A method for preparing nanometer gold spheres

Abstract

This invention discloses a method for preparing gold nanospheres. The principle of this invention is based on the confinement effect of carbon cloth on the attached gold nanospheres, thereby inhibiting the agglomeration and fusion of nanoparticles under high-temperature conditions and ensuring the stable preparation of gold nanospheres. The specific preparation process is as follows: First, gold is attached to carbon cloth in the form of an oxide from a precursor solution under hydrothermal conditions. Simultaneously, the dried carbon cloth with the attached gold compound is reduced at high temperature in a tube furnace. Because the gold compound is tightly attached to the surface of the carbon cloth, the problem of gold nanosphere agglomeration and fusion is effectively avoided, and a large number of gold nanosphere particles are obtained after reduction attached to the surface of the carbon cloth. Finally, dispersed gold nanosphere particles are obtained by ultrasonication or combustion.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for synthesizing nanometer gold balls, which ingeniously utilizes the confinement effect of carbon cloth on in-situ generated nanometer gold balls to prevent the agglomeration and growth of gold nanoparticles under high temperature conditions, thereby obtaining nanometer gold balls. BACKGROUND

[0002] Nanometer gold refers to a small particle of gold with a diameter of 1-150 nm, which has high electron density, dielectric properties and catalytic effect, and is widely used in high-precision and high-tech fields such as biological monitoring, catalysis and electronics. The existing preparation of nanometer gold is accompanied by complex procedures, difficult purification and separation, and most of them are prepared in solution with various organic solvents, which is not environmentally friendly and has low yield. Therefore, there is an urgent need for a simple and easy-to-use and environmentally friendly method for efficient preparation of nanometer gold balls.

[0003] Patent No. 202010168975.0 discloses a method for preparing nanometer gold. The patent uses hexadecyl trimethyl ammonium bromide, chloroauric acid solution, and sodium borohydride solution to prepare gold seed solution, then adds relevant solution and centrifugal separates to obtain gold seed colloid, and continuously centrifugal mixes to obtain nanometer gold. The patent prepares nanometer gold by continuously mixing solution reaction and centrifugal separation. However, the efficiency of four times of centrifugal separation is low. The content of this patent is completely different from that of the present application.

[0004] Patent No. 201811430322.4 discloses a method for preparing nanometer gold. The patent adds tartaric acid or tartaric acid salt solution to chloroauric acid system, then heats and stirs at a temperature of 70-100℃ to obtain nanometer gold. The patent uses tartaric acid or tartaric acid salt solution to react with chloroauric acid solution to prepare nanometer gold. The preparation dosage of this patent is difficult to control, and the yield is low. The content of this patent is completely different from that of the present application.

[0005] Patent No. 201310304293.8 discloses a method for preparing nanometer gold. The patent uses monovalent gold complex as raw material, one or both of water and hydrophilic organic solvent with molecular weight less than 100 as solvent, adds raw material to the solvent to obtain reaction liquid, controls the monovalent gold concentration in the reaction liquid to be 0.1-2 g / L, the temperature to be 80-95℃, the pH value to be 0.3-1.5, and reacts for 3-20 min to obtain nanometer gold product. The patent reacts and synthesizes in solution all the time, the reaction is complicated, and the patent does not solve the agglomeration of nanometer gold in the reaction process. The content of this patent is completely different from that of the present application.

[0006] Obviously, the preparation of existing gold nanospheres is prepared by solvent chemistry method, and the following problems exist generally: 1) a complicated filtration separation process is needed, and more than four filtration steps are needed in some methods, which inevitably causes the yield to decrease; 2) a pollution organic solvent is needed to participate in the reaction or a strong reducing agent such as sodium borohydride is needed to participate, which is not environment-friendly and the process is not easy to control. SUMMARY

[0007] In view of the problems in the prior art, one of the problems to be solved by the present application is to provide a method for preparing gold nanospheres, which is low in cost, environment-friendly and easy to realize large-scale preparation.

[0008] The present application adopts the following technical solutions:

[0009] A method for preparing gold nanospheres, comprising the following steps:

[0010] Step one, placing gold-containing precursors and carbon cloth treated in a special way in a solvent, and treating by stirring, hydrothermal reaction or evaporation drying to obtain carbon cloth with gold-containing precursors attached.

[0011] Step two, reducing the gold-containing precursor carbon cloth in a hydrogen atmosphere to obtain carbon cloth with gold nanospheres adhered.

[0012] Step three, obtaining gold nanospheres by ultrasonic or direct air combustion of gold-containing carbon cloth.

[0013] Preferably, the carbon cloth treated in a special way is soaked in a mixed solution of concentrated nitric acid and concentrated sulfuric acid for more than 12 hours, and the concentration of the concentrated sulfuric acid and the concentrated nitric acid is 5mol / L~15mol / L, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid in the mixed solution of the concentrated sulfuric acid and the concentrated nitric acid is 1:1.

[0014] Preferably, the gold precursor comprises one or more of KAu(CN)4, K[Au(OH)2] and HAuCl4;

[0015] Preferably, the solvent comprises one or a mixture of ultrapure water, ethanol and ethylene glycol;

[0016] Preferably, the physical stirring adopts conventional magnetic stirring;

[0017] Preferably, the hydrothermal reaction refers to a reaction in a sealed reaction kettle at 80 o C~200 o for 2 hours;

[0018] Preferably, the evaporation drying refers to a process of evaporating the solvent in an open system at 80 o C~100 o C until the solvent is completely volatilized.

[0019] Preferably, the hydrogen reduction temperature is 500 o C ~800 o C, and the reaction time is 2 hours to 10 hours.

[0020] Preferably, the ultrasonic separation refers to placing the carbon with gold-containing nanoballs in anhydrous ethanol for ultrasonic separation for more than 10 hours.

[0021] Preferably, the direct combustion refers to placing the carbon with gold-containing nanoballs in air for combustion, and the reaction temperature is 500 o C ~600 o C, and the reaction time is 6 hours to 12 hours.

[0022] Preferably, the diameter of the obtained gold nanoballs is between 50 nm and 200 nm.

[0023] The method for preparing gold nanoballs provided by the present application has the following beneficial effects:

[0024] (1) In principle, the pinning effect between the gold nanoballs generated in situ under high temperature conditions and the carbon cloth substrate is effectively utilized, and the carbon cloth limits the migration and aggregation of the gold nanoballs to inhibit their growth.

[0025] (2) In terms of process, the preparation process of the gold nanoballs can reduce the addition of chemical reagents, and improves the process environment of the preparation of the gold nanoballs in a solution environment, without any volatile organic compounds, and the process is clean and easy to control.

[0026] (3) The present application provides a new method for preparing gold nanoballs, which is low in cost, environmentally friendly, and easy to realize large-scale preparation. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the carbon cloth with gold-containing precursors attached in Example 1;

[0028] Figure 2 Carbon cloth with gold nanoballs attached obtained after hydrogen reduction in Example 1;

[0029] Figure 3 TEM image of the gold nanoballs obtained by ultrasonic separation in Example 1. DETAILED DESCRIPTION

[0030] In order to make the above features and advantages of the present application more obvious and easy to understand, the following examples are specifically described. The method of the present application is a conventional method in the art unless otherwise specified.

[0031] Example 1

[0032] The carbon cloth is immersed in a mixed solution of concentrated nitric acid with a concentration of 5 mol / L and concentrated sulfuric acid with a concentration of 5 mol / L at a volume ratio of 1:1 for 12 hours; 0.3g of HAuCl4 and the carbon cloth are placed in 30ml of 30wt% ethanol solution and magnetically stirred for 8 hours, and the carbon cloth is taken out and dried at 60°C for 1h; the dried carbon cloth is placed in a tube furnace, the tube furnace is connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 800°C for 2h; the reduced carbon cloth is taken out and ultrasonically separated in an ultrasonic machine for 10h to obtain gold spheres with a diameter of about 100nm.

[0033] Example 2

[0034] The carbon cloth is immersed in a mixed solution of concentrated nitric acid with a concentration of 10 mol / L and concentrated sulfuric acid with a concentration of 10 mol / L at a volume ratio of 1:1 for 13 hours; 0.3g of KAu(CN)4 and the carbon cloth are placed in 30ml of 30wt% ethanol solution and placed in a hydrothermal reaction kettle at 80°C for 2h, and the carbon cloth is taken out and dried at 60°C for 1h; the dried carbon cloth is placed in a tube furnace, the tube furnace is connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 500°C for 10h; the reduced carbon cloth is taken out and ultrasonically separated in an ultrasonic machine for 12h to obtain gold spheres with a diameter of about 50nm.

[0035] Example 3

[0036] The carbon cloth is immersed in a mixed solution of concentrated nitric acid with a concentration of 10 mol / L and concentrated sulfuric acid with a concentration of 8 mol / L at a volume ratio of 1:1 for 12 hours; 0.3g of K[Au(OH)2] and the carbon cloth are placed in 30ml of 30wt% ethanol solution and placed in a hydrothermal reaction kettle at 200°C for 2h, and the carbon cloth is taken out and dried at 60°C for 1h; the dried carbon cloth is placed in a tube furnace, the tube furnace is connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 600°C for 8h; the reduced carbon cloth is taken out, and the carbon cloth containing gold nanospheres is burned in air at a reaction temperature of 500°C for 12 hours to obtain gold spheres with a diameter of about 100nm.

[0037] Example 4

[0038] The carbon cloth is placed in a mixed solution of concentrated nitric acid with a concentration of 15 mol / L and concentrated sulfuric acid with a concentration of 15 mol / L at a volume ratio of 1:1 for 12 hours; 0.3 g of HAuCl4 and the carbon cloth are placed in 30 ml of a 30 wt% ethanol solution and placed in a hydrothermal reaction kettle at 100°C for 2 h, and the carbon cloth is taken out and dried at 60° for 1 h; the dried carbon cloth is taken out and placed in a tube furnace, the tube furnace is connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 600°C for 8 h; the reduced carbon cloth is taken out, and the carbon cloth containing gold nanospheres is placed in air and burned at a reaction temperature of 500°C for 12 hours to obtain gold spheres with a diameter of about 150 nm.

[0039] Example 5

[0040] The carbon cloth is placed in a mixed solution of concentrated nitric acid with a concentration of 5 mol / L and concentrated sulfuric acid with a concentration of 15 mol / L at a volume ratio of 1:1 for 14 hours; 0.3 g of KAu(CN)4 and the carbon cloth are placed in 30 ml of a pure water solvent, the solution is evaporated to dryness at 100°, and then placed in a tube furnace connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 600°C for 9 h; the reduced carbon cloth is taken out, and the carbon cloth containing gold nanospheres is placed in air and burned at a reaction temperature of 600°C for 6 hours to obtain gold spheres with a diameter of about 200 nm.

[0041] Example 6

[0042] The carbon cloth is placed in a mixed solution of concentrated nitric acid with a concentration of 15 mol / L and concentrated sulfuric acid with a concentration of 5 mol / L at a volume ratio of 1:1 for 12 hours; 0.3 g of HAuCl4 and the carbon cloth are placed in 30 ml of a 30 wt% ethylene glycol solution, and the solution is evaporated to dryness at 80°, and then placed in a tube furnace connected to a mixed gas of 5% H2-95% N2, and the temperature is raised to 600°C for 9 h; the reduced carbon cloth is taken out, and the carbon cloth containing gold nanospheres is placed in air and burned at a reaction temperature of 550°C for 8 hours to obtain gold spheres with a diameter of about 200 nm.

[0043] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A method for preparing gold nanospheres, characterized by, The method comprises the following steps: Step one, placing the gold-containing precursor and the specially treated carbon cloth into a solvent, and treating by physical stirring, hydrothermal reaction or evaporation drying to obtain the carbon cloth with the gold-containing precursor attached thereto; Step two, reducing the gold-containing precursor carbon cloth in a hydrogen atmosphere to obtain the carbon cloth with nano gold spheres attached thereto; Step three, obtaining the nano gold spheres by ultrasonic or direct air combustion of the gold-containing carbon cloth; The gold-containing precursor in step one comprises one or more of KAu(CN)4, K[Au(OH)2], and HAuCl4; and the solvent comprises one or a mixture of ultrapure water, ethanol, and ethylene glycol. The specially treated carbon cloth refers to the carbon cloth obtained by placing a commercial carbon cloth in a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a concentration of 1 mol / L to 10 mol / L for acidification for more than 12 hours.

2. The method of claim 1, wherein: The physical stirring refers to conventional magnetic stirring for 8 hours; the hydrothermal reaction refers to 2 hours at 80 o C~200 o C in a closed reaction kettle; the evaporation to dryness refers to 80 o C~100 o C until the solvent completely evaporates.

3. The method of claim 1, wherein: The hydrogen reduction temperature is 500 o C ~ 800 o C, and the reaction time is 2 hours to 10 hours.

4. The method of claim 1, wherein: The ultrasonic refers to the gold-containing nanoballs carbon is placed in the anhydrous ethanol for ultrasonic 10 hours above; the direct combustion refers to the gold-containing nanoballs carbon is placed in the air for combustion, the reaction temperature is 500 o C ~600 o C, the reaction time is 6 hours~12 hours.

5. The gold nanospheres prepared according to the method of any one of claims 1-4, wherein: The obtained nano gold spheres have a diameter of 50 nm to 200 nm.

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