Synthesis method and use method of large-particle gold-silver core-shell structure composite nanoparticles

Abstract

The invention discloses a synthesis method and a use method of large-particle gold-silver core-shell structure composite nanoparticles. According to the method, an acetic acid-chlorine-gold compound solution is prepared through the steps of dissolving, concentrating, crystallizing, washing and the like, and a pure gold salt solution without halogen is obtained, so that halogenated precipitates are prevented from being generated on the surface of a silver core. Meanwhile, ascorbic acid is adopted as a reducing agent to control the reaction to be mild, and the gold-shell silver-core nanoparticles which are stable in structure and uniform in coating are obtained. According to the method, the composite nanoparticles which are high in purity and firm in wrapping are provided, the method is suitable for the fields of immunodetection, surface enhanced Raman scattering and the like, the material cost is effectively reduced, and the detection effect is improved.

Description

Technical Field

[0001] The invention relates to a synthesis method and a use method of large-particle gold-silver core-shell structure composite nanoparticles, belonging to the field of nanomaterials. Background Art

[0002] Noble metal nanomaterials organically combine the unique physical and chemical properties of precious metals with the special properties of nanomaterials, and have broad applications in chemical catalysis, biomedicine, optical enhancement, energy, and electronics.

[0003] Gold and silver core-shell structured nanoparticles have many special physical and chemical properties. Compared with single metal nanoparticles, bimetallic composites can combine the advantages of different materials and have better physical and chemical properties than single metals. Gold and silver are both face-centered cubic metals with similar lattice parameters, which enables them to be epitaxially grown under appropriate conditions to prepare core-shell gold and silver nanoparticles, so that the obtained particles have the special properties of gold and silver, for example: they have both the stability of gold and the high SERS activity of silver.

[0004] The existing method for synthesizing gold-shell silver-core nanoparticles is usually chemical reduction. In the process of chemical reduction, the gold salt generally used is a common reagent such as tetrachlorohydric acid. However, these halogen-containing reagents will cause silver halide precipitation during the synthesis process, which will hinder the attachment and growth of gold on the surface of the silver core; on the other hand, reagents such as tetrachlorohydric acid will cause the silver nanoparticles to be severely etched during the process.

[0005] At the same time, it is difficult to obtain large-particle (particle size 70-110nm) silver nanoparticles by general methods in practice. Silver nanoparticles produced by chemical reduction are generally in the range of 20-50nm. To produce large-particle silver nanoparticles, it is necessary to promote the formation of stable crystal nuclei and further grow them fully to grow into large-particle nanoparticles.

[0006] In short, how to prevent silver halide precipitation from hindering the attachment of gold to the surface of the silver core, allow gold to grow uniformly and stably on the large-grain silver core, and avoid silver being etched in the process to obtain large-grain nanoparticles with uniform, continuous and stable core-shell structure is a difficult problem in practice. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for synthesizing and using large-particle gold-silver core-shell structure composite nanoparticles to overcome the problems existing in the above-mentioned prior art.

[0008] The technical solution of the present invention is:

[0009] In the first aspect, a method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles is proposed, the method comprising:

[0010] Step 1, dissolving acetic acid in water at a volume ratio of 1:90-1:8, further dissolving sodium chloride in the solution at a mass ratio of 1:500-1:50, adding gold to the solution at a mass ratio of 1:1000-1:100, heating to 50-100° C., dripping nitric acid until the gold is completely dissolved, stopping dripping, and obtaining an “acetic acid-chlorine-gold” complex solution;

[0011] Step 2, concentrating and crystallizing the prepared "acetic acid-chlorine-gold" complex solution, washing the crystals, removing impurities, and dissolving the gold salt in deionized water to prepare a gold salt solution;

[0012] Step 3, add PVP to deionized water, the concentration of PVP is 0.8-8g / L; add the gold salt solution with a concentration of 0.01-0.06M prepared in step 2 at a volume ratio of 1:100-1:1000, and then stir; add NaBH with a concentration of 0.05-0.5M at a volume ratio of 1:4-1:25 4 solution; continue stirring and then let stand to prepare a gold nano seed solution;

[0013] Step 4, using the gold salt solution generated in step 3 to prepare a gold nano seed solution to prepare silver nanoparticles, the preparation method is: adding ammonia water to the silver nitrate solution until a silver ammonia solution is prepared, taking a silver ammonia solution with a concentration of 0.02-0.4M, adding PVP, the PVP concentration is 0.8-8g / L, adding acetonitrile at a volume ratio of 1:5-1:30, adding a 0.1M ascorbic acid solution at a volume ratio of 1:5-1:20, stirring and heating to 40-80°C, adding the gold nano seed solution prepared in step 3 at a volume ratio of 1:100000-1:300000, stirring at the same time, to prepare an AgNPs solution;

[0014] Step 5: using the silver nanoparticles generated in step 4 and the gold salt solution generated in step 2 to prepare gold-shell silver-core nanoparticles, the preparation method is as follows:

[0015] ① Centrifuge the AgNPs solution prepared in step 4, wash it, remove the lower nanolayer, add deionized water at a volume ratio of 1:5 to 1:50, stir evenly, and obtain a colloidal solution;

[0016] ② Add SDS to the AgNPs colloidal solution, the SDS concentration is 1-8g / L, and then stir;

[0017] ③ Add the gold salt solution containing Au ions of 0.001-0.005M prepared in step 2 at a volume ratio of 1:1 to 1:30;

[0018] ④ After 3-5 minutes, add 0.1-0.3M ascorbic acid solution at a volume ratio of 1:5-1:20;

[0019] ⑤Continue stirring;

[0020] ⑥ Add 5-20 g / L sodium citrate solution at a volume ratio of 1:20 to 1:40 to obtain gold-coated silver core-shell composite nanoparticles.

[0021] Preferably, in step 3, the gold salt solution prepared in step 2 is added at a volume ratio of 1:100 to 1:1000 and the stirring time is 1-5 minutes.

[0022] Preferably, in step 3, NaBH with a concentration of 0.05-0.5 M is added at a volume ratio of 1:4 to 1:25. 4 The solution is stirred for 5-20 minutes and allowed to stand for 3-12 hours.

[0023] Preferably, in step 4, when the gold nano seed solution prepared in step 3 is added at a volume ratio of 1:100000 to 1:300000, the stirring speed is 1000-2000 r / min, and the stirring time is 20 to 50 min.

[0024] Preferably, the stirring time in step 5 is 1-10 min, and the stirring speed is 1000-2000 r / min.

[0025] Preferably, the stirring time in step 5 is 20-50 min.

[0026] In the second aspect, a method for using large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method described in the first aspect is proposed, and the method is to use the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for immunoassay.

[0027] In the third aspect, a method for using the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method described in the first aspect is proposed, and the method is to use the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for surface enhanced Raman scattering.

[0028] The beneficial effects of the present invention are: compared with the prior art,

[0029] 1) The present invention uses acetic acid and nitric acid to dissolve metallic gold, prepares an "acetic acid-chlorine-gold" complex solution, and removes excess chloride ions and impurities through concentration, crystallization and washing to obtain a pure gold salt solution. On the one hand, since the gold salt solution contains almost no chloride ions, the possibility of silver ions and chloride ions generating AgCl is greatly reduced, thereby avoiding the formation of a barrier layer. This process ensures that the halogen content in the gold salt solution is extremely low, thereby avoiding the interference of chloride ions in subsequent reactions. During the chemical reduction process, the silver halide precipitation generated on the surface of the silver core is extremely low, thereby enabling gold to be uniformly and continuously wrapped on the surface of the silver core. On the other hand, the electrode potential of the halogen-free gold salt precursor is low, the reaction is milder, the oxidation etching of the silver core is reduced, and the structure of the gold shell silver core nanoparticle is more stable. The pure gold salt precursor is conducive to the uniform reduction and deposition of gold ions on the surface of the silver core, thereby forming a continuous and stable gold shell.

[0030] 2) In the present invention, ascorbic acid (vitamin C) is used as a reducing agent in step 3 and step 5. Ascorbic acid is a mild reducing agent that can control the reduction rate of gold ions and promote the uniform growth of the gold shell;

[0031] 3) The present invention synthesizes large-grained silver nanoparticles, and uses the excellent affinity of the new gold complex with the silver core to uniformly grow a gold shell on the surface of the silver core, which is evenly and firmly wrapped. The composite nanoparticles are composed of the single substance form of gold and silver metals and have high purity. This provides good conditions for the application of this composite nanomaterial in immunoassay and surface enhanced Raman scattering;

[0032] 4) The present invention uses gold-shell silver-core nanoparticles instead of colloidal gold. Since nano-scale gold particles are uniformly attached to the surface, they can also be adsorbed by proteins and firmly coated, and further aggregated and colored. The application of gold-shell silver-core nanoparticles in immunoassays can significantly reduce material costs and achieve better color development effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The morphology of the large-particle gold-silver core-shell structure composite nanoparticles prepared by the present invention at TEM 43000x;

[0034] Figure 2 The morphology of the large-particle gold-silver core-shell structure composite nanoparticles prepared by the present invention at TEM 71000x;

[0035] Figure 3 The morphology of another large-particle gold-silver core-shell structure composite nanoparticle prepared by the present invention at TEM 71000x;

[0036] Figure 4 The morphology of the large-particle gold-silver core-shell structure composite nanoparticles prepared by the present invention at TEM 195000x;

[0037] Figure 5 The morphology of another large-particle gold-silver core-shell structure composite nanoparticle prepared by the present invention at TEM 195000x;

[0038] Figure 6 The morphology of the large-particle gold-silver core-shell structure composite nanoparticles prepared by the present invention at TEM 1050000x. DETAILED DESCRIPTION

[0039] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0040] Implementation Example 1:

[0041] The experimental steps are as follows:

[0042] 1. Preparation of large silver nanoparticles:

[0043] 1) Preparation of gold seeds:

[0044] ① Dissolve acetic acid in water at a volume ratio of 1:90-1:8, and further dissolve sodium chloride in the solution at a mass ratio of 1:500-1:50. Add gold to the solution at a mass ratio of 1:1000-1:100, heat to 50-100°C, drip nitric acid until the gold is completely dissolved, and stop dripping. The "acetic acid-chlorine-gold" complex solution is obtained.

[0045] The prepared "acetic acid-chlorine-gold" solution is concentrated and crystallized, the crystals are washed to remove impurities, and the gold salt is dissolved in deionized water to prepare a gold salt solution.

[0046] Metallic gold is chemically inert and difficult to dissolve directly. Acetic acid and chloride ions are used to form ligands with gold, which effectively reduces the electrode potential. Gold can be dissolved under the oxidation of a small amount of nitric acid to form a stable "acetic acid-chloride-gold" complex. Through crystallization, washing crystals, and re-dissolution, a new type of gold salt solution is formed. On the one hand, this gold salt has a low electrode potential, which can effectively slow down the etching of silver in subsequent reactions, and on the other hand, it can effectively reduce the generation of silver halide in subsequent reactions.

[0047] ② Add polyvinyl pyrrolidone (PVP) to deionized water, the concentration of PVP is 0.8-8g / L; add the gold salt solution prepared in the above step ① with a concentration of 0.01-0.06M at a volume ratio of 1:100-1:1000, stir for 1-5min; add NaBH with a concentration of 0.05-0.5M at a volume ratio of 1:4-1:25 4 solution; continue stirring for 5-20 minutes and then let stand for 3-12 hours to prepare the gold nano seed solution.

[0048] NaBH 4As a strong reducing agent, gold ions (Au 3+ ) is reduced to gold nanoparticles (Au). PVP forms a protective layer on the surface of the nanoparticles to prevent the particles from agglomerating. The gold nanoseeds promote the formation and further growth of crystal nuclei, guiding the growth of silver nanoparticles.

[0049] 2) Preparation of large silver nanoparticles

[0050] Add ammonia water to the silver nitrate solution until a silver ammonia solution is obtained. Take a silver ammonia solution with a concentration of 0.02-0.4M, add PVP, the PVP concentration is 0.8-8g / L, add acetonitrile at a volume ratio of 1:5-1:30, and add a 0.1M ascorbic acid solution at a volume ratio of 1:5-1:20. Heat to 40-80°C in a constant temperature magnetic stirrer, quickly add the above gold nano seed solution at a volume ratio of 1:100000-1:300000, and stir at 1000-2000r / min for 20-50min.

[0051] Ascorbic acid converts silver ions (Ag + ) is reduced to silver nanoparticles (Ag). The gold nanoseeds promote the formation and further growth of crystal nuclei, resulting in the full growth of silver nanoparticles. The presence of PVP and acetonitrile improves the dispersibility and stability of the nanoparticles.

[0052] 2. Preparation of Large Gold Shell Silver Core Nanoparticles

[0053] ① Centrifuge the above AgNPs solution, wash it, remove the lower nanolayer, add deionized water at a volume ratio of 1:5 to 1:50, stir evenly, and obtain a colloidal solution with good light channel transmission when irradiated by a laser pen.

[0054] ② Add sodium dodecyl sulfate (SDS) to the AgNPs colloidal solution, the SDS concentration is 1-8 g / L, stir for 1-10 min, and the rotation speed is 1000-2000 r / min.

[0055] ③ Add "acetic acid-chloride-gold" solution containing Au ion concentration of 0.001-0.005M at a volume ratio of 1:1 to 1:30.

[0056] ④After 3-5 minutes, add 0.1-0.3M ascorbic acid solution at a volume ratio of 1:5 to 1:20.

[0057] ⑤Continue stirring for 20-50 minutes.

[0058] ⑥ Add 5-20g / L sodium citrate solution at a volume ratio of 1:20 to 1:40 as a protective agent to prevent agglomeration.

[0059] First, remove the unreacted substances and impurities to ensure the uniform coating of the subsequent gold shell. SDS, as an anionic surfactant, can form a stable double layer on the surface of silver nanoparticles and promote the adsorption of gold ions. Ascorbic acid will adsorb the gold ions (Au 3+ ) is reduced to gold (Au 0 ), forming a gold shell. The role of sodium citrate is to further stabilize the nanoparticles, prevent agglomeration, and improve dispersibility.

[0060] That is, large-particle gold-silver core-shell structure composite nanoparticles are obtained.

[0061] The overall advantages and innovations of the present invention are as follows:

[0062] 1) Slow down the etching of silver core: The new gold salt precursor electrode has a lower potential, which effectively slows down the etching of silver core compared with the traditional method.

[0063] 2) Effectively reduce silver halide precipitation: By preparing a new type of gold salt precursor, the problem of silver halide hindering the growth of gold shell is effectively reduced compared with the traditional method.

[0064] 3) High stability and dispersibility: The synergistic effect of PVP, SDS and sodium citrate improves the stability and dispersibility of nanoparticles.

[0065] 4) Large-particle nanoparticle size: Large-particle gold-shell silver-core nanoparticles with large particle size (70-110nm), uniform size and controllable morphology were obtained.

[0066] Experimental results:

[0067] The prepared nanoparticles were scanned by transmission electron microscopy (TEM) to obtain Figure 1-Figure 6 The results show that the large-particle gold-silver core-shell structure nanoparticles synthesized by this method are uniform and stable, the silver core particle size can be 50-100nm, and the gold atom clusters can grow evenly attached to the silver core. The nanoparticles prepared by the traditional method using tetrachloro and gold acid as gold sources are to some extent a mixture of gold and silver nanoparticles, and the gold attachment and growth of some composite nanoparticles are poor. This method is significantly different from them. The new gold source plays a good role in hindering the attachment of gold and silver cores by silver halide precipitation. At the same time, the silver core in the composite nanoparticles prepared by the traditional method is severely etched, but this method significantly improves this problem. The electron microscope scanning results show that the silver core is not obviously etched.

[0068] Implementation Example 2:

[0069] In this embodiment, a method for using the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method proposed in Example 1 is proposed. This method is to use the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for immunoassay.

[0070] Implementation Example 3:

[0071] In this embodiment, a method for using the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method proposed in Example 1 is proposed. The method is to use the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for surface enhanced Raman scattering.

[0072] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles, characterized in that: The method is: Step 1, dissolve acetic acid in water at a volume ratio of 1:90-1:8, further dissolve sodium chloride in the solution at a mass ratio of 1:500-1:50, add gold to the solution at a mass ratio of 1:1000-1:100, heat to 50-100°C, drip nitric acid until the gold is completely dissolved, stop dripping, and obtain an "acetic acid-chlorine-gold" complex solution; Step 2, concentrating and crystallizing the prepared "acetic acid-chlorine-gold" complex solution, washing the crystals, removing impurities, and dissolving the gold salt in deionized water to prepare a gold salt solution; Step 3, adding PVP to deionized water, the concentration of PVP is 0.8-8 g / L; adding the gold salt solution with a concentration of 0.01-0.06 M prepared in step 2 at a volume ratio of 1:100-1:1000, and then stirring; adding NaBH4 solution with a concentration of 0.05-0.5 M at a volume ratio of 1:4-1:25; continuing to stir and then standing to prepare a gold nano seed solution; Step 4, using the gold salt solution generated in step 3 to prepare a gold nano seed solution to prepare silver nanoparticles, the preparation method is: adding ammonia water to the silver nitrate solution until a silver ammonia solution is prepared, taking a silver ammonia solution with a concentration of 0.02-0.4M, adding PVP, the PVP concentration is 0.8-8g / L, adding acetonitrile at a volume ratio of 1:5-1:30, adding a 0.1M ascorbic acid solution at a volume ratio of 1:5-1:20, stirring and heating to 40-80°C, adding the gold nano seed solution prepared in step 3 at a volume ratio of 1:100000-1:300000, stirring at the same time, to prepare an AgNPs solution; Step 5: using the silver nanoparticles generated in step 4 and the gold salt solution generated in step 2 to prepare gold-shell silver-core nanoparticles, the preparation method is as follows: ① Centrifuge the AgNPs solution prepared in step 4, wash it, remove the lower nanolayer, add deionized water at a volume ratio of 1:5 to 1:50, stir evenly, and obtain a colloidal solution; ② Add SDS to the AgNPs colloidal solution at a concentration of 1-8 g / L and then stir; ③ Add the gold salt solution containing Au ions of 0.001-0.005M prepared in step 2 at a volume ratio of 1:1 to 1:30; ④ After 3-5 minutes, add 0.1-0.3M ascorbic acid solution at a volume ratio of 1:5-1:20; ⑤Continue stirring; ⑥ Add 5-20 g / L sodium citrate solution at a volume ratio of 1:20 to 1:40 to obtain gold-coated silver core-shell composite nanoparticles.

2. The method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles according to claim 1, characterized in that: In step 3, the gold salt solution prepared in step 2 is added at a volume ratio of 1:100 to 1:1000 and the stirring time is 1 to 5 minutes.

3. The method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles according to claim 1, characterized in that: In the step 3, after adding a NaBH4 solution with a concentration of 0.05-0.5M at a volume ratio of 1:4 to 1:25, the stirring time is continued for 5-20 minutes, and the standing time after stirring is 3-12 hours.

4. The method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles according to claim 1, characterized in that: In the step 4, when the gold nano seed solution prepared in step 3 is added at a volume ratio of 1:100000 to 1:300000, the stirring speed is 1000-2000 r / min, and the stirring time is 20 to 50 min.

5. The method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles according to claim 1, characterized in that: The stirring time in step 5 is 1-10 min, and the stirring speed is 1000-2000 r / min.

6. The method for synthesizing large-particle gold-silver core-shell structure composite nanoparticles according to claim 1, characterized in that: The stirring time in step 5 is 20-50 minutes.

7. A method for using large-particle gold-silver core-shell composite nanoparticles synthesized by the method of claims 1-6, characterized in that: The method comprises the following steps: using the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for immunoassay.

8. A method for using large-particle gold-silver core-shell composite nanoparticles synthesized by the method of claims 1-6, characterized in that: The method comprises the following steps: using the large-particle gold-silver core-shell structure composite nanoparticles synthesized by the method for surface enhanced Raman scattering.

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