KR20180065493A - Gas sensor and member using metal oxide nanotubes including nanoscale heterogeneous catalysts by using metal-organic framework, and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a member for a metal oxide nanotube gas sensor bound with a heterogeneous catalyst, a gas sensor using the same, and a manufacturing method thereof. According to the metal oxide nanotube bound with a heterogeneous catalyst of the present invention, a first metal oxide-based heterogeneous catalysts including a nanoparticle catalyst are bound to a surface of a second metal oxide nanotube, and then functionalized. Therefore, disclosed are the member for a gas sensor with has excellent sensing characteristics, the gas sensor, and the manufacturing method thereof.

Description

TECHNICAL FIELD [0001] The present invention relates to a metal oxide nanotube having a nano-scale heterogeneous catalyst bound thereto using a porous metal organic structure, a member for a gas sensor using the same, a gas sensor and a method for manufacturing the same, organic framework, and manufacturing method thereof}

The present invention relates to a member for a gas sensor, a gas sensor using the same, and a manufacturing method thereof. More particularly, the present invention relates to a gas sensor using a metal sensor A nanoparticle catalyst composed of nanoparticle catalysts synthesized through electrospinning and heat treatment and a heterogeneous catalyst composed of a first metal oxide uniformly bind to the inside and the surface of the second metal oxide nanotube to form a functionalized metal oxide nano- Tube, a member for a gas sensor using the same, a gas sensor, and a manufacturing method thereof.

With the increase of various pollutants such as industrial pollutants, automobile exhaust gas and factory exhaust, the air pollution problem becomes serious due to the inflow of yellow sand from China. Therefore, it is possible to quickly detect various environmentally harmful gases in the atmosphere and to detect harmful information The sensor technology that can be provided is attracting much attention. In addition, a sensor technology capable of detecting the biomarker gas contained in a person's exhalation and monitoring health signs of the human body is receiving great attention. Among various gas detection methods, resistance-based gas sensors based on metal oxide semiconductors operate as a simple driving principle that measures the change in electrical resistance caused by the adsorption and desorption of a specific gas on the surface of a sensing material, Therefore, it is advantageous that the sensor system is simple in structure, easy to miniaturize, and easily interlocked with other devices. Therefore, it is attempted to commercialize a metal oxide semiconductor based gas sensor in mobile or wearable devices in various fields such as harmful environmental gas alarm, indoor / outdoor air quality meter, alcohol drinking meter, and sick house syndrome gas detector Is actively proceeding.

In order for such metal oxide-based gas sensors to be commercialized as environmentally harmful gas detectors, it is necessary to be able to selectively detect extremely small amounts of gas at the level of ppm (parts per million). Environmental standards for air pollutants in accordance with government standards in 2016 include sulfur dioxide (SO ₂ ) of less than 0.03 ppm, carbon monoxide (CO) of less than 8 ppm, nitrogen oxides (NO ₂ ) of less than 0.05 ppm and ozone (O ₃ ) of less than 0.02 ppm , Emission standards of various kinds of soot are 250 ppm or less of ammonia (NH ₃ ), 400 ppm or less of carbon monoxide (CO), 25 ppm or less of hydrogen chloride (HCl), and 10 ppm or less of chlorine (Cl ₂ ). In order to be used as an illness analyzer for diagnosis of diseases, acetone (CH ₃ COCH ₃ ), ammonia, nitrogen monoxide, hydrogen sulfide (H ₂ S), toluene (C ₆ H ₅ CH ₃ ), pentane ₅ H ₁₂₎ as biomarkers gas (each of diabetes, kidney disease, asthma, bad breath, lung cancer, biomarkers) for heart disease were 10 ppb (part per billion), since the emission with a very low concentration of 10 ppm range in the same this optional . In addition, since there are hundreds or more kinds of mixed gases in the air, it is required to develop a sensor of high sensitivity and selectivity capable of selectively detecting specific gases at ppm / ppb level. In addition, in order to be used as a real-time sensing device, it is required not only to miniaturize the sensor with a size that can be carried by a human, but also to accelerate the reaction speed and the recovery speed for gas detection within a few seconds. However, since metal oxide based gas sensors detect the gas by measuring the electrical resistance change through the surface reaction of the gas and the sensing material, there is a disadvantage that it is difficult to measure the gas with a level of several ppb and the selectivity to react only to the specific gas is low. Therefore, it is urgent to develop a metal oxide sensing material having high sensitivity and high selectivity.

In order to overcome the disadvantages mentioned above, synthesis of sensing materials based on various nanostructures including nanoparticles, nanofibers, nanotubes and nanospheres and sensor application using them . Sensing materials using nanostructures are expected to achieve higher sensitivity because they have a relatively larger area of reacting with gases than conventional thick films or powder structures. do. In addition, the sensing material of the hollow structure can be expected to have higher sensitivity and faster response speed because gases readily diffuse into the sensing material and react on the outer and inner surfaces of the sensing material.

In addition, the development of sensing materials having high sensitivity and selectivity by binding a catalyst to the surface of a nanostructure is actively under way. Metal oxide based gas sensors can greatly enhance sensing properties by binding chemical sensitizers and electronic sensitizers. Representative chemical sensitizers include platinum (Pt) and gold (Au), which increase the concentration of gases participating in the surface reaction, thereby enhancing the properties of the gas sensor. In addition, representative electronic sensitization catalysts include palladium (Pd), nickel (Ni), cobalt (Co), and silver (Ag). These catalysts include metal oxides such as PdO, NiO, Co ₂ O ₃ , and Ag ₂ O And the sensitivity is improved by using the change in the oxidation number which is formed.

In addition to the development of various types of nanostructures, various researches have been carried out to utilize sensing materials that have been bound with various catalysts. However, Oxide semiconductor based sensing materials have not been used yet. Therefore, it is urgent to develop a sensing material capable of selectively sensing a very small amount of gas in order to detect atmospheric harmful environments and realize an aerial sensor for healthcare.

In order to overcome the above-mentioned limitations, it is necessary to develop a sensing material utilizing not only a novel heterogeneous catalyst but also a nanoparticle catalyst of several nanometers in size. There is also a need for a technique that facilitates binding of catalysts to nanostructure-based sensing materials having a large surface area. There is a need for a material synthesis technique and a sensor manufacturing technology that can realize a sensor capable of selectively sensing biomarker gases in the air environment and harmful gases in actual atmospheric environment and the human body by simultaneously satisfying the above-described aspects.

The present invention relates to a method for fabricating a metal organic structure using a porous nanomaterial, which is a metal-organic framework having a size of 50-500 nm formed by combining metal ions and organic ligands, Polymer nanocomposite / nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite The present invention provides a method of functionalizing the first metal oxide particles to which the particle catalysts are bound on the surface of the second metal oxide nanotube.

Particularly, even after the heat treatment, the metal nanoparticle catalysts contained in the metal organic structure are uniformly dispersed on the surface of the first metal oxide without mutual agglomeration, so that a single catalyst particle exhibits a chemical sensitization or an electronic sensitization catalyst effect. In addition, since the metal oxide of the metal organic structure is oxidized during the heat treatment process, the first metal oxide formed by the first metal oxide forms a heterojunction with the second metal oxide nanotube to increase the sensitivity, The porous first metal oxide particles including the nanoparticle catalyst are uniformly adhered to the inside and the surface of the second metal oxide nanotube so that the gas sensing property is remarkably increased because the metal nanoparticles easily diffuse into the sensing material and react with the heterogeneous catalyst The synthesis technology of functionalized metal oxide nanotube sensing material and the application technology of gas sensor using it are presented.

This is a method for solving the problems of the prior art, in which a heterogeneous catalyst containing a very small nanoparticle catalyst having a size of 10 nm or less is uniformly dispersed on the surface of the metal oxide nanotube without agglomerating with each other, A sensor member, a gas sensor using the same, and a manufacturing method thereof.

In order to solve the above-mentioned problems, the present invention provides a method of synthesizing a metal organic structure according to an aspect of the present invention, and a nanoparticle catalyst is uniformly dispersed in the synthesized metal organic structure to bond the nanoparticle catalysts to the first metal oxide particle A sensing material including a nano-sized heterogeneous catalyst uniformly distributed over the first metal oxide particles and uniformly bonded to the inside and the outside of the second metal oxide nanotube, And a method for manufacturing the member for use. A method for manufacturing a sensing material and a gas sensor using the same according to the present invention includes the steps of: (a) synthesizing a metal organic structure by reacting a metal ion with an organic ligand; (b) embedding a nanoparticle catalyst in the hollow structure of the metal organic structure; (c) a step of preparing nanoparticle catalyst / metal organic structure / polymer / metal oxide precursor composite nanofiber in which the nanoparticle catalyst and the metal organic structure are contained on the surface or inside of the metal oxide precursor / polymer composite nanofiber through electrospinning ; (d) removing the organic matter of the polymer and the metal organic structure through the heat treatment process, oxidizing the metal oxide precursor and the metal of the metal organic structure, and diffusing the diffusion rate of the second metal oxide and the metal oxide precursor inside the nanofiber Forming a functionalized metal oxide nanotube by uniformly binding the first metal oxide particles including the nanoparticle catalyst to the inside and the surface of the second metal oxide nanotube to synthesize the nanotube structure through the first metal oxide nanotube; (e) dispersing and pulverizing the metal oxide nanotubes to which the nanoscale heterogeneous catalyst is bound in ethanol, and coating the nanotube on an electrode for measuring a gas sensor; and (f) fabricating a gas sensor array by utilizing metal oxide nanotubes to which a plurality of nano-sized heterogeneous catalysts are bound. The present invention also provides a method of manufacturing a metal oxide nanotube in which a nano-sized heterogeneous catalyst is bound.

In the step (a), the metal organic structure is a porous material formed by binding a metal ion and an organic ligand, and has various structures depending on the kind of the metal ion and the organic ligand. In general, the metal organic structure is in the form of a hollow structure having an internal void, and the size of the internal pore is 0.5 nm depending on the type of the metal organic structure. And have various sizes of about 30 nm. These unit metal organic structures aggregate to form metal organic structure molecular sieves ranging from 0 nm to 500 nm in size. Representative metal organic structures include ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-5, ZIF-6, ZIF-7, ZIF- ZIF-12, ZIF-22, ZIF-65, ZIF-69, ZIF-71, ZIF-78, ZIF-90 and ZIF-95. typical metal salts capable of _{will, Zn 4 O (CO 2)} 6, Zn 3 O (CO 2) 6, Cr 3 O (CO 2) 6, in 3 O (CO 2) 6, Ga 3 O (CO 2 _{) 6, Cu 2 O (CO} 2) 4, Zn 2 O (CO 2) 4, Fe 2 O (CO 2) 4, Mo 2 O (CO 2) 4, Cr 2 O (CO 2) 4, Co 2 _{O (CO 2) 4, Ru} 2 O (CO 2) 4, Zr 6 O 4 (OH 4), Zr 6 O 4 (CO 2) 12, Zr 6 O 8 (CO 2) 8, In (C 5 HO _{4 N 2) 4, Na (} OH) 2 (SO 3) 3, Cu 2 (CNS) 4, Zn (C 3 H 3 N 2) 4, Ni 4 (C 3 H 3 N 2) 8, Zn 3 O ₃ (CO ₂ ) ₃ , _{Mg 3 O 3 (CO 2)} 3, Co 3 O 3 (CO 2) 3, Ni 3 O 3 (CO 2) 3, Mn 3 O 3 (CO 2) 3, Fe 3 O 3 (CO 2) 3, _{Cu 3 O 3 (CO 2)} 3, Al (OH) (CO 2) 2, VO (CO 2) 2, Zn (NO 3) 2, Zn (O 2 CCH 3), Co (NO 3) 2, Co (O ₂ CCH ₃ ), and the like. Further typical organic ligand capable of forming a metal-organic structures are, oxalic acid, fumaric acid, H 2 BDC, H 2 BDC-Br, H 2 BDC-OH, H 2 BDC-NO 2, H 2 BDC-NH 2, _{H 4 DOT, H 2 BDC- (} Me) 2, H 2 BDC- (Cl) 2, H 2 BDC- (COOH) 2, H 2 BDC- (OC 3 H 5) 2, H 2 BDC- (OC 7 _{H 7) 2, H 3 BTC} , H 3 BTE, H 3 BBC, H 4 ATC, H 3 THBTS, H 3 ImDC, H 3 BTP, DTOA, H 3 BTB, H 3 TATB, H 4 ADB, TIPA, ADP _{, H 6 BTETCA, DCDPBN, BPP34C10DA} , Ir (H 2 DPBPyDC) (PPy) 2 +, H 4 DH 9 PhDC, H 4 DH11PhDC, H 6 TPBTM, H 6 BTEI, H 6 BTPI, H 6 BHEI, H 6 BTTI , H ₆ PTEI, H ₆ TTEI, H ₆ BNETPI, H ₆ BHEHPI, and HMeIM. The above-mentioned metal ions and organic ligands can be synthesized by various methods such as solvent thermo-synthesis, hydrothermal synthesis, microwave synthesis, ultrasonic synthesis, mechanochemical synthesis, dry-gel conversion, solvent minimization synthesis, electrochemical synthesis, The structure of the metal organic structure, the molecular sieve size, the pore size, and the internal hollow size can be controlled according to the type of the metal ion and the organic ligand.

In the step (b), metal ions are diffused into the hollow structure inside the metal organic structure, and the metal ions injected are reduced using a reducing agent, thereby forming a metal organic structure with a nanoparticle catalyst embedded therein . Due to the unique porous hollow structure of the metal organic structure, the size of the embedded nanoparticles can be controlled to 0.1 nm by controlling the quantification of the metal salt precursor. Adjustable in the 10 nm range. In addition, since the nanoparticles bind to different unit metal organic structures, they are uniformly dispersed in the metal organic structure without agglomeration. Ruthenium (III) chloride, ruthenium acetate, iridium (III) chloride, iridium acetate, and the like can be used as the typical salt type catalysts. (III) chloride, Palladium (II) chloride, Copper (II) nitrate, Copper (II) chloride, Cobalt (II) nitrate, Cobalt (II) acetate, Lanthanum (III) nitrate, Lanthanum (III) acetate, Silver (III) acetate, Silver chloride, Silver acetate, Iron (III) chloride, Iron (III) acetate, Nickel (II) chloride, Nickel II) acetate, and there is no restriction on the kind of a metal salt if it is in the form of a salt containing a metal ion.

In the step (c), nanofiber catalyst / metal organic structure / polymer / metal oxide precursor composite nanofiber is synthesized by electrospinning a solution containing a metal organic structure, a metal oxide precursor and a polymer bound with a nanoparticle catalyst . The nanoparticle / metal organic structures may be uniformly distributed on the inside and the surface of the composite nanofiber due to the excellent dispersibility of the metal organic structure bound to the nanoparticle catalyst synthesized in the step (b). In order to proceed with electrospinning, a spinning solution can be prepared by dissolving a polymer and a metal precursor serving as a template for easily forming nanofibers in a solvent. Specifically, the polymer may be selected from the group consisting of polymethylmethacrylate (PMMA), polyvinylpyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polypropylene (PEO), polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone, And polyvinylidene fluoride. Representative metal salts include metal salts such as acetate, chloride, acetylacetonate, nitrate, methoxide, ethoxide, butoxide, isopropoxide, and sulfide . Also, the electrospun solution may be prepared by adding the metal organic structure molecular sieve having the nanoparticle catalyst prepared in the step (b) to the electrospinning solution. When preparing an electrospinning solution, the concentration of the metal organic structure to which the nanoparticle catalyst is bound is 0.01 wt% ?? 2 wt%. ≪ / RTI > The content of the nano-sized heterogeneous catalyst contained in the metal oxide nanotubes is controlled according to the concentration of the metal organic structure molecular sieve.

In the step (d), a high-temperature heat treatment at a rapid heating rate is performed to synthesize the metal oxide nanotubes finally bonded with the nano-sized heterogeneous catalyst. Through the high-temperature heat treatment process of 400 ° C to 800 ° C, the polymer and organic ligands constituting the nanoparticle catalyst / metal organic structure / polymer / metal oxide precursor composite nanofiber are decomposed and removed, and the metal ion and the metal oxide The precursor is oxidized and crystallized by the first metal oxide and the second metal oxide, respectively. At this time, if the heat treatment is performed at a rapid heating rate (10 ㅀ C / min), the metal salt on the surface of the nanofiber is oxidized and crystallized to form a second metal oxide, and the inner metal salt is not oxidized. 2 Due to the difference in the diffusion rate between the metal oxide and the metal precursor, a Kirkendall effect forms an empty space in the inside and finally forms a nanotube structure. Accordingly, the first metal oxide particles including the nanoparticle catalyst can be uniformly bound to the surface of the second metal oxide nanotube through a heat treatment process at a rapid heating rate to form a functionalized metal oxide nanotube structure. Here, the first metal oxide means a metal oxide formed by oxidizing the metal ions constituting the metal organic structure, and the second metal oxide means the metal oxide formed by oxidizing the metal oxide precursor included in the electrolytic solution.

Also, in the step (e), the metal oxide nanotubes bound to the nano-sized heterogeneous catalyst obtained in the step (d) are dispersed in a solvent, and then the dispersion solution is applied to the sensor electrode A coating process such as drop coating, spin coating, ink-jet printing, dispensing, or the like is performed on an alumina (Al ₂ O ₃ ) , And coating. If the method of uniformly coating metal oxide nanotubes with nano-scale heterogeneous catalysts on the sensor substrate is not particularly restricted, the coating method is not restricted.

In addition, the step (f) may further include the step of separating the nano-sized particles of the first metal oxide, which is different from the nanoparticle catalyst of the metal oxide nanotube structure, A second metal oxide nanotube, and a second metal oxide nanotube, wherein the second metal oxide nanotube is combined with the first metal oxide nanotube catalyst / first metal oxide / second metal oxide nanotube sensing material.

In the metal oxide nanotube structure in which the prepared nanoscale heterogeneous catalyst is bound, the nanoparticle catalyst can be defined in a size range of 0.1-10 nm, and the size of the first metal oxide based on the metal organic structure is 50-500 nm, and the diameters and lengths of the second metal oxide nanotubes are each 100 nm. 5 μm, 500 nm ?? It can be defined in the length range of 10 μm.

In addition, the weight ratio of the nanoparticle catalyst in the second metal oxide nanotube sensing material bonded with the first metal oxide heterogeneous catalyst comprising the nanoparticle catalyst made by the above-mentioned manufacturing method may be a ratio of the weight ratio of the first metal oxide, the second metal oxide nanotube 0.001 wt% respectively. 25 wt%, 0.01 wt% ?? 2 wt%.

In this case, the first metal oxide bound to the fine nanoparticle catalyst having a diameter of 10 nm or less is uniformly functionalized on the surface of the second metal oxide nanotube to form a hetero-junction, The gas can easily diffuse into and out of the sensing material, and the characteristic of the heterogeneous catalyst can be maximized. Therefore, it is possible to selectively and rapidly detect a very small amount of specific gas present in the atmospheric environment and human exhalation.

According to the present invention, when a metal organic structure including a nanoparticle catalyst is dispersed together in an electrospinning solution to synthesize a second metal oxide nanotube sensing material functionalized with a first metal oxide heterogeneous catalyst containing a nanoparticle catalyst , Nanoparticle catalysts provide electronic or chemical sensitization effects, and nanoparticle catalysts, first metal oxides and second metal oxides form a number of heterogeneous junctions, exhibiting novel material properties, and having a one-dimensional nanotube structure It is possible to manufacture a nanotube sensing material having excellent sensitivity and selectivity that can easily react with a heterogeneous catalyst both inside and outside the sensing material by diffusing gas easily into the sensing material. In particular, by forming various combinations of nanoparticle catalyst / first metal oxide / second metal oxide composite nanotubes, it is possible to provide a library having excellent selectivity in the production of multiple gas sensor arrays. In addition, since the nanoparticle catalyst is bound to the porous first metal oxide based on the metal organic structure and the heterogeneous catalyst is uniformly dispersed on the surface of the second metal oxide nanotube, It is possible to expect a very excellent catalytic effect, and it has the effect of being able to disclose a member for a gas sensor, a gas sensor and a manufacturing method thereof, which have excellent sensing characteristics such as long life, high sensitivity and high selectivity.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a schematic view of a member for a metal oxide nanotube gas sensor in which a first metal oxide on which a nanoparticle catalyst according to an embodiment of the present invention is bound is uniformly dispersed on a surface of a second metal oxide nanotube.
2 is a flow chart of a method of manufacturing a gas sensor using a metal oxide nanotube structure in which a first metal oxide on which a nanoparticle catalyst according to an embodiment of the present invention is bound is uniformly dispersed on a surface of a second metal oxide nanotube to be.
FIG. 3 is a graph showing the results of the electrospinning and heat treatment of the metal oxide nanotube structure of the present invention, in which the first metal oxide on which the nanoparticle catalyst is bound is uniformly dispersed on the surface of the second metal oxide nanotube This figure shows the manufacturing process.
4 is a scanning electron micrograph of a Zn-based metal organic structure (ZIF-8) comprising a Pd nanoparticle catalyst according to Example 1 of the present invention.
5 is a transmission electron micrograph of a Zn-based metal organic structure (ZIF-8) comprising a Pd nanoparticle catalyst according to Example 1 of the present invention.
6 is a scanning electron microscope and transmission electron micrograph of a Zn-based metal organic structure / polyvinylpyrrolidone / tin oxide precursor composite nanofiber comprising a Pd nanoparticle catalyst obtained after electrospinning according to Example 2 of the present invention .
FIG. 7 is a scanning electron microscope (SEM) image of a ZnO-bound SnO ₂ nanotube containing a PdO nanoparticle catalyst obtained after heat treatment according to Example 2 of the present invention.
8 is a transmission electron microscope photograph and a component analysis photograph of SnO ₂ nanotubes bonded with ZnO containing a PdO nanoparticle catalyst obtained after heat treatment according to Example 2 of the present invention.
9 is a scanning electron microscope (SEM) image of SnO ₂ nanotubes prepared through Comparative Example 1 of the present invention in which the prepared metal organic structure-based heterogeneous catalyst is not bound.
FIG. 10 is a scanning electron microscope (SEM) image of a SnO ₂ nanofiber without metal-organic structure-based heterogeneous catalyst prepared according to Comparative Example 2 of the present invention.
11 is a graph showing the results of Experimental Example 1 of the present invention showing SnO ₂ nanotubes, SnO ₂ nanotubes, and SnO ₂ nanotubes bonded with ZnO-based heterogeneous catalysts containing PdO nanoparticle catalysts according to Example 2 and Comparative Examples 1 and 2 It is a graph of reactivity of the fiber-based gas sensor to acetone gas (0.15 ppm) at 400 ° C.
12 is a graph showing the results of Experimental Example 1 of the present invention showing SnO ₂ nanotubes, SnO ₂ nanotubes, and SnO ₂ nanotubes bonded with a ZnO-based heterogeneous catalyst containing PdO nanoparticle catalyst according to Example 2 and Comparative Examples 1 and 2 The results of the characterization of reaction speed and recovery speed of gas sensor when the concentration of acetone is 1, 2, 3, 4, 5 ppm at 400 ㅀ C of fiber based gas sensor.
FIG. 13 is a graph showing the relationship between the concentration of 1 ppm of the sensing materials at 400 ° C of a SnO ₂ nanotube-based gas sensor bonded with a ZnO-based heterogeneous catalyst containing PdO nanoparticle catalyst according to Example 2 Acetone, hydrogen sulfide, toluene, carbon monoxide, pentane, ammonia).
FIG. 14 is a graph showing the results of experiment 1 of the present invention showing that SnO ₂ nanotube-based gas sensor bonded with a ZnO-based heterogeneous catalyst containing PdO nanoparticle catalyst according to Example 2 has a repetitive effect on 1 ppm of acetone at 400 ° C This is the sensitivity measurement result.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments will be described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components are not limited by the terms, and the terms are used only for the purpose of distinguishing one component from another Is used.

Hereinafter, the first metal oxide heterogeneous catalysts including the nanoparticle catalyst synthesized using the metal organic structure are bonded to the surface of the second metal oxide nanotube uniformly to form a member for a gas sensor using functionalized metal oxide nanotubes, And a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

Embodiments of the present invention use a metal organic structure to provide 0.1 nm ?? A metal organic structure having a size of 50 nm to 500 nm with nanoparticle catalysts having a size range of 10 nm to 10 nm is synthesized and the metal organic structure with the nanoparticle catalyst is mixed with a metal oxide precursor / Spinning was performed so that the metal organic structure containing the nanoparticle catalyst was uniformly bound to the surface and inside of the metal oxide precursor / polymer composite nanofiber. In addition, by removing the organic ligand of the metal organic structure and removing the polymer constituting the nanofibers, the nanotube structure is formed through the high-temperature heat treatment at a rapid heating rate, so that the first metal oxide heterogeneous catalysts including the nanoparticle catalyst 2 metal oxide nanotubes on the surface of a functionalized gas sensor.

Here, the nanoparticle catalysts are uniformly distributed in the very small size of the first metal oxide particles, maximizing the effect of the catalyst when the gases react with the sensing material, . The heterogeneous bonding between the first metal oxide and the second metal oxide nanotube formed by oxidizing the metal ion of the metal organic structure and the metal oxide precursor respectively exhibits new properties rather than physical properties when the metal oxide is a single metal oxide, The sensitivity of the single species metal oxide sensing material was exceeded. Also, by binding the catalyst to the surface of the nanotube structure, the gas easily diffuses into and out of the sensing material to cause a surface reaction, resulting in a dramatic increase in sensitivity. A gas sensor member, a gas sensor, and a manufacturing method thereof are implemented in an efficient and easy process for manufacturing a gas sensor member having the above characteristics.

FIG. 1 is a cross-sectional view of a first metal oxide 122 including a nanoparticle catalyst 121 according to an embodiment of the present invention. The first metal oxide 122 is a metal A schematic view of the gas sensor member 100 using the oxide nanotubes 110 is shown. And is bonded to a second metal oxide of a first metal oxide valence structure containing a very small nanoparticle catalyst having a size of 0.1 ?? 10 nm to form a multi-heterojunction so that excellent gas sensing characteristics are exhibited.

By implementing the sensor having high sensitivity and selectivity with respect to a specific gas by using the member 100 for a gas sensor using the metal oxide nanotube with the nano-sized heterogeneous catalyst bonded thereto, it is possible to detect a bio- And can be used as an environmental sensor that can monitor the noxious gases in the atmosphere. In addition, it is possible to quantitatively control the amount of the heterogeneous catalyst bound to the nanotubes, thereby effectively controlling the catalyst characteristics, and also to synthesize various nanoparticle catalysts / first metal oxide / second metal oxide composite nanotube sensing materials , It is possible to easily and quickly manufacture various gas sensor members.

FIG. 2 is a flowchart illustrating a method of manufacturing a member for a gas sensor using metal oxide nanotubes bonded with a nano-sized heterogeneous catalyst according to an embodiment of the present invention. As shown in the flowchart of FIG. 2, the method for manufacturing the gas sensor member includes synthesizing a metal organic structure (S210), binding the nanoparticle catalyst inside the synthesized metal organic structure (S220) (S230) of preparing a mixed solution by adding a metal organic precursor / nanoparticle catalyst-containing metal organic structure to a metal oxide precursor / polymer electrospinning solution (S230). The nanoparticle catalyst is contained Metal oxide precursor composite nanofiber having uniformly bound metal organic structure (S240), and a step of subjecting the first metal oxide including the nanoparticle catalyst to a second metal And forming the functionalized metal oxide nanotube by uniformly binding to the surface of the oxide nanotube (S250). Each of the above steps will be described in more detail below.

First, a step S210 of synthesizing a metal organic structure will be described. The metal organic structure used in this step S210 is a porous material formed by combining metal ions and organic ligands, and has various structures depending on the type. Representative metal organic structures include ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-5, ZIF-6, ZIF-7, ZIF- ZIF-12, ZIF-22, ZIF-65, ZIF-69, ZIF-71, ZIF-78, ZIF- Metallic Organic Structures that Can Embed No limitations are placed on specific metal organic structures. Further, the metal salt used to form the metal organic structure _{Zn 4 O (CO 2) 6} , Zn 3 O (CO 2) 6, Cr 3 O (CO 2) 6, In 3 O (CO 2) 6 _{, Ga 3 O (CO 2)} 6, Cu 2 O (CO 2) 4, Zn 2 O (CO 2) 4, Fe 2 O (CO 2) 4, Mo 2 O (CO 2) 4, Cr 2 O ( _{CO 2) 4, Co 2 O} (CO 2) 4, Ru 2 O (CO 2) 4, Zr 6 O 4 (OH 4), Zr 6 O 4 (CO 2) 12, Zr 6 O 8 (CO 2) _{8, In (C 5 HO 4} N 2) 4, Na (OH) 2 (SO 3) 3, Cu 2 (CNS) 4, Zn (C 3 H 3 N 2) 4, Ni 4 (C 3 H 3 N ₂ ) _8, Zn ₃ O ₃ (CO ₂ ) ₃ , _{Mg 3 O 3 (CO 2)} 3, Co 3 O 3 (CO 2) 3, Ni 3 O 3 (CO 2) 3, Mn 3 O 3 (CO 2) 3, Fe 3 O 3 (CO 2) 3, _{Cu 3 O 3 (CO 2)} 3, Al (OH) (CO 2) 2, VO (CO 2) 2, Zn (NO 3) 2, Zn (O 2 CCH 3), Co (NO 3) 2, Co (O ₂ CCH ₃₎ and the like, and organic ligands are, oxalic acid, fumaric acid, H 2 BDC, H 2 BDC-Br, H 2 BDC-OH, H 2 BDC-NO 2, H 2 BDC-NH 2, _{H 4 DOT, H 2 BDC- (} Me) 2, H 2 BDC- (Cl) 2, H 2 BDC- (COOH) 2, H 2 BDC- (OC 3 H 5) 2, H 2 BDC- (OC 7 _{H 7) 2, H 3 BTC} , H 3 BTE, H 3 BBC, H 4 ATC, H 3 THBTS, H 3 ImDC, H 3 BTP, DTOA, H 3 BTB, H 3 TATB, H 4 ADB, TIPA, ADP _{, H 6 BTETCA, DCDPBN, BPP34C10DA} , Ir (H 2 DPBPyDC) (PPy) 2 +, H 4 DH 9 PhDC, H 4 DH11PhDC, H 6 TPBTM, H 6 BTEI, H 6 BTPI, H 6 BHEI, H 6 BTTI , H ₆ PTEI, H ₆ TTEI, H ₆ BNETPI, H ₆ BHEHPI, and HMeIM. If the metal organic structure of the hollow structure mentioned above can be produced, there is no limitation on the specific metal ion and the organic ligand. The metal ions and the organic ligands mentioned above may be synthesized using at least one of the synthesis methods of room temperature synthesis, hydrothermal synthesis, solvent thermoassay, ion thermal synthesis, ultrasonic synthesis, solvent minimization synthesis, and mechanical chemical synthesis do.

Next, a step S220 of synthesizing a nanoparticle catalyst using the synthesized metal organic structure will be described. The metal organic structure is immersed in a solution containing the metal salt for 1 to 24 hours so that the metal salt can be sufficiently diffused into the hollow structure of the metal organic structure synthesized above. At this time, the concentration of the metal salt in the solution is 0.1 mg / ml ?? 200 mg / ml. The solvent used in the preparation of the solution is ethanol, deionized water (DI-water), chloroform, N, N'-dimethylformamide ), N, N'-dimethylacetamide, and N-methylpyrrolidone. If the metal salt is a soluble solvent, it may be dissolved in a specific solvent . Here, the metal that can be synthesized inside the hollow structure of the unit metal organic structure does not have any particular restriction as long as it exists in ionic form. (II) chloride, cobalt (II) acetate, lanthanum (III) nitrate, lanthanum (III) acetate, platinum (IV) chloride and platinum (II) chloride, nickel (II) acetate, ruthenium (III) chloride, iron (III) acetate, Pd, Rh, Ru, Ni, Co, Cr, Ir, Au, Pd, and Pd are used as the precursors. Nanoparticle catalysts such as Ag, Zn, W, Sn, Sr, In, Pb, Fe, Cu, V, Ta, Sb, Sc, Ti, Mn, Ga and Ge can be synthesized. Metal organic structure The reducing agent that reduces the metal salt contained in the hollow structure includes sodium borohydride (NaBH ₄ ), formic acid (HCOOH), oxalic acid (C ₂ H ₂ O ₄ and lithium aluminum hydride (LiAlH ₄ ) can be used. If the reducing agent is capable of forming a metal nanoparticle catalyst by reducing a metal salt, it can be used without any particular limitation . The solution in which the metal salt inside the metal organic structure is reduced using a reducing agent is filtered through centrifugation to filter the metal organic structure including the nanoparticle catalyst. The size of the nanoparticle catalyst bound to the metal organic structure can be controlled in the range of 0.1 nm to 10 nm by controlling the amount of the precursor and each nanoparticle catalyst is attached to different hollow structures of the metal organic structure It has a very big advantage that it is dispersed well without clumping. Through the high temperature heat treatment process, the organic ligand of the metal organic structure is removed, the metal ion of the metal organic structure is oxidized, and the nanoparticle catalyst embedded in the metal organic structure is converted into metal or metal oxide. In this case, metal particles that are well oxidized are easily converted into metal oxide particles. Metal oxides formed the metal ion of the metal-organic structure is oxidized is _{ZnO, Fe 2 O 3, Fe} 3 O 4, NiO, CuO, In 2 O 3, Co 3 O 4, NiCo 2 O 4, ZrO 2, Cr ₃ O ₄ , MnO ₂ , MgO, and the like.

Next, a step S230 of fabricating a mixed solution of the metal organic structure / polymer / metal oxide precursor including the nanoparticle catalyst synthesized using the synthesized metal organic structure will be described. In this step S230, the polymer / metal oxide precursor mixed spinning solution having the uniformly dispersed metal organic structure using the nanoparticle catalyst prepared in S220 is prepared. Here, the solvent may be a compatible solvent such as N, N'-dimethylformamide, dimethylsulfoxide, N, N'-dimethylacetamide, N-methylpyrrolidone, deionized water, ethanol, A solvent that can dissolve the polymer at the same time should be selected. In addition, the polymer which can be used here is not limited to a specific polymer if it is a polymer which can be dissolved together with a solvent and can be removed through a high-temperature heat treatment. Specifically, examples of the polymer that can be used include polymethyl methacrylate, polyvinyl pyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyacrylonitrile polyethylene oxide, polypropylene oxide, polyethylene oxide copolymer, polypropylene oxide copolymer , Polycarbonate, polyvinyl chloride, polycaprolactone, polyvinyl fluoride, and the like. The metal oxide precursor used in this step is dissolved in a solvent and heated at a high temperature to form a precursor of ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, TiO ₂ , CuO, In ₂ O ₃ , Zn ₂ Or a combination of _two or more of SnO ₄ , Co ₃ O ₄ , PdO, LaCoO ₃ , NiCo ₂ O ₄ , Ca ₂ Mn ₃ O ₈ , V ₂ O ₅ , Cr ₂ O ₃ , 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 , InTaO ₄ , 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 , Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-7, and the like, the precursor including the metal salt capable of forming the metal oxide having the gas sensor characteristic does not limit the specific metal salt. The ratio of the polymer and the metal oxide precursor for forming the spinning solution preferably has a value between 1: 0.5 and 1: 2.

The electrospun solution is prepared by dissolving the metal oxide precursor in a solvent, adding the metal organic structure containing the nanoparticle catalyst prepared in the above step (S220) to the metal salt solution, and mixing and dispersing the metal organic structure. After sufficiently mixing, the polymer is added in an appropriate ratio and stirred until the polymer is completely dissolved in the mixed solution. And the mixture is agitated sufficiently for 5 to 48 hours at a temperature of 20 to 50 ° C to uniformly mix the nanoparticle catalyst-containing metal organic structure, the metal oxide precursor and the polymer in the solution.

The synthesized solution is subjected to electrospinning to produce a polymer / metal oxide precursor composite nanofiber having a metal organic structure-bound nanoparticle catalyst (S240). In the electrospinning, a syringe is filled with the nanoparticle catalyst / metal organic structure / polymer / metal oxide precursor complex solution prepared above, and the syringe is pushed at a constant speed using a syringe pump, To be discharged. The electrospinning system may include a high voltage, grounded conductive substrate, a syringe, and a syringe nozzle. When a high voltage (5 to 30 kV) electric field is applied between the syringe filled solution and the conductive substrate, the syringe nozzle The spinning solution to be discharged is received on the conductive substrate in the form of nanofibers. The rate of discharge can be adjusted from about 0.01 ml / min to about 0.5 ml / min, and nanoparticle catalyst / metal organic structure / polymer / metal oxide precursor composite nanofiber having a desired diameter can be manufactured through control of voltage and discharge amount .

Finally, a metal oxide nanotube is prepared by uniformly attaching the first metal oxide, which contains nanoparticle catalysts without agglomeration, to the surface of the second metal oxide nanotube through a high-temperature heat treatment of the prepared composite nanofiber, (S250), the organic ligands of the polymer and the metal organic structure are decomposed and removed through the heat treatment in the temperature range of 400 to 800 ㅀ C, the metal ions of the metal organic structure are oxidized to form the first metal oxide, The metal oxide precursor is oxidized to form a second metal oxide. Here, when the high temperature heat treatment (400 ?? 800 ?? C) is carried out at a rapid heating rate of 10? C / min, the second metal oxide is oxidized from the surface of the composite nanofiber, The metal oxide precursor is rapidly diffused to the surface of the nanofiber to form hollow pores therein and finally to form hollow nanotubes.

3 schematically shows a manufacturing process according to a method of manufacturing a member for a gas sensor using metal oxide nanotubes bonded with a nanoscale heterogeneous catalyst using an electrospinning method according to an embodiment of the present invention.

In the first step S310, a mixed solution composed of a metal organic structure, a metal oxide precursor, and a polymer including a nanoparticle catalyst is subjected to electrospinning so that a metal organic structure including a nanoparticle catalyst is uniformly dispersed An example of fabricating nanofibers is shown.

Step S320 of the second process is a process of high temperature heat treatment of the composite nanofibers synthesized in step S310. Through the high-temperature heat treatment (400 ° C to 800 ° C) at a rapid heating rate (10 ° C / min), the organic ligands of the polymer and the metal organic structure are all removed and the metal ions of the metal oxide precursor and the metal organic structure are oxidized, The first metal oxide heterogeneous catalyst to which the particle catalyst is bound forms a nanotube structure that is uniformly bound to the surface of the second metal oxide.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. The examples and comparative examples are merely intended to illustrate the present invention, and the present invention is not limited to the following examples.

Example 1: Preparation of zinc (Zn) based metal organic structure with Pd nanoparticle catalyst (zeolite imidazole framework, ZIF-8)

First, 2.933 g of Zn (NO ₃ ) ₂ H ₂ O and 6.489 g of an organic ligand (2-methylimidazole) were dissolved in 200 mL of methanol to prepare a Zn-based metal organic structure (ZIF-8) After complete dissolution, the two solutions were mixed and stirred at room temperature for 5 hours using a magnetic stirrer at a speed of 300 rpm. After removing the remaining Zn precursors and organic ligands without reacting by using a centrifuge, the solution changed into milky light and washed with ethanol. The centrifuge should preferably run at 3,000 rpm for at least 10 minutes. After the ethanol washing and centrifugation process is further performed three or more times, the purified ZIF-8 particles are collected by drying at 50 ° C for 12 hours or more.

In order to incorporate the Pd nanoparticle catalyst in the metal organic structure synthesized by the above process, the following process is performed. After dissolving 10 mg of Pd precursor (K ₂ PdCl ₄ ) and 40 mg of ZIF-8 in 1 g of deionized water, the metal salt aqueous solution was slowly dropped into a solution in which the metal organic structure was dispersed, , The Pd metal ions are diffused into the internal hollow structure of the metal organic structure. Here, stirring conditions for the preparation of the mixed solution proceed at room temperature for about one hour at 100 rpm. After the metal ions are diffused into the metal organic structure, NaBH ₄ reducing agent is used to reduce metal ions (Pd ²⁺ ) in the metal organic structure hollow body to metal (Pd) to form a nanoparticle catalyst. The reducing agent, NaBH _4, used in this step is formulated into a 40 mM aqueous solution and then added with 0.5 ml of NaBH ₄ . The metal organic structure containing the metal nanoparticle catalyst synthesized using a centrifugal separator is preferably extracted at a speed of about 10,000 rpm to about 12,000 rpm for at least 10 minutes. The ZIF-8 containing the Pd nanoparticle catalyst thus extracted is mixed with 2 mL of deionized water, and the dispersion thus prepared is used in the preparation of the electrospinning solution.

FIG. 4 shows a scanning electron microscope image of a Zn-based metal organic structure including the Pd nanoparticle catalyst prepared by the above process. It can be confirmed that the synthesized ZIF-8 has a size of about 80 nm.

FIG. 5 shows transmission electron microscope photographs of a Zn-based metal organic structure including Pd nanoparticle catalyst prepared by the above process. It can be seen that the Pd nanoparticle catalysts having a size of about 2 nm to 3 nm are uniformly dispersed in the Zn-based metal oxide, and the presence of the Pd particles is clearly shown through the partial component analysis.

Example 2: Fabrication of a tin oxide (SnO ₂ ) nanotube structure with a zinc oxide (ZnO) -based heterogeneous catalyst containing a PdO nanoparticle catalyst utilizing a Zn- based metal organic structure containing a Pd nanoparticle catalyst

First, 1.35 g of dimethylformamide and 1.35 g of ethanol are mixed, and 0.25 g of a tin oxide precursor (SnCl ₂ ? H ₂ O) is added to the mixed solution and dissolved. Next, 200 mg of the Zn-based metal organic structure aqueous solution containing the Pd nanoparticle catalyst prepared in Example 1 was added to the tin oxide precursor solution and mixed. To facilitate electrospinning, 0.35 g of polyvinylpyrrolidone (molecular weight: 1,300,000 g / mol) was added to the electrospinning solution and stirred at a rotational speed of 500 rpm for 5 hours at room temperature. The electrospinning solution prepared by giving the syringe packed in (Henke-Sass Wolf, 10 mL NORM-JECT ??) connected to the syringe pump pushes a 0.1 ml / min of discharge speed, ache's nozzle (needle, 21 gauge) and When a high voltage of 15 kV is applied between the stainless steel use plates of the current collectors, a Zn-based metal organic structure / polyvinylpyrrolidone / tin oxide precursor composite nanofiber including a Pd nanoparticle catalyst is synthesized on the current collector plate do.

6 is a scanning electron microscope and transmission electron micrograph of a Zn-based metal organic structure / polyvinylpyrrolidone / tin oxide precursor composite nanofiber comprising a Pd nanoparticle catalyst obtained after electrospinning. It is confirmed that the Zn-based metal organic structure including the Pd nanoparticle catalyst is uniformly dispersed and functionalized in the one-dimensional nanofiber.

The Zn-based metal organic structure / polyvinylpyrrolidone / tin oxide precursor composite nanofiber including the Pd nanoparticle catalyst prepared as described above was heated at 600 ° C for one hour at a heating rate of 10 ° C / Followed by cooling to room temperature at a descending rate of 40 ㅀ C / min. The heat treatment was carried out in air atmosphere using Ney 's Vulcan 3 - 550 compact electric furnace. Through the high-temperature heat treatment process, both the polymer and the organic matter in the composite nanofiber are decomposed and removed. In addition, since the Pd nanoparticle catalyst and the Zn constituting the metal organic structure and the tin oxide precursor inside the nanofiber are oxidized to form PdO, ZnO and SnO ₂ , respectively, because of the heat treatment in the air atmosphere, ZnO-SnO ₂ nanotube structure, in which SnO ₂ particles bound to ZnO hetero catalysts containing PdO nanoparticle catalyst of nanometer size are uniformly bound to the surface of nanotube.

7 is a scanning electron micrograph of ZnO-bound SnO ₂ nanotubes containing the PdO nanoparticle catalyst obtained after the heat treatment prepared in Example 2. FIG. The diameter of the formed SnO ₂ nanotubes is about 300 nm, and it can be confirmed that ZnO complex heterogeneous catalysts in which PdO is bound to the outside and inside of the nanotube are bonded.

FIG. 8 is a transmission electron micrograph of SnO ₂ nanotubes bonded with ZnO containing the PdO nanoparticle catalyst prepared in Example 2. FIG. Transmission electron microscopy lattice analysis showed that the ZnO complex hetero-catalyst including PdO nanoparticle catalyst was functionalized in SnO ₂ nanotubes. The electron diffraction analysis showed that PdO, ZnO and SnO ₂ crystallized have. The transmission electron microscopic analysis (EDS) shows that Pd and Zn are uniformly dispersed in SnO ₂ , and the structure of SnO ₂ nanotubes can be confirmed clearly by line analysis.

COMPARATIVE EXAMPLE 1 A heterogeneous catalyst based on a metal organic structure was used as a non-functionalized SnO ₂  Nanotube structure fabrication

As a comparative example compared with the example 2, there is a structure in which a heterogeneous catalyst based on a metal organic structure forms a non-functionalized SnO ₂ nanotube. In the same manner as in Example 2, 1.35 g of dimethylformamide and 1.35 g of ethanol were mixed, and 0.25 g of tin oxide precursor (SnCl ₂ ? H ₂ O) was added to the mixed solution and dissolved. Next, 0.35 g of polyvinylpyrrolidone (molecular weight: 1,300,000 g / mol) was added to the electrospinning solution and stirred at a rotational speed of 500 rpm for 5 hours at room temperature to facilitate electrospinning. The electrospinning solution prepared by giving the syringe packed in (Henke-Sass Wolf, 10 mL NORM-JECT ??) connected to the syringe pump pushes a 0.1 ml / min of discharge speed, ache's nozzle (needle, 21 gauge) and When a high voltage of 15 kV is applied between the stainless steel use plates of the current collectors, polyvinylpyrrolidone / tin oxide precursor composite nanofibers are synthesized on the current collector plate. The polyvinylpyrrolidone / tin oxide precursor composite nanofibers were maintained at 600 ° C for one hour at a heating rate of 10 ° C / min. After cooling to room temperature at a descending rate of 40 ° C / min, SnO 2 ₂ nanotubes were prepared.

FIG. 9 is a scanning electron micrograph of SnO ₂ nanotubes prepared in Comparative Example 1 in which the metal organic structure-based heterogeneous catalyst is not bound. The diameter of the formed SnO ₂ nanotubes was about 300 nm, and unlike the SnO ₂ nanotubes bonded with the metal organic structure-based heterogeneous catalyst of Experimental Example 2, it was confirmed that the heterogeneous catalyst did not adhere to the inner wall and the outer wall of the nanotube have.

Above which it does not include the production of metal organic structure-based heterogeneous catalyst SnO ₂ nanotubes are detected for the wide gas with the second embodiment the ZnO-based two kinds of SnO ₂ nanotubes, the catalyst is a binder manufactured containing the PdO nanoparticle catalyst in Were used to compare characteristics.

COMPARATIVE EXAMPLE 2 [0042] A heterogeneous catalyst based on a metal organic structure was used as a non-functionalized SnO ₂  Fabrication of nanofiber structure

As a comparative example compared with Example 2, there is a structure in which a heterogeneous catalyst based on a metal organic structure forms SnO ₂ nanofibers that are not functionalized. In the same manner as in Example 2, 1.35 g of dimethylformamide and 1.35 g of ethanol were mixed, and 0.25 g of tin oxide precursor (SnCl ₂ ? H ₂ O) was added to the mixed solution and dissolved. Next, 0.35 g of polyvinylpyrrolidone (molecular weight: 1,300,000 g / mol) was added to the electrospinning solution and stirred at a rotational speed of 500 rpm for 5 hours at room temperature to facilitate electrospinning. The prepared electrospinning solution was poured into a syringe (10 mL), connected to a syringe pump and pushed out at a discharge rate of 0.1 ml / min., And a high voltage of 15 kV was applied between a 21 gauge and a stainless steel plate On the other hand, the polyvinylpyrrolidone / tin oxide precursor composite nanofiber is synthesized on the collector plate. The polyvinylpyrrolidone / tin oxide precursor composite nanofibers were maintained at 600 ° C for one hour at a heating rate of 5 ° C / min and then cooled to room temperature at a descending rate of 40 ° C / minute to obtain SnO ₂ nanofibers were prepared.

10 is a scanning electron micrograph of SnO ₂ nanofibers prepared in Comparative Example 1 in which the metal organic structure-based heterogeneous catalyst is not bound. The diameter of the formed SnO ₂ nanotubes was about 350 nm. Unlike the SnO ₂ nanotubes bonded with the metal organic structure-based heterogeneous catalyst of Experimental Example 2, the nanofiber structure was formed, and the metal organic structure- .

The cost does not contain a metal organic structure-based heterogeneous catalyst produced SnO ₂ nanofibers detection for wide gas with the Example 2 containing the PdO nanoparticle catalyst ZnO based on two kinds of SnO ₂ nanotubes, the catalyst is a binder manufactured by Were used to compare characteristics.

Experimental Example 1. ZnO-based heterogeneous catalyst-bound SnO 2 containing PdO nanoparticle catalyst ₂  Nanotubes, SnO ₂  Nanotubes, and SnO ₂  Fabrication and Characterization of Gas Sensors Using Nanofibers

In order to fabricate the sensing material for the gas sensor manufactured in Examples 1 and 2 and Comparative Examples 1 and 2 using the exhalation sensor, a ZnO-based heterogeneous catalyst-containing SnO ₂ nanotube containing a PdO nanoparticle catalyst, SnO ₂ Nanotubes, and SnO ₂ nanofibers are dispersed in 100 μL of ethanol, and then pulverized by ultrasonic cleaning for 1 hour. A SnO ₂ nanotube, a SnO ₂ nanotube, and a SnO ₂ nanofiber mixed solution, which were bound with a ZnO-based heterogeneous catalyst containing 5 μL of a PdO nanoparticle catalyst dispersed in the prepared ethanol, Gold (Au) electrodes were coated on patterned 3 mm ㅧ 3 mm alumina (Al ₂ O ₃ ) substrates, and then dried on a 60 ㅀ C hot plate. Repeat this procedure 4-6 times, a sufficient amount of PdO the ZnO-based heterogeneous catalyst has a binder of SnO ₂ nanotubes, SnO ₂ nanotubes containing the nanoparticle catalyst, and SnO ₂ nanofibers was allowed to coat the upper alumina sensor substrate .

The concentration of acetone (CH ₃ COCH ₃ ) gas was increased to 5, 4, 3, 2, 1, 0.6, 0.4, 0.2 and 0.1 ppm at high humidity (90% RH) And the sensor operating temperature was maintained at 400 ° C and the acetone sensing characteristics were evaluated. In Experimental Example 1, not only acetone gas, which is a typical example of the volatile organic compound gas but also hydrogen sulfide (H ₂ S), toluene (C ₆ H ₅ CH ₃ ), carbon monoxide (CO), pentane (C ₅ H ₁₂ ) (NH ₃ ) and the like were evaluated to evaluate the selective gas sensing characteristics.

11 is a graph showing the degree of reaction (R _air / R _gas, where R _air represents the resistance value of the gas sensor when air is injected, when the concentration of acetone gas decreases from 5 ppm to 0.1 ppm at 400 ° C, And R _gas represents the resistance value of the gas material when the acetone gas is injected). As shown in Figure 11, the PdO SnO ₂ nanotubes sensor with a ZnO-based heterogeneous catalyst binder including nanoparticles catalysts show a SnO ₂ nanotubes and SnO ₂ 2 times or more better sensitivity than nanofibers with respect to the acetone gas Able to know.

12 shows the results of the characterization of the reaction speed and the recovery speed of the gas sensor when the concentration of acetone is 1, 2, 3, 4, and 5 ppm at 400 ° C. As shown in the results, the SnO ₂ nanotubes bound with the ZnO-based heterogeneous catalyst containing the PdO nanoparticle catalyst showed rapid improvement in the reaction rate and the recovery rate within 20 seconds and 75 seconds, respectively.

FIG. 13 shows the reactivity values of acetone, hydrogen sulfide, toluene, carbon monoxide, pentane, and ammonia of a SnO ₂ nanotube bonded with a ZnO-based heterogeneous catalyst containing a PdO nanoparticle catalyst measured at 400 ° C. As shown in FIG. 12, the sensor made of SnO ₂ nanotubes bonded with a ZnO-based heterogeneous catalyst containing a PdO nanoparticle catalyst is characterized in that it is very superior to acetone in comparison with hydrogen sulfide, toluene, carbon monoxide, pentane and ammonia gas And that it exhibits selective sensing characteristics.

FIG. 14 shows the result of repeated detection of acetone at 1 ppm using SnO ₂ nanotubes bonded with a ZnO-based heterogeneous catalyst containing PdO nanoparticle catalyst at 400 ° C. As shown in the results, it can be confirmed that stable detection characteristics are exhibited even when repeated measurement is repeated 10 times or more.

In the above example, the sensor characteristics of SnO ₂ nanotubes bonded with a ZnO-based heterogeneous catalyst containing PdO nanoparticle catalyst with high sensitivity, fast reaction rate, recovery rate and selectivity for acetone were shown. In addition, by utilizing various kinds of nanoparticle catalysts, metal organic structures, and metal oxide materials, it is possible to expect a change in gas selectivity characteristics, and it is possible to obtain a variety of nanoparticle catalysts containing a plurality of nanoparticle catalyst particles, Of the second metal oxide nanotubes can be synthesized and a gas sensor array having high sensitivity and selectivity for various kinds of gases can be manufactured. The second metal oxide nanotube sensing material bonded with the first metal oxide based heterogeneous catalyst comprising the nanoparticle catalyst obtained from the metal organic structure template is excellent in the harmful environmental gas sensor and the health for analysis and diagnosis of the exhalation volatile organic compound gas It can be used for gas sensors for care.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art 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 illustrate the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: Metal oxide nanotube with nano-sized heterogeneous catalyst attached Member for gas sensor
110: a metal oxide nanotube in which a first metal oxide including a nanoparticle catalyst is uniformly bound to a surface of a second metal oxide nanotube,
121: Nanoparticle catalyst attached to first metal oxide based on metal organic structure after high temperature heat treatment
122: a first metal oxide based heterogeneous catalyst comprising a nanoparticle catalyst formed by oxidation of metal ions and removing organic ligands of the metal organic structure after the high temperature heat treatment;
123: a second metal oxide nanotube formed by oxidation of a metal oxide precursor after high temperature heat treatment;

Claims (21)

Wherein the first metal oxide-based heterogeneous catalysts including the nanoparticle catalyst are subjected to heat treatment of the composite nanofibers including the porous metal organic structure including the nanoparticle catalysts in the inner hollow structure, Wherein the metal oxide nanotube is bound to the surface of the metal oxide nanotube. The method according to claim 1,
The second metal oxide nanotube may be formed by a high-temperature heat treatment process on a composite nanofiber including a metal organic structure including the nanoparticles, a metal oxide precursor, and a polymer, wherein the organic ligand and the polymer Wherein the metal oxide precursor is oxidized and crystallized from the outside of the nanofiber, and the metal oxide precursor is oxidized and crystallized to form an outer metal Wherein the second metal oxide nanotube structure is formed by the diffusion rate difference between the oxide and the inner metal oxide precursor. The method according to claim 1,
Wherein the weight ratio of the nanoparticle catalyst contained in the hollow structure inside the metal organic structure is in the range of 0.001 to 25 wt% with respect to the first metal oxide and in the concentration range of 0.01 to 2 wt% with respect to the second metal oxide nanotube Wherein the metal oxide nanotube is bound to a nano-sized heterogeneous catalyst. The method according to claim 1,
Wherein the metal organic structure is selected from the group consisting of ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-5, ZIF-6, ZIF-7, ZIF- At least one metal organic structure selected from the group consisting of ZIF-12, ZIF-22, ZIF-65, ZIF-69, ZIF-71, ZIF-78, ZIF-90, ZIF-95, ZIF-9-67 and SIM- Wherein the metal oxide nanotube is bound to a nano-sized heterogeneous catalyst. The method according to claim 1,
The metal organic structure is a porous molecular sieve material in which metal ions and organic ligands are connected to each other through self-assembly. One or two or more catalyst metal ions can be encapsulated in the hollow, nm ?? Wherein the nanoparticle catalyst comprises a nanoparticle catalyst having a diameter in the range of 10 nm to 10 nm. The method according to claim 1,
The metal organic structure may be selected from the group consisting of platinum (IV) chloride, platinum (II) acetate, gold (III) chloride, At least one metal salt selected from nickel (II) chloride, nickel (II) acetate, ruthenium (III) chloride, ruthenium acetate, iridium (III) chloride, iridium acetate, tantalum (V) chloride and palladium (II) Wherein the nano-sized heterogeneous catalyst is attached to the inner surface of the metal oxide nanotube. The method according to claim 1,
The nanoparticle catalyst contained in the hollow structure of the metal organic structure may be at least one selected from the group consisting of Pt, Pd, Rh, Ru, Ni, Co, Cr, Ir, Au, Ag, Zn, W, Sn, Sr, In, Pb, Wherein the nanoparticle catalyst comprises at least one nanoparticle catalyst selected from the group consisting of Cu, V, Ta, Sb, Sc, Ti, Mn, Ga and Ge. The method according to claim 1,
The nanoparticle catalyst contained within the hollow structure of the metal-organic structure is then heat-treated _{Pt, PdO, PdO 2, Rh} 2 O 3, RuO 2, NiO, Co 3 O 4, Cr 2 O 3, IrO 2, Au, Ag , ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, Fe ₂ O ₃ , CuO, V ₂ O ₅ , VO ₂ , VO, Ta ₂ O ₅ , Sb ₂ O ₃ , Sc ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O _3, and GeO _2. The metal oxide nanotube is bonded to a nano-sized heterogeneous catalyst. The method according to claim 1,
The metal organic structure has an inner pore size of 0.5 nm ?? Wherein the metal oxide nanotube has a value in the range of 30 nm to 30 nm and an outer diameter range of 50 nm to 500 nm. The method according to claim 1,
Metal ion constituting the metal organic structure is then heat-treated _{ZnO, Fe 2 O 3, Fe} 3 O 4, NiO, CuO, In 2 O 3, Co 3 O 4, NiCo 2 O 4, ZrO 2, Cr 3 O 4 , MnO ₂ and MgO Wherein the metal oxide nanotube is substituted with one metal oxide selected from the group consisting of a metal oxide nanotube and a metal oxide nanotube. The method according to claim 1,
The metal organic structure may include a metal or metal oxide nanoparticle catalyst after heat treatment, and the first metal oxide particles may be porous particles, tetrahedron, cube, octahedron, dodecahedron, dodecahedron, hollow sphere, wherein the metal oxide nanotube is uniformly bound to the surface of the second metal oxide nanotube with at least one of a cube and a cube. The method according to claim 1,
The second metal oxide nanotube may be at least one selected from the group consisting of 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 one or more composites selected from _3-7 Wherein the nanotube comprises a nanotube composed of a metal oxide nanotube. The method according to claim 1,
The first metal oxide and the second metal oxide, which are formed by oxidizing the metal ion of the metal organic structure and the metal oxide precursor of the composite nanofibers, form a heterojunction, and n-type metal oxides such as TiO ₂ , ZnO, WO ₃ , SnO ₂ , IrO ₂ , In ₂ O ₃ , V ₂ O ₃ , MoO ₃ and p-type metal oxides such as Ag ₂ O, PdO, RuO ₂ , Rh ₂ O ₃ , NiO, Co ₃ O ₄ , CuO, Fe ₂ O ₃ , Fe ₃ O ₄ , V ₂ O ₅ , Cr ₂ O ₃ , a metal oxide selected from the group consisting of n-type / n-type, n-type / p-type and p-type / p-type metal oxides. Wherein the metal oxide nanotubes are bound to a nano-sized heterogeneous catalyst. The gas sensor according to any one of claims 1 to 13, wherein the metal oxide nanotubes to which the nano-sized heterogeneous catalyst is bound are coated on a sensor electrode capable of measuring resistance change to form a sensing material. A method for producing a metal oxide natto tube having a nano-sized heterogeneous catalyst,
(a) synthesizing a metal organic structure composed of a metal ion and an organic ligand;
(b) synthesizing a nanoparticle catalyst inside the hollow structure of the metal organic structure;
(c) mixing the metal organic structure comprising the synthesized nanoparticle catalyst with an electrospinning solution in which a metal oxide precursor and a polymer are dissolved together to form a metal organic structure / metal oxide precursor / polymer composite spinning solution containing a nanoparticle catalyst Producing;
(d) electrospinning the composite spinning solution to prepare a composite nanofiber in which a metal organic structure containing a nanoparticle catalyst is bound to the surface or inside of the metal oxide precursor / polymer composite nanofiber;
(e) subjecting the composite nanofibers to high-temperature heat treatment to uniformly bind the first metal oxide including the nanoparticle catalyst to the surface of the second metal oxide nanotube to produce functionalized metal oxide nanotubes;
(f) dispersing or pulverizing the metal oxide nanotubes to which the nano-sized heterogeneous catalyst is bound, and performing at least one coating process such as drop coating, spin coating, inkjet printing, and dispensing on the sensor electrode for measuring the oxide semiconductor type gas sensor ;
Wherein the nano-sized heterogeneous catalyst is bonded to the metal oxide nanotube. The method of claim 15, wherein
The step (a)
Characterized in that the metal organic structure is synthesized by using at least one synthesis method of a room temperature synthesis method, a hydrothermal synthesis method, a solvent thermo synthetic method, an ion thermal synthesis method, an ultrasonic chemical synthesis method, a solvent minimization synthesis method and a mechanical chemical synthesis method Wherein the metal oxide nanotube is bonded to the metal oxide nanotube. The method of claim 15, wherein
The step (b)
Wherein the metal organic structure is immersed in a solution in which the catalytic metal salt is dissolved to inject the catalyst metal salt into the metal organic structure to embed the nanoparticle catalyst inside the metal organic structure,
Wherein the solution containing the metal organic structure has a salt ratio ranging from 0.1 to 200 mg / ml. 16. The method of claim 15,
The step (b)
Wherein when the specific metal ion is substituted in the metal organic structure, the specific metal ion is allowed to diffuse in the interior of the metal organic structure for at least 1 hour and no more than 24 hours. Wherein the metal oxide nanotube is bonded to the metal oxide nanotube. 16. The method of claim 15,
In the step (b)
The reducing agent for reducing the metal salt contained in the metal organic structure may be sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ), nascent 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) heterogeneous catalyst nano-size, comprising at least one of a sulfate Wherein the metal oxide nanotube is bonded to the metal oxide nanotube. 16. The method of claim 15,
In the step (e)
The oxidation heat treatment is carried out at a high temperature of 400 ° C to 800 ° C at a rapid heating rate of 10 ° C / min to allow the metal oxide precursor constituting the composite nanofiber to be oxidized from the outside, whereby the diffusion of the external metal oxide and internal metal ions Wherein the second metal oxide nanotube structure is formed by a Kirkendall effect due to the difference in speed between the first metal oxide nanotube structure and the second metal oxide nanotube structure. 16. The method of claim 15,
In the step (e)
The polymer composing the composite nanofiber and the organic ligand of the metal organic structure are thermally decomposed and removed through the heat treatment, and the metal ion and the metal oxide precursor of the metal organic structure are oxidized and crystallized, Oxide, and a second metal oxide nanotube, respectively, to form a heterojunction between the first metal oxide and the second metal oxide, and the n-type metal oxide such as TiO ₂ , ZnO, WO ₃ , SnO ₂ , IrO ₂ , In ₂ O ₃ , V ₂ O ₃ , MoO ₃ and p-type metal oxides such as Ag ₂ O, PdO, RuO ₂ , Rh ₂ O ₃ , NiO, Co ₃ O ₄ , CuO, Fe ₂ O ₃ , Fe ₃ O ₄ , V ₂ O ₅ , Cr ₂ O ₃ , a metal oxide selected from the group consisting of n-type / n-type, n-type / p-type and p-type / p-type metal oxides number, and the first nanoparticle catalyst nanoparticle catalyst that is included in the metal oxide is _{Pt, PdO, PdO 2, Rh} 2 O 3, RuO 2, NiO, Co 3 O 4, Cr 2 O 3, IrO 2, Au , Ag, ZnO, WO ₃ , SnO ₂ , SrO, In ₂ O ₃ , PbO, Fe ₂ O ₃ , CuO, V ₂ O ₅ , VO ₂ , VO, Ta ₂ O ₅ , Sb ₂ O ₃ , Sc ₂ O ₃ , TiO ₂ , MnO ₂ , Ga ₂ O _3, and GeO _{2. The} method of manufacturing the metal oxide nanotube according to claim 1,

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