KR20190097755A - Gas sensor and mebber using metal oxide nanofibers including nanoscale catalysts and multichannel, and manufacturing method thereof - Google Patents

Abstract

Embodiments of the present invention relate to a gas sensor member, a gas sensor using the same, and a method for manufacturing the same, and more specifically, relate to a member for a gas sensor using a multichannel metal oxide nanofiber material in which a nanoparticle catalyst is functionalized by utilizing apoferritin containing the nanoparticle catalyst in an internal hollow structure to be uniformly bound to an internal multichannel and an external surface of nanofibers, a gas sensor, and a method for manufacturing the same.

Description

GAS SENSOR AND MEBBER USING METAL OXIDE NANOFIBERS INCLUDING NANOSCALE CATALYSTS AND MULTICHANNEL, AND MANUFACTURING METHOD THEREOF}

Embodiments of the present invention relate to a gas sensor member, a gas sensor, and a method for manufacturing the same using a nanoparticle catalyst and metal oxide nanofibers containing multi-channel pores, and specifically, phase separation of two polymers that are not mixed with each other. By combining phenomena and electrospinning to form multichannel pores inside the nanofibers, and using the animal protein apoferritin as a means of binding the nanoparticle catalysts, the nanoparticle catalysts are the internal multichannel and outer surfaces of the nanofibers. The present invention relates to a multi-channel metal oxide nanofiber uniformly bound to and functionalized to a gas sensor and a gas sensor utilizing the multi-channel metal oxide nanofiber as a member for a gas sensor and a method of manufacturing the same.

Resistance change type gas sensors based on metal oxide semiconductors have attracted much attention for their advantages such as simple manufacturing method, portability, and high sensitivity. Attempts to commercialize the metal oxide semiconductor-based resistance change type gas sensor in various fields, such as observing air pollutants, alcohol breathalyzers, sick house syndrome gas detectors and disease diagnosis using these advantages. In particular, as health care becomes more and more important, the exhalation analysis gas sensor technology, which can be used for early diagnosis and daily diagnosis of disease, has attracted much attention. Human exhalation contains a biomarker gas that represents a particular disease, and in a person's exhalation, a specific biomarker gas is present 2-10 times more than a healthy person. Diabetics, for example, contain two to six times more acetone gas in their exhalations than healthy people. Therefore, if a gas sensor can be used to selectively detect a specific biomarker gas contained in a person's exhalation, a specific disease can be diagnosed early. However, since human exhalation is very high and includes hundreds of mixed gases, it is required to develop a high sensitivity and high selectivity sensor capable of selectively detecting a specific biomarker gas even in a high humidity atmosphere. In addition, the biomarker gases in the exhalation are emitted at very low concentrations ranging from 10 parts per billion (ppb) to 10 parts per million (ppm), requiring the study of sensing materials that can selectively detect trace amounts of gases. Do.

The metal oxide semiconductor-based resistance change type gas sensor detects a specific gas by measuring a change in electrical resistance caused by adsorption and desorption reactions of gases generated on the surface of the sensing material. Therefore, in order to increase the sensitivity of the gas sensor, it is necessary to increase the surface area of the sensing material, thereby increasing the surface reaction of the sensing material and the specific gas. In addition, the hollow sensing material promotes the diffusion of gas into the inside as well as the outside of the sensing material, allowing the sensing material to react more efficiently with the gas. In addition, it is possible to increase the selective surface reaction by binding a catalyst to the sensing material surface. Catalysts used in metal oxides for gas sensors typically include chemical sensitizers such as platinum (Pt) and gold (Au) and electronic sensitizers such as palladium (Pd) and nickel (Ni). have. These catalysts enhance the selective surface reaction of the sensing material and the target gas, and promote the adsorption and desorption reaction of the gas, thereby greatly improving the sensing characteristics of the gas sensor.

It is essential to utilize nanomaterials with functionalized catalysts in order to meet the above-mentioned gas sensor enhancement strategies. Nanomaterials are expected to effectively increase the reaction of gases because they have a very large surface area. Therefore, researches using various nanostructures such as nanoparticles, nanofibers, and nanosheets as sensing materials of gas sensors have been actively conducted. In particular, nanofibers have a one-dimensional structure with a high aspect ratio, and are promoted as a sensing material of gas sensors because they promote the diffusion of gas through a plurality of pores formed by intertwining nanofibers. Electrospinning is a method of synthesis of nanofibers, which is very simple and variously applicable. In particular, the electrospinning can synthesize the one-dimensional nanofibers with the catalyst bound very simply by mixing the catalyst particles in the solution. Because of these advantages, researches using nanofibers synthesized through electrospinning as sensing materials for gas sensors have been actively conducted.

Despite these findings, disease-detecting gas sensors have not been commercialized yet. In fact, for the commercialization of gas sensors capable of diagnosing diseases through exhalation analysis, high-sensitivity characteristics capable of detecting 10 ppb to 10 ppm level gas, fast response time within seconds for use as a real-time analysis device, and specific gas only are selected. Both the ability to detect and the stability to which the reaction force does not decrease even after hundreds of reactions must be secured. In order to meet the above-mentioned elements, not only the nano-sized catalyst should be uniformly bound to the sensing material, but also the synergy between the catalyst and the nanostructure should be created through the shape control of the sensing material. In other words, it is necessary to study the structure that can maximize the effect of the catalyst.

Embodiments according to the present invention comprises a nanoparticle catalyst having a size of 1-5 nm in the inner hollow of the apoferritin, which is an animal protein, and combines phase separation and electrospinning of two polymers that are not mixed with each other. , A composite nanofiber having a plurality of second polymer fibers occupying a discontinuous phase inside the first polymer fiber occupying a continuous phase of the nanofibers, and having apoferritin containing nanoparticle catalysts in the inner hollow uniformly in and on the surface thereof The second polymer fibers are decomposed through high temperature heat treatment, and multi-channel pores are formed in the nanofibers, the apoferritin is decomposed, and the nanoparticle catalysts are uniformly bound to the inner multi-channel and outer surface of the nanofibers. To provide a method for synthesizing functionalized sensing materials.

In particular, the formation of multiple channels not only increases the gas response through increasing the specific surface area, but also increases the sensitivity, and provides an efficient gas reaction through the structure in which gas can diffuse into the nanofibers. Sensing properties are dramatically increased because the internally bound catalyst is also functionalized. In addition, in the high temperature heat treatment process of the nanofibers, as the thermal decomposition of the second polymer occupying the discontinuous phase occurs at a higher temperature than the crystallization of the metal oxide precursor, the heat transferred to the metal oxide particles is reduced, and the plurality of second polymer fibers The growth of the metal oxide particles is suppressed by the support in the interior of the dummy nanofibers, thereby forming a metal oxide having a small particle size. This small particle size maximizes the resistance change depending on the presence or absence of gas, resulting in high sensitivity to detect even the smallest amount of gas. In the present invention, the nanoparticle catalyst is uniformly bound to the internal multi-channel and the outside of the nanofiber, and functionalized, multi-channel metal oxide nanofiber sensing material synthesis technology having a small particle size and a gas sensor technology using the same .

The metal oxide precursor is oxidized and crystallized by heat treatment to a composite nanofiber including apoferritin containing a nanoparticle catalyst in an internal hollow, two polymers and metal oxide precursors which are not mixed with each other to form metal oxide nanofibers. In the metal oxide nanofibers, multichannels are formed by phase separation of the two polymers, and the apoferritin is removed by the heat treatment. It provides a multi-channel metal oxide nanofiber, characterized in that the nanoparticle catalyst is bound and functionalized.

According to one side, the composite nanofiber, by the phase separation of the two polymers, comprises a first polymer fiber mixed with the metal oxide precursor while occupying a continuous phase of the nanofiber, the inside of the first polymer fiber It further comprises a plurality of second polymer fibers occupying a discontinuous phase, it may be characterized in that it further comprises the apoferritin on the surface and inside.

According to another aspect, through the heat treatment, the metal oxide precursor is in the form of a multi-channel formed in the nanofibers by removing the second polymer fibers in the process of thermal decomposition of the first polymer fibers and the second polymer fibers Oxidized and maintained while crystallizing with a metal oxide, and the apoferritin is thermally decomposed to form pores in the nanofibers, and at the same time, the nanoparticle catalyst contained in the inner hollow of the apoferritin binds to the surface of the nanofibers and inside each of the multichannels. It may be characterized by.

According to another aspect, in the heat treatment process for the composite nanofibers, as the pyrolysis of the plurality of second polymer fibers occupying the discontinuous phase occurs at a relatively higher temperature than the crystallization of the metal oxide precursor, Heat may be reduced to limit the size of the metal oxide particles.

According to another aspect, the pyrolysis of the second polymer fiber may be characterized in that it occurs at a relatively higher temperature by a temperature included in the range of 50 to 150 ℃ than the crystallization of the metal oxide precursor.

According to another aspect, the size of the metal oxide particles forming the metal oxide nanofibers may be included in the range of 1 to 20 nm.

According to another aspect, the two polymers, polyvinylpyrrolidone, poly (styreneacrylonitrile), polystyrene, cellulose acetate, poly ( It is composed of a combination of a first polymer selected from ethylene oxide (poly (ethylene oxide)), poly (methyl methacrylate) (poly (methylmethacrylate)) and a second polymer containing polyacrylonitrile (polyacrylonitrile) It can be characterized.

According to another aspect, the weight ratio of the second polymer occupying the discontinuous phase in the composite nanofibers to the weight of the first polymer occupying the continuous phase in the composite nanofibers may be included in the range of 50 to 150% Can be.

According to another aspect, the number of the multi-channel, it is included in the range of 5 to 20 per one composite nanofiber, the diameter of the individual channels may be characterized in that it is included in the range of 10 to 50 nm.

According to another aspect, the apoferritin is a structure having a hollow inside, encapsulating one or more catalytic metal ions in the inner hollow, the diameter of the nanoparticle catalyst produced by reducing the catalytic metal ion is 1 to It may be characterized by being included in the range of 5 nm.

According to another aspect, the weight ratio of the nanoparticle catalyst may be included in the concentration range of 0.01 to 1 wt% compared to the multi-channel metal oxide nanofibers.

According to another aspect, the nanoparticle catalyst is platinum (IV) chloride, platinum (II) acetate, gold (I, III) chloride, gold (III) acetate, silver chloride, silver acetate, Iron (III) chloride, Iron (III) acetate, Nickel (II) chloride, Nickel (II) acetate, Ruthenium (III) chloride, Ruthenium Acetate, Iridium (III) chloride, Iridium acetate, Tantalum (V) chloride, Palladium (II) chloride, Lanthanum (III) It may be characterized by being formed by a catalytic metal ion synthesized, including at least one metal salt selected from acetate, copper (II) sulfate and Rhodium (III) chloride.

According to another aspect, the nanoparticle catalyst, Pt, Au, Ag, Fe, Ni, Ru, Ir, Ta, Pd, La, Cu, as the catalytic metal ions contained in the inner hollow of the apoferritin is reduced At least one nanoparticle catalyst selected from Rh, Co, Cr, Zn, W, Sn, Sr, In, Pb, V, Sb, Sc, Ti, Mn, Ga, and Ge, which is included in the interior hollow of the apoferritin, The nanoparticle catalyst contained in the hollow structure of the apoferritin is Pt, PtO, PtO ₂ , Au, Ag, Fe ₂ O ₃ , NiO, RuO ₂ , IrO ₂ , Ta ₂ O ₅ , PdO, PdO ₂ , after heat treatment. CuO, Rh ₂ O ₃ , Co ₃ O ₄ , Cr ₂ O ₃ , ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, V ₂ O ₅ , VO ₂ , VO, Sb ₂ O ₃ , Sc ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O ₃ and GeO _{2 may} be substituted with at least one nanoparticle catalyst to bind to the metal oxide nanofiber outer surface.

It provides a gas sensor comprising a sensing material formed by coating the multi-channel metal oxide nanofibers according to any one of the embodiments described above on a sensor electrode capable of measuring the resistance change.

A method for producing a multichannel metal oxide nanofiber, comprising the steps of: (a) synthesizing a nanoparticle catalyst inside a hollow structure of apoferritin; (b) dissolving two polymers which are not mixed with each other in a solvent together with a metal oxide precursor to synthesize an electrospinning solution; (c) composite electrospinning comprising apoferritin comprising the synthesized nanoparticle catalyst into the synthesized electrospinning solution and apoferritin containing a nanoparticle catalyst, a metal oxide precursor, and two polymers not mixed with each other Preparing a solution; (d) electrospinning the complex electrospinning solution to prepare a composite nanofiber in which apoferritin containing a nanoparticle catalyst is bound on and inside the metal oxide precursor and the polymer composite nanofiber; And (e) heat treating the composite nanofibers to produce functionalized multichannel metal oxide nanofibers by uniformly binding a nanoparticle catalyst to the inner multichannel and outer surface of the multichannel metal oxide nanofibers. Provided is a method for producing a multichannel metal oxide nanofiber.

According to one side, in the step (a), in order to embed the nanoparticle catalyst in the inner hollow of the apoferritin, the catalyst metal salt is added to the solution in which the apoferritin is dissolved to incorporate catalyst metal ions, and a reducing agent is added. To reduce the catalytic metal ions to catalytic metal particles.

According to another aspect, the step (a), the reducing agent for reducing the catalytic metal ions embedded in the hollow of the apoferritin, sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ), nascent (atomic) hydrogen , zinc-mercury amalgam (Zn (Hg)), oxalic acid (C ₂ H ₂ O ₄ ), formic acid (HCOOH), ascorbic acid (C ₆ H ₈ O ₆ ), sodium amalgam, diborane and iron (II) sulfate It may be characterized by including at least one of.

According to another aspect, in the step (e), in the process of thermally decomposing the apoferritin and the two polymers by the heat treatment, the second polymer occupying the discontinuous phase is decomposed to form a multi-channel The first polymer, which is a continuous phase, is decomposed and the metal oxide precursor mixed with the first polymer is oxidized and crystallized while maintaining the form of the formed multichannel, and the apoferritin is decomposed and the nanoparticle catalyst contained in the internal hollow is It may be characterized in that the binding to the inside of the formed multi-channel and the table of nanofibers.

According to another aspect, in the step (e), the apoferritin is a hollow structured animal protein, the pores having a size in the range of 1 to 15 nm in the nanofibers as the protein shell is decomposed during the heat treatment process It may be characterized by forming a.

According to another aspect, the manufacturing method of the multi-channel metal oxide nanofibers, (f) the multi-channel metal oxide nanofibers are pulverized and dispersed in a solvent, spin coating, drop coating on the sensor electrode for resistance-type gas sensor And coating by using at least one coating process of inkjet printing.

According to the present invention, when synthesizing a multi-channel metal oxide nanofibers in which a nano-sized catalyst is bound by using a phase separation phenomenon of two polymers that are not mixed with each other and apoferritin including a nanoparticle catalyst, the nanoparticle catalyst It provides electronic or chemical sensitization effect, the specific surface area is increased through multi-channel nanofiber structure to increase the gas reaction area, and gas can easily penetrate into the channel, so that gas can be The efficiency of the catalyst is maximized because it provides the efficiency of all reactions and the catalyst present inside the nanofibers through the channel, thereby producing multi-channel metal oxide nanofiber sensing materials with excellent sensitivity and selective sensing ability. have. In addition, in the high temperature heat treatment process of the nanofibers, as the thermal decomposition of the second polymer occupying the discontinuous phase occurs at a higher temperature than the crystallization of the metal oxide precursor, the heat transferred to the metal oxide particles is reduced, and the plurality of second polymer fibers The growth of the metal oxide particles is suppressed by the support in the interior of the dummy nanofibers, thereby forming a metal oxide having a small particle size. This small particle size maximizes the resistance change depending on the presence or absence of gas, resulting in high sensitivity to detect even the smallest amount of gas. In addition, since the nanostructured catalyst is embedded in the hollow structure of apoferritin and these nanoparticle catalysts are uniformly bound to the surface of the metal oxide nanofiber due to the excellent dispersibility of the apoferritin, agglomeration between the catalyst particles is maintained even at a high driving temperature. It can be expected that very excellent catalytic effect does not occur, has the effect to disclose a gas sensor member, a gas sensor and a method of manufacturing the same having a selective sensing ability, stability and excellent sensing characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings included as part of the detailed description in order to provide a thorough understanding of the present invention provide examples of the present invention and together with the detailed description, describe the technical idea of the present invention.
1 is a schematic view of a member for a multi-channel metal oxide nanofiber gas sensor functionalized by the nano-sized catalyst uniformly bound to the inner multi-channel and outer surface of the nanofiber according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a method of manufacturing a gas sensor using a multi-channel metal oxide nanofiber structure in which a nano-sized catalyst is uniformly bound to an inner multi-channel and an outer surface of a nanofiber according to an embodiment of the present invention.
Figure 3 is a process for producing a multi-channel metal oxide nanofiber structure functionalized by the nano-sized catalyst uniformly bound to the inner multi-channel and the outer surface of the nanofiber through the electrospinning and heat treatment process according to an embodiment of the present invention It is a picture showing.
Figure 4 is a transmission electron micrograph of apoferritin containing Pt nanoparticle catalyst according to Example 1 of the present invention.
5 is a composite comprising apoferritin, polyvinylpyrrolidone, polyacrylonitrile, and tin oxide precursors including a Pt nanoparticle catalyst synthesized after electrospinning according to Example 2 of the present invention. Scanning electron micrographs of nanofibers.
FIG. 6 is a scanning electron micrograph of multi-channel SnO ₂ nanofibers in which Pt nanoparticles synthesized after the high-temperature heat treatment according to Example 2 of the present invention are uniformly bound to the inner multichannel and outer surface of the nanofibers.
FIG. 7 is a transmission electron microscope photograph and a component analysis photograph of multi-channel SnO ₂ nanofibers in which Pt nanoparticles synthesized after the heat treatment according to Example 2 of the present invention are uniformly bound to the inner multichannel and outer surface of the nanofibers.
8 is a scanning electron micrograph of the SnO ₂ nanofibers to which the Pt nanoparticle catalyst prepared in Comparative Example 1 of the present invention is bound.
FIG. 9 is a scanning electron micrograph of SnO ₂ nanofibers having no Pt nanoparticle catalyst prepared through Comparative Example 3 of the present invention.
Figure 10 is an experimental example of the present invention, Comparative Example 3 and the embodiment according to 2, Pt nanoparticle catalyst is not a binding SnO ₂ nanofibers and Pt nanoparticle catalysts that form the binding of the multi-channel SnO ₂ nanofiber In the process, polyvinylpyrrolidone, composite nanofibers of tin oxide precursors and apoferritin containing Pt nanoparticle catalysts, polyvinylpyrrolidone, polyacrylonitrile, and tin oxide precursors It is a graph showing the change of mass and the degree of heat transfer according to the heat treatment of the composite nanofibers.
11 shows Experimental Example 2 of the present invention, Example 2 and Comparative Examples 1, 2, and 3 according to the Pt nanoparticle catalyst-bound multi-channel SnO ₂ nanofibers, Pt nanoparticle catalyst-binding SnO ₂ nanofibers, Reactivity graph of acetone gas (0.4-5 ppm) at 400 ° C. of a multichannel SnO ₂ nanofiber without Pt nanoparticle catalyst and SnO ₂ nanofiber based gas sensor without Pt nanoparticle catalyst.
12 shows Experimental Example 2 of the present invention, Example 2 and Comparative Examples 1, 2, and 3 according to the Pt nanoparticle catalyst-bound multi-channel SnO ₂ nanofibers, Pt nanoparticle catalyst-binding SnO ₂ nanofibers, When the concentration of acetone is 1, 2, 3, 4, 5 ppm at 400 ° C. of a multichannel SnO ₂ nanofiber without Pt nanoparticle catalyst and SnO ₂ nanofiber based gas sensor without Pt nanoparticle catalyst This is a property evaluation result of reaction speed of gas sensor.
FIG. 13 shows Experimental Example 2 of the present invention, wherein 1 ppm of gases (acetone, hydrogen sulfide, toluene, ethanol, at 400 ° C.) of a multi-channel SnO ₂ nanofiber-based gas sensor bound with a Pt nanoparticle catalyst according to Example 2 Methane, carbon monoxide, formaldehyde, ammonia).
FIG. 14 shows experimental results of repeated sensitivity measurement of 1 ppm of acetone gas at 400 ° C. of a multi-channel SnO ₂ nanofiber-based gas sensor in which Pt nanoparticle catalysts according to Example 2 are bound.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be described in detail with reference to the accompanying drawings.

In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as 'first' and 'second' may be used to describe various components, but the components are not limited by the terms, and the terms are only used to distinguish one component from another component. Used.

Hereinafter, a gas sensor member, a gas sensor and a nanoparticle catalyst embedded in the hollow structure of apoferritin are functionally bound to the internal multichannel and the external surface of the multichannel metal oxide nanofibers and functionalized. The manufacturing method will be described in detail with reference to the accompanying drawings.

In one embodiment of the present invention by synthesizing apoferritin / catalyst, the nanoparticle catalysts are uniformly bound to the inner multi-channel and outer surface of the nanofibers, the effect of the multi-channel and uniformly distributed nano-sized catalyst It provides a sensing material including the effect and a member manufacturing method for a gas sensor using the same.

According to this embodiment, a sensing material and a method for manufacturing a gas sensor member using the same include: (a) embedding a nanoparticle catalyst in a hollow structure of apoferritin; (b) dissolving two polymers and a metal oxide precursor which are not mixed with each other in a solvent to synthesize an electrospinning solution; (c) mixing the apoferritin containing the nanoparticle catalyst with the electrospinning solution to prepare a composite electrospinning solution composed of the apopertin / metal oxide precursor / two polymers with the nanoparticle catalyst; (d) electrospinning the complex electrospinning solution to prepare a composite nanofiber in which apoferritin containing the nanoparticle catalyst is uniformly contained on the surface and inside of the metal oxide precursor / two polymer composite nanofibers; (e) Through high temperature heat treatment, the polymer is thermally decomposed to form multichannels in the nanofibers, the metal oxide precursor is oxidized and crystallized, and the apoferritin is thermally decomposed so that the nanoparticle catalyst is multi-channeled inside the multichannel metal oxide nanofibers. Preparing functionalized multichannel metal oxide nanofibers uniformly bound to the channel and the outer surface; (f) Grinding and dispersing the multi-channel metal oxide nanofibers in which the nano-sized catalyst is bound in a solvent, and coating at least one of spin coating, drop coating, inkjet printing, and dispensing on the sensor electrode for a resistive gas sensor. It may include the step of coating using.

At this time, in step (a), apoferritin is an animal protein having an internal hollow of 8 nm in size, and may include one or more catalytic metal ions in the internal hollow, and have a diameter of 1-5 nm through a reduction process. To form nanoparticles with a range. In order to embed the catalytic metal ions into the interior hollow of the apoferritin, a catalyst metal salt is added to the solution in which the apoferritin is dissolved to embed the catalyst metal ions, and a reducing agent is added to reduce the catalyst metal ions to the catalyst metal particles. Representative metal salts used to embed catalytic metal ions into the internal hollow of apoferritin include platinum (IV) chloride, platinum (II) acetate, gold (I, III) chloride, gold (III) acetate, silver chloride, silver acetate, Iron (III) chloride, Iron (III) acetate, Nickel (II) chloride, Nickel (II) acetate, Ruthenium (III) chloride, Ruthenium Acetate, Iridium (III) chloride, Iridium acetate, Tantalum (V) chloride, Palladium (II) chloride, Lanthanum (III) acetate, Copper (II) sulfate, and Rhodium (III) chloride, and the metal ions embedded in these metal salts are reduced and Pt, Au, Ag, Fe, Ni , Ru, Ir, Ta, Pd, La, Cu, Rh, Co, Cr, Zn, W, Sn, Sr, In, Pb, V, Sb, Sc, Ti, Mn, Ga, and Ge. Reducing agents for reducing metal ions include sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ), nascent (atomic) hydrogen, zinc-mercury amalgam (Zn (Hg)), oxalic acid (C ₂ H ₂ O ₄ ), formic acid (HCOOH), ascorbic acid (C ₆ H ₈ O ₆ ), sodium amalgam, diborane and iron (II) sulfate. The final synthesized, apoferritin containing the nanoparticle catalyst is prepared by centrifugation and washing followed by dispersion in a solvent.

In addition, step (b) is a step of dissolving two polymers that are not mixed with the metal oxide precursor in one solvent. Representative metal oxide precursors include acetates, nitrates, chlorides, acetylacetonates, methoxides, ethoxides, butoxides, butoxides containing metals, Isopropoxide and sulfide are two types of polymers that are not mixed with each other. , polystyrene and polyacrylonitrile, poly (ethylene oxide) and polyacrylonitrile. These two polymers can be dissolved in the same solvent, but they cannot be mixed with each other, resulting in phase separation into a first polymer occupying a continuous phase in a solvent and a second polymer occupying a discontinuous phase. The weight ratio of the second polymer may be variously adjusted in the range of 50-150% relative to the weight of the first polymer.

In addition, in step (c), the apoferritin containing the nanoparticle catalyst synthesized in the step (a) is mixed with the electrospinning solution synthesized in the step (b), and the nanoparticle catalyst is embedded in the apoferritin / It is a step of preparing a composite electrospinning solution consisting of a metal oxide precursor / two polymers. In the state in which the solution synthesized in step (b) is stirred, a solution of apopertin in which the nanoparticle catalyst is embedded is slowly added to prepare a composite electrospinning solution. When the electrospinning solution is prepared, the concentration of the apoferritin in which the nanoparticle catalyst is embedded may be adjusted in a range of 0.01-1 wt% relative to the metal oxide.

In addition, the step (d), by electrospinning the composite electrospinning solution synthesized in the step (c) to synthesize a composite nanofiber composed of apopertin / metal oxide precursor / two polymers containing a nanoparticle catalyst Step. In the process of electrospinning the nanofibers, due to the phase separation of the two polymers that are not mixed with each other, a plurality of second polymer fibers that occupy the discontinuous phase inside the first polymer fibers occupying the continuous phase of the nanofibers, The metal oxide precursor is present with the first polymer which can be mixed, and due to the excellent dispersibility of the apoferritin in which the nanoparticle catalyst is embedded, the apoferritin / catalyst is uniformly distributed inside and on the surface of the composite nanofiber. Have

In addition, in the step (e), through the high temperature heat treatment of the composite nanofibers synthesized in the step (d) at 500-700 ℃, the second polymer occupying the discontinuous phase is decomposed to leave multiple channels inside the nanofibers. The multi-channel metal oxide nanofibers, in which the metal oxide precursor is oxidized and crystallized while maintaining the multi-channel form, and the nanoparticle catalyst, which is decomposed and contained in the inner hollow, is uniformly bound to the multi-channel and outer surface of the nanofibers. Synthesize. In this heat treatment process, since the temperature at which the second polymer is pyrolyzed is 50 to 150 ° C. higher than the crystallization temperature of the metal oxide precursor, the heat transferred to the metal oxide particles is reduced, and the plurality of second polymer fibers are separated from the nanofibers. The growth of the metal oxide particles is suppressed by the support therein, thereby forming a metal oxide having a small particle size of 1 to 20 nm. In addition, the apoferritin is an animal protein consisting of an outer diameter of 12 nm and an inner diameter of 8 nm, and is characterized by leaving micropores having a size range of 1 to 15 nm in the nanofibers as the protein shell is decomposed during the heat treatment. In addition, the nanoparticle catalyst contained in the hollow structure of apoferritin is Pt, PtO, PtO ₂ , Au, Ag, Fe ₂ O ₃ , NiO, RuO ₂ , IrO ₂ , Ta ₂ O ₅ , PdO, PdO ₂ after heat treatment. , CuO, Rh ₂ O ₃ , Co ₃ O ₄ , Cr ₂ O ₃ , ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, V ₂ O ₅ , VO ₂ , VO, Sb ₂ O ₃ , It may be substituted with at least one nanoparticle catalyst of Sc ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O _3, and GeO ₂ . In addition, the metal oxide nanofibers formed at this time are ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, TiO ₂ , CuO, In ₂ O ₃ , Zn ₂ SnO ₄ , Co ₃ O ₄ , PdO, LaCoO ₃ , NiCo ₂ O ₄ , Ca ₂ Mn ₃ O ₈ , ZrO ₂ , Al ₂ O ₃ , B ₂ O ₃ , V ₂ O ₅ , Cr ₃ O ₄ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Ag ₂ V ₄ O ₁₁ , Ag ₂ O, Li _0.3 La _0.57 TiO ₃ , LiV ₃ O ₈ , RuO ₂ , IrO ₂ , MnO ₂ , InTaO ₄ , ITO, IZO, InTaO ₄ , MgO, Ga ₂ O ₃ , CaCu ₃ Ti _{4 O 12, Ag 3 PO 4} , BaTiO 3, NiTiO 3, SrTiO 3, Sr 2 Nb 2 O 7, Sr 2 Ta 2 O 7 and _{Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2} O more than one or two selected from _3-7 It can be composed of a variety of composite materials.

In addition, the step (f), after crushing the multi-channel metal oxide nanofibers with the nano-sized catalyst synthesized in the step (e) is dispersed in a solvent, the dispersion solution is prepared in advance for the resistance change type gas sensor Coating the sensor electrode using at least one coating process of spin coating, drop coating, ink-jet printing, and dispensing. As long as the sensing material can be uniformly coated on the sensor electrode, any coating method can be used.

Here, the size of the nanoparticle catalyst bound to the synthesized nanofibers has a range of 1-5 nm, the diameter of the nanofibers has a range of 300-500 nm. In addition, the size of one channel present in the interior of the nanofibers is in the range of 10-50 nm, the number is in the range of 5-20.

In the case of the synthesized sensing material, the nanoparticle catalyst of 5 nm or less is uniformly bound to the internal multichannel and the surface of the nanofiber, and functionalized, and as the multichannel is formed, the specific surface area increases, thereby increasing the gas reaction. The gas can be diffused in the nanofibers to provide an efficient gas reaction, and the catalyst particles present in the nanofibers can be functionalized to maximize the effect of the catalyst.

As such, two nanocomposite composite spinning solutions in which nanoparticle catalysts having a size range of 1-5 nm are embedded in the inner hollow of apoferritin, and apoferritin containing the nanoparticle catalyst is not mixed with a metal oxide precursor / After mixing, electrospinning may be performed to uniformly bind the apoferritin containing the nanoparticle catalyst to the surface and the inside of the metal oxide precursor / polymer composite nanofiber. During electrospinning, a plurality of second polymer fibers occupying discontinuous phases exist inside the first polymer fiber occupying the continuous phase of the nanofibers by phase separation of the two polymers, and the metal oxide precursor may be mixed with the first polymer. Apoferritin, which is present together in the fiber and contains the nanoparticle catalyst, may be uniformly included in the surface and the inside of the nanofiber. After the high temperature heat treatment process, the second polymer is thermally decomposed to leave multiple channels inside the fiber, the metal oxide precursor is oxidized and crystallized while maintaining a multi-channel form, and the apoferritin is thermally decomposed to form micropores in the nanofibers. In addition, the nanoparticle catalyst contained in the inner hollow is uniformly bound on the surface of the nanofibers and the multi-channels, thereby enabling the synthesis of functionalized sensing materials for gas sensors in large quantities.

Here, the nanoparticle catalysts are uniformly bound to a very small size (1-5 nm), thereby maximizing the effect of the catalyst when the gas reacts with the nanofibers, and the catalyst particles aggregate with each other even at high operating temperatures. This increases the stability of the gas sensor. In addition, the metal oxide having a small particle size is formed by the role of the second polymer in the high temperature heat treatment process, which maximizes the resistance change according to the presence or absence of gas, resulting in a high sensitivity characteristic that can detect a very small amount of gas. In addition, the structure of the multi-channel formed inside the nanofiber, resulting in an increased specific surface area, gas can easily penetrate the inside of the nanofiber to provide an efficient gas reaction, and the catalyst is also bound to the gas The contact characteristics of the catalyst can be maximized, maximizing the effect of the catalyst, thereby significantly increasing the detection characteristics.

1 shows that apoferritin 121 having a nanoparticle catalyst 122 embedded therein according to an embodiment of the present invention is decomposed after high temperature heat treatment, and the nanoparticle catalyst is uniformly bound to the inner and outer surfaces of the multi-channel of the nanofibers to be functionalized. A schematic diagram of the gas sensor member 100 using the multi-channel metal oxide nanofibers 110 is shown. A very small nanoparticle catalyst of 1-5 nm is uniformly contained inside and outside of the nanofibers, which is characterized by excellent gas detection properties.

The gas sensor member 100 using the multi-channel metal oxide nanofibers in which the nano-sized catalyst particles are bound to realize a sensor having excellent sensitivity and selective sensing ability for a specific gas, which is included in human exhalation Selective detection of indicator gases enables early and daily diagnosis of the disease. In addition, it is possible to effectively control the catalyst properties by quantitatively controlling the amount of the catalyst contained in the multi-channel nanofibers, and through the synthesis of various types of nano-particle catalyst / metal oxide complex multi-channel nanofibers, to detect various kinds of gases The gas sensor member can be easily manufactured.

Figure 2 shows a flow chart of a method for manufacturing a gas sensor using a multi-channel metal oxide nanofiber structure functionalized by the nano-sized catalyst uniformly bonded to the inner multi-channel and the outer surface of the nanofiber according to an embodiment of the present invention. As can be seen in the flow chart, the gas sensor manufacturing method, the step of binding the nanoparticle catalyst to the inner hollow of the apoferritin (S210), the nanoparticle catalyst embedded apoferritin metal oxide precursor / two polymer electrospinning solution Preparing a complex electrospinning solution by adding to (S220), the first solution / discontinuous phase of the mixed solution prepared above occupies the apoferritin / metal oxide precursor / continuous phase containing the nanoparticle catalyst by using the electrospinning method Synthesizing the composite nanofibers composed of the second polymer occupying (S230), through the high temperature heat treatment of the synthesized composite nanofibers nanoparticle catalyst is uniformly bound to the inner multi-channel and outer surface of the nanofibers functionalized multiple It may be configured to include a channel metal oxide nanofibers manufacturing step (S240). In the following, each of the above steps will be described in more detail.

First, look at the step (S210) of binding the nanoparticle catalyst to the inner hollow of the apoferritin. Apoferritin used in this step is an animal protein and has a hollow structure having an outer diameter of 12 nm and an inner diameter of 8 nm. One or more catalytic metal ions may be embedded in the internal hollow structure, and nanoparticles having a diameter range of 1-5 nm may be formed through a reduction process. In order to embed the catalytic metal ions into the internal hollow of the apoferritin, a catalytic metal salt is added to the solution in which the apoferritin is dissolved to diffuse the catalytic metal ions into the internal hollow of the apoferritin, and a reducing agent is added to the catalytic metal ions. Reduced to. Representative metal salts used to embed metal ions into the internal hollow of apoferritin include platinum (IV) chloride, platinum (II) acetate, gold (I, III) chloride, gold (III) acetate, silver chloride, silver acetate , Iron (III) chloride, Iron (III) acetate, Nickel (II) chloride, Nickel (II) acetate, Ruthenium (III) chloride, RutheniumAcetate, Iridium (III) chloride, Iridium acetate, Tantalum (V) chloride, Palladium ( II) chloride, Lanthanum (III) acetate, Copper (II) sulfate, and Rhodium (III) chloride. Metal salts containing metal ions that can diffuse into the interior hollow are not limited to specific metal salts. Metal ions embedded using these metal salts undergo a reduction process, and Pt, Au, Ag, Fe, Ni, Ru, Ir, Ta, Pd, La, Cu, Rh, Co, Cr, Zn, W, Sn, Sr , In, Pb, V, Sb, Sc, Ti, Mn, Ga, and Ge. Reducing agents for reducing metal ions include sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ), nascent (atomic) hydrogen, zinc-mercury amalgam (Zn (Hg)), oxalic acid (C ₂ H ₂ O ₄ ), formic acid (HCOOH), ascorbic acid (C ₆ H ₈ O ₆ ), sodium amalgam, diborane and iron (II) sulfate. Among them, it is reduced by using at least one reducing agent. The final synthesized, apoferritin containing the nanoparticle catalyst is prepared by centrifugation and washing followed by dispersion in a solvent.

Subsequently, the step of preparing the polymer composite electrospinning solution of the apoferritin / metal oxide precursor / two polymer particles in which the nanoparticle catalyst is embedded by adding the synthesized apoferritin will be described (S220). In this step (S220) by using the nanoparticle catalyst built-in apoferritin prepared in S210, to prepare a metal oxide precursor / two polymer composite electrospinning solution in which they are uniformly dispersed. Here, the two polymers have a property that they can be dissolved in one solvent but cannot be mixed with each other. Two polymers that are not mixed with each other are polyvinylpyrolidone and polyacrylonitrile, poly (styreneacrylonitrile) and polyacrylonitrile, cellulose acetate and polyacrylonitrile, poly (methylmethacrylate) and polyacrylonitrile, polystyrene and polyacrylonitrile, and poly (ethylene oxide) and polyacrylonitrile. These two polymers, in one solvent, will undergo phase separation into a first polymer occupying a continuous phase and a second polymer occupying a discontinuous phase. The weight ratio of the second polymer may be variously adjusted in the range of 50-150% relative to the weight of the first polymer. In addition, the metal oxide precursor used in this step is a change in resistance after high temperature heat treatment such as acetate, nitrate, chloride, acetylacetonate, methoxide, ethoxide, butoxide, isopropoxide, sulfide, etc., typically containing metal Any precursor that forms a metal oxide having the characteristics of a formula gas sensor sensing material is not limited to a specific metal salt. The solvent used in this step is a compatible solvent such as N, N'-dimethylformamide, dimethyl sulfoxide, N, N'-dimethylacetamide, N-methylpyrrolidone, deionized water, ethanol, etc. A solvent that can dissolve two polymers that are not mixed with each other must be selected.

In the process of preparing the electrospinning solution, the metal oxide precursor and the first polymer are sufficiently dissolved in a solvent, the second polymer is added and dissolved, and the mixture is stirred for 5 hours or 24 hours, and finally, the process (S210) is performed. The nanoparticle catalyst synthesized through is added and mixed with apoferritin. Finally, the mixture is stirred for 2 to 6 hours to uniformly mix the two polymers, the apoferritin containing the nanoparticle catalyst and the metal oxide precursor, in the solution.

Subsequently, the composite solution prepared above was synthesized using an electrospinning method to synthesize a composite nanofiber composed of apopertin / metal oxide precursor having a nanoparticle catalyst embedded therein / a first polymer having a continuous phase / a second polymer having a discontinuous phase. Step S230 is performed. In performing the electrospinning method, after filling the syringe (syringe) with the apopertin / metal oxide precursor / two polymer composite electrospinning solution containing the nanoparticle catalyst prepared above, the syringe at a constant speed using a syringe pump By pushing, a fixed amount of spinning solution is discharged per unit time. The electrospinning system may comprise a high voltage generator, a grounded conductive substrate, a syringe, a syringe pump, and a high voltage (5-30 kV) electric field is applied between the needle end of the syringe filled with the solution and the conductive substrate. The spinning solution discharged through is transformed into nanofiber form and integrated on the conductive substrate. The discharge rate can be variously adjusted to within 0.01 ml / min or 0.5 ml / min, and control the diameter and length of the nanofibers by controlling the voltage and the discharge amount, the apoptotin with a nanoparticle catalyst having a desired size It is possible to fabricate composite nanofibers composed of / metal oxide precursors / two polymers. In the electrospinning of this step, due to the phase separation phenomenon of two polymers that are not mixed with each other, a large number of second polymer fibers occupying discontinuous phases exist inside the first polymer fibers occupying the continuous phase of the nanofibers, and the metal oxide precursor Is present with the first polymer that can be mixed, and due to the excellent dispersibility of the apoferritin containing the nanoparticle catalyst, nanoparticles / apoferritin are uniformly distributed inside and on the surface of the composite nanofiber.

Finally, the high temperature heat treatment of the produced composite nanofibers, nanoparticle catalysts are uniformly bound to the inner multi-channel and outer surface of the multi-channel metal oxide to produce a functionalized multi-channel metal oxide nanofibers (S240) To perform. In this step, by heat treatment in the temperature range of 500-700 ℃, pyrolysis of the polymer and apoferritin, forming a multi-channel inside the nanofiber and the nanoparticle catalyst embedded in the apoferritin inside and outside the nanofiber Ensure uniform binding. In the heat treatment process, the second polymer occupying the discontinuous phase is decomposed to leave multichannels, the metal oxide precursor is oxidized and crystallized while maintaining the multichannel form, and the apoferritin is decomposed to be included in the interior hollow nanoparticles. Multichannel metal oxide nanofibers are synthesized in which the catalyst is uniformly bound to the multichannel and outer surfaces of the nanofibers. In this heat treatment process, since the temperature at which the second polymer is pyrolyzed is 50-150 ° C. higher than the crystallization temperature of the metal oxide precursor, the heat transferred to the metal oxide particles is reduced, and the plurality of second polymer fibers are separated from the nanofibers. The growth of the metal oxide particles is suppressed by the support therein, thereby forming a metal oxide having a small particle size of 1 to 20 nm. In addition, the apoferritin is an animal protein consisting of an outer diameter of 12 nm and an inner diameter of 8 nm, and is characterized by leaving micropores having a size range of 1 to 15 nm in the nanofibers as the protein shell is decomposed during the heat treatment. In addition, the nanoparticle catalyst contained in the hollow structure of apoferritin is Pt, PtO, PtO ₂ , Au, Ag, Fe ₂ O ₃ , NiO, RuO ₂ , IrO ₂ , Ta ₂ O ₅ , PdO, PdO ₂ after heat treatment. , CuO, Rh ₂ O ₃ , Co ₃ O ₄ , Cr ₂ O ₃ , ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, V ₂ O ₅ , VO ₂ , VO, Sb ₂ O ₃ , It is substituted with a nanoparticle catalyst of at least one of Sc ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O _3, and GeO ₂ . In addition, the metal oxide nanofibers formed in this step are ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, TiO ₂ , CuO, In ₂ O ₃ , Zn ₂ SnO ₄ , Co ₃ O ₄ , PdO, LaCoO ₃ , NiCo ₂ O ₄ , Ca ₂ Mn ₃ O ₈ , ZrO ₂ , Al ₂ O ₃ , B ₂ O ₃ , V ₂ O ₅ , Cr ₃ O ₄ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Ag ₂ V ₄ O ₁₁ , Ag ₂ O, Li _{0 . 3} La _{0 . 57} TiO ₃ , LiV ₃ O ₈ , RuO ₂ , IrO ₂ , MnO ₂ , InTaO ₄ , ITO, IZO, InTaO ₄ , MgO, Ga ₂ O ₃ , CaCu ₃ Ti ₄ O ₁₂ , Ag ₃ PO ₄ , BaTiO ₃ , _{NiTiO 3, SrTiO 3, Sr 2} Nb 2 O 7, Sr 2 Ta 2 O 7 and Ba _{0. 5} Sr _{0 . 5} Co _{0 . 8} Fe _{0 . 2} O _{3 -} and it may be variously configured with one or more composites selected from the group consisting of _7.

FIG. 3 schematically illustrates a manufacturing process sequence according to a method for manufacturing a gas sensor member using multi-channel metal oxide nanofibers in which a nano-sized catalyst is bound using an electrospinning method according to an embodiment of the present invention.

The first step (S310) is the electrospinning of a composite electrospinning solution composed of apopertin / metal oxide precursor / two polymers with a nanoparticle catalyst, the apoferritin with a nanoparticle catalyst is uniformly dispersed The example which manufactures a composite nanofiber is shown.

Step S320, which is a second process, represents a process of high temperature heat treatment of the composite nanofibers synthesized in step S310. The second polymer, which occupies the discontinuous phase, is pyrolyzed, leaving a plurality of channels inside the nanofibers, apopertin is decomposed, and the nanoparticle catalysts embedded therein are uniformly bound to the nanofibers.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. The examples and comparative examples are only for illustrating the present invention, and the present invention is not limited to the following examples.

Example  1: Preparation of Apoferritin with Pt Nanoparticle Catalyst

First, 0.5 g of apoferritin is treated with sodium hydroxide (NaOH) solution (0.1 mol / L) to adjust the pH to 8.5. Thereafter, a separately prepared aqueous solution of Pt precursor (H ₂ PtCl ₆ H ₂ O) (1.6 wt%) was added to the apoferritin solution, and stirred at a rate of 100 rpm at room temperature for 1 to 3 hours, whereby Pt ions were separated from the apoferritin. To diffuse into the internal hollow structure. Subsequently, in order to reduce the Pt ions embedded in the apoferritin to Pt particles, an aqueous solution of sodium borohydride (NaBH ₄ ) (0.1 mol / L) is added and stirred at room temperature at a speed of 200 rpm for 10 minutes to 30 minutes. Thereafter, the stirred solution is centrifuged to separate apoferritin containing Pt nanoparticles from the solution and washed with ethanol. After performing the centrifugation and ethanol washing three times or more, the collected apoferritin was dispersed in 2.5 g of N, N'-dimethylformamide (DMF) solution, and the prepared dispersion was Used to prepare electrospinning solutions.

4 shows a transmission electron microscope image of the apoferritin containing the Pt nanoparticle catalyst prepared by the above process. It can be seen that the synthesized Pt nanoparticles have a size of about 5 nm.

Example  2: By utilizing apoferritin embedded Pt nanoparticle catalyst, Pt nanoparticle catalyst Bound  Fabrication of multichannel metal oxide nanofibers

First, 0.12 g of polyvinylpyrolidone (PVP, molecular weight: 1,300,000 g / mol) and 0.15 g of tin precursor (SnCl ₂ 2H ₂ O) were mixed in 2 ml of DMF solution, and at 300 rpm for 1 to 3 hours at room temperature. Stir at speed. Thereafter, 0.18 g of polyacrylonitrile (PAN, molecular weight: 150,000 g / mol) is added and stirred at a speed of 300 rpm for 6 to 12 hours at a temperature of about 70 ° C. Finally, 120 μL of the apoferritin dispersion synthesized in Example 1 is added to the stirred solution to prepare a final composite electrospinning solution. Transfer the prepared electrospinning solution to a syringe (Henke-Sass Wolf, 10 mL NORM-JECT ^® ), connect it to a syringe pump and push it at a discharge rate of 0.15 ml / min, and place the syringe needle (21 gauge) When a high voltage of 15 kV is applied between the stainless steel plates (stainless use steel), a composite nanofiber composed of apoferritin / tin precursor / PVP / PAN containing Pt nanoparticles in the current collector is synthesized.

FIG. 5 is a scanning electron micrograph of the composite nanofiber composed of apoferritin / tin precursor / PVP / PAN containing Pt nanoparticles collected after electrospinning. The diameter of the synthesized nanofibers ranges from 700 to 900 nm, and it can be seen that the surface of the nanofibers is uneven. It can be seen that the phase separation of the two polymers that do not mix with each other occurs through the shape of the surface.

After the composite nanofibers composed of apoferritin / tin precursor / PVP / PAN containing Pt nanoparticles prepared as described above were heated at a rate of 5 ° C./min for 1 hour at 280 ° C., then 600 ° C. After one more hour of retention, the mixture was cooled to room temperature at a rate of 40 ° C./min. The heat treatment was performed in an air atmosphere using Ney's Vulcan 3-550 small electric furnace. Here, the reason that the heat treatment for 1 hour at 280 ℃ is to stabilize the PAN, conditions may vary depending on the type of polymer. In addition, during heat treatment at 600 ° C., organic materials (apoferritin, PVP, PAN) are decomposed, tin precursors are oxidized and crystallized, and Pt nanoparticle catalysts are bound to form functionalized multichannel Pt—SnO ₂ nanofibers.

Figure 6 shows a scanning electron micrograph of the multichannel Pt-SnO ₂ nanofibers synthesized in Example 2. The synthesized nanofibers have a reduced diameter of 300 to 400 nm as the organics decompose. It can be seen that the number of channels of the multichannel Pt-SnO ₂ nanofibers has a range of 5 to 20 per one nanofiber, and the diameter of the channel has a range of 10 to 50 nm.

Figure 7 shows the transmission electron micrograph and component analysis of the multi-channel Pt-SnO ₂ nanofibers synthesized in Example 2. Transmission electron micrographs clearly show the presence of multiple channels inside the nanofibers. In addition, the transmission electron microscope lattice analysis shows that the Pt nanoparticle catalyst is SnO ₂ It shows the binding to the nanofibers, and shows the crystallization of SnO ₂ through electron diffraction analysis. In addition, through transmission electron microscopy (EDS), it can be seen that Pt is evenly dispersed in SnO ₂ nanofibers without agglomeration with each other, and the multi-channel structure is clearly identified as the line component analysis shows a continuous zigzag shape. Can be.

Comparative example  1. Pt nanoparticle catalyst Bound SnO ₂  Nano Fiber

As a comparative example that can be compared with Example 2, there is a SnO ₂ nanofiber structure in which an apoferritin-based nanoparticle catalyst is bound. 0.30 g PVP and 0.15 g tin precursor are mixed in 2 ml of DMF solution and stirred at a speed of 300 rpm for 6 to 10 hours at room temperature. To the stirred solution, 120 μl of the apoferritin dispersion synthesized in Example 1 was added to prepare a final composite electrospinning solution. Transfer the prepared electrospinning solution to a syringe (Henke-Sass Wolf, 10 mL NORM-JECT ^® ), connect it to a syringe pump and push it at a discharge rate of 0.15 ml / min, and place the syringe needle (21 gauge) Applying a high voltage of 15 kV between the stainless steel plate (stainless use steel), a composite nanofiber composed of apoferritin / tin precursor / PVP with a Pt nanoparticle catalyst embedded in the collector plate. The apoferritin / tin precursor / PVP composite nanofibers containing the Pt nanoparticle catalyst were maintained at 600 ° C. for 1 hour at a temperature increase rate of 5 ° C./min, and then cooled to room temperature at a rate of 40 ° C./min. Heat treatment was performed in an air atmosphere using Ney's Vulcan 3-550 small electric furnace. During heat treatment at 600 ° C., PVP is thermally decomposed, apoferritin is decomposed, and the embedded nanoparticle catalyst is bound to the inside and outside of the nanofibers, and the tin precursor is oxidized and crystallized to synthesize Pt-SnO ₂ nanofibers.

8 shows a scanning electron micrograph of SnO ₂ nanofibers to which the Pt nanoparticle catalyst prepared in Comparative Example 1 is bound. The synthesized SnO ₂ nanofibers have an average diameter of about 250 nm, and unlike the multichannel SnO ₂ nanofibers prepared in Example 2, a channelless nanofiber structure was formed.

The prepared SnO ₂ nanofibers to which the Pt nanoparticle catalysts were bound were used to compare the sensing characteristics of various gases with the multi-channel SnO ₂ nanofibers to which the Pt nanoparticle catalysts prepared in Example 2 were bound.

Comparative example  2. Pt nanoparticle catalyst Not binding  Multichannel SnO ₂  Nano Fiber

A comparative example that can be compared with Example 2 includes a multichannel SnO ₂ nanofiber structure in which the Pt nanoparticle catalyst is not bound. 0.12 g of PVP and 0.15 g of tin precursor are mixed in 2 ml of DMF solution and stirred at a speed of 300 rpm for 1 to 3 hours at room temperature. Thereafter, 0.18 g of PAN is added and stirred at a speed of 300 rpm for 6 to 12 hours at a temperature of about 70 ° C. to produce the final composite electrospinning solution. Transfer the prepared electrospinning solution to a syringe (Henke-Sass Wolf, 10 mL NORM-JECT ^® ), connect it to a syringe pump and push it at a discharge rate of 0.15 ml / min, and place the syringe needle (21 gauge) Applying a high voltage of 15 kV between the stainless steel plate (stainless use steel), a composite nanofiber composed of tin precursor / PVP / PAN to the current collector plate.

After maintaining the composite nanofiber composed of the tin precursor / PVP / PAN prepared by the above method at a temperature increase rate of 5 ℃ / min for 1 hour at 280 ℃, then further maintained at 600 ℃ for one hour, 40 It cooled to room temperature at the falling rate of ° C / min. Heat treatment was performed in an air atmosphere using Ney's Vulcan 3-550 small electric furnace. Here, the reason that the heat treatment for 1 hour at 280 ℃ is to stabilize the PAN, conditions may vary depending on the type of polymer. In addition, during the heat treatment at 600 ℃ organic matter (PVP, PAN) is decomposed, the tin precursor is oxidized and crystallized to form a multi-channel SnO ₂ nanofibers.

The prepared multi-channel SnO ₂ nanofibers not bound with the Pt nanoparticle catalyst were used to compare the sensing characteristics of multiple gases with the multi-channel SnO ₂ nanofibers with the Pt nanoparticle catalyst prepared in Example 2 It was.

Comparative example 3. Pt  Nanoparticle catalyst Not binding  Not SnO ₂  Nano Fiber

As a comparative example that can be compared with Example 2, there is a SnO ₂ nanofiber structure in which the apoferritin-based nanoparticle catalyst is not bound. 0.30 g PVP and 0.15 g tin precursor are mixed in 2 ml of DMF solution and stirred at a speed of 300 rpm for 6 to 10 hours at room temperature. Transfer the prepared electrospinning solution to a syringe (Henke-Sass Wolf, 10 mL NORM-JECT ^® ), connect it to a syringe pump and push it at a discharge rate of 0.15 ml / min, and place the syringe needle (21 gauge) When a high voltage of 15 kV is applied between the front plate stainless steel, a composite nanofiber composed of tin precursor / PVP is synthesized on the current collector plate. The tin precursor / PVP composite nanofibers were maintained at 600 ° C. for one hour at a temperature increase rate of 5 ° C./min, and then cooled to room temperature at a rate of 40 ° C./min. Heat treatment was performed in an air atmosphere using Ney's Vulcan 3-550 small electric furnace. During heat treatment at 600 ° C., PVP is thermally decomposed, tin precursors are oxidized and crystallized to synthesize SnO ₂ nanofibers.

FIG. 9 shows a scanning electron micrograph of SnO ₂ nanofibers in which the Pt nanoparticle catalyst synthesized in Comparative Example 3 is not bound. The synthesized SnO ₂ nanofibers have an average diameter of about 250 nm, and unlike the multichannel SnO ₂ nanofibers prepared in Example 2, no pores in the form of channels are seen. The results show the role of two polymers that do not mix with each other in forming a multichannel structure.

The prepared SnO ₂ nanofibers not bound with the Pt nanoparticle catalyst were used to compare the sensing characteristics of various gases with the multi-channel SnO ₂ nanofibers with the Pt nanoparticle catalyst prepared in Example 2 above.

Experimental Example  One. PVP Apoferritin containing tin oxide precursor composite nanofibers and Pt nanoparticle catalysts / PVP The change of mass and the degree of heat transfer according to the heat treatment of the / PAN / tin oxide precursor composite nanofiber

As can be seen from the scanning electron micrographs, the nanofibers prepared in Comparative Example 3 showed a particle size of about 20 nm, whereas the multichannel nanofibers prepared in Example 2 showed a small particle size of about 10 nm. . In order to determine the cause of the apopertin / PVP / PAN / tin oxide precursor composite nanofibers comprising the PVP / tin oxide precursor composite nanofibers prepared in Comparative Example 3 and Example 2 and the Pt nanoparticle catalyst The change in mass and the degree of heat transfer were confirmed. Each of 0.05 g of nanofibers was heat-treated in an air atmosphere from room temperature to 700 ° C. at a heating rate of 5 ° C./min to determine the change in mass and the degree of heat transfer.

Figure 10 is an experimental example of the present invention, Comparative Example 3 and the embodiment according to 2, Pt nanoparticle catalyst is not a binding SnO ₂ nanofibers and Pt nanoparticle catalysts that form the binding of the multi-channel SnO ₂ nanofiber In the process, it is a graph showing the change of mass and the degree of heat transfer according to the heat treatment of the apoferritin / PVP / PAN / tin oxide precursor composite nanofibers including PVP / tin oxide precursor composite nanofibers and Pt nanoparticle catalyst. In the case of PVP / tin oxide precursor composite nanofibers, the mass loss occurring at 400 ° C. or higher is about 20%, whereas in the case of apoferritin / PVP / PAN / tin oxide precursor composite nanofibers containing a Pt nanoparticle catalyst It can be seen that the mass loss occurring at 400 ° C. or higher is about 45%. This can be seen as a difference depending on the presence or absence of PAN, as previously reported, PVP decomposes below 450 ℃ and PAN decomposes above 450 ℃. Crystallization of SnO ₂ also begins at 400 ° C. That is, in the case of the apoferritin / PVP / PAN / tin oxide precursor composite nanofibers, as the decomposition of PAN occupying a discontinuous phase inside the nanofiber occurs at a higher temperature than the crystallization of SnO ₂ , the heat transferred to the SnO ₂ particles is reduced. As the number of PAN fibers is reduced therein, the growth of SnO ₂ particles is suppressed to form SnO ₂ having a small particle size.

Experimental Example  2. Pt nanoparticle catalyst Bound  Multichannel SnO ₂  Nanofiber, Pt nanoparticle catalyst Bound SnO ₂  Nanofiber, Pt nanoparticle catalyst Not bound  Multichannel SnO ₂  Nanofibers, and Pt nanoparticle catalysts Not binding  Not SnO ₂  Fabrication and Characterization of Gas Sensors Using Nanofibers

In order to utilize the sensing material prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 in the gas sensor for exhalation analysis, the multi-channel SnO ₂ nanofibers with Pt nanoparticle catalyst and Pt nanoparticle catalyst in which the binder of SnO ₂ nanofibers, Pt nanoparticle catalyst is not a binding multichannel SnO ₂ nanofibers, and dispersing SnO ₂ the Pt nanoparticle catalyst is not a binding nanofibers to 5 mg ethanol 250 μL each after 1 hour During ultrasonic grinding. Then, the multi-channel Pt nanoparticle catalyst dispersed in a using a micropipette the production of ethanol the binder SnO ₂ nanofibers, Pt is the binding of SnO ₂ nanofiber, the non-binder multiple Pt nanoparticle catalyst nanoparticle catalyst Channel SnO ₂ nanofibers and Pt nanoparticle catalyst-dropped SnO ₂ nanofiber solutions are each drop-coated onto a 3 mm Х 3 mm alumina (Al ₂ O ₃ ) substrate patterned with parallel gold (Au) electrodes. After that, the drying is performed on a hot plate at 60 ° C. This process was repeated 3 to 5 times to ensure that a sufficient amount of nanofibers were uniformly coated on the alumina sensor substrate.

In order to evaluate the characteristics of the manufactured gas sensor, the driving temperature of the sensor was maintained at 400 ° C. in a high humidity environment (95% RH), and the concentration of acetone (CH ₃ COCH ₃ ) gas was 5, 4, 3, 2, The acetone detection characteristics were evaluated by changing to 1, 0.6 and 0.4 ppm. In addition, in Experimental Example 2, not only acetone gas, which is a representative example of volatile organic compound gas, but also ethanol (C ₂ H ₅ OH), methane (CH ₄ ), carbon monoxide (CO), ammonia (NH ₃ ), and formaldehyde (HCHO). The selective gas detection capability was evaluated by evaluating the detection characteristics of hydrogen sulfide (H ₂ S) and toluene (C ₆ H ₅ CH ₃ ).

11 shows the concentration of acetone gas at 400 ° C. from 5 ppm to 0.4 ppm with time, and the reaction degree (R _air / R _{gas ,} where R _air is the resistance of the gas sensor when air is injected, R _gas Is the resistance of the gas sensor when acetone gas is injected. As shown in FIG. 11, the multi-channel SnO ₂ nanofibers to which the Pt nanoparticle catalyst is bound are SnO ₂ nanofibers to which the Pt nanoparticle catalyst is bound and the multi-channel of Pt nanoparticle catalyst is not bound to 5 ppm of acetone gas. SnO ₂ nanofibers and Pt nanoparticle catalyst showed more than 8 times better sensitivity than unbound SnO ₂ nanofibers. This clearly shows the effect of multichannel structure and uniformly dispersed nano sized catalyst.

Figure 12 is when the concentration of acetone, 1, 2, 3, 4, 5 ppm il eseo 400 ℃, Pt nanoparticle catalyst is a binder multichannel SnO ₂ nanofibers, Pt nanoparticle catalysts binder SnO ₂ nanofibers, Pt a multi-channel non-nanoparticle catalyst is not a binding SnO ₂ nanofibers, and the characteristics evaluation results of the reaction rate of the SnO ₂ nanofibers Pt nanoparticle catalyst that is not a binder based gas sensor. As shown in the results, the reaction rate of the multichannel nanofiber structure is very fast, within 12 seconds, while the reaction rate of the general nanofiber structure is relatively slow, within 28 seconds. These results show that the multi-channel structure promotes gas penetration into the nanofibers, leading to instantaneous resistance changes, resulting in rapid reactions.

FIG. 13 shows the reaction rate of acetone, ethanol, methane, carbon monoxide, ammonia, formaldehyde, hydrogen sulfide, and toluene 1 ppm of Pt nanoparticle catalyst-bound multichannel SnO ₂ nanofibers measured at 400 ° C. FIG. As shown in FIG. 13, the multi-channel SnO ₂ nanofiber based gas sensor to which the Pt nanoparticle catalyst is bound shows a degree of reaction of less than 9.1 to ethanol, methane, carbon monoxide, ammonia, formaldehyde, hydrogen sulfide, toluene gas, and acetone. It showed a very good response rate of more than 22 for the selective gas detection ability.

FIG. 14 shows the results of repeated evaluation of detection characteristics for 1 ppm acetone of a multichannel SnO ₂ nanofiber based gas sensor to which Pt nanoparticle catalyst is bound at 400 ° C. FIG. As shown in the results, it showed stable sensing characteristics even after 30 times of repeated reactions and recovery. Through this, the multi-channel SnO ₂ nanofiber based gas sensor to which Pt nanoparticle catalyst is bound has the ability to stably detect for a long time, and it has been confirmed that the sensing capability does not decrease even after several detections.

In the above experimental example, the sensor characteristics of a multi-channel SnO ₂ nanofiber based gas sensor bound with Pt nanoparticle catalyst having high sensitivity, fast reaction rate, and selectivity to acetone were shown. In addition, by changing the type of nanoparticle catalyst and metal oxide material, it is possible to expect a change in gas selectivity characteristics, to synthesize a multi-channel metal oxide nanofibers in which a variety of nanoparticle catalyst particles are bound, and to a variety of gases It is possible to manufacture a gas sensor array having high sensitivity and selectivity. The multi-channel metal oxide nanofiber sensing material including the nanoparticle catalyst realized through the apoferritin may be used in a gas sensor for health care for analyzing and diagnosing volatile organic compound gas in an exhalation.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention but to describe the present invention, and are not limited to these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100: member for multi-channel metal oxide nanofiber gas sensor to which nano-sized catalyst is bound
110: A multi-channel metal oxide nanofiber functionalized by uniformly binding nanoparticle catalyst on the multichannel inner and outer surfaces of the nanofiber
121: apoferritin with nanoparticle catalyst embedded in the inner cavity
122: nanoparticle catalyst in which apoferritin is pyrolyzed and bound after high temperature heat treatment

Claims (20)

The metal oxide precursor is oxidized and crystallized by heat treatment to a composite nanofiber including apoferritin containing a nanoparticle catalyst in an internal hollow, two polymers and metal oxide precursors which are not mixed with each other to form metal oxide nanofibers. In the metal oxide nanofibers, multichannels are formed by phase separation of the two polymers, and the apoferritin is removed by the heat treatment. Multi-channel metal oxide nanofibers, characterized in that the nanoparticle catalyst is bound and functionalized. The method of claim 1,
The composite nanofiber includes a first polymer fiber in which the metal oxide precursor is mixed while occupying a continuous phase of the nanofibers by phase separation of the two polymers, and occupying a discontinuous phase inside the first polymer fiber. The multi-channel metal oxide nanofibers, further comprising a plurality of second polymer fibers, and further comprising the apoferritin on the surface and the inside. The method of claim 2,
Through the heat treatment, in the process of thermally decomposing the first polymer fiber and the second polymer fiber, the metal oxide precursor is oxidized to a metal oxide in the form of a multi-channel in which the second polymer fiber is removed and formed inside the nanofiber. While maintaining crystallization, the apoferritin is thermally decomposed to form pores in the nanofibers, and at the same time, the nanoparticle catalyst contained in the inner hollow of the apoferritin is bound to the surface of the nanofibers and inside of each of the multichannels. Multichannel Metal Oxide Nanofibers. The method of claim 2,
In the heat treatment process for the composite nanofibers, as the thermal decomposition of the plurality of second polymer fibers occupying the discontinuous phase occurs at a relatively higher temperature than the crystallization of the metal oxide precursor, the heat transferred to the metal oxide particles is reduced Multi-channel metal oxide nanofibers, characterized in that the size of the metal oxide particles is limited. The method of claim 4, wherein
The pyrolysis of the second polymer fiber is multi-channel metal oxide nanofibers, characterized in that occurs at a temperature relatively higher than the temperature included in the range of 50 to 150 ℃ than the crystallization of the metal oxide precursor. The method of claim 1,
Multi-channel metal oxide nanofibers, characterized in that the size of the metal oxide particles forming the metal oxide nanofibers included in the range of 1 to 20 nm. The method of claim 1,
The two polymers are polyvinylpyrrolidone, poly (styreneacrylonitrile), polystyrene, cellulose acetate, poly (ethylene oxide) (poly ( ethylene oxide), poly (methylmethacrylate), and a multi-channel metal comprising a combination of a first polymer selected from poly (methylmethacrylate) and a second polymer including polyacrylonitrile. Oxide nanofibers. The method of claim 1,
Multi-channel metal oxide nanofibers, characterized in that the weight ratio of the second polymer occupying the discontinuous phase in the composite nanofibers to the weight of the first polymer occupying the continuous phase in the composite nanofibers is in the range of 50 to 150% . The method of claim 1,
The number of the multi-channel, the multi-channel metal oxide nanofibers, characterized in that included in the range of 5 to 20 per one composite nanofiber, the diameter of the individual channel is in the range of 10 to 50 nm. The method of claim 1,
The apoferritin has a hollow structure inside, encapsulates one or more catalytic metal ions in the hollow inside,
Multi-channel metal oxide nanofibers, characterized in that the diameter of the nanoparticle catalyst produced by the reduction of the catalytic metal ion is included in the range of 1 to 5 nm. The method of claim 1,
The weight ratio of the nanoparticle catalyst is multi-channel metal oxide nanofibers, characterized in that included in the concentration range of 0.01 to 1 wt% compared to the multi-channel metal oxide nanofibers. The method of claim 1,
The nanoparticle catalyst is platinum (IV) chloride, platinum (II) acetate, gold (I, III) chloride, gold (III) acetate, silver chloride, silver acetate, Iron (III) chloride, Iron (III) acetate, Nickel (II) chloride, Nickel (II) acetate, Ruthenium (III) chloride, Ruthenium Acetate, Iridium (III) chloride, Iridium acetate, Tantalum (V) chloride, Palladium (II) chloride, Lanthanum (III) acetate, Copper (II) A multi-channel metal oxide nanofiber, characterized in that formed by catalytic metal ions synthesized, including at least one metal salt selected from sulfate and Rhodium (III) chloride. The method of claim 1,
The nanoparticle catalyst, Pt, Au, Ag, Fe, Ni, Ru, Ir, Ta, Pd, La, Cu, Rh, Co, Cr, as the catalytic metal ions contained in the inner hollow of the apoferritin is reduced At least one nanoparticle catalyst selected from Zn, W, Sn, Sr, In, Pb, V, Sb, Sc, Ti, Mn, Ga, and Ge, which is included in the interior hollow of the apoferritin,
The nanoparticle catalyst contained in the hollow structure of the apoferritin is Pt, PtO, PtO ₂ , Au, Ag, Fe ₂ O ₃ , NiO, RuO ₂ , IrO ₂ , Ta ₂ O ₅ , PdO, PdO ₂ , after heat treatment. CuO, Rh ₂ O ₃ , Co ₃ O ₄ , Cr ₂ O ₃ , ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, V ₂ O ₅ , VO ₂ , VO, Sb ₂ O ₃ , Sc _The multi-channel metal oxide nanofibers, which are substituted with at least one nanoparticle catalyst of ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O _3, and GeO ₂ to bind to the outer surface of the metal oxide nanofibers. 14. A gas sensor comprising a sensing material formed by coating the multi-channel metal oxide nanofibers of any one of claims 1 to 13 on a sensor electrode capable of measuring a resistance change. In the method of manufacturing a multichannel metal oxide nanofiber,
(a) synthesizing a nanoparticle catalyst inside the hollow structure of apoferritin;
(b) dissolving two polymers which are not mixed with each other in a solvent together with a metal oxide precursor to synthesize an electrospinning solution;
(c) composite electrospinning comprising apoferritin comprising the synthesized nanoparticle catalyst into the synthesized electrospinning solution and apoferritin containing a nanoparticle catalyst, a metal oxide precursor, and two polymers not mixed with each other Preparing a solution;
(d) electrospinning the complex electrospinning solution to prepare a composite nanofiber in which apoferritin containing a nanoparticle catalyst is bound on and inside the metal oxide precursor and the polymer composite nanofiber; And
(e) heat treating the composite nanofibers to prepare functionalized multichannel metal oxide nanofibers by uniformly binding a nanoparticle catalyst to the inner multichannel and outer surface of the multichannel metal oxide nanofibers
Method for producing a multi-channel metal oxide nanofibers, comprising a. The method of claim 15
In step (a),
In order to embed the nanoparticle catalyst in the inner hollow of the apoferritin, the catalyst metal salt is added to the solution in which the apoferritin is dissolved to embed the catalyst metal ion, and a reducing agent is added to reduce the catalyst metal ion to the catalyst metal particle. Method for producing a multi-channel metal oxide nanofibers, characterized in that. The method of claim 15
In step (a),
Reducing agents for reducing the catalytic metal ions embedded in the hollow of the apoferritin, sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ), nascent (atomic) hydrogen, zinc-mercury amalgam (Zn (Hg)), Multichannel comprising at least one of oxalic acid (C ₂ H ₂ O ₄ ), formic acid (HCOOH), ascorbic acid (C ₆ H ₈ O ₆ ), sodium amalgam, diborane and iron (II) sulfate Method for producing metal oxide nanofibers. The method of claim 15,
In the step (e),
In the process of thermally decomposing the apoferritin and the two polymers through the heat treatment, the second polymer occupying the discontinuous phase is decomposed to form a multi-channel, and the first polymer as a continuous phase is decomposed and the first polymer is decomposed. The metal oxide precursor mixed in the oxidized and crystallized while maintaining the form of the formed multichannel, and the apoferritin is decomposed and the nanoparticle catalyst contained in the inner hollow is bound to the inside of the formed multichannel and the table of the nanofibers. Method for producing a multi-channel metal oxide nanofibers, characterized in that. The method of claim 15,
In the step (e),
The apoferritin is a hollow protein protein, multi-channel metal oxide nanofibers, characterized in that to form pores of the size within the range of 1 to 15 nm in the nanofibers as the protein shell is decomposed during the heat treatment process Manufacturing method. The method of claim 15,
(f) pulverizing the multi-channel metal oxide nanofibers and dispersing them in a solvent, and coating the at least one coating process among spin coating, drop coating, and inkjet printing on a sensor electrode for a resistance change gas sensor.
Method for producing a multi-channel metal oxide nanofiber, characterized in that it further comprises.

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