Nano-silver particles and preparation method thereof

Abstract

The invention provides a preparation method of nano silver salt particles, which specifically comprises the following steps: step 1, mixing quantum dots and silver salt, dispersing into a solvent, and stirring in a dark place until no solid exists to obtain a mixed solution; step 2, transferring the mixed solution obtained in the step 1 into a visual window high-pressure reaction kettle, filling carbon dioxide until the pressure intensity in the visual window high-pressure reaction kettle is 12-20 MPa, providing certain illumination, stirring and reacting for a period of time under the condition that the temperature is 40-80 DEG C, and releasing the carbon dioxide to normal pressure to obtain a mixed solution; and thirdly, the mixed solution obtained in the second step is centrifuged, washed and dried, and finally the nano-silver particles are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to nano silver particles and a preparation method thereof. Background Art

[0002] Nanosilver particles are widely used in the biomedical field. They can be used to manufacture antibacterial medical materials, thus helping to reduce the risk of infection during medical procedures. Combining nanosilver particles with fiber materials can produce textiles with antibacterial properties, such as antibacterial socks and antibacterial fabrics.

[0003] Nanosilver particles can be used to prepare flexible conductive circuits. The prepared circuits are highly flexible and can be deformed at will. They also have high conductivity and can reduce energy consumption. There are many methods for preparing nanosilver particles, but how to prepare nanosilver particles with controllable particle size and good dispersion is the key. Summary of the invention

[0004] The main purpose of the present invention is to provide a nano silver particle and a preparation method thereof, which can prepare nano silver particles with controllable particle size and good dispersibility.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a method for preparing nano silver salt particles, which specifically comprises the following steps:

[0006] Step 1: Mix the quantum dots and the silver salt and disperse them in a solvent, and stir in a dark place until no solid is present to obtain a mixed solution;

[0007] Step 2: Transfer the mixed solution obtained in step 1 to a high-pressure reactor with a visual window, fill it with carbon dioxide until the pressure in the high-pressure reactor with a visual window is 12-20 MPa, provide a certain amount of light, and stir and react for a period of time at a temperature of 40-80°C.

[0008] Step 3: After the reaction in step 2 is completed, the carbon dioxide in the reaction kettle is released to normal pressure to obtain a mixed solution;

[0009] Step 4: centrifuge, wash and dry the mixed solution obtained in step 3 to finally obtain nanosilver particles.

[0010] Preferably, the quantum dots in step 1 are selected from one or more of cadmium sulfide quantum dots, carbon quantum dots, silicon quantum dots and zinc oxide quantum dots;

[0011] Preferably, the silver salt is selected from one or more of silver nitrate, silver sulfate, silver acetate, and organic silver salts containing long alkane chains, wherein the carbon chain length of the organic silver salt is 4-7, the added mass ratio of silver salt to quantum dots is 10:1 to 20:1, and the concentration of the silver salt in the solution is 3-10 g / L.

[0012] Preferably, the solvent in step 1 is one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide.

[0013] Preferably, the stirring in step 1 is magnetic stirring, and the stirring speed is 500-1500 rpm.

[0014] The inner cavity volume of the high-pressure reactor with a visual window in the step 2 is 3-5 times the volume of the added mixed solution; the stirring is magnetic stirring at a speed of 500-1500rpm; the reaction time is 1-5h; the time taken to release carbon dioxide to normal pressure is 6-10min; and the specific light is visible light with a wavelength between 380nm and 750nm.

[0015] Preferably, the centrifugal speed in step 4 is 5000-10000rpm, and the centrifugal time is 5-10min; the solvent required for washing is selected from one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide; during washing, the product obtained by centrifugation is placed in the solvent required for washing, and after washing, it is filtered, and the filtered product is placed in the solvent required for washing again, and the process is repeated 3-5 times; the drying temperature is 40-60°C, and the time is 8-12h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] First, the present invention adopts a photoreduction method in the process of reducing silver salt to obtain nanosilver. The photoreduction method is adopted in the reaction process, and no other reducing reagent is used, which is environmentally friendly and pollution-free; second, in the atmosphere of supercritical carbon dioxide, the size of the generated nanosilver particles is more uniform, and the size of the nanosilver particles can be controlled by controlling the reaction conditions; third, the obtained nanosilver particles are modified with quantum dots and can be stably dispersed in deionized water without using any surfactant, which is convenient for the subsequent application of the nanosilver particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is an X-ray diffraction pattern of the nanosilver particles prepared in Example 1 of the present invention;

[0019] Figure 2 is a transmission electron microscope image of the nano silver particles prepared in Example 1 of the present invention;

[0020] Figure 3 is an X-ray diffraction pattern of the nanosilver particles prepared in Example 2 of the present invention;

[0021] Figure 4 3 is a transmission electron microscope image of the nanosilver particles prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0023] A method for preparing nano silver salt particles comprises the following steps:

[0024] Step 1: Mix the quantum dots and the silver salt and disperse them in a solvent, and stir in a dark place until no solid is present to obtain a mixed solution;

[0025] Step 2: Transfer the mixed solution in step 1 to a visual window autoclave, fill it with carbon dioxide until the pressure in the visual window autoclave is 12-20MPa, give specific light, and stir and react for a period of time at a temperature of 40-80°C. In this step, the silver salt is irradiated with light and reduced to nanosilver particles. The light acts as a reducing agent, and no other actual reducing materials are used. The quantum dots act as photocatalysts in this process, which can greatly accelerate the photoreduction process and improve the reaction efficiency. At the same time, the quantum dots can also be adsorbed on the surface of nanosilver to improve the dispersibility of nanosilver, so that a stably dispersed nanosilver dispersion can be obtained without using any surfactant. Supercritical carbon dioxide is used as a solvent in the photoreduction process, which is conducive to the uniform nucleation of nanosilver, thereby forming spherical nanosilver. In a supercritical environment, the reduction of nanosilver is also more controllable, and the size of nanosilver particles can be controlled.

[0026] Step 3: After the reaction in step 2 is completed, release the carbon dioxide in the reaction kettle to normal pressure to obtain a mixed solution;

[0027] Step 4: centrifuge, wash and dry the mixed solution after the reaction to finally obtain nanosilver particles.

[0028] Preferably, the quantum dots in the step one are selected from one or more of cadmium sulfide quantum dots, carbon quantum dots, silicon quantum dots and zinc oxide quantum dots; the silver salt is selected from one or more of silver nitrate, silver sulfate, silver acetate, and organic silver salts containing long alkane chains, wherein the carbon chain length of the organic silver salt is 4-7, the added mass ratio of silver salt to quantum dots is 10:1 to 20:1, and the concentration of silver salt in the solution is 3-10 g / L; the solvent is one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide; the stirring is magnetic stirring, and the stirring speed is 500-1500 rpm.

[0029] The inner cavity volume of the high-pressure reactor with a visual window in the step 2 is 3-5 times the volume of the added mixed solution; the stirring is magnetic stirring at a speed of 500-1500rpm; the reaction time is 1-5h; the time taken to release carbon dioxide to normal pressure is 6-10min; and the specific light is visible light with a wavelength between 380nm and 750nm.

[0030] Preferably, the centrifugal speed in step 4 is 5000-10000 rpm, and the centrifugal time is 5-10 min; the solvent required for washing is selected from one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide; during washing, the product obtained by centrifugation is placed in the solvent required for washing, and filtered after washing is completed, and the process is repeated 3-5 times; the drying temperature is 40-60°C, and the time is 8-12h.

[0031] Experimental Example 1

[0032] A method for preparing nano silver particles comprises the following steps:

[0033] Step 1: Prepare a mixed solution of quantum dots and silver salts: disperse 1 g of carbon quantum dots and 15 g of silver nitrate in 2 L of deionized water, and stir the mixture under light-proof magnetic stirring at a speed of 700 rpm until all solids are completely dissolved to obtain a mixed solution of carbon quantum dots and silver salts;

[0034] Step 2, performing a supercritical reaction: adding the obtained mixed solution to a high-pressure reactor with a volume of 8L, continuously filling the high-pressure reactor with carbon dioxide until the pressure in the high-pressure reactor reaches 15MPa, placing the high-pressure reactor in a 60°C oven, performing magnetic stirring, the stirring speed is 900rpm, the stirring time is 2h, and visible light is used throughout the stirring process. After the stirring is completed, the carbon dioxide in the high-pressure reactor is completely released within 7min, and the mixed solution after the reaction is taken out;

[0035] Step 3, obtaining nanosilver particles: centrifuging the mixed solution with a centrifuge at a speed of 9000 rpm for 7 min to obtain nanosilver particles and redispersing them in 4 L of ultrapure water, repeating the centrifugation and redispersion operations 3 times; finally placing the obtained solid sample in an oven for drying at a temperature of 40° C. for 12 h to obtain nanosilver particles.

[0036] Experimental Example 2

[0037] A method for preparing nano silver particles comprises the following steps:

[0038] Step 1: Prepare a mixed solution of quantum dots and silver salts: disperse 1 g of carbon quantum dots and 18 g of silver nitrate into 3 L of deionized water, and stir the mixture in a dark place with magnetic stirring at a speed of 800 rpm until all solids are completely dissolved to obtain a mixed solution of carbon quantum dots and silver salts;

[0039] Step 2, performing a supercritical reaction: adding the obtained mixed solution to a high-pressure reactor with a volume of 10L, continuously filling the high-pressure reactor with carbon dioxide until the pressure in the high-pressure reactor reaches 18MPa, placing the high-pressure reactor in a 60°C oven, performing magnetic stirring, the stirring speed is 1000rpm, the stirring time is 4h, and visible light is used throughout the stirring process. After the stirring is completed, the carbon dioxide in the high-pressure reactor is completely released within 8min, and the mixed solution after the reaction is taken out;

[0040] Step 3, obtaining nanosilver particles: centrifuge the mixed solution at a speed of 7000 rpm for 8 min to obtain nanosilver particles and redisperse them in 5 L of ultrapure water, repeat the centrifugation and redispersion operations 3 times, and finally place the obtained solid sample in an oven for drying at a temperature of 50° C. for 10 h to obtain nanosilver particles.

[0041] Embodiment 3

[0042] A method for preparing nano silver particles comprises the following steps:

[0043] Step 1: Prepare a mixed solution of quantum dots and silver salts. Disperse 0.5 g of carbon quantum dots and 8 g of silver nitrate into 2 L of deionized water, and stir magnetically in a dark place at a speed of 1000 rpm until all solids are completely dissolved to obtain a mixed solution of carbon quantum dots and silver salts.

[0044] Step 2: Perform a supercritical reaction, add the obtained mixed solution into a 6L autoclave, continuously charge carbon dioxide into the autoclave until the pressure in the autoclave reaches 17MPa, place the autoclave in an oven at 60°C, perform magnetic stirring at a speed of 800rpm for 2h, irradiate with visible light throughout the stirring process, release the carbon dioxide in the autoclave completely within 6min after the stirring is completed, and take out the mixed solution after the reaction;

[0045] Step 3: Obtaining nanosilver particles, centrifuging the mixed solution with a centrifuge at a speed of 6000 rpm for 10 min to obtain nanosilver particles and redispersing them in 2 L of ultrapure water, repeating the centrifugation and redispersion operations 4 times, and finally placing the obtained solid sample in an oven for drying at a temperature of 60° C. for 8 h to obtain nanosilver particles.

[0046] The preparation method of the present invention adopts a photoreduction method in the reaction process under a supercritical carbon dioxide environment, does not use any other reducing agents and surfactants, and is environmentally friendly and pollution-free. The nano silver particles prepared by the present invention have uniform size, controllable size, and excellent dispersibility, and can be used as conductive functional components in conductive inks, and can also be used as bactericidal active ingredients in daily disinfection and sterilization.

[0047] from Figure 1 It can be seen that the nanosilver particles prepared in Experimental Example 1 are pure silver and do not contain any diffraction peaks of impurities. Its standard PDF card is 04-0783 and its space group is Fm-3m. Figure 2 It can be seen that the nanosilver particles prepared in Experimental Example 1 are uniform in size and spherical in shape, with a particle size of 2-3 nm. Figure 3 It can be seen that the crystal structure of the nanosilver particles obtained by Experimental Example 2 is the same as that of Example 1, that is, the difference in synthesis conditions does not change the crystal form of the nanosilver. Figure 4 It can be seen that the size of the nanosilver particles obtained by Experimental Example 2 is 18-20 nm, indicating that nanosilver particles of different sizes can be obtained by adjusting the preparation conditions.

[0048] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing nano silver salt particles, characterized in that: The specific steps include: Step 1: Mix the quantum dots and the silver salt and disperse them in a solvent, and stir in a dark place until no solid is present to obtain a mixed solution; Step 2, transferring the mixed solution obtained in step 1 to a visual window autoclave, charging carbon dioxide until the pressure in the visual window autoclave is 12-20 MPa, applying a certain amount of light, stirring and reacting at a temperature of 40-80° C. for a period of time, during which the silver salt is irradiated by light and then reduced to nanosilver particles, and quantum dots are adsorbed on the surface of the obtained nanosilver; Step 3: After the reaction in step 2 is completed, the carbon dioxide in the reaction kettle is released to normal pressure to obtain a mixed solution; Step 4: centrifuge, wash and dry the mixed solution obtained in step 3 to finally obtain nanosilver particles.

2. The method for preparing nano silver salt particles according to claim 1, characterized in that: The quantum dots in step 1 are selected from one or more of cadmium sulfide quantum dots, carbon quantum dots, silicon quantum dots and zinc oxide quantum dots.

3. The method for preparing nano silver salt particles according to claim 1, characterized in that: The silver salt is selected from one or more of silver nitrate, silver sulfate, silver acetate, and organic silver salts containing long alkane chains, wherein the carbon chain length of the organic silver salt is 4-7, the added mass ratio of silver salt to quantum dots is 10:1 to 20:1, and the concentration of the silver salt in the solution is 3-10 g / L.

4. The method for preparing nano silver salt particles according to claim 1, characterized in that: The solvent in step 1 is one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide.

5. The method for preparing nano silver salt particles according to claim 1, characterized in that: The stirring in step 1 is magnetic stirring, and the stirring speed is 500-1500 rpm.

6. The method for preparing nano silver salt particles according to claim 1, characterized in that: The inner cavity volume of the high-pressure reactor with a visual window in the step 2 is 3-5 times the volume of the added mixed solution; the stirring is magnetic stirring at a speed of 500-1500rpm; the reaction time is 1-5h; the time taken to release carbon dioxide to normal pressure is 6-10min; and the specific light is visible light with a wavelength between 380nm and 750nm.

7. The method for preparing nano silver salt particles according to claim 1, characterized in that: The centrifugal speed in step 4 is 5000-10000rpm, and the centrifugal time is 5-10min; the solvent required for washing is selected from one or more of ultrapure water, ethanol, acetone, ethyl acetate, glycerol, and dimethyl sulfoxide; during washing, the product obtained by centrifugation is placed in the solvent required for washing, filtered after washing, and the filtered product is placed in the solvent required for washing again, and the process is repeated 3-5 times; the drying temperature is 40-60°C, and the time is 8-12h.

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