High-sphericity nanogold sol and preparation method thereof

Abstract

The invention provides high-sphericity nanogold sol and a preparation method thereof, and belongs to the field of nanomaterials, according to the preparation method, the nanogold sol is prepared from a base solution, a gold source precursor, a morphology stabilizer, a reducing agent, a nucleating agent and a protective agent under the heating condition, and the high-sphericity nanogold sol is obtained by accurately controlling reaction conditions, reagent types and concentrations. The high-sphericity nanogold sol can be prepared by adjusting the usage ratio of the tannic acid to the reducing agent and the adding time of the tannic acid, the growth speed of the nanogold sol is increased and the size distribution is reduced through the combined action of the citric acid / sodium citrate dual reducing agent, and the content of the tannic acid in the nanogold sol is increased by adjusting the usage ratio of the tannic acid to the reducing agent and the adding time of the tannic acid. The generation speed and size of the crystal nucleus are controlled, so that the effect of regulating and controlling the size is achieved. The prepared nanogold sol is high in stability and low in biotoxicity, raw materials are non-toxic and pollution-free, and the nanogold sol can be applied to the field of biomedical treatment.

Description

Technical Field

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

[0002] Nano-gold sol has shown wide application potential in many fields due to its unique physical and chemical properties. The main features of the 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. In particular, its application in the biomedical field has attracted extensive attention from researchers.

[0003] At present, the common method for preparing nano gold sol is Turkevich reduction method, but this method has certain limitations, for example, the particle size distribution of gained nano gold sol is wider, and along with the increase of particle diameter, the morphology of particle can change, and causes sphericity to reduce. In order to address the above problems, existing preparation method needs to add a large amount of organic stabilizers in system usually. However, this method is not only unfavorable for the purification of nanoparticles, and can significantly increase biological toxicity, limits its application in 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 technology, 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 to control morphology and sphericity, and high biological toxicity of the nano-gold sol.

[0006] In a first aspect, the present application provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps: S1. Prepare tetrahydrate chloroauric acid solution as a gold source precursor; prepare sodium carbonate solution as a morphology stabilizer; prepare citric acid solution as a reducing agent; prepare tannic acid solution as a nucleating agent; prepare sodium citrate solution as a protective agent; S2. Add 100~200mL of ultrapure water into the container as the base liquid, heat to boiling, then add the gold source precursor, add the morphology stabilizer to adjust the pH value of the solution to the predetermined range, stir evenly, add the reducing agent and protective agent at the same time, react for a predetermined time, add the nucleating agent, and continue stirring for 5~15 minutes under boiling state to obtain a nano-gold sol with high sphericity.

[0007] 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.

[0008] 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.

[0009] 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).

[0010] As a further improvement of the present application, the particle size of the highly spherical nano-gold sol is 10-50 nm.

[0011] 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.

[0012] The beneficial effects of this application are: 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 -] concentration, which increases the isotropic growth degree of the particles, and the nano-gold sol presents a high sphericity morphology. At the same time, under this pH reaction condition, the reducing ability of the reducing agent is improved, which accelerates the nucleation and growth process, the morphology is stable, and the particle size distribution is narrow; through the combined action of the citric acid / sodium citrate dual 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, and a large number of negatively charged groups are coated on the surface of the nanoparticles after they are generated, thereby 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 speed and size of the crystal nucleus can be controlled, thereby achieving the effect of regulating the size.

[0013] The present invention improves the reaction rate and reduces the growth deviation between particles by carrying out the above reaction in a boiling bottom liquid, thereby achieving a narrower 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, which meets the requirements of "green production".

[0014] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 TEM image of the nano-gold sol prepared in Example 1 of the present application; Figure 2 TEM image of the nano-gold sol prepared in Comparative Example 1; Figure 3 TEM image of the nano-gold sol prepared in Comparative Example 3; Figure 4 TEM image of the nano-gold sol prepared in Comparative Example 5; Figure 5 The ultraviolet absorption spectra of the nano-gold sols prepared in Examples 1-3 and Comparative Examples 1-5 of the present application. DETAILED DESCRIPTION

[0017] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians 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" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0019] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0020] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] The existing method for preparing nano gold sol has certain limitations, and the particle size distribution of the obtained nano gold sol is wider, and along with the increase of particle diameter, the morphology of particles can change, causing the sphericity to reduce. In order to solve the above problems, it is usually necessary to add a large amount of organic stabilizers in the system. However, this method is not only unfavorable for the purification of nanoparticles, and can significantly increase biotoxicity, limiting its application in biomedical fields.

[0022] In order to solve the technical problems of wide particle size distribution, difficult to control morphology and sphericity, and high biological toxicity of nano-gold sol, the present application provides a spherical nano-gold sol and a preparation method thereof, wherein a liquid phase reduction preparation method is adopted, 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 protective 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 nano-gold sol can be controlled, thereby achieving the goal of reducing the width of the particle size distribution while maintaining the high sphericity of the nano-gold sol, and reducing biological toxicity, so as to be better suitable for research and application in biomedicine and other fields.

[0023] In a first aspect, the present invention provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps: S1. Prepare tetrahydrate chloroauric acid solution as a gold source precursor; prepare sodium carbonate solution as a morphology stabilizer; prepare citric acid solution as a reducing agent; prepare tannic acid solution as a nucleating agent; prepare sodium citrate solution as a protective agent; S2. Add 100~200mL of ultrapure water into the container as the base liquid, heat to boiling, then add the gold source precursor, add the morphology stabilizer to adjust the pH value of the solution to the predetermined range, stir evenly, add the reducing agent and protective agent at the same time, react for a predetermined time, add the nucleating agent, and continue stirring for 5~15 minutes under boiling state to obtain a nano-gold sol with high sphericity.

[0024] In the technical scheme of the embodiment of the present application, by accurately controlling the reaction conditions, including the type and concentration of the gold source precursor, morphology stabilizer, reducing agent, nucleating agent and protective agent, as well as the temperature and time of the reaction, a nano gold sol with high sphericity can be prepared. By using specific stabilizers and protective agents, it is helpful to improve the dispersibility of nano gold particles and prevent particles from aggregating, thereby obtaining a stable sol. By adjusting the concentration and reaction time of the nucleating agent, the size of the nano gold particles can be effectively controlled to meet the special requirements of different application fields for the size of the nano gold particles. The preparation method has simple steps, is easy to amplify production, and 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 the characteristics of high sphericity, good dispersibility, controllable size and good stability, the nano gold sol has a wide range of application prospects in the fields of catalysis, drug carriers, biomarkers, electronic materials and optical materials. At the same time, the solvents and reagents used in the method are relatively environmentally friendly, reducing the impact on the environment during the production process.

[0025] Further, in some embodiments, 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.

[0026] In the technical scheme of the embodiment of the present application, the tetrahydrate chloroauric acid solution helps to accurately control the amount of the gold source precursor, thereby affecting the size of the final nano-gold particles. A higher concentration may result in larger particles, while a lower concentration may produce smaller particles. As a morphology stabilizer, the sodium carbonate solution helps to maintain the spherical morphology of the nano-gold particles during their growth, prevents particle aggregation, and improves dispersibility. The citric acid solution provides sufficient reduction efficiency without reducing the gold ions too quickly, helps to form uniform nano-gold particles, and maintains the stability of the sol. The sodium citrate solution helps to form a stable double electrical layer on the surface of the nano-gold particles, preventing aggregation between the particles. The tannic acid solution helps to uniformly nucleate, thereby forming nano-gold particles with high sphericity.

[0027] Furthermore, in some embodiments, the pH value of the solution is adjusted to 8-9.

[0028] In the technical scheme of the embodiment of the present application, pH value is an important factor affecting the growth process of nanoparticles. In an alkaline environment with a pH value of 8 to 9, the reduction rate and nucleation process of gold atoms can be optimized, and the dispersibility between gold atoms can be improved, which is conducive to the formation of nano-gold particles with high sphericity. Under alkaline conditions, the charge state on the surface of nano-gold particles can be better regulated, which helps the stable dispersion of particles in the solution and reduces the agglomeration between particles. The regulation of pH value can affect the reducing ability of reducing agents such as citric acid, and then affect the reduction rate and nucleation density of gold atoms, so as to achieve effective control of the size of nano-gold particles. Under suitable pH value, the nucleation and growth process of gold atoms are more uniform, which helps to prepare nano-gold particles with better size and shape uniformity.

[0029] Further, in some embodiments, 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).

[0030] In the technical scheme of the embodiment of the present application, the ratio of reducing agent and protective agent can ensure that in the formation process of nano gold, the reducing agent can effectively reduce the gold source precursor to gold atoms, and the protective agent can protect the newly generated gold atoms to prevent them from overgrowth or agglomeration, thereby obtaining nano gold particles with uniform size and regular shape. The ratio of gold source precursor and reducing agent can ensure that there are enough reducing agents to completely reduce the gold source precursor, while avoiding excessive use of reducing agent, which may cause instability in the particle growth process. The appropriate amount of protective agent added helps to form a stable protective layer on the surface of nano gold particles, enhances the stability of particles, and prevents them from agglomerating during storage and use. The ratio of nucleating agent and reducing agent helps to accurately control the nucleation process, so that gold atoms can be uniformly nucleated to form nano gold particles with high sphericity.

[0031] Furthermore, in some embodiments, the predetermined reaction time is 10-60 seconds. The particle size of the obtained high sphericity nano-gold sol is 10-50 nm.

[0032] In the technical scheme of the embodiment of the present application, after the tetrahydrate chloroauric acid solution is added to the boiling bottom liquid, the gold ions are released into the solution, and the citric acid added subsequently is used as a reducing agent to start reducing the gold ions to gold atoms. In this process, the gold atoms begin to gather and form the primary stage of the crystal nucleus. Within 10 to 60 seconds after the reaction starts, the process of citric acid reducing gold ions is in progress, and the crystal nucleus begins to form but is not yet fully mature. Tannic acid is added in this time window. Tannic acid, as a nucleating agent, can promote the further aggregation of gold atoms and accelerate the formation of crystal nucleus. Tannic acid molecules contain multiple hydroxyls, which can interact with the charge on the surface of gold atoms, reduce the surface energy between gold atoms, thereby promoting the aggregation of gold atoms and the formation of crystal nucleus. The addition of tannic acid provides a rapid nucleation environment for gold atoms, which helps to form a large number of uniformly sized crystal nuclei. Adding tannic acid after reacting for 10 to 60 seconds can ensure that the nucleation process is quickly started on the basis of citric acid reducing gold ions to generate gold atoms. This time window allows a certain degree of aggregation of gold atoms, but not too long to cause excessive growth of the nuclei, which helps control the size of the final gold nanoparticles. Therefore, by adding tannic acid within a specific time range, the speed and number of nuclei formation can be regulated, thereby affecting the width of the particle size distribution. If tannic acid is added too early, it may lead to too many nuclei and the nucleation process becomes uneven; if it is added too late, the nuclei may be too large and the particle size distribution becomes wider. After the tannic acid is added and the nucleation process is completed, continuous heating and stirring help the growth of the nuclei to form the final gold nanoparticles.

[0033] Specifically, the addition rate of citric acid solution, sodium citrate solution and tannic acid solution is 1 mL / s. By quickly adding citric acid solution, sodium citrate solution and tannic acid solution, the conditions of the reaction system can be quickly changed, the rapid nucleation of gold atoms can be promoted, and the nucleation efficiency can be improved. Through the above method, a nano-gold sol with a particle size of 10~50nm can be obtained. Nano-gold particles in this particle size range have excellent optical properties and a high specific surface area, and are suitable for catalysis, drug delivery, biological imaging and other fields.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 1. Preparation method Example 1 This embodiment provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps: S1. Preparation of gold source precursor: Using ultrapure water as solvent, prepare 0.025mmol / L tetrahydrate chloroauric acid solution; Preparation of morphology stabilizer: Use ultrapure water as solvent to prepare 0.05 mol / L sodium carbonate solution; Reducing agent preparation: Use ultrapure water as solvent to prepare 0.075mmol / L citric acid solution; Preparation of nucleating agent: Use ultrapure water as solvent to prepare 6.25×10-3 mmol / L tannic acid solution; Preparation of protective agent: Use ultrapure water as solvent to prepare 0.075mmol / L sodium citrate solution; 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.

[0039] Example 2 This embodiment provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps: S1. Preparation of gold source precursor: Using ultrapure water as solvent, prepare 0.025mmol / L tetrahydrate chloroauric acid solution; Preparation of morphology stabilizer: Use ultrapure water as solvent to prepare 0.05 mol / L sodium carbonate solution; Reducing agent preparation: Use ultrapure water as solvent to prepare 0.125mmol / L citric acid solution; Preparation of nucleating agent: Use ultrapure water as solvent to prepare 6.25×10 -3 mmol / L tannic acid solution; Preparation of protective agent: Use ultrapure water as solvent to prepare 0.125mmol / L sodium citrate solution; 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 15 seconds. 2 mL of tannic acid solution is also added at a rate of 1 mL / s. The reaction is continued under stirring for 10 minutes under boiling conditions to obtain nano-gold sol. The particle size distribution of the obtained nano-gold sol is shown in Tables 1 and 2, the ZETA potential results are shown in Table 3, and the UV absorption spectrum is shown in Table 4. Figure 5 shown.

[0040] Example 3 This embodiment provides a method for preparing a nano-gold sol with high sphericity, comprising the following steps: S1. Preparation of gold source precursor: Using ultrapure water as solvent, prepare 0.025mmol / L tetrahydrate chloroauric acid solution; Preparation of morphology stabilizer: Use ultrapure water as solvent to prepare 0.05 mol / L sodium carbonate solution; Reducing agent preparation: Use ultrapure water as solvent to prepare 0.25mmol / L citric acid solution; Preparation of nucleating agent: Use ultrapure water as solvent to prepare 6.25×10 -3 mmol / L tannic acid solution; Preparation of protective agent: Use ultrapure water as solvent to prepare 0.25mmol / L sodium citrate solution; 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 30 seconds. 1 mL of tannic acid solution is also added at a rate of 1 mL / s. The reaction is continued under stirring for 15 minutes under boiling conditions to obtain nano-gold sol. The particle size distribution of the obtained nano-gold sol is shown in Tables 1 and 2, the ZETA potential results are shown in Table 3, and the UV absorption spectrum is shown in Table 4. Figure 5 shown.

[0041] Comparative Example 1 Comparative Example 1 provides a method for preparing a nano-gold sol with high sphericity. Compared with Example 1, the only difference is that no sodium carbonate solution is added. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here. The particle size distribution of the obtained nano-gold sol is shown in Table 1, the zeta potential results are shown in Table 3, and the TEM images are shown in Table 4. Figure 2 The UV absorption spectrum is shown in Figure 5 shown.

[0042] Comparative Example 2 Comparative Example 2 provides a method for preparing a nano-gold sol with high sphericity. Compared with Example 3, the only difference is that no tannic acid solution is added. Other experimental parameters and conditions are basically the same as those in Example 3, which will not be repeated here. The particle size distribution is shown in Table 1, the zeta potential results are shown in Table 3, and the ultraviolet absorption spectrum is shown in Table 4. Figure 5 shown.

[0043] Comparative Example 3 Comparative Example 3 provides a method for preparing a nano-gold sol with high sphericity. Compared with Example 1, the only difference is that sodium carbonate solution is added to adjust the solution pH to 7. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here. The particle size distribution is shown in Table 1, the zeta potential results are shown in Table 3, and the TEM images are shown in Table 4. Figure 3 The UV absorption spectrum is shown in Figure 5 shown.

[0044] Comparative Example 4 Comparative Example 4 provides a method for preparing a nano-gold sol with high sphericity. Compared with Example 1, the only difference is that sodium carbonate solution is added to adjust the solution pH to 10. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here. The particle size distribution is shown in Table 1, the zeta potential results are shown in Table 3, and the ultraviolet absorption spectrum is shown in Table 4. Figure 5 shown.

[0045] Comparative Example 5 Comparative Example 5 provides a method for preparing a nano-gold sol with high sphericity. Compared with Example 3, the only difference is that citric acid, tannic acid, and sodium citrate are added after being mixed evenly. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here. The particle size distribution is shown in Table 1, the zeta potential results are shown in Table 3, and the TEM images are shown in Table 4. Figure 4 The UV absorption spectrum is shown in Figure 5 shown.

[0046] 2. Test Method 1. TEM test The nano-gold sol obtained in the embodiment and the comparative example was tested using a F20S-TWIN high-resolution transmission electron microscope.

[0047] 2. Particle size test The nano-gold sol obtained in the embodiment and the comparative example was tested using a Malvern Nano Particle Size Analyzer-3000.

[0048] 3. Ultraviolet absorption spectrum test The nano-gold sol obtained in the embodiment and the comparative example was tested using Japan's Shimadzu UV-2600.

[0049] 4. Zeta potential test The nano-gold sol obtained in the embodiment and the comparative example was tested using a Malvern Nano Particle Size Analyzer-3000.

[0050] III. Analysis of test results of various embodiments and comparative examples From Table 1 and Figures 1 to 4It can be seen that the nano-gold sol obtained in Example 1 is uniformly dispersed, the particle size is concentrated, and the morphology is uniformly spherical; in Comparative Example 1, no sodium carbonate solution is added, and it can be seen that the nano-gold particle size distribution is wide, and there is agglomeration phenomenon, and the ellipsoidal morphology of the nano-gold sol is the majority; in Comparative Example 2, no tannic acid solution is added, and the nano-gold sol particle size distribution is wide. Since tannic acid helps to quickly aggregate and nucleate, it will reduce the particle size distribution of the nano-gold sol; in Comparative Example 3, the reaction pH value is 7, which is a neutral condition, which reduces the reducing ability of the reducing agent, and cannot achieve concentrated rapid reaction in the system. The obtained nano-gold sol particle size distribution is wide and there is agglomeration phenomenon; in Comparative Example 4, the reaction pH value is 10, the alkalinity of the solution is enhanced, and citric acid undergoes an oxidation reaction to generate a series of complex pyrophosphates, etc. The product is a mixed product with almost no reducing ability. Sodium citrate in the system serves as both a reducing agent and a stabilizer, which leads to a widening of the particle size of the nanogold sol and a decrease in stability. In Comparative Example 5, the order and time of adding the solutions are adjusted. It can be seen that the particle size distribution of the nanogold 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 period of time, the tannic acid solution is added to rapidly nucleate, thereby generating nanogold particles of a fixed size, thereby ensuring the concentration of the solution particle size distribution. In Comparative Example 5, citric acid, tannic acid, and sodium citrate are mixed and then added together, resulting in the nucleation effect of tannic acid failing to be effectively exerted, making the nucleation process of the nanogold particles uneven, resulting in a wide particle size distribution and agglomeration of a small amount of nanogold particles.

[0051] It can be seen from Table 2 and Table 3 that in Examples 1-3, due to the uniform particle size distribution, the absolute value of the ZETA potential value is relatively high, indicating that the system has good stability. After the solution was left to stand for 1 month, no coagulation was observed, and the particle size distribution test results did not change much compared with 1 month ago; in Comparative Example 1, the absolute value of the ZETA potential data decreased, indicating that the solution stability was reduced. From the TEM results, it can be seen that there was agglomeration. After the solution was left to stand for 1 month, the agglomeration could be observed with the naked eye, and the particle size distribution data could not be accurately tested; in Comparative Examples 3-4, due to the decrease in the reducing ability of the reducing agent, the solution particle size distribution was uneven, and the system stability also decreased accordingly. After standing for 1 month, visible agglomeration occurred; in Comparative Example 5, due to the large and uneven particle size, the absolute value of the ZETA potential value decreased, and visible agglomeration also occurred after standing for 1 month.

[0052] from Figure 5It can be seen that the ultraviolet absorption peak corresponding to Example 1 is at 514nm, the ultraviolet absorption peak corresponding to Example 2 is at 521nm, and the ultraviolet absorption peak corresponding to Example 3 is at 539nm, and the distribution is relatively narrow; Comparative Examples 1, 3-4, compared with Example 1, have a wider particle size distribution and a wider distribution of ultraviolet absorption peaks. At the same time, due to the agglomeration phenomenon in the solution, the peaks have a partial rainbow shift phenomenon; Comparative Examples 2 and Comparative Examples 5 are compared with Example 3, because the particle size distribution is relatively wide, the ultraviolet absorption peak position is also widely distributed. Therefore, the nano gold sol with high sphericity provided in the present application has a narrow particle size distribution, a specific ultraviolet absorption peak position and a narrow distribution, indicating that it has good uniformity. At the same time, the agglomeration phenomenon of the sol in the solution is significantly reduced, and the rainbow shift phenomenon of the ultraviolet absorption peak position is effectively avoided, thereby ensuring the stability and reliability of the sol.

[0053] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in 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 100~200mL of ultrapure water into the container as the base liquid, heat to boiling, then add the gold source precursor, add the morphology stabilizer to adjust the pH value of the solution to the predetermined range, stir evenly, add the reducing agent and protective agent at the same time, react for a predetermined time, add the nucleating agent, and continue stirring for 5~15 minutes under boiling state to obtain a nano-gold sol with high sphericity.

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 In step S2, the pH value of the solution is adjusted to 8-9.

5. The method for preparing a nano-gold sol with high sphericity according to claim 1, wherein In step S2, the molar ratio of the reducing agent to the protective agent is 1:(1-5).

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

7. The method for preparing a nano-gold sol with high sphericity according to claim 4, wherein: The molar ratio of the nucleating agent to the reducing agent is 1:(6-60).

8. The method for preparing a nano-gold sol with high sphericity according to claim 7, characterized in that: The predetermined reaction time is 10 to 60 seconds.

9. 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.

10. 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 9.

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