CN102847951B - Process for preparing gold nano particles through reduction of chloroauric acid by catalase - Google Patents

Abstract

The invention discloses a method for preparing gold nanoparticles by reducing tetrachloroauric acid with catalase, comprising the following steps: adding catalase solution dropwise into the tetrachloroauric acid solution and stirring evenly; adjusting the pH of the mixed solution The value is alkaline, and the reaction occurs in a water bath at 20-37°C. After the reaction is completed, gold nanoparticles are separated and obtained. The present invention introduces catalase as a reducing agent and a protective agent, and the reducing functional group on the catalase has strong reducibility under alkaline conditions, which is beneficial to the synthesis of gold nanoparticles. Under salt conditions (0.5MNaCl) will not agglomerate.

Description

A method for preparing gold nanoparticles by reducing tetrachloroauric acid with catalase

technical field

The invention relates to a preparation method of gold nanoparticles, in particular to a method for preparing gold nanoparticles by reducing tetrachloroauric acid with catalase.

Background technique

Gold nanoparticles refer to particles with a diameter of 1-100 nm. Gold nanoparticles have special surface effects, volume effects, quantum size effects and macroscopic quantum tunneling effects, and have important applications in many fields such as catalysis, electronics and optical devices, and biotechnology. Gold nanoparticles have an absorption peak in the visible spectral range of 510-550nm, and the absorption wavelength increases with the diameter of gold nanoparticles. When the particle size increases from small to large, the apparent color changes from light orange yellow, wine color, deep red and blue purple in sequence.

The surface of gold nanoparticles is atomically arranged. Due to the existence of a large number of crystal defects such as twins, dislocations, and stacking faults, a large number of dangling bonds and unsaturated bonds are caused, which significantly increases the surface area and the number of surface active points of the particles. Due to the nature of saturation, there are multiple active centers, which have high chemical activity and are easy to combine with other atoms and tend to be stable. Therefore, there is a problem that gold nanoparticles are easy to agglomerate. The agglomeration of gold nanoparticles will further affect the size of gold nanoparticles. However, the special properties of gold nanoparticles such as optics, electricity, and catalysis are largely affected by the particle size. The properties of nanomaterials are of great significance.

In order to solve the agglomeration problem of gold nanoparticles, the synthesis of gold nanoparticles is often carried out simultaneously with the surface modification. First, the reducing agent reduces the gold compound into gold atoms, and the gold atoms are further aggregated to form gold nanoparticles. While forming gold nanoparticles, add Stabilizers are adsorbed on the surface to increase stability, or modified molecules are assembled directly onto its surface, forming gold nanoparticles with self-assembled monolayers. The reducing agents used include sodium citrate, sodium borohydride, ascorbic acid, white phosphorus, ethanol or polyols, etc., and the stabilizers used include sodium citrate, polymers, organic ligands, etc.

The most classic method of synthesizing gold nanoparticles is the sodium citrate reduction method, which is still widely used today. In the process of preparing gold nanoparticles by this method, sodium citrate is not only used as a reducing agent but also as a stabilizer. By changing sodium citrate and four The molar ratio of chloroauric acid can control the size of the particles, but as the size increases, the polydispersity of the particles also increases, the particle morphology is ellipsoid or other irregular shapes, and the particle stability decreases, especially in the In batch synthesis, it is difficult to control the repeatability between different batches.

The phase transfer method is also one of the commonly used methods for the preparation of gold nanoparticles. During the preparation process, organic solvent extraction is required to obtain an organic sol, and then dehydration and removal of organic solvents are used to obtain gold nanomaterials. The gold nanoparticles prepared by this method The particles are uniform and dispersible, but the operation process is complicated, and the organic solvent is consumed in the preparation process, which has a great impact on the environment.

Contents of the invention

The invention provides a method for preparing gold nanoparticles by reducing tetrachloroauric acid with catalase, and the method solves the problems of easy aggregation of gold nanoparticles, poor repeatability, complex process, and large environmental impact of reagents used in the preparation in the traditional method.

A method for preparing gold nanoparticles by reducing tetrachloroauric acid with catalase, comprising the following steps: adding the catalase solution dropwise to the tetrachloroauric acid solution and stirring evenly; adjusting the pH value of the mixed solution to be alkaline , and react under a water bath condition of 20-37° C., and separate and obtain gold nanoparticles after the reaction is completed.

As a protein molecule, catalase has a wide range of sources, low price and good biocompatibility, and is used as a template for synthesizing gold nanoparticles in the present invention. The catalase molecule contains a large number of amino and sulfhydryl binding sites, which can be used to fix tetrachloroauric acid, provide a good space structure for the growth of gold nanoparticles, and can effectively prevent the aggregation of gold nanoparticles during the synthesis process; in addition, peroxidation Tyrosine in hydrogenase, lysine and arginine containing primary amino groups are reductive under alkaline conditions, and can reduce tetrachloroauric acid in situ.

The catalase is preferably bovine liver catalase.

The concentration of the catalase solution is preferably 5-50 mg/mL, more preferably 5-20 mg/mL, and most preferably 5 mg/mL. The less the catalase is used, the lower the preparation cost.

When the concentration of tetrachloroauric acid solution is too high, it will cause the aggregation of gold nanoparticles, and finally the performance of gold nanoparticles will be reduced. The concentration of the tetrachloroauric acid solution is preferably 0.1%～1%, more preferably 0.5%～ 1%, most preferably 1%.

Binding sites for a single catalase molecule are limited, so the molar ratio between catalase and tetrachloroauric acid affects the size and yield of gold nanoparticles, and the molar ratio between catalase and tetrachloroauric acid The higher the molar ratio, the stronger the reduction of the mixed solution, and the more binding sites of catalase molecules are provided, the less the amount of gold nanoparticles bound to a single site, and thus the smaller the size of the gold nanoparticles formed Therefore, by adjusting the mol ratio of catalase and tetrachloroauric acid, gold nanoparticles with controllable size can be obtained, and the mol ratio of catalase and tetrachloroauric acid is preferably 0.00221: 1～0.221: 1, Within this molar ratio range, gold nanoparticles with a particle size of 10-40 nm can be obtained, the particle size range of the gold nanoparticles is relatively narrow, and the obtained gold nanoparticles have better properties.

The mol ratio of catalase and tetrachloroauric acid is more preferably 0.00221: 1～0.0885: 1, within this molar ratio range, can obtain the gold nanoparticle that particle diameter is 10～30nm, and higher mol ratio causes gold nanoparticle The particles are more of an enzymatic nature.

Under alkaline conditions, it is beneficial to improve the reducibility of the catalase reducing group, and the pH value of the mixed solution is preferably 10-12; more preferably 12.

The completion of the reaction refers to the reaction until the ultraviolet spectrum curve of the generated gold nanoparticle sol does not change, which means that the output of gold nanoparticles has reached a stable state.

The separation method is preferably centrifugation, and the rotation speed during centrifugation is preferably 5000-10000 r/min. This method is easy to operate, can realize rapid separation of gold nanoparticles, and has little impact on the product.

Compared with prior art, the beneficial effects of the present invention are:

(1) The present invention introduces catalase as reducing agent and protective agent, and the reductive functional group on the catalase has strong reducibility under alkaline condition, is beneficial to the synthetic of gold nanoparticle, and the gold nanoparticle of generation Particles will not agglomerate under high salt conditions (0.5MNaCl).

(2) The price of catalase in the present invention is low, and the cost of preparing gold nanoparticles is low.

(3) The present invention has simple operation steps, good repeatability, fast reaction speed, mild reaction conditions, environmentally friendly reagents, and the prepared gold nanoparticles have good biocompatibility.

Description of drawings

FIG. 1 is a transmission electron microscope image of gold nanoparticles prepared in Example 1 of the present invention, and the scale bar is 10 nm.

Fig. 2 is a comparison diagram of gold nanoparticles prepared in Example 1 of the present invention before and after adding 0.5M NaCl.

Fig. 3 is a transmission electron microscope image of gold nanoparticles prepared in Example 2 of the present invention, and the scale bar is 20nm.

Fig. 4 is a transmission electron microscope image of gold nanoparticles prepared in Example 3 of the present invention, and the scale bar is 50nm.

Fig. 5 is a visible spectrum diagram of gold nanoparticles prepared under different catalase/tetrachloroauric acid molar ratios (0.00221:1, 0.0221:1, 0.0885:1) according to the present invention.

Detailed ways

Example 1

(1) under magnetic stirring condition, the bovine liver catalase (Aladdin Reagent Co., Ltd.) aqueous solution that concentration is 5mg/mL is added dropwise in the tetrachloroauric acid aqueous solution that concentration is 1%, until catalase and The mol ratio of tetrachloroauric acid is 0.00221: 1, magnetic stirring 4h;

(2) Add 1mol/L sodium hydroxide solution to the solution obtained in (1), adjust the pH of the solution to 10, stir in a water bath at 25°C, until the UV spectrum curve of the gold nanoparticle sol generated by the reaction does not change, The obtained gold nanoparticle sol is centrifuged at a rotational speed of 8000 r/min to obtain gold nanoparticles.

It can be seen from Figure 1 that the obtained material is gold nanoparticles with a particle size between 10-20nm; Figure 2 shows that the generated gold nanoparticles will not agglomerate under high salt conditions (0.5MNaCl).

Example 2

(1) under magnetic stirring condition, be that the bovine liver catalase aqueous solution of 5mg/mL is added dropwise in the tetrachloroauric acid aqueous solution of concentration by 5mg/mL, until the mol ratio of catalase and tetrachloroauric acid 0.0221:1, magnetically stirred for 2h;

(2) Add 1mol/L sodium hydroxide solution to the solution obtained in 1), adjust the pH of the solution to 11, stir in a water bath at 30°C, until the reaction generates gold nanoparticles sol UV spectrum curve does not change, and the obtained The gold nanoparticle sol is centrifuged at a speed of 8000 r/min to obtain gold nanoparticles.

It can be seen from FIG. 3 that the obtained material is gold nanoparticles with a particle size between 10-40 nm.

Example 3

(1) under magnetic stirring condition, be that the bovine liver catalase aqueous solution of 20mg/mL is added dropwise in the tetrachloroauric acid aqueous solution of concentration by 20mg/mL, until the mol ratio of catalase and tetrachloroauric acid 0.0885:1, magnetically stirred for 60 minutes;

(2) Add 2mol/L sodium hydroxide solution to the solution obtained in (1), adjust the pH of the solution to 10, stir in a water bath at 35°C, until the reaction generates gold nanoparticles sol UV spectrum curve does not change, the The obtained gold nanoparticle sol is centrifuged at a rotational speed of 8000 r/min to obtain gold nanoparticles.

It can be seen from FIG. 4 that the obtained material is gold nanoparticles with a particle size between 10-40 nm.

Among Fig. 5, three curves correspond to embodiment 1～3 respectively, are the visible spectrum absorption curves of the gold nanoparticles that make under different catalase/tetrachloroauric acid molar ratio conditions, the absorption peaks of three spectrum absorption curves and gold The plasma absorption peaks of nanoparticle characteristics are consistent, which proves the effective reduction of catalase to tetrachloroauric acid and the generation of gold nanoparticles, and when the molar ratio of catalase to tetrachloroauric acid is 0.0221: 1, The absorption value corresponding to the absorption peak of the visible spectrum curve is the largest, indicating that the concentration of gold nanoparticles generated under this molar ratio is the highest.

Claims (7)

1. catalase reduction tetra chlorauric acid prepares a method for golden nanometer particle, comprises the following steps:

Catalase solution is added drop-wise in tetra chlorauric acid solution, stirs; Regulate the pH value of mixed solution to be alkalescence, and react under the water bath condition of 20 ~ 37 DEG C, after having reacted, be separated and obtain golden nanometer particle;

The concentration of described tetra chlorauric acid solution is 0.1% ~ 1%;

The mol ratio of catalase and tetra chlorauric acid is 0.00221:1 ~ 0.221:1;

The particle diameter of described golden nanometer particle is 10 ~ 40nm.

2. the method for claim 1, is characterized in that, described catalase is beef liver catalase.

3. the method for claim 1, is characterized in that, described Catalase solution concentration is 5 ~ 50mg/mL.

4. method as claimed in claim 3, it is characterized in that, described Catalase solution concentration is 5 ~ 20mg/mL.

5. the method for claim 1, is characterized in that, the mol ratio of catalase and tetra chlorauric acid is 0.00221:1 ~ 0.0885:1.

6. the method for claim 1, is characterized in that, the pH value of described mixed solution is 10 ~ 12.

7. method according to claim 6, is characterized in that, the pH value of described mixed solution is 12.