A method for synthesizing gold / silver core-shell structure nanoparticles

Abstract

The application discloses a method for synthesizing gold / silver core-shell structure nanoparticles, which comprises the following steps: S01, preparing silver sol and diluting the silver sol with water to obtain a silver sol solution, wherein the volume ratio of the silver sol to the water is 1:0.5 to 1:2; S02, adding sodium dodecyl sulfonate into the silver sol solution, and the mass ratio of the sodium dodecyl sulfonate to the silver sol is 1:300-1:1000; S03, adding an "acetic acid-chlorine-gold" complex solution into the product in the step S02 at 30-80 DEG C, and the volume ratio is 1:200-1:50; S04, adding ascorbic acid into the product in the step S03, and the mass ratio is 1:2000-1:200, and stirring for 2-20 min; and S05, obtaining noble metal sol by standing and cooling the solution in the step S04. The gold shell silver core nanoparticles generated by the prior art all have compound forms, and are not in the form of pure gold and silver.

Description

Technical Field

[0001] This invention relates to a method for synthesizing gold / silver core-shell structured nanoparticles, belonging to the field of nanomaterials. Background Technology

[0002] Gold and silver nanoparticles belong to the category of metal-based synthetic nanomaterials. They possess both the chemical properties of noble metals and the performance characteristics of nanoparticles, exhibiting unique properties and functions. They have wide applications in catalysts, sensing elements, optical devices, and biomedicine. Currently, colloidal gold (gold nanoparticles) is rapidly developing in applications such as immunotherapy, food safety, chemical catalysis, and surface enhancement. Gold nanoparticles are uniform and stable, while silver nanoparticles have advantages such as good optical properties and low cost. Synthesizing gold-shelled nanomaterials with gold encapsulating a silver core can combine the advantages of both, creating a cost-effective application advantage.

[0003] The synthesis of gold-shelled silver-core nanoparticles presents significant technical challenges. It requires achieving robust adhesion, uniform growth, and uniform encapsulation of gold clusters on silver core nanoparticles at the micro- and nano-scale, while also ensuring good dispersion and stability. To date, successful examples are few, and the reported cases all have unresolved technical issues.

[0004] Limited reports on the synthesis of gold-shelled silver-core nanoparticles generally involve adding tetrachloroalloyic acid to synthesized silver nanoparticles, allowing the silver to reduce the gold through a displacement reaction, or adding a reducing agent to reduce the gold. However, the synthesized nanoparticles are unstable and prone to aggregation, with gold loosely adhering to the silver core surface. Furthermore, the rapid formation of silver chloride precipitate from silver ions and chloride ions hinders the affinity and encapsulation of gold on the silver core surface. Tetraiodoalloyic acid has been used instead of tetrachloroalloyic acid, but the effects are similar, resulting in unsatisfactory synthesis outcomes. Nanoparticles obtained by these methods, as detected under transmission electron microscopy, all exhibit compound morphologies, rather than being entirely elemental gold or silver. This limits the applications of these gold-shelled silver-core composite nanoparticles, preventing their effective application in fields such as immunology, food safety, and chemical catalysis. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for synthesizing gold / silver core-shell structured nanoparticles, so as to overcome the problems existing in the prior art.

[0006] The technical solution of this invention is: a method for synthesizing gold / silver core-shell structured nanoparticles, comprising the following steps:

[0007] S01. Prepare silver sol and dilute it with water to obtain a silver sol solution, wherein the volume ratio of silver sol to water is 1:0.5 to 1:2;

[0008] S02. Add sodium dodecyl sulfonate to the silver sol solution, with the mass ratio of sodium dodecyl sulfonate to silver sol being 1:300 to 1:1000.

[0009] S03. Under conditions of 30-80℃, add an acetic acid-chlorine-gold complex solution to the product in step S02 at a volume ratio of 1:200-1:50.

[0010] S04. Add ascorbic acid to the product of step S03 at a mass ratio of 1:2000 to 1:200, and stir for 2 to 20 minutes.

[0011] S05. Allow the solution in step S04 to stand and cool to obtain a noble metal sol;

[0012] The preparation method of the "acetic acid-chlorine-gold" complex solution is as follows: prepare an acetic acid solution by dissolving sodium chloride in the acetic acid solution to obtain a sodium chloride-acetic acid solution; add gold to the sodium chloride-acetic acid solution at 60-95℃ and add nitric acid until the gold is completely dissolved to obtain the "acetic acid-chlorine-gold" complex solution.

[0013] Preferably, the method for preparing silver sol in step S01 includes the following steps:

[0014] S01-1. Dissolve α-cyclodextrin or β-cyclodextrin in water at a mass ratio of 1:500 to 1:50 to obtain an α-cyclodextrin solution or a β-cyclodextrin solution; dissolve silver nitrate in water at a mass ratio of 1:6000 to 1:1000 to obtain a silver nitrate solution;

[0015] S01-2. Add n-butanol to the α-cyclodextrin solution or β-cyclodextrin solution at a volume ratio of 1:100 to 1:10, and add ethanol to the α-cyclodextrin solution or β-cyclodextrin solution at a volume ratio of 1:100 to 1:10.

[0016] Under the conditions of S01-3 and 30-90℃, add the silver nitrate solution prepared in step S01-1 to the product of step S01-2 at a volume ratio of 1:250-1:25.

[0017] After S01-4 and 1-10 min, add NaOH solution dropwise to the product from step S01-3 to adjust the pH to 10-12, and continue stirring for 10-30 min.

[0018] Preferably, the reaction conditions for step S01-3 further include vigorous stirring in a water bath.

[0019] The beneficial effects of this invention are as follows: Compared with the prior art, this invention has the following advantages: This invention prepares silver nanoparticles by reduction with α-cyclodextrin or β-cyclodextrin. Simultaneously, α-cyclodextrin or β-cyclodextrin has a special adsorption effect on gold. Under adjusted polarity, the surface tension environment of the cyclodextrin solution is conducive to the growth of gold on the surface of the silver core. Affinity and adhesion of the two metals are achieved in a microscopic environment, resulting in strong gold adhesion on the silver core surface and uniform dispersion of the sol system. By dissolving gold in an unconventional manner as a gold source, the new gold complex exhibits excellent affinity with the silver core in the cyclodextrin solution, showing good performance. A uniform gold shell grows on the surface of the silver core, providing a uniform and strong coating. Furthermore, compared with gold salt reagents such as tetrachloroalloyic acid, the synthesis process reduces the introduction of halides, resulting in better performance. The composite nanoparticles are composed of elemental forms of both gold and silver, exhibiting high purity. These factors provide favorable conditions for the application of this composite nanomaterial. Attached Figure Description

[0020] Figure 1 This is a crystal diffraction diagram of the gold complex obtained in this invention;

[0021] Figure 2 This is a diffraction pattern of another crystal of the gold complex obtained in this invention;

[0022] Figure 3 This is a diffraction pattern of another crystal of the gold complex obtained in this invention;

[0023] Figure 4 This is a diffraction pattern of another crystal of the gold complex obtained in this invention;

[0024] Figure 5 TEM images of the gold-shelled silver-core composite nanoparticles prepared in this invention at different magnifications;

[0025] Figure 6 The TEM image of (a) particles of the gold-shelled silver-core composite nanomaterial prepared in this invention is shown.

[0026] Figure 7 The TEM image shows (b) of the gold-shelled silver-core composite nanomaterial prepared in this invention.

[0027] Figure 8 for Figure 6 EDS analysis results of particles (a) in the middle;

[0028] Figure 9 for Figure 7 EDS results analysis diagram of particles (b);

[0029] Figure 10 A photograph of the silver sol prepared from the β-cyclodextrin obtained in this invention.

[0030] Figure 11 This is a physical image of the gold-shelled silver-core composite nanomaterial prepared according to the present invention;

[0031] Figure 12 This is another physical image of the gold-shelled silver-core composite nanomaterial prepared according to the present invention. Detailed Implementation

[0032] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0033] Implementation Example 1:

[0034] 1) Dissolve α-cyclodextrin or β-cyclodextrin in water at a mass ratio of 1:500 to 1:50; dissolve silver nitrate in water at a mass ratio of 1:6000 to 1:1000.

[0035] 2) Take 200ml of α-cyclodextrin solution or β-cyclodextrin solution, add n-butanol at a volume ratio of 1:100-1:10 and ethanol at a volume ratio of 1:100-1:10, pour into a 250ml three-necked flask, add 1-10ml of the prepared silver nitrate solution, and stir vigorously in a water bath at 30-90℃.

[0036] 3) After 1-10 minutes, add NaOH solution (1.0 mol / L) dropwise to adjust the pH to 10-12. Continue stirring for 10-30 minutes to obtain a yellow silver sol.

[0037] 4) Dissolve acetic acid in water at a volume ratio of 1:50 to 1:5, and further dissolve sodium chloride in the solution at a mass ratio of 1:300 to 1:30. Take 100 ml of this solution and add it to a 400 ml beaker. Add gold to the solution at a mass ratio of 1:1000 to 1:100, heat to 60-95°C, and add nitric acid dropwise until the gold is completely dissolved. This yields an acetic acid-chlorine-gold complex solution.

[0038] 5) Dilute the silver sol obtained in step 3) with water, with a volume ratio of silver sol to water of 1:0.5 to 1:2. Add sodium dodecyl sulfonate to the sol, with a mass ratio of sodium dodecyl sulfonate to silver sol of 1:300 to 1:1000. Take 200 ml of this solution and place it in a three-necked flask.

[0039] 6) Heat to 30-80℃, add the "acetic acid-chlorine-gold" complex solution prepared in step 4) at a volume ratio of 1:200-1:50, mix well, and after 1-5 minutes, add ascorbic acid at a mass ratio of 1:2000-1:200, and stir for 2-20 minutes.

[0040] 7) Remove the three-necked flask and allow it to cool. Pour out the precious metal sol and place it in an Erlenmeyer flask. Store the flask in a refrigerator at 4°C.

[0041] Experimental results:

[0042] 1) The silver sol prepared by the above method using β-cyclodextrin is shown in the figure. Figure 10 As shown;

[0043] 2) The gold-shelled silver-core nanoparticles prepared by the above method are as follows: Figure 11 and Figure 12 As shown;

[0044] 3) Using acetic acid and sodium chloride as ligands and nitric acid as an oxidant to dissolve gold is an unconventional method. This method yields rapid and effective gold dissolution. The resulting complex is a well-defined, typical complex, distinct from tetrachloroalloyic acid. It is the first time that acetate and chloride anions have been found to simultaneously coordinate with gold. Its crystal diffraction data is as follows: Figure 1-4 As shown; the diffraction results show that the crystals are highly regular, and gold forms good coordination with acetate and chlorine; it is a complex different from tetrachloroalloyic acid.

[0045] 4) The gold-shelled silver-core nanoparticles obtained can remain uniform and stable without agglomeration when stored at 4℃ for 100 days;

[0046] 5) TEM detection

[0047] The obtained gold-shelled silver-core nanoparticles were analyzed by transmission electron microscopy (TEM) at the Guiyang Institute of Geochemistry, Chinese Academy of Sciences. The results are as follows: Figure 5 As shown.

[0048] from Figure 5 It is evident that the composite nanomaterials prepared by this method exhibit good dispersion, uniform dispersion, and excellent crystal morphology.

[0049] Depend on Figure 6 and Figure 7 As can be seen, further scanning of the composite nanoparticles revealed a typical crystalline morphology, indicating that the gold atom clusters grew well on the silver core and formed a well-crystallized elemental form. The composite nanoparticles exhibited two distinct contrasts, one light and one dark, due to the significant difference in atomic weight between gold and silver, which was reflected in the TEM scan. The composite nanoparticles had a diameter of 20-40 nm, were well-crystallized, and had a uniform outer layer.

[0050] 6) Energy Dispersive X-ray Spectroscopy (EDS)

[0051] right Figure 6 and Figure 7 The nanoparticles in the sample underwent X-ray energy dispersive spectroscopy (EDS) analysis, and their composition is shown in Table 1 and... Figures 8 to 9 .

[0052]

[0053] Table 1 Component Analysis

[0054] Analysis of the composite material composition (Table 1) shows that the silver core accounts for approximately 75-80% of the mass, while the gold shell accounts for approximately 15-20%.

[0055] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method of synthesizing gold / silver core-shell structure nanoparticles, characterized in that, The method comprises the following steps: S01, preparing silver sol and diluting the silver sol with water to obtain a silver sol solution, wherein the volume ratio of the silver sol to the water is 1:0.5 to 1:2; S02, adding sodium dodecyl sulfonate to the silver sol solution, wherein the mass ratio of the sodium dodecyl sulfonate to the silver sol is 1:300 to 1:1000; S03, adding an "acetic acid-chlorine-gold" complex solution to the product of step S02 at a volume ratio of 1:200 to 1:50 at 30 to 80 °C; S04, adding ascorbic acid to the product of step S03 at a mass ratio of 1:2000 to 1:200, and stirring for 2 to 20 min; S05, obtaining a noble metal sol by allowing the solution in step S04 to stand and cool; The method for preparing the "acetic acid-chlorine-gold" complex solution comprises the following steps:

2. The method of claim 1, wherein the synthetic gold / silver core-shell structure nanoparticles are characterized by, S01-1, dissolving α-cyclodextrin or β-cyclodextrin in water at a mass ratio of 1:500 to 1:50 to obtain an α-cyclodextrin solution or a β-cyclodextrin solution; dissolving silver nitrate in water at a mass ratio of 1:6000 to 1:1000 to obtain a silver nitrate solution; S01-2, adding n-butanol to the α-cyclodextrin solution or the β-cyclodextrin solution at a volume ratio of 1:100 to 1:10, and adding ethanol to the α-cyclodextrin solution or the β-cyclodextrin solution at a volume ratio of 1:100 to 1:10; S01-3, adding the silver nitrate solution prepared in step S01-1 to the product of step S01-2 at a volume ratio of 1:250 to 1:25 at 30 to 90 °C; S01-4, after 1 to 10 min, adding a NaOH solution dropwise to the product of step S01-3 to adjust the pH to 10 to 12, and continuing to stir for 10 to 30 min. The reaction conditions of step S01-3 further comprise: stirring vigorously under a water bath.

3. The method of synthesizing gold / silver core-shell structure nanoparticles according to claim 2, wherein, ​

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