EP0914244A1 - Organisch funktionalisierte monodisperse metallnanokristalle - Google Patents

Organisch funktionalisierte monodisperse metallnanokristalle

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Publication number
EP0914244A1
EP0914244A1 EP96945950A EP96945950A EP0914244A1 EP 0914244 A1 EP0914244 A1 EP 0914244A1 EP 96945950 A EP96945950 A EP 96945950A EP 96945950 A EP96945950 A EP 96945950A EP 0914244 A1 EP0914244 A1 EP 0914244A1
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Prior art keywords
metal
solution
particles
organic
group
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French (fr)
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EP0914244A4 (de
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James R. Heath
Daniel V. Leff
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University of California
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B01J35/45—Nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0545—Dispersions or suspensions of nanosized particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/102—Metallic powder coated with organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • This invention relates to metal and metal alloy nanocrystals. In one of its more particular aspects, this invention relates to organically-functionalized monodisperse nanocrystals of metals and metal alloys and methods of preparation thereof.
  • nanoparticle metal and metal oxide hydrosols are known.
  • the myriad methods for preparing these particles include, but are not limited to: (1) the synthesis of colloidal dispersions of various transition metals (Pt, Pd, Ir, Rh, Os, Au, Ag, Fe, Co, and the like) in aqueous media, stabilized by added polymers as protective colloids; (2) the synthesis of ultrasmall metal oxide particles by the combination of water and metal chlorides, hydroxides, or acetates, in aqueous media; (3) the synthesis of Ag nanoparticles by the reduction of Ag+ in aqueous media; (4) the formation of colloidal silver and gold in aqueous media by ultrasonic radiation; (5) the formation of colloidal gold in aqueous media by the reduction of a gold salt; and (6) the formation of colloidal platinum and palladium in aqueous media by synthetic routes analogous to those for preparing gold colloids.
  • transition metals Pt, Pd, Ir, Rh, Os, Au, Ag, Fe
  • Nanometer-scale crystallites of various metals and non-metals have received a great deal of attention in the past decade.
  • the electronic, thermodynamic, and chemical properties depend sensitively on size, shape, and surface composition; therefore, these materials have been marked for a number of technological applications ranging from chemical catalysis, photoelectronics, film growth seeding, electronic materials, reprography, xerography, electron microscopy, and others.
  • a major challenge to this field in general and a great barrier to actualizing such applications of these novel particles is the complete control over particle size, morphology, and surface structure.
  • the preparation and isolation of crystallites characterized by well-defined surface compositions, narrow size distributions, and uniform shape is paramount to their success as applied materials.
  • metal particles involved in these various technologies include ferromagnetic materials (e.g. Fe 2 O 3 , Co), noble metals (Pd, Pt), coinage metals (Au, Ag), alloys of these metals (e.g. Co x Au y ), oxides of these metals (e.g. Ag 2 0), and others.
  • ferromagnetic materials e.g. Fe 2 O 3 , Co
  • noble metals Pd, Pt
  • coinage metals Au, Ag
  • alloys of these metals e.g. Co x Au y
  • oxides of these metals e.g. Ag 2 0
  • the products synthesized in these reports are marred by some or all of the following characteristics: 1) the resulting materials are x-ray amorphous (non-crystalline); 2) the resulting materials have poor surface compositions; 3) the resulting materials have poor solubility in aqueous and organic media; and 4) the resulting materials have broad relative size distributions (mean diameter ⁇ 50 %).
  • organically-functionalized gold nanocrystals limited to certain "average" sizes, characterized by broad size distributions, and which are not soluble in aqueous media have been disclosed.
  • the nanocrystal products of the present invention avoid the previously discussed problems.
  • the "as prepared" spherical nanoparticles are crystalline and are characterized by narrow relative size distributions (as low as ⁇ 10 %). More importantly, however, is the fact that they are functionalized with well-defined organic groups covalently bound to the particle surface. These organic functional groups may be altered both chemically and with respect to percent coverage on the surface. Such chemistry is tremendously useful in the following ways: 1) the organic functional groups, coupled with the size-dependent curvature of a particle surface, yield varying solubilities as a function of particle size.
  • the method for the preparation and isolation of crystallites according to the present invention is characterized by well-defined surface compositions, narrow size distributions, and uniform shape. Also, two- and three-dimensional close-packed ordered arrays (superlattices) of these nanocrystals have been fabricated on half-micron length scales.
  • Catalytically active metals such as Pt, Pd, and Ag and non-catalytically active matals and alloys such as Au and Co x Au y have been prepared.
  • the present invention provides techniques for the synthesis of various metallic nanocrystal materials in which the resultant particles are characterized by the following properties: (1) they are soluble and resoluble in various organic media, including organic solutions containing dissolved polymers; (2) they are stable as powders or monodisperse (non-aggregated) colloids under ambient conditions for at least several days; (3) they are stable for months when stored under low temperature conditions as powders or monodisperse (non-aggregated) colloids in solution; (4) they can exist as monodisperse entities (when prepared as organic colloids) which can be readily separated into arbitrarily narrow size distributions via various chemical and chromatographic techniques; (5) they can be prepared in at least gram quantities; (6) they may consist of a host of metallic elements prepared as either pure metal particles or alloys, synthesized from the combination of a host of specific metal-containing inorganic compounds, phase transfer catalysts, surface passivants, and reducing agents; (7) they are readily dispersed into various matrices or onto various substrates (gels,
  • Particles that have been prepared and that meet the above criteria include Au, Ag, Pt, Pd, and Co/Au (alloy). Particle sizes range from 1 - 20 nm diameter.
  • a major advancement of the technology over existing prior art is the use of covalently-bound organic ligands, which form excellent kinetic and/or thermodynamically stable monolayers on the surfaces of the nanocrystals, as a route toward stabilizing these particles in solution. This enables chemically tailored solubility, monodispersity, and size control to the final metal nanocrystal product.
  • the ligands in general have a chemical component which interacts with the metal nanocrystal surface, and a chemical component which interacts with the surrounding solvent, polymer, matrix, etc. Both components can be modified within the limits of chemical compatibility.
  • the invention is not limited to simple single component metallic systems. Indeed, for some systems it is difficult to chemically stabilize a bare metal particle through the use of covalent organic ligands.
  • alloys of the metal may be made in which a second metal is included.
  • this second metal is characterized by a lower surface energy (so it coats the surface of the particle), and is itself readily stabilized by a certain organic ligand.
  • Co has magnetic properties which lend it to potential technological applications.
  • Such ligands are readily found for the Au system, and, furthermore, Au has a lower surface energy.
  • the organically functionalized metal and metal alloy nanoparticles of the present invention are prepared by providing a solution or dispersion of a metal precursor, providing a solution of an organic surface passivant, mixing the metal precursor solution or dispersion with the organic surface passivant solution, reacting the resulting mixture with a reducing agent to reduce the metal precursor to free metal while concomitantly binding the organic surface passivant to the resulting free metal surface to produce organically functionalized metal or metal alloy nanoparticles having a particle diameter of 10 - 20 ⁇ A.
  • an organic solution of a phase transfer agent is mixed with the metal percursor prior to mixing with the organic surface passivant.
  • An inorganic gold compound such as HAuCI 4 is dissolved in H 2 O to generate a solution containing AuCl 4 " as the active metal reagent.
  • AuCl 4 * is phase transferred from H 2 0 into an organic phase such as toluene using an excess of a phase transfer reagent or catalyst such as N(C 8 H 17 ) 4 Br.
  • a stoichiometric amount of an alkylthiol such as C 6 H 13 SH dissolved in an organic solvent such as toluene is added to the organic phase.
  • Excess reducing agent such as NaBH 4 is dissolved in H 2 O, added to the organic mixture with rapid stirring, and allowed to continue to stir for several hours.
  • the aqueous layer is removed and discarded.
  • the organic layer is passed through submicron filter paper (no material is removed, and all color passes through the paper).
  • the organically-functionalized metal nanocrystals are precipitated using an alcohol solution such as ethanol kept at low temperature.
  • the filtrate is washed with this same alcohol.
  • the particles are re-dissolved in an organic solvent such as toluene, re- precipitated, and re-washed.
  • the particles are finally re-dissolved in an organic solvent such as hexane or toluene.
  • Au particles with one phase transfer reagent and an alkylamine as the surface passivant can be prepared using an akylamine such as C 12 H 25 NH 2 or C 18 H 35 NH 2 as the surface passivant rather than an akylthiol.
  • Au particles with no phase transfer reagent and an alkylamine as the surface passivant can be prepared using an akylamine such as C 12 H 25 NH 2 or C lg H 35 NH 2 as the surface passivant rather than an akylthiol, and no phase transfer reagent.
  • akylamine such as C 12 H 25 NH 2 or C lg H 35 NH 2 as the surface passivant rather than an akylthiol
  • phase transfer reagent a small amount of insoluble black solid particulate material is generated during the synthesis. This precipitate is removed by filtration of the two-phase system with submicron filter paper. The precipitation of the organically-functionalized metal nanocrystals then proceeds in the same manner above.
  • Ag particles with one phase transfer reagent and an alkylthiol as the surface passivant can be prepared using an inorganic silver compound such as AgNO or AgCI0 4 H 2 O as the metal source, which, when dissolved in H 2 O, yields Ag + as the active metal reagent.
  • Pt particles with one phase transfer reagent and an alkylamine as the surface passivant can be prepared using an akylamine such as C 12 H 2S NH 2 or C lg H 35 NH 2 as the surface passivant and an inorganic platinum compound such as H 2 PtCl 3H 2 O as the metal source, which, when dissolved in H 2 O, yields PtCl 6 " as the active metal reagent.
  • Pd particles with one phase transfer reagent and an alkylamine as the surface passivant can be prepared using an akylamine such as C I2 H 25 NH 2 or C l g H 5 NH 2 as the surface passivant and an inorganic palladium compound such as Na 2 PdCl 6 4H 2 0 as the metal source, which, when dissolved in H 2 O, yields PdCl 6 ⁇ as the active metal reagent.
  • an akylamine such as C I2 H 25 NH 2 or C l g H 5 NH 2
  • an inorganic palladium compound such as Na 2 PdCl 6 4H 2 0 as the metal source
  • Co/Au alloy particles with two phase transfer reagents and an akylthiol as the surface passivant can be prepared as follows.
  • An inorganic cobalt compound (here CoCl 2 H 2 0) is dissolved in H 2 0 to generate a solution containing Co + as the active metal reagent.
  • Co +2 is phase transferred from H 2 O into an organic phase such as toluene using an excess of a phase transfer reagent or catalyst such as (C H 5 ) 4 BNa.
  • the aqueous layer is removed and the organic layer is washed with H 2 0.
  • An inorganic gold compound such as HAuCl 4 is dissolved in H 2 O to generate a solution containing AuCl 4 as the active metal reagent.
  • AuCl 4 is phase transferred from H 2 O into an organic phase such as toluene using an excess of a phase transfer reagent or catalyst such as N(C g H 17 ) 4 Br.
  • the aqueous layer is removed and the organic layer is washed with H 2 O.
  • the two organic solutions are combined to form a mixture of Co +2 and AuCl 4 .
  • a stoichiometric amount of an alkylthiol such as C ]2 H 25 SH dissolved in toluene is added to the organic mixture.
  • Excess reducing agent such as NaBH 4 is dissolved in H 2 0, added to the organic mixture with rapid stirring, and allowed to continue to stir for several hours.
  • the aqueous layer is removed and discarded.
  • the organic layer is passed through submicron filter paper (no material is removed, and all color passes through the filter paper).
  • the organically- functionalized alloy nanocrystals are precipitated using an alcohol solution such as ethanol kept at low temperature.
  • the filtrate is washed with this same alcohol.
  • the particles are re ⁇ dissolved in an organic solvent such as toluene, re-precipitated, and re-washed.
  • the particles are finally re-dissolved in an organic solvent such as hexane or toluene.
  • Solubilization of organically-functionalized nanocrvstals in aqueous media can be accomplished as follows.
  • the nanocrystals are first prepared according to one of the synthetic schemes described above.
  • a concentrated solution e.g., 6 mg/ml
  • an organic solvent such as hexane to yield an intensely-colored (e.g., purple brown, etc.) solution.
  • a separate solution consisting of a specific weight % of a soap or detergent molecule in aqueous media is prepared.
  • soap or detergent is general here and is taken to mean any molecule that has a polar (hydrophilic) ionic region and a nonpolar (hydrophobic) hydrocartion region (e.g., a fatty acid, an alkali metal alkane sulfonate salt, etc.).
  • a micelle is basically any water-soluble aggregate, spontaneously and reversibly formed from amphiphile molecules. These aggregates can adopt a variety of three-dimensional structures (e.g., spheres, disks, bilayers, etc.) in which the hydrophobic moieties are segregated from the solvent by self- aggregation. If the hydrophobic portion of the amphiphile is a hydrocarbon chain, the micelles will consist of a hydrocarbon core, with the polar groups at the surface serving to maintain solubility in water. A nonpolar substance is solubilized in the hydrophobic region of these micelle structures.
  • metal-doped matrices such as metal-doped polymer films.
  • Thin polymer films for exmaple containing a high weight percent of metal particles may provide a route to materials with a unique combination of mechanical, dielectric, optical, electric, and even magnetic properties.
  • narrow particle size distributions, coupled with uniform distribution of the particles throughout the polymer film is necessary to make these properties microscopically uniform throughout a macroscopic film.
  • Fabricating such a film would involve preparing polymer/solvent/particle solutions with relatively high and adjustable particle/polymer weight ratios and with the particles existing as monodisperse entities in the solution.
  • the polymer/particle thin film could then be prepared from the solution through various standard spin-coating or evaporation techniques.
  • Other suitable matrices include sol-gels, alumina, and glassy carbon.
  • a second example of a potential application of these materials deals with using silver particles in reprography.
  • reprographic processes which have stages that intimately depend on the nucleation and growth of small silver particles.
  • small silver particles form the amplification (latent image) center in conventional photographic processes.
  • This latent image center formed by the action of light on silver halide crystals, acquires catalytic properties that enable it to trigger the reduction of the entire silver halide crystal to metallic silver by the reducing agent of the developer.
  • uniform particle size distributions lead to uniform film quality, and small particle sizes lead to enhanced film resolution.
  • gold since gold is frequently used in small quantities as a sensitizer for photographic emulsions, the Au particles may be applicable here as well.
  • a third example of a potential application of these materials pertains to chemical catalysis.
  • the size and morphology of the particle is often of great concern as it determines catalytic reactivity and selectivity.
  • Organicaliy-functionalized nanometer-scale particles of catalytically-active metals have extremely high surface areas (a large number of catalytically active sites per particle) and unique size-dependent chemical behavior which enables their application as highly selective catalysts in a variety of homogeneous and heterogeneous catalytic processes from petroleum cracking to polymer synthesis.
  • the Pt, Pd, and Ag particles are applicable here.
  • nanocrystals as functional units in innovative micro and nanoelectronic devices. These applications are based on the idea that two- and three-dimensional close-packed ordered arrays (superlattices) of these nanocrystals will exhibit novel electronic properties dominated by single electron phenomena, due to the quantum confined electronic properties of the individual particles as well as their collective coherence effects.
  • the particles were finally either stored as a powder in the freezer or at room temperature, or they were re-dissolved in a preferred amount of an organic solvent (e.g., hexane, toluene, chloroform, etc.) to yield a solution with a concentration ranging from 1-30 mg/ml.
  • an organic solvent e.g., hexane, toluene, chloroform, etc.
  • XRD X-ray diffraction
  • UV/vis UV-visible spectroscopy
  • IR infrared spectroscopy
  • the particles were finally either stored as a powder in the freezer or at room temperature, or they were re-dissolved in a preferred amount of an organic solvent (e.g., hexane, toluene, chloroform, etc.) to yield a solution with a concentration ranging from 1-30 mg/ml.
  • an organic solvent e.g., hexane, toluene, chloroform, etc.
  • These solutions were either stored in the freezer or at room temperature.
  • the particles When stored as powders at room temperature, the particles exhibit a certain degree a metastability. That is, the particles are unstable with respect to particle aggregation and quickly lose their solubility over a matter of a few days.
  • XRD X-ray diffraction
  • UV/vis Ultraviolet-visible spectrscopy
  • IR infrared spectroscopy
  • Particle composition, size, and properties may be varied by means of the following changes: the variation of the metal precursor used, the variation of phase transfer reagents used or their omission from the synthetic procedure, the variation of one or more surface passivants used, the variation of the reducing agent used, or the variation of some of the reactant molar ratios, or any combination thereof.
  • XRD X-ray diffraction
  • UV/vis UV-visible spectroscopy
  • IR infrared spectroscopy
  • the corresponding Au:N molar ratio of the nanoparticles was 8.6:1, and the C:H and C:N ratios are those of neat dodecylamine, within experimental uncertainties;
  • DSC Differential scanning calorimetry
  • TGA Thermogravimetric analysis
  • the filtrate was clear and the particles were black.
  • the weight of residue on the filter paper was 41 mg. This residue was re-dissolved in 5 ml toluene, and the solution was sonnicated for 15 minutes and filtered. Then, the particles were precipitated again (using 200 ml of methanol) and filtered. The weight of the re-soluble, final residue was 20 mg.
  • the particles were finally either stored as a powder in the freezer or at room temperature, or they were re-dissolved in a preferred amount of an organic solvent (e.g., hexane, toluene, chloroform, etc.) to yield a solution with a concentration ranging from 1-30 rng/ml. These solutions were either stored in the freezer or at room temperature.
  • an organic solvent e.g., hexane, toluene, chloroform, etc.
  • the nanoparticles were characterized by the following materials characterization techniques: (a) X-ray diffraction (XRD): This characterization, performed on a powder of the particles, showed that the particles were crystalline with diffraction peaks like those of fee Au (except for the broadening at finite size). The main reflections were: (1 1 1) at 2 ⁇ « approx. 38.2°, (200) at 2 ⁇ * approx. 44.4°, (220) at 2 ⁇ * approx. 64.6°, (311) at 2 ⁇ « approx. 77.5°, (222) at 2 ⁇ « approx. 81.8°. Cobalt reflections were masked by those of gold.
  • XRD X-ray diffraction
  • the average domain size was determined to be 30 ⁇ 5 A;
  • UV/vis Ultraviolet/visible spectroscopy
  • IR Infrared spectroscopy
  • the peak positions, line shapes, and peak-to-peak distance of the Au 4f doublet are the standard measure of the gold oxidation state.
  • the binding energies for the Au 4f doublet are 83.5(3) and 87.2(3) eV (peak-to-peak distance of 3.7 eV). These measurements are consistent with the Au oxidation state.
  • EXAMPLE 5 (a) lOg of DDAB was dissolved in 104 ml of toluene and sonnicated for 10 minutes; (b) 119 mg of CoCl 2 6H 2 O was dissolved in the DDAS/toluene solution and sonnicated for 5 hours to dissolve all ofthe Co salt in the toluene.
  • the CoCl 2 /DDAB/toluene solution had a typical cobalt blue color;
  • step (f) A solution of 283 mg NaBH 4 (reducing agent) in 3 ml H 2 O was added to the toluene phase resulting from step (a), and the reaction was allowed to proceed for 5 hours while stirring. After 5 hours of reaction time, the toluene phase was diluted with 200 ml a toluene and washed with 500 ml of H 2 O. A viscous, white DDAB/water emulsion was formed and allowed to precipitate out of the thiol-capped Au/Co particles/toluene solution. The black particle/toluene solution was then separated and rotary evaporated to a concentrated 10 ml solution. 500 ml of methanol was then added to precipitate the particles.
  • the particles/toluene/methanol solution was sonnicated for 30 min and then filtered through a 0.2 ⁇ m nylon filter paper. The filtrate was clear and the particles were black. The weight of residdue on the filter paper was 69 mg.
  • the residue was re-dissolved in 100 ml of toluene by sonnication for 15 minutes and the solution was then filtered. 31 mg of the residue were not dissolved.
  • the toluene solution was rotary evaporated down to 5 ml and the particles were precipitated again by addition of 300 ml of methanol and 15 minutes sonnication. After filtering, the weight of the resoluble, final residue was 21 mg.
  • the particles were finally either stored as a powder in the freezer or at room temperature, or they were re-dissolved in a preferred amount of an organic solvent (e.g., hexane, toluene, chloroform, etc.) to yield solution with a concentration ranging from 1-30 mg/ml.
  • an organic solvent e.g., hexane, toluene, chloroform, etc.
  • UV/vis UV-visible spectroscopy
  • IR Infrared spectroscopy
  • the peak positions, line shapes, and peak-to-peak distance of the Au 4f doublet are the standard measure of the gold oxidation state.
  • the binding energies for the Au 4f doublet are 83.5(3) and 87.2(3) eV (peak-to-peak distance of 3.7 eV). These measurements are consistent with the Au° oxidation state. Also observed were the signals for cobalt (3s at 57 ev; 2p 3/2 and 2p 1 2 at 779 ev and 794 ev, respectively) and sulfur (2p 3 2 and 2p ] 2 at 163 ev and 164 ev, respectively).
  • a separate solution consisting of 20 g of sodium dodecylsulfate (SDS) dissolved in 300 ml of deionized H 2 O was prepared. This yielded a 6.25 weight percent solution of SDS in H 2 O;
  • 1 ml of the 6 mg/ml Ag particle/hexane solution was added to 20 ml of the 6.25 weight percent solution of SDS in H 2 O resulting in a two-layer mixture (organic layer on top and aqueous layer on the bottom). This mixture was stirred vigorously for a period of 6 hours.
  • XRD X-ray diffraction
  • UV/vis Ultraviolet-viswible spectroscopy
  • IR infrared spectroscopy
  • the particles were finally either stored as a powder in the freezer or at room temperature, or they were re-dissolved in a preferred amount of an organic solvent (e.g., hexane, chloroform, etc.) to yield a solution with a concentration ranting from 1-30 mg/ml.
  • an organic solvent e.g., hexane, chloroform, etc.
  • XRD X-ray diffraction
  • the film thickness was measured by profilometry to be 20 ⁇ m.
  • the dielectric measurements of the metal nanocrystal-doped polymer thin film yielded unique dielectric values as copared to the 'pure' or un-doped polymer.
  • the dielectric characteristics for the metal nanocrystal-doped polymer thin film were: a) dielectric constant - 15; b) breadown voltate - 1.2 kv/mm. As can be seen, the dielectric constant of the doped film increases by about a factor of 10.
  • organically-functionalized Ag nanocrystal single or multilayer films include, but are not limited to: organically-functionalized Ag nanocrystal single or multilayer films; organically-functionalized Au nanocrystal single or multilayer films; organically-functionalized Pt nanocrystal single or multilayer films; organically-functionalized Pd nanocrystal single or multilayer films; organically-functionalized Au/Co nanocrystal single or multilayer films; any combination therein of the organically-functionalized metal nanocrystals (e.g.. a multilayer structure with an Ag/Au Ag nanocrystal configuration or Ag/Pt/Au nanocrystal configuration. etc.); any variable stoichiometric combination of the organically-functionalized metal nanocrystals (e.g., a 20% Ag / 20% Au / 10%) Pt nanocyrstal / 50% polymer configuration).
  • organically-functionalized Ag nanocrystal single or multilayer films include, but are not limited to: organically-functionalized Ag nanocrystal
  • dodecylamine-capped Pt nanocrystals were prepared and characterized according to the procedure of Example 7.
  • the particles used here for catalysis had an average domain size of approximately 25 A;
  • the pressure of H 2(g) remains constant at the initial value of 662 torr over the course of 250 minutes. This indicates that no reaction took place (i.e., no conversion of 1-hexene to hexane occurred).
  • an aliquot of a hexane solution of dodecylamine-functionalized Pt nanocrystals (avg. diameter « 25 A) was initially added, the pressure of H 2(g) initially decreases in a logarithmic fashion and then reaches some steady-state value (the conversion of 1-hexene to hexane is presumably complete within about 75 minutes or the catalyst is used up).
  • Any 10- 100 A Pt and Pd nanocrystals functionalized with amine surface groups that will bind to the particles such as dodecylamine, octadecylamine, or pyridine can be used to produce similar results.

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EP96945950A 1995-12-28 1996-12-27 Organisch funktionalisierte monodisperse metallnanokristalle Withdrawn EP0914244A1 (de)

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WO1997024224A1 (en) 1997-07-10
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CA2241183A1 (en) 1997-07-10
EP0914244A4 (de) 1999-05-19

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