Submicron silver and a method for preparing the same

Abstract

The application discloses sub-micron silver and a preparation method thereof, and the method comprises the following steps: firstly, silver nitrate solution and disulfide bond cleavage agent solution are simultaneously added into a protein solution to slowly form a colloidal mixture containing sub-micron silver; secondly, sodium hydroxide solution or hydrochloric acid solution is added into the colloidal mixture, and then ultrapure water is added and the mixture is left to stand to obtain nascent sub-micron silver; and finally, the nascent sub-micron silver is repeatedly cleaned with ultrapure water and dried to obtain sub-micron silver. In the application, the disulfide bond cleavage agent is used to convert the protein into a colloidal substance, and the silver ions in the silver nitrate are reduced at the same time. The colloidal substance is used as a carrier site to promote nucleation and form sub-micron particles, and the space steric hindrance effect is used to avoid the aggregation of silver particles, so that the sub-micron silver with high dispersion, high crystallinity and regular spherical shape is obtained. The process is simple, efficient, controllable, does not use organic solvents, and is easy to scale up. The sub-micron silver is suitable for high-end electronic paste such as solar cell front silver paste.

Description

Technical Field

[0001] This invention belongs to the field of micro / nano silver technology, specifically relating to a submicron silver and its preparation method. Background Technology

[0002] Silver possesses excellent electrical and thermal conductivity, unique antibacterial properties, catalytic activity, and chemical stability, making it widely used in electronics, photovoltaics, biomedicine, and chemical industries. In recent years, with the rapid development of new energy and the electronics industry, ultrafine silver powder has become a research hotspot in functional materials. The morphology, dispersibility, particle size, and tap density of silver powder have a significant impact on the usability of silver paste. Photovoltaic silver pastes and high-end electronic silver pastes typically require well-dispersed, uniformly sized micro- and nano-spherical silver powders. Currently, many researchers have prepared various types of silver powder using liquid-phase chemical reduction methods, including spherical or near-spherical, flake-like, and linear forms. However, this method introduces some synthetic polymers, such as polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol, which are difficult to completely remove later and require large quantities. Furthermore, the prepared silver powder has poor dispersibility, a rough surface, a wide particle size distribution, and unsatisfactory performance. Many reports describe silver particle sizes in the micrometer or nanometer range, while the development of submicron silver is relatively rare. Therefore, it is very important to select a simple and efficient process to prepare high-purity and highly dispersed submicron silver, which can make up for the shortcomings of micron and nano silver in terms of usability and will have great significance in the electronics and photovoltaic industries. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a method for preparing submicron silver, addressing the shortcomings of the prior art. This method uses a disulfide bond cleaving agent to convert proteins into a gel-like substance, while simultaneously reducing silver ions in silver nitrate. The gel-like substance acts as a carrier site to promote nucleation and formation of submicron particles, and its steric hindrance prevents silver particle aggregation, resulting in highly dispersed, highly crystalline, and regularly shaped spherical submicron silver. This solves the problems of poor dispersibility, irregular morphology, and low purity of existing submicron silver powders.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing submicron silver, characterized in that the method includes the following steps:

[0005] Step 1: Silver nitrate solution and disulfide bond cleaving agent solution are simultaneously added dropwise to the protein solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated to grow, slowly forming a colloidal mixture containing submicron silver.

[0006] Step 2: First, add sodium hydroxide solution or hydrochloric acid solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to settle. After solid-liquid separation, the nascent submicron silver is obtained.

[0007] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0008] The above-described method for preparing submicron silver is characterized in that the protein in the protein solution in step one is collagen, gelatin, bovine serum albumin, or lysozyme, and the concentration of the protein solution is 1 mg / mL to 20 mg / L. These types of proteins readily react with disulfide bond cleaving agents, causing their molecular chains to unfold and reassemble tightly into a gel-like substance. This gel provides an independent site, i.e., a carrier site, for silver nucleus growth. The steric hindrance isolates the silver particles from each other, reducing silver particle aggregation and improving dispersibility. Combined with controlled protein solution concentration, submicron silver is precisely formed with good dispersibility.

[0009] The above-described method for preparing submicron silver is characterized in that the disulfide bond cleaving agent in the disulfide bond cleaving agent solution in step one is tris(2-carboxyethyl)phosphonic acid hydrochloride, cysteine, or dithiothreitol, and the concentration of the disulfide bond cleaving agent solution is 10 mg / mL to 100 mg / L. While breaking down disulfide bonds in proteins and causing them to assemble into a gel-like substance, the aforementioned disulfide bond cleaving agent also causes silver ions in silver nitrate to be slowly reduced and nucleated, effectively controlling the size and morphology of the submicron silver.

[0010] The above-described method for preparing submicron silver is characterized in that the concentration of the silver nitrate solution in step one is 3 mg / mL to 50 mg / L; and the concentration of the sodium hydroxide solution or hydrochloric acid solution in step two is 0.2 mol / L to 2 mol / L. This invention uses sodium hydroxide solution or hydrochloric acid solution to etch and dissolve the colloidal substance, causing the submicron silver to detach from the colloidal carrier and settle. By strictly controlling the solution concentration, the final submicron silver is highly dispersed and has a spherical morphology, avoiding the problems of irregular morphology and severe agglomeration of submicron silver.

[0011] Furthermore, the present invention also discloses a submicron silver, characterized in that it is prepared by the above-described method.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. This invention utilizes a disulfide bond cleaving agent to break the disulfide bonds in proteins, causing the protein molecular chains to unfold and form a gel-like substance. Simultaneously, silver ions in silver nitrate are reduced. This gel-like substance acts as a carrier site to promote the nucleation and growth of the reduced silver atoms into silver particles. The steric hindrance of the gel-like substance prevents the silver particles from agglomerating, allowing each silver nucleus to grow independently to a submicron-sized silver particle. After sedimentation, solid-liquid separation, washing, and drying to remove the gel-like substance, highly dispersed and highly crystalline submicron silver with a regular morphology and a near-spherical shape is obtained.

[0014] 2. The preparation process of the present invention is simple, efficient, and controllable, and is easy to scale up for production.

[0015] 3. The preparation process of this invention does not use organic solvents, does not involve synthetic polymers, is green and environmentally friendly, and has a simple cleaning process.

[0016] 4. The submicron silver particles prepared by this invention have uniform particle size, regular morphology, good dispersibility, and high crystallinity and purity, making them suitable for high-end electronic pastes such as silver paste for the front side of solar cells.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the submicron silver prepared in Example 1 of this invention.

[0019] Figure 2 This is a scanning electron microscope image of the submicron silver prepared in Example 2 of the present invention.

[0020] Figure 3 This is an X-ray diffraction pattern of submicron silver prepared in Example 2 of this invention.

[0021] Figure 4 This is a scanning electron microscope image of the submicron silver prepared in Example 3 of the present invention.

[0022] Figure 5 This is a scanning electron microscope image of submicron silver prepared in Example 5 of this invention.

[0023] Figure 6 This is a scanning electron microscope image of the submicron silver prepared in Example 6 of this invention. Detailed Implementation

[0024] Example 1

[0025] This embodiment includes the following steps:

[0026] Step 1: Simultaneously add 3 mg / L silver nitrate solution and 10 mg / L tris(2-carboxyethyl)phosphonic acid hydrochloride solution to 3 mg / mL gelatin solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grown. After standing for 20 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0027] Step 2: First, add 0.5 mol / L sodium hydroxide solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0028] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0029] Figure 1 This is a scanning electron microscope image of the submicron silver prepared in this embodiment. Figure 1 It can be seen that the silver particles have a spherical morphology, a very smooth surface, and a particle size of 0.3μm~0.7μm, exhibiting excellent dispersibility.

[0030] Example 2

[0031] This embodiment includes the following steps:

[0032] Step 1: Simultaneously add 15 mg / L silver nitrate solution and 100 mg / L tris(2-carboxyethyl)phosphine hydrochloride solution to 20 mg / mL gelatin solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grown. After standing for 20 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0033] Step 2: First, add 1 mol / L sodium hydroxide solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0034] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0035] Figure 2 This is a scanning electron microscope image of the submicron silver prepared in this embodiment. Figure 2 It can be seen that the silver particles have a spherical morphology, a relatively smooth surface, and a particle size of 0.2μm~0.5μm, exhibiting excellent dispersibility.

[0036] Figure 3 This is the X-ray diffraction pattern of submicron silver prepared in this embodiment. Figure 3 The mid-wave diffraction peaks show that the submicron silver is of very high purity and free of impurities, and the sharp peaks indicate that its crystallinity is also very high.

[0037] Example 3

[0038] This embodiment includes the following steps:

[0039] Step 1: Add 10 mg / L silver nitrate solution and 50 mg / L cysteine ​​solution dropwise to 1 mg / mL lysozyme solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grow. After standing for 20 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0040] Step 2: First, add 0.2 mol / L sodium hydroxide solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0041] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0042] Figure 4 This is a scanning electron microscope image of the submicron silver prepared in this embodiment. Figure 4 It can be seen that the silver particles are relatively smooth, with a particle size of 0.3μm~0.5μm, and have good dispersibility with no obvious agglomeration.

[0043] Example 4

[0044] This embodiment includes the following steps:

[0045] Step 1: Simultaneously add 30 mg / L silver nitrate solution and 100 mg / L dithiothreitol solution to 20 mg / mL bovine serum albumin solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grow. After standing for 20 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0046] Step 2: First, add 1 mol / L hydrochloric acid solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0047] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0048] Testing revealed that the submicron silver particles prepared in this embodiment had a particle size of 0.4 μm to 0.8 μm and exhibited good dispersibility.

[0049] Example 5

[0050] This embodiment includes the following steps:

[0051] Step 1: Simultaneously add 50 mg / L silver nitrate solution and 80 mg / L tris(2-carboxyethyl)phosphine hydrochloride solution to 15 mg / mL lysozyme solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grow. After standing for 30 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0052] Step 2: First, add 2 mol / L hydrochloric acid solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0053] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0054] Figure 5 This is a scanning electron microscope image of the submicron silver prepared in this embodiment. Figure 5 It can be seen that the silver particles have a relatively smooth surface, a particle size of 0.15μm~0.35μm, and good dispersibility.

[0055] Example 6

[0056] This embodiment includes the following steps:

[0057] Step 1: Simultaneously add 25 mg / L silver nitrate solution and 80 mg / L tris(2-carboxyethyl)phosphine hydrochloride solution to 18 mg / mL bovine serum albumin solution. While breaking the disulfide bonds of the protein, silver ions are reduced and nucleated and grow. After standing for 30 minutes, a gel-like mixture containing submicron silver is slowly formed.

[0058] Step 2: First, add 2 mol / L sodium hydroxide solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to precipitate. After solid-liquid separation, the nascent submicron silver is obtained.

[0059] Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

[0060] Figure 6 This is a scanning electron microscope image of the submicron silver prepared in this embodiment. Figure 6 It can be seen that the silver particles have a relatively smooth surface, a particle size of 0.25μm~0.55μm, good dispersibility, and no obvious agglomeration.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing submicron silver, characterized in that, The method includes the following steps: Step 1: Silver nitrate solution and disulfide bond cleaving agent solution are simultaneously added dropwise to the protein solution. While breaking the disulfide bonds in the protein, silver ions are reduced and nucleated, slowly forming a colloidal mixture containing submicron silver. The concentration of the protein solution is 1 mg / mL to 20 mg / L. The disulfide bond cleaving agent in the disulfide bond cleaving agent solution is tris(2-carboxyethyl)phosphonic acid hydrochloride or cysteine, and the concentration of the disulfide bond cleaving agent solution is 10 mg / mL to 100 mg / L. Step 2: First, add sodium hydroxide solution or hydrochloric acid solution to the gel-like mixture formed in Step 1, then add ultrapure water and let it stand to allow the submicron silver to settle. After solid-liquid separation, the nascent submicron silver is obtained. Step 3: Wash the nascent submicron silver obtained in Step 2 with ultrapure water more than three times, and then dry it to obtain submicron silver.

2. The method for preparing submicron silver according to claim 1, characterized in that, The protein in the protein solution mentioned in step one is collagen, gelatin, bovine serum albumin, or lysozyme.

3. The method for preparing submicron silver according to claim 1, characterized in that, The concentration of the silver nitrate solution in step one is 3 mg / mL to 50 mg / L; the concentration of the sodium hydroxide solution or hydrochloric acid solution in step two is 0.2 mol / L to 2 mol / L.

4. A submicron silver, characterized in that, Prepared by the method described in any one of claims 1 to 3.

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