KR100881905B1 - Gas Sensor for Detecting Freshness of Fish and Manufacturing Method at the same and Apparatus for Detecting using the Gas Sensor - Google Patents

Abstract

The present invention relates to a gas sensor capable of measuring the freshness of a fish and an apparatus for detecting falsity using the same.

To this end, the present invention is a semiconductor gas sensor, a memory unit for measuring the resistance for each concentration in advance as a standard gas and calculates it as a sensitivity to store the sensitivity of the sensor material reacting to the standard gas, and resistance of the VBN gas A control unit for measuring and comparing the calculated and converted to a sensitivity of the standard gas stored in the memory unit, a display unit for displaying the measured concentration of the VBN gas, and an input unit including a function key for system operation. We propose a gas detection device.

Therefore, by measuring the change in electrical resistance according to the amount of VBN by using the gas detection device to detect the amount of VBN to determine whether the fish freshness, sellers and consumers can safely sell and buy.

VBN, Gas Sensors, Freshness

Description

Semiconductor gas sensor for measuring freshness of fish, its manufacturing method and gas sensing device using the same {{Gas Sensor for Detecting Freshness of Fish and Manufacturing Method at the same and Apparatus for Detecting using the Gas Sensor}

1 is a cross-sectional view showing a semiconductor gas sensor according to a preferred embodiment of the present invention;

2 is a graph showing the sensitivity characteristics of the semiconductor gas sensor according to the preferred embodiment of the present invention described in Table 1 compared with the conventional SnO ₂ sensor,

3 is a graph illustrating sensitivity characteristics of a semiconductor gas sensor according to an exemplary embodiment of the present invention described in Table 3;

4 is a flowchart illustrating a process of manufacturing a VBN gas sensing material in a semiconductor gas sensor according to a preferred embodiment of the present invention;

5 is a flowchart illustrating a process of manufacturing a sensing film through the VBN gas sensing material manufactured through the process of FIG. 4;

6 is a flowchart illustrating a process of detecting a VBN gas using a gas detection apparatus according to a preferred embodiment of the present invention;

7 is a view showing the operation of the semiconductor gas sensor according to the present invention;

8 is a view showing freshness of fish according to the concentration of VBN gas.

* Description of Major Symbols in Drawings *

10: Substrate

20: electrode

30: detection film

40: heater

100: sensor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor gas sensor, and more particularly, to a semiconductor gas sensor and a gas sensing device using the same, which enable a non-expert to analyze fish freshness in real time.

Using a semiconductor gas sensor, the freshness of the fish can be measured indirectly, which uses the property that the conductivity of the sensor material changes as the resistance changes due to gas adsorption.

Materials of such semiconductor gas sensors include SnO ₂ and ZnO. Etc. are widely used.

Semiconductors are classified into n-type and p-type semiconductors according to their electrical conductivity mechanisms. SnO _{2, the} most representative sensitizer, belongs to an n-type semiconductor, and the number of cations (Sn) is quantitatively smaller than the number of anions (O) to generate excess electrons, which contributes to electrical conductivity. Such SnO ₂ tends to solve the imbalance of positive / negative number ratio by adsorbing insufficient oxygen in the air, and localizes electrons on the surface of adsorbed oxygen to contribute to the electronegativity of the adsorbed oxygen. It becomes the state that it is. Therefore, the electrical conductivity is lost at this time.

If a reducing gas such as volatile basic nitrogen (VBN) gas is exposed to SnO ₂ in such a state, the adsorbed oxygen on the surface is desorbed again. At this time, the electrons trapped around the oxygen are free again to contribute to the electrical conductivity. Therefore, the electrical conductivity of the semiconductor sensor changes according to the gas to be detected, and thus the presence and concentration of the gas can be known.

The semiconductor gas sensor principle can be used for food.

In recent years, the management of food has become more stringent due to the implementation of ISO 9000. However, in the case of vegetables, meat, and fish, which are raw materials of food, there are many problems in determining freshness. This is because the vacuum packaging is not carried out immediately after production, so it is exposed to air and oxidized to rot. In addition, since the shelf life is also different according to the storage conditions, and the freshness is shown a great difference, there is a need to represent physically and chemically accurate figures. Of these fish, the VBN gas is rapidly increased by the oxidation of various chemicals in the tissue from the moment of death. As this substance is a carcinogen, it has a harmful effect on the human body when ingested, so measuring the freshness of fish is also important for health.

Conventional fish freshness measurement includes sensory test, specific gravity, pH test, ammonia test, protein precipitation reaction, volatile basic nitrogen measurement, and trimethylamine determination.

Here, although the state of the fish to grasp the naked eye is called a sensory test, there is a problem that even the expert can not know the exact state.

Specific gravity, pH test, ammonia test, protein precipitation reaction, volatile basic nitrogen measurement, trimethylamine quantification, etc. is a problem that takes a long time because it is a specialized analysis equipment by experts in specialized institutions. In addition, even during the analysis, corruption occurs, the shape of the fish is not available for sale because the change, and only a portion of the sale of the fish because there is a disadvantage that can not accurately know the status of each fish.

Accordingly, there is an urgent need for a technology in which non-experts express the freshness in real time by chemical or physical value for each fish using semiconductor gas sensor technology.

The present invention has been made in order to solve the above problems, a semiconductor gas sensor that enables a non-expert to grasp the freshness of fish in real time by measuring the presence or absence of VBN gas in real time, and a manufacturing method and the same An object of the present invention is to provide a gas detection device.

In order to achieve the above object, according to an aspect of the present invention, the substrate; An electrode formed on an upper surface of the substrate; A sensing film covering the electrode and formed of a sensing material made by adding TiO ₂ to SnO ₂ ; It provides a semiconductor gas sensor comprising a; heater formed on the lower surface of the substrate.

In addition, the TiO ₂ relative to the total weight of the sensing material is characterized in that it has a range of 1 to 20% by weight.

In addition, the sensing material further comprises a metal catalyst, the metal catalyst has a range of 0.5 to 2% by weight based on the total weight of the sensing material, the metal catalyst is any one of Pd, Pt, In, Ru, Rh It is characterized by that.

According to another aspect of the invention, forming an electrode on the upper surface of the substrate; Forming a sensing material by adding TiO ₂ to SnO ₂ and forming a sensing film covering the electrode using the sensing material; Forming a heater on a bottom surface of the substrate; It provides a method of manufacturing a semiconductor gas sensor comprising a.

In addition, in the sensing material, the TiO ₂ relative to the total weight is characterized in that it is added in the range of 1 to 20% by weight.

In addition, in the sensing material, any one of the metal catalysts of Pd, Pt, In, Ru, Rh is further added, and the metal catalyst is added in the range of 0.5 to 2% by weight based on the total weight.

The sensing film may be formed by any one of a screen printing method and a plasma film deposition method.

In addition, the sensing material is characterized in that it is produced by a process by any one of a physical mixing method, impregnation method, coprecipitation method, sol-gel method or a combination of two or more of them.

Thus, a semiconductor gas sensor having the above-described configuration, a memory unit for measuring the resistance of each concentration in advance as a standard gas and calculating the sensitivity and storing the sensitivity of the sensor material reacting to the standard gas, and VBN gas A control unit for measuring resistance and converting the sensitivity into a sensitivity of the standard gas stored in the memory unit, comparing and calculating the display unit, a display unit displaying the measured concentration of the VBN gas, and an input unit including a function key for system operation. It provides a gas detection device comprising.

Hereinafter, a preferred embodiment of the present invention shown in the accompanying drawings will be described in detail.

First, Figure 1 is a cross-sectional view showing a semiconductor gas sensor 100 according to a preferred embodiment of the present invention.

As shown in FIG. 1, the sensor 100 is made using a sensing material according to the present invention. An alumina (Al ₂ O ₃ ) substrate may be used as the substrate 10, and the substrate 10 may be used. Platinum (Pt) electrode 20 is formed on the upper surface of the heater, and a heater 40 made of platinum is formed on the lower surface.

In addition, the substrate 10 may be a substrate such as SiO ₂ , in addition to the alumina, and the heater 40 may have a pair of platinum electrodes 41, and a platinum paste may be applied to a resistor having a resistance of 10 kΩ. have.

In addition, the sensing material used in the sensor 100 may cover the platinum electrode 20 and form the sensing film 30.

The semiconductor gas sensor 100 according to the present invention is particularly a metal oxide semiconductor for VBN gas sensing, and SnO ₂ is mainly used as the VBN gas sensing material and another metal may be additionally added.

First, TiO ₂ may be added in a range of 1 to 20 wt% as shown in Table 1 to lower the reaction temperature with the gas and give electrical thermal stability.

Example SnO ₂ (% by weight) TiO ₂ (% by weight) 20wt% TiO ₂ / SnO ₂ 80% 20% 10wt% TiO ₂ / SnO ₂ 90% 10% 5wt% TiO ₂ / SnO ₂ 95% 5% 1wt% TiO ₂ / SnO ₂ 99% One%

2 is a graph showing the sensitivity characteristics of the semiconductor gas sensor according to the preferred embodiment of the present invention described in Table 1 compared with the conventional SnO ₂ sensor.

In Fig. 2, Sensitivity is defined as S (sensitivity) = Ra / Rg. At this time, Ra refers to resistance before gas injection, and Rg refers to resistance after gas injection.

Here, it can be seen that the semiconductor gas sensor according to the preferred embodiment of the present invention described in Table 1 shows higher sensitivity than the conventional SnO ₂ sensor. For example, at 1000 ppm of VBN standard gas, the sensor according to the present invention shows a sensitivity of up to 50 to 350% higher than that of a conventional SnO ₂ sensor. In particular, it can be seen that 10 wt% TiO ₂ / SnO ₂ has the best sensitivity characteristic. have.

Second, the semiconductor gas sensor 100 according to the present invention, the sensing material is a metal oxide semiconductor, SnO ₂ as the main material, TiO ₂ is added in the range of 1 to 20% by weight, as shown in Table 1, Catalyst metals may be added to give sensitivity and selectivity to other gases. In this case, Pd, Pt, In, Ru, Rh, etc. may be used as the added catalyst metal, and the amount of the catalyst metal is preferably in the range of 0.5 to 2 wt% based on the total weight.

Table 2 illustrates an example in which 1% by weight of catalytic metal (eg, Pd) is added to the semiconductor gas sensor described in Table 1, and Table 3 shows 10% by weight of TiO ₂ / SnO ₂ having the best sensitivity characteristics. In the sensor, Pd, Pt, In, Ru, and Rh are each added at 1% by weight as catalyst metal.

Example SnO ₂ (% by weight) TiO ₂ (% by weight) Pd (% by weight) 1wt% -Pd + 20wt%-TiO ₂ / SnO ₂ 79 20 One 1wt% -Pd + 10wt%-TiO ₂ / SnO ₂ 89 10 One 1wt% -Pd + 5wt%-TiO ₂ / SnO ₂ 94 5 One 1wt% -Pd + 1wt%-TiO ₂ / SnO ₂ 98 One One

Example SnO ₂ (% by weight) TiO ₂ (% by weight) Catalytic metal (% by weight) 1wt% -Pd + 10wt%-TiO2 / SnO2 89 10 One 1wt% -Pt + 10wt%-TiO2 / SnO2 89 10 One 1wt% -In + 10wt%-TiO2 / SnO2 89 10 One 1wt% -Ru + 10wt%-TiO2 / SnO2 89 10 One 1wt% -Rh + 10wt%-TiO2 / SnO2 89 10 One

3 is a graph showing the sensitivity characteristics of the semiconductor gas sensor according to the preferred embodiment of the present invention described in Table 3.

As shown in FIG. 3, the semiconductor gas sensor according to the preferred embodiment of the present invention described in Table 3 shows the highest sensitivity when Pd is added among the catalytic metals (Pd, Pt, In, Ru, and Rh). It can be seen.

In addition, among the examples described in Table 1, 10wt% TiO ₂ / SnO ₂ has the best sensitivity characteristics, and when the 1wt% Pd catalyst metal is added to the 10wt% TiO ₂ / SnO ₂ , the sensitivity characteristics are better. Can be. For example, VBN standard gas to the catalyst metal Pd is not added for 800ppm 10wt% TiO ₂ / SnO ₂ sensor gajina a sensitivity of about _{6.5, 10wt% TiO 2 / SnO} 2 sensors Pd is added is approximately 10 degree Since it has a sensitivity characteristic, it can be seen that the sensitivity characteristic is better as the catalyst metal is added.

Hereinafter, the manufacturing process of the TiO ₂ / SnO ₂ sensor according to the above-described preferred embodiment of the present invention will be described.

The sensing film 30 used in the sensor may include SnO ₂ as a VBN gas sensing material and TiO ₂ in a range of 1 to 20 wt%. In addition, catalytic metals such as Pd, Pt, In, Ru, and Rh may be further added in the range of 0.5 to 2 wt%.

4 is a flowchart illustrating a process of manufacturing a VBN gas sensing material in a semiconductor gas sensor according to an exemplary embodiment of the present invention, and FIG. 5 illustrates a process of manufacturing a sensing film through a VBN gas sensing material manufactured through the process of FIG. 4. It is a flow chart.

 Here, the manufacturing of the sensing material will be described mainly based on the impregnation method, but is not limited thereto, and may also be prepared by a physical mixing method, a coprecipitation method, a sol-gel method, or the like, and may be prepared by a process by combining two or more of them. Can be.

In addition, the formation of the sensing film using the sensing material may be performed by any one of a screen printing method and a plasma film deposition method.

As shown in FIG. 4, the sensing material is prepared by impregnating pure metal SnO ₂ (Aldrich, 99.9%) with a metal oxide and a catalytic metal. In this process, in order to give sensitivity and selectivity, Pd, a catalyst metal, has a weight ratio of 1 wt% of a sensing material, and hydrochloric acid (HCl) is added to completely dissolve the catalyst metal, and then distilled water is added to make a uniform solution (S410) (S420). ).

Subsequently, 10% wt of metal oxide TiO ₂ is added to impregnate the metal catalyst salt by impregnating with SnO ₂ in order to give electrical stability, and then preparing the mixture by heating with stirring with a magnetic stirrer (S430) (S440) (S450). ). It is calcined at 600 ° C. for 2 hours and then ground to prepare a sensing material.

Subsequently, as shown in FIG. 5, 15 wt% of ethylene glycol (Ethylene Glycol) is added as a binder to the sensor material (85 wt%) prepared through the process of FIG. The coating is made by screen printing (Screen printing) (S510) (S520).

Then, after drying for 24 hours at 110 ℃ calcined for 2 hours at 600 ℃ to form a thick film (S530) (S540) (S550). The VBN gas may be detected by measuring and analyzing through the sensor manufactured as described above (S560) (S570).

It looks at the process of detecting the VBN gas by using the VBN gas detection device having a semiconductor sensor 100 according to the present invention made as described above.

The gas detecting apparatus according to the present invention includes a semiconductor gas sensor 100 capable of measuring the VBN gas shown in FIG. 1, a ventilator unit for circulating air, and delivering VBN gas from a food such as fish to the inside of the apparatus. Displays a gas injection unit, a memory unit for storing the sensitivity of a sensing substance reacting to a standard gas, a concentration measurement control unit for detecting and comparing the VBN gas from a food and a standard gas, and a measured concentration of the VBN gas The display unit and an input unit for inputting a function key for operating the system. In this case, the display unit may be an LCD window, and the input unit may be a button or a touch screen. In addition, the pump is connected to the other side of the gas inlet so that the air can circulate to allow the outside air to enter the inside. At this time, the gas injection unit is to collect the VBN gas from the fish to react with the sensing material of the semiconductor gas sensor through a glass tube of 2cm in diameter, 10cm in length.

6 is a flowchart illustrating a process of detecting a VBN gas using the gas detection device configured as described above.

As shown in FIG. 6, when the sensing gas is exposed for 5 seconds after the start button of the gas sensing device is operated, a resistance value is measured through a sensing material (sensor material) of the gas sensor (S610) (S620).

Thereafter, the resistance value measured by the sensor and the reference value of the standard gas stored in the memory unit are compared / operated (S630). In this case, the memory unit measures the resistance for each concentration in advance as the VBN standard gas, calculates the sensitivity, and stores the sensitivity of the sensor material reacting to the standard gas. Typically, the sensitivity S is defined as S = Ra / Rg, where Ra is a resistance before gas injection and Rg is a resistance after gas injection.

In addition, the concentration measurement control unit may measure the resistance of the VBN gas from the fish and convert it into sensitivity to compare / calculate the sensitivity of the standard gas stored in the memory unit in advance to know the concentration.

Thereafter, the display unit displays the measured concentration of the measured VBN gas on the LCD window (S640). Through this, the freshness of the fish can be confirmed.

As such, the button unit for operating the system operates the pump in the ventilator unit while supplying power to operate the heater of the Al ₂ O ₃ substrate, and the memory unit, the concentration measurement control unit and the LCD window unit. After the VBN gas has been measured, run it again and shut down all systems.

7 is a view showing the operation of the semiconductor gas sensor according to the present invention.

As shown in FIG. 7, in the semiconductor gas sensor according to the present invention, SnO ₂ is used as the main material and TiO ₂ is added in an amount of 10 wt% to lower the reaction temperature with the gas and to provide electrical and thermal stability. Thereafter, in order to give sensitivity and selectivity with other gases, Pd, which is a catalytic metal, was added at 1wt%, respectively, and synthesized by impregnation. The synthesized sensor material decomposes the VBN gas at 250 ° C. at low temperature to generate electrons. At this time, the generated electrons cause a change in resistance, and by measuring the freshness of the fish can be known. That is, the state of the fish can be grasped by measuring the presence or absence of VBN gas, which is a gas generated when the fish is decaying, or the change in concentration in real time.

8 is a view showing freshness of fish according to the concentration of VBN gas.

As shown in Figure 8, the concentration of VBN gas is between 5-100ppm fresh state, less than 300ppm is an initial decay state, when more than 500ppm is decayed can not be ingested. That is, it is possible to know whether cooking or ingestion is possible depending on the concentration of VBN gas of the fish.

As described above, the gas sensor according to the present invention is a VBN gas detection sensor, and is not limited to the freshness test of fish, and may be applicable to other foods. In addition, it will be applicable to similar gas in addition to VBN.

Therefore, the present invention may determine whether the fish is fresh by detecting the amount of VBN by measuring a change in electrical resistance according to the amount of VBN using the gas sensor and the gas detecting device. Accordingly, it may have the following effects.

First, using the sensor and the device according to the present invention that the expert took a long time as a professional analysis device, the non-expert in the field can grasp the freshness of the fish in real time easily and quickly.

Second, sellers and consumers can buy and sell fish with confidence. In other words, the buyer can grasp the state of the fish to be eaten more stable food by different ways of storage and cooking of fish. For example, in a sushi restaurant that prioritizes the freshness of fish, it is difficult to grasp the degree of decay of fish flesh with the naked eye, but by using this, it is possible to provide safer sushi.

Third, the measurement can be done without destroying the shape of the fish, so both the seller and the buyer are profitable. Thus, by accurately measuring the freshness of the fish it is possible to reduce the accidents caused by the intake of the decayed fish.

Claims (12)

delete delete delete delete delete delete delete delete delete delete delete A semiconductor gas sensor comprising a substrate, an electrode formed on an upper surface of the substrate, a sensing film covering the electrode and formed of a sensing material formed by adding TiO ₂ to SnO ₂ , and a heater formed on the lower surface of the substrate; A memory unit for measuring resistance of each concentration in advance as a standard gas and calculating the sensitivity to store the sensitivity of the sensor material reacting to the standard gas; A control unit for measuring resistance of the VBN gas, converting the sensitivity into sensitivity, and comparing / operating with the sensitivity of the standard gas stored in the memory unit; A display unit displaying the measured concentration of VBN gas; And Gas sensing device comprising an input unit having a function key for system operation.

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