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Sample records for supported au nanoparticles

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    Transformation (FFT) analyses confirmed that the nanoparticles indeed were bimetallic. The bimetallic nanoparticles did not have a core-shell structure, but were superior to monometallic particles at reducing p-nitrophenol to p-aminophenol. Hence, formation of microbially supported nanoparticles may be a cheap......(II) to the bio-supported particles resulted in increased particle size. UV-Vis spectrophotometry and HR-TEM analyses indicated that the previously monometallic nanoparticles had become fully or partially covered by Au(0) or Pd(0), respectively. Furthermore, Energy Dispersive Spectrometry (EDS) and Fast Fourier...

  2. Three-dimensional structure of Au nanoparticles supported on amorphous silica and carbon substrates

    International Nuclear Information System (INIS)

    Bruma, A; Li, Z Y

    2012-01-01

    Scanning Transmission Electron Microscope (STEM) has been employed to study the three-dimensional structure of gold (Au) nanoparticles deposited by means of thermal evaporation in high vacuum on amorphous silica (a-SiO 2 ) and amorphous carbon (a-C) supports. By performing quantitative analysis on the evolution of the high angle annular dark field (HAADF) images, we studied the influence of the nature and the temperature of support on the growth mode of gold nanoparticles.

  3. Microwave heated polyol synthesis of carbon supported PtAuSn/C nanoparticles for ethanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Hong; Han, Kefei [School of Science, State key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Liu, Yingli; Chang, Zhaorong [College of Chemistry and Environmental Science, Henan Normal University, Xinxiang, Henan (China); Shen, Liangbo [Beijing No.4 High School, Beijing (China); Wei, Yongsheng; Guo, Zhijun (School of Science Beijing Jiaotong University Beijing P. R. China); Wang, Haijiang [Institute for Fuel Cell Innovation, National Research Council of (Canada)

    2010-04-15

    Carbon-supported PtAuSn/C nanoparticle catalyst was synthesized by a microwave-assisted polyol process. The process is a quick process that only requires a few minutes to complete. The catalyst thus obtained was characterized by transmission electron microscopy and X-ray diffraction analysis. The electrochemical performance of the catalyst, for the ethanol oxidation reaction, was also investigated. The results indicated that the PtAuSn/C catalyst was uniformly dispersed on carbon and was in the nano-size range. The electrochemical measurements indicated that PtAuSn/C nanoparticle catalyst synthesized by the microwave-assisted polyol method demonstrated a significantly higher electrochemically active area and higher catalytic activity than Pt/C for the ethanol oxidation reaction. (author)

  4. Role of Au-C Interactions on the Catalytic Activity of Au Nanoparticles Supported on TiC(001) toward Molecular Oxygen Dissociation

    International Nuclear Information System (INIS)

    Rodriguez, J.; Feria, L.; Jirsak, T.; Takahashi, Y.; Nakamura, K.; Illas, F.

    2010-01-01

    High-resolution photoemission and density functional calculations on realistic slab surface models were used to study the interaction and subsequent dissociation of O 2 with Au nanoparticles supported on TiC(001). The photoemission results indicate that at 150 K O 2 adsorbs molecularly on the supported gold nanoparticles, and upon heating to temperatures above 200 K the O 2 → 2O reaction takes place with migration of atomic oxygen to the TiC(001) substrate. The addition of Au to TiC(001) substantially enhances the rate of O 2 dissociation at room temperature. The reactivity of Au nanoparticles supported on TiC(001) toward O 2 dissociation is much larger than that of similar nanoparticles supported either on TiO 2 (110) or MgO(001) surfaces, where the cleavage of O-O bonds is very difficult. Density functional calculations carried out on large supercells show that the contact of Au with TiC(001) is essential for charge polarization and an enhancement in the chemical activity of Au. Small two-dimensional particles which expose Au atoms in contact with TiC(001) are the most reactive. While O 2 prefers binding to Au sites, the O atoms interact more strongly with the TiC(001) surface. The oxygen species active during the low-temperature ( 2 . Once atomic O binds to TiC(001), the chemisorption bond is so strong that temperatures well above 400 K are necessary to remove the O adatoms from the TiC(001) substrate by direct reaction with CO. The high reactivity of Au/TiC(001) toward O 2 at low-temperature opens the route for the transformation of alcohols and amines on the supported Au nanoparticles.

  5. Mesoporous Silica Supported Au Nanoparticles with Controlled Size as Efficient Heterogeneous Catalyst for Aerobic Oxidation of Alcohols

    Directory of Open Access Journals (Sweden)

    Xuefeng Chu

    2015-01-01

    Full Text Available A series of Au catalysts with different sizes were synthesized and employed on amine group functionalized ordered mesoporous silica solid supports as catalyst for the aerobic oxidation of various alcohols. The mesoporous silica of MCM-41 supported Au nanoparticles (Au-1 exhibited the smallest particle size at ~1.8 nm with superior catalytic activities owing to the confinement effect of the mesoporous channels. Au-1 catalyst is also very stable and reusable under aerobic condition. Therefore, this presented work would obviously provide us a platform for synthesizing more size-controlled metal catalysts to improve the catalytic performances.

  6. Polymeric carbon nitride/mesoporous silica composites as catalyst support for Au and Pt nanoparticles.

    Science.gov (United States)

    Xiao, Ping; Zhao, Yanxi; Wang, Tao; Zhan, Yingying; Wang, Huihu; Li, Jinlin; Thomas, Arne; Zhu, Junjiang

    2014-03-03

    Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CNx )/mesoporous silica (SBA-15) composites, which were synthesized by thermal polycondensation of dicyandiamide-impregnated preformed SBA-15. By changing the condensation temperature, the degree of condensation and the loading of CNx can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA-15 support, coating of SBA-15 with polymeric CNx resulted in much smaller and better-dispersed metal NPs. Furthermore, under catalytic conditions the CNx coating helps to stabilize the metal NPs. However, metal NPs on CNx /SBA-15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CNx support. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Carbon nanotubes-supported PtAu-alloy nanoparticles for electro-oxidation of formic acid with remarkable activity

    International Nuclear Information System (INIS)

    Bai Yancui; Zhang Weide; Chen Caihong; Zhang Jiaqi

    2011-01-01

    Research highlights: → Electro-oxidation of HCOOH over PtAu at lower potential, higher peak current. → The stability of the PtAu catalyst is high. → Au in the PtAu catalyst promotes utilization of Pt. - Abstract: PtAu-alloy nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) were successfully prepared by simultaneous reduction of H 2 PtCl 6 .6H 2 O and HAuCl 4 .3H 2 O with sodium borohydride as a reducing reagent and sodium citrate as a stabilizing reagent. The morphology and composition of the composite catalyst were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The results show that the PtAu alloy nanoparticles with an average diameter of about 3.5 nm and narrow size distribution are supported on MWCNTs. Electrocatalytic oxidation of formic acid at the PtAu/MWCNTs nanocomposite electrode was investigated in a solution containing 0.50 M H 2 SO 4 as a supporting electrolyte and 0.50 M formic acid by cyclic voltammogram and chronoamperometry. The results demonstrate that the PtAu/MWCNTs catalyst exhibits higher activity and stability for electro-oxidation of formic acid than the commercial Pt/C catalyst, reflecting by its lower onset potential (-0.05 V), oxidation mainly occurring in low potential range of -0.05 ± 0.65 V and higher peak current density of 3.12 mA cm -2 . The result of CO stripping voltammetry discloses that gold in the PtAu/MWCNTs nanocomposite enhances the catalytic activity and stability.

  8. Simultaneous AuIII Extraction and In Situ Formation of Polymeric Membrane-Supported Au Nanoparticles: A Sustainable Process with Application in Catalysis.

    Science.gov (United States)

    Mora-Tamez, Lucía; Esquivel-Peña, Vicente; Ocampo, Ana L; Rodríguez de San Miguel, Eduardo; Grande, Daniel; de Gyves, Josefina

    2017-04-10

    A polymeric membrane-supported catalyst with immobilized gold nanoparticles (AuNPs) was prepared through the extraction and in situ reduction of Au III salts in a one-step strategy. Polymeric inclusion membranes (PIMs) and polymeric nanoporous membranes (PNMs) were tested as different membrane-support systems. Transport experiments indicated that PIMs composed of cellulose triacetate, 2-nitrophenyloctyl ether, and an aliphatic tertiary amine (Adogen 364 or Alamine 336) were the most efficient supports for Au III extraction. The simultaneous extraction and reduction processes were proven to be the result of a synergic phenomenon in which all the membrane components were involved. Scanning electron microscopy characterization of cross-sectional samples suggested a distribution of AuNPs throughout the membrane. Transmission electron microscopy characterization of the AuNPs indicated average particle sizes of 36.7 and 2.9 nm for the PIMs and PNMs, respectively. AuNPs supported on PIMs allowed for >95.4 % reduction of a 0.05 mmol L -1 4-nitrophenol aqueous solution with 10 mmol L -1 NaBH 4 solution within 25 min. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Catalytic activity of Au nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Janssens, Ton V.W.; Clausen, Bjerne

    2007-01-01

    Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change with par......Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change...... with particle size. We find that the fraction of low-coordinated Au atoms scales approximately with the catalytic activity, suggesting that atoms on the corners and edges of Au nanoparticles are the active sites. This effect is explained using density functional calculations....

  10. Insights into the Reactivity of Supported Au Nanoparticles: Combining Theory and Experiments

    DEFF Research Database (Denmark)

    Janssens, Ton V.W.; Clausen, Bjerne S.; Larsen, Britt Hvolbæk

    2007-01-01

    The origin of the extraordinary catalytic activity of gold nanoparticles is discussed on the basis of density-functional calculations, adsorption studies on single crystal surfaces, and activity measurements on well characterized supported gold particles. A number of factors are identified...

  11. Yolk-shell gold nanoparticles as model materials for support-effect studies in heterogeneous catalysis: Au, @C and Au, @ZrO2 for CO oxidation as an example.

    Science.gov (United States)

    Galeano, Carolina; Güttel, Robert; Paul, Michael; Arnal, Pablo; Lu, An-Hui; Schüth, Ferdi

    2011-07-18

    The use of nanostructured yolk-shell materials offers a way to discriminate support and particle-size effects for mechanistic studies in heterogeneous catalysis. Herein, gold yolk-shell materials have been synthesized and used as model catalysts for the investigation of support effects in CO oxidation. Carbon has been selected as catalytically inert support to study the intrinsic activity of the gold nanoparticles, and for comparison, zirconia has been used as oxidic support. Au, @C materials have been synthesized through nanocasting using two different nonporous-core@mesoporous-shell exotemplates: Au@SiO(2)@ZrO(2) and Au@SiO(2)@m-SiO(2). The catalytic activity of Au, @C with a gold core of about 14 nm has been evaluated and compared with Au, @ZrO(2) of the same gold core size. The strong positive effect of metal oxide as support material on the activity of gold has been proved. Additionally, size effects were investigated using carbon as support to determine only the contribution of the nanoparticle size on the catalytic activity of gold. Therefore, Au, @C with a gold core of about 7 nm was studied showing a less pronounced positive effect on the activity than the metal oxide support effect. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A Discovery of Strong Metal-Support Bonding in Nanoengineered Au-Fe3O4 Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy.

    Science.gov (United States)

    Han, Chang Wan; Choksi, Tej; Milligan, Cory; Majumdar, Paulami; Manto, Michael; Cui, Yanran; Sang, Xiahan; Unocic, Raymond R; Zemlyanov, Dmitry; Wang, Chao; Ribeiro, Fabio H; Greeley, Jeffrey; Ortalan, Volkan

    2017-08-09

    The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" Fe 3 O 4 substrates by in situ microscopy. During in situ vacuum annealing of Au-Fe 3 O 4 dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe 3 O 4 on Au nanoparticles, the gold nanoparticles transform into the gold thin films and wet the surface of nano-Fe 3 O 4 , as the surface reduction of nano-Fe 3 O 4 proceeds. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe 3 O 4 and the extremely strong adhesion between Au and the reduced Fe 3 O 4 . This strong metal-support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and ultimately for the development of improved catalysts and functional nanostructures.

  13. Au and Pd nanoparticles supported on CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} oxides

    Energy Technology Data Exchange (ETDEWEB)

    Nascente, P.A.P., E-mail: nascente@ufscar.br [Federal University of Sao Carlos, Department of Materials Engineering, Sao Carlos, SP (Brazil); Maluf, S.S.; Afonso, C.R.M. [Federal University of Sao Carlos, Department of Materials Engineering, Sao Carlos, SP (Brazil); Landers, R. [State University of Campinas, Institute of Physics, Department of Applied Physics, Campinas, SP (Brazil); Pinheiro, A.N.; Leite, E.R. [Federal University of Sao Carlos, Department of Chemistry, Sao Carlos, SP (Brazil)

    2014-10-01

    Highlights: • CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supported Au and Pd nanoparticles. • Additions of 0.5 wt% of Au and Pd onto CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supports. • Characterization by XRD, XPS, EDS, TEM, HRTEM, STEM, and EFTEM. - Abstract: Gold and palladium nanoparticles were incorporated on CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supports prepared by a sol–gel method. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution TEM (HRTEM), scanning TEM (STEM) in high angle annular dark field mode (HAADF), and energy filtered TEM (EFTEM) using electron energy loss spectroscopy (EELS). The XRD diffractograms presented sharp and intense peaks indicating that the samples are highly crystalline, but it did not detected any peak corresponding to Au or Pd phases. This indicates that the Au and Pd NPs were incorporated into the structures of the oxides. It was not possible to obtain an Au 4f spectrum for Au/Mn{sub 2}O{sub 3} due to an overlap with the Mn 3p spectrum. The XPS Au 4f spectra for Au/CeO{sub 2} and Au/TiO{sub 2} present negative chemical shifts that could be attributed to particle-size-related properties. The XPS Pd 3d spectra indicate that for both CeO{sub 2} and TiO{sub 2} substrates, the Pd NPs were in the metallic state, while for the Mn{sub 2}O{sub 3} substrate, the Pd NPs were oxidized. The HRTEM results show the formation of nanocrystalline oxides having particles sizes between 50 and 200 nm. TEM micrographs show that the addition of Au caused the formation of Au clusters in between the CeO{sub 2} NPS, formation of Au NPs for the TiO{sub 2} support, and homogeneous distribution of Au clusters for the Mn{sub 2}O{sub 3} support. The addition of Pd yielded a homogeneous dispersion throughout the CeO{sub 2} and TiO{sub 2}, but caused the formation of Pd clusters for the Mn{sub 2}O

  14. Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

    Science.gov (United States)

    Deng, Weiping; Chen, Jiashu; Kang, Jincan; Zhang, Qinghong; Wang, Ye

    2016-05-21

    Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

  15. and Au nanoparticles for SERS applications

    Directory of Open Access Journals (Sweden)

    Fazio Enza

    2018-01-01

    Full Text Available The morphological and optical properties of noble metal nanoparticles prepared by picosecond laser generated plasmas in water were investigated. First, the ablation efficiency was maximized searching the optimal focusing conditions. The nanoparticle size, measured by Scanning Transmission Electron Microscopy, strongly depends on the laser fluence, keeping fixed the other deposition parameters such as the target to scanner objective distance and laser repetition frequency. STEM images indicate narrow gradients of NP sizes. Hence the optimization of ablation parameters favours a fine tuning of nanoparticles. UV-Visible spectroscopy helped to determine the appropriate laser wavelength to resonantly excite the localized surface plasmon to carry out Surface Enhanced Raman Scattering (SERS measurements. The SERS activity of Ag and Au substrates, obtained spraying the colloids synthesized in water, was tested using crystal violet as a probe molecule. The good SERS performance, observed at excitation wavelength 785 nm, is attributed to aggregation phenomena of nanoparticles sprayed on the support.

  16. Thiols make for better catalysts: Au nanoparticles supported on functional SBA-15 for catalysis of Ullmann-type homocouplings

    KAUST Repository

    Chen, Tianyou

    2017-09-21

    A strategy for arraying small gold nanoparticles on a mesoporous support modified with single-component or mixed self-assembled monolayers is described. The use of mixed surface modifiers allows easy access to a range of surface chemistries and modalities of interaction between nanoparticles and supports. A combination of thiol groups and linear semifluorinated chains effectively stabilized the nanoparticles against aggregation, while preserving their catalytic activity. The thiol-fluorous-supported catalyst was found active in Ullmann-type homocoupling of aryl halides and showed exceptional selectivity in this reaction.

  17. Thiols make for better catalysts: Au nanoparticles supported on functional SBA-15 for catalysis of Ullmann-type homocouplings

    KAUST Repository

    Chen, Tianyou; Chen, Batian; Bukhriakov, Konstantin; Rodionov, Valentin

    2017-01-01

    A strategy for arraying small gold nanoparticles on a mesoporous support modified with single-component or mixed self-assembled monolayers is described. The use of mixed surface modifiers allows easy access to a range of surface chemistries and modalities of interaction between nanoparticles and supports. A combination of thiol groups and linear semifluorinated chains effectively stabilized the nanoparticles against aggregation, while preserving their catalytic activity. The thiol-fluorous-supported catalyst was found active in Ullmann-type homocoupling of aryl halides and showed exceptional selectivity in this reaction.

  18. Au and AuCu Nanoparticles Supported on SBA-15 Ordered Mesoporous Titania-Silica as Catalysts for Methylene Blue Photodegradation

    Directory of Open Access Journals (Sweden)

    Isabel Barroso-Martín

    2018-05-01

    Full Text Available The photocatalytic degradation of methylene blue (MB dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt % and AuCu (Au/Cu = 1, 2.0 wt %, and supported on SBA-15-ordered mesoporous silica, with and without titania (Si/Ti = 3, in order to evaluate the versatility of this mesoporous support in this type of reaction of great impact from the environmental point of view. Samples were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, N2 adsorption-desorption at −196 °C, and X-ray photoelectron spectroscopy (XPS, so as to study their structural, optical, and chemical properties. All the prepared catalysts were found to be active in the test reaction. The bimetallic AuCu-based catalysts attained very high MB degradation values, in particular AuCu/SBA-15 titania-silica sample reached 100% of dye oxidation after the monitored reaction period (120 min.

  19. Dicationic ionic liquid mediated fabrication of Au@Pt nanoparticles supported on reduced graphene oxide with highly catalytic activity for oxygen reduction and hydrogen evolution

    Science.gov (United States)

    Shi, Ya-Cheng; Chen, Sai-Sai; Feng, Jiu-Ju; Lin, Xiao-Xiao; Wang, Weiping; Wang, Ai-Jun

    2018-05-01

    Ionic liquids as templates or directing agents have attracted great attention for shaping-modulated synthesis of advanced nanomaterials. In this work, reduced graphene oxide supported uniform core-shell Au@Pt nanoparticles (Au@Pt NPs/rGO) were fabricated by a simple one-pot aqueous approach, using N-methylimidazolium-based dicationic ionic liquid (1,1-bis(3-methylimadazoilum-1-yl)butylene bromide, [C4(Mim)2]2Br) as the shape-directing agent. The morphology evolution, structural information and formation mechanism of Au@Pt NPs anchored on rGO were investigated by a series of characterization techniques. The obtained nanocomposites displayed superior electrocatalytic features toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) compared with commercial Pt/C catalyst. This approach provides a novel route for facile synthesis of nanocatalysts in fuel cells.

  20. Preparation and characterization of mesoporous TiO{sub 2}-sphere-supported Au-nanoparticle catalysts with high activity for CO oxidation at ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lili; Huang, Shouying; Zhu, Baolin; Zhang, Shoumin; Huang, Weiping, E-mail: hwp914@nankai.edu.cn [Nankai University, College of Chemistry, The Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), and Tianjin Key Lab of Metal and Molecule-based Material Chemistry (China)

    2016-11-15

    Mesoporous TiO{sub 2}-sphere-supported Au-nanoparticles (Au/m-TiO{sub 2}-spheres) catalysts have been synthesized by a simple method using tetrabutyl titanate as TiO{sub 2} precursor and characterized with XRD, BET, ICP, SEM, TEM, UV-Vis DRS, XPS, as well as FT-IR. The samples with the size in the range of 200–400 nm were almost perfectly spherical. The average diameter of pores was about 3.6 nm, and the mesopore size distribution was in the range of 2–6 nm with a narrow distribution. When the catalyst was calcined at 300 °C, the Au NPs with the size ca. 5 nm were highly dispersed on the surfaces of m-TiO{sub 2} spheres and partially embedded in the supports. Remarkably, the specific surface area of the Au/m-TiO{sub 2}-spheres was as high as 117 m{sup 2} g{sup −1}. The CO-adsorbed catalyst showed an apparent IR adsorption peak at 1714 cm{sup −1} that matched with bridging model CO. It means the catalysts should be of high catalytic activity for the CO oxidation due to they could adsorb and activate CO commendably. When Au-content was 0.48 wt.%, the Au/m-TiO{sub 2}-spheres could convert CO completely into CO{sub 2} at ambient temperature.

  1. Novel synthesis of core-shell Au-Pt dendritic nanoparticles supported on carbon black for enhanced methanol electro-oxidation

    Science.gov (United States)

    Cao, Ribing; Xia, Tiantian; Zhu, Ruizhi; Liu, Zhihua; Guo, Jinming; Chang, Gang; Zhang, Zaoli; Liu, Xiong; He, Yunbin

    2018-03-01

    Core-shell Au-Pt dendritic nanoparticles (Au-Pt NPs) has been synthesized via a facile seed-mediated growth method, in which dendritic Pt nanoparticles as shell grow on the surface of gold nanocores by using ascorbic acid (AA) as "green" reducing reagents. The morphologies and compositions of the as-prepared nanocomposites with core-shell structure are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical experiments, including cyclic voltammetry (CV) and chronoamperometry (CA) are performed to investigate the electrocatalytic properties of the Au-Pt NPs loaded carbon black composites (Au-Pt NPs/V) towards methanol oxidation in an alkaline solution. It is found that the reduction time of AA could regulate the thickness and amount of Pt on the Au nanocores, which significantly affect catalytic activity of the Au-Pt NPs/V toward methanol oxidation. Au-Pt NPs/V with optimum reduction time 4 h exhibit 2.3-times higher electrocatalytic activity than that of a commercial catalyst (Pt/carbon black) and an excellent CO tolerance toward methanol oxidation. This behavior is attributed to large active electrochemical area of the bimetallic nanocomposites and the change in the electronic structure of Pt when Au surface modified with fewer Pt nanoparticles.

  2. Effect of Au Precursor and Support on the Catalytic Activity of the Nano-Au-Catalysts for Propane Complete Oxidation

    Directory of Open Access Journals (Sweden)

    Arshid M. Ali

    2015-01-01

    Full Text Available Catalytic activity of nano-Au-catalyst(s for the complete propane oxidation was investigated. The results showed that the nature of both Au precursor and support strongly influences catalytic activity of the Au-catalyst(s for the propane oxidation. Oxidation state, size, and dispersion of Au nanoparticles in the Au-catalysts, surface area, crystallinity, phase structure, and redox property of the support are the key aspects for the complete propane oxidation. Among the studied Au-catalysts, the AuHAuCl4-Ce catalyst is found to be the most active catalyst.

  3. Au nanoparticles films used in biological sensing

    International Nuclear Information System (INIS)

    Rosales Perez, M; Delgado Macuil, R; Rojas Lopez, M; Gayou, V L; Sanchez Ramirez, J F

    2009-01-01

    Lactobacillus para paracasei are used commonly as functional food and probiotic substances. In this work Au nanoparticles self-assembled films were used for Lactobacillus para paracasei determination at five different concentrations. Functionalized substrates were immersed in a colloidal solution for one and a half hour at room temperature and dried at room temperature during four hours. After that, drops of Lactobacillus para paracasei in aqueous solution were put into the Au nanoparticles film and let dry at room temperature for another two hours. Infrared spectroscopy in attenuated total reflectance sampling mode was used to observe generation peaks due to substrate silanization, enhancement of Si-O band intensity due to the Au colloids added to silanized substrate and also to observe the enhancement of Lactobacillus para paracasei infrared intensity of the characteristic frequencies at 1650, 1534 and 1450 cm -1 due to surface enhancement infrared absorption.

  4. Au nanoparticles films used in biological sensing

    Energy Technology Data Exchange (ETDEWEB)

    Rosales Perez, M; Delgado Macuil, R; Rojas Lopez, M; Gayou, V L [Centro de Investigacion en BiotecnologIa Aplicada del IPN, Tepetitla Tlaxcala Mexico C.P. 90700 (Mexico); Sanchez Ramirez, J F, E-mail: mrosalespe@ipn.m [CICATA Legaria Instituto Politecnico Nacional, Mexico Distrito Federal (Mexico)

    2009-05-01

    Lactobacillus para paracasei are used commonly as functional food and probiotic substances. In this work Au nanoparticles self-assembled films were used for Lactobacillus para paracasei determination at five different concentrations. Functionalized substrates were immersed in a colloidal solution for one and a half hour at room temperature and dried at room temperature during four hours. After that, drops of Lactobacillus para paracasei in aqueous solution were put into the Au nanoparticles film and let dry at room temperature for another two hours. Infrared spectroscopy in attenuated total reflectance sampling mode was used to observe generation peaks due to substrate silanization, enhancement of Si-O band intensity due to the Au colloids added to silanized substrate and also to observe the enhancement of Lactobacillus para paracasei infrared intensity of the characteristic frequencies at 1650, 1534 and 1450 cm{sup -1} due to surface enhancement infrared absorption.

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

    DEFF Research Database (Denmark)

    Su, Ren; Tiruvalam, Ramchandra; He, Qian

    2012-01-01

    Noble metal nanoparticles (Au, Pd, AuPd alloys) with a narrow size distribution supported on nanocrystalline TiO2 (M/TiO2) have been synthesized via a sol-immobilization route. The effect of metal identity and size on the photocatalytic performance of M/TiO2 has been systematically investigated u...

  6. La-doped Al2O3 supported Au nanoparticles: highly active and selective catalysts for PROX under PEMFC operation conditions.

    Science.gov (United States)

    Lin, Qingquan; Qiao, Botao; Huang, Yanqiang; Li, Lin; Lin, Jian; Liu, Xiao Yan; Wang, Aiqin; Li, Wen-Cui; Zhang, Tao

    2014-03-14

    La-doped γ-Al2O3 supported Au catalysts show high activity and selectivity for the PROX reaction under PEMFC operation conditions. The superior performance is attributed to the formation of LaAlO3, which suppresses H2 oxidation and strengthens CO adsorption on Au sites, thereby improving competitive oxidation of CO at elevated temperature.

  7. Electric field changes on Au nanoparticles on semiconductor supports--the molecular voltmeter and other methods to observe adsorbate-induced charge-transfer effects in Au/TiO2 nanocatalysts.

    Science.gov (United States)

    McEntee, Monica; Stevanovic, Ana; Tang, Wenjie; Neurock, Matthew; Yates, John T

    2015-02-11

    Infrared (IR) studies of Au/TiO2 catalyst particles indicate that charge transfer from van der Waals-bound donor or acceptor molecules on TiO2 to or from Au occurs via transport of charge carriers in the semiconductor TiO2 support. The ΔνCO on Au is shown to be proportional to the polarizability of the TiO2 support fully covered with donor or acceptor molecules, producing a proportional frequency shift in νCO. Charge transfer through TiO2 is associated with the population of electron trap sites in the bandgap of TiO2 and can be independently followed by changes in photoluminescence intensity and by shifts in the broad IR absorbance region for electron trap sites, which is also proportional to the polarizability of donors by IR excitation. Density functional theory calculations show that electron transfer from the donor molecules to TiO2 and to supported Au particles produces a negative charge on the Au, whereas the transfer from the Au particles to the TiO2 support into acceptor molecules results in a positive charge on the Au. These changes along with the magnitudes of the shifts are consistent with the Stark effect. A number of experiments show that the ∼3 nm Au particles act as "molecular voltmeters" in influencing ΔνCO. Insulator particles, such as SiO2, do not display electron-transfer effects to Au particles on their surface. These studies are preliminary to doping studies of semiconductor-oxide particles by metal ions which modify Lewis acid/base oxide properties and possibly strongly modify the electron-transfer and catalytic activity of supported metal catalyst particles.

  8. Controlled synthesis of PbS-Au nanostar-nanoparticle heterodimers and cap-like Au nanoparticles

    Science.gov (United States)

    Zhao, Nana; Li, Lianshan; Huang, Teng; Qi, Limin

    2010-11-01

    Uniform PbS-Au nanostar-nanoparticle heterodimers consisting of one Au nanoparticle grown on one horn of a well-defined six-horn PbS nanostar were prepared using the PbS nanostars as growth substrates for the selective deposition of Au nanoparticles. The size of the Au nanoparticles on the horns of the PbS nanostars could be readily adjusted by changing the PbS concentration for the deposition of Au nanoparticles. An optimum cetyltrimethylammonium bromide concentration and temperature were essential for the selective deposition of uniform Au nanoparticles on single horns of the PbS nanostars. Unusual PbS-Au nanoframe-nanoparticle heterodimers were obtained by etching the PbS-Au nanostar-nanoparticle heterodimers with oxalic acid while novel cap-like Au nanoparticles were obtained by etching with hydrochloric acid. The obtained heterodimeric nanostructures and cap-like nanoparticles are promising candidates for anisotropic nanoscale building blocks for the controllable assembly of useful, complex architectures.

  9. Defect-rich Ni-Ti layered double hydroxide as a highly efficient support for Au nanoparticles in base-free and solvent-free selective oxidation of benzyl alcohol.

    Science.gov (United States)

    Liu, Mengran; Fan, Guoli; Yu, Jiaying; Yang, Lan; Li, Feng

    2018-04-17

    Tuning the surface properties of supported metal catalysts is of vital importance for governing their catalytic performances in nanocatalysis. Here, we report highly dispersed nanometric gold nanoparticles (NPs) supported on Ni-Ti layered double hydroxides (NiTi-LDHs), which were employed in solvent-free and base-free selective oxidation of benzyl alcohol. A series of characterization techniques demonstrated that defect-rich NiTi-LDHs could efficiently stabilize Au NPs and decrease surface electron density of Au NPs. The as-formed Au/NiTi-LDH catalyst with a Ni/Ti molar ratio of 3 : 1 and an Au loading of 0.71 wt% yielded the highest turnover frequency value of ∼4981 h-1 at 120 °C among tested Au/NiTi-LDH catalysts with different Ni/Ti molar ratios, along with a high benzaldehyde selectivity of 98%. High catalytic efficiency of the catalyst was mainly correlated with surface cooperation between unique defects (i.e. defective Ti3+ species and oxygen vacancies) and abundant hydroxyl groups on the brucite-like layers of the NiTi-LDH support, which could lead to the preferential adsorption and activation of an alcohol hydroxyl moiety in benzyl alcohol and oxygen molecule, as well as the formation of more electron-deficient Ni3+ and Au0 species on the catalyst surface. Furthermore, the present Au/NiTi-LDH catalyst tolerated the oxidation of a wide variety of substrate structures into the corresponding aldehydes, acids or ketones. Our primary results illustrate that defect-rich NiTi-LDHs are promising supports which can efficiently modify surface structure and electronic properties of supported metal catalysts and consequently improve their catalytic performances.

  10. Au-nanoparticles grafted on plasma treated PE

    International Nuclear Information System (INIS)

    Svorcik, V.; Chaloupka, A.; Rezanka, P.; Slepicka, P.; Kolska, Z.; Kasalkova, N.; Hubacek, T.; Siegel, J.

    2010-01-01

    Polyethylene (PE) surface was treated with Ar plasma. Activated surface was grafted from methanol solution of 1,2-ethanedithiol. Then the sample was immersed into freshly prepared colloid solution of Au-nanoparticles. Finally Au layer was sputtered on the samples. Properties of the modified PE were studied using various methods: AFM, EPR, RBS and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain (AFM) and creation of free radicals by EPR. After grafting with dithiol, the concentration of free radicals declines. The presence of Au and S in the surface layer after the coating with Au-nanoparticles was proved by RBS. Plasma treatment changes PE surface morphology and increases surface roughness, too. Another significant change in surface morphology and roughness was observed after deposition of Au-nanoparticles. Nanoindentation measurements show that the grafting with Au-nanoparticles increases adhesion of subsequently sputtered Au layer.

  11. The point-defect of carbon nanotubes anchoring Au nanoparticles

    DEFF Research Database (Denmark)

    Lv, Y. A.; Cui, Y. H.; Li, X. N.

    2010-01-01

    The understanding of the interaction between Au and carbon nanotubes (CNTs) is very important since Au/CNTs composites have wide applications in many fields. In this study, we investigated the dispersion of Au nanoparticles on the CNTs by transmission electron microscopy and the bonding mechanism...

  12. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Directory of Open Access Journals (Sweden)

    M. Vinod

    2014-12-01

    Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  13. Magnetic order of Au nanoparticle with clean surface

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Ryuju; Ishikawa, Soichiro; Sato, Hiroyuki; Sato, Tetsuya, E-mail: satoh@appi.keio.ac.jp

    2015-11-01

    Au nanoparticles, which are kept in vacuum after the preparation by gas evaporation method, show ferromagnetism even in 1.7 nm in diameter. The intrinsic magnetism is examined by detecting the disappearance of spontaneous magnetization in Au bulk prepared by heating the nanoparticles without exposure to the air. The temperature dependence of spontaneous magnetization is not monotonic and the increase in magnetization is observed after Au nanoparticles are exposed to the air. The magnetic behavior can be interpreted by the ferrimagnetic-like core–shell structure with shell thickness of 0.16±0.01 nm and magnetic moment of (1.5±0.1)×10{sup −2} μ{sub B}/Au atom, respectively. - Highlights: • Au nanoparticles with clean surface were prepared by the gas evaporation method. • The spontaneous magnetization was observed in Au nanoparticles. • Temperature dependent spontaneous magnetization of smaller Au particles was not monotonic. • The magnetic behavior was interpreted by the ferrimagnetic-like core–shell model. • The shell thickness and the magnetic moment per Au atom were estimated.

  14. The effect of Au amount on size uniformity of self-assembled Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S-H; Wang, D-C; Chen, G-Y; Chen, K-Y [Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Taiwan (China)

    2008-03-15

    The self-assembled fabrication of nanostructure, a dreaming approach in the area of fabrication engineering, is the ultimate goal of this research. A finding was proved through previous research that the size of the self-assembled gold nanoparticles could be controlled with the mole ratio between AuCl{sub 4}{sup -} and thiol. In this study, the moles of Au were fixed, only the moles of thiol were adjusted. Five different mole ratios of Au/S with their effect on size uniformity were investigated. The mole ratios were 1:1/16, 1:1/8, 1:1, 1:8, 1:16, respectively. The size distributions of the gold nanoparticles were analyzed by Mac-View analysis software. HR-TEM was used to derive images of self-assembled gold nanoparticles. The result reached was also the higher the mole ratio between AuCl{sub 4}{sup -} and thiol the bigger the self-assembled gold nanoparticles. Under the condition of moles of Au fixed, the most homogeneous nanoparticles in size distribution derived with the mole ratio of 1:1/8 between AuCl{sub 4}{sup -} and thiol. The obtained nanoparticles could be used, for example, in uniform surface nanofabrication, leading to the fabrication of ordered array of quantum dots.

  15. Spin Polarization and Quantum Spins in Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    Wen-Hsien Li

    2013-08-01

    Full Text Available The present study focuses on investigating the magnetic properties and the critical particle size for developing sizable spontaneous magnetic moment of bare Au nanoparticles. Seven sets of bare Au nanoparticle assemblies, with diameters from 3.5 to 17.5 nm, were fabricated with the gas condensation method. Line profiles of the X-ray diffraction peaks were used to determine the mean particle diameters and size distributions of the nanoparticle assemblies. The magnetization curves M(Ha reveal Langevin field profiles. Magnetic hysteresis was clearly revealed in the low field regime even at 300 K. Contributions to the magnetization from different size particles in the nanoparticle assemblies were considered when analyzing the M(Ha curves. The results show that the maximum particle moment will appear in 2.4 nm Au particles. A similar result of the maximum saturation magnetization appearing in 2.3 nm Au particles is also concluded through analysis of the dependency of the saturation magnetization MP on particle size. The MP(d curve departs significantly from the 1/d dependence, but can be described by a log-normal function. Magnetization can be barely detected for Au particles larger than 27 nm. Magnetic field induced Zeeman magnetization from the quantum confined Kubo gap opening appears in Au nanoparticles smaller than 9.5 nm in diameter.

  16. Prolonged reorganization of thiol-capped Au nanoparticles layered structures

    Directory of Open Access Journals (Sweden)

    Sarathi Kundu

    2013-09-01

    Full Text Available Prolonged reorganization behaviour of mono-, di-, tri- and multi-layer films of Au nanoparticles prepared by Langmuir-Blodgett method on hydrophobic Si(001 substrates have been studied by using X-ray scattering techniques. Out-of-plane study shows that although at the initial stage the reorganization occurs through the compaction of the films keeping the layered structure unchanged but finally all layered structures modify to monolayer structure. Due to this reorganization the Au density increases within the nanometer thick films. In-plane study shows that inside the reorganized films Au nanoparticles are distributed randomly and the particle size modifies as the metallic core of Au nanoparticles coalesces.

  17. Electronic and magnetic properties of MnAu nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Safi 46000 (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Mounkachi, O; El moussaoui, H. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2014-03-15

    Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles.

  18. Electronic and magnetic properties of MnAu nanoparticles

    International Nuclear Information System (INIS)

    Masrour, R.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.; Mounkachi, O; El moussaoui, H.

    2014-01-01

    Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles

  19. Unravelling Thiol’s Role in Directing Asymmetric Growth of Au Nanorod–Au Nanoparticle Dimers

    KAUST Repository

    Huang, Jianfeng

    2015-12-15

    Asymmetric nanocrystals have practical significance in nanotechnologies but present fundamental synthetic challenges. Thiol ligands have proven effective in breaking the symmetric growth of metallic nanocrystals but their exact roles in the synthesis remain elusive. Here, we synthesized an unprecedented Au nanorod-Au nanoparticle (AuNR-AuNP) dimer structure with the assistance of a thiol ligand. On the basis of our experimental observations, we unraveled for the first time that the thiol could cause an inhomogeneous distribution of surface strains on the seed crystals as well as a modulated reduction rate of metal precursors, which jointly induced the asymmetric growth of monometallic dimers. © 2015 American Chemical Society.

  20. Fabrication of catalytically active Au/Pt/Pd trimetallic nanoparticles by rapid injection of NaBH{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haijun, E-mail: zhanghaijun@wust.edu.cn [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China); Lu, Lilin [College of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); Cao, Yingnan; Du, Shuang [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China); Cheng, Zhong [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Zhang, Shaowei [State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2014-01-01

    Graphical abstract: The synthesis and characterization of 2.0 nm-diameter Au/Pt/Pd nanoparticles are reported. The catalytic activity for glucose oxidation of the nanoparticles is several times higher than that of Au nanoparticles with nearly same size. - Highlights: • PVP-protected Au/Pt/Pd trimetallic nanoparticles (TNPs) of 2.0 nm in diameter were prepared. • The catalytic activity of TNPs is several times higher than that of Au nanoparticles. • Negatively charged Au atoms in the TNPs were confirmed by DFT calculation. - Abstract: Au/Pt/Pd trimetallic nanoparticles (TNPs) with an alloyed structure and an average diameter of about 2.0 nm were prepared via reducing the corresponding ions with rapidly injected NaBH{sub 4}, and characterized by UV–vis, TEM and HR-TEM. The catalytic activity of as-prepared TNPs for the aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with about the same average size, which could be attributed to the catalytically active sites provided by the negatively charged Au atoms as a result of the electron donation from the neighboring Pd atoms. This was well supported by the electron density calculations based on the density functional theory.

  1. Fabrication of catalytically active Au/Pt/Pd trimetallic nanoparticles by rapid injection of NaBH4

    International Nuclear Information System (INIS)

    Zhang, Haijun; Lu, Lilin; Cao, Yingnan; Du, Shuang; Cheng, Zhong; Zhang, Shaowei

    2014-01-01

    Graphical abstract: The synthesis and characterization of 2.0 nm-diameter Au/Pt/Pd nanoparticles are reported. The catalytic activity for glucose oxidation of the nanoparticles is several times higher than that of Au nanoparticles with nearly same size. - Highlights: • PVP-protected Au/Pt/Pd trimetallic nanoparticles (TNPs) of 2.0 nm in diameter were prepared. • The catalytic activity of TNPs is several times higher than that of Au nanoparticles. • Negatively charged Au atoms in the TNPs were confirmed by DFT calculation. - Abstract: Au/Pt/Pd trimetallic nanoparticles (TNPs) with an alloyed structure and an average diameter of about 2.0 nm were prepared via reducing the corresponding ions with rapidly injected NaBH 4 , and characterized by UV–vis, TEM and HR-TEM. The catalytic activity of as-prepared TNPs for the aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with about the same average size, which could be attributed to the catalytically active sites provided by the negatively charged Au atoms as a result of the electron donation from the neighboring Pd atoms. This was well supported by the electron density calculations based on the density functional theory

  2. Thermally stable nanoparticles on supports

    Science.gov (United States)

    Roldan Cuenya, Beatriz; Naitabdi, Ahmed R.; Behafarid, Farzad

    2012-11-13

    An inverse micelle-based method for forming nanoparticles on supports includes dissolving a polymeric material in a solvent to provide a micelle solution. A nanoparticle source is dissolved in the micelle solution. A plurality of micelles having a nanoparticle in their core and an outer polymeric coating layer are formed in the micelle solution. The micelles are applied to a support. The polymeric coating layer is then removed from the micelles to expose the nanoparticles. A supported catalyst includes a nanocrystalline powder, thin film, or single crystal support. Metal nanoparticles having a median size from 0.5 nm to 25 nm, a size distribution having a standard deviation .ltoreq.0.1 of their median size are on or embedded in the support. The plurality of metal nanoparticles are dispersed and in a periodic arrangement. The metal nanoparticles maintain their periodic arrangement and size distribution following heat treatments of at least 1,000.degree. C.

  3. Computer simulation of formation and decomposition of Au13 nanoparticles

    Science.gov (United States)

    Stishenko, P.; Svalova, A.

    2017-08-01

    To study the Ostwald ripening process of Au13 nanoparticles a two-scale model is constructed: analytical approximation of average nanoparticle energy as function of nanoparticle size and structural motive, and the Monte Carlo model of 1000 particles ensemble. Simulation results show different behavior of particles of different structural motives. The change of the distributions of atom coordination numbers during the Ostwald ripening process was observed. The nanoparticles of the equal size and shape with the face-centered cubic structure of the largest sizes appeared to be the most stable.

  4. One step electrochemical synthesis of bimetallic PdAu supported on nafion–graphene ribbon film for ethanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Shendage, Suresh S., E-mail: sureshsshendage@gmail.com; Singh, Abilash S.; Nagarkar, Jayashree M., E-mail: jm.nagarkar@ictmumbai.edu.in

    2015-10-15

    Highlights: • Electrochemical deposition of bimetallic PdAu NPs. • Highly loaded PdAu NPs are obtained. • Nafion–graphene supported PdAu NPs shows good activity for ethanol electrooxidation. - Abstract: A nafion–graphene ribbon (Nf–GR) supported bimetallic PdAu nanoparticles (PdAu/Nf–GR) catalyst was prepared by electrochemical codeposition of Pd and Au at constant potential. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The average particle size of PdAu nanoparticles (NPs) determined from XRD was 3.5 nm. The electrocatalytic activity of the PdAu/Nf–GR catalyst was examined by cyclic voltametry. It was observed that the as prepared catalyst showed efficient activity and good stability for ethanol electrooxidation in alkaline medium.

  5. Water-dispersable hybrid Au-Pd nanoparticles as catalysts in ethanol oxidation, aqueous phase Suzuki-Miyaura and Heck reactions

    KAUST Repository

    Song, Hyon Min; Moosa, Basem; Khashab, Niveen M.

    2012-01-01

    The catalytic activities of water-dispersable Au@Pd core-shell nanoparticles (NPs) and Au-Pd alloy NPs were examined. There is growing interest in Au-Pd hybridized NPs in a supported matrix or non-supported forms as catalysts in various reactions

  6. Theoretical studies of acrolein hydrogenation on Au20 nanoparticle

    Science.gov (United States)

    Li, Zhe; Chen, Zhao-Xu; He, Xiang; Kang, Guo-Jun

    2010-05-01

    Gold nanoparticles play a key role in catalytic processes. We investigated the kinetics of stepwise hydrogenation of acrolein on Au20 cluster model and compared with that on Au(110) surface. The rate-limiting step barrier of CC reduction is about 0.5 eV higher than that of CO hydrogenation on Au(110) surface. On Au20 nanoparticle, however, the energy barrier of the rate-determining step for CC hydrogenation turns out to be slightly lower than the value for the CO reduction. The selectivity difference on the two substrate models are attributed to different adsorption modes of acrolein: via the CC on Au20, compared to through both CC and CO on Au(110). The preference switch implies that the predicted selectivity of competitive hydrogenation depends on substrate model sensitively, and particles with more low-coordinated Au atoms than flat surfaces are favorable for CC hydrogenation, which is in agreement with experimental result.

  7. Au3+/Au0 Supported on Chromium(III Terephthalate Metal Organic Framework (MIL-101 as an Efficient Heterogeneous Catalystfor Three-Component Coupling Synthesis of Propargylamines

    Directory of Open Access Journals (Sweden)

    Lili Liu

    2017-01-01

    Full Text Available Post-synthesis modification is a useful method for the functionalization of metal–organic frameworks (MOFs. A novel catalyst Au@MIL-101-ED-SA (ED = ethylenediamine, SA = salicylaldehyde, containing coexisting Au3+ ions and Au0 nanoparticles, was prepared successfully by post-synthesis modification with ethylenediamine, salicylaldehyde and gold. Gold nanoparticles supported on MIL-101 (Au@MIL-101 were prepared successfully by the impregnation method. Au@MIL-101-ED-SA and Au@MIL-101 were characterized by N2 adsorption–desorption, X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and inductively coupled plasma-optical emission spectrometry. Au@MIL-101-ED-SA and Au@MIL-101 were applied as environmentally friendly catalysts in the three-component coupling reaction of aldehydes, amines, and alkynes for the preparation of diverse propargylamines. Au@MIL-101-ED-SA contained a fraction of cationic gold (Au3+/Au0 = 0.9 and showed higher catalytic activity than Au@MIL-101, which was prepared by the impregnation method. Furthermore, the reactions were performed under heterogeneous conditions and the novel catalyst was successfully recycled for four consecutive runs.

  8. Glucose-mediated catalysis of Au nanoparticles in microgels.

    Science.gov (United States)

    Wu, Qingshi; Cheng, Han; Chang, Aiping; Xu, Wenting; Lu, Fan; Wu, Weitai

    2015-11-18

    The catalytic activity of Au nanoparticles in phenylboronic acid-containing polymer microgels can be tuned through the swelling-deswelling transition of the microgels in response to changes in glucose concentration. Upon adding glucose, the model catalytic reduction of hydrophilic 4-nitrophenol is accelerated, while the reduction of relatively more hydrophobic nitrobenzene slows down.

  9. Visible light photoactivity of TiO{sub 2} loaded with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gołąbiewska, Anna, E-mail: annagolabiewska@o2.pl [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland); Lisowski, Wojciech [Mazovia Center for Surface Analysis, Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw (Poland); Jarek, Marcin; Nowaczyk, Grzegorz [NanoBioMedical Center, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Zielińska-Jurek, Anna; Zaleska, Adriana [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland)

    2014-10-30

    Graphical abstract: - Highlights: • Au/Pt nanoparticles enhanced TiO{sub 2} photocatalytic activity under visible irradiation. • Higher photoactivity of Au/Pt-TiO{sub 2} resulted from smaller Au/Pt particles. • Intermetallic state of AuPt favors charge transfer between the metals. • TiO{sub 2} obtained by TIP hydrolysis seems to be best matrix for Au/Pt-TiO{sub 2}. - Abstract: TiO{sub 2} modified with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles have been prepared using a water-in-oil microemulsion system (water/AOT/cyclohexane) followed by calcination step. The effect of metal ratio, reducing agent type (NaBH{sub 4} or N{sub 2}H{sub 4}), TiO{sub 2} matrix type (P-25, ST-01, TiO-5, TiO{sub 2} nanotubes or TiO{sub 2} obtained by TIP hydrolysis) as well as calcination temperature (from 350 to 650 °C) were systematically investigated. Obtained photocatalysts were characterized by UV–vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning transmission microscopy (STEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity under visible light (λ > 420 nm) has been estimated in phenol degradation reaction in aqueous phase. The results showed that phenol degradation rate under visible light in the presence of TiO{sub 2} loaded with Au/Pt nanoparticles differed from 0.7 to 2.2 μmol dm{sup −3} min{sup −1} for samples prepared using different reducing agent. Sodium borohydride (NaBH{sub 4}) favors formation of smaller Au/Pt nanoparticles and higher amount gold in Au/Pt is in the form of electronegative species (Au{sup δ−}) resulted in higher photoactivity. TiO{sub 2} obtained by TIP hydrolysis in microemulsion system seems to be the best support for Au/Pt nanoparticles from all among investigated matrix. It was also observed that enhancement of calcination temperature from 450 to 650 °C resulted in rapid drop of Au/Pt-TiO{sub 2} photoactivity under visible light

  10. Au/SiO2 nanocomposite film substrates with a high number density of Au nanoparticles for molecular conductance measurement

    International Nuclear Information System (INIS)

    Kim, Dae-Gun; Koyama, Emiko; Kikkawa, Yoshihiro; Kirihara, Kazuhiro; Naitoh, Yasuhisa; Kim, Deok-Soo; Tokuhisa, Hideo; Kanesato, Masatoshi; Koshizaki, Naoto

    2007-01-01

    Au/SiO 2 nanocomposite films consisting of an extremely high number density of Au nanoparticles dispersed in a SiO 2 matrix a few nanometres thick were deposited by a co-sputtering method, and employed for molecular conductance measurement by immobilizing and bridging conjugated biphenyl molecules on dispersed Au nanoparticles. The number density of Au nanoparticles in the insulating SiO 2 matrix was approximately 14 000 μm 2 , and the average interparticle distance from their neighbours was about 8 nm. The current increased considerably up to the range of nanoamperes after the immobilization of the conjugated biphenyl molecules, 10 5 times larger than without molecules before immobilization. Although the Au nanoparticles can be connected to only 30% of all combinations of neighbouring Au nanoparticles by biphenyl molecules 2.4 nm long from the topological analysis, the biphenyl molecules can bridge most of the Au nanoparticles, and their bridging continuity is over 100 nm in length. Thus the measured current is suggested to come from the continuously bridged molecules between the Au nanoparticles. Furthermore the I-V data of the whole Au/SiO 2 nanocomposite film immobilized with conjugated molecules are confirmed to be in a reasonable range in comparison with the scanning tunnelling spectroscopy data of similar conjugated molecules

  11. Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tianyu; Chen, Wei; Hua, Yuxiang; Liu, Xiaoheng, E-mail: xhliu@mail.njust.edu.cn

    2017-01-15

    Highlights: • An inversed Au/ZnO nanostructure was fabricated with ZnO loaded onto Au. • The Au/ZnO nanocomposites showed enhanced properties in visible-light photocatalysis. • The SPR effect of Au was considered important for visible-light photocatalysis. - Abstract: In this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.

  12. Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light

    International Nuclear Information System (INIS)

    Liu, Tianyu; Chen, Wei; Hua, Yuxiang; Liu, Xiaoheng

    2017-01-01

    Highlights: • An inversed Au/ZnO nanostructure was fabricated with ZnO loaded onto Au. • The Au/ZnO nanocomposites showed enhanced properties in visible-light photocatalysis. • The SPR effect of Au was considered important for visible-light photocatalysis. - Abstract: In this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.

  13. Strain Distribution of Au and Ag Nanoparticles Embedded in Al2O3 Thin Film

    Directory of Open Access Journals (Sweden)

    Honghua Huang

    2014-01-01

    Full Text Available Au and Ag nanoparticles embedded in amorphous Al2O3 matrix are fabricated by the pulsed laser deposition (PLD method and rapid thermal annealing (RTA technique, which are confirmed by the experimental high-resolution transmission electron microscope (HRTEM results, respectively. The strain distribution of Au and Ag nanoparticles embedded in the Al2O3 matrix is investigated by the finite-element (FE calculations. The simulation results clearly indicate that both the Au and Ag nanoparticles incur compressive strain by the Al2O3 matrix. However, the compressive strain existing on the Au nanoparticle is much weaker than that on the Ag nanoparticle. This phenomenon can be attributed to the reason that Young’s modulus of Au is larger than that of Ag. This different strain distribution of Au and Ag nanoparticles in the same host matrix may have a significant influence on the technological potential applications of the Au-Ag alloy nanoparticles.

  14. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min; Anjum, Dalaver H.; Sougrat, Rachid; Hedhili, Mohamed N.; Khashab, Niveen M.

    2012-01-01

    that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au

  15. Ethanol Sensing Properties of Au-functionalized NiO Nanoparticles

    International Nuclear Information System (INIS)

    Park, Sunghoon; Kheel, Hyejoon; Sun, Gun-Joo; Hyun, Soong Keun; Park, Sang Eon; Lee, Chongmu

    2016-01-01

    Pristine and Au-functionalized nickel oxide (NiO) nanoparticles were synthesized via a simple solvo thermal route and the ethanol sensing properties of multiple-networked Au-doped and undoped NiO nanoparticle sensors were examined. The pristine and Au-functionalized NiO nanoparticle sensor showed responses of 442 and 273%, respectively, to 1000 ppm of ethanol at 325 .deg. C. The Au-functionalized NiO nanoparticle sensor showed faster response than the pristine NiO counterpart, whereas the recovery time of the former was similar to that of the latter. The optimal operating temperature of the pristine and Au-functionalized NiO nanoparticles was 325 and 350 .deg. C, respectively, by Au-doping. Both the pristine and Au-functionalized NiO nanoparticle sensors showed selectivity for ethanol gas over methanol, acetone, benzene, and toluene gases. The underlying mechanism of the enhanced sensing performance of the Au-functionalized NiO nanoparticles toward ethanol might be due to modulation of the depletion layer formed around Au particles and the Schottky barriers formed at the Au-NiO junction accompanying ethanol adsorption and desorption, the spill-over effect and high catalytic activity of Au nanoparticles and the smaller diameter of the particles in the Au-functionalized NiO sensor.

  16. Ethanol Sensing Properties of Au-functionalized NiO Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sunghoon; Kheel, Hyejoon; Sun, Gun-Joo; Hyun, Soong Keun; Park, Sang Eon; Lee, Chongmu [Inha University, Incheon (Korea, Republic of)

    2016-05-15

    Pristine and Au-functionalized nickel oxide (NiO) nanoparticles were synthesized via a simple solvo thermal route and the ethanol sensing properties of multiple-networked Au-doped and undoped NiO nanoparticle sensors were examined. The pristine and Au-functionalized NiO nanoparticle sensor showed responses of 442 and 273%, respectively, to 1000 ppm of ethanol at 325 .deg. C. The Au-functionalized NiO nanoparticle sensor showed faster response than the pristine NiO counterpart, whereas the recovery time of the former was similar to that of the latter. The optimal operating temperature of the pristine and Au-functionalized NiO nanoparticles was 325 and 350 .deg. C, respectively, by Au-doping. Both the pristine and Au-functionalized NiO nanoparticle sensors showed selectivity for ethanol gas over methanol, acetone, benzene, and toluene gases. The underlying mechanism of the enhanced sensing performance of the Au-functionalized NiO nanoparticles toward ethanol might be due to modulation of the depletion layer formed around Au particles and the Schottky barriers formed at the Au-NiO junction accompanying ethanol adsorption and desorption, the spill-over effect and high catalytic activity of Au nanoparticles and the smaller diameter of the particles in the Au-functionalized NiO sensor.

  17. Thermal induced structural transformation of bimetallic AuPd nanoparticles

    International Nuclear Information System (INIS)

    Bruma, A; Li, Z Y

    2014-01-01

    High Angle Annular Dark Field Scanning Transmission Electron Microscope (HAADF-STEM) has been employed for the study of thermal effects of structural transformation of AuPd nanoparticles produced by physical vapour deposition. Depending on the duration of annealing at a temperature of 500 K, atomic resolved imaging analysis reveals the formation of various structure morphologies from the ordered L1 2 superlattice to the core-shell structure. The effects of Pd-oxides are also discussed

  18. A simple approach for facile synthesis of Ag, anisotropic Au and bimetallic (Ag/Au) nanoparticles using cruciferous vegetable extracts

    International Nuclear Information System (INIS)

    Jacob, Jasmine; Mukherjee, Tulsi; Kapoor, Sudhir

    2012-01-01

    We present a simple and straightforward approach for the synthesis and stabilization of relatively monodisperse Ag, Au and bimetallic (Ag/Au) nanoparticles by using cruciferous vegetable (green/red) extracts by simply adjusting the pH environment in the aqueous medium. The vegetable extracts act both as reducing and capping agents. The monometallic and bimetallic nanoparticles of Ag and Au so obtained were characterized by UV–visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is shown that red cabbage extract can be used for the preparation of anisotropic Au nanoparticles. The formation of Au anisotropic nanoparticles was found to depend on a number of environmental factors, such as the pH of the reaction medium, reaction time, and initial reactant concentrations. Additionally, it is shown that these extract-stabilized Au and Ag nanoparticles can be used as a seed for preparation of bimetallic Au/Ag nanoparticles. For bimetallic alloy nanoparticles the absorption peak was observed between the two maxima of the corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changed linearly with increasing Au mole ratio content in various alloy compositions. It has been shown that the formation of hollow Au spheres depends on the experimental conditions. - Graphical abstract: TEM image of gold nanoparticles at pH 3.27 formed by red cabbage extract. Highlights: ► First report on the reactivity of the extracts toward metal ions using a spectrophotometric technique. ► Red cabbage extract has better reducing properties than green cabbage extract. ► Red cabbage extract can reduce metal ions at any pH. ► Reduction of metal ions can have important consequences in the study of soil chemistry.

  19. A simple approach for facile synthesis of Ag, anisotropic Au and bimetallic (Ag/Au) nanoparticles using cruciferous vegetable extracts

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, Jasmine; Mukherjee, Tulsi; Kapoor, Sudhir, E-mail: sudhirk@barc.gov.in

    2012-10-01

    We present a simple and straightforward approach for the synthesis and stabilization of relatively monodisperse Ag, Au and bimetallic (Ag/Au) nanoparticles by using cruciferous vegetable (green/red) extracts by simply adjusting the pH environment in the aqueous medium. The vegetable extracts act both as reducing and capping agents. The monometallic and bimetallic nanoparticles of Ag and Au so obtained were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is shown that red cabbage extract can be used for the preparation of anisotropic Au nanoparticles. The formation of Au anisotropic nanoparticles was found to depend on a number of environmental factors, such as the pH of the reaction medium, reaction time, and initial reactant concentrations. Additionally, it is shown that these extract-stabilized Au and Ag nanoparticles can be used as a seed for preparation of bimetallic Au/Ag nanoparticles. For bimetallic alloy nanoparticles the absorption peak was observed between the two maxima of the corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changed linearly with increasing Au mole ratio content in various alloy compositions. It has been shown that the formation of hollow Au spheres depends on the experimental conditions. - Graphical abstract: TEM image of gold nanoparticles at pH 3.27 formed by red cabbage extract. Highlights: Black-Right-Pointing-Pointer First report on the reactivity of the extracts toward metal ions using a spectrophotometric technique. Black-Right-Pointing-Pointer Red cabbage extract has better reducing properties than green cabbage extract. Black-Right-Pointing-Pointer Red cabbage extract can reduce metal ions at any pH. Black-Right-Pointing-Pointer Reduction of metal ions can have important consequences in the study of soil chemistry.

  20. Photoluminescence from Au nanoparticles embedded in Au:oxide composite films

    Science.gov (United States)

    Liao, Hongbo; Wen, Weijia; Wong, George K.

    2006-12-01

    Au:oxide composite multilayer films with Au nanoparticles sandwiched by oxide layers (such as SiO2, ZnO, and TiO2) were prepared in a magnetron sputtering system. Their photoluminescence (PL) spectra were investigated by employing a micro-Raman system in which an Argon laser with a wavelength of 514 nm was used as the pumping light. Distinct PL peaks located at a wavelength range between 590 and 680 nm were observed in most of our samples, with Au particle size varying from several to hundreds of nanometers. It was found that the surface plasmon resonance (SPR) in these composites exerted a strong influence on the position of the PL peaks but had little effect on the PL intensity.

  1. Photoluminescence from Au nanoparticles embedded in Au:oxide composite films

    International Nuclear Information System (INIS)

    Liao Hongbo; Wen Weijia; Wong, George K. L.

    2006-01-01

    Au:oxide composite multilayer films with Au nanoparticles sandwiched by oxide layers (such as SiO 2 , ZnO, and TiO 2 ) were prepared in a magnetron sputtering system. Their photoluminescence (PL) spectra were investigated by employing a micro-Raman system in which an Argon laser with a wavelength of 514 nm was used as the pumping light. Distinct PL peaks located at a wavelength range between 590 and 680 nm were observed in most of our samples, with Au particle size varying from several to hundreds of nanometers. It was found that the surface plasmon resonance (SPR) in these composites exerted a strong influence on the position of the PL peaks but had little effect on the PL intensity

  2. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    Science.gov (United States)

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-08

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

  3. Laser-produced Au nanoparticles as X-ray contrast agents for diagnostic imaging

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Restuccia, N.; Cuzzocrea, S.; Paterniti, I.; Ielo, I.; Pergolizzi, S.; Cutroneo, Mariapompea; Kováčik, L.

    2017-01-01

    Roč. 50, č. 1 (2017), s. 51-60 ISSN 0017-1557 R&D Projects: GA MŠk LM2015056; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389005 Keywords : Au nanoparticles * Laser * X-ray diagnostic s * medical imaging * contrast medium Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Inorganic and nuclear chemistry Impact factor: 1.638, year: 2016

  4. Synthesis by picosecond laser ablation of ligand-free Ag and Au nanoparticles for SERS applications

    Science.gov (United States)

    Fazio, Enza; Spadaro, Salvatore; Santoro, Marco; Trusso, Sebastiano; Lucotti, Andrea.; Tommasini, Matteo.; Neri, Fortunato; Maria Ossi, Paolo

    2018-01-01

    The morphological and optical properties of noble metal nanoparticles prepared by picosecond laser generated plasmas in water were investigated. First, the ablation efficiency was maximized searching the optimal focusing conditions. The nanoparticle size, measured by Scanning Transmission Electron Microscopy, strongly depends on the laser fluence, keeping fixed the other deposition parameters such as the target to scanner objective distance and laser repetition frequency. STEM images indicate narrow gradients of NP sizes. Hence the optimization of ablation parameters favours a fine tuning of nanoparticles. UV-Visible spectroscopy helped to determine the appropriate laser wavelength to resonantly excite the localized surface plasmon to carry out Surface Enhanced Raman Scattering (SERS) measurements. The SERS activity of Ag and Au substrates, obtained spraying the colloids synthesized in water, was tested using crystal violet as a probe molecule. The good SERS performance, observed at excitation wavelength 785 nm, is attributed to aggregation phenomena of nanoparticles sprayed on the support.

  5. Summary of gold nanoparticles obtained by reduction Au3+

    International Nuclear Information System (INIS)

    Corzo Lucioni, Alberto

    2012-01-01

    In the present investigation were synthesized nanoparticles (NPs) of gold by oxidation-reduction reactions at boiling temperature, starting from dilute solutions of acid tetrachloroauric: H[AuCl 4 ].3H 2 O as a precursor in the presence of organic reducing agents such as trisodium citrate: Na 3 C 6 H 5 O 7 .2H 2 O; potassium sodium tartrate: KNaC 4 H 4 O 6 .4H 2 O and sodium borohydride: inorganic reducing agent NaBH 4 . With the aim of evaluating the particle size according to the type of reducing agent, is designed a series of experiments in which the reducing agent is changed, keeping it constant concentrations, but varying the concentration of H[AuCl 4 ]. The particle size and the absorbance of the plasmon Au were measured in a particle size analyzer and a UV - visible, respectively. In turn, the effect of pH variation on the size of the NP Au, maintaining concentrations of H [AuCl 4 ] constant and reducing agent trisodium citrate, at different pH values under the same conditions. (author).

  6. Gold surfaces and nanoparticles are protected by Au(0)-thiyl species and are destroyed when Au(I)-thiolates form

    DEFF Research Database (Denmark)

    Reimers, Jeffrey R.; Ford, Michael J.; Halder, Arnab

    2016-01-01

    that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)-thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s-d hybridization and charge polarization effects that perturbatively mix in some Au(I)-thiolate character. A simple method...

  7. Synthesis of triangular Au core-Ag shell nanoparticles

    International Nuclear Information System (INIS)

    Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali

    2007-01-01

    In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules

  8. Magnetic Au Nanoparticles on Archaeal S-Layer Ghosts as Templates

    Directory of Open Access Journals (Sweden)

    Sonja Selenska-Pobell

    2011-10-01

    Full Text Available Cell‐ghosts representing empty cells of the archaeon Sulfolobus acidocaldarius, consisting only of their highly ordered and unusually stable outermost proteinaceous surface layer (S‐layer, were used as templates for Au nanoparticles fabrication. The properties of these archaeal Au nanoparticles differ significantly from those produced earlier by us onto bacterial S‐layer sheets. The archaeal Au nanoparticles, with a size of about 2.5 nm, consist exclusively of metallic Au(0, while those produced on the bacterial S‐layer had a size of about 4 nm and represented a mixture of Au(0 and Au(III in the ratio of 40 to 60 %. The most impressive feature of the archaeal Au nanoparticles is that they are strongly paramagnetic, in contrast to the bacterial ones and also to bulk gold. SQUID magnetometry and XMCD measurements demonstrated that the archaeal Au nanoparticles possess a rather large magnetic moment of about 0.1 µB/atom. HR‐ TEM‐EDX analysis revealed that the archaeal Au nanoparticles are linked to the sulfur atoms of the thiol groups of the amino acid cysteine, characteristic only for archaeal S‐layers. This is the first study demonstrating the formation of such unusually strong magnetic Au nanoparticles on a non‐modified archaeal S‐layer.

  9. Synthesis and Characterization of Poly(Amidoamine Dendrimers Encapsulatd 198Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    R. Ritawidya1,2

    2012-12-01

    Full Text Available Brachytherapy or internal radiotherapy is one of many methods used for treatment of cancer. This modality requires an agent with radionuclides that emits  or β particle with a proper energy. 198Au (99% β max = 0.96 MeV and t1/2 = 2.69 days is one of radionuclides that has been considered to be effective for the above-mentioned purpose. The purpose of this research was to synthesis and characterize poly(amidoamine (PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles as a new brachytherapy agent. PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles was successfully synthesized by a bottom-up method using sodium borohydride as a reductor. Purification was then performed by a size exclusion chromatography in order to separate large Au nanoparticles that were formed outside the cavity of PAMAM G3.0 dendrimers. Prior to the synthesis of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles, the synthetic procedure was first established by using a non-radioactive Au. The PAMAM G3.0 dendrimers encapsulated Au nanoparticles produced was then characterized by using an UV-Vis spectroscopy, a transmission electron microscopy (TEM, particle size analyzer (PSA, and an atomic absorption spectroscopy (AAS. Characterization results revealed that PAMAM G3.0 dendrimers encapsulated Au nanoparticles that were prepared from a reaction mixture of PAMAM G3.0 dendrimers and Au HAuCl4 with mol ratio of 2.8, was found to be a proper formula. It produced PAMAM G3.0 dendrimers encapsulated Au nanoparticles with diameter of 1.743 nm, spheris, uniform and drug loading value of 26.34%. This formula was then used in synthesis using radioactive Au, 198Au. Characterization results of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles gave a radiochemical purity of 99.4% and zero charge.

  10. Synthesis of Au and Au/Cu alloy nanoparticles on multiwalled carbon nanotubes by using microwave irradiation

    International Nuclear Information System (INIS)

    Rangari, Vijaya K.; Dey, Sanchita; Jeelani, Shaik

    2010-01-01

    Gold nanoparticles and gold-copper alloy nanoparticles were synthesized by reduction of chloroauric acid (HAuCl_4.xH_2O) and co-reduction of chloroauric acid (HAuCl_4.xH_2O) and Copper(II) acetate [(CH_3COO)_2Cu.H_2O] by ethylene glycol through microwave irradiation technique. In this reaction ethylene glycol used as a solvent and also reducing agent. The cetyltrimethyl ammonium bromide (CTAB) used as surfactant. Au nanoparticles and Au-Cu nanoparticles on the surface of multiwalled carbon nanotube also produced by using same procedure. The XRD analysis confirmed the formation of Au and Au-Cu alloy nanoparticles on multiwalled carbon nanotubes(CNTs). The morphology and size of the particles were examined by the transmission electron microscopy. The EDS analysis on individual particles confirmed that the presence of two metals in a particle in case of alloy nanoparticle. The results presented here show that a variety of well defined metal and metal alloy nanoparticles can be produced by using the microwave polyol process with in a short period of time. (author)

  11. Understanding promotion of photocatalytic activity of TiO2 by Au nanoparticles

    NARCIS (Netherlands)

    Amrollahi Buky, Rezvaneh; Hamdy, Mohamed S.; Mul, Guido

    2014-01-01

    Au nanoparticles prepared by deposition–precipitation were evaluated in promoting photocatalytic activity of TiO2 (P25) in the oxidation of methylcyclohexane. At 375 nm and in particular at 425 nm, Au was found to significantly enhance the rate induced by P25. Illumination of Au-promoted P25 at 525

  12. On the preferential crystallographic orientation of Au nanoparticles: Effect of electrodeposition time

    International Nuclear Information System (INIS)

    El-Deab, Mohamed S.

    2009-01-01

    The crystallographic orientation of Au nanoparticles electrodeposited at glassy carbon (nano-Au/GC) electrodes (prepared by potential step electrolysis) is markedly influenced by the width of the potential step. The oxygen reduction reaction (ORR) and the reductive desorption of cysteine have been studied on nano-Au/GC electrodes. Furthermore, electron backscatter diffraction (EBSD) technique has been used to probe the crystallographic orientation of the electrodeposited Au nanoparticles. That is, Au nanoparticles prepared in short time (5-60 s) have been found rich in the Au(1 1 1) facet orientation and are characterized by a relatively small particle size (ca. 10-50 nm) as well as high particle density (number of particles per unit area) as revealed by SEM images. Whereas Au nanoparticles prepared by longer electrolysis time (>60 s) are found to be much enriched in the Au(1 0 0) and Au(1 1 0) facets and are characterized by a relatively large particle size (>100 nm). EBSD patterns provided definitive information about the crystal orientations mapping of Au nanoparticles prepared at various deposition times.

  13. Synthesis and characterization of hollow magnetic nanospheres modified with Au nanoparticles for bio-encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Seisno, Satoshi, E-mail: seino@mit.eng.osaka-u.ac.jp; Suga, Kent; Nakagawa, Takashi; Yamamoto, Takao A.

    2017-04-01

    Hollow magnetic nanospheres modified with Au nanoparticles were successfully synthesized. Au/SiO{sub 2} nanospheres fabricated by a radiochemical process were used as templates for ferrite templating. After the ferrite plating process, Au/SiO{sub 2} templates were fully coated with magnetite nanoparticles. Dissolution of the SiO{sub 2} core lead to the formation of hollow magnetic nanospheres with Au nanoparticles inside. The hollow magnetic nanospheres consisted of Fe{sub 3}O{sub 4} grains, with an average diameter of 60 nm, connected to form the sphere wall, inside which Au grains with an average diameter of 7.2 nm were encapsulated. The Au nanoparticles immobilized on the SiO{sub 2} templates contributed to the adsorption of the Fe ion precursor and/or Fe{sub 3}O{sub 4} seeds. These hollow magnetic nanospheres are proposed as a new type of nanocarrier, as the Au grains could specifically immobilize biomolecules inside the hollow sphere. - Highlights: • A procedure to synthesize hollow magnetic nanospheres with Au inside was reported. • The Au nanoparticles inside the hollow showed high Au-S binding affinity. • The nanospheres are expected to be suitable as a new magnetic carrier for DDS.

  14. Studies on L-histidine capped Ag and Au nanoparticles for dopamine detection

    Energy Technology Data Exchange (ETDEWEB)

    Nivedhini Iswarya, Chandrasekaran; Kiruba Daniel, S.C.G. [Division of Nanoscience and Technology, Anna University-BIT Campus, Tiruchirappalli 620024 (India); Sivakumar, Muthusamy, E-mail: muthusiva@gmail.com [Division of Nanoscience and Technology, Anna University-BIT Campus, Tiruchirappalli 620024 (India); Department of Chemistry, Anna University-BIT Campus, Tiruchirappalli 620024 (India)

    2017-06-01

    This work demonstrates the effective surface functionalization of Ag, Au and bimetallic Ag-Au nanoparticles using L-histidine for colorimetric detection of dopamine (DA) which plays majorly in recognizing the neurological disorder. L-Histidine (L-His) capped Ag, Au, and bimetallic Ag-Au nanoparticles are characterized using physico-chemical techniques. The optical behaviour of nanoparticles has been analysed at various time intervals using UV–Vis absorption spectroscopy. FT-IR results provide the evidence of chemical bonding between L-histidine and metal nanoparticles. Its structure with the capping of L-His was clearly shown in HR-TEM images. The average size of nanoparticles has calculated from TEM image fringes are 11 nm, 5 nm and 6.5 nm respectively, matches with crystals size calculated from X-ray diffraction pattern. Enhanced optical nature of nanoparticles provides the best platform to develop a colorimetric-based biosensor for DA detection. After addition of DA, a rapid colour change has been noted in colloids of nanoparticles. The substantial changes in absorbance and λ{sub max} in metal nanoparticles respect to DA concentration have been observed and formulated. This is one of the successive methods for trace level determination of DA and will be going to a significant material for designing biosensor to determine DA in real extracellular body fluids. - Highlights: • L-His functionalized Ag, Au and bimetallic Ag-Au nanoparticles were prepared and its properties were studied. • L-His based Ag, Au, Ag-Au nanoparticles have characterized by spectroscopy, XRD and microscopic studies. • Enhanced optical nature of nanoparticles delivers the best platform to develop a biosensor for DA detection. • For qualitative determination of dopamine, SPR of metal nanoparticles plays a major role in dopamine determination. • This basic finding can be utilized for further identification of imbalanced DA concentration in body fluids.

  15. Synthesis and optical properties of Au decorated colloidal tungsten oxide nanoparticles

    International Nuclear Information System (INIS)

    Tahmasebi, Nemat; Mahdavi, Seyed Mohammad

    2015-01-01

    Highlights: • Tungsten oxide nanoparticles were prepared by pulsed laser ablation (PLA). • A very fine metallic Au particles or coating are decorated on the surface of tungsten oxide nanoparticles. • UV–Vis spectroscopy shows an absorption peak at ∼530 nm which is due to SPR effect of gold. • After exposing to hydrogen gas, Au/WO_3 colloidal nanoparticles show excellent gasochromic coloring. - Abstract: In this study, colloidal tungsten oxide nanoparticles were fabricated by pulsed laser ablation of tungsten target using the first harmonic of a Nd:YAG laser (1064 nm) in deionized water. After ablation, a 0.33 g/lit HAuCl_4 aqueous solution was added into as-prepared colloidal nanoparticles. In this process, Au"3"+ ions were reduced to decorate gold metallic state (Au"0) onto colloidal tungsten oxide nanoparticles surface. The morphology and chemical composition of the synthesized nanoparticles were studied by AFM, XRD, TEM and XPS techniques. UV–Vis analysis reveals a distinct absorption peak at ∼530 nm. This peak can be attributed to the surface plasmon resonance (SPR) of Au and confirms formation of gold state. Moreover, X-ray photoelectron spectroscopy reveals that Au ions’ reduction happens after adding HAuCl_4 solution into as-prepared colloidal tungsten oxide nanoparticles. Transmission electron microscope shows that an Au shell has been decorated onto colloidal WO_3 nanoparticles. Noble metal decorated tungsten oxide nanostructure could be an excellent candidate for photocatalysis, gas sensing and gasochromic applications. Finally, the gasochromic behavior of the synthesized samples was investigated by H_2 and O_2 gases bubbling into the produced colloidal Au/WO_3 nanoparticles. Synthesized colloidal nanoparticles show excellent coloration contrast (∼80%) through NIR spectra.

  16. Electrophoretic deposition on graphene of Au nanoparticles generated by laser ablation of a bulk Au target in water

    International Nuclear Information System (INIS)

    Semaltianos, N G; Hendry, E; Chang, H; Wears, M L

    2015-01-01

    The characteristic property of nanoparticles generated by laser ablation of metallic targets in liquids to be surface electrically charged can be exploited for the deposition of the nanoparticles onto electrically conducting substrates directly from the synthesized colloidal solution by using the method of electrophoretic deposition (EPD). The method benefits from the high quality of the interface between the deposited nanoparticles and the substrate due to the ligand-free nanoparticle surfaces and thus providing hybrid materials with advanced and novel properties. In this letter, an Au bulk target was laser ablated in deionized (DI) water for the generation of an Au nanoparticle colloidal solution. Under the present conditions of ablation, nanoparticles with diameters from 4 and up to 67 nm are formed in the solution with 80% of the nanoparticles having diameters below ∼20 nm. Their size distribution follows a log-normal function with a median diameter of 8.6 nm. The nanoparticles were deposited onto graphene on a quartz surface by anodic EPD performed at 30 V for 20 min and a longer time of 1 h. A quite uniform surface distribution of the nanoparticles was achieved with surface densities ranging from ∼15 to ∼40 nanoparticles per μm 2 . The hybrid materials exhibit clearly the plasmon resonance absorption of the Au nanoparticles. Deposition for short times preserves the integrity of graphene while longer time deposition leads to the conversion of graphene to graphene oxide, which is attributed to the electrochemical oxidation of graphene. (letter)

  17. Morphological effects on the selectivity of intramolecular versus intermolecular catalytic reaction on Au nanoparticles.

    Science.gov (United States)

    Wang, Dan; Sun, Yuanmiao; Sun, Yinghui; Huang, Jing; Liang, Zhiqiang; Li, Shuzhou; Jiang, Lin

    2017-06-14

    It is hard for metal nanoparticle catalysts to control the selectivity of a catalytic reaction in a simple process. In this work, we obtain active Au nanoparticle catalysts with high selectivity for the hydrogenation reaction of aromatic nitro compounds, by simply employing spine-like Au nanoparticles. The density functional theory (DFT) calculations further elucidate that the morphological effect on thermal selectivity control is an internal key parameter to modulate the nitro hydrogenation process on the surface of Au spines. These results show that controlled morphological effects may play an important role in catalysis reactions of noble metal NPs with high selectivity.

  18. The fabrication of nanopatterns with Au nanoparticles-embedded micelles via nanoimprint lithography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jung-Pil; Kim, Eun-Uk; Koh, Haeng-Deog; Kang, Nam-Goo; Jung, Gun-Young; Lee, Jae-Suk, E-mail: gyjung@gist.ac.k, E-mail: jslee@gist.ac.k [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-dong), Buk-gu Gwangju 500-712 (Korea, Republic of)

    2009-09-09

    We fabricated nanopatterns with Au nanoparticles-embedded micelles (Au-micelles) by self-assembly of block copolymers via nanoimprint lithography. The micelle structure prepared by self-assembled block copolymers was used as a template for the synthesis of Au nanoparticles (Au NPs). Au NPs were synthesized in situ inside the micelles of polystyrene-block-poly(2-vinylpyridine) (PS- b-P2VP). Au-micelles were arranged on the trenches of the polymer template, which was imprinted by nanoimprint lithography. The fabrication of line-type and dot-type nanopatterns was carried out by the combined method. In addition, multilayer nanopatterns of the Au-micelles were also proposed.

  19. Conjugating folate on superparamagnetic Fe3O4@Au nanoparticles using click chemistry

    International Nuclear Information System (INIS)

    Shen, Xiaofang; Ge, Zhaoqiang; Pang, Yuehong

    2015-01-01

    Gold-coated magnetic core@shell nanoparticles, which exhibit magneto-optical properties, not only enhance the chemical stability of core and biocompatibility of surface, but also provide a combination of multimodal imaging and therapeutics. The conjugation of these tiny nanoparticles with specific biomolecules allows researchers to target the desired location. In this paper, superparamagnetic Fe 3 O 4 @Au nanoparticles were synthesized and functionalized with the azide group on the surface by formation of self-assembled monolayers. Folate (FA) molecules, non-immunogenic target ligands for cancer cells, are conjugated with alkyne and then immobilized on the azide-terminated Fe 3 O 4 @Au nanoparticles through copper(I)-catalyzed azide-alkyne cycloaddition (click reaction). Myelogenous leukemia K562 cells were used as a folate receptor (FR) model, which can be targeted and extracted by magnetic field after interaction with the Fe 3 O 4 @Au–FA nanoparticles. - Graphical abstract: Self-assembled azide-terminated group on superparamagnetic Fe 3 O 4 @Au nanoparticles followed by click reaction with alkyne-functionalized folate, allowing the nanoparticles target folate receptor of cancer cells. - Highlights: • Azidoundecanethiol was coated on the superparamagnetic Fe 3 O 4 @Au nanoparticles by forming self-assembled monolayers. • Alkyne-terminated folate was synthesized from a reaction between the amine and the carboxylic acid. • Conjugation of Fe 3 O 4 @Au nanoparticles with folate was made by copper-catalyzed azide-alkyne cycloaddition click chemistry

  20. Study of Ag and Au Nanoparticles Synthesized by Arc Discharge in Deionized Water

    Directory of Open Access Journals (Sweden)

    Der-Chi Tien

    2010-01-01

    Full Text Available The paper presents a study of Ag and Au nanofluids synthesized by the arc discharge method (ADM in deionized water. The metallic Ag nanoparticle (Ag0 and ionic Ag (Ag+ have played an important role in the battle against germs which are becoming more drug-resistant every year. Our study indicates that Ag nanoparticle suspension (SNPS fabricated by using ADM without added surfactants exclusively contains the metallic Ag nanoparticle and ionic Ag. Besides that, the ADM in deionized water has also been employed for the fabrication process of Au nanoparticles. The experimental results indicate that the prepared Ag nanoparticles can react with the dissolved H2CO3 in deionized water, leading to the formation of Ag2CO3. Significantly different to Ag, the prepared Au nanoparticles with their surfaces bonded by oxygen are suspended in deionized water by the formation of hydrogen bonded with the neighboring water molecules.

  1. Shaping of Au nanoparticles embedded in various layered structures by swift heavy ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dawi, E.A., E-mail: elmuez.dawi@gmail.com [Ajman University of Science and Technology, Basic Science and Education, Physics Department, P.O. Box 346 (United Arab Emirates); Debye Institute for Nanomaterials, Nanophotonics Section, Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands); ArnoldBik, W.M. [Eindhoven University of Technology, Irradiation Technology, 5600 GM Eindhoven (Netherlands); Ackermann, R.; Habraken, F.H.P.M. [Debye Institute for Nanomaterials, Nanophotonics Section, Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

    2016-10-01

    We present a novel method to extend the ion-beam induced shaping of metallic nanoparticles in various layered structures. Monodisperse Au nanoparticles having mean diameter of 30 nm and their ion-shaping process is investigated for a limited number of experimental conditions. Au nanoparticles were embedded within a single plane in various layered structures of silicon nitride films (Si{sub 3}N{sub 4}), combinations of oxide-nitride films (SiO{sub 2}-Si{sub 3}N{sub 4}) and amorphous silicon films (a-Si) and have been sequentially irradiated at 300 K at normal incidence with 50 and 25 MeV Ag ions, respectively. Under irradiation with heavy Ag ions and with sequential increase of the irradiation fluence, the evolution of the Au peak derived from the Rutherford Backscattering Spectrometry show broadening in Au peak, which indicates that the Au becomes distributed over a larger depth region, indicative of the elongation of the nanoparticles. The latter is observed almost for every layer structure investigated except for Au nanoparticles embedded in pure a-Si matrix. The largest elongation rate at all fluences is found for the Au nanoparticles encapsulated in pure Si{sub 3}N{sub 4} films. For all irradiation energy applied, we again demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned.

  2. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  3. Atomistic modelling of friction of Cu and Au nanoparticles adsorbed on graphene

    Directory of Open Access Journals (Sweden)

    A.V. Khomenko

    2013-01-01

    Full Text Available We present classical molecular dynamics calculations of the behavior of copper and gold nanoparticles on a graphene sheet, sheared with a constant applied force Fa. The force Fs acting on the particle from the substrate depends on the material of the nanoparticles (Au or Cu, and exhibits a sawtooth dependency on time, which we attribute to local commensurability between the metal nanoparticle surface atomic positions with the graphene lattice. The time-averaged value of Fs (the friction force acting on Au nanoparticles increases linearly with the contact area, having slopes close to the experimentally observable ones. A qualitative model is proposed to explain the observed results.

  4. Electrocrystallization of Au nanoparticles on glassy carbon from HClO4 solution containing [AuCl4]-

    International Nuclear Information System (INIS)

    Komsiyska, L.; Staikov, G.

    2008-01-01

    The mechanism and kinetics of electrocrystallization of Au nanoparticles on glassy carbon (GC) were investigated in the system GC/1 mM KAuCl 4 + 0.1 M HClO 4 . Experimental results show that the gold electrodeposition follows the so-called Volmer-Weber growth mechanism involving formation and growth of 3D Au nanoparticles on an unmodified GC substrate. The analysis of current transients shows that at relatively positive electrode potentials (E ≥ 0.84 V) the deposition kinetics corresponds to the theoretical model for progressive nucleation and diffusion-controlled 3D growth of Au nanoparticles. The potential dependence of the nucleation rate extracted from the current transients is in agreement with the atomistic theory of nucleation. At sufficiently negative electrode potentials (E ≤ 0.64 V) the nucleation frequency becomes very high and the nucleation occurs instantaneously. Based on this behaviour is applied a potentiostatic double-pulse routine, which allows controlled electrodeposition of Au nanoparticles with a relatively narrow size distribution

  5. Enhanced absorption in Au nanoparticles/a-Si:H/c-Si heterojunction solar cells exploiting Au surface plasmon resonance

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, Maria; Giangregorio, Maria M.; Bianco, Giuseppe V.; Sacchetti, Alberto; Capezzuto, Pio; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari (Italy)

    2009-10-15

    Au nanoparticles (NPs)/(n-type)a-Si:H/(p-type)c-Si heterojunctions have been deposited combining plasma-enhanced chemical-vapour deposition (PECVD) with Au sputtering. We demonstrate that a density of {proportional_to}1.3 x 10{sup 11} cm{sup -2} of Au nanoparticles with an approximately 20 nm diameter deposited onto (n-type)a-Si:H/(p-type)c-Si heterojunctions enhance performance exploiting the improved absorption of light by the surface plasmon resonance of Au NPs. In particular, Au NPs/(n-type)a-Si:H/(p-type)c-Si show an enhancement of 20% in the short-circuit current, J{sub SC}, 25% in the power output, P{sub max} and 3% in the fill factor, FF, compared to heterojunctions without Au NPs. Structures have been characterized by spectroscopic ellipsometry, atomic force microscopy and current-voltage (I-V) measurements to correlate the plasmon resonance-induced enhanced absorption of light with photovoltaic performance. (author)

  6. Surface-enhanced Raman spectroscopy with Au-nanoparticle substrate fabricated by using femtosecond pulse

    Science.gov (United States)

    Zhang, Wending; Li, Cheng; Gao, Kun; Lu, Fanfan; Liu, Min; Li, Xin; Zhang, Lu; Mao, Dong; Gao, Feng; Huang, Ligang; Mei, Ting; Zhao, Jianlin

    2018-05-01

    Au-nanoparticle (Au-NP) substrates for surface-enhanced Raman spectroscopy (SERS) were fabricated by grid-like scanning a Au-film using a femtosecond pulse. The Au-NPs were directly deposited on the Au-film surface due to the scanning process. The experimentally obtained Au-NPs presented local surface plasmon resonance effect in the visible spectral range, as verified by finite difference time domain simulations and measured reflection spectrum. The SERS experiment using the Au-NP substrates exhibited high activity and excellent substrate reproducibility and stability, and a clearly present Raman spectra of target analytes, e.g. Rhodamine-6G, Rhodamine-B and Malachite green, with concentrations down to 10‑9 M. This work presents an effective approach to producing Au-NP SERS substrates with advantages in activity, reproducibility and stability, which could be used in a wide variety of practical applications for trace amount detection.

  7. Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    De Julian Fernandez, C; Novak, R L; Bogani, L; Caneschi, A [INSTM RU at the Department of Chemistry of the University of Firenze, via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Mattei, G; Mazzoldi, P [Department of Physics, CNISM and University of Padova, via Marzolo 8, 35131 Padova (Italy); Paz, E; Palomares, F J [Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid (Spain); Cavigli, L, E-mail: cesar.dejulian@unifi.it [Department of Physics-LENS, University of Florence, via Sansone 1, 50019 Sesto Fiorentino (Italy)

    2010-04-23

    Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO{sub 2} matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

  8. Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

    International Nuclear Information System (INIS)

    De Julian Fernandez, C; Novak, R L; Bogani, L; Caneschi, A; Mattei, G; Mazzoldi, P; Paz, E; Palomares, F J; Cavigli, L

    2010-01-01

    Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO 2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

  9. Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

    Science.gov (United States)

    de Julián Fernández, C.; Mattei, G.; Paz, E.; Novak, R. L.; Cavigli, L.; Bogani, L.; Palomares, F. J.; Mazzoldi, P.; Caneschi, A.

    2010-04-01

    Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

  10. Size and composition tunable Ag-Au alloy nanoparticles by replacement reactions

    International Nuclear Information System (INIS)

    Zhang Qingbo; Lee, J Y; Yang Jun; Boothroyd, Chris; Zhang Jixuan

    2007-01-01

    Ag-Au alloy nanoparticles with tunable size and composition were prepared by a replacement reaction between Ag nanoparticles and HAuCl 4 at elevated temperatures. The formation of homogeneous alloy nanoparticles was confirmed by selected-area energy-dispersive x-ray spectroscopy (SAEDX), UV-visible absorption spectroscopy, high resolution transmission electron microscopy (HRTEM) and electron diffraction. This method leverages upon the rapid interdiffusion of Ag and Au atoms in the reduced dimension of a nanoparticle, elevated temperatures and the large number of vacancy defects created in the replacement reaction. This method of preparation has several notable advantages: (1) independent tuning of the size and composition of alloy nanoparticles; (2) production of alloy nanoparticles in high concentrations; (3) general utility in the synthesis of alloy nanoparticles that cannot be obtained by the co-reduction method

  11. Atomistic Simulations of Functional Au-144(SR)(60) Gold Nanoparticles in Aqueous Environment

    DEFF Research Database (Denmark)

    Heikkila, E.; Gurtovenko, A. A.; Martinez-Seara, H.

    2012-01-01

    and Cl-/Na+ counterions, respectively. The radial distribution functions show that the side chains and terminal groups show significant flexibility. The orientation of water is distinct in the first solvation shell, and AuNPs cause a long-range effect in the solvent structure. The radial electrostatic...... of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups...... in aqueous solutions. They suggest that electrostatics is one of the central factors in complexation of AuNPs with other nanomaterials and biological systems, and that effects of electrostatics as water-mediated interactions are relatively long-ranged, which likely plays a role in, e.g., the interplay...

  12. Effects of Au/Fe and Fe nanoparticles on Serratia bacterial growth and production of biosurfactant

    International Nuclear Information System (INIS)

    Liu, Jia; Vipulanandan, Cumaraswamy

    2013-01-01

    The overall objective of this study was to compare the effects of Au/Fe and Fe nanoparticles on the growth and performance of Serratia Jl0300. The nanoparticle effect was quantified not only by the bacterial growth on agar plate after 1 hour interaction with the nanoparticles, but also by its production of a biosurfactant from used vegetable oil. The nanoparticles were prepared using the foam method. The concentrations of the nanoparticles used for the bacterial interaction study were varied from 1 mg/L to 1 g/L. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied with nanoparticle type, concentrations, and interaction time with the bacteria. Au/Fe nanoparticles didn't show toxicity to Serratia after short time (1 h) exposure, while during 8 days fermentation Au/Fe nanoparticles inhibited the growth of Serratia as well as the biosurfactant production when the concentration of the nanoparticles was higher than 10 mg/L. Fe nanoparticles showed inhibition effects to bacterial growth both after short time and long time interaction with Serratia, as well as to biosurfactant production when its concentration was higher than 100 mg/L. Based on the trends observed in this study, analytical models have been developed to predict the bacterial growth and biosurfactant production with varying concentrations of nanoparticles. - Highlights: • Modeled the effect of nanoparticles on the bacterial growth and biosurfactant production. • Effects of Au/Fe nonoparticles on Serratia Bacterial Growth and Production of Biosurfactant. • Scanning Electron Micrograph of bacteria-nanoparticles interaction

  13. Effects of Au/Fe and Fe nanoparticles on Serratia bacterial growth and production of biosurfactant

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jia; Vipulanandan, Cumaraswamy, E-mail: cvipulanandan@uh.edu

    2013-10-15

    The overall objective of this study was to compare the effects of Au/Fe and Fe nanoparticles on the growth and performance of Serratia Jl0300. The nanoparticle effect was quantified not only by the bacterial growth on agar plate after 1 hour interaction with the nanoparticles, but also by its production of a biosurfactant from used vegetable oil. The nanoparticles were prepared using the foam method. The concentrations of the nanoparticles used for the bacterial interaction study were varied from 1 mg/L to 1 g/L. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied with nanoparticle type, concentrations, and interaction time with the bacteria. Au/Fe nanoparticles didn't show toxicity to Serratia after short time (1 h) exposure, while during 8 days fermentation Au/Fe nanoparticles inhibited the growth of Serratia as well as the biosurfactant production when the concentration of the nanoparticles was higher than 10 mg/L. Fe nanoparticles showed inhibition effects to bacterial growth both after short time and long time interaction with Serratia, as well as to biosurfactant production when its concentration was higher than 100 mg/L. Based on the trends observed in this study, analytical models have been developed to predict the bacterial growth and biosurfactant production with varying concentrations of nanoparticles. - Highlights: • Modeled the effect of nanoparticles on the bacterial growth and biosurfactant production. • Effects of Au/Fe nonoparticles on Serratia Bacterial Growth and Production of Biosurfactant. • Scanning Electron Micrograph of bacteria-nanoparticles interaction.

  14. Hierarchical nanoflowers assembled with Au nanoparticles decorated ZnO nanosheets toward enhanced photocatalytic properties

    DEFF Research Database (Denmark)

    Yu, Cuiyan; Yu, Yanlong; Xu, Tao

    2017-01-01

    Hierarchical nanoflowers assembled with Au nanoparticles (NPs) decorated ZnO nanosheets (Au-ZnO nanosheet flowers, AZNSFs) were successful synthesized. The AZNSFs showed more efficient activity to photodegradation of RhB than that of pure ZnO nanosheet flowers and commercial ZnO nanopowders. The ...

  15. Green synthesis of Au nanoparticles using potato extract: stability and growth mechanism

    Science.gov (United States)

    Castillo-López, D. N.; Pal, U.

    2014-08-01

    We report on the synthesis of spherical, well-dispersed colloidal gold nanoparticles of 17.5-23.5 nm average sizes in water using potato extract (PE) both as reducing and stabilizing agent. The effects of PE content and the pH value of the reaction mixture have been studied. Formation and growth dynamics of the Au nanoparticles in the colloids were studied using transmission electron microscopy and UV-Vis optical absorption spectroscopy techniques. While the reductor content and, hence, the nucleation and growth rates of the nanoparticles could be controlled by controlling the PE content in the reaction solution, the stability of the nanoparticles depended strongly on the pH of the reaction mixture. The mechanisms of Au ion reduction and stabilization of Au nanoparticles by potato starch have been discussed. The use of common natural solvent like water and biological reductor like PE in our synthesis process opens up the possibility of synthesizing Au nanoparticles in fully green (environmental friendly) way, and the Au nanoparticles produced in such way should have good biocompatibility.

  16. In Situ Detection of Trace Furfural in Aqueous Solution Based on Au Nanoparticle/Au Film Surface-Enhanced Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Wei Qi

    2016-01-01

    Full Text Available Furfural is an important chemical solvent and intermediate. Sensitive detection of this compound has attracted great interest in various fields. Surface-enhanced Raman spectroscopy (SERS is a highly sensitive method for material detection because of its optical enhancement effect of plasmonic nanostructures. This study presents a simple and versatile method to synthesize a SERS substrate, where polyaminothiophenol (PATP was used to realize the stable combination of Au nanoparticles (AuNPs and Au film via self-assembly. The near-field electric field distribution was calculated using the finite difference time domain (FDTD simulation to determine the parameters responsible for electric field enhancement. The simulation results show that SERS enhanced factors are sensitive to interparticle spacing and materials for solid support but insensitive to particle size. Moreover, the experimental results show that the optimized substrates with the highest Raman activity were formed by six layers of 60 nm AuNPs decorated on a 30 nm thick Au film, thereby validating the simulation results. The SERS factor of the optimal substrates is approximately 5.57 × 103, and the in situ detection limit is 4.8 ppm. The 3D Raman spectra, relative standard deviation values for major peaks, and changes in signal intensity with time show the good reproducibility and stability of the substrates.

  17. Interaction of Au with thin ZrO2 films: influence of ZrO2 morphology on the adsorption and thermal stability of Au nanoparticles.

    Science.gov (United States)

    Pan, Yonghe; Gao, Yan; Kong, Dandan; Wang, Guodong; Hou, Jianbo; Hu, Shanwei; Pan, Haibin; Zhu, Junfa

    2012-04-10

    The model catalysts of ZrO(2)-supported Au nanoparticles have been prepared by deposition of Au atoms onto the surfaces of thin ZrO(2) films with different morphologies. The adsorption and thermal stability of Au nanoparticles on thin ZrO(2) films have been investigated using synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The thin ZrO(2) films were prepared by two different methods, giving rise to different morphologies. The first method utilized wet chemical impregnation to synthesize the thin ZrO(2) film through the procedure of first spin-coating a zirconium ethoxide (Zr(OC(2)H(5))(4)) precursor onto a SiO(2)/Si(100) substrate at room temperature followed by calcination at 773 K for 12 h. Scanning electron microscopy (SEM) investigations indicate that highly porous "sponge-like nanostructures" were obtained in this case. The second method was epitaxial growth of a ZrO(2)(111) film through vacuum evaporation of Zr metal onto Pt(111) in 1 × 10(-6) Torr of oxygen at 550 K followed by annealing at 1000 K. The structural analysis with low energy electron diffraction (LEED) of this film exhibits good long-range ordering. It has been found that Au forms smaller particles on the porous ZrO(2) film as compared to those on the ordered ZrO(2)(111) film at a given coverage. Thermal annealing experiments demonstrate that Au particles are more thermally stable on the porous ZrO(2) surface than on the ZrO(2)(111) surface, although on both surfaces, Au particles experience significant sintering at elevated temperatures. In addition, by annealing the surfaces to 1100 K, Au particles desorb completely from ZrO(2)(111) but not from porous ZrO(2). The enhanced thermal stability for Au on porous ZrO(2) can be attributed to the stronger interaction of the adsorbed Au with the defects and the hindered migration or coalescence resulting from the porous structures. © 2012 American Chemical Society

  18. Core–shell Au/Ag nanoparticles embedded in silicate sol–gel ...

    Indian Academy of Sciences (India)

    Administrator

    Dedicated to the memory of the late Professor S K Rangarajan. *For correspondence. Core–shell Au/Ag nanoparticles embedded in silicate sol–gel network for sensor .... An immediate colour change was observed for the mixed solution, indicating the dis- persion of metal nanoparticles in the MTMOS sol– gel matrix.

  19. Facile synthesis of Au/ZnO nanoparticles and their enhanced ...

    Indian Academy of Sciences (India)

    Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for ... et al 2009). Doping with metals (Akyol et al 2004; Kabra et al 2004 ..... of benzene as that under visible light irradiation were ca-.

  20. Au@AuPt nanoparticles embedded in B-doped graphene: A superior electrocatalyst for determination of rutin

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xianlan; Yang, Guangming; Feng, Shaoping; Shi, Ling; Huang, Zhaolong [School of Science, Honghe University (China); Key Laboratory of Natural Pharamaceutical & Chemical Biology of Yunnan Province Mengzi, Yunnan 661100 (China); Pan, Haibo [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Liu, Wei, E-mail: liuwei4728@126.com [School of Science, Honghe University (China); Key Laboratory of Natural Pharamaceutical & Chemical Biology of Yunnan Province Mengzi, Yunnan 661100 (China)

    2017-04-30

    Highlights: • The formation of B-doped graphene (BG) with high content of a total B species use hydrothermal method with B{sub 2}O{sub 3} as reducing agent and boron source. • BG was exfoliated into monolayer nanosheet impregnated by Au@AuPt NPs because B atom creates a net positive charge to facilitate NPs adsorption. • The dispersed carboxyl units of BG can form hydrogen bonding with the phenolic hydroxyl groups of rutin, making more rutin participate in reaction. • Au@AuPt NPs can form charge accumulation or valence change on prominent part of the surface, improving the catalytic effect to rutin. • More electroactive sites were generated by doping B atoms into graphene structures, which act as multidimensional electron transport pathways. - Abstract: A hydrothermal approach was used to prepare B-doped graphene with B{sub 2}O{sub 3} as reductant and boron source. Results reveal that the boron atoms have been successfully embedded into graphene with a high content of a total B species (2.85 at.%). Then, B-doped graphene was exfoliated further into monolayer nanosheet by impregnating Au@AuPt core-shell nanoparticles (Au@AuPt NPs) because boron atom creates a net positive charge, which facilitates Au@AuPt NPs adsorption to form Au@AuPt NPs/B-doped graphene hybrid nanocatalysts. After that, the Au@AuPt NPs/B-doped hybrid suspension was dropped on glassy carbon electrode for sensing rutin. In this way, the dispersed carboxyl units of B-doped graphene can form hydrogen bonding with the phenolic hydroxyl groups of rutin, making rutin enrich easily on modified electrode surface to enhance the electrochemical response. At the same time, its electrochemical mechanism on the modified electrode was elucidated using cyclic voltammetry. It was found that its electrochemical behavior on modified electrode surface was a surface-controlled quasi-reversible process, and the charge transfer coefficient (α) and electron transfer number (n) were 0.296 and 2, respectively

  1. Supporting Table A4 MULLICAN CHARGES (a.u.) and ...

    Indian Academy of Sciences (India)

    Windows User

    1.135621. 64 H. 0.01933. -1.132721. 65 H. -0.259245. -1.126795. Supporting Table A5. MULLICAN CHARGES (a.u.) and ELECTROSTATIC POTENTIAL(a.u.). OF ATOMS OF 1CH4@512-METHANOL. ATOM ID. ATOM TYPE MULLIKAN CHARGES.

  2. Asymmetric photoelectric property of transparent TiO2 nanotube films loaded with Au nanoparticles

    International Nuclear Information System (INIS)

    Wang, Hui; Liang, Wei; Liu, Yiming; Zhang, Wanggang; Zhou, Diaoyu; Wen, Jing

    2016-01-01

    Highlights: • Highly transparent films of TiO 2 nanotube arrays were directly fabricated on FTO glasses. • Semitransparent TNT-Au composite films were obtained and exhibited excellent photoelectrocatalytic ability. • Back-side of TNT-Au composite films was firstly irradiated and tested to compare with front-side of films. - Abstract: Semitransparent composite films of Au loaded TiO 2 nanotubes (TNT-Au) were prepared by sputtering Au nanoparticles on highly transparent TiO 2 nanotubes films, which were fabricated directly on FTO glasses by anodizing the Ti film sputtered on the FTO glasses. Compared with pure TNT films, the prepared TNT-Au films possessed excellent absorption ability and high photocurrent response and improved photocatalytic activity under visible-light irradiation. It could be concluded that Au nanoparticles played important roles in improving the photoelectrochemical performance of TNT-Au films. Moreover, in this work, both sides of TNT-Au films were researched and compared owing to theirs semitransparency. It was firstly found that the photoelectric activity of TNT-Au composite films with back-side illumination was obviously superior to front-side illumination.

  3. Asymmetric photoelectric property of transparent TiO{sub 2} nanotube films loaded with Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hui [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); College of Applied Science, Taiyuan University of Science and Technology, Taiyuan, Shanxi 030024 (China); Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China); Liang, Wei, E-mail: 986903124@qq.com [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China); Liu, Yiming; Zhang, Wanggang; Zhou, Diaoyu; Wen, Jing [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China)

    2016-11-15

    Highlights: • Highly transparent films of TiO{sub 2} nanotube arrays were directly fabricated on FTO glasses. • Semitransparent TNT-Au composite films were obtained and exhibited excellent photoelectrocatalytic ability. • Back-side of TNT-Au composite films was firstly irradiated and tested to compare with front-side of films. - Abstract: Semitransparent composite films of Au loaded TiO{sub 2} nanotubes (TNT-Au) were prepared by sputtering Au nanoparticles on highly transparent TiO{sub 2} nanotubes films, which were fabricated directly on FTO glasses by anodizing the Ti film sputtered on the FTO glasses. Compared with pure TNT films, the prepared TNT-Au films possessed excellent absorption ability and high photocurrent response and improved photocatalytic activity under visible-light irradiation. It could be concluded that Au nanoparticles played important roles in improving the photoelectrochemical performance of TNT-Au films. Moreover, in this work, both sides of TNT-Au films were researched and compared owing to theirs semitransparency. It was firstly found that the photoelectric activity of TNT-Au composite films with back-side illumination was obviously superior to front-side illumination.

  4. Stabilization of Pt nanoparticles by single stranded DNA and the binary assembly of Au and Pt nanoparticles without hybridization

    International Nuclear Information System (INIS)

    Yang, J.; Lee, Jim Yang; Too, Heng-Phon; Chow, Gan-Moog; Gan, Leong M.

    2006-01-01

    The non-specific interaction between single stranded DNA (ssDNA) and 12 nm Pt nanoparticles is investigated in this work. The data show a strong and non-specific interaction between the two which can be exploited for the stabilization of Pt nanoparticles in aqueous solutions. Based on the experimental findings, a non-hybridization based protocol to assemble 17 nm Au and Pt nanoparticles (12 nm cubic and 3.6 nm spherical) by single-stranded DNA was developed. Transmission electron microscopy (TEM) and UV-visible spectroscopy confirmed that Au and Pt nanoparticles could be assembled by the non-specific interaction in an orderly manner. The experimental results also caution against the potential pitfalls in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization

  5. Picosecond laser fabricated Ag, Au and Ag-Au nanoparticles for detecting ammonium perchlorate using a portable Raman spectrometer

    Science.gov (United States)

    Byram, Chandu; Moram, Sree Sathya Bharathi; Soma, Venugopal Rao

    2018-04-01

    In this paper, we present the results from fabrication studies of Ag, Au, and Ag-Au alloy nanoparticles (NPs) using picosecond laser ablation technique in the presence of liquid media. The alloy formation in the NPs was confirmed from UV-Visible measurements. The shape and crystallinity of NPs were investigated by using high resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED) and energy dispersive spectroscopy (EDS). The SERS effect of fabricated NPs was tested with methylene blue and an explosive molecule (ammonium perchlorate) using a portable Raman spectrometer and achieved EFs of ˜106.

  6. Facile method for CLSM imaging unfunctionalized Au nanoparticles through fluorescent channels

    International Nuclear Information System (INIS)

    Yuan Lan; Wei Wei; Li Juan; Sun, Zhiwei; Wang Hongfang; Zhang Xiuzhi; Chen Yueyue

    2009-01-01

    The microscopic visualization of metal nanoparticles has become a useful tool for the investigation of their applications in cell labeling and the study of their bio-effects. In the current study, we have developed a facile method with confocal laser scanning microscope (CLSM) to observe unfunctionalized Au nanoparticles through fluorescent channels. The sharp reflected signal and photostable property of the metal nanoparticles makes the present method very ideal for fluorescent co-localization, real-time imaging, and further quantitative analysis.

  7. Thickness-Dependent Strain Effect on the Deformation of the Graphene-Encapsulated Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    Shuangli Ye

    2014-01-01

    Full Text Available The strain effect on graphene-encapsulated Au nanoparticles is investigated. A finite-element calculation is performed to simulate the strain distribution and morphology of the monolayer and multilayer graphene-encapsulated Au nanoparticles, respectively. It can be found that the inhomogeneous strain and deformation are enhanced with the increasing shrinkage of the graphene shell. Moreover, the strain distribution and deformation are very sensitive to the layer number of the graphene shell. Especially, the inhomogeneous strain at the interface between the graphene shell and encapsulated Au nanoparticles is strongly tuned by the graphene thickness. For the mono- and bilayer graphene-encapsulated Au nanoparticles, the dramatic shape transformation can be observed. However, with increasing the graphene thickness further, there is hardly deformation for the encapsulated Au nanoparticles. These simulated results indicate that the strain and deformation can be designed by the graphene layer thickness, which provides an opportunity to engineer the structure and morphology of the graphene-encapsulated nanoparticles.

  8. Gold Nanoparticles Supported on Fibrous Silica Nanospheres (KCC-1) as Efficient Heterogeneous Catalysts for CO Oxidation

    KAUST Repository

    Qureshi, Ziyauddin S.; Sarawade, Pradip B.; Hussain, Irshad; Zhu, Haibo; Al-Johani, Hind; Anjum, Dalaver H.; Hedhili, Mohamed N.; Maity, Niladri; D'Elia, Valerio; Basset, Jean-Marie

    2016-01-01

    Gold nanoparticles (Au NPs) of different sizes were supported on fibrous silica nanospheres (KCC-1) by various methods. The size and the location of the Au NPs on the support were found to depend on the preparation method. The KCC-1-supported Au NPs were thoroughly characterized by using HR-TEM, XRD, X-ray photoelectron spectroscopy, UV, and Brunauer-Emmett-Teller surface area measurements and were applied in catalysis for the oxidation of CO. The catalytic performance is discussed in relation to the morphological properties of KCC-1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Gold Nanoparticles Supported on Fibrous Silica Nanospheres (KCC-1) as Efficient Heterogeneous Catalysts for CO Oxidation

    KAUST Repository

    Qureshi, Ziyauddin S.

    2016-04-13

    Gold nanoparticles (Au NPs) of different sizes were supported on fibrous silica nanospheres (KCC-1) by various methods. The size and the location of the Au NPs on the support were found to depend on the preparation method. The KCC-1-supported Au NPs were thoroughly characterized by using HR-TEM, XRD, X-ray photoelectron spectroscopy, UV, and Brunauer-Emmett-Teller surface area measurements and were applied in catalysis for the oxidation of CO. The catalytic performance is discussed in relation to the morphological properties of KCC-1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Sonochemical synthesis, structure and magnetic properties of air-stable Fe3O4/Au nanoparticles

    International Nuclear Information System (INIS)

    Wu Wei; He Quanguo; Chen Hong; Tang Jianxin; Nie Libo

    2007-01-01

    Air-stable nanoparticles of Fe 3 O 4 /Au were prepared via sonolysis of a solution mixture of hydrogen tetrachloroaureate(III) trihydrate (HAuCl 4 ) and (3-aminopropyl)triethoxysilane (APTES)-coated Fe 3 O 4 nanoparticles with further drop-addition of sodium citrate. The Fe 3 O 4 /Au nanoparticles were characterized by x-ray powder diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetometry. Nanoparticles of Fe 3 O 4 /Au obtained under appropriate conditions possess a very high saturation magnetization of about 63 emu g -1 and their average diameter is about 30 nm

  11. Twin-assisted growth of nominally stable substrates underneath dewetted Au nanoparticles

    International Nuclear Information System (INIS)

    Liu, Fang; Xie, Dong Yue; Majdi, Tahereh; Zhu, Guo-zhen

    2016-01-01

    By applying a simple and inexpensive thermal treatment, we synthesized supported gold-oxide nanostructures, which have potential applications to plasmonic devices and biosensors. The regrowth of nominally stable substrates under gold nanoparticles is associated with the appearance of preferential orientations of dewetted nanoparticles and the formation of atomically sharp interfacial monolayers. Steps present at the interfacial monolayer usually occur at defects including the intersection points of twin planes at the interface. They were related to the nucleation and immigration of the interfacial monolayers, prompting the substrate regrowth. Accordingly, we proposed the twin-assisted growth mechanism, which provides insight on the synthesis of gold-oxide nanostructures. - Highlights: • The twin-assisted growth mechanism is proposed for the abnormal regrowth of substrate underneath Au nanoparticles. • The substrate regrowth is related to the steps and ledges that are present at the Au–MgAl_2O_4 interfacial monolayers. • Interfacial steps are detected at defects such as the intersecting points of twin planes at the interface.

  12. Twin-assisted growth of nominally stable substrates underneath dewetted Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Xie, Dong Yue [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240 (China); Majdi, Tahereh [Department of Engineering Physics, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4L7 (Canada); Zhu, Guo-zhen, E-mail: zhugz@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240 (China)

    2016-03-15

    By applying a simple and inexpensive thermal treatment, we synthesized supported gold-oxide nanostructures, which have potential applications to plasmonic devices and biosensors. The regrowth of nominally stable substrates under gold nanoparticles is associated with the appearance of preferential orientations of dewetted nanoparticles and the formation of atomically sharp interfacial monolayers. Steps present at the interfacial monolayer usually occur at defects including the intersection points of twin planes at the interface. They were related to the nucleation and immigration of the interfacial monolayers, prompting the substrate regrowth. Accordingly, we proposed the twin-assisted growth mechanism, which provides insight on the synthesis of gold-oxide nanostructures. - Highlights: • The twin-assisted growth mechanism is proposed for the abnormal regrowth of substrate underneath Au nanoparticles. • The substrate regrowth is related to the steps and ledges that are present at the Au–MgAl{sub 2}O{sub 4} interfacial monolayers. • Interfacial steps are detected at defects such as the intersecting points of twin planes at the interface.

  13. Dual structural transition in small nanoparticles of Cu-Au alloy

    Science.gov (United States)

    Gafner, Yuri; Gafner, Svetlana; Redel, Larisa; Zamulin, Ivan

    2018-02-01

    Cu-Au alloy nanoparticles are known to be widely used in the catalysis of various chemical reactions as it was experimentally defined that in many cases the partial substitution of copper with gold increases catalytic activity. However, providing the reaction capacity of alloy nanoparticles the surface electronic structure strongly depends on their atomic ordering. Therefore, to theoretically determine catalytic properties, one needs to use a most real structural model complying with Cu-Au nanoparticles under various external influences. So, thermal stability limits were studied for the initial L12 phase in Cu3Au nanoalloy clusters up to 8.0 nm and Cu-Au clusters up to 3.0 nm at various degrees of Au atom concentration, with molecular dynamics method using a modified tight-binding TB-SMA potential. Dual structural transition L12 → FCC and further FCC → Ih is shown to be possible under the thermal factor in Cu3Au and Cu-Au clusters with the diameter up to 3.0 nm. The temperature of the structural transition FCC → Ih is established to decrease for small particles of Cu-Au alloy under the increase of Au atom concentration. For clusters with this structural transition, the melting point is found to be a linear increasing function of concentration, and for clusters without FCC → Ih structural transition, the melting point is a linear decreasing function of Au content. Thus, the article shows that doping Cu nanoclusters with Au atoms allows to control the forming structure as well as the melting point.

  14. The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hrubovčák, Pavol [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňáková, Adriana, E-mail: adriana.zelenakova@upjs.sk [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňák, Vladimir [Department of Inorganic Chemistry, P.J. Šafárik University, Moyzesova 11, Košice (Slovakia); Kováč, Jozef [Institute of Experimental Physics, SAS, Watsonova 41, Košice (Slovakia)

    2015-11-15

    Co/Au bimetallic fine nanoparticles were prepared employing the method of microemulsion using reverse micelle as nanoreactor, controlling the particles size. Magnetic and structural properties of two different samples Co/Au1 and Co/Au2 with almost comparable size of Co core and different size of Au layer were studied. The investigation of magnetic relaxation processes present in the particles was carried out by means of ac and dc magnetization data obtained at different temperatures and magnitudes of magnetic field. We observed the existence of superspin glass state characterized by the strong inter-particle interactions in the nanoparticle systems. In this paper, we discuss the attributes of novel superspin glass magnetic state reflected on various features (saturated FC magnetization at low temperatures, shift of the Cole–Cole arc downwards) and calculated parameters (relaxation time, critical exponent zv ∼ 10 and frequency dependent criterion p < 0.05). Comparison of the magnetic properties of two studied samples show that the thickness of diamagnetic Au shell significantly influences the magnetic interactions and change the relaxation dynamics. - Highlights: • Co/Au fine nanoparticles prepared by reverse micelle as nanoreactor, controlling the size. • Existence of superspin glass state confirmed from ac magnetic susceptibility study. • Individual particles exhibit the collective behavior below glass temperature T{sub SSG}. • Influence of diamagnetic shell on the magnetic properties of core–shell nanoparticles.

  15. Recent advances in the synthesis of Fe3O4@AU core/shell nanoparticles

    International Nuclear Information System (INIS)

    Salihov, Sergei V.; Ivanenkov, Yan A.; Krechetov, Sergei P.; Veselov, Mark S.; Sviridenkova, Natalia V.; Savchenko, Alexander G.; Klyachko, Natalya L.; Golovin, Yury I.; Chufarova, Nina V.; Beloglazkina, Elena K.; Majouga, Alexander G.

    2015-01-01

    Fe 3 O 4 @Au core/shell nanoparticles have unique magnetic and optical properties. These nanoparticles are used for biomedical applications, such as magnetic resonance imaging, photothermal therapy, controlled drug delivery, protein separation, biosensors, DNA detection, and immunosensors. In this review, recent methods for the synthesis of core/shell nanoparticles are discussed. We divided all of the synthetic methods in two groups: methods of synthesis of bi-layer structures and methods of synthesis of multilayer composite structures. The latter methods have a layer of “glue” material between the core and the shell. - Highlights: • Fe 3 O 4 nanoparticles are promising for biomedical applications but have some disadvantages. • Covering Fe 3 O 4 nanoparticles with Au shell leads to better stability and biocompatibility. • Core/shell nanoparticles are widely used for biomedical applications. • There are two types of Fe 3 O 4 @Au core/shell nanoparticles structures: bi-layer and multilayer composite. • Different synthetic methods enable production of nanoparticles of different sizes

  16. Photoluminescence enhancement in few-layer WS2 films via Au nanoparticles

    Directory of Open Access Journals (Sweden)

    Sin Yuk Choi

    2015-06-01

    Full Text Available Nano-composites of two-dimensional atomic layered WS2 and Au nanoparticles (AuNPs have been fabricated by sulfurization of sputtered W films followed by immersing into HAuCl4 aqueous solution. The morphology, structure and AuNPs distribution have been characterized by electron microscopy. The decorated AuNPs can be more densely formed on the edge and defective sites of triangle WS2. We have compared the optical absorption and photoluminescence of bare WS2 and Au-decorated WS2 layers. Enhancement in the photoluminescence is observed in the Au-WS2 nano-composites, attributed to localized surface plasmonic effect. This work provides the possibility to develop photonic application in two-dimensional materials.

  17. Preparation of Au and Ag nanoparticles using Artemisia annua and their in vitro antibacterial and tyrosinase inhibitory activities

    Energy Technology Data Exchange (ETDEWEB)

    Basavegowda, Nagaraj; Idhayadhulla, Akber; Lee, Yong Rok, E-mail: yrlee@yu.ac.kr

    2014-10-01

    This work describes a plant-mediated approach to the preparation of metal nanoparticles using leaf extract of Artemisia annua (A. annua), an ethno-medicinal plant widely found in Asia, which was used as reducing and stabilizing agent. A. annua is used in traditional Chinese medicine to alleviate fever. Au and Ag nanoparticles were prepared using a one-step aqueous method at room temperature without any toxic chemicals. The formation of Au and Ag nanoparticles was monitored by UV–vis spectroscopy. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). TEM analysis of Au nanoparticles showed that they had triangular and spherical shapes with sizes ranging from 15 to 40 nm. The silver nanoparticles were predominantly spherical and uniformly sized (30–50 nm). The Au and Ag nanoparticles produced showed significant tyrosinase inhibitory and antibacterial effects. These results suggest that the synthesized nanoparticles provide good alternatives in varied medical and industrial applications. - Highlights: • Au and Ag nanoparticles were synthesized using Artemisia annua leaf aqueous extract. • Nanoparticles were characterized by UV–vis spectroscopy, FT-IR, TEM, EDX, XRD, and TGA. • Au and Ag nanoparticles were of size 25 and 30 nm respectively, in spherical forms. • Nanoparticles showed significant tyrosinase inhibitory and antibacterial activities.

  18. Preparation of Au and Ag nanoparticles using Artemisia annua and their in vitro antibacterial and tyrosinase inhibitory activities

    International Nuclear Information System (INIS)

    Basavegowda, Nagaraj; Idhayadhulla, Akber; Lee, Yong Rok

    2014-01-01

    This work describes a plant-mediated approach to the preparation of metal nanoparticles using leaf extract of Artemisia annua (A. annua), an ethno-medicinal plant widely found in Asia, which was used as reducing and stabilizing agent. A. annua is used in traditional Chinese medicine to alleviate fever. Au and Ag nanoparticles were prepared using a one-step aqueous method at room temperature without any toxic chemicals. The formation of Au and Ag nanoparticles was monitored by UV–vis spectroscopy. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). TEM analysis of Au nanoparticles showed that they had triangular and spherical shapes with sizes ranging from 15 to 40 nm. The silver nanoparticles were predominantly spherical and uniformly sized (30–50 nm). The Au and Ag nanoparticles produced showed significant tyrosinase inhibitory and antibacterial effects. These results suggest that the synthesized nanoparticles provide good alternatives in varied medical and industrial applications. - Highlights: • Au and Ag nanoparticles were synthesized using Artemisia annua leaf aqueous extract. • Nanoparticles were characterized by UV–vis spectroscopy, FT-IR, TEM, EDX, XRD, and TGA. • Au and Ag nanoparticles were of size 25 and 30 nm respectively, in spherical forms. • Nanoparticles showed significant tyrosinase inhibitory and antibacterial activities

  19. Electrochemical fabrication of clean dendritic Au supported Pt clusters for electrocatalytic oxidation of formic acid

    International Nuclear Information System (INIS)

    Xia Yue; Liu Jun; Huang Wei; Li Zelin

    2012-01-01

    Highlights: ► A smooth Au surface was rebuilt into clean dendrite via square wave potential pulses. ► It was performed in blank H 2 SO 4 solution without Au(III) species and other additives. ► Dendritic Au provided certain advantage for dispersing Pt due to its unique structure. ► Pt-decorated dendritic Au demonstrated high activity for the HCOOH electrooxidation. - Abstract: We report here the fabrication of clean dendritic gold (DG) directly on a smooth Au electrode via square wave potential pulses (SWPPs) in a blank H 2 SO 4 solution containing no Au(III) species and additives. The effects of potential range, frequency and duration time of SWPPs and H 2 SO 4 concentration on the construction of DG were systematically investigated. A possible mechanism was proposed to explain the growth of DG. The whole process was templateless and surfactantless, and therefore effectively avoided possible contaminations that occurred in other synthetic routes. Further, the prepared DG electrode functioned as a scaffold to support electrodeposited Pt clusters, producing Pt-decorated DG (Pt-DG) electrodes. The electrocatalytic properties of Pt-DG electrodes with various Pt loadings were examined for the oxidation of formic acid. The low Pt loading Pt-DG demonstrated different electrochemical behavior from that on Pt-decorated smooth gold (Pt-SG) and on Pt-decorated gold nanoparticles because there were more defect sites like steps and edges on the DG surface. Ensemble effect, as well as electronic effect, accounts for the improved electrocatalytic activity of low Pt loading Pt-DG.

  20. Au nanoparticles in PMMA matrix: In situ synthesis and the effect of Au nanoparticles on PMMA conductivity

    International Nuclear Information System (INIS)

    Yilmaz, Eda; Suzer, Sefik

    2010-01-01

    Thin PMMA films with and without gold nanoparticles were subjected to ±10 V d.c. and a.c. (square wave) excitations in various frequencies while recording their XPS spectra, and the resulting differences due to charging were examined. Both pure PMMA films and films containing gold nanoparticles showed charging shifts, but those of pure PMMA were more extensive than of PMMA containing gold nanoparticles, suggesting enhanced conductivity, induced by the incorporated gold nanoparticles. Non-charging behavior for these films was also observed with the increase of gold nanoparticle concentration. Gold nanoparticles were in situ synthesized and photo-patterned within the polymer films by UV irradiation.

  1. Spherical and polygonal shape of Au nanoparticles coated functionalized polymer microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Ting; Li, Yingzhi; Zhang, Junxian; Qi, Yalong; Zhao, Xin; Zhang, Qinghua, E-mail: qhzhang@dhu.edu.cn

    2015-08-01

    Highlights: • PS/PPy with well-defined core/shell structures was prepared in aqueous solution. • Au NPs were coated on PS/PPy by the fixation and continuous growth process. • Mercapto-groups played a role in the number and morphology of Au shell. • PS/PPy/Au had homogeneous and dense Au coatings with different shape. - Abstract: Uniform polystyrene (PS)/polypyrrole (PPy) composite microspheres with well-defined core/shell structures are synthesized by chemical oxidative polymerization. Gold nanoparticles (Au NPs) are successfully coated on the surface of PS/PPy microspheres by means of electrostatic interactions due to the functionalized PPy coatings supplying sufficient amino groups and the additive of mercapto acetic acid. Furthermore, the as-prepared PS/PPy/Au microspheres serving as seeds facilitate Au NPs further growth by in situ reduction in HAuCl{sub 4} solution to obtain PS/PPy/Au spheres with the core/shell/shell structure. Morphology observation demonstrates that the monodisperse PS/PPy/Au microspheres compose of uniform cores and the compact coatings containing distinct two layers. X-ray diffraction and X-ray photoelectron spectroscope confirm the existence of PPy and Au on the surface of the composite spheres. This facile approach to preparing metal-coated polymer spheres supplies the potential applications in biosensors, electronics and medical diagnosis.

  2. Surface-Plasmon-Enhanced Emissions of Phosphors with Au Nanoparticles Embedded in ITO

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ja-Yeon [Korea Photonics Technology Institute (KOPTI), Gwangju (Korea, Republic of); Oh, Seung Jong; Park, Hyun-Sun; Kim, Min-Woo; Cho, Yoo-Hyun; Kwon, Min-Ki [Chosun University, Gwangju (Korea, Republic of)

    2017-03-15

    Au nanoparticles were embedded in a transparent conducting layer of indium tin oxide in order to evaluate the feasibility of applying a surface-plasmon (SP)-enhanced phosphor to light-emitting diodes (LEDs). The efficiency of the phosphor was improved by energy matching between the phosphor and the SP of the Au nanoparticles. After the density of the Au nanoparticles and the thickness of the spacer layer had been optimized, the efficiency of a green phosphor was improved by 64% compared to that of an isolated green phosphor. This work provides a way to fabricate high-efficiency LEDs with high color-rendering indices and wide color gamuts in white LEDs.

  3. Effects of different additives on bimetallic Au-Pt nanoparticles electrodeposited onto indium tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ballarin, Barbara, E-mail: ballarin@ms.fci.unibo.i [Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, V.le Risorgimento, 4, 40136-Bologna (Italy)] [INSTM, UdR Bologna (Italy); Gazzano, Massimo [ISOF-CNR, V. Selmi, 40126-Bologna (Italy); Tonelli, Domenica [Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, V.le Risorgimento, 4, 40136-Bologna (Italy)] [INSTM, UdR Bologna (Italy)

    2010-09-01

    Bimetallic Au-Pt nanoparticles (Au-Pt{sub NPs}) have been synthesized using an electrochemical reduction approach. The effects of the addition of different additives in the electrodeposition bath namely KI, 1-nonanesulfonic acid sodium salt and Triton X-100 have been investigated. The structural characterization of the bimetallic nanoparticles has been carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy, X-ray diffraction (XRD) and cyclic voltammetry (CV). The Au-Pt{sub NPs} prepared in the presence of KI and Triton X-100 characterized by a relatively narrow size distribution as well as a higher particle density and surface coverage whereas no changes in the morphology were observed. These results suggest a dependence of the size and distribution of the bimetallic nanoparticles from the type and concentration of the additives employed.

  4. The fabrication and single electron transport of Au nano-particles placed between Nb nanogap electrodes

    International Nuclear Information System (INIS)

    Nishino, T; Negishi, R; Ishibashi, K; Kawao, M; Nagata, T; Ozawa, H

    2010-01-01

    We have fabricated Nb nanogap electrodes using a combination of molecular lithography and electron beam lithography. Au nano-particles with anchor molecules were placed in the gap, the width of which could be controlled on a molecular scale (∼2 nm). Three different anchor molecules which connect the Au nano-particles and the electrodes were tested to investigate their contact resistance, and a local gate was fabricated underneath the Au nano-particles. The electrical transport measurements at liquid helium temperatures indicated single electron transistor (SET) characteristics with a charging energy of about ∼ 5 meV, and a clear indication of the effect of superconducting electrodes was not observed, possibly due to the large tunnel resistance.

  5. Highly sensitive and rapid bacteria detection using molecular beacon-Au nanoparticles hybrid nanoprobes.

    Science.gov (United States)

    Cao, Jing; Feng, Chao; Liu, Yan; Wang, Shouyu; Liu, Fei

    2014-07-15

    Since many diseases are caused by pathogenic bacterial infections, accurate and rapid detection of pathogenic bacteria is in urgent need to timely apply appropriate treatments and to reduce economic costs. To end this, we designed molecular beacon-Au nanoparticle hybrid nanoprobes to improve the bacterial detection efficiency and sensitivity. Here, we show that the designed molecular beacon modified Au nanoparticles could specifically recognize synthetic DNAs targets and can readily detect targets in clinical samples. Moreover, the hybrid nanoprobes can recognize Escherichia coli within an hour at a concentration of 10(2) cfu/ml, which is 1000-folds sensitive than using molecular beacon directly. Our results show that the molecular beacon-Au nanoparticle hybrid nanoprobes have great potential in medical and biological applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Positronic probe of vacancy defects on surfaces of Au nanoparticles embedded in MgO

    International Nuclear Information System (INIS)

    Xu, Jun; Moxom, J.; Somieski, B.; White, C. W.; Mills, A. P.; Suzuki, R.; Ishibashi, S.

    2001-01-01

    Clusters of four atomic vacancies were found in Au nanoparticle-embedded MgO by positron lifetime spectroscopy [Phys. Rev. Lett. 83, 4586 (1999)]. These clusters were also suggested to locate at the surface of Au nanoparticles by one-detector measurements of Doppler broadening of annihilation radiation. In this work we provide evidence, using two-detector coincidence experiments of Doppler broadening (2D-DBAR), to clarify that these vacancy clusters reside on the surfaces of Au nanoparticles. This work also demonstrates a method for identifying defects at nanomaterials interfaces: a combination of both positron lifetime spectroscopy, which tells the type of the defects, and 2D-DBAR measurements, which reveals chemical environment of the defects

  7. Positronic probe of vacancy defects on surfaces of Au nanoparticles embedded in MgO

    Science.gov (United States)

    Xu, Jun; Moxom, J.; Somieski, B.; White, C. W.; Mills, A. P., Jr.; Suzuki, R.; Ishibashi, S.

    2001-09-01

    Clusters of four atomic vacancies were found in Au nanoparticle-embedded MgO by positron lifetime spectroscopy [Phys. Rev. Lett. 83, 4586 (1999)]. These clusters were also suggested to locate at the surface of Au nanoparticles by one-detector measurements of Doppler broadening of annihilation radiation. In this work we provide evidence, using two-detector coincidence experiments of Doppler broadening (2D-DBAR), to clarify that these vacancy clusters reside on the surfaces of Au nanoparticles. This work also demonstrates a method for identifying defects at nanomaterials interfaces: a combination of both positron lifetime spectroscopy, which tells the type of the defects, and 2D-DBAR measurements, which reveals chemical environment of the defects.

  8. Sustainable green catalysis by supported metal nanoparticles.

    Science.gov (United States)

    Fukuoka, Atsushi; Dhepe, Paresh L

    2009-01-01

    The recent progress of sustainable green catalysis by supported metal nanoparticles is described. The template synthesis of metal nanoparticles in ordered porous materials is studied for the rational design of heterogeneous catalysts capable of high activity and selectivity. The application of these materials in green catalytic processes results in a unique activity and selectivity arising from the concerted effect of metal nanoparticles and supports. The high catalytic performances of Pt nanoparticles in mesoporous silica is reported. Supported metal catalysts have also been applied to biomass conversion by heterogeneous catalysis. Additionally, the degradation of cellulose by supported metal catalysts, in which bifunctional catalysis of acid and metal plays the key role for the hydrolysis and reduction of cellulose, is also reported. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

  9. Development and characterisation of a novel composite electrode material consisting of poly(3,4-ethylenedioxythiophene) including Au nanoparticles

    International Nuclear Information System (INIS)

    Zanardi, C.; Terzi, F.; Pigani, L.; Heras, A.; Colina, A.; Lopez-Palacios, J.; Seeber, R.

    2008-01-01

    Composite material consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), including Au nanoparticles encapsulated by N-dodecyl-N,N-dimethyl-3-ammonium-1-propanesulphonate (SB12) is synthesised by constant-current method on ITO glass, in aqueous medium, leading to an electrode coating. The synthesis process is followed by UV-vis spectroelectrochemistry, both in normal-beam and in parallel-beam configurations. Under the same experimental conditions PEDOT is also synthesised by electropolymerisation only in the presence of LiClO 4 supporting electrolyte, as well in solutions also containing SB12. The data relative to the electrosynthesis of the three materials are compared. The composite material based on the conductive polymer matrix including Au nanoparticles has been characterised by SEM, TEM, ICP, Raman and UV-vis spectroscopies. The behaviour of the three different electrode coatings with respect to p-doping process has been studied by conventional electrochemical techniques and by potentiostatic and potentiodynamic UV-vis spectroelectrochemical methods. Conclusions are drawn out about the effect of the presence of the surfactant and of Au nanoparticles on the electrochemical properties of the electrode system

  10. Characterization of self-assembled electrodes based on Au-Pt nanoparticles for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, E. [Politecnica Univ. de Chiapas, Tuxtla Gutierrez, Chiapas (Mexico). Energia y Sustentabilidad; Sebastian, P.J. [Politecnica Univ. de Chiapas, Chiapas (Mexico). Energia y Sustentabilidad; Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Gamboa, S.A. [Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Pal, U. [Inst. de Fisica, Universidad Autonoma de Puebla Univ., Puebla (Mexico). Inst. de Fisica; Gonzalez, I. [Autonoma Metropolitana Univ. (Mexico). Dept. de Quimica

    2008-07-01

    This paper reported on a study in which membrane electrode assemblies (MEAs) were fabricated by depositing Au, Pt and AuPt nanoparticles on Nafion 115 membrane for use in a proton exchange membrane fuel cell (PEMFC). A Rotating Disc Electrode (RDE) was used to measure the nanoparticle catalyst activity. After deposition of the nanoparticles on the membrane, the surface was studied by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The membrane proton conduction process was studied by Electrochemical Impedance Spectroscopy (EIS) with the 4 probe technique. The MEAs fabricated with Nafion/Metal membranes were evaluated in a PEMFC under standard conditions. Colloidal solutions were used to prepare self-assembled electrodes with nanoparticles deposited on Nafion membrane. The particles deposited on Nafion showed good stability and had homogeneous distribution along the membrane surface. The impedance results revealed an increase in the membrane proton resistance of the self-assembled electrodes compared to unmodified Nafion. The Au-Pt nanoparticles were obtained by chemical reduction. The nanoparticle size in the three systems was about 2 nm. The self-assembled electrodes performed well in standard conditions. The optimum colloidal concentration and immersion time must be determined in order to obtain good catalytic activity and high membrane conductance. The self-assembled Nafion/AuPt had the best open circuit potential (887 mV). The Au and Pt self-assemblies showed a similar performance in terms of maximum power and maximum current density. The performance of the Nafion/Au self-assembly was influenced more by ohmic losses, particularly in the membrane. The maximum power generation was obtained at 0.35 V. The mass transport losses increased after this value, thereby affecting the efficiency of the PEMFC. 2 figs.

  11. Predicting catalyst-support interactions between metal nanoparticles and amorphous silica supports

    Science.gov (United States)

    Ewing, Christopher S.; Veser, Götz; McCarthy, Joseph J.; Lambrecht, Daniel S.; Johnson, J. Karl

    2016-10-01

    Metal-support interactions significantly affect the stability and activity of supported catalytic nanoparticles (NPs), yet there is no simple and reliable method for estimating NP-support interactions, especially for amorphous supports. We present an approach for rapid prediction of catalyst-support interactions between Pt NPs and amorphous silica supports for NPs of various sizes and shapes. We use density functional theory calculations of 13 atom Pt clusters on model amorphous silica supports to determine linear correlations relating catalyst properties to NP-support interactions. We show that these correlations can be combined with fast discrete element method simulations to predict adhesion energy and NP net charge for NPs of larger sizes and different shapes. Furthermore, we demonstrate that this approach can be successfully transferred to Pd, Au, Ni, and Fe NPs. This approach can be used to quickly screen stability and net charge transfer and leads to a better fundamental understanding of catalyst-support interactions.

  12. Influence of Au Nanoparticle Shape on Au@Cu2O Heterostructures

    Directory of Open Access Journals (Sweden)

    Jie Zhu

    2015-01-01

    Full Text Available Synthesis of metal-semiconductor heterostructures may allow the combination of function of the corresponding components and/or the enhanced performance resulting from the interactions between all the components. In this paper, Au@Cu2O core-shell heterostructures are prepared by a seed-growth method, using different-shaped Au nanocrystals as the seeds such as nanorods, octahedra, decahedra, dots, and nanocubes. The results revealed that the final structure of Au@Cu2O was greatly influenced by the shape of the seeds used. Exposure of Cu2O{111} and Cu2O{001} favored when the overgrowth happened on Au{111} and Au{001} surface, respectively. The size of the product can also be tuned by the amount of the seeds. The results reported here provide a thinking clue to modulate the shape and size of core-shell nanocrystals, which is useful in developing new materials with desired performance.

  13. Investigation on enhancing effects of Au nanoparticles on solar steam generation in graphene oxide nanofluids

    International Nuclear Information System (INIS)

    Fu, Yang; Mei, Tao; Wang, Gang; Guo, Ankang; Dai, Guangchao; Wang, Sheng; Wang, Jianying; Li, Jinhua; Wang, Xianbao

    2017-01-01

    Graphical abstract: Nanocomposites of graphene oxide (GO) and gold (Au) were explored to generate solar vapor under nature sunlight, and the water vaporization efficiency of GO-Au nanofluids at a temperature far below the boiling point could be up to 59.2%. - Highlights: • Graphene oxide/gold nanofluids were used to generate solar vapor under nature sunlight. • Water vaporization efficiency of GO-Au nanofluids could be up to 59.2%. • GO can be reduced to graphene by sunlight irradiation without reductants. - Abstract: Solar vapor generation enabled by nanoparticles is a green, efficient and direct approach to utilize solar energy. In this work, nanocomposites of graphene oxide (GO) and gold (Au) nanoparticles were prepared to generate solar steam under sunlight irradiation. The changes on steam pressure, mass loss and temperature of water were used to study the solar photothermal properties of GO-Au nanocomposites in water, which demonstrated that the synergistic interaction between GO nanosheets and Au nanoparticles played an active role in the photothermal effect of the nanocomposites. Trace of Au nanoparticles (15.6 wt‰) in the GO nanofluids could significantly improve the efficiency of solar vapor generation. More interestingly, the morphology and color of GO-Au nanofluids varied with irradiation times under sunlight, and our results suggested that GO sheets were reduced to graphene sheets. This process of photothermal deoxygenation of GO provides an available solution for preparing graphene sheets under ambient conditions without any reductions, and the solar steam generation method can enable potential applications like sterilization of waste, seawater desalination, and disinfection.

  14. Formation of Au nanoparticles in sapphire by using Ar ion implantation and thermal annealing

    International Nuclear Information System (INIS)

    Zhou, L.H.; Zhang, C.H.; Yang, Y.T.; Li, B.S.; Zhang, L.Q.; Fu, Y.C.; Zhang, H.H.

    2009-01-01

    In this paper, we present results of the synthesis of gold nanoclusters in sapphire, using Ar ion implantation and annealing in air. Unlike the conventional method of Au implantation followed by thermal annealing, Au was deposited on the surface of m- and a- cut sapphire single crystal samples including those pre-implanted with Ar ions. Au atoms were brought into the substrate by subsequent implantation of Ar ions to form Au nanoparticles. Samples were finally annealed stepwisely in air at temperatures ranging from 400 to 800 deg. C and then studied using UV-vis absorption spectrometry, transmission electron microscopy and Rutherford backscattered spectrometry. Evidence of the formation Au nanoparticles in the sapphire can be obtained from the characteristic surface plasmon resonance (SPR) absorption band in the optical absorption spectra or directly from the transmission electron microscopy. The results of optical absorption spectra indicate that the specimen orientations and pre-implantation also influence the size and the volume fraction of Au nanoparticles formed. Theoretical calculations using Maxwell-Garnett effective medium theory supply a good interpretation of the optical absorption results.

  15. Au nanoparticles on tryptophan-functionalized graphene for sensitive detection of dopamine

    International Nuclear Information System (INIS)

    Lian, Qianwen; Luo, Ai; An, Zhenzhen; Li, Zhuang; Guo, Yongyang; Zhang, Dongxia; Xue, Zhonghua; Zhou, Xibin; Lu, Xiaoquan

    2015-01-01

    Graphical abstract: - Highlights: • A novel AuNPs/Trp-GR composite was fabricated by directly electrochemical deposition. • The composite exhibited excellent electrocatalytic activity towards DA. • The proposed method was applied to real samples. - Abstract: A novel and uniform gold nanoparticles/tryptophan-functionalized graphene nanocomposite (AuNPs/Trp-GR) has been successfully fabricated by directly electrochemical depositing gold onto the surface of tryptophan-functionalized graphene (Trp-GR). The nanostructure of AuNPs/Trp-GR was characterized by using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). It was demonstrated that Au nanoparticles were well dispersed on the surface of Trp-GR which might attribute to the more binding sites provided by Trp-GR for the formation of Au nanoparticles. The electrocatalytic activity of the AuNPs/Trp-GR towards the dopamine (DA) was systematically investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimum conditions, a wide and valuable linear range (0.5–411 μM), a low detection limit (0.056 μM, S/N = 3), good repeatability and stability were obtained for the determination of DA. Furthermore, the modified electrode was successfully applied to real samples analysis

  16. Au nanoparticles on tryptophan-functionalized graphene for sensitive detection of dopamine

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Qianwen; Luo, Ai; An, Zhenzhen; Li, Zhuang; Guo, Yongyang; Zhang, Dongxia [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Geography and Environment Science, Northwest Normal University, 730070, Lanzhou (China); Xue, Zhonghua [College of Chemistry and Chemical Engineering, Northwest Normal University, 730070, Lanzhou (China); Zhou, Xibin, E-mail: zhouxb@nwnu.edu.cn [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Geography and Environment Science, Northwest Normal University, 730070, Lanzhou (China); Lu, Xiaoquan, E-mail: Luxq@nwnu.edu.cn [College of Chemistry and Chemical Engineering, Northwest Normal University, 730070, Lanzhou (China)

    2015-09-15

    Graphical abstract: - Highlights: • A novel AuNPs/Trp-GR composite was fabricated by directly electrochemical deposition. • The composite exhibited excellent electrocatalytic activity towards DA. • The proposed method was applied to real samples. - Abstract: A novel and uniform gold nanoparticles/tryptophan-functionalized graphene nanocomposite (AuNPs/Trp-GR) has been successfully fabricated by directly electrochemical depositing gold onto the surface of tryptophan-functionalized graphene (Trp-GR). The nanostructure of AuNPs/Trp-GR was characterized by using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). It was demonstrated that Au nanoparticles were well dispersed on the surface of Trp-GR which might attribute to the more binding sites provided by Trp-GR for the formation of Au nanoparticles. The electrocatalytic activity of the AuNPs/Trp-GR towards the dopamine (DA) was systematically investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimum conditions, a wide and valuable linear range (0.5–411 μM), a low detection limit (0.056 μM, S/N = 3), good repeatability and stability were obtained for the determination of DA. Furthermore, the modified electrode was successfully applied to real samples analysis.

  17. Growth of Au nanoparticle films and the effect of nanoparticle shape on plasmon peak wavelength

    Energy Technology Data Exchange (ETDEWEB)

    Horikoshi, S., E-mail: horikoshi@sstl.info; Matsumoto, N.; Kato, T. [Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo 113-8656 (Japan); Omata, Y. [Application and Technical Support, Elionix, Inc., 3-7-6 Motoyokoyama Hachioji, Tokyo 192-0063 (Japan)

    2014-05-21

    Metal nanoparticles (NPs) exhibit localized surface plasmon resonance (LSPR) and thus have potential for use in a wide range of applications. A facile technique for the preparation of NP films using an electron-cyclotron-resonance plasma sputtering method without a dewetting process is described. Field emission scanning electron microscopy (FE-SEM) observations revealed that the Au NPs grew independently as island-like particles during the first stage of sputtering and then coalesced with one another as sputtering time increased to ultimately form a continuous film. A plasmon absorption peak was observed via optical measurement of absorption efficiency. The LSPR peak shifted toward longer wavelengths (red shift) with an increase in sputtering time. The cause of this plasmon peak shift was theoretically investigated using the finite-difference time-domain calculation method. A realistic statistical distribution of the particle shapes based on FE-SEM observations was applied for the analysis, which has not been previously reported. It was determined that the change in the shape of the NPs from spheroidal to oval or slender due to coalescence with neighbouring NPs caused the LSPR peak shift. These results may enable the design of LSPR devices by controlling the characteristics of the nanoparticles, such as their size, shape, number density, and coverage.

  18. Growth of Au nanoparticle films and the effect of nanoparticle shape on plasmon peak wavelength

    Science.gov (United States)

    Horikoshi, S.; Matsumoto, N.; Omata, Y.; Kato, T.

    2014-05-01

    Metal nanoparticles (NPs) exhibit localized surface plasmon resonance (LSPR) and thus have potential for use in a wide range of applications. A facile technique for the preparation of NP films using an electron-cyclotron-resonance plasma sputtering method without a dewetting process is described. Field emission scanning electron microscopy (FE-SEM) observations revealed that the Au NPs grew independently as island-like particles during the first stage of sputtering and then coalesced with one another as sputtering time increased to ultimately form a continuous film. A plasmon absorption peak was observed via optical measurement of absorption efficiency. The LSPR peak shifted toward longer wavelengths (red shift) with an increase in sputtering time. The cause of this plasmon peak shift was theoretically investigated using the finite-difference time-domain calculation method. A realistic statistical distribution of the particle shapes based on FE-SEM observations was applied for the analysis, which has not been previously reported. It was determined that the change in the shape of the NPs from spheroidal to oval or slender due to coalescence with neighbouring NPs caused the LSPR peak shift. These results may enable the design of LSPR devices by controlling the characteristics of the nanoparticles, such as their size, shape, number density, and coverage.

  19. Au nanoparticles attached carbon nanotubes as a high performance active element in field effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Myeongsoon; Kim, Don, E-mail: donkim@pknu.ac.kr

    2016-08-15

    The Au nanoparticles attached carbon nanotubes (Au-CNTs), diameter ranged from 40 to 250 nm, were prepared and discussed their chemical and electrical properties. The shape and crystallinity of the carbon nanotubes (CNTs) phase depended main2ly on the diameter of CNTs (r{sub Au-CNT}). Highly crystalline, straight CNTs were observed when the r{sub Au-CNT} exceeded 80 nm, and less crystalline noodle-shaped CNTs were observed when the r{sub Au-CNT} was smaller than 80 nm. The crystallinity of the CNT phase was confirmed by analyzing the G and D bands in their Raman spectra and the electrical conductivities of the Au-CNTs. The electrical conductivity of the highly crystalline carbon phase of Au-CNTs (r{sub Au-CNT} = 250 nm) was ∼10{sup 4} S/cm. The back-gated field effect transistors (FETs) based on the Au-CNTs, which were assembled on a SiO{sub 2}/Si wafer using the dielectrophoresis technique, showed that the Au-CNTs would be a good functional electronic material for future electronic and sensing applications. The transconductance and hole mobility of the FETs, which were assembled with the highly crystalline Au-CNTs (r{sub Au-CNT} = 250 nm), reached to 3.6 × 10{sup −4} A/V and 3.1 × 10{sup 4} cm{sup 2}/V s, respectively. These values are in the middle of those of reported for single walled carbon nanotubes and graphene. However, we could not find any field effect in a CNTFET, which assembled without Au nanoparticles, through the same process. - Highlights: • The shape and crystallinity of the CNTs depended mainly on the diameter of CNTs. • The electrical conductivity of the highly crystalline Au-CNTs was ∼10{sup 4} S/cm. • The Au-CNT FET shows typical p-channel gate effect with the on/off ratio of ∼10{sup 4}. • The Au-CNT FET shows very high transconductance (g{sub m}) and carrier mobility (μ{sub h}).

  20. Green synthesis and characterization of Au@Pt core-shell bimetallic nanoparticles using gallic acid

    Science.gov (United States)

    Zhang, Guojun; Zheng, Hongmei; Shen, Ming; Wang, Lei; Wang, Xiaosan

    2015-06-01

    In this study, we developed a facile and benign green synthesis approach for the successful fabrication of well-dispersed urchin-like Au@Pt core-shell nanoparticles (NPs) using gallic acid (GA) as both a reducing and protecting agent. The proposed one-step synthesis exploits the differences in the reduction potentials of AuCl4- and PtCl62-, where the AuCl4- ions are preferentially reduced to Au cores and the PtCl62- ions are then deposited continuously onto the Au core surface as a Pt shell. The as-prepared Au@Pt NPs were characterized by transmission electron microscope (TEM); high-resolution transmission electron microscope (HR-TEM); scanning electron microscope (SEM); UV-vis absorption spectra (UV-vis); X-ray diffraction (XRD); Fourier transmission infrared spectra (FT-IR). We systematically investigated the effects of some experimental parameters on the formation of the Au@Pt NPs, i.e., the reaction temperature, the molar ratios of HAuCl4/H2PtCl6, and the amount of GA. When polyvinylpyrrolidone K-30 (PVP) was used as a protecting agent, the Au@Pt core-shell NPs obtained using this green synthesis method were better dispersed and smaller in size. The as-prepared Au@Pt NPs exhibited better catalytic activity in the reaction where NaBH4 reduced p-nitrophenol to p-aminophenol. However, the results showed that the Au@Pt bimetallic NPs had a lower catalytic activity than the pure Au NPs obtained by the same method, which confirmed the formation of Au@Pt core-shell nanostructures because the active sites on the surfaces of the Au NPs were covered with a Pt shell.

  1. Evaluation of the photophysicochemical properties and photodynamic therapy activity of nanoconjugates of zinc phthalocyanine linked to glutathione capped Au and Au3Ag1 nanoparticles

    CSIR Research Space (South Africa)

    Oluwole, DA

    2018-03-01

    Full Text Available , Charles Maphanga, Saturnin Ombinda-Lemboumba, Patience Mthunzi-Kufa, Tebello Nyokong ABSTRACT: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold– silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn...

  2. Influence of Au Nanoparticle Shape on Au@Cu2O Heterostructures

    OpenAIRE

    Zhu, Jie; Lu, Na; Chen, Wei; Kong, Lina; Yang, Yun; Ma, Dekun; Huang, Shaoming

    2015-01-01

    Synthesis of metal-semiconductor heterostructures may allow the combination of function of the corresponding components and/or the enhanced performance resulting from the interactions between all the components. In this paper, Au@Cu2O core-shell heterostructures are prepared by a seed-growth method, using different-shaped Au nanocrystals as the seeds such as nanorods, octahedra, decahedra, dots, and nanocubes. The results revealed that the final structure of Au@Cu2O was greatly influenced by ...

  3. Bendable solid-state supercapacitors with Au nanoparticle-embedded graphene hydrogel films

    Science.gov (United States)

    Yang, Kyungwhan; Cho, Kyoungah; Yoon, Dae Sung; Kim, Sangsig

    2017-01-01

    In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded GH supercapacitors (NP-GH SCs) exhibit excellent capacitive performances, with large specific capacitance (135 F/g) and high energy density (15.2 W·h/kg). Moreover, the NP-GH SCs exhibit comparable areal capacitance (168 mF/cm2) and operate under tensile/compressive bending. PMID:28074865

  4. Negative effect of Au nanoparticles on an IGZO TFT-based nonvolatile memory device

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Myunghoon; Yoo, Gwangwe; Lee, Jongtaek; Jeong, Seokwon; Roh, Yonghan; Park, Jinhong; Kwon, Namyong [Sungkyunkwan University, Suwon (Korea, Republic of); Jung, Wooshik [Stanford University, Stanford, CA (United States)

    2014-02-15

    In this letter, the electrical characteristics of nonvolatile memory devices based on back gate type indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) are investigated in terms of the Au nanoparticles (NPs) employed in the floating gate-stack of the device. The size of the Au NPs is controlled using a by 500 .deg. C annealing process after the Au thin-film deposition. The size and the roughness of the Au NPs were observed by using scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. In order to analyze the electrical properties according to Au NP size, we measured the current-voltage (I{sub D}-V{sub G}) characteristics of the nonvolatile memory devices fabricated without Au NPs and with Au NPs of various sizes. The size of the Au NP increased, so did the surface roughness of the gate. This resulted in increased carrier scattering, which subsequently degraded the on-current of the memory device. In addition, inter-diffusion between the Au and the α-IGZO through the non-uniform Al{sub 2}O{sub 3} tunneling layer seemed to further degrade the device performance.

  5. Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

    Science.gov (United States)

    Maharaj, Dave

    2012-01-01

    Summary Nano-object additives are used in tribological applications as well as in various applications in liquids requiring controlled manipulation and targeting. On the macroscale, nanoparticles in solids and liquids have been shown to reduce friction and wear. On the nanoscale, atomic force microscopy (AFM) studies have been performed in single- and multiple-nanoparticle contact, in dry environments, to characterize friction forces and wear. However, limited studies in submerged liquid environments have been performed and further studies are needed. In this paper, spherical Au nanoparticles were studied for their effect on friction and wear under dry conditions and submerged in water. In single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the nanoscale with AFM as well as on the macroscale by using a ball-on-flat tribometer to relate friction and wear reduction on the nanoscale and macroscale. Results indicate that the addition of Au nanoparticles reduces friction and wear. PMID:23213639

  6. Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

    Directory of Open Access Journals (Sweden)

    Dave Maharaj

    2012-11-01

    Full Text Available Nano-object additives are used in tribological applications as well as in various applications in liquids requiring controlled manipulation and targeting. On the macroscale, nanoparticles in solids and liquids have been shown to reduce friction and wear. On the nanoscale, atomic force microscopy (AFM studies have been performed in single- and multiple-nanoparticle contact, in dry environments, to characterize friction forces and wear. However, limited studies in submerged liquid environments have been performed and further studies are needed. In this paper, spherical Au nanoparticles were studied for their effect on friction and wear under dry conditions and submerged in water. In single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the nanoscale with AFM as well as on the macroscale by using a ball-on-flat tribometer to relate friction and wear reduction on the nanoscale and macroscale. Results indicate that the addition of Au nanoparticles reduces friction and wear.

  7. Controllable synthesis and characterization of Fe3O4/Au composite nanoparticles

    International Nuclear Information System (INIS)

    Xing, Yan; Jin, Yan-Yan; Si, Jian-Chao; Peng, Ming-Li; Wang, Xiao-Fang; Chen, Chao; Cui, Ya-Li

    2015-01-01

    Fe 3 O 4 /Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe 3 O 4 nanoparticles. Many efforts have been devoted to the synthesis of these composite nanoparticles. Herein, GoldMag NPs were reported to be synthesized by two-step method. Fe 3 O 4 nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe 3 O 4 nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl 4 . The size of obtained nanoparticles was geared from 25 to 300 nm by controlling the concentration of reactants. The GoldMag NPs were characterized by UV–vis spectrometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The GoldMag NPs showed good superparamagnetism at room temperature and were well dispersed in water with surface plasmon resonance absorption peak varied from 538 nm to 570 nm. - Highlights: • A low cost, simple manipulation and nontoxic approach was designed for preparation of magnetic Fe 3 O 4 /Au (GoldMag NPs) nanocomposites. • The size of GoldMag NPs could be controlled from 25 to 300 nm by varying the concentration of reactants. • GoldMag NPs possessed good magnetic response, high dispersion, and good stability

  8. The characteristics and mechanisms of Au nanoparticles processed by functional centrifugal procedures

    Science.gov (United States)

    Shiau, Bo-Wen; Lin, Chien-Hung; Liao, Ying-Yen; Lee, Ya-Rong; Liu, Shih-Hao; Ding, Wei-Cheng; Lee, Jia-Ren

    2018-05-01

    In this work, the optical properties of Au nanoparticles processed by centrifugation techniques are studied. Most of the literature related to the control of nanoparticle size has focused on different preparation parameters; however, the wide size distribution is commonly an issue for follow-up investigations and further applications. Therefore, we developed a method in which specific-diameter particles can be effectively separated using different centrifugal procedures. The initial nanoparticle solution with a primary absorption peak at 534 nm is separated into discernible resonance wavelengths from 526 to 537 nm, with corresponding particle sizes from 30 to 55 nm. For the atomic force microscopy analysis of nanoparticle size, a dry cetyltrimethylammonium bromide (CTAB) film often covers the particles and interferes with the measurement; thus, CTAB has to be removed. However, if too much CTAB is removed, the surface of the Au nanoparticle becomes unstable, and the particles aggregate. Accordingly, we used UV spectroscopy to monitor the CTAB content; properly adjust the rotational speed and the number of centrifugation stages; and design a method that can effectively remove impurities, avoid clustering, and enable particle size measurement. The usually complicated procedures and high cost of preparation of specific-size Au nanoparticles are greatly simplified and reduced by the convenient extraction process proposed in this work, which would benefit related research and applications.

  9. Synthesis of gold nanoparticles on multi-walled carbon nanotubes (Au-MWCNTs) via deposition precipitation method

    Science.gov (United States)

    Zulikifli, Farah Wahida Ahmad; Yazid, Hanani; Halim, Muhammad Zikri Budiman Abdul; Jani, Abdul Mutalib Md

    2017-09-01

    Carbon nanotubes (CNTs) have received impressive consideration as support materials of noble metal catalysts in heterogeneous catalysis due to their good mechanical strength, large surface area and good durability under harsh conditions. The interaction between CNTs and noble metal nanoparticles (NPs) gives an unusual unique microstructure properties and or modification of the electron density of the noble metal clusters, and enhances the catalytic activity. In this study, the MWCNTs were first treated with a mixture of concentrated sulfuric and nitric acid by sonication to improve its dispersibility and to introduce the carboxylic (-COOH) groups on CNTs surfaces. Gold nanoparticles (Au NPs) on multiwalled carbon nanotubes (MWCNTs) were synthesized by the deposition precipitation (DP) method as this method is simpler, low cost, and excellent method. Then, the effect of reducing agent (NaBH4) on gold distribution on the support of MWCNTs was also studied. Dispersion test, Fourier Transform Infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) are all used to characterize the functionalized MWCNTs (fCNTs) and the Au NPs-fCNTs catalyst. There are three important peaks in functionalized MWCNTs which correspond to C=O, O-H, and C-O absorption peaks, as a result of the oxidation of COOH groups on the surface of CNTs. The absorption band at 1717 cm-1 is corresponded to C=O stretching of COOH, while the absorption bands at 3384 cm-1 and 1011cm-1 are associated with O-H bending and C-O stretching, respectively. Surface morphology of Au NPs-fCNTs R4 and Au NPs- fCNTs WR catalyst by FESEM showed that the Au NPs of 19.22 ± 2.33 nm and 23.05 ± 2.57 nm size were successfully deposited on CNTs, respectively.

  10. A facile approach to fabricate Au nanoparticles loaded SiO{sub 2} microspheres for catalytic reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingyi, E-mail: mingyitjucu@163.com [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Huang, Guanbo, E-mail: gbhuang2007@hotmail.com [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Li, Xianxian; Pang, Xiaobo [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Qiu, Haixia [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China)

    2015-07-15

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO{sub 2}@Au composite particles. The influence of polymers on the morphology of SiO{sub 2}@Au particles with different size of SiO{sub 2} cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO{sub 2}@Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO{sub 2} microspheres. The SiO{sub 2}@Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO{sub 2} microspheres. SiO{sub 2}@Au particles can be also prepared from SiO{sub 2} microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO{sub 2} or other microspheres. The SiO{sub 2}@Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres.

  11. A facile approach to fabricate Au nanoparticles loaded SiO2 microspheres for catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Tang, Mingyi; Huang, Guanbo; Li, Xianxian; Pang, Xiaobo; Qiu, Haixia

    2015-01-01

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO 2 @Au composite particles. The influence of polymers on the morphology of SiO 2 @Au particles with different size of SiO 2 cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO 2 @Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO 2 microspheres. The SiO 2 @Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO 2 microspheres. SiO 2 @Au particles can be also prepared from SiO 2 microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO 2 or other microspheres. The SiO 2 @Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres

  12. SERS-active Ag, Au and Ag–Au alloy nanoparticles obtained by laser ablation in liquids for sensing methylene blue

    Energy Technology Data Exchange (ETDEWEB)

    Olea-Mejía, Oscar, E-mail: oleaoscar@yahoo.com.mx [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Universidad Autónoma del Estado de México, km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50200, México (Mexico); Fernández-Mondragón, Mariana; Rodríguez-de la Concha, Gabriela [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Universidad Autónoma del Estado de México, km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50200, México (Mexico); Camacho-López, Marco [Laboratorio de Investigación y Desarrollo de Materiales Avanzados, Universidad Autónoma del Estado de México, Km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50925, México (Mexico)

    2015-09-01

    Highlights: • We synthesized Ag/Au nanoparticles by laser ablation in liquids. • We characterized such particles by UV–vis, TEM and EDS/STEM. • The SERS effect was studied for the obtained nanoparticles. • Pure silver nanoparticles showed the highest SERS signals. • We can sense methylene blue at a concentration of 10{sup −10} mole/L. - Abstract: We have synthesized Ag–Au nanoparticles by laser ablation in liquids using five different targets: 100% Ag, 80%Ag/20%Au, 50%Ag/50%Au, 20%Ag/80%Au and 100% Au (weight percentages). We used ethanol and methylene blue solutions in ethanol as the liquid media. The nanoparticles were mostly spherical with diameters 15, 19, 18, 23 and 11 nm, respectively. When alloyed targets were used, the resulting nanoparticles were completely alloyed forming solid solutions as evidenced by UV–vis Spectroscopy and Scanning Transmission Electron Microscopy. The obtained nanoparticles were employed to study the SERS effect of the methylene blue molecule. All the samples showed good SERS activity, however the ones composed of pure silver showed the greatest Raman signal enhancement. Finally, pure Ag nanoparticles were used for sensing methylene blue at different concentrations. While almost no signal can be discerned from the Raman spectrum when no particles are used at a concentration of methylene blue of 1 × 10{sup −2} M (∼3000 ppm), when Ag nanoparticles are used one can observe the characteristic peak of the molecule at concentrations as low as 1 × 10{sup −10} M (∼3 × 10{sup −5} ppm)

  13. Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

    Science.gov (United States)

    Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

    2015-12-01

    Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

  14. Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

    International Nuclear Information System (INIS)

    Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

    2015-01-01

    Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611}high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H_2PtCl_6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells. (paper)

  15. Spectroscopic and Physical Characterization of Functionalized Au Nanoparticles: A Multiweek Experimental Project

    Science.gov (United States)

    Masson, Jean-Francois; Yockell-Lelièvre, Hélène

    2014-01-01

    A term project was introduced in teaching advanced spectroscopy and notions of nanotechnology to chemistry students at the graduate level (M.Sc. and Ph.D.). This project could also be suited for an honor's thesis at the undergraduate level. Students were assigned a unique combination of nanoparticle synthesis (13 nm Au nanospheres, ~100 nm…

  16. Evidence for Bioavailability of Au Nanoparticles from Soil and Biodistribution within Earthworms (Eisenia fetida)

    Energy Technology Data Exchange (ETDEWEB)

    J Unrine; S Hunyadi; O Tsyusko; W Rao; A Shoults-Wilson; P Bertsch

    2011-12-31

    Because Au nanoparticles (NPs) are resistant to oxidative dissolution and are easily detected, they have been used as stable probes for the behavior of nanomaterials within biological systems. Previous studies provide somewhat limited evidence for bioavailability of Au NPs in food webs, because the spatial distribution within tissues and the speciation of Au was not determined. In this study, we provide multiple lines of evidence, including orthogonal microspectroscopic techniques, as well as evidence from biological responses, that Au NPs are bioavailable from soil to a model detritivore (Eisenia fetida). We also present limited evidence that Au NPs may cause adverse effects on earthworm reproduction. This is perhaps the first study to demonstrate that Au NPs can be taken up by detritivores from soil and distributed among tissues. We found that primary particle size (20 or 55 nm) did not consistently influence accumulated concentrations on a mass concentration basis; however, on a particle number basis the 20 nm particles were more bioavailable. Differences in bioavailability between the treatments may have been explained by aggregation behavior in pore water. The results suggest that nanoparticles present in soil from activities such as biosolids application have the potential to enter terrestrial food webs.

  17. Au Nanoparticle Sub-Monolayers Sandwiched between Sol-Gel Oxide Thin Films

    Science.gov (United States)

    Della Gaspera, Enrico; Menin, Enrico; Sada, Cinzia

    2018-01-01

    Sub-monolayers of monodisperse Au colloids with different surface coverage have been embedded in between two different metal oxide thin films, combining sol-gel depositions and proper substrates functionalization processes. The synthetized films were TiO2, ZnO, and NiO. X-ray diffraction shows the crystallinity of all the oxides and verifies the nominal surface coverage of Au colloids. The surface plasmon resonance (SPR) of the metal nanoparticles is affected by both bottom and top oxides: in fact, the SPR peak of Au that is sandwiched between two different oxides is centered between the SPR frequencies of Au sub-monolayers covered with only one oxide, suggesting that Au colloids effectively lay in between the two oxide layers. The desired organization of Au nanoparticles and the morphological structure of the prepared multi-layered structures has been confirmed by Rutherford backscattering spectrometry (RBS), Secondary Ion Mass Spectrometry (SIMS), and Scanning Electron Microscopy (SEM) analyses that show a high quality sandwich structure. The multi-layered structures have been also tested as optical gas sensors. PMID:29538338

  18. Controlled formation of metallic nanowires via Au nanoparticle ac trapping

    International Nuclear Information System (INIS)

    Bernard, L; Calame, M; Molen, S J van der; Liao, J; Schoenenberger, C

    2007-01-01

    Applying ac voltages, we trapped gold nanoparticles between micro-fabricated electrodes under well-defined conditions. We demonstrate that the nanoparticles can be controllably fused together to form homogeneous gold nanowires with pre-defined diameters and conductance values. Whereas electromigration is known to form a gap when a dc voltage is applied, this ac technique achieves the opposite, thereby completing the toolkit for the fabrication of nanoscale junctions

  19. Controlled formation of metallic nanowires via Au nanoparticle ac trapping

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, L; Calame, M; Molen, S J van der; Liao, J; Schoenenberger, C [Institute of Physics, University of Basel, CH-4056 Basel (Switzerland)

    2007-06-13

    Applying ac voltages, we trapped gold nanoparticles between micro-fabricated electrodes under well-defined conditions. We demonstrate that the nanoparticles can be controllably fused together to form homogeneous gold nanowires with pre-defined diameters and conductance values. Whereas electromigration is known to form a gap when a dc voltage is applied, this ac technique achieves the opposite, thereby completing the toolkit for the fabrication of nanoscale junctions.

  20. Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

    Energy Technology Data Exchange (ETDEWEB)

    Rubina, M.S.; Kamitov, E.E. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Zubavichus, Ya. V.; Peters, G.S. [National Research center «Kurchatov Institute», Moscow, 123182 Russian Federation (Russian Federation); Naumkin, A.V. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Suzer, S. [Department of Chemistry, Bilkent University, Ankara, 06800 Turkey (Turkey); Vasil’kov, A.Yu., E-mail: alexandervasilkov@yandex.ru [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation)

    2016-03-15

    Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

  1. Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

    International Nuclear Information System (INIS)

    Rubina, M.S.; Kamitov, E.E.; Zubavichus, Ya. V.; Peters, G.S.; Naumkin, A.V.; Suzer, S.; Vasil’kov, A.Yu.

    2016-01-01

    Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

  2. Water-dispersable hybrid Au-Pd nanoparticles as catalysts in ethanol oxidation, aqueous phase Suzuki-Miyaura and Heck reactions

    KAUST Repository

    Song, Hyon Min

    2012-01-01

    The catalytic activities of water-dispersable Au@Pd core-shell nanoparticles (NPs) and Au-Pd alloy NPs were examined. There is growing interest in Au-Pd hybridized NPs in a supported matrix or non-supported forms as catalysts in various reactions that are not limited to conventional Pd-related reactions. Four different Au@Pd core-shell NPs in this study were prepared at room temperature with help from the emulsion phase surrounding the Au core NPs. Au-Pd alloy NPs were prepared over 90 °C, and underwent phase transfer to aqueous medium for their catalytic use. Au@Pd core-shell NPs show catalytic activity in ethanol oxidation reactions as electrocatalysts, and both core-shell and alloy NPs are good to excellent catalysts in various Suzuki-Miyaura and Heck reactions as heterogeneous catalysts. Specifically, Au@Pd core-shell NPs with sharp branched arms show the highest yield in the reactions tested in this study. A relatively small amount (0.25 mol%) was used throughout the catalytic reactions. © 2012 The Royal Society of Chemistry.

  3. Gold nanoparticles supported on magnesium oxide for CO oxidation

    Science.gov (United States)

    Carabineiro, Sónia Ac; Bogdanchikova, Nina; Pestryakov, Alexey; Tavares, Pedro B.; Fernandes, Lisete Sg; Figueiredo, José L.

    2011-06-01

    Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

  4. Gold nanoparticles supported on magnesium oxide for CO oxidation

    Directory of Open Access Journals (Sweden)

    Bogdanchikova Nina

    2011-01-01

    Full Text Available Abstract Au was loaded (1 wt% on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved. The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

  5. Conduction and reversible memory phenomena in Au-nanoparticles-incorporated TeO{sub 2}–ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Bontempo, L., E-mail: bontempo@usp.br [Laboratório de Sistemas Integráveis, Escola Politécnica da Universidade de São Paulo, Av. Prof. Luciano Gualberto, 158, Travessa 3, 05508-900 São Paulo, SP (Brazil); Laboratório de Materiais Fotônicos e Optoeletrônicos, Faculdade de Tecnologia de São Paulo, Praça Cel. Fernando Prestes, 30, 01124-060 São Paulo, SP (Brazil); Santos Filho, S.G. dos, E-mail: sgsantos@usp.br [Laboratório de Sistemas Integráveis, Escola Politécnica da Universidade de São Paulo, Av. Prof. Luciano Gualberto, 158, Travessa 3, 05508-900 São Paulo, SP (Brazil); Kassab, L.R.P., E-mail: kassablm@osite.com.br [Laboratório de Materiais Fotônicos e Optoeletrônicos, Faculdade de Tecnologia de São Paulo, Praça Cel. Fernando Prestes, 30, 01124-060 São Paulo, SP (Brazil)

    2016-07-29

    A reversible memory behavior in TeO{sub 2}–ZnO thin films containing Au nanoparticles prepared using the sputtering technique has been observed. The current–voltage characteristics of the films, having Al and Si as electrodes, showed a switching behavior starting from an initial state of low conductivity to a high conductivity one. As a result, an abrupt increase of current (10{sup −7} to 10{sup −3} A) was observed for 6.5 V (100 nm thickness). Au nanoparticles provide a larger electron storage capability, and do not favor the transport through the insulator; they present a higher trapped charge concentration, which reduces the leakage current to lower levels. The influence of the Au nanoparticle diameter and volumetric concentration to reach the abrupt current transition and the value of the transition voltage was studied. These parameters were found to play an important role on reversible memory phenomena as they determine the facility/difficulty to fill and saturate the traps (Au nanoparticles) with electrons. - Highlights: • TeO{sub 2}–ZnO thin films with Au nanoparticles grown by magnetron co-sputtering for memory devices • Nucleation of gold nanoparticles by annealing process • Electrical properties of TeO{sub 2}–ZnO thin films with and without gold nanoparticles • Reversible memory phenomenum in Au-nanoparticles-incorporated TeO{sub 2}–ZnO thin films.

  6. Au-coated 3-D nanoporous titania layer prepared using polystyrene-b-poly(2-vinylpyridine) block copolymer nanoparticles.

    Science.gov (United States)

    Shin, Won-Jeong; Basarir, Fevzihan; Yoon, Tae-Ho; Lee, Jae-Suk

    2009-04-09

    New nanoporous structures of Au-coated titania layers were prepared by using amphiphilic block copolymer nanoparticles as a template. A 3-D template composed of self-assembled quaternized polystyrene-b-poly(2-vinylpyridine) (Q-PS-b-P2VP) block copolymer nanoparticles below 100 nm was prepared. The core-shell-type nanoparticles were well ordered three-dimensionally using the vertical immersion method on the substrate. The polar solvents were added to the polymer solution to prevent particle merging at 40 degrees C when considering the interaction between polymer nanoparticles and solvents. Furthermore, Au-coated PS-b-P2VP nanoparticles were prepared using thiol-capped Au nanoparticles (3 nm). The 3-D arrays with Au-coated PS-b-P2VP nanoparticles as a template contributed to the preparation of the nanoporous Au-coated titania layer. Therefore, the nanoporous Au-coated titania layer was fabricated by removing PS-b-P2VP block copolymer nanoparticles by oxygen plasma etching.

  7. Organic nonvolatile resistive memory devices based on thermally deposited Au nanoparticle

    Science.gov (United States)

    Jin, Zhiwen; Liu, Guo; Wang, Jizheng

    2013-05-01

    Uniform Au nanoparticles (NPs) are formed by thermally depositing nominal 2-nm thick Au film on a 10-nm thick polyimide film formed on a Al electrode, and then covered by a thin polymer semiconductor film, which acts as an energy barrier for electrons to be injected from the other Al electrode (on top of polymer film) into the Au NPs, which are energetically electron traps in such a resistive random access memory (RRAM) device. The Au NPs based RRAM device exhibits estimated retention time of 104 s, cycle times of more than 100, and ON-OFF ratio of 102 to 103. The carrier transport properties are also analyzed by fitting the measured I-V curves with several conduction models.

  8. Au Nanoparticles as Interfacial Layer for CdS Quantum Dot-sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Zhu Guang

    2010-01-01

    Full Text Available Abstract Quantum dot-sensitized solar cells based on fluorine-doped tin oxide (FTO/Au/TiO2/CdS photoanode and polysulfide electrolyte are fabricated. Au nanoparticles (NPs as interfacial layer between FTO and TiO2 layer are dip-coated on FTO surface. The structure, morphology and impedance of the photoanodes and the photovoltaic performance of the cells are investigated. A power conversion efficiency of 1.62% has been obtained for FTO/Au/TiO2/CdS cell, which is about 88% higher than that for FTO/TiO2/CdS cell (0.86%. The easier transport of excited electron and the suppression of charge recombination in the photoanode due to the introduction of Au NP layer should be responsible for the performance enhancement of the cell.

  9. Time-dependent optical response of three-dimensional Au nanoparticle arrays formed on silica nanowires

    Science.gov (United States)

    Di Mario, Lorenzo; Otomalo, Tadele Orbula; Catone, Daniele; O'Keeffe, Patrick; Tian, Lin; Turchini, Stefano; Palpant, Bruno; Martelli, Faustino

    2018-03-01

    We present stationary and transient absorption measurements on 3D Au nanoparticle (NP)-decorated Si O2 nanowire arrays. The 3D NP array has been produced by the dewetting of a thin Au film deposited on silica nanowires produced by oxidation of silicon nanowires. The experimental behaviors of the spectral and temporal dynamics observed in the experiment are accurately described by a two-step, three-temperature model. Using an arbitrary set of Au NPs with different aspect ratios, we demonstrate that the width of the experimental spectra, the energy shift of their position with time, and the asymmetry between the two positive wings in the dynamical variation of absorption can all be attributed to the nonuniform shape distribution of the Au NPs in the sample.

  10. Manipulating the optical properties of dual implanted Au and Zn nanoparticles in sapphire

    Science.gov (United States)

    Epie, E. N.; Scott, D.; Chu, W. K.

    2017-11-01

    We have synthesized and manipulated the optical properties of metallic nanoparticles (NPs) by using a combination of low-energy high-fluence dual implantation and thermal annealing. We demonstrated that by implanting Zn before Au, the resulting absorption peak is enormously blue-shifted by 120 nm with respect to that of Au-only implanted samples. This magnitude of optical shift is not characteristic of unalloyed Au and to the best of our knowledge cannot be attributed to NP size change alone. On the other hand, the absorption peak for samples implanted with Au followed by Zn is blue-shifted about 20 nm. Additionally, by carefully annealing all implanted samples, both NP size distribution and corresponding optical properties can be further modified in a controlled manner. We attribute these behaviours to nanoalloy formation. This work provides a direct method for synthesizing and manipulating both the plasmonic and structural properties of metallic alloy NP in various transparent dielectrics for diverse applications.

  11. Growth and size distribution of Au nanoparticles in annealed Au/TiO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Reymond-Laruinaz, S.; Saviot, L.; Potin, V. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Lopes, C.; Vaz, F. [Centro de Física, Universidade do Minho, 4710-057 Braga (Portugal); Marco de Lucas, M.C., E-mail: delucas@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France)

    2014-02-28

    Nanocomposites consisting of noble metal nanoparticles (NPs) embedded in TiO{sub 2} thin films are of great interest for applications in optoelectronics, photocatalysis and solar-cells for which the plasmonic properties of the metal NPs play a major role. This work investigates the first stages of the formation of gold NPs by thermal annealing of Au-doped TiO{sub 2} thin films grown by magnetron sputtering. A low concentration of gold in the films is considered (5 at.%) in order to study the first stages of the formation of the NPs. Raman spectroscopy is used to follow the crystallization of TiO{sub 2} when increasing the annealing temperature. In addition, low-frequency Raman scattering (LFRS) is used to investigate the formation of gold NPs and to determine their size. Resonant LFRS measurements obtained by using a laser wavelength matching the surface plasmon resonance of the metallic NPs significantly enhances the Raman peak intensity enabling to focus on the first stages of the NPs formation. A double size distribution is observed at T{sub a} = 800 °C calling for additional investigations by transmission electron microscopy (TEM). TEM observations reveal an inhomogeneous in-depth size distribution of gold NPs. The annealed films are structured in two sublayers with bigger NPs at the bottom and smaller NPs at the top. At T{sub a} = 800 °C, a double size distribution is confirmed near the surface. A mechanism is proposed to explain the formation of the sublayers. The modification of the diffusion of gold atoms by stresses in the film near the substrate is assumed to be responsible for the observed two layers structure. - Highlights: • Gold-doped TiO{sub 2} thin films were grown by magnetron sputtering. • The first stages of the formation of Au nanoparticles after annealing are studied. • Au nanoparticles and crystallized TiO{sub 2} are observed above 400 °C. • The size distribution of the gold nanoparticles is complex and depth-dependent.

  12. Biosynthesis of gold nanoparticles by Aspergillum sp. WL-Au for degradation of aromatic pollutants

    Science.gov (United States)

    Qu, Yuanyuan; Pei, Xiaofang; Shen, Wenli; Zhang, Xuwang; Wang, Jingwei; Zhang, Zhaojing; Li, Shuzhen; You, Shengnan; Ma, Fang; Zhou, Jiti

    2017-04-01

    A simple method for synthesis of gold nanoparticles (AuNPs) using Aspergillum sp. WL-Au was presented in this study. According to UV-vis spectra and transmission electron microscopy images, the shape and size of AuNPs were affected by different parameters, including buffer solution, pH, biomass and HAuCl4 concentrations. Phosphate sodium buffer was more suitable for extracellular synthesis of AuNPs, and the optimal conditions for AuNPs synthesis were pH 7.0, biomass 100 mg/mL and HAuCl4 3 mM, leading to the production of spherical and pseudo-spherical nanoparticles. The biosynthesized AuNPs possessed excellent catalytic activities for the reduction of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-nitroaniline and m-nitroaniline in the presence of NaBH4, and the catalytic rate constants were calculated to be 6.3×10-3 s-1, 5.5×10-3 s-1, 10.6×10-3 s-1, 8.4×10-3 s-1 and 13.8×10-3 s-1, respectively. The AuNPs were also able to catalyze the decolorization of various azo dyes (e.g. Cationic Red X-GRL, Acid Orange II and Acid scarlet GR) using NaBH4 as the reductant, and the decolorization rates reached 91.0-96.4% within 7 min. The present study should provide a potential candidate for green synthesis of AuNPs, which could serve as efficient catalysts for aromatic pollutants degradation.

  13. Effects of Au nanoparticle addition to hole transfer layer in organic solar cells based on copper naphthalocyanine and fullerene

    Institute of Scientific and Technical Information of China (English)

    Akihiko Nagata; Takeo Okun; Tsuyoshi Akiyaman; Atsushi Suzuki

    2014-01-01

    Organic solar cells based on copper naphthalocyanine (CuNc) and fullerene (C60) were fabricated, and their photovoltaic properties were investigated. C60 and CuNc were used as n-type and p-type semiconductors, respectively. In addition, the effect of Au nanoparticle addition on a hole transfer layer was investigated, and the power conversion efficiency of the devices was improved after blending the Au nanoparticles into the hole transport layer. Nanostructures of Au nanoparticles were investigated by transmission electron microscopy and X-ray diffraction. Energy levels of molecules were calculated by molecular orbital calculations, and the nanostructure and electronic properties were discussed.

  14. Passive accumulation of Au nanoparticles in tumours in mice

    International Nuclear Information System (INIS)

    Kempson, I.M.; Wang, C.H.; Lai, S.F.; Cai, X.; Hwu, Y.; Yang, C.S.; Margaritondo, G.

    2011-01-01

    Full text: Enhance biocompatibility and passive accumulation of gold nanoparticles into tumours in vivo. Improved biocompatible nanoparticles synthesized by radical synthesis in solution by X-ray irradiation (5,000 Gy/sec). As an alternative to the use of chemical reducing agents, irradiation solutions can cause the reduction of dissolved ions to form nuclei form in sub-second times and growth is easily controlled by physically the X-ray intensity. The intensity can be used to manipulate growth rates for different applications and in the information of spherical and rod-structures. Size is easily controlled by exposure time and capping agents and provides high reproducibility with small size distributions. Resulting body burden in subcutaneous tumour mouse models was determined in various organs with ICP-MS. Cellular distributions were analysed with transmission x-ray Microscopy and conventional histology. The resulting nanoparticle sols were highly concentrated. naturally sterile, have high temperature stability and synthesised with fewer chemical reactants; providing greater chemical and biological adaptability. The results demonstrated that a passivated biocompatible surface, minimizing physiological clearance from the animal allows non-specific accumulation of large concentrations of nanoparticles into tumour tissues and significant penetration and circumnavigation of the binding site barrier effect. Concentrations of gold reached ∼ 25 times greater than surrounding muscle tissue and were retained for many hours. Physicochemical properties of nanoparticles impart significant influence on their ability to penetrate and accumulate in tumour tissues. Effective synthesis enables high concentrations of gold nanoparticles to accumulate in tumour tissues which could be applied to development in radiation oncology applications.

  15. Synthesis of Core/Shell MnFe2O4/Au Nanoparticles for Advanced Proton Treatment

    International Nuclear Information System (INIS)

    Park, Jeong Chan

    2014-01-01

    Among many approaches for the surface modification with materials, such as polymers, organic ligands and metals, one of the most attractive ways is using metals. The fabrication of metal-based, monolayer-coated magnetic nanoparticles has been intensively studied. However, the synthesis of metal-capped magnetic nanoparticles with monodIspersities and controllable sizes is still challenged. Recently, gold-capped magnetic nanoparticles have been reported to increase stability and to provide biocompatibility. Magnetic nanoparticle with gold coating is an attractive system, which can be stabilized in biological conditions and readily functionalized through well-established surface modification (Au-S) chemistry. The Au coating offers plasmonic properties to magnetic nanoparticles. The core/shell nanoparticles were transferred from organic to aqueous solutions for biomedical applications. The core/shell structured MnFe 2 O 4 /Au nanoparticles have been prepared and transferred from organic phase to aqueous solutions. The resulting Au-coated nanocrystals may be an attractive system for biomedical applications, which are needed both magnetic resonance imaging and optical imaging. The phase transferred core/shell nanoparticles can be decorated with targeting moiety, such as antibodies, peptides, aptamers, small molecules and ligands for biological applications. The proton treatment with the resulting Au-MnFe 2 O 4 nanoparticles is undergoing.

  16. Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

    International Nuclear Information System (INIS)

    Zhan, Wangcheng; Wang, Jinglin; Wang, Haifeng; Zhang, Jinshui; Liu, Xiaofei

    2017-01-01

    Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

  17. Experimental and Theoretical Structural Investigation of AuPt Nanoparticles Synthesized Using a Direct Electrochemical Method.

    Science.gov (United States)

    Lapp, Aliya S; Duan, Zhiyao; Marcella, Nicholas; Luo, Long; Genc, Arda; Ringnalda, Jan; Frenkel, Anatoly I; Henkelman, Graeme; Crooks, Richard M

    2018-05-11

    In this report, we examine the structure of bimetallic nanomaterials prepared by an electrochemical approach known as hydride-terminated (HT) electrodeposition. It has been shown previously that this method can lead to deposition of a single Pt monolayer on bulk-phase Au surfaces. Specifically, under appropriate electrochemical conditions and using a solution containing PtCl 4 2- , a monolayer of Pt atoms electrodeposits onto bulk-phase Au immediately followed by a monolayer of H atoms. The H atom capping layer prevents deposition of Pt multilayers. We applied this method to ∼1.6 nm Au nanoparticles (AuNPs) immobilized on an inert electrode surface. In contrast to the well-defined, segregated Au/Pt structure of the bulk-phase surface, we observe that HT electrodeposition leads to the formation of AuPt quasi-random alloy NPs rather than the core@shell structure anticipated from earlier reports relating to deposition onto bulk phases. The results provide a good example of how the phase behavior of macro materials does not always translate to the nano world. A key component of this study was the structure determination of the AuPt NPs, which required a combination of electrochemical methods, electron microscopy, X-ray absorption spectroscopy, and theory (DFT and MD).

  18. Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhan, Wangcheng [East China Univ. of Science and Technology, Shanghai (China); Wang, Jinglin [East China Univ. of Science and Technology, Shanghai (China); Wang, Haifeng [East China Univ. of Science and Technology, Shanghai (China); Zhang, Jinshui [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Xiaofei [East China Univ. of Science and Technology, Shanghai (China); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhang, Pengfei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chi, Miaofang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Guo, Yanglong [East China Univ. of Science and Technology, Shanghai (China); Guo, Yun [East China Univ. of Science and Technology, Shanghai (China); Lu, Guanzhong [East China Univ. of Science and Technology, Shanghai (China); Sun, Shouheng [Brown Univ., Providence, RI (United States); Dai, Sheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Zhu, Huiyuan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-06-07

    Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

  19. Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, Sedigheh, E-mail: dadras@alzahra.ac.ir; Gharehgazloo, Zahra

    2016-07-01

    In this research, we prepared different Au nanoparticles (0.1–2 wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76 nm to 47 nm as well. The critical current density (J{sub c}) and transition temperature (T{sub c}) were determined using current versus voltage (I–V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest J{sub c} is for 1 wt% Au doped YBCO compound that its critical current density is about 8 times more than the J{sub c} of pure one in 0.7 T magnetic field.

  20. Preliminary investigations on the preparation of gold nanoparticles intrinsically radiolabeled with 199Au

    International Nuclear Information System (INIS)

    Vimalnath, K.V.; Chakraborty, Sudipta; Dash, Ashutosh

    2016-01-01

    Radiolabeled nanoparticles are of great interest in the current perspective of the nuclear medicine. Water dispersible materials with nanoscale dimensions are finding role in biomedical application owing to their size. These particles can access otherwise unreachable regions in tumor mainly due to Enhanced Permeability and Retention (EPR) effect. Nanoparticles of gold (AuNPs) can bind to a wide range of biologically active molecules with functional groups that have high affinity for the gold surface. Sulfur containing compounds (e.g. thiols, disulfides), organic phosphates, amines, PEG, etc. are some of the well known surface modifiers. Functional thiolates, oligonucleotides, peptides and PEGs are introduced upon subsequent bimolecular substitution of a ligand by a functional thiol easily attached to AuNPs. Owing to its favourable decay characteristics 199 Au (T 1/2 = 3.15 d, E âmax = 474 keV, Eg 158.4 keV (36.9 %) and 208.2 keV (8.4 %)) is an attractive radionuclide for theragnostic applications. In the present work, we have carried out preliminary radiochemical investigations on the preparation of gold nanoparticles intrinsically radiolabeled with 199 Au for its potential utility as a theragnostic agent targeted delivery to the tumors

  1. Combined spectroscopy and microscopy of supported MoS2 nanoparticles

    DEFF Research Database (Denmark)

    Nielsen, Jane Hvolbæk; Bech, Lone; Nielsen, Kenneth

    2009-01-01

    Supported molybdenum-sulfide nanoparticles are known catalysts for petroleum hydrodesulfurization as well as for electrochemical hydrogen evolution. In this study, we investigate molybdenum-sulfide nanoparticles supported on Au(111) using X-ray photoelectron spectroscopy (XPS) and scanning...... tunneling microscopy (STM), aiming to correlate spectroscopically determined chemical states with atomically resolved nanostructure. The results of this study allow us to conclude the following: (1) the XPS results from our model system are in good agreement with previously published results on supported Mo...

  2. AuScope research infrastructure - supporting Australian mineral discovery

    Science.gov (United States)

    McInnes, B.; Rawling, T.

    2016-12-01

    Earth and geospatial scientists are heavy users of data products. When industry geologists access spatial data from the field and the exploration office they require data products that are discoverable, searchable, interoperable and attributed with robust metadata. Over the last decade AuScope has utilised NCRIS funding to provide a variety of data products including geophysical data (reflection and passive seismic, magnetotellurics and gravity), GIS layers from state and national geological survey organisations, hyperspectral core logging (National Virtual Core Library) and time-series geospatial data from GNSS and VLBI instruments - all delivered using AuScope GRID technologies based on the Spatial Information Services Stack (SiSS). Perhaps one of the best examples of collaboration to deliver data products to industry users is the National Mineral Library. Working with researchers at Curtin Universities John de Laeter Centre and ANDS, AuScope has also supported the development of a Laboratory Information Management System (LIMS). The project has produced an entirely new workflow, based around a TESCAN TIMA field emission scanning electron microscope, that allows metadata to be collected and recorded from the sample collection and preparation right through to data delivery and publication. This process has facilitated the scanning of a large stockpile of mineral samples from across Western Australia that will produce a state-wide Mineral Library, allowing mineral explorers to better understand the composition of critical rock outcrop samples from all over the state. This new NCRIS supported initiative provides a dataset that underpins both academic and applied research programs and is important for the economic future of Australia. Mining companies do a lot of heavy mineral analysis in research and development but, because there isn't a baseline for mineralogy across each state, it is difficult to have full confidence in the heavy mineral data. This creates an

  3. Fabrication of Au-Pd Core-shell Nanoparticles using Au Thin-Film Dewetting at High Temperature and Chemical Synthesis Methods

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Gyu; Lee, Hye-Jung; Oh, Yong-Jun [Hanbat National Univ., Daejeon (Korea, Republic of)

    2016-07-15

    Au-Pd bimetallic nanoparticles (NPs) have received a lot of attention in the fields of catalysts and hydrogen sensors. In this study, Au-Pd core-shell NP arrays were successfully fabricated using two steps: formation of the ordered array of Au NPs cores via solid-state dewetting of a Au thin film on a topographic silica substrate, and Pd shell formation via chemical synthesis using two different surfactants (CTAB and CTAC). Using the CTAB surfactant in particular, a 2-D composite structure comprised of an ordered array of Au-Pd NPs, with smaller Pd NPs on the nanoscopic gaps between the Au-Pd NPs, could be formed. This structure is expected to have potential application in resistance-base hydrogen sensors.

  4. Novel anti-reflection technology for GaAs single-junction solar cells using surface patterning and Au nanoparticles.

    Science.gov (United States)

    Kim, Youngjo; Lam, Nguyen Dinh; Kim, Kangho; Kim, Sangin; Rotermund, Fabian; Lim, Hanjo; Lee, Jaejin

    2012-07-01

    Single-junction GaAs solar cell structures were grown by low-pressure MOCVD on GaAs (100) substrates. Micro-rod arrays with diameters of 2 microm, 5 microm, and 10 microm were fabricated on the surfaces of the GaAs solar cells via photolithography and wet chemical etching. The patterned surfaces were coated with Au nanoparticles using an Au colloidal solution. Characteristics of the GaAs solar cells with and without the micro-rod arrays and Au nanoparticles were investigated. The short-circuit current density of the GaAs solar cell with 2 microm rod arrays and Au nanoparticles increased up to 34.9% compared to that of the reference cell without micro-rod arrays and Au nanoparticles. The conversion efficiency of the GaAs solar cell that was coated with Au nanoparticles on the patterned surface with micro-rod arrays can be improved from 14.1% to 19.9% under 1 sun AM 1.5G illumination. These results show that micro-rod arrays and Au nanoparticle coating can be applied together in surface patterning to achieve a novel cost-effective anti-reflection technology.

  5. Ether gas-sensor based on Au nanoparticles-decorated ZnO microstructures

    Directory of Open Access Journals (Sweden)

    Roberto López

    Full Text Available An ether gas-sensor was fabricated based on gold nanoparticles (Au-NPs decorated zinc oxide microstructures (ZnO-MS. Scanning electron microscope (SEM and high-resolution transmission electron microscope (HRTEM measurements were performed to study morphological and structural properties, respectively, of the ZnO-MS. The gas sensing response was evaluated in a relatively low temperature regime, which ranged between 150 and 250 °C. Compared with a sensor fabricated from pure ZnO-MS, the sensor based on Au-NPs decorated ZnO-MS showed much better ether gas response at the highest working temperature. In fact, pure ZnO-MS based sensor only showed a weak sensitivity of about 25%. The improvement of the ether gas response for sensor fabricated with Au-NPs decorated ZnO-MS was attributed to the catalytic activity of the Au-NPs. Keywords: ZnO microstructures, Au nanoparticles, Ether, Gas sensor

  6. Cu2O-directed in situ growth of Au nanoparticles inside HKUST-1 nanocages.

    Science.gov (United States)

    Liu, Yongxin; Liu, Ting; Tian, Long; Zhang, Linlin; Yao, Lili; Tan, Taixing; Xu, Jin; Han, Xiaohui; Liu, Dan; Wang, Cheng

    2016-12-07

    Controllable integration of metal nanoparticles (MNPs) and metal-organic frameworks (MOFs) is attracting considerable attention as the obtained composite materials always show synergistic effects in applications of catalysis, delivery, as well as sensing. Herein, a Cu 2 O-directed in situ growth strategy was developed to integrate Au nanoparticles and HKUST-1. In this strategy, Cu 2 O@HKUST-1 core-shell heterostructures, HKUST-1 nanocages, Cu 2 O@Au@HKUST-1 sandwich core-shell heterostructures and Au@HKUST-1 balls-in-cage heterostructures were successfully synthesized. Cu 2 O@HKUST-1 core-shell heterostructures were synthesized by soaking Cu 2 O nanocrystals in benzene-1,3,5-tricarboxylic acid solution. The well-defined Cu 2 O@HKUST-1 core-shell heterostructures were demonstrated to be dominated by the ratio of Cu 2+ cations to btc 3- ligands in solution during the period of HKUST-1 formation. Cu 2 O@Au@HKUST-1 sandwich core-shell or Au@HKUST-1 balls-in-cage heterostructures were obtained by impregnating HAuCl 4 into Cu 2 O@HKUST-1 core-shell heterostructures. Due to the porosity of HKUST-1 and reducibility of Cu 2 O, HAuCl 4 could pass through the HKUST-1 shell and be reduced by the Cu 2 O core in situ forming Au nanoparticles. Finally, CO oxidation reaction at high temperatures was carried out to assess the catalytic functionality of the obtained composite heterostructures. This strategy can circumvent some drawbacks of the existing approaches for integrating MNPs and MOFs, such as nonselective deposition of MNPs at the outer surface of the MOF matrices, extreme treatment conditions and additional surface modifications.

  7. Mechanical control of the plasmon coupling with Au nanoparticle arrays fixed on the elastomeric film via chemical bond

    Science.gov (United States)

    Bedogni, Elena; Kaneko, Satoshi; Fujii, Shintaro; Kiguchi, Manabu

    2017-03-01

    We have fabricated Au nanoparticle arrays on the flexible poly(dimethylsiloxane) (PDMS) film. The nanoparticles were bound to the film via a covalent bond by a ligand exchange reaction. Thanks to the strong chemical bonding, highly stable and uniformly dispersed Au nanoparticle arrays were fixed on the PDMS film. The Au nanoparticle arrays were characterized by the UV-vis, scanning electron microscope (SEM) and surface enhanced Raman scattering (SERS). The UV-vis and SEM measurements showed the uniformity of the surface-dispersed Au nanoparticles, and SERS measurement confirmed the chemistry of the PDMS film. Reflecting the high stability and the uniformity of the Au nanoparticle arrays, the plasmon wavelength of the Au nanoparticles reversely changed with modulation of the interparticle distance, which was induced by the stretching of the PDMS film. The plasmon wavelength linearly decreased from 664 to 591 nm by stretching of 60%. The plasmon wavelength shift can be explained by the change in the strength of the plasmon coupling which is mechanically controlled by the mechanical strain.

  8. Au-CuO core-shell nanoparticles design and development for the selective determination of Vitamin B6

    International Nuclear Information System (INIS)

    Kumar, Deivasigamani Ranjith; Manoj, Devaraj; Santhanalakshmi, Jayadevan; Shim, Jae-Jin

    2015-01-01

    Highlights: • Seed mediated growth of Au-CuO core-shell nanoparticle. • Au-CuO core-shell nanoparticle provided good peak current for pyridoxine. • Au-CuO/MWCNTs/GC exhibited excellent vitamin B 6 peak separation with other vitamin. - Abstract: This paper reports the synthesis of gold (core)-copper oxide (shell) nanoparticles using a simple seed mediated growth method. Pre-synthesized Au nanoparticles were used as seed materials for copper oxide shell growth, which were shown to be effective for Au-CuO core-shell formation. The novelty of this assembly strategy is that the exploitation of the Cu-ligand, which is thermolyzed on the Au nanoseed surface, results in the formation of CuO. Au-CuO core-shell nanoparticles were characterized by UV-visible spectroscopy, high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The as prepared Au-CuO was used to fabricate a Au-CuO/MWCNTs/GC-modified electrode, which was applied to Vitamin B 6 (pyridoxine) determination by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The MWCNTs enhance the pyridoxine oxidation rate by increasing the peak current with Au-CuO, hence pyridoxine oxidized lower operating potentials. The Au-CuO/MWCNTs/GC-modified electrode showed excellent electrochemical performance towards pyridoxine (PY) in the presence of other typical vitamins, such as riboflavin, ascorbic acid and uric acid. The linear calibration graph was obtained over the PY concentration range of 0.79 μM–18.4 μM and the detection limit (S/N = 3) was 0.15 μM. The Au-CuO/MWCNTs/GC-modified electrode showed good stability, repeatability and recovery of real sample analysis

  9. Atomically thin Pt shells on Au nanoparticle cores: facile synthesis and efficient synergetic catalysis

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Poreddy, Raju

    2016-01-01

    in electrooxidation of sustainable fuels (i.e. formic acid, methanol and ethanol), and selective hydrogenation of benzene derivatives. Especially high activity was achieved for formic acid oxidation, 549 mA (mgPt)−1 (at 0.6 V vs. SCE), which is 3.5 fold higher than a commercial ... properties were thoroughly characterized by ultraviolet-visible light spectrophotometry, transmission electron microscopy, nanoparticle tracking analysis and electrochemistry. The 8 ± 2 nm Au@PtNPs contained 24 ± 1 mol% Pt and 76 ± 1 mol% Au corresponding to an atomically thin Pt shell. Electrochemical data...

  10. Au nanoparticles attached carbon nanotubes as a high performance active element in field effect transistor

    International Nuclear Information System (INIS)

    Lee, Myeongsoon; Kim, Don

    2016-01-01

    The Au nanoparticles attached carbon nanotubes (Au-CNTs), diameter ranged from 40 to 250 nm, were prepared and discussed their chemical and electrical properties. The shape and crystallinity of the carbon nanotubes (CNTs) phase depended main2ly on the diameter of CNTs (r_A_u_-_C_N_T). Highly crystalline, straight CNTs were observed when the r_A_u_-_C_N_T exceeded 80 nm, and less crystalline noodle-shaped CNTs were observed when the r_A_u_-_C_N_T was smaller than 80 nm. The crystallinity of the CNT phase was confirmed by analyzing the G and D bands in their Raman spectra and the electrical conductivities of the Au-CNTs. The electrical conductivity of the highly crystalline carbon phase of Au-CNTs (r_A_u_-_C_N_T = 250 nm) was ∼10"4 S/cm. The back-gated field effect transistors (FETs) based on the Au-CNTs, which were assembled on a SiO_2/Si wafer using the dielectrophoresis technique, showed that the Au-CNTs would be a good functional electronic material for future electronic and sensing applications. The transconductance and hole mobility of the FETs, which were assembled with the highly crystalline Au-CNTs (r_A_u_-_C_N_T = 250 nm), reached to 3.6 × 10"−"4 A/V and 3.1 × 10"4 cm"2/V s, respectively. These values are in the middle of those of reported for single walled carbon nanotubes and graphene. However, we could not find any field effect in a CNTFET, which assembled without Au nanoparticles, through the same process. - Highlights: • The shape and crystallinity of the CNTs depended mainly on the diameter of CNTs. • The electrical conductivity of the highly crystalline Au-CNTs was ∼10"4 S/cm. • The Au-CNT FET shows typical p-channel gate effect with the on/off ratio of ∼10"4. • The Au-CNT FET shows very high transconductance (g_m) and carrier mobility (μ_h).

  11. The synthesis and characterization of polymer-coated FeAu multifunctional nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hongling; Hou Peng; Zhang Wengxing [Institute of Molecular and Crystal Engineering, School of Chemistry and Chemical Engineering, Henan University, Kaifeng 475001, Henan (China); Kim, Young Keun [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Wu Junhua, E-mail: feitianshenhu@yahoo.com [Research Institute of Engineering and Technology, Korea University, Seoul 136-713 (Korea, Republic of)

    2010-08-20

    We report the one-pot nanoemulsion synthesis of FeAu magnetic-optical multifunctional nanoparticles coated by the biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO). The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the resulting nanoparticles. The structural characterization identifies the crystallographic parameter 4.072 A of the cubic phase and the morphology analysis gives the nanoparticle shape, size and size distribution, showing the high crystallinity of the FeAu nanoparticles and an average particle size of {approx} 6.5 nm. In addition there is direct confirmation of the alloying by elemental point probing of an individual nanoparticle. Following the visual demonstration of a rapid, efficient and reversible dispersion-collection process of the nanoparticles in solution, the magnetic measurement manifests a soft ferromagnetic behavior of the nanoparticles with a small coercivity of {approx} 60 Oe at room temperature. The corresponding magnetic hysteresis curves were effectively assessed by modified bi-phase Langevin equations, which were satisfactorily explained in terms of a bimodal particle size distribution. The UV-vis studies display the broadband absorption of the PEO-PPO-PEO-coated nanoparticles with the maximum surface plasmon resonance around 585 nm. The characterization and analysis, therefore, shows the unification of iron and gold into one alloy nanostructure entity covered by the biocompatible triblock copolymer thin film, preserving the optical and magnetic properties of the individual constituents. This gives the prospect of enhanced performance in applications.

  12. The synthesis and characterization of polymer-coated FeAu multifunctional nanoparticles

    International Nuclear Information System (INIS)

    Liu Hongling; Hou Peng; Zhang Wengxing; Kim, Young Keun; Wu Junhua

    2010-01-01

    We report the one-pot nanoemulsion synthesis of FeAu magnetic-optical multifunctional nanoparticles coated by the biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO). The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the resulting nanoparticles. The structural characterization identifies the crystallographic parameter 4.072 A of the cubic phase and the morphology analysis gives the nanoparticle shape, size and size distribution, showing the high crystallinity of the FeAu nanoparticles and an average particle size of ∼ 6.5 nm. In addition there is direct confirmation of the alloying by elemental point probing of an individual nanoparticle. Following the visual demonstration of a rapid, efficient and reversible dispersion-collection process of the nanoparticles in solution, the magnetic measurement manifests a soft ferromagnetic behavior of the nanoparticles with a small coercivity of ∼ 60 Oe at room temperature. The corresponding magnetic hysteresis curves were effectively assessed by modified bi-phase Langevin equations, which were satisfactorily explained in terms of a bimodal particle size distribution. The UV-vis studies display the broadband absorption of the PEO-PPO-PEO-coated nanoparticles with the maximum surface plasmon resonance around 585 nm. The characterization and analysis, therefore, shows the unification of iron and gold into one alloy nanostructure entity covered by the biocompatible triblock copolymer thin film, preserving the optical and magnetic properties of the individual constituents. This gives the prospect of enhanced performance in applications.

  13. Stability and enzyme inhibition activities of au nanoparticles using an aqueous extract of clove as a reducing and stabilizing agent

    International Nuclear Information System (INIS)

    Hameed, A.; Khan, I.; Naz, S.S.; Islam, N.U.

    2014-01-01

    Gold nanoparticles (AuNPs) were synthesized in one pot using aqueous extract of clove buds (CB) to reduce HAuCl/sub 4/ and stabilize gold in its atomic form at room temperature. To determine the potential of gold nanoparticles with clove buds (AuCB) for in vivo applications, the stability of the nanoparticles was explored as a function of temperature, pH and salt concentration. The suspensions were found to be stable for salt concentrations up to 1 mol/L, temperatures of up to 100 degree C and a pH range of 2-13. Our results indicate that CB exhibited comparable activities to standards of urease and carbonic anhydrase, but its conjugation to Au knocks out the enzyme inhibition activity by about two times. In case of xanthine oxidase activity, CB and its gold Au bio-conjugates (AuCB) are found to be absolutely inactive. (author)

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

    KAUST Repository

    Song, Hyon Min; Anjum, Dalaver H.; Khashab, Niveen M.

    2012-01-01

    The shape-controlled synthesis of Au@Pd core-shell nanoparticles (NPs) was successfully achieved through the emulsion phase generated during the phase transfer from organic to aqueous medium. Contrary to conventional epitaxial growth for obtaining

  15. A rapid green strategy for the synthesis of Au "meatball"-like nanoparticles using green tea for SERS applications

    Science.gov (United States)

    Wu, Shichao; Zhou, Xi; Yang, Xiangrui; Hou, Zhenqing; Shi, Yanfeng; Zhong, Lubin; Jiang, Qian; Zhang, Qiqing

    2014-09-01

    We report a simple and rapid biological approach to synthesize water-soluble and highly roughened "meatball"-like Au nanoparticles using green tea extract under microwave irradiation. The synthesized Au meatball-like nanoparticles possess excellent monodispersity and uniform size (250 nm in diameter). Raman measurements show that these tea-generated meatball-like gold nanostructures with high active surface areas exhibit a high enhancement of surface-enhanced Raman scattering. In addition, the Au meatball-like nanoparticles demonstrate good biocompatibility and remarkable in vitro stability at the biological temperature. Meanwhile, the factors that influence the Au meatball-like nanoparticles morphology are investigated, and the mechanisms behind the nonspherical shape evolution are discussed.

  16. Large enhancement of Faraday rotation by localized surface plasmon resonance in Au nanoparticles embedded in Bi:YIG film

    International Nuclear Information System (INIS)

    Uchida, H.; Masuda, Y.; Fujikawa, R.; Baryshev, A.V.; Inoue, M.

    2009-01-01

    A large enhancement of the Faraday rotation, which is associated with localized surface plasmon resonance (LSPR), was obtained in a sample with Au nanoparticles embedded in a Bi-substituted yttrium iron garnet (Bi:YIG) film. On a quartz substrate, Au nanoparticles were formed by heating an Au thin film, and a Bi:YIG film was then deposited on them. A sample containing the Au nanoparticles produced by 1000 deg. C heating showed a resonant attenuation with narrower bandwidth in the transmission spectrum than nanoparticles of other samples formed by low-temperature heating. The sharp resonant Faraday rotation angle was 4.4 times larger than the estimated intrinsic Bi:YIG film at the LSPR wavelength; the angular difference was 0.14 deg. A discrepancy in the bandwidth between the transmission attenuation and the resonant Faraday rotation is discussed

  17. Cell adhesion and proliferation on polyethylene grafted with Au nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Kasálková-Slepičková, N.; Slepička, P.; Kolská, Z.; Sajdl, P.; Bačáková, Lucie; Rimpelová, S.; Švorčík, V.

    2012-01-01

    Roč. 272, FEB 1 (2012), s. 391-395 ISSN 0168-583X. [International Conference on Ion Beam Modification of Materials /17./. Montreal, 22.08.2010-27.08.2010] R&D Projects: GA ČR(CZ) GAP108/10/1106; GA AV ČR(CZ) KAN400480701 Institutional research plan: CEZ:AV0Z50110509 Keywords : polyenthyne * gold nanoparticles * grafting * cell proliferation Subject RIV: EI - Biotechnology ; Bionics Impact factor: 1.266, year: 2012

  18. Effect of Interface energy and electron transfer on shape, plasmon resonance and SERS activity of supported surfactant-free gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Giangregorio, Maria M. [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Dastmalchi, Babak [Ames Laboratory; Suvorova, Alexandra [University of Western Australia; Bianco, Giuseppe V. [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Hingerl, Kurt [Johannes Kepler University Linz; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP

    2014-01-01

    For device integration purposes plasmonic metal nanoparticles must be supported/deposited on substrates. Therefore, it is important to understand the interaction between surfactant-free plasmonic metal nanoparticles and different substrates, as well as to identify factors that drive nanoparticles nucleation and formation. Here we show that for nanoparticles grown directly on supports, the substrate/nanoparticle interfacial energy affects the equilibrium shape of nanoparticles. Therefore, oblate, spherical and prolate Au nanoparticles (NPs) with different shapes have been deposited by radiofrequency sputtering on substrates with different characteristics, namely a dielectric oxide Al2O3 (0001), a narrow bandgap semiconductor Si (100), and a polar piezoelectric wide bandgap semiconductor 4H–SiC (0001). We demonstrate that the higher the substrate surface energy, the higher the interaction with the substrate, resulting in flat prolate Au nanoparticles. The resulting localized surface plasmon resonance characteristics of Au NPs/Al2O3, Au NPs/Si and Au NPs/SiC have been determined by spectroscopic ellipsometry and correlated with their structure and shape studied by transmission electron microscopy. Finally, we have demonstrated the diverse response of the tailored plasmonic substrates as ultrasensitive SERS chemical sensors. Flat oblates Au NPs on SiC result in an enhanced and more stable SERS response. The experimental findings are validated by numerical simulations of electromagnetic fields.

  19. Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

    Science.gov (United States)

    Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

    2007-09-25

    The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

  20. Optical Property Characterization of Novel Graphene-X (X=Ag, Au and Cu Nanoparticle Hybrids

    Directory of Open Access Journals (Sweden)

    Sumit Ranjan Sahu

    2013-01-01

    Full Text Available The present investigation reports new results on optical properties of graphene-metal nanocomposites. These composites were prepared by a solution-based chemical approach. Graphene has been prepared by thermal reduction of graphene oxide (GO at 90°C by hydrazine hydrate in an ammoniacal medium. This ammoniacal solution acts as a solvent as well as a basic medium where agglomeration of graphene can be prevented. This graphene solution has further been used for functionalization with Ag, Au, and Cu nanoparticles (NPs. The samples were characterized by X-ray diffraction (XRD, Raman spectroscopy, UV-Vis spectroscopy, scanning electron microscopy (SEM, and transmission electron microscopy (TEM to reveal the nature and type of interaction of metal nanoparticles with graphene. The results indicate distinct shift of graphene bands both in Raman and UV-Vis spectroscopies due to the presence of the metal nanoparticles. Raman spectroscopic analysis indicates blue shift of D and G bands in Raman spectra of graphene due to the presence of metal nanoparticles except for the G band of Cu-G, which undergoes red shift, reflecting the charge transfer interaction between graphene sheets and metal nanoparticles. UV-Vis spectroscopic analysis also indicates blue shift of graphene absorption peak in the hybrids. The plasmon peak position undergoes blue shift in Ag-G, whereas red shift is observed in Au-G and Cu-G.

  1. Sputtering and mixing of supported nanoparticles

    International Nuclear Information System (INIS)

    Jiménez-Sáez, J.C.; Pérez-Martín, A.M.C.; Jiménez-Rodríguez, J.J.

    2013-01-01

    Sputtering and mixing of Co nanoparticles supported in Cu(0 0 1) under 1-keV argon bombardment are studied using molecular-dynamics simulations. Particles of different initial size have been considered. The cluster height decreases exponentially with increasing fluence. In nanoparticles, sputtering yield is significantly enhanced compared to bulk. In fact, the value of this magnitude depends on the cluster height. A theoretical model for sputtering is introduced with acceptable results compared to those obtained by simulation. Discrepancies happen mainly for very small particles. Mixing rate at the interface is quantified; and besides, the influence of border effects for clusters of different initial size is assessed. Mixing rate and border length–surface area ratio for the initial interface show a proportionality relation. The phenomenon of ion-induced burrowing of metallic nanoparticles is analysed

  2. Simple and convenient preparation of Au-Pt core-shell nanoparticles on surface via a seed growth method

    International Nuclear Information System (INIS)

    Qian Lei; Sha Yufang; Yang Xiurong

    2006-01-01

    Au-Pt core-shell nanoparticles were prepared on glass surface by a seed growth method. Gold nanoparticles were used as seeds and ascorbic acid-H 2 PtCl 6 solutions as growth solutions to deposit Pt shell on the surface of gold nanoparticles. These core-shell nanoparticles and their growth process were examined by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and field-emission environmental scanning electron microscopy and the results indicated that the deposition speed was fast and nanoparticles with obvious core-shell structure could be obtained after 2 min. Moreover, this seed growth method for preparation of the core-shell nanoparticles is simple and convenient compared with other seed growth methods with NH 4 OH as a mild reductant. In addition, electrochemical experiments indicated that these Au-Pt core-shell nanoparticles had similar electrochemical properties to those of the bulk Pt electrode

  3. Synthesis of unidirectional structures of SiO2-Ag using Au nanoparticles as nucleation centers

    International Nuclear Information System (INIS)

    Villa S, G.; Mendoza A, D.; Gutierrez W, C.; Perez H, R.

    2008-01-01

    This paper reports a method to synthesize Ag unidirectional structures covered with SiO 2 by sol-gel technique using Au nanoparticles as nucleation centers of the unidirectional structures. In the first phase unidirectional structures of SiO 2 -Ag CI are obtained by sol-gel, using TEOS as a precursor of metallic structures (Ag) and the incorporation of Au nanoparticles as nucleation centers for growth of unidirectional structures. In the second stage, one-way systems are subjected to thermal treatment in H 2 atmosphere for obtain AG 0 particles through mechanisms that diffusion and coalescence of silver to form structures that have a thin cover of SiO 2 . Analysis by scanning electron microscopy, transmission and atomic force microscopy allowed to determine the chemical composition and microstructural properties of unidirectional systems SiO 2 -Ag. (Author)

  4. Preparation of Multifunctional Fe@Au Core-Shell Nanoparticles with Surface Grafting as a Potential Treatment for Magnetic Hyperthermia

    Directory of Open Access Journals (Sweden)

    Ren-Jei Chung

    2014-01-01

    Full Text Available Iron core gold shell nanoparticles grafted with Methotrexate (MTX and indocyanine green (ICG were synthesized for the first time in this study, and preliminarily evaluated for their potential in magnetic hyperthermia treatment. The core-shell Fe@Au nanoparticles were prepared via the microemulsion process and then grafted with MTX and ICG using hydrolyzed poly(styrene-alt-maleic acid (PSMA to obtain core-shell Fe@Au-PSMA-ICG/MTX nanoparticles. MTX is an anti-cancer therapeutic, and ICG is a fluorescent dye. XRD, TEM, FTIR and UV-Vis spectrometry were performed to characterize the nanoparticles. The data indicated that the average size of the nanoparticles was 6.4 ± 09 nm and that the Au coating protected the Fe core from oxidation. MTX and ICG were successfully grafted onto the surface of the nanoparticles. Under exposure to high frequency induction waves, the superparamagnetic nanoparticles elevated the temperature of a solution in a few minutes, which suggested the potential for an application in magnetic hyperthermia treatment. The in vitro studies verified that the nanoparticles were biocompatible; nonetheless, the Fe@Au-PSMA-ICG/MTX nanoparticles killed cancer cells (Hep-G2 via the magnetic hyperthermia mechanism and the release of MTX.

  5. Preparation of Multifunctional Fe@Au Core-Shell Nanoparticles with Surface Grafting as a Potential Treatment for Magnetic Hyperthermia.

    Science.gov (United States)

    Chung, Ren-Jei; Shih, Hui-Ting

    2014-01-24

    Iron core gold shell nanoparticles grafted with Methotrexate (MTX) and indocyanine green (ICG) were synthesized for the first time in this study, and preliminarily evaluated for their potential in magnetic hyperthermia treatment. The core-shell Fe@Au nanoparticles were prepared via the microemulsion process and then grafted with MTX and ICG using hydrolyzed poly(styrene-alt-maleic acid) (PSMA) to obtain core-shell Fe@Au-PSMA-ICG/MTX nanoparticles. MTX is an anti-cancer therapeutic, and ICG is a fluorescent dye. XRD, TEM, FTIR and UV-Vis spectrometry were performed to characterize the nanoparticles. The data indicated that the average size of the nanoparticles was 6.4 ± 09 nm and that the Au coating protected the Fe core from oxidation. MTX and ICG were successfully grafted onto the surface of the nanoparticles. Under exposure to high frequency induction waves, the superparamagnetic nanoparticles elevated the temperature of a solution in a few minutes, which suggested the potential for an application in magnetic hyperthermia treatment. The in vitro studies verified that the nanoparticles were biocompatible; nonetheless, the Fe@Au-PSMA-ICG/MTX nanoparticles killed cancer cells (Hep-G2) via the magnetic hyperthermia mechanism and the release of MTX.

  6. Statistical analysis of support thickness and particle size effects in HRTEM imaging of metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    House, Stephen D., E-mail: sdh46@pitt.edu [Chemical and Petroleum Engineering, and Physics, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Bonifacio, Cecile S.; Grieshaber, Ross V.; Li, Long; Zhang, Zhongfan [Chemical and Petroleum Engineering, and Physics, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Ciston, Jim [National Center of Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Stach, Eric A. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973 (United States); Yang, Judith C. [Chemical and Petroleum Engineering, and Physics, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

    2016-10-15

    High-resolution transmission electron microscopy (HRTEM) examination of nanoparticles requires their placement on some manner of support – either TEM grid membranes or part of the material itself, as in many heterogeneous catalyst systems – but a systematic quantification of the practical imaging limits of this approach has been lacking. Here we address this issue through a statistical evaluation of how nanoparticle size and substrate thickness affects the ability to resolve structural features of interest in HRTEM images of metallic nanoparticles on common support membranes. The visibility of lattice fringes from crystalline Au nanoparticles on amorphous carbon and silicon supports of varying thickness was investigated with both conventional and aberration-corrected TEM. Over the 1–4 nm nanoparticle size range examined, the probability of successfully resolving lattice fringes differed significantly as a function both of nanoparticle size and support thickness. Statistical analysis was used to formulate guidelines for the selection of supports and to quantify the impact a given support would have on HRTEM imaging of crystalline structure. For nanoparticles ≥1 nm, aberration-correction was found to provide limited benefit for the purpose of visualizing lattice fringes; electron dose is more predictive of lattice fringe visibility than aberration correction. These results confirm that the ability to visualize lattice fringes is ultimately dependent on the signal-to-noise ratio of the HRTEM images, rather than the point-to-point resolving power of the microscope. This study provides a benchmark for HRTEM imaging of crystalline supported metal nanoparticles and is extensible to a wide variety of supports and nanostructures. - Highlights: • The impact of supports on imaging nanoparticle lattice structure is quantified. • Visualization probabilities given particle size and support thickness are estimated. • Aberration-correction provided limited benefit

  7. Statistical analysis of support thickness and particle size effects in HRTEM imaging of metal nanoparticles

    International Nuclear Information System (INIS)

    House, Stephen D.; Bonifacio, Cecile S.; Grieshaber, Ross V.; Li, Long; Zhang, Zhongfan; Ciston, Jim; Stach, Eric A.; Yang, Judith C.

    2016-01-01

    High-resolution transmission electron microscopy (HRTEM) examination of nanoparticles requires their placement on some manner of support – either TEM grid membranes or part of the material itself, as in many heterogeneous catalyst systems – but a systematic quantification of the practical imaging limits of this approach has been lacking. Here we address this issue through a statistical evaluation of how nanoparticle size and substrate thickness affects the ability to resolve structural features of interest in HRTEM images of metallic nanoparticles on common support membranes. The visibility of lattice fringes from crystalline Au nanoparticles on amorphous carbon and silicon supports of varying thickness was investigated with both conventional and aberration-corrected TEM. Over the 1–4 nm nanoparticle size range examined, the probability of successfully resolving lattice fringes differed significantly as a function both of nanoparticle size and support thickness. Statistical analysis was used to formulate guidelines for the selection of supports and to quantify the impact a given support would have on HRTEM imaging of crystalline structure. For nanoparticles ≥1 nm, aberration-correction was found to provide limited benefit for the purpose of visualizing lattice fringes; electron dose is more predictive of lattice fringe visibility than aberration correction. These results confirm that the ability to visualize lattice fringes is ultimately dependent on the signal-to-noise ratio of the HRTEM images, rather than the point-to-point resolving power of the microscope. This study provides a benchmark for HRTEM imaging of crystalline supported metal nanoparticles and is extensible to a wide variety of supports and nanostructures. - Highlights: • The impact of supports on imaging nanoparticle lattice structure is quantified. • Visualization probabilities given particle size and support thickness are estimated. • Aberration-correction provided limited benefit

  8. An enhanced photocatalytic response of nanometric TiO2 wrapping of Au nanoparticles for eco-friendly water applications.

    Science.gov (United States)

    Scuderi, Viviana; Impellizzeri, Giuliana; Romano, Lucia; Scuderi, Mario; Brundo, Maria V; Bergum, Kristin; Zimbone, Massimo; Sanz, Ruy; Buccheri, Maria A; Simone, Francesca; Nicotra, Giuseppe; Svensson, Bengt G; Grimaldi, Maria G; Privitera, Vittorio

    2014-10-07

    We propose a ground-breaking approach by an upside-down vision of the Au/TiO2 nano-system in order to obtain an enhanced photocatalytic response. The system was synthesized by wrapping Au nanoparticles (∼8 nm mean diameter) with a thin layer of TiO2 (∼4 nm thick). The novel idea of embedding Au nanoparticles with titanium dioxide takes advantage of the presence of metal nanoparticles, in terms of electron trapping, without losing any of the TiO2 exposed surface, so as to favor the photocatalytic performance of titanium dioxide. A complete structural characterization was made by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The remarkable photocatalytic performance together with the stability of the nano-system was demonstrated by degradation of the methylene blue dye in water. The non-toxicity of the nano-system was established by testing the effect of the material on the reproductive cycle of Mytilus galloprovincialis in an aquatic environment. The originally synthesized material was also compared to conventional TiO2 with Au nanoparticles on top. The latter system showed a dispersion of Au nanoparticles in the liquid environment, due to their instability in the aqueous solution that clearly represents an environmental contamination issue. Thus, the results show that nanometric TiO2 wrapping of Au nanoparticles has great potential in eco-friendly water/wastewater purification.

  9. Photoinduced Glycerol Oxidation over Plasmonic Au and AuM (M = Pt, Pd and Bi) Nanoparticle-Decorated TiO2 Photocatalysts

    Science.gov (United States)

    Jedsukontorn, Trin; Saito, Nagahiro; Hunsom, Mali

    2018-01-01

    In this study, sol-immobilization was used to prepare gold nanoparticle (Au NP)-decorated titanium dioxide (TiO2) photocatalysts at different Au weight % (wt. %) loading (Aux/TiO2, where x is the Au wt. %) and Au–M NP-decorated TiO2 photocatalysts (Au3M3/TiO2), where M is bismuth (Bi), platinum (Pt) or palladium (Pd) at 3 wt. %. The Aux/TiO2 photocatalysts exhibited a stronger visible light absorption than the parent TiO2 due to the localized surface plasmon resonance effect. Increasing the Au content from 1 wt. % to 7 wt. % led to increased visible light absorption due to the increasing presence of defective structures that were capable of enhancing the photocatalytic activity of the as-prepared catalyst. The addition of Pt and Pd coupled with the Au3/TiO2 to form Au3M3/TiO2 improved the photocatalytic activity of the Au3/TiO2 photocatalyst by maximizing their light-absorption property. The Au3/TiO2, Au3Pt3/TiO2 and Au3Pd3/TiO2 photocatalysts promoted the formation of glyceraldehyde from glycerol as the principle product, while Au3Bi3/TiO2 facilitated glycolaldehyde formation as the major product. Among all the prepared photocatalysts, Au3Pd3/TiO2 exhibited the highest photocatalytic activity with a 98.75% glycerol conversion at 24 h of reaction time. PMID:29690645

  10. Synthesis of Au nanoparticles at the surface and embedded in carbonaceous matrix by 150 keV Ar ion irradiation

    International Nuclear Information System (INIS)

    Prakash, Jai; Tripathi, Jalaj; Tripathi, A; Kumar, P; Asokan, K; Avasthi, D K; Rigato, V; Pivin, J C; Chae, Keun Hwa; Gautam, Sanjeev

    2011-01-01

    We report on synthesis of spherical Au nanoparticles at the surface and embedded in carbonaceous matrix by 150 keV Ar ion irradiation of thin Au film on polyethyleneterepthlate (PET). The pristine and irradiated samples are characterized by Rutherford backscattering spectrometry (RBS), atomic force microscopy, scanning electron microscopy and transmission electron microscopy (TEM) techniques. RBS spectra reveal the sputtering of Au film and interface mixing, increasing with increasing fluence. Surface morphology shows that at the fluence of 5 x 10 15 ions cm -2 , dewetting of thin Au film begins and partially connected nanostructures are formed whereas, at the higher fluence of 5 x 10 16 ions cm -2 , isolated spherical Au nanoparticles (45 ± 20 nm) are formed at the surface. Cross-sectional TEM observations also evidence the Au nanoparticles at the surface and mixed metal-polymer region indicating the formation of nanocomposites with small Au nanoparticles. The results are explained by the crater formation, sputtering followed by dewetting of the thin Au film and interdiffusion at the interface, through molten zones due to thermal spike induced by Ar ions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-01

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

  12. Tunable long-distance light transportation along Au nanoparticle chains: promising for optical interconnect

    Science.gov (United States)

    Lin, Z.; Li, X. D.; Chen, T. P.

    2014-10-01

    Tunable light resonance transportation along a single long Au hemisphere nanoparticles (NPs) chain was studied. The realistic experimentally determined gold dielectric function was used for the simulation of Au localized surface plasmon polariton (LSPPs) effect. The resonance light energy with minimized attenuation and its bandwidth were quantitatively analyzed by inducing the effective mass which was observed to increase only with the length of Au NPs between the source and the test point. The geometric ratio g/ r of NP size and gap were investigated at 5 µm far of NPs with different gaps from 0 to 70 nm. Strongest resonance can be achieved with g/ r = 1.2 by the factor of 1.5 than the connected NPs. This resonance mode falls in the wavelength λ = 555 nm (green light), which is exactly the maximum sensitivity of a light-adapted eye of human beings.

  13. Synthesis of Ag and Au nanoparticles embedded in carbon film: Optical, crystalline and topography analysis

    Science.gov (United States)

    Gholamali, Hediyeh; Shafiekhani, Azizollah; Darabi, Elham; Elahi, Seyed Mohammad

    2018-03-01

    Atomic force microscopy (AFM) images give valuable information about surface roughness of thin films based on the results of power spectral density (PSD) through the fast Fourier transform (FFT) algorithms. In the present work, AFM data are studied for silver and gold nanoparticles (Ag NPs a-C: H and Au NPs a-C: H) embedded in amorphous hydrogenated carbon films and co-deposited on glass substrate via of RF-Sputtering and RF-Plasma Enhanced Chemical Vapor Deposition methods. Here, the working gas is acetylene and the targets are Ag and Au. While time and power are constant, the only variable parameter in this study is initial pressure. In addition, the crystalline structure of Ag NPs a-C: H and Au NPs a-C: H are studied using X-ray diffraction (XRD). UV-visible spectrophotometry will also investigate optical properties and localized surface plasmon resonance (LSPR) of samples.

  14. The Enhanced Photo-Electrochemical Detection of Uric Acid on Au Nanoparticles Modified Glassy Carbon Electrode

    Science.gov (United States)

    Shi, Yuting; Wang, Jin; Li, Shumin; Yan, Bo; Xu, Hui; Zhang, Ke; Du, Yukou

    2017-07-01

    In this work, a sensitive and novel method for determining uric acid (UA) has been developed, in which the glassy carbon electrode (GCE) was modified with electrodeposition Au nanoparticles and used to monitor the concentration of UA with the assistant of visible light illumination. The morphology of the Au nanoparticles deposited on GCE surface were characterized by scanning electron microscope (SEM) and the nanoparticles were found to be well-dispersed spheres with the average diameter approaching 26.1 nm. A series of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements have revealed that the introduction of visible light can greatly enhance both the strength and stability of response current due to the surface plasmon resonance (SPR). Specifically, the DPV showed a linear relationship between peak current and UA concentration in the range of 2.8 to 57.5 μM with the equation of I pa (μA) = 0.0121 c UA (μM) + 0.3122 ( R 2 = 0.9987). Herein, the visible light illuminated Au/GCE possesses a potential to be a sensitive electrochemical sensor in the future.

  15. Nonlinear optical effects from Au nanoparticles prepared by laser plasmas in water

    Energy Technology Data Exchange (ETDEWEB)

    Fazio, E., E-mail: enfazio@unime.it [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universitá di Messina, V.le F. Stagno d’Alcontres 31, I-98166, Messina (Italy); Neri, F. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universitá di Messina, V.le F. Stagno d’Alcontres 31, I-98166, Messina (Italy)

    2013-05-01

    The optical limiting properties of Au nanoparticles prepared by laser generated plasmas in water were investigated. The ablation processes were carried out irradiating an Au target with the second harmonic (532 nm) output of a Nd:YAG laser, changing the water level above the target, the lens position and the laser pulse energy. Different surface morphologies, from isolated nearly spherical nanoparticles to elongated structures, were observed by TEM imaging. A significant nonlinear optical response was probed by the Z-scan technique. The efficiency and the nature of the nonlinear response are found to be strongly dependent on the morphological properties of the nanostructures. The third order optical susceptibility χ{sup (3)} assumes the values of 1.83 × 10{sup −6} esu and 6.34 × 10{sup −6} esu for the smaller nanoparticles size obtained at the lower ablation energies (10–20 mJ), 8.25 × 10{sup −6} esu and 2.13 × 10{sup −5} esu for the particles agglomerations obtained at the higher ablation energies (50–100 mJ). The high value of χ{sup (3)} and the possibility to tailor the nonlinear optical response by changing the morphological properties of the Au nanostructures make them interesting materials for potential applications in the nonlinear optics field.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-12-15

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

  17. A Novel Synthesis of Gold Nanoparticles Supported on Hybrid Polymer/Metal Oxide as Catalysts for p-Chloronitrobenzene Hydrogenation

    Directory of Open Access Journals (Sweden)

    Cristian H. Campos

    2017-01-01

    Full Text Available This contribution reports a novel preparation of gold nanoparticles on polymer/metal oxide hybrid materials (Au/P[VBTACl]-M metal: Al, Ti or Zr and their use as heterogeneous catalysts in liquid phase hydrogenation of p-chloronitrobenzene. The support was prepared by in situ radical polymerization/sol gel process of (4-vinyl-benzyltrimethylammonium chloride and 3-(trimethoxysilylpropyl methacrylate in conjunction with metal-alkoxides as metal oxide precursors. The supported catalyst was prepared by an ion exchange process using chloroauric acid (HAuCl4 as gold precursor. The support provided the appropriate environment to induce the spontaneous reduction and deposition of gold nanoparticles. The hybrid material was characterized. TEM and DRUV-vis results indicated that the gold forms spherical metallic nanoparticles and that their mean diameter increases in the sequence, Au/P[VBTACl]-Zr > Au/P[VBTACl]-Al > Au/P[VBTACl]-Ti. The reactivity of the Au catalysts toward the p-CNB hydrogenation reaction is attributed to the different particle size distributions of gold nanoparticles in the hybrid supports. The kinetic pseudo-first-order constant values for the catalysts in the hydrogenation reaction increases in the order, Au/P[VBTACl]-Al > Au/P[VBTACl]-Zr > Au/P[VBTACl]-Ti. The selectivity for all the catalytic systems was greater than 99% toward the chloroaniline target product. Finally the catalyst supported on the hybrid with Al as metal oxide could be reused at least four times without loss in activity or selectivity for the hydrogenation of p-CNB in ethanol as solvent.

  18. Architecture effects of glucose oxidase/Au nanoparticle composite Langmuir-Blodgett films on glucose sensing performance

    Science.gov (United States)

    Wang, Ke-Hsuan; Wu, Jau-Yann; Chen, Liang-Huei; Lee, Yuh-Lang

    2016-03-01

    The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

  19. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    Energy Technology Data Exchange (ETDEWEB)

    Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Schaaf, P. [Department of Materials for Electronics and Electrical Engineering, Institute of Materials Science and Engineering and Institute of Micro- and Nanotechnologies MacroNano, TU Ilmenau, D-98693 Ilmenau (Germany); Friák, M. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic); Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno (Czech Republic); Holec, D. [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria); Šob, M. [Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno (Czech Republic); Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic); Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno (Czech Republic); Schneeweiss, O. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic)

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  20. Fabrication and characterizations of ZnO nanorods/Au nanoparticle composites on the electropolished Ti substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hsiang, E-mail: hchen@ncnu.edu.tw [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China); Yeh, Yih-Min [WuFeng University, No. 117, Sec 2, Chiankuo Rd, Minhsiung, Chiayi County 62153, Taiwan, ROC (China); Chen, Jian-Zhi [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China); Liu, Song-Ming [WuFeng University, No. 117, Sec 2, Chiankuo Rd, Minhsiung, Chiayi County 62153, Taiwan, ROC (China); Huang, Bo Yun; Wu, Zhi-Huei; Tsai, Shaung-Lin; Chang, Hung-Wei; Chu, Yu-Cheng; Liao, Chuan Hao [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China)

    2013-12-31

    Au nanoparticles (NPs) were spread on ZnO nanorods (NRs) on the polished Ti substrate to form Au/ZnO nanocomposites. Multiple material analyses including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analyses, Fourier-transform infrared spectrometer (FTIR) and images taken by optical microscope were performed on Au NPs of 2 nm and 20 nm on ZnO NRs. The FESEM and optical images under optical microscope indicate that 20 nm NPs can form more and larger clusters than 2 nm NPs on ZnO nanorod. Furthermore, more Au can be detected by EDS and XRD. We studied the behaviors of Au NPs on ZnO NR applications for future potential biosensing and antiseptic devices. - Highlights: • Nanocomposites of Au nanoparticles were spread on ZnO nanorods on Ti substrate. • Multiple material analyses were performed on 2 nm and 20 nm nanoparticles. • 20 nm nanoparticles formed more and larger clusters. • Optical images show well-distributed nanoparticle ZnO nanorods.

  1. Mesostructured Au/C materials obtained by replication of functionalized SBA-15 silica containing highly dispersed gold nanoparticles

    KAUST Repository

    Kerdi, Fatmé

    2011-04-01

    The preparation and characterization of highly dispersed gold nanoparticles in ordered mesoporous carbons CMK-3 are reported. These carbons were obtained using gold-containing functionalized SBA-15 silicas as hard templates. Two series of Au/SiO2 templates were prepared, depending on the nature of the functionalization molecule. While ammonium-functionalized silicas gave gold particles with a size determined by the pores of the silica support, the use of mercaptopropyltrimethoxysilane as grafting molecule afforded the possibility to control the particle size inside the mesopores. Both series gave highly ordered mesoporous carbons with gold particles incorporated in the carbon nanorods. However, the gold particle size in mesoporous carbons was the same for both series and apparently did not depend on the nature of the silica template. Both Au/SiO2 templates and their corresponding Au/CMK-3 materials have been characterized by X-ray diffraction, nitrogen adsorption/desorption, chemical analysis, solid-state nuclear magnetic resonance and transmission electron microscopy. They were also used as catalysts in the aerobic oxidation of cyclohexene and trans-stilbene in the liquid phase. © 2010 Elsevier Inc. All rights reserved.

  2. Ligand-modulated interactions between charged monolayer-protected Au144 (SR)60 gold nanoparticles in physiological saline

    Science.gov (United States)

    Villarreal, Oscar; Chen, Liao; Whetten, Robert; Yacaman, Miguel

    2015-03-01

    We studied the interactions of functionalized Au144 nanoparticles (NPs) in a near-physiological environment through all-atom molecular dynamics simulations. The AuNPs were coated with a homogeneous selection of 60 thiolates: 11-mercapto-1-undecanesulfonate, 5-mercapto-1-pentanesulfonate, 5-mercapto-1-pentane-amine, 4-mercapto-benzoate or 4-mercapto-benzamide. These ligands were selected to elucidate how the aggregation behavior depends on the ligands' sign of charge, length, and flexibility. Simulating the dynamics of a pair of identical AuNPs in a cell of saline of 150 mM NaCl in addition to 120 Na+/Cl- counter-ions, we computed the aggregation affinities from the potential of mean force as a function of the pair separation. We found that NPs coated with negatively charged, short ligands have the strongest affinities mediated by multiple Na+ counter-ions residing on a plane in-between the pair and forming ``salt bridges'' to both NPs. Positively charged NPs have weaker affinities, as Cl counter-ions form fewer and weaker salt bridges. The longer ligands' large fluctuations disfavor the forming of salt bridges, enable hydrophobic contact between the exposed hydrocarbon chains and interact at greater separations due to the fact that the screening effect is rather incomplete. Supported by the CONACYT, NIH, NSF and TACC.

  3. Very Green Photosynthesis of Gold Nanoparticles by a Living Aquatic Plant: Photoreduction of AuIII by the Seaweed Ulva armoricana.

    Science.gov (United States)

    Mukhoro, Ofhani C; Roos, Wiets D; Jaffer, Mohammed; Bolton, John J; Stillman, Martin J; Beukes, Denzil R; Antunes, Edith

    2018-02-01

    Light-assisted in vivo synthesis of gold nanoparticles (NPs) from aqueous solutions of dilute Au III salts by a living green marine seaweed (Ulva armoricana) is reported for the first time. NPs synthesised using typical procedures have many associated environmental hazards. The reported methods involve green, nontoxic, eco-friendly synthetic procedures. The formation of AuNPs was extremely rapid (≈15 min) following illumination of the living U. armoricana, while the rate of NP formation in the dark was very slow (over 2 weeks). The properties of the AuNPs formed were confirmed using a battery of spectroscopic techniques. U. armoricana were found to be very efficient in Au 0 uptake, and this, together with the rapid formation of AuNPs under illumination, indicated that the seaweed remained living during NP formation. The TEM images supported this, revealing that the thylakoid membranes and cell structure remained intact. The AuNPs formed on the surface of U. armoricana thallus, along the cell walls and in the chloroplasts. Without further workup, the dried, U. armoricana-supported AuNPs were efficient in the catalytic reduction of 4-nitrophenol, demonstrating the completely green cycle of AuNP formation and catalytic activity. The results mean that an aquatic plant growing in water rich in gold salts could bio-accumulate AuNPs from its aquatic environment, simply with the activation of sunlight. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Rich Ground State Chemical Ordering in Nanoparticles: Exact Solution of a Model for Ag-Au Clusters

    DEFF Research Database (Denmark)

    Larsen, Peter Mahler; Jacobsen, Karsten Wedel; Schiøtz, Jakob

    2018-01-01

    We show that nanoparticles can have very rich ground state chemical order. This is illustrated by determining the chemical ordering of Ag-Au 309-atom Mackay icosahedral nanoparticles. The energy of the nanoparticles is described using a cluster expansion model, and a Mixed Integer Programming (MIP......) approach is used to find the exact ground state configurations for all stoichiometries. The chemical ordering varies widely between the different stoichiometries, and display a rich zoo of structures with non-trivial ordering....

  5. Catalytic reduction of 4-nitrophenol using gold nanoparticles biosynthesized by cell-free extracts of Aspergillus sp. WL-Au

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Wenli; Qu, Yuanyuan, E-mail: qyy@dlut.edu.cn; Pei, Xiaofang; Li, Shuzhen; You, Shengnan; Wang, Jingwei; Zhang, Zhaojing; Zhou, Jiti

    2017-01-05

    Highlights: • A green process for AuNPs synthesis was achieved by fungus Aspergillus. • Uniform spherical AuNPs with well dispersity and stability were biosynthesized. • The biogenic AuNPs possessed remarkable catalytic activities for 4-NP reduction. - Abstract: A facile one-pot eco-friendly process for synthesis of gold nanoparticles (AuNPs) with high catalytic activity was achieved using cell-free extracts of Aspergillus sp. WL-Au as reducing, capping and stabilizing agents. The surface plasmon resonance band of UV–vis spectrum at 532 nm confirmed the presence of AuNPs. Transmission electron microscopy images showed that quite uniform spherical AuNPs were synthesized and the average size of nanoparticles increased from 4 nm to 29 nm with reaction time. X-ray diffraction analysis verified the formation of nano-crystalline gold particles. Fourier transform infrared spectra showed the presence of functional groups on the surface of biosynthesized AuNPs, such as O−H, N−H, C=O, C−H, C−OH and C−O−C groups, which increased the stability of AuNPs. The biogenic AuNPs could serve as a highly efficient catalyst for 4-nitrophenol reduction. The reaction rate constant was linearly correlated with the concentration of AuNPs, which increased from 0.59 min{sup −1} to 1.51 min{sup −1} with the amount of AuNPs increasing form 1.46 × 10{sup −6} to 17.47 × 10{sup −6} mmol. Moreover, the as-synthesized AuNPs exhibited a remarkable normalized catalytic activity (4.04 × 10{sup 5} min{sup −1} mol{sup −1}), which was much higher than that observed for AuNPs synthesized by other biological and conventional chemical methods.

  6. Catalytic reduction of 4-nitrophenol using gold nanoparticles biosynthesized by cell-free extracts of Aspergillus sp. WL-Au

    International Nuclear Information System (INIS)

    Shen, Wenli; Qu, Yuanyuan; Pei, Xiaofang; Li, Shuzhen; You, Shengnan; Wang, Jingwei; Zhang, Zhaojing; Zhou, Jiti

    2017-01-01

    Highlights: • A green process for AuNPs synthesis was achieved by fungus Aspergillus. • Uniform spherical AuNPs with well dispersity and stability were biosynthesized. • The biogenic AuNPs possessed remarkable catalytic activities for 4-NP reduction. - Abstract: A facile one-pot eco-friendly process for synthesis of gold nanoparticles (AuNPs) with high catalytic activity was achieved using cell-free extracts of Aspergillus sp. WL-Au as reducing, capping and stabilizing agents. The surface plasmon resonance band of UV–vis spectrum at 532 nm confirmed the presence of AuNPs. Transmission electron microscopy images showed that quite uniform spherical AuNPs were synthesized and the average size of nanoparticles increased from 4 nm to 29 nm with reaction time. X-ray diffraction analysis verified the formation of nano-crystalline gold particles. Fourier transform infrared spectra showed the presence of functional groups on the surface of biosynthesized AuNPs, such as O−H, N−H, C=O, C−H, C−OH and C−O−C groups, which increased the stability of AuNPs. The biogenic AuNPs could serve as a highly efficient catalyst for 4-nitrophenol reduction. The reaction rate constant was linearly correlated with the concentration of AuNPs, which increased from 0.59 min −1 to 1.51 min −1 with the amount of AuNPs increasing form 1.46 × 10 −6 to 17.47 × 10 −6 mmol. Moreover, the as-synthesized AuNPs exhibited a remarkable normalized catalytic activity (4.04 × 10 5 min −1 mol −1 ), which was much higher than that observed for AuNPs synthesized by other biological and conventional chemical methods.

  7. Tuning the nonlinear optical absorption in Au/BaTiO3 nanocomposites with gold nanoparticle concentration

    Science.gov (United States)

    Bijeesh, M. M.; Shakhi, P. K.; Varier, Geetha K.; Nandakumar, P.

    2018-06-01

    We report on the nonlinear optical absorption coefficient of Au/BaTiO3 nanocomposite films and its dependence on gold nanoparticle concentration. Au/BaTiO3 nanocomposite films with different molar ratio of Au/Ba are prepared by sol-gel technique and characterized by X-ray diffraction, UV Visible absorption spectroscopy and high resolution transmission electron microscopy. An open aperture Z-scan technique is employed to study the third order nonlinear optical properties of Au/BaTiO3 thin films. An Nd:YAG laser operating at 532 nm wavelength having a pulse width of 5 ns is used for the measurements. The two-photon absorption coefficient of the films increases linearly with gold nanoparticle concentration and significant enhancement of nonlinear optical absorption is observed. This ability to fine tune the nonlinear optical coefficients of Au/BaTiO3 films would be handy in optical device applications.

  8. Investigation of the Origin of Catalytic Activity in Oxide-Supported Nanoparticle Gold

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Ian [Univ. of Virginia, Charlottesville, VA (United States)

    2017-05-26

    Since Haruta’s discovery in 1987 of the surprising catalytic activity of supported Au nanoparticles, we have seen a very large number of experimental and theoretical efforts to explain this activity and to fully understand the nature of the behavior of the responsible active sites. In 2011, we discovered that a dual catalytic site at the perimeter of ~3nm diameter Au particles supported on TiO2 is responsible for oxidative catalytic activity. O2 molecules bind with Au atoms and Ti4+ ions in the TiO2 support and the weakened O-O bond dissociates at low temperatures, proceeding to produce O atoms which act as oxidizing agents for the test molecule, CO. The papers supported by DOE have built on this finding and have been concerned with two aspects of the behavior of Au/TiO2 catalysts: (1). Mechanistic behavior of dual catalytic sites in the oxidation of organic molecules such as ethylene and acetic acid; (2). Studies of the electronic properties of the TiO2 (110) single crystal in relation to its participation in charge transfer at the occupied dual catalytic site. A total of 20 papers have been produced through DOE support of this work. The papers combine IR spectroscopic investigations of Au/TiO2 catalysts with surface science on the TiO2(110) and TiO2 nanoparticle surfaces with modern density functional modeling. The primary goals of the work were to investigate the behavior of the dual Au/Ti4+ site for the partial oxidation of alcohols to acids, the hydrogenation of aldehydes and ketones to alcohols, and the condensation of oxygenate intermediates- all processes related to the utilization of biomass in the production of useful chemical energy sources.

  9. Low-cost mercury (II) ion sensor by biosynthesized gold nanoparticles (AuNPs)

    Science.gov (United States)

    Guerrero, Jet G.; Candano, Gabrielle Jackie; Mendoza, Aileen Nicole; Paderanga, Marciella; Cardino, Krenz John; Locsin, Alessandro; Bibon, Cherilou

    2017-11-01

    Biosynthesis of gold nanoparticles has attracted the curiosity of scientists over the past few decades. Nanoparticles have been proven to exhibit enhanced properties and offer a variety of applications in different fields of study. Utilizing nanoparticles instead of bulky equipment and noxious chemicals has become more convenient; reagents needed for synthesis have been proven to be benign (mostly aqueous solutions) and are cost-effective. In this study, gold nanoparticles were biosynthesized using guyabano (Annonamuricata) peel samples as the source of reducing agents. The optimum concentration ratio of gold chloride to guyabano extract was determined to be 1:7. Characterization studies were accomplished using UV Vis Spectroscopy, Fourier Transform Electron Microscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic maximum absorbance was found to be at 532 nm thereby confirming the presence of gold nanoparticles. Hydroxyl (O-H stretching), carbonyl (C=O stretching), and amide (N-H stretching) functional groups shown in the FTIR spectra are present on possible reducing agents such as phenols, alkaloids, and saponins found in the plant extract. SEM images revealed spherical shaped nanoparticles with mean diameter of 23.18 nm. It was observed that the bio-synthesized AuNPs were selective to mercury ions through uniform color change from wine red to yellow. A novel smartphone-based mercury (II) ions assay was developed using the gold nanoparticles. A calibration curve correlated the analytical response (Red intensity) to the concentrations of Hg 2+ ions. Around 94% of the variations in the intensity is accounted for by the variations in the concentration of mercury (II) ions suggesting a good linear relationship between the two variables. A relative standard deviation (RSD) of less than 1% was achieved at all individual points. The metal sensor displayed a sensitivity of 0.039 R.I./ppm with an LOD of 93.79 ppm. Thus, the bio-fabricated gold nanoparticles

  10. Digestive ripening facilitated atomic diffusion at nanosize regime: Case of AuIn{sub 2} and Ag{sub 3}In intermetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Neha [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India); Jagirdar, Balaji R., E-mail: jagirdar@ipc.iisc.ernet.in [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India); Klabunde, Kenneth J. [Department of Chemistry, Kansas State University, Manhattan, KS 66506 (United States)

    2014-10-15

    Highlights: • A digestive ripening facilitated interatomic diffusion process is presented. • Nearly monodisperse AuIn{sub 2} and Ag{sub 3}In intermetallic nanoparticles were synthesized. • Optimization of reaction temperature facilitates interatomic transfer. • Presence of excess ligand plays a crucial role in the digestive ripening process. - Abstract: Monodisperse colloidal gold–indium (AuIn{sub 2}) intermetallic nanoparticles have been synthesized from Au and In colloids using the digestive ripening process. Formation of the intermetallic proceeds via digestive ripening facilitated atomic diffusion of Au and In atoms from the Au and In nanoparticles followed simultaneously by their growth in the solution. Optimization of the reaction temperature was found to be crucial for the formation of AuIn{sub 2} intermetallic from gold and indium nanoparticles. Transmission electron microscopy revealed the presence of nearly monodisperse nanoparticles of Au and AuIn{sub 2} with particle size distribution of 3.7 ± 1.0 nm and 5.0 ± 1.6 nm, respectively. UV–visible spectral studies brought out the absence of SPR band in pure AuIn{sub 2} intermetallic nanoparticles. Optical study and electron microscopy, in combination with powder X-ray diffraction established phase pure AuIn{sub 2} intermetallic nanoparticles unambiguously. The potential of such an unprecedented approach has been further exploited in the synthesis of Ag{sub 3}In intermetallic nanoparticles with the dimension of less than 10 nm.

  11. Morphology evolution of gold nanoparticles as function of time, temperature, and Au(III)/sodium ascorbate molar ratio

    Energy Technology Data Exchange (ETDEWEB)

    Priolisi, Ornella, E-mail: ornella.priolisi@depretto.gov.it [ITIS “De Pretto” (Italy); Fabrizi, Alberto, E-mail: fabrizi@gest.unipd.it [University of Padova, Department of Management and Engineering (Italy); Deon, Giovanna, E-mail: giovanna.deon@depretto-vi.it [ITIS “De Pretto” (Italy); Bonollo, Franco, E-mail: bonollo@gest.unipd.it [University of Padova, Department of Management and Engineering (Italy); Cattini, Stefano, E-mail: stefano.cattini@unimore.it [University of Modena and Reggio Emilia, Department of Engineering Enzo Ferrari (Italy)

    2016-01-15

    In this work the morphology evolution of Au nanoparticles (AuNPs), obtained by direct reduction, was studied as a function of time, temperature, and Au(III)/sodium ascorbate molar ratio. The NPs morphology was examined by transmission electron microscope with image analysis, while time evolution was investigated by visible and near-infrared absorption spectroscopy and dynamic light scattering. It is found that initially formed star-like NPs transform in more spheroidal particles and the evolution appears more rapid by increasing the temperature while a large amount of reducing agent prevents the remodeling of AuNPs. An explication of morphology evolution is proposed.

  12. Rhombic Coulomb diamonds in a single-electron transistor based on an Au nanoparticle chemically anchored at both ends.

    Science.gov (United States)

    Azuma, Yasuo; Onuma, Yuto; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

    2016-02-28

    Rhombic Coulomb diamonds are clearly observed in a chemically anchored Au nanoparticle single-electron transistor. The stability diagrams show stable Coulomb blockade phenomena and agree with the theoretical curve calculated using the orthodox model. The resistances and capacitances of the double-barrier tunneling junctions between the source electrode and the Au core (R1 and C1, respectively), and those between the Au core and the drain electrode (R2 and C2, respectively), are evaluated as 4.5 MΩ, 1.4 aF, 4.8 MΩ, and 1.3 aF, respectively. This is determined by fitting the theoretical curve against the experimental Coulomb staircases. Two-methylene-group short octanedithiols (C8S2) in a C8S2/hexanethiol (C6S) mixed self-assembled monolayer is concluded to chemically anchor the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes even when the Au nanoparticle is protected by decanethiol (C10S). This is because the R1 value is identical to that of R2 and corresponds to the tunneling resistances of the octanedithiol chemically bonded with the Au core and the Au electrodes. The dependence of the Coulomb diamond shapes on the tunneling resistance ratio (R1/R2) is also discussed, especially in the case of the rhombic Coulomb diamonds. Rhombic Coulomb diamonds result from chemical anchoring of the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes.

  13. Gold nanoparticles production using reactor and cyclotron based methods in assessment of {sup 196,198}Au production yields by {sup 197}Au neutron absorption for therapeutic purposes

    Energy Technology Data Exchange (ETDEWEB)

    Khorshidi, Abdollah, E-mail: abkhorshidi@yahoo.com

    2016-11-01

    Medical nano-gold radioisotopes is produced regularly using high-flux nuclear reactors, and an accelerator-driven neutron activator can turn out higher yield of {sup 197}Au(n,γ){sup 196,198}Au reactions. Here, nano-gold production via radiative/neutron capture was investigated using irradiated Tehran Research Reactor flux and also simulated proton beam of Karaj cyclotron in Iran. {sup 197}Au nano-solution, including 20 nm shaped spherical gold and water, was irradiated under Tehran reactor flux at 2.5E + 13 n/cm{sup 2}/s for {sup 196,198}Au activity and production yield estimations. Meanwhile, the yield was examined using 30 MeV proton beam of Karaj cyclotron via simulated new neutron activator containing beryllium target, bismuth moderator around the target, and also PbF{sub 2} reflector enclosed the moderator region. Transmutation in {sup 197}Au nano-solution samples were explored at 15 and 25 cm distances from the target. The neutron flux behavior inside the water and bismuth moderators was investigated for nano-gold particles transmutation. The transport of fast neutrons inside bismuth material as heavy nuclei with a lesser lethargy can be contributed in enhanced nano-gold transmutation with long duration time than the water moderator in reactor-based method. Cyclotron-driven production of βeta-emitting radioisotopes for brachytherapy applications can complete the nano-gold production technology as a safer approach as compared to the reactor-based method. - Graphical abstract: This figure describes gold nanoparticles production via cyclotron based method. The aim of investigating is to estimate activity and saturation yield of {sup 197}Au(n,γ){sup 198}Au and {sup 197}Au(n,2n){sup 196}Au reactions using Karaj cyclotron available in Iran. The feasibility of a cyclotron-driven production of βeta-emitting radioisotopes was investigated for therapeutic applications via a new neutron activator design. - Highlights: • Nano-gold radioisotope production

  14. Biocompatibility of Fe3O4@Au composite magnetic nanoparticles in vitro and in vivo

    Directory of Open Access Journals (Sweden)

    Li Y

    2011-11-01

    Full Text Available Yuntao Li1,2, Jing Liu1, Yuejiao Zhong3, Jia Zhang1, Ziyu Wang1, Li Wang1, Yanli An1, Mei Lin1, Zhiqiang Gao2, Dongsheng Zhang11School of Medicine, Southeast University, Nanjing, Jiangsu Province, People's Republic of China; 2Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, People's Republic of China; 3Jiangsu Cancer Hospital and Jiangsu Institute of Cancer Research, Nanjing, Jiangsu Province, People's Republic of ChinaPurpose: This research was conducted to assess the biocompatibility of the core-shell Fe3O4@Au composite magnetic nanoparticles (MNPs, which have potential application in tumor hyperthermia. Methods: Fe3O4@Au composite MNPs with core-shell structure were synthesized by reduction of Au3+ in the presence of Fe3O4-MNPs prepared by improved co-precipitation. Cytotoxicity assay, hemolysis test, micronucleus (MN assay, and detection of acute toxicity in mice and beagle dogs were then carried out.Results: The result of cytotoxicity assay showed that the toxicity grade of this material on mouse fibroblast cell line (L-929 was classified as grade 1, which belongs to no cytotoxicity. Hemolysis rates showed 0.278%, 0.232%, and 0.197%, far less than 5%, after treatment with different concentrations of Fe3O4@Au composite MNPs. In the MN assay, there was no significant difference in MN formation rates between the experimental groups and negative control (P > 0.05, but there was a significant difference between the experimental groups and the positive control (P < 0.05. The median lethal dose of the Fe3O4@Au composite MNPs after intraperitoneal administration in mice was 8.39 g/kg, and the 95% confidence interval was 6.58-10.72 g/kg, suggesting that these nanoparticles have a wide safety margin. Acute toxicity testing in beagle dogs also showed no significant difference in body weight between the treatment groups at 1, 2, 3, and 4 weeks after liver injection and no behavioral changes. Furthermore, blood

  15. Impedimetric Aptasensor for Ochratoxin A Determination Based on Au Nanoparticles Stabilized with Hyper-Branched Polymer

    Directory of Open Access Journals (Sweden)

    Gennady Evtugyn

    2013-11-01

    Full Text Available An impedimetric aptasensor for ochratoxin A (OTA detection has been developed on the base of a gold electrode covered with a new modifier consisting of electropolymerized Neutral Red and a mixture of Au nanoparticles suspended in the dendrimeric polymer Botlorn H30®. Thiolated aptamer specific to OTA was covalently attached to Au nanoparticles via Au-S bonding. The interaction of the aptamer with OTA induced the conformational switch of the aptamer from linear to guanine quadruplex form followed by consolidation of the surface layer and an increase of the charge transfer resistance. The aptasensor makes it possible to detect from 0.1 to 100 nM of OTA (limit of detection: 0.02 nM in the presence of at least 50 fold excess of ochratoxin B. The applicability of the aptasensor for real sample assay was confirmed by testing spiked beer samples. The recovery of 2 nM OTA was found to be 70% for light beer and 78% for dark beer.

  16. Characterization of self-assembled electrodes based on Au-Pt nanoparticles for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, E. [Univ. Politecnica de Chiapas (Mexico). Energia y Sustentabilidad; Sebastian, P.J.; Gamboa, S.A.; Joseph, S. [Univ. Nacional Autonoma de Mexico, Morelos (Mexico). Centrode Investigacion en Energia; Pal, U. [Univ. Autonoma de Puebla, Pue (Mexico). Inst. de Fisica; Gonzalez, I. [Univ. Autonoma Metropolitana, Mexico City (Mexico). Dept. de Quimica

    2010-07-01

    This paper described the synthesis and characterization of gold (Au), platinum (Pt) and Au-Pt nanoparticles impregnated on a Nafion membrane in a proton exchange membrane fuel cell (PEMFC). The aim of the study was to fabricate the membrane electrode assembly (MEA) by depositing the nanoparticles on the membrane using an immersion technique. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to study the deposition process. Electrochemical impedance spectroscopy (EIS) was used to study the membrane proton conduction process. An elemental mapping analysis was performed in order to study the location of the Au and Pt in the self-assemblies. Results of the study showed that the particles deposited on the Nafion had good stability and a homogenous distribution along the membrane surface. The particles showed a direct relation in size and location with the hydrophilic and hydrophobic distribution phases of the membrane. The main membrane resistance was located between the membrane and the electrolyte. The self-assembled electrodes demonstrated a good performance at standard conditions. 33 refs., 4 tabs., 11 figs.

  17. Facile SILAR approach to air-stable naked silver and gold nanoparticles supported by alumina.

    Science.gov (United States)

    Stamplecoskie, Kevin G; Manser, Joseph S

    2014-10-22

    A synthetically convenient and scalable SILAR (successive ion layer adsorption and reaction) method is used to make air-stable films of silver and gold nanoparticles supported on alumina scaffolds. This solution-based deposition technique yields particles devoid of insulating capping agents or ligands. The optical properties of the nanoparticle films were investigated using femtosecond transient absorption spectroscopy. A linear absorption arising from intraband excitation (775 nm laser pulse) is seen only for Au nanoparticles at low intensity. However, both Au and Ag particles exhibit plasmon resonance responses at high excitation intensity via two photon absorption of the 775 nm pump pulse. The difference in optical response to near-IR laser excitation is rationalized based on the known density of states for each metal. To demonstrate the potential applications of these films, alumina-supported Ag nanoparticles were utilized as substrates for surface enhanced Raman spectroscopy, resulting in a 65-fold enhancement in the Raman signal of the probe molecule rhodamine 6G. The exceptional stability and scalability of these SILAR films opens the door for further optical and photocatalytic studies and applications, particularly with ligand-free Ag nanoparticles that typically oxidize under ambient conditions. Additionally, isolating plasmonic and interband electronic excitations in stable AgNP under visible light irradiation could enable elucidation of the mechanisms that drive noble metal-assisted photocatalytic processes.

  18. Calcium oxide supported gold nanoparticles as catalysts for the selective epoxidation of styrene by t-butyl hydroperoxide.

    Science.gov (United States)

    Dumbre, Deepa K; Choudhary, Vasant R; Patil, Nilesh S; Uphade, Balu S; Bhargava, Suresh K

    2014-02-01

    Gold nanoparticles are deposited on basic CaO supports as catalysts for the selective conversion of styrene into styrene oxide. Synthetic methods, gold loading and calcination temperatures are varied to permit an understanding of their influence on gold nanoparticle size, the presence of cationic gold species and the nature of interaction between the gold nanoparticles and the CaO support. Based on these studies, optimal conditions are designed to make the Au/CaO catalyst efficient for the selective epoxidation of styrene. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Method for forming thermally stable nanoparticles on supports

    Science.gov (United States)

    Roldan Cuenya, Beatriz; Naitabdi, Ahmed R.; Behafarid, Farzad

    2013-08-20

    An inverse micelle-based method for forming nanoparticles on supports includes dissolving a polymeric material in a solvent to provide a micelle solution. A nanoparticle source is dissolved in the micelle solution. A plurality of micelles having a nanoparticle in their core and an outer polymeric coating layer are formed in the micelle solution. The micelles are applied to a support. The polymeric coating layer is then removed from the micelles to expose the nanoparticles. A supported catalyst includes a nanocrystalline powder, thin film, or single crystal support. Metal nanoparticles having a median size from 0.5 nm to 25 nm, a size distribution having a standard deviation .ltoreq.0.1 of their median size are on or embedded in the support. The plurality of metal nanoparticles are dispersed and in a periodic arrangement. The metal nanoparticles maintain their periodic arrangement and size distribution following heat treatments of at least 1,000.degree. C.

  20. Novel multifunctional graphene sheets with encased Au/Ag nanoparticles for advanced electrochemical analysis of organic compounds.

    Science.gov (United States)

    Pruneanu, Stela; Biris, Alexandru R; Pogacean, Florina; Lazar, Diana Mihaela; Ardelean, Stefania; Watanabe, Fumyia; Dervishi, Enkeleda; Biris, Alexandru S

    2012-11-12

    This work is the first presentation of the synthesis of few-layer graphene decorated with gold and silver nanoparticles (Gr-Au-Ag) by chemical vapor deposition over a catalytic system formed of bimetallic Au-Ag nanoclusters supported on MgO and with methane used as the source of carbon. The sheetlike morphology of the graphene nanostructures, with mean sizes in the range of hundreds of nanometers, was observed by high-resolution electron microscopy. The distinctive feature found in all the samples was the regular rectangular or square shapes. This multi-component organic-inorganic nanomaterial was used to modify a platinum substrate and subsequently employed for the detection of carbamazepine, an anti-convulsion drug. UV/Vis spectroscopy revealed that a strong hypochromism occurred over time, after mixing solutions of graphene-Au-Ag with carbamazepine. This can be attributed to π-π stacking between the aromatic groups of the two compounds. Linear sweep voltammetry (LCV) provided evidence that the modified platinum substrate presented a significant electrocatalytic reaction toward the oxidation of carbamazepine. The intensity of the current was found to increase by up to 2.5 times, and the oxidation potential shifted from +1.5 to +1.35 V(Ag/AgCl) in comparison with the unmodified electrode. Electrochemical impedance spectroscopy (EIS) was further used to thoroughly assess the activity of the platinum electrode that was modified by the deposition of the Gr-Au-Ag composites in the presence of various concentrations of carbamazepine. The experimental EIS records were used for the generation of an equivalent electrical circuit, based on the charge-transfer resistance (R(ct)), Warburg impedance (Z(D)), solution resistance (R(s)), and a constant phase element (CPE) that characterizes the non-ideal interface capacitive responses. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Recent advances in the synthesis of Fe{sub 3}O{sub 4}@AU core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Salihov, Sergei V. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Ivanenkov, Yan A.; Krechetov, Sergei P.; Veselov, Mark S. [Moscow Institute of Physics and Technology (State University), 9 Institutskiy lane, Dolgoprudny City, Moscow Region, 141700 (Russian Federation); Sviridenkova, Natalia V.; Savchenko, Alexander G. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Klyachko, Natalya L. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Golovin, Yury I. [Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Chufarova, Nina V., E-mail: chnv@pharmcluster.ru [Moscow Institute of Physics and Technology (State University), 9 Institutskiy lane, Dolgoprudny City, Moscow Region, 141700 (Russian Federation); Beloglazkina, Elena K. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Majouga, Alexander G., E-mail: majouga@org.chem.msu.ru [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation)

    2015-11-15

    Fe{sub 3}O{sub 4}@Au core/shell nanoparticles have unique magnetic and optical properties. These nanoparticles are used for biomedical applications, such as magnetic resonance imaging, photothermal therapy, controlled drug delivery, protein separation, biosensors, DNA detection, and immunosensors. In this review, recent methods for the synthesis of core/shell nanoparticles are discussed. We divided all of the synthetic methods in two groups: methods of synthesis of bi-layer structures and methods of synthesis of multilayer composite structures. The latter methods have a layer of “glue” material between the core and the shell. - Highlights: • Fe{sub 3}O{sub 4} nanoparticles are promising for biomedical applications but have some disadvantages. • Covering Fe{sub 3}O{sub 4} nanoparticles with Au shell leads to better stability and biocompatibility. • Core/shell nanoparticles are widely used for biomedical applications. • There are two types of Fe{sub 3}O{sub 4}@Au core/shell nanoparticles structures: bi-layer and multilayer composite. • Different synthetic methods enable production of nanoparticles of different sizes.

  2. Synthesis and characterization of water-dispersible core/shell Mn-doped magnetite/Au nanoparticles for proton radiotherapy

    International Nuclear Information System (INIS)

    Park, Jeong Chan

    2015-01-01

    The surface modification of the nanomaterials is required for the biomedical use to give physiological stability, surface reactivity and targeting properties. Among many approaches for the surface modification with materials, such as polymers, organic ligands and metals, one of the most attractive ways is to employ metals. The fabrication of metal-based, monolayer coated magnetic nanoparticles has been intensively studied. However, the synthesis of metal-capped magnetic nanoparticles with monodispersities and controllable sizes is still challenged. Recently, gold-capped magnetic nanoparticles have been reported to increase stability and to provide biocompatibility. Gold-coated magnetic nanoparticles are an attractive system, which can be stabilized in biological conditions and readily functionalized through well-established surface modification chemistry. In addition, the Au coating offers plasmonic properties to magnetic nanoparticles. This makes the magnetic/Au core/shell combinations interesting for magnetic and optical applications. The monodisperse Mn:Fe3O4/Au nanoparticles have been prepared in organic solvent first and then transferred from an organic phase to an aqueous solution. The resulting core/shell-structured nanoparticles may be an attractive system for biomedical applications, which are needed both magnetic resonance imaging and optical imaging. In addition, the resulting nanoparticles may be useful for proton radiotherapy due to the enhanced therapeutic effects of secondary radiation stemmed from gold and proton beam bombardment

  3. Optical sensing properties of Au nanoparticle/hydrogel composite microbeads using droplet microfluidics

    Science.gov (United States)

    Li, Huilin; Men, Dandan; Sun, Yiqiang; Zhang, Tao; Hang, Lifeng; Liu, Dilong; Li, Cuncheng; Cai, Weiping; Li, Yue

    2017-10-01

    Uniform Au nanoparticle (NP)/poly (acrylamide-co-acrylic acid) [P(AAm-co-AA)] hydrogel microbeads were successfully prepared using droplet microfluidics technology. The microbeads exhibited a good stimuli-responsive behavior to pH value. Particularly in the pH value ranging from pH 2-pH 9, the composite microbead sizes gradually increased along with the increase of pH value. The homogeneous Au NPs, which were encapsulated in the P(AAm-co-AA) hydrogel microbeads, could transform the volume changes of hydrogel into optical signals by a tested single microbead with a microspectrometre system. The glucose was translated into gluconic acid by glucose oxidase. Thus, the Au NP/P(AAm-co-AA) hydrogel microbeads were used for detecting glucose based on pH effects on the composite microbeads. For this, the single Au NP/P(AAm-co-AA) hydrogel microbead could act as a good pH- or glucose-visualizing sensor.

  4. Two-dimensional ZnO ultrathin nanosheets decorated with Au nanoparticles for effective photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jin; You, Ning; Yu, Zhe; Zhou, Gang [College of Physics Science and Technology, Yangzhou University, Yangzhou 225002 (China); Xu, Xiaoyong, E-mail: xxy@yzu.edu.cn [College of Physics Science and Technology, Yangzhou University, Yangzhou 225002 (China); State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096 (China)

    2016-08-21

    Two-dimensional (2D) materials, especially the inorganic 2D nanosheets (NSs), are of particular interest due to their unique structural and electronic properties, which are favorable for photoelectronic applications such as photocatalysis. Here, we design and fabricate the ultrathin 2D ZnO NSs decorated with Au nanoparticles (AuNPs), though molecular modelling 2D hydrothermal growth and followed by surface modification are used as an effective photocatalyst for photocatalytic organic dye degradation and hydrogen production. The ultrathin 2D nature enables ultrahigh atom ratio near surface to proliferate the active sites, and the Au plasmon plays a promoting role in the visible-light absorption and photogenerated charge separation, thus integrating the synergistic benefits to boost the redox reactions at catalyst/electrolyte interface. The AuNPs-decorated ZnO NSs yield the impressive photocatalytic activities such as the dye degradation rate constant of 7.69 × 10{sup −2} min{sup −1} and the hydrogen production rate of 350 μmol h{sup −1} g{sup −1}.

  5. Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection

    Science.gov (United States)

    Qi, Zhiyang; Zhai, Yusheng; Wen, Long; Wang, Qilong; Chen, Qin; Iqbal, Sami; Chen, Guangdian; Xu, Ji; Tu, Yan

    2017-07-01

    The heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, the quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on a Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction. The large-area and lithography-free photodetector is realized by using an anisotropic chemical wet etching and rapid thermal annealing (RTA) of a thin Au film. We experimentally demonstrate that these hot electron detectors have broad photoresponsivity spectra in the NIR region of 1200-1475 nm, with a low dark current on the order of 10-5 A cm-2. The observed responsivities enable these devices to be competitive with other reported Si-based NIR hot electron photodetectors using perfectly periodic nanostructures. The improved performance is attributed to the pyramid surface which can enhance light trapping and the localized electric field, and the nano-sized Au NPs which are beneficial for the tunneling of hot electrons. The simple and large-area preparation processes make them suitable for large-scale thermophotovoltaic cell and low-cost NIR detection applications.

  6. Plasmonic Coupling in Three-Dimensional Au Nanoparticle Assemblies Fabricated by Anodic Aluminum Oxide Templates

    Directory of Open Access Journals (Sweden)

    Ahrum Sohn

    2013-01-01

    Full Text Available We investigated optical properties of three-dimensional (3D assemblies of Au nanoparticles (NPs, which were fabricated by dewetting of thin Au layers on anodic aluminum oxides (AAO. The NP assembly had hexagonal array of repeated multiparticle structures, which consisted of six trimers on the AAO surface and one large NP in the AAO pore (pore-NP. We performed finite-difference time-domain simulation to explain the optical response of the NP assemblies and compared the calculation results with experimental data. Such complementary studies clearly revealed how the plasmonic coupling between the constituent NPs influenced the spectral response of our NP assemblies. In particular, comparison of the assemblies with and without pore-NPs suggested that strong plasmonic coupling between trimers and pore-NP significantly affected the spectra and the field distribution of the NP assemblies. Plasmonic multi-NP assemblies could provide us new platforms to realize novel optoelectronic devices.

  7. Graphene-Au nanoparticle based vertical heterostructures: a novel route towards high- ZT Thermoelectric devices

    KAUST Repository

    Juang, Zhen-Yu; Tseng, Chien-Chih; Shi, Yumeng; Hsieh, Wen-Pin; Ryuzaki, Sou; Saito, Noboru; Hsiung, Chia-En; Chang, Wen-Hao; Hernandez, Yenny; Han, Yu; Tamada, Kaoru; Li, Lain-Jong

    2017-01-01

    Monolayer graphene exhibits impressive in-plane thermal conductivity (>1000Wm–1 K–1). However, the out-of-plane thermal transport is limited due to the weak van der Waals interaction, indicating the possibility of constructing a vertical thermoelectric (TE) device. Here, we propose a cross-plane TE device based on the vertical heterostructures of few-layer graphene and gold nanoparticles (AuNPs) on Si substrates, where the incorporation of AuNPs further inhibits the phonon transport and enhances the electrical conductivity along vertical direction. A measurable Seebeck voltage is produced vertically between top graphene and bottom Si when the device is put on a hot surface and the figure of merit ZT is estimated as 1 at room temperature from the transient Harman method. The polarity of the output voltage is determined by the carrier polarity of the substrate. The device concept is also applicable to a flexible and transparent substrate as demonstrated.

  8. Graphene-Au nanoparticle based vertical heterostructures: a novel route towards high- ZT Thermoelectric devices

    KAUST Repository

    Juang, Zhen-Yu

    2017-06-03

    Monolayer graphene exhibits impressive in-plane thermal conductivity (>1000Wm–1 K–1). However, the out-of-plane thermal transport is limited due to the weak van der Waals interaction, indicating the possibility of constructing a vertical thermoelectric (TE) device. Here, we propose a cross-plane TE device based on the vertical heterostructures of few-layer graphene and gold nanoparticles (AuNPs) on Si substrates, where the incorporation of AuNPs further inhibits the phonon transport and enhances the electrical conductivity along vertical direction. A measurable Seebeck voltage is produced vertically between top graphene and bottom Si when the device is put on a hot surface and the figure of merit ZT is estimated as 1 at room temperature from the transient Harman method. The polarity of the output voltage is determined by the carrier polarity of the substrate. The device concept is also applicable to a flexible and transparent substrate as demonstrated.

  9. Au/CdS Hybrid Nanoparticles in Block Copolymer Micellar Shells.

    Science.gov (United States)

    Koh, Haeng-Deog; Changez, Mohammad; Lee, Jae-Suk

    2010-10-18

    A polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) micellar structure with a P2VP core containing 5 nm CdS nanoparticles (NPs) and a PS shell formed in toluene that is a good solvent for PS block undergoes the core-shell inversion by excess addition of methanol that is a good solvent for P2VP block. It leads to the formation of micellar shell-embedded CdS NPs in the methanol major phase. The spontaneous crystalline growth of Au NPs on the CdS surfaces positioned at micellar shells without a further reduction process is newly demonstrated. The nanostructure of Au/CdS/PS-b-P2VP hybrid NPs is confirmed by transmission electron microscopy, energy-dispersive X-ray, and UV-Vis absorption. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Three-dimensional nanoporous MoS2 framework decorated with Au nanoparticles for surface-enhanced Raman scattering

    Science.gov (United States)

    Sheng, Yingqiang; Jiang, Shouzhen; Yang, Cheng; Liu, Mei; Liu, Aihua; Zhang, Chao; Li, Zhen; Huo, Yanyan; Wang, Minghong; Man, Baoyuan

    2017-08-01

    The three-dimensional (3D) MoS2 decorated with Au nanoparticles (Au NPs) hybrids (3D MoS2-Au NPs) for surface-enhanced Raman scattering (SERS) sensing was demonstrated in this paper. SEM, Raman spectroscopy, TEM, SAED, EDX and XRD were performed to characterize 3D MoS2-Au NPs hybrids. Rhodamine 6G (R6G), fluorescein and gallic acid molecules were used as the probe for the SERS detection of the 3D MoS2-Au NPs hybrids. In addition, we modeled the enhancement of the electric field of MoS2-Au NPs hybrids using Finite-difference time-domain (FDTD) analysis, which can further give assistance to the mechanism understanding of the SERS activity.

  11. Formation and characterization of nanoparticles formed by sequential ion implantation of Au and Co into SiO2

    International Nuclear Information System (INIS)

    Kluth, P.; Hoy, B.; Johannessen, B.; Dunn, S.G.; Foran, G.J.; Ridgway, M.C.

    2007-01-01

    Nanoparticles (NPs) were formed by sequential ion implantation of Au and Co into thin SiO 2 . After Au implantation and annealing, Co implantations were carried out at room temperature (RT) and 400 deg. C, respectively, with no subsequent annealing. The NPs were investigated by means of Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM) and extended X-ray absorption fine structure spectroscopy (EXAFS). TEM shows the formation of Co-Au core-shell NPs for the Co implantation at 400 deg. C. EXAFS measurements indicate significant strain in the NPs and a bond-length expansion of the Co-Co bonds in the NP core with a concomitant contraction of the Au-Au bonds in the Au shells. NPs are also observed by TEM for the Co implantation performed at RT, however, a lack of crystallinity is apparent from electron diffraction and EXAFS measurements

  12. Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Hareesh, K., E-mail: appi.2907@gmail.com [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Joshi, R.P. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Sunitha, D.V. [School of Physics, Reva University, Bangalore 560064 (India); Bhoraskar, V.N. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

    2016-12-15

    Highlights: • Ag-Au-rGO nanocomposite was synthesized by gamma radiation assisted method. • Ag-Au nanoparticles of size (5–19) nm were decorated on rGO. • Ag-Au-rGO showed enhanced catalytic activity for reduction of 4-Nitrophenol. - Abstract: One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV–vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5–19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp{sup 2} domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

  13. Arrays of Au-TiO{sub 2} Janus-like nanoparticles fabricated by block copolymer templates and their photocatalytic activity in the degradation of methylene blue

    Energy Technology Data Exchange (ETDEWEB)

    Fu Xiaoning; Liu Jun; Yang Hui; Sun Jiuchuan [Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, School of Chemistry and Chemical Engineering, University of Jinan, 106 Jiwei Road, Jinan 250022 (China); Li Xue, E-mail: lixue0312@yahoo.com [Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, School of Chemistry and Chemical Engineering, University of Jinan, 106 Jiwei Road, Jinan 250022 (China); Zhang Xiaokai [College of Physics and Electronics, Shandong Normal University, 88 Wenhuadong Road, Jinan 250014 (China); Jia Yuxi, E-mail: jia_yuxi@sdu.edu.cn [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China)

    2011-10-17

    Highlights: {center_dot} Fabrication of an array of Au-titania Janus nanoparticles on silicon substrate. {center_dot} PS-b-PEO block copolymer is used as templates. {center_dot} Au-TiO{sub 2} Janus-like nanoparticles exhibit higher photocatalytic activity. - Abstract: A simple approach towards the fabrication of an array of Au-titania Janus-like nanoparticles is presented. Monolayer organic-inorganic hybrid films are produced by spin coating the mixture of polystyrene-block-poly (ethylene oxide) (PS-b-PEO)/HAuCl{sub 4} solution and titania sol-gel precursor solution. HAuCl{sub 4} and titania are incorporated in the PEO domains. After removing the organic matrix by deep UV irradiation, arrays of Au-TiO{sub 2} Janus-like nanoparticles on the substrate surface are obtained. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements are employed to characterize the Janus-like nanoparticles. The photocatalytic degradation of methylene blue (MB) chosen as the test reaction to examine the photocatalytic activity of the Au-TiO{sub 2} Janus-like nanoparticles is shown to be more effective as compared to that of TiO{sub 2} nanoparticles or Au-TiO{sub 2} composite nanoparticles. The increased photocatalytic activity of Au-TiO{sub 2} Janus-like nanoparticles is attributed to the Au-TiO{sub 2} heterointerfaces.

  14. Atomistic simulations of anionic Au-144(SR)(60) nanoparticles interacting with asymmetric model lipid membranes

    DEFF Research Database (Denmark)

    Heikkila, E.; Martinez-Seara, H.; Gurtovenko, A. A.

    2014-01-01

    whose lipid composition and transmembrane distribution are to a large extent consistent with real plasma membranes of eukaryotic cells. To this end, we use a model system which comprises two cellular compartments, extracellular and cytosolic, divided by two asymmetric lipid bilayers. The simulations...... clearly show that AuNP- attaches to the extracellular membrane surface within a few tens of nanoseconds, while it avoids contact with the membrane on the cytosolic side. This behavior stems from several factors. In essence, when the nanoparticle interacts with lipids in the extracellular compartment...

  15. Synthesis and characterization of Au102(p-MBA)44 nanoparticles.

    Science.gov (United States)

    Levi-Kalisman, Yael; Jadzinsky, Pablo D; Kalisman, Nir; Tsunoyama, Hironori; Tsukuda, Tatsuya; Bushnell, David A; Kornberg, Roger D

    2011-03-09

    The synthesis of Au(102)(p-MBA)(44) nanoparticles on a preparative scale in high yield is described. Various analytical methods are shown to give results consistent with the composition and known structure of the particles, showing the preparation is essentially homogeneous, and attesting to the validity of the methods as well. Derivatization of the particles with proteins and DNA is demonstrated, and conditions are described for imaging individual particles by cryo-EM at low electron dose, close to focus, conditions optimal for recording high-resolution details.

  16. Size Determination of Au Aerosol Nanoparticles by Off-Line TEM/STEM Observations

    Science.gov (United States)

    Karlsson, Lisa S.; Deppert, Knut; Malm, Jan-Olle

    2006-12-01

    Determination of particle size distributions of Au aerosol nanoparticles has been performed by a TEM/STEM investigation. The particles are generated by an evaporation/condensation method and are size-selected by differential mobility analyzers (DMA) based on their electrical mobility. Off-line TEM measurements resulted in equivalent projected area diameters assuming that the particles are spherical in shape. In this paper critical factors such as magnification calibration, sampling, image analysis, beam exposure and, particle shape are treated. The study shows that the measures of central tendency; mean, median and mode, are equal as expected from a narrow size distribution. Moreover, the correlation between TEM/STEM and DMA are good, in practice 1:1. Also, STEM has the advantage over TEM due to enhanced contrast and is proposed as an alternative route for determination of particle size distributions of nanoparticles with lower contrast.

  17. Size Determination of Au Aerosol Nanoparticles by Off-Line TEM/STEM Observations

    International Nuclear Information System (INIS)

    Karlsson, Lisa S.; Deppert, Knut; Malm, Jan-Olle

    2006-01-01

    Determination of particle size distributions of Au aerosol nanoparticles has been performed by a TEM/STEM investigation. The particles are generated by an evaporation/condensation method and are size-selected by differential mobility analyzers (DMA) based on their electrical mobility. Off-line TEM measurements resulted in equivalent projected area diameters assuming that the particles are spherical in shape. In this paper critical factors such as magnification calibration, sampling, image analysis, beam exposure and, particle shape are treated. The study shows that the measures of central tendency; mean, median and mode, are equal as expected from a narrow size distribution. Moreover, the correlation between TEM/STEM and DMA are good, in practice 1:1. Also, STEM has the advantage over TEM due to enhanced contrast and is proposed as an alternative route for determination of particle size distributions of nanoparticles with lower contrast

  18. Electronic structure of thiolate-covered gold nanoparticles: Au102(MBA)44.

    Science.gov (United States)

    Li, Yan; Galli, Giulia; Gygi, François

    2008-09-23

    We present first principles, density functional theory (DFT) calculations of the structural and electronic properties of thiolate-protected gold nanoparticles [Au(102)(MBA)(44) ] that have been recently crystallized and measured by X-ray diffraction. Our calculations yield structural properties in very good agreement with experiment and reveal the impact of thiolate adsorption on both the surface geometry and the electronic structure of the gold core; in particular, within DFT we observe the emergence of an energy gap of about 0.5 eV, upon MBA adsorption. Using a localized orbital analysis, we characterize the electron distribution in the nanoparticle and provide insight into the bonding of thiolates on curved gold surfaces.

  19. SERS activity of Au nanoparticles coated on an array of carbon nanotube nested into silicon nanoporous pillar

    International Nuclear Information System (INIS)

    Jiang Weifen; Zhang Yanfeng; Wang Yusheng; Xu Lei; Li Xinjian

    2011-01-01

    A novel composite structure, Au nanoparticles coated on a nest-shaped array of carbon nanotube nested into a silicon nanoporous pillar array (Au/NACNT/Si-NPA), was fabricated for surface-enhanced Raman scattering (SERS). The morphology of the Au/NACNT/Si-NPA composite structure was characterized with the aid of scanning electron microscopy, X-ray diffraction instrumentation and Transmission electron microscopy. Compared with SERS of rhodamine 6G (R6G) adsorbed on SERS-active Au substrate reported, the SERS signals of R6G adsorbed on these gold nanoparticles were obviously improved. This was attributed to the enlarged specific surface area for adsorption of target molecules brought by the nest-shaped CNTs structure.

  20. Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 2. Anabaena cylindrica

    Directory of Open Access Journals (Sweden)

    Liz M. Rösken

    2016-03-01

    Full Text Available Microbial biosynthesis of metal nanoparticles as needed in catalysis has shown its theoretical ability as an extremely environmentally friendly production method in the last few years, even though the separation of the nanoparticles is challenging. Biosynthesis, summing up biosorption and bioreduction of diluted metal ions to zero valent metals, is especially ecofriendly, when the bioreactor itself is harmless and needs no further harmful reagents. The cyanobacterium Anabaena cylindrica (SAG 1403.2 is able to form crystalline Au0-nanoparticles from Au3+ ions and does not release toxic anatoxin-a. X-ray powder diffraction (XRD, transmission electron microscopy (TEM and laser-induced breakdown spectroscopy (LIBS are applied to monitor the time-dependent development of gold nanoparticles for up to 40 hours. Some vegetative cells (VC are filled with nanoparticles within minutes, while the extracellular polymeric substances (EPS of vegetative cells and the heterocyst polysaccharide layer (HEP are the regions, where the first nanoparticles are detected on most other cells. The uptake of gold starts immediately after incubation and within four hours the average size remains constant around 10 nm. Analyzing the TEM images with an image processing program reveals a wide distribution for the diameter of the nanoparticles at all times and in all regions of the cyanobacteria. Finally, the nanoparticle concentration in vegetative cells of Anabaena cylindrica is about 50% higher than in heterocysts (HC. These nanoparticles are found to be located along the thylakoid membranes.

  1. Time-dependent growth of crystalline Au(0)-nanoparticles in cyanobacteria as self-reproducing bioreactors: 2. Anabaena cylindrica.

    Science.gov (United States)

    Rösken, Liz M; Cappel, Felix; Körsten, Susanne; Fischer, Christian B; Schönleber, Andreas; van Smaalen, Sander; Geimer, Stefan; Beresko, Christian; Ankerhold, Georg; Wehner, Stefan

    2016-01-01

    Microbial biosynthesis of metal nanoparticles as needed in catalysis has shown its theoretical ability as an extremely environmentally friendly production method in the last few years, even though the separation of the nanoparticles is challenging. Biosynthesis, summing up biosorption and bioreduction of diluted metal ions to zero valent metals, is especially ecofriendly, when the bioreactor itself is harmless and needs no further harmful reagents. The cyanobacterium Anabaena cylindrica (SAG 1403.2) is able to form crystalline Au(0)-nanoparticles from Au(3+) ions and does not release toxic anatoxin-a. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and laser-induced breakdown spectroscopy (LIBS) are applied to monitor the time-dependent development of gold nanoparticles for up to 40 hours. Some vegetative cells (VC) are filled with nanoparticles within minutes, while the extracellular polymeric substances (EPS) of vegetative cells and the heterocyst polysaccharide layer (HEP) are the regions, where the first nanoparticles are detected on most other cells. The uptake of gold starts immediately after incubation and within four hours the average size remains constant around 10 nm. Analyzing the TEM images with an image processing program reveals a wide distribution for the diameter of the nanoparticles at all times and in all regions of the cyanobacteria. Finally, the nanoparticle concentration in vegetative cells of Anabaena cylindrica is about 50% higher than in heterocysts (HC). These nanoparticles are found to be located along the thylakoid membranes.

  2. Preparation and catalytic activities for H{sub 2}O{sub 2} decomposition of Rh/Au bimetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haijun, E-mail: zhanghaijun@wust.edu.cn [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); The State Key Laboratory of Refractory and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Deng, Xiangong; Jiao, Chengpeng; Lu, Lilin; Zhang, Shaowei [The State Key Laboratory of Refractory and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2016-07-15

    Graphical abstract: PVP-protected Rh/Au bimetallic nanoparticles (BNPs) were prepared by using hydrogen sacrificial reduction method, the activity of Rh80Au20 BNPs were about 3.6 times higher than that of Rh NPs. - Highlights: • Rh/Au bimetallic nanoparticles (BNPs) of 3∼5 nm in diameter were prepared. • Activity for H{sub 2}O{sub 2} decomposition of BNPs is 3.6 times higher than that of Rh NPs. • The high activity of BNPs was caused by the existence of charged Rh atoms. • The apparent activation energy for H{sub 2}O{sub 2} decomposition over the BNPs was calculated. - Abstract: PVP-protected Rh/Au bimetallic nanoparticles (BNPs) were prepared by using hydrogen sacrificial reduction method and characterized by UV–vis, XRD, FT-IR, XPS, TEM, HR-TEM and DF-STEM, the effects of composition on their particle sizes and catalytic activities for H{sub 2}O{sub 2} decomposition were also studied. The as-prepared Rh/Au BNPs possessed a high catalytic activity for the H{sub 2}O{sub 2} decomposition, and the activity of the Rh{sub 80}Au{sub 20} BNPs with average size of 2.7 nm were about 3.6 times higher than that of Rh monometallic nanoparticles (MNPs) even the Rh MNPs possess a smaller particle size of 1.7 nm. In contrast, Au MNPs with size of 2.7 nm show no any activity. Density functional theory (DFT) calculation as well as XPS results showed that charged Rh and Au atoms formed via electronic charge transfer effects could be responsible for the high catalytic activity of the BNPs.

  3. Self-assembled Au nanoparticles on heated Corning glass by dc magnetron sputtering: size-dependent surface plasmon resonance tuning

    Energy Technology Data Exchange (ETDEWEB)

    Grammatikopoulos, S.; Pappas, S. D. [University of Patras, Laboratory of High-Tech Materials, School of Engineering (Greece); Dracopoulos, V. [Hellas-Institute of Chemical Engineering and High Temperature Chemical Processes, (FORTH/ICE-HT), Foundation for Research and Technology (Greece); Poulopoulos, P., E-mail: poulop@upatras.gr [University of Patras, Laboratory of High-Tech Materials, School of Engineering (Greece); Fumagalli, P. [Freie Universitaet Berlin, Institut fuer Experimentalphysik (Germany); Velgakis, M. J.; Politis, C. [University of Patras, Laboratory of High-Tech Materials, School of Engineering (Greece)

    2013-02-15

    We report on the growth of Au nanoparticles on Corning glass by direct current magnetron sputtering and on the optical absorption of the films. The substrate temperature was kept to relatively high temperatures of 100 or 450 Degree-Sign C. This lead to the growth of Au nanoparticles instead of smooth Au films as the surface energy of Au is much larger than the one of glass. The size of the particles depended on the substrate temperature and deposition time and was shown to follow a logarithmic normal distribution function. Both, the surface plasmon resonance position and bandwidth, were found to depend upon the average particle size. The surface plasmon resonance position showed a 75 nm continuous blue shift from 14 nm down to 2.5 nm average particle size. Thus, we have shown how to tune the nanoparticle size and surface plasmon resonance of Au by varying the substrate temperature and deposition time. The experimental results are reproduced reasonably using a method which is based on the size- and wavelength-dependent complex dielectric function of Au within the framework of the Mie theory for the optical properties of metallic nanospheres.

  4. Catalytic activity of bimetallic AuPd alloys supported MgO and MnO2 nanostructures and their role in selective aerobic oxidation of alcohols

    Directory of Open Access Journals (Sweden)

    Hamed Alshammari

    2017-10-01

    Full Text Available The use of metal oxides as supports for gold and palladium (Au-Pd nano alloys constitutes new horizons to improve catalysts materials for very important reactions. From the literatures, Pd-based bimetallic nanostructures have great properties and active catalytic performance. In this study, nanostructures of magnesium oxide (MgO and manganese dioxide (MnO₂ were synthesised and utilized as supports for Au-Pd nanoparticle catalysts. Gold and palladium were deposited on these supports using sol-immobilisation method. The MgO and MnO2 supported Au-Pd catalysts were evaluated for the oxidation of benzyl alcohol and 1-octanol, respectively. These catalysts were found to be more selective, active and reusable than the corresponding monometallic Au and Pd catalysts. The effect of base supports on the disproportionation reaction during the oxidation process was investigated. The results show that MgO stopped the disproportionation reaction for both aromatic and aliphatic alcohols while MnO₂ stopped it in the case of benzyl alcohol only. The outcomes of this work shed light on the selective aerobic oxidation of alcohols using bimetallic Au-Pd nanoalloys and pave the way to a complete investigation of more basic metal oxides for various aliphatic alcohols.

  5. Enhanced photocatalysis, colloidal stability and cytotoxicity of synchrotron X-ray synthesized Au/TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Liu, Chi-Jen; Yang, Tsung-Yeh; Wang, Chang-Hai; Chien, Chia-Chi; Chen, Shin-Tai; Wang, Cheng-Liang; Leng, Wei-Hua; Hwu, Y.; Lin, Hong-Ming; Lee, Yao-Chang; Cheng, Chia-Liang; Je, J.H.; Margaritondo, G.

    2009-01-01

    Au/TiO 2 nanocomposite particles were synthesized by a method based on intense X-ray irradiation without adding any reducing agent or stabilizer. The nanocomposite exhibits promising photocatalytic and biological properties at physiologically relevant concentration ([Au] = 0.028 mM, [TiO 2 ] = 0.5 mM). The structure and photocatalysis were examined by X-ray diffraction, electron microscopy and ultraviolet-visible spectroscopy demonstrating that gold nanoparticles of 2-5 nm size were successfully deposited on TiO 2 nanoparticle surfaces. The nanocomposite exhibited good colloidal stability within a typical cellular environment and was nontoxic to cancer cell according to evaluations under controlled conditions. The Au/TiO 2 nanoparticles were also found to enhance the photocatalytic efficiency of UV radiation and even more that of X-ray radiation. In vitro studies indicated that the cell-killing effect under X-ray irradiation is more pronounced with the addition of Au/TiO 2 nanoparticles than of bare TiO 2 nanoparticles.

  6. Enhanced photocatalysis, colloidal stability and cytotoxicity of synchrotron X-ray synthesized Au/TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chi-Jen; Yang, Tsung-Yeh; Wang, Chang-Hai [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Chien, Chia-Chi [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Department of Engineering Science and System, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chen, Shin-Tai; Wang, Cheng-Liang; Leng, Wei-Hua [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Hwu, Y., E-mail: phhwu@sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Department of Engineering Science and System, National Tsing Hua University, Hsinchu 300, Taiwan (China); Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 202, Taiwan (China); National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Lin, Hong-Ming [Department of Materials Engineering, Tatung University, Taipei 10461, Taiwan (China); Lee, Yao-Chang [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Cheng, Chia-Liang [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Je, J.H. [X-ray Imaging Center, Pohang University of Science and Technology, Pohang (Korea, Republic of); Margaritondo, G. [Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2009-09-15

    Au/TiO{sub 2} nanocomposite particles were synthesized by a method based on intense X-ray irradiation without adding any reducing agent or stabilizer. The nanocomposite exhibits promising photocatalytic and biological properties at physiologically relevant concentration ([Au] = 0.028 mM, [TiO{sub 2}] = 0.5 mM). The structure and photocatalysis were examined by X-ray diffraction, electron microscopy and ultraviolet-visible spectroscopy demonstrating that gold nanoparticles of 2-5 nm size were successfully deposited on TiO{sub 2} nanoparticle surfaces. The nanocomposite exhibited good colloidal stability within a typical cellular environment and was nontoxic to cancer cell according to evaluations under controlled conditions. The Au/TiO{sub 2} nanoparticles were also found to enhance the photocatalytic efficiency of UV radiation and even more that of X-ray radiation. In vitro studies indicated that the cell-killing effect under X-ray irradiation is more pronounced with the addition of Au/TiO{sub 2} nanoparticles than of bare TiO{sub 2} nanoparticles.

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

    Science.gov (United States)

    Shang, Lei; Zhao, Faqiong; Zeng, Baizhao

    2014-05-15

    In this work, graphene oxide was reduced to graphene with an endogenous reducing agent from dimethylformamide, and then AuPd alloy nanoparticles were electrodeposited on the graphene film. The obtained AuPd-graphene hybrid film was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and voltammetry. The electrochemical behavior of vanillin was studied using the AuPd-graphene hybrid based electrode. It presented high electrocatalytic activity and vanillin could produce a sensitive oxidation peak at it. Under the optimal conditions, the peak current was linear to the concentration of vanillin in the ranges of 0.1-7 and 10-40 μM. The sensitivities were 1.60 and 0.170 mA mM(-1) cm(-2), respectively; the detection limit was 20 nM. The electrode was successfully applied to the detection of vanillin in vanilla bean, vanilla tea and biscuit samples. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts

    International Nuclear Information System (INIS)

    Liang Miao; Liu Xia; Qi Wei; Su Rongxin; Huang Renliang; Yu Yanjun; He Zhimin; Wang Libing

    2013-01-01

    Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts. (paper)

  9. Formation of multifunctional Fe3O4/Au composite nanoparticles for dual-mode MR/CT imaging applications

    International Nuclear Information System (INIS)

    Hu Yong; Li Jing-Chao; Shen Ming-Wu; Shi Xiang-Yang

    2014-01-01

    Recent advances with iron oxide/gold (Fe 3 O 4 /Au) composite nanoparticles (CNPs) in dual-modality magnetic resonance (MR) and computed tomography (CT) imaging applications are reviewed. The synthesis and assembly of “dumbbelllike” and “core/shell” Fe 3 O 4 /Au CNPs is introduced. Potential applications of some developed Fe 3 O 4 /Au CNPs as contrast agents for dual-mode MR/CT imaging applications are described in detail. (topical review - magnetism, magnetic materials, and interdisciplinary research)

  10. 1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

    International Nuclear Information System (INIS)

    Hou Xiaomiao; Zhan, Xiaoling; Fang Yan; Chen Shutang; Li Na; Zhou Qi

    2011-01-01

    1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

  11. 1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

    Energy Technology Data Exchange (ETDEWEB)

    Hou Xiaomiao; Zhan, Xiaoling, E-mail: zhangxl@bit.edu.cn [Beijing Institute of Technology, Department of Chemistry, School of Science (China); Fang Yan, E-mail: fangyan@mail.cnu.edu.cn [Capital Normal University, Beijing Key Lab for Nano-Photonics and Nano-Structure (NPNS), Department of Physics (China); Chen Shutang; Li Na; Zhou Qi [Beijing Institute of Technology, Department of Chemistry, School of Science (China)

    2011-05-15

    1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs' surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

  12. Au@Pt nanoparticles as catalase mimics to attenuate tumor hypoxia and enhance immune cell-mediated cytotoxicity

    Science.gov (United States)

    Liang, Hong; Wu, Ying; Ou, Xiang-Yu; Li, Jing-Ying; Li, Juan

    2017-11-01

    Hypoxic tumor microenvironment (TME) is closely linked to tumor progression, heterogeneity and immune suppression. Therefore, the development of effective methods to overcome hypoxia and substantially enhance the immunotherapy efficacy remains a desirable goal. Herein, we engineered a biocompatible Au core/Pt shell nanoparticles (Au@Pt NPs) to reoxygenate the TME by reacting with endogenous H2O2. Treatment with Au@Pt NPs appeared to improve oxygen in intracellular environments and decrease hypoxia-inducible factor-1α expression. Furthermore, the integration of high catalytic efficiency of Au@Pt NPs with cytokine-induced killer (CIK) cell immunotherapy, could lead to significantly improve the effect of CIK cell-mediated cytotoxicity. These results suggest great potential of Au@Pt NPs for regulation of the hypoxic TME and enhance immune cell mediated anti-tumor immunity.

  13. Extracellular Saccharide-Mediated Reduction of Au3+ to Gold Nanoparticles: New Insights for Heavy Metals Biomineralization on Microbial Surfaces.

    Science.gov (United States)

    Kang, Fuxing; Qu, Xiaolei; Alvarez, Pedro J J; Zhu, Dongqiang

    2017-03-07

    Biomineralization is a critical process controlling the biogeochemical cycling, fate, and potential environmental impacts of heavy metals. Despite the indispensability of extracellular polymeric substances (EPS) to microbial life and their ubiquity in soil and aquatic environments, the role played by EPS in the transformation and biomineralization of heavy metals is not well understood. Here, we used gold ion (Au 3+ ) as a model heavy metal ion to quantitatively assess the role of EPS in biomineralization and discern the responsible functional groups. Integrated spectroscopic analyses showed that Au 3+ was readily reduced to zerovalent gold nanoparticles (AuNPs, 2-15 nm in size) in aqueous suspension of Escherichia coli or dissolved EPS extracted from microbes. The majority of AuNPs (95.2%) was formed outside Escherichia coli cells, and the removal of EPS attached to cells pronouncedly suppressed Au 3+ reduction, reflecting the predominance of the extracellular matrix in Au 3+ reduction. XPS, UV-vis, and FTIR analyses corroborated that Au 3+ reduction was mediated by the hemiacetal groups (aldehyde equivalents) of reducing saccharides of EPS. Consistently, the kinetics of AuNP formation obeyed pseudo-second-order reaction kinetics with respect to the concentrations of Au 3+ and the hemiacetal groups in EPS, with minimal dependency on the source of microbial EPS. Our findings indicate a previously overlooked, universally significant contribution of EPS to the reduction, mineralization, and potential detoxification of metal species with high oxidation state.

  14. Efficiency Of The Photodynamic Therapy Using Gold Nanoparticles (np-Au) And PpIX Induced And Not Induced

    International Nuclear Information System (INIS)

    Maldonado-Alvarado, Elizabeth; Ramon-Gallegos, Eva; Arenas-Huertero, Francisco jesus; Reyes-Arellano, Alicia; Tanori-Cordova, Judith; Sanchez-Espindola, Maria Esther; Jimenez-Perez, Jose Luis; Cruz-Orea, Alfredo

    2008-01-01

    The use of gold nanoparticles (np-Au) to eliminate cancer has proved to be very effective due to the fact that cancerous cells accumulate it 600% more than healthy cells. In addition they have a high capacity of absorption and dispersion of light. Therefore, the effectiveness of photodynamic therapy (PDT) could be improved by the simultaneous use of np-Au and photosensitizes (Ps), emphasizing the high efficiency of the PDT to diagnose and to treat pre-malignant and malignant processes. The aim of this work was to determine the efficiency of PDT using np-Au and protoporphyrin IX (PpIX) induced and not induced by the δ-aminolevulinic acid (ALA). It were found the conditions of synthesis of hydrosoluble np-Au, and were characterized by transmission electronic microscopy (TEM) and UV-VIS spectroscopy. It was realized a kinetic by TEM to determine the cellular incorporation time of np-Au, the maximum incorporation of np-Au was of 16 h. PDT was applied using different doses of np-Au and photosensitizers. It was observed that the use of PDT simultaneously with np-Au did not increase the mortality of HeLa cells. In the case of C33, when PpIX not induced is used as photosensitizer simultaneously with np-Au, the mortality increased 20%

  15. Imaging of Au nanoparticles deeply buried in polymer matrix by various atomic force microscopy techniques

    International Nuclear Information System (INIS)

    Kimura, Kuniko; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2013-01-01

    Recently, some papers reported successful imaging of subsurface features using atomic force microscopy (AFM). Some theoretical studies have also been presented, however the imaging mechanisms are not fully understood yet. In the preceeding papers, imaging of deeply buried nanometer-scale features has been successful only if they were buried in a soft matrix. In this paper, subsurface features (Au nanoparticles) buried in a soft polymer matrix were visualized. To elucidate the imaging mechanisms, various AFM techniques; heterodyne force microscopy, ultrasonic atomic force microscopy (UAFM), 2nd-harmonic UAFM and force modulation microscopy (FMM) were employed. The particles buried under 960 nm from the surface were successfully visualized which has never been achieved. The results elucidated that it is important for subsurface imaging to choose a cantilever with a suitable stiffness range for a matrix. In case of using the most suitable cantilever, the nanoparticles were visualized using every technique shown above except for FMM. The experimental results suggest that the subsurface features buried in a soft matrix with a depth of at least 1 µm can affect the local viscoelasticity (mainly viscosity) detected as the variation of the amplitude and phase of the tip oscillation on the surface. This phenomenon presumably makes it possible to visualize such deeply buried nanometer-scale features in a soft matrix. - Highlights: • We visualized subsurface features buried in soft matrix, and investigated its imaging mechanism. • AFM techniques; UAFM, FMM, HFM and 2nd-harmonic UAFM were applied to elucidate the mechanism. • Au nanoparticles buried under 960 nm from surface were visualized, which has never been achieved. • Imaging at contact resonance using a cantilever of suitable stiffness is important. • Subsurface features in a soft matrix affect surface viscoelasticity, which are detected by AFM

  16. Reduced graphene oxide supported gold nanoparticles for electrocatalytic reduction of carbon dioxide

    Science.gov (United States)

    Saquib, Mohammad; Halder, Aditi

    2018-02-01

    Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst "reduced graphene oxide supported gold nanoparticles" for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.

  17. Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

    Directory of Open Access Journals (Sweden)

    Tanujjal Bora

    2011-10-01

    Full Text Available Zinc oxide (ZnO nanorods decorated with gold (Au nanoparticles have been synthesized and used to fabricate dye-sensitized solar cells (DSSC. The picosecond-resolved, time-correlated single-photon-count (TCSPC spectroscopy technique was used to explore the charge-transfer mechanism in the ZnO/Au-nanocomposite DSSC. Due to the formation of the Schottky barrier at the ZnO/Au interface and the higher optical absorptions of the ZnO/Au photoelectrodes arising from the surface plasmon absorption of the Au nanoparticles, enhanced power-conversion efficiency (PCE of 6.49% for small-area (0.1 cm2 ZnO/Au-nanocomposite DSSC was achieved compared to the 5.34% efficiency of the bare ZnO nanorod DSSC. The TCSPC studies revealed similar dynamics for the charge transfer from dye molecules to ZnO both in the presence and absence of Au nanoparticles. A slower fluorescence decay associated with the electron recombination process, observed in the presence of Au nanoparticles, confirmed the blocking of the electron transfer from ZnO back to the dye or electrolyte by the Schottky barrier formed at the ZnO/Au interface. For large area DSSC (1 cm2, ~130% enhancement in PCE (from 0.50% to 1.16% was achieved after incorporation of the Au nanoparticles into the ZnO nanorods.

  18. Development of bimetallic (Zn@Au) nanoparticles as potential PET-imageable radiosensitizers.

    Science.gov (United States)

    Cho, Jongmin; Wang, Min; Gonzalez-Lepera, Carlos; Mawlawi, Osama; Cho, Sang Hyun

    2016-08-01

    Gold nanoparticles (GNPs) are being investigated actively for various applications in cancer diagnosis and therapy. As an effort to improve the imaging of GNPs in vivo, the authors developed bimetallic hybrid Zn@Au NPs with zinc cores and gold shells, aiming to render them in vivo visibility through positron emission tomography (PET) after the proton activation of the zinc core as well as capability to induce radiosensitization through the secondary electrons produced from the gold shell when irradiated by various radiation sources. Nearly spherical zinc NPs (∼5-nm diameter) were synthesized and then coated with a ∼4.25-nm gold layer to make Zn@Au NPs (∼13.5-nm total diameter). 28.6 mg of these Zn@Au NPs was deposited (∼100 μm thick) on a thin cellulose target and placed in an aluminum target holder and subsequently irradiated with 14.15-MeV protons from a GE PETtrace cyclotron with 5-μA current for 5 min. After irradiation, the cellulose matrix with the NPs was placed in a dose calibrator to assess the induced radioactivity. The same procedure was repeated with 8-MeV protons. Gamma ray spectroscopy using an high-purity germanium detector was conducted on a very small fraction (<1 mg) of the irradiated NPs for each proton energy. In addition to experimental measurements, Monte Carlo simulations were also performed with radioactive Zn@Au NPs and solid GNPs of the same size irradiated with 160-MeV protons and 250-kVp x-rays. The authors measured 168 μCi of activity 32 min after the end of bombardment for the 14.15-MeV proton energy sample using the (66)Ga setting on a dose calibrator; activity decreased to 2 μCi over a 24-h period. For the 8-MeV proton energy sample, PET imaging was additionally performed for 5 min after a 12-h delay. A 12-h gamma ray spectrum showed strong peaks at 511 keV (2.05 × 10(6) counts) with several other peaks of smaller magnitude for each proton energy sample. PET imaging showed strong PET signals from mostly decaying (66)Ga

  19. Development of bimetallic (Zn@Au) nanoparticles as potential PET-imageable radiosensitizers

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jongmin, E-mail: jongmin.cho@okstate.edu [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Wang, Min [Department of Chemistry, Rice University, Houston, Texas 77005 (United States); Gonzalez-Lepera, Carlos [Department of Nuclear Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Mawlawi, Osama [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Cho, Sang Hyun [Departments of Radiation Physics and Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

    2016-08-15

    Purpose: Gold nanoparticles (GNPs) are being investigated actively for various applications in cancer diagnosis and therapy. As an effort to improve the imaging of GNPs in vivo, the authors developed bimetallic hybrid Zn@Au NPs with zinc cores and gold shells, aiming to render them in vivo visibility through positron emission tomography (PET) after the proton activation of the zinc core as well as capability to induce radiosensitization through the secondary electrons produced from the gold shell when irradiated by various radiation sources. Methods: Nearly spherical zinc NPs (∼5-nm diameter) were synthesized and then coated with a ∼4.25-nm gold layer to make Zn@Au NPs (∼13.5-nm total diameter). 28.6 mg of these Zn@Au NPs was deposited (∼100 μm thick) on a thin cellulose target and placed in an aluminum target holder and subsequently irradiated with 14.15-MeV protons from a GE PETtrace cyclotron with 5-μA current for 5 min. After irradiation, the cellulose matrix with the NPs was placed in a dose calibrator to assess the induced radioactivity. The same procedure was repeated with 8-MeV protons. Gamma ray spectroscopy using an high-purity germanium detector was conducted on a very small fraction (<1 mg) of the irradiated NPs for each proton energy. In addition to experimental measurements, Monte Carlo simulations were also performed with radioactive Zn@Au NPs and solid GNPs of the same size irradiated with 160-MeV protons and 250-kVp x-rays. Results: The authors measured 168 μCi of activity 32 min after the end of bombardment for the 14.15-MeV proton energy sample using the {sup 66}Ga setting on a dose calibrator; activity decreased to 2 μCi over a 24-h period. For the 8-MeV proton energy sample, PET imaging was additionally performed for 5 min after a 12-h delay. A 12-h gamma ray spectrum showed strong peaks at 511 keV (2.05 × 10{sup 6} counts) with several other peaks of smaller magnitude for each proton energy sample. PET imaging showed strong PET

  20. Fe3O4@Au composite magnetic nanoparticles modified with cetuximab for targeted magneto-photothermal therapy of glioma cells.

    Science.gov (United States)

    Lu, Qianling; Dai, Xinyu; Zhang, Peng; Tan, Xiao; Zhong, Yuejiao; Yao, Cheng; Song, Mei; Song, Guili; Zhang, Zhenghai; Peng, Gang; Guo, Zhirui; Ge, Yaoqi; Zhang, Kangzhen; Li, Yuntao

    2018-01-01

    Thermoresponsive nanoparticles have become an attractive candidate for designing combined multimodal therapy strategies because of the onset of hyperthermia and their advantages in synergistic cancer treatment. In this paper, novel cetuximab (C225)-encapsulated core-shell Fe 3 O 4 @Au magnetic nanoparticles (Fe 3 O 4 @Au-C225 composite-targeted MNPs) were created and applied as a therapeutic nanocarrier to conduct targeted magneto-photothermal therapy against glioma cells. The core-shell Fe 3 O 4 @Au magnetic nanoparticles (MNPs) were prepared, and then C225 was further absorbed to synthesize Fe 3 O 4 @Au-C225 composite-targeted MNPs. Their morphology, mean particle size, zeta potential, optical property, magnetic property and thermal dynamic profiles were characterized. After that, the glioma-destructive effect of magnetic fluid hyperthermia (MFH) combined with near-infrared (NIR) hyperthermia mediated by Fe 3 O 4 @Au-C225 composite-targeted MNPs was evaluated through in vitro and in vivo experiments. The inhibitory and apoptotic rates of Fe 3 O 4 @Au-C225 composite-targeted MNPs-mediated combined hyperthermia (MFH+NIR) group were significantly higher than other groups in vitro and the marked upregulation of caspase-3, caspase-8, and caspase-9 expression indicated excellent antitumor effect by inducing intrinsic apoptosis. Furthermore, Fe 3 O 4 @Au-C225 composite-targeted MNPs-mediated combined hyperthermia (MFH+NIR) group exhibited significant tumor growth suppression compared with other groups in vivo. Our studies illustrated that Fe 3 O 4 @Au-C225 composite-targeted MNPs have great potential as a promising nanoplatform for human glioma therapy and could be of great value in medical use in the future.

  1. Radioiodination of cyclin dependent kinase inhibitor Olomoucine loaded Fe rate at Au nanoparticle and evaluation of the therapeutic efficacy on cancerous cells

    Energy Technology Data Exchange (ETDEWEB)

    Takan, Gokhan; Guldu, Ozge Kozgus; Medine, Emin Ilker [Ege Univ., Izmir (Turkey). Dept. of Nuclear Applications

    2017-06-01

    Magnetic nanoparticles have promising biomedical applications such as drug delivery, novel therapeutics and diagnostic imaging. Magnetic drug delivery combination works on the delivery of magnetic nanoparticles loaded with drug to the target tissue by means of an external magnetic field. Gold coated iron oxide (Fe rate at Au) nanoparticles can provide useful surface chemistry and biological reactivity. Covalent conjugation to the Fe rate at Au nanoparticles through cleavable linkages can be used to deliver drugs to tumor cells, then the drug can be released by an external. In this paper, purine based cyclin dependent kinases (CDKs) inhibitor Olomoucine (Olo) [2-(Hydroxyethylamino)-6-benzylamino-9-methylpurine] was loaded on gold coated iron oxide (Fe rate at Au) nanoparticles and radiolabeled with {sup 131}I to combine magnetic targeted drug delivery and radiotherapy. Fe rate at Au nanoparticles were synthesized by microemulsion method. The characterization of nanoparticles was examined by TEM, VSM and XRD. Amine activation was utilized by cysteamine hydrochloride and then CDI was used for conjugation of Olomoucine. Antiproliferative effect and cytotoxicity of Olomoucine loaded Fe rate at Au nanoparticles (Fe rate at Au-Olo) were investigated on MCF7 and A549 cell lines. Proliferation rate was decreased while uptake of Fe rate at Au-Olo on both cell lines was high in comparison with Olomoucine. Also, enhanced incorporation ratio was observed under external magnetic field.

  2. Radioiodination of cyclin dependent kinase inhibitor Olomoucine loaded Fe rate at Au nanoparticle and evaluation of the therapeutic efficacy on cancerous cells

    International Nuclear Information System (INIS)

    Takan, Gokhan; Guldu, Ozge Kozgus; Medine, Emin Ilker

    2017-01-01

    Magnetic nanoparticles have promising biomedical applications such as drug delivery, novel therapeutics and diagnostic imaging. Magnetic drug delivery combination works on the delivery of magnetic nanoparticles loaded with drug to the target tissue by means of an external magnetic field. Gold coated iron oxide (Fe rate at Au) nanoparticles can provide useful surface chemistry and biological reactivity. Covalent conjugation to the Fe rate at Au nanoparticles through cleavable linkages can be used to deliver drugs to tumor cells, then the drug can be released by an external. In this paper, purine based cyclin dependent kinases (CDKs) inhibitor Olomoucine (Olo) [2-(Hydroxyethylamino)-6-benzylamino-9-methylpurine] was loaded on gold coated iron oxide (Fe rate at Au) nanoparticles and radiolabeled with "1"3"1I to combine magnetic targeted drug delivery and radiotherapy. Fe rate at Au nanoparticles were synthesized by microemulsion method. The characterization of nanoparticles was examined by TEM, VSM and XRD. Amine activation was utilized by cysteamine hydrochloride and then CDI was used for conjugation of Olomoucine. Antiproliferative effect and cytotoxicity of Olomoucine loaded Fe rate at Au nanoparticles (Fe rate at Au-Olo) were investigated on MCF7 and A549 cell lines. Proliferation rate was decreased while uptake of Fe rate at Au-Olo on both cell lines was high in comparison with Olomoucine. Also, enhanced incorporation ratio was observed under external magnetic field.

  3. Aerobic methylcyclohexane-promoted epoxidation of stilbene over gold nanoparticles supported on Gd-doped titania

    KAUST Repository

    Mendez, Violaine; Guillois, Kevin; Daniè le, Sté phane; Tuel, Alain; Caps, Valerie

    2010-01-01

    Aerobic partial oxidations of alkanes and alkenes are important processes of the petrochemical industry. The radical mechanisms involved can be catalyzed by soluble salts of transition metals (Co, Cu, Mn...). We show here that the model methylcyclohexane/stilbene co-oxidation reaction can be efficiently catalyzed at lower temperature by supported gold nanoparticles. The support has little influence on gold intrinsic activity but more on the apparent reaction rates which are a combination of catalytic activity and diffusion limitations. These are here minimized by using gadolinium-doped titania nanocrystallites as support for gold nanoparticles. This material is obtained by mild hydrolysis of a new Gd4TiO(OiPr)14 bimetallic oxoalkoxide. It leads to enhanced wettability of the < 3 nm gold particles in the tert-butyl hydroperoxide (TBHP)-initiated epoxidation of stilbene in methylcyclohexane; Au/TiO2:Gd3+ is in turn as active as the state-of-the-art hydrophobic Au/SiO2 catalyst. The rate-determining step of this reaction is identified as the gold-catalyzed homolytic decomposition of TBHP generating radicals and initiating the methylcyclohexane-mediated epoxidation of stilbene, yielding a methylcyclohexan-1-ol/trans-stilbene oxide mixture. Methylcyclohexan-1-ol can also be obtained in the absence of the alkene in the gold-catalyzed solvent-free autoxidation of methylcyclohexane, evidencing the catalytic potential of gold nanoparticles for low temperature C-H activation. © 2010 The Royal Society of Chemistry.

  4. Superior catalytic properties in aerobic oxidation of olefins over Au nanoparticles on pyrrolidone-modified SBA-15

    Czech Academy of Sciences Publication Activity Database

    Wang, L.; Wang, H.; Hapala, Prokop; Zhu, L.; Ren, L.; Meng, X.; Lewis, J.P.; Xiao, F.-S.

    2011-01-01

    Roč. 281, č. 1 (2011), s. 30-39 ISSN 0021-9517 Institutional research plan: CEZ:AV0Z10100521 Keywords : Au nanoparticles * pyrrolidone * cyclohexene oxidation * styrene oxidation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.002, year: 2011

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

    KAUST Repository

    Zou, Houbing

    2015-01-01

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

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

    KAUST Repository

    Song, Hyon Min

    2012-01-01

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

  7. Radiation-induced synthesis of gold, iron-oxide composite nanoparticles

    International Nuclear Information System (INIS)

    Seino, Satoshi; Yamamoto, Takao; Nakagawa, Takashi; Kinoshita, Takuya; Kojima, Takao; Taniguchi, Ryoichi; Okuda, Shuichi

    2007-01-01

    Composite nanoparticles consisting of magnetic iron oxide nanoparticles and gold nanoparticles were synthesized using gamma-rays or electron beam. Ionizing irradiation induces the generation of reducing species inside the aqueous solution, and gold ions are reduced to form metallic Au nanoparticles. The size of Au nanoparticles depended on the dose rate and the concentration of support iron oxide. The gold nanoparticles on iron oxide nanoparticles selectively adsorb biomolecules via Au-S bonding. By using magnetic property of the support iron oxide nanoparticles, the composite nanoparticles are expected as a new type of magnetic nanocarrier for biomedical applications. (author)

  8. Spontaneous decoration of Au nanoparticles on micro-patterned reduced graphene oxide shaped by focused laser beam

    International Nuclear Information System (INIS)

    Wan, Y. C.; Tok, E. S.; Teoh, H. F.; Sow, C. H.

    2015-01-01

    We report a facile, two-step method for the micro-landscaping of Au nanoparticles(NPs) on reduced graphene oxide (rGO) film en route to micro-patterned Au(NPs)-rGO hybrid functional materials. This method employs a focused laser beam to first locally convert GO to rGO before immersing the micro-patterned GO-rGO film into HAuCl 4 solution. The rGO micro-pattern, shaped by the focused laser beam, serves as nucleation sites for the reduction of Au ions. The reduction mechanism that governs the decoration of Au NPs on rGO films is akin to electroless deposition process. In this instance, surface charges that are formed during laser reduction of GO to rGO provide active nucleation sites for Au 3+ ions to form Au NPs when HAuCl 4 solution is introduced. The number density, the size, and size distribution of the Au NPs can thus be directly tuned and preferentially anchored onto the rGO micro-pattern by varying the incident laser power, the scanning speed of the laser, or the concentration of HAuCl 4 . The resulting hybrid materials can be used as a substrate for Surface Enhanced Raman Spectroscopy (SERS). Using Rhodamine 6G as the test subject, we found an improvement of SERS enhancement over bare rGO of up to four times, depending on the size of the Au NPs

  9. Long-term antibacterial characteristics and cytocompatibility of titania nanotubes loaded with Au nanoparticles without photocatalytic effects

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guomin [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Feng, Hongqing, E-mail: fenghongqing@binn.cas.cn [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, National Center for Nanoscience and Technology (NCNST), Beijing 100083 (China); Jin, Weihong; Gao, Ang; Peng, Xiang; Li, Wan; Wu, Hao [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Li, Zhou [Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, National Center for Nanoscience and Technology (NCNST), Beijing 100083 (China); Chu, Paul K., E-mail: paul.chu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

    2017-08-31

    Highlights: • Au@TiO{sub 2}-NT shows long-term antibacterial effects without photocatalytical effects. • An ROS-free antibacterial process is confirmed. • Au@TiO{sub 2}-NT shows good compatibility with osteoblasts and does not induce ROS production. - Abstract: Au nanoparticles (NPs) can endow titania nanotubes (Au@TiO{sub 2}-NT) with light-independent antibacterial properties which bode well for in vivo application because of the dark environment inside tissues. In this work, the long-term antibacterial bactericidal properties and cytocompatibility of Au@TiO{sub 2}-NT without photocatalytic effects are studied in details. The materials exhibit antibacterial effects against Staphylococcus aureus according to antibacterial tests carried out for a total time of 21 days, which are normally long enough for early stage tissue healing after surgery. In addition, adhesion and proliferation of MC3T3-E1 osteoblasts on Au@TiO{sub 2}-NT reveal cytocompatibility comparable to that of TiO{sub 2}-NT. No reactive oxygen species (ROS) are detected from either the bacteria or MC3T3-E1 cells cultured on the Au@TiO{sub 2}-NT surface. The absence of ROS, long-term antibacterial properties, and cytocompatibility make Au@TiO{sub 2}-NT promising biomaterials in orthopedic devices and implants.

  10. Spontaneous decoration of Au nanoparticles on micro-patterned reduced graphene oxide shaped by focused laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Y. C.; Tok, E. S. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Teoh, H. F. [Graduate School of Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore); Sow, C. H. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Graduate School of Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore)

    2015-02-07

    We report a facile, two-step method for the micro-landscaping of Au nanoparticles(NPs) on reduced graphene oxide (rGO) film en route to micro-patterned Au(NPs)-rGO hybrid functional materials. This method employs a focused laser beam to first locally convert GO to rGO before immersing the micro-patterned GO-rGO film into HAuCl{sub 4} solution. The rGO micro-pattern, shaped by the focused laser beam, serves as nucleation sites for the reduction of Au ions. The reduction mechanism that governs the decoration of Au NPs on rGO films is akin to electroless deposition process. In this instance, surface charges that are formed during laser reduction of GO to rGO provide active nucleation sites for Au{sup 3+} ions to form Au NPs when HAuCl{sub 4} solution is introduced. The number density, the size, and size distribution of the Au NPs can thus be directly tuned and preferentially anchored onto the rGO micro-pattern by varying the incident laser power, the scanning speed of the laser, or the concentration of HAuCl{sub 4}. The resulting hybrid materials can be used as a substrate for Surface Enhanced Raman Spectroscopy (SERS). Using Rhodamine 6G as the test subject, we found an improvement of SERS enhancement over bare rGO of up to four times, depending on the size of the Au NPs.

  11. Label-Free Electrochemical Detection of Vanillin through Low-Defect Graphene Electrodes Modified with Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jingyao Gao

    2018-03-01

    Full Text Available Graphene is an excellent modifier for the surface modification of electrochemical electrodes due to its exceptional physical properties and, for the development of graphene-based chemical and biosensors, is usually coated on glassy carbon electrodes (GCEs via drop casting. However, the ease of aggregation and high defect content of reduced graphene oxides degrade the electrical properties. Here, we fabricated low-defect graphene electrodes by catalytically thermal treatment of HPHT diamond substrate, followed by the electrodeposition of Au nanoparticles (AuNPs with an average size of ≈60 nm on the electrode surface using cyclic voltammetry. The Au nanoparticle-decorated graphene electrodes show a wide linear response range to vanillin from 0.2 to 40 µM with a low limit of detection of 10 nM. This work demonstrates the potential applications of graphene-based hybrid electrodes for highly sensitive chemical detection.

  12. A new metal electrocatalysts supported matrix: Palladium nanoparticles supported silicon carbide nanoparticles and its application for alcohol electrooxidation

    International Nuclear Information System (INIS)

    Dai Hong; Chen Yanling; Lin Yanyu; Xu Guifang; Yang Caiping; Tong Yuejin; Guo Longhua; Chen Guonan

    2012-01-01

    In this paper, we propose a facile approach for palladium nanoparticles load using silicon carbide nanoparticles as the new supported matrix and a familiar NaBH 4 as reducer. Detailed X-ray photoelectron spectrum (XPS) and transmission electron microscopy (TEM) analysis of the resultant products indicated that palladium nanoparticles are successfully immobilized onto the surface of the silicon carbide nanoparticles with uniform size distribution between 5 and 7 nm. The relative electrochemical characterization clearly demonstrated excellent electrocatalytic activity of this material toward alcohol in alkaline electrolytes. Investigation on the characteristics of the electrocatalytic activity of this material further indicated that the palladium nanoparticles supporting on SiC are very promising for direct alcohol fuel cells (DMFCs), biosensor and electronic devices. Moreover, it was proved that silicon carbide nanoparticles with outstanding properties as support for catalysis are of strong practical interest. And the silicon carbide could perform attractive role in adsorbents, electrodes, biomedical applications, etc.

  13. Universal Multifunctional Nanoplatform Based on Target-Induced in Situ Promoting Au Seeds Growth to Quench Fluorescence of Upconversion Nanoparticles.

    Science.gov (United States)

    Wu, Qiongqiong; Chen, Hongyu; Fang, Aijin; Wu, Xinyang; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2017-12-22

    Construction of a new multifunctional chemo/biosensing platform for small biomolecules and tumor markers is of great importance in analytical chemistry. Herein, a novel universal multifunctional nanoplatform for biomolecules and enzyme activity detection was proposed based on fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and target-inducing enlarged gold nanoparticles (AuNPs). The reductive molecule such as H 2 O 2 can act as the reductant to reduce HAuCl 4 , which will make the Au seeds grow. The enlarged AuNPs can effectively quench the fluorescence of UCNPs owing to the good spectral overlap between the absorption band of the AuNPs and the emission band of the UCNPs. Utilizing the FRET between the UCNPs and enlarged AuNPs, good linear relationship between the fluorescence of UCNPs and the concentration of H 2 O 2 can be found. Based on this strategy, H 2 O 2 related molecules such as l-lactate, glucose, and uric acid can also be quantified. On the basis of UCNPs and PVP/HAuCl 4 , a general strategy for other reductants such as ascorbic acid (AA), dopamine (DA), or enzyme activity can be established. Therefore, the universal multifunctional nanoplatform based on UCNPs and the target-inducing in situ enlarged Au NPs will show its potential as a simple method for the detection of some life related reductive molecules, enzyme substrates, as well as enzyme activity.

  14. SERS study of surface plasmon resonance induced carrier movement in Au@Cu2O core-shell nanoparticles

    Science.gov (United States)

    Chen, Lei; Zhang, Fan; Deng, Xin-Yu; Xue, Xiangxin; Wang, Li; Sun, Yantao; Feng, Jing-Dong; Zhang, Yongjun; Wang, Yaxin; Jung, Young Mee

    2018-01-01

    A plasmon induced carrier movement enhanced mechanism of surface-enhanced Raman scattering (SERS) was investigated using a charge-transfer (CT) enhancement mechanism. Here, we designed a strategy to study SERS in Au@Cu2O nanoshell nanoparticles with different shell thicknesses. Among the plasmonically coupled nanostructures, Au spheres with Cu2O shells have been of special interest due to their ultrastrong electromagnetic fields and controllable carrier transfer properties, which are useful for SERS. Au@Cu2O nanoshell nanoparticles (NPs) with shell thicknesses of 48-56 nm are synthesized that exhibit high SERS activity. This high activity originates from plasmonic-induced carrier transfer from Au@Cu2O to 4-mercaptobenzoic acid (MBA). The CT transition from the valence band (VB) of Cu2O to the second excited π-π* transition of MBA, and is of b2 electronic symmetry, which was enhanced significantly. The Herzberg-Teller selection rules were employed to predict the observed enhanced b2 symmetry modes. The system constructed in this study combines the long-range electromagnetic effect of Au NPs, localized surface plasmon resonance (LSPR) of the Au@Cu2O nanoshell, and the CT contribution to assist in understanding the SERS mechanism based on LSPR-induced carrier movement in metal/semiconductor nanocomposites.

  15. Surface Reconstruction for Preparation of Plasmonic Au/TiO₂ Nanoparticle with Perfect Hetero Interface and Improved Photocatalytic Capacity.

    Science.gov (United States)

    Yuan, Guoqiu; Ping, Chen; Zhao, Qin; Cao, Min; Jin, Yonglong; Ge, Cunwang

    2018-07-01

    The photocatalytic activity of plasmonic Au/TiO2 nanoparticles (NPs) is dependent on distances between Au and TiO2. The preparation of plasmonic NPs is still a challenge because of an inherent lattice mismatch on heterogeneous interfaces. The combination between Au and TiO2 NPs often exhibits physical adsorption, which affect block the electron transferring process by photo-induction from TiO2 to Au NPs and weaken the photocatalytic activity. In this work an approach for preparing plasmonic Au/TiO2 NPs with perfect hetero-interface was proposed based on reconstruction of anatase TiO2 with (101) surface and in-situ reduction of Au NPs. Under UV-irradiation, anatase TiO2 NPs with a high percentage of (001) facets in formaldehyde solution undergo photochemical reactions to reconstruct the (101) surface of TiO2 and simultaneously allow polyformaldehyde to absorb on the same surface. Thus, Au(OH)-4 ions could be adsorbed on the (101) surfaces of TiO2 through electrostatic adsorption and reduced to form nano-Au in situ after recrystallization at 180 °C. The high-resolution transmission electron microscopy (HRTEM) images showed clear nanoscale lattice transition on heterogeneous interfaces of Au/TiO2 NPs. The surface structure of TiO2 NPs and the growth mechanism of Au/TiO2 NPs were evaluated with HRTEM, X-ray photoelectron spectra (XPS) and Fourier transform infrared spectroscopy (FTIR). It was demonstrated that the as-prepared plasmonic Au/TiO2 NPs had higher photocatalytic activity and corrosion resistance in comparison with primary TiO2 NPs by photo-electrochemical measurements. The reinforcing mechanism could be interpreted with Mott-Schottky analysis in terms of quantum mechanics. Our study implied that the reconstruction based synthesis may open up more opportunities to obtain lattice-mismatch nanomaterials for photocatalysis.

  16. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    Czech Academy of Sciences Publication Activity Database

    Herz, A.; Friák, Martin; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D.; Holec, D.; Šob, Mojmír; Schneeweiss, Oldřich; Schaaf, P.

    2015-01-01

    Roč. 107, č. 7 (2015), art.n. 073109 ISSN 0003-6951 Institutional support: RVO:68081723 Keywords : GENERALIZED GRADIENT APPROXIMATION * NANOPOROUS GOLD NANOPARTICLES * AUGMENTED-WAVE METHOD * ELASTIC-CONSTANTS * BILAYER * NICKEL Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.142, year: 2015

  17. Effect of Refractive Index of Substrate on Fabrication and Optical Properties of Hybrid Au-Ag Triangular Nanoparticle Arrays

    Directory of Open Access Journals (Sweden)

    Jing Liu

    2015-05-01

    Full Text Available In this study, the nanosphere lithography (NSL method was used to fabricate hybrid Au-Ag triangular periodic nanoparticle arrays. The Au-Ag triangular periodic arrays were grown on different substrates, and the effect of the refractive index of substrates on fabrication and optical properties was systematically investigated. At first, the optical spectrum was simulated by the discrete dipole approximation (DDA numerical method as a function of refractive indexes of substrates and mediums. Simulation results showed that as the substrates had the refractive indexes of 1.43 (quartz and 1.68 (SF5 glass, the nanoparticle arrays would have better refractive index sensitivity (RIS and figure of merit (FOM. Simulation results also showed that the peak wavelength of the extinction spectra had a red shift when the medium’s refractive index n increased. The experimental results also demonstrated that when refractive indexes of substrates were 1.43 and 1.68, the nanoparticle arrays and substrate had better adhesive ability. Meanwhile, we found the nanoparticles formed a large-scale monolayer array with the hexagonally close-packed structure. Finally, the hybrid Au-Ag triangular nanoparticle arrays were fabricated on quartz and SF5 glass substrates and their experiment extinction spectra were compared with the simulated results.

  18. Random telegraph signals by alkanethiol-protected Au nanoparticles in chemically assembled single-electron transistors

    International Nuclear Information System (INIS)

    Kano, Shinya; Azuma, Yasuo; Tanaka, Daisuke; Sakamoto, Masanori; Teranishi, Toshiharu; Smith, Luke W.; Smith, Charles G.; Majima, Yutaka

    2013-01-01

    We have studied random telegraph signals (RTSs) in a chemically assembled single-electron transistor (SET) at temperatures as low as 300 mK. The RTSs in the chemically assembled SET were investigated by measuring the source–drain current, using a histogram of the RTS dwell time, and calculating the power spectrum density of the drain current–time characteristics. It was found that the dwell time of the RTS was dependent on the drain voltage of the SET, but was independent of the gate voltage. Considering the spatial structure of the chemically assembled SET, the origin of the RTS is attributed to the trapped charges on an alkanethiol-protected Au nanoparticle positioned near the SET. These results are important as they will help to realize stable chemically assembled SETs in practical applications

  19. Identification of inhomogenous optical absorptive response by chaotic photonic signals in Au nanoparticles

    International Nuclear Information System (INIS)

    Muñoz-César, J C; Torres-Torres, C; Urriolagoitia-Sosa, G; Moreno-Valenzuela, J; Torres-Torres, D; Trejo-Valdez, M

    2013-01-01

    A chaotic circuit allows us to identify with a high sensitivity the optical absorption associated with a highly transparent sample with Au nanoparticles embedded in a TiO 2 thin film prepared by a sol–gel method. The measurements are based on a comparison of the correlation between a controlled optical irradiance that propagates through different zones of the sample. Nanosecond nonlinear optical measurements were obtained by monitoring the transmittance and the amplitude modification for the vectorial components of the electric fields in a two-wave mixing interaction. In addition, we theoretically study chaotic physical behavior exhibited by optical signals under nonlinear optical absorption. Our numerical results point out that small intensity fluctuations related to excitations of the absorptive nonlinearity can be described using a simple fractal model. Potential applications for developing sensors and instrumentation of the optical response of advanced materials are contemplated. (paper)

  20. Synthesis of fluorescent diblock copolymer nanoparticle supported ...

    Indian Academy of Sciences (India)

    2017-06-09

    Jun 9, 2017 ... and induction time (Ti) were determined from the UV–visible spectral data. ... The photo- degradation of rhodamine dye was carried out in the presence ... ence of hierarchical structured polystyrene/polyaniline@Au.

  1. Silica-covered star-shaped Au-Ag nanoparticles as new electromagnetic nanoresonators for Raman characterisation of surfaces.

    Science.gov (United States)

    Krajczewski, Jan; Kołątaj, Karol; Pietrasik, Sylwia; Kudelski, Andrzej

    2018-03-15

    One of the tools used for determining the composition of surfaces of various materials is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS is a modification of "standard" surface-enhanced Raman spectroscopy (SERS), in which, before Raman spectra are recorded, the surfaces analysed are covered with a layer of plasmonic nanoparticles protected by a very thin layer of a transparent dielectric. The plasmonic cores of the core-shell nanoparticles used in SHINERS measurements generate a local enhancement of the electric field of the incident electromagnetic radiation, whereas the transparent coatings prevent the metal cores from coming into direct contact with the material being analysed. In this contribution, we propose a new type of SHINERS nanoresonators that contain spiky, star-shaped metal cores (produced from a gold/silver alloy). These spiky, star-shaped Au-Ag nanoparticles have been covered by a layer of silica. The small radii of the ends of the tips of the spikes of these plasmonic nanostructures make it possible to generate a very large enhancement of the electromagnetic field there, with the result that such SHINERS nanoresonators are significantly more efficient than the standard semi-spherical nanostructures. The Au-Ag alloy nanoparticles were synthesised by the reduction of a solution containing silver nitrate and chloroauric acid by ascorbic acid. The final geometry of the nanostructures thus formed was controlled by changing the ratio between the concentrations of AuCl 4 - and Ag + ions. The shape of the synthesised star-shaped Au-Ag nanoparticles does not change significantly during the two standard procedures for depositing a layer of silica (by the decomposition of sodium silicate or the decomposition of tetraethyl orthosilicate). Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Silica-covered star-shaped Au-Ag nanoparticles as new electromagnetic nanoresonators for Raman characterisation of surfaces

    Science.gov (United States)

    Krajczewski, Jan; Kołątaj, Karol; Pietrasik, Sylwia; Kudelski, Andrzej

    2018-03-01

    One of the tools used for determining the composition of surfaces of various materials is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS is a modification of "standard" surface-enhanced Raman spectroscopy (SERS), in which, before Raman spectra are recorded, the surfaces analysed are covered with a layer of plasmonic nanoparticles protected by a very thin layer of a transparent dielectric. The plasmonic cores of the core-shell nanoparticles used in SHINERS measurements generate a local enhancement of the electric field of the incident electromagnetic radiation, whereas the transparent coatings prevent the metal cores from coming into direct contact with the material being analysed. In this contribution, we propose a new type of SHINERS nanoresonators that contain spiky, star-shaped metal cores (produced from a gold/silver alloy). These spiky, star-shaped Au-Ag nanoparticles have been covered by a layer of silica. The small radii of the ends of the tips of the spikes of these plasmonic nanostructures make it possible to generate a very large enhancement of the electromagnetic field there, with the result that such SHINERS nanoresonators are significantly more efficient than the standard semi-spherical nanostructures. The Au-Ag alloy nanoparticles were synthesised by the reduction of a solution containing silver nitrate and chloroauric acid by ascorbic acid. The final geometry of the nanostructures thus formed was controlled by changing the ratio between the concentrations of AuCl4- and Ag+ ions. The shape of the synthesised star-shaped Au-Ag nanoparticles does not change significantly during the two standard procedures for depositing a layer of silica (by the decomposition of sodium silicate or the decomposition of tetraethyl orthosilicate).

  3. [INVITED] Design of turn around point long period fiber grating sensor with Au-nanoparticle self monolayer

    Science.gov (United States)

    Bandyopadhyay, Sankhyabrata; Basumallick, Nandini; Bysakh, Sandip; Dey, Tanoy Kumar; Biswas, Palas; Bandyopadhyay, Somnath

    2018-06-01

    In this paper studies on the design and fabrication of a long period fiber grating (LPFG) with a self mono layer of gold nanoparticle (AuNP) has been presented. Refractive index (RI) sensitivity of a dispersed cladding mode (DCM) near turn around point (TAP) of its phase matching curve (PMC) has been investigated with and also without AuNP coated LPFG. The typical role played by the intermediate layer of AuNP on the effective index and thus on the sensitivity of the cladding mode to the surrounding RI has also been explored by carrying out coupled mode analysis of the requisite multilayer waveguide. Deposition of AuNP enhanced the sensitivity by more than a factor of 2. Measured sensitivity was found to be ∼3928 nm/refractive index unit (RIU) in the range of 1.3333-1.3428.

  4. Magneto-plasmonic Au-Coated Co nanoparticles synthesized via hot-injection method

    Science.gov (United States)

    Souza, João B., Jr.; Varanda, Laudemir C.

    2018-02-01

    A synthetic procedure is described for the obtaining of superparamagnetic Co nanoparticles (NPs) via hot-injection method in the presence of sodium borohydride. The Co NPs obtained have an average diameter of 5.3 nm and saturation magnetization of 115 emu g-1. A modified Langevin equation is fitted to the magnetization curves using a log-normal distribution for the particle diameter and an effective field to account for dipolar interactions. The calculated magnetic diameter of the Co NPs is 0.6 nm smaller than TEM-derived values, implying a magnetic dead layer of 0.3 nm. The magnetic core is coated with Au to prevent oxidation, resulting in water-stable magneto-plasmonic Co/Au core/shell NPs with saturation of 71.6 emu g-1. The coating adds a localized surface plasmon resonance property with absorbance in the so-called ‘therapeutic window’ (690-900 nm), suitable for biomedical applications. It is suggested that these multifunctional NPs are distinguished as a potential platform for applied and fundamental research.

  5. Three-dimensional TiO2/Au nanoparticles for plasmon enhanced photocatalysis

    Science.gov (United States)

    Yu, Jianyu; Zhou, Lin; Wang, Yang; Tan, Yingling; Wang, Zhenlin; Zhu, Shining; Zhu, Jia

    2018-03-01

    The mechanisms of plasmonic nanostructures assisted photocatalytic processes are fundamental and of great importance and interest for decades. Therefore, we adopt a unique porous structure of three-dimensional TiO2/Au nanoparticles to experimentally explore the potential mechanisms of rhodamine B (RhB) based photocatalytic degradation. The highly efficient absorbance measured across the entire ultraviolet and infrared regions shows the broadband light harvesting capability and photocatalytic activity, in which the direct bandgap transition, plasmon sensitization as well as the plasmonic photothermal effect can be beneficial for the photocatalytic reaction. The RhB photocatalytic degradation experiments were conducted systematically under solar irradiance with finely chosen optical filters. Apart from the ultraviolet-driven degradation of TiO2, the plasmon assisted photocatalytic rate of our TiO2/Au structure can be enhanced by >30% as compared to the referenced TiO2 structure (equivalent to 2-4 times promotion with respect to the same quantity of the active material TiO2). Detailed wavelength-dependent analyses have revealed that the visible-driven degradation rate can be enhanced by 10 times because of the plasmon sensitization effect; while infrared-driven degradation rate is enhanced by 4 times as well for the plasmonic photothermal effect, respectively. Our experimental results may provide a clear understanding for the wavelength-dependent plasmon enhanced photocatalytic processes.

  6. Electrochemical Sensor Coating Based on Electrophoretic Deposition of Au-Doped Self-Assembled Nanoparticles.

    Science.gov (United States)

    Zhang, Rongli; Zhu, Ye; Huang, Jing; Xu, Sheng; Luo, Jing; Liu, Xiaoya

    2018-02-14

    The electrophoretic deposition (EPD) of self-assembled nanoparticles (NPs) on the surface of an electrode is a new strategy for preparing sensor coating. By simply changing the deposition conditions, the electrochemical response for an analyte of deposited NPs-based coating can be controlled. This advantage can decrease the difference between different batches of sensor coating and ensure the reproducibility of each sensor. This work investigated the effects of deposition conditions (including deposition voltage, pH value of suspension, and deposition time) on the structure and the electrochemical response for l-tryptophan of sensor coating formed from Au-doped poly(sodium γ-glutamate) with pendant dopamine units nanohybrids (Au/γ-PGA-DA NBs) via the EPD method. The structure and thickness of the deposited sensor coating were measured by atomic force microscopy, which demonstrated that the structure and thickness of coating can be affected by the deposition voltage, the pH value of the suspension, and the deposition time. The responsive current for l-tryptophan of the deposited sensor coating were measured by differential pulse voltammetry, which showed that the responsive current value was affected by the structure and thickness of the deposited coating. These arguments suggested that a rich design-space for tuning the electrochemical response for analyte and a source of variability in the structure of sensor coating can be provided by the deposition conditions. When Au/γ-PGA-DA NBs were deposited on the electrode surface and formed a continuous coating with particle morphology and thinner thickness, the deposited sensor coating exhibited optimal electrochemical response for l-tryptophan.

  7. Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

    KAUST Repository

    Li, Lidong; Anjum, Dalaver H.; Zhou, Lu; Laveille, Paco; Basset, Jean-Marie

    2015-01-01

    Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles

  8. Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

    KAUST Repository

    Li, Lidong

    2015-06-25

    Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles, and the like.

  9. Enhanced photoelectric performance in self-powered UV detectors based on ZnO nanowires with plasmonic Au nanoparticles scattered electrolyte

    Science.gov (United States)

    Zeng, Yiyu; Ye, Zhizhen; Lu, Bin; Dai, Wei; Pan, Xinhua

    2016-04-01

    Vertically aligned ZnO nanowires (NWs) were grown on a fluorine-doped tin-oxide-coated glass substrate by a hydrothermal method. Au nanoparticles were well dispersed in the mixed solution of ethanol and deionized water. A simple self-powered ultraviolet detector based on solid-liquid heterojunction was fabricated, utilizing ZnO NWs as active photoanode and such prepared mixed solution as electrolyte. The introduction of Au nanoparticles results in considerable improvements in the responsivity and sensitivity of the device compared with the one using deionized water as electrolyte, which is attributed to the enhanced light harvesting by Au nanoparticles.

  10. A3-Coupling catalyzed by robust Au nanoparticles covalently bonded to HS-functionalized cellulose nanocrystalline films

    Directory of Open Access Journals (Sweden)

    Jian-Lin Huang

    2013-07-01

    Full Text Available We decorated HS-functionalized cellulose nanocrystallite (CNC films with monodisperse Au nanoparticles (AuNPs to form a novel nanocomposite catalyst AuNPs@HS-CNC. The uniform, fine AuNPs were made by the reduction of HAuCl4 solution with thiol (HS- group-functionalized CNC films. The AuNPs@HS-CNC nanocomposites were examined by X-ray photoelectron spectroscopy (XPS, TEM, ATR-IR and solid-state NMR. Characterizations suggested that the size of the AuNPs was about 2–3 nm and they were evenly distributed onto the surface of CNC films. Furthermore, the unique nanocomposite Au@HS-CNC catalyst displayed high catalytic efficiency in promoting three-component coupling of an aldehyde, an alkyne, and an amine (A3-coupling either in water or without solvent. Most importantly, the catalyst could be used repetitively more than 11 times without significant deactivation. Our strategy also promotes the use of naturally renewable cellulose to prepare reusable nanocomposite catalysts for organic synthesis.

  11. One-step synthesis of graphene-Au nanoparticle hybrid materials from metal salt-loaded micelles

    International Nuclear Information System (INIS)

    Liu, X; Zhang, X W; Meng, J H; Wang, H L; Yin, Z G; Wu, J L; Gao, H L

    2014-01-01

    In this study, we present a facile one-step method to synthesize graphene-Au nanoparticle (NP) hybrid materials by using HAuCl 4 -loaded poly(styrene)-block-poly(2-vinylpyridine) (PS-P2VP) micelles as solid carbon sources. N-doped graphene with controllable thickness can be grown from PS-P2VP micelles covered by a Ni capping layer by an annealing process; simultaneously, the HAuCl 4 in the micelles were reduced into Au NPs under a reductive atmosphere to form Au NPs on graphene. The decoration of Au NPs leads to an obviously enhanced electrical conductivity and a slightly increased work function of graphene due to the electron transfer effect. The graphene-Au NP hybrid materials also exhibit a localized surface plasmon resonance feature of Au NPs. This work provides a novel and accessible route for the one-step synthesis of graphene-Au NP hybrid materials with high quality, which might be useful for future applications in optoelectronic devices. (paper)

  12. Au Nanoparticles Decorated TiO2 Nanotube Arrays as a Recyclable Sensor for Photoenhanced Electrochemical Detection of Bisphenol A.

    Science.gov (United States)

    Hu, Liangsheng; Fong, Chi-Chun; Zhang, Xuming; Chan, Leo Lai; Lam, Paul K S; Chu, Paul K; Wong, Kwok-Yin; Yang, Mengsu

    2016-04-19

    A photorefreshable and photoenhanced electrochemical sensing platform for bisphenol A (BPA) detection based on Au nanoparticles (NPs) decorated carbon doped TiO2 nanotube arrays (TiO2/Au NTAs) is described. The TiO2/Au NTAs were prepared by quick annealing of anodized nanotubes in argon, followed by controllable electrodeposition of Au NPs. The decoration of Au NPs not only improved photoelectrochemical behavior but also enhanced electrocatalytic activities of the resulted hybrid NTAs. Meanwhile, the high photocatalytic activity of the NTAs allowed the electrode to be readily renewed without damaging the microstructures and surface states after a short UV treatment. The electrochemical detection of BPA on TiO2/Au NTAs electrode was significantly improved under UV irradiation as the electrode could provide fresh reaction surface continuously and the further increased photocurrent resulting from the improved separation efficiency of the photogenerated electron-hole pairs derived from the consumption of holes by BPA. The results showed that the refreshable TiO2/Au NTAs electrode is a promising sensor for long-term BPA monitoring with the detection limit (S/N = 3) of 6.2 nM and the sensitivity of 2.8 μA·μM(-1)·cm(-2).

  13. Construction of Au@Pt core—satellite nanoparticles based on in-situ reduction of polymeric ionic liquid protected gold nanoparticles

    Science.gov (United States)

    Wu, Wenlan; Li, Junbo; Zou, Sheng; Guo, Jinwu; Zhou, Huiyun

    2017-03-01

    A method of in-situ reduction to prepare Au@Pt core-satellite nanoparticles (NPs) is described by using Au NPs coating poly[1-methyl 3-(2-methacryloyloxy propylimidazolium bromine)] (PMMPImB-@-Au NPs) as the template. After electrostatic complex chloroplatinic acid with PMMPImB shell, the composite NP was directly reduced with N2H4 to produce Au@Pt core-satellite NPs. The characterization of composite and core-satellite NPs under different amounts of chloroplatinic acid were studied by DLS, UV-vis absorption spectrum and TEM. The satellite Pt NPs with a small size ( 2 nm) dotted around Au core, and the resulting Au@Pt core-satellite NPs showed a red-shift surface plasmon resonance (SPR) and a good dispersion due to effectively electrostatic repulsion providing by the polymeric ionic liquid (PIL) shell. Finally, Au@Pt core-satellite NPs exhibit an enhanced catalytic activity and cycled catalytic capability for the reduction of p-nitrophenol with NaBH4.

  14. Studied Localized Surface Plasmon Resonance Effects of Au Nanoparticles on TiO2 by FDTD Simulations

    Directory of Open Access Journals (Sweden)

    Guo-Ying Yao

    2018-06-01

    Full Text Available Localized surface plasmon resonance (LSPR plays a significant role in the fields of photocatalysis and solar cells. It can not only broaden the spectral response range of materials, but also improve the separation probability of photo-generated electron-hole pairs through local field enhancement or hot electron injection. In this article, the LSPR effects of Au/TiO2 composite photocatalyst, with different sizes and shapes, have been simulated by the finite difference time domain (FDTD method. The variation tendency of the resonance-absorption peaks and the intensity of enhanced local enhanced electric field were systematically compared and emphasized. When the location of Au nanosphere is gradually immersed into the TiO2 substrate, the local enhanced electric field of the boundary is gradually enhanced. When Au nanoshperes are covered by TiO2 at 100 nm depths, the local enhanced electric field intensities reach the maximum value. However, when Au nanorods are loaded on the surface of the TiO2 substrate, the intensity of the corresponding enhanced local enhanced electric field is the maximum. Au nanospheres produce two strong absorption peaks in the visible light region, which are induced by the LSPR effect and interband transitions between Au nanoparticles and the TiO2 substrate. For the LSPR resonance-absorption peaks, the corresponding position is red-shifted by about 100 nm, as the location of Au nanospheres are gradually immersed into the TiO2 substrate. On the other hand, the size change of the Au nanorods do not lead to a similar variation of the LSPR resonance-absorption peaks, except to change the length-diameter ratio. Meanwhile, the LSPR effects are obviously interfered with by the interband transitions between the Au nanorods and TiO2 substrate. At the end of this article, three photo-generated carrier separation mechanisms are proposed. Among them, the existence of direct electron transfer between Au nanoparticles and the TiO2

  15. Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

    Science.gov (United States)

    Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-Jun

    2014-01-01

    Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

  16. Fast and facile preparation of CTAB based gels and their applications in Au and Ag nanoparticles synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Ravi Kant, E-mail: rkupadhyay85@gmail.com [Department of Chemistry, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar, 201314 Uttar Pradesh (India); Soin, Navneet, E-mail: n.soin@bolton.ac.uk [Knowledge Centre for Materials Chemistry (KCMC), Institute for Materials Research and Innovation (IMRI), University of Bolton, Deane Road, Bolton BL3 5AB (United Kingdom); Saha, Susmita, E-mail: ssaha@bose.res.in [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Barman, Anjan, E-mail: abarman@bose.res.in [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Sinha Roy, Susanta, E-mail: susanta.roy@snu.edu.in [Department of Physics, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar, 201314 Uttar Pradesh (India)

    2015-04-15

    We have demonstrated that the gel-like mesophase of Cetyltrimethylammonium bromide (CTAB) can be synthesized by judicial adjustment of water to surfactant molar ratio (W{sub 0}), without using any additional salts, gelating agents or co-surfactants. Gel formation was found to be highly dependent on the water to surfactant molar ratio (W{sub 0}), with the lowest value of W{sub 0} (41.5) resulting in rapid gel formation. Environmental scanning electron microscope (ESEM) analysis revealed that the gel was comprised of interconnected cylindrical structures. The presence of hydrogen bonding in the gel-like mesophase was confirmed by Fourier Transform Infrared spectroscopy (FTIR) analysis. Rheology measurements revealed that all the gel samples were highly viscoelastic in nature. Furthermore, Au and Ag containing CTAB gels were explored as precursors for the preparation of spherical Gold (Au) and Silver (Ag) nanoparticles using Sodium borohydride (NaBH{sub 4}) as reducing agent. The effects of NaBH{sub 4} concentration on the particle size and morphology of the Au and Ag nanoparticles have also been studied. - Highlights: • A facile synthesis of CTAB based gel-like mesophase is reported. • CTAB gels were obtained by adjusting water to surfactant molar ratio (W{sub 0}). • FTIR analysis revealed that hydrogen bonding plays a key role in gel formation. • Au, Ag nanoparticles were synthesized by using CTAB gel and NaBH{sub 4}.

  17. Mapping the electrostatic potential of Au nanoparticles using hybrid electron holography

    Energy Technology Data Exchange (ETDEWEB)

    Ozsoy-Keskinbora, Cigdem, E-mail: c.ozsoy@fkf.mpg.de [Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Boothroyd, Chris B.; Dunin-Borkowski, Rafal E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich (Germany); Aken, Peter A. van [Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Koch, Christoph T. [Structure Research & Electron Microscopy group, Department of Physics, Humboldt University of Berlin, Newtonstraße 15, 12489 Berlin (Germany)

    2016-06-15

    Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. - Highlights: • Hybrid electron holography approach applied to Au nanoparticles. • Proof of principle of atomic resolution hybrid electron holography experiment demonstrated. • Dynamical scattering artifacts decrease by varying the illumination direction. • The effect of the number of iterations and noise on the low spatial frequencies in the phase are discussed.

  18. Mapping the electrostatic potential of Au nanoparticles using hybrid electron holography

    International Nuclear Information System (INIS)

    Ozsoy-Keskinbora, Cigdem; Boothroyd, Chris B.; Dunin-Borkowski, Rafal E.; Aken, Peter A. van; Koch, Christoph T.

    2016-01-01

    Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. - Highlights: • Hybrid electron holography approach applied to Au nanoparticles. • Proof of principle of atomic resolution hybrid electron holography experiment demonstrated. • Dynamical scattering artifacts decrease by varying the illumination direction. • The effect of the number of iterations and noise on the low spatial frequencies in the phase are discussed.

  19. Catalytic CO Oxidation over Au Nanoparticles Loaded Nanoporous Nickel Phosphate Composite

    Directory of Open Access Journals (Sweden)

    Xiaonan Leng

    2015-01-01

    Full Text Available Au/nickel phosphate-5 (Au/VSB-5 composite with the noble metal loading amount of 1.43 wt.% is prepared by using microporous VSB-5 nanocrystals as the support. Carbon monoxide (CO oxidation reaction is carried out over the sample with several catalytic cycles. Complete conversion of CO is achieved at 238°C over the catalyst at the first catalytic cycle. The catalytic activity improved greatly at the second cycle with the complete conversion fulfilled at 198°C and preserved for the other cycles. A series of experiments such as X-ray diffraction (XRD, high resolution transmission electron microscopy (HRTEM, ultraviolet-visible (UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS are carried out to characterize the catalysts before and after the reaction to study the factors influencing this promotion at the second cycle.

  20. Nanocomposite films containing Au nanoparticles formed by electrochemical reduction of metal ions in the multilayer films as electrocatalyst for dioxygen reduction

    International Nuclear Information System (INIS)

    Huang Minghua; Shen Yan; Cheng Wenlong; Shao Yong; Sun Xuping; Liu Baifeng; Dong Shaojun

    2005-01-01

    Through electrostatic layer-by-layer assembly, AuCl 4 - anions and [tetrakis(N-methylpyridyl)porphyrinato] cobalt (CoTMPyP) cations were alternately deposited on indium tin oxide (ITO) substrates, and 4-aminobenzoic acid modified glassy carbon electrode. Electrochemical reduction of AuCl 4 - anions sandwiched between CoTMPyP layers leads to the in situ formation of Au nanoparticles in the multilayer films. Regular growth of the multilayer films is monitored by UV-vis spectroscopy. UV-vis spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry confirm the formation of Au nanoparticles in the multilayer films after electrochemical reduction of AuCl 4 - anions. Atomic force spectroscopy verifies that the as-prepared Au nanoparticles are uniformly distributed with average particles diameters of 20-25 nm. The resulting composite films containing Au nanoparticles with high stability exhibit high electrocatalytic activity for the reduction of dioxygen. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry demonstrate the Au nanoparticles-containing films can catalyze two-electron reduction of O 2 to H 2 O 2 in O 2 -saturated 0.1 M H 2 SO 4 solution

  1. Enzymatic glucose sensor based on Au nanoparticle and plant-like ZnO film modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Kun [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Alex, Saji [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Department of Chemistry, Government College for Women, Thiruvananthapuram, Kerala 695014 (India); Siegel, Gene [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Tiwari, Ashutosh, E-mail: tiwari@eng.utah.edu [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States)

    2015-01-01

    A novel electrochemical glucose sensor was developed by employing a composite film of plant-like Zinc oxide (ZnO) and chitosan stabilized spherical gold nanoparticles (AuNPs) on which Glucose oxidaze (GOx) was immobilized. The ZnO was deposited on an indium tin oxide (ITO) coated glass and the AuNPs of average diameter of 23 nm were loaded on ZnO as the second layer. The prepared ITO/ZnO/AuNPs/GOx bioelectrode exhibited a low value of Michaelis–Menten constant of 1.70 mM indicating a good bio-matrix for GOx. The studies of electrochemical properties of the electrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that, the presence of AuNPs provides significant enhancement of the electron transfer rate during redox reactions. The linear sweep voltammetry (LSV) shows that the ITO/ZnO/AuNPs/GOx based sensor has a high sensitivity of 3.12 μA·mM{sup −1}·cm{sup −2} in the range of 50 mg/dL to 400 mg/dL glucose concentration. The results show promising application of the gold nanoparticle modified plant-like ZnO composite bioelectrode for electrochemical sensing of glucose.

  2. A Study of the Influence of Percentage of Copper on the Structural and Optical Properties of Au-Cu Nanoparticle

    Directory of Open Access Journals (Sweden)

    Parivash Mashayekhi Shams

    2016-07-01

    Full Text Available Here we present our experimental results in synthesizing Au-Cu nano-particles with tunable localized surface plasmon resonance frequency through wet-chemical at temperature room. The reaction is performed in the presence of ascorbic acid as a reducing agent and polyvinyl pyrrolidone as capping agent via four different procedures: (1 mixture of 90% HAuCl4 and 10% CuSO4.5H2O precursors, (2 mixture of 75% HAuCl4 and 25% CuSO4.5H2O precursors, (3 mixture of 50% HAuCl4 and 50% CuSO4.5H2O precursors (4 mixture of 25% HAuCl4 and 75% CuSO4.5H2O precursors. Effect of different percentages of Cu on Au nanoparticles has been analyzed using X-ray diffraction (XRD, scanning electron microscopy (SEM with EDAX analysis, DRS UV-Vis, and Fourier transform IR spectra (FTIR analysis. X-ray diffraction (XRD analysis revealed that the nanoparticles are of cubic structure without an impure phase. The successful doping of the Cu into the Au host was evident by XRD line shiftings. The increasing percentage of copper leads to the decreasing grain size. With the increase of Cu2+ to Au3+ ratio in the Cu2+/Au3+ mixed solution (> 50% Cu, XRD lines show no shifting. The average crystal sizes of the particles at room temperature were less than 9.9 nm. The surface plasmon resonance peak shifts from 380 to 340 nm, party due to the change in particle size. SEM images show a spherical shape and the size of nanoparticles becomes smaller with increasing the percentage of copper. Moreover, in the molar ratio of Cu2+/Au3+ = 75/25 (>50% Cu, mixture of spherical and trigonal nanoparticles were prepared. Fourier transform infrared spectroscopy (FT-IR showed the coordination and conjugation nanoparticles with N and O atoms of C-N and C=O bonds.

  3. Architecture-dependent surface chemistry for Pt monolayers on carbon-supported Au.

    Science.gov (United States)

    Cheng, Shuang; Rettew, Robert E; Sauerbrey, Marc; Alamgir, Faisal M

    2011-10-01

    Pt monolayers were grown by surface-limited redox replacement (SLRR) on two types of Au nanostructures. The Au nanostructures were fabricated electrochemically on carbon fiber paper (CFP) by either potentiostatic deposition (PSD) or potential square wave deposition (PSWD). The morphology of the Au/CFP heterostructures, examined using scanning electron microscopy (SEM), was found to depend on the type of Au growth method employed. The properties of the Pt deposit, as studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV), were found to depend strongly on the morphology of the support. Specifically, it was found that smaller Au morphologies led to a higher degree of cationicity in the resulting Pt deposit, with Pt(4+) and Pt(2+) species being identified using XPS and XAS. For fuel-cell catalysts, the resistance of ultrathin catalyst deposits to surface area loss through dissolution, poisoning, and agglomeration is critical. This study shows that an equivalent of two monolayers (ML) is the low-loading limit of Pt on Au. At 1 ML or below, the Pt film decreases in activity and durability very rapidly due to presence of cationic Pt. © 2011 American Chemical Society

  4. Tunable shapes in supported metal nanoparticles: From nanoflowers to nanocubes

    International Nuclear Information System (INIS)

    Luque, Rafael; Balu, Alina Mariana; Campelo, Juan Manuel; Gonzalez-Arellano, Camino; Gracia, Maria Jose; Luna, Diego; Marinas, Jose Maria; Romero, Antonio Angel

    2009-01-01

    The facile preparation of a range of supported nanoparticles on porous materials was successfully accomplished through the use of a range of environmentally friendly protocols including a modified impregnation/reduction methodology, ultrasounds and microwave irradiation. Materials were characterised by transmission electron microscopy (TEM) and XPS. Different morphologies including conventional nanospheres, nanoflower aggregates, nanorod-like structures and nanocubes were achieved under different conditions. The reported supported nanoparticles are envisaged to have interesting applications in various areas including catalysis, optics and sensors.

  5. Gold nano-particle formation from crystalline AuCN: Comparison of thermal, plasma- and ion-beam activated decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Beck, Mihály T.; Bertóti, Imre, E-mail: bertoti.imre@ttk.mta.hu; Mohai, Miklós; Németh, Péter; Jakab, Emma; Szabó, László; Szépvölgyi, János

    2017-02-15

    In this work, in addition to the conventional thermal process, two non-conventional ways, the plasma and ion beam activations are described for preparing gold nanoparticles from microcrystalline AuCN precursor. The phase formation at plasma and ion beam treatments was compared with that at thermal treatments and the products and transformations were characterized by thermogravimetry-mass-spectrometry (TG-MS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TG-MS measurements in Ar atmosphere revealed that AuCN decomposition starts at 400 °C and completes at ≈700 °C with evolution of gaseous (CN){sub 2}. XPS and TEM show that in heat treatment at 450 °C for 1 h in Ar, loss of nitrogen and carbon occurs and small, 5–30 nm gold particles forms. Heating at 450 °C for 10 h in sealed ampoule, much larger, 60–200 nm size and well faceted Au particles develop together with a fibrous (CN){sub n} polymer phase, and the Au crystallites are covered by a 3–5 nm thick polymer shell. Low pressure Ar plasma treatment at 300 eV energy results in 4–20 nm size Au particles and removes most of the nitrogen and part of carbon. During Ar{sup +} ion bombardment with 2500 eV energy, 5–30 nm size Au crystallites form already in 10 min, with preferential loss of nitrogen and with increased amount of carbon residue. The results suggest that plasma and ion beam activation, acting similarly to thermal treatment, may be used to prepare Au nanoparticles from AuCN on selected surface areas either by depositing AuCN precursors on selected regions or by focusing the applied ionized radiation. Thus they may offer alternative ways for preparing tailor-made catalysts, electronic devices and sensors for different applications. - Graphical abstract: Proposed scheme of the decomposition mechanism of AuCN samples: heat treatment in Ar flow (a) and in sealed ampoule (b); Ar{sup +} ion treatment at 300 eV (c) and at 2500 eV (d). Cross section sketches

  6. Evaluation of Cytotoxic Effects of Different Concentrations of Porous Hollow Au Nanoparticles (PHAuNPs) on Cells

    International Nuclear Information System (INIS)

    Rao, S.; Tata, U.; Lin, V.K.; Chiao, J.C.; Huang, Ch.; Hao, Y.; Wu, P.; Arora, N.; Ahn, J.

    2014-01-01

    Nanoparticles (NPs) have been introduced as a suitable alternative in many in vivo bio applications. The risks of utilizing nanoparticles continue to be an ongoing research. Furthermore, the various chemicals used in their synthesis influence the cytotoxic effects of nanoparticles. We have investigated the cytotoxicity of Porous Hollow Au Nanoparticles (PHAuNPs) on cancer cell lines PC-3, PC-3ML, and MDA-MB-231 and the normal cell line PNT1A. Cell proliferation for the different cells in the presence of different concentrations of the PHAuNPs was assessed after 24 hours and 72 hours of incubation using MTT assay. The study also included the cytotoxic evaluation of pegylated PHAuNPs. Identical cell seeding densities, particle concentrations, and incubation times were employed for these two types of Au nanoparticles. Our results indicated that (1) impact on cell proliferation was concentration dependent and was different for the different cell types without cellular necrosis and (b) cellular proliferation might be impacted more based on the cell line.

  7. Impedance analysis of oxygen reduction in Au nanoparticles; Analisis por impedancia de la reduccion de oxigeno sobre nanoparticulas de Au

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez-Huerta, G.; Ramos-Sanchez, G. [Cinvestav-IPN, Mexico, D.F. (Mexico)]. E-mail: gervazkez@gmail.com; Antano-Lopez, R. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S. C., Pedro Escobedo, Queretaro (Mexico); Solorza-Feria, O. [Cinvestav-IPN, Mexico, D.F. (Mexico)

    2009-09-15

    Nanometric-sized ({approx}5nm) Au particles were synthesized using the chemical reduction of AuCl{sub 3} with NaBH{sub 4}. The Au particles were analyzed with x-ray diffraction (XRD), finding that the particles are highly crystalline, with a face-centered cubic (FCC) structure. The impedance spectrums obtained in 0.5M H{sub 2}SO{sub 4} solution saturated with O{sub 2}, at potentials greater than 0.38 V vs NHE, show one single temperature constant associated with the reduction in O{sub 2} on Au particles, producing hydrogen peroxide (O{sub 2} +2H{sup +} + 2e{sup -} =H{sub 2}O{sub 2}). At potentials less than 0.38 V, a second constant temperature appears associated with a second process, that is, the reduction of H{sub 2}O{sub 2} to H{sub 2}O. [Spanish] Particulas de Au con tamano nanometrico ({approx}5nm) fueron sintetizadas a partir de la reduccion quimica del AuCl{sub 3} con NaBH{sub 4}. Las particulas de Au fueron analizadas con difraccion de rayos X (XRD), se encontro que las particulas son altamente cristalinas, con una estructura cubica centrada en las caras (FCC). Los espectros de impedancia obtenidos en solucion 0.5M H{sub 2}SO{sub 4} saturada con O{sub 2}, a potenciales mayores de 0.38 V vs NHE muestran una sola constante de tiempo, asociada a la reduccion de O{sub 2} sobre las particulas de Au, dando como producto peroxido de hidrogeno (O{sub 2} +2H{sup +} + 2e{sup -} =H{sub 2}O{sub 2}). A potenciales menores de 0.38 V aparece una segunda constante de tiempo, asociada a un segundo proceso, i.e. la reduccion del H{sub 2}O{sub 2} a H{sub 2}O.

  8. Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas.

    Science.gov (United States)

    Song, Han; Luo, Zhijie; Liu, Mingyao; Zhang, Gang; Peng, Wang; Wang, Boyi; Zhu, Yong

    2018-05-06

    In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost.

  9. 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.

  10. Preparation of Ag{sub core}/Au{sub shell} bimetallic nanoparticles from physical mixtures of Au clusters and Ag ions under dark conditions and their catalytic activity for aerobic glucose oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haijun, E-mail: zhanghaijun@wust.edu.cn [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); Toshima, Naoki; Takasaki, Kanako [Department of Applied Chemistry, Tokyo University of Science Yamaguchi, SanyoOnoda-shi, Yamaguchi 756-0884 (Japan); Okumura, Mitsutaka [Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)

    2014-02-15

    Graphical abstract: The synthesis, characterization and catalytic activities for glucose oxidation of AgAu bimetallic nanoparticles (BNPs) with size of less than 2 nm are reported. The catalytic activity of Ag{sub 10}Au{sub 90} BNPs was about two times higher than that of Au NPs, even the BNPs have a larger particle size than that of Au NPs. -- Highlights: • Ag{sub core}/Au{sub shell} BNPs with size of less than 2.0 nm were prepared. • No any reducing reagents and lights were used for the preparation of the BNPs. • The catalytic activity of the BNPs is about two times higher than that of Au NPs. -- Abstract: AgAu bimetallic nanoparticles (BNPs), one of the most extensively studied bimetallic systems in the literatures, could have various structures and compositions depending on their preparation conditions. In the present work, catalytically highly active PVP-protected Ag{sub core}/Au{sub shell} BNPs of about 2.5 nm in diameter were fabricated from physical mixtures of aqueous dispersions of Au nanoparticles and Ag{sup +} ions under dark conditions without using any reducing agents. The prepared Ag{sub core}/Au{sub shell} BNP colloidal catalysts, which possessed a high activity for aerobic glucose oxidation, were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), Inductive coupled plasma emission spectrometer (ICP), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Energy disperse spectroscopy (EDS) in High-resolution scanning transmission electron microscopy (HR-STEM). The highest activity (11,360 mol-glucose h{sup −1} mol-metal{sup −1}) was observed for the BNPs with the Ag/Au atomic ratio of 1/9, the TOF value of which is about two times higher than that of Au nanoparticles with the particle size of 1.3 nm. The enhanced catalytic activity of the prepared Ag{sub core}/Au{sub shell} BNPs compared to Au NPs can be ascribed to the presence of negatively charged Au atoms resulted from electron donations

  11. Biological synthesis of Au nanoparticles using liquefied mash of cassava starch and their functionalization for enhanced hydrolysis of xylan by recombinant xylanase.

    Science.gov (United States)

    Zeng, Sumei; Du, Liangwei; Huang, Meiying; Feng, Jia-Xun

    2016-05-01

    Au nanoparticles (AuNPs) have shown the potential for a variety of applications due to their unique physical and chemical properties. In this study, a facile and affordable method for the synthesis of AuNPs via the liquefied mash of cassava starch has been described and the functionalized AuNPs by L-cysteine improved activity of recombinant xylanase was demonstrated. UV-Vis absorption spectroscopy, transmission electron microscopy, and zeta potential measurements were performed to characterize the AuNPs and monitor their synthesis. The presence of Au was confirmed by energy-dispersive X-ray spectroscopy (EDX) and the X-ray diffraction patterns showed that Au nanocrystals were face-centered cubic. The C=O stretching vibration in the Fourier transform infrared spectrum of AuNPs suggested that the hemiacetal C-OH of sugar molecules performed the reduction of Au³⁺ to Au⁰. The presence of C and O in the EDX spectrum and the negative zeta potential of AuNPs suggested that the biomolecules present in liquefied cassava mash were responsible for the stabilization of AuNPs. The surface of AuNPs was easily functionalized by L-cysteine, which improved the stability of AuNPs. Moreover, cysteine-functionalized AuNPs could significantly improve recombinant xylanase efficiency and stability.

  12. Controlled Clustering of Gold Nanoparticles using Solid-support for Surface-enhanced Raman Spectroscopic Probes

    International Nuclear Information System (INIS)

    Chang, Hyejin; Chae, Jinjoo; Jeong, Hong; Kang, Homan; Lee, Yoonsik

    2014-01-01

    We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature

  13. Controlled Clustering of Gold Nanoparticles using Solid-support for Surface-enhanced Raman Spectroscopic Probes

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hyejin; Chae, Jinjoo; Jeong, Hong [Department of Chemistry Education, Seoul (Korea, Republic of); Kang, Homan; Lee, Yoonsik [Interdisciplinary Program in Nano-Science and Technology, Pohang (Korea, Republic of)

    2014-03-15

    We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature.

  14. X-ray spectroscopy study of electronic structure of laser-irradiated Au nanoparticles in a silica film

    International Nuclear Information System (INIS)

    Jonnard, P.; Bercegol, H.; Lamaignere, L.; Morreeuw, J.-P.; Rullier, J.-L.; Cottancin, E.; Pellarin, M.

    2005-01-01

    The electronic structure of gold nanoparticles embedded in a silica film is studied, both before and after irradiation at 355 nm by a laser. The Au 5d occupied valence states are observed by x-ray emission spectroscopy. They show that before irradiation the gold atoms are in metallic states within the nanoparticles. After irradiation with a fluence of 0.5 J/cm 2 , it is found that gold valence states are close to those of a metal-poor gold silicide; thanks to a comparison of the experimental Au 5d states with the calculated ones for gold silicides using the density-functional theory. The formation of such a compound is driven by the diffusion of the gold atoms into the silica film upon the laser irradiation. At higher fluence, 1 J/cm 2 , we find a higher percentage of metallic gold that could be attributed to annealing in the silica matrix

  15. Structure sensitivity in CO oxidation by a single Au atom supported on ceria

    NARCIS (Netherlands)

    Song, W.; Hensen, E.J.M.

    2013-01-01

    The mechanism of CO oxidation by a CeO2(110)-supported gold atom has been investigated by DFT calculations. A novel stable surface structure has been identified in which one surface O atom of ceria migrates toward the isolated Au atom, resulting in a surface Au–O species that can react with CO.

  16. Complete Au@ZnO core-shell nanoparticles with enhanced plasmonic absorption enabling significantly improved photocatalysis

    Science.gov (United States)

    Sun, Yiqiang; Sun, Yugang; Zhang, Tao; Chen, Guozhu; Zhang, Fengshou; Liu, Dilong; Cai, Weiping; Li, Yue; Yang, Xianfeng; Li, Cuncheng

    2016-05-01

    Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic absorption in the visible range due to the Au NP cores. They also show a significantly improved photocatalytic performance in comparison with their single-component counterparts, i.e., the Au NPs and ZnO NPs. Moreover, the high catalytic activity of the as-synthesized Au@ZnO core-shell NPs can be maintained even after many cycles of photocatalytic reaction. Our results shed light on the fact that the Au@ZnO core-shell NPs represent a promising class of candidates for applications in plasmonics, surface-enhanced spectroscopy, light harvest devices, solar energy conversion, and degradation of organic pollutants.Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic

  17. Adsorption characteristics of Au nanoparticles onto poly(4-vinylpyridine) surface revealed by QCM, AFM, UV/vis, and Raman scattering spectroscopy.

    Science.gov (United States)

    Kim, Kwan; Ryoo, Hyunwoo; Lee, Yoon Mi; Shin, Kuan Soo

    2010-02-15

    In this work, we report that the adsorption and aggregation processes of Au nanoparticles on a polymer surface can be monitored by means of surface-enhanced Raman scattering (SERS) spectroscopy. Specifically, we were able to analyze the adsorption process of citrate-stabilized Au nanoparticles onto a film of poly(4-vinylpyridine) (P4VP) by taking a series of SERS spectra, during the self-assembly of Au nanoparticles onto the polymer film. In order to better analyze the SERS spectra, we separately conducted quartz crystal microbalance (QCM), UV/vis spectroscopy, and atomic force microscope (AFM) measurements. The adsorption kinetics revealed by QCM under the in situ conditions was in fair agreement with that determined by the ex situ AFM measurement. The number of Au nanoparticles adsorbed on P4VP increased almost linearly with time: 265 Au nanoparticles per 1microm(2) were adsorbed on the P4VP film after 6h of immersion. The SERS signal measured in the ex situ condition showed a more rapid increase than that of QCM; however, its increasing pattern was quite similar to that of UV/vis absorbance at longer wavelengths, suggesting that Au nanoparticles actually became agglomerated on P4VP. Copyright 2009 Elsevier Inc. All rights reserved.

  18. Anionic solid lipid nanoparticles supported on protamine/DNA complexes

    International Nuclear Information System (INIS)

    Ye Jiesheng; Liu Chunxi; Chen Zhijin; Zhang Na; Wang Aihua

    2008-01-01

    The objective of this study was to design novel anionic ternary nanoparticles for gene delivery. These ternary nanoparticles were equipped with protamine/DNA binary complexes (150-200 nm) as the support, and the anionic formation was achieved by absorption of anionic solid lipid nanoparticles (≤20 nm) onto the surface of the binary complexes. The small solid lipid nanoparticles (SLNs) were prepared by a modified film dispersion-ultrasonication method, and adsorption of the anionic SLNs onto the binary complexes was typically carried out in water via electrostatic interaction. The formulated ternary nanoparticles were found to be relatively uniform in size (257.7 ± 10.6 nm) with a 'bumpy' surface, and the surface charge inversion from 19.28 ± 1.14 mV to -17.16 ± 1.92 mV could be considered as evidence of the formation of the ternary nanoparticles. The fluorescence intensity measurements from three batches of the ternary nanoparticles gave a mean adsorption efficiency of 96.75 ± 1.13%. Circular dichroism spectra analysis showed that the protamine/DNA complexes had been coated by small SLNs, and that the anionic ternary nanoparticles formed did not disturb the construction of the binary complexes. SYBR Green I analysis suggested that the ternary nanoparticles could protect the DNA from nuclease degradation, and cell viability assay results showed that they exhibit lower cytotoxicity to A549 cells compared with the binary complexes and lipofectamine. The transfection efficiency of the ternary nanoparticles was better than that of naked DNA and the binary complexes, and almost equal to that of lipofectamine/DNA complexes, as revealed by inversion fluorescence microscope observation. These results indicated that the anionic ternary nanoparticles could facilitate gene transfer in cultured cells, and might alleviate the drawbacks of the conventional cationic vector/DNA complexes for gene delivery in vivo

  19. Au nanoparticles decorated SiO{sub 2} nanowires by dewetting on curved surfaces: facile synthesis and nanoparticles-nanowires sizes correlation

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-15

    We report a solid-state synthesis for SiO{sub 2} nanowires (NWs) (up to 20 microns in length and from about 40 to about 150 nm in diameter) coated by Au nanoparticles (NPs) (from about 20 to about 80 nm in diameter). This protocol is based on three steps: (1) large area production of very long SiO{sub 2} NWs on a Si surface exploiting a simple Au/Si solid-state reaction at high temperature; (2) coating of the SiO{sub 2} NWs by a Au film of desired thickness using sputtering depositions; and (3) a thermal process to induce a dewetting process of the Au-film coating the SiO{sub 2} NWs to obtain Au NPs on the curved surface of the NWs. The morphology evolution of the SiO{sub 2} NWs was followed, in each step, by scanning electron microscopy analyses. They allowed to correlate the evolution of the NPs size with the NWs sizes for different thicknesses of the starting Au-film coating the NWs and different annealing temperatures of the dewetting process. Some theoretical concepts, related to the dewetting process of a film on a curved surface were used to describe the experimental data. The main advantages of the proposed protocols include: (i) simplicity and low-cost (it is based only on sputtering depositions and thermal processes), and (ii) versatility based on the possibility of tuning Au-film thickness and annealing temperature to tune the NPs-NWs sizes ratio. These advantages can make this technique suitable for the mass production of Au NPs-coated SiO{sub 2} NWs toward applications in electronic devices, biosensors, and nanoscale optical devices.

  20. Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution

    International Nuclear Information System (INIS)

    Sivashanmugan, Kundan; Liao, Jiunn-Der; Liu, Bernard Haochih; Yao, Chih-Kai

    2013-01-01

    Graphical abstract: -- Highlights: •Well-ordered Au-nanorod array with a controlled tip ring diameter (Au N Rs d ) is made by focused ion beam. •Au N Rs d coupled with Ag nanoparticles (Ag NPs/Au N Rs d ) is competent to sense target molecules in a solution. •Ag NPs/Au N Rs d SERS active substrate can detect a single molecule of crystal violet. •Ag NPs/Au N Rs d as a SERS-active substrate can distinguish melamine contaminants at low concentrations (e.g., 10 −12 M). -- Abstract: A well-ordered Au-nanorod array with a controlled tip ring diameter (Au N Rs d ) was fabricated using the focused ion beam method. Au N Rs d was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au N Rs d and Ag NPs/Au N Rs d was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au N Rs d was estimated by an enhancement factor of ≈10 7 in magnitude, which increased ≈10 12 in magnitude for that on Ag NPs/Au N Rs d . A highly SERS-active Ag NPs/Au N Rs d was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10 −3 to 10 −12 M) in water or milk solution upon Au N Rs d or Ag NPs/Au N Rs d were well distinguished. The peaks at 680 and 702 cm −1 for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm −1 was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au N Rs d ) or Ag (i.e., Ag NPs/Au N Rs d ) surface. At the interface of Ag NPs/Au N Rs d and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and competent to sense low-concentration MEL molecules interacting with Ag and Au surfaces. Accordingly, Ag NPs/Au N Rs d is very promising to be used as a fast and sensitive tool for

  1. One-pot preparation of PEDOT:PSS-reduced graphene decorated with Au nanoparticles for enzymatic electrochemical sensing of H{sub 2}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mercante, Luiza A., E-mail: lamercante@gmail.com [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Facure, Murilo H.M. [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Center for Exact Sciences and Technology, Federal University of São Carlos (UFSCar), 13565-905, São Carlos, SP (Brazil); Sanfelice, Rafaela C.; Migliorini, Fernanda L.; Mattoso, Luiz H.C. [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Correa, Daniel S., E-mail: daniel.correa@embrapa.br [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Center for Exact Sciences and Technology, Federal University of São Carlos (UFSCar), 13565-905, São Carlos, SP (Brazil)

    2017-06-15

    Highlights: • Hybrid ternary nanocomposite PEDOT:PSS-rGO-AuNPs is developed by a one-step approach. • Horseradish peroxidase is used to build a novel hybrid biomaterial. • The PEDOT:PSS-rGO-AuNPs-HRP displays excellent electrochemical activity toward the reduction of H{sub 2}O{sub 2}. • A significant low detection limit of 0.08 μM and wider linear range is achieved. • The constructed electrode is used detecting H{sub 2}O{sub 2} in real samples. - Abstract: The development of novel graphene-based nanocomposites is a hotspot in materials science due to their unique optical, electronic, thermal, mechanical and catalytic properties for varied applications. The present work reports on the development of a graphene-based ternary nanocomposite of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), reduced graphene oxide and gold nanoparticles (PEDOT:PSS-rGO-AuNPs) for the detection of hydrogen peroxide (H{sub 2}O{sub 2}). The hybrid nanocomposite showed superior electrochemical properties and higher stability compared to each individual component as electrode materials, showing a synergistic effect between PEDOT, rGO and AuNPs. The nanocomposite was obtained via a facile one-step approach and was assembly with horseradish peroxidase (HRP). The PEDOT:PSS-rGO-AuNPs-HRP modified electrode has been used for the amperometric detection of H{sub 2}O{sub 2} and exhibited a high sensitivity of up to 677 μA mM{sup −1} cm{sup −2}, with a wide linear range from 5 to 400 μM and a low detection limit of 0.08 μM (S/N = 3). This developed enzymatic biosensor showed to be highly stable and unresponsive to potentially interfering substances, and it could be used for sensing H{sub 2}O{sub 2} in real samples, including tap water and bovine milk samples. These enhanced sensing performance could be ascribed to the intimate contact of AuNPs onto the rough surface of the PEDOT:PSS-rGO nanocomposite, which has a high electrical conductivity and large surface area, providing

  2. Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

    Science.gov (United States)

    Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

    2016-04-06

    A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO₃ solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

  3. Methionine – Au Nanoparticle Modified Glassy Carbon Electrode: a Novel Platform for Electrochemical Detection of Hydroquinone

    Directory of Open Access Journals (Sweden)

    Jiahong HE

    2014-12-01

    Full Text Available A high sensitive electrochemical sensor based on methionine/gold nanoparticles (MET/AuNPs modified glassy carbon electrode (GCE was fabricated for the quantitative detection of hydroquinone (HQ. The as-modified electrode was characterized by scanning electron microscopy (SEM and X-ray diffraction (XRD techniques. The electrochemical performance of the sensor to HQ was investigated by using cyclic and differential pulse voltammetry, which revealed its excellent electrocatalytic activity and reversibility towards HQ. The separation of anodic and cathodic peak (∆Ep was decreased from 471 mV to 75 mV. The anodic peak current achieved under the optimum conditions was linear with the HQ concentration ranging from 8 μM to 400 μM with the detection limit 0.12 μM (3σ. The as-fabricated sensor also showed a good selectivity towards HQ without demonstrating interference from other coexisting species. Furthermore, the sensor showed a good performance for HQ detection in environmental water, which suggests its potential practical application. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6477

  4. Cationic Au Nanoparticle Binding with Plasma Membrane-like Lipid Bilayers: Potential Mechanism for Spontaneous Permeation to Cells Revealed by Atomistic Simulations

    DEFF Research Database (Denmark)

    Heikkila, E.; Martinez-Seara, H.; Gurtovenko, A. A.

    2014-01-01

    Despite being chemically inert as a bulk material, nanoscale gold can pose harmful side effects to living organisms. In particular, cationic Au nanoparticles (AuNP+) of 2 nm diameter or less permeate readily through plasma membranes and induce cell death. We report atomistic simulations of cationic...... to be governed by cooperative effects where AuNP+, counterions, water, and the two membrane leaflets all contribute. On the extracellular side, we find that the nanoparticle has to cross a free energy barrier of about 5 k(B)T prior forming a stable contact with the membrane. This results in a rearrangement...

  5. Harvesting multiple electron-hole pairs generated through plasmonic excitation of Au nanoparticles.

    Science.gov (United States)

    Kim, Youngsoo; Smith, Jeremy G; Jain, Prashant K

    2018-05-07

    Multi-electron redox reactions, although central to artificial photosynthesis, are kinetically sluggish. Amidst the search for synthetic catalysts for such processes, plasmonic nanoparticles have been found to catalyse multi-electron reduction of CO 2 under visible light. This example motivates the need for a general, insight-driven framework for plasmonic catalysis of such multi-electron chemistry. Here, we elucidate the principles underlying the extraction of multiple redox equivalents from a plasmonic photocatalyst. We measure the kinetics of electron harvesting from a gold nanoparticle photocatalyst as a function of photon flux. Our measurements, supported by theoretical modelling, reveal a regime where two-electron transfer from the excited gold nanoparticle becomes prevalent. Multiple electron harvesting becomes possible under continuous-wave, visible-light excitation of moderate intensity due to strong interband transitions in gold and electron-hole separation accomplished using a hole scavenger. These insights will help expand the utility of plasmonic photocatalysis beyond CO 2 reduction to other challenging multi-electron, multi-proton transformations such as N 2 fixation.

  6. Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

    Science.gov (United States)

    Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

    2015-11-01

    Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures.

  7. Electrochemical Glucose Oxidation Using Glassy Carbon Electrodes Modified with Au-Ag Nanoparticles: Influence of Ag Content

    Directory of Open Access Journals (Sweden)

    Nancy Gabriela García-Morales

    2015-01-01

    Full Text Available This paper describes the application of glassy carbon modified electrodes bearing Aux-Agy nanoparticles to catalyze the electrochemical oxidation of glucose. In particular, the paper shows the influence of the Ag content on this oxidation process. A simple method was applied to prepare the nanoparticles, which were characterized by transmission electron microscopy, Ultraviolet-Visible spectroscopy, X-ray diffraction spectroscopy, and cyclic voltammetry. These nanoparticles were used to modify glassy carbon electrodes. The effectiveness of these electrodes for electrochemical glucose oxidation was evaluated. The modified glassy carbon electrodes are highly sensitive to glucose oxidation in alkaline media, which could be attributed to the presence of Aux-Agy nanoparticles on the electrode surface. The voltammetric results suggest that the glucose oxidation speed is controlled by the glucose diffusion to the electrode surface. These results also show that the catalytic activity of the electrodes depends on the Ag content of the nanoparticles. Best results were obtained for the Au80-Ag20 nanoparticles modified electrode. This electrode could be used for Gluconic acid (GA production.

  8. Tuning of platinum nano-particles by Au usage in their binary alloy for direct ethanol fuel cell: Controlled synthesis, electrode kinetics and mechanistic interpretation

    Science.gov (United States)

    Dutta, Abhijit; Mondal, Achintya; Datta, Jayati

    2015-06-01

    Understanding of the electrode-kinetics and mechanism of ethanol oxidation reaction (EOR) is of considerable interest for optimizing electro-catalysis in direct ethanol fuel cell (DEFC). This work attempts to design Pt based electro-catalyst on carbon support, tuned with gold nano-particles (NPs), for their use in DEFC operating in alkaline medium. The platinum-gold alloyed NPs are synthesized at desired compositions and size (2-10 nm) by controlled borohydride reduction method and successfully characterized by XRD, TEM, EDS and XPS techniques. The kinetic parameters along with the activation energies for the EOR are evaluated over the temperature range 20-80 °C and the oxidation reaction products estimated through ion chromatographic analysis. Compared to single Pt/C catalyst, the over potential of EOR is reduced by ca. 500 mV, at the onset during the reaction, for PtAu/C alloy with only 23% Pt content demonstrating the ability of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pt. Furthermore, a considerable increase in the peak power density (>191%) is observed in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC using the best performing Au covered Pt electrode (23% Pt) compared to the monometallic Pt catalyst.

  9. One-step electrodeposition of Au-Pt bimetallic nanoparticles on MoS2 nanoflowers for hydrogen peroxide enzyme-free electrochemical sensor

    International Nuclear Information System (INIS)

    Zhou, Juan; Zhao, Yanan; Bao, Jing; Huo, Danqun; Fa, Huanbao; Shen, Xin; Hou, Changjun

    2017-01-01

    The rationally designed sensor architecture is very important to improve the sensitivity and selectivity for H 2 O 2 enzyme-free electrochemical sensor. In this work, a sensitive H 2 O 2 biosensor was fabricated by electrochemical deposition of Au-Pt bimetallic nanoparticles (NPs) on molybdenum disulfide nanoflowers (MoS 2 NFs). Au-Pt NPs was dispersed or stabilized by the effective support matrix of MoS 2 nanosheets, which was effectively enhance the conductivity, catalytic performance and long-term stability. The experimental results show that MoS 2 -Au/Pt nanocomposites exhibit excellent catalytic activity for specific detection of H 2 O 2, and electrochemical measurement results show that the enzyme-free electrochemical sensor has large linear range of 10 μM to 19.07 mM with high sensitivity of 142.68 μA mM −1 cm −2 . This novel sensor produced satisfactory reproducibility and stability, and exhibited superior potential for the practical quantitative analysis of H 2 O 2 in serum samples.

  10. Microstructure evolution during 300 °C storage of sintered Ag nanoparticles on Ag and Au substrates

    Energy Technology Data Exchange (ETDEWEB)

    Paknejad, S.A. [King’s College London, Physics Department, Strand, London WC2R 2LS (United Kingdom); Dumas, G. [Eltek Semiconductors Ltd, Nelson Road Industrial Estate, Dartmouth, Devon TQ6 9LA (United Kingdom); West, G. [Loughborough University, Materials Department, Loughborough LE11 3TU (United Kingdom); Lewis, G. [Eltek Semiconductors Ltd, Nelson Road Industrial Estate, Dartmouth, Devon TQ6 9LA (United Kingdom); Mannan, S.H., E-mail: samjid.mannan@kcl.ac.uk [King’s College London, Physics Department, Strand, London WC2R 2LS (United Kingdom)

    2014-12-25

    Highlights: • Shear strength of pressure-free sintered Ag found to increase during ageing at 300 °C on Ag substrate. • Rapid collapse of void number density after 24 h ageing in the sintered Ag layer. • Higher porosity at edge of joint compared to the middle. • Shear strength of pressure-free sintered Ag decreases during ageing at 300 °C due to high porosity layer growth. • Void free layer and high porosity layer growth explained in terms of atomic diffusion and grain boundary migration. - Abstract: A silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The assemblies were stored at 300 °C for up to 500 h and the morphology of the sintered Ag and the shear strength were monitored as a function of time. On Ag substrate it was found that die shear strength increased and that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. On Au substrate, it was observed that the initially high die shear strength decreased with storage time and that voids migrated away from the Ag/Au interface and into the Ag joint. This has led to the formation of a void free layer at the interface followed by a high porosity region, which weakened the joint. The microstructure reveals a high density of grain and twin boundaries which facilitate the Ag and Au atomic diffusion responsible. The grain structure of the plated Au led to diffusion of Au into the Ag via high-angle tilt grain boundaries, and grain boundary migration further dispersed the Au into the Ag layer.

  11. Gold Nanoparticles Supported on a Layered Double Hydroxide as Efficient Catalysts for the One-Pot Synthesis of Flavones.

    Science.gov (United States)

    Yatabe, Takafumi; Jin, Xiongjie; Yamaguchi, Kazuya; Mizuno, Noritaka

    2015-11-02

    Flavones are a class of natural products with diverse biological activities and have frequently been synthesized by step-by-step procedures using stoichiometric amounts of reagents. Herein, a catalytic one-pot procedure for the synthesis of flavone and its derivatives is developed. In the presence of gold nanoparticles supported on a Mg-Al layered double hydroxide (Au/LDH), various kinds of flavones can be synthesized starting from 2'-hydroxyacetophenones and benzaldehydes (or benzyl alcohols). The present one-pot procedure consists of a sequence of several reactions, and Au/LDH can catalyze all these different types of reactions. The catalysis is shown to be truly heterogeneous, and Au/LDH can be readily recovered and reused. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. TS-1 supported highly dispersed sub-5 nm gold nanoparticles toward direct propylene epoxidation using H2 and O2

    Science.gov (United States)

    Li, Naixu; Chen, Yong; Shen, Quanhao; Yang, Bin; Liu, Ming; Wei, Lingfei; Tian, Wei; Zhou, Jiancheng

    2018-05-01

    We report a simple and efficient method for the preparation of highly dispersed Au nanoparticles (< 5 nm) on TS-1 substrate. The synthesis relies on the use of NaBH4 as a reductant for rapid Au atom generation, as well as PVA as a capping agent confining the particle size and dispersion. The samples were characterized by N2 physisorption, inductively coupled plasma mass spectrometry, power X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, CO pulse chemisorption and thermogravimetric analysis. The size of Au particles can be controlled in the range of 3-5 nm. The supported catalyst shows both good activity and selectivity for propylene oxide (PO) generation from direct propylene epoxidation. An optimal performance with PO formation rate of 102.94 gPO h-1 kg-1cat and selectivity of 84.83% is achieved over 2.0 wt% Au/TS-1 catalyst, which is prepared by controlling PVA/Au3+ mass ratio of 1.5/1 and NaBH4/Au3+ mole ratio of 5/1. After 50 h test at 200 °C, no significant decrement of both catalytic activity and PO selectivity can be observed, indicating the excellent thermally stability of the catalyst. Furthermore, a possible reaction mechanism is described on basis of the previous researches and our experimental results.

  13. Carbon supported ultrafine gold phosphorus nanoparticles as highly efficient electrocatalyst for alkaline ethanol oxidation reaction

    International Nuclear Information System (INIS)

    Li, Tongfei; Fu, Gengtao; Su, Jiahui; Wang, Yi; Lv, Yinjie; Zou, Xiuyong; Zhu, Xiaoshu; Xu, Lin; Sun, Dongmei; Tang, Yawen

    2017-01-01

    Graphical abstract: We develop a new kind of carbon supported gold-phosphorus (Au-P/C) electrocatalyst by a facile and novel phosphorus reduction method, and demonstrate the Au-P/C is a highly active and stable electrocatalyst for the ethanol oxidation reaction. - Highlights: • Au-P/C catalyst is synthesized by a facile and novel white-phosphorus reduce method. • AuP particles with ultrafine particle-size are uniformly dispersed on carbon support. • Au-P/C catalyst exhibits much higher content of P 0 than reported metal/P catalysts. • Au-P/C catalysts show excellent catalytic properties for ethanol oxidation reaction. - Abstract: Herein, we develop a new kind of carbon supported gold-phosphorus (Au-P/C) electrocatalyst for the alkaline ethanol oxidation reaction (EOR). The Au-P/C catalysts with different Au/P ratio (i.e., AuP/C, Au 3 P 2 /C and Au 4 P 3 /C) can be obtained by a facile and novel hot-reflux method with white phosphorus (P 4 ) as reductant and ethanol as solvent. The crystal structure, composition and particle-size of the Au-P/C catalysts are investigated by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. The results demonstrate that Au-P/C catalysts present an alloy phase with the high content of P, ultrafine particle-size and high dispersity on carbon support, which results in excellent electrocatalytic activity and stability towards the EOR compared with that of the free-phosphorus Au/C catalyst. In addition, among the various Au-P/C catalysts with different Au/P ratio, the AuP/C sample exhibits the best electrocatalytic performance in comparison with other Au 3 P 2 /C and Au 4 P 3 /C samples.

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

    KAUST Repository

    Chng, Ting Ting

    2011-05-03

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

  15. Gold nanoparticle plasmon resonance in near-field coupled Au NPs layer/Al film nanostructure: Dependence on metal film thickness

    Science.gov (United States)

    Yeshchenko, Oleg A.; Kozachenko, Viktor V.; Naumenko, Antonina P.; Berezovska, Nataliya I.; Kutsevol, Nataliya V.; Chumachenko, Vasyl A.; Haftel, Michael; Pinchuk, Anatoliy O.

    2018-05-01

    We study the effects of coupling between plasmonic metal nanoparticles and a thin metal film by using light extinction spectroscopy. A planar monolayer of gold nanoparticles located near an aluminum thin film (thicknesses within the range of 0-62 nm) was used to analyze the coupling between the monolayer and the thin metal film. SPR peak area increase for polymer coated Au NPs, non-monotonical behavior of the peak area for bare Au NPs, as well as red shift and broadening of SPR at the increase of the Al film thickness have been observed. These effects are rationalized as a result of coupling of the layer of Au NPs with Al film through the field of localized surface plasmons in Au NPs that causes the excitation of collective plasmonic gap mode in the nanostructure. An additional mechanism for bare Au NPs is the non-radiative damping of SPR that is caused by the electrical contact between metal NPs and film.

  16. Nanoparticle-Supported Molecular Polymerization Catalysts

    OpenAIRE

    Amgoune, Abderramane; Krumova, Marina; Mecking, Stefan

    2008-01-01

    Homogeneous molecular catalysts are immobilzed in a well-defined fashion on individual silica nanoparticles with a narrow particle size distribution by covalent attachment. This synthetic methodology is demonstrated with modified salicylaldiminato-substituted titanium(IV) complexes incorporating a trimethoxysilane-terminated linker: dichloro-bis[κ2-N,O-6-(3-(trimethoxysilyl)propoxyphenylimino)-2-tert-butyl-phenolato]titanium(IV) (3) and dichlorobis[κ2-N,O-6-(4-(trimethoxysilyl)propoxy-2,3,5,6...

  17. Electrostatic Self-Assembly of Au Nanoparticles onto Thermosensitive Magnetic Core-Shell Microgels for Thermally Tunable and Magnetically Recyclable Catalysis.

    Science.gov (United States)

    Liu, Guoqiang; Wang, Daoai; Zhou, Feng; Liu, Weimin

    2015-06-01

    A facile route to fabricate a nanocomposite of Fe3O4@poly[N-isopropylacrylamide (NIPAM)-co-2-(dimethylamino)ethyl methacrylate (DMAEMA)]@Au (Fe3O4@PND@Au) is developed for magnetically recyclable and thermally tunable catalysis. The negatively charged Au nanoparticles with an average diameter of 10 nm are homogeneously loaded onto positively charged thermoresponsive magnetic core-shell microgels of Fe3O4@poly(NIPAM-co-DMAEMA) (Fe3O4@PND) through electrostatic self-assembly. This type of attachment offers perspectives for using charged polymeric shell on a broad variety of nanoparticles to immobilize the opposite-charged nanoparticles. The thermosensitive PND shell with swollen or collapsed properties can be as a retractable Au carrier, thereby tuning the aggregation or dispersion of Au nanoparticles, which leads to an increase or decrease of catalytic activity. Therefore, the catalytic activity of Fe3O4@PND@Au can be modulated by the volume transition of thermosensitive microgel shells. Importantly, the mode of tuning the aggregation or dispersion of Au nanoparticles using a thermosensitive carrier offers a novel strategy to adjust and control the catalytic activity, which is completely different with the traditional regulation mode of controlling the diffusion of reactants toward the catalytic Au core using the thermosensitive poly(N-isopropylacrylamide) network as a nanogate. Concurrent with the thermally tunable catalysis, the magnetic susceptibility of magnetic cores enables the Fe3O4@PND@Au nanocomposites to be capable of serving as smart nanoreactors for thermally tunable and magnetically recyclable catalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Preparation of Agcore/Aushell bimetallic nanoparticles from physical mixtures of Au clusters and Ag ions under dark conditions and their catalytic activity for aerobic glucose oxidation

    International Nuclear Information System (INIS)

    Zhang, Haijun; Toshima, Naoki; Takasaki, Kanako; Okumura, Mitsutaka

    2014-01-01

    Graphical abstract: The synthesis, characterization and catalytic activities for glucose oxidation of AgAu bimetallic nanoparticles (BNPs) with size of less than 2 nm are reported. The catalytic activity of Ag 10 Au 90 BNPs was about two times higher than that of Au NPs, even the BNPs have a larger particle size than that of Au NPs. -- Highlights: • Ag core /Au shell BNPs with size of less than 2.0 nm were prepared. • No any reducing reagents and lights were used for the preparation of the BNPs. • The catalytic activity of the BNPs is about two times higher than that of Au NPs. -- Abstract: AgAu bimetallic nanoparticles (BNPs), one of the most extensively studied bimetallic systems in the literatures, could have various structures and compositions depending on their preparation conditions. In the present work, catalytically highly active PVP-protected Ag core /Au shell BNPs of about 2.5 nm in diameter were fabricated from physical mixtures of aqueous dispersions of Au nanoparticles and Ag + ions under dark conditions without using any reducing agents. The prepared Ag core /Au shell BNP colloidal catalysts, which possessed a high activity for aerobic glucose oxidation, were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), Inductive coupled plasma emission spectrometer (ICP), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Energy disperse spectroscopy (EDS) in High-resolution scanning transmission electron microscopy (HR-STEM). The highest activity (11,360 mol-glucose h −1 mol-metal −1 ) was observed for the BNPs with the Ag/Au atomic ratio of 1/9, the TOF value of which is about two times higher than that of Au nanoparticles with the particle size of 1.3 nm. The enhanced catalytic activity of the prepared Ag core /Au shell BNPs compared to Au NPs can be ascribed to the presence of negatively charged Au atoms resulted from electron donations from neighboring Ag atoms and PVP due to electronic charge

  19. Design and fabrication of an electrochemical aptasensor using Au nanoparticles/carbon nanoparticles/cellulose nanofibers nanocomposite for rapid and sensitive detection of Staphylococcus aureus.

    Science.gov (United States)

    Ranjbar, Saba; Shahrokhian, Saeed

    2018-04-27

    Since that pathogenic bacteria are major threats to human health, this paper describes the fabrication of an effective and durable sensing platform based on gold nanoparticles/carbon nanoparticles/cellulose nanofibers nanocomposite (AuNPs/CNPs/CNFs) at the surface of glassy carbon electrode for sensitive and selective detection of Staphylococcus aureus (S. aureus). The AuNPs/CNPs/CNFs nanocomposite with the high surface area, excellent conductivity, and good biocompatibility was used for self-assembled of the thiolated specific S. aureus aptamer as a sensing element. The surface morphology of AuNPs/CNPs/CNFs nanocomposite was characterized with field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), dynamic light scattering (DLS) and ultraviolet-visible (UV-Vis) spectrophotometric methods. Each aptasensor modification step was monitored with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The fabricated aptasensor exhibited a wide linear dynamic range (1.2 × 10 1 to 1.2 × 10 8 ) CFU mL -1 with a LOD of 1 CFU mL -1 and was be capable to accurate detection and determination of Staphylococcus aureus in human blood serum as a clinical sample with a complex matrix. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Molybdenum disulfide nanoflower-chitosan-Au nanoparticles composites based electrochemical sensing platform for bisphenol A determination

    International Nuclear Information System (INIS)

    Huang, Ke-Jing; Liu, Yu-Jie; Liu, Yan-Ming; Wang, Ling-Ling

    2014-01-01

    Highlights: • This work constructs a novel electrochemical biosensor for bisphenol A detection. • Flower-like MoS 2 are prepared by a simple hydrothermal procedure. • AuNPs are assembled on MoS 2 nanoflowers modified electrode for signal amplification. • The developed sensor exhibits low detection limit and wide linear range. - Abstract: Two-dimensional transition metal dichalcogenide are attracting increasing attention in electrochemical sensing due to their unique electronic properties. In this work, flower-like molybdenum disulfide (MoS 2 ) was prepared by a simple hydrothermal method. The scanning electron microscopy and transmission electron microscopy images showed the MoS 2 nanoflower had sizes with diameter of about 200 nm and was constructed with many irregular sheets as a petal-like structure with thickness of several nanometers. A novel electrochemical sensor was constructed for the determination of bisphenol A (BPA) based on MoS 2 and chitosan-gold nanoparticles composites modified electrode. The sensor showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. A good linear relationship between the oxidation peak current and BPA concentration was obtained in the range from 0.05 to 100 μM with a detection limit of 5.0 × 10 −9 M (S/N = 3). The developed sensor exhibited high sensitivity and long-term stability, and it was successfully applied for the determination of BPA in different samples. This work indicated MoS 2 nanoflowers were promising in electrochemical sensing and catalytic applications

  1. Femtosecond Laser Fabricated Ag@Au and Cu@Au Alloy Nanoparticles for Surface Enhanced Raman Spectroscopy Based Trace Explosives Detection

    Directory of Open Access Journals (Sweden)

    Moram Sree Satya Bharati

    2018-03-01

    Full Text Available Herein we present results from our detailed studies on the fabrication of Ag@Au and Cu@Au alloy nanoparticles (NPs using the femtosecond laser ablation in liquid technique. The NPs were obtained by ablating the pure Ag, Cu targets (bulk in HAuCl4 (5 mM solution. The absorption properties of the obtained NPs colloids were characterized using UV-Visible absorption spectrometer and their size, shape, and crystallinity were investigated using the XRD, FESEM and TEM techniques. The fabricated NPs were utilized for sensing of explosive molecules such as 2,4,6-trinitrophenol (PA, 2,4-dinitrotoluene (DNT and a common dye methylene blue (MB using the surface enhanced Raman spectroscopy (SERS technique. The detection limit in terms of weight was as low as few nano-grams in the case of nitroaromatic explosive compounds (PA, DNT and few picograms in the case of a common dye molecule (MB. Typical enhancement factors achieved were estimated to be ~104, ~105, and ~107, respectively, for PA, DNT, and MB. The significance of the present work lies in exploring the performance of the prepared NPs being used as SERS substrates for explosives detection using a portable Raman instrument. Such capability enables one to carry the spectrometer to the point of interest in the field and evaluate any hazardous samples within a short period of time.

  2. Interfacial and thermal energy driven growth and evolution of Langmuir-Schaefer monolayers of Au-nanoparticles.

    Science.gov (United States)

    Mukhopadhyay, Mala; Hazra, S

    2018-01-03

    Structures of Langmuir-Schaefer (LS) monolayers of thiol-coated Au-nanoparticles (DT-AuNPs) deposited on H-terminated and OTS self-assembled Si substrates (of different hydrophobic strength and stability) and their evolution with time under ambient conditions, which plays an important role for their practical use as 2D-nanostructures over large areas, were investigated using the X-ray reflectivity technique. The strong effect of substrate surface energy (γ) on the initial structures and the competitive role of room temperature thermal energy (kT) and the change in interfacial energy (Δγ) at ambient conditions on the evolution and final structures of the DT-AuNP LS monolayers are evident. The strong-hydrophobic OTS-Si substrate, during transfer, seems to induce strong attraction towards hydrophobic DT-AuNPs on hydrophilic (repulsive) water to form vertically compact partially covered (with voids) monolayer structures (of perfect monolayer thickness) at low pressure and nearly covered buckled monolayer structures (of enhanced monolayer thickness) at high pressure. After transfer, the small kT-energy (in absence of repulsive water) probably fluctuates the DT-AuNPs to form vertically expanded monolayer structures, through systematic exponential growth with time. The effect is prominent for the film deposited at low pressure, where the initial film-coverage and film-thickness are low. On the other hand, the weak-hydrophobic H-Si substrate, during transfer, appears to induce optimum attraction towards DT-AuNPs to better mimic the Langmuir monolayer structures on it. After transfer, the change in the substrate surface nature, from weak-hydrophobic to weak-hydrophilic with time (i.e. Δγ-energy, apart from the kT-energy), enhances the size of the voids and weakens the monolayer/bilayer structure to form a similar expanded monolayer structure, the thickness of which is probably optimized by the available thermal energy.

  3. Wrinkling of graphene membranes supported by silica nanoparticles on substrates

    Science.gov (United States)

    Yamamoto, Mahito; Cullen, William; Fuhrer, Michael; Einstein, Theodore; Department of Physics, University of Maryland Team

    2011-03-01

    The challenging endeavor of modulating the morphology of graphene via a patterned substrate to produce a controlled deformation has great potential importance for strain engineering the electronic properties of graphene. An essential step in this direction is to understand the response of graphene to substrate features of known geometry. Here we employ silica nanoparticles with a diameter of 10-100 nm to uniformly decorate Si O2 and mica substrates before depositing graphene, to promote nanoscale modulation of graphene geometry. The morphology of graphene on this modified substrate is then characterized by atomic force spectroscopy. We find that graphene on the substrate is locally raised by the supporting nanoparticles, and wrinkling propagates radially from the protrusions to form a ridge network which links the protrusions. We discuss the dependence of the wrinkled morphology on nanoparticle diameter and graphene thickness in terms of graphene elasticity and adhesion energy. Supported by NSF-MRSEC, Grant DMR 05-20471

  4. A label-free electrochemical immunosensor based on the novel signal amplification system of AuPdCu ternary nanoparticles functionalized polymer nanospheres.

    Science.gov (United States)

    Yan, Qin; Yang, Yuying; Tan, Zhaoling; Liu, Qing; Liu, Hui; Wang, Ping; Chen, Lei; Zhang, Daopeng; Li, Yueyun; Dong, Yunhui

    2018-04-30

    A sensitive label-free electrochemical immunosensor was designed using a novel signal amplification system for quantitative detecting hepatitis B surface antigen (HBsAg). Nitrogen-doped graphene quantum dots (N-GQDs) supported surfactant-free AuPdCu ternary nanoparticles (AuPdCu/N-GQDs), which featured with good conductivity and excellent catalytic properties for the reduction of hydrogen peroxide (H 2 O 2 ), was synthesized by a simple and benign hydrothermal procedure. At the same time, the electroactive polymer nanospheres (PS) was synthesized by infinite coordination polymers of ferrocenedicarboxylic acid, which could play as carrier and electronic mediator to load AuPdCu/N-GQDs. The PS not only improved the ability to load antibodies because of the good biocompatibility, but also accelerated electron transport of the electrode interface attribute to plentiful ferrocene unit. Thus, the prepared AuPdCu/N-GQDs@PS has abilities of good biocompatibility, catalytic activity and electrical conductivity to be applied as transducing materials to amplify electrochemical signal in detection of HBsAg. Under optimal conditions, the fabricated immunosensor exhibited high sensitivity and stability in the detection of HBsAg. A linear relationship between current signals and the concentrations of HBsAg was obtained in the range from 10fg/mL to 50ng/mL and the detection limit of HBsAg was 3.3fg/mL (signal-to-noise ratio of 3). Moreover, the designed immunosensor with excellent selectivity, reproducibility and stability shows excellent performance in detection of human serum samples. Furthermore, this label-free electrochemical immunosensor has promising application in clinical diagnosis of HBsAg. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Crystallographic investigation of Au nanoparticles embedded in a SrTiO{sub 3} thin film for plasmonics applications by means of synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Pincini, Davide, E-mail: davide.pincini@mail.polimi.it [European Synchrotron Radiation Facility, CS 40220, 71, avenue des Martyrs, F-38043 Grenoble Cedex 9 (France); Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Mazzoli, Claudio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Bernhardt, Hendrik; Katzer, Christian; Schmidl, Frank [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Helmholtzweg 5, 07743 Jena (Germany); Uschmann, Ingo [Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Detlefs, Carsten [European Synchrotron Radiation Facility, CS 40220, 71, avenue des Martyrs, F-38043 Grenoble Cedex 9 (France)

    2015-03-14

    Self-organized monocrystalline Au nanoparticles with potential applications in plasmonics are grown in a SrTiO{sub 3} matrix by a novel two-step deposition process. The crystalline preferred orientation of these Au nanoparticles is investigated by synchrotron hard x-ray diffraction. Nanoparticles preferentially align with the (111) direction along the substrate normal (001), whereas two in-plane orientations are found with [110]{sub SrTiO{sub 3}}∥[110]{sub Au} and [100]{sub SrTiO{sub 3}}∥[110]{sub Au}. Additionally, a smaller diffraction signal from nanoparticles with the (001) direction parallel to the substrate normal (001) is observed; once again, two in-plane orientations are found, with [100]{sub SrTiO{sub 3}}∥[100]{sub Au} and [100]{sub SrTiO{sub 3}}∥[110]{sub Au}. The populations of the two in-plane orientations are found to depend on the thickness of the gold film deposited in the first step of the growth.

  6. Improving the sensitivity of immunoassay based on MBA-embedded Au@SiO2 nanoparticles and surface enhanced Raman spectroscopy

    Science.gov (United States)

    Wei, Chao; Xu, Min-Min; Fang, Cong-Wei; Jin, Qi; Yuan, Ya-Xian; Yao, Jian-Lin

    2017-03-01

    Traditional "sandwich" structure immunoassay is mainly based on the self-assembly of "antibody on solid substrate-antigen-antibody with nanotags" architectures, and the sensitivity of this strategy is critically depended on the surface enhanced Raman scattering (SERS) activities and stability of nanotags. Therefore, the rational design and fabrication on the SERS nanotags attracts the common interests to the bio-related detecting and imaging. Herein, silica encapsulated Au with mercaptobenzoic acid (MBA) core-shell nanoparticles (Au-MBA@SiO2) are fabricated instead of the traditional naked Au or Ag nanoparticles for the SERS-based immunoassay on human and mouse IgG antigens. The MBA molecules facilitate the formation of continuous pinhole-free silica shell and are also used as SERS labels. The silica shell is employed to protect MBA labels and to isolate Au core from the ambient solution for blocking the aggregation. This shell also played the similar role to BSA in inhibiting the nonspecific bindings, which allowed the procedures for constructing "sandwich" structures to be simplified. All of these merits of the Au-MBA@SiO2 brought the high performance in the related immunoassay. Benefiting from the introduction of silica shell to encapsulate MBA labels, the detection sensitivity was improved by about 1- 2 orders of magnitude by comparing with the traditional approach based on naked Au-MBA nanoparticles. This kind of label-embedded core-shell nanoparticles could be developed as the versatile nanotags for the bioanalysis and bioimaging.

  7. Fast and simple microwave synthesis of TiO2/Au nanoparticles for gas-phase photocatalytic hydrogen generation

    Science.gov (United States)

    May-Masnou, Anna; Soler, Lluís; Torras, Miquel; Salles, Pol; Llorca, Jordi; Roig, Anna

    2018-04-01

    The fabrication of small anatase titanium dioxide (TiO2) nanoparticles (NPs) attached to larger anisotropic gold (Au) morphologies by a very fast and simple two-step microwave-assisted synthesis is presented. The TiO2/Au NPs are synthesized using polyvinylpyrrolidone (PVP) as reducing, capping and stabilizing agent through a polyol approach. To optimize the contact between the titania and the gold and facilitate electron transfer, the PVP is removed by calcination at mild temperatures. The nanocatalysts activity is then evaluated in the photocatalytic production of hydrogen from water/ethanol mixtures in gas-phase at ambient temperature. A maximum value of 5.3 mmol·gcat-1·h-1 (7.4 mmol·gTiO2-1·h-1) of hydrogen is recorded for the system with larger gold particles at an optimum calcination temperature of 450 °C. Herein we demonstrate that TiO2-based photocatalysts with high Au loading and large Au particle size (≈ 50 nm) NPs have photocatalytic activity.

  8. Controlled Vectorial Electron Transfer and Photoelectrochemical Applications of Layered Relay/Photosensitizer-Imprinted Au Nanoparticle Architectures on Electrodes.

    Science.gov (United States)

    Metzger, Tzuriel S; Tel-Vered, Ran; Willner, Itamar

    2016-03-23

    Two configurations of molecularly imprinted bis-aniline-bridged Au nanoparticles (NPs) for the specific binding of the electron acceptor N,N'-dimethyl-4,4'-bipyridinium (MV(2+) ) and for the photosensitizer Zn(II)-protoporphyrin IX (Zn(II)-PP-IX) are assembled on electrodes, and the photoelectrochemical features of the two configurations are discussed. Configuration I includes the MV(2+) -imprinted Au NPs matrix as a base layer, on which the Zn(II)-PP-IX-imprinted Au NPs layer is deposited, while configuration II consists of a bilayer corresponding to the reversed imprinting order. Irradiation of the two electrodes in the presence of a benzoquinone/benzohydroquinone redox probe yields photocurrents of unique features: (i) Whereas configuration I yields an anodic photocurrent, the photocurrent generated by configuration II is cathodic. (ii) The photocurrents obtained upon irradiation of the imprinted electrodes are substantially higher as compared to the nonimprinted surfaces. The high photocurrents generated by the imprinted Au NPs-modified electrodes are attributed to the effective loading of the imprinted matrices with the MV(2+) and Zn(II)-PP-IX units and to the effective charge separation proceeding in the systems. The directional anodic/cathodic photocurrents are rationalized in terms of vectorial electron transfer processes dictated by the imprinting order and by the redox potentials of the photosensitizer/electron acceptor units associated with the imprinted sites in the two configurations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Ultrasensitive molecularly imprinted electrochemical sensor based on magnetism graphene oxide/β-cyclodextrin/Au nanoparticles composites for chrysoidine analysis

    International Nuclear Information System (INIS)

    Wang, Xiaojiao; Li, Xiangjun; Luo, Chuannan; Sun, Min; Li, Leilei; Duan, Huimin

    2014-01-01

    Highlights: • Synthesis and application of MGO/β-CD@AuNPs as a sensor for chrysoidine analysis. • The synthesized polymer had a laminar structure with high surface. • The propose sensor showed high selectivity and good sensitivity. - Abstract: A imprinted electrochemical sensor based on glassy carbon electrode (GCE) for ultrasensitive detection of chrysoidine was fabricated. A GCE was modified by magnetic graphene oxide/β-cyclodextrin/gold nanoparticles composites (MGO/β-CD@AuNPs). The sensing surface area and electronic transmission rate were increased, which was benefited from the distribution property of MGO/β-CD@AuNPs. The MGO/β-CD@AuNPs composite improved electrochemical response and sensitivity of the sensor. The molecularly imprinted electrochemical sensor was prepared by electropolymerization on modified electrode. Chrysoidine and pyrrole were used as template molecule and functional monomer, respectively. Under the optimization experimental conditions, the electrochemical sensor exhibited excellent analytical performance: the detection of chrysoidine ranged from 5.0 × 10 −8 mol/L to 5.0 × 10 −6 mol/L with the detection limit of 1.7 × 10 −8 mol/L. The sensor was applied to determine chrysoidine in spiked water samples and showed high selectivity, good sensitivity and acceptable reproducibility. The proposed method provides a promising platform for trace amount detection of other food additives

  10. Bioselective synthesis of gold nanoparticles from diluted mixed Au, Ir, and Rh ion solution by Anabaena cylindrica

    Science.gov (United States)

    Rochert, Anna S.; Rösken, Liz M.; Fischer, Christian B.; Schönleber, Andreas; Ecker, Dennis; van Smaalen, Sander; Geimer, Stefan; Wehner, Stefan

    2017-11-01

    Over the last years, an environmentally friendly and economically efficient way of nanoparticle production has been found in the biosynthesis of metal nanoparticles by bacteria and cyanobacteria. In this study, Anabaena cylindrica, a non-toxic cyanobacterium, is deployed in a diluted ionic aqueous mixture of equal concentrations of gold, iridium, and rhodium, of 0.1 mM each, for the selective biosynthesis of metal nanoparticles (NPs). To analyze the cyanobacterial metal uptake, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometry (ICP-MS) were applied. Only gold can be found in crystalline and nanoparticle form inside the cells of A. cylindrica, and it is the only metal for which ICP-MS analyses show a rapid decrease of the concentration in the culture medium. A slight decrease of rhodium and none of iridium was observed in the evaluated timeline of 51 h. The average diameter size of the emerging gold nanoparticles increased over the first few days, but is found to be below 10 nm even after more than 2 days. A new evaluation method was used to determine the spatially resolved distribution of the nanoparticles inside the cyanobacterial cells. This new method was also used to analyze TEM images from earlier studies of A. cylindrica and Anabaena sp., both incubated with an overall concentration of 0.8 mM Au3+ to compare the metal uptake. A. cylindrica was found to be highly selective towards the formation of gold nanoparticles in the presence of rhodium and iridium.

  11. Tunable UV- and Visible-Light Photoresponse Based on p-ZnO Nanostructures/n-ZnO/Glass Peppered with Au Nanoparticles.

    Science.gov (United States)

    Hsu, Cheng-Liang; Lin, Yu-Hong; Wang, Liang-Kai; Hsueh, Ting-Jen; Chang, Sheng-Po; Chang, Shoou-Jinn

    2017-05-03

    UV- and visible-light photoresponse was achieved via p-type K-doped ZnO nanowires and nanosheets that were hydrothermally synthesized on an n-ZnO/glass substrate and peppered with Au nanoparticles. The K content of the p-ZnO nanostructures was 0.36 atom %. The UV- and visible-light photoresponse of the p-ZnO nanostructures/n-ZnO sample was roughly 2 times higher than that of the ZnO nanowires. The Au nanoparticles of various densities and diameter sizes were deposited on the p-ZnO nanostructures/n-ZnO samples by a simple UV photochemical reaction method yielding a tunable and enhanced UV- and visible-light photoresponse. The maximum UV and visible photoresponse of the Au nanoparticle sample was obtained when the diameter size of the Au nanoparticle was approximately 5-35 nm. On the basis of the localized surface plasmon resonance effect, the UV, blue, and green photocurrent/dark current ratios of Au nanoparticle/p-ZnO nanostructures/n-ZnO are ∼1165, ∼94.6, and ∼9.7, respectively.

  12. Revisiting magnetism of capped Au and ZnO nanoparticles: Surface band structure and atomic orbital with giant magnetic moment

    Energy Technology Data Exchange (ETDEWEB)

    Hernando, Antonio; Crespo, Patricia [Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas. P.O. Box 155, 28230 Madrid (Spain); Dept. Fisica de Materiales, Universidad Complutense, Madrid (Spain); Garcia, Miguel Angel [Instituto de Ceramica y Vidrio, CSIC, C/ Kelsen, 5, Madrid 28049 (Spain); Coey, Michael [Trinity College Dublin, Dublin (Ireland); Ayuela, Andres; Echenique, Pedro Miguel [Centro de Fisica de Materiales, CFM-MPC CSIC-UPV/EHU, Donostia International Physics Center (DIPC), 20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Fac. de Quimicas, Universidad del Pais Vasco UPV-EHU, 20018 San Sebastian (Spain)

    2011-10-15

    In this article we review the exotic magnetism of nanoparticles (NPs) formed by substances that are not magnetic in bulk as described with generality in Section 1. In particular, the intrinsic character of the magnetism observed on capped Au and ZnO NPs is analysed. X-ray magnetic circular dichroism (XMCD) analysis has shown that the magnetic moments are intrinsic and lie in the Au and Zn atoms, respectively, as analysed in Section 2, where the general theoretical ideas are also revisited. Since impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states, the anomalous magnetic response is analysed in terms of the surface band in Section 3. Finally, Section 4 summarizes our last theoretical proposal. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Electrogenerated Chemiluminescence Behavior of Au nanoparticles-hybridized Pb (II) metal-organic framework and its application in selective sensing hexavalent chromium.

    Science.gov (United States)

    Ma, Hongmin; Li, Xiaojian; Yan, Tao; Li, Yan; Liu, Haiyang; Zhang, Yong; Wu, Dan; Du, Bin; Wei, Qin

    2016-02-23

    In this work, a novel electrochemiluminescence (ECL) sensor based on Au nanoparticles-hybridized Pb (II)-β-cyclodextrin (Pb-β-CD) metal-organic framework for detecting hexavalent chromium (Cr(VI)) was developed. Pb-β-CD shows excellent ECL behavior and unexpected reducing ability towards Au ions. Au nanoparticles could massively form on the surface of Pb-β-CD (Au@Pb-β-CD) without use of any additional reducing agent. In the presence of coreactant K2S2O8, the ECL emission of Pb-β-CD was enhanced by the formation of Au nanoparticles. Cr(VI) can collisionally quench the ECL behavior of Au@Pb-β-CD/S2O8(2-) system and the detection mechanism was investigated. This ECL sensor is found to have a linear response in the range of 0.01-100 μM and a low detection limit of 3.43 nM (S/N = 3) under the optimal conditions. These results suggest that metal-organic framework Au@Pb-β-CD has great potential in extending the application in the ECL field as an efficient luminophore.

  14. Polarimetric Detection of Enantioselective Adsorption by Chiral Au Nanoparticles – Effects of Temperature, Wavelength and Size

    Directory of Open Access Journals (Sweden)

    Nisha Shukla

    2015-01-01

    Full Text Available R- and S-propylene oxide (PO have been shown to interact enantiospecifically with the chiral surfaces of Au nanopar‐ ticles (NPs modified with D- or L-cysteine (cys. This enantiospecific interaction has been detected using optical polarimetry measurements made on solutions of the D- or L-cys modified Au (cys/Au NPs during addition of racemic PO. The selective adsorption of one enantiomer of the PO onto the cys/Au NP surfaces results in a net rotation of light during addition of the racemic PO to the solution. In order to optimize the conditions used for making these measurements and to quantify enantiospecific adsorption onto chiral NPs, this work has measured the effect of temperature, wavelength and Au NP size on optical rotation by solutions containing D- or L-cys/Au NPs and racemic PO. Increasing temperature, decreasing wave‐ length and decreasing NP size result in larger optical rotations.

  15. Evolution of Ternary AuAgPd Nanoparticles by the Control of Temperature, Thickness, and Tri-Layer

    Directory of Open Access Journals (Sweden)

    Sundar Kunwar

    2017-11-01

    Full Text Available Metallic alloy nanoparticles (NPs possess great potential to enhance the optical, electronic, chemical, and magnetic properties for various applications by the control of morphology and elemental composition. This work presents the fabrication of ternary AuAgPd alloy nanostructures on sapphire (0001 via the solid-state dewetting of sputter-deposited tri-metallic layers. Based on the systematic control of temperature, thickness, and deposition order of tri-layers, the composite AuAgPd alloy nanoparticles (NPs with various shape, size, and density are demonstrated. The metallic tri-layers exhibit various stages of dewetting based on the increasing growth temperatures between 400 and 900 °C at 15 nm tri-layer film thickness. Specifically, the nucleation of tiny voids and hillocks, void coalescence, the growth and isolated nanoparticle formation, and the shape transformation with Ag sublimation are observed. With the reduced film thickness (6 nm, tiny alloy NPs with improved structural uniformity and spatial arrangement are obtained due to enhanced dewetting. The growth trend of alloy NPs is drastically altered by changing the deposition order of metallic tri-layers. The overall evolution is governed by the surface diffusion and inter-mixing of metallic atoms, Rayleigh-like instability, surface and interface energy minimization, and equilibrium state of the system. The UV-VIS-NIR reflectance spectra reveal the formation of an absorption band and reflectance maxima at specific wavelengths based on the morphology and composition of AuAgPd alloy NPs. In addition, Raman spectra analysis shows the modulation of intensity and peak position of natural vibration modes of sapphire (0001.

  16. Bifunctional Au@TiO_2 core–shell nanoparticle films for clean water generation by photocatalysis and solar evaporation

    International Nuclear Information System (INIS)

    Huang, Jian; He, Yurong; Wang, Li; Huang, Yimin; Jiang, Baocheng

    2017-01-01

    Highlights: • Au@TiO_2 core-shell nanoparticles were prepared in this study. • Bifunctional films for photocatalysis and solar evaporation were designed. • The evaporation and photodegradation with core-shell structures were investigated. - Abstract: With water scarcity becoming an increasingly critical issue for modern society, solar seawater desalination represents a promising approach to mitigating water shortage. In addition, solar seawater desalination shows great potential for mitigating the energy crisis due to its high photo-thermal conversion efficiency. However, the increasing contamination of seawater makes it difficult to generate clean water through simple desalination processes. In this work, clean water is generated by a newly designed bifunctional Au@TiO_2 core-shell nanoparticle film with a high photo-thermal conversion efficiency that is capable of photocatalysis and solar evaporation for seawater desalination. Bifunctional films of Au@TiO_2 core-shell nanoparticles with good stability were prepared. It was found that the formation of the core-shell structures played a key role in promoting the photo-thermal conversion efficiency and the evaporation of seawater, while the photocatalytic function demonstrated herein could contribute to the purification of polluted seawater. Furthermore, the film structure can serve to concentrate the NPs for the photo-reaction, as well as heat for water evaporation, improving both the photo-reaction efficiency and photo-thermal conversion efficiency. This efficient approach to solar seawater desalination, which combines evaporation with the photodegradation of pollutants, could help to address the dual issues of water scarcity and water pollution.

  17. Sol–gel synthesis of palladium nanoparticles supported on reduced ...

    Indian Academy of Sciences (India)

    average particle size of the Pd nanoparticles supported on rGO obtained from TEM is ... Ag|AgCl|KCl3M, the current is .... was used for chemical characterization of a specimen. The ... mer's method.36 In a typical procedure, about 20 mg of GO.

  18. Silica-supported Preyssler Nanoparticles as New Catalysts in the ...

    African Journals Online (AJOL)

    A new and efficient method for the preparation of 4(3H)-quinazolinones from the condensation of anthranilic acid, orthoester and substituted anilines, in the presence of catalytic amounts of silica-supported Preyssler nanoparticles is reported. The catalyst performs very well in comparison with other catalysts reported before.

  19. Architecture of Pd-Au bimetallic nanoparticles in sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles as investigated by X-ray absorption spectroscopy.

    Science.gov (United States)

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

    2007-09-01

    In this study, we demonstrate the unique application of X-ray absorption spectroscopy (XAS) as a fundamental characterization tool to help in designing and controlling the architecture of Pd-Au bimetallic nanoparticles within a water-in-oil microemulsion system of water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane. Structural insights obtained from the in situ XAS measurements recorded at each step during the formation process revealed that Pd-Au bimetallic clusters with various Pd-Au atomic stackings are formed by properly performing hydrazine reduction and redox transmetalation reactions sequentially within water-in-oil microemulsions. A structural model is provided to explain reasonably each reaction step and to give detailed insight into the nucleation and growth mechanism of Pd-Au bimetallic clusters. The combination of in situ XAS analysis at both the Pd K-edge and the Au L(III)-edge and UV-vis absorption spectral features confirms that the formation of Pd-Au bimetallic clusters follows a (Pd(nuclei)-Au(stack))-Pd(surf) stacking. This result further implies that the thickness of Au(stack) and Pd(surf) layers may be modulated by varying the dosage of the Au precursor and hydrazine, respectively. In addition, a bimetallic (Pd-Au)(alloy) nanocluster with a (Pd(nuclei)-Au(stack))-(Pd-Au(alloy))(surf) stacking was also designed and synthesized in order to check the feasibility of Pd(surf) layer modification. The result reveals that the Pd(surf) layer of the stacked (Pd(nuclei)-Au)(stack) bimetallic clusters can be successfully modified to form a (Au-Pd alloy)(surf) layer by a co-reduction of Pd and Au ions by hydrazine. Further, we demonstrate the alloying extent or atomic distribution of Pd and Au in Pd-Au bimetallic nanoparticles from the derived XAS structural parameters. The complete XAS-based methodology, demonstrated here on the Pd-Au bimetallic system, can easily be extended to design and control the alloying extent or atomic distribution, atomic

  20. Interfacial oxygen under TiO2 supported Au clusters revealed by a genetic algorithm search

    DEFF Research Database (Denmark)

    Vilhelmsen, Lasse Baarvig; Hammer, B.

    2013-01-01

    We present a density functional theory study of the oxidation of 1D periodic rods supported along the [001] direction on the rutile TiO2(110) surface. The study shows evidence for an oxidation of the interface between the supported Au and the TiO2 crystal. The added O atoms adsorb at the 5f......-Ti atoms in the through under the Au rod and are stabilized by charge transfer from the nearest Au atoms. Despite an extensive search, we find no low energy barrier pathways for CO oxidation involving CO adsorbed on Au and O at the perimeter of the Au/TiO2 interface. This is in part attributed the weak...

  1. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

    Science.gov (United States)

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-12-07

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  2. Observation of ZnS nanoparticles sputtered from ZnS films under 2 MeV Au irradiation

    Science.gov (United States)

    Kuiri, P. K.; Joseph, B.; Ghatak, J.; Lenka, H. P.; Sahu, G.; Acharya, B. S.; Mahapatra, D. P.

    2006-07-01

    ZnS nanoparticles have been observed on catcher foils due to 2 MeV Au ion irradiation of ZnS films thermally evaporated on Si(1 0 0) substrates. The structure and size distribution of nanoclusters collected were studied using transmission electron microscopy for irradiation fluences in the range of 1 × 10 11-1 × 10 15 ions cm -2. The nanoclusters were found to have a hexagonal wurtzite structure. Optical absorption measurements on similarly deposited ZnS on silica glass indicate the film to be also composed of hexagonal wurtzite ZnS. Based on this and available data we argue that the observed nanoparticles on the catcher foils are the results of shock waves induced emission of material chunks with the same atomic coordination as in the target.

  3. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

    Science.gov (United States)

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-11-01

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  4. Characterization of spatial manipulation on ZnO nanocomposites consisting of Au nanoparticles, a graphene layer, and ZnO nanorods

    Science.gov (United States)

    Huang, Shen-Che; Lu, Chien-Cheng; Su, Wei-Ming; Weng, Chen-Yuan; Chen, Yi-Cian; Wang, Shing-Chung; Lu, Tien-Chang; Chen, Ching-Pang; Chen, Hsiang

    2018-01-01

    Three types of ZnO-based nanocomposites were fabricated consisting of 80-nm Au nanoparticles (NPs), a graphene layer, and ZnO nanorods (NRs). To investigate interactions between the ZnO NRs and Au nanoparticle, multiple material analysis techniques including field-emission scanning electron microscopy (FESEM), surface contact angle measurements, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic characterizations were performed. Results indicate that incorporating a graphene layer could block the interaction between the ZnO NRs and the Au NPs. Furthermore, the Raman signal of the Au NPs could be enhanced by inserting a graphene layer on top of the ZnO NRs. Investigation of these graphene-incorporated nanocomposites would be helpful to future studies of the physical properties and Raman analysis of the ZnO-based nanostructure design.

  5. A highly selective and sensitive cocaine aptasensor based on covalent attachment of the aptamer-functionalized AuNPs onto nanocomposite as the support platform

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com; Shahdost-fard, Faezeh

    2015-01-01

    Highlights: • Functionalized thiol-terminated cocaine aptamer was functionalized with AuNPs. • MWCNTs/IL/Chit was employed for covalent attachment of Apt-capture probe onto electrode. • (K{sub 3}Fe(CN){sub 6}) was used as the redox probe and DPV as analytical technique. • The aptasensor showed high sensitivity and selectivity. • Linear range from 1 nM to 11,000 nM with LOD of 100 pM for cocaine detection was obtained. - Abstract: Based on the conformational changes of the aptamer-functionalized gold nanoparticles (AuNPs) onto MWCNTs/IL/Chit nanocomposite as the support platform, we have developed a sensitive and selective electrochemical aptasensor for the detection of cocaine. The 5′-amine-3′-AuNP terminated aptamer is covalently attached to a MWCNTs/IL/Chit nanocomposite. The interaction of cocaine with the aptamer functionalized AuNP caused the aptamer to be folded and the AuNPs with negative charge at the end of the aptamer came to the near of electrode surface therefore, the electron transfer between ferricyanide (K{sub 3}Fe(CN){sub 6}) as redox probe and electrode surface was inhibited. A decreased current of (K{sub 3}Fe(CN){sub 6}) was monitored by differential pulse voltammetry technique. In an optimized condition the calibration curve for cocaine concentration was linear up to 11 μM with detection limit (signal-to-noise ratio of 3) of 100 pM. To test the selectivity of the prepared aptasensor sensing platform applicability, some analgesic drugs as the interferes were examined. The potential of the aptasensor was successfully applied for measuring cocaine concentration in human blood serum. Based on our experiments it can be said that the present method is absolutely beneficial in developing other electrochemical aptasensor.

  6. A highly selective and sensitive cocaine aptasensor based on covalent attachment of the aptamer-functionalized AuNPs onto nanocomposite as the support platform

    International Nuclear Information System (INIS)

    Roushani, Mahmoud; Shahdost-fard, Faezeh

    2015-01-01

    Highlights: • Functionalized thiol-terminated cocaine aptamer was functionalized with AuNPs. • MWCNTs/IL/Chit was employed for covalent attachment of Apt-capture probe onto electrode. • (K 3 Fe(CN) 6 ) was used as the redox probe and DPV as analytical technique. • The aptasensor showed high sensitivity and selectivity. • Linear range from 1 nM to 11,000 nM with LOD of 100 pM for cocaine detection was obtained. - Abstract: Based on the conformational changes of the aptamer-functionalized gold nanoparticles (AuNPs) onto MWCNTs/IL/Chit nanocomposite as the support platform, we have developed a sensitive and selective electrochemical aptasensor for the detection of cocaine. The 5′-amine-3′-AuNP terminated aptamer is covalently attached to a MWCNTs/IL/Chit nanocomposite. The interaction of cocaine with the aptamer functionalized AuNP caused the aptamer to be folded and the AuNPs with negative charge at the end of the aptamer came to the near of electrode surface therefore, the electron transfer between ferricyanide (K 3 Fe(CN) 6 ) as redox probe and electrode surface was inhibited. A decreased current of (K 3 Fe(CN) 6 ) was monitored by differential pulse voltammetry technique. In an optimized condition the calibration curve for cocaine concentration was linear up to 11 μM with detection limit (signal-to-noise ratio of 3) of 100 pM. To test the selectivity of the prepared aptasensor sensing platform applicability, some analgesic drugs as the interferes were examined. The potential of the aptasensor was successfully applied for measuring cocaine concentration in human blood serum. Based on our experiments it can be said that the present method is absolutely beneficial in developing other electrochemical aptasensor

  7. Fabrication of Au{sub nanoparticle}@mSiO{sub 2}@Y{sub 2}O{sub 3}:Eu nanocomposites with enhanced fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huiqin [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Materials Science, Northwest University, Xi' an, 710069 (China); College of Chemistry & Chemical Engineering, Baoji University of Arts & Sciences, Baoji, 721013 (China); Kang, Jianmiao [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Materials Science, Northwest University, Xi' an, 710069 (China); Yang, Jianhui, E-mail: jianhui@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Materials Science, Northwest University, Xi' an, 710069 (China); Wu, Biao, E-mail: wubiao@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Materials Science, Northwest University, Xi' an, 710069 (China)

    2016-07-15

    Herein, Au{sub nanoparticle}@mSiO{sub 2}@Y{sub 2}O{sub 3}:Eu nanocomposites are synthesized through layer-by-layer assembly technology. Au{sub nanoparticle}@mSiO{sub 2} core–shell nanospheres were prepared at first in the presence of CTAB in aqueous solution system by the modified one-pot method. A chemical precipitation method and a succeeding calcination process were adopted to the growth of Y{sub 2}O{sub 3}:Eu shells on the surfaces of Au{sub nanoparticle}@mSiO{sub 2} core–shell nanospheres. The structure, morphology and composition of the nanocomposites were confirmed by XRD, TEM and UV–vis absorption spectrum. The prepared Au{sub nanoparticle}@mSiO{sub 2}@Y{sub 2}O{sub 3}:Eu nanocomposites have showed the emission intensity enhances to 6.23 times at 30 nm thickness of the silica spacer between the core of Au nanoparticle and the shell of Y{sub 2}O{sub 3}:Eu. According to the observations of fluorescent lifetime and the modeling of local electric field, the metal-enhanced and quenched fluorescence is closely related with the enhancement of excitation and radiative decay rate and the quenching by NRET comes as a result of competition between the distance-dependent mechanisms. This kind of multifunctional inorganic material will be widely used in electronics, biology and medical drug loading, etc. - Highlights: • Fabrication of Au{sub nanoparticle}@mSiO{sub 2}@Y{sub 2}O{sub 3}:Eu nanocomposites with core-spacer-shell structure. • The controllable fluorescence is achieved by adjusting the spacer thickness of silica. • The fluorescence enhancement is 6.23-fold at an optimal spacer thickness about 30 nm. • The metal-enhanced fluorescence mechanism is proposed.

  8. 197Au Moessbauer study of nano-sized gold catalysts supported on Mg(OH)2 and TiO2

    International Nuclear Information System (INIS)

    Kobayashi, Y.; Nasu, S.; Tsubota, S.; Haruta, M.

    2000-01-01

    We have studied nano-sized Au catalysts supported on Mg(OH) 2 and TiO 2 using 197 Au Moessbauer spectroscopy. 197 Au Moessbauer spectra observed for Au/Mg(OH) 2 catalysts can be decomposed into one singlet with zero isomer shift and several doublets. One of the doublets shows an isomer shift that is typical for Au I , and other doublets are due to Au III . The relative area of the Au I component shows the maximum value for a specimen calcined at 523 K, which also shows the highest catalytic activity

  9. Electrical and photoelectric properties of Si-based metal–insulator–semiconductor structures with Au nanoparticles at the insulator–semiconductor interface

    Energy Technology Data Exchange (ETDEWEB)

    Koryazhkina, M. N., E-mail: mahavenok@mail.ru; Tikhov, S. V.; Gorshkov, O. N.; Kasatkin, A. P.; Antonov, I. N. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation)

    2016-12-15

    It is shown that the formation of Au nanoparticles at the insulator–silicon interface in structures with a high density of surface states results in a shift of the Fermi-level pinning energy at this interface towards the valence-band ceiling in silicon and in increasing the surface-state density at energies close to the Fermi level. In this case, a band with a peak at 0.85 eV arises on the photosensivity curves of the capacitor photovoltage, which is explained by the photoemission of electrons from the formed Au-nanoparticle electron states near the valence-band ceiling in silicon.

  10. Arrays of Ag and Au nanoparticles with terpyridine- and thiophene-based ligands: morphology and optical responses

    Czech Academy of Sciences Publication Activity Database

    Prusková, M.; Sutrová, V.; Šlouf, Miroslav; Vlčková, B.; Vohlídal, J.; Šloufová, I.

    2017-01-01

    Roč. 33, č. 17 (2017), s. 4146-4156 ISSN 0743-7463 R&D Projects: GA ČR(CZ) GAP108/12/1143 Institutional support: RVO:61389013 Keywords : nanocomposite monolayers * self-assembly * Ag and Au arrays Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.833, year: 2016

  11. Synthesis of Mg2Cu nanoparticles on carbon supports with enhanced hydrogen sorption kinetics

    NARCIS (Netherlands)

    Au, Y.S.; Ponthieu, M.; van Zwienen, M.; Zlotea, C.; Cuevas, F.; de Jong, K.P.; de Jongh, P.E.

    2013-01-01

    The reaction kinetics and reversibility for hydrogen sorption were investigated for supported Mg2Cu nanoparticles on carbon. A new preparation method is proposed to synthesize the supported alloy nanoparticles. The motivation of using a support is to separate the nanoparticles to prevent sintering

  12. CEMS and XRD studies on changing shape of iron nano-particles by irradiation of Au ions of Fe-implanted Al2O3 granular layer

    International Nuclear Information System (INIS)

    Kato, T.; Wakabayashi, H.; Hashimoto, M.; Toriyama, T.; Taniguchi, S.; Hayashi, N.; Sakamoto, I.

    2007-01-01

    In order to observe an inverse Ostwald ripening of Fe nano-particles in Fe-implanted Al 2 O 3 granular layers, 3 MeV Au ions were irradiated to Fe nano-particles in these layers with doses of 0.5x and 1.5x10 16 ions/cm 2 . It was found by Conversion Electron Mossbauer Spectroscopy (CEMS) that the inverse Ostwald ripening occurred by fractions of percentages and the magnetic anisotropy of Fe nano-particles was induced to the direction of Au ion beam, i.e. perpendicular to the granular plane. The average crystallite diameters of Fe nano-particles for Au ions unirradiated and irradiated samples were measured using Scherrer's formula from FWHM of Fe (110) X-ray Diffraction (XRD) patterns obtained by 2θ and 2θ/θ methods. It was confirmed that the average crystallite diameters of Fe nano-particles in Fe-implanted Al 2 O 3 granular layers were extended by Au ions irradiation. (author)

  13. Size effect on L10 ordering and magnetic properties of chemically synthesized FePt and FePtAu nanoparticles

    Science.gov (United States)

    Jia, Zhiyong; Kang, Shishou; Shi, Shifan; Nikles, David E.; Harrell, J. W.

    2005-05-01

    There is growing evidence that FePt nanoparticles become increasingly difficult to chemically order as the size approaches a few nanometers. We have studied the chemical ordering of FePt and FePtAu nanoparticle arrays as a function of particle size. Monodisperse Fe49Pt51 and Fe48Pt44Au8 nanoparticles with a size about 6nm were synthesized by the simultaneous decomposition of iron pentacarbonyl and reduction of platinum acetylacetonate and gold (III) acetate in a mixture of phenyl ether and hexadecylamine (HDA), with 1-adamantanecarboxylic acid and HDA as stabilizers. The nanoparticles were dispersed in toluene, films of the particles were cast onto silicon wafers from the dispersion, and the films were annealed in a tube furnace with flowing Ar +5%H2. The magnetic anisotropy and switching volumes were determined from time- and temperature-dependent coercivity measurements. By comparing with 3-nm FePt and FePtAu nanoparticles of comparable composition, the phase transformation is easier for the larger particles. Under the same annealing conditions, the larger particles have higher anisotropy and order parameter. Additive Au is very effective in enhancing the chemical ordering in both small and large particles, with x-ray diffraction superlattice peaks appearing after annealing at 350°C. Dynamic remnant coercivity measurements and magnetic switching volumes suggest particle aggregation at the higher annealing temperatures in both small and large particles.

  14. Simultaneous determination of paracetamol and ascorbic acid using tetraoctylammonium bromide capped gold nanoparticles immobilized on 1,6-hexanedithiol modified Au electrode

    International Nuclear Information System (INIS)

    Nair, Santhosh S.; John, S. Abraham; Sagara, Takamasa

    2009-01-01

    Tetraoctylammonium bromide stabilized gold nanoparticles (TOAB-AuNPs) attached to 1,6-hexanedithiol (HDT) modified Au electrode was used for the simultaneous determination of paracetamol (PA) and ascorbic acid (AA) at physiological pH. The attachment of TOAB-AuNPs on HDT modified Au surface was confirmed by attenuated total reflectance (ATR)-FT-IR spectroscopy and atomic force microscope (AFM). The ATR-FT-IR spectrum of TOAB-AuNPs attached to the HDT monolayer showed a characteristic stretching modes corresponding to -CH 2 and -CH 3 of TOAB, confirming the immobilization of AuNPs with surface-protecting TOAB ions on the surface of the AuNPs after being attached to HDT modified Au electrode. AFM image showed that the immobilized AuNPs were spherical in shape and densely packed to a film of ca. 7 nm thickness. Interestingly, TOAB-AuNPs modified electrode shifted the oxidation potential of PA towards less positive potential by 70 mV and enhanced its oxidation current twice when compared to bare Au electrode. In addition, the AuNPs modified electrode separated the oxidation potentials of AA and PA by 210 mV, whereas bare Au electrode failed to resolve them. The amperometry current of PA was increased linearly from 1.50 x 10 -7 to 1.34 x 10 -5 M with a correlation coefficient of 0.9981 and the lowest detection limit was found to be 2.6 nM (S/N = 3). The present method was successfully used to determine the concentration of PA in human blood plasma and commercial drugs.

  15. Simultaneous determination of paracetamol and ascorbic acid using tetraoctylammonium bromide capped gold nanoparticles immobilized on 1,6-hexanedithiol modified Au electrode

    Energy Technology Data Exchange (ETDEWEB)

    Nair, Santhosh S. [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India); John, S. Abraham [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India)], E-mail: abrajohn@yahoo.co.in; Sagara, Takamasa [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India)], E-mail: sagara@nagasaki-u.ac.jp

    2009-11-30

    Tetraoctylammonium bromide stabilized gold nanoparticles (TOAB-AuNPs) attached to 1,6-hexanedithiol (HDT) modified Au electrode was used for the simultaneous determination of paracetamol (PA) and ascorbic acid (AA) at physiological pH. The attachment of TOAB-AuNPs on HDT modified Au surface was confirmed by attenuated total reflectance (ATR)-FT-IR spectroscopy and atomic force microscope (AFM). The ATR-FT-IR spectrum of TOAB-AuNPs attached to the HDT monolayer showed a characteristic stretching modes corresponding to -CH{sub 2} and -CH{sub 3} of TOAB, confirming the immobilization of AuNPs with surface-protecting TOAB ions on the surface of the AuNPs after being attached to HDT modified Au electrode. AFM image showed that the immobilized AuNPs were spherical in shape and densely packed to a film of ca. 7 nm thickness. Interestingly, TOAB-AuNPs modified electrode shifted the oxidation potential of PA towards less positive potential by 70 mV and enhanced its oxidation current twice when compared to bare Au electrode. In addition, the AuNPs modified electrode separated the oxidation potentials of AA and PA by 210 mV, whereas bare Au electrode failed to resolve them. The amperometry current of PA was increased linearly from 1.50 x 10{sup -7} to 1.34 x 10{sup -5} M with a correlation coefficient of 0.9981 and the lowest detection limit was found to be 2.6 nM (S/N = 3). The present method was successfully used to determine the concentration of PA in human blood plasma and commercial drugs.

  16. Raman spectra of Au nanoparticles in polycrystalline LiF film

    International Nuclear Information System (INIS)

    Kurbatova, N.V.; Galyautdinov, M.F.; Stepanov, A.L.; Ivanov, N.A.; Kolesnikov, S.S.; Papernyj, V.L.

    2011-01-01

    The modification of the size of gold nanoparticles in LiF matrix during laser annealing was studied fort he first time by Raman spectroscopy. Laser annealing was carried out at the wavelength of the plasmon absorption of gold nanoparticles. The experimental spectra were compared with the calculated modes of in-phase bending vibrations in nanoparticles. The observed effects were discussed from the standpoint of the size quantization of acoustic vibrations in nanostructures. (authors)

  17. Controlled growth of Au nanoparticles in co-evaporated metal/polymer composite films and their optical and electrical properties

    Science.gov (United States)

    Takele, H.; Schürmann, U.; Greve, H.; Paretkar, D.; Zaporojtchenko, V.; Faupel, F.

    2006-02-01

    Nanocomposite films containing Au nanoparticles embedded in a polymer matrix were prepared by vapour phase co-deposition of Au and polymers (Teflon AF and Poly(α -methylstyrene)) in high vacuum. The microstructure of the composite materials as well as metal content strongly depend on the condensation coefficient of the Au atoms, the deposition rates of the components, the substrate temperature, and the type of polymer matrix. The condensation coefficient, which varies between 0.03 and 1, was determined from energy dispersive X-ray spectrometer (EDX) and surface profilometry. It is shown that the microstructure of nanocomposites (size, size distribution, and interparticle separation of metal clusters), which was determined by transmission electron microscopy, can be controlled by the deposition parameters and the choice of polymer matrix. The optical absorption in the visible region due to the particle plasmon resonance has a strong dependence on the metal filling factor. The correlation between the microstructure of nanocomposites and optical properties, studied using UV-Vis spectroscopy, was also established. Further more, the electrical properties of the composites were studied as a function of the metal volume fraction. It was observed that the nanocomposite films exhibit a percolation threshold at a metal volume fraction of 0.43 and 0.20 for gold nanoclusters in Teflon AF and Poly(α-methylstyrene), respectively.

  18. Effect of Au irradiation energy on ejection of ZnS nanoparticles from ZnS film

    Science.gov (United States)

    Kuiri, P. K.; Ghatak, J.; Joseph, B.; Lenka, H. P.; Sahu, G.; Mahapatra, D. P.; Tripathi, A.; Kanjilal, D.; Mishra, N. C.

    2007-01-01

    ZnS films deposited on Si have been irradiated with Au ions at 35 keV, 2, and 100 MeV. Sputtered particles, collected on catcher foils during irradiation, were analyzed using transmission electron microscopy. For the case of 35 keV Au irradiation, no nanoparticle (NP) could be observed on the catcher foil. However, NPs 2-7 nm in size, have been observed on the catcher foils for MeV irradiations at room temperature. For particle sizes ≥3 nm, the distributions could be fitted to power law decays with decay exponents varying between 2 and 3.5. At 2 MeV, after correction for cluster breakup effects, the decay exponent has been found to be close to 2, indicating shock waves induced ejection to be the dominant mechanism. The corrected decay exponent for the 100 MeV Au irradiation case has been found to be about 2.6. Coulomb explosion followed by thermal spike induced vaporization of ZnS seems to be the dominant mechanism regarding material removal at such high energy. In such a case the evaporated material can cool down going into the fragmentation region forming clusters.

  19. Effects of coating molecules on the magnetic heating properties of Au-Fe3O4 heterodimer nanoparticles

    Science.gov (United States)

    Yamamoto, Y.; Ogasawara, J.; Himukai, H.; Itoh, T.

    2016-10-01

    In this paper, we report the heating properties of gold-magnetite (Au-Fe3O4) heterodimer nanoparticles (NPs) subjected to an alternating magnetic field. The Au-Fe3O4 NPs coated with oleic acid and oleylamine (OA) were synthesized through a method that combines seed mediation and high-temperature decomposition. The coating was replaced with dimercaptosuccinic acid (DMSA) by the ligand-exchange method. The specific absorption rates (SARs) for the OA- and DMSA-coated Au-Fe3O4 NPs coated with OA and DMSA at room temperature were determined through the calorimetric and magnetometric methods. SAR depended on the square of the magnetic field H up to an H value of 4 kA/m. The absolute value of the SAR for DMSA-coated NPs is about fivefold higher than that of the OA-coated NPs. The AC magnetic hysteresis measurements showed the recovery of the magnetic volume and the decrease in the magnetic anisotropy of the DMSA-coated NPs relative to those of the OA-coated NPs. These results suggest that the protective agent influences the magnetic properties of magnetite NPs via gold NPs.

  20. One-pot nucleation, growth, morphogenesis, and passivation of 1.4 nm Au nanoparticles on self-assembled rosette nanotubes.

    Science.gov (United States)

    Chhabra, Rahul; Moralez, Jesus G; Raez, Jose; Yamazaki, Takeshi; Cho, Jae-Young; Myles, Andrew J; Kovalenko, Andriy; Fenniri, Hicham

    2010-01-13

    A one-pot strategy for the nucleation, growth, morphogenesis, and passivation of 1.4 nm Au nanoparticles (NPs) on self-assembled rosette nanotubes (RNTs) is described. Tapping-mode atomic force microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, and selected-area electron diffraction were used to establish the structure and organization of this hybrid material. Notably, we found that the Au NPs formed were nearly monodisperse clusters of Au(55) (1.4-1.5 nm) nestled in pockets on the RNT surface.

  1. Systematic Control of Self-Assembled Au Nanoparticles and Nanostructures Through the Variation of Deposition Amount, Annealing Duration, and Temperature on Si (111).

    Science.gov (United States)

    Li, Ming-Yu; Sui, Mao; Pandey, Puran; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

    2015-12-01

    The size, density, and configurations of Au nanoparticles (NPs) can play important roles in controlling the electron mobility, light absorption, and localized surface plasmon resonance, and further in the Au NP-assisted nanostructure fabrications. In this study, we present a systematical investigation on the evolution of Au NPs and nanostructures on Si (111) by controlling the deposition amount (DA), annealing temperature (AT), and dwelling time (DT). Under an identical growth condition, the morphologies of Au NPs and nanostructures drastically evolve when the DA is only slightly varied, based on the Volmer-Weber and coalescence models: i.e. I: mini NPs, II: mid-sized round dome-shaped Au NPs, III: large Au NPs, and IV: coalesced nanostructures. With the AT control, three distinctive ranges are observed: i.e., NP nucleation, Au NPs maturation and melting. The gradual dimensional expansion of Au NPs is always compensated with the density reduction, which is explained with the thermodynamic theory. The DT effect is relatively minor on Au NPs, a sharp contrast to other metallic NPs, which is discussed based on the Ostwald-ripening.

  2. Fe2O3-Au hybrid nanoparticles for sensing applications via SERS analysis

    Energy Technology Data Exchange (ETDEWEB)

    Searles, Emily [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Murph, Simona Hunyadi [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Univ. of Georgia, Athens, GA (United States)

    2017-07-27

    Multifunctional iron oxide-gold hybrid nanostructures have been produced via solution chemistries and investigated for analyte detection. Gold nanoparticles of various shapes have been used for probing surface-enhanced Raman scattering (SERS) effects as they display unique optical properties in the visible-near IR region of the spectrum. When coupled with other nanoparticles, namely iron oxide nanoparticles, hybrid structures with increased functionality were produced. By exploiting their magnetic properties, nanogaps or “hot spots” were rationally created and evaluated for SERS enhancement studies. The “hot spots” were created by using a seeded reaction to increase the gold loading on the iron oxide support by 43% by weight. SERS Nanomaterials were evaluated for their ability to promote surface-enhanced Raman scattering of a model analyte, 4-mercaptophenol. The data shows an enhancement effect of the model analyte on gold decorated iron oxide nanoparticles.

  3. Tunable thermodynamic stability of Au-CuPt core-shell trimetallic nanoparticles by controlling the alloy composition: insights from atomistic simulations.

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua; Sun, Shi-Gang

    2014-11-07

    A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts.

  4. Synergistic effect in the oxidation of benzyl alcohol using citrate-stabilized gold bimetallic nanoparticles supported on alumina

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Villarraga, Fernando, E-mail: ferchogomezv@gmail.com; Radnik, Jörg; Martin, Andreas; Köckritz, Angela [Leibniz-Institut für Katalyse e.V. an der Universität Rostock (Germany)

    2016-06-15

    Bimetallic nanoparticles (NPs) containing gold and various second metals (M = Pd, Pt, Cu, and Ag) supported on alumina (AuM/Alumina) were prepared using sodium citrate as stabilizer. In addition, supported monometallic Au/Alumina and Pd/Alumina were synthesized and tested to reveal synergistic effects in the catalytic evaluation of the bimetallic catalysts. The monometallic and bimetallic NPs revealed average sizes below 10 nm. The oxidation of benzyl alcohol with molecular oxygen as oxidant at mild conditions in liquid phase in the absence and presence (toluene or NaOH aqueous solution, 0.2 M) of a solvent was selected as test reaction to evaluate the catalytic properties of the above-mentioned solids. AuPd/Alumina exhibited the best catalytic activity among all bimetallic catalysts using toluene as solvent and under solvent-free conditions, respectively. In comparison to the monometallic catalysts, a synergistic effect with AuPd/Alumina was only evident in the solvent-free reaction. The AuPd/Alumina catalyst was able to oxidize benzyl alcohol selectively depending on the reaction medium into benzaldehyde (toluene or solvent-free) or benzoic acid (NaOH aqueous solution, 0.2 M). However, the catalyst deactivated due to particle growth of the bimetallic AuPd NPs by Ostwald ripening and leaching was not observed in the oxidation using toluene as solvent. The size of the catalytically active NPs, the metal composition of the particles, and the reaction conditions greatly influenced the catalytic oxidation results.Graphical Abstract.

  5. Thiol-PEG-carboxyl-stabilized Fe2O3/Au nanoparticles targeted to CD105: Synthesis, characterization and application in MR imaging of tumor angiogenesis

    International Nuclear Information System (INIS)

    Zhang, Song; Gong, Mingfu; Zhang, Dong; Yang, Hua; Gao, Fabao; Zou, Liguang

    2014-01-01

    Objective: To detect tumor angiogenesis in tumor-bearing mice using thiol-PEG-carboxyl-stabilized Fe 2 O 3 /Au nanoparticles targeted to CD105 on magnetic resonance imaging (MRI). Methods: Fe 2 O 3 /Au nanoparticles (hybrids) were prepared by reducing Au 3+ on the surface of Fe 2 O 3 nanoparticles. Hybrids were stabilized with thiol-PEG-carboxyl via the Au–S covalent bond, and further conjugated with anti-CD105 antibodies through amide linkages. Characteristics of the hybrid-PEG-CD105 nanoparticles were evaluated. Using these nanoparticles, the labeling specificity of human umbilical vein endothelial cells (HUVECs) was evaluated in vitro. MRI T2*-weighted images were obtained at different time points after intravenous administration of the hybrid-PEG-CD105 nanoparticles in the tumor-bearing mice. After MR imaging, the breast cancer xenografts were immediately resected for immunohistochemistry staining and Prussian blue staining to measure the tumor microvessel density (MVD) and evaluate the labeling of blood microvessels by the hybrid-PEG-CD105 nanoparticles in vivo. Results: The mean diameter of the hybrid-PEG-CD105 nanoparticles was 56.6 ± 8.0 nm, as measured by transmission electron microscopy (TEM). Immune activity of the hybrid-PEG-CD105 nanoparticles was 53% of that of the anti-CD105 antibody, as detected by enzyme-linked immunosorbent assay (ELISA). The specific binding of HUVECs with the hybrid-PEG-CD105 nanoparticles was proved by immunostaining and Prussian blue staining in vitro. For breast cancer xenografts, the combination of the hybrid-PEG-CD105 nanoparticles with blood microvessels was detectable by MRI after 60 min administration of the contrast agent. The T2* relative signal intensity (SI R ) was positively correlated with the tumor MVD (R 2 = 0.8972). Conclusion: Anti-CD105 antibody-coupled, thiol-PEG-carboxyl-stabilized core–shell Fe 2 O 3 /Au nanoparticles can efficiently target CD105 expressed by HUVECs. Furthermore, the hybrid-PEG-CD105

  6. Interaction of bilirubin with Ag and Au ions: green synthesis of bilirubin-stabilized nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Shashi P. [Bhabha Atomic Research Centre, Radiation and Photochemistry Division (India); Roy, Mainak [Bhabha Atomic Research Centre, Chemistry Division (India); Mukherjee, Poulomi [Bhabha Atomic Research Centre, Nuclear Agriculture and Biotechnology Division (India); Tyagi, A. K. [Bhabha Atomic Research Centre, Chemistry Division (India); Mukherjee, Tulsi [Bhabha Atomic Research Centre, Chemistry Group (India); Adhikari, Soumyakanti, E-mail: asoumya@barc.gov.in [Bhabha Atomic Research Centre, Radiation and Photochemistry Division (India)

    2012-07-15

    We report a simple green chemistry to synthesize and stabilize monodispersed silver and gold nanoparticles sols by reducing aqueous solution of the respective metal salts in the presence of bilirubin (BR). No additional capping agent was used in the process of stabilization of the nanoparticles. As a completely new finding, we have observed that BR known to be toxic at higher concentration in one hand and conversely an antioxidant at physiological concentration reduces these metal ions to form the respective metal nanoparticles. Moreover, BR and its oxidized products also serve as capping agents to the nanoparticles. The particles were characterized by transmission electron microscopy. BR and its oxidized products capped nanoparticles are stable for months. The UV-Vis absorption spectra of the silver sol show the plasmon peak of symmetric spherical particles which was further reflected in the TEM images. The sizes of the silver particles were about 5 nm. These silver particles showed reasonably high antibacterial activity in Gram negative wild type E. coli. In the case of interaction of BR with gold ions, we could obtain cubic gold nanoparticles of average sizes 20-25 nm. Possible modes of anchorage of BR and/its oxidized products to silver nanoparticles were demonstrated by surface-enhanced resonance Raman spectroscopy (SERS) that in turn demonstrated the feasibility of using these nanoparticles as SERS substrates.

  7. Interaction of bilirubin with Ag and Au ions: green synthesis of bilirubin-stabilized nanoparticles

    Science.gov (United States)

    Shukla, Shashi P.; Roy, Mainak; Mukherjee, Poulomi; Tyagi, A. K.; Mukherjee, Tulsi; Adhikari, Soumyakanti

    2012-07-01

    We report a simple green chemistry to synthesize and stabilize monodispersed silver and gold nanoparticles sols by reducing aqueous solution of the respective metal salts in the presence of bilirubin (BR). No additional capping agent was used in the process of stabilization of the nanoparticles. As a completely new finding, we have observed that BR known to be toxic at higher concentration in one hand and conversely an antioxidant at physiological concentration reduces these metal ions to form the respective metal nanoparticles. Moreover, BR and its oxidized products also serve as capping agents to the nanoparticles. The particles were characterized by transmission electron microscopy. BR and its oxidized products capped nanoparticles are stable for months. The UV-Vis absorption spectra of the silver sol show the plasmon peak of symmetric spherical particles which was further reflected in the TEM images. The sizes of the silver particles were about 5 nm. These silver particles showed reasonably high antibacterial activity in Gram negative wild type E. coli. In the case of interaction of BR with gold ions, we could obtain cubic gold nanoparticles of average sizes 20-25 nm. Possible modes of anchorage of BR and/its oxidized products to silver nanoparticles were demonstrated by surface-enhanced resonance Raman spectroscopy (SERS) that in turn demonstrated the feasibility of using these nanoparticles as SERS substrates.

  8. The effect of SiO2/Au core-shell nanoparticles on breast cancer cell's radiotherapy.

    Science.gov (United States)

    Darfarin, Ghazal; Salehi, Roya; Alizadeh, Effat; Nasiri Motlagh, Behnam; Akbarzadeh, Abolfazl; Farajollahi, Alireza

    2018-05-09

    Recently it has been shown that radiation dose enhancement could be achievable in radiotherapy using nanoparticles (NPs). In this study, evaluation was made to determine efficiency of gold-silica shell-core NP in megavoltage irradiation of MCF7 breath cancer cells. Gold-silicon oxide shell-core NPs were obtained by conjugation of gold NP with amine or thiol functionalized silica NPs (AuN@SiO 2 and AuS@SiO 2 ). Cellular uptake and cytotoxicity of NPs were examined by fluorescent microscopy and MTT assay, respectively. MCF-7 breast cancer cells were treated with both NPs and irradiation was made with X-ray energies of 6 and 18 MV to the absorbed dose of 2, 4 and 8 Gy using Simense linear accelerator. The efficiency of radiation therapy was then evaluated by MTT and Brdu assay, DAPI staining and cell cycle analysis. TEM images indicated that synthesized NPs had average diameter of 25 nm. Cellular uptake demonstrated that the internalization of AuS@SiO 2 and AuN@SiO 2 NPs amounted to 18% and 34%, 3 h post treatment, respectively. Nontoxicity of prepared NPs on MCF-7 cells was proved by MTT and Brdu assays as well as DAPI staining and cell cycle studies. The highest enhancement in radiation dose was observed in the cells that irradiated with radiation energy of 18 MV and absorbed of 8 Gy at NPs concentration of 200 ppm. The Brdu findings revealed that the cytotoxicity and apoptosis on MCF-7 cells are dose dependent with a significantly more death in AuN@SiO 2 (amine) exposed cells (p < .05). Analysis also revealed interruption in cell cycle by demonstrating lack of cells, in S phase in amine treated cells (AuN@SiO 2 ) at given dose of 8 Gy using 18 MV X-ray in comparison to thiol treated cells. Based on the results of the study it can be concluded that the gold-silicon oxide shell-core NPs could play an effective role in radiotherapy of MCF-7 breast cancer cells.

  9. Optimization of the composition of bimetallic core/shell Fe{sub 2}O{sub 3}/Au nanoparticles for MRI/CT dual-mode imaging

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Song; Qi, Yueyong; Yang, Hua; Gong, Mingfu; Zhang, Dong; Zou, Liguang, E-mail: zlgxqyy@163.com [Third Military Medical University, Department of Radiology, Xinqiao Hospital (China)

    2013-11-15

    Bimetallic core/shell Fe{sub 2}O{sub 3}/Au nanoparticles are promising candidate dual-mode contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT) imaging. However, the gold coating on the hybrid nanoparticles (hybrids) affects the MRI and CT imaging quality. A thick gold nanoshell increases the X-ray attenuation effect but decreases the magnetic saturation of the hybrids. Therefore, we studied the effect of the Fe{sub 2}O{sub 3} and Au composition on these properties to find a suitable hybrid for MRI and CT imaging. Water-soluble, Au-coated magnetic nanoparticles were synthesized by iteratively reducing Au{sup 3+} onto the Fe{sub 2}O{sub 3} surface via hydroxylamine seeding. The properties of the hybrids obtained after different numbers of Au seeding cycles were studied using transmission electron microscopy, UV–Vis spectrophotometry, a vibrating swatch gaussmeter, MRI, CT, and an MTT assay. The hybrids obtained after three Au seeding cycles had an Fe{sub 2}O{sub 3}:Au molar ratio of 7.2:26.8, a mean diameter of 48.3 nm, a UV–Vis absorbance peak of 550 nm, a saturation magnetization of 49.0 emu/g, and no cytotoxicity at a concentration of 500 μg/mL after incubation with RAW 264.7 cells for up to 72 h. The hybrids obtained after three Au seeding cycles are the preferred candidates for MRI and CT applications because of their relatively high R2 relaxivity (95 mM{sup −1 }s{sup −1}) and X-ray attenuation (1.87 times that of iodine) compared to those of the other hybrids investigated in this study.

  10. Optimization of the composition of bimetallic core/shell Fe2O3/Au nanoparticles for MRI/CT dual-mode imaging

    International Nuclear Information System (INIS)

    Zhang, Song; Qi, Yueyong; Yang, Hua; Gong, Mingfu; Zhang, Dong; Zou, Liguang

    2013-01-01

    Bimetallic core/shell Fe 2 O 3 /Au nanoparticles are promising candidate dual-mode contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT) imaging. However, the gold coating on the hybrid nanoparticles (hybrids) affects the MRI and CT imaging quality. A thick gold nanoshell increases the X-ray attenuation effect but decreases the magnetic saturation of the hybrids. Therefore, we studied the effect of the Fe 2 O 3 and Au composition on these properties to find a suitable hybrid for MRI and CT imaging. Water-soluble, Au-coated magnetic nanoparticles were synthesized by iteratively reducing Au 3+ onto the Fe 2 O 3 surface via hydroxylamine seeding. The properties of the hybrids obtained after different numbers of Au seeding cycles were studied using transmission electron microscopy, UV–Vis spectrophotometry, a vibrating swatch gaussmeter, MRI, CT, and an MTT assay. The hybrids obtained after three Au seeding cycles had an Fe 2 O 3 :Au molar ratio of 7.2:26.8, a mean diameter of 48.3 nm, a UV–Vis absorbance peak of 550 nm, a saturation magnetization of 49.0 emu/g, and no cytotoxicity at a concentration of 500 μg/mL after incubation with RAW 264.7 cells for up to 72 h. The hybrids obtained after three Au seeding cycles are the preferred candidates for MRI and CT applications because of their relatively high R2 relaxivity (95 mM −1  s −1 ) and X-ray attenuation (1.87 times that of iodine) compared to those of the other hybrids investigated in this study

  11. A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Haghshenas, Esmaeel; Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Afkhami, Abbas

    2015-12-01

    An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe{sub 3}O{sub 4} to the AC solution and stirring for 20 min, the AuNPs@Fe{sub 3}O{sub 4} was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe{sub 3}O{sub 4} were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe{sub 3}O{sub 4} and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV–Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0 μmol L{sup −1} with the detection limit of 4.5 × 10{sup −2} μmol L{sup −1}. This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response. - Highlights: • Magneto Au nanoparticle/carbon paste electrode was fabricated. • Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}). • It is the first time AuNPs@Fe{sub 3}O{sub 4} and magneto electrode are used for the determination of AC. • The proposed sensor showed a wide linear range, low detection limit, and high sensitivity. • This sensor is also used for the determination of AC in real samples.

  12. Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution

    Energy Technology Data Exchange (ETDEWEB)

    Sivashanmugan, Kundan [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liao, Jiunn-Der, E-mail: jdliao@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liu, Bernard Haochih; Yao, Chih-Kai [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2013-10-24

    Graphical abstract: -- Highlights: •Well-ordered Au-nanorod array with a controlled tip ring diameter (Au{sub N}Rs{sub d}) is made by focused ion beam. •Au{sub N}Rs{sub d} coupled with Ag nanoparticles (Ag NPs/Au{sub N}Rs{sub d}) is competent to sense target molecules in a solution. •Ag NPs/Au{sub N}Rs{sub d} SERS active substrate can detect a single molecule of crystal violet. •Ag NPs/Au{sub N}Rs{sub d} as a SERS-active substrate can distinguish melamine contaminants at low concentrations (e.g., 10{sup −12} M). -- Abstract: A well-ordered Au-nanorod array with a controlled tip ring diameter (Au{sub N}Rs{sub d}) was fabricated using the focused ion beam method. Au{sub N}Rs{sub d} was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au{sub N}Rs{sub d} and Ag NPs/Au{sub N}Rs{sub d} was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au{sub N}Rs{sub d} was estimated by an enhancement factor of ≈10{sup 7} in magnitude, which increased ≈10{sup 12} in magnitude for that on Ag NPs/Au{sub N}Rs{sub d}. A highly SERS-active Ag NPs/Au{sub N}Rs{sub d} was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10{sup −3} to 10{sup −12} M) in water or milk solution upon Au{sub N}Rs{sub d} or Ag NPs/Au{sub N}Rs{sub d} were well distinguished. The peaks at 680 and 702 cm{sup −1} for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm{sup −1} was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au{sub N}Rs{sub d}) or Ag (i.e., Ag NPs/Au{sub N}Rs{sub d}) surface. At the interface of Ag NPs/Au{sub N}Rs{sub d} and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and

  13. Progress in controlling the size, composition and nanostructure of supported gold-palladium nanoparticles for catalytic applications

    NARCIS (Netherlands)

    Paalanen, P.P.|info:eu-repo/dai/nl/370602013; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397; Sankar, M.

    2013-01-01

    This review article gives an overview of the recent developments in the synthesis strategies of supported goldbased bimetallic nanoparticle catalysts. The catalytic efficiency of these supported bimetallic nanoparticles, similar to monometallic nanoparticles, depends on their structural

  14. Silica sacrificial layer-assisted in-plane incorporation of Au nanoparticles into mesoporous titania thin films through different reduction methods.

    Science.gov (United States)

    Liang, Chih-Peng; Yamauchi, Yusuke; Liu, Chia-Hung; Wu, Kevin C-W

    2013-06-28

    This study focuses on the incorporation of gold nanoparticles (Au NPs) into our previously synthesized mesoporous titania thin films consisting of titania nanopillars and inverse mesospace (C. W. Wu, T. Ohsuna, M. Kuwabara and K. Kuroda, J. Am. Chem. Soc., 2006, 128, 4544-4545, denoted as MTTFs). Recently, mesoporous titania materials doped with noble metals such as gold have attracted considerable attention because noble metals can enhance the efficiency of mesoporous titania-based devices. In this research, we attempted to use four different reduction methods (i.e., thermal treatment, photo irradiation, liquid immersion, and vapor contacting) to introduce gold nanoparticles (Au NPs) into MTTFs. The synthesized Au@MTTFs were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We further systematically investigated the formation mechanism of gold nanoparticles on the external and internal surfaces of the MTTFs. With the assistance of a silica sacrificial layer, well-dispersed Au NPs with sizes of 4.1 nm were obtained inside the MTTF by photo irradiation. The synthesized Au@MTTF materials show great potential in various photo-electronic and photo-catalytic applications.

  15. Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe3O4-silica-Au magnetic nanoparticles

    International Nuclear Information System (INIS)

    Wang Aijun; Li Yongfang; Li Zhonghua; Feng Jiuju; Sun Yanli; Chen Jianrong

    2012-01-01

    Monodisperse Fe 3 O 4 magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe 3 O 4 -silica-Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 × 10 −9 mol·cm −2 , and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 ± 0.6 s −1 . The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 μA·mM −1 cm −2 and fast response (less than 5 s). - Graphical abstract: Core-shell structured Fe 3 O 4 -silica-Au nanoparticles were prepared and used as matrix to construct an amperometric glucose sensor based on glucose oxidase, which showed broad linear range, high sensitivity, and fast response. Highlights: ► Synthesis of monodispersed Fe 3 O 4 nanoparticles. ► Fabrication of core/shell Fe 3 O 4 -silica-Au nanoparticles. ► Construction of a novel glucose sensor with wide linear range, high sensitivity and fast response.

  16. The sandwich-type electrochemiluminescence immunosensor for {alpha}-fetoprotein based on enrichment by Fe{sub 3}O{sub 4}-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Hankun [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Gan Ning, E-mail: ganning@nbu.edu.cn [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Li Tianhua; Cao Yuting; Zeng Saolin [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Zheng Lei, E-mail: nfyyzl@163.com [Department of Laboratory Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515 (China); Guo Zhiyong [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China)

    2012-10-09

    Highlights: Black-Right-Pointing-Pointer Sandwich immunoreaction, testing a large number of samples simultaneously. Black-Right-Pointing-Pointer The magnetic separation and enrichment by Fe{sub 3}O{sub 4}-Au magnetic nano probes. Black-Right-Pointing-Pointer The amplification of detection signal by CdS-Au composite nanoparticles labeled anti-AFP. Black-Right-Pointing-Pointer Almost no background signal, which greatly improve the sensitivity of detection. - Abstract: A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of {alpha}-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe{sub 3}O{sub 4}-Au nanoparticles, which was first employed to capture AFP antigens to form Fe{sub 3}O{sub 4}-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe{sub 3}O{sub 4}-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe{sub 3}O{sub 4}-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0 ng mL{sup -1} with a detection limit of 0.2 pg mL{sup -1}. The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the

  17. Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO2 reforming of methane

    KAUST Repository

    Biausque, Gregory; Laveille, Paco; Anjum, Dalaver H.; Caps, Valerie; Basset, Jean-Marie

    2015-01-01

    Embodiments of the present disclosure provide for NiPt nanoparticles, compositions and supports including NiPt nanoparticles, methods of making NiPt nanoparticles, methods of supporting NiPt nanoparticles, methods of using NiPt nanoparticles, and the like.

  18. Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO2 reforming of methane

    KAUST Repository

    Biausque, Gregory

    2015-09-24

    Embodiments of the present disclosure provide for NiPt nanoparticles, compositions and supports including NiPt nanoparticles, methods of making NiPt nanoparticles, methods of supporting NiPt nanoparticles, methods of using NiPt nanoparticles, and the like.

  19. Initial in vitro and in vivo assessment of Au@DTDTPA-RGD nanoparticles for Gd-MRI and 68Ga-PET dual modality imaging

    Energy Technology Data Exchange (ETDEWEB)

    Tsoukalas, Charalmpos [National Center for Scientific Research ' Demokritos' (Greece); Laurent, Gautier; Jiménez Sánchez, Gloria [Université de Franche-Comté, Institut UTINAM (France); Tsotakos, Theodoros [National Center for Scientific Research ' Demokritos' (Greece); Bazzi, Rana [Université de Franche-Comté, Institut UTINAM (France); Stellas, Dimitris; Anagnostopoulos, Constantinos [Biomedical Research Foundation, Academy of Athens (Greece); Moulopoulos, Lia; Koutoulidis, Vasilis [Department of Radiology, Areteion Hospital, University of Athens Medical School (Greece); Paravatou-Petsotas, Maria; Xanthopoulos, Stavros [National Center for Scientific Research ' Demokritos' (Greece); Roux, Stephane [Université de Franche-Comté, Institut UTINAM (France); Bouziotis, Penelope [National Center for Scientific Research ' Demokritos' (Greece)

    2015-05-18

    Gadolinium chelate coated gold nanoparticles (Au@DTDTPA) can be applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. In this work, our aim was to radiolabel and evaluate this gold nanoparticle with Ga-68, in order to produce a dual modality PET/MRI imaging probe. For a typical preparation of 68Ga-labeled nanoparticles, the Au@DTDTPA nanoparticles (Au@DTDTPA/Au@DTDTPA-RGD) were mixed with ammonium acetate buffer, pH 5 and 40 MBq of 68Ga eluate. The mixture was then incubated for 45 min at 65 ÅãC. Radiochemical purity was determined by ITLC. In vitro stability of both radiolabeled species was assessed in saline and serum. In vitro cell binding experiments were performed on integrin ανβ3 receptor-positive U87MG cancer cells. Non-specific Au@DTDTPA was used for comparison. Ex vivo biodistribution studies and in vivo PET and MRI imaging studies in U87MG tumor-bearing SCID mice followed. The Au@DTDTPA nanoparticles were labeled with Gallium-68 at high radiochemical yield (>95%) and were stable at RT, and in the presence of serum, for up to 3 h. The cell binding assay on U87MG glioma cells proved that 68Ga-cRGD-Au@DTDTPA had specific recognition for these cells. Biodistribution studies in U87MG tumor-bearing SCID mice showed that the tumor to muscle ratio increased from 1 to 2 h p.i. (3,71 ± 0.22 and 4,69 ± 0.09 respectively), showing a clear differentiation between the affected and the non-affected tissue. The acquired PET and MRI images were in accordance to the ex vivo biodistribution results. The preliminary results of this study warrant the need for further development of Au@DTDTPA nanoparticles radiolabeled with Ga-68, as possible dual-modality PET/MRI imaging agents.

  20. Initial in vitro and in vivo assessment of Au@DTDTPA-RGD nanoparticles for Gd-MRI and 68Ga-PET dual modality imaging

    International Nuclear Information System (INIS)

    Tsoukalas, Charalmpos; Laurent, Gautier; Jiménez Sánchez, Gloria; Tsotakos, Theodoros; Bazzi, Rana; Stellas, Dimitris; Anagnostopoulos, Constantinos; Moulopoulos, Lia; Koutoulidis, Vasilis; Paravatou-Petsotas, Maria; Xanthopoulos, Stavros; Roux, Stephane; Bouziotis, Penelope

    2015-01-01

    Gadolinium chelate coated gold nanoparticles (Au@DTDTPA) can be applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. In this work, our aim was to radiolabel and evaluate this gold nanoparticle with Ga-68, in order to produce a dual modality PET/MRI imaging probe. For a typical preparation of 68Ga-labeled nanoparticles, the Au@DTDTPA nanoparticles (Au@DTDTPA/Au@DTDTPA-RGD) were mixed with ammonium acetate buffer, pH 5 and 40 MBq of 68Ga eluate. The mixture was then incubated for 45 min at 65 ÅãC. Radiochemical purity was determined by ITLC. In vitro stability of both radiolabeled species was assessed in saline and serum. In vitro cell binding experiments were performed on integrin ανβ3 receptor-positive U87MG cancer cells. Non-specific Au@DTDTPA was used for comparison. Ex vivo biodistribution studies and in vivo PET and MRI imaging studies in U87MG tumor-bearing SCID mice followed. The Au@DTDTPA nanoparticles were labeled with Gallium-68 at high radiochemical yield (>95%) and were stable at RT, and in the presence of serum, for up to 3 h. The cell binding assay on U87MG glioma cells proved that 68Ga-cRGD-Au@DTDTPA had specific recognition for these cells. Biodistribution studies in U87MG tumor-bearing SCID mice showed that the tumor to muscle ratio increased from 1 to 2 h p.i. (3,71 ± 0.22 and 4,69 ± 0.09 respectively), showing a clear differentiation between the affected and the non-affected tissue. The acquired PET and MRI images were in accordance to the ex vivo biodistribution results. The preliminary results of this study warrant the need for further development of Au@DTDTPA nanoparticles radiolabeled with Ga-68, as possible dual-modality PET/MRI imaging agents.

  1. The sandwich-type electrochemiluminescence immunosensor for α-fetoprotein based on enrichment by Fe3O4-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP.

    Science.gov (United States)

    Zhou, Hankun; Gan, Ning; Li, Tianhua; Cao, Yuting; Zeng, Saolin; Zheng, Lei; Guo, Zhiyong

    2012-10-09

    A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of α-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe(3)O(4)-Au nanoparticles, which was first employed to capture AFP antigens to form Fe(3)O(4)-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe(3)O(4)-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe(3)O(4)-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0 ng mL(-1) with a detection limit of 0.2 pg mL(-1). The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the amplification of the signal tag, the immunosensor is highly sensitive, which can offer great promise for rapid, simple, selective and cost-effective detection of effective biomonitoring for clinical application. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Synthesis, characterization of Ag-Au core-shell bimetal nanoparticles and its application for electrocatalytic oxidation/sensing of L-methionine

    Energy Technology Data Exchange (ETDEWEB)

    Murugavelu, M.; Karthikeyan, B., E-mail: bkarthi_au@yahoo.com

    2017-01-01

    The Ag-Au core-shell bimetal nanoparticles (BNPs) was prepared using chemical reduction method. The prepared Ag-Au core-shell BNPs were characterized by UV–Visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) pattern. These results showed the Ag-Au BNPs exhibited core-shell shape. The Ag-Au core-shell BNPs was examined towards electrocatalytic oxidation of L-methionine (L-Met) by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. According to the results, L-Met is determined with detection limit of 30 μM. Interference studies in biological buffer was also studied. - Highlights: • The Ag-Au core-shell BNPs are synthesized and characterized • Ag-Au core-shell BNPs modified (Ag-Au/GCE) has been examined for L-methionine oxidation/sensing by using electrochemical method. • The Ag-Au/GCE exhibited good performance for the detection of L-methionine.

  3. Synthesis of a novel Au nanoparticles decorated Ni-MOF/Ni/NiO nanocomposite and electrocatalytic performance for the detection of glucose in human serum.

    Science.gov (United States)

    Chen, Jingyuan; Xu, Qin; Shu, Yun; Hu, Xiaoya

    2018-07-01

    A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles (AuNPs) decorated Ni metal-organic-framework (MOF)/Ni/NiO nanocomposite. Ni-MOF/Ni/NiO nanocomposite was synthesized by one-step calcination of Ni-MOF. Then AuNPs were loaded onto the Ni-based nanocomposites' surface through electrostatic adsorption. Through characterization by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy disperse spectroscopy (EDS) mapping, it is found that the AuNPs were well distributed on the surface of Ni-based nanocomposite. Cyclic voltammetric (CV) study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto it. Amperometric study demonstrated that the Au-Ni nanocomposites modified glassy carbon electrode (GCE) exhibited a high sensitivity of 2133.5 mA M -1 cm -2 and a wide linear range (0.4-900 μM) toward the oxidation of glucose with a detection limit as low as 0.1 μM. Moreover, the reproducibility, selectivity and stability of the sensor all exhibited outstanding performance. We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results. It is believed that AuNPs decorated Ni MOF/Ni/NiO nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Tuning the reactivity of Ru nanoparticles by defect engineering of the reduced graphene oxide support

    KAUST Repository

    Liu, Xin; Sui, Yanhui; Meng, Changgong; Han, Yu

    2014-01-01

    We systematically investigated the electronic structure of Ru nanoparticles supported on various local structures on reduced graphene oxide (rGO) by first-principles-based calculations. We showed that Ru nanoparticles prefer to nucleate

  5. Fe2O3-Au hybrid nanoparticles for sensing applications via sers analysis

    International Nuclear Information System (INIS)

    Murph, Simona Hunyadi; Searles, Emily

    2017-01-01

    Nanoparticles with large amounts of surface area and unique characteristics that are distinct from their bulk material provide an interesting application in the enhancement of inelastic scattering signal. Surface Enhanced Raman Spectroscopy (SERS) strives to increase the Raman scattering effect when chemical species of interest are in the close proximity of metallic nnaostructures. Gold nanoparticles of various shapes have been used for sensing applications via SERS as they demonstrate the greatest effect of plasmonic behavior in the visible-near IR region of the spectrum. When coupled with other nanoparticles, namely iron oxide nanoparticles, hybrid structures with increased functionality were produced. Multifunctional iron oxide-gold hybrid nanostructures have been created via solution chemistries and investigated for analyte detection of a model analyte. By exploiting their magnetic properties, nanogaps or “hot spots” were rationally created and evaluated for SERS enhancement studies.

  6. A novel enzyme-mimic nanosensor based on quantum dot-Au nanoparticle@silica mesoporous microsphere for the detection of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang; Ma, Qiang; Liu, Ziping [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Wang, Xinyan [Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Changchun 130022 (China); Su, Xingguang, E-mail: suxg@jlu.edu.cn [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

    2014-08-20

    Highlights: • Design QD-Au NP@silica mesoporous microspheres as a novel enzyme-mimic nanosensor. • Composition of two kinds of nanoparticle can be controlled through silica layers coating. • Our nanosensor for glucose detection has high sensitivity and selectivity. - Abstract: QD-Au NP@silica mesoporous microspheres have been fabricated as a novel enzyme-mimic nanosensor. CdTe quantum dots (QDs) were loaded into the core, and Au nanoparticles (NPs) were encapsulated in the outer mesoporous shell. QDs and Au NPs were separated in the different space of the nanosensor, which prevent the potential energy or electron transfer process between QDs and Au NPs. As biomimetic catalyst, Au NPs in the mesoporous silica shell can catalytically oxidize glucose as glucose oxidase (GOx)-mimicking. The resultant hydrogen peroxide can quench the photoluminescence (PL) signal of QDs in the microsphere core. Therefore the nanosensor based on the decrease of the PL intensity of QDs was established for the glucose detection. The linear range for glucose was in the range of 5–200 μM with a detection limit (3σ) of 1.32 μM.

  7. Formation of patterned arrays of Au nanoparticles on SiC surface by template confined dewetting of normal and oblique deposited nanoscale films

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Grimaldi, M.G.

    2013-06-01

    We report on the formation of patterned arrays of Au nanoparticles (NPs) on 6H SiC surface. To this end, we exploit the thermal-induced dewetting properties of a template confined deposited nanoscale Au film. In this approach, the Au surface pattern order, on the SiC substrate, is established by a template confined deposition using a micrometric template. Then, a dewetting process of the patterned Au film is induced by thermal processes. We compare the results, about the patterns formation, obtained for normal and oblique deposited Au films. We show that the normal and oblique depositions, through the same template, originate different patterns of the Au film. As a consequence of these different starting patterns, after the thermal processes, different patterns for the arrays of NPs originating from the dewetting mechanisms are obtained. For each fixed deposition angle α, the pattern evolution is analyzed, by scanning electron microscopy, as a function of the annealing time at 1173 K (900 °C). From these analyses, quantitative evaluations on the NPs size evolution are drawn. - Highlights: • Micrometric template-confined nanoscale gold films are deposited on silicon carbide. • The dewetting process of template-confined gold films on silicon carbide is studied. • Comparison of dewetting process of normal and oblique deposited gold films is drawn. • Patterned arrays of gold nanoparticles on silicon carbide surface are produced.

  8. Formation of patterned arrays of Au nanoparticles on SiC surface by template confined dewetting of normal and oblique deposited nanoscale films

    International Nuclear Information System (INIS)

    Ruffino, F.; Grimaldi, M.G.

    2013-01-01

    We report on the formation of patterned arrays of Au nanoparticles (NPs) on 6H SiC surface. To this end, we exploit the thermal-induced dewetting properties of a template confined deposited nanoscale Au film. In this approach, the Au surface pattern order, on the SiC substrate, is established by a template confined deposition using a micrometric template. Then, a dewetting process of the patterned Au film is induced by thermal processes. We compare the results, about the patterns formation, obtained for normal and oblique deposited Au films. We show that the normal and oblique depositions, through the same template, originate different patterns of the Au film. As a consequence of these different starting patterns, after the thermal processes, different patterns for the arrays of NPs originating from the dewetting mechanisms are obtained. For each fixed deposition angle α, the pattern evolution is analyzed, by scanning electron microscopy, as a function of the annealing time at 1173 K (900 °C). From these analyses, quantitative evaluations on the NPs size evolution are drawn. - Highlights: • Micrometric template-confined nanoscale gold films are deposited on silicon carbide. • The dewetting process of template-confined gold films on silicon carbide is studied. • Comparison of dewetting process of normal and oblique deposited gold films is drawn. • Patterned arrays of gold nanoparticles on silicon carbide surface are produced

  9. Synergistic Use of Gold Nanoparticles (AuNPs) and “Capillary Enzyme-Linked Immunosorbent Assay (ELISA)” for High Sensitivity and Fast Assays

    Science.gov (United States)

    Kim, Wan-Joong; Cho, Hyo Young; Jeong, Bongjin; Byun, Sangwon; Huh, JaeDoo; Kim, Young Jun

    2017-01-01

    Using gold nanoparticles (AuNPs) on “capillary enzyme-linked immunosorbent assay (ELISA)”, we produced highly sensitive and rapid assays, which are the major attributes for point-of-care applications. First, in order to understand the size effect of AuNPs, AuNPs of varying diameters (5 nm, 10 nm, 15 nm, 20 nm, 30 nm, and 50 nm) conjugated with Horseradish Peroxidase (HRP)-labeled anti-C reactive protein (antiCRP) (AuNP•antiCRP-HRP) were used for well-plate ELISA. AuNP of 10 nm produced the largest optical density, enabling detection of 0.1 ng/mL of CRP with only 30 s of incubation, in contrast to 10 ng/mL for the ELISA run in the absence of AuNP. Then, AuNP of 10 nm conjugated with antiCRP-HRP (AuNP•antiCRP-HRP) was used for “capillary ELISA” to detect as low as 0.1 ng/mL of CRP. Also, kinetic study on both 96-well plates and in a capillary tube using antiCRP-HRP or AuNP•antiCRP-HRP showed a synergistic effect between AuNP and the capillary system, in which the fastest assay was observed from the “AuNP capillary ELISA”, with its maximum absorbance reaching 2.5 min, while the slowest was the typical well-plate ELISA with its maximum absorbance reaching in 13.5 min. PMID:29278402

  10. NaNO3/NaCl Oxidant and Polyethylene Glycol (PEG) Capped Gold Nanoparticles (AuNPs) as a Novel Green Route for AuNPs Detection in Electrochemical Biosensors.

    Science.gov (United States)

    López-Marzo, Adaris M; Hoyos-de-la-Torre, Raquel; Baldrich, Eva

    2018-03-20

    Gold nanoparticles (AuNPs) have been exploited as signal-producing tags in electrochemical biosensors. However, the electrochemical detection of AuNPs is currently performed using corrosive acid solutions, which may raise health and environmental concerns. Here, oxidant salts, and specifically the environmentally friendly and occupational safe NaNO 3 /NaCl mixture, have been evaluated for the first time as potential alternatives to the acid solutions traditionally used for AuNPs electrooxidation. In addition, a new strategy to improve the sensitivity of the biosensor through PEG-based ligand exchange to produce less compact and easier to oxidize AuNPs immunoconjugates is presented too. As we show, the electrochemical immunosensor using NaNO 3 /NaCl measurement solution for AuNPs electrooxidation and detection, coupled to the employment of PEG-capped nanoimmunoconjugates, produced results comparable to classical HCl detection. The procedure developed was next tested for human matrix metallopeptidase-9 (hMMP9) analysis, exhibiting a 0.18-23 ng/mL linear range, a detection limit of 0.06 ng/mL, and recoveries between 95 and 105% in spiked human plasma. These results show that the procedure developed is applicable to the analysis of protein biomarkers in blood plasma and could contribute to the development of more environmentally friendly AuNP-based electrochemical biosensors.

  11. Nanoparticle Metamorphosis: An in Situ High-Temperature Transmission Electron Microscopy Study of the Structural Evolution of Heterogeneous Au:Fe 2 O 3 Nanoparticles

    KAUST Repository

    Baumgardner, William J.

    2014-05-27

    High-temperature in situ electron microscopy and X-ray diffraction have revealed that Au and Fe2O3 particles fuse in a fluid fashion at temperatures far below their size-reduced melting points. With increasing temperature, the fused particles undergo a sequence of complex structural transformations from surface alloy to phase segregated and ultimately core-shell structures. The combination of in situ electron microscopy and spectroscopy provides insights into fundamental thermodynamic and kinetic aspects governing the formation of heterogeneous nanostructures. The observed structural transformations present an interesting analogy to thin film growth on the curved surface of a nanoparticle. Using single-particle observations, we constructed a phase diagram illustrating the complex relationships among composition, morphology, temperature, and particle size. © 2014 American Chemical Society.

  12. Nanoparticle Metamorphosis: An in Situ High-Temperature Transmission Electron Microscopy Study of the Structural Evolution of Heterogeneous Au:Fe 2 O 3 Nanoparticles

    KAUST Repository

    Baumgardner, William J.; Yu, Yingchao; Hovden, Robert; Honrao, Shreyas; Hennig, Richard G.; Abruñ a, Hé ctor D.; Muller, David; Hanrath, Tobias

    2014-01-01

    High-temperature in situ electron microscopy and X-ray diffraction have revealed that Au and Fe2O3 particles fuse in a fluid fashion at temperatures far below their size-reduced melting points. With increasing temperature, the fused particles undergo a sequence of complex structural transformations from surface alloy to phase segregated and ultimately core-shell structures. The combination of in situ electron microscopy and spectroscopy provides insights into fundamental thermodynamic and kinetic aspects governing the formation of heterogeneous nanostructures. The observed structural transformations present an interesting analogy to thin film growth on the curved surface of a nanoparticle. Using single-particle observations, we constructed a phase diagram illustrating the complex relationships among composition, morphology, temperature, and particle size. © 2014 American Chemical Society.

  13. Formation of Ag2, Au2 and AgAu particles on MgO(1 0 0): DFT study on the role of support-induced charge transfer in metal-metal interactions

    International Nuclear Information System (INIS)

    Fuente, Silvia A.; Belelli, Patricia G.; Branda, Maria M.; Ferullo, Ricardo M.; Castellani, Norberto J.

    2009-01-01

    The formation of Ag 2 , Au 2 and AgAu particles oriented perpendicularly to the MgO(1 0 0) surface was studied using the density functional theory. While the support induces a slight enhancement of the Ag-Ag bond (by 0.3-0.4 eV), the Au-Au bond is strongly enhanced (by 0.8-1.1 eV). Concerning the bimetallic particle, the Ag-Au bond stabilization depends on the relative position of each atom. Thus, in general terms, the strength of the metal-metal bond is determined by the nature of the terminal atom; the bond is stronger in Au-terminal particles. The partial electronic charge transfer to the terminal Au atom and its ability to polarize this charge are responsible for this energetic stabilization.

  14. Simultaneous Detection and Removal of Formaldehyde at Room Temperature: Janus Au@ZnO@ZIF-8 Nanoparticles

    Science.gov (United States)

    Wang, Dawei; Li, Zhiwei; Zhou, Jian; Fang, Hong; He, Xiang; Jena, Puru; Zeng, Jing-Bin; Wang, Wei-Ning

    2018-03-01

    The detection and removal of volatile organic compounds (VOCs) are of great importance to reduce the risk of indoor air quality concerns. This study reports the rational synthesis of a dual-functional Janus nanostructure and its feasibility for simultaneous detection and removal of VOCs. The Janus nanostructure was synthesized via an anisotropic growth method, composed of plasmonic nanoparticles, semiconductors, and metal organic frameworks (e.g., Au@ZnO@ZIF-8). It exhibits excellent selective detection to formaldehyde (HCHO, as a representative VOC) at room temperature over a wide range of concentrations (from 0.25 to 100 ppm), even in the presence of water and toluene molecules as interferences. In addition, HCHO was also found to be partially oxidized into non-toxic formic acid simultaneously with detection. The mechanism underlying this technology was unraveled by both experimental measurements and theoretical calculations: ZnO maintains the conductivity, while ZIF-8 improves the selective gas adsorption; the plasmonic effect of Au nanorods enhances the visible-light-driven photocatalysis of ZnO at room temperature. [Figure not available: see fulltext.

  15. Label-Free Impedance Sensing of Aflatoxin B1 with Polyaniline Nanofibers/Au Nanoparticle Electrode Array

    Directory of Open Access Journals (Sweden)

    Ajay Kumar Yagati

    2018-04-01

    Full Text Available Aflatoxin B1 (AFB1 is produced by the Aspergillus flavus and Aspergillus parasiticus group of fungi which is most hepatotoxic and hepatocarcinogenic and occurs as a contaminant in a variety of foods. AFB1 is mutagenic, teratogenic, and causes immunosuppression in animals and is mostly found in peanuts, corn, and food grains. Therefore, novel methodologies of sensitive and expedient strategy are often required to detect mycotoxins at the lowest level. Herein, we report an electrochemical impedance sensor that selectively detects AFB1 at the lowest level by utilizing polyaniline nanofibers (PANI coated with gold (Au nanoparticles composite based indium tin oxide (ITO disk electrodes. The Au-PANI nanocomposites were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD spectroscopy, and electrochemical impedance spectroscopy (EIS. The composite electrode exhibited a 14-fold decrement in |Z|1 Hz in comparison with the bare electrode. The Au-PANI acted as an effective sensing platform having high surface area, electrochemical conductivity, and biocompatibility which enabled greater loading deposits of capture antibodies. As a result, the presence of AFB1 was screened with high sensitivity and stability by monitoring the changes in impedance magnitude (|Z| in the presence of a standard iron probe which was target specific and proportional to logarithmic AFB1 concentrations (CAFB1. The sensor exhibits a linear range 0.1 to 100 ng/mL with a detection limit (3σ of 0.05 ng/mL and possesses good reproducibility and high selectivity against another fungal mycotoxin, Ochratoxin A (OTA. With regard to the practicability, the proposed sensor was successfully applied to spiked corn samples and proved excellent potential for AFB1 detection and development of point-of-care (POC disease sensing applications.

  16. A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles.

    Science.gov (United States)

    Li, Tianhua; Li, Yonglong; Zhang, Yujie; Dong, Chen; Shen, Zheyu; Wu, Aiguo

    2015-02-21

    Excessive uptake of NO2(-) is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2(-) detection system based on a redox etching strategy of CTAB-stabilized Ag-Au core-shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2(-) concentration. The selectivity of detection of NO2(-), both with the unaided eye and by measurement of UV-Vis spectra, is excellent in relation to other ions, including Cu(2+), Co(2+), Ni(2+), Cr(3+), Al(3+), Pb(2+), Cd(2+), Ca(2+), Ba(2+), Zn(2+), Mn(2+), Mg(2+), Fe(3+), Hg(2+), Ag(+), K(+), F(-), PO4(3-), C2O4(2-), SO3(2-), CO3(2-), SO4(2-), NO3(-) and CH3-COO(-) (Ac(-)). The limit of detection (LOD) for NO2(-) is 1.0 μM by eye and 0.1 μM by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 μM). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 μM NO2(-), which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2(-) in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2(-) in complex environmental samples, with excellent selectivity and high sensitivity.

  17. Sputtering-growth of seeded Au nanoparticles for nanogap-assisted surface-enhanced Raman scattering (SERS) biosensing

    Science.gov (United States)

    Fu, Chit Yaw; U. S., Dinish; Rautela, Shashi; Goh, Douglas Wenda; Olivo, Malini

    2011-12-01

    Gold-coated array patterned with tightly-packed nanospheres was developed as a substrate base for constructing SERSenriched nanogaps with Au-nanoparticles (GNPs). Using 1,2-ethanedithiol as a linker, Au-NPs (=17-40nm) were anchored covalently on the sphere-array. Thin Au layer was sputtered on the substrate to mask the citrate coating of GNPs that could demote the sensing mechanism. The negatively-charged GNP surface warrants the colloidal stability, but the resulting repulsive force keeps the immobilized NPs apart by about 40nm. The attained gap size is inadequately narrow to sustain any intense enhancement owing to the near-field nature of SERS. Minimal amount of NaCl was then added to slightly perturb the colloidal stability by reducing their surface charge. Notably, the interparticle-gap reduces at increasing amount of salt, giving rise to increased packing density of GNPs. The SERS enhancement is also found to exponentially increase at decreasing gap size. Nevertheless, the minimum gap achieved is limited to merely 7nm. Excessive addition of salt would eventually induce complete aggregation of particles, forming clustered NPs on the array. A simple sputtering-growth approach is therefore proposed to further minimize the interparticle gap by enlarging the seeded NPs based on mild sputtering. The SEM images confirm that the gap below 7nm is achievable. With advent of the colloidal chemistry, the combined salt-induced aggregation and sputtering-growth techniques can be applied to engineer interparticle gap that is crucial to realize an ultrasensitive SERS biosensor. The proposed two-step preparation can be potentially adopted to fabricate the SERS-enriched nanogaps on the microfluidics platform.

  18. Au@NiO core-shell nanoparticles as a p-type gas sensor: Novel synthesis, characterization, and their gas sensing properties with sensing mechanism

    KAUST Repository

    Majhi, Sanjit Manohar

    2018-04-25

    In this work, Au@NiO core-shell nanoparticles (C-S NPs) as a p-type gas sensing material was synthesized by a facile wet-chemical method, and evaluated their gas sensing properties as compared to the pristine NiO NPs gas sensors. Transmission electron microscope (TEM) results exhibited the well-dispersed formation of Au@NiO C-S NPs having the total size of 70–120 nm and NiO shells having 30–50 nm thickness. The C-S morphology as well as the overall particle sizes are unchanged even at 500 °C. The gas sensing result reveals that the response of Au@NiO C-S NPs gas sensor is higher than pristine NiO NPs gas sensor for 100 ppm of ethanol at 200 °C operating temperature. The baseline resistance in the air for Au@NiO C-S NPs sensor is lowered as compared to pristine NiO NPs, which is due to the increased number of holes as charge carriers in Au@NiO C-S NPs. The high response of Au@NiO core-shell NPs as compared to pristine NiO NPs is attributed to electronic and chemical sensitization effects of Au. In Au@NiO C-S structure, the contact between metal (Au) and semiconductor (NiO) formed a Schottky junction since Au metal acted as electron acceptor, a withdrawal of electrons from NiO by Au metal core leaved behind number of holes as charge carriers in Au@NiO C-S NPs. Therefore, the baseline resistance of Au@NiO C-S NPs greatly decreased than pristine NiO NPs, as a result the Au@NiO C-S NPs showed higher response. On the other hand, in chemical sensitization effect, Au NPs catalyzed to dissociate O2 molecules into ionic species. This work will give some clue to the researchers for the further development of p-type based C-S NPs sensors.

  19. Au/ZnO nanocomposites: Facile fabrication and enhanced photocatalytic activity for degradation of benzene

    International Nuclear Information System (INIS)

    Yu, Hang; Ming, Hai; Zhang, Hengchao; Li, Haitao; Pan, Keming; Liu, Yang; Wang, Fang; Gong, Jingjing; Kang, Zhenhui

    2012-01-01

    Au nanoparticles supported on highly uniform one-dimensional ZnO nanowires (Au/ZnO hybrids) have been successfully fabricated through a simple wet chemical method, which were first used for photodegradation of gas-phase benzene. Compared with bare ZnO nanowires, the as-prepared Au/ZnO hybrids were found to possess higher photocatalytic activity for degradation of benzene under UV and visible light (degradation efficiencies reach about 56.0% and 33.7% after 24 h under UV and visible light irradiation, respectively). Depending on excitation happening on ZnO semiconductor or on the surface plasmon band of Au, the efficiency and operating mechanism are different. Under UV light irradiation, Au nanoparticles serve as an electron buffer and ZnO nanowires act as the reactive sites for benzene degradation. When visible light is used as the light irradiation source, Au nanoparticles act as the light harvesters and photocatalytic sites alongside of charge-transfer process, simultaneously. -- Graphical abstract: Under visible light irradiation, Au nanoparticles, which are supported on ZnO nanowires, dominate their catalytic properties in gas-phase degradation benzene reaction. Highlights: ► The composites that Au nanoparticles supported on ZnO nanowires were synthesized. ► Au/ZnO composites were firstly used as effective photocatalysts for benzene degradation. ► Two operating mechanisms were proposed depending on excitation wavelength.

  20. Visible-light promoted catalytic activity of dumbbell-like Au nanorods supported on graphene/TiO2 sheets towards hydrogenation reaction

    Science.gov (United States)

    Dai, Yunqian; Zhu, Mingyun; Wang, Xiaotian; Wu, Yanan; Huang, Chengqian; Fu, Wanlin; Meng, Xiangyu; Sun, Yueming

    2018-06-01

    In this work, the rationally-designed sharp corners on Au nanorods tremendously improved the catalytic activity, particularly in the presence of visible light irradiation, towards the hydrogenation of 4-nitrophenol to 4-aminophenol. A strikingly increased rate constant of 50.6 g‑1 s‑1 L was achieved in M-Au-3, which was 41.8 times higher than that of parent Au nanorods under dark conditions. The enhanced activities were proportional to the extent of the protruding sharp corners. Furthermore, remarkably enhanced activities were achieved in novel ternary Au/RGO/TiO2 sheets, which were endowed with a 52.0 times higher rate constant than that of straight Au nanorods. These remarkably enhanced activities were even higher than those of previously reported 3–5 nm Au and 3 nm Pt nanoparticles. It was systematically observed that there are three aspects to the synergistic effects between Au and RGO sheets: (i) electron transfer from RGO to Au, (ii) a high concentration of p-nitrophenol close to dumbbell-like Au nanorods on RGO sheets, and (iii) increased local reaction temperature from the photothermal effect of both dumbbell-like Au nanorods and RGO sheets.

  1. Thiol-modified gold nanoparticles deposited on silica support using dip coating

    International Nuclear Information System (INIS)

    Magura, Jozef; Zeleňáková, Adriana; Zeleňák, Vladimír; Kaňuchová, Maria

    2014-01-01

    Graphical abstract: - Highlights: • Thin layers of gold were deposited on glass substrate. • Layers were modified by two different ligands, 1,4-dithiothreitol and L-glutathione. • Red shift of SPR band was observed in spectra after modification of Au by thiols. • Charge transfer between Au and S atoms leads to ferromagnetic behaviour of samples. - Abstract: In our work, we have prepared thin layers of gold nanoparticles deposited via dip coating technique on silica glass substrate. The prepared thin layers were modified by two different ligands, namely 1,4-dithiothreitol (sample Au-DTT NPs) and L-glutathione (sample Au-GSH NPs). The spectral, structural and magnetic properties of the prepared samples were investigated. The modification of Au nanoparticles with thiol ligands leads to change of their plasmon resonance fields, as indicated by UV–vis spectra. The magnetic measurements showed that the magnetization of the samples is composed from two magnetic contributions: diamagnetic contribution and low field ferromagnetic contribution. Our experimental results show that the charge transfer between Au and S atoms gives rise to the ferromagnetic behaviour of prepared thin layers

  2. Facile approach to synthesize uniform Au@mesoporous SnO{sub 2} yolk–shell nanoparticles and their excellent catalytic activity in 4-nitrophenol reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ya [Changchun University of Science and Technology, School of Chemistry & Environmental Engineering (China); Li, Lu; Wang, Chungang, E-mail: wangcg925@nenu.edu.cn [Northeast Normal University, Faculty of Chemistry (China); Wang, Tingting, E-mail: wangtt@cust.edu.cn [Changchun University of Science and Technology, School of Chemistry & Environmental Engineering (China)

    2016-01-15

    Monodispersed and uniform Au@mesoporous SnO{sub 2} yolk–shell nanoparticles (Au@mSnO{sub 2} yolk–shell NPs) composed of the moveable Au NP cores and mSnO{sub 2} shells have been successfully fabricated via a facile and reproducible approach. The outside mSnO{sub 2} shells of Au@mSnO{sub 2} yolk–shell NPs not only prevent Au NPs from aggregating and corroding by the reaction solution but also allow the Au NPs to contact with reactant molecules easily through the mesoporous channels. The obtained Au@mSnO{sub 2} yolk–shell NPs are characterized by means of transmission electron microscope, scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectrum, and UV–vis absorption spectroscopy. The synthesized materials exhibit excellent catalytic performance and high stability towards the reduction of 4-nitrophenol with NaBH{sub 4} as a reducing agent, which may be ascribed to their high specific surface area and unique mesoporous structure. Moreover, the synthetic strategy reported in this paper can be extended to fabricate a series of multifunctional noble metal@metal oxide yolk–shell nanocomposite materials with unique properties for various applications.

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

    Science.gov (United States)

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

    2014-06-24

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

  4. Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape-Controlled Au Nanoparticles.

    Science.gov (United States)

    Lee, Mi Gyoung; Moon, Cheon Woo; Park, Hoonkee; Sohn, Woonbae; Kang, Sung Bum; Lee, Sanghan; Choi, Kyoung Jin; Jang, Ho Won

    2017-10-01

    The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape-controlled Au NPs on bismuth vanadate (BiVO 4 ) are studied, and a largely enhanced photoactivity of BiVO 4 is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO 4 achieves 2.4 mA cm -2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO 4 . It is the highest value among the previously reported plasmonic Au NPs/BiVO 4 . Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Vacancy Clusters on Surfaces of Au Nanoparticles Embedded in MgO

    International Nuclear Information System (INIS)

    Xu, Jun; Mills, A. P. Jr.; Ueda, A.; Henderson, D. O.; Suzuki, R.; Ishibashi, S.

    1999-01-01

    MeV implantation of gold ions into MgO(100) followed by annealing is a method to form gold nanoparticles for obtaining modified optical properties. We show from variable-energy positron spectroscopy that clusters of 2 Mg and 2 O vacancies (v 4 ) are attached to the gold nanoparticle surfaces within the projected range (R p ) . We also find that v 4 vacancy clusters are created at depths less than R p , and extend into the region greater than R p due to damage induced by knock-on collisions. (c) 1999 The American Physical Society

  6. Determination of the structure and composition of Au-Ag bimetallic spherical nanoparticles using single particle ICP-MS measurements performed with normal and high temporal resolution.

    Science.gov (United States)

    Kéri, Albert; Kálomista, Ildikó; Ungor, Ditta; Bélteki, Ádám; Csapó, Edit; Dékány, Imre; Prohaska, Thomas; Galbács, Gábor

    2018-03-01

    In this study, the information that can be obtained by combining normal and high resolution single particle ICP-MS (spICP-MS) measurements for spherical bimetallic nanoparticles (BNPs) was assessed. One commercial certified core-shell Au-Ag nanoparticle and three newly synthesized and fully characterized homogenous alloy Au-Ag nanoparticle batches of different composition were used in the experiments as BNP samples. By scrutinizing the high resolution spICP-MS signal time profiles, it was revealed that the width of the signal peak linearly correlates with the diameter of nanoparticles. It was also observed that the width of the peak for same-size nanoparticles is always significantly larger for Au than for Ag. It was also found that it can be reliably determined whether a BNP is of homogeneus alloy or core-shell structure and that, in the case of the latter, the core comprises of which element. We also assessed the performance of several ICP-MS based analytical methods in the analysis of the quantitative composition of bimetallic nanoparticles. Out of the three methods (normal resolution spICP-MS, direct NP nebulization with solution-mode ICP-MS, and solution-mode ICP-MS after the acid dissolution of the nanoparticles), the best accuracy and precision was achieved by spICP-MS. This method allows the determination of the composition with less than 10% relative inaccuracy and better than 3% precision. The analysis is fast and only requires the usual standard colloids for size calibration. Combining the results from both quantitative and structural analyses, the core diameter and shell thickness of core-shell particles can also be calculated. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Optical properties of supported core-shell and alloy silver/gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hubenthal, Frank; Traeger, Frank [Universitaet Kassel (Germany)

    2008-07-01

    For many applications like surface enhanced Raman scattering in which the optical field enhancement associated with surface plasmon excitation is exploited, tunability of this collective resonance over a wide range is required. For this purpose we have prepared core-shell and alloy nanoparticles consisting of Ag and Au. The core-shell nanoparticles were made by subsequent deposition of Ag and Au atoms and vice versa on dielectric substrates followed by diffusion and nucleation. One of the most interesting among the numerous results is that the plasmon frequency can be tuned from 2.8 eV (442 nm) to 2.1 eV (590 nm) depending on the Au shell thickness. Subsequent annealing of the core-shell nanoparticles causes a shift of the resonance frequency to 2.6 eV. Theoretical modelling allows us to attribute this observation to the formation of alloy nanoparticles. Finally, we have measured the dephasing time T{sub 2} of the alloy nanoparticles by means of spectral hole burning. T{sub 2} amounts to 8.1{+-}1.6 fs, in good agreement with the dephasing time T{sub 2}=8.9 fs that is included in the dielectric function of the bulk.

  8. RGO/Au NPs/N-doped CNTs supported on nickel foam as an anode for enzymatic biofuel cells.

    Science.gov (United States)

    Zhang, He; Zhang, Lingling; Han, Yujie; Yu, You; Xu, Miao; Zhang, Xueping; Huang, Liang; Dong, Shaojun

    2017-11-15

    In this study, three-dimensional reduced graphene oxide/Au NPs/nitrogen-doped carbon nanotubes (RGO/Au NPs/N-doped CNTs) assembly supported on nickel foam was utilized as an anode for enzymatic biofuel cells (EBFCs). 3D RGO/Au NPs was obtained by electrodepositing reduced graphene oxide on nickel foam (Ni foam), while Au NPs were co-deposited during the process. Afterwards, nitrogen doped CNTs (N-CNTs) were allowed to grow seamlessly on the surfaces of 3D RGO/Au NPs via a simple chemical vapor deposition (CVD) process. In this nanostructure, Au NPs co-deposition and nitrogen doping offer more active sites for bioelectrocatalysis. Additionally, N-CNTs were demonstrated providing high specific surface area for enzyme immobilization and facilitating the electron transfer between glucose oxidase (GOx) and electrode. The resulting bioanode achieved efficient glucose oxidation with high current densities of 7.02mAcm -2 (0.3V vs. Ag/AgCl). Coupling with a Pt cathode, the fabricated glucose/air biofuel cell exhibited an open-circuit potential of 0.32V and generated a maximum power density 235µWcm -2 at 0.15V. This novel electrode substrate achieved high performance in current density at bioelectrochemical systems and could be useful for further exploiting the application of three dimensional carbon-based nanomaterials in EBFCs. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core–shell nanoparticles

    International Nuclear Information System (INIS)

    Kang, Fei; Xu, Kun; Hou, Xiangshu

    2015-01-01

    Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core–shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H 2 O 2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core–shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum. (paper)

  10. A highly sensitive nanoscale pH-sensor using Au nanoparticles linked by a multifunctional Raman-active reporter molecule.

    Science.gov (United States)

    Lawson, Latevi S; Chan, James W; Huser, Thomas

    2014-07-21

    Chemical sensing on the nanoscale has been breaking new ground since the discovery of surface enhanced Raman scattering (SERS). For nanoparticles, controlled particle aggregation is necessary to achieve the largest SERS enhancements. Therefore, aggregating agents such as salts or linker molecules are used in conjunction with chemically sensitive reporters in order to develop robust environmentally sensitive SERS probes. While salt-induced colloidal nanosphere aggregates have produced robust SERS signals, their variability in aggregate size contributes significantly to poor SERS signal reproducibility, which can complicate their use in in vitro cellular studies. Such systems often also lack reproducibility in spectral measurements between different nanoparticle clusters. Preaggregation of colloids via linkers followed by surface functionalization with reporter molecules results in the linker occupying valuable SERS hotspot volume which could otherwise be utilized by additional reporter molecules. Ideally, both functionalities should be obtained from a single molecule. Here, we report the use of 3,5-dimercaptobenzoic acid, a single multifunctional molecule that creates SERS hotspots via the controlled aggregation of nanoparticles, and also reports pH values. We show that 3,5-dimercaptobenzoic acid bound to Au nanospheres results in an excellent pH nanoprobe, producing very robust, and highly reproducible SERS signals that can report pH across the entire physiological range with excellent pH resolution. To demonstrate the efficacy of our novel pH reporters, these probes were also used to image both the particle and pH distribution in the cytoplasm of human induced pluripotent stem cells (hiPSCs).

  11. Photocatalytic degradation of malachite green dye using Au/NaNbO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Baeissa, E.S., E-mail: elhambaeissa@gmail.com

    2016-07-05

    The morphology of sodium niobate, which was produced using a hydrothermal method, was studied by changing the hydrothermal temperature from 100 to 250 °C. Using 250 °C hydrothermal temperature resulted in sodium niobate with a nanocube structure. The sodium niobate nanocubes were doped with gold by impregnation with an aqueous solution of HAuCl{sub 4}. The band gap of sodium niobate is approximately 3.4 eV, and it was decreased to 2.45 eV by gold doping. The surface area of sodium niobate is higher than that of Au/NaNbO{sub 3} due to blockage of some pores of sodium niobate by gold doping. The photocatalytic performance of gold-doped sodium niobate was studied by degradation of malachite green dye using visible light irradiation. The results demonstrate that the photocatalytic performance of gold-doped sodium niobate is higher than that of sodium niobate and TiO{sub 2} Degussa under visible light irradiation. - Highlights: • Au/NaNbO{sub 3} were used for photocatalytic degradation of malachite green dye. • Photocatalytic degradation was dependent on wt % of Au; reaction time, and weight of catalyst. • Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles.

  12. Photocatalytic degradation of malachite green dye using Au/NaNbO_3 nanoparticles

    International Nuclear Information System (INIS)

    Baeissa, E.S.

    2016-01-01

    The morphology of sodium niobate, which was produced using a hydrothermal method, was studied by changing the hydrothermal temperature from 100 to 250 °C. Using 250 °C hydrothermal temperature resulted in sodium niobate with a nanocube structure. The sodium niobate nanocubes were doped with gold by impregnation with an aqueous solution of HAuCl_4. The band gap of sodium niobate is approximately 3.4 eV, and it was decreased to 2.45 eV by gold doping. The surface area of sodium niobate is higher than that of Au/NaNbO_3 due to blockage of some pores of sodium niobate by gold doping. The photocatalytic performance of gold-doped sodium niobate was studied by degradation of malachite green dye using visible light irradiation. The results demonstrate that the photocatalytic performance of gold-doped sodium niobate is higher than that of sodium niobate and TiO_2 Degussa under visible light irradiation. - Highlights: • Au/NaNbO_3 were used for photocatalytic degradation of malachite green dye. • Photocatalytic degradation was dependent on wt % of Au; reaction time, and weight of catalyst. • Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles.

  13. Cage-like effect in Au-Pt nanoparticle synthesis in microemulsions: a simulation study.

    Science.gov (United States)

    Tojo, C; de Dios, M; Buceta, D; López-Quintela, M A

    2014-09-28

    The different distributions of metals in bimetallic nanoparticles synthesized in microemulsions were studied by computer simulation. The simulations demonstrated that if the difference between the reduction potentials of both metals is about 0.15-0.3 V, the compartmentalization of the reaction media causes the accumulation of slower reduction reactants in the microemulsions droplets, which favours the chemical reaction like a cage effect: increasing the local concentration of the slower reduction metal salt gives rise to a faster reduction, so the differences in reduction rates of both metals are attenuated. A more coincidental reduction of both metals deeply affects the nanoparticle structure, causing a better mixed alloy. This effect will be more pronounced when the concentration is higher and the intermicellar exchange rate is faster. This means that for any fixed microemulsion the nanoparticle structure can be modified by changing the reactant concentration: the core can be enriched in the faster reduction metal by lower concentrations, and the shell can be enriched in the slower metal by higher concentrations. Based on these observations, this study suggests a route to help experimentalists better create nanoparticles with a pre-defined structure.

  14. Gd-functionalised Au nanoparticles as targeted contrast agents in MRI: relaxivity enhancement by polyelectrolyte coating.

    Science.gov (United States)

    Warsi, Muhammad Farooq; Adams, Ralph W; Duckett, Simon B; Chechik, Victor

    2010-01-21

    Monolayer-protected, Gd(3+)-functionalised gold nanoparticles with enhanced spin-lattice relaxivity (r(1)) were prepared;