Method for preparing gold nanoparticle coated with yolk-shell structure silica

Abstract

This invention discloses a method for preparing gold-coated silica nanoparticles with an egg yolk shell structure. The method involves adding trisodium citrate solution, tannic acid solution, and sodium carbonate solution to a flask and stirring. After heating, chloroauric acid solution is added, and stirring continues while maintaining a certain temperature to obtain a gold nanoparticle solution. The gold nanoparticle solution, anhydrous ethanol, ammonia, and hexadecyltrimethylammonium bromide are then added to the flask, stirred, and resorcinol is added, with continued stirring. After the reaction, formaldehyde is added dropwise, followed by tetraethyl orthosilicate. The reaction product is washed multiple times with deionized water by centrifugation, dried overnight in an oven, calcined, and then washed multiple times with deionized water by centrifugation and dried in an oven to obtain gold-coated silica nanoparticles with an egg yolk shell structure. This one-pot sol-gel method is low-cost, simple, and rapid, producing gold particles with uniform morphology, a uniform silica shell thickness, and a large internal space within the egg yolk shell.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically relating to a method for preparing gold-coated silica nanoparticles with an egg yolk shell structure. Background Technology

[0002] In recent years, gold nanoparticles have shown great promise for applications in gene expression and disease treatment due to their unique optical and electrical properties and ease of surface modification. Meanwhile, nano-silica, with its large specific surface area and good dispersibility, and its superior stability, strong mechanical properties, and bioinertness, has made silicon-based nanocomposites prepared by coating gold nanoparticles with silica a hot research topic in drug delivery and other fields. Compared to conventional core-shell structured silica-coated gold nanoparticles, yolk-shell structured silica-coated gold nanoparticles have a larger specific surface area and greater structural functionality. However, current methods for preparing yolk-shell structured silica-coated gold nanoparticles suffer from cumbersome procedures, irregular morphology of the gold nanoparticles, and high costs.

[0003] Current technologies involve in-situ growth of gold nanoparticles on the surface of amino-terminated polystyrene (PS) nanospheres, followed by coating the gold-modified PS nanospheres with a layer of silica using a modified Stöber method. The resulting nanoparticles are then calcined at 450°C for 2 hours to obtain egg-yolk-shell structured silica-coated gold nanoparticles. However, the polystyrene microspheres used in this technology are expensive, and the synthesized egg-yolk-shell-like gold nanoparticles exhibit irregular morphologies. Another existing technology involves adding silver nitrate solution to 1,5-pentanediol, then adding vinylpyrrolidone and chloroauric acid solutions to the mixture to obtain colloidal gold particles. Ammonium hydroxide is then added to the gold colloidal solution in 2-propanol, followed by deionized water and tetraethyl orthosilicate. Vigorous stirring ensures complete polymerization of the silica, and the product is centrifuged and dispersed in 2-propanol for the next reaction. A solution of core-shell structured silica-coated gold nanoparticles was added to 2-propanol, then water was added and stirred at room temperature. Potassium cyanide aqueous solution was added to the colloidal solution and stirred. After centrifugation, the resulting mixture was washed several times with 2-propanol to obtain yolk-shell structured silica-coated gold nanoparticles. The problem with this method is that the steps are cumbersome and the morphology of the gold nanoparticles in the synthesized yolk-shell particles is irregular.

[0004] Therefore, developing new methods to synthesize gold-coated silica nanoparticles with egg yolk shell structures that are simple in procedure, low in cost, and have controllable morphology and particle size has profound practical significance and broad application prospects. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for preparing gold-coated silica nanoparticles with egg yolk shell structure that is low in cost, simple and quick, with uniform morphology and adjustable size.

[0006] Technical Solution: To solve the above-mentioned technical problems, this invention provides a method for preparing gold-coated silica nanoparticles with an egg yolk shell structure, comprising the following steps: (1) Synthesis of gold nanoparticles: Add trisodium citrate solution, tannic acid solution and sodium carbonate solution to a flask and stir. After heating, add chloroauric acid solution and continue stirring while maintaining a certain temperature to obtain gold nanoparticle solution. (2) Synthesis of gold-coated silica nanoparticles with egg yolk shell structure: Gold nanoparticle solution, anhydrous ethanol, ammonia and hexadecyltrimethylammonium bromide were added to a flask and stirred. Resorcinol was added and stirring continued. After the reaction, formaldehyde was added dropwise. After the reaction was completed, tetraethyl orthosilicate was added dropwise. The reaction was carried out for 6 hours. The reaction product was washed several times by centrifugation with deionized water, dried overnight in an oven, calcined in a muffle furnace, and then washed several times by centrifugation with deionized water and dried in an oven to obtain gold-coated silica nanoparticles with egg yolk shell structure.

[0007] The volume ratio of the trisodium citrate solution, tannic acid solution, sodium carbonate solution and chloroauric acid solution in step (1) is 300mL:0.2mL:2mL:2mL.

[0008] In step (1), the stirring speed is 500 rpm.

[0009] In step (1), the temperature for heating is 70°C, the temperature for holding is 70°C, and the holding time is 10 minutes.

[0010] In step (2), the mass-to-volume ratio of hexadecyltrimethylammonium bromide and gold nanoparticle solution, anhydrous ethanol and ammonia is 0.2~0.4g:16-20mL:6-10ml:0.1-0.2ml.

[0011] In step (2), the mass-to-volume ratio of hydroquinone, formaldehyde, and tetraethyl orthosilicate is 0.2g:0.3-0.4ml:0.6-0.7ml.

[0012] The reaction temperature in step (2) is 30-40℃.

[0013] In step (2), the centrifugation speed is 10000 rpm.

[0014] In step (2), the heating rate is 1-5℃ / min, the calcination temperature is 400℃-550℃, and the calcination time is 4-7h.

[0015] The mechanism of this invention: The initial addition of resorcinol undergoes hydrolysis, increasing the electron density of the ortho and para-positions of the hydroxyl groups and enhancing the reactivity of hydrogen. Subsequently, formaldehyde attacks the active hydrogens at the ortho and para positions of the hydroxyl groups in the phenolic ring. Ammonia molecules provide an alkaline environment while catalyzing the polymerization of resorcinol / formaldehyde within the droplet, forming phenolic (RF) resin microspheres encapsulating gold particles. Next, tetraethyl orthosilicate is added, hydrolyzing and gelling to coat the phenolic resin surface, forming silica microspheres. Finally, high-temperature calcination removes the phenolic resin, yielding yolk-shell-structured silica-coated gold nanoparticles.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following advantages: The one-pot sol-gel method of the present invention has low cost, simple and quick preparation, uniform gold particle morphology, uniform silica shell thickness, and large internal space of egg yolk shell. Attached Figure Description

[0017] Figure 1 A schematic diagram illustrating the synthesis of gold-coated silica nanoparticles with an egg yolk shell structure. Figure 2 TEM image of gold-coated silica-based yolk shell nanoparticles prepared in Example 1; Figure 3 TEM image of gold-coated silica-based yolk shell nanoparticles prepared in Example 2; Figure 4 TEM image of gold-coated silica nanoparticles with egg yolk shell structure prepared for Comparative Example 1.

[0018] Figure 5 TEM image of gold-coated silica nanoparticles with egg yolk shell structure prepared for Comparative Example 2. Detailed Implementation

[0019] All materials used in the following examples were obtained through conventional purchase. Example 1

[0020] 1. Add 300 ml of 2.2 mmol trisodium citrate solution, 0.2 ml of 2.5 mmol tannic acid solution, and 2 ml of 150 mmol sodium carbonate solution to a 500 ml flask and stir at 500 rpm. After heating to 70°C, add 2 ml of 25 mmol chloroauric acid solution and maintain the temperature at 70°C. Continue stirring at 500 rpm for 10 minutes to obtain a gold particle solution.

[0021] 2. Add 19 mL of gold particle solution, 8 mL of anhydrous ethanol, 0.1 mL of ammonia water and 0.2 g of hexadecyltrimethylammonium bromide to a 100 mL flask. Stir at 30 °C for 30 min, then add 0.2 g of resorcinol and continue stirring. After reacting for 30 min, add 0.3 mL of formaldehyde dropwise, and then add 0.7 mL of tetraethyl orthosilicate dropwise. React at 30 °C for 6 h. Wash the reaction product three times with deionized water by centrifugation at 10,000 rpm, dry in an oven at 50 °C overnight, and calcine in a muffle furnace at a heating rate of 1 °C / min to 550 °C for 6 h.

[0022] 3. The product was washed three times by centrifugation with deionized water at 10,000 rpm and dried in an oven at 50°C to obtain gold-coated silica nanoparticles with an egg yolk shell structure.

[0023] TEM images of the gold-coated silica nanoparticles with yolk shell structure prepared in this embodiment are shown below. Figure 2 As shown in the figure, the overall size is d2 400 nm, the thickness of the silica shell is d1 45 nm, the particle size of the gold particles is d3 20 nm, and the internal size of the shell is d4 310 nm. The particle sizes of the silica shell and the gold particles are relatively uniform. Each silica shell contains gold nanoparticles. The large internal space of the shell can increase the drug loading capacity. Example 2

[0024] 1. Add 300 ml of 2.2 mmol trisodium citrate solution, 0.2 ml of 2.5 mmol tannic acid solution, and 2 ml of 150 mmol sodium carbonate solution to a 500 ml flask and stir at 500 rpm. After heating to 70°C, add 2 ml of 25 mmol chloroauric acid solution and maintain the temperature at 70°C. Continue stirring at 500 rpm for 10 minutes to obtain a gold particle solution.

[0025] 2. Add 20 mL of gold particle solution, 10 mL of anhydrous ethanol, 0.2 mL of ammonia water and 0.4 g of hexadecyltrimethylammonium bromide to a 100 mL flask. Stir at 30 °C for 30 min, then add 0.2 g of resorcinol and continue stirring. After reacting for 30 min, add 0.4 mL of formaldehyde dropwise, and then add 0.6 mL of tetraethyl orthosilicate dropwise. React at 30 °C for 6 h. Wash the reaction product three times with deionized water at 10,000 rpm by centrifugation, dry it overnight at 50 °C in an oven, and calcine it in a muffle furnace at a heating rate of 5 °C / min to 450 °C for 6 h.

[0026] 3. The product was washed three times by centrifugation with deionized water at 10,000 rpm and dried in an oven at 50°C to obtain gold-coated silica nanoparticles with an egg yolk shell structure.

[0027] TEM images of the gold-coated silica nanoparticles with yolk shell structure prepared in this embodiment are shown below. Figure 3 The overall size is 450 nm, with a silica shell thickness of 40 nm, gold particle size of 20 nm, and an internal size of 370 nm. The silica shell and gold particles have uniform particle size, and each silica shell contains gold nanoparticles. The large internal space of the shell can increase the drug loading capacity.

[0028] Comparative Example 1 1. Add 300 ml of 2.2 mmol trisodium citrate solution, 0.2 ml of 2.5 mmol tannic acid solution, and 2 ml of 150 mmol sodium carbonate solution to a 500 ml flask and stir at 500 rpm. After heating to 70°C, add 2 ml of 25 mmol chloroauric acid solution and maintain the temperature at 70°C. Continue stirring at 500 rpm for 10 minutes to obtain a gold particle solution.

[0029] 2. Add 22 mL of gold particle solution, 12 mL of anhydrous ethanol, 0.3 mL of ammonia water and 0.5 g of hexadecyltrimethylammonium bromide to a 100 mL flask. Stir at 30 °C for 30 min, then add 0.2 g of resorcinol and continue stirring. After reacting for 30 min, add 0.3 mL of formaldehyde dropwise. After the reaction, add 0.7 mL of tetraethyl orthosilicate dropwise. React at 30 °C for 6 h. Wash the reaction product three times with deionized water at 10,000 rpm by centrifugation. Dry in an oven at 50 °C overnight. Calcine in a muffle furnace at a heating rate of 1 °C / min to 550 °C for 6 h.

[0030] 3. The product was washed three times by centrifugation with deionized water at 10,000 rpm and dried in an oven at 50°C to obtain gold-coated silica nanoparticles with an egg yolk shell structure.

[0031] TEM images of the gold-coated silica nanoparticles with egg yolk shell structure prepared in this comparative example are shown below. Figure 4 As shown in the figure, by adjusting the ratio of gold particle solution, anhydrous ethanol, ammonia and cetyltrimethylammonium bromide outside the reasonable ratio range, the prepared egg yolk shell structure silica-coated gold nanoparticles have inconsistent shapes and uneven silica shell thickness and gold particle size, with many impurities.

[0032] Comparative Example 2 1. Add 300 ml of 2.2 mmol trisodium citrate solution, 0.2 ml of 2.5 mmol tannic acid solution, and 2 ml of 150 mmol sodium carbonate solution to a 500 ml flask and stir at 500 rpm. After heating to 70°C, add 2 ml of 25 mmol chloroauric acid solution and maintain the temperature at 70°C. Continue stirring at 500 rpm for 10 minutes to obtain a gold particle solution.

[0033] 2. Add 19 mL of gold particle solution, 8 mL of anhydrous ethanol, 0.1 mL of ammonia water and 0.2 g of hexadecyltrimethylammonium bromide to a 100 mL flask. Stir at 30 °C for 30 min, then add 0.2 g of resorcinol and continue stirring. After reacting for 30 min, first add 0.7 mL of tetraethyl orthosilicate, then add 0.3 mL of formaldehyde. React at 30 °C for 6 h. Wash the reaction product three times with deionized water at 10,000 rpm by centrifugation, dry in an oven at 50 °C overnight, and calcine in a muffle furnace at a heating rate of 1 °C / min to 550 °C for 6 h.

[0034] 3. The product was washed three times by centrifugation with deionized water at 10,000 rpm and dried in an oven at 50°C to obtain gold-coated silica nanoparticles with an egg yolk shell structure.

[0035] TEM images of the gold-coated silica nanoparticles with egg yolk shell structure prepared in this comparative example are shown below. Figure 5 As shown in the figure, by changing the order of adding formaldehyde and tetraethyl orthosilicate, gold particles were observed outside the silica shell. The morphology and particle size of the silica shell and the gold particles were not uniform, and the morphology was poor.

Claims

1. A method for preparing gold-coated silica nanoparticles with an egg yolk shell structure, characterized in that, Includes the following steps: (1) Synthesis of gold nanoparticles: Add trisodium citrate solution, tannic acid solution and sodium carbonate solution to a flask and stir. After heating, add chloroauric acid solution and continue stirring while maintaining a certain temperature to obtain gold nanoparticle solution. The volume ratio of trisodium citrate solution, tannic acid solution, sodium carbonate solution and chloroauric acid solution is 300mL:0.2mL:2mL:2mL. The stirring speed is 500rpm. Heat to 70℃ and maintain 70℃ for 10 minutes. (2) Synthesis of gold-coated silica nanoparticles with egg yolk shell structure: Gold nanoparticle solution, anhydrous ethanol, ammonia and hexadecyltrimethylammonium bromide were added to a flask and stirred. Resorcinol was added and stirring continued. Formaldehyde was added dropwise after the reaction, and tetraethyl orthosilicate was added dropwise after the reaction. The reaction was carried out for 6 hours. The reaction product was washed several times by centrifugation with deionized water, dried overnight in an oven, calcined in a muffle furnace, and then washed several times by centrifugation with deionized water and dried in an oven to obtain gold-coated silica nanoparticles with egg yolk shell structure. In step (2), the mass-to-volume ratio of hexadecyltrimethylammonium bromide and gold nanoparticle solution, anhydrous ethanol and ammonia is 0.4g:20mL:10mL:0.2mL. In step (2), the mass-to-volume ratio of hydroquinone, formaldehyde and tetraethyl orthosilicate is 0.2g:0.4mL:0.6mL. In step (2), the reaction temperature is 30℃. In step (2), the centrifugation speed is 10000rpm. In step (2), the heating rate is 5℃ / min. The calcination temperature is 450℃ and the calcination time is 6h. The overall particle size of the gold-coated silica nanoparticles in the yolk shell structure is 450 nm, the silica shell thickness is 40 nm, the gold particle size is 20 nm, and the internal cavity size is 370 nm.

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