KR20120124673A - Porous zinc stannate nanofibers, fabrication method for the same, and gas sensors using the same - Google Patents

Abstract

PURPOSE: A porosity zinc stannate nanofiber and a method for fabricating the same are provided to control the concentration of polymers and zinc stannate precursor and to be applied to a gas sensor. CONSTITUTION: A zinc stannate(Zn_2SnO_4) nanofiber contains one or more nanoparticles extended in a longitudinal directioin and has a porous structure. The porous structure has one or more micropores with a size of 2-20 nm. The nanoparticle has a diameter of 2-50 nm and a length of 2-500 nm. A gas sensor contains the porous zinc stannate(Zn_2SnO_4) nanofiber as a sensing material. A method for fabricating the nanofiber comprises: a step of mixing zinc stannate precursor, polymers, and solvent to prepare a mixture solution(S10); a step of spinning the mixture solution to fabricate zinc stannate precursor/polymer composite fiber(S11); and a step of crystallizing the precursors of the composite fiber through thermal treatment. [Reference numerals] (S10) Preparing solution containing zinc stannate precursor dissolved in solvent; (S11) Preparing spinning solution by dissolving polymers in the zinc stannate precursor solution; (S20) Spinning the precursor solution and preparing composite fiber containing phase-separated zinc stannate precursor and polymers; (S30) Preparing porous zinc stannate precursor nanofiber by thermal treatment of the composite fiber

Description

Porous zinc stannate nanofibers, fabrication method for the same, and gas sensors using the same

The present invention relates to a porous zinc stannate nanofibers, a method of manufacturing the same and a gas sensor using the same, and more particularly, by adjusting the concentration of the zinc stannate precursor and the polymer can be adjusted in diameter, phase separation phenomenon between the zinc stannate precursor and the polymer. Using Including pores and particles elongated in the longitudinal direction of the nanofiber Provide nanofibers. In particular, it is possible to rapidly diffuse gases and electrolytes, which can be applied to photovoltaic electrodes for solar cells or electrode active materials for secondary batteries. Zinc nanofibers, a method of manufacturing the same and a gas sensor using the same.

Zinc stannate (Zinc Stannate, Zn ₂ SnO ₄ ) is an n-type semiconductor oxide, and has high electron conductivity (~ 10 ⁴ S / cm) and excellent optical and chemical resistance properties, making it the next-generation transparent electrode material and electrochemical device material. (DL Young, et. Al., J. Appl. Phys. (2002) 91, 1464; MK Jayaraj, et. Al., J. Vac. Sci. Technol. B, (2008) 26 Zinc stannate is prepared from nanoparticles with large surface area / volume ratios or nanostructures of one-dimensional shape, and thus is characterized by an ultraviolet detector (Y. Zhang, et. Al, J. Mater, Chem, 2010, 20, 9858), a photocatalyst. (MA Alpuche-Aviles, et. Al., JACS), dye-sensitized solar cells (B. Tan, et. Al., JACS), gas sensors (Z. Lu, et. Al., Mater. Chem, Phys. 2005 , 92, 5) and lithium ion secondary batteries (A. Rong, et. Al., J. Phys. Chem. B, 2006, 110, 14754). In order to manufacture zinc stannate nanostructures, processes such as chemical vapor deposition or hydrothermal synthesis have been introduced. However, the above synthesis methods are inferior in reproducibility in the production of zinc stannate having a three-component system, and are particularly limited in large area processes. Therefore, there is a need for a technique for preparing a large-area zinc stannate nanostructure having a large area, easy production, high yield, and high porosity and high purity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

First, an object of the present invention is to provide a method for producing zinc stannate nanofibers having a diameter of nanometer size by electrospinning a solution of a precursor salt such as tin salt and zinc salt and a polymer in a solvent.

Second, in the polymer composite fiber comprising a zinc stannate precursor obtained after electrospinning, a method of producing zinc stannate nanofibers having a porous structure including pores and particles stretched in the longitudinal direction of the nanofibers by using a phase separation phenomenon between the precursor and the polymer. To provide,

Third, the purpose is to produce an ultra-high sensitivity gas sensor using porous zinc stannate nanofibers.

In order to prepare zinc stannate nanofibers according to the present invention, a zinc stannate precursor including zinc salt and tin salt is used, and a precursor-polymer mixed solution in which a polymer having a phase separation characteristic from the precursor is dissolved in a solvent is used. Proceed with spinning. As stated above, the zinc salt and tin salt precursors are characterized by phase separation without mixing with the polymer when the solvent is removed. Therefore, the nanofibers obtained by spinning with the polymer mixed solution in which the electrospinning precursor is dissolved have a microstructure in which zinc salt, tin salt and polymer are phase separated. In addition, the zinc stannate precursor / polymer composite fiber obtained after electrospinning is heat-treated to remove the polymer, and zinc salt and tin salt form zinc stannate (Zn ₂ SnO ₄ ) nanofibers having a stoichiometric ratio of 2: 1. do. Hereinafter, the method for producing the porous zinc stannate nanofibers will be described in detail for each step. Zinc acetate and tin acetate were used as the zinc stannate precursor used in the present invention, vinyl acetate resin (PVAc) was used as the polymer, and DMF (dimethylformamide) was used as the solvent, but the scope of the present invention is not limited thereto. .

The zinc stannate nanofiber manufacturing method according to the present invention can control the diameter by adjusting the concentration of the zinc stannate precursor and the polymer, by using the phase separation phenomenon between the zinc stannate precursor and the polymer. Including pores and particles elongated in the longitudinal direction of the nanofiber Provide nanofibers. In particular, it is possible to rapidly diffuse the gas and electrolyte can be applied to photovoltaic electrodes for solar cells or electrode active materials for secondary batteries, it can be applied to a gas sensor with excellent sensitivity due to the high selectivity for a particular gas and a large specific surface area.

1 is a flow chart schematically showing a method for producing a porous zinc stannate nanofiber according to an embodiment of the present invention.
FIG. 2 is a view schematically illustrating the steps of the formation process of the composite nanofibers and the porous zinc stannate nanofibers in which the zinc stannate precursor and the polymer of FIG. 1 are phase separated.
Figure 3 is a scanning electron microscope (Scanning Electron Microscope) photograph of the composite nanofiber prepared according to Example 1.
4 is a scanning electron micrograph of the zinc stannate nanofibers prepared according to Example 1;
FIG. 5 is an enlarged scanning electron micrograph of FIG. 4.
6 is a scanning electron micrograph showing a cross section of the zinc stannate nanofiber of FIG. 5.
FIG. 7 is a scanning transmission electron microscope image of FIG. 4. FIG.
FIG. 8 is a photograph of FIG. 7 observed using a transmission electron microscope, and is a diagram showing the result of elemental analysis of a specific line region in the vertical direction of the fiber using an energy dispersive spectrum.
Figure 9 is a view showing the X-ray diffraction results of the zinc stannate nanofibers heat treated according to Example 1.
FIG. 10 is a confocal micrograph of a gas sensor manufactured according to Example 2. FIG.
FIG. 11 is a scanning electron microscope photograph of an enlarged portion of the zinc stannate nanofiber coated in the sensor of FIG. 10.
12 is a graph showing a result of measuring a change in resistance to ethanol gas (1 to 100 ppm) of the porous zinc stannate nanofiber gas sensor manufactured in Example 2. FIG.
FIG. 13 is a graph showing high selectivity for ethanol gas of the porous zinc stannate nanofiber gas sensor prepared in Example 2. FIG.
14 is a scanning electron micrograph of the dense zinc stannate nanofibers prepared in Comparative Example 1.
FIG. 15 is a graph showing pore distributions obtained from N ₂ adsorption-desorption reactions of the porous zinc stannate nanofibers obtained in Example 1 and the dense zinc stannate nanofibers obtained in Comparative Example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” include plural forms as well, unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” embodies a particular characteristic, region, integer, step, operation, element and / or component, and the presence of another characteristic, region, integer, step, operation, element and / or component or It does not exclude the addition.

The term “nano” described in the specification means nanoscale and may include micro units. In addition, the term "nanoparticle" described in the specification means a nano-scale object having a particle shape, the particle shape is not limited to a specific shape may be variously modified.

Figure 1 is a schematic diagram schematically showing a method of manufacturing a nanofiber composite according to the experimental example of the present invention, but the method of manufacturing a nanofiber composite of Figure 1 is merely to illustrate the present invention, the present invention is It is not limited. Therefore, the manufacturing method of the nanofiber composite can be modified into other forms.

As shown in Figure 1, the porous zinc stannate nanofiber manufacturing method, i) preparing a solution in which a zinc stannate precursor (zinc salt, tin salt) is dissolved in a solvent (S10), by dissolving the polymer in the zinc stannate precursor solution Preparing a solution for electrospinning (S11), ii) spinning the precursor solution to prepare a composite fiber in which the zinc stannate precursor and the polymer are phase separated (S20), and iii) heat treating the composite fiber to obtain porous zinc stannate nanofibers. It includes the step of manufacturing (S30). In addition, the method for producing the porous zinc stannate nanofibers may further include other steps, hereinafter, the steps of the method for producing a nanofiber according to the present invention according to FIG.

First, in step (S10) to prepare a mixed solution. Wherein the mixed solution comprises a zinc stannate precursor consisting of a tin precursor and a zinc precursor and a solvent. Here, the solvent is water, ethanol, chloroform, N, N'-dimethylformaldehyde (N, N'-dimethylformamide), dimethylsulfoxide, N, N'-dimethylacetamide (N, N ' Compatible solvents such as -dimethylacetamide) and N-methylpyrrolidone may be used, and the zinc stannate precursor and the polymer should be dissolved simultaneously.

The zinc stannate precursor may use a zinc salt-containing material or tin salt-containing material such as zinc acetate, tin acetate, and the like, and there is no limitation on the type of anionic material that is ionically or covalently bonded with zinc or tin. The tin and zinc precursors of the electrospinning solution obtained in step S10 and tin acetate and zinc acetate are then located inside the (tin acetate, zinc acetate) / vinyl acetate resin composite fiber obtained through electrospinning. In addition, the amount of the tin precursor and the zinc precursor may be 5 wt% to 30 wt% of the solution. If the zinc salt or tin salt concentration of the precursor is too high or low, the porous zinc stannate nanofibers are not well formed. If the concentration is too low, the fibers are broken in the final heat treatment step, and if the concentration is too high, the smooth electrical No radiation

In step (S11) while dissolving in the solvent and at the same time to dissolve the polymer phase is separated from zinc salt, tin salt when the solvent volatilized to prepare an electrospinning solution.

As the polymer, a species which is phase-separated from the zinc stannate precursor in the mixed solution may be used, and a thermoplastic resin or a thermosetting resin soluble in a solvent may be used as the polymer. For example, a polyurethane copolymer, a cellulose derivative or other polymer may be used as the polymer. Polyurethane or a polyether urethane etc. can be used as a polyurethane copolymer. Examples of the cellulose derivatives include cellulose acetate, cellulose acetate propionate, and the like. Other polymers include polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymer, polyvinylacetate copolymer, polyperfuryl alcohol (PPFA), polyvinyl acetate (PVAc), polystyrene (PS) ), Polystyrene copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone, polyvinyl fluoride, polyvinylidene fluoride copolymer or polyamide, polyetherimide Etc. can be used.

The amount of polymer in step S11 may be from 8 wt% to 20 wt% of the solution. If the amount of polymer is too small or too large, the solution does not have a viscosity suitable for electrospinning.

Next, in step S20 to spin the precursor solution. The spinning may use electrospinning, flash spinning or electrostatic melt-blown. Here, the spinning process can be easily understood by those skilled in the art, the detailed description thereof will be omitted.

In the step (S20), the polymer gives a viscosity to the spinning solution, to enable smooth spinning, and thermally decomposed after the heat treatment to have a porous structure.

In step S20, when the precursor solution is spun by electrospinning, the precursor solution is filled into a syringe pump, and then spouted at a constant speed, and the sputtered precursor solution is electrospun. During the electrospinning process, the sol-gel reaction occurs due to evaporation of the solvent inside the precursor solution. As a result, a polymer fiber in a solid form is obtained, and at the same time, due to the phase separation property, the inside of the polymer fiber has a structure in which a portion of the zinc stannate precursor and a portion of the polymer are separated from each other. In addition, the zinc stannate precursor is elongated into thin fine fibers as the solvent evaporates, that is, stretched and phase separated from the polymer. If the polymer forms a complex compound or chemical bond with the zinc stannate precursor, the composite fiber obtained from electrospinning does not phase separate into a portion containing a large amount of zinc stannate precursor and a portion containing a large amount of polymer, thereby forming a uniform mixture. Therefore, in order to make nanofibers having a porous structure as in the present invention, the zinc stannate precursor and the polymer should be selected from species that do not form a complex or chemical bond with each other.

Finally, in step S30, the manufactured composite nanofibers are heat treated. Heat treatment step according to an embodiment of the present invention can be largely divided into two steps. First, the first heat treatment step is performed at 150 ℃ to 200 ℃, the first heat treatment is to maintain the shape even at high temperature by reacting and crosslinking the polymer of the composite fiber with oxygen. The second heat treatment step may be performed at 200 ° C to 900 ° C. Here, the phase-separated polymer in the composite fiber is thermally decomposed and the zinc stannate precursor is oxidized in shape to form porous zinc stannate nanofibers. As described above, the second heat treatment proceeds in a temperature range of 200 to 900 ° C., if the heat treatment temperature of the composite fiber is too low, the polymer is not decomposed and the zinc stannate precursor is not crystallized well. Conversely, if the heat treatment temperature of the composite fiber is too high, the shape of the fiber may not be maintained or unwanted crystal phases may be formed. In order to remove the polymer smoothly, the heat treatment is preferably performed at a temperature of 400 ° C. or higher. More preferably, the heat treatment is performed at a temperature of 600 ° C. or higher to prepare a nanofiber having a single phase zinc stannate crystal structure. After the heat treatment, crystalline zinc stannate nanofibers including pores and particles elongated in the longitudinal direction of the nanofibers are prepared due to the phase separation between the zinc stannate precursor and the polymer.

In consideration of the above-described steps, the present invention can produce zinc stannate nanofibers having different diameters and different pore sizes.

FIG. 2 is a schematic view of each step schematically showing the steps of the formation process of the composite nanofibers and the porous zinc stannate nanofibers in which the zinc stannate precursor and the polymer of phase 1 are separated.

As such, the present invention can control the width of the porous zinc stannate nanofibers according to the zinc stannate precursor used in the spinning solution, the type and concentration of the polymer, the spinning conditions, and the heat treatment conditions. However, as long as the nanofibers are produced by the electrospinning process, there is no restriction on the width of the particular nanofibers.

The zinc stannate nanofibers prepared according to the present invention have nanoparticles as described above, but the nanoparticles necessarily include elongated nanoparticles having a diameter of 2 nm to 50 nm and a length of 2 nm to 500 nm. It may also include unstretched spherical nanoparticles having a diameter size of 2 to 50 nm.

Hereinafter, the present invention will be described through Examples and Comparative Examples. However, the following examples are merely to illustrate the present invention, but the present invention is not limited thereto.

As an embodiment of the present invention, a vinyl acetate resin (PVAc, molecular weight: 1.3 million), zinc acetate, tin acetate, and dimethylformamide solvent were used to prepare a polymer composite fiber including a zinc stannate precursor. Here, vinyl acetate resin is a typical polymer that does not form a complex or chemical bond with zinc acetate and tin acetate at room temperature.

[Example 1: Preparation of porous zinc stannate nanofibers using (zinc acetate, tin acetate) / vinyl acetate composite fiber]

First, 1.756 g of zinc acetate is added to 15 g of dimethylformamide as a solvent, and completely dissolved. Then, 1.42 g of tin acetate is added and completely dissolved again. 1.5 g of vinyl acetate resin was added to the thus prepared solution, and the mixture was stirred and dissolved.

The prepared precursor solution was filled in a 20 ml syringe and slowly ejected at a discharge rate of 10 μl / min using a syringe pump (humidity: 20%, available voltage: 17.4 kV, ambient temperature: 30). C), a vinyl acetate resin composite fiber comprising a zinc stannate precursor in solid form is obtained by a sol-gel reaction while the solvent is evaporated. In addition to the outer surface of the fiber, zinc acetate and tin acetate precursors are also elongated into fine microfibers with evaporation of the solvent, resulting in phase separation with the vinyl acetate fiber, resulting in tin acetate and zinc acetate / vinyl acetate composite fiber. Will be.

Figure 3 shows a scanning electron microscope (Scanning Electron Microscope, SEM) photograph of the vinyl acetate resin composite nanofibers containing a zinc stannate precursor prepared according to Example 1. The total diameter of the composite fiber was 380 nm to 720 nm, as shown in the inset SEM photograph of FIG. 3. It was confirmed from FIG. 3 that the continuous composite nanofibers were well formed by electrospinning. When the zinc stannate precursor / polymer composite fiber obtained through electrospinning is maintained at 180 ° C. for 1 hour in an air atmosphere, and heat treated at 700 ° C. for 1 hour, a porous zinc stannate fiber having a diameter of several hundred nanometers can be obtained. The rate of temperature rise is 4 per minute ° C.

4 is a scanning electron micrograph of the zinc stannate nanofibers obtained after heat treatment at 700 ° C. for 1 hour.

Referring to FIG. 4, a slight shrinkage phenomenon was observed between 350 nm and 705 nm in total diameter before and after heat treatment, and the fiber showed continuous nanofiber shape even after heat treatment.

FIG. 5 is an enlarged scanning electron micrograph of FIG. 4.

Referring to FIG. 5, it can be seen that the surface of the zinc stannate nanofiber obtained through high temperature heat treatment has a porous structure including a plurality of nanometer-sized pores. In particular, the fine pore structure is observed on the surface in Figure 5, it can be observed that the initial particles constituting the Zn ₂ SnO ₄ nanofibers are deformed in the elongated form of the fiber.

In order to clearly observe that the inside of the zinc stannate nanofibers also have a fine pore structure distribution, the nanofibers were cut using the Focused Ion Beam, and the cut surface was again observed with a scanning electron microscope. FIG. 6 is a scanning electron micrograph showing a cross section of the zinc stannate nanofiber of FIG. 5, and it can be seen that it has a nanofiber inner structure having a porous pore main fabric.

In order to more clearly observe the internal structure of the zinc stannate nanofibers, the nanofibers were observed using a scanning electron transmission microscope. 7 is a scanning transmission electron microscope (Scanning Transmission Electron Microscope) of Figure 4, it can be seen that the heat treated zinc stannate nanofibers have a porous core structure. FIG. 8 is a photograph of FIG. 7 observed using a transmission electron microscope, and the results of elemental analysis using energy dispersive spectra of a specific line region in the vertical direction of the fiber are shown on the photograph. As shown in FIG. 8, the zinc stannate nanofibers were found to have an element ratio of 1: 2 in tin to zinc.

9 is a view showing the X-ray diffraction results of the heat-treated zinc stannate fiber prepared in Example 1, the crystal structure of the porous zinc stannate nanofibers (220), (311), (222), (400), ( 331), (422), and (551) cubic inverse spinels with picks.

Example 2 Gas Sensor Fabrication Using Porous Zinc Tartrate Nanofibers and Sensor Characteristics Evaluation

The sensor device was manufactured using porous zinc stannate nanofibers having a fine pore distribution prepared in Example 1. The zinc stannate nanofibers prepared in Example 1 were mixed with a binder to form a paste, and then coated on a sensor electrode, followed by heat treatment at 550 ° C. to prepare a gas sensor.

The electrode used for the measurement of resistance was an electrode consisting of two fingers having a length of 900 μm, a width of 600 μm, and a gap of 100 μm. In order to confirm the reactivity of the manufactured gas sensor, while changing the concentration of ethanol (C ₂ H ₅ OH) gas, the resistance change before and after the reaction at 450 ℃ was measured.

The sensor, which consists of a layer of zinc stannate, is mounted in a quartz tube in a tube furnace, and a Pt / Pt-Rh (type S) thermocouple is applied to various gases (H) in the thin layer of zinc stannate. ₂ , CO, C ₂ H ₅ OH) to measure the change in temperature while measuring the change in temperature. Gas flow rate was controlled by MFC (Tylan UFC-1500A mass flow controller and Tylan R0-28 controller). The reaction was reversible and the response time was very fast. These measurements can be made not only with tubes, but also in chambers with heating elements.

Hereinafter, a gas sensor analysis result of the porous zinc stannate nanofibers formed using the electrospinning according to the present invention will be described.

FIG. 10 is a confocal micrograph of a gas sensor composed of zinc stannate nanofibers prepared in Example 2. FIG. Gas sensor obtained by preparing porous zinc stannate nanofibers in paste form using solvent and polymer binder, applying gold electrode on patterned alumina substrate, and heat-treating at 550 ℃ for 1 hour to remove organic substances remaining in binder Can be observed in FIG. 10.

FIG. 11 is a scanning electron micrograph of a portion of the zinc stannate nanofiber coated in the gas sensor of FIG. 10. As shown in FIG. 11, it can be seen that the porous zinc stannate nanofibers are well connected to each other to constitute a sensing material of the gas sensor. Individual nanofibers contain fine nanopores as observed in FIGS. 6 and 7, and as shown in FIG. 11, huge pores are distributed between zinc stannate nanofibers. Therefore, a gas sensor composed of zinc stannate nanofibers can have high gas sensitivity and reaction rate characteristics due to its bi-modal pore distribution.

12 is a graph showing the results of measuring the change in resistance to ethanol (1 ~ 100 ppm) concentration change of the gas sensor made of porous zinc stannate nanofibers prepared in Example 2. Referring to FIG. 12, the gas sensor using the thin zinc stannate nanofiber layer of Example 2 shows typical n-type semiconductor characteristics of decreasing resistance during exposure to reducing gas (ethanol). Therefore, it was confirmed again that the zinc stannate nanofibers prepared by electrospinning according to the present invention were n-type metal oxide semiconductors. As shown in the sensor measurement results, it can be seen that the change in the resistance of the porous zinc stannate nanofiber layer was observed even at low ethanol concentration of 1 ppm. This is because porous zinc stannate nanofibers exhibit a high porosity structure and a large specific surface area, thereby increasing accessibility of ethanol gas, and providing a large surface area from which the reaction can occur from the nanofiber structure.

FIG. 13 is a diagram evaluating the selectivity of a gas sensor composed of porous zinc stannate nanofibers prepared in Example 2. FIG. As shown in FIG. 13, the resistance change reactivity of the zinc stannate nanofiber gas sensor was observed for hydrogen (H ₂ ), carbon monoxide (CO), and ethanol (C ₂ H ₅ OH) gases having a concentration of 100 ppm, respectively. In particular, gas sensors composed of porous zinc stannate nanofibers showed superior selectivity for ethanol over other types of reducing gases such as hydrogen (H ₂ ) and carbon monoxide (CO). The gas reactivity (Ra / Rg) value for ethanol gas was 290 times higher. In comparison, hydrogen and carbon monoxide showed weak gas reactivity. From these results, it can be predicted that the porous zinc stannate nanofiber network sensor can have excellent selectivity for volatile organic compound (VOC) gas containing ethanol.

Comparative Example 1 Preparation of Dense Zinc Tartrate Nanofibers Comprising Spherical Nanoparticles

Experiments were carried out in the same manner as in Example 1, but nanofibers were prepared using polyvinylpyrrolidone (PVP) polymer instead of vinyl acetate resin (PVAc). Since the PVP polymer forms a complex compound with zinc acetate and tin acetate by a pyrrolidone group, the PVP polymer does not phase separate from the tin precursor and the zinc precursor, thereby forming a composite fiber in a uniform mixture form.

FIG. 14 shows a scanning electron micrograph obtained after heat treatment of a zinc stannate precursor / PVP composite nanofiber obtained after electrospinning at 700 ° C. for 1 hour.

Referring to FIG. 14, it can be seen that the structure of the nanofibers is a very dense structure, which is completely different from the microstructure observed in Example 1. As such, when the nanofiber having a very dense structure is used as the gas sensor sensing material, only the outer surface of the fiber participates in the gas reaction, so that gas sensitivity is lower than that of the porous nanofiber structure.

However, the present invention can control the porosity of the nanofibers by using the phase separation characteristics of the precursor and the polymer, unlike the prior art using such a dense nanofiber structure, and further, the phase separation from the precursor material in the mixed solution It is also possible to control the mobility and the density of the nanofibers by mixing a specific ratio of the polymer having no characteristic of phase separation with the polymer.

FIG. 15 is a graph showing pore distributions obtained from N ₂ adsorption-desorption reactions of the porous zinc stannate nanofibers obtained in Example 1 and the dense zinc stannate nanofibers obtained in Comparative Example 1. FIG. As observed in FIG. 15, as the relative pressure ratio increases, the amount of N ₂ adsorbed and desorbed per 1 g of porous zinc stannate (porous Zn ₂ SnO ₄ ) nanofibers is about 3 times higher than that of the dense zinc stannate fiber. In addition, the porous zinc stannate in accordance with the present invention shows a porous structure having a pore distribution of 5 ~ 20 nm, in the case of dense zinc stannate nanofibers show the highest peak at 8 ~ 9 nm. In addition, even in the absolute volume ratio of pores, the porous zinc stannate nanofibers according to the present invention show much higher values than the dense zinc stannate nanofibers.

Although the gas sensor is illustrated as an application device using the porous zinc stannate nanofibers according to the present invention, an application electronic device using the porous zinc stannate nanofibers according to the present invention is observed that a change in resistance when adsorption of external gas is observed. In addition to the gas sensor described above, there is a transistor using Zn ₂ SnO ₄ having n-type metal oxide semiconductor properties as a channel layer. In addition, Zn ₂ SnO ₄ may be used as a negative electrode active material of a secondary battery, which is an energy storage device, and negative electrode active materials such as Si, Sn, and SnO ₂ have a volume expansion of about 200 to 400% when reacted with Li. . The Zn ₂ SnO ₄ negative electrode active material also has a large volume expansion. When the negative electrode active material having the porous Zn ₂ SnO ₄ nanofiber structure obtained in this embodiment is used as an electrode material, the pore distribution is well developed, The deformation can be absorbed by the volume expansion in the reaction, thereby minimizing the occurrence of cracks in the negative electrode active material and desorption from the electrode current collector.

Although the technical details of the production of the porous zinc stannate nanofiber of the present invention and the gas sensor using the same have been described with the accompanying drawings, this is illustrative of the best embodiment of the present invention and is not intended to limit the present invention. . It is also apparent to those skilled in the art that various modifications and variations can be made within the scope of the appended claims without departing from the scope of the spirit of the invention.

Claims (20)

Zinc stannate (Zn ₂ SnO ₄ ) nanofibers composed of nanoparticles and having a porous structure. The method of claim 1,
The nanofiber is zinc stannate (Zn ₂ SnO ₄ ) nanofibers containing at least one or more nanoparticles extending in the longitudinal direction of the nanofibers. The zinc stannate (Zn ₂ SnO ₄ ) nanofiber of claim 1, wherein the porous structure comprises at least one of micropores having a size of 2 nm to 20 nm that are elongated in the longitudinal direction of the nanofiber. The zinc stannate (Zn ₂ SnO ₄ ) nanofiber of claim 1, wherein the nanoparticles comprise spherical nanoparticles having a diameter of 2 to 50 nm. The zinc stannate (Zn ₂ SnO ₄ ) nanofibers according to claim 2, wherein the nanoparticles have a diameter of 2 nm to 50 nm and a length distribution of 2 nm to 500 nm. The porous zinc stannate (Zn ₂ SnO ₄ ) nanofiber according to any one of claims 1 to 5 as a sensing material, the porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers of the sensing material is networked with each other Gas sensor. (a) preparing a mixed solution in which a zinc stannate precursor, a polymer, and a solvent are mixed;
(b) spinning the mixed solution to produce a zinc stannate precursor / polymer composite fiber; And
(c) by the heat treatment to determine nitride the precursor of the composite fibers tartaric acid zinc (Zn ₂ SnO ₄₎ porous tartaric zinc containing nanoparticles (Zn ₂ SnO ₄₎ porous tartaric zinc comprising the step of producing a nanofiber ( Zn ₂ SnO ₄ ) nanofiber manufacturing method. The method of claim 7, wherein the zinc stannate precursor comprises a tin precursor and a zinc precursor, and the polymer is a porous zinc stannate (Zn ₂ SnO ₄ ) nanofiber manufacturing method having a property of phase separation from the zinc stannate precursor and the mixed solution. . The method of claim 7, wherein the porous polymer is thermally decomposed by the heat treatment of zinc stannate (Zn ₂ SnO ₄₎ nano-fiber production method. 9. The method of claim 8 wherein the tin precursor and a zinc precursor method of producing nanofibers in a porous zinc stannate (Zn ₂ SnO ₄₎ material, each of which includes a tin salt and a zinc salt. The method of claim 7, wherein the polymer may be a polyurethane copolymer, a cellulose derivative or other polymer, wherein the polyurethane copolymer may be polyurethane or polyether urethane, and the cellulose derivative is cellulose oacetate , Cellulose acetate propionate, and other polymers include polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymer, polyvinylacetate copolymer, polyvinyl alcohol (PVA), poly Perfuryl alcohol (PPFA), polyvinyl acetate (PVAc), polystyrene (PS), polystyrene copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone, polyvinyl pullo Ride, polyvinylidene fluoride copolymer, polyamide, and polyetherimide Porous zinc stannate with one or more polymers selected from the group can be used (Zn ₂ SnO ₄₎ nano-fiber production method. The method of claim 7, wherein the solvent is a group consisting of water, ethanol, chloroform, dimethylformamide, N-methylpyrrolidone, N-methylpyrrolidone, dimethylacetamide, and dimethylsulfoxide. Porous zinc stannate (Zn ₂ SnO ₄ ) nanofiber manufacturing method, characterized in that the solvent containing at least one material selected from. The method of claim 7, wherein the heat treatment is a porous zinc stannate (Zn ₂ SnO ₄ ) nanofiber manufacturing method is carried out in an air or an oxidizing atmosphere at a temperature of 150 ~ 900 ℃. Porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers prepared by the method according to any one of claims 7 to 13. 15. A method for preparing porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers by the method according to any one of claims 7 to 13; And
The method of manufacturing a gas sensor comprising the step of making the prepared nanofibers in a paste form and coating the nanofiber paste with a sensing material on a substrate including an electrode. The method of claim 15, wherein the porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers used as a gas sensor sensing material are connected to each other and networked. An electronic device comprising porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers having porous pores, and nanoparticles constituting the nanofibers are elongated in the longitudinal direction. The method of claim 17, wherein the electronic device including a nanofiber porous zinc stannate (Zn ₂ SnO ₄₎ nanofiber porous zinc stannate according to claim 14 wherein (Zn ₂ SnO _4). An energy storage device comprising porous zinc stannate (Zn ₂ SnO ₄ ) nanofibers having porous pores, and nanoparticles constituting the nanofibers are elongated in the longitudinal direction. The method of claim 19, wherein the energy storage device of the porous zinc stannate (Zn ₂ SnO ₄₎ nanofibers including nanofiber porous zinc stannate (Zn ₂ SnO ₄₎ according to claim 14.

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