CN112705723A

CN112705723A - Control method for size and density of noble metal nanoparticles with ordered structures

Info

Publication number: CN112705723A
Application number: CN201911024067.8A
Authority: CN
Inventors: 王志达; 闫常峰
Original assignee: Guangzhou Institute of Energy Conversion of CAS
Current assignee: Guangzhou Institute of Energy Conversion of CAS
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2021-04-27
Anticipated expiration: 2039-10-25
Also published as: CN112705723B

Abstract

The invention discloses a method for controlling the size and the density of noble metal nano-particles with ordered structures, which can accurately control the size and the density of the noble metal nano-particles by regulating and controlling the molecular weight of hydrophilic and hydrophobic blocks in a polystyrene-polyvinyl pyridine amphiphilic block copolymer, further influence the electron distribution of atoms on the surface of each particle, the interaction among the particles and the energy density which can be converted by the whole array, have important significance for the application of the ordered noble metal nano-particle array in the aspects of catalysis, light, electricity and the like, and provide a material preparation method and a process for optimizing various performances closely related to the size or the density of the particles.

Description

Control method for size and density of noble metal nanoparticles with ordered structures

The technical field is as follows:

the invention relates to a method for controlling the size and density of noble metal nanoparticles with ordered structures.

Background art:

the noble metal (platinum and gold) nano particles with controllable density and size are important functional materials, have extremely high application value in the aspects of medicine, biochemical sensing and the like, and have wide application prospect in the fields of catalytic conversion, photoelectric materials, energy storage and the like. Particularly, after the noble metal nano particles are uniformly and orderly arranged, the probability of agglomeration of the particles in the application process can be remarkably reduced, and the coexistence of high activity and high stability of the metal nano particles is ensured by combining the unique nano effects on the micro scale such as small-size effect, surface effect and the like. However, in the current methods for preparing nanomaterials, such as a sol method, a hydrothermal method and the like, precise control of the size and the density of nanoparticles is difficult to realize.

The invention content is as follows:

the invention aims to provide a method for controlling the size and the density of noble metal nanoparticles with ordered structures, which accurately controls the size and the density of the noble metal nanoparticles by regulating and controlling the number average molecular weights of hydrophilic blocks and hydrophobic blocks in a polystyrene-polyvinyl pyridine amphiphilic block copolymer.

The invention is realized by the following technical scheme:

a method for controlling the size and density of noble metal nanoparticles with ordered structures comprises the following steps:

1) amphiphilic block copolymers with different number average molecular weights are dissolved in selective solvents of polystyrene such as tetrahydrofuran, toluene and the like to form copolymer micelle solution with the concentration of 5mg/ml, and then the micelle solution is dip-plated on a carrier in a dip-coating manner to form a corresponding polymer template; the amphiphilic block copolymer is one of polystyrene-poly 4 vinylpyridine and polystyrene-poly 2 vinylpyridine, the number average molecular weight of polystyrene in the block copolymer is 31900-252000, and the number average molecular weight of the polyvinylpyridine is 13200-43000; the carrier comprises one of a semiconductor, conductive glass and the like;

2) immersing the polymer template obtained in the step (1) into a noble metal precursor solution to prepare a corresponding metal precursor ordered array, then putting the metal precursor ordered array into a plasma cleaning machine for reduction and removing polymers to obtain an ordered structure metal nanoparticle array arranged according to a hexagonal lattice, wherein the particle size and the distribution are uniform, the distribution density of corresponding noble metal particles is controlled by regulating the number average molecular weight of a polystyrene block in an amphiphilic block copolymer, and the size of corresponding noble metal nanoparticles is regulated by regulating the number average molecular weight of a polyvinyl pyridine block in the amphiphilic block copolymer.

The dipping and pulling mode is specifically as follows: and (3) placing the carrier into the solution of the amphiphilic block copolymer micelle, soaking for more than 30s, then pulling the carrier out of the solution at a constant speed of 2-4 mm/min, and standing to obtain the ordered structure polymer template.

The noble metal precursor comprises more than one of chloroplatinic acid, chloroplatinic acid salt, chloroauric acid and chloroauric acid salt.

The concentration of the noble metal precursor is 0.01-0.1 g/ml.

Immersing the polymer template noble metal precursor solution in the step (2) for 20 min-1 h; the plasma is one of oxygen or air; the reduction time is 30 s-2 min.

The invention has the following advantages: firstly, loading the noble metal nanoparticle array prepared by the method on a polymer micelle to obtain an inorganic/organic composite material; secondly, the particles approach to single distribution in the aspects of size, spacing, shape and the like, the dispersibility, the orderliness and the uniformity required by the preparation of the noble metal nanoparticles are realized, and the particles have the advantages that other technologies cannot compare favourably in the control of uniform and ordered distribution; finally, the control of the distribution density of the nano particles is realized by changing the number average molecular weight of polystyrene in the amphiphilic block copolymer, the control of the size of the nano particles is realized by changing the molecular weight of polyvinyl pyridine in the amphiphilic block copolymer, the electronic distribution of surface atoms of all the particles, the interaction among the particles and the energy density which can be converted by the whole array can be influenced, the method has important significance for the application of the ordered noble metal nano particle array in the aspects of catalysis, light, electricity and the like, and a material preparation method and a process are also provided for optimizing various performances closely related to the particle size or the density.

Description of the drawings:

in FIG. 1, a-c are AFM profiles of polymer templates of three block copolymers with different number average molecular weights obtained in step (1) of example 1; in FIG. 1, d-f are the AFM profiles of the gold nanoparticles prepared by using three polymers with different number average molecular weights as templates in step (2) of example 1.

FIG. 2 is the AFM profile and EDS profile of the gold nano-array using the block copolymer template with the number average molecular weight of 41500 and 17500 in example 2.

FIG. 3 is an AFM and SEM images of the ITO supported platinum nanoparticle array prepared in example 3.

FIG. 4 is SEM morphology of platinum nanoparticles carried by FTO in example 4.

The specific implementation mode is as follows:

the following is a further description of the invention and is not intended to be limiting.

Example 1: method for regulating and controlling size of gold nanoparticles with ordered structures

The method comprises the following steps:

(1) 30mg of polystyrene-poly-4-vinylpyridine with number average molecular weights of 31900 (as polystyrene number average molecular weight) -13200 (as poly-4-vinylpyridine number average molecular weight), 37500 (as polystyrene number average molecular weight) -16000 (as poly-4-vinylpyridine number average molecular weight) and 252000 (as polystyrene number average molecular weight) -43000 (as poly-4-vinylpyridine number average molecular weight) were dissolved in 6ml of tetrahydrofuran solution and stirred to form a 5mg/ml micelle solution. At room temperature, the silicon wafer is put into the solution of amphiphilic block copolymer micelle to be soaked for more than 30s, then the carrier is pulled out of the solution at a constant speed of 2mm/min, and the polymer template of the ordered structure block copolymer is obtained by standing and airing, as shown in figures 1 a-1 c.

(2) The three block copolymer templates are put into a chloroauric acid solution of 0.01mg/ml for 20min, washed by deionized water after being taken out, dried by nitrogen, and then put into an air plasma cleaning machine for 30s, and the obtained metal nanoparticle array is shown as d-f in figure 1, and the size and the density distribution are shown in table 1. It can be seen that the diameter of the obtained gold nanoparticles becomes larger as the number average molecular weight of polyvinylpyridine increases; and as the number average molecular weight of the polystyrene increases, the density distribution of the gold nanoparticles decreases. Therefore, the control of the size and the density distribution of the noble metal nano gold particles is realized by adjusting the number average molecular weight of the hydrophilic chain segment and the hydrophobic chain segment of the amphiphilic block copolymer.

TABLE 1

In the tables, 31900, 37500 and 252000 represent the number average molecular weights of polystyrene corresponding to the hydrophobic segment of the amphiphilic block copolymer, and 13200, 16000 and 43000 represent the number average molecular weights of poly (4-vinylpyridine) corresponding to the hydrophilic segment of the amphiphilic block copolymer.

Example 2

The same procedure as in example 1 was followed, except that a block copolymer having a number average molecular weight of 41500 (polystyrene number average molecular weight) to 17500 (poly 4 vinylpyridine number average molecular weight) was used, and the same procedure was followed, and the obtained polymer template and the corresponding noble metal nanoparticles were as shown in FIG. 2, and EDS showed that gold element was present together with the polymer, thus confirming that gold element was supported on the polymer.

The noble metal particles had an average diameter of 21nm and a density distribution of 557/μm²。

Example 3:

the same procedure as in example 2 was followed, except that in the step (2), the noble metal precursor was changed to chloroplatinic acid, the carrier was changed to ITO glass, and the remaining steps were the same, whereby the final product was as shown in fig. 3.

Example 4:

the same procedure as in example 2 was followed, except that the carrier was changed to FTO glass, the pulling rate was changed to 4mm/min, the gold chlorate concentration was 0.1g/ml, and the remaining steps were the same, and the final product was as shown in FIG. 4 (in the figure, the sheet layer was the non-smooth surface protrusions of FTO glass, and the non-noble metal particles).

Example 5:

the same procedure as in example 1 was followed, except that the noble metal precursor in step (2) was changed to sodium chloroaurate, the plasma was changed to oxygen, and the remaining steps were the same, and the final product was the same as in example 1.

Example 6:

the same procedure as in example 2 was followed, except that the solvent was changed to toluene and the noble metal precursor was changed to sodium chloroplatinate, and the remaining steps were the same as in example 3.

Claims

1. A method for controlling the size and the density of noble metal nanoparticles with an ordered structure is characterized by comprising the following steps:

(1) amphiphilic block copolymers with different number average molecular weights are dissolved in a selective solvent of polystyrene to form a copolymer micelle solution with the concentration of 5mg/ml, and then the micelle solution is dip-plated on a carrier in a dip-and-pull mode to form a corresponding polymer template; the amphiphilic block copolymer is one of polystyrene-poly 4 vinylpyridine and polystyrene-poly 2 vinylpyridine, the number average molecular weight of polystyrene in the block copolymer is 31900-252000, and the number average molecular weight of the polyvinylpyridine is 13200-43000; the carrier comprises one of a semiconductor, conductive glass and the like;

(2) immersing the polymer template obtained in the step (1) into a noble metal precursor solution to prepare a corresponding metal precursor ordered array, then putting the metal precursor ordered array into a plasma cleaning machine for reduction and removing polymers to obtain an ordered structure metal nanoparticle array arranged according to a hexagonal lattice, wherein the particle size and the distribution are uniform, the distribution density of corresponding noble metal particles is controlled by regulating the number average molecular weight of a polystyrene block in an amphiphilic block copolymer, and the size of corresponding noble metal nanoparticles is regulated by regulating the number average molecular weight of a polyvinyl pyridine block in the amphiphilic block copolymer.

2. The method for controlling the size and density of ordered-structure noble metal nanoparticles according to claim 1, wherein the impregnation and drawing method is specifically as follows: and (3) placing the carrier into the solution of the amphiphilic block copolymer micelle, soaking for more than 30s, then pulling the carrier out of the solution at a constant speed of 2-4 mm/min, and standing to obtain the ordered structure polymer template.

3. The method for controlling the size and density of ordered-structure noble metal nanoparticles according to claim 1 or 2, wherein the noble metal precursor comprises one or more of chloroplatinic acid, chloroplatinic acid salt, chloroauric acid, and chloroauric acid salt.

4. The method for controlling the size and density of ordered noble metal nanoparticles according to claim 1 or 2, wherein the noble metal precursor concentration is between 0.01 and 0.1 g/ml.

5. The method for controlling the size and density of ordered structure noble metal nanoparticles of claim 1 or 2, wherein the polystyrene selective solvent is tetrahydrofuran or toluene.

6. The method for controlling the size and density of ordered structure noble metal nanoparticles according to claim 1 or 2, wherein the polymer template noble metal precursor solution in the step (2) is immersed for 20min to 1 h; the plasma is one of oxygen or air; the reduction time is 30 s-2 min.