KR100993171B1 - Gas sensor using nano-porous indium oxide spherical structure and fabrication method thereof - Google Patents

Abstract

Provided is a gas sensor composed of In ₂ O ₃ having a gas sensitive layer having a nanoporous hollow structure or a nanoporous layer structure. The gas sensor according to the present invention can not only obtain high sensitivity and fast response speed when H ₂ S and CO are sensitive, but also realize the property of reversibly recovering resistance when the sensor is exposed to air again. The present invention also provides a method of manufacturing such a gas sensor. The gas sensor according to the present invention can be easily synthesized into an In ₂ O ₃ monocomponent system and can be made in various structures.

Description

Gas sensor using nano-porous indium oxide spherical structure and fabrication method

The present invention relates to an oxide semiconductor gas sensor and a method for manufacturing the same, and more particularly, to the development of a new gas-sensitive material, a gas sensor having a new structure using the same, and a method for manufacturing the same.

To detect various harmful environmental gas species (H ₂ S, H ₂ , CO, NOx, SOx, NH _3, VOCs, etc.) due to air pollution, environmental pollution and industrial site stability problems caused by industrial development. The need for gas sensors is increasing. Among them, H ₂ S is a gas contained in bad smell such as bad smell, bad breath, etc., and should be measured to clean the environment and establish a comfortable living environment. In addition, CO is a gas contained in the exhaust gas of gasoline cars and the smoke emitted from industrial sites. Measurement is necessary to maintain the environment.

Oxide semiconductor type gas sensors are widely used in a wide range of areas such as hazardous environmental gas species detection. When the n-type oxide semiconductor is heated to 300 to 400 ° C, oxygen is adsorbed on the surface of the oxide semiconductor and then negatively charged. In this process, electrons on the surface of the oxide semiconductor are consumed, and an electron depletion layer is formed on the surface of the oxide semiconductor. Thereafter, when reducing gases such as H ₂ S, CO, C ₃ H ₈ , CH ₄ , and H ₂ are present, these gases react with the negatively charged oxygen on the oxide semiconductor surface to oxidize. The electrons generated in this process are injected back into the oxide semiconductor, which shows a decrease in resistance in proportion to the gas concentration.

As discussed in the above gas sensitive principle, the oxide semiconductor type gas sensor is advantageous for detecting a low concentration of gas. When a gas consisting of C, H, O, N, such as H ₂ , CO, NOx, SOx, NH _3, VOCs is exposed to the gas sensor, a decrease in resistance caused by the gas occurs, and then the sensor is exposed to the air again. It is common for the recovery of resistance to occur reversibly. However, in the case of H ₂ S, which is a major component of the odor, the resistance decreases when exposed to gas, but even when the gas disappears, a problem arises in that the recovery of the resistance is not good. To date, the exact cause of this problem has not been determined, but it is believed that the S component remains between the surface or the gas sensor material aggregate and irreversibly changes the electrical characteristics. In the case of CO, high sensitivity and reversible reactions at low ppm levels are also important, but the response and recovery speeds of gas response are more important.

The challenge to be addressed in H ₂ S and CO response is to ensure high sensitivity and rapid response time to detect low concentrations in a short time. In particular, H ₂ S is a level at which the odor is felt even at the concentration of suppppm, and the odor can respond quickly to a cause only by quick response, so very high gas sensitivity is required and quick response speed is required.

Gas sensitization is a reaction between oxygen and gas adsorbed on the particle surface, so nanostructure is advantageous to maximize the surface area of the sensitizer. The nanoparticles, which are 0-dimensional nanostructures, were effective in increasing sensitivity. However, when the size of the particles is reduced to several to several tens of nm, van der Waals attraction becomes very large, and thus, aggregation between primary particles becomes very severe. Aggregated secondary particles mainly have a dense structure and small pores, so only the primary particles on the surface of the secondary particles participate in the gas-sensing reaction, resulting in a decrease in sensitivity. Even if a small amount of pores exists, a long time gas diffusion is required for the test gas to react with the primary particles therein. Therefore, it is common to take a long time of 50 seconds or more to change the resistance after exposure to the gas to be measured. Afterwards, when the gas sensor is exposed to air again, the by-product gas remaining near the nanoparticles must diffuse out of the sensor, and the oxygen recovery in the air needs to be adsorbed on the surface of the oxide semiconductor. .

Another challenge to be addressed in H ₂ S and CO response is the resistance of the sensor. Currently, SnO ₂ , which is a representative material of oxide semiconductor gas sensor, has excellent gas sensitivity but high sensor resistance, and when manufactured with nano structures such as nanowires or nanotubes, the contact between nano structures is small, so the resistance of the sensor is low. Frequently, this becomes larger than MΩ. Hundreds of ohms to tens of kΩs are most desirable for resistance measurement of sensors.

As described above, aggregation of oxide nanoparticles for a general gas sensor generates a problem of inhibiting high sensitivity and rapid response. In addition, the nanostructures of typical oxides such as SnO ₂ are not easy to measure because of their high resistance.

The problem to be solved by the present invention is to improve the reversible signal change, high sensitivity, fast response speed required for use in the detection of harmful environmental gases (premature warning of chemical terrorism, toxic, explosive, environmental pollution gas, etc.) To provide an oxide semiconductor gas sensor having a structure and a method of manufacturing the same.

Gas sensor according to the present invention for solving the above technical problem, the gas sensitive layer is a gas sensor made of In ₂ O ₃ having a nano-porous hollow structure or nano-porous layer structure.

In the present specification, both nanoporous hollow structures and nanoporous hierarchical structures are defined as "nanoporous spherical structures". Nanoporous hollow structure is a structure in which nano-sized holes are formed in the middle of the particle. And, in contrast to the rounded secondary agglomerated secondary nanoparticles, the nanoporous hierarchical structure is characterized by the fact that primary particles with zero, one or two-dimensional nanostructures of points, lines, or faces are gathered to create a new, larger shape. It is defined as what constitutes a particle. Nanoporous hierarchies contain many nanopores, which provide a large surface area to promote a relatively large number of oxidation and reduction reactions per unit volume.

According to one configuration of the gas sensor manufacturing method according to the present invention for solving the above technical problem, by forming a hydrothermal synthesis reaction of the In precursor to form a fine powder In ₂ O ₃ having a nanoporous hollow structure or nanoporous layer structure Next, a step of forming a film with the fine powder and heat treatment to form a gas sensitive layer consisting of In ₂ O ₃ having a nanoporous hollow structure or a nanoporous layer structure.

In this case, an amino acid may be added to the In precursor or an inorganic salt may be further added to the In precursor to cause the hydrothermal synthesis reaction.

According to another configuration of the gas sensor manufacturing method according to the present invention for solving the above technical problem, after obtaining a mixed solution of In precursor, inorganic salt and amino acid, by adding a template to the mixed solution and stirred to In the surface of the template The raw material is coated by hydration control to obtain a precipitate. Then, the template is removed from the precipitate to form an In ₂ O ₃ fine powder having a nanoporous hollow structure, a film is formed of the fine powder and then heat treated to form a gas sensitive layer.

According to the present invention, by manufacturing a porous gas sensor using In ₂ O ₃ having a nano-porous spherical structure it can be produced a gas sensor that is small but not agglomerated primary particles.

The gas sensor according to the present invention has a very rapid diffusion of the test gas due to the nano-porous structure, so that the response speed to the gas is very fast. And the sensitivity to H ₂ S and CO is very large. Furthermore, recovery is very good.

The gas sensor according to the present invention can be easily synthesized with In ₂ O ₃ single component system, and the gas sensor manufacturing method according to the present invention provides a synthesis method for making various structures. Based on this, when the H ₂ S sensor is manufactured, the performance is also 2 to 4 times better in terms of recoverability, sensitivity, and response speed.

In ₂ O ₃ nanoporous hollow structure and layer structure newly proposed as a sensor structure in the present invention shows the following advantages. In ₂ O ₃ nanoporous spherical structure can simultaneously achieve high sensitivity rapid response. In the case of the nanoporous hollow structure, the aggregate size of the particles is limited to several tens of nm or less, and in the case of the nanoporous hierarchical structure, the unit nanostructure is well dispersed in the spherical secondary particles. Simultaneous achievement of high sensitivity and rapid response is believed to be due to rapid gas diffusion and full nanostructure participation in gas response.

Another advantage of the In ₂ O ₃ nanoporous hollow structure and the hierarchical structure of the present invention is that reversible recovery occurs after H ₂ S response. In the case of conventional nano fine powder aggregates, S remains in the neck and nanopores between particles, making it difficult to desorb, whereas in the case of the nanoporous hollow structure of the present invention, the reaction mainly occurs and stops at the surface of the hollow structure. Recovery is reversible. In the case of the nanoporous hierarchical structure, most of the nanostructures are directly exposed to the outside air, and thus, recovery is easy.

Another advantage of the In ₂ O ₃ nanoporous hollow structure and the layered structure of the present invention is that the resistance is small. In the case of the conventional SnO ₂ nanostructured sensor, the resistance is several MΩ, while using the In ₂ O ₃ nanoporous hollow structure and the hierarchical structure according to the present invention, a sensor having a resistance range of hundreds of Ω to several tens of kΩ is easy to measure. Can be manufactured.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a clearer description.

Gas sensor according to the invention is a gas sensor consisting of In ₂ O ₃ having a nano-porous hollow structure or nano-porous layer structure. Prior to the present invention, the In ₂ O ₃ gas sensor structure having a nano-porous hollow structure or a nano-porous layer structure is unknown and can be used as an H ₂ S gas sensor having excellent reversibility. .

1 and 2 are schematic cross-sectional views of a gas sensor according to the present invention. However, the structure of the gas sensor according to the present invention is not limited to that shown here, and any structure corresponds to any structure of the gas sensor having a gas sensitive layer made of In ₂ O ₃ having a nanoporous spherical structure.

The gas sensor shown in FIG. 1 has a structure in which electrodes 10 and 30 are provided on the upper and lower surfaces of the gas sensitive layer 20, respectively. The gas sensor shown in FIG. 2 has a structure in which a gas sensitive layer 70 is provided on a substrate 40 on which a micro heater 50 is formed on a lower surface and two electrodes 60 and 65 are formed on an upper surface. The gas sensitive layers 20 and 70 are both made of In ₂ O ₃ having a nanoporous hollow structure or a nanoporous layer structure, and may be doped with an appropriate catalyst component as necessary.

The gas sensor provided with the gas sensitive layers 20 and 70 made of In ₂ O ₃ having a nanoporous hollow structure or a nanoporous layer structure is an n-type semiconductor gas sensor. As shown in the following examples, the nanoporous hollow structure formed by the hydrothermal synthesis according to the present invention may have a diameter of about 500 to 1000 nm, thickness of 5 to 60 nm. In particular, the nano-porous hollow structure formed using the metal template according to the present invention is very fine pores of the nano-nm size, when using a polymer template, the pores of about 5 to 50 nm size is formed on the surface of the spherical hollow structure. In addition, according to the present invention, the nanoporous layer structure formed by using the hydrothermal synthesis reaction may have a form in which one-dimensional In ₂ O ₃ nanowires are self-assembled into a three-dimensional sphere.

3 is a flow chart of a gas sensor manufacturing method according to the present invention.

First, the hydrothermal synthesis reaction of the In precursor is performed to form an In ₂ O ₃ fine powder having a nanoporous hollow structure or a nanoporous layer structure. To this end, first, an inorganic salt and an amino acid are added to the In precursor (step S1) to generate a hydrothermal reaction (step S2).

The amino acid may be any one of L (+)-Lysine monohydrate, L-Arginine, Glutamine and Glutamic acid, and the inorganic salt is dode Sodium dodecyl sulfate (SDS, C ₁₂ H ₂₅ SO ₄ Na).

When both the inorganic salt and the amino acid are added, the inorganic salt may be added first, followed by the sequential addition method of adding the amino acid, and a fine powder having a nanoporous hollow structure is obtained. When only an amino acid is added without adding an inorganic salt, the fine powder of a nanoporous hierarchical structure is obtained (step S3). In order to obtain fine powder, a general procedure such as drying, washing and heat treating the precipitate of hydrothermal synthesis may be performed.

Next, by forming a gas sensitive layer using the fine powder of such nanoporous spherical structure, a gas sensor is manufactured with the structure as shown in FIG. 1 or 2 (step S4). Gas sensor manufacturing is prepared by dispersing the fine powder in a suitable solvent or binder, etc., and a suitable substrate, for example, a substrate 40 (microheater 50) is formed on the lower surface, as shown in Figure 2, the two electrodes (60, 65) Formed on). The coating is used herein to include various methods such as printing, brushing, blade coating, dispensing, micro pipette dropping, and the like. Next, the solvent is removed therefrom to form a gas sensitive layer. Heating may be involved if necessary to aid in removal of the solvent. When the film is formed on the substrate using the fine powder obtained in the previous step and heat-treated, the particles having the nanoporous spherical structure are heat-treated, so that the gas-sensitive layer is made of a porous material including the nanoporous spherical structure.

4 is a flow chart of another gas sensor manufacturing method according to the present invention.

Here, the template is used to form a nanoporous hollow structure In ₂ O ₃ fine powder. To this end, first, an inorganic salt and an amino acid are added to the In precursor to obtain a mixed solution (step S11), and then a template is added and stirred (step S12). Coating the raw material In material on the template surface by the hydration reaction control method to obtain a precipitate.

Next, the template is removed from the precipitate to form In ₂ O ₃ fine powder having a nanoporous hollow structure (step S13).

Next, by forming a gas sensitive layer using the fine powder of the nano-porous hollow structure, a gas sensor is manufactured with a structure as shown in FIG. 1 or 2 (step S14).

The template may be a metal spherical powder or a polymer spherical powder, and may be a metal template such as Ni, Co, Fe, or Cu, and the polymer template may be a PS or PMMA ball.

Hereinafter, In ₂ O ₃ nano-porous hollow structure fine powder (Example 1-1, Example 1-2, Example 1-3) and nano-porous layered fine powder (Example 1-4) were prepared by a gas sensor a rear compared the response and recovery rate of the H ₂ S and CO with pure in ₂ O ₃ nano-fine powder (Comparative example 1-1), the response and recovery time for the H ₂ S and CO.

Example 1-1

0.01 mol of In (NO ₃ ) ₃ o xH ₂ O [Indium (III) Nitrate chloride hydrate, 99.9% metals basis, Sigma-Aldrich. Inc., USA] was dissolved in 50 ml of ethanol to make a clear solution. 0.005 mol of SDS [99% +, ACS reagent, Sigma-Aldrich. Inc., USA], of 0.005 mol L (+) - lysine monohydrate _{[C 6 H 14 N 2 O} 2 o _{H 2 O, L (+)} - Lysine monohydrate, 99%, Acros Organics. USA] was added in order to obtain a finally translucent stock solution. The translucent solution was transferred to a 100 cc Teflon container, and then subjected to hydrothermal synthesis at 120 ° C. for 18 hours using an autoclave. The precipitate obtained is washed 5 times with ethanol and then dried at 60 ° C. for 24 hours. The dried powder was heated to 600 ° C. for 2 hours and then heat-treated at 600 ° C. for 2 hours.

The heat-treated fine powder was mixed with an organic binder to screen print on an alumina substrate on which an Au electrode was formed, dried at 100 ° C. for 5 hours, and heat treated at 500 ° C. for 1 hour to prepare a gas sensor. The prepared sensor was placed in a quartz tube high temperature electric furnace (inner diameter of 30 mm) at 400 ° C, and pure air or air + mixed gas (H ₂ S 0.5 ppm or CO 10 ppm) was alternately injected to measure the change in resistance. The gases were premixed and then rapidly changed in concentration using a four-way valve. The total flow rate was fixed at 500 SCCM so that the temperature difference did not occur when the gas concentration changed.

5 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Example 1-1, (a) is a SEM photograph, (b) is a TEM photograph. As can be seen from (a) and (b) of Figure 5, when hydrothermal reaction after the addition of SDS and L (+)-lysine monohydrate, the diameter of about 500 ~ 1000 nm, the thickness of 30 ~ 60nm Nanoporous hollow structures were synthesized.

[Example 1-2]

L-arginine instead of L (+)-lysine monohydrate in Example 1-1 [C ₆ H ₁₄ N ₄ O ₂ , L-Arginine,> = 98% reagent (TLC), Sigma-Aldrich. Inc., USA] was prepared in the same manner as in Example 1-1 except that the hydrothermal synthesis was carried out for 12 hours to prepare In ₂ O ₃ nano-porous hollow particles. Thereafter, a gas sensor was manufactured in the same manner as in Example 1-1, and a change in resistance was measured.

6 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Examples 1-2, (a) shows a SEM picture, (b) shows a TEM picture. As can be seen from (a) and (b) of Figure 6, when the hydrothermal reaction after the addition of SDS and L-arginine nanoporous hollow of about 500 ~ 1000 nm in diameter, 30 ~ 60 nm thick The structure was synthesized.

[Example 1-3]

In Example 1-1, the same procedure was performed until the stock solution was obtained. The template was then added in a translucent solution and stirred for 24 hours. As a result, In raw material is coated on the surface of the template by hydration control. This opaque solution was filtered to give a precipitate, which was dried at 60 ° C. for 24 hours. The dried coating powder was then heat treated at 400 ° C. for 1 hour.

At this time, in the case of using a metal spherical template, the dried powder was added to 250 cc of 10% hydrochloric acid, and the hydrochloric acid solution was changed for 1 day, dissolved for 3 days, washed five times with distilled water, and dried at 60 ° C. for 24 hours. Template removal using. In the case of using the polymer spherical template, the dried powder was heated at 400 ° C. for 2 hours and then heat treated for 2 hours to remove the template. The dried powder and the powder from which the template was removed were heated to 600 ° C. for 2 hours and then heat-treated at 600 ° C. for 2 hours (template removal using heat treatment oxidation). Thereafter, the manufacturing method of the sensor and the measurement of gas sensitivity are the same as in Example 1-1.

7 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Examples 1-3, (a) is a SEM photograph when using a Ni spherical template, (b) is a polymer spherical template The SEM photograph in the case of using is shown. In the case of using a metal template as shown in (a) of FIG. 7, the pores of the hollow structure were nano nm in size, and in the case of using a polymer template as shown in FIG. Pores were formed. It can be seen that both methods provide a method of making uniform nanoporous hollow structures.

Example 1-4

In ₂ O ₃ nano-porous layered particles were prepared in the same manner as in Example 1-1 except that 0.005 mol of SDS was not added in Example 1-1 and the hydrothermal synthesis reaction was performed for 12 hours. It was. Thereafter, the manufacturing method of the sensor and the measurement of gas sensitivity were the same as in Example 1-1.

8 is an SEM image of In ₂ O ₃ nanoporous layered particles prepared by the method of Examples 1-4. The nanostructure synthesized by hydrothermal reaction after the addition of only L (+)-lysine monohydrate confirmed that the one-dimensional In ₂ O ₃ nanowire forms a three-dimensional spherical self-assembled nanoporous layer structure. Can be.

[Comparative Example 1-1]

In Example 1-2, except that L-arginine was not added, the process was performed in the same manner as in Example 1-2 to obtain a powder, and a sensor was prepared and gas sensitivity was measured.

9 is a SEM photograph of the In ₂ O ₃ nano fine powder of Comparative Example 1-1, it can be seen that the nanoparticles of several tens of nm has an aggregated form.

The sensor device was manufactured with the In ₂ O ₃ nanostructure and the fine powder, and the result was measured at various temperatures, and the optimum operating performance was observed at 400 ° C. All of the reducing gases measured exhibited n-type semiconducting properties with reduced resistance. Therefore, the gas sensitivity was defined as R _a / R _g . (R _a : device resistance in air, R _g : device resistance in gas) The gas sensitivity was measured at 400 ° C., and the gas sensitivity was calculated.

When the resistance of the sensor became constant in the air, the atmosphere was suddenly changed to 0.5 ppm H ₂ S or 10 ppm CO. At this time, the resistance of the resistance was decreased. The final resistance reached when exposed to gas is called R _g , and when the resistance in air is called R _a , 90% of (R _a -R _g ) changes to reach a point close to gas resistance (R _g ). The time taken was defined as 90% response time. If there is a change the atmosphere in the air in the resistance (R _g) when exposed to the gas resistance is increased, also at this time (R _a -R _g) 90% of which has been changed reach a point near the air resistance (R _g) The time taken was defined as 90% recovery time.

10 and Table 1 show the sensor of Example 1-1, Example 1-2, Example 1-3, Example 1-4, and Comparative Example 1-1 when exposed to 0.5-2 ppm H ₂ S. Gas response characteristics and gas response time are shown. (0.5 ppm H ₂ S for Examples 1-2, 1-3, 1-4, and Comparative Example 1-1)

Examples 1-1, 1-2, and 1-3 show gas-sensing characteristics of the In ₂ O ₃ nanoporous hollow structure. The 90% response speed of the porous hollow structure of Example 1-1 was 21 seconds and 90% recovery speed of 125 seconds, which was 5 times faster than the response time of 124 seconds and 614 seconds of Comparative Example 1-1.

Example 1-2 is a porous porous structure synthesized using L-arginine, and exhibits excellent H ₂ S response characteristics with Example 1-1. The 90% response time of Example 1-2 was 18 seconds, and the 90% recovery speed was 54 seconds. The recovery speed was about 2 times higher than that of Example 1-1. 12 times faster recovery.

Example 1-3 is a porous hollow structure synthesized using two kinds of templates, showing 90% response speed of 16 seconds and 90% recovery rate of 80 seconds. 8 times better

Example 1-4 shows the gas-sensing characteristics of the nano-porous layer structure, showing a fast response rate and a recovery rate of 24 seconds and 38 seconds, respectively. In Example 1-4, the recovery rate was improved by about 20 times compared with Comparative Example 1-1.

When the In ₂ O ₃ nanoporous spherical structures of Examples 1-1, 1-2, 1-3, and 1-4 were used, the resistance of the sensor was almost completely restored, whereas in Comparative Example 1-1, 0.5 ppm H ₂ Even after only one exposure to S, resistance did not recover. To date, the exact cause of this problem has not been determined, but it is believed that the S component remains between the surface or the gas sensor material aggregate and irreversibly changes the electrical characteristics.

This indicates that the In ₂ O ₃ nanoporous spherical structure of the present invention not only has excellent recovery characteristics, but also has excellent gas sensitivity and response speed. Its excellent recovery characteristics make it easy to diffuse the test gas (H ₂ S) through the nanopores, so it diffuses quickly on the surface of the sensor material. This is because it is removed well in response to outdoor air. In particular, a fast recovery rate is very important in the absence of a catalyst that promotes surface reactions.

11 and Table 2 show gas response characteristics and gas response time when the sensors of Examples 1-1, 1-4, and Comparative Example 1-1 are exposed to 10 ppm of CO.

The sensitivity of the porous hollow structure of Example 1-1 to 10 ppm of CO was 2.04, and the 90% response rate was 12 seconds and the 90% recovery rate was 53 seconds, which was 144 seconds and 258 seconds in Comparative Example 1-1. The response and recovery speeds were 11 and 5 times faster, respectively. The porosity hierarchical structure of Example 1-4 showed CO2 sensitivity of 2.68, 90% response time of 3 seconds, and 90% recovery rate of 28 seconds. Compared with Comparative Example 1-1, the sensitivity was improved 2.5 times, 90% response time 48 times, 90% recovery was 9.2 times improved. This is considered to be an effect by maximizing the gas diffusion path and the reaction surface area of the porous layer structure.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible by those skilled in the art within the technical idea of the present invention. Is obvious. Embodiments of the invention have been considered in all respects as illustrative and not restrictive, which include the scope of the invention as indicated by the appended claims rather than the detailed description therein, the equivalents of the claims and all modifications within the means. I want to.

1 and 2 are schematic cross-sectional views of a gas sensor according to the present invention.

3 is a flow chart of a gas sensor manufacturing method according to the present invention.

4 is a flow chart of another gas sensor manufacturing method according to the present invention.

5 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Example 1-1, (a) is a SEM photograph, (b) is a TEM photograph.

6 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Examples 1-2, (a) shows a SEM picture, (b) shows a TEM picture.

7 is a photograph of In ₂ O ₃ nanoporous hollow particles prepared by the method of Examples 1-3, (a) is a SEM photograph when using a Ni spherical template, (b) is a polymer spherical template The SEM photograph in the case of using is shown.

8 is an SEM image of In ₂ O ₃ nanoporous layered particles prepared by the method of Examples 1-4.

9 is a SEM photograph of In ₂ O ₃ nano fine powder of Comparative Example 1-1.

10 is a gas response characteristic when the sensors of Example 1-1, Example 1-2, Example 1-3, Example 1-4, and Comparative Example 1-1 are exposed to H ₂ S of 0.5 to 2 ppm; And gas response time.

11 illustrates gas response characteristics and gas response time when the sensors of Examples 1-1, 1-4, and Comparative Example 1-1 are exposed to 10 ppm of CO.

Claims (8)

delete delete delete Hydrothermal synthesis of In precursor, amino acid and inorganic salt to form In ₂ O ₃ fine powder having nanoporous hollow structure or nanoporous layer structure; And Forming a film with the fine powder and then heat-treating to form a gas sensitive layer. Obtaining a mixed solution of an In precursor, an inorganic salt, and an amino acid; Adding a template to the mixed solution and stirring to coat an In raw material on the surface of the template by a hydration reaction control method to obtain a precipitate; Removing the template from the precipitate to form In ₂ O ₃ fine powder having a nanoporous hollow structure; And Forming a film with the fine powder and then heat-treating to form a gas sensitive layer. The gas sensor manufacturing method according to claim 5, wherein the template uses metal spherical powder or polymer spherical powder. The method according to claim 4 or 5, wherein the amino acid is L (+)-lysine monohydrate [L (+)-Lysine monohydrate], L-arginine (L-Arginine), glutamine (glutamine) and glutamic acid Gas sensor manufacturing method characterized in that using any one of. The method of claim 4, wherein the inorganic salt is sodium dodecyl sulfate (SDS, C ₁₂ H ₂₅ SO ₄ Na).

Images