JP5140035B2 - Colloidal solution containing metal nanoparticles - Google Patents

Description

  The present invention relates to a colloid solution applied to a plating film nucleation application, a catalyst metal support application to a catalyst carrier, and the like. Specifically, the present invention relates to a colloidal solution containing metal nanoparticles and having little aggregation of metal nanoparticles even when heated after coating.

  Colloidal solution in which nano-order fine metal particles are dispersed can apply and fix metal preliminarily adjusted to a fine particle size to various substrates with good dispersibility. Has been.

  For example, in the formation of electrode patterns on circuit boards, electrode films for various sensors, etc., these electrodes are often formed by plating, but a colloid solution is applied for nucleation to grow the plating film. (Patent Document 1). It is expected that a homogeneous plating film can be formed by nucleating with a colloid before forming the plating film.

  Colloids are also suitable for the production of functional materials such as catalysts (Patent Document 2). Although the characteristics of the catalyst are affected by the particle size and dispersibility of the catalyst metal supported on the carrier, the colloid can satisfactorily disperse the metal particles having an appropriate particle size from the supporting step.

JP 2006-270118 A JP 2002-001095 A

  By the way, when the colloid solution is applied to the above-described uses, heat is often applied to the base material after the colloid coating. For example, in nucleation for forming a plating film, heat treatment is performed at 300 to 1600 ° C. after colloid coating to activate metal particles (nuclei), thereby promoting the subsequent formation of the plating film. .

  However, the heat treatment may cause the metal particles on the base material to aggregate and form coarse particles. The formation of such coarse particles is unsuitable as the core of the plating film, and even the catalyst metal deviates from the intended particle size and cannot exhibit desired characteristics.

  The present invention has been made based on the background as described above, and provides a colloid solution for various uses as described above, which is less likely to cause agglomeration even if it is subjected to heat treatment after application to a substrate. The task is to do.

  In order to solve the above-mentioned problems, the present inventors have intensively studied and studied to add an additive having an effect of suppressing aggregation of metal nanoparticles during heating to the colloidal solution. As a result, the inventors have conceived a colloidal solution containing an organometallic compound of a predetermined metal as an aggregation inhibitor.

  That is, the present invention is characterized in that a colloidal solution in which metal nanoparticles are dispersed in an organic solvent contains an organometallic compound of any one of zirconium, aluminum, titanium, and magnesium and a resin as an aggregation inhibitor. It is a colloidal solution.

  As described above, the present invention adds a predetermined metal organometallic compound and a resin together as an aggregation inhibitor for metal nanoparticles during heating. Here, the reason why the organometallic compounds of zirconium, aluminum, titanium, and magnesium are selected as the aggregation inhibitor is that these exhibit the aggregation suppression effect of the metal nanoparticles, and other metals have such an action. Because it is not possible. The reason why the effect is limited to zirconium or the like is not clear, but it is presumed that these organometallic compounds are likely to intervene in the gap when the colloidal metal moves and aggregates due to heat. It is also considered that these organometallic compounds form oxides during heating and have a high melting point.

  The organometallic compound is preferably an aliphatic carboxylic acid compound of the above metal, more preferably an ethylhexanoic acid compound or a naphthenic acid compound. This is because these are easily dispersed uniformly throughout the paste.

  And as a coagulation inhibitor at the time of heating, a resin is further contained, and the cohesion inhibitory effect improves more by the additional addition. That is, according to the study by the present inventors, the above-mentioned organometallic compound exhibits an aggregation suppressing effect even if it is added alone, but the effect is insufficient. Therefore, a resin is added at the same time in order to make the aggregation suppressing effect more reliable. In this respect, the resin also has an aggregation-inhibiting effect, but it is possible to obtain only an insufficient effect by itself. As the resin, either a cellulose resin or a vinyl resin is preferable, and specifically, ethyl cellulose, nitrocellulose, polyvinyl acetal, and polyvinyl alcohol are preferable.

  As content of these aggregation inhibitor, it is preferable to contain 1-20 weight% of organometallic compounds in conversion of the metal in an organometallic compound with respect to the quantity of a metal nanoparticle. This is because if it is less than 1% by weight, the sintering-preventing effect is hardly recognized, and if it exceeds 20% by weight, the unique properties of the metal nanoparticles are deteriorated. The resin is preferably 0.1 to 3.0% by weight based on the entire colloidal solution.

  The particle size of the metal nanoparticles is preferably 1 to 50 nm, more preferably 1 to 10 nm. The action as a plating nucleus or catalytic metal is taken into consideration. In view of its use, the metal nanoparticles are preferably composed of at least one of Pt and Pd. Further, the colloidal solution may have metal nanoparticles covered with a protective agent in connection with the production process. The protective agent is a compound added to prevent aggregation between colloidal particles formed in the process of producing a colloid, and examples thereof include alkylamine, carboxylic acid amide, fatty acid, alkoxysilyl and the like.

  The organic solvent in which the metal nanoparticles are dispersed is appropriately selected according to the application, and examples thereof include toluene, chloroform, hexane, terpineol, and the like. And it is preferable that the metal nanoparticle in a solvent shall be 0.1-5.0 weight% with respect to the whole colloid solution.

  As a method for producing a colloidal solution according to the present invention, metal nanoparticles are produced and dispersed in an organic solvent. The method for producing metal nanoparticles can be produced by a conventionally known method. As a general production method, there is a method in which a reducing agent and an appropriate protective agent are added to a metal salt solution of a target metal to reduce metal ions into metal nanoparticles. And the manufactured metal nanoparticle is isolate | separated by filtration etc., and it can be set as the colloidal solution which concerns on this invention by adding an aggregation inhibitor while being disperse | distributed to an organic solvent.

  The colloidal solution according to the present invention described above can maintain its dispersibility without agglomeration of metal fine particles even by heat treatment after coating on a substrate. INDUSTRIAL APPLICABILITY The present invention is useful for catalyst metal loading using a nucleation process for a plating film and a heat treatment for a catalyst carrier.

The figure which shows the external appearance (SEM) after application | coating heating of the colloidal solution of an Example and a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described. In the present embodiment, a colloidal solution in which metal nanoparticles of platinum, palladium, and platinum-palladium are dispersed was manufactured, and the dispersibility maintenance characteristics were examined.

Preparation of Metal Nanoparticles (Colloid Particles) 10 mL of 0.1 M dinitroammine platinum salt solution and 200 mL of toluene were mixed, and 40 mmol of decylamine was added as a protective agent and stirred. Then, 10 mL of 0.2 M sodium borohydride as a reducing agent was added to the mixed solution, and the mixture was stirred until it was completely reduced. As a result, platinum ions in the toluene phase are reduced to platinum particles, and the protective agent is combined with the platinum particles to form metal nanoparticles (platinum colloid). The platinum colloid produced in the production process has a platinum particle diameter of 5 nm. In the present embodiment, a plurality of platinum colloids were produced by changing the platinum particle diameter while adjusting the concentration ratio of the metal ions, the protective agent, and the reducing agent.

  Moreover, in this embodiment, the colloid of palladium and the platinum-palladium mixed particle was manufactured besides the platinum colloid. The production method in this case was basically the same as described above, and dinitroammine palladium was used as the palladium salt.

Production of colloidal solution A colloidal solution was produced using the produced metal nanoparticles. In the present embodiment, a plurality of colloidal solutions were manufactured by changing the content of metal nanoparticles, the type of aggregation inhibitor, and the amount added. The colloid solution was prepared by dispersing metal nanoparticles in terpineol, which is an organic solvent, and adding an organometallic compound and a resin that serve as an aggregation inhibitor. For comparison, a colloidal solution in which one or both of the aggregation inhibitors was not added was also produced.

  And about each manufactured colloid solution, they were apply | coated to the base material and it heat-processed and confirmed the effect of aggregation suppression. In this evaluation, 10 μL of a colloidal solution was collected with a micropipette and dropped onto an alumina substrate and applied. Then, it dried at 120 degreeC for 10 minutes, and heat-processed at 500 degreeC for 30 minutes. And the heat-processed board | substrate was observed by SEM, and the particle size of the metal nanoparticle and the surface form of the coating surface were evaluated. Further, in this evaluation, the metal nanoparticle having a particle size of 300 nm or less was evaluated as “◎”, the metal nanoparticle having a particle size of 300 to 500 nm as “◯”, and the metal nanoparticle exceeding 500 nm as “x”. The evaluation results are shown in Tables 1 to 3. In addition, SEM photographs of some examples (Examples 3 and 9) and comparative examples (Comparative Examples 1 to 3) are shown in FIG.

  From Tables 1-3 and FIG. 1, in each Example, the metal nanoparticle is maintaining the fine particle state (particle diameter of 500 nm or less), and is maintaining the favorable dispersion state. On the other hand, when the aggregation inhibitor of Comparative Example 1 is not added at all, the metal fine particles aggregate to form a film.

  When only the zirconium ethylhexanoate of Comparative Example 2 was added, no film was formed and aggregation was slightly suppressed, but fine support was not achieved. Further, in the case of adding only ethylcellulose of Comparative Example 3, although uniform platinum particles are supported, aggregation is still occurring, and many platinum particles exceed 1 μm. For this reason, it is necessary to add both an organometallic compound and a resin as an aggregation inhibitor.

  However, even when both the organometallic compound and the resin are added, when the particle size and content of the metal nanoparticles are excessive (Comparative Examples 5, 6, and 8), the addition amount of the organometallic compound is large (Comparative Example). In 7), the particle size after heating tends to increase. Moreover, even if it says an organometallic compound, when the organometallic compound of tin is added (comparative example 4), it turns out that there is no aggregation inhibitory effect at the time of a heating.

  The colloidal solution according to the present invention is useful for the nucleation of the plating film because the metal fine particles are less aggregated by heating. Therefore, it is useful for manufacturing sensor electrodes and pattern electrodes of various electric circuits. Further, in the production of a catalyst using noble metal fine particles such as a fuel cell, an oxygen sensor, a combustion catalyst, and VOC as a catalyst metal, a fine catalyst metal can be supported with suitable dispersibility.

Claims (5)

In a colloidal solution in which metal nanoparticles are dispersed in an organic solvent,
As an aggregation inhibitor at the time of heating, it contains an organometallic compound of either zirconium, aluminum, titanium, or magnesium and a resin,
The organometallic compound is an aliphatic carboxylic acid compound, and the content thereof is 1 to 20% by weight (in terms of metal in the organometallic compound) based on the amount of metal nanoparticles,
The content of the resin is 0.1 to 3.0% by weight with respect to the entire colloidal solution,
The metal nanoparticles have a particle size of 1 to 50 nm and a content of 0.1 to 5.0% by weight with respect to the entire colloid solution. The colloidal solution according to claim 1 , wherein the organometallic compound is one of an ethylhexyl acid compound and a naphthenic acid compound. The colloidal solution according to claim 1 , wherein the resin is either a cellulose resin or a vinyl resin. The colloidal solution according to any one of claims 1 to 3 , wherein the metal nanoparticles have a particle size of 1 to 10 nm. The colloidal solution according to any one of claims 1 to 4 , wherein the metal nanoparticles comprise at least one noble metal of Pt and Pd.

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