KR20050114803A - Manufacturing method of silver superfine nanoparticles - Google Patents

Abstract

The present invention relates to a method for producing nanosilver, wherein inorganic silver laponite is used as a stabilizer to produce nano-sized silver particles. In the manufacture of nanosilver, (1) laponite clay is dispersed in water, and When the dispersion is left transparent, sodium borohydride (NaBH ₄ ) is added thereto, followed by stirring to prepare a reducing solution for preparing a reducing solution; (2) preparing a silver nitrate (AgNO ₃ ) aqueous solution separately from the reducing solution preparation step, and adding ammonia water to the silver nitrate aqueous solution to prepare a silver nitrate solution; (3) mixing the silver nitrate solution slowly dropwise with the reducing solution and then vigorously stirring for 1 to 3 hours; And (4) a stationary step of allowing the mixture obtained in the mixing step to stand in the shade for 20 to 30 hours.

Description

Manufacturing method of silver superfine nanoparticles

The present invention relates to a method for producing nano silver. More specifically, the present invention relates to a method for producing nanosilver, which manufactures nano-sized silver particles using inorganic clay laponite as a stabilizer.

Nanotechnology is roughly divided into two fields: material synthesis, such as carbon nanotubes, mesoporous material metals, and semiconductor nanocrystals, and control and application through STM, AFM, and lithography. In the case of crystalline, the chemical and physical properties of the crystalline act regardless of the size of the particle, but when the size is less than the nano-size (10 ^-9 ), the ratio of the mass to the surface area of the particle becomes very large, and the increase in surface atoms It causes a large change in the thermodynamic properties of the melting point (falling point, phase transition, etc.). In particular, nano-sized metal / ceramic colloids are very fine particles and have a high volume ratio with respect to the same mass ratio, thereby exhibiting many functions in a small amount and having an electron repulsion force that overcomes gravity even in the water phase. It can exhibit high functionality such as improvement, antibacterial and electromagnetic shielding.

In addition, it is also very important to make the size of the particles uniform as much as the size of the particles in the technology of utilizing the particles. If the particle size is non-uniform, each particle has different performance and physical properties, thereby limiting its application to advanced fields. For example, particle-type materials are used in a wide range of fields such as catalysts, sensors, information recording media (magnetic materials), abrasives, antibacterial and antiseptic particles, pharmaceuticals, electromagnetic shielding purposes, and display fields. Is actively underway.

On the other hand, silver colloid, an example of nano silver, has been widely used especially for antimicrobial agents. The production method of the silver colloid is an electrical method, a chemical method, a grinding method, the quality of these colloids are usually divided into colors, the most ideal color is known as golden (golden yellow). In the particle utilization technology, when the particle size is reduced to fine units (300 nm or less), the physical properties and performance of the particle are very different from those when the particle size is larger than the micrometer size. This results in an increase in the surface-to-mass ratio of the particles, which increases the surface area per unit mass, which improves the performance of the particles, reduces the melting point of the particles, and changes the properties of the particles. It is different from the case. The physical state that the colloidal silver produced as described above should have as many particles of silver as possible, and should be colloidal state in which the silver particles continue brown movement in water for a long time, and have a uniform particle size. In general, silver particles are known to change in order of yellow, red, purple, blue, green and black. The electrical method of the above method is to obtain a high purity silver colloid, but it is difficult to realize a high concentration, the grinding method is difficult to realize in many aspects, such as particle size, dispersion, grinding efficiency, and the chemical method is unnecessary anion generated in the manufacturing process It can only be removed, but it has the advantage of realizing high concentration, so it can be applied to industrial use.

On the other hand, Korean Laid-Open Patent Publication No. 2003-69502 discloses 'the preparation of colloidal silver in an organic solvent containing ethanol', where it has a narrow particle distribution stably dispersed in an organic solvent containing ethanol. It describes the preparation of colloidal silver. However, since it is a colloid in an organic solvent including ethanol, it is suitable for use for imparting antimicrobial activity to fibers or plastics, but there is a problem in that the use of organic solvents may limit the use thereof.

In addition, Japanese Laid-Open Publication No. 2003-75231 describes a method for preparing high concentration silver colloid, in which silver colloid is used instead of metal salt to suppress the generation of ions in the production of silver colloid by chemical reduction method. In addition, the use of a surfactant inhibits the growth of the silver particles, and controls the size of the particles by adjusting the amount, concentration and reaction conditions of the reducing agent. As a result, fine and uniform silver colloids are produced in high concentration and high purity. It describes. However, since it uses a nonionic surfactant, cationic surfactant, anionic surfactant amphoteric hydrocarbon-based, silicone-based and fluorocarbon-based surfactants, preferably organic surfactants such as polyvinylpyrrolidone, These organic surfactants remain, which may help to keep the inorganic silver particles in the colloidal state, but due to the presence of the organic surfactant is advantageous for dispersion in the polymer film, but rather the presence of the organic surfactant There is a problem that can be followed due to restrictions on use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing nanosilver, which prepares nano-sized silver particles using inorganic clay laponite as a stabilizer.

In the method for producing nanosilver according to the present invention, in the production of nanosilver, (1) when laponite clay is dispersed in water, and the dispersion is left to be transparent, sodium borohydride (NaBH ₄ ) is added thereto. After adding, the reducing solution preparation step of preparing a reducing solution by stirring; (2) preparing a silver nitrate (AgNO ₃ ) aqueous solution separately from the reducing solution preparation step, and adding ammonia water to the silver nitrate aqueous solution to prepare a silver nitrate solution; (3) mixing the silver nitrate solution slowly dropwise with the reducing solution and then vigorously stirring for 1 to 3 hours; And (4) a stationary step of allowing the mixture obtained in the mixing step to stand in the shade for 20 to 30 hours.

The laponite clay is a strong anionic inorganic material, and may have a negative charge of 40 to 60 mmol / 100 g.

In addition, the laponite gel in which the laponite clay which does not contain a surfactant continuously dissolved in water after the stationary step is added to the silver colloid obtained after the stationary step with vigorous stirring, and mixed in a shade of 20 to 30 After standing for a period of time, after drying for 4 to 6 hours at a temperature of 180 to 220 ℃, the powdering step of grinding; may further include.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the method for producing nanosilver according to the present invention, in the production of nanosilver, (1) when laponite clay is dispersed in water, and the dispersion is left to be transparent, sodium borohydride (NaBH ₄ ) is added thereto. After adding, the reducing solution preparation step of preparing a reducing solution by stirring; (2) preparing a silver nitrate (AgNO ₃ ) aqueous solution separately from the reducing solution preparation step, and adding ammonia water to the silver nitrate aqueous solution to prepare a silver nitrate solution; (3) mixing the silver nitrate solution slowly dropwise with the reducing solution and then vigorously stirring for 1 to 3 hours; And (4) a stationary step of allowing the mixture obtained in the mixing step to stand in the shade for 20 to 30 hours. In the preparing of the reducing solution of (1), the silver nitrate is reduced to metallic silver while the metal silver formed at the same time functions to maintain a dispersed colloidal state without being agglomerated again. The laponite clay is dispersed in water and the dispersion is left When it becomes transparent, sodium borohydride (NaBH ₄ ) is added thereto, followed by stirring. Laponite clay in the above is a synthetic smectite clay, which is very similar to natural clay mineral in structure and composition. It is a layered structured hydrated magnesium silicate that is hydrothermally synthesized from silicates, lithium salts and magnesium salts simply in the presence of mineralizers. When dispersed in water, it easily becomes a colorless, transparent, highly thixotropic gel, and has a very useful function in the colloid industry. Laponite clay is considered to have a physical surface area of 900 cm 2 / g or more, which is itself a strong anionic inorganic material having a negative charge of 40 to 60 mmol / 100 g by crystal surface structure. The laponite clay may be purchased by using the trade names 'Laponite RDS' and 'Laponite RD' of Rockwood Additives Limited, UK. In particular, the laponite clay used in the production of silver colloids preferably contains conventional surfactants, and laponite clay RDS can be used. The amount of laponite clay and sodium borohydride in the above may vary depending on the concentration of silver to be obtained in the finally obtained silver colloid, and as a result, may be used in proportion to the amount of silver nitrate used. In other words, as the amount of silver nitrate increases, the amount of laponite clay and sodium borohydride increases accordingly, which may be apparent in embodiments attached to the present specification, and those skilled in the art may obtain it based on this. The amount of laponite clay and sodium borohydride can be determined according to the concentration of silver in the silver colloid. Preferably, the laponite clay is used in an amount of at least 2 kg or more, and sodium borohydride may be used in an amount of 4 to 6 moles based on 1 mole of the nitric acid. When the laponite clay is used at less than 2 kg based on 1 mole (about 171.7 g) of silver nitrate, nano silver is produced in an amount more than that can be dispersed by laponite clay, so that silver particles are aggregated to form particles. There may be a problem that the size of the coarse, and when used in excess of 2kg may have a problem indicating a physical property change that increases the viscosity of the sol as used. The preparation of the silver nitrate solution of (2) is made of silver nitrate (AgNO ₃ ) aqueous solution separately from the reducing solution preparation step, and then the addition of ammonia water to the silver nitrate aqueous solution. Here, the amount of silver nitrate may vary depending on the concentration of silver in the silver colloid to be obtained. The higher the amount of silver nitrate used, the higher the content of silver in the silver colloid. Therefore, it will be understood by those skilled in the art that the amount of silver nitrate can be determined in proportion to the concentration of silver in the silver colloid to be obtained. In addition, the amount of ammonia water used may also increase or decrease in proportion to the amount of silver nitrate used. The aqueous ammonia may be used in slightly more excess from about the same mole number to about 0.1 to 0.2 times silver nitrate. If the amount of ammonia water is insufficient, there may be a problem in that the formation of Ag (NH ₃ ) ₂ ⁺ ions is insufficient, and the silver nitrate may not be sufficiently reduced. There may be. In the mixing step (3), the silver nitrate solution is slowly added dropwise to the reducing solution, followed by vigorous stirring for 1 to 3 hours. By this mixing, the silver nitrate is reduced to metallic silver. Here, if the stirring time is less than 1 hour, there may be a problem that the reduction reaction is not enough, the time exceeding 3 hours may have a problem that only takes a lot of time without improving the obvious effects such as a decrease in productivity. The standing step of (4) consists of allowing the mixture obtained in the mixing step to stand in the shade for 20 to 30 hours, so that silver nitrate is sufficiently reduced to metallic silver. The reduced metal silver can maintain a stable silver colloidal state for a long time without aggregation by laponite clay which already functions as a reducing solution. Therefore, the reduced metal silver does not aggregate even when left standing for a sufficient time, but rather, the reduction reaction can be continued for a sufficiently long time to increase the yield of metal silver. Here, if the settling time is less than 20 hours, there may be a problem that the reduction reaction is not enough, there is a problem that the productivity is lowered by remaining unnecessarily long time exceeding 3 hours unnecessarily.

It is possible to finally obtain a liquid silver colloid by the above production method.

In addition, the laponite gel (laponite clay RD) in which the surfactant is not continuously added after the stationary step is dissolved in water is added to the silver colloid obtained after the stationary step with vigorous stirring, and mixed. And, after standing for 20 to 30 hours in the shade, and dried for 4 to 6 hours at a temperature of 180 to 220 ℃, the powdering step of grinding; may further include. Here, the reaction conditions such as the amount of laponite used, settling time, and stirring conditions may be understood to be the same as or similar to those of the preparation method of the silver colloid. Preferably, based on 100 ml of 250 ppm / ml silver colloid, for example, 4-10 g of laponite clay is mixed with laponite gel (without surfactant) dissolved in 130-170 ml of water, After stirring, the mixture was allowed to stand for 20 to 30 hours in the shade, dried at a temperature of 180 to 220 ° C. for 4 to 6 hours, and then pulverized to obtain powdered nano silver.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

Examples 1-6

Laponite clay was dispersed in distilled water, stirred vigorously for 30 minutes, and when the dispersion was left to become transparent, 98% sodium borohydride (NaBH ₄ ) was added thereto and stirred vigorously for 5 minutes. Thereafter, a reducing solution was prepared by stirring, and 99.8% silver nitrate (AgNO ₃ ) was dissolved in 500 ml of distilled water to make a silver nitrate aqueous solution. Then, 25% of ammonia water was added to the silver nitrate aqueous solution to prepare a silver nitrate solution. At this time, the amount of each component is shown in Table 1 below. Thereafter, the silver nitrate solution was slowly added dropwise to the reducing solution, mixed with vigorous stirring for 2 hours, and left standing in the shade for 24 hours.

Example Laponite 99.8% AgNO ₃ 25% ammonia water 98% NaBH ₄ Silver concentration One 0.15 g / ℓ 7.35 * 10 ^-5 mol (1.3 * 10 ^-2 g) 8.80 * 10 ^-4 mol (1.5 * 10 ^-2 g) 3.68 * 10 ^-4 mol (1.40 * 10 ^-2 g) 8ppm / ml 2 0.74 g / ℓ 3.68 * 10 ^-4 mol (6.3 * 10 ^-2 g) 4.40 * 10 ^-3 mol (7.5 * 10 ^-2 g) 1.84 * 10 ^-3 mol (0.07 g) 40 ppm / ml 3 1.5g / ℓ 7.35 * 10 ^-4 mol (0.13 g) 8.80 * 10 ^-3 mol (0.15 g) 3.68 * 10 ^-3 mol (0.14 g) 80 ppm / ml 4 2.9 g / ℓ 1.47 * 10 ^-3 mol (0.25 g) 1.76 * 10 ^-2 mol (0.3 g) 7.36 * 10 ^-3 mol (0.28 g) 160 ppm / ml 5 4.6 g / ℓ 2.3 * 10 ^-3 mol (0.39 g) 2.76 * 10 ^-2 mol (0.47 g) 1.15 * 10 ^-2 mol (0.44 g) 250 ppm / ml 6 18.4 g / ℓ 9.2 * 10 ^-5 mol (1.58 g) 0.110 mol (1.88 g) 4.60 * 10 ^-2 mol (1.76 g) 1,000 ppm / ml  * Silver concentration; The concentration of silver in the silver colloid finally obtained

1 shows the ultraviolet-visible light absorption spectrum of the silver colloid obtained in Examples 1 to 4 using an ultraviolet-visible light spectrometer (UV2201 manufactured by Shimadzu, Japan).

As shown in FIG. 1, the absorption peak at 390 nm is well characterized by the plasma resonance absorption of silver nanoparticles.

In addition, it was confirmed that the absorption peak position remained almost in the same wavelength band even with the increase of the concentration of silver. Since the wavelength of each absorption peak corresponds to the characteristic size of one silver particle, as shown in FIG. 1, the size of the silver nanoparticles was maintained to be substantially the same even when the concentration of silver was increased.

In addition, FIG. 2 shows a transmission electron microscope (TEM) of the silver colloid obtained in Example 1 (JEM-1200 EX, manufactured by JEOL, Japan). According to this photograph, silver particles having a particle diameter of a narrow band of 4 to 7 nm are shown, and the shape of the silver particles was confirmed to be spherical.

3 shows the X-ray diffractometer (XRD; X-Ray Diffratometer; XD-D1, manufactured by Shimadzu, Japan) of the silver colloid obtained in Example 1 above. According to this diagram, it was confirmed that the reduction to metal silver was sufficiently performed.

Examples 7-11

250 ppm / ml silver colloid obtained in Example 5 was powdered. First, a laponite gel in which laponite clay (laponite clay RD) containing no surfactant was dissolved in 150 ml of water was prepared using the amount shown in Table 2 below, and the silver colloid of Example 5 was vigorously stirred. While mixing, the mixture was allowed to stand for 24 hours in the shade, dried at a temperature of 200 ° C. for 5 hours, and then ground to obtain a powder composition including nano-sized silver powder.

Silver colloid volume (ml) Laponite Weight (g) Weight of Nano Silver (%) 100 9.97 0.24 200 9.50 0.48 300 9.33 0.70 400 9.03 0.92 1,400 4.50 3.42  * Silver colloid; Volume of silver colloid (250 ppm / ml) used * laponite; Laponite without surfactant * Weight of nano silver; Weight (%) of silver in the powdered composition obtained

As can be seen in Table 2 above, in order to obtain a powder composition containing nano silver from silver colloid, regardless of the amount of laponite clay (not including surfactant) added substantially It was confirmed that the nano silver is not agglomerated by the laponite clay even when the water is effectively removed and the water is removed, so that the nano silver in powder form can be included in the powder composition. It is believed that this is due to the fact that laponite aldehydes have already been used in sufficient amounts in the preparation of silver colloids and are already included.

As a result of the synthesis of the above embodiments, according to the present invention, it is possible to obtain nano-sized fine powdered silver, such as silver colloidal state and silver nanoparticles, from metal nitrate, particularly stabilized silver, using laponite clay. Colloids and the like can be obtained not only known uses such as antibacterial agents, in particular pure inorganic silver colloids, etc. that do not contain organic solvents or organic compounds, etc., and thus can be used as silver colloids in various colloidal industries. there was. Moreover, the silver colloid obtained has a very narrow range of particle size distribution and can be obtained as a highly stable colloidal phase containing spherical silver particles. The advantage is that it can be widely used as a colloid.

Therefore, according to the present invention, there is an effect of providing a method for preparing nano silver to prepare nano-sized silver particles using inorganic clay laponite as a stabilizer, and nano silver colloid and nano silver powder obtained by the same.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications are within the scope of the appended claims.

1 is an ultraviolet-visible light absorption spectrum of a silver colloid obtained according to one specific embodiment of the present invention.

Figure 2 is a transmission electron micrograph of a silver colloid obtained in accordance with one specific embodiment of the present invention.

3 is an X-ray diffraction diagram of a silver colloid obtained in accordance with one specific embodiment of the present invention.

Claims (4)

In the production of nano silver, (1) When the laponite clay containing the surfactant is dispersed in water, and this dispersion is left to be transparent, sodium borohydride (NaBH ₄ ) is added thereto, followed by stirring to prepare a reducing solution. Preparation step; (2) preparing a silver nitrate (AgNO ₃ ) aqueous solution separately from the reducing solution preparation step, and adding ammonia water to the silver nitrate aqueous solution to prepare a silver nitrate solution; (3) mixing the silver nitrate solution slowly dropwise with the reducing solution and then vigorously stirring for 1 to 3 hours; And (4) a stationary step of allowing the mixture obtained in the mixing step to stand in the shade for 20 to 30 hours; Nano silver manufacturing method characterized in that made. The method of claim 1, The laponite clay is a strong anionic inorganic material, characterized in that it has a negative charge of 40 to 60mmol / 100g. The method of claim 1, Laponite gel in which the laponite clay which does not contain surfactant was dissolved in water was added to the silver colloid obtained after the above step by vigorous stirring, mixed, left to stand in the shade for 20 to 30 hours, and then 180 to 220 After drying for 4 to 6 hours at a temperature of ℃, the powdering step of pulverizing; manufacturing method of nano silver characterized in that it further comprises. Nano silver obtained by the method of claim 1 to 3.