Method for modifying metal oxide powder with silver nanoparticles

Abstract

FIELD: nanoparticles.SUBSTANCE: invention relates to a method for modifying metal oxide powder with silver nanoparticles. Silver nanoparticles are applied to the surface of the metal oxide powder. Subsequent heat treatment of the said powder with applied silver nanoparticles is carried out at a temperature of 400 °C for 5 hours, with heating at a rate of 5 degrees / min.EFFECT: produces metal oxide powders modified with silver nanoparticles for various applications, such as antimicrobial agents and photocatalysts.3 cl, 6 dwg, 3 tbl, 4 ex

Description

[0001] FIELD OF TECHNOLOGY

[0002] The invention can be used to modify various powder and porous materials that are stable at a temperature of 400°C, for example, ceramic powders, activated carbon, carbon nanotubes, porous ceramic and metallic materials with silver nanoparticles, to obtain new modified materials with improved biological, optical, photocatalytic properties for use as antimicrobial agents, filters, catalysts, sensors.

[0003] PRIOR ART

[0004] A composite filter material and a method for its preparation are known from Russian patent 2315649, published on 27.01.2008 [1].

[0005] The invention relates to filter materials with antimicrobial activity. A method for producing the material is proposed, according to which a carrier selected from the following series: aluminosilicate, silicon dioxide, aluminum oxide, or titanium dioxide is purified, treated with a stannous salt solution, then with a silver nitrate solution, rinsed with demineralized water, and photoactivated to reduce silver ions and form a three-layer structure of silver nanoparticles, silver oxides, and silver clusters on the carrier surface. The resulting material is dried in a microwave oven. The invention provides a material with high antimicrobial activity and excellent filtering properties.

[0006] The disadvantage of the known technical solution is the use of a wide range of chemical reagents that can introduce unwanted impurities, as well as the multi-stage nature of the technological process.

[0007] A method for producing antimicrobial composite nanostructures Al2O3×H2O / Ag from bimetallic nanoparticles Al / Ag obtained by joint electrical explosion of Al and Ag wires is known, disclosed by the authors Lozhkomoev Alexander, Pervikov Alexander, Bakina Olga, Kazantsev Sergeya and Gotman Irena in the article Synthesis of antimicrobial AlOOH-Ag composite nanostructures by water oxidation of bimetallic Al-Ag nanoparticles [RSC Adv., 2018, 8, 36239 36244] [2].

[0008] In the known method, the synthesis of bimetallic Ag-Al nanoparticles is first carried out by the method of electrical explosion of twisted wires in an argon atmosphere at a pressure of 2×10 5Pa: silver wire with a diameter of d ¼ 0.15 mm and aluminum wire with a diameter of d ¼ 0.35 mm, both 80 mm long; The atomic ratio of Al to Ag in the wires was about 85 at. % Al and 15 at. % Ag. Then, aqueous oxidation of the obtained bimetallic Ag-Al nanoparticles was carried out; the reaction of bimetallic Ag-Al nanoparticles was carried out in a dilute aqueous suspension: 1 g of Ag-Al nanopowder suspended in 100 ml of deionized water was placed in a thermally insulated glass reactor equipped with a combined pH electrode (ESK-10601) and a temperature sensor (DTS-4-01); the suspension was heated from 23 to 67 °C at a heating rate of 1.0 C per minute, with continuous stirring.

[0009] The disadvantages of the above include the fact that Al / Ag particles with an atomic Ag content of 15 at.% are used, which contain an excess amount of Ag, which in turn affects the specific surface area of ​​the nanostructures synthesized from them, their toxicity and cost.

[0010] Thus, there is still a need to obtain Al2O3-based aluminum oxide nanostructures with comparable antimicrobial efficiency, lower silver content, lower toxicity and lower cost.

[0011] A method for producing an antimicrobial composite nanostructure of boehmite-silver or bayerite-silver and a method for producing an antimicrobial composite nanostructure of γ-aluminum oxide-silver are known from the Russian Federation patent 2794900, published on 25.04.2023 [3].

[0012] The group of inventions relates to chemical technology and can be used in the production of composite nanostructures of aluminum oxides / hydroxides intended for use as components of sorption-antimicrobial materials for water purification and disinfection, treatment of wound infections, as well as in catalysis processes. A method for producing an antimicrobial composite nanostructure of the chemical formula AlOOH / Ag or Al(OH)3 / Ag is disclosed, including the production of bimetallic Al / Ag nanoparticles with a given Ag content by the method of electric explosion of aluminum and silver wires twisted together and aqueous oxidation of the obtained bimetallic Al / Ag nanoparticles, wherein the said Al / Ag nanoparticles with an Ag content of 9 at. % are obtained by the method of electric explosion of two aluminum wires with a diameter of 0.35±0.01 mm and one silver wire with a diameter of 0.15±0.01 mm twisted together. A method for producing an antimicrobial composite nanostructure of gamma-aluminum oxide is also disclosed.The group of inventions ensures the production of a low-toxic sorption-antimicrobial material with improved antimicrobial properties.

[0013] A drawback of the known technical solution is the limited silver content in the bimetallic particles, due to the production method (electrical explosion of the conductor). This limitation is determined by the wire diameter. The minimum silver content in particles that can be obtained by this method, based on the wire diameter, is 9 at.% (26 wt.%).

[0014] A method for producing nanosized titanium dioxide with variable optical properties, modified with metal plasmonic nanoparticles, is known from Russian patent 2771768, published 11.05.2022 [4].

[0015] The invention relates to the synthesis of nanosized titanium dioxide modified with metallic plasmonic nanoparticles of a noble metal, which can be used to create highly efficient solar cells and materials for electronic equipment. The method consists of preparing a solution of a titanium-containing precursor consisting of sodium borohydride, isopropyl alcohol and titanium tetraisopropylate, and adding a noble metal precursor, isopropyl alcohol and nitric acid to said solution, followed by stirring, centrifugation and washing with distilled water to remove residual impurity ions, drying at a temperature of 150 ° C to remove residual water, wherein gold or silver is used as the noble metal;To prepare a solution of a titanium-containing precursor using the precise weighing method, weigh the required amount of sodium borohydride and transfer it quantitatively into a beaker, add isopropyl alcohol to it and place the beaker on a magnetic stirrer. Add titanium tetraisopropylate to the resulting mixture and stir the solution for 15-20 minutes; then, using the precise weighing method, weigh the precursor of the corresponding noble metal, transfer it quantitatively into a beaker and dissolve it in isopropyl alcohol with constant stirring. Then, pipette nitric acid and add it to the beaker. Finally, add distilled water, thus obtaining the initial precipitation solution.a burette with the initial precipitation solution is placed in a stand over a beaker with a titanium tetraisopropylate solution on a magnetic stirrer, which is added dropwise with constant stirring for 40 minutes, the solution is left on a magnetic stirrer until the gelation process is complete, and after centrifugation, washing and drying of the gel at the final stage it is calcined for 3 hours at a temperature of 500-800 °C to obtain nanosized titanium dioxide modified with plasmonic gold or silver nanoparticles, with the following ratio of components, wt. %: plasmonic gold or silver nanoparticles 0.001-5;Titanium dioxide nanoparticles - the rest. Modification of nanosized titanium dioxide with metal plasmonic nanoparticles leads to the appearance of additional absorption regions in the wavelength ranges of 390-420 nm and 500-600 nm. Varying the concentration of metal plasmonic nanoparticles of silver and gold in nanosized titanium dioxide makes it possible to vary the absorption intensity of incident light at certain wavelengths characteristic of the surface plasmon resonance of silver and gold nanoparticles, as well as the width of the band gap, thereby providing a material based on nanosized titanium dioxide with specified spectral characteristics and variable optical properties.

[0016] The disadvantage of the known technical solution is the complexity of the technological process using chemical reagents that can introduce unwanted impurities into the product.

[0017] The technical objective of the invention is to develop a method for modifying metal oxide powder with silver nanoparticles by thermal fragmentation of electroexplosive silver nanoparticles on the surface of the metal oxide powder.

[0018] The technical result of the invention is the production of metal oxide powders modified with silver nanoparticles for various applications, for example, as antimicrobial agents and photocatalysts.

[0019] An additional technical result of the invention is that the method does not use chemical reagents that can introduce unwanted impurities into the final product.

[0020] The specified technical result is achieved by the method of modifying a metal oxide powder with silver nanoparticles, which includes applying silver nanoparticles to the surface of the metal oxide powder and subsequent heat treatment of the said powder with the applied silver nanoparticles, wherein the heat treatment is carried out at a temperature of 400°C for 5 hours, and wherein the heating is carried out at a rate of 5 degrees / min.

[0021] In this case, aluminum oxide (Al2O3), titanium oxide (TiO2) or zirconium oxide (ZrO2) powder with an average particle size of 100 nm is used as the metal oxide powder.

[0022] The application of silver nanoparticles to the surface of the metal oxide powder is carried out as follows: a mechanical mixture of metal oxide powder, which is TiO2 or Al2O3, with 1-10 wt. % of silver nanoparticles is prepared, then the said mixture is placed in ethyl alcohol and treated with ultrasound, then the ethyl alcohol is evaporated at a temperature of 75°C or the said mixture is stirred for 30 minutes using a turbulent mixer.

[0023] DISCLOSURE OF THE INVENTION

[0024] As the analysis of the prior art has shown, there is still a need to obtain composite materials based on aluminum oxide (Al2O3), zirconium oxide (ZrO2) or titanium oxide (TiO2) powders, with comparable antimicrobial efficiency, having a lower silver content, lower toxicity and a lower cost of the method for obtaining these materials.

[0025] The solution to this technical problem can be the use of silver nanoparticles in smaller quantities as an antimicrobial agent, which are currently considered the best antibacterial nanoparticles used in dressings, glass, ceramic coatings, implant coatings and filter membranes [Xu, Y., Zhou, F., Zhang, T., Lin, L., Wu, J., Zhang, M., & Chen, H. (2019). Advances in Preparation and Application of Supported Nano-Silver Composites. Nanoscience and Nanotechnology Letters, 11(11), 1477-1488.] [5].

[0026] The present invention utilizes Ag nanopowder preliminarily obtained using silver wires of various diameters and a working gas (argon or helium, or a mixture of helium and 20 vol.% oxygen). For this purpose, silver wire of various diameters 0.30 (0.15, 0.2) ± 0.01 mm was fed into the electric explosion chamber of the UDP-2M installation [http: / / www.nanosized-powders.com / technology / technologies / equipment.php], pre-filled with a working gas to a pressure of 0.2 MPa, in the direction from the grounded electrode of the installation to its high-voltage electrode. The length of the dispersed conductor ranged from 40 to 112 mm. When the electric circuit was closed, a current pulse with a density of 3.08×10 7 up to 4.52 A / cm 2 in a time of about 2.0×10 -6 c. The ratio of the introduced energy E to the sublimation energy of the dispersed metals E svaried from 1.50 to 3.50 depending on the experimental conditions. To ensure equivalent energy conditions, a well-known dimensional coefficient derived from the similarity theory of electrical explosion was used:

[0027]

[0028] where: C is the capacity of the capacitor bank, F;

[0029] L - inductance, H;

[0030] d - diameter of the exploding wire, mm;

[0031] υ - the ratio of the time constants of the circuit and the explosion of conductors, (GN⋅F) 1 / 2 / mm

[0032] Transmission electron microscopy (TEM) data show that, regardless of the production conditions, electrical explosion of a conductor results in the formation of spherical, highly agglomerated silver particles. Furthermore, in most cases, adhesions are observed at the point of contact between the particles. As an example, Fig. 1a shows a TEM image of silver nanoparticles obtained in an argon atmosphere at E / Es =2.4; υ=5.24 (H∙F) 1 / 2 / mm; d=0.3mm. In all cases, silver crystallizes in a face-centered cubic (FCC) lattice, forming a cubic phase; the cell parameter changes insignificantly depending on the conditions for obtaining silver particles (Table 1). The average size of agglomerated silver particles, depending on the synthesis conditions, varies from 95 to 145 nm (Table 1). Changes in the lattice parameters and the average size of silver particles do not affect the effect of thermal fragmentation of agglomerated silver particles used to modify various metal oxide powders.

[0033]

[0034] Initially, when heated at a rate of 5°C / min, silver particles temporarily coalesce into larger particles. Subsequently, upon reaching a temperature of 400°C, stresses in the larger particles cause thermal fragmentation into smaller silver particles of varying sizes, ranging from 2 to 20 nm (Fig. 1b). The authors determined the heating rate and the stated thermal fragmentation temperature (400°C) of the silver particles experimentally.

[0035] Based on this effect, the following are examples of modification of metal oxide powders with silver nanoparticles.

[0036] In the invention, the examples used the initial metal oxide powders with the following characteristics.

[0037] Al2O3 powder TU 1791-003-36280340-2008. White powder, bulk density from 0.6 to 1.7 g / cm 3 The particles are spherical. The specific surface area measured by the BET method is 35-40 m 2 / g. Melting point: 2000°C. The powder is fire- and explosion-proof. Aluminum oxide powder was used for modification with silver nanoparticles due to its physicochemical properties. It is one of the most common materials used in various industries, for example, as catalyst carriers, as a bacterial cell sorbent, and other applications.

[0038] TiO2 powder - TU 1791-002-36280340-2005. Appearance and color: powder from light yellow to white, bulk density from 0.5 to 2.0 g / cm 3 The particles are spherical. The specific surface area measured by the BET method is 35-40 m 2 / g. Melting point: 1843°C. The powder is fire- and explosion-proof. Titanium dioxide powder was used for modification with silver nanoparticles due to its high photocatalytic activity, chemical stability, low cost, and non-toxicity. It is a common material used in photocatalytic processes and is also used in medicine for the manufacture of implants.

[0039] ZrO2 powder, obtained by the sol-gel method and stabilized with yttrium oxide grade TZY-010DP (Nova-Health, Russia), was used to produce aluminum-zirconium ceramics. The study of the modification of aluminum-zirconium ceramics with silver nanoparticles, obtained from a mixture of corresponding metal oxide powders by pressing and sintering, was motivated by the fact that this ceramic material has high mechanical properties and is widely used in the manufacture of medical instruments and implants.

[0040] The invention is illustrated by the following figures 1-6.

[0041] Brief description of the figures.

[0042] Fig. 1. TEM images of silver nanoparticles (a) obtained in an argon atmosphere at E / E s =2.4; υ=5.24 (H⋅F) 1 / 2 / mm; d=0.3 mm and silver nanoparticles after thermal fragmentation (b).

[0043] Fig. 2 - TEM images of Al2O3(a) and TiO2(b) nanoparticles modified with silver nanoparticles are shown.

[0044] Fig. 3 - TEM images of Al2O3(a) and TiO2(b) nanoparticles modified with silver nanoparticles are shown.

[0045] Fig. 4 - Kinetic curves of methylene blue (MB) decolorization in the presence of TiO2 nanoparticles and after modification with silver nanoparticles.

[0046] Fig. 5 - Antibacterial activity of TiO2 and Al2O3 nanoparticles before and after modification with silver nanoparticles.

[0047] Fig. 6 - Fluorescence microscopy of S. aureus cells stained with DiBAC4(3) in the presence of TiO2 nanoparticles modified with silver nanoparticles (a), in the presence of TiO2 nanoparticles (b), in the absence of nanoparticles (c).

[0048] In the examples, the authors used aluminum oxide, titanium oxide, and zirconium oxide powders with an average size of 100 nm as metal oxide powder.

[0049] Below are examples of specific implementation of the invention.

[0050] Example 1.

[0051] To apply silver nanoparticles, a mechanical mixture of aluminum oxide powder with an average size of 100 nm and agglomerated silver particles with an average size of 95 to 145 nm was prepared. The content of silver nanoparticles in the mechanical mixture was 5% by weight of the mixture (can vary from 1 to 10 wt.%). For this, a sample of aluminum oxide powder weighing 0.49 g and 0.01 g of silver powder were placed in 10 ml of ethyl alcohol (95%) and treated in an ultrasonic bath for 20 minutes. The alcohol was then evaporated at a temperature of 75°C. Afterwards, the powder mixture was calcined for 5 hours at a temperature of 400°C at a heating rate of 5 deg / min.

[0052] According to Example 1, the morphology of the resulting composite nanoparticles is shown in Figure 2a. After thermal fragmentation, aluminum oxide is represented by spherical particles with an average size of 100 nm, on the surface of which spherical-like silver nanoparticles ranging in size from 2 to 20 nm are located.

[0053] Example 2.

[0054] The procedure is similar to Example 1. The difference is that titanium oxide powder with an average particle size of 100 nm was used instead of aluminum oxide powder. A mechanical mixture of titanium oxide powder and agglomerated silver particles was prepared, with a silver content of 10% by weight.

[0055] According to Example 2, the morphology of the obtained composite nanoparticles is shown in Figure 2b. As shown in Figure 2b, after thermal fragmentation, spherical titanium oxide particles with an average size of 100 nm are modified with spherical-like silver nanoparticles with a size of 2 to 20 nm.

[0056] Example 3.

[0057] To apply silver nanoparticles, a mechanical mixture of Al2O3 powder and agglomerated silver nanoparticles was prepared with a component ratio similar to that in Example 1. The dry mixture was then stirred for 30 minutes using a turbulent mixer (V-shaped, centrifugal screw, or other mixers). The mixture was then calcined for 5 hours at 400°C, with a heating rate of 5°C / min.

[0058] According to Example 3, the morphology of the obtained composite nanoparticles is shown in Figure 3a. According to TEM analysis, after thermal fragmentation, silver nanoparticles with a size of 2-20 nm cover the surface of spherical aluminum oxide particles with an average size of 100 nm.

[0059] Example 4.

[0060] Conducted similarly to Example 3. The difference is that titanium oxide powder was used instead of aluminum oxide powder. A mechanical mixture of titanium oxide powder and agglomerated silver nanoparticles was prepared, with the silver content being 10% by weight.

[0061] Following Example 4, the morphology of the obtained TiO2 / Ag composite nanoparticles is shown in Figure 3b. As can be seen, spherical titanium oxide particles with an average size of 100 nm are also coated with silver nanoparticles ranging in size from 2 to 20 nm.

[0062] Table 2 presents the samples of TiO2 / Ag composite nanoparticles with silver content of 1, 3, 5 and 10 wt%, and the photochemical activity depending on the composite composition was investigated.

[0063] To evaluate the effect of silver nanoparticles on the absorption band edge (ABE), the absorption spectrum of an aqueous suspension of TiO2 / Ag composite nanoparticles with different silver nanoparticle contents, pre-dispersed in an ultrasonic bath, was obtained using an SF-2000 spectrophotometer (OKB Spektr, Russia). The obtained spectrum was reconstructed into Tauc coordinates, yielding a dependence in coordinates (Aλ -1 ) 2- E. The value of the absorption coefficient in eV was determined from the intersection of the tangent with the abscissa axis (Table 2). When studying the optical properties of the obtained composite nanoparticles, it was found that the absorption edge of the TiO2 / Ag composite nanoparticles shifts towards the visible region (450 nm) with an increase in the content of silver nanoparticles in the composite nanoparticles (Table 2).

[0064]

[0065] Fig. 4 shows the decolorization curves, which show that with an increase in the number of silver nanoparticles in the composite nanoparticles, their photochemical activity increases.

[0066] The degree of dye degradation was calculated using the formula:

[0067]

[0068] where C к - dye concentration, minus the adsorption component, mg / l;

[0069] C t - concentration of dye after irradiation at time t, mg / l.

[0070] According to Table 3, the maximum degree of MS degradation in 60 minutes of contact is achieved when using TiO2-10% Ag composite nanoparticles and is about 36%.

[0071]

[0072] Antibacterial activity studies (Fig. 5) showed that after modification with silver nanoparticles, TiO2 / Ag (10 wt.% Ag) and Al2O3 / Ag (5 wt.% Ag) composite nanoparticles show 100% suppression of S.aureus bacteria at a bacterial concentration of 10 5 CFU / ml and a concentration of composite nanoparticles of 1 mg / ml for 3 hours of contact in saline.

[0073] The effect of TiO2 powder particles before and after modification with silver nanoparticles on changes in bacterial membrane potential was studied using fluorescence microscopy. For this purpose, S. aureus bacteria incubated with the studied TiO2 / Ag composite nanoparticles were stained with a fluorescent dye, DiBAC4(3), which, upon depolarization of the bacterial membrane, binds to intracellular proteins of the cytoplasm and begins to glow in the green spectrum (Fig. 6). It was found that when incubated with TiO2 / Ag composite nanoparticles, the dye more intensely stains the bacterial cytoplasm (Fig. 6a) than bacteria incubated with TiO2 nanoparticles (Fig. 6b), in contrast to (Fig. 6c), which does not contain any nanoparticles and, accordingly, does not glow in the green spectrum.

[0074] Thus, TiO2 nanoparticles and TiO2 / Ag composite nanoparticles cause a change in bacterial membrane potential.

Claims

1. A method for modifying a metal oxide powder with silver nanoparticles, which includes applying silver nanoparticles to the surface of the metal oxide powder and subsequent heat treatment of said powder with the applied silver nanoparticles, characterized in that the heat treatment is carried out at a temperature of 400°C for 5 hours, while heating is carried out at a rate of 5 degrees / min.

2. The method according to paragraph 1, characterized in that the metal oxide powder used is aluminum oxide (Al2O3), titanium oxide (TiO2) or zirconium oxide (ZrO2) powder with an average particle size of 100 nm.

3. The method according to claim 1, characterized in that the application of silver nanoparticles to the surface of the metal oxide powder is carried out as follows: a mechanical mixture of metal oxide powder, which is TiO2 or Al2O3, with 1-10 wt.% of silver nanoparticles is prepared, then said mixture is placed in ethyl alcohol and treated with ultrasound, then ethyl alcohol is evaporated at a temperature of 75°C or said mixture is stirred for 30 minutes using a turbulent mixer.

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