WO2012105631A1 - 貴金属-酸化物接合ナノ粒子、及び、その高純度製造方法 - Google Patents
貴金属-酸化物接合ナノ粒子、及び、その高純度製造方法 Download PDFInfo
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- WO2012105631A1 WO2012105631A1 PCT/JP2012/052329 JP2012052329W WO2012105631A1 WO 2012105631 A1 WO2012105631 A1 WO 2012105631A1 JP 2012052329 W JP2012052329 W JP 2012052329W WO 2012105631 A1 WO2012105631 A1 WO 2012105631A1
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- nanoparticles
- base metal
- noble metal
- alloy
- composite nanoparticles
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Definitions
- the present invention is expected to be applied to a catalyst or the like, and is a bonded nanoparticle in which one noble metal nanoparticle and one oxide nanoparticle are bonded (hereinafter, “bonded nanoparticle” is sometimes referred to as “composite nanoparticle”). ) And its high-purity production method.
- junctions between p-type and n-type semiconductors produce properties such as rectification performance, photovoltaic effect, and electroluminescence, and are widely applied to devices such as diodes and transistors.
- the heterojunction occupies a very important position as one of physical property control, such as a tunnel magnetoresistive effect and a giant magnetoresistive effect which are manifested by the junction structure of the magnetic thin film.
- Non-Patent Documents (1) to (5) and Patent Documents (1) to (4) gold-oxide composite nanoparticles by liquid phase synthesis are used.
- Patent Document (5) noble metal and sulfide are mixed.
- Composite nanoparticles are described.
- Patent Document (3) describes a mixture of nanoparticles and a precursor containing a hydrophobic outer coat as a method for producing dumbbell-shaped or flower-shaped nanoparticles that can be applied to biomedical medicine, nanodevices, and the like.
- the first part is made of any one of PbS, CdSe, CdS, ZnS, Au, Ag, Pd, and Pt
- the second part is made of Au, Ag, Pd, Pt, Fe, Co, Ni, etc.
- Patent Document (4) as a composite catalyst used in an oxygen electrode of a fuel cell, one noble metal nanoparticle (average particle size less than 10 nm) epitaxially bonded to one ferrite particle (average particle size is 5 to 50 nm) ) And flower-shaped composite nanoparticles composed of two or more noble metal nanoparticles that are epitaxially bonded to one ferrite particle, with the addition of a metal oxide precursor and noble metal nanoparticles.
- a mixed solution of an organic solvent and a surfactant is heated and refluxed to precipitate composite nanoparticles, and the ferrite particles are represented by the chemical formula A 2+ B 3+ 2 O 4 (where A 2+ is , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Mg 2+ , Zn 2+ and Cd 2+ , and B 3+ is Fe 3 +, ions der selected from the group consisting of Cr 3+ and Mn 3+ Ferrite comprises at least a), the noble metal nanoparticles are those containing at least one element selected from the group consisting of at least Pt, Pd and Ag are described. However, as an example, only Pt—Fe 3 O 4 is described.
- Patent Document (5) describes anisotropically phase-separated acorn-shaped bimetallic nanoparticles produced by polyol reduction of two metal salts at high temperature in the presence of a thiol compound, These metals are Fe, Co, Ni, or Cu, and the other metal is Pd, Pt, Au, or Ag, and those that are expected to be used in the fields of magnetic chemistry and catalytic chemistry are described. However, as examples, only binary nanoparticles composed of Co sulfide and Pd sulfide are described. Nanoparticles containing pure noble metal parts, nanoparticles containing base metal oxides and their production No method is described at all.
- Non-patent documents (1) to (5) describe dumbbell-shaped Au—Fe 3 O 4 , Au—ZnO, and Au—MnO nanoparticles by liquid phase synthesis, but other than Fe, Zn, and Mn. No mention is made of using non-metallic elements.
- Patent Documents (1) to (4) and Non-Patent Documents (1) to (3) the use of Fe, Co, Ni, Mn, Cu, Mg, Zn, Cd, and Cr as oxide elements
- Sn, Ti, Al, Zr, Ce, Y, La, Si, Ge is not described at all, and the oxidation mentioned in the use possibility is only described.
- the compound used in the case of adopting the element is not disclosed, so it cannot be said that the element is described to the extent that can be easily carried out by those skilled in the art.
- the gold-oxide composite nanoparticles produced by such liquid phase synthesis inevitably contain various impurities such as ions and organic substances, when used as a catalyst or the like, cleaning of poisonous ions is performed.
- a removal or cleaning process by burning the nanoparticle-protected organic material is indispensable.
- these cleaning steps can always be performed stably, completely and reproducibly at the atomic level.
- dangerous materials such as metal carbonyl are used as raw materials and that various oxide elements other than those used above cannot be easily selected, the gold- There are many problems to be solved in the production of oxide composite nanoparticles.
- noble metal-base metal nanoparticles are generated in an inert gas using an arc melting method, and then the nanoparticle sample is oxidized.
- the oxidation treatment temperature and time are a slow oxidation treatment at room temperature or 200 to 600 ° C., 2 minutes to 4 hours, and the like.
- the alloy nanoparticles are already aggregated, the obtained substance is a precious metal deposited irregularly and non-uniformly on the base metal oxide aggregate. Therefore, by this method, composite nanoparticles in which one noble metal nanoparticle is bonded to the surface of one base metal oxide nanoparticle cannot be obtained in an independently dispersed state.
- noble metal-oxide composite nanoparticles are generated by evaporating a raw material alloy in an inert gas containing oxygen.
- this method of the noble metal atoms and base metal atoms evaporated by heating the raw material alloy, only the base metal atoms react with oxygen, and an association of base metal atoms and oxygen is generated in advance. Thereafter, a large number of noble metal atoms and base metal atoms-oxygen aggregates are combined in the gas phase to grow into noble metal-base metal oxide composite nanoparticles. It has been reported that the particles generated in such a process are in a form in which a plurality of noble metal nanoparticles are adhered on the base metal oxide particles.
- the ultrafine particles collected by the filter are subjected to an oxidation heat treatment in a state of being bonded or aggregated with each other, and are not subjected to an oxidation heat treatment in a floating state in which each ultrafine particle is dispersed independently. Therefore, it is only possible to obtain composite ultrafine particles in which a large number of fine particles composed of noble metals such as Au and Pd and / or their compounds are precipitated and dispersed in ultrafine particles composed of metal oxides such as Ti and Al. Therefore, even by the production method, composite nanoparticles in which one noble metal nanoparticle is bonded to the surface of one base metal oxide nanoparticle cannot be obtained in an independently dispersed state.
- Non-Patent Document (6) the present inventors produced Cu-46 at.% Au alloy nanoparticles in helium gas in the same process as the gas evaporation method of the embodiment of the present invention. After that, high-temperature oxidation treatment was performed in the gas phase to produce composite nanoparticles composed of a metal portion and a copper oxide portion. However, because the content of Au in the alloy nanoparticles is too high, the alloy nanoparticles cannot be completely oxidized, and the metal part of the composite nanoparticles is in the state of an Au-17at.% Cu alloy. , Separation of Au alone could not be realized.
- the catalyst generation methods such as coprecipitation method and precipitation method have the advantage that a noble metal-supported oxide catalyst can be obtained very easily, but at the time of high-temperature firing to generate a heterojunction between noble metal and oxide.
- There are problems such as coarsening of gold particles and residual poisonous substances such as chlorine ions.
- the hetero interface between the gold nanoparticle and the oxide is generally generated at various atomic planes, it is impossible to uniformly control the hetero interface for each nanoparticle.
- the present invention is a novel composite nanoparticle in which one high-purity noble metal nanoparticle and one oxide nanoparticle are joined, and there is no poisonous substance remaining, and a heterointerface between nanoscale phases having completely different physical properties.
- the present invention provides a conventional liquid phase synthesis method by subjecting alloy nanoparticles of a noble metal such as gold or platinum and a base metal that is easily oxidized at a high temperature to thermal oxidation at a high temperature in a state of floating in the gas phase.
- a noble metal such as gold or platinum
- a base metal that is easily oxidized at a high temperature to thermal oxidation at a high temperature in a state of floating in the gas phase.
- composite nanoparticles (M-A x O y ) in which one high-purity noble metal particle (M) was bonded to the surface of a specific base metal oxide (A x O y ) which could not be obtained by
- the generation of the composite nanoparticles is based on the knowledge that there is no risk of inevitable contamination of impurities, and has the following characteristics.
- the base metal component in the floating alloy (AM) nanoparticles by heating the alloy (AM) nanoparticles and bringing them into contact with the introduced oxidizing gas in the middle of transporting with an inert gas Oxidizing (A) and phase-separating the oxidized base metal component (A x O y ) with the noble metal component (M), one noble metal particle (M) on the surface of the particulate base metal oxide (A x O y ) method of producing composite nanoparticles (M-a x O y) but to obtain a bonded composite nanoparticles (M-a x O y) .
- ( AM ) The method for producing composite nanoparticles (MA x O y ) according to any one of (1) to (3), wherein the nanoparticles are heated during heating in an inert gas.
- (5) The above-mentioned (1), characterized in that any one of a gas evaporation method, a laser ablation method, a sputtering method, an arc plasma method, and an atmospheric pressure plasma method is used as a method for producing alloy (AM) nanoparticles.
- Base metal oxide (A x O y ) of the base metal (A) is Cu, Sn, Ti, V, Cr, Mn, Co, Fe, Ni, Zn, Al, Y, Zr, Mo, In, It is at least one selected from Mg, La, Ce, Nd, Sm, Eu, Gd, Si, Ge, Pb, Bi, and the noble metal (M) is from Au, Pt, Pd, Rh, Ag, Ru, Ir
- the method for producing composite nanoparticles (MA x O y ) according to any one of the above (1) to (5), which is one or more selected.
- Alloy (AM) nanoparticles containing 0.1-30 at.% Noble metal (M), the balance consisting of base metal (A) and inevitable impurities, and having a particle size of 1-200 nm are generated in an inert gas.
- the base metal component in the floating alloy (AM) nanoparticles by heating the alloy (AM) nanoparticles and bringing them into contact with the introduced oxidizing gas in the middle of transporting with an inert gas
- One region of particulate base metal oxide (A x O y ) by oxidizing (A) and phase-separating the oxidized base metal component (A x O y ) with the noble metal component (M), and particulate noble metal the method of manufacturing the composite nanoparticles composed of a single region of the (M) (M-a x O y) the obtained composite nanoparticles (M-a x O y) , a base metal (a) is, Cu , Sn, Al, Ni, Co, Ti, Zr, In, Si,
- Base metal (A) of the base metal oxide (A x O y ) component is Cu, Sn, Ti, V, Cr, Mn, Co, Ni, Zn, Al, Y, Zr, Mo, In, Mg, La, Ce.
- composite nanoparticles (MA x O y ).
- composite nanoparticles (M-A x O y) is Au-Cu 2 O or composite nanoparticles according to the above (8), a Au-SnO 2 (M-A x O y).
- the base metal (A) of the base metal oxide (A x O y ) component is at least one selected from Cu, Sn, Al, Ni, Co, Ti, Zr, In, Si, La, Ce, Eu,
- the noble metal (M) is at least one selected from Au, Pt, Pd, Rh, and Ag.
- the base metal (A) of the base metal oxide (A x O y ) component is at least one selected from Cu, Sn, Al,
- the noble metal (M) is at least one selected from Au and Pt.
- the production method of the present invention has a remarkable advantage that particles obtained by heterojunction of noble metal nanoparticles represented by gold on various oxide nanoparticles can be easily generated in a gas phase.
- the product is obtained in a very high purity state, and there is no contamination of impurities such as chlorine ions and organic substances. Therefore, these are washed and burned off.
- Non-patent documents (1) to (3) and patent documents (1 ) To (4) do not require any essential steps. The point that these post-processes are unnecessary is very important especially for stable production of a catalyst sample.
- the alloy nanoparticles are completely oxidized by adjusting the precious metal content in the alloy nanoparticles so as not to become too high. As a result, separation of only precious metals can be realized.
- the noble metal-oxide bonded nanoparticles (MA x O y ) of the present invention have a particle diameter of 1 on the surface of base metal oxide particles (A x O y ) having a particle diameter of 1 to 200 nm (preferably 1 to 100 nm).
- noble metal particle (M) with a purity of ⁇ 100 nm (preferably 1 to 10 nm) is bonded at the atomic level, and is derived from the heterointerface between nanoscale phases with completely different physical properties. It is expected to exhibit various physical and chemical properties and functions that are reactive, electronic, magnetic, and optical.
- the noble metal-oxide bonded nanoparticles (MA-O x O y ) of the present invention are effective when used as, for example, an oxidation catalyst, but by selecting a noble metal and an oxide, a very wide range of industrial Application can be expected.
- FIG. 1 is a drawing showing a process for producing noble metal-oxide bonded nanoparticles of the present invention.
- FIG. 1 shows that the oxidizing gas is introduced between G and H, it can be introduced at any internal position in H instead.
- (a) is an electron diffraction pattern of a sample in which Au—Cu 2 O composite nanoparticles are diluted on an amorphous carbon film.
- (b) is a drawing showing the electron diffraction pattern of (a) converted into an intensity distribution with respect to the wave vector s.
- the manufacturing method of the composite nanoparticle of this invention is shown in FIG.
- the method for producing composite nanoparticles of the present invention comprises 0.1 to 30 at.% Of noble metal (M), the remainder is composed of base metal (A) and inevitable impurities, and the particle diameter is 1 to 200 nm (preferably 1 to 100 nm).
- the alloy (AM) nanoparticles are heated and brought into contact with the introduced oxidizing gas.
- noble metals or base metals as soluble compounds [eg, HAuCl 4 , H 2 PtCl 6 , Fe (CO) 5 ], and alloy (AM) nanoparticles are used in an inert gas.
- Any precious metal or base metal that can be generated can be employed. Therefore, there are no restrictions on the types of precious metals and base metals due to compound restrictions such as liquid phase synthesis, so a wide range of precious metals and base metals other than Au, Pt, Cu, Sn, and Al used in the examples described later should be used. Can do.
- the composite nanoparticle production apparatus used in the implementation of this production method includes a raw material noble metal-base metal alloy nanoparticle production apparatus (G; hereinafter referred to as “alloy nanoparticle production apparatus”), a high-temperature thermal oxidation treatment apparatus (H ), A collector (C), and an exhaust pump (P) connected in series.
- the exhaust pump (P) is an inert gas introduced into the alloy nanoparticle generator (G), and generates alloy nanoparticles.
- the exhaust pump (P) is an inert gas introduced into the alloy nanoparticle generator (G), and generates alloy nanoparticles.
- the oxidizing gas introduced between the apparatus (G) and the high-temperature thermal oxidation processor (H) or the high-temperature part of the high-temperature thermal oxidation processor Used for.
- the base metal A which comprises a raw material is not limited, For example, Cu, Sn, Ti, V, Cr, Mn, Co, Fe, Ni, Zn, Al, Y, Zr, Mo, In, Mg, La, Ce, One or more selected from Nd, Sm, Eu, Gd, Si, Ge, Pb, and Bi can be used. Preferably, it can be at least one selected from Cu, Sn, Al, Ni, Co, Ti, Zr, In, Si, La, Ce, and Eu.
- the noble metal M which comprises a raw material is not limited, For example, it can be set as 1 or more types chosen from Au, Pt, Pd, Rh, Ag, Ru, and Ir.
- the base metal A-noble metal M alloy as a raw material has a noble metal M content of the AM alloy nanoparticles of about 0.1 to 30 at.% (More preferably 1 to 15 at.%, Still more preferably 2 to 10 at. %), The content of the noble metal M is preferably determined in consideration of the vapor pressure of the base metal A and the noble metal M.
- the noble metal content of the base metal A-noble metal M alloy as a raw material can be in the range of 1 to 60 at.%, For example, depending on the type of base metal element.
- the amount is 30 to 60 at.% (Preferably 35 to 55 at.%, More preferably 40 to 50 at.%).
- the precious metal content of the raw base metal A-precious metal M alloy is about 0.1-30 at.% (More preferably 1-15 at.%, (2-10 at.%) Is preferable.
- AM alloy nanoparticles of base metal A and precious metal M as raw materials in the gas phase, it is possible to operate in a pressure range from low pressure (for example, about 0.1 to 10 kPa) to atmospheric pressure (101.3 kPa).
- a generator can be used.
- a gas evaporation method, a laser ablation method, a sputtering method, an arc plasma method, an atmospheric pressure plasma method, and the like, and various other nanoparticle generation methods in a gas phase can be appropriately used.
- noble metal-base metal alloy nanoparticles of about 1 to 200 nm (preferably 1 to 100 nm, more preferably 2 to 80 nm, and further preferably 5 to 60 nm) are obtained using an inert gas such as helium, argon, or nitrogen. Generate.
- the particle diameter of the alloy nanoparticles generally increases as the temperature of the evaporation source (energy input to the evaporation source) increases or as the pressure of the inert gas increases and the flow rate decreases. It is possible to adjust.
- noble metal-base metal alloy nanoparticles When producing noble metal-base metal alloy nanoparticles, if nano-sized secondary particles composed of aggregates of primary particles of the alloy are produced, before the thermal oxidation treatment is performed in the high-temperature thermal oxidation treatment device (H), for example, preliminary By a heating mechanism or the like, it is heated and sintered in an inert atmosphere to form isolated dispersed particles.
- H high-temperature thermal oxidation treatment device
- the produced alloy nanoparticles are mixed with the oxidizing gas while being transported in the gas phase by an inert gas or in a high-temperature thermal oxidation treatment device.
- an inert gas oxygen gas alone or a mixture of air, oxygen gas and inert gas can be used.
- the oxidizing gas is introduced before the high temperature thermal oxidation processor, the alloy nanoparticles are partially oxidized together with the mixed gas of the inert gas and the oxidizing gas, and then flowed into the high temperature thermal oxidation processor. Only the base metal elements constituting the alloy nanoparticles are completely oxidized by the oxygen gas in the mixed gas heated to a high temperature.
- the alloy nanoparticles are introduced into the high-temperature thermal oxidation processor together with the inert gas and heated to a high temperature (high-temperature solid or molten In this state, only the base metal elements are rapidly and completely oxidized by exposure to high-temperature oxygen.
- the oxidation rate and the degree of evaporation of the base metal and the noble metal due to the oxidation heat change depending on the supply position of the oxidizing gas. In any case, the noble metal and the base metal oxide are in a nanoscale phase during the heating.
- base metal oxide (a x O y) surface noble metal particles (M) composite nanoparticles in which one is joined (M-a x O y) is produced.
- a uniform hetero interface may be generated for each particle by a high-temperature heat treatment performed simultaneously.
- the alloy nanoparticles in the high-temperature thermal oxidation processor may be heated indirectly by a mixed gas heated to a high temperature using a tubular electric furnace with a quartz tube as a core tube, It may be heated directly using means such as wave heating.
- High-temperature thermal oxidation treatment depends on the type of precious metal and base metal, but in general, the temperature should be 400 ° C or higher (preferably 500 to 1200 ° C, more preferably 600 to 1100 ° C), and the processing time should be within 10 seconds. Can do. When the processing temperature is increased, the processing time can be shortened. In the high-temperature thermal oxidation processor, a heating region along the conveyance path of the alloy nanoparticles is set so that the alloy nanoparticles are heated during such a processing time.
- the noble metal-base metal oxide composite nanoparticles flowing out of the high-temperature thermal oxidation processor are cooled to about room temperature by natural cooling or appropriate cooling means, and then collected in the collector.
- a collection method a dry method or a wet method used for aerosol collection can be appropriately used.
- the composition of the noble metal M is about 0.1 to 30 at.% (More preferably 1 to 15 at. %, More preferably 2 to 10 at.%), And the oxygen concentration of the mixed gas is preferably 10% or more.
- the AM alloy nanoparticles have as little impurity content as possible. Impurities derived from these impurities and the like may be contained. It is desirable to select the raw materials so that the impurity content is in a range that does not significantly impair the intended function (for example, less than 0.01 at.%, Preferably less than 0.001 at.%).
- Noble metal of the present invention - base metal oxide composite nanoparticles are continuously produced in a very clean state by the above processes, base metal oxides of particle size 1 ⁇ 200 nm (preferably 1 ⁇ 100nm) (A x O y) the particle size 1 ⁇ 100 nm (preferably on the surface of a noble metal particles (M) 1 piece is formed by joining the composite nanoparticles of 1 ⁇ 10nm) (M-a x O y), the base metal oxide
- the base metal (A) of the (A x O y ) component is Cu, Sn, Ti, V, Cr, Mn, Co, Ni, Zn, Al, Y, Zr, Mo, In, Mg, La, Ce, Nd, One or more selected from Sm, Eu, Gd, Si, Ge, Pb, Bi (except when the base metal oxide is ZnO, MnO), and the noble metal (M) is Au, Pt, Pd, One or more selected from Rh, Ag, Ru and Ir.
- This composite nanoparticle is composed of one region of base metal oxide (A x O y ) having a size of 1 to 200 nm and one region of noble metal (M) having a size of 1 to 100 nm. It can be said that.
- the particle diameter of the base metal oxide is 1 to 200 nm, preferably 1 to 100 nm, more preferably 2 to 50 nm, and further preferably 5 to 30 nm.
- the particle diameter of the noble metal particles is 1 to 100 nm, preferably 1 to 10 nm, More preferably, it is 1 to 8 nm, and still more preferably 1 to 5 nm.
- the particle size of the base metal oxide is affected not only by the particle size of the noble metal-base metal alloy nanoparticles, but also by the evaporation of the base metal due to the oxidation heat in the high temperature thermal oxidation treatment.
- the particle diameter of the base metal oxide can also be adjusted by adjusting the position where the oxidizing gas is introduced.
- the average value of the maximum diameter and the minimum diameter passing through the center of gravity of a particle image obtained by TEM (Transmission Electron Microscope) is defined as “particle diameter”.
- the size of the base metal oxide or noble metal region is regarded as a particle, and the average value of the maximum diameter and the minimum diameter passing through the center of gravity of the image is defined as the “size” of the region.
- the noble metal (M) of the composite nanoparticles (MA-O x O y ) produced according to the present invention may be one kind of noble metal or a mixture of plural kinds of noble metals.
- the purity of the precious metal (M) is about the precious metal raw material (usually about 99.99 to 99.999%) or more (for example, by passing through the phase separation process from the alloy nanoparticle generation process and the base metal oxide component (A x O y )) (for example, 99.9999% or more).
- Example 1 Production of Au-Cu 2 O composite nanoparticles and measurement of CO oxidation catalytic activity
- a generator by gas evaporation method was used as a source of alloy nanoparticles.
- Helium was introduced into the apparatus at an inflow rate of 0.4 L / min, and the pressure in the apparatus was maintained at a reduced pressure of 2 kPa by an oil rotary pump.
- a Cu-46 at.% Au ingot was placed in a carbon-pBN (Pyrolytic Boron Nitride) double crucible and heated at 1200 ° C. by high frequency heating. From the above experimental conditions, Cu-4at.% Au alloy nanoparticles were formed in helium.
- the reason why the Au content of the nanoparticles was decreased compared to the raw material ingot was that the vapor pressure of Cu was higher than the vapor pressure of Au.
- the produced alloy nanoparticles were transported into a quartz tube heated to 1100 ° C. together with oxygen gas with an inflow rate of 0.2 L / min added to helium gas and subjected to high temperature oxidation treatment. Thermal oxidation treatment time is about 0.1 seconds.
- Au-Cu 2 O composite nanoparticles produced after the oxidation treatment were diluted and spontaneously deposited on the amorphous carbon film placed in the collector, and became a sample for electron microscope observation. Samples for measuring catalytic activity could be collected with silica nanopowder (Sigma-Aldrich, 637238) as buffer particles.
- FIG. 2 shows a TEM (Transmission Electron Microscope) photograph of Au—Cu 2 O composite nanoparticles having an average particle diameter of 9.8 ⁇ 4.6 nm. It can be seen that there are minute portions of dark contrast in some of all particles.
- FIG. 3A shows the electron diffraction pattern of the sample
- FIG. 3B shows the electron diffraction pattern converted into an intensity distribution with respect to the wave vector s. The clear peaks appearing in FIG. 3B are all diffractions due to the Cu 2 O plane index. Although very weak, a peak (arrow) due to Au could be confirmed.
- the lattice constants of Cu 2 O and Au were found to be 0.4271 ⁇ 0.0004 nm and 0.4070 ⁇ 0.0034 nm, respectively, and within the error range, Cu 2 O (document value: 0.42696 nm) and Au (document value) : 0.4079 nm). From this, it was confirmed that the high-contrast minute portion of the particle in FIG. 2 is Au, and the other large portion is Cu 2 O.
- the Au: Cu molar composition ratio of the composite nanoparticles was 5:95 according to the result of ICP (Inductively Coupled Plasma) analysis, which was almost the same as the molar composition ratio of the alloy nanoparticles before oxidation.
- FIGS. 4A and 4B are high-resolution TEM photographs of 17 nm Au—Cu 2 O composite nanoparticles.
- a clear lattice image is observed in the Cu 2 O part, and when the crystallographic orientation is determined from the relative angle between the lattice fringe spacing and the different lattice fringes, (a) is ⁇ 100> and (b) is ⁇ 110. Matches>.
- a clear lattice image can be confirmed in the Au portion as well, and its crystallographic orientation is completely coincident with Cu 2 O. Since the lattice stripes are completely connected between the two phases, the two phases are heteroepitaxial junctions.
- 4 (c) and 4 (d) are high-resolution TEM photographs of 14 nm and 7 nm Au—Cu 2 O composite nanoparticles. It can be seen that even in these particles, both phases are very well heterojunctioned. Common to all particles, half of the Au portion is buried in Cu 2 O. Under the above experimental conditions, when particles were generated by changing the heat treatment temperature, a structure in which Au was separated at a temperature of 400 ° C. or higher was obtained, and was not obtained at 300 ° C. or lower.
- a sample for measuring catalytic activity was prepared by mixing Au—Cu 2 O composite nanoparticles and silica powder.
- the total amount of silica powder and Au—Cu 2 O composite nanoparticles used for the measurement was 81 mg, and the content of Au—Cu 2 O composite nanoparticles was 0.65 wt.%.
- the catalytic activity for CO oxidation reaction was measured using a fixed bed flow reactor. CO (1%) + O 2 (20%) + He mixed gas was allowed to flow at a flow rate of 0.1 L / min. The heating rate was set to 1 ° C / min.
- FIG. 5 shows the results of temperature dependence of the conversion rate of carbon monoxide to carbon dioxide. The conversion rate rapidly increased above about 200 ° C, and T 50% was 215 ° C.
- reaction rate per unit weight of Au-Cu 2 O composite nanoparticles excluding silica was calculated, and compared with the activity of the previously reported catalyst from the Arrhenius plot, the alumina-supported gold prepared by the liquid phase method (precipitation precipitation method) It was found that the catalyst performance was equivalent to that of a catalyst. This is because, in the process of the present invention, the individual particles are subjected to heat treatment at a high temperature, so that Au and Cu 2 O form a strong hetero interface and are joined as shown in FIG.
- Example 2 Formation of Au-SnO 2 composite nanoparticles and measurement of CO oxidation catalytic activity
- Raw material Sn-5at.% Au alloy nanoparticles were obtained in helium gas by heating a Sn-50at.% Au ingot at 1180 ° C. by the same gas evaporation method as in Example 1.
- Au-SnO 2 composite nanoparticles were obtained by high-temperature thermal oxidation of the alloy nanoparticles at 700 ° C. for about 0.1 seconds in the gas phase.
- the other experimental conditions are almost the same as in Example 1.
- FIG. 6 shows a TEM photograph of the Au—SnO 2 composite nanoparticles. Analysis of the electron diffraction pattern confirmed that the thin contrast portion was SnO 2 phase.
- Example 2 In the same manner as in Example 1, the sample for catalytic activity measurement was obtained by collecting together with silica powder. The total amount of silica powder and Au—SnO 2 composite nanoparticles (content: 0.64 wt.%) Used for the measurement was 50 mg. Under the same conditions as in Example 1, the temperature dependence of the conversion rate of carbon monoxide to carbon dioxide was measured. FIG. 7 shows the result, and it can be seen that the Au—SnO 2 composite nanoparticles also show the oxidation catalytic ability of carbon monoxide. The conversion rate rapidly increased above about 300 ° C, and T 50% was 345 ° C.
- Example 3 Production of Au-Al 2 O 3 composite nanoparticles
- a generator by laser ablation was used as an alloy nanoparticle generation source.
- Helium gas was introduced into the apparatus at an inflow rate of 0.5 L / min, and the pressure in the apparatus was maintained at a reduced pressure of 1.6 kPa by an oil rotary pump.
- the second harmonic of Nd: YAG laser (wavelength: 532nm, output: 90mJ / pulse, repetition frequency: 10Hz) is focused on the surface. Irradiation caused the target surface to evaporate instantaneously, and aggregates of nanoparticles of the alloy were generated in helium gas.
- the resulting alloy nanoparticle aggregates were moved on a helium gas stream, sintered with a preheating mechanism and converted into isolated dispersed particles, and then heated to 900 ° C. with oxygen gas at an inflow rate of 0.25 L / min. It was transported into a quartz tube and subjected to high temperature oxidation treatment. The thermal oxidation treatment time is about 0.01 seconds.
- Au—Al 2 O 3 composite nanoparticles produced after the oxidation treatment were diluted and spontaneously deposited on the amorphous carbon film placed in the collector, and used as a sample for electron microscope observation.
- FIG. 8 shows a TEM photograph of Au—Al 2 O 3 composite nanoparticles. As shown in the photograph, each particle shows a shape in which a small portion with high contrast and a large portion with low contrast are joined. Analysis of the electron diffraction pattern revealed that the oxide of Al constituting the particles was a ⁇ -Al 2 O 3 phase. Therefore, the dark contrast portion is Au, and the thin contrast portion is ⁇ -Al 2 O 3 .
- Example 4 Production of Pt-Cu 2 O composite nanoparticles
- Example 4 Production of Pt-Cu 2 O composite nanoparticles
- each particle shows a shape in which a small portion with high contrast and a large portion with low contrast are joined.
- Analysis of the electron diffraction pattern revealed that the Cu oxide composing the particles was a Cu 2 O phase. Therefore, the dark contrast portion is Pt and the thin contrast portion is Cu 2 O.
- Example 5 Production of Pt—Al 2 O 3 composite nanoparticles
- Example 5 Production of Pt—Al 2 O 3 composite nanoparticles
- each particle shows a shape in which a small portion with high contrast and a large portion with low contrast are joined.
- Analysis of the electron diffraction pattern revealed that the oxide of Al constituting the particles was a ⁇ -Al 2 O 3 phase. Accordingly, the dark contrast portion is Pt and the thin contrast portion is ⁇ -Al 2 O 3 phase.
- the present invention is a method for producing composite nanoparticles of noble metal and oxide, and is a method for producing a heterojunction between both nanoscale phases. Further, the present invention is a high-purity noble metal / oxide composite nanoparticle, and a heterojunction is formed between both nanoscale phases. Therefore, chemical-reactive, electronic, magnetic, and optical physical / chemical properties derived from the heterointerface between two phases having completely different physical properties are attached to the nanoscale particles. Therefore, the embodiments of the heterojunction noble metal-oxide composite nanoparticles according to the present invention are not limited to the catalyst application of the above examples, but by selecting noble metals and oxides, a very wide range Industrial application can be expected.
Abstract
Description
具体的には、特許文献(3)には、生医学、ナノデバイス等へ応用し得るダンベル形状又はフラワー形状のナノ粒子の製造方法として、疎水性外側コートを含むナノ粒子と前駆体との混合物に基づき、第1の部分がPbS,CdSe,CdS,ZnS,Au,Ag,Pd,Ptのいずれかからなり、第2の部分がAu,Ag,Pd, Pt,Fe,Co,Ni等からなるナノ粒子を製造する旨が記載されているが、貴金属と酸化物の接合ナノ粒子については、Au-Fe2O3,Ag-Fe3O4の実施例が記載されているだけである。
特許文献(4)には、燃料セルの酸素電極において用いられる複合触媒として、1つのフェライト粒子(平均粒子サイズが5~50nm)にエピタキシャルに結合した1つの貴金属ナノ粒子(平均粒子サイズが10nm未満)からなるダンベル形状複合ナノ粒子や、1つのフェライト粒子にエピタキシャルに結合した2つ以上の貴金属ナノ粒子からなるフラワー形状の複合ナノ粒子であって、金属酸化物前駆体及び貴金属ナノ粒子が添加された有機溶媒と界面活性剤との混合溶液を加熱、還流させ、複合ナノ粒子を沈殿させる等の工程により製造され、フェライト粒子が化学式 A2+B3+ 2O4(但し、A2+は、Mn2+,Fe2+,Co2+,Ni2+,Cu2+,Mg2+,Zn2+及びCd2+からなる群から選択されるイオンであり、B3+は、Fe3+,Cr3+及びMn3+からなる群から選択されたイオンである)のフェライトを少なくとも含み、前記貴金属ナノ粒子は、少なくともPt,Pd及びAgからなる群から選択された少なくとも1つの元素を含むものが記載されている。しかしながら、実施例としては、Pt-Fe3O4が記載されているだけである。
特許文献(5)には、チオール化合物の存在下、2種の金属塩を高温でポリオール還元することにより製造される異方的に相分離したどんぐり形状の二元金属ナノ粒子であって、一方の金属がFe,Co,Ni又はCuで、他方の金属がPd,Pt,Au又はAgであり、磁性化学の分野や触媒化学の分野などでの用途が期待されるものが記載されている。しかしながら、実施例としては、Coの硫化物とPdの硫化物からなる二元ナノ粒子が記載されているに過ぎず、純粋な貴金属部分を含むナノ粒子や卑金属酸化物を含むナノ粒子やその製造方法については全く記載されていない。
非特許文献(1)~(5)には、液相合成によるダンベル形状のAu-Fe3O4,Au-ZnO,Au-MnOのナノ粒子が記載されているが、Fe,Zn,Mn以外の非金属元素を用いる旨については全く記載されていない。
しかも、特許文献(1)~(4)、非特許文献(1)~(3)では、酸化物の元素としては、Fe,Co,Ni,Mn,Cu,Mg,Zn,Cd,Crの使用乃至使用可能性が記載されているだけで、Sn,Ti,Al,Zr,Ce,Y,La,Si,Geを用いることは、全く記載されていないし、また、使用可能性が言及された酸化物の元素についても、該元素を採用する場合に用いる化合物等の開示がなされていないので、当業者が容易に実施をすることができる程度に記載されているとは言えない。しかも、このような液相合成により生成された金-酸化物複合ナノ粒子には、イオンや有機物等の各種不純物が不可避的に含まれるため、触媒等として用いる場合には、被毒物イオンの洗浄や、ナノ粒子保護有機物の焼成による除去乃至清浄化工程が不可欠である。その上、これらの清浄化工程が、原子レベルで常に安定かつ完全に、かつ再現性良く行うことができる保証は無い。そして、原料に金属カルボニルなどの危険物を使用する点や、上記で用いられた以外の様々な酸化物の元素を簡単に選択することができない点から見ても、上記液相合成による金-酸化物複合ナノ粒子の生成には多くの解決すべき問題が存在する。
特許文献(9)では、T・M(TはTi、Al等、MはAu、Pd等)の原材料を、水素ガス、窒素ガス及び不活性ガスからなる群から選ばれた少なくとも1種のガスを含む雰囲気中で加熱溶解し、超微粒子を生成させてフィルターで捕集後、捕集された超微粒子を酸素を含む雰囲気中で熱処理すること等からなる複合超微粒子の製造方法が記載されている。この製造方法では、フィルターで捕集された超微粒子は、相互に結合乃至凝集した状態で酸化熱処理され、各超微粒子が独立分散した浮遊状態で酸化熱処理されない。そのため、Ti、Al等の金属酸化物からなる超微粒子にAu、Pd等の貴金属又は/及びその化合物からなる多数の微細な粒子が析出、分散した複合超微粒子が得られるだけである。それ故、当該製造方法によっても、卑金属酸化物ナノ粒子1個の表面に貴金属ナノ粒子が1個接合された複合ナノ粒子を独立分散させた状態で得ることはできない。
本発明は、高純度の貴金属ナノ粒子1個と酸化物ナノ粒子1個が接合された新規な複合ナノ粒子であって、被毒物の残存がなく、物性の全く異なるナノスケール両相間のヘテロ界面に由来して、化学反応的、電子的、磁気的、光学的などの各種の物理・化学的に特異な物性、機能を発揮することが期待される複合ナノ粒子やその製造方法を提供することを課題とする。
(2)複合ナノ粒子(M-AxOy)が独立分散させた状態で得られることを特徴とする上記(1)に記載の複合ナノ粒子(M-AxOy)の製造方法。
(3)合金(A-M)ナノ粒子の熱酸化処理は気相中で行い、温度400℃以上、処理時間が10秒以内であることを特徴とする上記(1)又は(2)に記載の複合ナノ粒子(M-AxOy)の製造方法。
(4)酸化性ガスの導入を合金(A-M)ナノ粒子の加熱前に行い、該加熱を酸化性ガスと不活性ガスの混合ガス中で行うか、又は、酸化性ガスの導入を合金(A-M)ナノ粒子の不活性ガス中での加熱中に行う上記(1)~(3)のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
(5)合金(A-M)ナノ粒子の生成法として、ガス中蒸発法、レーザーアブレーション法、スパッタリング法、アークプラズマ法、大気圧プラズマ法のいずれかを用いることを特徴とする上記(1)~(4)のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
(6)卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Ti,V,Cr,Mn,Co,Fe,Ni,Zn,Al,Y,Zr,Mo,In,Mg,La,Ce,Nd,Sm,Eu,Gd,Si,Ge,Pb,Biから選ばれる1種以上であり、貴金属(M)が、Au,Pt,Pd,Rh,Ag,Ru,Irから選ばれる1種以上である上記(1)~(5)のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
(7)貴金属(M)を0.1~30at.%含有し、残部が卑金属(A)と不可避不純物からなり、粒子径が1~200nmの合金(A-M)ナノ粒子を不活性ガス中で生成させ、不活性ガスで搬送する途中で、合金(A-M)ナノ粒子の加熱、及び、導入された酸化性ガスと接触させることによって、浮遊する合金(A-M)ナノ粒子中の卑金属成分(A)を酸化させ、かつ、酸化卑金属成分(AxOy)を貴金属成分(M)と相分離させて粒子状卑金属酸化物(AxOy)の1個の領域と、粒子状貴金属(M)の1個の領域から構成される複合ナノ粒子(M-AxOy)を得る複合ナノ粒子(M-AxOy)の製造方法であって、卑金属(A)が、Cu,Sn,Al,Ni,Co,Ti,Zr,In,Si,La,Ce,Euから選ばれる1種以上であり、
貴金属(M)が、Au,Pt,Pd,Rh,Agから選ばれる1種以上である、複合ナノ粒子(M-AxOy)の製造方法。
(8)粒子径1~100nmの卑金属酸化物(AxOy)の表面に粒子径1~10nmの貴金属粒子(M)1個が接合してなる複合ナノ粒子(M-AxOy)であって、
卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Ti,V,Cr,Mn,Co,Ni,Zn,Al,Y,Zr,Mo,In,Mg,La,Ce,Nd,Sm,Eu,Gd,Si,Ge,Pb,Biから選ばれる1種以上であり(ただし、卑金属酸化物がZnO,MnOである場合を除く)、
貴金属(M)が、Au,Pt,Pd,Rh,Ag,Ru,Irから選ばれる1種以上である、
複合ナノ粒子(M-AxOy)。
(9)複合ナノ粒子(M-AxOy)がAu-Cu2O又はAu-SnO2である上記(8)に記載の複合ナノ粒子(M-AxOy)。
(10)1~200nmの大きさをもつ卑金属酸化物(AxOy)の1個の領域と、1~100nmの大きさをもつ貴金属(M)の1個の領域から構成される複合ナノ粒子(M-AxOy)であって、
卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Al,Ni,Co,Ti,Zr,In,Si,La,Ce,Euから選ばれる1種以上であり、
貴金属(M)が、Au,Pt,Pd,Rh,Agから選ばれる1種以上である、
複合ナノ粒子(M-AxOy)。
(11)卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Alから選ばれる1種以上であり、
貴金属(M)が、Au,Ptから選ばれる1種以上である、
上記(10)に記載の複合ナノ粒子(M-AxOy)。
また、本発明の貴金属-酸化物接合ナノ粒子(M-AxOy)は、粒子径1~200nm(好ましくは1~100nm)の卑金属酸化物粒子(AxOy)表面に粒子径1~100nm(好ましくは1~10nm)の純度の高い貴金属粒子(M)1個が原子レベルで接合した極めて微細な粒子であり、物性の全く異なるナノスケール両相間のヘテロ界面に由来して、化学反応的、電子的、磁気的、光学的などの各種の物理・化学的に特異な物性、機能を発揮することが期待される。本発明の貴金属-酸化物接合ナノ粒子(M-AxOy)は、例えば、酸化触媒として用いた場合に有効であるが、貴金属と酸化物を選択することによって、非常に幅広い産業上の応用が期待できる。
本発明の複合ナノ粒子の製造方法を図1に示す。本発明の複合ナノ粒子の製造方法は、貴金属(M)を0.1~30at.%含有し、残部が卑金属(A)と不可避不純物からなり、粒子径が1~200nm(好ましくは1~100nm)の合金(A-M)ナノ粒子を不活性ガス中で生成させ、不活性ガスで搬送する途中で、合金(A-M)ナノ粒子の加熱、及び、導入された酸化性ガスと接触させることによって、浮遊する合金(A-M)ナノ粒子中の卑金属成分(A)を酸化させ、かつ、酸化卑金属成分(AxOy)を貴金属成分(M)と相分離させる等の工程を含む。
この製造方法では、貴金属や卑金属を溶解性の化合物〔例えば、HAuCl4,H2PtCl6,Fe(CO)5〕として用いる必要がなく、合金(A-M)ナノ粒子を不活性ガス中で生成させることができる貴金属、卑金属であれば採用することができる。それ故、液相合成のような化合物の制約による貴金属や卑金属の種類の制限がないので、後述の実施例で用いたAu、Pt、Cu、Sn、Al以外の貴金属や卑金属も幅広く採用することができる。
原料を構成する貴金属Mは、限定されないが、例えば、Au,Pt,Pd,Rh,Ag,Ru,Irから選ばれる1種以上とすることができる。好ましくは、Au,Pt,Pd,Rh,Agから選ばれる1種以上とすることができる。
原料の卑金属A-貴金属M合金は、後述の理由によりA-M合金ナノ粒子の貴金属Mの含有率が0.1~30at.%程度(より好ましくは1~15at.%、さらに好ましくは2~10at.%)となるように、卑金属Aと貴金属Mの蒸気圧等を考慮して、その貴金属Mの含有率を決定することが好ましい。ガス中蒸発法では原料の卑金属A-貴金属M合金の貴金属含有率は、卑金属元素の種類にもよるが、例えば、1~60at.%の範囲にすることができ、卑金属元素がCu、Snの場合には、30~60at.%(好ましくは、35~55at.%、より好ましくは40~50at.%)とすることが適当である。レーザーアブレーション法では原料合金の組成と合金ナノ粒子の組成はほぼ一致するため、原料の卑金属A-貴金属M合金の貴金属含有率は0.1~30at.%程度(より好ましくは1~15at.%、さらに好ましくは2~10at.%)とすればよい。
貴金属-卑金属合金ナノ粒子を生成させる際、合金の一次粒子の凝集体からなるナノサイズの二次粒子が生成する場合、高温熱酸化処理器(H)で熱酸化処理される前に、例えば予備加熱機構等によって、不活性雰囲気中で加熱、焼結して孤立分散粒子化される。
高温熱酸化処理器における合金ナノ粒子は、石英管を炉心管とした管状型電気炉等を用い、高温に加熱された混合ガスにより間接的に加熱しても良いし、また、誘導加熱、マイクロ波加熱等の手段を用い、直接的に加熱しても良い。
高温熱酸化処理は、貴金属と卑金属の種類にも依存するが、一般的には温度400℃以上(好ましくは500~1200℃、より好ましくは600~1100℃)、処理時間10秒以内とすることができる。処理温度を高くすると処理時間を短くすることができる。高温熱酸化処理器は、そのような処理時間の間、合金ナノ粒子を加熱されるように、合金ナノ粒子の搬送経路に沿った加熱領域が設定される。
上記プロセスにおいて、A-M合金ナノ粒子を気相中で熱酸化させることによって貴金属Mを完全に相分離させるためには、貴金属Mの組成は0.1~30at.%程度(より好ましくは1~15at.%、さらに好ましくは2~10at.%)、混合ガスの酸素濃度は10%以上が好ましい。
なお、電子デバイスや触媒等の用途では、複合ナノ粒子の高純度生成が非常に重要となるため、A-M合金ナノ粒子は、不純物含有率が極力少ないことが望ましいが、原料の貴金属や卑金属の不純物等に由来する不純物を含有しうる。不純物の含有率が目的とする機能を大きく損なわない範囲(例えば、0.01at.%未満、好ましくは0.001at.%未満)となるように原料を選択することが望ましい。
卑金属酸化物の粒子径は1~200nm、好ましくは1~100nm、より好ましくは2~50nm、さらに好ましくは5~30nmであり、貴金属粒子の粒子径は、1~100nm、好ましくは1~10nm、より好ましくは1~8nm、さらに好ましくは1~5nmである。卑金属酸化物の粒子径は、貴金属-卑金属合金ナノ粒子の粒子径だけでなく、高温熱酸化処理における酸化熱による卑金属の蒸発によっても影響を受けるので、蒸発性の高い卑金属の場合には、前述の酸化性ガスの導入位置の調整により卑金属酸化物の粒子径を調整することもできる。
なお、本発明では、TEM(Transmission Electron Microscope)で得られる粒子の像の重心を通る最大径と最小径の平均値を”粒子径”とする。また、卑金属酸化物や貴金属の領域の大きさとは、該領域を粒子とみなし、その像の重心を通る最大径と最小径の平均値を領域の”大きさ”とする。
本発明により製造される複合ナノ粒子(M-AxOy)の貴金属(M)は、1種類の貴金属であっても良いし、複数種類の貴金属混合物であっても良い。該貴金属(M)の純度は、合金ナノ粒子生成過程や酸化卑金属成分(AxOy)から相分離する過程を経ることで、貴金属原料程度(通常99.99~99.999%程度)又はそれ以上(例えば、99.9999%以上)となる。
合金ナノ粒子発生源としてガス中蒸発法による生成装置を用いた。装置内へ流入速度0.4L/minでヘリウムを導入し、油回転ポンプによって装置内の圧力を2kPaの減圧に保った。炭素-pBN(Pyrolytic Boron Nitride)二重坩堝内にCu-46at.%Auインゴットを設置し、高周波加熱によって1200℃で加熱した。以上の実験条件よりCu-4at.%Au合金ナノ粒子がヘリウム中に生成された。ここで、ナノ粒子のAu含有率が原料インゴットよりも減少したのは、Cuの蒸気圧がAuの蒸気圧よりも高いことに起因する。生成した合金ナノ粒子は、ヘリウムガスに加えられた、流入速度0.2L/minの酸素ガスとともに、1100℃に加熱された石英管内へと運ばれ、高温酸化処理された。熱酸化処理時間は0.1秒程度である。酸化処理後に生成したAu-Cu2O複合ナノ粒子は、捕集器内に設置した非晶質炭素膜上に希薄に自然付着させ、電子顕微鏡観察のための試料となった。触媒活性測定用の試料は、バッファ粒子としてのシリカナノ粉末(Sigma-Aldrich,637238)とともに捕集し得た。
原料Sn-5at.%Au合金ナノ粒子は、実施例1と同様のガス中蒸発法によって、Sn-50at.%Auインゴットを1180℃で加熱してヘリウムガス中に得た。その合金ナノ粒子を気相中において、約0.1秒間700℃で高温熱酸化することによって、Au-SnO2複合ナノ粒子が得られた。その他の実験条件は実施例1とほぼ同じである。図6にAu-SnO2複合ナノ粒子のTEM写真を示す。電子回折パターンの解析より、薄いコントラスト部分はSnO2相であることが確認された。SnO2とAuの回折パターンのピークが重なってしまう部分が非常に多いために、Auのみに由来するピークを分離することが出来なかったが、濃いコントラスト部分は、Snを含まないAuであると考えられる。写真の通り、AuとSnO2夫々1個のナノ粒子が1枚の界面を介して接合された粒子が得られた。
合金ナノ粒子発生源として、レーザーアブレーション法による生成装置を用いた。装置内へ流入速度0.5L/minでヘリウムガスを導入し、油回転ポンプによって装置内の圧力を1.6kPaの減圧に保った。Al-5at.%Au合金のペレット(20mmφ×5mmt)を原料ターゲットとし、その表面へNd:YAGレーザーの第二高調波(波長:532nm、出力:90mJ/pulse、繰り返し周波数:10Hz)を集光・照射することにより、ターゲット表面を瞬間的に蒸発させ、上記合金のナノ粒子の凝集体がヘリウムガス中に生成された。生成した合金ナノ粒子凝集体はヘリウムガス流に乗って移動しつつ、予備加熱機構で焼結され孤立分散粒子化された後、流入速度0.25L/minの酸素ガスとともに、900℃に加熱された石英管内へと運ばれ、高温酸化処理された。熱酸化処理時間は0.01秒程度である。酸化処理後に生成したAu-Al2O3複合ナノ粒子は、捕集器内に設置した非晶質炭素膜上に希薄に自然付着させ、電子顕微鏡観察のための試料となった。
実施例3と同様に、レーザーアブレーション法によって、Cu-5at.%Pt合金のペレットを原料ターゲットとし実験を行った。レーザー光をターゲットへ集光・照射することにより、ターゲット表面を瞬間的に蒸発させ、上記合金のナノ粒子の凝集体をヘリウムガス中に生成させた。凝集体は予備加熱機構で焼結させた後、酸素ガスとともに900℃に加熱された石英管内へと運ばれ、高温酸化処理されることで、Pt-Cu2O複合ナノ粒子が得られた。実験諸条件は、実施例3と同じである。図9にPt-Cu2O複合ナノ粒子のTEM写真を示す。写真の通り、個々の粒子は、コントラストの濃い小さな部分と、コントラストの薄い大きな部分が接合した形状を示している。電子回折パターンの解析により、粒子を構成するCuの酸化物はCu2O相であることがわかった。従って、粒子の濃いコントラスト部分はPt、薄いコントラスト部分はCu2Oである。
実施例3と同様に、レーザーアブレーション法によって、Al-5at.%Pt合金のペレットを原料ターゲットとし実験を行った。レーザー光をターゲットへ集光・照射することにより、ターゲット表面を瞬間的に蒸発させ、上記合金のナノ粒子の凝集体をヘリウムガス中に生成させた。凝集体は予備加熱機構で焼結させた後、酸素ガスとともに900℃に加熱された石英管内へと運ばれ、高温酸化処理されることで、Pt-Al2O3複合ナノ粒子が得られた。実験諸条件は、実施例3と同じである。図10にPt-Al2O3複合ナノ粒子のTEM写真を示す。写真の通り、個々の粒子は、コントラストの濃い小さな部分と、コントラストの薄い大きな部分が接合した形状を示している。電子回折パターンの解析により、粒子を構成するAlの酸化物はγ-Al2O3相であることがわかった。従って、粒子の濃いコントラスト部分はPt、薄いコントラスト部分はγ-Al2O3相である。
Claims (11)
- 貴金属(M)を0.1~30at.%含有し、残部が卑金属(A)と不可避不純物からなり、粒子径が1~100nmの合金(A-M)ナノ粒子を不活性ガス中で生成させ、不活性ガスで搬送する途中で、合金(A-M)ナノ粒子の加熱、及び、導入された酸化性ガスと接触させることによって、浮遊する合金(A-M)ナノ粒子中の卑金属成分(A)を酸化させ、かつ、酸化卑金属成分(AxOy)を貴金属成分(M)と相分離させて粒子状卑金属酸化物(AxOy)の表面に貴金属粒子(M)1個が接合した複合ナノ粒子(M-AxOy)を得る複合ナノ粒子(M-AxOy)の製造方法。
- 複合ナノ粒子(M-AxOy)が独立分散させた状態で得られることを特徴とする請求項1に記載の複合ナノ粒子(M-AxOy)の製造方法。
- 合金(A-M)ナノ粒子の熱酸化処理は気相中で行い、温度400℃以上、処理時間が10秒以内であることを特徴とする請求項1又は2に記載の複合ナノ粒子(M-AxOy)の製造方法。
- 酸化性ガスの導入を合金(A-M)ナノ粒子の加熱前に行い、該加熱を酸化性ガスと不活性ガスの混合ガス中で行うか、又は、酸化性ガスの導入を合金(A-M)ナノ粒子の不活性ガス中での加熱中に行う請求項1~3のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
- 合金(A-M)ナノ粒子の生成法として、ガス中蒸発法、レーザーアブレーション法、スパッタリング法、アークプラズマ法、大気圧プラズマ法のいずれかを用いることを特徴とする請求項1~4のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
- 卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Ti,V,Cr,Mn,Co,Fe,Ni,Zn,Al,Y,Zr,Mo,In,Mg,La,Ce,Nd,Sm,Eu,Gd,Si,Ge,Pb,Biから選ばれる1種以上であり、貴金属(M)が、Au,Pt,Pd,Rh,Ag,Ru,Irから選ばれる1種以上である請求項1~5のいずれか1項に記載の複合ナノ粒子(M-AxOy)の製造方法。
- 貴金属(M)を0.1~30at.%含有し、残部が卑金属(A)と不可避不純物からなり、粒子径が1~200nmの合金(A-M)ナノ粒子を不活性ガス中で生成させ、不活性ガスで搬送する途中で、合金(A-M)ナノ粒子の加熱、及び、導入された酸化性ガスと接触させることによって、浮遊する合金(A-M)ナノ粒子中の卑金属成分(A)を酸化させ、かつ、酸化卑金属成分(AxOy)を貴金属成分(M)と相分離させて粒子状卑金属酸化物(AxOy)の1個の領域と、粒子状貴金属(M)の1個の領域から構成される複合ナノ粒子(M-AxOy)を得る複合ナノ粒子(M-AxOy)の製造方法であって、卑金属(A)が、Cu,Sn,Al,Ni,Co,Ti,Zr,In,Si,La,Ce,Euから選ばれる1種以上であり、
貴金属(M)が、Au,Pt,Pd,Rh,Agから選ばれる1種以上である、複合ナノ粒子(M-AxOy)の製造方法。 - 粒子径1~100nmの卑金属酸化物(AxOy)の表面に粒子径1~10nmの貴金属粒子(M)1個が接合してなる複合ナノ粒子(M-AxOy)であって、
卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Ti,V,Cr,Mn,Co,Ni,Zn,Al,Y,Zr,Mo,In,Mg,La,Ce,Nd,Sm,Eu,Gd,Si,Ge,Pb,Biから選ばれる1種以上であり(ただし、卑金属酸化物が ZnO,MnOである場合を除く)、
貴金属(M)が、Au,Pt,Pd,Rh,Ag,Ru,Irから選ばれる1種以上である、
複合ナノ粒子(M-AxOy)。 - 複合ナノ粒子(M-AxOy)がAu-Cu2O又はAu-SnO2である請求項8に記載の複合ナノ粒子(M-AxOy)。
- 1~200nmの大きさをもつ卑金属酸化物(AxOy)の1個の領域と、1~100nmの大きさをもつ貴金属(M)の1個の領域から構成される複合ナノ粒子(M-AxOy)であって、
卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Al,Ni,Co,Ti,Zr,In,Si,La,Ce,Euから選ばれる1種以上であり、
貴金属(M)が、Au,Pt,Pd,Rh,Agから選ばれる1種以上である、
複合ナノ粒子(M-AxOy)。 - 卑金属酸化物(AxOy)成分の卑金属(A)が、Cu,Sn,Alから選ばれる1種以上であり、
貴金属(M)が、Au,Ptから選ばれる1種以上である、
請求項10に記載の複合ナノ粒子(M-AxOy)。
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JP2016525998A (ja) * | 2013-05-06 | 2016-09-01 | バル・イラン・ユニバーシティBar Ilan University | ドープ化金属酸化物ナノ粒子及びその使用 |
WO2021208232A1 (zh) * | 2020-03-02 | 2021-10-21 | 深圳市捷安纳米复合材料有限公司 | 一种纳米银铜合金材料及其制备方法 |
CN115055678A (zh) * | 2022-05-25 | 2022-09-16 | 北京信息科技大学 | 一种金颗粒-氧化亚铜纳米杯的制备方法 |
CN115055678B (zh) * | 2022-05-25 | 2023-06-27 | 北京信息科技大学 | 一种金颗粒-氧化亚铜纳米杯的制备方法 |
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US20140038815A1 (en) | 2014-02-06 |
EP2671846A1 (en) | 2013-12-11 |
EP2671846A4 (en) | 2017-11-22 |
JP5750731B2 (ja) | 2015-07-22 |
EP2671846B1 (en) | 2019-04-03 |
CN103402920B (zh) | 2016-10-26 |
CN103402920A (zh) | 2013-11-20 |
JPWO2012105631A1 (ja) | 2014-07-03 |
US9675964B2 (en) | 2017-06-13 |
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