates can have only self-trapped excitons, because 1D excitons must adhere to barrier-free self-trapping at any exciton-phonon coupling constant g = ɛLR/2β, wherein ɛLR is the lattice relaxation energy, and 2β is the half-width of the exciton band. In contrast, very often only the luminescence of free, mobile excitons would manifest in experiments involving J-aggregates. Using the Urbach rule in order to analyze the low-frequency region of the low-temperature exciton absorption spectra has shown that J-aggregates can have both a weak (g 1) exciton-phonon coupling. Moreover, it is experimentally demonstrated that under certain conditions, the J-aggregate excited state can have both free and self-trapped excitons, i.e., we establish the existence of a self-trapping barrier for 1D Frenkel excitons. We demonstrate and analyze the reasons behind the anomalous existence of both free and self-trapped excitons in J-aggregates, and demonstrate how exciton-self trapping efficiency can be managed in J-aggregates by varying the values of g, which is fundamentally impossible in bulk crystals. We discuss how the exciton-self trapping phenomenon can be used as an alternate interpretation of the wide band emission of some J-aggregates, which has thus far been explained by the strongly localized exciton model.

  20. A ratiometric nanoprobe based on silver nanoclusters and carbon dots for the fluorescent detection of biothiols

    Science.gov (United States)

    Zhang, Shuming; Lin, Bixia; Yu, Ying; Cao, Yujuan; Guo, Manli; Shui, Lingling

    2018-04-01

    Ratiometric fluorescent probes could eliminate the influence from experimental factors and improve the detection accuracy. In this article, a ratiometric nanoprobe was constructed based on silver nanoclusters (AgNCs) with nitrogen-doped carbon dots (NCDs) and used for the detection of biothiols. The fluorescence peak of AgNCs was observed at 650 nm with excitation wavelength at 370 nm. In order to construct the ratiometric fluorescent probe, NCDs with the excitation and emission wavelengths at 370 nm and 450 nm were selected. After adding AgNCs, the fluorescence of NCDs was quenched. The mechanism of the fluorescence quenching was studied by fluorescence, UV-Vis absorption and the fluorescence lifetime spectra. The results indicated that the quenching could be ascribed to the inner filter effect (IFE). With the addition of biothiols, the fluorescence of AgNCs at 650 nm decreased due to the breakdown of AgNCs, and the fluorescence of NCDs at 450 nm recovered accordingly. Thus, the relationship between the ratio of the fluorescence intensities (I450/I650) and biothiol concentration was used to establish the determination method for biothiols. Cysteine (Cys) was taken as the model of biothiols, and the working curve for Cys was I450/I650 = 0.60CCys - 1.86 (CCys: μmol/L) with the detection limit of 0.14 μmol/L (S/N = 3). Then, the method was used for the detection of Cys in human urine and serum samples with satisfactory accuracy and recovery ratios. Furthermore, the probe could be applied for the visual semi-quantitative determination of Cys by naked eyes.