JP2014198908A - Metal nanoparticle and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal nanoparticle having an extremely large surface area to its volume, having large action effect as a nanoparticle for purpose of its utilization such as a catalytic action, capable of stably controlling particle size and shape in a colloidal state, and having low manufacturing cost including material costs.SOLUTION: In manufacturing a metal nanoparticle by a wet reduction method, a reduction reaction is conducted by using methoxy poly(oxyethylene/oxypropylene)-2-propylamine of primary amine of a block copolymer CH3O(OCH2CH2)a[OCH2CH(CH3)]bOCH2CH(CH3)NH2, where a=18.6 and b=1.6, as a dispersant and a mixture of ethylene glycol (EG) and polyethylene glycol (PEG) as a solvent and reductant.

Description

  The present invention relates to metal nanoparticles and a method for producing the same, and more specifically to metal nanoparticles having a branched structure and a method for producing the same.

  In recent years, metal nanoparticles with a particle size of 100 nm or less have physical properties different from those of the same kind of bulk metal, or have a very large surface area relative to the volume. There are great expectations for the use of features, and the possibility of use in the industrial field including catalysts is expected, and many improvements have been proposed.

  For example, in the field of utilization using noble metals such as platinum, attention is focused on the size of the surface area relative to the volume, and the utilization for catalysts is being promoted.

  In the industrial use of noble metal nanoparticles, high performance is expected, and at the same time, high cost becomes a problem. For example, a material that replaces platinum as a material for a catalyst that used platinum. Cost reduction is expected, such as trying an invention or reducing the amount of platinum used.

  For this reason, we tried to form metal nanoparticles in the form of nets, but it was difficult to control the size and shape of the particles, so we could not obtain practical level nanoparticles, or the skeleton of metal nanoparticles on a single body carrying metal nanoparticles Attempts were made to form metal nanoparticles, but the size and shape of the particles could not be controlled, and metal nanoparticles of a practical level could not be obtained.

  The present invention has been made in view of the circumstances concerned, the purpose of the present invention is that the surface area of the metal nanoparticles is extremely large compared to its volume, and the action and effects as nanoparticles for its intended use, such as catalytic action, The object is to provide metal nanoparticles that can stably control the particle size and shape in a colloidal state and are low in production cost including material costs.

  The present invention made to solve the problem lies in that metal nanoparticles are produced in a branched shape, and the first invention (hereinafter referred to as Invention 1) as an example of the present invention is branched. In the metal nanoparticles formed on the metal nanoparticles, the plurality of branches constituting the branches are in the shape of metal nanoparticles having a particle size of 100 nm or less (hereinafter referred to as element nanoparticles) or in a state where a plurality of them are connected. The length of the branch in a photograph (hereinafter referred to as a TEM photograph) in which the element nanoparticles constituting the plurality of branches are photographed by a transmission electron microscope (hereinafter referred to as a TEM photograph). The dimension in the direction is L, the maximum dimension is Lm, the dimension in the direction perpendicular to the length direction is D, the maximum dimension is Dm, and the dimension D of the portion connected to other element nanoparticles is Dc. When Dc is smaller than Lm, Dc is smaller than Dm, and the element nanoparticles at least at the tips of a plurality of branches have a crystal structure showing interference fringes parallel to each other in a TEM photograph. Metal nanoparticles.

  A second invention (hereinafter referred to as Invention 2) made by developing Invention 1 is a metal nanoparticle according to Invention 1, wherein Dm is smaller than Lm.

  A third invention (hereinafter referred to as invention 3) made by developing invention 1 or 2 is that in the metal nanoparticles according to invention 1, at least a part of the element metal is covered with a dispersant. It is a featured metal nanoparticle.

  A fourth invention (hereinafter referred to as invention 4) made by developing invention 3 is the metal nanoparticle according to invention 2, wherein the dispersant is methoxypoly (oxyethylene / oxypropylene) -2-propylamine CH30 ( OCH2CH2) a [OCH2CH (CH3)] b A metal nanoparticle characterized by being a dispersant of a = 18.6 and b = 1.6 in OCH2CH (CH3) NH2.

  A fifth invention (hereinafter referred to as invention 5) made by developing inventions 1 to 4 is a metal nanoparticle according to inventions 1 to 4, wherein the metal is platinum. is there.

  A sixth invention made by developing the inventions 1 to 5 (hereinafter referred to as invention 6) is the metal nanoparticles according to inventions 1 to 5, wherein the metal nanoparticles are formed by a wet reduction method. A plurality of metal nanoparticles grown from the reaction solution for growing metal nanoparticles in the state of the element nanoparticles are connected to each other, and the entire particle has a branched structure. Metal nanoparticles.

A seventh invention as an example of the present invention, which has been made to solve the problem, is a methoxypoly (1) block copolymer primary amine as a dispersant in the production process for producing the metal nanoparticles according to the first to sixth inventions. Oxyethylene / oxypropylene) -2-propylamine CH3O (OCH2CH2) a [OCH2CH (CH3)] bOCH2CH (CH3) NH2 (where a = 18.6, b = 1.6) This is a method for producing metal nanoparticles having a branched structure.
In the divisional application of the present application, the following claims have been filed based on the above-described invention and a mode for carrying out the invention described below.
Claim 1 made in order to solve the problem of the present invention is a metal nanoparticle formed in a structure having a plurality of peripheral components (hereinafter referred to as branches) that look like branches and cores. A plurality of branch portions constituting the branch portion are in the form of metal nanoparticles having a particle size of 100 nm or less (hereinafter referred to as element nanoparticles) or a shape formed by connecting a plurality of them. In the photograph (referred to as TEM photograph) taken by a transmission electron microscope (referred to as TEM) of the element nanoparticles constituting the branches of the branch, the dimension in the length direction of the branches is defined as L, and the maximum dimension is defined as Lm. When the dimension in the direction orthogonal to the length direction is D, the maximum dimension is Dm, and the dimension D of the portion connected to other element nanoparticles is Dc, Dc is smaller than Lm, c is smaller than Dm, the element nanoparticles at least at the tip of a plurality of branches have a crystal structure, and the plurality of branches are arranged around the core Nanoparticles.
Claim 2 made by developing Claim 1 is a metal nanoparticle according to Claim 1, wherein at least a part of the element metal is covered with a dispersant. .
Claim 3 made by expanding Claim 1 or 2 is a metal nanoparticle according to Claim 1 or 2, wherein the metal nanoparticle is grown by a wet reduction method. A metal nanoparticle characterized in that a plurality of metal nanoparticles grown from the reaction solution in the state of the element nanoparticle are connected to each other so that the entire particle has the structure of the branch part. It is.

  The metal nanoparticles of the present invention have a multi-branched shape in which a plurality of branches in a state where a plurality of element nanoparticles, which can be said to be basic elements of construction, are gathered, and therefore the surface area with respect to the volume is extremely large. For example, when the platinum nanoparticle according to the present invention is used as a catalyst for a battery electrode, the electrolyte solution can enter the inside of the nanoparticle because it has a branch structure, compared with the conventional nanoparticle having the same external shape. In addition to the very small amount of platinum, the surface area of platinum in contact with the electrolyte is much larger than that of conventional platinum nanoparticles, so it has a much larger catalytic effect than conventional platinum nanoparticles with the same external dimensions. In addition, the amount of platinum is small and the material cost is greatly reduced, the shape and dimension can be controlled reliably, the manufacturing yield is high, and the manufacturing cost including the material cost is included. It is intended to achieve the great advantage of being able to greatly reduce.

It is a TEM photograph of platinum nanoparticles as an example of an embodiment of metal nanoparticles of the present invention. It is a TEM photograph of platinum nanoparticles as an example of an embodiment of metal nanoparticles of the present invention.

  Hereinafter, examples in which the present invention is applied to platinum nanoparticles will be described as embodiments of the present invention.

  As a preferred example, a dinitroamine platinum solution was used as a precursor as a platinum raw material. As a dispersant, the primary amine methoxypoly (oxyethylene / oxypropylene) -2-propylamine CH3O (OCH2CH2) a [OCH2CH (CH3)] bOCH2CH (CH3) NH2 (where a = 18.6, b = 1.6) (for example, product name: Jeffamine (registered trademark) M-1000 manufactured by Huntsman) (hereinafter referred to as M-1000), ethylene glycol (hereinafter referred to as EG) and polyethylene as a solvent and reducing agent The platinum nanoparticles of the present invention can be produced by reducing alcohol in a heating environment using a mixture of glycol (hereinafter referred to as PEG) in a one-to-one relationship. .

  As a specific example, first, a mixed solution (hereinafter referred to as a mixed solution 1) in which 200 g of EG as a solvent and dispersion medium, 180 g of PEG having a molecular weight of 400, and 40 g of an M-1000 mixed solution having a concentration of 50% by EG is mixed. The precursor (containing 1 g of platinum) prepared separately by mixing with the heated mixture 1 before being heated to 150 ° C., M-1000, and a 1: 1 EG / PEG mixture. A mixed solution (hereinafter, referred to as “mixed solution 2”) is dropped little by little to advance the reduction reaction.

  A suitable speed at which the mixed liquid 2 is dropped into the mixed liquid 1 is dripped into the mixed liquid 1 at 150 ° C. with stirring at a rate of 320 μL per minute for about 9 hours, and then 80 g PEG, 80 g of EG and 40 g of 50% M-1000 (EG 50% concentration) was added dropwise at a rate of 300 μL / min to proceed the reduction reaction. The reduction reaction was carried out.

  As a result, the branched platinum nanoparticles shown in FIG. 1 could be produced. FIG. 1 and FIG. 2 are TEM photographs of platinum nanoparticles as an embodiment of the metal nanoparticles of the present invention produced according to the above-mentioned examples, and a line segment showing 5 nm is shown in the figures.

  In FIG. 1, the main part of the platinum nanoparticles including the central part of the figure is not clearly shown in the figure, but peripheral components (branches) that appear as branches around the core part in the vicinity of the central part. It is formed in a structure with multiple lines. Each branch part is in a state where one or a plurality of element nanoparticles such as spheroids are connected and connected to the core part to form the branched platinum nanoparticles of the present invention.

  In FIG. 2, reference numeral 1 is a platinum nanoparticle, 2 to 4 are element nanoparticles, 5 is a reference numeral for explaining the position where the core is located, and 6 is a single nanoparticle that is not grown on the platinum nanoparticle of the present invention. In the element nanoparticles 2 to 4, interference fringes aligned in the same direction showing crystallinity as seen in FIG.

  In the platinum nanoparticle 1 of FIG. 2, many element nanoparticles are gathered in a branch shape around a core portion in the vicinity of a portion indicated by reference numeral 5 to form a group of platinum nanoparticles. Such a form of platinum nanoparticles has a very large surface area compared to its volume. Moreover, it can exist stably without agglomeration even at a high temperature of 250 ° C.

  The platinum nanoparticles shown in FIGS. 1 and 2 were reacted without applying ultrasonic waves, but the size and shape of the element nanoparticles differed depending on the frequency and power of the ultrasonic waves and could be changed depending on the reaction conditions. .

  As described above, dinitroamine platinum was used as a precursor as a platinum raw material, but other precursors as a platinum raw material include hexahedroxoplatinum, hexachloroplatinate, tetrachloroplatinate, and tetrabromoplatinate. , Tetraammineplatinate, hexaammineplatinum hydrate, and bisoxalatoplatinate.

  The present invention is not limited to platinum, but can be applied to other metal nanoparticles.

  The present invention has a great effect that it greatly contributes to industrial development in a wide range of industries such as automobiles, batteries, electronics, biotechnology, functional materials and the like.

Claims (3)

Periphery components visible to the nucleus portion and the branched (hereinafter, referred to as branches) in the metal nanoparticles are formed on the structure that is attached plurality of partial particle size of the plurality of branches constituting the branch portion 100nm The shape of the following metal nanoparticles (hereinafter referred to as element nanoparticles) or a shape formed by connecting a plurality of them, and the element nanoparticles constituting the plurality of branches are a transmission electron microscope In a photograph (referred to as a TEM photograph) taken by a photograph (referred to as a TEM photograph), the dimension in the length direction of the branch is L, the maximum dimension is Lm, and the dimension in a direction perpendicular to the length direction is D, When the maximum dimension is Dm and the dimension D of the portion connected to other element nanoparticles is Dc, Dc is smaller than Lm, Dc is smaller than Dm, and at least the tips of the plurality of branches. It said element nanoparticles in minute has a crystal structure, the metal nanoparticles, wherein the plurality of branch portions is disposed around the core portion. The metal nanoparticles according to claim 1 , wherein at least a part of the element metal is covered with a dispersant. The metal nanoparticles according to claim 1 or 2 , wherein the metal nanoparticles are grown into a state of the element nanoparticles from a reaction solution for growing the metal nanoparticles in a process of forming the metal nanoparticles by a wet reduction method. metal nanoparticles, wherein the objects together is that the entire particle connecting a plurality is configured to have a structure of the branch portion.