Nanocolloidal gold and a method for preparing the same

Abstract

The application belongs to the technical field of nanometer colloidal gold, and particularly relates to a kind of nanometer colloidal gold and a preparation method thereof. The method is to first mix surfactant solution, chloroauric acid solution and reducing agent solution in uniform stirring after preheating water by microwave, then carry out microwave heating reaction, and finally obtain nanometer colloidal gold after stirring and natural cooling at room temperature. The microwave synthesis method disclosed in the application is simple, fast and efficient, and the reaction system can achieve high concentration which is difficult to achieve by traditional heating method. High concentration colloidal gold can be obtained without concentration, and the synthesized colloidal gold is uniform and stable, with controllable particle size, adjustable concentration and good dispersibility, which has wide application prospect in the field of micro-nano material synthesis.

Description

Technical Field

[0001] This invention belongs to the field of nanocolloidal gold technology, specifically relating to a nanocolloidal gold and its preparation method. Background Technology

[0002] Elemental gold nanoparticles exist in a stable alternating state within a system due to electrostatic forces, hence the name colloidal gold. Colloidal gold typically has a particle size of 10–100 nm and is widely used in energy, medical diagnostics, environmental monitoring, and food safety fields due to its good biocompatibility and characteristic surface plasmon resonance.

[0003] Traditional nanomaterial synthesis generally includes top-down and bottom-up methods. The classic top-down method for synthesizing gold nanoparticles is ball milling. Its advantage is that it allows for large-scale synthesis in a single step. However, its disadvantages include poor particle size uniformity and exposed particle surfaces that are difficult to disperse in an aqueous phase to form a colloid, thus limiting its further applications and leading to its gradual phasing out in practical applications. The classic bottom-up method—the chloroauric acid reduction method—involves heating a reducing agent to induce a stable redox reaction with chloroauric acid, uniformly reducing elemental gold to form gold nanoparticles. Simultaneously, the oxidized reducing agent deposits on the surface of the gold nanoparticles, forming an electrostatic layer that allows the gold particles to be uniformly and stably dispersed in the aqueous phase, forming colloidal gold. This method is green, relatively simple to operate, and does not require sophisticated synthesis equipment. The synthesized colloidal gold is stable and biocompatible, and therefore widely used.

[0004] However, traditional heating methods, such as direct heating and oil bath heating, involve slow temperature conduction and a gradient temperature distribution within the system. This prevents the reaction from occurring uniformly and fully, easily leading to side reactions, specifically manifested as relatively uneven colloidal gold particle size. Furthermore, traditional reduction methods minimize these side reactions by reducing the system concentration, resulting in low yields and low efficiency. Therefore, developing a new preparation method for colloidal gold is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nano-colloidal gold and its preparation method, specifically adopting the following technical solution: A method for preparing colloidal gold nanoparticles includes the following steps: Water was preheated by microwave, and then surfactant solution, chloroauric acid solution and reducing agent solution were added one after another under uniform stirring and mixed. Then, the mixture was heated by microwave and the reaction was carried out. After the reaction was completed, the mixture was stirred and cooled naturally at room temperature to finally obtain nano-colloidal gold.

[0006] This invention innovatively utilizes microwave technology for the chemical reaction preparation of colloidal gold nanoparticles, unlike traditional heating methods. The principle of this microwave heating method is to rapidly change the electric field, causing the charged substances in the system to vibrate and generate heat through friction. Therefore, it achieves uniform heating of the entire system, a consistent temperature distribution, and a stable reaction process. Specifically, for the synthesized colloidal gold, this results in gold particles with uniform morphology and size. Furthermore, the microwave heating method provided by this invention reduces side reactions, ensures monodispersity with surfactants, and significantly increases reaction concentration, reduces the size of the reaction system, and improves production efficiency. Gram-level or higher colloidal gold can be obtained even in small to medium-sized systems. In addition, microwave heating greatly reduces the requirements for reaction equipment and space. This avoids the problems of traditional homogeneous synthesis, which is limited to milligram or even microgram levels, and the difficulty in controlling particle uniformity and dispersion at low concentrations in bottom-up nanomaterial synthesis. Moreover, conventional methods for increasing yield generally involve expanding the reaction system, which places extremely high demands on production equipment and space.

[0007] As a further preferred embodiment, the aforementioned ionic and nonionic surfactants specifically include at least one of sodium dodecyl sulfonate, polyvinylpyrrolidone, and polyethylene glycol. These surfactants are widely used and have good water solubility.

[0008] As a further preferred embodiment, the reducing agent includes at least one selected from sodium citrate, cyclodextrin, and glucose. Such reducing agents exhibit mild reactions and high biocompatibility.

[0009] As a further preferred embodiment, the above-mentioned microwave preheating and microwave heating are achieved through a microwave device, which includes at least one of a microwave reactor, a microwave digester, and a household microwave oven. Microwave reactors are suitable for large and medium-sized systems, microwave digesters are suitable for small systems, and household microwave ovens are simple and convenient.

[0010] As a further preferred embodiment, the power of the microwave preheating is 200 W to 1000 W, and the time is 10 s to 50 s. Preheating is to ensure that the reducing agent reacts immediately with chloroauric acid after its addition, thereby forming gold nanoparticles of suitable particle size.

[0011] As a further preferred embodiment, the power of the microwave heating reaction is 400 W to 2000 W, the time is 5 s to 40 s, and the cycle is repeated 3 to 10 times. Cyclic heating can ensure that there is no bumping and make the heating curve smooth.

[0012] As a further preferred embodiment, the stirring speed during the addition of materials after preheating is 300~800 r / min.

[0013] As a further preferred embodiment, the concentrations of the added surfactant solution, chloroauric acid solution, and reducing agent solution are 4 mg / mL to 10 mg / mL, 0.2% to 2%, and 0.2% to 2%, respectively.

[0014] As a further preferred embodiment, the volume ratio of water, surfactant solution, chloroauric acid solution and reducing agent solution is 50 mL-100 mL: 5 mL: 10 mL-20 mL: 10 mL-15 mL.

[0015] This invention also provides a colloidal gold nanoparticle prepared by the above method, wherein the size of the colloidal gold nanoparticle is 10 nm to 100 nm, and the concentration is 0.5 mg / mL to 5 mg / mL. This particle size of colloidal gold has the widest range of applications.

[0016] The beneficial effects of the present invention are as follows: (1) The present invention is based on microwave heating to reduce chloroauric acid to prepare colloidal gold, which overcomes the problem of slow temperature rise and uneven distribution of the system during traditional direct heating and oil bath heating, thus providing the possibility for rapid preparation of high-quality colloidal gold.

[0017] (2) This invention breaks through the bottleneck of high-concentration synthesis of colloidal gold by adding surfactants to disperse nanoparticles and combining them with the uniform heating characteristics of microwaves.

[0018] (3) The microwave synthesis method disclosed in this invention is simple, fast and efficient, and the reaction system can achieve high concentrations that are difficult to achieve by traditional heating methods. High concentrations of colloidal gold can be obtained without concentration. The synthesized colloidal gold is uniform and stable, with controllable particle size, adjustable concentration and good dispersibility. It has broad application prospects in the field of micro and nanomaterial synthesis. Attached Figure Description

[0019] Figure 1 The diagram shows the preparation process of the microwave method for rapid synthesis of high-concentration colloidal gold according to the present invention; wherein 1 is ultrapure water, 2 is surfactant, 3 is chloroauric acid, and 4 is reducing agent; Figure 2 The image shows a 10-fold concentration 30 nm colloidal gold (30 nm MwAuNP 10×) prepared by the microwave method of this invention, Example 1. Figure 2 a) Traditional oil bath method for 30 nm colloidal gold (30 nm AuNP, Comparative Example 1, Figure 2 b) and 10 times the concentration of conventional oil bath method for 30 nm colloidal gold (30 nm AuNP 10×, Comparative Example 2, Figure 2 c) Microscopic characterization comparison diagram and corresponding hydration particle size characterization ( Figure 2 d); Figure 3The image shown is a microstructure of 20 nm colloidal gold (20 nm MwAuNP 20×, Example 2) prepared by the microwave method of the present invention at a concentration of 20 times. Figure 3 a) and corresponding hydration particle size characterization ( Figure 3 b) Figure 4 The image shows a comparison of the physical samples of 30 nm MwAuNP 10× prepared by the microwave method of this invention, 30 nm AuNP prepared by the traditional oil bath method, 30 nm AuNP prepared by the traditional oil bath method at 10 times the concentration, and 20 nm MwAuNP 20× prepared by the microwave method under natural light. Figure 4 a) and ultraviolet-visible absorption spectrum ( Figure 4 (b), where 1 / 10 and 1 / 20 represent dilutions of 10 times and 20 times, respectively. Detailed Implementation

[0020] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0021] Example 1 A method for preparing colloidal gold nanoparticles, specifically comprising the following steps: (1) System preheating: Take 85 mL of ultrapure water and place it in an Erlenmeyer flask. Heat it in a microwave reactor at 800 W for 30 s. (2) Adding samples: Add 5 mL of polyethylene glycol solution (4 mg / mL) and 10 mL of chloroauric acid (1%) to the preheated ultrapure water in sequence, and then add 13 mL of sodium citrate solution (1%) at 800 r / min while stirring for 2 min; (3) Microwave reaction: Transfer the conical flask containing the above mixture to a microwave reactor, heat at 400 W for 20 s as one cycle, repeat 5 times, then heat at 200 W for 20 s and repeat 3 times to make the reaction complete; (4) Cooling and preservation: Take out the conical flask and place it on a conventional magnetic stirrer. Stir at 400 r / min and let it cool naturally to room temperature to obtain 30 nm, 10 times the concentration of colloidal nanoparticles. Finally, store at 4℃.

[0022] Example 2 A method for preparing colloidal gold nanoparticles, specifically comprising the following steps: (1) System preheating: Take 75 mL of ultrapure water and place it in an Erlenmeyer flask. Heat it in a microwave reactor at 600 W for 25 s. (2) Adding samples: Add 5 mL of polyvinylpyrrolidone solution (10 mg / mL) and 20 mL of chloroauric acid (1%) to the preheated ultrapure water in sequence. Add 10 mL of sodium citrate solution (2%) at 800 r / min and keep stirring for 2 min. (3) Microwave reaction: Transfer the conical flask containing the above mixture to a microwave reactor, heat at 600 W for 20 s as one cycle, repeat 5 times, then heat at 200 W for 20 s and repeat 3 times to make the reaction complete; (4) Cooling and preservation: Take out the conical flask and place it on a conventional magnetic stirrer. Stir at 500 r / min and let it cool naturally to room temperature to obtain 20 nm, 20 times the concentration of colloidal nanoparticles. Finally, store at 4℃.

[0023] Comparative Example 1 A method for preparing colloidal gold in an oil bath, specifically comprising the following steps: (1) System preheating: Take 90 mL of ultrapure water and place it in a round bottom flask. Preheat it to a gentle boil by reflux in an oil bath at 120°C. (2) Addition and reaction: Add 10 mL of chloroauric acid (1%) to the preheated ultrapure water, and then add 13 mL of sodium citrate solution (1%) at a time while stirring at 1000 r / min. Continue heating and stirring for 40 min after the color stabilizes. (3) Cooling and preservation: Lift the flask to remove it from the oil bath, stir at 200 r / min and cool naturally to room temperature to obtain 30 nm colloidal gold nanoparticles, and finally transfer them to a storage container for storage at 4℃.

[0024] Comparative Example 2 A method for preparing colloidal gold in an oil bath, specifically comprising the following steps: (1) System preheating: Take 99 mL of ultrapure water and place it in a round bottom flask. Preheat it to a gentle boil by reflux in an oil bath at 120°C. (2) Addition and reaction: Add 1 mL of chloroauric acid (1%) to the preheated ultrapure water, and then add 1.35 mL of sodium citrate solution (1%) at a time while stirring at 800 r / min. Continue heating and stirring for 30 min after the color stabilizes. (3) Cooling and preservation: Lift the flask to remove it from the oil bath, stir at 200 r / min and cool naturally to room temperature to obtain 30 nm, 10 times the concentration of colloidal nanoparticles. Transfer to a storage container and store at 4℃.

[0025] Figure 2 The image shows a 10-fold concentration 30 nm colloidal gold (30 nm MwAuNP 10×) prepared by the microwave method of this invention, Example 1. Figure 2a) Traditional oil bath method for 30 nm colloidal gold (30 nm AuNP, Comparative Example 1, Figure 2 b) and 10 times the concentration of conventional oil bath method for 30 nm colloidal gold (30 nm AuNP 10×, Comparative Example 2, Figure 2 c) Microscopic characterization comparison diagram and corresponding hydration particle size characterization ( Figure 2 d); by Figure 2 It can be seen that the 30 nm colloidal gold (30 nm MwAuNP 10×) prepared by the microwave method of this invention... Figure 2 a) It exhibits regular spherical shape, with an average hydration particle size of 32.7 nm and a particle monodispersity index (PDI) of 0.147; 30 nm colloidal gold (30 nm AuNP) produced by the traditional oil bath method. Figure 2 b) The overall particle shape is spherical and ellipsoidal, with an average hydration particle size of 33.5 nm and a particle monodispersity index (PDI) of 0.237; while the concentration of 30 nm colloidal gold (30 nm AuNP 10×) obtained by the traditional oil bath method at 10 times the concentration is significantly higher. Figure 2 c) It exhibits an irregular ellipsoidal shape and some aggregation, with poor monodispersity, an average hydration particle size of 35.2 nm, and a particle monodispersity index (PDI) of 0.361.

[0026] Figure 3 The image shown is a microstructure of 20 nm colloidal gold (20 nm MwAuNP 20×, Example 2) prepared by the microwave method of the present invention at a concentration of 20 times. Figure 3 a) and corresponding hydration particle size characterization ( Figure 3 b); by Figure 3 It can be seen that the 20-fold concentration 20 nm colloidal gold (20 nm MwAuNP 20×) prepared by the microwave method of this invention... Figure 3 a) The particles are regular and uniform spherical with an average hydration particle size of 23.2 nm and a particle monodispersity index (PDI) of 0.106.

[0027] Figure 4 The image shows a comparison of the physical samples of 30 nm MwAuNP 10× prepared by the microwave method of this invention, 30 nm AuNP prepared by the traditional oil bath method, 30 nm AuNP prepared by the traditional oil bath method at 10 times the concentration, and 20 nm MwAuNP 20× prepared by the microwave method under natural light. Figure 4 a) and ultraviolet-visible absorption spectrum ( Figure 4 b), where 1 / 10 and 1 / 20 represent dilutions of 10-fold and 20-fold, respectively; by Figure 4It can be seen that 30 nm MwAuNP 10×, 30 nm AuNP and 30 nm AuNP 10×, when diluted to 1:1, all appear as a slightly purplish wine red, while 20 nm MwAuNP 20× appears as a vermilion red. The maximum absorption peak wavelengths of 30 nm MwAuNP 10×, 30 nm AuNP, 30 nm AuNP 10× and 20 nm MwAuNP 20× are 525 nm, 526 nm, 530 nm and 521 nm, respectively.

[0028] Although the description of the invention has been quite detailed and particularly of several described embodiments, it is not intended to limit it to any of these details or embodiments or any particular embodiment, but should be considered as providing a broad possible interpretation of the claims by referring to the appended claims and taking into account the prior art, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

Claims

1. A method for preparing nano-colloidal gold, characterized in that, Includes the following steps: Water was preheated by microwave, and then surfactant solution, chloroauric acid solution and reducing agent solution were added one after another under uniform stirring and mixed. Then, the reaction was carried out by microwave heating. After the reaction was completed, the mixture was stirred and cooled naturally at room temperature to finally obtain nano-colloidal gold. The microwave preheating power is 200 W to 1000 W, and the time is 10 s to 50 s; the microwave heating reaction power is 400 W to 21000 W, and the time is 5 s to 40 s, and the cycle is repeated 3 to 10 times. The concentrations of the added surfactant solution, chloroauric acid solution, and reducing agent solution are 4 mg / mL~10 mg / mL, 0.2~2%, and 0.2~2%, respectively; the volume ratio of water, surfactant solution, chloroauric acid solution, and reducing agent solution is 50 mL~100 mL: 5 mL: 10 mL~20 mL: 10 mL~15 mL.

2. The method for preparing nano-colloidal gold according to claim 1, characterized in that, The surfactant specifically includes at least one of sodium dodecyl sulfonate, polyvinylpyrrolidone, and polyethylene glycol.

3. The method for preparing nano-colloidal gold according to claim 1, characterized in that, The reducing agent includes at least one of sodium citrate, cyclodextrin, and glucose.

4. The method for preparing colloidal gold nanoparticles according to claim 1, characterized in that, Microwave preheating and microwave heating are achieved through microwave equipment, including at least one of a microwave reactor, a microwave digester, and a household microwave oven.

5. The method for preparing nano-colloidal gold according to claim 1, characterized in that, The stirring speed during feeding after preheating is 300~800 r / min.

6. The method for preparing nano-colloidal gold according to claim 1, characterized in that, The colloidal gold nanoparticles have a size of 10 nm to 100 nm and a concentration of 0.5 mg / mL to 5 mg / mL.

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