KR20190018851A - Gas sensor and membrane using metal oxide semiconductor combination of cellulose and apoferritin bio-templates derived nanotube functionalized by nanoparticle catalyst, and manufacturing mehtod thereof - Google Patents

Abstract

Disclosed are a gas sensor member based on a one-dimensional metal oxide semiconductor nanotube to which a metal nanoparticle catalyst using a complex bio template of cellulose and apoferritin is uniformly bound, and a manufacturing method thereof. According to the present invention, the metal oxide nanotube forms a core-shell complex nanofiber of a shape aggregating a cellulose template to a core during an electric spinning process and forms a hollow structure as the cellulose of the core is pyrolyzed during a high temperature heat treatment process. A metal nanoparticle catalyst functionalized by an apoferritin template is uniformly bound to the inner and outer walls of the tube. Accordingly, provided are effects of providing high sensitivity characteristic to detect a very small amount of gas, excellent selectivity to selectively react with only the specific gas, and excellent catalytic effect due to the metal nanoparticle catalyst functionalized by being uniformly bound without aggregation. Moreover, provided are effects of easily realizing mass production through a processing method that simultaneously realizes efficiency structure control and high performance catalyst bounding due to a processing method using a complex bio template.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a member for a gas sensor in which a one-dimensional metal oxide semiconductor nanotube and a nanoparticle catalyst are functionalized using a composite biotemplate of cellulose and apoferritin, and a method for manufacturing the same. DERIVED NANOTUBE FUNCTIONALIZED BY NANOPARTICLE CATALYST, AND MANUFACTURING MEHTOD THEREOF}

The present invention relates to a member for a gas sensor, a gas sensor using the same and a method of manufacturing the same, and more particularly, to a method for controlling a shape of a one-dimensional metal oxide nanotube by using a composite biotemplate of cellulose and apoferritin, To a metal oxide semiconductor nanotube in which a nanoparticle catalyst embedded in apoferritin is uniformly bound, a member for a gas sensor using the same, a gas sensor, and a manufacturing method thereof.

BACKGROUND ART A metal oxide semiconductor based gas sensor utilizes a phenomenon of change in electrical resistance due to a surface adsorption-desorption reaction in which a target gas molecule adsorbs and desorbs from the surface of a metal oxide semiconductor sensing material. By analyzing resistance ratio (R _air / R _gas ) when exposed to specific gas compared with resistance in air, it is easy to construct simple sensor array system at relatively low price because it uses simple principle that can detect specific gas, , Portability and real-time measurement. The resistance-type metal oxide semiconductor gas sensor having various advantages has been widely used in various fields such as an alcohol detector, an air pollution meter, and an alarm as well as a noxious gas leak detection.

Recently, as the interest in healthcare has increased rapidly, research on an expiratory sensor has been actively carried out to precisely detect a trace amount of biomarker gas included in exhaled breath of a human body and diagnose the presence or absence of a specific disease early have. (CH ₃ COCH ₃ ), toluene (C ₆ H ₅ CH ₃ ), ammonia (C ₆ H ₅ CH ₃ ), and ammonia are used as the typical disease agent gas. In the course of metabolism, a specific disease agent gas serving as a biomarker is generated and excreted through exhalation. (NH ₃ ), and hydrogen sulfide (H ₂ S). Each gas is known to be associated with diabetes, lung disease, kidney disease, bad breath. In order to prepare a gas sensor for early monitoring health care that diagnoses the bio-surface gas, a sensor having high sensitivity, high selectivity and high response is required even at a low gas concentration. However, the conventional metal oxide semiconductor gas sensor has a long response time (response time) in response to the gas and a recovery time (recovery time) in the initial resistance value, which is longer than several tens of seconds to several minutes, The performance of the sensor is rapidly changed depending on the temperature. In addition, existing gas sensors based on metal oxide semiconductors have poor selectivity in response to specific target gases, and have a very low gas sensing capability, i.e., limit of detection performance, of ppb level. In order to overcome these problems, it is necessary to develop technology that can detect and detect ultra-high sensitivity and high selectivity sensing material for gas sensor.

In order to fabricate ultra-sensitive metal oxide semiconductor gas sensors, various nanostructure-based sensing materials such as nanoparticles, nanofibers, nanowires, and nanotubes have been actively studied and applied to gas sensors. Since the nanostructures have a large specific surface area, the nanostructures can react with the gas over a wide area to increase the gas sensing property. Due to the porous structure, the gas quickly diffuses into the sensing material, It is possible to achieve a high-speed reaction.

In addition to research on obtaining high sensitivity and high response characteristics through synthesis of nanostructures with high specific surface area and porosity, metal or metal oxide catalyst particles are bound and functionalized in sensing materials to detect trace amounts of gas of several tens ppb level, Research to maximize is also actively proceeding. In the case of using a catalyst, a chemical sensitization which increases the concentration of oxygen adsorbing species (O ^- , O ^2- and O ₂ ^- ) participating in the surface reaction of the gas by using a noble metal catalyst such as platinum (Pt) mainly using two methods of chemical sensitization or electronic sensitization for improving sensitivity based on the change in oxidation number (PdO or Ag ₂ O) such as palladium (Pd), silver (Ag) Studies for improving the sensing property and selectivity have been actively conducted.

However, in the synthesis of the sensing material, the structure control of the sensing material having a high porosity and a wide specific surface area requires not only the disadvantages of complicated multi-step process accompanied with various deposition methods and chemical growth methods, but also high production cost and mass production There is a disadvantage in that it is difficult.

In the case of a catalyst that binds to a nanostructure sensing material, the metal or metal oxide catalyst is limited to a few nanometers or less and has a limitation in uniformly distributing the metal throughout the sensing material. In the commonly used polyol process, the size of the metal catalyst particles is relatively large (3-10 nm) and aggregation easily occurs during the high temperature heat treatment process. Therefore, There is a great difficulty in making it.

In order to overcome the disadvantages, a nanostructure having a high specific surface area and a gas inflowing property is manufactured through a simple synthesis method, and the coagulation phenomenon between the catalyst particles is minimized in a high temperature heat treatment process, which is essential for the metal oxide synthesis process, Process development should be accompanied by the ability to bind the nanoparticle catalyst uniformly to the sensing material. In addition, it is possible to overcome the limitations of conventional precious metal catalysts and simultaneously synthesize a very high sensitivity sensing material having a maximized catalyst activity in a large amount, thereby selectively and precisely extracting various volatile organic compounds emitted through exhalation It is necessary to fabricate a sensor that can detect it.

In an embodiment of the present invention, a nanoparticle catalyst of several nanometers in size is synthesized internally using a protein template called apoferritin having a hollow structure of 7-8 nm in size and dispersed in an electrospinning solution, The present invention provides a method for uniformly binding a metal nanoparticle catalyst embedded in apoferritin by inducing aggregation of a cellulose template inside the nanofiber after electrospinning by dispersing a cellulose template together to form a tube structure. Particularly, the cellulose template agglomerated in the interior through the high-temperature heat treatment process is pyrolyzed to form a hollow structure, and the apoperi- tine template is also pyrolyzed, so that the built-in nanoparticle catalyst is homogeneously bound on the inner and outer walls of the nanotube structure, Oxide nanotube electrospinning synthesis method.

Particularly, a cellulose template having a diameter of several nm to several hundreds of nm and a length of several tens of nanometers to several tens of micrometers depending on its kind and degree of polymerization coagulates to nanofiber cores during electrospinning to form core (shell) / shell Metal precursors and polymer matrix) and removes the cellulose template of the core through a high-temperature heat treatment process, the nanostructure utilizing the biotemplate inexpensive and eco-friendly in comparison with the conventional nanotube synthesis method Control method. Dimensional metal oxide nanotube sensing material that simultaneously induces the catalytic effect by increasing the specific surface area and the gas inlet property through the interaction with the functionalized metal nanoparticle catalyst through apoferritin and the gas sensor application technology using the same present.

In order to overcome the limitations of the prior art, miniaturized nanoparticle catalysts having a size range of 1 to 3 nm are uniformly bound with each other with minimal aggregation, and at the same time, a nanotube structure utilizing sacrificial layer bio- And a gas sensor using the gas sensor and a method of manufacturing the same, which can easily detect and synthesize extremely small amounts of gas with high selectivity and ultra high sensitivity.

In order to solve the above problems, according to one aspect of the present invention, a nanoparticle catalyst is synthesized and embedded in an apo-peritone template having excellent dispersibility, and a cellulosic template having excellent dispersibility is simultaneously applied to an electrospinning solution, The present invention provides a sensing material including a one-dimensional metal oxide nanotube easily functionalized by uniformly binding a nanoparticle catalyst, and a method of manufacturing a member for a gas sensor using the same. A method for manufacturing a sensing material and a gas sensor member using the same according to the present invention comprises the steps of: (a) preparing a uniformly dispersed first dispersion solution by synthesizing a nanoparticle catalyst in an apoperiolin template; (b) synthesizing a second dispersion solution in which the cellulose template is uniformly dispersed; (c) mixing the first dispersion solution and the second dispersion solution with a metal oxide precursor and a solvent in which the polymer is dissolved to prepare an electrospinning solution; (d) forming a core-shell structure of the electrospinning solution in the form of a cellulosic template agglomerated within the metal oxide / polymer composite nanofibers by using a single nozzle electrospinning method, wherein the nanoparticle catalyst embedded in the apoferritin template To form composite nanofibers uniformly distributed throughout the core-shell structure; (e) The metal precursor composing the composite nanofiber is oxidized to form a metal oxide by heat treatment, and the aggregated cellulosic template, the apoperi- tin template with the nanoparticle catalyst, and the organic material including the polymer are decomposed by thermal decomposition Forming a one-dimensional metal oxide nanotube that is uniformly bound to the inner and outer walls, and between the inner and outer walls forming the nanotube; (f) dispersing or pulverizing the one-dimensional metal oxide nanotube, and performing at least one coating process such as drop coating, spin coating, inkjet printing, and dispensing on a substrate on which a sensor electrode is formed for measuring a semiconductor type gas sensor Manufacture of a resistance-variable semiconductor gas sensor capable of detecting biomarker gas (oxidizing gas: NO ₂ , NO, reducing gases: H ₂ S, C ₂ H ₅ OH, CH ₄ , CO) for environmentally hazardous gases and diseases ; (g) fabricating a plurality of metal oxide nanotube complexes to produce a plurality of resistance variable semiconductor gas sensor arrays; And a method for manufacturing a catalyst-metal oxide nanotube complex sensing material capable of detecting a biomarker gas for diagnosis of environmentally harmful gases and diseases.

In the step (a), apoferritin has a spherical shape of a hollow structure with an empty interior, and is capable of substituting various metal ions therein. By reducing a substituted metal ion, A particle catalyst can be synthesized. (II) nitrate, copper (II) chloride, lanthanum (III) nitrate, lanthanum (III) acetate, and the like. (III) chloride, Iron (III) acetate, Silver (III) chloride, Silver acetate, Cobalt (II) nitrate, Cobalt (II) chloride, Iridium (III) chloride, etc .; and metal ions are included. The type and form of the particular metal salt is not limited. Since the metal nanoparticle catalyst synthesized through the above process is embedded in the apo-peritone template having a positive surface charge, it has an advantage of minimizing coagulation between the two and maintaining the dispersibility effectively.

The step (b) is a step of synthesizing a spinning solution to be used for electrospinning including a cellulose template having excellent dispersibility, and it is a step of synthesizing a spinning solution for mechanical spinning such as sonication, mechanical chemical dispersion methods of oxidation and mechanical agitation and chemical and mechanical dispersion methods such as acid hydrolysis and enzymatic hydrolysis. And at least one of the dispersion methods is used to increase the dispersibility in a solvent.

The step (c) is a step of preparing an electrospinning solution for progressing electrospinning. The step (c) is a step of dissolving a polymer and a metal oxide precursor, which serve as a support for efficiently synthesizing nanofibers through an electrospinning process, . Typical polymers used herein include polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA) ), Polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide block copolymer (PEO BP), polypropylene oxide copolymer polypropylene oxide block copolymer (PPO BCP), polyvinylchloride (PVC), polycarbonate (PC), polycaprolactone (PCL) and polyvinylidene fluoride (PVDF) Representative metal salts include acetates including metal salts, acetylacetonate, chloride, nitrate, methoxide, ethoxide, Ethoxide, isopropoxide, a form of sulfide. In addition, the solution containing the nanoparticle catalyst dispersion solution embedded in apoferritin and the cellulose template uniformly dispersed in the solvent synthesized in steps (a) and (b) is uniformly dispersed in the electrospinning solution, Can be prepared.

The step (d) is a step of synthesizing composite nanofibers in which the metal nanoparticle catalyst embedded in apoferritin is homogeneously bound using the electrospinning method and the cellulose template is agglomerated in the metal salt / polymer nanofiber . In the course of the electrospinning, the nanofibers are formed by discharging from a plurality of nozzles by using a nozzle electrospinning, or by using a wire type or syringe type electric radiator. The apoperi- tine template with the nanoparticle catalyst is mostly distributed inside the metal salt / polymer composite nanofiber, and a part thereof may be exposed to the outside.

In the step (e), the composite nanofibers synthesized in step (d) are heat-treated at a high temperature to decompose and remove the polymer serving as a structural framework of the nanofiber, and the cellulose template that has been aggregated in the core of the composite nanofiber is also thermally decomposed Hollow hollow nanotubes are formed. In addition, the apoferritin template is also removed and the built-in metal nanoparticle catalyst is exposed to the outside, and the metal oxide precursor is oxidized to form a one-dimensional metal oxide nanotube.

In the step (f), a dispersion solution obtained by dispersing the one-dimensional metal oxide nanotubes synthesized in the step (e) in a solvent is applied to a sensor electrode (alumina having parallel electrodes capable of measuring resistance change and electrical conductivity, Coating with a coating process such as drop coating, spin coating, inkjet printing, or dispensing on an insulating substrate. At this time, if the method can uniformly coat the one-dimensional metal oxide nanotubes including the nanoparticle catalyst, there is no particular restriction on the coating method.

The prepared one-dimensional metal oxide nanotube structure has a length of 50 nm to 10 μm in outer diameter, a length of 40 nm to 5 μm in inner diameter, and a thickness between the inner wall and outer wall of the nanotube Can be defined in the thickness range of 10 nm - 5 μm. In addition, the length can range from 1 μm to 100 μm.

According to the present invention, since the one-dimensional metal oxide nanotube structure formed by utilizing the complex biotemplate of apoferritin and cellulose and removing the template through a high-temperature heat treatment process, an increased specific surface area of several tens times or more The structural advantages of the tubular structure can improve the inlet characteristics of the gas molecules and dramatically improve the sensor characteristics through cooperative effects with uniformly bound metal nanoparticle catalysts on the inner and outer walls of the tube . The metal nanoparticle catalysts embedded in the apoferritin are characterized by their small size and uniform distribution in the range of 1-5 nm, minimizing coagulation during the high-temperature heat treatment process, and attaching to the inner / outer wall of the 1-dimensional metal oxide nanotubes Maximizing the surface exposure of the nanoparticle catalysts and maximizing the catalytic reaction effect through reaction with the gas molecules. As mentioned above, by maximizing the sensor characteristics through the control of the shape of the gas sensor member and the catalytic effect, it is possible to obtain not only excellent gas sensing performance capable of selectively sensing a specific target gas with a very high sensitivity, A gas sensor member, a gas sensor, and a manufacturing method thereof, which can be easily mass produced.

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 one-dimensional metal oxide nanotube gas sensor in which a nanoparticle catalyst according to an embodiment of the present invention is uniformly bound.
2 is a flowchart illustrating a method of manufacturing a gas sensor using a one-dimensional metal oxide nanotube using a cellulose template including a nanoparticle catalyst synthesized using apoferritin according to an embodiment of the present invention.
FIG. 3 is a view showing a process of manufacturing a one-dimensional metal oxide nanotube structure using a cellulosic template and uniformly binding a nanoparticle catalyst using an electrospinning method according to an embodiment of the present invention.
4 is a transmission electron micrograph of a cellulose template serving as a sacrificial layer template according to an embodiment of the present invention.
FIG. 5 illustrates nanofibers obtained by electrospinning a tungsten oxide precursor / polyvinylpyrrolidone (PVP) complex spinning solution containing apoferritin and a cellulose template containing a Pt nanoparticle catalyst according to an embodiment of the present invention, Dimensional SEM micrograph of a one-dimensional tungsten oxide nanotube formed as a Pt nanoparticle catalyst is homogeneously bound and thermally decomposed in a cellulose template which has been agglomerated therein.
FIG. 6 is a transmission electron micrograph of apoferritin particles embedded in a Pt nanoparticle catalyst according to Example 1 of the present invention and a size distribution diagram of the Pt nanoparticle catalyst.
Fig. 7 is a graph showing the results obtained by electrospinning a composite tungsten oxide precursor / polyvinyl pyrrolidone (PVP) spinning solution containing a cellulose template without incorporating a Pt nanoparticle catalyst according to Comparative Example 1 of the present invention at a high temperature 1 is a scanning electron microscope (SEM) image of a one-dimensional tungsten oxide nanotube obtained by heat treatment.
8 is a scanning electron microscope (SEM) image of a one-dimensional tungsten oxide nanofiber obtained by high-temperature heat treatment of a composite nanofiber obtained by electrospinning a tungsten oxide precursor / polyvinylpyrrolidone (PVP) complex spinning solution according to Comparative Example 2 of the present invention It is a photograph.
9 is a transmission electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS) photograph of a 1-dimensional tungsten oxide nanotube uniformly bound to a Pt nanoparticle catalyst according to Example 2 of the present invention.
Fig. 10 is a graph showing the results of measurement of a nanofiber obtained by electrospinning a tungsten oxide precursor / polyvinylpyrrolidone (PVP) composite spinning solution according to Comparative Example 2 of the present invention and a nanofiber obtained by electrospinning a Pt nanoparticle catalyst according to Example 2 And thermogravimetric analysis and differential scanning calorimetry analysis of nanofibers obtained by electrospinning a tungsten oxide precursor / polyvinylpyrrolidone (PVP) composite spinning solution containing a cellulose template.
FIG. 11 is a graph showing the results of measurement of a one-dimensional tungsten oxide nanotube according to Example 2 of the present invention, a one-dimensional tungsten oxide nanotube according to Comparative Example 1, and a one- (5-0.15 ppm) at 450 < 0 > C of a gas sensor having a tungsten oxide nanofiber structure.
Fig. 12 is a graph showing the results of measurement of a one-dimensional tungsten oxide nanotube uniformly bound to Pt nanoparticle catalyst according to Example 2 of the present invention, a one-dimensional tungsten oxide nanotube according to Comparative Example 1, (H ₂ S), acetone (CH ₃ COCH ₃ ), toluene (C ₆ H ₅ CH ₃ ), formaldehyde (HCHO), ethanol (C ₂ H ₂ O) at 450 ° C of a gas sensor having a tungsten oxide nanofiber structure ₅ OH), carbon monoxide (CO), ammonia (NH ₃ ) and methane (CH ₄ ).

The present invention can be flexibly applied to various transformations and may have various embodiments. Hereinafter, specific embodiments will be described in detail 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 member for a gas sensor using a one-dimensional metal oxide nanotube structure utilizing nanoparticle catalysts synthesized inside apoferritin and utilizing internal coagulation characteristics of a cellulose template during electrospinning, a gas sensor, Will be described in detail with reference to the drawings.

The present invention relates to a nanoparticle catalyst synthesized inside apoferritin, and the composite nanofiber obtained by coagulating the cellulose template in the tungsten oxide precursor / polymer nanofiber upon electrospinning is pyrolyzed through a high-temperature heat treatment process to remove the nanofiber Dimensional tungsten oxide nanotube structure, and at the same time, the nanoparticle catalysts are uniformly bound to the inner and outer walls of the nanotubes to be functionalized. In the case of gas sensor research using existing metal oxides, in order to improve the sensor characteristics of the metal oxide sensing material, a study was made to increase the specific surface area capable of reacting with the gas molecules, and the metal or metal oxide catalyst was uniformly bound to the sensing material Studies have been conducted to activate the reaction. That is, two of the most important factors for sensor characteristics are the increase of specific surface area through the control of the shape of the sensing material and the effective catalytic activation. However, there are disadvantages of the studies that have been carried out so far not only in that the shape control process and the catalyst binding process are individualized, but each process is complicated and requires complicated process steps. Specifically, nanoparticle catalysts of several nm or less in size are uniformly bound and functionalized, and the synthesis of a one-dimensional metal oxide nanotube structure having a hollow shape is relatively complicated and requires a long time and cost have. However, in order to overcome these shortcomings and to simplify each process and to expect an optimum effect, a complex biotemplate of apoferritin and cellulose is introduced in the present invention. A very small and uniform nanoparticle catalyst in the 1-5 nm range (preferably 1-3 nm in size) can be synthesized through a simple process through the apoferritin template and the type and degree of polymerization Then, the metal oxide precursor / polymer mixed spinning solution containing a cellulose template having a diameter ranging from several nm to several hundred nm and a length ranging from several tens of nanometers to several tens of micrometers according to a dispersion method was agglomerated into a cellulose template At the same time, metal oxide precursor / polymer composite nanofibers can be formed in which a nanoparticle catalyst embedded in apoferritin is uniformly distributed. As the synthesized composite nanofibers are thermally treated at high temperatures, the cellulosic template agglomerated in the apo-ferritin and the composite nanofibers embedded in the nanoparticle catalyst is pyrolyzed and removed, so that the nanoparticle catalyst is uniformly bound to the inner / Oxide nanotube structure can be easily synthesized in a single process at a low cost and a large amount of sensing materials can be synthesized that maximize the specific surface area and catalytic activity.

Here, the introduction of the gas molecules into the hollow structure of the one-dimensional metal oxide nanotubes formed by the cellulose can be induced, and the sensing material of the gases from the uniformly bound metal nanoparticle catalyst on the inner / The reactivity of the catalyst can be maximized to a minimum amount of catalyst. The present invention is characterized in that a very high level of high sensitivity gas sensor sensing material can be manufactured compared with existing sensing materials through the cooperation effect between the catalytic activation effect and the geometrical yaguering effect of the hollow nanotube structure. In particular, a variety of metal or metal oxide nanoparticle catalysts can be synthesized within the apo-peritone template depending on the purpose, thereby synthesizing a sensing substance that imparts selectivity to various gases. A gas sensor member, a gas sensor, and a manufacturing method thereof are implemented by a simple and efficient electrospinning process technique to fabricate a member for a gas sensor having the above-described characteristics.

FIG. 1 is a cross-sectional view of a one-dimensional metal oxide nanotube 100 including a nanoparticle catalyst 110 and a nanotube structure 120 according to an embodiment of the present invention and a one-dimensional metal oxide nanotube 100 to which a nanoparticle catalyst is uniformly bound. And a gas sensor member of the tube. The nanoparticle catalyst synthesized in the apoferritin template and the metal oxide precursor / polymer blend solution containing the cellulose template are electrospun to uniformly bind the nanoparticle catalyst embedded in the apoferritin template, and the cellulose template is mixed with the metal oxide precursor / Synthesized composite nanofiber in polymer nanofiber. As the composite nanofibers formed by the above method are heat-treated at a high temperature, the cellulose template that has been agglomerated therein is thermally decomposed and removed to form a tube structure and the metal oxide precursor is oxidized to form one-dimensional metal oxide nanotubes. Also, since the apo-peritone template is thermally decomposed and removed, the built-in nanoparticle catalyst can be uniformly bound to the inner / outer wall of the metal oxide nanotube to function as a one-dimensional metal oxide nanotube .

Here, the metals that can be synthesized inside the apophyte do not have any particular restriction if they are salts in the form of ions. (III) nitrate, lanthanum (III) acetate, and platinum (IV) chloride were added to the solution. (III) acetate, Gold (III) acetate, Tantalum (V) chloride, Silver chloride, Silver acetate, Iron (III) , Pt, Pd, Rh, Ru, Ni, Co, Cr, Ir, Au, and Ni 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. The synthesized nanoparticle catalyst can control the size distribution and the nanoparticle size by adjusting the amount of the metal precursor. In addition, the apopherin surface has an advantage of being uniformly dispersed in the electrospinning solution without agglomeration because of its positive charge property at a pH of about 7-8.5. The catalytic effect applied to gas sensor sensing materials can be divided into two major categories. First, the decomposition reaction of oxygen molecules existing between the surface of the sensing material and the air layer through noble metal catalysts such as platinum (Pt) and gold (Au) And the concentration of adsorbed oxygen ions that participate in the surface reaction with the gas may be increased. Secondly, there may be a chemical change effect such as PdO, NiO, ZnO, Co ₃ O ₄ , Fe ₂ O ₃ , There may be a method of inducing the catalytic effect by an electron increasing /

The cellulose template used to synthesize the one-dimensional metal oxide nanotubes as described above has a characteristic of being agglomerated in the course of electrospinning and is a template that can be pyrolyzed and removed by high temperature heat treatment. There are no special restrictions. Concretely, there are wood, cotton, bacteria and the like as an extracting source of the cellulose template, and a mechanical dispersion method such as sonication, grinding and homogenization for producing various sizes of cellulose, Chemical-mechanical mixed dispersion methods of oxidation and mechanical agitation and chemical dispersion methods such as acid hydrolysis and enzymatic hydrolysis Various types of cellulose having a diameter ranging from 1 nm to 100 nm and a length ranging from 10 nm to 10 μm can be prepared through the dispersion method and the degree of polymerization, and one kind or a mixture of two or more kinds selected therefrom. The cellulose template synthesized through the above process has excellent dispersibility in various kinds of solvents and is uniformly dispersed when it is mixed with the electrospinning solution. If the diameter and length of the cellulose template are not adequate and longer than the length of the spinning fiber, the cellulosic template may not uniformly flocculate inside the spinning conjugate fiber during electrospinning. Therefore, the above-mentioned cellulosic template having a proper diameter and length distribution can be used to effectively induce the internal agglomeration phenomenon of the cellulose template to control the shape of the one-dimensional metal oxide nanotubes.

By dispersing the nanoparticle catalyst and the cellulose template synthesized in the above-described apo-peritone template in an electrospinning solution and spinning, the cellulose template is aggregated inside the spinning fiber, and the nanoparticle catalyst synthesized inside the apoferritin is uniformly dispersed in the metal oxide Precursor / polymer composite nanofiber can be prepared. The composite nanofibers synthesized through the above method were subjected to a high temperature heat treatment at a heating rate of 5 ° C / min to remove the agglomerated cellulose template to form a hollow nanotube structure, and the apoperiol template was further pyrolyzed and removed to form a nanoparticle catalyst Dimensional metal oxide nanotube structure that is uniformly bound and distributed on the inner and outer walls of the nanotube. The outer diameter of the nanotube structure is 50 nm to 10 μm, the inner diameter is 40 nm to 5 μm, and the thickness between the inner wall and the outer wall of the nanotube is 10 nm to 5 μm Lt; / RTI > The length of the nanotubes is in the range of 1 μm to 100 μm. If the diameter and the length of the nanotube structure are less than the above range, instability of the structure and excessive contact resistance between the nanotubes may be caused respectively after thermal decomposition of the cellulose template agglomerated in the core. In addition, when the diameter of the nanotube structure exceeds the above-mentioned range, a tube structure in which the thickness between the inner wall and the outer wall is excessively thick is formed in the process of forming the tube structure through the coagulation phenomenon of the cellulose template and the high temperature heat treatment, And the surface area capable of reacting with the gas can be very small as compared with a tube having a small diameter. Therefore, the diameter and length of the appropriate nanotubes should be within the above range, so that the sensing material in the most efficient shape can be synthesized with the gas sensor.

The one-dimensional metal oxide nanotube constituting the nanostructure is a sensing material of a semiconductor type gas sensor and does not impose a restriction on a specific substance if there is a change in electric resistance and electric conductivity value by adsorption and desorption of gas. Specific examples of the metal oxides include 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 , 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 , Or a one-dimensional metal oxide nanotube comprising interconnected multi-dimensional pore structures composed of two or more composite materials.

By using the gas sensor member formed by coating the one-dimensional metal oxide nanotube with the prepared nanoparticle catalyst as a sensing material, the biological surface gas discharged from the human exhalation can be selectively sensed with high sensitivity, It is possible to construct an ultra-high-sensitivity / high-selectivity sensor array that can be used as an environmental sensor for monitoring the hazardous environment gas in real time. Particularly, since the hollow nanotube structure is formed, the specific surface area of the sensing material can be increased and the inflow characteristics of the gas can be improved to provide a highly effective structure for adsorption and desorption reaction between the gas and the sensing material. Based on the above structure, it is possible to maximize the sensor characteristics of the sensing material even with a small amount of catalyst, and it has an advantage that mass production of various gas sensor members can be easily performed at low cost.

FIG. 2 is a flowchart illustrating a method of manufacturing a member for a gas sensor using a one-dimensional metal oxide semiconductor nanotube in which a nanoparticle catalyst is uniformly bound by an electrospinning method according to an embodiment of the present invention. According to the flowchart of FIG. 2, the method for manufacturing a member for a gas sensor includes the steps of synthesizing a nanoparticle catalyst in an interior through an apo-peritone template (S210), forming an apo-peritone template and a cellulosic template, (S220), and mixing the electrospinning solution prepared by the electrospinning to disperse the nanoparticle catalyst uniformly in the interior and the exterior of the cell, Polymerized nanofibers (S230), and a high temperature heat treatment is performed to thermally decompose the cellulosic template, the polymer, and the synthesized nanoparticle catalyst-containing apoferritin template, Nanotube structure and the nanoparticle catalyst is formed on the inner and outer walls of the nanotube A one-dimensional metal oxide nanotubes to be distributed may be configured to include a step (S240) of synthesizing. Each of the above steps will be described in more detail below.

First, a step (S210) of synthesizing a nanoparticle catalyst using an apoferritin template will be described.

The apo-ferritin template used in this step (S210) includes ferritin extracted from horse spleen, and iron ions present therein are removed using ferritin obtained irrespective of the extraction site through human or pig liver or spleen Can be used. Various concentrations of sodium chloride (NaCl) solution including saline solution can be used as the apoperi- tin stock solution, and it is necessary to store at 4 ° C or below. a solution state in an acidic atmosphere of pH 2-3 or a basic atmosphere of pH 7.5-8.5 is suitable for the metal salt to diffuse into the apoperi- tin template and to be synthesized, Immerse the apoferritin in a solution of metal salts for a sufficient period of time. The concentration of the saline solution containing the apoferritin template is in the range of 0.1-200 mg / ml. The solvent used for preparing the metal salt solution is ethanol, deionized water, chloroform, N, A compatible solvent such as N, N'-dimethylformamide, N-methylpyrrolidone or the like can be used. If the solution is a solution in which the metal salt is well dissolved, Do not. As the type of the metal salt embedded in the apo-peritone template, it is possible to use a metal such as Pt, Pd, Rh, Ru, Ni, Co, Cr, Ir, Au, Ag, Zn, Mn, Ga, Ge, W, Sn, Ta, Sb, Sc, Ti, and the like, and can be present in the form of metal ions. Examples of the reducing agent used for reducing the metal salt embedded in the apoferritin template to a metal form include sodium botohydride (NaBH ₄ ), oxalic acid (C ₂ H ₂ O ₄ ), formic acid (HCOOH ), And there is no particular restriction as long as it is a reducing agent capable of reducing a metal salt to form a metal nanoparticle catalyst. Centrifugation was carried out at a rotation speed of about 12,000 rpm in order to selectively extract the apo ferritin template containing the metal nanoparticles reduced through the reducing agent, and the apoferritin template containing the extracted metal nanoparticles was redispersed in deionized water .

Next, a step S220 of preparing a metal oxide precursor / polymer mixture spinning solution containing the synthesized nanoparticle catalyst-containing apoferritin template and the cellulose template will be described.

In this step S220, the apoperiol template and the cellulose template having the built-in nanoparticle catalyst prepared above are added to the mixed solution of the metal oxide precursor / polymer, and the nanoparticle catalyst and the cellulose template are stirred so as to be uniformly dispersed in the spinning solution A mixed spinning solution is prepared. Examples of the solvent used for preparing the spinning solution include deionized water, N, N'-dimethylformamide, N, N'-dimethylacetamide (N, N ' -dimethylacetamide, ethanol, and the like can be used. However, a solvent capable of solubilizing the metal oxide precursor and the polymer at the same time should be selected. If this condition is satisfied, the kind of the solvent is not particularly restricted. In addition, the polymer matrix contained in the electrodeposition solution does not limit the specific substance as long as it is pyrolyzed and removed during the high-temperature heat treatment. Specific examples of the solvent include polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA) (PEO), polypropylene oxide (PPO), polyethylene oxide block copolymer (PEO BCP), and polypropylene oxide block copolymer , PPO BP, polyvinylchloride (PVC), polycarbonate (PC), polycaprolactone (PCL), and polyvinylidene fluoride (PVDF)

In addition, the metal oxide precursor used in this step should be dissolved well in an electrospinning solvent. In the high temperature heat treatment, SnO ₂ , WO ₃ , CuO, NiO, ZnO, Zn ₂ SnO ₄ , Co ₃ O ₄ , Cr ₂ O ₃ , LaCoO ₃ , V ₂ O ₅ , IrO ₂ , TiO ₂ , Er ₂ O ₃ , Tb ₂ O ₃ , Lu ₂ O ₃ There is no limitation on a specific metal salt as long as it is a precursor including a metal salt capable of forming a semiconductor metal oxide nanotube in which resistance change and electrical conductivity change occurs through adsorption with a gas upon desorption of a gas and desorption surface reaction.

The weight ratio of the metal oxide precursor to the polymer forming the electric discharge solution is preferably about 1: 1-2, and the ratio of the polymer to the nanoparticle catalyst embedded in the apoferritin template is preferably about 1: 0.00001 to 0.1. If the content of the catalyst is too small, it is difficult to induce a sufficient catalytic effect. If the content of the catalyst is too large, problems such as excessive initial resistance value and deterioration of the catalyst property due to agglomeration phenomenon between the catalysts may occur. Therefore, the indicated appropriate amount of catalyst should be set. The weight ratio of the cellulose template to the polymer matrix used in step S220 is preferably about 1: 0.01-1. If the weight ratio of the cellulose template to the polymer matrix is too small, it is difficult to induce the hollow tube shape sufficiently effectively. If the weight ratio is too high, the hollow structure formed through the thermal decomposition process after heat treatment may collapse the nanotube shape In addition, the excessive viscosity of the electrospinning solution may lead to difficulties in electrospinning. Therefore, it is effective to synthesize one-dimensional metal oxide nanotubes by setting an appropriate weight ratio as shown in the above-described range. In the case of the nanoparticle catalyst to be embedded in apoperi- tine template, the metal salt corresponding to the targeted gas is selected in consideration of the selectivity of the target gas. By appropriately adjusting the above conditions, a member for a gas sensor having various structures and characteristics can be manufactured.

 In step S220, a nanoparticle catalyst embedded in an apo-peritone template is first dispersed in a solvent, and then the solution is added to a solution in which cellulose is dispersed. In order to impart viscosity to the prepared solution, the polymer is added in an appropriate ratio, and then a metal oxide precursor is added to dissolve. And sufficiently stirred in the electrospinning solution until both the polymer and the metal oxide precursor are dissolved. At this time, it is preferable that the stirring condition is sufficiently stirred at room temperature for about 6-24 hours. Through the above process, an electrospinning mixed solution in which an apo ferritin template and a cellulose template having a nanoparticle catalyst are uniformly distributed in a metal oxide precursor / polymer solution is prepared.

The prepared electrospinning mixed solution is electrospun and the apoperi- tin template with the nanoparticle catalyst is uniformly bound to the inside / outside of the metal oxide precursor / polymer composite nanofiber, and the cellulose template is agglomerated inside the composite nanofiber (Step S230) of fabricating the composite nanofibers of the present invention.

In step S230, the electrospinning solution is filled in a syringe, and the syringe is pushed at a constant speed using a syringe pump to discharge the electrospinning solution. As a result, . In this case, the electrospinning system is composed of a high voltage generator, a syringe, a nozzle, a grounded conductive substrate, etc., and a high voltage of about 4-40 kV is applied between the electrospinning solution filled in the syringe and the conductive substrate, The electrospinning solution is ejected and radiated in the form of nanofibers to be collected on the conductive substrate. During the electrospinning process, the solvent of the spinning solution is mostly evaporated and volatilized and the metal oxide precursor, polymer, cellulose template and nanoparticle catalyst embedded in the apoferritin template are combined and collected in the form of one-dimensional solid composite nanofibers. At this time, the discharge rate can be adjusted to about 0.01-0.5 ml / min. The metal oxide precursor / polymer and cellulosic template to which the apoferritin template is bound by the appropriate control of the voltage and the discharge amount are aggregated and the diameter of the composite nanofiber Can be synthesized by controlling.

Finally, the prepared composite nanofibers are heat-treated at a high temperature to oxidize the metal oxide precursor to form a metal oxide, and at the same time, the cellulose, the apoferritin template and the polymer are thermally decomposed and removed, so that the nanoparticle catalyst is uniformly bound The oxide nanotube shape can be produced through step S240. In particular, the nanotube structure is formed by removing the cellulose template, the polymer matrix, and the apoferritin template used as the sacrificial layer template by high temperature heat treatment in the temperature range of 500-800 ° C., and the metal oxide precursor is oxidized, Crystallized through grain growth to form a one-dimensional metal oxide nanotube structure. The structure ultimately formed through step S240 includes a nanotube structure formed by pyrolysis of a cellulose template that is agglomerated therein during electrospinning and a nanoparticle catalyst uniformly bound to the inner and outer walls of the nanotube to be functionalized. Dimensional metal oxide nanotube structure.

FIG. 3 schematically shows a manufacturing process sequence according to a method of manufacturing a member for a gas sensor using a one-dimensional metal oxide nanotube in which a nanoparticle catalyst using electrospinning is uniformly bound according to an embodiment of the present invention.

Step S310 of the first step is a step of electrospinning the solution containing the prepared metal oxide precursor and the polymer matrix uniformly dispersed with the apoperi- tin template and the cellulose template having the built-in nanoparticle catalyst. It is a schematic diagram showing.

Figure 4 shows a transmission electron micrograph of a cellulose template serving as a sacrificial layer template for tubular fabrication according to one embodiment of the present invention.

In the second step S320, the nanoparticle catalyst embedded in the apoferritin template collected on the conductive substrate after electrospinning is uniformly distributed, and the cellulose template is agglomerated to form a complex nano-particle, which is present in the metal oxide precursor / polymer matrix nanofiber The fiber is subjected to heat treatment at a high temperature to form a cellulosic template that is agglomerated therein, an apo-peritone template surrounding the nanoparticle catalyst, and a gas using a one-dimensional metal oxide nanotube in which the polymer matrix is pyrolyzed and finally bonded uniformly with the nanoparticle catalyst Is a schematic diagram showing the synthesis of a member for a sensor.

FIG. 5 is a graph showing the results of a comparison between a composite nano fiber obtained by electrospinning a tungsten oxide precursor / polyvinylpyrrolidone (PVP) complex spinning solution containing an apo-peritone template having a Pt nanoparticle catalyst according to an embodiment of the present invention and a cellulose template And a one-dimensional tungsten oxide nanotube in which a Pt nanoparticle catalyst is uniformly bound by high-temperature heat treatment.

As described above, the method of manufacturing the gas sensor member using the one-dimensional metal oxide nanotube in which the nanoparticle catalyst is uniformly bound using the electrospinning method and the composite biotemplate according to the embodiments of the present invention, The nanoparticle catalyst synthesized by using a protein template having excellent dispersibility by positively charged surface charge can be expected to improve the inflow characteristics of the gas and the sensor characteristics according to the increase of the reaction area, It is possible to dramatically improve the reaction rate characteristic, the sensitivity characteristic and the selectivity compared to the conventional gas sensor by causing an optimal catalytic effect in a very small amount.

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 are not intended to limit the present invention to the following examples.

Example  1: Preparation of Pt nanoparticle catalyst using apoferritin

The following procedure is used to synthesize a Pt nanoparticle catalyst having a size range of 1 to 5 nm (preferably in the range of 1 to 3 nm in size) using an apoferritin template.

To embed the metal salt in the apoperi- tin, first prepare a solution (Sigma Aldrich) in which apoferritin is dispersed in 0.15 M aqueous NaCl solution at a concentration of 35 mg / ml. A basic aqueous solution such as NaOH is added to the above apoferritin solution to adjust the pH to about 8.5, so that the optimal conditions for the metal salt to flow well into the apoferritin are adjusted. The precursor of the Pt metal ion used to synthesize the Pt nanoparticle catalyst is H ₂ PtCl ₆ · H ₂ O and 16 mg of H ₂ PtCl ₆ · H ₂ O is dissolved in 1 g of deionized water to prepare an aqueous solution . The metal salt precursor aqueous solution prepared above is slowly added dropwise to the apo ferritin solution adjusted to pH 8.5 with a dropper while stirring. Agitation is performed so that the Pt metal ions in the mixed solution can flow well into the apoperi- tin. At this time, the agitation time is about 1 hour at about 100 rpm. After sufficient stirring, NaBH ₄ A Pt nanoparticle catalyst is synthesized inside the apoferritin by reducing the Pt metal ion existing in apoferritin using a reducing agent. The reducing agent NaBH ₄ To 40 mM and then add 0.5 ml of the solution. Since the aqueous solution containing Pt nanoparticle catalysts dispersed in the synthesized apo-peritone template contains a reducing agent and a ligand impurity of a metal salt, it is centrifuged at about 12,000 rpm for about 10 minutes using a centrifugal separator, It is possible to prepare a solution in which the Pt nanoparticle catalyst synthesized in the apoferritin template is dispersed in an aqueous solution.

FIG. 6 shows a transmission electron microscope photograph and a size distribution of apoferritin template embedded with the Pt nanoparticle catalyst synthesized through the above process. Through the transmission electron microscope, it is confirmed that the nanoparticles of Pt (200) and Pt (111) are uniformly dispersed in a uniform size, and that the nanoparticle catalysts exist in the size of about 1-3 nm.

Example  2: Pt nanoparticle catalyst uniformly Concluded  One-dimensional tungsten oxide (WO ₃ ) Fabrication of nanotubes (100)

First, 0.1 g of the cellulose template is dispersed in 1.9 g of deionized water, and then about 40 mg of the Pt nanoparticle catalyst aqueous solution synthesized in Example 1 is mixed. Thereafter, 0.2 g of ammonium tungsten metatungstate hydrate as a precursor of tungsten oxide and 0.2 g of a polyvinylpyrrolidone (PVP) polymer having a molecular weight of 1,300,000 g / mol were added to 0.25 g of the above- And stirred at room temperature for 12 hours at a rotation speed of 500 rpm to prepare a spinning solution. The prepared spinning solution was placed in a syringe (12 mL NORM-JECT) and connected to a syringe pump. The spinning solution was pushed out at a discharge rate of 0.1 ml / min and the needle , 25 gauge) and the current collecting the nanofibers is 17 kV. At this time, a stainless steel plate is used as the collector plate, and the distance between the nozzle and the collector is set to 20 cm.

FIG. 5 is a graph showing the relationship between the number of metal oxide precursor / polymer composite nanofibers including the apoferritin template and the cellulose template embedded in a nanoparticle catalyst synthesized by electrospinning and the one-dimensional metal Scanning electron micrograph of oxide nanotubes. At this time, the high-temperature heat treatment process was maintained at 600 ° C for 1 hour and the rate of temperature increase was 5 Lt; 0 > C / min and the descending speed is set at 40 [deg.] C / min. Heat treatment is carried out in an air atmosphere using Ney's Vulcan 3-550 compact electric furnace. The apoferritin template surrounding the metal nanoparticle catalyst, the cellulosic template and the polymer matrix, which have been agglomerated, are thermally decomposed and removed to form a one-dimensional nanotube structure in which the Pt nanoparticle catalyst is uniformly bound.

9 is a transmission electron micrograph of a 1-dimensional tungsten oxide nanotube including the Pt nanoparticle catalyst synthesized in Example 1. FIG. In addition, the TEM analysis of the components (EDS elemental mapping and EDS line profile) showed that the Pt nanoparticle catalysts were uniformly dispersed throughout the structure of the tungsten oxide nanotubes, and the distribution of tungsten, oxygen, and Pt catalysts Is hollow nanotube structure hollowed out with a minute fraction in the nanotube. Through the TEM analysis, the cellulose template formed on the core is thermally decomposed after the high-temperature heat treatment to form a hollow tube structure, and uniform distribution characteristics of the catalyst can be confirmed.

Comparative Example  1. One-dimensional tungsten oxide without nanoparticle catalyst (WO ₃ ) Fabrication of nanotubes

Comparative Example 1 compared to Example 2 above relates to the synthesis of one-dimensional tungsten oxide nanotubes that do not include a Pt nanoparticle catalyst. Specifically, the preparation process is the same as that of Example 2, except that the apo-ferritin solution containing the Pt nanoparticle catalyst is not added. That is, after 0.1 g of the cellulose template was dispersed in 1.9 g of deionized water, 0.2 g of ammonium tungstate metatungstate hydrate as a precursor of tungstic oxide and 0.2 g of ammonium tungstate metatungstate hydrate were added to a polyvinyl alcohol having a molecular weight of 1,300,000 g / mol A polyvinylpyrrolidone (PVP) polymer was added to 0.25 g of the above solution and stirred at a rotational speed of 500 rpm at room temperature for 12 hours to prepare a spinning solution. The thus-prepared tungsten oxide precursor / polymer matrix electrospinning solution containing the cellulose template thus formed was placed in a syringe (Henke-Sass Wolf, 12 mL NORM-JECT) and connected to a syringe pump. The needle used for electrospinning is a 25 gauge needle. The distance between the nozzle and the collector collecting the nanofibers is maintained at 20 cm, and a high voltage of 17 kV is applied to conduct electrospinning.

The tungsten oxide precursor / polymer matrix composite nanofiber in which the cellulose template synthesized through the above process is agglomerated is thermally decomposed and removed from the polymer matrix and the cellulosic template agglomerated therein through the heat treatment at high temperature, and the oxidation process of tungsten oxide Tungsten oxide. The high-temperature heat treatment condition is performed by raising the temperature to 600 ° C at a heating rate of 5 ° C / min and then maintaining the temperature at that temperature for 1 hour. The temperature lowering rate can be kept constant at 40 ° C / min.

FIG. 7 is a scanning electron microscope (SEM) image of a one-dimensional tungsten oxide nanotube fabricated by high temperature heat treatment of composite nanofibers of a metal oxide precursor / polymer matrix in which a cellulosic template synthesized by electrospinning is aggregated. It can be confirmed that the sensing material of hollow hollow one-dimensional tungsten oxide nanotubes is well synthesized.

Comparative Example  2. Production of pure tungsten oxide nanofiber

Comparative Example 2 compared to Example 2 above relates to the synthesis of one-dimensional tungsten oxide nanofibers without addition of a Pt nanoparticle catalyst and without a cellulose template. Specifically, 0.2 g of ammonium tungstate metatungstate hydrate as a precursor of tungsten oxide and 0.25 g of polyvinylpyrrolidone (PVP) polymer having a molecular weight of 1,300,000 g / mol were added to 1.9 g of Dispersed in deionized water, and stirred at room temperature for 12 hours at a rotation speed of 500 rpm to prepare a spinning solution. The thus prepared tungsten oxide precursor / polymer matrix mixed electrospinning solution was placed in a syringe (Henke-Sass Wolf, 12 ml NORM-JECT) and connected to a syringe pump to push the solution at a discharge rate of 0.1 ml / The needle used for electrospinning uses a 25 gauge. The distance between the nozzle and the collector collecting the nanofibers is maintained at 20 cm, and a high voltage of 17 kV is applied to conduct electrospinning. The tungsten oxide precursor / polymer matrix composite nanofiber can be prepared through the above process.

The tungsten oxide / polymer matrix composite nanofiber synthesized above is thermally decomposed and removed by high temperature heat treatment to form one-dimensional tungsten oxide nanofibers. At this time, the high temperature heat treatment condition is performed at 600 ° C. for 1 hour, and the temperature rising rate and the falling rate can be kept constant at 5 ° C./min and 40 ° C./min, respectively.

8 is a scanning electron microscope (SEM) image of a one-dimensional pure tungsten oxide nanofiber prepared by high-temperature heat treatment of a tungsten oxide precursor / polymer matrix composite nanofiber synthesized by electrospinning. It can be confirmed that the synthesized one-dimensional pure tungsten oxide nanofibers are formed in a dense nanofiber structure in which the inside of the nanofibers is not empty but grain grown grains are connected and distributed.

10 is a thermogravimetric analysis and differential scanning calorimetry analysis of a tungsten oxide precursor / polymer matrix composite nanofiber including a tungsten oxide precursor / polymer matrix composite nanofiber synthesized by electrospinning and a cellulose template. In the case of the sample containing the cellulose template, it can be confirmed that a thermogravimetric decrease and an exothermic peak not observed in the sample not yet formed are additionally formed at about 250 ° C and around 550 ° C. As a result, thermal decomposition of the surface amorphous region of the cellulosic template existing inside the cellulosic template aggregated during electrospinning is performed primarily at around 250 ° C., and the main crystalline region of the cellulose is pyrolyzed at about 550 ° C., As a result, a hollow structure is formed and tungsten oxide nanotubes are formed.

Experimental Example  1. The Pt nanoparticle catalyst is uniformly distributed in and out of the nanofiber Concluded  One-dimensional tungsten oxide nanotubes, catalyst Do not settle  Fabrication and characterization of gas sensor using 1-D tungsten oxide nanotube and 1-D pure tungsten oxide nanofiber

In order to fabricate the sensing material for the gas sensor manufactured in Examples 1 and 2 and Comparative Examples 1 and 2 using an expiratory sensor, a one-dimensional tungsten oxide nanotube in which a Pt nanoparticle catalyst is uniformly bound, One-dimensional tungsten oxide nanotubes and pure 1-dimensional tungsten oxide nanofibers are dispersed in 300 μl of ethanol, and then pulverized by sonication for 30 minutes to 1 hour. The 1-dimensional tungsten oxide nanotube and the nanofiber structure synthesized in the pulverization process may be further shortened in the longitudinal direction.

One-dimensional tungsten oxide nanotubes with Pt nanoparticle catalyst uniformly bound, one-dimensional tungsten oxide nanotubes without catalyst binding, and pure one-dimensional tungsten oxide nanofibers were immersed in two parallel gold (Au ) Electrode can be coated by drop coating on the 3 mm x 3 mm alumina substrate. In the coating process, 6 μl of Pt nanoparticle catalyst dispersed in ethanol using a micropipette was uniformly bound with one-dimensional tungsten oxide nanotubes, one-dimensional tungsten oxide nanotubes with no catalysts, and one-dimensional tungsten oxide nano- The fiber mixture solution was coated on an alumina substrate having a sensor electrode and then dried on a hot plate at 70 ° C. This process was repeated 2-5 times to uniformly apply a sufficient amount of the sensing material on the alumina sensor substrate .

Simulation gas sensing characteristics evaluation as an expiratory sensor is performed by using a sensor coated with a sensing material. The evaluation is performed at a relative humidity (RH) of 85-95%, which is similar to the humidity of a gas discharged through human exhalation The concentration of acetone (CH ₃ COCH ₃ ), hydrogen sulfide (H ₂ S), and toluene (C ₆ H ₅ CH ₃ ) gases, which are biomarkers for diagnosis of diabetes, bad breath and lung cancer, 1, 0.6, 0.4, 0.25, 0.2, and 0.15 ppm, and the sensor operating temperature is maintained at 450 ° C. In the present Experimental Example 1, formaldehyde (HCHO), ethanol (C ₂ H ₅ OH), carbon monoxide (CO), ammonia (NH ₃ ) as well as the above three gases, which are typical examples of volatile organic compounds (VOCs) , Methane (CH ₄ ) gas can also be evaluated to evaluate the selective gas sensing characteristics.

Figure 11 shows the response (R _air / R _gas , where R _air is injected with air) as the hydrogen sulfide gas is reduced to 5, 4, 3, 2, 1, 0.6, 0.4, 0.25, And R _gas is the resistance value of the metal oxide sensing material when the hydrogen sulfide gas is injected.

As can be seen from the graph of FIG. 11, in the case of the one-dimensional tungsten oxide nanotube sensing material in which the Pt nanoparticle catalyst is uniformly bound, the one-dimensional tungsten oxide nanotube not having catalyst attached to 5 ppm hydrogen sulfide gas, Dimensional tungsten oxide nanofiber sensing material exhibits an improvement of about 25 times and 52 times, respectively. Also, it can be seen that the 1-dimensional tungsten oxide nanotubes to which the catalyst is bound show very high sensitivity of 10.4 even at a very low hydrogen sulfide concentration of 0.15 ppm.

FIG. 12 is a graph showing the relationship between the concentration of hydrogen sulfide gas and the concentration of hydrogen sulphide gas in the case of using one-dimensional tungsten oxide nanotubes uniformly bound with Pt nanoparticle catalyst at 450 ° C, one-dimensional tungsten oxide nanotubes not bound to catalyst, Which is known as biomass surface gas of acetone, toluene, formaldehyde, carbon monoxide, ammonia and methane gas at a concentration of 5 ppm. Pure 1-dimensional tungsten oxide nanofibers exhibit high sensitivity to not only hydrogen sulfide but also acetone and toluene gas, but also have a relatively high reactivity to the other five gases. Falls. However, in the case of one-dimensional tungsten oxide nanotubes using a cellulose template and one-dimensional tungsten oxide nanotubes having a Pt nanoparticle catalyst bonded, the reactivity to the seven kinds of gases other than hydrogen sulfide gas is very low, It is confirmed that only the sensitivity characteristic to hydrogen sulfide is increased exponentially.

The sensor characteristics of the gas sensor sensing material can be confirmed by taking the bio-indicator gas as an example. In addition to the biosurfactant biosurfactant gas, which exhibits excellent detection properties, various catalytic particles such as Au, Pd, Ru, Co, and Ni are synthesized and used in addition to the Pt nanoparticle catalyst embedded in apoferritin, When various kinds of metal oxide nanotubes are synthesized by functionalizing various kinds of metal oxide particles, it is possible to synthesize nanotubes having various functions such as CO ₂ , NO _x , SO _x and H ₂ , A sensor array can be manufactured. The one-dimensional metal oxide nanotube sensing material utilizing a composite biotemplate composed of the nanoparticle catalyst synthesized from the apo-peritone template has excellent gas sensor for environment, gas for volatile organic compounds in exhalation and gas for analysis and diagnosis of volatile sulfur compound gas As a sensor, it can have a positive impact contributing to the development of healthcare industry.

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: One-dimensional metal oxide nanotube gas sensor incorporating nanoparticle catalyst and utilizing complex biotemplate
110: After thermal treatment of apoferritin is thermally decomposed to form a metal nano-particle catalyst,
120: One-dimensional metal oxide nanotube structure having a hollow structure formed by thermal decomposition of cellulose agglomerated therein after high-temperature heat treatment

Claims (17)

1. A member for a metal oxide nanotube-based gas sensor, which is produced through composite nanofibers having a core-shell structure and is uniformly bound with a catalyst,
Wherein the core of the core-shell structure comprises a thermally decomposable cellulose template, the shell comprises a metal oxide precursor and a polymer, and the metal nanoparticle catalyst embedded in the protein template is uniformly distributed throughout the core- Distributed,
Wherein the cellulose nanoparticle catalyst is removed from the core by the heat treatment of the composite nanofibers having the core-shell structure, wherein the cellulose nanoparticles incorporated in the protein template are removed from the core as the cellulose template, the polymer, The metal oxide nanotubes formed according to the removal are uniformly bound and functionalized on the inner wall surface, the outer wall surface, and the inner wall surface and the outer wall surface
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method according to claim 1,
The core-shell structure is formed through a process of aggregating the cellulose template onto the core of the metal precursor / polymer composite nanofiber through an electrospinning process
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method according to claim 1,
The cellulose template has a diameter range of 1 nm to 100 nm and a length distribution of 10 nm to 10 μm depending on the extraction source, dispersion method and degree of polymerization
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method according to claim 1,
In the core-shell structure, the cellulose template formed by agglomeration in the core is decomposed at a temperature range of 250 ° C to 550 ° C
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method according to claim 1,
The metal oxide nanotubes have an outer diameter in a range of 50 nm to 10 μm, an inner diameter in a range of 40 nm to 5 μm,
The thickness between the inner wall and the outer wall of the metal oxide nanotube is in the range of 10 nm to 5 μm and the length of the nanotube is in the range of 1 μm to 100 μm
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method of claim 1,
The 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, 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 One or more of
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method of claim 1,
The metal catalyst particles were prepared from an apoferritin protein template having a hollow structure with a pore size of 7 nm - 8 nm inside
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method of claim 1,
The metal catalyst particles 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, Fe, Cu, V, Ta, , One or more of Mn, Ga and Sc
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. The method of claim 1,
The size of the metal catalyst particles is in the range of 1 nm to 5 nm
Member for a gas sensor based on a one-dimensional metal oxide nanotube utilizing a complex biotemplate. A method for manufacturing a one-dimensional metal oxide nanotube using a composite biotemplate,
(a) preparing a uniformly dispersed first dispersion solution by synthesizing a nanoparticle catalyst in an apo-peritone template;
(b) synthesizing a second dispersion solution in which the cellulose template is uniformly dispersed;
(c) mixing the first dispersion solution and the second dispersion solution with a metal oxide precursor and a solvent in which the polymer is dissolved to prepare an electrospinning solution;
(d) forming a core-shell structure of the electrospinning solution in the form of a cellulosic template agglomerated within the metal oxide / polymer composite nanofibers by using a single nozzle electrospinning method, wherein the nanoparticle catalyst embedded in the apoferritin template To form composite nanofibers uniformly distributed throughout the core-shell structure;
(e) The metal precursor composing the composite nanofiber is oxidized to form a metal oxide by heat treatment, and the aggregated cellulosic template, the apoperi- tin template with the nanoparticle catalyst, and the organic material including the polymer are decomposed by thermal decomposition Forming a one-dimensional metal oxide nanotube that is uniformly bound to the inner and outer walls, and between the inner and outer walls of the nanotube catalyst to form the nanotube,
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (a)
The apoperiol protein is synthesized by injecting a metal salt into the internal pores and reducing through a reducing agent to synthesize a metal particle catalyst in the hollow structure
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (b)
In order to uniformly disperse the cellulose template in a solvent, the solvent is homogeneously dispersed using at least one of a mechanical dispersion method, a chemical-mechanical mixed dispersion method, and a chemical dispersion method, Then,
The mechanical dispersion method may include at least one of sonication, grinding, and homogenization,
The chemical-mechanical mixing and dispersion method includes at least one of oxidation and mechanical agitation,
The chemical dispersion method includes at least one of acid hydrolysis and enzymatic hydrolysis
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (b)
The weight ratio of the cellulose template to the polymer matrix is in the range of 1: 0.01 to 1: 1
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (d)
The cellulose template is agglomerated inside the metal oxide precursor / polymer composite nanofiber during electrospinning to form a core-shell structure,
The apo-peritone template incorporating the metal nanoparticle catalyst is uniformly dispersed throughout the entirety of the metal-oxide composite nanofiber of the core-shell structure without agglomeration among each other
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (e)
The heat treatment process is maintained for 1 to 3 hours within a temperature range of 500 ° C to 800 ° C,
The cellulose template located at the core of the composite nanofiber formed through the electrospinning is pyrolyzed and removed at a temperature of 250 ° C to 550 ° C to form a hollow nanotube structure therein
Wherein the method comprises the steps of: 11. The method of claim 10,
In the step (e)
The metal nanoparticle catalyst is uniformly bound to the inner wall and the outer wall of the metal oxide nanotube, and between the inner wall and the outer wall after the heat treatment
Wherein the method comprises the steps of: 11. The method of claim 10,
At least one of the complex bio templates one-dimensional metal oxide nanotubes utilizing the environmentally harmful gases (NO _x, SO _x,) and biomarkers (biomarker) gas _{(CH 3 COCH 3, H 2} S, C 7 H 8) one Used as a gas sensor material capable of gas detection
Wherein the method comprises the steps of:

Images