KR20230137703A - Heterogeneous metal nanowire composite, manufacturing method for thereof and sensor for carbon monoxide using the same - Google Patents

Abstract

The heterogeneous metal nanofiber composite according to the present invention includes hollow nanofibers containing heterogeneous metal oxides; It is a heterogeneous metal nanofiber composite comprising; and metal nanoparticles dispersed on the outer and inner surfaces of the nanofibers, wherein the metal nanoparticles are included in 2 wt% to 5 wt% of the heterogeneous metal nanofiber composite.

Description

Heterogeneous metal nanofiber composite, manufacturing method thereof, and carbon monoxide detection sensor comprising the same {HETEROGENEOUS METAL NANOWIRE COMPOSITE, MANUFACTURING METHOD FOR THEREOF AND SENSOR FOR CARBON MONOXIDE USING THE SAME}

The present invention relates to a heterogeneous metal nanofiber composite, a manufacturing method thereof, and a carbon monoxide detection sensor comprising the same. More specifically, it relates to a heterogeneous metal nanofiber composite containing nanoparticles with reduced nanoparticle size and increased specific surface area, a manufacturing method thereof, and a carbon monoxide detection sensor comprising the same.

A transformer is an electrical element that converts and transmits electrical energy transmitted through power plants and transmission lines into a form that is easy to consume. It consists of insulating oil, insulating paper, press board, and bakelite that prevent electric leakage for stable long-term operation. It includes liquid and solid insulating materials such as liquid and solid insulating materials, but if a problem occurs in the transformer and local overheating or insulation breakdown occurs, the insulating material decomposes due to the heat generated, causing hydrogen (H ₂ ), acetylene (C ₂ H ₂ ), and methane (CH ₄ ), carbon monoxide (CO), carbon dioxide (CO ₂ ) and other hydrocarbon gases are generated.

Meanwhile, the condition of the transformer can be checked by qualitatively and quantitatively analyzing these gases dissolved in the insulating oil. In particular, carbon monoxide is known to be generated when solid insulating materials are decomposed when heated over hundreds of degrees Celsius, and if a high carbon monoxide concentration is observed, it becomes the basis for determining that a major defect has occurred in the transformer.

Transformer condition diagnosis through insulating oil gas analysis is generally done by collecting gas samples from the transformer and performing mass analysis. However, it takes a long time, which limits rapid response, incurs a lot of cost, and is not very reliable. There is.

On the other hand, metal oxide semiconductors used as resistance change sensing materials utilize the principle that the electrical resistance value of a material fluctuates as a result of various chemical reactions that occur through interaction between gas molecules and the material surface, that is, adsorption and desorption. It is possible to quantitatively observe the gas by calculating the resistance ratio when the concentration of a specific gas is increased due to an abnormal phenomenon compared to the resistance in the gas environment within the insulating oil.

In particular, metal oxide semiconductor sensing materials are synthesized from nanostructures with a large specific surface area such as nanoparticles, nanotubes, and nanosheets, thereby maximizing the frequency of surface reactions to produce sensors with high sensitivity.

However, despite ongoing research to develop a gas sensor based on a metal oxide semiconductor with a nanostructure with a large specific surface area, it is not easy to develop a gas sensor that shows selectivity for a specific gas, and this is because general resistance change sensing materials are based on surface reaction. This is because a single sensing material can show resistance changes to several types of gas molecules, making selective detection difficult.

Therefore, in the development of a high-sensitivity and high-selectivity sensor for carbon monoxide, it is urgent to develop an appropriate sensing material by considering the physical/chemical mechanisms that affect resistance changes.

As background technology for the present invention, Korean Patent Publication No. 10-2022-0013827 discloses a metal oxide semiconductor nanofiber-based gas sensor member functionalized with alkali metal and precious metal and a method for manufacturing the same.

The purpose of the present invention is to provide a heterogeneous metal nanofiber composite that can observe the gas concentration in the insulating oil of a transformer in real time by increasing the interaction between gas molecules and the surface of the semiconductor material in a metal oxide composed of a nanostructure with a large specific surface area. It is for.

Another object of the present invention is to provide a method for producing a high-capacity concentrated heterometal nanofiber composite using a selective solvent substitution process.

Another object of the present invention is to provide a carbon monoxide detection sensor comprising a heterogeneous metal nanofiber composite.

The above and other objects of the present invention can all be achieved by the present invention described below.

1. One aspect of the present invention relates to a bimetallic nanofiber composite.

The heterogeneous metal nanofiber composite is a hollow nanofiber containing a heterogeneous metal oxide; and

It is a heterogeneous metal nanofiber composite containing metal nanoparticles dispersed on the outer and inner surfaces of the nanofibers,

The metal nanoparticles are included in an amount of 2 wt% to 5 wt% in the heterogeneous metal nanofiber composite.

2. In the first embodiment, the different metal oxide includes 100 parts by weight of the first metal oxide and 1 to 30 parts by weight of the second metal oxide,

The first metal oxide is copper oxide (CuO),

The second metal oxide may include one or more types from the group consisting of ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, Co ₃ O ₄ , CeO ₂ , and MnO ₂ .

3. In embodiment 1 or 2, the metal nanoparticles are gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir). It may include one or more types.

4. In any one of the embodiments of 1 to 3, the heterogeneous metal nanofiber composite may have an average diameter of 50 nm to 10 μm and an average length of 1 μm to 500 μm.

5. Another aspect of the present invention relates to a method for producing a heterogeneous metal nanofiber composite.

The method for producing a heterogeneous metal nanofiber composite includes (a) preparing a first mixed solution containing a metal nanoparticle dispersion and a first polymer solution;

(b) preparing a metal nanoparticle concentrate by evaporating the first mixed solution;

(c) preparing a second mixed solution containing a first metal oxide precursor, a second metal oxide precursor, and a second polymer solution;

(d) preparing an electrospinning solution by mixing the second mixed solution with the metal nanoparticle concentrate;

(e) producing nanofibers by electrospinning the electrospinning solution; and

(f) heat treating the nanofibers.

6. In the above 5 embodiments, the metal nanoparticle dispersion contains one or more of silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir). can do.

7. In embodiment 5 or 6 above, the metal nanoparticle dispersion may be a state in which the metal nanoparticle precursor is dispersed in water.

8. In any one of the embodiments of 5 to 7, the first polymer solution includes a polymer and a solvent, and the solvent is N-methylpyrrolidone, dimethyl sulfoxide, iso Isopropyl myristate, Trichlorobenzene, Dichlorobenzene, Dimethyl acetamide, N,N'-dimethylformamide, Isoamyl Alcohol ( Isoamylalcohol, Propyl alcohol, Butyl alcohol, Pentyl alcohol, Ethylene glycol, Methoxyethanol, Methyl isobutyl ketone, Butyl acetate (Butyl acetate), Tetrachloroethane, Pentachloroethane, Chlorobenzene, Xylene, and Tetrachloroethylene.

9. In any one of embodiments 5 to 8, the first polymer solution is polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral ( Polyvinyl butyral, polyvinylidene fluoride, polysulphone, polyethersulphone, polyarylsulphone, epoxypolyurethane, polyimide, polyvinyl chloride ( Polyvinyl chloride, Polyetherketone, Aromatic polyester, Polyamidoimide, Polyvinylacetate, Polymethylmethacrylate, Polystyrene, Polyoxy It may include one or more of polyoxymethylene, polyacrylic acid, polyurethane, polyethylene, and polytrimethylene terephthalate.

10. In any one of the embodiments 5 to 9 above, the first polymer solution may contain 5 wt% to 20 wt% of the polymer.

11. In any one of the embodiments 5 to 10 above, in step (a), 0.05 to 10 parts by volume of the first polymer solution may be mixed with the metal nanoparticle dispersion.

12. In any one of embodiments 5 to 11, the first metal oxide precursor is copper (II) nitrate trihydrate, copper (II) chloride, copper (II) nitrate, copper (II) acetate, copper (II) It may include one or more of acetylacetonate, copper (II) sulfate, and their derivatives.

13. In any one of embodiments 5 to 12, the second metal oxide precursor is cerium (III) nitrate hexahydrate, cerium (III) chloride, cerium (III) nitrate, cerium (III) sulfate, zinc (II) chloride, zinc (II) nitrate, tin (IV) chloride, cobalt (II) chloride, cobalt (II) nitrate, nickel (II) chloride, nickel (II) nitrate, iron (II) chloride, iron (II) nitrate, It may include ammonium metatungstate hydrate and one or more of its derivatives.

14. In any one of embodiments 5 to 13, the second metal oxide precursor may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the first metal oxide precursor.

15. In any one of embodiments 5 to 14 above, the heat treatment in step (d) may be performed at 400 to 800°C.

16. Another aspect of the present invention relates to a carbon monoxide detection sensor comprising a bimetallic nanofiber composite.

The carbon monoxide detection sensor includes a substrate; and

It includes a heterogeneous metal nanofiber composite laminated on the substrate.

17. In the 16th embodiment above, the carbon monoxide detection sensor may have a carbon monoxide reactivity increase rate of 15% or more according to Equation 1 below.

[Equation 1]

Carbon monoxide reactivity increase rate = [electrical resistance change (R/R ₀ ) / gas concentration (ppm)] × 100

The heterogeneous metal nanofiber composite according to the present invention is a one-dimensional nanofiber containing a copper oxide-based heterogeneous metal oxide, and nanometal particles, which are metal catalysts, are dispersed at a high concentration on the outer and inner surfaces of the nanofiber, thereby providing selectivity for carbon monoxide gas. Excellent.

In addition, the heterogeneous metal nanofiber composite manufacturing method concentrates the metal nanoparticles through solvent substitution through selective evaporation of the metal nanoparticle solution, which can greatly increase the concentration of metal nanoparticles without agglomeration between nanoparticles, thereby producing a high concentration of metal nanoparticles. Containing nanofibers can be manufactured.

In addition, a carbon dioxide detection sensor containing a heterogeneous metal nanofiber composite has selectivity for carbon monoxide gas among various types of gases, and the reactivity of carbon monoxide can be increased by more than 15% compared to the case where metal nanoparticles, which are metal catalysts, are not included. You can.

Figure 1 is a process flow chart of a heterogeneous nanofiber composite manufacturing method according to another aspect of the present invention.
Figure 2 is a photograph of a flask containing 150 mL of a mixed solution of an aqueous gold nanoparticle solution and a first polymer solution in a rotary evaporator and a solvent-exchanged concentrate in one embodiment of the present invention.
Figure 3 is a transmission scanning electron microscope photograph of a solvent-exchanged concentrate according to one embodiment of the present invention.
Figure 4 is a scanning electron microscope photograph of a heterogeneous nanofiber composite according to one embodiment of the present invention.
Figure 5 is a graph showing the amount of change in electrical resistance (R/R ₀ ) according to gas concentration of a carbon monoxide gas detection sensor including a heterogeneous metal nanofiber composite containing gold nanoparticles according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings. However, the following drawings are provided only to aid understanding of the present invention, and the present invention is not limited by the following drawings. In addition, the shape, size, ratio, angle, number, etc. disclosed in the drawings are illustrative and the present invention is not limited to the matters shown.

Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

When the positional relationship between two parts is described as ‘on’, ‘at the top’, ‘at the bottom’, ‘next to’, etc., unless ‘immediately’ or ‘directly’ is used, there is no difference between the two parts. One or more different parts may be located.

Positional relationships such as 'upper', 'top', 'lower', 'lower', etc. are only written based on the drawings, and do not represent absolute positional relationships. In other words, depending on the observation position, the positions of 'top' and 'bottom' or 'top' and 'bottom' may change.

In this specification, “a to b” indicating a numerical range is defined as “≥a and ≤b”.

One aspect of the present invention relates to bimetallic nanofiber composites.

The heterogeneous metal nanofiber composite includes nanofibers and metal nanoparticles.

The nanofibers are hollow and contain different metal oxides.

The heterogeneous metal oxide may include one or more different metal oxides.

In one embodiment, the different metal oxide may include a first metal oxide and a second metal oxide.

The first metal oxide includes copper oxide (CuO).

The heterogeneous metal oxide can contain copper oxide and form a one-dimensional nanofiber by electrospinning, and a p-type metal oxide such as copper oxide can form a p-n junction at the interface with the n-type metal oxide, which is formed at this time. The p-n junction interface is capable of efficient hole generation and can exhibit excellent electronic conductivity when carbon monoxide gas is added.

The second metal oxide may include one or more types from the group consisting of ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, Co ₃ O ₄ , CeO ₂ , and MnO ₂ .

The nanofiber may contain 1 to 30 parts by weight of the second metal oxide based on 100 parts by weight of the first metal oxide.

Within the above range, one-dimensional nanofibers made of copper oxide-based heterogeneous metal oxides including the first metal oxide and the second metal oxide can be manufactured, and within the above range, the p-n junction within the nanofiber is formed uniformly to detect carbon monoxide. It can be used as a sensor.

Metal nanoparticles may be dispersed on the outer and inner surfaces of the nanofiber.

Since the nanofiber is one-dimensional and hollow, metal nanoparticles can be dispersed on the outer and inner surfaces of the nanofiber.

The metal nanoparticle may be one or more of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir).

The above type of metal nanoparticles act as a catalyst for the decomposition reaction of gases on the surface of the metal oxide, and the products produced by decomposition can be transferred to the surface of the metal oxide through a spill over phenomenon to increase the resistance change effect. .

Specifically, when the metal nanoparticle is selected as gold (Au), it is highly desirable because it increases the resistance change effect through strong interaction with carbon monoxide.

In one embodiment, the metal nanoparticles are included in an amount of 2wt% to 5wt%.

The heterogeneous metal nanofiber composite can increase gas reactivity by including the metal nanoparticles within the above range. If it is less than the above range, the change in resistance is small, making it difficult to increase the gas reactivity, and the selectivity to carbon monoxide is reduced. If it exceeds the above range, it is dispersed on the surface of the heterogeneous metal oxide while preventing agglomeration of the metal nanoparticles, and the outer surface of the nanofiber. It is difficult to distribute uniformly on the inner surface.

In one embodiment, the heterogeneous nanofiber composite may have an average diameter of 50 nm to 10 μm and an average length of 1 μm to 500 μm.

The heterogeneous nanofiber composite is formed by electrospinning and has dimensions within the above range, and is capable of selective reaction bonding to various gases, especially carbon monoxide, to induce a change in resistance.

Another aspect of the present invention relates to a method for producing a heterogeneous metal nanofiber composite.

Figure 1 is a process flow chart of a heterogeneous nanofiber composite manufacturing method according to another aspect of the present invention.

Referring to Figure 1, the method for producing a heterogeneous metal nanofiber composite includes (a) preparing a first mixed solution containing a metal nanoparticle dispersion and a first polymer solution;

(b) preparing a metal nanoparticle concentrate by evaporating the first mixed solution;

(c) preparing a second mixed solution containing a first metal oxide precursor, a second metal oxide precursor, and a second polymer solution;

(d) preparing an electrospinning solution by mixing the second mixed solution with the metal nanoparticle concentrate;

(e) producing nanofibers by electrospinning the electrospinning solution; and

(f) heat treating the nanofibers.

First, prepare a first mixed solution containing a metal nanoparticle dispersion and a first polymer solution (S100).

In one embodiment, the metal nanoparticle precursor may include one or more of silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir). .

The above types of metals can be formed into nanoparticles and used as catalysts for gas decomposition reactions on the surface of metal oxides.

The metal nanoparticle dispersion may contain 0.001 wt% to 0.1 wt% of metal nanoparticles.

The metal nanoparticle dispersion is a state in which metal nanoparticle precursors are dispersed in water. The metal nanoparticle dispersion contains the metal nanoparticles within the above content range, and the metal nanoparticle dispersion can be concentrated to a high concentration. If the content exceeds the above range, aggregation of the metal nanoparticles may occur.

The first polymer solution is intended to increase the concentration of metal nanoparticles by replacing water, which is the solvent of the metal nanoparticle dispersion.

In one embodiment, the first polymer solution includes a polymer and a solvent, and the solvent is N-methylpyrrolidone, dimethyl sulfoxide, isopropyl myristate, Trichlorobenzene, Dichlorobenzene, Dimethyl acetamide, N,N'-dimethylformamide, Isoamylalcohol, Propyl alcohol ), Butyl alcohol, Pentyl alcohol, Ethylene glycol, Methoxyethanol, Methyl isobutyl ketone, Butyl acetate, Tetrachloroethane It may include one or more of Tetrachloroethane, Pentachloroethane, Chlorobenzene, Xylene, and Tetrachloroethylene.

This type of solvent has a lower vapor pressure than water (H ₂ O), which is the solvent for the metal nanoparticle precursor, and does not evaporate when the pressure is reduced to close to a vacuum, so the concentration of metal nanoparticles can be increased by replacing the water.

The first polymer solution contains polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, polyvinylidene fluoride, Polysulphone, Polyethersulphone, Polyarylsulphone, Epoxypolyurethane, Polyimide, Polyvinyl chloride, Polyetherketone, Aromatic Polyester (Aromatic polyester), Polyamidoimide, Polyvinylacetate, Polymethylmethacrylate, Polystyrene, Polyoxymethylene, Polyacrylic acid, poly It may include one or more of urethane, polyethylene, and polytrimethylene terephthalate.

The above type of polymer can be dissolved in the solvent of the first polymer solution to form a uniform first polymer solution, and is very advantageous for producing one-dimensional nanofibers by electrospinning.

In one embodiment, the first polymer solution may include 5wt% to 20wt% of the polymer.

Within the above range, one-dimensional nanofibers can be manufactured by electrospinning including the polymer, and the polymer can be efficiently removed by heat treatment.

In one embodiment, in S100, 0.05 to 10 parts by volume of the first polymer solution may be mixed with the metal nanoparticle precursor.

The first polymer solution is added in a small amount compared to the metal nanoparticle precursor, and the solvent of the metal nanoparticle dispersion disappears in the subsequent concentration process, so the polymer solution occupies most of the volume of the metal nanoparticle concentrate, During electrospinning, the amount of the first polymer solution added can be determined by considering the volume of the second polymer solution.

When an electrospinning solution is prepared and electrospun using a metal nanoparticle precursor to which the first polymer solution is not added, agglomeration of metal nanoparticles occurs, but when the first polymer solution is added within the above range, the metal nanoparticles While preventing agglomeration, a metal nanoparticle concentrate can be effectively produced by evaporating water, which is a solvent for the metal nanoparticle precursor.

The first mixed solution is evaporated to prepare a metal nanoparticle concentrate (S200).

In the case of a metal oxide nanofiber substrate sensing material using metal nanoparticles as a catalyst, metal nanoparticles are added as is to the electrospinning solution and dispersed on the outer and inner surfaces of the nanofiber, resulting in a metal nanofiber with high uniformity and small size. Because particles are used, the types of electrospinning solution and metal nanoparticle solution are different, which not only greatly reduces electrospinning efficiency, but also causes agglomeration between metal nanoparticles, making it difficult to increase the content of metal nanoparticles above 1 wt%.

When water, which is the solvent of the metal nanoparticle dispersion, is evaporated and replaced with the solvent in the first polymer solution, the concentration of metal nanoparticles can be effectively increased, and the final content of metal nanoparticles contained in the nanofibers is reduced to 2 wt% or more. can be increased.

Specifically, in S200, a rotary evaporation concentrator is used to evaporate the metal nanoparticle dispersion, and when the inside of the concentrator is depressurized to form an atmosphere close to a vacuum, water, which is a solvent in the metal nanoparticle dispersion, is evaporated and more than the water. The solvent in the first polymer solution, which has a low vapor pressure, may remain and cause solvent displacement.

In order to form an atmosphere close to the vacuum, it is preferable to maintain a pressure lower than the vapor pressure of water and higher than the vapor pressure of the first polymer solution, and when the volume of the concentrate is reduced to the range of 50 to 99%, the concentrate from the rotary evaporator The metal nanoparticle concentrate preparation step can be completed by separating, and in this case, concentration is possible without agglomeration or reaction of the metal nanoparticles in the concentration process by solvent substitution.

A second mixed solution containing a first metal oxide precursor, a second metal oxide precursor, and a second polymer solution is prepared (S300).

The first metal oxide precursor and the second metal oxide precursor are inorganic metal salts, and different metal oxide precursors can be mixed to form metal oxide nanofibers.

In one embodiment, the first metal oxide precursor is copper (II) nitrate trihydrate, copper (II) chloride, copper (II) nitrate, copper (II) acetate, copper (II) acetylacetonate, copper (II) sulfate, and these. It may be one or more types of derivatives.

The first metal oxide precursor may form copper oxide to form one-dimensional nanofibers.

In one embodiment, the second metal oxide precursor is a metal salt different from the first metal oxide precursor, and specifically, cerium (III) nitrate hexahydrate, cerium (III) chloride, cerium (III) nitrate, cerium (III) sulfate, zinc (II) chloride, zinc (II) nitrate, tin (IV) chloride, cobalt (II) chloride, cobalt (II) nitrate, nickel (II) chloride, nickel (II) nitrate, iron (II) chloride, iron ( II) It may contain one or more of nitrate, ammonium metatungstate hydrate, and their derivatives.

The above types of metal salts can be added to form heterogeneous metal nanofibers.

In one embodiment, the second polymer solution may include 1 to 30 parts by weight of the second metal oxide precursor based on 100 parts by weight of the first metal oxide precursor.

If a heterogeneous metal oxide precursor is included within the above range, a heterogeneous nanofiber composite in which a p-n junction is formed can be produced by electrospinning.

Meanwhile, the second polymer solution containing the first metal oxide precursor and the second metal oxide precursor preferably contains the same solvent and polymer as the first polymer solution.

When the second polymer solution contains the same solvent and polymer as the first polymer solution, it is easy to mix with the solvent and polymer remaining in the concentrate, so the second polymer solution and the metal nanoparticle concentrate are mixed to conduct electricity. A spinning solution can be prepared.

An electrospinning solution is prepared by mixing the second mixed solution with the metal nanoparticle concentrate (S400).

An electrospinning solution can be prepared by mixing the second mixed solution with the metal nanoparticle concentrate.

Nanofibers are manufactured by electrospinning the electrospinning solution (S500).

The electrospinning solution is concentrated in metal nanoparticles and contains heterogeneous metal oxides to form heterogeneous metal nanofibers.

The nanofibers are heat treated (S600).

The heat treatment in step (d) may be performed at 400 to 800°C.

The heat treatment temperature is higher than the thermal decomposition temperature of the polymer in the first and second polymer solutions, so that the polymer can be thermally decomposed and removed, forming one-dimensional nanofibers.

Another aspect of the present invention relates to a carbon monoxide detection sensor comprising a bimetallic nanofiber composite.

The carbon monoxide detection sensor includes a substrate; and

It includes a heterogeneous metal nanofiber composite laminated on the substrate.

Specifically, the substrate may be alumina, and interdigitated gold electrodes may be formed on the upper surface at regular intervals.

The carbon monoxide detection sensor can increase carbon monoxide reactivity by more than 15% according to Equation 1 below.

[Equation 1]

Carbon monoxide reactivity increase rate = [electrical resistance change (R/R ₀ ) / gas concentration (ppm)] × 100

The carbon monoxide detection sensor has selectivity for carbon monoxide among various gases, and the increased amount of metal nanoparticles can increase the reactivity increase rate by more than 15% compared to the case where metal nanoparticles are not added.

Therefore, the heterogeneous metal nanofiber composite according to the present invention is formed from an electrospinning solution containing a concentrate formed by a solvent substitution method to prevent metal nanoparticles from agglomerating, so that the metal nanoparticles are uniformly dispersed on the outer and inner surfaces of the one-dimensional nanofiber. This can increase the gas decomposition reaction efficiency, and in particular, the selectivity for carbon monoxide and gas reactivity are increased, so it can be used as a carbon monoxide detection sensor.

Hereinafter, preferred examples are presented to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention and the scope of the present invention is not limited to the following examples.

Example 1: Preparation of heterogeneous metal nanofiber composite

(1) Manufacturing metal nanoparticle concentrate

Copper-cerium oxide composite nanofibers were manufactured as a heterogeneous nanofiber composite in which gold nanoparticles were added at a high dose.

First, to prepare a gold nanoparticle dispersion, 150 mL of a 2.2mM aqueous solution of sodium citrate tribasic dihydrate, 0.1 mL of a 2.5mM aqueous solution of tannic acid, and 150mM potassium carbonate (K ₂ CO ₃ ) 1 mL of aqueous solution was prepared and mixed in a 250 mL round flask, stirred at a speed of 260 RPM using a temperature-controllable magnetic stirrer, and heated until the temperature of the mixture reached 70°C.

When the mixed solution reached 70°C, 1 mL of 25 mM chloroauric acid trihydrate aqueous solution was added while stirring was in progress. At this time, the solution went from being transparent to immediately turning dark brown, and after about 5 minutes, the growth of the gold particles was completed, producing a gold nanoparticle dispersion with a bright red color. After removing the flask from the stirrer, it was immersed in running water and cooled to room temperature to prevent further reaction and agglomeration.

The first polymer solution in which polyvinylpyrrolidone (hereinafter referred to as 'PVP') with a molecular weight of 40,000 was mixed and dissolved in an N,N'-dimethylformamide (N,N'-dimethylformamide (hereinafter referred to as 'DMF') solvent at the same mass ratio. was prepared and mixed with the gold nanoparticle aqueous solution.

1 mL of the first polymer solution was added to about 150 mL of aqueous gold nanoparticle solution, and stirred at room temperature at a speed of 260 RPM for 10 minutes to prepare a mixed solution.

The round flask containing the mixed solution was mounted on a rotary evaporator, and the water bath of the rotary evaporator was maintained at 40°C. The mounted flask rotated at a speed of 60 RPM, and evaporation was induced by applying a vacuum pressure of 50 mBar.

The pressure was slowly reduced from normal pressure to 50 mBar to prevent the mixed solution from boiling over. At 40°C, water evaporates at 72 mBar, but DMF evaporates at 11 mBar, so water selectively evaporates under 50 mBar conditions and DMF remains. Then, the solvent was replaced to prepare a concentrate. At this time, the added PVP polymer served as a dispersant for the gold nanoparticles, preventing aggregation between gold nanoparticles even during selective evaporation.

Under the above conditions, it took about 15 minutes to evaporate 4 mL of solution.

(2) Manufacturing of heterogeneous metal nanofibers

First, 0.435 g of copper(II) nitrate trihydrate and 0.087 g of cerium(III) nitrate hexahydrate were dissolved in 4.72 g of DMF solvent, and 0.655 g of PVP with a molecular weight of 1,300,000 was added and dissolved through a magnetic bar. A second polymer solution was prepared by stirring. An electrospinning solution was prepared by adding 0.94 mL of gold nanoparticle concentrate to the second polymer solution and stirring it for 5 hours at room temperature at a speed of 300 RPM using a magnetic bar.

1.45 mL of the gold nanoparticle concentrate has a concentration of about 17.24 mM when the yield of gold nanoparticles is set to 100%. Based on this, when about 0.94 mL of the concentrate is mixed with the electrospinning solution, the final copper-cerium produced is Gold nanoparticles may be included in an amount of about 2 wt% based on the weight of the oxide heterogeneous nanofiber. Therefore, it was confirmed that the content of gold nanoparticles in heterogeneous nanofibers could be controlled by adjusting the amount of concentrate added because it was proportional to the gold nanoparticle concentrate.

The stirred electrospinning solution is placed in a syringe for electrospinning and connected to a syringe pump (Henke-Sass Wolf, 10 mL NORMJECT), and the electrospinning solution is discharged at a discharge rate of 0.01 mL/min. Electrospinning was performed by applying a voltage of 15 kV between a stainless steel needle (21 gauge) and a stainless steel current collector (SUS, 0.5 T) placed at a distance of 15 cm. The current collector plate rotated at a speed of 100 RPM and collected the electrospun nanofibers.

The nanofibers were then heat-treated in an air atmosphere using a small electric furnace (Ney, Vulcan 3-550). Heat treatment was performed by heating to a temperature of 550°C at a temperature increase rate of 5°C per minute, maintaining it for 2 hours, and then naturally cooling to room temperature. At this time, PVP, which constitutes the nanofiber, and organic substances such as citric acid and tannic acid added during the production of gold nanoparticles were thermally decomposed and removed, and the copper precursor and cerium precursor were oxidized to form copper oxide and cerium oxide, respectively, and finally, gold nanoparticles were removed. A copper-cerium heterogeneous metal nanofiber composite with a large amount of particles bound was manufactured.

Experimental Example 1: Confirmation of metal nanoparticle concentrate

Figure 2 is a photograph of a flask containing 150 mL of a mixed solution of an aqueous gold nanoparticle solution and a first polymer solution in a rotary evaporator and a solvent-exchanged concentrate in one embodiment of the present invention.

Referring to Figure 2, it was confirmed that 150 mL of gold nanoparticle aqueous solution was finally changed to 1.45 mL of concentrated solution after a process of about 10 hours.

In particular, it was confirmed that it was possible to concentrate more than 100 times without significant difference in color.

Figure 3 is a transmission scanning electron microscope photograph of a solvent-exchanged concentrate according to one embodiment of the present invention.

Referring to Figure 3, as a result of analysis at various magnifications, it was confirmed that the gold nanoparticles had an even distribution and small size even after concentration by solvent replacement, and existed in a uniform size without agglomeration.

Additionally, as a result of analyzing the lattice arrangement of the high-magnification image, it was confirmed that gold nanoparticles were formed.

Experimental Example 2. Confirmation of heterogeneous metal nanofiber composite

Figure 4 is a scanning electron microscope photograph of a heterogeneous nanofiber composite according to one embodiment of the present invention.

Referring to FIG. 4, the polymer was thermally decomposed and removed through a high-temperature heat treatment process in an oxidizing atmosphere, and the metal oxide precursor containing copper was completely oxidized to form a copper-cerium oxide complex containing a one-dimensional copper oxide-based heterogeneous metal oxide. Nanofibers were formed, and it was confirmed that gold nanoparticles were dispersed and distributed on the outer and inner surfaces.

Manufacturing Example 1. Nanofiber without metal nanoparticles

In order to confirm the effect of high-capacity gold nanoparticles on carbon monoxide detection performance, the copper-cerium heterometal nanofiber composite with a large amount of gold nanoparticles bound to it prepared in the example was compared with the copper-cerium heterometal nanofiber composite to which no gold nanoparticles were added. Metal nanofibers were prepared separately.

To prepare copper-cerium bimetallic nanofibers without gold nanoparticles, the same method as prepared in Example 2 was performed, but without adding gold nanoparticle concentrate.

Example 2. Manufacturing of carbon monoxide detection sensor

A detection sensor was manufactured to confirm the high selectivity and sensitivity to carbon monoxide of the copper-cerium bimetallic nanofiber composite prepared in Example 1.

The copper-cerium metal nanofiber composite with gold nanoparticles bound was dispersed in ethanol and then ultrasonic waves were applied for 10 minutes to evenly pulverize the nanofibers. The pulverized nanofibers were drop casted on an alumina (Al ₂ O ₃ ) substrate with an area of 3 mm It was coated using the (drop-casting) method. The coating method was performed by applying 4 μL of the pulverized nanofiber mixture onto the sensor substrate, drying it on a hot plate at a temperature of 60°C, and repeating the process 3 to 5 times to ensure that the sensing material was tightly applied between the gold electrodes. A micro heater was attached to the bottom of the sensor board to control the temperature of the board according to the applied voltage.

Comparative Example 1. Manufacturing of a carbon monoxide detection sensor without gold nanoparticles

Nanofibers without metal nanoparticles were prepared according to Preparation Example 1, and a gas detection sensor was manufactured by the method of Example 2.

Experimental Example 3. Confirmation of gas selectivity

In order to check the selective carbon monoxide detection pattern by assuming operating conditions in the insulating oil inside the transformer, the gas detection sensor characteristic evaluation device was set to have an oxygen (O ₂ ) concentration of 2% at all times, and acetylene (acetylene), a representative gas generated from insulating oil, was set to have a constant oxygen (O 2 ) concentration of 2%. While changing the concentrations of C ₂ H ₂ ), carbon monoxide (CO), and hydrogen (H ₂ ) within the range of 1-10 ppm, 100-180 ppm, and 10-100 ppm, respectively, the Responsiveness characteristics were evaluated.

The sensitivity of the sensor was measured by using Agilent's 34972A model to detect the resistance value that changes when each specific gas is flowed, and the reactivity to each gas (Response: R/R ₀ change in resistance, R: the amount of change in resistance through which the measurement gas is flowing). The sensitivity characteristics were confirmed by analyzing the resistance (R ₀ : base resistance in the measurement atmosphere). In particular, when setting R ₀ , an atmosphere filled with 2% oxygen and 98% nitrogen is set as the basic condition, which is intended to simulate the hypoxic atmosphere in the transformer as much as possible.

Figure 5 is a graph showing the amount of change in electrical resistance (R/R ₀ ) according to gas concentration of a carbon monoxide gas detection sensor including a heterogeneous metal nanofiber composite containing gold nanoparticles according to an embodiment of the present invention.

Referring to FIG. 5, test results of a gas sensor composed of copper-cerium bimetallic nanofibers prepared according to Example 2 and Comparative Example 1 and copper-cerium bimetallic nanofiber composites in which gold nanoparticles are dispersed are shown. It was.

From the left graph, the reactivity at 300°C when the concentration of acetylene gas increases to 1, 5, and 10 ppm, the reactivity when the concentration of carbon monoxide gas increases to 100, 150, and 180 ppm, and the concentration of hydrogen gas at 10, The reactivity when increasing to 50 and 100 ppm was shown over time.

The detection sensor (CC_ref) that does not contain gold nanoparticles shows relatively high reactivity to acetylene and hydrogen gas, and is similar to the reactivity level of carbon monoxide, showing no selectivity. However, when the amount of gold nanoparticles was increased to about 2 wt% for materials containing a large amount of gold nanoparticles, the reactivity to carbon monoxide increased by up to 15% in all concentration ranges, while the sensitivity to acetylene and hydrogen increased at all levels. It was confirmed that the concentration range was reduced by up to 40% and 75%, showing a selective response to carbon monoxide.

On the other hand, in the case of materials containing a small amount of gold nanoparticles, that is, materials added at 0.5 wt% or 1 wt%, the tendency for the sensitivity to acetylene and hydrogen to decrease is the same, but the sensitivity to carbon monoxide also decreases. Therefore, it was confirmed that adding a large amount of gold nanoparticles can have a clear effect for selective detection of carbon monoxide.

Therefore, the heterogeneous metal nanofiber composite according to the present invention can be used to manufacture nanofibers using heterogeneous metal oxides, but by increasing the content of metal nanoparticles using solvent substitution, they can be uniformly dispersed on the outer and inner surfaces of the nanofibers. , when the content of metal nanoparticles reached 2wt%, there was selectivity for carbon monoxide gas, and the gas reaction also increased by more than 15%, confirming that it could be used as a sensor for detecting carbon monoxide generated from insulating oil inside a transformer.

So far, the present invention has been examined focusing on the embodiments. A person skilled in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a restrictive perspective. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the equivalent scope should be construed as being included in the present invention.

Claims (17)

Hollow nanofibers containing different metal oxides; and
It is a heterogeneous metal nanofiber composite containing metal nanoparticles dispersed on the outer and inner surfaces of the nanofibers,
The metal nanoparticles are contained in 2 wt% to 5 wt% of the heterogeneous metal nanofiber composite,
Bimetallic nanofiber composite.
The method of claim 1, wherein the different metal oxides include 100 parts by weight of the first metal oxide and 1 to 30 parts by weight of the second metal oxide,
The first metal oxide is copper oxide (CuO),
The second metal oxide is a heterogeneous metal oxide containing one or more types from the group consisting of ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, Co ₃ O ₄ , CeO ₂ , and MnO ₂ . Metal nanofiber composite.
The method of claim 1, wherein the metal nanoparticles are one or more of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir). A heterogeneous metal nanofiber composite comprising a.
The heterogeneous metal nanofiber composite of claim 1, wherein the heterogeneous nanofiber composite has an average diameter of 50 nm to 10 μm and an average length of 1 μm to 500 μm.
(a) preparing a first mixed solution containing a metal nanoparticle dispersion and a first polymer solution;
(b) preparing a metal nanoparticle concentrate by evaporating the first mixed solution;
(c) preparing a second mixed solution containing a first metal oxide precursor, a second metal oxide precursor, and a second polymer solution;
(d) preparing an electrospinning solution by mixing the second mixed solution with the metal nanoparticle concentrate;
(e) producing nanofibers by electrospinning the electrospinning solution; and
(f) heat treating the nanofibers; including,
Method for manufacturing heterogeneous metal nanofiber composite.
The method of claim 5, wherein the metal nanoparticle precursor contains one or more of silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and iridium (Ir). Phosphorus, bimetallic nanofiber composite manufacturing method.
The method of claim 5, wherein the metal nanoparticle dispersion is a state in which the metal nanoparticle precursor is dispersed in water.
The method of claim 5, wherein the first polymer solution includes a polymer and a solvent, and the solvent is N-methylpyrrolidone, dimethyl sulfoxide, and isopropyl myristate. , Trichlorobenzene, Dichlorobenzene, Dimethyl acetamide, N,N'-dimethylformamide, Isoamylalcohol, Propyl Alcohol alcohol), Butyl alcohol, Pentyl alcohol, Ethylene glycol, Methoxyethanol, Methyl isobutyl ketone, Butyl acetate, Tetrachloro A method for producing a heterogeneous metal nanofiber composite comprising one or more of ethane, pentachloroethane, chlorobenzene, xylene, and tetrachloroethylene.
The method of claim 5, wherein the first polymer solution is polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, and polyvinylidene fluoride. Polyvinylidene fluoride, polysulphone, polyethersulphone, polyarylsulphone, epoxypolyurethane, polyimide, polyvinyl chloride, polyester ketone ( Polyetherketone, Aromatic polyester, Polyamidoimide, Polyvinylacetate, Polymethylmethacrylate, Polystyrene, Polyoxymethylene, Polyacrylic acid A method for producing a heterogeneous metal nanofiber composite comprising one or more of (polyacrylic acid), polyurethane, polyethylene, and polytrimethylene terephthalate.
The method of claim 5, wherein the first polymer solution contains 5 wt% to 20 wt% of the polymer.
The method of claim 5, wherein in step (a), 0.05 to 10 parts by volume of the first polymer solution is mixed with the metal nanoparticle dispersion.
The method of claim 5, wherein the first metal oxide precursor is copper (II) nitrate trihydrate, copper (II) chloride, copper (II) nitrate, copper (II) acetate, copper (II) acetylacetonate, copper (II) sulfate, and A method for producing a heterogeneous metal nanofiber composite, comprising one or more of these derivatives.
The method of claim 5, wherein the second metal oxide precursor is cerium (III) nitrate hexahydrate, cerium (III) chloride, cerium (III) nitrate, cerium (III) sulfate, zinc (II) chloride, zinc (II) nitrate, Among tin (IV) chloride, cobalt (II) chloride, cobalt (II) nitrate, nickel (II) chloride, nickel (II) nitrate, iron (II) chloride, iron (II) nitrate, ammonium metatungstate hydrate and their derivatives A method for producing a heterogeneous metal nanofiber composite comprising one or more types.
The method of claim 5, wherein the second polymer solution adds 1 to 30 parts by weight of the second metal oxide precursor based on 100 parts by weight of the first metal oxide precursor.
The method of claim 5, wherein the heat treatment is performed at 400 to 800°C.
Board; and
A carbon monoxide detection sensor comprising a heterogeneous metal nanofiber composite of any one of claims 1 to 4, which is laminated on the substrate.
The carbon monoxide detection sensor of claim 16, wherein the carbon monoxide detection sensor has a carbon monoxide reactivity increase rate of 15% or more according to the following equation 1:
[Equation 1]
Carbon monoxide reactivity increase rate = [electrical resistance change (R/R ₀ ) / gas concentration (ppm)] × 100