A barometrically regulated room temperature ethanol gas sensing system and method of use

Abstract

The present application relates to the technical field of ethanol sensing, and particularly relates to a barometrically regulated room-temperature ethanol gas sensing system and a use method thereof. The ethanol gas sensing system comprises a chamber, an air inlet valve, an air outlet valve and a resistance testing component. The air inlet valve and the air outlet valve are arranged on the side wall of the chamber, and the resistance testing component is arranged in the chamber. The resistance testing component comprises a substrate, interdigital electrodes and a gas sensitive material. The interdigital electrodes are arranged on the substrate, and the gas sensitive material is arranged on the interdigital electrodes. The ethanol gas sensing system further comprises a suction cylinder and a piston. The suction cylinder is connected to the chamber, and the piston is arranged in the suction cylinder. The piston is used for regulating the air pressure in the chamber. The present application regulates the air pressure in the chamber, so that water molecules are desorbed from the semiconductor material, instead of using the traditional heating method, thereby improving the safety of system operation, and having a good application prospect in the field of ethanol gas detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ethanol sensing, in particular to a barometrically regulated room temperature ethanol gas sensing system and a use method thereof. BACKGROUND

[0002] Since ethanol is an important raw material in industrial production, ethanol gas concentration detection is of great significance to safety production and product quality improvement.

[0003] Studies have shown that semiconductor materials can achieve high-sensitivity ethanol gas detection and are relatively low in cost. The steps for applying semiconductor materials to achieve ethanol gas detection include: first, in an oxygen environment, oxygen negative ions appear on the surface of the semiconductor through the following process.

[0004] O2(gas)→O2(ads),

[0005]

[0006] Wherein, "gas" refers to gaseous, and "ads" refers to adsorbed on the surface of the semiconductor. After the semiconductor releases electrons, the resistance of the semiconductor increases, and the resistance at this time is recorded as Ra. Then, the semiconductor material is placed in ethanol gas. When the semiconductor is in ethanol gas, ethanol molecules react with oxygen negative ions adsorbed on the semiconductor to release captured electrons back into the semiconductor conduction band, and the resistance of the semiconductor decreases, and the resistance at this time is recorded as Rg, and the sensitivity S is S = Ra / Rg. The reaction formula of ethanol molecules and oxygen negative ions is as follows:

[0007] C2H5OH(gas)→C2H5OH(ads),

[0008] C2H5OH(ads)+6O - (ads)→2CO2(gas)+3H2O(gas)+6e - .

[0009] As can be seen, ethanol reacts with oxygen negative ions to form water molecules, and water molecules occupy the active sites of the semiconductor. When air or oxygen is re-introduced, the semiconductor ethanol gas sensor is difficult to restore the original value, resulting in a decrease in the sensitivity of the semiconductor ethanol gas sensor. The traditional method is to apply a heating method, that is, to set a heating electrode outside the semiconductor material and heat the semiconductor material to above 200 degrees Celsius, which reduces the safety of the system operation. SUMMARY

[0010] To solve the above problems, that is, to avoid heating and improve system operation safety, the present application provides, in one aspect, a gas pressure regulated room temperature ethanol gas sensing system, comprising a chamber, an air inlet valve, an air outlet valve, and a resistance testing component, the air inlet valve and the air outlet valve are arranged on the side wall of the chamber, and the resistance testing component is arranged in the chamber; the resistance testing component comprises a substrate, an interdigital electrode, and a gas sensitive material, the interdigital electrode is arranged on the substrate, and the gas sensitive material is arranged on the interdigital electrode; the system further comprises a suction cylinder and a piston, the suction cylinder is connected to the chamber, and the piston is arranged in the suction cylinder and used to regulate the air pressure in the chamber.

[0011] The core idea of the present application is that before discharging the ethanol gas to be measured, the piston is used to suck air, so as to reduce the air pressure in the chamber, make water molecules desorb from the semiconductor material, release active sites, and thus make more oxygen negative ions generated on the surface of the semiconductor material when air or oxygen is introduced again, so that the resistance of the semiconductor material changes more, thereby realizing high-sensitivity ethanol gas detection. The present application regulates the air pressure in the chamber by using the suction cylinder and the piston, so that water molecules can desorb from the semiconductor material without heating, thereby improving the system operation safety.

[0012] Further, the gas sensitive material is a molybdate.

[0013] Further, the molybdate is iron molybdate.

[0014] Further, the material of the substrate is alumina.

[0015] Further, the chamber is a cuboid, the air inlet valve and the air outlet valve are arranged on two opposite faces in the length direction respectively, the resistance testing component is fixed on the bottom face of the middle part of the chamber, and the suction cylinder is arranged on the upper side of the resistance testing component on the top face of the chamber.

[0016] Further, the system further comprises a support part, the support part is fixed on the bottom face of the chamber on the lower side of the suction cylinder, and the resistance testing component is fixed on the support part.

[0017] Further, the surface area of the support part is greater than the surface area of the resistance testing component.

[0018] Further, the system further comprises a first baffle and a second baffle, the first baffle is arranged between the resistance testing component and the air inlet valve, the second baffle is arranged between the resistance testing component and the air outlet valve, and the first baffle and the second baffle are used to block the airflow when the piston sucks air.

[0019] Further, the first baffle and the second baffle are movable baffles.

[0020] In another aspect, the present application provides a use method of the above-mentioned gas pressure regulated room temperature ethanol gas sensing system, comprising the following steps:

[0021] Step 1: open the inlet valve and outlet valve, set the piston to a lower state, and introduce air or oxygen;

[0022] Step 2: close the inlet valve and outlet valve, and measure the resistance Ra of the gas sensitive material;

[0023] Step 3: open the inlet valve and outlet valve, and introduce ethanol gas;

[0024] Step 4: close the inlet valve and outlet valve, and measure the resistance Rg of the gas sensitive material;

[0025] Step 5: keep the inlet valve and outlet valve closed, and the piston pumps out air to reduce the air pressure in the chamber;

[0026] Step 6: open the inlet valve and outlet valve, and pump out the ethanol gas; at the same time, the piston returns to a lower state;

[0027] Step 7: calculate the sensitivity of ethanol gas sensing according to the ratio of Ra and Rg.

[0028] The beneficial effects of the present application are:

[0029] (1) The present application uses the air pump and the piston to control the air pressure in the chamber, especially when releasing ethanol gas, the air pressure in the chamber is reduced, so that water molecules are quickly desorbed from the semiconductor material, releasing active sites; when oxygen or air is introduced again, more oxygen anions can be generated on the surface of the semiconductor material, improving the sensitivity of ethanol gas detection. The present application controls the air pressure in the chamber to make water molecules desorb from the semiconductor material, instead of using the traditional heating method, which improves the safety of the system operation.

[0030] (2) The present application uses the first baffle and the second baffle to reduce the surrounding space of the resistance testing component; when the piston pumps out air, the air pressure around the resistance testing component is reduced more, and water molecules are more easily desorbed from the semiconductor material.

[0031] (3) The present application uses the support to elevate the resistance testing component, i.e. the resistance testing component is closer to the end face of the air pump, when the piston pumps out air, more air pressure drop is formed on the surface of the resistance testing component, so that water molecules are more easily desorbed from the semiconductor material.

[0032] (4) In the present application, when the surface area of the support is greater than the surface area of the resistance testing component, an air flow channel is formed on the outside of the resistance testing component; when the piston pumps out air, the gas converges from the above channel to the air pump, forming an air flow on the surface of the resistance testing component, which accelerates the desorption of water molecules from the semiconductor material.

[0033] In summary, the present application has good application prospects in the field of ethanol gas sensing technology.

[0034] The application will be described in further detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of a gas pressure regulated room temperature ethanol gas sensing system.

[0036] Figure 2 is a schematic diagram of a resistance testing component.

[0037] Figure 3 is a SEM picture of a square flower-shaped microporous plate of iron molybdate.

[0038] Figure 4 is a schematic diagram of another gas pressure regulated room temperature ethanol gas sensing system.

[0039] Figure 5 is a schematic diagram of still another gas pressure regulated room temperature ethanol gas sensing system.

[0040] In the figure: 1, chamber; 2, air inlet valve; 3, air outlet valve; 4, resistance testing component; 5, air extraction cylinder; 6, piston; 7, first baffle; 8, second baffle; 9, support part. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be described in further detail below with reference to the drawings and by taking examples.

[0042] In one aspect, the present application provides a gas pressure regulated room temperature ethanol gas sensing system, as shown in Figure 1 including a chamber 1, an air inlet valve 2, an air outlet valve 3, and a resistance testing component 4. The chamber 1 is cuboid-shaped, and the areas of the two opposite sides in the length direction are small. The air inlet valve 2 and the air outlet valve 3 are respectively arranged on the two opposite sides in the length direction. The air inlet valve 2 and the air outlet valve 3 are arranged on the side wall of the chamber 1, and the resistance testing component 4 is arranged in the chamber 1. Specifically, the resistance testing component 4 is fixed on the bottom surface of the middle part of the chamber 1 and adhered to the bottom surface of the middle part of the chamber 1 by solid glue. The resistance testing component 4 includes a substrate, interdigital electrodes, and a gas sensitive material. The material of the substrate is alumina. The interdigital electrodes are arranged on the substrate, and the interdigital electrodes are selected from gold, silver, copper, platinum and the like. In the present application, since the interdigital electrodes do not need to be heated, the interdigital electrodes do not necessarily need to be a material resistant to corrosion at high temperature. The interdigital spacing of the differential electrodes is greater than 0.3 millimeters and less than 0.5 millimeters. The gas sensitive material is a semiconductor material, wherein the semiconductor material is a metal oxide semiconductor, which can be zinc oxide, tin oxide, iron oxide, cobalt oxide, etc. The gas sensitive material is arranged on the interdigital electrodes. Figure 2The interdigital electrode used in the present application is not provided with a heating electrode outside the interdigital electrode. The ethanol gas sensing system of the present application further comprises a suction cylinder 5 and a piston 6, the suction cylinder 5 is communicated with the chamber 1, the piston 6 is arranged in the suction cylinder 5, the piston 6 can move up and down, and is used for regulating the air pressure in the chamber 1; specifically, before the ethanol gas is released, the air pressure in the chamber 1 is reduced by the piston 6 (in the process, the piston 6 moves upwards), so as to accelerate the desorption of water molecules from the metal oxide material. Figure 1 In actual application, the air pressure in the chamber 1 can be adjusted by changing the distance that the piston 6 moves upwards, so that more water molecules are desorbed from the metal oxide semiconductor material.

[0043] The principle of ethanol gas detection based on the metal oxide semiconductor material is based on the resistance change of the metal oxide semiconductor material: in the oxygen gas environment, the oxygen in the surrounding environment is physically or chemically adsorbed on the surface of the metal oxide semiconductor material, the electrons in the conduction band near the surface of the metal oxide semiconductor material are captured by the oxygen in the air, forming negatively charged oxygen anions, thereby changing the conductive properties of the metal oxide semiconductor material, and the resistance is recorded as Rg. When the semiconductor material is a metal oxide, the gas sensing mechanism is attributed to the electron core-shell structure formed by oxygen adsorption. The metal oxide can be divided into p-type semiconductor and n-type semiconductor, and the carriers are mainly holes and electrons, respectively. Regardless of whether the metal oxide is a p-type semiconductor or an n-type semiconductor, the formation of oxygen anions in the oxygen environment leads to a change in the resistance of the metal oxide. In the ethanol gas environment to be detected, the ethanol molecules have a redox reaction with the adsorbed oxygen anions, release the captured electrons back to the conduction band of the metal oxide, resulting in a change in the resistance of the metal oxide, recorded as Rg. The sensitivity of ethanol gas detection is determined by the ratio of the two resistances.

[0044] The present application uses the piston 6 to suck air, regulates the pressure in the chamber 1, and makes the water molecules desorb from the semiconductor material. Specifically, before the ethanol gas to be detected is discharged, the piston 6 sucks air, reduces the air pressure in the chamber 1, makes the water molecules desorb from the semiconductor material, releases the active sites, so that more oxygen anions are generated on the surface of the semiconductor material when air or oxygen is introduced again, the resistance change of the semiconductor material is more, thereby realizing high-sensitivity ethanol gas detection. In summary, the present application regulates the air pressure in the chamber by using the suction cylinder 5 and the piston 6, and the water molecules can be desorbed from the semiconductor material without heating, thereby improving the safety of system operation.

[0045] Preferably, the gas sensitive material is iron molybdate, specifically a square flower-shaped microporous plate of iron molybdate, as shown in Figure 3 The square flower-shaped microporous plate of iron molybdate is synthesized by a hydrothermal method, and the main steps include: (1) preparing a solution of (NH3)6Mo7O 24• 4H2O was dissolved in deionized water in a first beaker, and FeCl3·6H2O was dissolved in deionized water in a second beaker; (2) under the condition of continuous magnetic stirring, the iron nitrate solution was slowly poured into the sodium molybdate solution, a yellow suspension was obtained after continuous stirring, and the stirring was continued for 30 minutes; (3) the pH measuring instrument cleaned with deionized water was placed in the yellow suspension obtained in the previous step, the initial pH value was recorded, concentrated hydrochloric acid was diluted with water at a ratio of 1:4, and then the diluted nitric acid was slowly dropped with a rubber bulb dropper, and the pH value of the solution was observed until the pH value of the solution was adjusted to 1, and the solution was continuously stirred in the process; (4) after magnetic stirring for 1 hour, the yellow-green suspension obtained was poured into a 100 ml polytetrafluoroethylene reaction kettle at 170°C for constant temperature reaction for 12 hours, and then naturally cooled to room temperature; (5) the sample solution was suction filtered, and washed with ethanol and deionized water for three times respectively, the final product was left on the filter paper, and the product was placed in a vacuum drying oven at a temperature of 80°C for drying for 12 hours, and finally the green Fe2(MoO4)3 square flower-shaped microporous plate was obtained. The square flower-shaped microporous plate of iron molybdate shows a slight (200)、 crystal face orientation deviation, the high-energy face has high activity in adsorbing ethanol gas, the surface is loose, and is beneficial to gas diffusion. In addition, compared with the spherical iron molybdate microstructure, the square flower-shaped microporous plate of iron molybdate has a larger size, is more firmly combined with the interdigital electrode when the piston pumps gas, and improves the accuracy of resistance measurement.

[0046] Preferably, as shown in Figure 1 , the gas pumping cylinder 5 is arranged on the top surface of the chamber 1 on the upper side of the resistance test component 4. When the piston 6 pumps gas, the air pressure at the resistance test component 4 is reduced, and the gas at other places in the chamber 1 enters the gas pumping cylinder 5 through the resistance test component 4, not only forming a low pressure at the gas sensitive material, but also forming a gas flow at the gas sensitive material, which is all conducive to the desorption of water molecules from the gas sensitive material.

[0047] Preferably, as shown in Figure 3 , further comprising a support part 9, the support part 9 is fixed on the bottom surface of the chamber 1 on the lower side of the gas pumping cylinder 5, and the resistance test component 4 is fixed on the support part 9. In this way, the gas sensitive material is closer to the end surface of the gas pumping cylinder 5, a lower air pressure is formed at the gas sensitive material, a stronger gas flow is formed at the gas sensitive material, which is more conducive to the desorption of water molecules from the gas sensitive material, releases more active sites, and improves the sensitivity of ethanol gas detection. Preferably, the surface area of the support part 9 is greater than the surface area of the resistance test component 4, a longer distance gas flow path is formed on the upper surface of the support part 9, the gas resistance is increased, the air pressure on the surface of the gas sensitive material is lower, the above-mentioned gas flow is mainly in the horizontal direction, the mechanical effect on the gas sensitive material is stronger, and the water molecules are more easily desorbed from the surface of the gas sensitive material.

[0048] Preferably, as shown in Figure 4As shown, the chamber 1 further comprises a first baffle 7 and a second baffle 8, the first baffle 7 is arranged between the resistance testing component 4 and the air inlet valve 2, the second baffle 8 is arranged between the resistance testing component 4 and the air outlet valve 3, the first baffle 7 and the second baffle 8 are used to block the air flow when the piston 6 is pumping air. The first baffle 7 and the second baffle 8 are movable baffles, for example, a rubber with a slit, under the action of air pressure difference, the rubber bends, thus showing the slit; when there is no air pressure difference, the rubber does not bend, and the slit is not obvious. Due to the blocking effect of the first baffle 7 and the second baffle 8, the time of the gas flowing in the chamber 1 is prolonged, the air flow can act on the surface of the gas sensitive material for a long time, and the gas sensitive material is in a low pressure environment for a long time, which is beneficial to the desorption of water molecules from the surface of the gas sensitive material.

[0049] In another aspect, the present application also provides a method for using the above-mentioned chamber for sensing ethanol gas at room temperature, comprising the following steps:

[0050] Step 1: open the air inlet valve 2 and the air outlet valve 3, and set the piston 6 to a lower state, and then introduce air or oxygen. The lower state of the piston 6 refers to a state in which the volume of the chamber 1 is small, preferably, the piston 6 is substantially flush with the inner surface of the chamber 1, so as to minimize the volume of the chamber 1, and when oxygen or air is introduced, other gases can be fully discharged;

[0051] Step 2: close the air inlet valve 2 and the air outlet valve 3, and measure the resistance Ra of the gas sensitive material, i.e. measure the resistance of the gas sensitive material in the air or oxygen environment;

[0052] Step 3: open the air inlet valve 2 and the air outlet valve 3, and introduce ethanol gas, so that the gas sensitive material is placed in the ethanol gas;

[0053] Step 4: close the air inlet valve 2 and the air outlet valve 3, and measure the resistance Rg of the gas sensitive material, i.e. measure the resistance of the gas sensitive material in the ethanol gas environment;

[0054] Step 5: keep the air inlet valve 2 and the air outlet valve 3 closed, and pump air by the piston 6 to reduce the air pressure in the chamber 1, so that the water molecules are desorbed from the gas sensitive material;

[0055] Step 6: open the air inlet valve 2 and the air outlet valve 3, and pump out the ethanol gas; at the same time, the piston 6 returns to the lower state, i.e. the state in which the piston 6 is substantially flush with the inner surface of the chamber 1;

[0056] Step 7: calculate the sensitivity of the ethanol gas sensing according to the ratio of Ra and Rg.

[0057] In summary, the application provides a kind of air pressure regulated room temperature ethanol gas sensing system, including chamber 1, air inlet valve 2, air outlet valve 3, resistance test component 4, air inlet valve 2 and air outlet valve 4 are arranged on the side wall of chamber 1, resistance test component 4 is arranged in chamber 1;Resistance test component 4 includes substrate, interdigital electrode, gas sensitive material, interdigital electrode is placed on the substrate, gas sensitive material is placed on the interdigital electrode;It also includes suction cylinder 5 and piston 6, suction cylinder 5 is communicated with chamber 1, piston 6 is arranged in suction cylinder 5, and piston 6 is used to regulate the air pressure in chamber 1.The application regulates the air pressure in chamber 1, so that water molecules are desorbed from semiconductor material, instead of using traditional heating method, which improves the safety of system operation.

[0058] The above only describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A barometrically regulated room temperature ethanol gas sensing system comprising a chamber, an inlet valve, an outlet valve, a resistive test element, the inlet valve and the outlet valve disposed on a side wall of the chamber, the resistive test element disposed within the chamber, the resistive test element comprising a substrate, an interdigital electrode, a gas sensitive material, the interdigital electrode disposed on the substrate, the gas sensitive material disposed on the interdigital electrode, characterized in that, The device further comprises a suction cylinder and a piston, wherein the suction cylinder is connected to the chamber and the piston is arranged in the suction cylinder and used to regulate the air pressure in the chamber, and the air pressure in the chamber is reduced before the ethanol gas is discharged; the chamber is cuboid, the air inlet valve and the air outlet valve are arranged on two opposite faces in the length direction respectively, the resistance testing component is fixed on the bottom face of the middle part of the chamber, the suction cylinder is arranged on the top face of the chamber and above the resistance testing component, and the device further comprises a first baffle and a second baffle, wherein the first baffle is arranged between the resistance testing component and the air inlet valve, the second baffle is arranged between the resistance testing component and the air outlet valve, and the first baffle and the second baffle are used to block the air flow when the piston is sucking air, thereby prolonging the time of the air flow in the chamber.

2. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 1, wherein: The gas sensitive material is molybdate.

3. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 2, wherein: The molybdate is iron molybdate.

4. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 1, wherein: The material of the substrate is alumina.

5. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 1, wherein: The device further comprises a support part, wherein the support part is fixed on the bottom face of the chamber and below the suction cylinder, and the resistance testing component is fixed on the support part.

6. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 5, wherein: The surface area of the support part is greater than that of the resistance testing component.

7. The barometrically regulated room temperature ethanol vapor gas sensing system of claim 1, wherein, The first baffle and the second baffle are movable baffles.

8. The method of using a barometrically regulated room temperature ethanol vapor gas sensing system according to any one of claims 1-7, wherein, The method comprises the following steps: Step 1: open the air inlet valve and the air outlet valve, arrange the piston to a lower state, and introduce air or oxygen; Step 2: Close the inlet valve and the outlet valve and measure the resistance of the gas sensitive material R a; Step 3: open the air inlet valve and the air outlet valve, and introduce ethanol gas; Step 4: Close the inlet valve and the outlet valve and measure the resistance of the gas sensitive material R g; Step 5: keep the air inlet valve and the air outlet valve closed, and the piston sucks air to reduce the air pressure in the chamber; Step 6: open the air inlet valve and the air outlet valve, and discharge ethanol gas; meanwhile, the piston returns to the lower state. Step 7: The sensitivity of the ethanol gas sensor was calculated from the ratio of a and g. R a and R g. The sensitivity of the ethanol gas sensor was calculated from the ratio of a and g.

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