RU2390344C2 - Method of obtaining silver nanoparticles in aqueous medium - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining silver nanoparticles distributed in water containing organic and inorganic stabilisers, and can be used in making medical, veterinary and cosmetic preparations. The method of obtaining silver nanoparticles in an aqueous medium involves dissolving stabilisers in distilled water, putting an anode in form of a silver plate and a cathode in form of a stainless steel plate into the obtained solution, electrochemical dissolution of the anode while passing stabilised direct current through the solution. The stabilisers are dissolved in two steps: first, a stabiliser selected from polyglycol, polyvinylpyrrolidone, gelatin or sodium or potassium acrylate is dissolved in distilled water while heating to 45 - 55°C and stirring, and then after cooling, a stabiliser selected from ammonium, potassium or sodium citrates is added to the obtained solution while stirring.

EFFECT: invention provides high yield factor of silver nanoparticles in an aqueous medium and high stability of the obtained silver nanoparticles.

1 tbl, 6 ex

Description

The invention relates to the field of producing silver nanoparticles distributed in an aqueous medium and stabilized by compounds (stabilizers).

Silver nanoparticles are atomic silver agglomerates with sizes of 1-100 nm, the surface of which is surrounded by a layer of stabilizer molecules, which allows reaching the “life” of the water / stabilizer / silver nanoparticle system for at least 12 months.

Silver nanoparticles, thanks to pronounced biocidal properties in relation to more than 250 types of pathogens, are promising materials and are used in medicine, veterinary medicine and the manufacture of cosmetics.

Obtaining silver nanoparticles in liquid media consists of 2 main operations:

1. Preparation of a liquid medium by dissolving stabilizers in an organic or inorganic solvent.

2. Isolation into the resulting medium of silver in atomic and / or ionic form by chemical or electrochemical reactions with the formation of silver nanoparticles.

Several methods are known for producing silver nanoparticles in liquid media, among which the most traditional is the chemical reduction of soluble silver compounds with various reducing agents.

For example, a method for producing silver nanoparticles in an aqueous medium is described (A.V. Vegera, A.D. Zimon. Synthesis and physicochemical properties of silver nanoparticles stabilized by acid gelatin. Journal of Applied Chemistry, 2006. V.79. Vol. 9-C.1419-1422), in which the synthesis of silver nanoparticles is carried out by reducing silver nitrate, which is in an aqueous solution, with sodium borohydride. In a solution of silver nitrate cooled to 0 ° C, a solution of equimolecular sodium borohydride is gradually added dropwise with stirring. As a result of the redox reaction, the final aqueous medium contains silver nanoparticles with a diameter of 3 to 50 nm.

The disadvantages of the described method include the presence in the finish medium of an equimolecular amount of sodium nitrate, which is recognized as unhealthy, as well as the release of a sufficiently large volume of gaseous hydrogen (74.8 l per 1 mol of the original silver nitrate). The latter places high demands on industrial safety on an industrial scale.

Also known is a method for producing silver nanoparticles by means of erosion-explosive dispersion of a material (V.G. Kaplunenko, N.V. Kosinov, D.V. Polyakov. Obtaining new biogenic and biocidal nanomaterials using erosion-explosive dispersion of metals. Physical vacuum and nature. Kiev, 2008. Issue 1 - P.18-22), in which charged silver nanoparticles surrounded by ligands (water molecules) are obtained by creating an electric arc discharge in the gap of a silver conductor placed in an aqueous medium. In this case, chelate complexes of metallic silver are formed, forming spherical nanoparticles.

The disadvantages of the described method are the high current strength (more than 100 A), i.e. high energy intensity of the process, as well as a short “life” time of the obtained nanoparticles (no more than 1 month) due to the absence of any stabilizers.

Closest to the claimed is the method described in (Rodrigues-Sanchez L., Blanko ML, Lopez-Quintela MA Electro-chemical Synthesis of Silver Nanoparticles. J.Phys. Chem. B. 2000. Vol.104. P 9683-9688) selected by us for the prototype.

It consists of the following stages:

1. Dissolution of the stabilizer (tetrabutylammonium bromide) in an organic solvent (acetonitrile).

2. Electrochemical dissolution of the anode (silver plate) in the organic medium obtained in the first stage.

In this case, platinum or aluminum is used as a cathode when passing a constant electric current through the solution. In the described method, a large part (55-80%) of electrochemically dissolved silver is deposited on the cathodes in the form of films (i.e., the yield coefficient of silver nanoparticles in solution is not higher than 45%). Another significant disadvantage of this method is the use of toxic acetonitrile as a solvent, which excludes the possibility of using a finishing medium containing silver nanoparticles for medicine, veterinary medicine, and the manufacture of cosmetic preparations.

The objective of the present invention is to obtain silver nanoparticles in an aqueous medium by electrochemical dissolution of the anode, made in the form of a silver plate in an aqueous medium.

The problem is solved as follows: instead of toxic acetonitrile, use distilled water as a solvent, and use a stabilizer selected from polyglycols, polyvinylpyrrolidone, gelatin or sodium polyacrylate, or potassium, and a stabilizer selected from ammonium, potassium, or sodium citrates as a stabilizer.

The feasibility of the proposed method is as follows:

1. High stability of silver nanoparticles (at least 12 months) is ensured.

2. A high yield coefficient of silver nanoparticles in the aquatic environment (not less than 90%), low sedimentation of silver at the cathode is ensured.

3. It is intended to use the obtained nanoparticles for the production of medical, veterinary and cosmetic preparations.

The process of obtaining silver nanoparticles consists of the following operations:

1. Dissolving with stirring in distilled water while heating to 45-55 ° C a stabilizer selected from polyglycols, polyvinylpyrrolidone, gelatin or sodium or potassium polyacrylate.

2. Cooling the resulting solution to room temperature.

3. Add with stirring a stabilizer selected from ammonium, potassium or sodium citrates.

4. Placement in the resulting aqueous medium of the anode made in the form of a silver plate and a cathode made of stainless steel. Passing direct electric current during the calculated time with stirring.

Example 1

A mixture of polyglycols (TU 2483-008-71150986-2006) with a molecular weight of 400 to 4000 is dissolved in distilled water heated to 45-55 ° C (GOST R6709-72) with a polyglycol: water ratio of 15:85 to 40: 60 wt. parts with stirring for 1 hour. Then cooled to a temperature of 20-25 ° C. Ammonium citrate (GOST 7234-71) is added to the resulting solution with stirring at the rate of 1.0 g per 1 liter of solution with stirring. Then, the electrode system is placed in the resulting medium, where the silver plate (GOST R ISO 9001-2001) serves as the anode, and the stainless steel plate (GOST 5582-95 grade 12X18H10T) serves as the anode. With stirring, stabilized direct current with a density of 10-20 A / sq is supplied to the electrodes. m and a voltage of 10-20 V. Electrochemical dissolution of silver is carried out for 10-30 minutes based on the output of silver nanoparticles in an aqueous solution of stabilizers 10-1000 mg per 1 liter of solution. The properties of the obtained aqueous medium containing silver nanoparticles are presented in the table (Example 1).

Example 2

It is carried out as example 1, but instead of polyglycols at the 1st stage, gelatin (GOST 11293-89 or GOST 25183.10-82) is used as an organic stabilizer at the rate of 1-20 g per 1 liter of distilled water, and sodium citrate is used as an inorganic stabilizer (GOST 22280-76). The properties of the obtained aqueous medium containing silver nanoparticles are presented in the table (Example 2).

Example 3

It is carried out as example 1, but polyglycols are used as organic stabilizers with a ratio of polyglycols: distilled water from 10:90 to 25:75 and gelatin in an amount of 0.5-10.0 g per 1 liter of a solution of organic stabilizers, and as an inorganic stabilizer potassium citrate is used (GOST 5538-78). The properties of the obtained aqueous medium containing silver nanoparticles are presented in the table (Example 3).

Example 4

It is carried out as Example 1, but medical polyvinylpyrrolidone (FS 42-1194-98) with a molecular weight of 8000-35000 with a ratio of polyvinylpyrrolidone: distilled water from 10:90 to 20:90 is used as an organic stabilizer, and ammonium citrate is used as an inorganic stabilizer . The properties of the obtained aqueous medium containing silver nanoparticles are presented in the table (Example 4).

Example 5

It is carried out as example 1, but potassium polyacrylate (brand HENGDRILL 67003, made in China) with a molecular weight of 50,000-120,000 with a ratio of polyacrylate: distilled water from 2:98 to 10:90 is used as an organic stabilizer, and ammonium citrate is used as an inorganic stabilizer . The properties of the obtained aqueous medium containing silver nanoparticles are presented in the table (Example 5).

For comparison, the table shows the performance of a solution of silver nanoparticles from an article in J. Phys. Chem. B. 2000. Vol. 4. P.9683-9688. Silver nanoparticles were obtained by electrochemical dissolution of a silver anode in acetonitrile in the presence of a tetrabutylammonium bromide stabilizer (Example 6).

Table Properties of media containing silver nanoparticles Silver Nanoparticle Medium Basic solvent The average diameter of silver particles, nm The concentration of nanoparticles in the medium, mg / l The yield coefficient of silver nanoparticles in a liquid medium,% The toxicity of a medium containing silver nanoparticles Example 1 Water
distilled 5-20 155 92.6 Non toxic Example 2 Also 7-25 210 94.0 Non toxic Example 3 Also 3-22 98 90.5 Non toxic Example 4 Also 6-18 64 Non toxic Example 5 Also 5-15 710 Non toxic Example 6 Acetonitrile 2-7 5-8 20.0-45.0 Toxic

The sizes of the nanoparticles were determined by electron microscopy. The yield coefficient of silver nanoparticles in a liquid medium was determined gravimetrically.

Claims (1)

A method of producing silver nanoparticles, including dissolving stabilizers in a solvent, placing an anode made in the form of a silver plate and a cathode in the resulting solution, electrochemical dissolving the anode when a stabilized direct current is passed through the solution, characterized in that distilled water is used as a solvent, as the cathode use a stainless steel plate, and the process of dissolution of the stabilizers takes place in two stages: first in distilled water when heated to 45-55 ° C and with stirring, a stabilizer selected from polyglycols, polyvinylpyrrolidone, gelatin or sodium or polyacrylate polyacrylate is dissolved, and then, after cooling, a stabilizer selected from ammonium, potassium or sodium citrates is added to the resulting solution with stirring.