Nano gold sol with high sphericity and its preparation method

Abstract

The present application provides a nano-gold sol with high sphericity and a preparation method thereof, belonging to the field of nano materials. The preparation method prepares the nano-gold sol by heating a bottom liquid, a gold source precursor, a morphology stabilizer, a reducing agent, a nucleating agent, and a protective agent. By precisely controlling the reaction conditions, the types and concentrations of reagents, and the addition time of the nucleating agent, a nano-gold sol with high sphericity can be prepared. Through the combined action of citric acid / sodium citrate as double reducing agents, the growth rate of the nano-gold sol is increased and the size distribution is reduced. By adjusting the dosage ratio of tannic acid to the reducing agent and the addition time of tannic acid, the generation rate and size of crystal nuclei are controlled, thereby achieving the effect of regulating the size. The nano-gold sol prepared by the present invention has high stability, low biological toxicity, and non-toxic and pollution-free raw materials, and can be applied to the field of biomedicine.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly to a nano gold sol with high sphericity and a preparation method thereof. Background Art

[0002] Due to its unique physical and chemical properties, nano gold sol has shown extensive application potential in many fields. The main characteristics of this sol include high stability, high specific surface area, high biological activity, high electron density, adjustable morphology and size, surface effect, quantum size effect, macroscopic quantum tunneling effect, as well as excellent optical and thermal properties and good biocompatibility. Especially its application in the biomedical field has received extensive attention from researchers.

[0003] Currently, the commonly used method for preparing nano gold sol is the Turkevich reduction method. However, this method has certain limitations. For example, the particle size distribution of the obtained nano gold sol is relatively wide, and as the particle size increases, the morphology of the particles will change, resulting in a decrease in sphericity. To solve the above problems, existing preparation methods usually require adding a large amount of organic stabilizers to the system. However, this method is not only unfavorable for the purification of nanoparticles but also significantly increases the biological toxicity, limiting its application in the biomedical field.

[0004] In view of this, it is necessary to design an improved nano gold sol with high sphericity and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a nano gold sol with high sphericity and a preparation method thereof, aiming to solve the technical problems of wide particle size distribution, difficult control of morphology and sphericity, and high biological toxicity of nano gold sol.

[0006] In the first aspect, the present application provides a preparation method of a nano gold sol with high sphericity, including the following steps:

[0007] S1. Prepare a chloroauric acid tetrahydrate solution as a gold source precursor; prepare a sodium carbonate solution as a morphology stabilizer; prepare a citric acid solution as a reducing agent; prepare a tannic acid solution as a nucleating agent; prepare a sodium citrate solution as a protective agent;

[0008] S2. Add 100 - 200 mL of ultrapure water into a container as a bottom liquid, heat it to boiling, then add the gold source precursor, add the morphology stabilizer to adjust the pH value of the solution to a predetermined range, stir evenly, and at the same time add the reducing agent and the protective agent. After reacting for a predetermined time, add the nucleating agent, and continuously stir for 5 - 15 min under the boiling state to obtain a nano gold sol with high sphericity.

[0009] As a further improvement of the present application, in step S1, the concentration of the tetrahydrate chloroauric acid solution is 0.025-0.05 mmol / L; the concentration of the sodium carbonate solution is 0.05-0.1 mol / L; the concentration of the citric acid solution is 0.075-0.375 mmol / L; the concentration of the sodium citrate solution is 0.075-0.375 mmol / L; the concentration of the tannic acid solution is 6.25×10 -3 ~1.25×10 -2 mmol / L.

[0010] As a further improvement of the present application, in step S2, the pH value of the solution is adjusted to 8 to 9. The predetermined reaction time is 10 to 60 seconds.

[0011] As a further improvement of the present application, the molar ratio of the reducing agent to the protecting agent is 1:(1-5). The molar ratio of the gold source precursor to the reducing agent is 1:(3-15). The molar ratio of the nucleating agent to the reducing agent is 1:(6-60).

[0012] As a further improvement of the present application, the particle size of the highly spherical nano-gold sol is 10-50 nm.

[0013] In a second aspect, the present application provides a nano-gold sol with high sphericity, which is prepared by the preparation method of the nano-gold sol with high sphericity described in the first aspect.

[0014] The beneficial effects of this application are:

[0015] The present application provides a nano-gold sol with high sphericity and a preparation method thereof, wherein ultrapure water is added to a container as a base liquid, heated to boiling, then a gold source precursor is added, a morphology stabilizer is added to adjust the pH value of the solution to a predetermined range, stirred evenly, a reducing agent and a protective agent are added at the same time, and after a predetermined reaction time, a nucleating agent is added, and stirring is continued for 5 to 15 minutes under boiling conditions to obtain a nano-gold sol with high sphericity. The present application adjusts the pH value of the gold source solution to 8 to 9 so that the gold source solution generates HAuCl to the greatest extent. x (OH) 4-x Complex, reduce free [AuCl4 -The concentration is increased to enhance the isotropic growth degree of the particles, and the nano-gold sol exhibits a high sphericity morphology. Meanwhile, under this pH reaction condition, the reduction ability of the reducing agent is improved, accelerating the nucleation and growth processes, with stable morphology and narrow particle size distribution. Through the combined action of citric acid / sodium citrate as double reducing agents, the growth rate of the nano-gold sol is increased, and the size distribution is reduced. At the same time, sodium citrate also acts as a stabilizer, coating a large number of negatively charged groups on the surface after the formation of the nanoparticles, improving the dispersibility of the nano-gold sol. By adjusting the dosage ratio of tannic acid to the reducing agent and the addition time of tannic acid, the generation rate and size of the crystal nuclei can be controlled, thereby achieving the effect of regulating the size.

[0016] By conducting the above reaction in a boiling bottom liquid in this application, the reaction rate is increased, and the growth deviation between particles is reduced, thereby achieving a narrow particle size distribution. The nano-gold sol prepared by the present invention has high stability, low biological toxicity, and non-toxic and pollution-free raw materials, meeting the requirements of "green production".

[0017] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically exemplified below. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solution of this application, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 TEM image of the nano-gold sol prepared in Example 1 of this application;

[0020] Figure 2 TEM image of the nano-gold sol prepared in Comparative Example 1;

[0021] Figure 3 TEM image of the nano-gold sol prepared in Comparative Example 3;

[0022] Figure 4 TEM image of the nano-gold sol prepared in Comparative Example 5;

[0023] Figure 5 UV absorption spectra of the nano-gold sols prepared in Examples 1-3 and Comparative Examples 1-5 of this application. Detailed Description of the Embodiments

[0024] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means more than two, unless otherwise specifically defined.

[0027] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0028] Existing methods for preparing gold nanosols have certain limitations. The obtained gold nanosols have a relatively wide particle size distribution, and as the particle size increases, the morphology of the particles will change, resulting in a decrease in sphericity. To solve the above problems, a large amount of organic stabilizer usually needs to be added to the system. However, this method is not only unfavorable for the purification of nanoparticles, but also significantly increases the biological toxicity, limiting its application in the biomedical field.

[0029] To solve the technical problems of wide particle size distribution, difficult control of morphology and sphericity, and high biological toxicity of gold nanosols, this application provides a gold nanosol with sphericity and a preparation method thereof. Among them, by adopting a liquid-phase reduction preparation method, sodium carbonate is used as a morphology stabilizer, citric acid is used as a reducing agent, trace tannic acid is used as a nucleating agent, and sodium citrate is used as both a reducing agent and a protecting agent. By controlling the ratio of tannic acid to citric acid and sodium citrate and the time when tannic acid is added to the system, the size of the gold nanosol can be controlled, so that while maintaining the high sphericity of the gold nanosol, the width of the particle size distribution can be reduced, and the biological toxicity can be reduced, so as to be better applicable to the research and application in the biomedical and other fields.

[0030] In a first aspect, an embodiment of the present application provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps:

[0031] S1. Prepare a chloroauric acid tetrahydrate solution as a gold source precursor; prepare a sodium carbonate solution as a morphology stabilizer; prepare a citric acid solution as a reducing agent; prepare a tannic acid solution as a nucleating agent; prepare a sodium citrate solution as a protective agent;

[0032] S2. Add 100-200 mL of ultrapure water into a container as a bottom liquid, heat it to boiling, then add the gold source precursor, add the morphology stabilizer to adjust the pH value of the solution to a predetermined range, stir evenly, and at the same time add the reducing agent and the protective agent. After reacting for a predetermined time, add the nucleating agent, and continuously stir for 5-15 min under the boiling state to obtain a nano-gold sol with high sphericity.

[0033] In the technical solution of the embodiment of the present application, by precisely controlling the reaction conditions, including the types and concentrations of the gold source precursor, morphology stabilizer, reducing agent, nucleating agent and protective agent, as well as the reaction temperature and time, a nano-gold sol with high sphericity can be prepared. By using specific stabilizers and protective agents, it helps to improve the dispersibility of nano-gold particles and prevent particle aggregation, thereby obtaining a stable sol. By adjusting the concentration of the nucleating agent and the reaction time, the size of nano-gold particles can be effectively controlled to meet the special requirements of different application fields for the size of nano-gold particles. The preparation method has simple steps and is easy to scale up production, which is conducive to realizing the large-scale preparation of nano-gold sol. The nano-gold sol prepared by the method of the present application has good stability during storage, is not easy to precipitate, and has a long service life. Due to its characteristics of high sphericity, good dispersibility, size controllability and good stability, the nano-gold sol has broad application prospects in the fields of catalysis, drug carriers, biological labeling, electronic materials and optical materials. At the same time, the solvents and reagents used in this method are relatively environmentally friendly, reducing the impact on the environment during the production process.

[0034] Further, in some embodiments, the concentration of the chloroauric acid tetrahydrate solution is 0.025-0.05 mmol / L; the concentration of the sodium carbonate solution is 0.05-0.1 mol / L; the concentration of the citric acid solution is 0.075-0.375 mmol / L; the concentration of the sodium citrate solution is 0.075-0.375 mmol / L; the concentration of the tannic acid solution is 6.25×10 -3 ~1.25×10 -2 mmol / L.

[0035] In the technical solution of the embodiment of the present application, the chloroauric acid tetrahydrate solution helps to accurately control the amount of the gold source precursor, thereby affecting the size of the final gold nanoparticles. A higher concentration may result in larger particles, while a lower concentration may produce smaller particles. The sodium carbonate solution, as a morphology stabilizer, helps to maintain the spherical morphology of the gold nanoparticles during the growth process, prevent particle aggregation, and improve the dispersibility. The citric acid solution provides sufficient reduction efficiency without reducing the gold ions too quickly, helps to form uniform gold nanoparticles, and maintains the stability of the sol. The sodium citrate solution helps to form a stable double electric layer on the surface of the gold nanoparticles to prevent aggregation between particles. The tannic acid solution helps to achieve uniform nucleation, thereby forming gold nanoparticles with high sphericity.

[0036] Further, in some embodiments, the pH value of the solution is adjusted to 8-9.

[0037] In the technical solution of the embodiment of the present application, the pH value is an important factor affecting the growth process of the nanoparticles. In an alkaline environment with a pH value of 8-9, the reduction rate and nucleation process of gold atoms can be optimized, the dispersibility between gold atoms can be improved, which is conducive to the formation of gold nanoparticles with high sphericity. Under alkaline conditions, the charge state on the surface of the gold nanoparticles can be better regulated, which helps to stably disperse the particles in the solution and reduce the aggregation between particles. The adjustment of the pH value can affect the reduction ability of reducing agents such as citric acid, and further affect the reduction rate and nucleation density of gold atoms, thereby realizing the effective control of the size of the gold nanoparticles. At an appropriate pH value, the nucleation and growth processes of gold atoms are more uniform, which helps to prepare gold nanoparticles with better size and shape uniformity.

[0038] Further, in some embodiments, the molar ratio of the reducing agent to the protective agent is 1:(1-5). The molar ratio of the gold source precursor to the reducing agent is 1:(3-15). The molar ratio of the nucleating agent to the reducing agent is 1:(6-60).

[0039] In the technical solution of the embodiment of the present application, the ratio of the reducing agent to the protective agent can ensure that during the formation of gold nanoparticles, the reducing agent can effectively reduce the gold source precursor to gold atoms, while the protective agent can protect the newly generated gold atoms from excessive growth or aggregation, so as to obtain gold nanoparticles with uniform size and regular shape. The ratio of the gold source precursor to the reducing agent can ensure that there is sufficient reducing agent to completely reduce the gold source precursor, while avoiding the excessive use of the reducing agent, which may lead to instability during the particle growth process. The appropriate addition of the protective agent helps to form a stable protective layer on the surface of the gold nanoparticles, enhance the stability of the particles, and prevent aggregation during storage and use. The ratio of the nucleating agent to the reducing agent helps to accurately control the nucleation process, enable the gold atoms to nucleate uniformly, and form gold nanoparticles with high sphericity.

[0040] Further, in some embodiments, the reaction is carried out for a predetermined time of 10 to 60 s. The obtained nano-gold sol with high sphericity has a particle size of 10 to 50 nm.

[0041] In the technical solution of the embodiment of the present application, after the chloroauric acid tetrahydrate solution is added to the boiling bottom liquid, gold ions are released into the solution. Subsequently, citric acid added as a reducing agent starts to reduce the gold ions into gold atoms. During this process, the gold atoms begin to aggregate, forming the primary stage of crystal nuclei. Within 10 to 60 s after the reaction starts, the process of citric acid reducing gold ions is ongoing, and the crystal nuclei start to form but are not yet fully mature. Adding tannic acid within this time window, as a nucleating agent, can promote the further aggregation of gold atoms and accelerate the formation of crystal nuclei. Tannic acid molecules contain multiple hydroxyl groups, which can interact with the charges on the surface of gold atoms, reducing the surface energy between gold atoms, thereby promoting the aggregation of gold atoms and the formation of crystal nuclei. The addition of tannic acid provides a rapid nucleation environment for gold atoms, contributing to the formation of a large number of uniformly sized crystal nuclei. Adding tannic acid after 10 to 60 s of reaction can ensure that, based on the reduction of gold ions by citric acid to generate gold atoms, the nucleation process is rapidly initiated. This time window allows a certain degree of gold atom aggregation but is not too long to cause excessive growth of crystal nuclei, thus helping to control the size of the final nano-gold particles. Therefore, by adding tannic acid within a specific time range, the formation rate and number of crystal nuclei can be regulated, thereby affecting the width of the particle size distribution. If tannic acid is added too early, it may lead to an excessive number of crystal nuclei and an uneven nucleation process; if added too late, the crystal nuclei may be too large and the particle size distribution may become wider. After adding tannic acid and completing the nucleation process, continuous heating and stirring contribute to the growth of crystal nuclei to form the final nano-gold particles.

[0042] Specifically, the addition rates of the citric acid solution, sodium citrate solution, and tannic acid solution are 1 mL / s. By rapidly adding the citric acid solution, sodium citrate solution, and tannic acid solution, the conditions of the reaction system can be rapidly changed, promoting the rapid nucleation of gold atoms and improving the nucleation efficiency. By the above method, a nano-gold sol with a particle size of 10 to 50 nm can be obtained. The nano-gold particles in this particle size range have excellent optical properties and a high specific surface area, and are suitable for fields such as catalysis, drug delivery, and bioimaging.

[0043] Due to the precise control of reaction time and the speed of adding reagents, the particle size distribution of nanogold particles can be made more uniform, reducing the heterogeneity of particle size. Nanogold particles of 10-50nm usually show strong surface plasmon resonance absorption, which makes them have potential application value in photothermal therapy, biosensing and other fields. Small-sized nanogold particles have a higher specific surface area, which helps to enhance their activity in fields such as catalysis and drug delivery. Due to the small particle size and uniform distribution, nanogold sol is easier to separate and purify by centrifugation, filtration and other means.

[0044] In a second aspect, an embodiment of the present application provides a nano-gold sol with high sphericity, which is prepared by the preparation method of the first aspect.

[0045] Sphericity is an important property of nano-gold sol, which has a significant impact on the performance of nano-gold sol in various application fields. The color and light absorption characteristics of nano-gold sol mainly depend on its size and shape. Highly spherical nano-gold particles can produce more uniform and predictable light scattering and plasmon resonance absorption, which is crucial for applications such as color sensors, biomarkers, and optical imaging. Spherical nano-gold particles have a higher surface area to volume ratio and can provide more catalytic active sites. Particles with high sphericity show more uniform catalytic performance in catalytic reactions, which is beneficial to improve the stability and efficiency of the catalyst. In the fields of drug delivery, cancer treatment, and bioimaging, nano-gold sols with high sphericity can more easily pass through cell membranes and are more easily metabolized by organisms. Nano-gold particles with high sphericity have better biocompatibility and lower toxicity.

[0046] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0047] 1. Preparation method

[0048] Example 1

[0049] This embodiment provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps:

[0050] S1. Preparation of gold source precursor: Using ultrapure water as solvent, prepare 0.025mmol / L tetrahydrate chloroauric acid solution;

[0051] Preparation of morphology stabilizer: Use ultrapure water as solvent to prepare 0.05 mol / L sodium carbonate solution;

[0052] Reducing agent preparation: Use ultrapure water as solvent to prepare 0.075mmol / L citric acid solution;

[0053] Preparation of nucleating agent: Use ultrapure water as solvent to prepare 6.25×10 -3 mmol / L tannic acid solution;

[0054] Preparation of protective agent: Use ultrapure water as solvent to prepare 0.075mmol / L sodium citrate solution;

[0055] S2. Preparation of nano-gold sol: The base liquid is 150 mL of ultrapure water, which is added to a three-necked flask. The base liquid is heated to boiling, and 1 mL of tetrahydrate chloroauric acid solution is added. Sodium carbonate solution is added to adjust the solution pH to 9. At the same time, 1 mL of citric acid solution and 1 mL of sodium citrate solution are added at a rate of 1 mL / s. The reaction is continued for 10 seconds. 4 mL of tannic acid solution is also added at a rate of 1 mL / s. The reaction is continued under stirring for 5 minutes under boiling conditions to obtain nano-gold sol. The TEM image of the obtained nano-gold sol is shown in the figure below. Figure 1 The particle size distribution is shown in Tables 1 and 2, the zeta potential results are shown in Table 3, and the ultraviolet absorption spectrum is shown in Table 4. Figure 5 shown.

[0056] Example 2

[0057] This embodiment provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps:

[0058] S1. Preparation of gold source precursor: Using ultrapure water as solvent, prepare 0.025mmol / L tetrahydrate chloroauric acid solution;

[0059] Preparation of morphology stabilizer: Use ultrapure water as solvent to prepare 0.05 mol / L sodium carbonate solution;

[0060] Reducing agent preparation: Use ultrapure water as solvent to prepare 0.125mmol / L citric acid solution;

[0061] Preparation of nucleating agent: Use ultrapure water as solvent to prepare 6.25×10 -3 mmol / L tannic acid solution;

[0062] Preparation of protective agent: Use ultrapure water as solvent to prepare 0.125mmol / L sodium citrate solution;

[0063] S2. Preparation of gold nanoparticle sol: 150 mL of ultrapure water was used as the bottom solution and added to a three-necked flask. The bottom solution was heated to boiling, 1 mL of chloroauric acid tetrahydrate solution was added, and the pH of the solution was adjusted to 9 by adding sodium carbonate solution. At the same time, 1 mL of citric acid solution and 1 mL of sodium citrate solution were added at a rate of 1 mL / s, and the reaction was carried out for 15 s. Then, 2 mL of tannic acid solution was added at the same rate of 1 mL / s, and the reaction was continuously stirred at the boiling state for 10 min to obtain the gold nanoparticle sol. The particle size distribution of the obtained gold nanoparticle sol is shown in Tables 1 to 2, the ZETA potential results are shown in Table 3, and the ultraviolet absorption spectrum is as Figure 5 shown.

[0064] Example 3

[0065] This example provides a method for preparing a gold nanoparticle sol with high sphericity, which includes the following steps:

[0066] S1. Preparation of gold source precursor: Using ultrapure water as the solvent, a 0.025 mmol / L chloroauric acid tetrahydrate solution was prepared;

[0067] Preparation of morphology stabilizer: Using ultrapure water as the solvent, a 0.05 mol / L sodium carbonate solution was prepared;

[0068] Preparation of reducing agent: Using ultrapure water as the solvent, a 0.25 mmol / L citric acid solution was prepared;

[0069] Preparation of nucleating agent: Using ultrapure water as the solvent, a 6.25×10 -3 mmol / L tannic acid solution was prepared;

[0070] Preparation of protective agent: Using ultrapure water as the solvent, a 0.25 mmol / L sodium citrate solution was prepared;

[0071] S2. Preparation of gold nanoparticle sol: 150 mL of ultrapure water was used as the bottom solution and added to a three-necked flask. The bottom solution was heated to boiling, 1 mL of chloroauric acid tetrahydrate solution was added, and the pH of the solution was adjusted to 9 by adding sodium carbonate solution. At the same time, 1 mL of citric acid solution and 1 mL of sodium citrate solution were added at a rate of 1 mL / s, and the reaction was carried out for 30 s. Then, 1 mL of tannic acid solution was added at the same rate of 1 mL / s, and the reaction was continuously stirred at the boiling state for 15 min to obtain the gold nanoparticle sol. The particle size distribution of the obtained gold nanoparticle sol is shown in Tables 1 to 2, the ZETA potential results are shown in Table 3, and the ultraviolet absorption spectrum is as Figure 5 shown.

[0072] Comparative Example 1

[0073] Comparative Example 1 provided a method for preparing highly spherical gold nanosol. Compared with Example 1, the only difference was that no sodium carbonate solution was added, and other experimental parameters and conditions were basically the same as those in Example 1, which will not be elaborated here. The particle size distribution of the obtained gold nanosol was shown in Table 1, the ZETA potential results were shown in Table 3, and the TEM image was as shown in Figure 2 shown, and the ultraviolet absorption spectrum was as shown in Figure 5 shown.

[0074] Comparative Example 2

[0075] Comparative Example 2 provided a method for preparing highly spherical gold nanosol. Compared with Example 3, the only difference was that no tannic acid solution was added, and other experimental parameters and conditions were basically the same as those in Example 3, which will not be elaborated here. The particle size distribution was shown in Table 1, the ZETA potential results were shown in Table 3, and the ultraviolet absorption spectrum was as shown in Figure 5 shown.

[0076] Comparative Example 3

[0077] Comparative Example 3 provided a method for preparing highly spherical gold nanosol. Compared with Example 1, the only difference was that a sodium carbonate solution was added to adjust the solution pH to 7, and other experimental parameters and conditions were basically the same as those in Example 1, which will not be elaborated here. The particle size distribution was shown in Table 1, the ZETA potential results were shown in Table 3, and the TEM image was as shown in Figure 3 shown, and the ultraviolet absorption spectrum was as shown in Figure 5 shown.

[0078] Comparative Example 4

[0079] Comparative Example 4 provided a method for preparing highly spherical gold nanosol. Compared with Example 1, the only difference was that a sodium carbonate solution was added to adjust the solution pH to 10, and other experimental parameters and conditions were basically the same as those in Example 1, which will not be elaborated here. The particle size distribution was shown in Table 1, the ZETA potential results were shown in Table 3, and the ultraviolet absorption spectrum was as shown in Figure 5 shown.

[0080] Comparative Example 5

[0081] Comparative Example 5 provided a method for preparing highly spherical gold nanosol. Compared with Example 3, the only difference was that citric acid, tannic acid, and sodium citrate were added after being mixed evenly, and other experimental parameters and conditions were basically the same as those in Example 1, which will not be elaborated here. The particle size distribution was shown in Table 1, the ZETA potential results were shown in Table 3, and the TEM image was as shown in Figure 4 shown, and the ultraviolet absorption spectrum was as shown in Figure 5 shown.

[0082]

[0083]

[0084]

[0085] II. Test Methods

[0086] 1. TEM Test

[0087] The obtained nano-gold sols in the examples and comparative examples were tested by using an F20S-TWIN high-resolution transmission electron microscope.

[0088] 2. Particle Size Test

[0089] The obtained nano-gold sols in the examples and comparative examples were tested by using a Malvern nano particle size analyzer - 3000.

[0090] 3. Ultraviolet Absorption Spectrum Test

[0091] The obtained nano-gold sols in the examples and comparative examples were tested by using a Shimadzu UV-2600 from Japan.

[0092] 4. ZETA Potential Test

[0093] The obtained nano-gold sols in the examples and comparative examples were tested by using a Malvern nano particle size analyzer - 3000.

[0094] III. Analysis of Test Results of Each Example and Comparative Example

[0095] From Table 1 and Figures 1 to 4It can be seen that the nano-gold sol obtained in Example 1 is uniformly dispersed, with a concentrated particle size and a uniform spherical morphology; in Comparative Example 1, no sodium carbonate solution was added. It can be seen that the particle size distribution of the nano-gold is relatively wide, and there is an agglomeration phenomenon, and the nano-gold sol with an ellipsoidal morphology accounts for the majority; in Comparative Example 2, no tannic acid solution was added, and the particle size distribution of the nano-gold sol is wide. Since tannic acid helps to rapidly aggregate and nucleate, the particle size distribution of the nano-gold sol will be reduced; in Comparative Example 3, the reaction pH value is 7, which is a neutral condition, reducing the reduction ability of the reducing agent and unable to achieve a concentrated and rapid reaction in the system. The obtained nano-gold sol has a wide particle size distribution and an agglomeration phenomenon; in Comparative Example 4, the reaction pH value is 10, the alkalinity of the solution is increased, and citric acid undergoes an oxidation reaction to generate a series of complex products such as pyrophosphoric acid, with almost no reduction ability. In the system, sodium citrate serves as both a reducing agent and a stabilizer, resulting in a wider particle size of the nano-gold sol and a decrease in stability; in Comparative Example 5, the addition order and addition time of the solution were adjusted. It can be seen that the particle size distribution of the nano-gold sol is relatively wide. This is because the mechanism of action of tannic acid as a nucleating agent is that after the solution reacts for a certain time, the tannic acid solution is added to rapidly nucleate, and then nano-gold particles of a fixed size are generated to ensure the concentration of the particle size distribution of the solution. In Comparative Example 5, since citric acid, tannic acid, and sodium citrate are mixed evenly and then added together, the nucleating effect of tannic acid fails to be effectively exerted, making the nucleation process of the nano-gold particles uneven, resulting in a wider particle size distribution and a small amount of agglomeration of the nano-gold particles.

[0096] As can be seen from Table 2 and Table 3, in Examples 1-3, due to the uniform particle size distribution and the relatively high absolute value of the ZETA potential, it indicates that the system has good stability. After the solution was left standing for 1 month, no precipitation phenomenon was observed, and the particle size distribution test results changed little compared with those 1 month ago; in Comparative Example 1, the absolute value of the ZETA potential data decreased, indicating a decrease in the stability of the solution. From the TEM results, it can be seen that there is an agglomeration phenomenon. After the solution was left standing for 1 month, the agglomeration phenomenon could be observed with the naked eye, and the particle size distribution data could not be accurately measured; in Comparative Examples 3-4, due to the decrease in the reduction ability of the reducing agent, the particle size distribution of the solution is non-uniform, and the stability of the system also decreases. After standing for 1 month, a visible agglomeration phenomenon occurred; in Comparative Example 5, due to the large and non-uniform particle size and the decrease in the absolute value of the ZETA potential, a visible agglomeration phenomenon also occurred after standing for 1 month.

[0097] From Figure 5It can be seen that the peak position of the ultraviolet absorption peak corresponding to Example 1 is at 514 nm, the peak position of the ultraviolet absorption peak corresponding to Example 2 is at 521 nm, and the peak position of the ultraviolet absorption peak corresponding to Example 3 is at 539 nm, and the distributions are all relatively narrow; compared with Example 1, Comparative Examples 1, 3 - 4 have a wider particle size distribution and a wider ultraviolet absorption peak position distribution. At the same time, due to the agglomeration phenomenon in the solution, there is a partial red shift in the peak position; compared with Example 3, Comparative Examples 2 and 5 have a wider particle size distribution and thus a wider ultraviolet absorption peak position distribution. Therefore, the high sphericity nano - gold sol provided by the present application has a narrow particle size distribution, a specific and narrow ultraviolet absorption peak position, indicating its good homogeneity. At the same time, the agglomeration phenomenon of the sol in the solution is significantly reduced, effectively avoiding the red shift phenomenon of the ultraviolet absorption peak position, thereby ensuring the stability and reliability of the sol.

[0098] It should be noted that the present application is not limited to the above - mentioned embodiments. The above - mentioned embodiments are only examples, and embodiments with the same structure and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a nano-gold sol with high sphericity, characterized in that: The following steps are involved: S1. Prepare tetrahydrate chloroauric acid solution as a gold source precursor; A sodium carbonate solution is prepared as a morphology stabilizer; a citric acid solution is prepared as a reducing agent; and a tannic acid solution is prepared as a nucleating agent; Prepare sodium citrate solution as a protective agent; S2. Add 100-200 mL of ultrapure water into a container as a base liquid, heat to boiling, then add a gold source precursor, add a morphology stabilizer to adjust the solution pH to 8-9, stir evenly, add a reducing agent and a protective agent at the same time, react for 10-60 seconds, add a nucleating agent, and continue stirring for 5-15 minutes under boiling conditions to obtain a nano-gold sol with high sphericity; the adding rate of the reducing agent, the protective agent and the nucleating agent is 1 mL / s; the molar ratio of the reducing agent to the protective agent is 1:(1-5); the molar ratio of the nucleating agent to the reducing agent is 1:(6-60).

2. The method for preparing a nano gold sol with high sphericity according to claim 1, wherein In step S1, the concentration of the tetrahydrate chloroauric acid solution is 0.025-0.05 mmol / L; the concentration of the sodium carbonate solution is 0.05-0.1 mol / L; the concentration of the citric acid solution is 0.075-0.375 mmol / L; and the concentration of the sodium citrate solution is 0.075-0.375 mmol / L.

3. The preparation method of the nano gold sol with high sphericity according to claim 2, characterized in that, The concentration of the tannic acid solution is 6.25×10 -3 ~1.25×10 -2 mmol / L.

4. The method for preparing a nano-gold sol with high sphericity according to claim 1, wherein The molar ratio of the gold source precursor to the reducing agent is 1:(3-15).

5. The method for preparing a nano-gold sol with high sphericity according to claim 1, wherein The particle size of the high-sphericity nano-gold sol is 10-50 nm.

6. A nano-gold sol with high sphericity, characterized in that: The nano-gold sol having high sphericity is prepared by the preparation method of any one of claims 1 to 5.

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