WO2024019102A1 - Matériau composite transportant un nanoagrégat d'au et procédé de fabrication dudit matériau composite - Google Patents

Matériau composite transportant un nanoagrégat d'au et procédé de fabrication dudit matériau composite Download PDF

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WO2024019102A1
WO2024019102A1 PCT/JP2023/026496 JP2023026496W WO2024019102A1 WO 2024019102 A1 WO2024019102 A1 WO 2024019102A1 JP 2023026496 W JP2023026496 W JP 2023026496W WO 2024019102 A1 WO2024019102 A1 WO 2024019102A1
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nanoclusters
carrier
composite material
ligand
cysteine
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PCT/JP2023/026496
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Japanese (ja)
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寛 岸
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田中貴金属工業株式会社
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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
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/26—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24
    • 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
    • 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
    • B01J37/04—Mixing

Definitions

  • the present invention relates to a composite material in which nanoclusters made of Au are supported on a suitable carrier. Specifically, the present invention relates to a composite material in which nano-order Au nanoclusters are supported on a hydrophobic carrier via a predetermined ligand. Furthermore, the present invention relates to a method for producing a composite material in which Au nanoclusters can be supported in a highly dispersed manner on a hydrophobic carrier in an aqueous solution system.
  • metals When metals are made into nanoparticles, they exhibit various properties not found in bulk materials, such as photoresponsive properties (photoluminescence properties), fluorescence emission properties, and light scattering/reflection properties. Therefore, metal nanoparticles are being considered for application in various fields such as light emitting elements and fluorescent materials used in display devices and the like, and electrode and wiring materials for various electronic and semiconductor devices.
  • metal nanoparticles in addition to materials related to electrical and optical devices as mentioned above, they are also extremely effective as catalysts for various chemical reactions.
  • Making metal into fine particles increases the surface area of the metal, so by making the metal fine to the nano-order, its catalytic activity can be greatly improved.
  • These metal particles that have been made into nano-sized particles are called metal nanoclusters. Although there is no fixed definition, a nanocluster is usually a collection of several to several hundred metal atoms.
  • Metal nanoclusters are often synthesized in a wet manner (liquid phase), and their usage is generally in the form of a dispersion in which metal nanoclusters are dispersed in a solvent. Furthermore, a common method for synthesizing metal nanoclusters is to add a reducing agent and a ligand (organic ligand) to a solution of a metal salt. In this synthesis method, a ligand binds to a plurality of metal atoms generated by reduction, thereby forming particles in which metal atoms are clustered.
  • the ligand is sometimes referred to as a protective agent/dispersant, and has the effect of suppressing aggregation of clustered metal nanoparticles and maintaining a dispersed state.
  • the metal nanoclusters are utilized by applying a dispersion in which the metal nanoclusters are dispersed onto a carrier such as a catalyst, and then adsorbing the carrier by immersion, thereby adsorbing and fixing the metal nanoclusters onto the carrier.
  • the present invention relates to the application of nanoclusters made of Au (gold) among metal nanoclusters.
  • noble metals such as Au and Ag are metals that significantly exhibit localized surface plasmon resonance (SPR).
  • SPR surface plasmon resonance
  • Au is a metal that is chemically stable and has suitable electrical properties.
  • nano-order Au has a catalytic effect on various chemical reactions such as the oxidation reaction of carbon monoxide. For these reasons, Au nanoclusters are expected to be a precursor material that can contribute to improved performance in the various applications described above.
  • Au nanoclusters known so far include those in which Au atoms are clustered by applying phosphine, thiol-based organic ligands (thiolates), etc. as ligands.
  • Au nanoclusters with the thiolate glutathione (GSH) as a ligand are highly stable due to strong Au-S bonds, and are also hydrophilic and stably dispersed in aqueous solvents. It is known.
  • a common way of utilizing metal nanoclusters is to adsorb and support metal nanoclusters dispersed in a solvent on a carrier.
  • the reason for this is considered to be the difference in polarity (hydrophilicity and hydrophobicity) between the Au nanoclusters and the carrier.
  • polarity hydrophilicity and hydrophobicity
  • Au nanoclusters having glutathione as a ligand are hydrophilic and stable in aqueous solvents, they are difficult to be adsorbed and supported on hydrophobic carbon powder. Therefore, most of the Au nanoclusters remain in the solvent without being supported on the hydrophobic carrier. Many catalyst carriers and device substrates have hydrophobic surfaces. Even if Au nanoclusters can stably maintain their nanoparticle state in a solvent, their significance will be diminished if they cannot be supported on these carriers.
  • Au nanoclusters that can be dispersed in non-aqueous solvents such as organic solvents.
  • Au nanoclusters that can stably exist in organic solvents are also known.
  • Au nanoclusters having phenylethanethiol as a ligand as described in Non-Patent Document 2 are stable in the state of nanoparticles of about 1 nm in an organic solvent.
  • the present invention was made against the above background, and relates to a composite material in which Au nanoclusters, which are fine particles, are highly dispersed and supported on a hydrophobic carrier at an appropriate supporting density.
  • An object of the present invention is to clarify a method for supporting Au nanoclusters on a hydrophobic carrier while using an aqueous solvent, and to provide a method for manufacturing the above-mentioned composite material.
  • the present inventors first studied the behavior of Au clusters synthesized with various thiolate-based ligands including glutathione in an aqueous solvent. As a result, it was found that L-cysteine and L-cysteine derivatives having a predetermined residue can synthesize Au nanoclusters in an aqueous solvent without the action of a reducing agent. It was also confirmed that Au nanoclusters synthesized using these ligands have hydrophobicity. However, since Au nanoclusters have hydrophobicity, it is difficult to stably disperse them in an aqueous solvent. The Au nanoclusters made of L-cysteine and L-cysteine derivatives studied by the present inventors cause precipitation and precipitation due to aggregation and the like in a solvent after synthesis, and cannot maintain a stable dispersion state.
  • Au nanoclusters synthesized from L-cysteine and L-cysteine derivatives have good adsorption to hydrophobic carriers, and adsorption to the carrier takes precedence over aggregation of nanoclusters.
  • the present invention provides a composite material in which Au nanoclusters containing two or more Au atoms are supported on a carrier via a ligand, wherein at least the portion on which the Au nanoclusters are supported is hydrophobic. and the ligand is a composite material that is L-cysteine or an L-cysteine derivative with a non-polar residue.
  • Composite material supporting Au nanoclusters according to the present invention is composed of a carrier, Au nanoclusters supported on the carrier, and a ligand that binds the two.
  • the carrier is a member for supporting the Au nanoclusters in a dispersed state.
  • the carrier of the composite material according to the present invention is a carrier that has hydrophobicity at least in the portion on which the Au nanoclusters are supported. Hydrophobicity is a property that has a low affinity for water and is difficult to dissolve or mix with water.
  • the constituent material of the carrier include carbon, cellulose, nitrocellulose, hydrophobic polymers (fluororesin, acrylic, epoxy, polyethylene, polystyrene, polyvinyl chloride, etc.), metal nitrides, and the like. There are no particular limitations on the shape and dimensions of the carrier. Particulate carriers are often used in catalysts.
  • bulk carriers such as plate-shaped, sheet, and film-shaped carriers are sometimes used as carriers for material applications related to electrical and optical devices.
  • specific criteria for the hydrophobicity of the carrier can be set for each of the particulate carrier and the bulk carrier as follows.
  • the particulate carrier is a particulate or powdery solid with a particle size of 10 ⁇ m or less that can be dispersed in a solvent such as water.
  • a solvent such as water.
  • the R SP value obtained from pulsed NMR (TD-NMR) measurement is suitable.
  • the hydrophobicity of a carrier dispersed in an aqueous solvent can be evaluated by the magnitude of interaction between the carrier surface and solvent molecules. According to pulse NMR, it is possible to measure the relaxation time of a solvent having protons (H) in its molecules, such as water, and the shorter the relaxation time, the stronger the interaction between the carrier and the solvent.
  • the RSP value is determined by measuring the relaxation time in each state of a solvent only state and a state in which a particulate carrier is dispersed in a solvent.
  • the R SP value is calculated from the following formula, and the smaller the R SP value, the higher the hydrophobicity tends to be.
  • the hydrophobicity of the carrier used in the present invention is determined by measuring the relaxation time (transverse relaxation time (spin-spin relaxation time)) by pulsed NMR using water as the solvent and calculating the R SP value using the above formula. . At this time, it is preferable to judge hydrophobicity using a correction value (R SP /TSA: hereinafter referred to as R SP (c)) obtained by dividing the R SP value by the total surface area (TSA) of the carrier at the time of measurement.
  • R SP (c) correction value obtained by dividing the R SP value by the total surface area (TSA) of the carrier at the time of measurement.
  • a carrier having an R SP (c) value of 0.5 or less is defined as a hydrophobic carrier. Note that the total surface area (TSA) of the carrier during pulsed NMR measurement can be calculated using the following formula.
  • the BET specific surface area as the specific surface area SA of the carrier.
  • the present invention is intended to be applied to catalysts, and carbon particles or the like are often used as catalyst carriers. Carbon particles take various forms, such as a structure with countless fine pores on the surface and a hollow structure.
  • Application of the BET specific surface area is suitable for determining the specific surface area of these various forms of particulate carriers.
  • the BET specific surface area it is preferable to apply a value measured by a gas adsorption method, and it is preferable to apply a value measured by nitrogen gas.
  • the mass-to-volume ratio concentration of the carrier during pulse NMR measurement is preferably 0.1% or more (0.001 g/mL or more) and 10% or less (0.1 g/mL or less).
  • the bulk-like carrier is intended to exclude the above-mentioned particulate carriers, and is a plate-like, lump-like, or thin-film-like solid with a minimum size of 10 ⁇ m or more.
  • the hydrophobicity of a bulk carrier can be defined by the contact angle with water.
  • a hydrophobic carrier is one that has a contact angle with water of 90° or more. Note that for a bulk carrier whose minimum size is larger than that of a particulate carrier, it is sufficient that at least the surface portion supporting the Au nanoclusters has the above-mentioned hydrophobicity.
  • hydrophobic materials Materials other than the above-mentioned hydrophobic materials may be used as long as the surface on which the Au nanoclusters are supported is treated to impart hydrophobicity.
  • hydrophobic treatment include a treatment for modifying the carrier surface with a nonpolar functional group (alkyl group, etc.), a firing treatment in an inert atmosphere, and coating with the above-mentioned hydrophobic material.
  • Au nanocluster Au nanocluster is a particle containing a group of two or more Au atoms.
  • the particle size of the Au nanoclusters supported on the hydrophobic carrier in the composite material of the present invention is preferably 0.5 nm or more and 5 nm or less, more preferably 3 nm or less.
  • the particle size of the Au nanocluster can be obtained, for example, by calculating the average value by measuring the particle size of a plurality of particles based on an image observed by electron microscopy such as TEM.
  • the particle size in an observed image can be measured by image analysis in addition to visual observation.
  • the particle size distribution can also be analyzed by statistical calculation of the measured particle size.
  • particle diameter shall mean the maximum distance (diameter equivalent to a circumscribed circle) among the distances between any two points on the contour line of a particle.
  • the Au nanocluster may be composed only of Au atoms, but may also contain atoms of other elements.
  • atoms of elements that have a high bonding property with Au such as S (sulfur), O (oxygen), N (nitrogen), C (carbon), Cu (copper), and Ag (silver), stabilize the Au nanocluster. It may contribute to sexual activity and high activation. It is preferable that atoms other than Au be contained in an amount of 50% or less in terms of number of atoms.
  • the amount of Au nanoclusters supported (supporting density) in the present invention is adjusted depending on the use of the composite material. According to the supporting method according to the present invention described below, the amount of Au nanoclusters supported can be 0.1% by mass or more and 50% by mass or less based on the entire composite material such as a catalyst. be.
  • the ligand is an organic ligand that coordinates to the Au atoms in order to maintain the collective state of the clustered Au atoms.
  • the ligand acts as an aid for binding the Au nanoclusters to the hydrophobic carrier when the Au nanoclusters are synthesized.
  • the ligand of the present invention is L-cysteine and L-cysteine derivatives represented by the following formula.
  • R is a residue (substituent), and is hydrogen or a nonpolar residue. According to the studies of the present inventors, when L-cysteine in which R is hydrogen or an L-cysteine derivative in which R is a nonpolar residue coordinates to an Au atom in an aqueous solvent to form a nanocluster. , imparts hydrophobicity to the Au nanoclusters.
  • the nonpolar residue is an acyl group (acetyl group (CH 3 CO: Ac), ethylcarbonyl group (CH 3 CH 2 CO), linear or branched propylcarbonyl group (C 3 H 7 CO), linear or branched butyl carbonyl group (C 4 H 9 CO)), or carbon number 1 Alkoxycarbonyl group having ⁇ 4 aliphatic hydrocarbon chains (methoxycarbonyl group (CH 3 OCO), ethoxycarbonyl group (CH 3 CH 2 OCO), linear or branched propoxycarbonyl group (C 3 H 7 OCO), linear or branched butoxycarbonyl group (C 4 H 9 OCO)) are preferred.
  • acetyl group (CH 3 CO:Ac) isopropylcarbonyl group ((CH 3 ) 2 CHCO)
  • tert-butoxycarbonyl group ((CH 3 ) 3 COCO) are more preferred.
  • the non-polar residue when an L-cysteine derivative having a non-polar residue is applied as a ligand, the non-polar residue exhibits an anchoring effect to a hydrophobic carrier and has the effect of suppressing the movement of Au nanoclusters in a high-temperature environment. It is believed that there is. This effect suppresses the aggregation of Au nanoclusters and the resulting coarsening of the particles.
  • Particularly preferred ligands are L-cysteine, where R is hydrogen, and N-acetyl-L-cysteine, where R is an acetyl group. This is because these have a small molecular weight and can be easily decomposed and removed by heat.
  • the content of the ligand is preferably 0.1% by mass or more and 50% by mass or less based on the entire composite material such as the catalyst. More preferably, it is 20% by mass or less.
  • the ligand only needs to be bonded to at least a portion of the Au nanocluster, and does not need to be bonded to the entire surface or all Au atoms.
  • the presence of the ligand L-cysteine or an L-cysteine derivative in which R is a non-polar residue can be detected by gas chromatography-mass spectrometry (GC/MS), especially thermal decomposition-gas It can be qualitatively confirmed by chromatography-mass spectrometry (Py-GC/MS). Non-polar residues of L-cysteine derivatives can also be confirmed using this analytical method.
  • the aqueous solvent is the step of synthesizing Au nanoclusters in the aqueous solvent and supporting the Au nanoclusters on the carrier by adding the other of the Au source and the ligand, wherein the ligand is L-cysteine.
  • it is a method of producing an L-cysteine derivative having a nonpolar residue.
  • the subject matter is the synthesis of Au nanoclusters, and the loading on a carrier is based on the premise that the synthesis of Au nanoclusters has been completed.
  • the loading on the carrier is completed simultaneously with the synthesis of the Au nanoclusters or immediately after the synthesis of the Au nanoclusters.
  • a reaction system is formed in which either the Au source or the ligand and a carrier coexist, and the other of the Au source or the ligand is allowed to act on this reaction system to synthesize Au nanoclusters. and supported on a carrier.
  • the present invention differs from the prior art in the timing of synthesis and loading of Au nanoclusters.
  • a method for manufacturing a composite material based on this method of supporting Au nanoclusters will be explained.
  • a state in which the carrier is in contact with an aqueous solvent containing either the Au source or the ligand it is first necessary to form a state in which the carrier is in contact with an aqueous solvent containing either the Au source or the ligand.
  • a state in which the aqueous solvent and the carrier are in contact may be formed, or a solution in which either the Au source or the ligand is added to the aqueous solvent is prepared in advance, and this solution and the carrier are brought into contact. Also good.
  • the state in which the carrier is in contact with the aqueous solvent or solution is preferably formed by immersing part or all of the carrier in the aqueous solvent or solution.
  • the carrier As the carrier, the above-mentioned carrier having hydrophobicity is applied.
  • aqueous solvent in addition to pure water, a mixed solvent of water and a water-soluble polar solvent (alcohol, N-methylpyrrolidone, etc.) can be used.
  • the amount of the aqueous solvent is preferably 2 times or more and 1000 times or less relative to the weight of the carrier.
  • Au salts such as tetrachloride gold (III) acid, gold halide, and potassium gold (I) cyanide can be used.
  • the amount of the Au source added here is related to the amount of Au nanoclusters supported on the carrier, so the concentration of the Au source should not be limited. For example, when considering catalyst applications, it is possible to obtain the above-mentioned supporting density of Au nanoclusters by setting the Au source to 0.1% by mass or more and 50% by mass or less based on the carrier weight in terms of Au mass. can.
  • the ligand L-cysteine or an L-cysteine derivative having a nonpolar residue is added as described above.
  • the amount of the ligand added is preferably from 1 to 10 times the number of moles of Au ions on a molar basis, taking into consideration the amount of Au nanoclusters to be supported.
  • the ligand, L-cysteine, etc. also acts as a reducing agent, and if the amount is less than 1 time, Au ions may not be completely reduced.
  • the lack of ligand also reduces the stability of Au nanoclusters.
  • the amount of ligand is 10 times or more, the nanocluster synthesis efficiency will decrease because the Au atom will tend to be stabilized in a complex state in which the ligand is coordinated with the ligand.
  • Au nanoclusters are synthesized by adding the other of the Au source and the ligand.
  • L-cysteine or an L-cysteine derivative functions not only as a ligand but also as a reducing agent. Therefore, in the present invention, when the Au source and the ligand coexist in the reaction system without adding a reducing agent, the synthesis of Au nanoclusters starts and progresses at the same time. The synthesized Au nanoclusters are then adsorbed and supported on a hydrophobic carrier. This support of Au clusters progresses instantaneously to such an extent that they cannot be distinguished by visual observation at the same time as or after the synthesis of Au clusters.
  • the temperature conditions of the reaction system in the synthesis and support of the above Au nanoclusters are preferably 0° C. or higher and 50° C. or lower, and room temperature may also be used. Further, the reaction atmosphere may be either air atmosphere or inert gas atmosphere.
  • a composite material can be obtained by completing the synthesis of Au nanoclusters and supporting them on a hydrophobic carrier.
  • the carrier carrying Au nanoclusters may be recovered by drying or filtration, and may be washed, dried, and heat treated as necessary.
  • the heat treatment is performed to control the particle size by decomposing and removing excess ligands and by associating Au nanoclusters.
  • the atmosphere for the heat treatment is preferably an atmospheric atmosphere, a mixed gas atmosphere of oxygen gas and an inert gas, a reduced pressure atmosphere (preferably a reduced pressure atmosphere of 100 Pa or less), or an inert gas atmosphere.
  • the heat treatment temperature is preferably 100°C or more and 800°C or less, more preferably 120°C or more and 400°C or less.
  • the composite material according to the present invention is a composite material in which Au nanoclusters are supported on a hydrophobic carrier.
  • the composite material according to the present invention supports fine Au nanoclusters at a high density, and can effectively exhibit the unique characteristics of the Au nanoclusters.
  • the present invention also reveals a method for manufacturing a composite material by efficiently supporting Au nanoclusters in an aqueous solvent.
  • a composite material can be produced by supporting Au nanoclusters on a hydrophobic carrier without relying on organic solvents that are difficult to use from the viewpoint of environmental impact.
  • Au nanoclusters By forming Au into nanoclusters, it has catalytic activity not found in bulk.
  • Au nanoclusters have catalytic activity for the oxidation reaction of carbon monoxide, alcohol, and styrene, and the hydrogenation reaction of unsaturated ketones.
  • the present invention can be applied as a catalyst for these chemical reactions. Examples include carbon monoxide removal catalysts and exhaust gas purification catalysts for producing reformed hydrogen gas.
  • Au nanoclusters have catalytic activity for oxygen reduction reaction (ORR) as an electrode catalyst.
  • ORR oxygen reduction reaction
  • the present invention can also be used as an electrode catalyst for fuel cells.
  • FIG. 3 is a diagram comparing the MS spectra of the composite materials of Example 1 and Example 2 before heat treatment.
  • FIG. 3 is a diagram comparing the MS spectra of the composite materials of Example 1 and Example 2 after heat treatment.
  • FIG. 3 is a diagram comparing the MS spectra of the composite materials of Example 1 and Example 2 after heat treatment.
  • carbon powder was used as the hydrophobic carrier.
  • a composite material was manufactured using L-cysteine and N-acetyl-L-cysteine (hereinafter referred to as acetylcysteine) as ligands for synthesizing Au nanoclusters.
  • the carbon powder used in this embodiment has an average particle size of 40 nm and a BET specific surface area of 800 m 2 /g.
  • a slurry in which 0.1 g of this carbon powder was dispersed in 100 mL of pure water was used as a measurement sample, and analyzed by pulsed NMR to measure the R SP value.
  • the measurement was performed using a pulsed NMR device manufactured by Resonance Systems, Inc., using a measurement sample volume of 1 mL, a measurement temperature of 30°C, a resonance frequency of about 20 MHz, and a 1 H-NMR observation nucleus to measure the relaxation time (transverse relaxation time T 2 ) (CMPG law).
  • the R SP value of the carbon powder of this embodiment with respect to water was 0.28. Further, from the BET specific surface area (800 m 2 /g) of the carbon powder, the total surface area (TSA) of the carrier is 0.8 m 2 . Therefore, the TSA correction value R SP (c) of the carbon powder of this embodiment was 0.35, and it was determined that the carbon powder was a hydrophobic carrier.
  • Example 1 (ligand: L-cysteine (C)) : 1 g of the above carbon powder was added and dispersed in 100 mL of pure water as an aqueous solvent. In the aqueous solvent in which this carbon powder carrier was dispersed, 0.75 g (2.2 mmol of Au) of tetrachloride gold (III) acid as an Au source was dissolved.
  • reaction solution was filtered to recover the composite material and filtrate.
  • the recovered composite material was subjected to two types of treatment: one was dried under reduced pressure (100 Pa or less), and the other was heat-treated after drying at 150° C. for 4 hours under reduced pressure (100 Pa or less) to complete the composite material.
  • Example 2 Carbon powder was dispersed in the same amount of pure water as in Example 1, and 0.75 g (2.2 mmol of Au) of tetrachloride gold (III) acid, which is an Au source, was dissolved. After that, 20 mL of an aqueous solution containing 1.5 g (9.3 mmol) of acetylcysteine as a ligand was added to produce a composite material (Au(NAC)/C). Thereafter, the composite material was collected and heat treated at 150°C in the same manner as in Example 1.
  • Example 3 (Ligand: L-cysteine (C)):
  • the order of addition of the Au source and the ligand was reversed with respect to Example 1, and Au nanoclusters were synthesized and supported.
  • the Au nanocluster supported composite materials produced in Examples 1 to 3 were observed using STEM (JEM-ARM200F manufactured by JEOL Ltd.) immediately after production (before heat treatment) and after heat treatment. STEM images of each example are shown in FIG. In the state in which Au nanoclusters are supported, in both Examples 1 and 2, fine Au nanoclusters of around 1 nm are supported. When this was heat-treated at 150°C, slight aggregation occurred, resulting in Au nanoclusters of 1.0 nm (Example 1), 1.0 nm (Example 2), and 0.9 nm (Example 3). . The particle size of these nanoclusters was calculated by fitting a scattering curve obtained when measuring with a camera length of 600 mm using a small-angle X-ray scattering device (NANOPIX manufactured by Rigaku Co., Ltd.).
  • Example 1 and 2 were analyzed by pyrolysis GC/MS to confirm the presence of the ligand and to determine whether nonpolar residues could be identified.
  • Thermal decomposition GC/MS was performed using a device named 7890A/5975C manufactured by Agilent Technologies, and the components decomposed at a heating furnace temperature of 600°C were introduced into the GC, separated, and analyzed by MS.
  • MS spectra of the composite materials of Examples 1 to 3 before and after heat treatment are shown in FIGS. 2 to 4.
  • Comparative Example Next, as a comparative example for confirming the supporting efficiency of Au nanoclusters for Examples 1 to 3, Au nanoclusters were synthesized using glutathione as a ligand and supported on carbon powder. In order to keep the conditions the same, in this comparative example, Au nanoclusters were synthesized and supported in a solvent in which the carrier was dispersed, as described below.
  • the proportion of Au in the filtrate was 0.03% in Example 1 (Au(C)/C), 0.015% in Example 2, and 0.075% in Example 3. there were. From these results, it was confirmed that most of the charged Au source was supported on the carrier as Au nanoclusters. On the other hand, the proportion of Au in the filtrate of the comparative example was 32.8%, which was clearly higher than that of Examples 1 to 3, confirming that there was a considerable amount of Au that was not supported on the carrier. It was done. It can be seen that the Au nanoclusters synthesized using glutathione, which is a ligand in the comparative example, are water-soluble and difficult to support on a hydrophobic carbon powder carrier.
  • the catalytic reaction here is an oxidative decomposition reaction of hydrogen peroxide, and the catalytic activity is evaluated by the intensity of the absorbance of the resulting tetramethylbenzidine dimer.
  • Second embodiment In this embodiment, the same carbon powder as in the first embodiment (average particle size 40 nm, BET specific surface area 800 m 2 /g, R SP (c) 0.35) is used as the hydrophobic carrier, and Au Acetylcysteine (NAC) was applied as a ligand for synthesizing nanoclusters, and a composite material was manufactured under manufacturing conditions different from those of the first embodiment.
  • the same carbon powder as in the first embodiment average particle size 40 nm, BET specific surface area 800 m 2 /g, R SP (c) 0.35
  • Au Acetylcysteine (NAC) was applied as a ligand for synthesizing nanoclusters, and a composite material was manufactured under manufacturing conditions different from those of the first embodiment.
  • Example 4 (ligand: acetylcysteine (NAC)) : 4 g of carbon powder was added and dispersed in 400 mL of pure water, which is an aqueous solvent. After adding 6 g (37.2 mmol) of acetyl cysteine, which is a ligand, to the aqueous solvent in which this carbon powder carrier is dispersed, 20 mL of an aqueous solution in which 3 g (8.8 mmol Au) of tetrachloride gold (III) acid, which is an Au source, is dissolved is added. was added to produce a composite material (Au(NAC)/C). Thereafter, in the same manner as in Example 1, the composite material was collected and dried, and then heat-treated at 150° C. under reduced pressure (100 Pa or less) for 4 hours to complete the composite material.
  • Au(NAC)/C gold
  • Example 5 (Ligand: Acetylcysteine (NAC)) : Under the same conditions as Example 4, after adding the ligand (NAC) to the aqueous solvent in which the carbon powder is dispersed, the Au source (tetrachloride gold (III) acid) was added. A composite material (Au(NAC)/C) was manufactured by adding an aqueous solution of. After collecting and drying the composite material, the composite material was heat-treated at 400° C. for 4 hours under reduced pressure (100 Pa or less) to complete the composite material.
  • the Au nanocluster-supported composite materials produced in Examples 4 and 5 were observed using a TEM. TEM images of these composite materials are shown in FIG. As in the first embodiment, the particle sizes of Au nanoclusters in these Au nanocluster-supporting composite materials were measured using a small-angle X-ray scattering device, and the results were 0.8 nm (Example 4) and 4.3 nm (Example 4). 5). It was confirmed that the particle size of Au nanoclusters can be changed by adjusting the heat treatment temperature.
  • a composite material was manufactured by using carbon powder different from that in the first embodiment as a hydrophobic carrier and applying L-cysteine (C) as a ligand.
  • the carbon powder used in this embodiment has an average particle size of 40 nm and a BET specific surface area of 220 m 2 /g.
  • a slurry in which 1 g of this carbon powder was dispersed in 100 mL of pure water was used as a measurement sample, and analyzed by pulsed NMR to measure the RSP value.
  • the measurement was carried out using a pulse NMR device manufactured by Bruker, using a sample volume of 2 mL, a measurement temperature of 30° C., a resonance frequency of about 20 MHz, and a 1 H-NMR observation nucleus to measure the relaxation time (transverse relaxation time T 2 ).
  • the R SP value of the carbon powder of this embodiment with respect to water was 1.70. Since the total surface area (TSA) of the carrier was 4.4 m 2 , the R SP (c) of the carbon powder of this embodiment was 0.39, and it was determined to be a hydrophobic carrier.
  • Example 6 (ligand: L-cysteine (C)) : 4 g of carbon powder was added and dispersed in 80 mL of pure water, which is an aqueous solvent. After adding 4.8 g (37.2 mmol) of L-cysteine as a ligand to the aqueous solvent in which this carbon powder carrier is dispersed, 3 g (8.8 mmol of Au) of tetrachloride gold (III) acid as an Au source is dissolved. 20 mL of the aqueous solution was added to produce a composite material (Au(C)/C). Thereafter, in the same manner as in Example 1, the composite material was collected and dried, and then heat-treated at 150° C. under reduced pressure (100 Pa or less) for 4 hours to complete the composite material.
  • Example 7 (ligand: L-cysteine (C)): Under the same conditions as Example 6, after adding the ligand (C) to the aqueous solvent in which the carbon powder is dispersed, the Au source (tetrachloride gold (III) acid ) was added to produce a composite material (Au(C)/C). After collecting and drying the composite material, the composite material was heat-treated at 230° C. for 4 hours under reduced pressure (100 Pa or less) to complete the composite material.
  • the Au source tetrachloride gold (III) acid
  • the Au nanocluster-supported composite materials produced in Examples 6 and 7 were observed using a TEM. TEM images of these composite materials are shown in FIG.
  • the particle diameters of the Au nanoclusters in these Au nanocluster-supporting composite materials were measured using a small-angle X-ray scattering device, and the results were 0.7 nm (Example 6) and 2.0 nm (Example 6). 7).
  • a hydrophobic carrier different from that in the first embodiment was used, it was confirmed that a composite material supporting fine Au nanoclusters could be manufactured in the same manner as in the first embodiment.
  • the particle size of the Au nanoclusters could be changed by adjusting the heat treatment temperature.
  • the present invention relates to a composite material in which Au nanoclusters are supported on a hydrophobic carrier in a suitable state.
  • the present invention also reveals a method for supporting Au nanoclusters on a hydrophobic carrier in an aqueous solvent.
  • Au nanoclusters can be efficiently supported on a hydrophobic carrier such as carbon powder.
  • the composite material according to the present invention can have a high surface area by applying Au nanoclusters and can exhibit catalytic activity that bulk Au does not have. Therefore, the present invention can be expected to be used as a catalyst for chemical reactions such as oxidation reactions of carbon monoxide, electrode catalysts for fuel cells, and amplification materials for photocatalysts. In addition, the present invention can be expected to be applied to various devices that utilize quantum effects, surface plasmon resonance, optical properties, etc. of Au nanoclusters.

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Abstract

La présente invention concerne un matériau composite formé en transportant des nanoagrégats d'Au, contenant chacun au moins deux atomes d'Au, sur des supports par l'intermédiaire de ligands. Dans la présente invention, des corps hydrophobes, tels que de la poudre de carbone, sont utilisés en tant que supports et une L-cystéine ou un dérivé de L-cystéine qui possède un résidu non polaire est utilisé en tant que ligands. La présente invention divulgue également un procédé permettant de transporter efficacement les nanoagrégats sur des supports hydrophobes. Grâce à la présente invention, suite à la réaction d'une source d'Au et de la L-cystéine ou analogue, servant de ligands, dans un état dans lequel les supports hydrophobes sont dispersés dans un solvant aqueux, la synthèse de nanogrégats d'Au et leur transport sur les supports hydrophobes se déroulent simultanément. La présente invention permet de fabriquer un matériau composite dans lequel des nanoagrégats d'Au sont ttransportés sur des supports hydrophobes de manière hautement dispersée.
PCT/JP2023/026496 2022-07-22 2023-07-20 Matériau composite transportant un nanoagrégat d'au et procédé de fabrication dudit matériau composite WO2024019102A1 (fr)

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Citations (3)

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