CN113118433B

CN113118433B - Method for reconstructing morphology of noble metal nanoparticles

Info

Publication number: CN113118433B
Application number: CN201911417471.1A
Authority: CN
Inventors: 邓承雨; 芦子哲
Original assignee: TCL Technology Group Co Ltd
Current assignee: TCL Technology Group Co Ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2022-06-24
Anticipated expiration: 2039-12-31
Also published as: CN113118433A

Abstract

The invention discloses a method for reconstructing the shape of a noble metal nano particle. The method comprises the following steps: providing a noble metal nanoparticle solution with a triangular plate structure; and mixing the noble metal nanoparticle solution with the triangular plate structure with a solution containing halogen ions, and carrying out oxidation treatment to obtain the reconstructed noble metal nanoparticles. The noble metal nano particles with the triangular plate structure are etched by utilizing the synergistic effect of halogen ion coordination and oxidation reaction, and are reconstructed into the disc-shaped noble metal nano particles. According to the invention, through the method, the monodisperse noble metal nano particles with regular shapes and specific structures are obtained. The shape reconstruction method of the noble metal nano particles provided by the invention has the advantages of simple operation, high repeatability, capability of applying industrial mass synthesis production and the like.

Description

Method for reconstructing morphology of noble metal nanoparticles

Technical Field

The invention relates to the technical field of noble metal nanoparticles, in particular to a method for reconstructing the morphology of noble metal nanoparticles.

Background

The intrinsic properties of a noble metal nanoparticle depend not only on its composition and crystal structure, but also are closely related to its size and shape. The properties of the nanoparticles can in principle be varied arbitrarily by controlling any of these parameters. Compared with common metal nanoparticles, the noble metal nanoparticles with specific morphologies and controllable sizes and shapes tend to show more unique properties and wider application prospects.

However, the controllable synthesis of noble metal nanoparticles with novel morphology is a great challenge. Because from the thermodynamic point of view, the growth of the noble metal nanoparticles follows the principle of lowest energy and smallest surface area. Therefore, a special growth environment is generally required for preparing the noble metal nanoparticles with complex shapes. The research on the preparation method of the noble metal nano material is always a very active and important research field. In the past hundred and fifty years, the reports about the preparation methods of the nano particles of noble metals such as gold, silver, platinum and the like are not very many, but the nano particles are basically irregular in shape, polydisperse in size and hard to define in structure. Methods for controlled synthesis of monodisperse, regularly shaped and structurally defined noble metal nanoparticles have been developed in recent years. At present, methods for preparing noble metal nanoparticles with novel appearance and controllable size are limited, and the search for effective synthetic methods for preparing noble metal nanoparticles with different appearances is always the leading direction of research.

Accordingly, the prior art remains to be improved and developed.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a method for reconstructing morphology of noble metal nanoparticles, which aims to solve the problem that the existing method for preparing noble metal nanoparticles with novel morphology is still limited.

The technical scheme of the invention is as follows:

a method for reconstructing morphology of noble metal nanoparticles, comprising the steps of:

providing a noble metal nanoparticle solution with a triangular plate structure;

and mixing the noble metal nanoparticle solution with the triangular plate structure with a solution containing halogen ions, and carrying out oxidation treatment to obtain the reconstructed noble metal nanoparticles.

Has the beneficial effects that: the invention utilizes the synergistic action of halogen ion coordination and oxidation reaction to etch triangular plate structure noble metal nano particles, and particularly utilizes the synergistic action of halogen ion coordination and oxidation reaction to etch {110} crystal faces of the triangular plate structure noble metal nano particles, so that the triangular plate structure noble metal nano particles are reconstructed into disc structure noble metal nano particles. According to the invention, through the method, the monodisperse noble metal nano particles with regular shapes and specific structures are obtained. The shape reconstruction method of the noble metal nano particles provided by the invention has the advantages of simple operation, high repeatability, capability of applying industrial mass synthesis production and the like.

Drawings

Fig. 1 is a schematic flow chart of a method for reconstructing a morphology of a noble metal nanoparticle according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a mechanism for reconstructing morphology of a noble metal nanoparticle according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a mechanism of forming a nanoparticle with a triangular plate structure by using spherical nanoparticles according to an embodiment of the present invention.

Detailed Description

The invention provides a method for reconstructing the morphology of a noble metal nanoparticle, which is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

Referring to fig. 1, fig. 1 is a schematic flow chart of a method for reconstructing morphology of a noble metal nanoparticle according to an embodiment of the present invention, as shown in the figure, the method includes the steps of:

s10, providing a noble metal nanoparticle solution with a triangular plate structure;

and S20, mixing the noble metal nanoparticle solution with the triangular plate structure with a solution containing halogen ions, and carrying out oxidation treatment to obtain the reconstructed noble metal nanoparticles.

In this embodiment, the noble metal nanoparticles with a triangular plate structure are etched by utilizing the synergistic effect of halogen ion coordination and oxidation reaction, specifically, the {110} crystal faces of the noble metal nanoparticles with a triangular plate structure are etched by utilizing the synergistic effect of halogen ion coordination and oxidation reaction, and the noble metal nanoparticles with a triangular plate structure are reconstructed into the noble metal nanoparticles with a disc-shaped structure. In this example, monodisperse noble metal nanoparticles having a regular shape and a specific structure were obtained by the above method. The shape reconstruction method of the noble metal nanoparticles provided by the embodiment has the advantages of simple operation, high repeatability, capability of applying industrial mass synthesis production and the like.

Referring to fig. 2, in the present embodiment, the nano particles of the noble metal triangular plate structure have a single crystal structure with major crystal planes of {111}, {110}, and {100}, and because lattice densities and surface free energies of different crystal planes are different, there is an energy difference γ {110}>γ{100}>Gamma {111}, because the {110} crystal face has higher activity than other crystal faces, the {110} crystal face of the noble metal triangular plate structure nano particle is easier to react. By introducing oxygen (O)₂) Watch with triangular plate structure and precious metal nano particlesThe surface is oxidized to form noble metal ions, the presence of which can generate a large amount of halogen ions (such as Cl)^-) When a large amount of halogen ions are adsorbed on the included angle of the {110} crystal face with higher energy, the noble metal ions are easy to dissociate to obtain larger surface area for loading the halogen ions. The sharp corner part is most easily attacked by halogen ions in terms of spatial configuration, and when the sharp corner ions are dissociated, a new included angle is formed and continues to be attacked by the halogen ions until the disc-shaped structure is generated.

In step S10, in one embodiment, the method for preparing a precious metal nanoparticle solution having a triangular plate structure includes the steps of:

mixing a soluble noble metal salt solution, an organic acid salt and a reducing agent, and carrying out reduction reaction to obtain a seed solution; and carrying out illumination reaction on the seed solution to obtain the noble metal nanoparticle solution with the triangular plate structure.

In a specific embodiment, the preparation method of the noble metal nanoparticle solution with the triangular plate structure comprises the following steps:

adding a reducing agent into the soluble noble metal salt solution and the organic acid salt, and carrying out reduction reaction under vigorous stirring to obtain a seed solution (bright yellow solution); and (3) placing the seed solution under a certain light source for illumination, carrying out illumination reaction, gradually changing the solution from bright yellow to green along with the progress of the illumination reaction, and finally changing the solution into blue, wherein the blue solution is the noble metal nano particle solution with the triangular plate structure.

In this embodiment, the reducing agent can rapidly reduce the noble metal ions to the noble metal nanoparticles. The organic acid radical plays a role of a reducing agent for noble metal ions in the solution and also plays a role of a stabilizing agent for generated noble metal nano particles. The organic acid radical has strong nucleophilicity, and can partially transfer charges with the noble metal nano particles after being adsorbed on the surfaces of the noble metal nano particles. The result of the action is that the potential of the Fermi level of the noble metal nano particles is negatively shifted, the oxidation-reduction potential of the organic acid radical is increased, the chemical activity of the surfaces of the noble metal nano particles is greatly increased, and metal ions are easier to reduce. In the absence of light, organic acid radicals are used as a stabilizer to wrap the surface of the small noble metal nano particles. The formation of the noble metal nano particles with the triangular plate structure is mainly divided into three stages of cracking, inducing and stopping, and after cracking the nano particles, the cracking products are induced by a light source to grow into the noble metal nano particles with the triangular plate structure. Specifically, as shown in fig. 3, firstly, a reducing agent reduces noble metal ions to noble metal spherical nanoparticles, the spherical nanoparticles are cracked under the action of light energy along with the progress of an illumination reaction to form some primary nanoparticles with a small triangular plate structure, and then organic acid radicals generate different adsorption actions on different crystal faces of the nanoparticles which are changed under the action of light induction to cause the difference of growth speeds of the crystal faces, so as to form the noble metal nanoparticles with the triangular plate structure which grow along a certain crystal face orientation.

Further in one embodiment, the mass ratio of the organic acid salt to the soluble noble metal salt is 1:10 to 1: 50. When the amount of the organic acid salt is less than the proportion, the obtained noble metal nanoparticles have insufficient dispersibility and are rapidly precipitated due to insufficient stabilizing effect of the organic acid salt in the solution; when the amount of the organic acid salt is larger than this ratio, the resulting noble metal nanoparticles are also aggregated and precipitated in a short time due to an excessively large salt concentration in the organic acid salt solution.

Further in one embodiment, the mass ratio of the organic acid salt to the reducing agent is (0.002-0.008): (0.0003-0.0005). In other words, when the amount of the organic acid salt is in the range of 0.002 to 0.008g, the amount of the reducing agent is in the range of 0.0003 to 0.0005 g. The reducing agent is used for reducing the noble metal ions into a basic shape to be synthesized subsequently. When the dosage of the reducing agent is less than 0.0003g, the obtained noble metal nano seed is long rod-shaped; when the dosage of the reducing agent is 0.0003g to 0.0005g, the obtained noble metal nano seed is triangular plate-shaped; when the dosage of the reducing agent is more than 0.0005g, the obtained noble metal nano-seeds are spherical.

Further in one embodiment, the soluble noble metal salt includes, but is not limited to: gold chloride, silver chloride, chloroauric acid, platinum nitrate, gold nitrate, silver nitrate, and the like.

Further in one embodiment, the organic acid salts include, but are not limited to: at least one of sodium citrate, potassium citrate, sodium oxalate, potassium oxalate, sodium succinate, potassium succinate, sodium tartrate and potassium tartrate.

Further in one embodiment, the reducing agent includes, but is not limited to: at least one of sodium borohydride, lithium borohydride, potassium borohydride, and the like.

Further in one embodiment, the light source includes, but is not limited to: at least one of a laser light source, a halogen lamp light source, an LED lamp light source, and a xenon lamp light source.

Further in one embodiment, the power of the light source is 5-20W. The size of the light source power determines the shape and size of basic nanoparticles (triangular plate structure noble metal nanoparticles), and when the light source power is lower than 5W, the obtained basic shape and size particles are too small; when the power of the light source is greater than 20W, the obtained basic morphology particles are too large, and the phenomenon of nonuniform size is caused. Specifically, spherical particles coexist with small triangular particles in the middle of the light reaction, and as the reaction proceeds, the spherical particles become smaller. And the particles of the triangular plate are continuously adsorbed from the solution, and are subjected to photoreduction under the action of sodium citrate, so that the nano particles of the triangular plate structure further grow up. The end result is that the spherical particles gradually become smaller until they disappear, while the particles with a triangular structure continue to grow. When all spherical particles in the solution are consumed, the size of the particles with the triangular plate structure is not increased. When the power of the light source is small, the spherical nanoparticles cannot be cracked or the cracking degree is low, and then only small triangular plate structured nanoparticles are obtained. When the power of the light source is high, the spherical nanoparticles are cracked too fast, the reaction rate is not effectively controlled, and the phenomenon that the size of the obtained triangular plate nanoparticles is not uniform is caused.

Further in one embodiment, the light reaction time is 30 to 90 min.

In one embodiment, step S20 specifically includes: and mixing the noble metal nanoparticle solution with the triangular plate structure with a solution containing halogen ions, adjusting the pH of the mixed solution to acidity by using inorganic acid, and introducing oxygen for oxidation treatment to obtain the noble metal nanoparticles with the disc-shaped structure.

In a specific embodiment, step S20 specifically includes:

adding a solution containing halogen ions into the noble metal nanoparticle solution with the triangular plate structure under stirring, and adjusting the pH value to weak acidity by using inorganic acid; then pure oxygen is introduced at a certain speed for oxidation treatment, and when the blue noble metal nano particle solution with the triangular plate structure is converted into mauve, the solution with the mauve is the disc-shaped noble metal nano particle converted from the noble metal nano particles with the triangular plate structure.

Further in one embodiment, the pH of the mixed solution is adjusted to 4.5 to 6.5 with a mineral acid. The oxidation etching effect is enhanced due to the existence of acid, thereby improving the yield of the noble metal nano particles with the disc-shaped structure and shortening the etching reaction time.

Further in one embodiment, the oxidation treatment is carried out by passing oxygen at a rate of 0.1 to 0.5 mL/min. The rate is too high, so that the oxygen content in the solution is too high in a short time, and the excessive triangular plate-shaped noble metal nano particles are quickly oxidized into noble metal ions by the too high oxygen content, so that the dissolution phenomenon is generated. Too slow a rate causes the noble metal to become too slow a rate of noble metal ions, affecting the rate of the entire etching reaction.

Further, in one embodiment, the triangular-plate-structured noble metal nanoparticle solution and the halogen ion-containing solution are mixed in such a manner that the molar ratio of the triangular-plate-structured noble metal nanoparticles to the halogen ions is 10:1 to 40: 1. The proportion of halogen ions is too large, the reaction rate is too high, the ion balance state of a system is damaged, and the coagulation phenomenon of the nano particles is easily caused; if the proportion is too small, the reaction is too slow, and the etching effect on the original appearance is not easy to realize.

Further in one embodiment, the halogen ion-containing solution includes, but is not limited to: at least one of a sodium chloride solution, a potassium chloride solution, a sodium bromide solution, a sodium iodide solution, a potassium bromide solution, a potassium iodide solution, and the like.

The invention is further illustrated by the following specific examples.

Example 1

(1) 0.0003g of sodium borohydride was added to a mixed solution of 0.02g of silver nitrate and 0.002g of sodium tartrate at a stirring rate of 2000r/min to obtain a bright yellow solution (seed solution). And (3) placing the bright yellow solution under a 5W LED lamp light source for illumination for 30 minutes, wherein the solution gradually changes from yellow to green and finally changes to blue along with the progress of illumination reaction, and the blue solution is the silver nanoparticle solution with the triangular plate structure.

(2) And (3) dropwise adding 0.01g of sodium chloride solution into the silver nanoparticle solution with the triangular plate structure prepared in the step (1), and uniformly stirring. And (3) adjusting the pH of the solution to 5 by using dilute sulfuric acid, then introducing pure oxygen at the rate of 0.5ml/min, and after the blue silver nanoparticle solution with the triangular plate structure is converted into the purple color, the purple color solution is the disc-shaped silver nanoparticle solution converted from the silver nanoparticle solution with the triangular plate structure.

Example 2

(1) 0.0005g of lithium borohydride was added to a mixed solution of 0.04g of chloroauric acid and 0.008g of sodium succinate at a stirring rate of 2500r/min to obtain a bright yellow solution. And (3) placing the bright yellow solution under a 45W laser source for illumination for 90 minutes, gradually changing the bright yellow solution into green and finally changing the bright yellow solution into blue along with the progress of illumination reaction, wherein the blue solution is the gold nanoparticle solution with the triangular plate structure.

(2) And (3) dropwise adding 0.03g of potassium bromide solution into the gold nanoparticle solution with the triangular plate structure prepared in the step (1), and uniformly stirring. And (3) regulating the pH of the solution to 6 by using dilute nitric acid, introducing pure oxygen at the speed of 0.8ml/min, and converting the blue gold nanoparticle solution with the triangular plate structure into a purplish red solution, namely the gold nanoparticle solution with the disc-shaped structure converted from the gold nanoparticle solution with the triangular plate structure.

Example 3

(1) To a mixed solution of 0.03g of platinum nitrate and 0.006g of potassium citrate was added 0.0004g of lithium borohydride with stirring at 3000r/min to give a bright yellow solution. And (3) placing the bright yellow solution under a 20W halogen light source for illumination for 40 minutes, wherein the solution gradually changes from bright yellow to green and finally changes to blue along with the progress of illumination reaction, and the blue solution is the platinum nanoparticle solution with the triangular plate structure.

(2) And (3) dropwise adding 0.02g of sodium iodide solution into the platinum nanoparticle solution with the triangular plate structure prepared in the step (1), and uniformly stirring. And (3) adjusting the pH of the solution to 5.5 by using dilute nitric acid, then introducing pure oxygen at the speed of 0.6ml/min, and converting the blue platinum nano particle solution with the triangular plate structure into a mauve color, wherein the mauve color solution is the disc-shaped platinum nano particle solution converted from the platinum nano particle solution with the triangular plate structure.

In summary, according to the method for reconstructing the morphology of the noble metal nanoparticles provided by the invention, the noble metal nanoparticles with the triangular plate structure are etched by utilizing the synergistic effect of the coordination and the oxidation reaction of the halogen ions, and specifically, the noble metal nanoparticles with the triangular plate structure are reconstructed into the noble metal nanoparticles with the disc-shaped structure by etching the {110} crystal faces of the noble metal nanoparticles with the triangular plate structure by utilizing the synergistic effect of the coordination and the oxidation reaction of the halogen ions. According to the invention, through the method, the monodisperse precious metal nanoparticles with regular shapes and specific structures are obtained. The shape reconstruction method of the noble metal nano particles provided by the invention has the advantages of simple operation, high repeatability, capability of applying industrial mass synthesis production and the like.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims

1. A method for reconstructing the morphology of noble metal nanoparticles is characterized by comprising the following steps:

mixing a soluble precious metal salt solution, an organic acid salt and a reducing agent, and carrying out reduction reaction to obtain a seed solution, wherein the mass ratio of the organic acid salt to the soluble precious metal salt is 1:10-1: 50; and/or the mass ratio of the organic acid salt to the reducing agent is (0.002-0.008): (0.0003-0.0005); carrying out illumination reaction on the seed solution to obtain a noble metal nanoparticle solution with a triangular plate structure;

mixing the noble metal nanoparticle solution with the triangular plate structure and the solution containing halogen ions according to the molar ratio of the noble metal nanoparticles to the halogen ions of 10:1-40:1, and introducing oxygen for oxidation treatment to obtain the reconstructed noble metal nanoparticles.

2. The method for reconstructing morphology of noble metal nanoparticles according to claim 1, wherein the soluble noble metal salt comprises at least one of silver nitrate, chloroauric acid, and platinum nitrate; and/or

The organic acid salt comprises at least one of sodium citrate, potassium citrate, sodium oxalate, potassium oxalate, sodium succinate, potassium succinate, sodium tartrate and potassium tartrate; and/or

The reducing agent includes at least one of sodium borohydride, lithium borohydride, and potassium borohydride.

3. The method for reconstructing the morphology of noble metal nanoparticles according to claim 1, wherein the seed solution is placed under a light source for light reaction, and the power of the light source is 5-20W; and/or the time of the light reaction is 30-90 min.

4. The method for reconstructing morphology of noble metal nanoparticles according to claim 1, wherein the step of mixing the solution of noble metal nanoparticles having a triangular plate structure with the solution containing halogen ions and introducing oxygen for oxidation treatment comprises: mixing the noble metal nanoparticle solution with the triangular plate structure with a solution containing halogen ions, adjusting the pH of the mixed solution to acidity by using inorganic acid, and introducing oxygen for oxidation treatment.

5. The method of claim 4, wherein the pH of the mixed solution is adjusted to 4.5-6.5 with an inorganic acid.

6. The method of claim 1, wherein the oxidation treatment is carried out by introducing oxygen at a rate of 0.1-0.5 mL/min.

7. The method of claim 1, wherein the solution containing halogen ions comprises at least one of a sodium chloride solution, a potassium chloride solution, a sodium bromide solution, a sodium iodide solution, a potassium bromide solution, and a potassium iodide solution.