KR101684738B1 - Gas Sensor Fabrication method of catalyst-loaded porous metal oxide nanofiber metal oxide nanofiber networks prepared by transferring of catalyst-coated polymeric sacrificial colloid template, and gas sensors using the same - Google Patents

Abstract

The present invention relates to a member for a gas sensor, a gas sensor using the same, and a method of manufacturing the same. Specifically, a polymer sacrificial layer template coated with a catalyst is pyrolyzed and removed, and the catalyst is transferred to function as a metal oxide semiconductor nanofiber A metal oxide nanofiber having a one-dimensional structure and pores are formed on the surface of the metal oxide nanofiber, and at the same time, a catalyst is bound to a position where pores are formed, thereby forming a member for a gas sensor using a catalyst- And a manufacturing method thereof.
In the present invention, a catalyst is coated on the surface of a polymer sacrificial layer template that can be removed through heat treatment at a high temperature, and a polymer sacrificial layer template coated with a catalyst is mixed with an electrospinning solution to form composite nanofibers Dimensional structure of the metal oxide nanofibers in which the pores of various sizes are formed by removing the sacrificial layer template through the high temperature heat treatment and the catalyst is selectively bound to the pores formed. It is possible to maximize the catalytic effect by using the selectively bound catalyst with excellent selectivity so that detection can be performed for various gases with a high sensitivity characteristic capable of detecting a trace amount of gas through a simple detection process, Which is a process that simultaneously forms pores and catalyzes. A gas sensor member, a gas sensor, and a method of manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing a porous metal oxide semiconductor nanofiber including a catalyst obtained by transferring a catalyst from a sacrificial layer template having a catalyst attached thereto, and a gas sensor using the catalyst metal oxide nanofiber metal oxide nanofiber -coated polymeric sacrificial colloid template, and gas sensors using the same}

The present invention relates to a member for a gas sensor, a gas sensor using the same, and a method of manufacturing the same. More specifically, the present invention relates to a catalyst-coated polymer-based template for forming pores in and on a surface of a metal oxide nanofiber, A gas sensor, and a method of manufacturing the same.

Since the gas sensing characteristics using metal oxide sensing materials have been revealed, sensors have been actively developed to detect specific gases using various metal oxide materials and structures. Many researches have been made because of the advantage that a sensor can be easily made because a specific principle of adsorption of a specific gas on the surface of the atmosphere changes the electrical resistance or electric conductivity of the metal oxide. Specific applications include the detection of hazardous environmental gases exposed to the atmosphere and information about the hazardous gas leakage in the vicinity. Typically, such harmful environmental gases include NO, NO ₂ , SO ₂ , CO, and CO ₂ . In recent years, development of super sensitive gas sensing materials has been made possible by the development of nano material synthesis technology, and development of a portable erosion diagnosis sensor has been made through miniaturization and cost reduction using metal oxide sensing materials. The exhalation diagnostic sensor is a sensor that detects the gas released from the mouth through the human lungs. It is a diagnostic sensor that detects the biomarker contained in the person's exhalation to determine the presence or absence of the disease. Representative biomarker gases included in the exhalation include volatile organic compounds (VOCs) such as acetone, toluene, and pentane. These gases are indicators of diabetes, lung cancer, and heart disease, respectively. In addition, biological surface gases such as hydrogen sulfide (H ₂ S), ammonia (NH ₃₎ , and nitrogen monoxide (NO) are known to be associated with halitosis, kidney disease and asthma.

Biological surface gases for the diagnosis of harmful environmental gases and diseases are generally detected in the range of ppb (parts per billion) to ppm (part per million), and in particular, the bioindicator gas released through exhalation is 10 ppb to 10 ppm Lt; RTI ID = 0.0 > very < / RTI > For example, in the case of diabetes, it can be judged based on the trace amount of acetone (CH ₃ COCH ₃ ) contained in the exhalation. In case of a normal person, acetone is contained in the exhalation of 900 ppb (parts per billion) , And diabetic patients will have high concentrations of acetone above 1800 ppb. In order to diagnose lung cancer, 30 ppb of toluene (C ₆ H ₅ CH ₃ ) should be detected, and 100 ppb of ammonia should be detected as a diagnostic parameter for kidney disease. Therefore, it is essential to develop an ultra-sensitive sensing material to effectively detect low-concentration gases.

A variety of nanostructures have been studied for the development of ultra-sensitive sensing materials. Basically, gas sensing using metal oxide has been studied to maximize the specific surface area since electrical resistance or electric conductivity changes through surface reaction. In addition, fabrication technology and synthesis technology of a hollow structure in which a large number of pores capable of gas permeation were distributed were developed, and the gas sensing characteristics were evaluated. A nanofiber structure having a one-dimensional structure has been proposed as a method for developing a sensing material in which a large number of pores are distributed while maximizing the specific surface area. The nanofiber structure with a one-dimensional structure has a wide specific surface area and induces rapid diffusion of gas due to the presence of pores between the fibers and the fibers to exhibit a shape suitable for a material for detecting a high sensitivity sensor. Electrospinning technology is one of the ways to easily fabricate a one-dimensional nanofiber structure. Electrospinning is a technique in which a pure polymer or a polymer / metal oxide precursor is dissolved in a specific solvent to prepare a mixed electrospinning solution, and then a high voltage is applied between the syringe nozzle and the current collector to form nanofibers. In addition to obtaining pure polymer nanofibers through electrospinning, metal oxide nanofibers can be prepared by heat treating the polymer / metal oxide precursor composite nanofibers at a high temperature.

The electrospinning technology can use various metal oxide precursors and has the advantage that various types of metal oxides can be obtained through a heat treatment process. A pure metal nanofiber may be used as a sacrificial layer template and a metal or metal oxide may be coated on the upper part by using physical vapor deposition (PVD) or chemical vapor deposition (CVD) Thereby forming nanotubes and a half-tube structure. By using the electrospinning technique, various kinds of one-dimensional metal oxide nanofibers can be formed. In addition, by adjusting process parameters (discharge amount, ratio of polymer / metal oxide precursor and combination, heat treatment conditions, etc.) It is possible to fabricate a structure having a wide pore structure. In addition, by introducing additional deposition process using pure polymer, it is possible to fabricate nanotube and half-tube structure, and it has been suggested that the specific surface area and porosity can be improved.

In addition to the method of increasing the specific surface area and the porosity, a method of synthesizing and binding a catalyst in the development of an ultra-sensitive metal oxide sensing material has been essentially used. For example, studies have been conducted to synthesize expensive metal catalysts such as Pt, Ir, Pd, Ag, and Au by a method such as a polyol process and bind them to metal oxides.

However, the process of forming pores in the metal oxide may be complicated and difficult, and a separate metal nanoparticle may be synthesized. In this case, It is pointed out that it is a disadvantage that it must go through cumbersome procedure to settle. In fact, the process of synthesizing the metal nanoparticle catalyst has a disadvantage in that the manufacturing process is complicated because it uses a chemical synthesis method, and there is a problem in that it requires additional heat treatment in order to bind the prepared catalyst and the metal oxide nanofibers I have. Therefore, the production cost is increased and the production time is prolonged, which can cause difficulties in mass production.

To overcome these disadvantages, there is a need for a manufacturing process method that can bind the catalyst very easily. Also, there is a need to propose a method of achieving pore formation at the same time as the binding of the catalyst to improve the specific surface area.

The embodiments of the present invention suggest a technology for developing a catalyst-metal oxide sensing material capable of simultaneously forming pores and binding of a catalyst in the above-mentioned one-dimensional metal oxide nanofibers, The present invention provides a gas sensor member capable of mass production in an efficient process as well as a high sensitivity characteristic capable of detecting a trace amount of gas through an easy manufacturing method, a gas sensor using the same, and a manufacturing method thereof.

According to an aspect of the present invention, there is provided a method of manufacturing a sensor material and a method of manufacturing the same, which comprises: (a) forming a metal oxide semiconductor nanofiber on a substrate, Coating a catalyst precursor on a sacrificial layer template; (b) preparing a metal oxide precursor / polymer mixed electrospin solution comprising a sacrificial layer template coated with a catalyst; (c) forming a metal oxide precursor / polymer composite fiber to which a catalyst-coated sacrificial layer template is added using electrospinning technology; And (d) oxidizing the metal oxide precursor and the catalyst by removing the sacrificial layer template and the polymer through a high-temperature heat treatment to form a pore in the one-dimensional metal oxide nanofiber, or at the same time, Wherein the catalyst is selectively bound to the surface of the one-dimensional nanofiber and the pores formed in the surface of the one-dimensional nanofiber and containing a plurality of pores therein.

Here, in the step (a), the sacrificial layer template may be coated with the catalyst using a chemical coating method or a physical vapor deposition method.

Also, in the step (a), the amount of the catalyst bound to the sacrificial layer template can be controlled quantitatively in the range of 0.001 wt% to 20 wt% by quantitatively controlling the coating amount of the catalyst.

Also, in the step (a), the sacrificial layer template may have various sizes and structures. For example, spherical, pentagonal, square, triangular or irregular in shape.

Also, the sacrificial layer template in the step (a) is characterized in that it can be removed in a high-temperature heat treatment.

Further, the sacrificial layer template may be coated with a single species or a plurality of catalysts in the step (a).

In addition, in the step (b), the electrospinning solution for electrospinning may be formed in various combinations using various kinds of metal oxide precursors and various polymer complexes.

Also, in the step (b), a sacrificial layer template coated with a catalyst may be added to the metal oxide precursor / polymer composite electrospinning solution to prepare a transfer spinning solution.

Also, in step (b), a sacrificial layer template coated with various concentrations of catalyst may be added to the metal oxide precursor / polymer composite electrospinning solution.

In the step (c), electrospinning can form a metal oxide nanofiber having a one-dimensional structure by mixing various kinds of metal oxide precursors and polymers, and the metal oxide nanofiber having a one- And a sacrificial layer template coated with a catalyst.

Also, in the step (c), the concentration of the sacrificial layer template coated with the catalyst bound to the one-dimensional metal oxide precursor / polymer composite fiber formed in the electrospinning process can be controlled.

In the step (d), the metal oxide precursor / polymer composite nanofiber having a one-dimensional structure is decomposed while the high-temperature heat treatment is performed, and the metal oxide precursor is oxidized to form a one-dimensional metal oxide nanofiber can do.

In addition, in the step (d), the sacrificial layer template coated with the formed catalyst may be removed while being subjected to a high-temperature heat treatment, and pores having various sizes may be formed while being removed. It can bind to the surface and inside of the fiber.

According to another aspect of the present invention, there is provided a method of manufacturing a gas sensor using a metal oxide nanofiber sensing material having a one-dimensional structure in which a catalyst is applied to a pore and selectively forming a porous structure, ; And coating the nanostructure on the sensor electrode.

Here, in coating the porous nanofibers having the one-dimensional structure selectively coated with the catalyst on the sensor electrode, one of coating, drop coating, screen printing, direct coating through electrospinning, and coating through transfer may be used .

The size of the sacrificial layer template according to another aspect of the present invention may have a size range of 50 nm to 5 μm and the sacrificial layer template does not have a template surface specific limitation that can be removed by a high temperature heat treatment process. Representative examples include polymethylmethacrylate (PMMA), polyvinylpyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polystyrene (PS) and polyacrylonitrile (PAN) And may be a mixture of one or two or more selected from the group consisting of lithium fluoride (PVDF), polyacrylic acid (PAA), polydianil dimethylammonium chloride (PDADMAC) and polystyrene sulfonate (PSS).

Here, depending on the size of the sacrificial layer template, the size of the pores formed after the electrospinning can be variously adjusted together with the metal oxide precursor / polymer mixed solution. Here, the size of the pores formed may be 15 nm to 3.5 μm, which is 30% to 70% shrunk compared to the size of the sacrificial layer template.

The formed pores may be formed on the surface and inside of the one-dimensional metal oxide, and may form pores of various shapes. Here, the shape of the pores is such that the pores formed by connecting the sacrificial layer template and the enlarged pores formed by aggregating the sacrificial layer template, the open pores connected to the inside of the one-dimensional metal oxide nanofiber surface and the sacrificial layer template, It is possible to form closed pores contained therein.

A catalyst-coated sacrificial layer template according to another aspect of the present invention can be formed by a chemical method such as a layer-by-layer coating, a coating using a chemical vapor deposition (CVD) method, an atomic layer deposition And the like. As a physical method, the catalyst can be bound by coating the surface of the sacrificial layer template by physical vapor deposition (evaporation) and sputtering.

The surface of the sacrificial layer template may be coated with at least one of Pt, Au, Ag, Fe, Ni, Ti, Sn, Si, Al, Cu, Mg, Sc, V, Cr, , Sr, W, Ru, Ir, Ta, Sb, in, Pb, can be coated with one or more than one metal of Pd, and various metal oxides Fe ₂ O to the catalyst _3, Fe ₃ O _4, NiO, CuO , Co ₃ O ₄ , PdO, V ₂ O ₅ , Cr ₃ O ₄ , CeO ₂ , Ag ₂ O, RuO ₂ , IrO ₂ and MnO ₂ .

Specifically, as a catalyst coating method, a catalyst is coated on a sacrificial layer template using a layer-by-layer coating, which is one of the chemical coating methods, through a solution process, and the catalyst used may be bound to a sacrificial layer template in the form of a salt .

(III) acetate, silver (III) acetate, silver chloride, silver acetate, iron (III) chloride, iron (III) chloride and platinum (III) chloride, iridium acetate, tantalum (V) chloride, and palladium (II) chloride. In addition, And any combination of two or more of these metal salts may be coated with a catalyst on the surface of the sacrificial layer template.

According to still another aspect of the present invention, metal oxide nanofibers having a one-dimensional structure can be formed by mixing various kinds of metal oxide precursors and polymers and heat treatment at a high temperature. Typical examples 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, may be composed of _{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 at least one or both of _3-7.

The metal oxide nanofibers of the one-dimensional structure may have a diameter in the range of 50 nm to 10 mu m and a length in the range of 1 mu m to 100 mu m.

In addition, the metal oxide nanofibers of the one-dimensional structure may have irregular shapes on the surface of the nanofibers by forming a plurality of pores on the surface and inside of the metal oxide nanofibers by the catalyst-coated sacrificial layer template. The porous metal oxide nanofibers may be formed by selectively transferring the catalyst while the sacrificial layer template coated with the catalyst is removed. The catalyst may have a weight ratio in the range of 0.001 wt% to 20 wt% relative to the metal oxide.

According to another aspect of the present invention, there is provided a sensing material using a porous 1-dimensional metal oxide nanofibers formed by binding a selective catalyst and a plurality of pores, comprising a member for a gas sensor according to the present invention, .

Here, the prepared porous one-dimensional metal oxide nanofibers selectively bound to the catalyst provide a space through which gas can easily permeate due to an effective pore distribution and increase the surface area capable of reacting with the gas through the change of the surface shape . In addition, by the catalyst selectively bound to the pores, it is possible to exhibit excellent gas sensing characteristics by utilizing the catalytic effect upon gas sensing.

Here, the gas sensor senses the concentration of a specific volatile organic compound gas from a person's exhalation to determine the presence or absence of a disease, and can detect harmful environmental gases in the room and outdoor.

According to the present invention, in the production of a metal oxide nanofiber having a one-dimensional structure, a sacrificial layer template coated with a catalyst is used to form a plurality of pores on the surface and inside of the one-dimensional metal oxide nanofiber, And the gas sensor can be effectively detected by activating the catalytic reaction during the gas reaction by selectively attaching the catalyst to the sites where the pores are formed, A gas sensor member, a gas sensor, and a method for manufacturing the gas sensor, which can be mass-produced with excellent selectivity so as to be able to detect various gases with a high sensitivity characteristic capable of detecting a trace amount of gas through the gas sensor Effect.

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 the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic view of a member for a gas sensor using one-dimensional porous metal oxide semiconductor nanofibers selectively catalyzed according to an embodiment of the present invention.
FIG. 2 is a flowchart of a method of manufacturing a gas sensor using a one-dimensional porous metal oxide semiconductor nanofibers in which a catalyst is selectively bonded at a position where pores are selectively formed using a sacrificial layer template coated with a catalyst according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) photograph of a polystyrene sacrificial layer template that is not coated with a catalyst according to an embodiment of the present invention.
4 is a scanning electron micrograph of a Pd catalyst coated polystyrene sacrificial layer template according to an embodiment of the present invention.
5 is a scanning electron microscope (SEM) image of a Pt-coated polystyrene sacrificial layer template according to an embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the Pd catalyst-coated polystyrene sacrificial layer template and the tungsten oxide precursor / polyvinylpyrrolidone (PVP) composite material after the formation of the one-dimensional nanofibers through the electrospinning technique according to an embodiment of the present invention It is an electron microscope photograph.
FIG. 7 is a scanning electron micrograph of a tungsten oxide precursor / polyvinylpyrrolidone (PVP) composite nanofiber comprising a polystyrene sacrificial layer template coated with a Pd catalyst according to an embodiment of the present invention after a high temperature heat treatment process .
FIG. 8 is a scanning electron micrograph of porous tungsten oxide nanofibers prepared using a polystyrene sacrificial layer template coated with a Pd catalyst according to an embodiment of the present invention, and selectively analyzing the components at positions where the Pd catalyst is bound.
9 is a graph showing the results of a scanning electron microscope (SEM) of a pure tungsten oxide precursor / polyvinylpyrrolidone (PVP) composite nanofiber without a Pd catalyst coated polystyrene sacrificial layer template according to a comparative example of the present invention, It is a photograph.
10 is a graph showing the reactivity of a gas sensor using a one-dimensional porous tungsten oxide nanofibers having a Pd catalyst bonded at an optional position according to an embodiment of the present invention to toluene gas (1-5 ppm) at 350 ° C to be.
11 is a graph of reactivity of a gas sensor using a one-dimensional structure of porous tungsten oxide nanofibers with a Pd catalyst bonded at an optional position according to an embodiment of the present invention to acetone gas (1-5 ppm) at 350 ° C to be.
12 is a graph of the reactivity of a gas sensor using a one-dimensional structure of porous tungsten oxide nanofibers in which a Pd catalyst is bonded at an optional position according to an embodiment of the present invention, at 350 ° C for hydrogen sulfide gas (1-5 ppm) to be.
FIG. 13 is a graph showing the relationship between the concentration of toluene and various biomarker gases (ethanol, carbon monoxide, carbon monoxide, and the like) at 350 ° C of a gas sensor using porous tungsten oxide nanofibers having a one- Nitrogen monoxide, ammonia, pentane) at 1 ppm.

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, a gas sensor member, a gas sensor and a method of manufacturing the same using a porous metal oxide nanofiber having a one-dimensional structure with a catalyst selectively bonded will be described in detail with reference to the accompanying drawings.

The present invention is characterized in that a plurality of pores are formed on the surface and inside of the one-dimensional metal oxide nanofiber, and the catalyst can be selectively bound to the pores. Conventionally, studies have been made on the development of a process for improving specific surface area and porosity in order to improve the gas sensing characteristics of metal oxides. In addition, a metal or metal oxide is synthesized by a catalyst, Research has been carried out to make it conclude. This research has a disadvantage that a process of forming pores in a metal oxide of a one-dimensional structure and a process of synthesizing and binding a complex catalyst are separately required. In particular, when a metal or metal oxide catalyst is additionally synthesized, the process becomes complicated, and it is disadvantageous that it may be time consuming and costly.

In order to overcome this disadvantage, in the present invention, when a sacrificial layer template coated with a catalyst is used for electrospinning together with a metal oxide precursor / polymer mixed solution, a sacrificial layer template coated with a catalyst is mixed with a metal oxide precursor / The sacrificial layer template is removed and a large number of pores are formed. At the same time, the catalyst is bound to the metal oxide nanofibers, and the pores are formed and the pores are formed And the catalyst can be selectively bound to the catalyst. Here, the porous metal oxide nanofibers having a one-dimensional structure in which the catalyst is bound to the selective site can easily penetrate the gas by the pores formed by the sacrificial layer template and induce an effective surface reaction of the gas by the improved specific surface area A sensitive gas sensing material can be produced. In addition, it is possible to provide a gas sensor member capable of exhibiting excellent selectivity so as to be able to detect various gases and capable of being produced in an efficient process, capable of expecting an improvement in gas sensing characteristics through an effective catalytic reaction by selectively bound catalyst, A gas sensor and a manufacturing method thereof can be implemented.

1 is a schematic view of a member 100 for a sensor in which a metal oxide semiconductor nanofiber 110 having a one-dimensional structure according to an embodiment of the present invention and a plurality of pores are formed and a catalyst is selectively bound to a pore position have. When the nanofibers prepared by electrospinning the sacrificial layer template coated with the catalyst together with the metal oxide precursor / polymer blend solution are subjected to heat treatment at a high temperature, numerous pores 121 and 122 are formed on the surface and inside thereof And the coated catalyst is transferred to the metal oxide nanofibers where the pores are formed, thereby selectively binding the catalyst 123.

Here, the sacrificial layer template refers to a template that can be removed during the high-temperature heat treatment, and there is no particular restriction on the shape of the sacrificial layer template. Specific examples of the solvent include polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polystyrene (PS) and polyacrylonitrile And may be a mixture of one or two or more selected from the group consisting of lithium fluoride (PVDF), polyacrylic acid (PAA), polydianil dimethylammonium chloride (PDADMAC) and polystyrene sulfonate (PSS). In addition, the sacrificial layer template has a size ranging from 50 nm to 5 μm and is characterized by being dispersed without being removed when mixed with the electrospinning solution.

In addition, although there is a chemical and physical method for coating the sacrificial layer template with a catalyst, the present invention uses a chemical layer-by-layer method to coat the sacrificial layer template with a catalyst I have. The layer-by-layer coating method is a method in which a charged polymer is bound to a sacrificial layer template, and then a charged catalyst precursor is coated on the surface. A representative example of a chargeable polymer is polyadenyl dimethyl ammonium chloride (PDADMAC) having a positive charge and polystyrene sulfonate (PSS) having a negative charge. In addition, the catalyst precursor is typically selected from the group consisting of platinum (IV) chloride, platinum (II) acetate, gold (III) chloride, (III) chloride, iridium acetate, Tantalum (V) chloride, and Palladium (II) chloride. Among them, one or two The coating can be made in the above combination.

In addition, in the step of coating the catalyst, a catalyst-coated polystyrene template can be formed by binding to a charged polystyrene template, in addition to the form of metal salt, metal or metal oxide nanoparticles. Representative nanoparticles are nanoparticles of Pt, Au, Ag, Fe, Ni, Ti, Sn, Si, Al, Cu, Mg, Sc, V, Cr, Mn, Co, Zn, Sr, W, Ru, , In, Pb and Pd, and can be coated with various metal oxides Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, CuO, Co ₃ O ₄ , PdO, V ₂ O ₅ , Cr ₃ O ₄ , CeO ₂ , Ag ₂ O, RuO ₂ , IrO ₂ , and MnO ₂ . The size of such nanoparticles is preferably in the range of 1 nm to 10 nm. There is no particular limitation to the method as long as the method can coat the sacrificial layer template with the catalyst.

Here, the sacrificial layer template coated with the catalyst can be bound to the inside and the surface of the electrospun nanofiber, and the sacrificial layer template can be decomposed and removed in the high temperature heat treatment process.

In addition, the one-dimensional metal oxide nanofibers can be formed using electrospinning technology. The metal oxide precursor / polymer composite nanofiber can be formed by spinning an electrospinning solution in which a metal oxide precursor / polymer is mixed, The metal oxide nanofiber having a one-dimensional structure can be produced through a heat treatment process. The diameter of the metal oxide nanofibers of the formed one-dimensional structure is in the range of 50 nm to 10 μm and the length is in the range of 1 μm to 100 μm.

The one-dimensional metal oxide nanofiber may be a metal oxide semiconductor which exhibits a resistance change when a gas is injected. The metal oxide semiconductor may be 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 _3-7 .

Here, when the sacrificial layer template coated with the catalyst is added to the metal oxide precursor / polymer blend solution and spun together, the sacrificial layer template coated with the catalyst may be bound to the surface of the metal oxide precursor / polymer composite nanofiber and the inside thereof . The polymer and the sacrificial layer template are removed while the high temperature heat treatment is performed, the metal oxide precursor is oxidized to form a metal oxide, and the catalyst coated on the sacrificial layer template is transferred and bound to the metal oxide surface . The disassembled sacrificial layer template forms a large number of pores on the surface and inside of the one-dimensional metal oxide nanofibers. The pore size of the sacrificial layer template is 30% to 70% And has a size of 15 nm - 3.5 μm. The shape of the pores may vary depending on where the sacrificial layer template is tied. For example, if the sacrificial layer template is located on the surface of the metal oxide precursor / polymer nanofiber, it can form open pores 122. If the sacrificial layer template is located inside the precursor / polymer nanofiber, ) Can be formed.

In addition, the catalyst coated on the surface of the polymer can be transferred to the surface of the metal oxide nanofiber, and the metal oxide nanofiber 100 having the one-dimensional structure in which the catalyst is bound to the selective site can be produced. It is preferable that the catalyst is selectively bound at a position where the pores are formed (123), and the weight of the bound catalyst is in the range of 0.001 wt% to 20 wt% relative to the metal oxide. The catalyst transferred and bound to the metal oxide nanofibers may vary depending on the amount of the catalyst coated on the surface of the polystyrene template. If the amount of the coated catalyst is small and coated in the form of dispersed particles, the catalyst transferred to the metal oxide nanofibers If the catalyst is coated in the form of a continuous thin film because the amount of the catalyst coated on the surface of the polystyrene template is large, the shape of the catalyst transferred onto the metal oxide nanofibers may have a continuous thin film shape Or in a heat treatment process, the thin film may be broken and transferred through plastic shrinkage or the like to be coated in the form of an irregular plate-like film.

When the catalyst is bound to the surface of the polystyrene template in the form of particles, the catalyst particles transferred to the metal oxide nanofibers through the high-temperature heat treatment are characterized in that the catalyst can bind to the pores without agglomeration or entanglement among the catalysts.

In addition, by quantitatively adjusting the amount of the sacrificial layer template coated with the catalyst, the distribution of the pores and the amount of the catalyst to be bound can be quantitatively controlled, thereby effectively forming the pores and developing the sensing material to which the catalyst is bound, It is possible to easily and quickly manufacture various gas sensor members.

FIG. 2 is a flow chart of a method of manufacturing a gas sensor using porous metal oxide nanofibers in which a catalyst is bonded at an optional position obtained by using a catalyst-coated sacrificial layer template according to an embodiment of the present invention. As shown in FIG. 2, a method for producing a porous metal oxide nanofiber 100 in which a catalyst is bound to an optional position obtained by using a catalyst-coated sacrificial layer template according to an embodiment of the present invention, (S210) coating the sacrificial layer template with a catalyst (S210), preparing a metal oxide precursor / polymer mixed electrospinning solution containing the polymer-sacrificial layer template coated with the catalyst (S220) (S230) of forming a metal oxide precursor / polymer composite nanofiber by adding a polymer sacrificial layer template coated with a polymeric sacrificial layer template (S230), removing the polymer sacrificial layer template and the polymer through a high temperature heat treatment, oxidizing the metal oxide precursor, As the layer template is pyrolyzed, pores are formed, and the polymer sacrificial layer template is coated And a step (S240) of forming the bound porous metal oxide nanofibers by transferring the catalyst to the nanofibers. At this time, the fabricated composite nanofibers can be heat-treated at a high temperature to form a plurality of pores 121 and 122 on the surface and inside of the metal oxide nanofibers having a one-dimensional structure. At the same time, (Not shown).

First, a step S210 of coating the catalyst on the sacrificial layer template is discussed.

The method of coating the catalyst on the sacrificial layer template has chemical and physical methods, and the method is not particularly limited as long as the method is capable of coating. For example, in the present invention, the catalyst was coated on the sacrificial layer template using the layer by layer method. The layer-by-layer method is based on a solution process and is a method of coating using the charge existing on the surface of the sacrificial layer template. Here, a sacrificial layer template coated with a catalyst can be prepared by coating a polymer having a charge opposite to that of the sacrificial layer template, and then coating a catalyst precursor having a charge opposite to that of the sacrificial layer template.

The sacrificial layer template used in the layer-by-layer coating method is characterized in that it is dispersed in a colloid form in a solvent. The sacrificial layer template does not limit the specific substance as long as it is characterized by decomposition at high temperature. Typically, polymers such as polymethylmethacrylate (PMMA), polyvinylpyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polystyrene (PS), and poly A mixture of at least one member selected from acrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polydanediamethyl ammonium chloride (PDADMAC) and polystyrene sulfonate (PSS) .

The charge state of the surface of the sacrificial layer can be changed by coating the charged polymer on the sacrificial layer template. Typically, a positive charge or negative charge is applied to the surface of the sacrificial layer template using polydanediamethylammonium chloride (PDADMAC) with positive charge, polystyrene sulfonate (PSS) polymers with negative charge Can be changed. As a specific method of coating the chargeable polymer on the sacrificial layer template, the sacrificial layer template is uniformly mixed with the solution in which the chargeable polymer is dispersed. Thereafter, centrifugation separates the charged polymer-coated template and removes the charged polymer that does not bind to the surface of the sacrificial layer template. The charged polymer can be mixed with the sacrificial layer template and filtered through centrifugation to change the charge on the surface.

Next, a step of coating a catalyst on a sacrificial layer template having a charge on its surface will be described. It may be dissolved in a solvent in the form of a metal salt and attached to the surface of the sacrificial layer template which is charged in the ionic state. Specifically, the solution in which the charge-trapping polymer-coated sacrificial layer template is dispersed and the solution in which the catalyst salt is dispersed are uniformly mixed. The charge is uniformly mixed for a sufficient period of time to allow the catalytic salt to bind to the surface of the sacrificial layer template coated with the polymer. Subsequently, the sacrificial layer template coated with the polymer and the unreacted catalyst salt are removed by centrifugation. Catalysts include platinum (IV) chloride, platinum (II) acetate, gold (III) chloride, (III) chloride, iridium acetate, Tantalum (V) chloride, and Palladium (II) chloride. Among them, one or two The coating can be applied to the surface of the sacrificial layer template that is charged with the above combination.

The sacrificial polymer template coated with the catalyst may be uniformly dispersed in an electrospinning solution prepared by electrospinning.

Next, a step S220 of preparing an electrospinning solution in which the metal oxide precursor including the sacrificial layer template coated with the catalyst and the polymer are dissolved together will be described.

The one - dimensional structure of metal oxide nanofibers fabricated by electrospinning technology begins with the preparation of a metal oxide precursor / polymer mixed electrospinning solution. The electric spinning solution is prepared by dissolving the metal oxide precursor and the polymer mixed together. The metal oxide precursor is composed of a salt containing a metal and may be typically an organic acid salt, a halogen salt, an inorganic acid salt, an alkoxy salt, a sulfide salt, an amide salt, and the like. Specifically, there may be mentioned, for example, acetates, chlorides, acetylacetonates, nitrates, methoxides, ethoxides, butoxides, isopropoxide, sulfides, oxytriisopropoxide, (ethyl or cetylethyl) hexanoate, , Ethylamide, amide, and the like can be used.

Also, the polymer may be selected from the group consisting of PVAc (polyvinyl acetate), PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), PEO (polyethylene oxide), PANi (polyaniline), PAN (polyacrylonitrile) Methyl methacrylate), PAA (polyacrylic acid), or PVC (polyvinyl chloride), and can be used without any particular limitation as long as it is a polymer capable of being dissolved in a solvent to form polymer nanofibers.

The solvent for dissolving the metal oxide precursor and the polymer includes dimethylformamide (DMF), ethanol, acetone, water, and the like. If the metal oxide precursor and the polymer can dissolve the polymer, .

The spinning solution may be prepared by controlling the content of the metal oxide precursor, the polymer, and the solvent, which are solutes. For example, the spinning solution may comprise a solvent comprising a metal precursor in a range of 5 to 30 weight percent (wt%), a polymer in a range of 5 to 20 weight percent (wt%), .

In order to prepare an electrospinning solution in which the metal oxide precursor and the polymer are dissolved together, the metal oxide precursor and the polymer are dissolved in a solvent, the sacrificial layer template dispersion Solution may be mixed together. The catalyst-coated sacrificial layer template dispersion solution and the metal oxide precursor / polymer-dissolved solution are mixed and stirred. The stirring temperature may be 25-80 ° C and the stirring time may be 1-48 hours.

Here, the sacrificial layer template coated with the catalyst should remain in a dispersed colloid form without being dissolved in the metal oxide precursor / polymer mixed solution. If the catalyst-coated sacrificial layer template is dissolved in a solvent in which the metal oxide precursor / polymer is dissolved, it may be difficult to effect effective pore formation during the post-electrospinning process and to bind the catalyst to a selective location.

Next, a step S230 of fabricating nanofibers in which the catalyst-coated sacrificial layer template is bound to the inside and the surface of the metal oxide precursor / polymer composite nanofiber using the electrospinning technique will be described.

The sacrificial layer template may be bound to the surface and inside of the metal oxide precursor / polymer composite nanofiber by electrospinning the metal oxide precursor / polymer spinning solution mixed with the prepared catalyst-coated sacrificial layer template dispersion solution. The electrospinning device for conducting the electrospinning process is composed of a spray nozzle connected to a metering pump capable of quantitatively injecting a spinning solution, a high voltage generator, and a grounded conductive substrate. The conductive substrate is a metal plate and electrospun using a spinning nozzle spaced 10 cm to 20 cm from the metal plate. The operating voltage for electrospinning can be 8 - 30 kV. In addition, the diameter of the nanofibers can be controlled according to the hole size of the spinning nozzle, the discharge speed, the concentration of the metal oxide precursor in the spinning solution, and the spinning length. The metal oxide precursor / polymer composite nanofiber in which the catalyst-coated sacrificial layer template formed by the electrospinning is bound to the surface or inside may have a web shape.

Next, a plurality of pores 121 and 122 are formed on the surface and inside of the metal oxide nanofibers having a one-dimensional structure by subjecting the produced composite nanofibers to heat treatment at a high temperature, (S240) of binding the catalyst to the catalyst (123).

After the electrospinning, the metal oxide precursor / polymer composite nanofibers bound to the surface or inside of the sacrificial layer template coated with the catalyst are subjected to a heat treatment. The heat treatment removes the polymer contained in the conjugated fiber and oxidizes the metal oxide precursor to form a metal oxide nanofiber having a one-dimensional structure. The average diameter of the one-dimensional metal oxide nanofibers (110) fabricated by electrospinning and heat treatment processes can be 50 nm to 10 μm.

In addition, the sacrificial layer template is decomposed to form pores on the surface of the metal oxide nanofiber, and the coated catalyst is oxidized to adhere to the surface and inside of the metal oxide nanofiber, do. Wherein the catalyst is bound to the surface of the metal oxide nanofiber and to the site where the sacrificial layer template attached to the inside is located.

The method of manufacturing the nanofibers may further include grinding the porous metal oxide nanofibers 110 selectively bonded with the catalyst. In the process of pulverizing nanofibers, long nanofibers may be shortened to form nano-rods.

The one-dimensional metal oxide nanofibers, such as the one-dimensional metal oxide nanofibers, can form a large number of pores on the surface and bind the catalyst to the sites where the pores are formed. It is possible to control the pore distribution and bind various catalysts to the pores The present invention can also be applied to a disease detection sensor that analyzes an exhalation gas of a person utilizing an excellent sensitivity characteristic.

Hereinafter, the present invention will be described in more detail by way of examples. However, it should be understood that the present invention is not limited thereto.

Example 1: Palladium (Pd) catalyst coating with polystyrene colloid sacrificial layer template

In order to prepare a sacrificial layer template coated with a catalyst, a sacrificial layer template was used as a polystyrene colloid in the present invention. The polystyrene colloid exhibits a spherical shape with an average size of 500 nm. In order to uniformly disperse the polystyrene colloid in the solvent, the polystyrene content was maintained at 2.5 wt% in water and dispersed. Polystyrene-dispersed solution of 100? Was coated on the surface of the polymer to form a charge.

In the present invention, 1 wt% of poly (diallyldimethylammonium chloride) (PDADMAC, M _w = 200,000 g / mol) as a positive charge polymer was dissolved in water, and 0.5 mol of NaCl was added Respectively. 1 wt% of polystyrene sulfonate (PSS, M _w = 70,000 g / mol) having a negative charge was dissolved in water and 0.5 mol of NaCl was added in the same manner.

The polystyrene template dispersed in water is uniformly mixed with the prepared positive charge polydanyl dimethyl ammonium chloride solution. In the mixing process, the polydanyl dimethyl ammonium chloride binds to the surface of the polystyrene template and becomes positively charged. The mixed solution is centrifuged at 10000 rpm for 10 minutes to separate the polystyrene template, and the residue is washed to remove polydanyl dimethyl ammonium chloride. The washing procedure by centrifugation is repeated 5 times.

Next, a polystyrene template coated with a positive charge is mixed with the negatively charged polystyrene sulfonate to prepare a negative charged polystyrene template. In the mixing process, the polystyrene sulfonate binds to the surface of the polystyrene template and becomes negatively charged. The solution is centrifuged at 10000 rpm for 10 minutes to separate the polystyrene template and to remove the remaining polystyrene sulfonate. The washing procedure by centrifugation is repeated 5 times.

Next, the polystyrene template coated with the negative charge is subjected to a process of making a polystyrene template having a positive charge by using the polydianil dimethyl ammonium chloride in the same manner. Likewise, the remaining polydanyl dimethyl ammonium chloride is removed through five washing steps using centrifugation. The surface of the polystyrene template fabricated so far forms a polymer layer having three layers of charge: polydianil dimethyl ammonium chloride / polystyrene sulfonate / polydianyl dimethyl ammonium chloride.

Then, in order to coat the metal catalyst, a solution in which the metal salt is dispersed is uniformly mixed with the charged polystyrene template. The solution in which the metal salt is dispersed is prepared by dispersing 0.01 g of calcium palladium chloride (K ₂ PdCl ₄ ) salt in ₂ g of water in the present invention. Palladium ions are bound to the surface through a process of uniformly mixing the prepared solution of the palladium salt with the charged polystyrene template. The solution of palladium ions bound to the polystyrene template is centrifuged at 10000 rpm for 10 minutes to separate the polystyrene template coated with palladium ions, and the palladium ions are removed to remove residual palladium ions. The washing procedure by centrifugation is repeated 5 times.

In the catalyst coating process, the metal salt is not limited to the palladium salt, but may be any other metal salt. For example, instead of using the solution in which the palladium salt is dissolved, hydrogensplatinum chloride (H ₂ PtCl ₆ ) salt is dispersed in water in the same ratio instead of the calcium palladium chloride salt and mixed with charged polystyrene If you give it, you can make a polystyrene template that is plated with platinum ions.

In addition, the amount of the catalyst to be coated on the surface of the polystyrene template can be controlled by adjusting the amount of the catalyst salt. For example, when a solution containing a large amount of a catalytic salt is prepared to bind a catalyst ion to a polystyrene template, the catalyst ion can be coated in a film form by completely coating the polystyrene sacrificial layer template surface, In the case of preparing a solution containing less and binding the catalyst ions to the polystyrene template, the catalyst ions can not completely coat the surface of the polystyrene sacrificial layer template, so that the coating can be performed in a nonuniform particle form.

FIG. 3 is a scanning electron micrograph of a polystyrene sacrificial layer template used in the present invention. The polystyrene sacrificial layer template has a spherical shape and has an average size of 500 nm.

4 is a scanning electron micrograph of a polystyrene template coated with a palladium salt using a layer-by-layer method. As shown in the image, it can be confirmed that the palladium ions are adsorbed on the polystyrene template to bind to the surface in the form of particles.

5 is a scanning electron micrograph of a polystyrene template coated with a platinum salt using a layer-by-layer method. As shown in the image, it can be confirmed that the platinum ions are adsorbed on the polystyrene template to bind to the surface in the form of particles.

Example 2 Production of Porous Tungsten Oxide Nanofibers Having Palladium (Pd) Catalyst-Coated Polystyrene Colloid on a Palladium Catalyst

0.25 g of polyvinylpyrrolidone (PVP) having a weight average molecular weight of 1,300,000 g / mol and 0.2 g of tungsten oxide precursor ammonium metatungstate hydrate are dissolved in 1.5 g of water at 25 ° C. The polystyrene template with the prepared palladium catalyst bound to the spinning solution is dispersed. The tungsten oxide precursor / polymer blend solution containing the polystyrene template with the palladium catalyst attached thereto was placed in a syringe and connected to a syringe pump (Henke-Sass Wolf, 10 mL NORM-JECT ^? ) To prepare a 0.1 mL / A voltage of 14 kV is applied between a needle (25 gauge) through which a spinning solution is discharged and a current collecting substrate for obtaining a nanofiber web to form a polystyrene template on which the catalyst is bound, To prepare a tungsten oxide precursor / polymer composite nanofiber web.

A scanning electron microscope photograph of the nanofiber web obtained after electrospinning the sacrificial layer template coated with the catalyst through the electrospinning technique together with the tungsten oxide precursor / polymer mixed electrospinning solution can be observed in FIG. In FIG. 6, it can be seen that the polystyrene template coated with palladium having a diameter of about 500 nm was uniformly bound to the surface and inside of the tungsten oxide precursor / polymer composite nanofiber. The tungsten oxide precursor / polymer composite nanofiber including the polystyrene template coated with palladium formed at this time exhibits a shape protruding from the surface, so that the portion where the polystyrene template coated with the catalyst is located can be easily found. This is the unusual microstructure observed because the size of the catalyst-coated template is about half the nanofiber diameter and very large templates are used. The diameter of the composite nanofibers was also found to range from 500 nm to 1 μm.

The metal oxide precursor / polymer composite nanofiber web having the catalyst-bound polystyrene template bonded to the surface and the interior thereof is subjected to heat treatment at a high temperature to remove the polymer and the polystyrene template inside the nanofiber, and oxidize the tungsten oxide precursor And the catalyst is bound to the metal oxide nanofibers by transferring the palladium catalyst surrounding the surface of the polystyrene template to the metal oxide nanofibers.

The high temperature annealing process was performed at 500 ° C for 1 hour, and the temperature rise and fall were kept constant at 4 ° C / min. In FIG. 7, the heat-treated tungsten oxide nanofibers were shrunk to 300 nm to 600 nm in diameter, and the polystyrene template coated with the catalyst was removed to form spherical pores. It can be confirmed that the formed pores have a diameter of 30% to 70% shrinked in comparison with the polystyrene template having a size of 500 nm used in the preparation of the electrospinning solution. The reason for the shrinkage of the pores is that the decomposition temperature of the polystyrene template starts at a lower temperature than that of the polyvinylpyrrolidone and the polystyrene template is first removed and the tungsten oxide precursor is oxidized after the polystyrene template is removed And the pores contracted. In addition, the formation of shrunken pores is closely related to the glass transition temperature of the polymer mixed with the polystyrene template and metal oxide precursor bound. Polystyrene templates have a glass transition temperature of 100 ° C, while polyvinylpyrrolidone, a polymer mixed with a metal oxide precursor, has a glass transition temperature of 150 ° C to 180 ° C. Thus, the polystyrene template having a relatively low glass transition temperature first begins to undergo glass transition, and additionally the polyvinylpyrrolidone undergoes glass transition later. Therefore, it can be confirmed that the pores formed from the polystyrene template are shrunk by the polyvinylpyrrolidone causing the glass transition later. As a result, when a polystyrene template is used with a polyvinylpyrrolidone polymer, a nanofiber structure in which a plurality of pores are dispersed can be produced while oxidizing the tungsten oxide precursor in a high-temperature heat treatment process. This can be used not only for the production of silk tungsten oxide nanofibers but also for forming pores for various metal oxides by changing the metal oxide precursor.

The polystyrene template is removed, and at the same time, the catalyst attached to the surface of the polystyrene template is transferred to the metal oxide nanofiber to be bound. 8 is a scanning electron microscope photograph showing the catalyst-coated polystyrene template being removed in a high-temperature heat treatment process and that the coated catalyst was transferred to the metal oxide nanofibers, and FIG. 8 is a photograph showing the result of the component analysis using the energy dispersive analyzer. As can be seen from the results, it can be confirmed that the palladium catalyst is selectively attached to the portion where the pores are located as the palladium element is detected at the position where the pores are formed.

As a result, the surface area and porosity of the tungsten oxide nanofibers are improved by forming pores on the surface and inside of the tungsten oxide. Also, by selectively binding the palladium catalyst to the pores formed, effective pore formation and catalytic And the sensing material can exhibit excellent sensing characteristics for a specific gas through active gas diffusion and catalytic reaction when a gas to be measured is injected.

Comparative Example 1. Production of pure tungsten oxide nanofibers without catalyst-coated polystyrene template

As a comparative example compared with the above-described embodiment, pure tungsten oxide nanofibers were formed without adding a catalyst-coated polystyrene template. Specifically, 0.25 g of polyvinylpyrrolidone (PVP) having a weight average molecular weight of 1,300,000 g / mol and 0.2 g of ammonium metatungstate hydrate, a precursor of tungsten oxide, were added to 1.5 g of water at 25 ° C It dissolves. The tungsten oxide precursor / polymer mixture spinning solution was placed in a syringe and connected to a syringe pump (Henck-Sass Wolf, 10 mL NORM-JECT ^? ), The spinning solution was pushed out at a discharge rate of 0.1 mL / min, A voltage of 14 kV was applied between a needle (25 gauge) for discharging the nanofibrous web and a current collector substrate for obtaining a nanofiber web, and a polystyrene template with a catalyst attached was bonded to the surface and inside of the tungsten oxide precursor / polymer composite To produce a nanofiber web. The prepared tungsten oxide precursor / polymer composite nanofiber web is subjected to high temperature heat treatment to remove the polymer, and the tungsten oxide precursor is oxidized to form tungsten oxide. The high temperature annealing process was performed at 500 ° C for 1 hour, and the temperature rise and fall were kept constant at 4 ° C / min.

FIG. 9 is a scanning electron microscope (SEM) image of a pure-type tungsten oxide nanofiber fabricated through a comparative example. The fabricated pure tungsten oxide nanofibers had diameters in the range of 500 nm - 2 μm, and it was confirmed that not only the nanofibers of the cylindrical structure but also the nanofibers having the nanobelt shape of the plate structure were formed.

The prepared pure tungsten oxide nanofibers were used to compare the sensing characteristics of the porous tungsten oxide nanofibers with the palladium catalyst bound to the selective sites prepared in Example 2 and specific gases.

Experimental Example 1. Preparation and characterization of a gas sensor using porous tungsten oxide nanofibers (110) and pure tungsten oxide nanofibers with a palladium (Pd) catalyst

Porous tungsten oxide nanofibers 110 and pure tungsten oxide nanofibers with palladium (Pd) catalysts prepared in Example 2 and Comparative Example 1 were dispersed in ethanol, respectively, and ultrasonicated for 10 minutes Followed by pulverization through washing. The porous tungsten oxide nanofibers 110 and the pure tungsten oxide nanofibers with palladium (Pd) catalysts formed in the milling process exhibit nano-rods that are further shortened in the longitudinal direction or further in the form of pulverized nanoparticles Pray.

The porous tungsten oxide nanofibers (110) and the pure tungsten oxide nanofibers with uniformly pulverized palladium (Pd) catalysts were immersed in a 3 mm x 3 mm sized And then coated on the alumina substrate using a drop coating method. The coating process was performed by applying a mixture of porous tungsten oxide nanofibers (110) and pure tungsten oxide nanofibers / ethanol mixed with 3 μl of palladium (Pd) catalyst on an alumina substrate on which sensor electrodes were formed using a micropipette, Lt; 0 > C on a hot plate. This procedure was repeated 2-3 times so that porous tungsten oxide nanofibers (110) and pure tungsten oxide nanofibers with a sufficient amount of palladium (Pd) catalyst were coated on the alumina substrate.

The characteristics of the expiratory sensor were evaluated by measuring the concentrations of hydrogen sulfide (H ₂ S), acetone (CH ₃ COCH 2, ₃ ), and toluene (C ₆ H ₅ CH ₃ ) gas at 5, 4, 3, 2, and 1 ppm, respectively. In addition, the present embodiment is applicable not only to hydrogen sulfide (H ₂ S), acetone (CH ₃ COCH ₃ ), and toluene (C ₆ H ₅ CH ₃ ) gases, which are typical examples of volatile organic compound gases, (C ₂ H ₅ OH), carbon monoxide (CO), nitrogen monoxide (NO), ammonia (NH ₃ ) and pentane (C ₅ H ₁₂ ) gases, which are biomarkers of asthma, To evaluate the selective gas sensing characteristics.

FIG. 10 shows the response (R _air / R _gas , where R _air is the resistance of the metal oxide material when air is injected) at 350 ° C when the concentration of toluene gas decreases to 5, 4, 3, Value, and R _gas is a resistance value of the metal oxide material when the toluene gas is injected).

As shown in FIG. 10, the sensor made of the porous tungsten oxide nanofibers 110 to which the palladium (Pd) catalyst was bound was superior to the pure tungsten oxide nanofiber sensor manufactured without using the polystyrene template with the palladium catalyst 8.2 times higher reaction characteristics than the conventional reaction.

FIG. 11 is a graph showing the time-dependent reactivity value when the concentration of acetone gas is reduced to 5, 4, 3, 2, and 1 ppm at 350 ° C.

As can be seen from FIG. 11, a sensor made of a porous tungsten oxide nanofiber 110 with a palladium (Pd) catalyst attached thereto is a pure tungsten oxide nanofiber sensor fabricated without using a polystyrene template with a palladium catalyst Reaction characteristics up to 2.3 times higher than that of the conventional method.

FIG. 12 is a graph showing the reaction value when the concentration of hydrogen sulfide gas is reduced to 5, 4, 3, 2, and 1 ppm at 350 ° C over time.

As shown in FIG. 12, the sensor made of the porous tungsten oxide nanofibers 110 to which the palladium (Pd) catalyst was bound was superior to the pure tungsten oxide nanofiber sensor manufactured without using the polystyrene template with the palladium catalyst 3.5 times lower than that of the reaction solution.

13 is a graph showing the relationship between the concentration of toluene gas and the biomarker gas of ethanol, carbon monoxide and carbon monoxide, which are different from toluene gas, known as the factor gas of lung cancer, by using a sensor made of porous tungsten oxide nanofibers 110 having palladium (Pd) And the reactivity value at a concentration of 1 ppm with respect to nitrogen monoxide, ammonia, and pentane gas.

As shown in FIG. 13, the sensor made of the porous tungsten oxide nanofibers 110 to which the palladium (Pd) catalyst is bound is distinguished from the biomarker gases of other diseases such as ethanol, carbon monoxide, nitrogen monoxide, ammonia, Indicating excellent detection characteristics for toluene, a biomarker gas of lung cancer. Sensitivity to toluene gas showed response values ranging from 1 ppm to 4.1, while reactivity values for biomarker gases of other diseases were less than 2.4.

In the above experimental example, the experimental results are shown by taking the volatile organic compound gas as an example. However, excellent sensor sensing characteristics can be expected for representative harmful environmental gases such as H ₂ , NO _x , CO and SO _x, and palladium (Pd) In the sensor fabricated with the porous tungsten oxide nanofibers 110 having the catalyst attached thereto, by arranging the sensor members having controlled porosity by adjusting the binding amount of the palladium catalyst and the concentration of the sacrificial layer template, And the sensitivity and selectivity of the diagnosis of the exhalation.

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: member for porous metal oxide nanofiber gas sensor optionally with catalyst attached
110: optionally porous metal oxide nanofibers to which the catalyst is bound
121: Closed structure pore
122: Open architecture
123: Catalyst selectively bound to pores

Claims (21)

delete delete delete delete delete delete delete delete delete delete delete delete (a) coating a catalyst on a polymer sacrificial layer template;
(b) preparing a metal oxide precursor / polymer mixed electrospinning solution comprising the catalyst-coated polymer sacrificial layer template;
(c) forming a metal oxide precursor / polymer composite nanofiber with the catalyst-coated polymer sacrificial layer template added using electrospinning technology; And
(d) removing the polymer sacrificial layer template and the polymer through a high-temperature heat treatment, oxidizing the metal oxide precursor to form pores as the polymer sacrificial layer template is thermally decomposed, and the catalyst coated on the polymer sacrificial layer template is a nanofiber To form the bound porous metal oxide nanofibers
Wherein the gas sensor comprises a gas sensor. 14. The method of claim 13,
(e) The porous metal oxide nanofibers are coated on the sensor electrode to generate biomarker gas (oxidizing gas: NO ₂ , NO, reducing gas: H ₂ , CO, C ₂ H ₅ OH, < _{RTI ID =} 0.0 > H2S) < / RTI >
Further comprising the steps of: 14. The method of claim 13,
The step (a)
Wherein the catalyst is coated on the polymer sacrificial layer template in the form of a film using a metal salt or the metal and metal oxide catalyst particles are directly bound to the polymer sacrificial layer template. 14. The method of claim 13,
The catalyst coated on the polymer sacrificial layer template may be at least one selected from the group consisting of Pt, Au, Ag, Fe, Ni, Ti, Sn, Si, Al, Cu, Mg, Sc, V, Cr, Mn, Co, Zn, , Ir, Ta, Sb, In, Pb and Pd or one or more metals of Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, CuO, Co ₃ O ₄ , PdO, V ₂ O ₅ , Cr ₃ O ₄ , CeO ₂ , Ag ₂ O, RuO ₂ , IrO ₂ , and MnO ₂ . 14. The method of claim 13,
In the step (a)
(1) mixing a nanoparticle catalyst-dispersed solution and a solution in which the polymer sacrificial layer template is dispersed are mixed with each other to bind nanoparticles to the surface of the polymer sacrificial layer template, or (2) the polymer sacrificial layer template The catalyst is regularly or irregularly adhered or coated on the surface of the polymer sacrificial layer template by changing the banding charge on the surface of the polymer sacrificial layer template through centrifugation of the catalyst to form the polymer sacrificial layer template Wherein the step of preparing the member for a gas sensor comprises the steps of: 14. The method of claim 13,
In the step (a)
Wherein the amount of the catalyst bound to the polymer sacrificial layer template is controlled in a range of 0.001 wt% to 20 wt% by quantitatively controlling the coating amount of the catalyst. 14. The method of claim 13,
In the step (b)
(1) the electrospinning solution for electrospinning is formed by a combination of a plurality of metal oxide precursors and a plurality of polymer complexes, or (2) the polymeric sacrificial particles coated with a catalyst in the metal oxide precursor / polymer composite electrospinning solution Layer template. ≪ RTI ID = 0.0 > 21. < / RTI > 14. The method of claim 13,
In the step (b)
Wherein the catalyst-coated polymer sacrificial layer template remains in a colloidal form dispersed without being dissolved in the metal oxide precursor / polymer mixed solution. 14. The method of claim 13,
In the step (c)
The metal oxide precursor / polymer composite nanofiber is decomposed by a high temperature heat treatment process and the metal oxide precursor is oxidized to form a one-dimensional metal oxide nanofiber,
Wherein the polymer-sacrificial layer template coated with the catalyst is removed while being subjected to a high-temperature heat treatment process to form pores of various sizes while being removed, and the catalyst is bound to the surface and inside of the metal oxide nanofibers Member manufacturing method.

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