A method for synthesizing gold shell-silver core nanoparticles

Abstract

The application discloses a synthesis method of gold-shell silver-core nanoparticles, which comprises the following steps: S01, preparing silver sol and diluting the silver sol with water, the volume ratio of the silver sol to the water being 1:1 to 1:4, and preparing a thiourea gold solution; S02, adding sodium dodecyl sulfonate into the diluted silver sol, the mass ratio of the sodium dodecyl sulfonate to the silver sol being 1:200 to 1:800; S03, adding the thiourea gold solution into the product of the step S02, the volume ratio of the thiourea gold solution to the product prepared in the step S02 being 1:400 to 1:40; S04, adding ascorbic acid into the product of the step S03, the mass ratio of the product of the step S03 to the ascorbic acid being 1:2000 to 1:200, heating to 30-60 DEG C, radiating for 1-5 min, and mixing for 1-7 min; S05, obtaining noble metal sol by standing and cooling the solution in the step S04; wherein the reaction conditions of the steps S03 and S04 comprise: being carried out under the ultraviolet radiation of an ultraviolet light source with a wavelength of 280-450 nm. 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-shelled silver-core 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 excellent 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, and the formation of silver halide precipitates cannot be avoided, resulting in unsatisfactory synthesis results. Nanoparticles obtained by these methods, as detected by transmission electron microscopy, all exhibit compound morphologies, rather than being entirely elemental gold or silver. This limits the application 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-shelled silver-core nanoparticles to overcome the problems existing in the prior art.

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

[0007] S01. Prepare silver sol and dilute it with water. The volume ratio of silver sol to water is 1:1 to 1:4. Prepare thiourea gold solution.

[0008] S02. Add sodium dodecyl sulfonate to the diluted silver sol, with the mass ratio of sodium dodecyl sulfonate to silver sol being 1:200 to 1:800.

[0009] S03. Add thiourea gold solution to the product obtained in step S02, wherein the volume ratio of thiourea gold solution to the product obtained in step S02 is 1:400 to 1:40.

[0010] S04. Add ascorbic acid to the product of step S03. The mass ratio of the product of step S03 to ascorbic acid is 1:2000-1:200. Heat to 30-60℃, irradiate with ultraviolet light for 1-5 min, and mix for 1-7 min.

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

[0012] The reaction conditions for steps S03 and S04 include: being carried out under ultraviolet irradiation from an ultraviolet light source with a wavelength of 280-450 nm.

[0013] Specifically, the method for preparing silver sol in step S01 is as follows:

[0014] Dissolve solid silver nitrate in deionized water at a mass ratio of 1:5000 to 1:1000. Stir and heat the silver nitrate solution. When the silver nitrate solution boils, add sodium citrate solution at a volume ratio of 1:20 to 1:5. After 20 to 120 seconds, add anhydrous ethanol at a volume ratio of 1:40 to 1:10. Stir for 10 to 40 minutes.

[0015] In the sodium citrate solution, the mass ratio of sodium citrate to water is 1:200 to 1:20.

[0016] Specifically, the method for preparing the thiourea gold solution in step S01 is as follows:

[0017] S02_1. Dissolve thiourea in deionized water to obtain a thiourea solution. The mass ratio of thiourea to water is 1:100 to 1:10.

[0018] SO2_2. Add dilute sulfuric acid dropwise to the thiourea solution to adjust the pH to 1-2;

[0019] S02_3. Add gold to the product of step S02_2 at a mass ratio of 1:2000 to 1:1000, heat to 40-50℃, add H2O2 dropwise until the gold is completely dissolved to obtain a thiourea gold solution.

[0020] Preferably, the ultraviolet light source is a surface light source with a power of 0.07-0.5KW.

[0021] The beneficial effects of this invention are as follows: Compared with the prior art, this invention has the following advantages: This invention uses an unconventional method to dissolve gold in thiourea, resulting in a lower potential for the thiourea alloy electrode, E 0 =0.36V, and has a different affinity for silver in solution than other reagents, thus allowing gold atom clusters to grow uniformly on the silver nucleus without introducing new metal ions and impurities; irradiation with electromagnetic waves or ultraviolet light with wavelengths of 280-450nm activates the surface atoms of the metals in a photochemical environment, thereby effectively achieving the affinity between the two metals; no halide precipitates or other substances are produced in the system, which do not hinder the attachment of gold and silver atoms, and achieves tight affinity and attachment of the two metals in a nanoscale micro-environment, with a uniform and firm gold shell. Attached Figure Description

[0022] Figure 1 TEM images of the gold-shelled silver-core composite nanoparticles prepared in this invention at different magnifications;

[0023] Figure 2 This is a TEM image of the gold-shelled silver-core composite nanomaterial prepared in this invention;

[0024] Figure 3 This is an EDS analysis diagram of one particle of the gold-shelled silver-core composite nanomaterial prepared in this invention.

[0025] Figure 4 This is an EDS analysis diagram of another particle of the gold-shelled silver-core composite nanomaterial prepared in this invention.

[0026] Figure 5 This is an EDS analysis diagram of another particle of the gold-shelled silver-core composite nanomaterial prepared in this invention.

[0027] Figure 6 This is an EDS analysis diagram of another particle of the gold-shelled silver-core composite nanomaterial prepared in this invention.

[0028] Figure 7 This is a physical image of the gold-shelled silver-core composite nanomaterial prepared according to the present invention;

[0029] Figure 8 This is a physical image of the gold-shelled silver-core composite nanomaterial prepared according to the present invention. Detailed Implementation

[0030] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0031] Implementation Example 1:

[0032] 1) Dissolve solid silver nitrate in deionized water at a mass ratio of 1:5000 to 1:1000. Take 200 ml of the prepared silver nitrate solution and place it in a 250 ml three-necked flask. Start the magnetic stirring and heating to heat the solution.

[0033] 2) Dissolve sodium citrate in deionized water at a mass ratio of 1:200–1:20. When the silver nitrate solution is heated to boiling, add the sodium citrate solution at a volume ratio of 1:20–1:5. After 20–120 seconds, add anhydrous ethanol at a volume ratio of 1:40–1:10 and stir for 10–40 minutes. This yields a silver sol.

[0034] 3) Dissolve thiourea in deionized water at a mass ratio of 1:100 to 1:10. Add dilute sulfuric acid dropwise to adjust the pH to 1-2. Add gold to the prepared thiourea solution at a mass ratio of 1:2000 to 1:1000, heat to 40-50℃, and add H2O2 dropwise until the gold is completely dissolved.

[0035] 4) Dilute the silver sol obtained in step 2) with water. The volume ratio of silver sol to water is 1:1 to 1:4. Add sodium dodecyl sulfonate to the sol. The mass ratio of sodium dodecyl sulfonate to silver sol is 1:200 to 1:800. Take 200 ml of the mixed silver sol and put it into a three-necked flask.

[0036] 5) Turn on the ultraviolet light source (surface light source) with a wavelength of 280-450nm and irradiate the three-necked flask with ultraviolet light at a power of 0.07-0.5KW.

[0037] 6) Under ultraviolet irradiation, add the thiourea gold solution prepared in step 3) to a three-necked flask. The volume ratio of the thiourea gold solution to the silver sol is 1:400-1:40. Add ascorbic acid at a mass ratio of 1:2000-1:200. Heat to 30-60℃, irradiate with ultraviolet light for 1-5 minutes, and stir for 1-7 minutes.

[0038] 7) Remove the three-necked flask and allow it to cool. Pour the gold-coated silver nanosol into an Erlenmeyer flask and store it in a refrigerator at 4°C.

[0039] Experimental results:

[0040] 1) The physical object obtained by the above method is as follows: Figure 7 and Figure 8 As shown;

[0041] 2) The gold-shelled silver-core nanoparticles obtained can remain uniform and stable without agglomeration when stored at 4℃ for 100 days;

[0042] 3) TEM detection

[0043] 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 1 As shown.

[0044] from Figure 1 It is evident that the composite nanomaterials prepared by this method exhibit good dispersion, uniform dispersion, and excellent crystal morphology.

[0045] Further electron microscopy scanning of the nanoparticles yielded the following results: Figure 2 As shown, by Figure 2 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.

[0046] 3) Energy Dispersive X-ray Spectroscopy (EDS)

[0047] right Figure 2 Nanoparticles were analyzed by energy-dispersive X-ray spectroscopy (EDS), and their composition is shown in Table 1 and... Figures 3 to 6 .

[0048]

[0049]

[0050] Table 1 Component Analysis

[0051] Compositional analysis of the composite material shows that the silver core accounts for approximately 70-90% of the mass, while the gold shell accounts for approximately 6-20%. This ratio is reasonable for the practical application of composite nanomaterials and for significantly reducing costs. It combines the stability and uniformity of gold nanoparticles with the excellent optical properties of silver nanoparticles, while also significantly reducing costs.

[0052] 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 for synthesizing gold-shelled silver-core nanoparticles, characterized in that, Includes the following steps: S01. Prepare silver sol and dilute it with water. The volume ratio of silver sol to water is 1:1 to 1:

4. Prepare thiourea gold solution. S02. Add sodium dodecyl sulfonate to the diluted silver sol, with the mass ratio of sodium dodecyl sulfonate to silver sol being 1:200 to 1:

800. S03. Add thiourea gold solution to the product obtained in step S02, wherein the volume ratio of thiourea gold solution to the product obtained in step S02 is 1:400 to 1:

40. S04. Add ascorbic acid to the product of step S03. The mass ratio of the product of step S03 to ascorbic acid is 1:2000-1:

200. Heat to 30-60℃, irradiate with ultraviolet light for 1-5 min, and mix for 1-7 min. S05. Allow the solution in step S04 to stand and cool to obtain a noble metal sol. The reaction conditions for steps S03 and S04 include: being carried out under ultraviolet irradiation from an ultraviolet light source with a wavelength of 280-450 nm.

2. The method for synthesizing gold-shelled silver-core nanoparticles according to claim 1, characterized in that, The method for preparing silver sol in step S01 is as follows: Dissolve solid silver nitrate in deionized water at a mass ratio of 1:5000 to 1:1000. Stir and heat the silver nitrate solution. When the silver nitrate solution boils, add sodium citrate solution at a volume ratio of 1:20 to 1:

5. After 20 to 120 seconds, add anhydrous ethanol at a volume ratio of 1:40 to 1:

10. Stir for 10 to 40 minutes. In the sodium citrate solution, the mass ratio of sodium citrate to water is 1:200 to 1:

20.

3. The method for synthesizing gold-shelled silver-core nanoparticles according to claim 1, characterized in that, The method for preparing the thiourea gold solution in step S01 is as follows: S02_1. Dissolve thiourea in deionized water to obtain a thiourea solution. The mass ratio of thiourea to water is 1:100 to 1:

10. SO2_2. Add dilute sulfuric acid dropwise to the thiourea solution to adjust the pH to 1-2; S02_3. Add gold to the product of step S02_2 at a mass ratio of 1:2000 to 1:1000, heat to 40-50℃, add H2O2 dropwise until the gold is completely dissolved to obtain a thiourea gold solution.

4. The method for synthesizing gold-shelled silver-core nanoparticles according to claim 1, characterized in that, The ultraviolet light source is a surface light source with a power of 0.07-0.5KW.

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