Quantum dot gas microsensor chip, sensor probe and fire detection system

Abstract

The invention belongs to the technical field of gas sensors, and discloses a quantum dot gas microsensor chip, a sensor probe and a fire monitoring system.The quantum dot gas microsensor chip comprises a substrate layer, a first insulating layer, a heating layer, a second insulating layer and a gas-sensitive sensing layer which are sequentially stacked; wherein the gas-sensitive sensing layer comprises a first metal film and a second metal film which are laminated, and the ratio of the thickness of the first metal film to the thickness of the second metal film is not less than 10; the material of the first metal film comprises tungsten oxide, and the material of the second metal film comprises cadmium sulfide. The quantum dot gas microsensor chip has extremely high sensitivity and response speed, fire accidents caused by overheating of a cable or a cable head can be eliminated in the bud, and cable fire is effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a quantum dot gas microsensor chip, a sensor probe and a fire monitoring system. Background Art

[0002] After entering modern society, the urban population continues to increase, the available surface area is tight, and the traffic pressure is very high. Therefore, large cities adopt underground cable transmission. Compared with overhead lines above the ground, underground cables have the advantages of small footprint, relatively reliable power transmission, and strong resistance to external interference. Among the wires and cables currently in large quantities, most of the insulation and sheath materials of wires and cables are composed of flammable polymer materials such as polyvinyl chloride (PVC), cross-linked polyethylene (XLPE), and ethylene propylene rubber (EPR). According to statistics, the number of cross-linked polyethylene cables has reached more than 99% of the total number of cables in service in my country. However, with the continuous expansion of the power system, some cable lines have overloads or excessive fault currents, resulting in excessive cable temperatures. In addition, the operating temperature of the cable intermediate joints may be too high due to poor production or moisture oxidation. Excessive temperature will accelerate the aging of the insulation material, resulting in a decrease in the insulation performance of the material, shortening the service life of the cable, and even thermal breakdown, causing arcing, and ultimately leading to cable fires. The insulation layer and outer sheath of power cables are usually flammable polymers with good combustion characteristics. After burning, they will release a large amount of toxic gases, posing a serious threat to rescue missions and rescuers.

[0003] In the prior art, a gas sensor constructed of metal oxide nanomaterials is usually used to monitor power fires. Its measurement principle is the adsorption and electron exchange between the material of the gas sensor and the target gas. When the material contacts the detection gas at a suitable working temperature, the surface carrier concentration of the material will change to a certain extent. When the surface carrier concentration of the material is higher, it is easier to exchange electrons with the target gas, and it is intuitively reflected through the output of the electrical signal, thereby realizing the monitoring of information such as gas concentration, and then realizing the detection of cable fires or power fires. For example, the Chinese invention patent application with publication number CN118458827A discloses a carbon nanotube-tungsten oxide composite material and a preparation method and application. By adding acid-treated semiconductor carbon nanotubes to tungsten oxide, the excellent conductive properties of carbon nanotubes are used to improve the conductivity of the composite material, and the acidic chemically active groups are made to become the center of the chemically adsorbed gas, so that the gas sensor can exert excellent gas-sensitive performance at room temperature. However, the carrier concentration of the single metal oxide WO3 used is relatively low, which makes its sensitivity to gas concentration testing limited and the response is relatively slow. Summary of the invention

[0004] The technical problem to be solved by the present invention is to improve the problems of low sensitivity and slow response of gas sensors in the prior art.

[0005] The present invention solves the above technical problems through the following technical means: The invention discloses a quantum dot gas microsensor chip, which comprises a substrate layer, a first insulating layer, a heating layer, a second insulating layer and a gas sensitive sensing layer which are stacked in sequence.

[0006] The gas sensitive sensing layer includes a first metal film and a second metal film stacked together, and the ratio of the thickness of the first metal film to the thickness of the second metal film is not less than 10; the material of the first metal film includes tungsten oxide, and the material of the second metal film includes cadmium sulfide.

[0007] Furthermore, the second metal film is in a granular shape and is arranged in an array on the first metal film.

[0008] The second metal film is formed on the surface of the first metal film by chemical bath deposition.

[0009] The second metal film is formed on the surface of the first metal film by using several chemical bath depositions, and the time of each chemical bath deposition does not exceed 10 minutes.

[0010] The thickness of the first metal film is 200 nm.

[0011] A through hole is formed on the substrate layer in an area corresponding to the heating layer.

[0012] The invention also discloses a sensor probe, which comprises a sealed shell, and a first PCB, a second PCB and a battery located in the shell.

[0013] Furthermore, a plurality of the above-mentioned quantum dot gas microsensor chips are integrated on the first PCB for measuring the target gas.

[0014] The second PCB is integrated with a signal processing unit, which is communicatively connected with the quantum dot gas microsensor chip; The battery is used to provide power signals for the quantum dot gas microsensor chip heating layer and the signal processing unit.

[0015] Also included is a cylindrical cover; wherein: A through hole is opened on the side of the shell, one end of the cylindrical cover is sleeved in the through hole, a waterproof breathable membrane is fixed to the other end surface of the cylindrical cover, and the first PCB is fixed in the cylindrical cover.

[0016] The present invention also discloses a fire monitoring system, comprising: Several sensor probes using the above-mentioned method are distributed at the position of the cable to be monitored, and are used to generate an alarm signal when gas generated on the cable surface due to temperature increase is detected; A receiving host is connected in communication with the sensor probe to obtain the alarm signal; The fire-fighting host is connected to the receiving host for initiating fire-fighting work according to the received alarm signal.

[0017] Furthermore, the communication connection between the sensor probe and the receiving host adopts a Lora wireless network transmission method.

[0018] The advantages of the present invention are: the present application forms a gas-sensitive layer by stacking a first metal film made of tungsten oxide and a second metal film made of cadmium sulfide, and the thickness of the first metal film and the second metal film are set according to a suitable ratio, which can greatly improve the carrier concentration of the quantum dot gas sensor and significantly reduce the resistance value of the gas sensor, making it more sensitive and responsive when monitoring fire. The tungsten trioxide used in the gas microsensor of the present application is a quantum dot structure of a zero-dimensional nanomaterial with a special electronic structure. The quantum dots can provide more adsorption sites for target molecules due to their small size and large specific surface area, thereby improving the sensitivity of the sensor. In addition, by adjusting the composition and size of the quantum dots, the absorption and emission of light of different wavelengths can be achieved, thereby improving the selectivity of the sensor. At the same time, the quantum dots also have high optical and chemical stability, and can maintain their stable performance in different environments. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a schematic structural diagram of a quantum dot gas microsensor chip according to Example 1 of the present invention; Figure 2 This is a photoelectric performance diagram of a gas sensitive sensing layer in Example 1 of the present invention; Figure 3 This is an exploded schematic diagram of a sensor probe according to Embodiment 2 of the present invention; Figure 4 A cross-sectional schematic diagram of a sensor probe according to Embodiment 2 of the present invention; Figure 5 This is a structural diagram of a fire monitoring system according to Embodiment 3 of the present invention.

[0019] Explanation of the reference numerals: 11 - lower shell; 12 - upper shell; 13 - first PCB; 14 - second PCB; 15 - battery; 21 - cylindrical cover; 22 - waterproof and breathable membrane; 101 - substrate layer; 102 - first insulating layer; 103 - heating layer; 104 - second insulating layer; 105 - gas sensitive sensing layer; 1051 - first metal film; 1052 - second metal film. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1 Cable fire is a vicious accident in the power system. When a fire occurs, the fire is fierce, the combustion is rapid, and the smoke is harmful. In addition, due to the small space around most cables, the smoke generated in the cable fire accident is large, and it is difficult to observe the specific source of fire. Firefighting is very difficult, resulting in difficulty in fire fighting, long repair time, and serious losses. It can be seen that the occurrence of cable fire accidents will bring huge losses to the national economy and the lives and property of the people. Therefore, great attention should be paid to the fire prevention of cables in the power system. Electrical fire accidents will also cause other chain accidents. Generally speaking, wires and cables not only burn and spread quickly, but also produce a large amount of toxic and harmful gases, such as hydrogen chloride and carbon monoxide, which put people in a state of suffocation and poisoning, and face the risk of death. At the same time, when extinguished, the chloride gas will generate strong acid mist through the combustion reaction, causing "secondary pollution", which will cause modern smart power grids and electrical equipment to be corroded by strong acid, and the consequences are also quite serious.

[0022] Power cable fires are mainly divided into three stages: the first stage is the early stage of the fire, when the cable core conductor heats up and the heat accumulates in abnormal parts, resulting in a local temperature rise and the release of organic gas; the second stage is the early stage of the fire, when the cable is in a smoldering state, accompanied by a large amount of smoke; the third stage is the late stage of the fire, when a large amount of open flames and thick smoke appear in the cable, and the fire spreads rapidly. Therefore, a gas sensor with high sensitivity and high responsiveness is needed to detect the fire in the early stage, eliminate the fire accidents caused by overheating of cables and cable heads in the bud, and effectively prevent the occurrence of cable fires.

[0023] As attached Figure 1 As shown, the embodiment of the present application provides a quantum dot gas microsensor chip, comprising a substrate layer 101, a first insulating layer 102, a heating layer 103, a second insulating layer 104, and a gas sensitive sensing layer 105 stacked in sequence; wherein the gas sensitive sensing layer comprises a first metal film 1051 and a second metal film 1052 stacked, and the ratio of the thickness of the first metal film 1051 to the thickness of the second metal film 1052 is not less than 10; the material of the first metal film 1051 comprises tungsten oxide, and the material of the second metal film 1052 comprises cadmium sulfide.

[0024] Specifically, the substrate layer 101 is used to support other layers stacked on its surface. The first insulating layer 102 and the second insulating layer 104 are respectively located at the upper and lower ends of the heating layer 103 to play an insulating role. The heating layer 103 is used to heat the gas sensing layer 105 so that the gas sensitive material in the gas sensing layer 105 is at an optimal working temperature.

[0025] The gas sensing layer 105 in this embodiment adopts a stacked two-layer metal film structure. The material of the first metal film 1051 located in the lower layer is selected from tungsten oxide material, which is a typical polycrystalline compound and also a common n-type semiconductor material. Due to its complex crystal structure, it has special physical properties. The photocurrent density changes with the change of light. When the light brightness increases, the carrier concentration of tungsten oxide is greatly improved. At the same time, even in the early stage of a fire, the concentration of gas generated by the cable is very low, and tungsten oxide can also exchange electrons and reflect them through the output of electrical signals, thereby sensitively monitoring cable fires.

[0026] Furthermore, a second metal film 1052 made of cadmium sulfide is formed on the surface of the first metal film 1051. Cadmium sulfide is also an n-type semiconductor material, which also has nonlinear optical properties and can be attached to the surface of tungsten oxide. Without affecting the crystallinity and carrier concentration of tungsten oxide itself, the carrier concentration of the two metal films can be greatly improved compared with the carrier concentration of a single tungsten oxide material, thereby improving the sensitivity of the reaction to the gas concentration. When the gas concentration is very weak, the output of the electrical signal can be significantly enhanced, so that the multi-layer gas sensitive sensing layer composed of the first metal film 1051 and the second metal film 1052 has stronger photoelectric properties, and has higher sensitivity and faster response when monitoring fire.

[0027] As attached Figure 2 The photoelectric performance diagram of the gas sensing layer shown in the test, the horizontal axis is the voltage applied to the gas microsensor, and the vertical axis is the carrier concentration of the gas sensing layer. Among them, a comparative test was used to test the gas sensing layer only including tungsten oxide material and the gas sensing layer including cadmium sulfide tungsten oxide material. Figure 2 It can be found that as the voltage increases, the carrier concentration of the gas-sensitive sensing layer using two layers of cadmium sulfide tungsten oxide material is higher, which can make it respond faster and more sensitive to the gas concentration.

[0028] Furthermore, when a second metal film of cadmium sulfide material is formed on a first metal film of tungsten oxide material, the ratio of the thickness of the first metal film to the thickness of the second metal film is not less than 10, that is, when the second metal film is formed on the surface of the first metal film, the thickness of the second metal film does not need to be too much, and is set to be adapted to the thickness of the first metal film, thereby reducing the thickness of the metal film and the size of the chip as much as possible while improving the photosensitivity of the first metal film.

[0029] For example, the thickness of the first metal film is 200 nm, and the thickness of the second metal film is 20 nm.

[0030] The present application forms a gas-sensitive layer by stacking a first metal film made of tungsten oxide and a second metal film made of cadmium sulfide, and the thicknesses of the first metal film and the second metal film are set in a suitable ratio, which can greatly improve the gas concentration detection capability, making fire monitoring more sensitive and responsive.

[0031] As an example, tungsten oxide is WO3. In the periodic table, tungsten is located in the VI B group of the 6th period and is a typical transition metal element. The outer electron structure of tungsten is 5d46s2. Due to this special outer electron configuration, tungsten has multiple valence states, mainly +2, +3, +4, +5 and +6. Therefore, tungsten often exists in tungsten oxide in multiple valence states, among which tungsten trioxide (tungsten is +6 valence) is the most stable. The relative molecular mass of WO3 is 231.85 and the density is 7.16g / cm 3 WO3 is an anhydride that is soluble in hot alkali and ammonia, slightly soluble in fluoric acid, poorly soluble in acid, and insoluble in water. Common WO3 is a yellow powder with a boiling point of about 1837°C and a melting point of about 1473°C. WO3 crystals can be considered to be an ideal cubic crystal structure (ReO3), which is formed by the corner-sharing stacking of [WO6] octahedrons.

[0032] Tungsten trioxide is a quantum dot structure of a zero-dimensional nanomaterial with a special electronic structure. The movement of carriers in the material is restricted in three dimensions. The change in the energy band gap of quantum dots depends on their size. The energy gap of the material can be regulated by adjusting the size of the quantum dots. All of these have an important impact on the performance of semiconductor gas sensors. Due to their small size and large specific surface area, quantum dots can provide more adsorption sites for target molecules, thereby improving the sensitivity of the sensor. In addition, by adjusting the composition and size of quantum dots, the absorption and emission of light of different wavelengths can be achieved, thereby improving the selectivity of the sensor. At the same time, quantum dots also have high optical and chemical stability, and can maintain their stable performance in different environments.

[0033] In other embodiments, the material of the first metal film may also be ZnO (zinc oxide), which exists in the form of wurtzite crystal structure (WZ), belongs to the hexagonal system, and has a P63mc space group. Both zinc oxide and tungsten oxide are semiconductor metal oxides.

[0034] In addition, if attached Figure 1As shown, when the second metal film is formed on the surface of the first metal film, the second metal film is in a granular shape and arranged in an array on the first metal film. Specifically, the second metal film is formed on the surface of the first metal film by chemical bath deposition, wherein the second metal film is formed on the surface of the first metal film by several chemical bath depositions, and the time of each chemical bath deposition does not exceed 10 minutes.

[0035] Prepare 50 mmolL cadmium nitrate ethanol solution and 50 mmolL sodium sulfide methanol solution. First, immerse the prepared WO3 nanosheet film in 50 mmol / L cadmium nitrate ethanol solution for 5 min, take it out, rinse it with ethanol, and blow it dry with nitrogen; then immerse the WO3 nanosheet film in 50 mmol / L methanol solution for 5 min, take it out, rinse it with methanol, and blow it dry with nitrogen. These two steps are called a chemical bath, and the total time does not exceed 10 minutes. After several chemical baths, the required CdS (cadmium sulfide) sensitized WO3 (tungsten trioxide) nanosheet film is obtained. The preparation principle is: after WO3 nanosheets are immersed in an alcohol solution containing Cd, a small amount of Cd' (after rinsing with an alcohol solution, the content is very small) will be adsorbed on the surface. When immersed in an alcohol solution containing S3, it will combine with S3, thereby forming a CdS particle covering the WO3 surface, forming a stacked structure of a second metal film made of cadmium sulfide and a first metal film made of tungsten trioxide.

[0036] Furthermore, a through hole is formed on the substrate layer in an area corresponding to the heating layer. By providing the through hole on the substrate layer, the energy dissipation of the heating layer can be reduced, the power of the chip can be reduced, and less power is required to heat to the same temperature.

[0037] Example 2 It should be further explained that, based on the same inventive concept as in Example 1, Example 2 of the present invention further provides a sensor probe, as shown in the attached Figure 3 and attached Figure 4 The sensor probe shown in FIG. Figure 3 The explosion diagram of the sensor probe is shown in Figure 2. Figure 4 A cross-sectional view of the sensor probe.

[0038] The sensor probe includes a sealed shell, and a first PCB 13, a second PCB 14 and a battery 15 located in the shell; wherein the shell includes a lower shell 11 and an upper shell 12 that can be covered, and the first PCB 13, the second PCB 14 and the battery 15 are all located in the lower shell 11; the first PCB 13 is integrated with a plurality of quantum dot gas microsensor chips of any one of the above-mentioned embodiments 1, which are used to measure the target gas; the second PCB 14 is integrated with a signal processing unit, which is communicatively connected with the quantum dot gas microsensor chip; the battery 15 is used to provide a power signal for the quantum dot gas microsensor chip and the signal processing unit (used to provide a power signal for the heating layer of the quantum dot gas microsensor chip).

[0039] A plurality of quantum dot gas microsensor chips based on cadmium sulfide tungsten oxide materials are integrated on the first PCB13, and the sensor probes are arranged around the cables to be monitored. When the quantum dot gas microsensor chip detects that a fire occurs at the cable head and causes a change in the gas concentration nearby, a voltage signal is generated and transmitted to the signal processing unit on the second PCB14. The signal processing unit generates a fire alarm signal and transmits it to the fire alarm center. Fire accidents caused by overheating of cables and cable heads can be eliminated in the bud, effectively preventing the occurrence of cable fires and improving the management level of power grid operation.

[0040] Further, as attached Figure 3 As shown, the sensor probe also includes a cylindrical cover 21; wherein: a through hole is opened on the side of the shell, one end of the cylindrical cover 21 is sleeved in the through hole, a waterproof breathable membrane 22 is fixed to the other end surface of the cylindrical cover, and the first PCB13 is fixed in the cylindrical cover 21.

[0041] A cylindrical cover 21 is used, and a waterproof breathable membrane 22 and a first PCB 13 integrating multiple quantum dot gas microsensor chips are fixed inside the cylindrical cover 21. By extending the length of the cylindrical cover 21 and fixing it around the cable for real-time monitoring, the occurrence of cable fires can be effectively prevented.

[0042] Example 3 It should be further explained that, based on the same inventive concept as in Example 2, Example 3 of the present invention further provides a fire monitoring system. Figure 5 As shown, the system includes several sensor probes, a receiving host and a fire-fighting host as described above, wherein the sensor probes are distributed at the positions of the cables to be monitored, and are used to generate an alarm signal when the gas generated on the cable surface due to the increase in temperature is monitored; the receiving host is communicated with the sensor probe to obtain the alarm signal; the fire-fighting host is communicated with the receiving host to start the fire-fighting work according to the received alarm signal.

[0043] The sensor probe can detect and identify the smell or brightness in the power cable corridor, greatly improving the early fire response capability and alarm accuracy of the sensor, achieving long-distance non-contact measurement, and realizing long-distance data transmission to the service background, realizing intelligent detection and intelligent identification. To a large extent, it can provide early warning before the accident occurs, so that the power system staff has time to investigate and deal with the accident, greatly reducing the significant economic losses and inestimable casualties caused by cable fire accidents.

[0044] Cable fire monitoring technology based on quantum dot MEMS sensors can be connected to network backend services and used in smart grid security monitoring applications, such as intelligent identification of power cable overheating and fire. The overall system design is shown in the attached figure. Figure 5 As shown. The system consists of multiple sensor probe acquisition terminals, receiving host terminals, and fire host terminals. These sensor probes are distributed near cables prone to fire. When a heat source or fire source that exceeds the normal threshold appears, the sensor terminal detects the specific gas generated by the temperature increase in the outer layer of the cable, and generates a fire alarm signal, which is sent to the receiving host through the Lora wireless network transmission method. After receiving the alarm signal, the receiving host generates an alarm response to the fire host, and the relevant staff handles it according to the alarm situation.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quantum dot gas microsensor chip, characterized in that: It includes a substrate layer, a first insulating layer, a heating layer, a second insulating layer, and a gas-sensitive sensing layer stacked in sequence; The gas sensitive sensing layer includes a first metal film and a second metal film stacked together, and the ratio of the thickness of the first metal film to the thickness of the second metal film is not less than 10; the material of the first metal film includes tungsten oxide, and the material of the second metal film includes cadmium sulfide.

2. The quantum dot gas microsensor chip according to claim 1, characterized in that: The second metal film is in a granular shape and is arranged in an array on the first metal film.

3. The quantum dot gas microsensor chip according to claim 1, characterized in that: The second metal film is formed on the surface of the first metal film by chemical bath deposition.

4. The quantum dot gas microsensor chip according to claim 1, characterized in that: The second metal film is formed on the surface of the first metal film by using several chemical bath depositions, and the time of each chemical bath deposition does not exceed 10 minutes.

5. The quantum dot gas microsensor chip according to claim 1, characterized in that: The thickness of the first metal film is 200 nm.

6. The quantum dot gas microsensor chip according to claim 1, characterized in that: A through hole is formed on the substrate layer in an area corresponding to the heating layer.

7. A sensor probe, characterized in that: It comprises a sealed shell, and a first PCB, a second PCB and a battery located in the shell; The first PCB is integrated with a plurality of quantum dot gas microsensor chips according to any one of claims 1 to 6 for measuring the target gas; The second PCB is integrated with a signal processing unit, which is communicatively connected with the quantum dot gas microsensor chip; A battery is used to provide power signals for the quantum dot gas microsensor chip heating layer and the signal processing unit.

8. The sensor probe according to claim 8, characterized in that: Also included is a cylindrical cover; wherein: A through hole is opened on the side of the shell, one end of the cylindrical cover is sleeved in the through hole, a waterproof breathable membrane is fixed to the other end surface of the cylindrical cover, and the first PCB is fixed in the cylindrical cover.

9. A fire monitoring system, characterized in that: include: A plurality of sensor probes as claimed in any one of claims 7 to 8, distributed at the position of the cable to be monitored, for generating an alarm signal when gas generated on the cable surface due to temperature increase is detected; A receiving host is connected in communication with the sensor probe to obtain the alarm signal; The fire-fighting host is connected to the receiving host for initiating fire-fighting work according to the received alarm signal.

10. A fire monitoring system according to claim 9, characterized in that: The communication connection between the sensor probe and the receiving host adopts the Lora wireless network transmission mode.

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