A method and system for loading gas-sensitive catalytic materials for high-performance gas sensors

Abstract

The present invention relates to a method and system for loading gas-sensitive catalytic materials for high-performance gas sensors, wherein the method at least includes the following steps: chemical bath deposition precursor solution configuration: dissolving two or more compounds capable of obtaining catalytic particles based on reactions in an alcohol solution; catalytic particle deposition: growing catalytic particles on the surface of a layer structure formed by gas-sensitive particles using a hydrothermal method based on the precursor solution; and a spin coating method based on the first method to encourage the catalytic particles to be evenly dispersed on the surface of the layer structure and limit the agglomeration tendency of the catalytic particles. The present invention deposits metal-modified particles on the inner wall of a nanotube based on a spin coating method, encourages metal particles to be distributed on the surface of the layer structure with a small diameter, so that the surface of the layer structure can be deposited to form more reactive sites, thereby achieving the purpose of improving the sensing performance of the sensor.

Description

Technical Field

[0001] The present invention relates to the field of sensor equipment, and in particular to a method and system for loading gas-sensitive catalytic materials of a high-performance gas sensor. Background Art

[0002] With the rapid development of industrial technology and the continuous improvement of human safety awareness, health problems caused by volatile organic compounds have become the focus of social attention. People are exposed to dangerous gases more and more frequently, such as natural gas with methane and carbon monoxide as the main components, organic volatile toxic gases such as formaldehyde, benzene, and xylene released from decoration materials, sulfur dioxide and nitrogen oxides in coal combustion and automobile exhaust, etc. Once these flammable, explosive, toxic and harmful gases are produced or leaked, they will pose a threat to people's health and life. Therefore, it is very necessary to develop gas sensors with high sensitivity and fast detection speed.

[0003] However, in some special occasions, it is necessary to have an extremely high detection limit for the target gas. A single gas-sensitive film often cannot meet the detection requirements, so it is necessary to improve the structure of the gas-sensitive film to improve the detection limit. Studies have shown that the heterogeneous structure formed by precious metal quantum dots and composite films prepared by hydrothermal method can greatly increase the gas-sensing effect, but this cannot guarantee the consistency of the sensor, and the cost is high. The development of MEMS technology has promoted the development of traditional gas sensors towards miniaturization. Miniaturized gas sensors based on MEMS technology not only ensure the consistency of gas-sensitive films, but also greatly reduce the price of gas sensors. It has become the development trend of gas sensors in the future. Therefore, it is necessary to study precious metal quantum dots and composite films to prepare high-sensitivity, high-consistency, and low-cost gas sensors based on MEMS technology.

[0004] In the prior art, a patent document with publication number CN105900236B discloses a semiconductor sensor device, including: a substrate; an unsuitable seed layer located above the substrate; at least one electrode located above the unsuitable seed layer; and a porous sensing layer directly supported by the unsuitable seed layer and electrically communicating with the at least one electrode, wherein the porous sensing layer defines a plurality of grain boundaries formed by spaced-apart nucleation on the unsuitable seed layer using atomic layer deposition.

[0005] Chinese patent CN113092542A discloses a planar nano gas sensor, array and preparation method thereof, which relates to the technical field of gas sensors. The gas sensor comprises a planar sensing electrode, a sensing layer, an electrical insulating layer and a micro heater from top to bottom; the sensing layer is formed after depositing nano-scale sensing material in a double-through-hole substrate; the double-through-hole substrate is composed of a plurality of double-through-hole nanotubes; the double-through-hole nanotubes are nanotubes with one end and the other end both open and one end connected to the other end; the nano-scale sensing material is deposited on the tube wall of the double-through-hole nanotubes; the heating area of ​​the micro heater overlaps the sensing area of ​​the planar sensing electrode in the vertical direction.

[0006] Chinese patent CN112798649A discloses a method for preparing a precious metal quantum dot modified multilayer nanocomposite film gas sensor, which uses a double-sided oxidized and nitride silicon wafer as a substrate, a multilayer nanocomposite film modified with precious metal quantum dots as a gas sensitive material, and is deposited on the silicon wafer substrate by a sputtering method, and is stacked with a test electrode in the center above the front side of the silicon nitride layer, and a test electrode with a comb-tooth-plug-tooth composite structure is arranged above the sensitive material; a heating wire is scissor-shaped and surrounds the test electrode in two layers, and the lead-out end of the comb-tooth-plug-tooth composite test electrode is arranged at the scissor mouth of the heating wire, and the heating wire and the test electrode are respectively connected to a pair of symmetrically distributed lead disks.

[0007] The above application document proposes the use of metal modification to improve the performance of the sensor. However, during the metal modification process, metal particles are prone to agglomeration under the action of van der Waals forces, which reduces the number of metal particle aggregates that can be accommodated per unit area on the surface of the sensing layer. In addition, large-sized metal particles will cover part of the gas-sensitive particles and the pores between the gas-sensitive particles, which is not conducive to the process in which the sensing layer adsorbs the gas to be detected and reacts with the gas to be detected.

[0008] In addition, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventor studied a large number of documents and patents when making the present invention, but due to space limitations, not all details and contents are listed in detail. However, this does not mean that the present invention does not have the characteristics of these prior arts. On the contrary, the present invention already has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art to the background technology. Summary of the invention

[0009] In order to solve at least part of the shortcomings of the above-mentioned prior art, the present application provides a high-performance gas sensor gas-sensitive catalytic material loading method, which at least includes the following steps: chemical bath deposition precursor solution configuration: dissolving two or more compounds that can obtain catalytic particles based on the reaction in an alcohol solution; catalytic particle deposition: growing catalytic particles on the surface of the layer structure formed by the gas-sensitive particles by a hydrothermal method based on the precursor; and the spin coating method based on the first method encourages the catalytic particles to be evenly dispersed on the surface of the layer structure and limits the agglomeration tendency of the catalytic particles. The present invention forms catalytic particles in an alcohol solution, avoiding the problems of large size, poor stability, and small surface area of ​​catalytic particles formed in traditional water, and further, the catalytic particle loading process in the present invention has low requirements on the ambient temperature, and does not require the high-temperature loading method in the traditional loading process, which has the characteristics of energy saving and high practicality. Furthermore, the selection of non-toxic ethanol as a solute can reduce the use of toxic and harmful substances in the loading process, and further improve the safety of the loading process.

[0010] Preferably, the spin coating method under the first method refers to controlling the rotation of the porous alumina template based on a straight line parallel to the axis of any nanotube on the porous alumina template as a rotating axis, so that the catalytic particles are dispersed and deposited on the surface of the layer structure under the action of centrifugal force, and the excess catalytic particles and alcohol solution after dispersion are discharged from the tube mouth of the nanotube under the action of their own gravity. In the present invention, the spin coating method is used to control the uniform dispersion of the catalytic particles on the surface of the layer structure formed by the gas-sensitive particles, and the spin coating method under the first method can control the catalytic particles from agglomerating during the deposition process, so that the catalytic particles maintain a small size and are deposited on the inner wall of the nanotube. The excess catalytic particles and alcohol solution that failed to be dispersed and deposited are discharged from the tube mouth of the nanotube under the action of their own gravity, further accelerating the deposition process of the catalytic particles. Further, in order to avoid the torque of the nanotubes at different positions having a greater impact on the dispersion effect of the catalytic particles, the axis of the nanotube as close to the middle position as possible is selected as the rotating axis for rotation, thereby reducing the dispersion difference of the catalytic particles on the nanotube wall with the minimum torque and the maximum torque.

[0011] Preferably, the catalytic particles that cannot be agglomerated can be distributed on the surface of the layer structure in a small-sized and uniformly dispersed array, so that the surface of the layer structure has more reactive sites, wherein the reactive sites refer to the distribution sites of the catalytic particles on the layer structure. As noble metal particles, the catalytic particles themselves have strong oxygen adsorption characteristics, so the adsorbed oxygen adsorbed on the surface of the catalytic particles will absorb electrons from the gas-sensitive particles, thereby further deepening the thickness of the electron depletion layer near the surface of the gas-sensitive particles, causing the conductivity of the gas-sensitive particles to decrease, and the gas-sensitive particles are in a high-resistance state. When a reducing gas appears, the adsorbed oxygen on the surface of the catalytic particles is reduced, and the absorbed electrons return to the interior of the gas-sensitive particles, causing the resistance of the material to decrease. The surface of the catalytic particles has an uneven surface potential energy, and the change in the adsorption potential energy is uneven. When the thermal motion energy exceeds the boundary potential barrier, the adsorbed electrons will be transferred from the original position to the surface of the catalytic particles. That is, when the gas molecules to be detected are adsorbed and accumulated on the surface of the catalytic particles and then overflow to the surface of the gas-sensitive particles, the catalytic particles are just like reactive sites, which will significantly promote the gas-sensitive reaction rate of the gas-sensitive particles. The present invention forms particles with smaller diameters that cannot agglomerate on the surface of the layer structure, so that the layer structure can form more reactive sites, thereby making the sensor have higher sensitivity.

[0012] Preferably, a sensing electrode is deposited on the sensing layer formed by the gas-sensitive particles, catalytic particles and the porous alumina template, and the sensing electrode is electrically connected to the layer structure formed by the gas-sensitive particles, so that the change in electrical properties when the gas-sensitive particles undergo a sensing reaction can be conducted through the sensing electrode.

[0013] Preferably, the sensing layer comprises a functional area and a non-functional area, the functional area and the non-functional area are connected via a suspension, and the shape of the non-functional area matches the sensing electrode arrangement.

[0014] Preferably, the loading method also includes setting a heating layer and an isolation layer, wherein the isolation layer is set between the heating layer and the sensing layer, and the isolation layer can transfer the heat generated by the heating layer to the functional area in a uniform conduction manner, and heating electrode holes are reserved on the isolation layer for leading the heating layer to an external heating power supply.

[0015] Preferably, the heating layer includes a heating electrode and a thermal resistance wire. The heating electrode is electrically connected to the thermal resistance wire through a connecting wire. The shape of the heating electrode matches the heating electrode hole, so that the heating electrode can be arranged in the heating electrode hole in a nested manner and maintain electrical connection with an external heating power supply. The shape of the heating area formed by the winding thermal resistance wire matches the functional area, so that the thermal resistance wire can heat the functional area as a whole.

[0016] Preferably, the loading method further comprises providing a substrate, on which a groove hole penetrating from top to bottom is provided, and the shape of the groove hole is a triangle with a stable structure, and the substrate is used to improve the physical strength of the sensor.

[0017] A high-performance gas sensor gas-sensitive catalytic material loading system, wherein catalytic particles are dispersed on the surface of a layer structure formed by stacking gas-sensitive particles based on a spin coating method under a first method, and the dispersed catalytic particles are restricted by centrifugal force due to their agglomeration tendency, so that the particle size formed by the catalytic particles is smaller.

[0018] Preferably, the spin coating method under the first method refers to controlling the rotation of the porous alumina template based on a straight line parallel to the axis of any nanotube on the porous alumina template as the axis of rotation, so that the catalytic particles are dispersed and deposited on the surface of the layer structure under the action of centrifugal force, and after dispersion, excess catalytic particles and alcohol solution are discharged from the tube mouth of the nanotube under the action of their own gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0020] Figure 2 is a schematic diagram of a sensing electrode of the present invention;

[0021] Figure 3 is a schematic diagram of the heating layer of the present invention;

[0022] Figure 4 It is a schematic diagram of the partitioning of the sensing layer of the present invention;

[0023] Figure 5 It is a cross-sectional view of the sensing layer of the present invention.

[0024] Reference numerals list

[0025] 1: sensing electrode; 11: interdigital electrode; 12: interdigital interval; 13: interdigital end; 14: interdigital panel; 2: sensing layer; 21: functional area; 22: non-functional area; 23: suspension; 24: channel; 25: aluminum base; 26: oxide layer; 27: barrier layer; 3: gas-sensitive particles; 4: isolation layer; 41: first overlapping area; 42: heating electrode hole; 5: heating layer; 51: heating electrode; 52: connecting wire; 53: thermal resistance wire; 6: support layer; 61: second overlapping area; 7: substrate; 71: groove hole; 8: catalytic particles. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings.

[0027] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative work belong to the scope of protection of the present invention.

[0028] The present invention provides a high-performance gas sensor gas-sensitive catalytic material loading system, such as Figure 1 As shown, it may include the following parts stacked in sequence from top to bottom:

[0029] The sensing electrode 1 is arranged at the top of the entire sensor and is used to transmit the electrical signal when the sensor reacts;

[0030] A sensing layer 2, which is arranged on the bottom layer of the sensing electrode 1 in a manner of at least partially vertically overlapping with the sensing electrode 1, and has gas-sensitive particles 3 for sensing a gas to be detected;

[0031] The isolation layer 4 is arranged on the side of the sensing layer 2 relative to the sensing electrode 1, and is used to uniformly and stably transmit the heat required for the gas-sensitive particles 3 to react when sensing to the sensing layer 2;

[0032] The heating layer 5 is arranged at the bottom of the isolation layer 4 and is used to provide heat to the sensing layer 2. The heat can be evenly conducted to the sensing layer 2 after being blocked by the isolation layer 4.

[0033] A support layer 6, which is arranged on a side of the heating layer 5 relative to the isolation layer 4, and is used to prevent the heat generated by the heating layer 5 from being dissipated from the side of the support layer 6;

[0034] The substrate 7 is arranged at the bottom layer of the entire sensor structure and serves as a carrier structure for supporting all the above layer structures.

[0035] According to a preferred embodiment, Figure 1 As shown, the sensing electrode 1 is arranged on the surface of the sensing layer 2, and the sensing electrode 1 contacts and is electrically connected to the gas-sensitive particles 3 on the sensing layer 2. Under the premise that the voltage across the sensing electrode 1 is constant, when the gas-sensitive particles 3 contact the gas to be detected that can react with the gas-sensitive particles 3, a sensing reaction can occur, and the resistance of the gas-sensitive particles 3 changes, so that the current of the circuit changes. By monitoring the current change in the circuit, it can be determined whether there is a gas that can be sensed in the scene where the sensor is located. Preferably, as Figure 2As shown, the sensing electrode 1 is composed of a pair of structurally matched interdigital electrodes 11. The interdigital electrodes 11 are centrally symmetrically arranged in a contactless manner, and the interdigital interval 12 between the two interdigital electrodes 11 is electrically connected to the interdigital ends 13 of the interdigital electrodes 11 through the gas-sensitive particles 3 on the sensing layer 2, so that a closed loop is formed between the two interdigital electrodes 11. Specifically, the interdigital electrodes 11 are constructed as a structure in which two branch wires are extended toward each other near the end positions of two wires arranged side by side, and optionally, the number of branch wires can be any value greater than two.

[0036] According to a preferred embodiment, Figure 1 As shown, the sensing electrode 1 is deposited on the surface of the sensing layer 2, and the sensing layer 2 is preferably a single-pass porous alumina template, wherein the orifice direction of the single-pass porous alumina template faces the sensing electrode 1, and the interdigital interval 12 formed by two interdigital electrodes 11 being symmetrically embedded in each other is deposited at the orifice position of the single-pass porous alumina template. The two interdigital electrodes 11 are deposited on the surface of the sensing layer 2 and contact the gas-sensitive particles 3 in the interdigital interval 12 to achieve electrical connection. The gas-sensitive particles 3 in the interdigital interval 12 include gas-sensitive particles on the surface outside the orifice and gas-sensitive particles deposited on the inner wall of the alumina template in the hole. Preferably, the interdigital interval 12 can be an area of ​​any shape that can be thought of by a person skilled in the art, matching the outline surrounded by the interdigital electrode 11 with which it cooperates. It is set as a triangle here. The two interdigital electrodes 11 are led out through their respective interdigital panels 14, and the interdigital panels 14 are used to connect to an external voltage source.

[0037] According to a preferred embodiment, the sensing layer 2 is formed by a single-pass porous alumina template with gas-sensitive particles 3 deposited on the surface. The single-pass porous alumina template is composed of a plurality of single-hole nanotubes, each of which has an opening connected to the outside. In particular, the double-pass alumina template is composed of a plurality of openings connected to each other at both ends. The common single-pass porous alumina template has a honeycomb structure, which is composed of hundreds, thousands, or even tens of thousands of regular hexagonal columnar oxide units. Figure 5 As shown, there is a circular channel 24 in the middle of each regular hexagon. The size of the channel 24 is generally nanometer-level, and the channel 24 is roughly perpendicular to the surface. The pore size is uniform but relatively adjustable, the structure is simple and the array is orderly. There is a barrier layer between the aluminum base 22 and the oxide layer 23, which is hemispherical. This special structure makes the preparation method of the alumina template in the nano-ordered array simple and low-cost, and suitable for the assembly of various materials. The ratio between the assembled and deposited substances and the morphology of the particles in the template is closely related to the performance of the nanomaterial. The two-step anodizing method can be used to prepare the alumina template. Because this template has the characteristics of high temperature resistance, high strength, and monodispersed pore size, it becomes an ideal preparation method for nano-alumina materials.

[0038] The gas-sensitive particles 3 are nano zinc oxide materials. Preferably, the gas-sensitive particles can also be gas-sensitive materials such as tin dioxide or tungsten trioxide (the gas can cause the electrical properties of the gas-sensitive material to change when it contacts the gas-sensitive material, such as an increase or decrease in resistance). It is arranged on the inner wall of the nanotubes and the surface of the nanotube orifices of the alumina template by adsorption deposition. The alumina template has a high specific surface area, can contact and adsorb more gas-sensitive particles 3, and greatly increases the expansion area of ​​the gas-sensitive particles 3, so that the gas molecules to be detected can more easily contact the gas-sensitive particles 3 and react with them.

[0039] According to a preferred embodiment, when the gas-sensitive particles 3 contact the gas molecules to be detected that can undergo a sensing reaction, they can gain or lose electrons based on the oxidizing and reducing properties of the gas to be detected. At this time, the electrical resistance of the gas-sensitive particles 3 themselves will change, the current passing through will also change, and the current on the sensing electrode 1 electrically connected to the gas-sensitive particles 3 will also change. Therefore, by monitoring the degree of change in the current, it can be determined whether the gas-sensitive particles 3 contact the gas molecules to be detected that can undergo a sensing reaction, and then by controlling the temperature environment, the gas-sensitive particles 3 can be controlled to undergo a sensing reaction only with the target molecules to be detected.

[0040] The alumina template of the sensing layer 2 can be divided into a functional area 21 and a non-functional area 22. The functional area 21 is connected to the non-functional area 22 by a suspension 23. Gas-sensitive particles 3 are deposited on both the functional area 21 and the non-functional area 22. The shape of the functional area 21 is adapted to the shape of the sensing electrode 1, so that the shape of the functional area 21 can match the interdigital interval 12. Here, the shape of the functional area 21 is set to a triangle that matches the outline of the sensing electrode 1. The non-functional area 22 is used for angle compensation when the functional area 21 is deformed in a high temperature environment. Only a single suspension 23 is set to be connected to the functional area 21 to reduce the heat loss of the functional area 22. The functional area 21 needs to be at a higher temperature when a sensing reaction occurs. The functional area 21 and the sensing electrodes 1 and the isolation layer 4 stacked on both sides have different Young's modulus and thermal expansion coefficients of the constituent materials. Therefore, under high temperature conditions, the surface stress of the functional area 21 will become larger and larger, and the stress at the connection position with the suspension 23 is relatively large, which is prone to rupture and breakage, which can be improved by angle compensation. The non-functional area 22, the suspension 23 and the functional area 21 are an integrated structure. Preferably, the non-functional area 22, the suspension 23 and the functional area 21 can be cut and separated from the complete alumina template by cutting.

[0041] According to a preferred embodiment, the sensing current when the sensing reaction occurs is mainly distributed on the gas-sensitive particles 3, including the surface of the alumina pore and the gas-sensitive particles in the alumina nanopores. In the present invention, the contact surface between the sensing electrode 1 and the sensing layer 2 is the overlapping area between the interdigital interval of the sensing electrode 1 and the functional area of ​​the sensing layer 2, that is, the area where the sensing reaction occurs is mostly concentrated on the nanopore wall with a higher expansion area, and a small part is located in the interdigital interval of the sensing electrode 1.

[0042] According to a preferred embodiment, the isolation layer 4 is arranged at the bottom of the sensing layer 2 to isolate the sensing layer 2 from the heating layer 5. The isolation layer 4 is used to prevent the temperature of the heating layer 5 from changing too fast, causing the gas-sensitive particles 3 to fail. Too fast temperature changes will cause a large change in the thermal stress of the device and a large change in the degree of thermal expansion, which can easily cause the material to deform and break. While ensuring heat conduction, the isolation layer 4 also plays a role in maintaining electrical isolation between the sensing layer 2 and the heating layer 5. The isolation layer 4 can be formed by processing a silicon oxide layer structure.

[0043] The isolation layer 4 is provided with a matching functional area 21, a suspension 23 and a first overlapping area 41 of the interdigital electrodes 11 for connecting the wires of the interdigital panel 14. Figure 1 As shown, the first overlapping area 41 is formed by cutting the isolation layer to remove a number of trapezoids whose mid-vertical lines intersect at one point and whose short sides are arranged facing each other. In the present invention, the first overlapping area 41 is formed by removing three trapezoids. The triangular area surrounded by the trapezoids matches the shape of the functional area 21, and the area of ​​the triangular area is slightly larger than the area of ​​the functional area 21 to ensure that the functional area 21 is completely within the triangular area. A reserved area is reserved between adjacent trapezoids for matching and overlapping with part of the wires of the suspension 23 and the interdigital electrode 11.

[0044] According to a preferred embodiment, the heating layer 5 is arranged on the side of the isolation layer 4 relative to the sensing layer 2. The heating layer 5 includes a heating electrode 51 and a thermal resistance wire 53. The thermal resistance wire 53 is connected to the heating electrode 51 through a connecting wire 52. The present invention mainly provides the heat source required for the sensing reaction for the entire sensor by the thermal resistance wire 53. The thermal resistance wire 53 is formed by a material with a large resistivity in a triangular area matching the first overlapping area 41, so that under the premise of a certain overall shape, the thermal resistance wire 53 can have a longer length to pass through the isolation layer 4 to centrally heat the functional area 21 of the sensing layer 2. The material of the connecting wire 52 can be the same as that of the thermal resistance wire 53. Even if the connecting wire 52 generates heat when current passes through it, since the thermal resistance wire 53 has a relatively long heat-generating length, the heat is more concentrated, so the heat of the connecting wire 52 has less effect on the sensing reaction of the functional area 21. The economic benefits brought by the thermal resistance wire 53 and the connecting wire 52 being able to be generated in one piece without the need to select other wires to be electrically connected to the thermal resistance wire 53 are the highest, and the material loss in the manufacturing process is saved. The connecting wire 52 is led out to the heating electrode 51 by overlapping the reserved area. The heating electrode 51 is preferably a rectangular structure, and the heating electrode 51 has a relatively large area so that it can be easily contacted and electrically connected with the voltage source. The heating electrode 51 is nested through the heating electrode hole reserved on the isolation layer 4 and is arranged on the isolation layer 4, so that one side of the heating electrode 51 is in a bare environment, which is convenient for the voltage source to be connected.

[0045] The heat generated by the thermal resistance wire 53 can be collected in the isolation layer 4 and evenly conducted to the functional area 21 on one side of the isolation layer 4 when passing through the isolation layer 4, so that the heat generated by the thermal resistance wire 53 will not directly act on the functional area, thereby avoiding the functional area 21 from being deformed due to uneven heating and causing thermal stress imbalance or the gas-sensitive particles 3 on the functional area 21 falling off.

[0046] According to a preferred embodiment, the support layer 6 is arranged at the bottom layer of the heating layer 5. A second overlapping area 61 is arranged at the position of the support layer 6 corresponding to the first overlapping area 41. The shape and size of the second overlapping area 61 match the first overlapping area 41. The second overlapping area 61 is used as the bearing area of ​​the thermal resistance wire 53 when the heating layer 5 is deposited on the support layer 6, and the second overlapping area 61 includes three cantilever beams for connecting to the remaining area of ​​the support layer 6. When the heat generated by the heating layer 5 is transferred to the bearing area, since the bearing area is only connected by three cantilever beams, the heat on the bearing area is dissipated by the cantilever beams at a slow thermal conductivity rate, so that the bearing area can concentrate the heat radiated from the heating layer 5 to the support layer 6, so that the temperature of the working area 21 adapted to the first overlapping area 41 and the second overlapping area 61 reaches the sensing temperature. The support layer 6 can be formed by grooving a silicon nitride or silicon oxide layer structure.

[0047] According to a preferred embodiment, the substrate 7 is located at the bottom of the entire sensor device to improve the overall physical strength of the sensor. Figure 1 As shown, the substrate 7 is a cubic structure with a relatively high thickness. The substrate 7 is provided with a groove hole 71 that runs through the entire body from top to bottom. In the present invention, the shape of the groove hole 71 is set to a triangular structure with high stability. Preferably, the shape of the groove hole 71 can also be a square, trapezoid, or other shapes that can be thought of by those skilled in the art. By making grooves on the substrate 7, the bending resistance of the substrate 7 can be increased, and the risk of bending of the sensor device when it falls can be further avoided, thereby further improving the reliability of the sensor device.

[0048] The shape of the cutout hole 71 matches the first overlapping area 41 and the second overlapping area 61, and the triangular size of the cutout hole 71 is larger than the first overlapping area 41, so that the sensor device passes through the cutout hole 71, the second overlapping area 62, the thermal resistance wire 53, the first overlapping area 41, and the sensing layer 2 from bottom to top. The gas to be detected can enter from one side of the sensor device and then pass out from the other side. The gas flowability of the device is strong, and it is easier for the gas to be detected to enter for detection. Preferably, in order to provide higher physical strength, the substrate 7 can preferably be selected as a silicon substrate.

[0049] According to a preferred embodiment, catalytic particles 8 are deposited on the surface of the gas-sensitive particles 3. The catalytic particles 8 are preferably precious metal particles. When the catalytic particles 8 are loaded on the surface of the gas-sensitive particles 3 as semiconductor materials, a Schottky barrier of metal-semiconductor contact will be formed. The precious metal particles themselves have strong oxygen adsorption characteristics, so the adsorbed oxygen adsorbed on the surface of the catalytic particles 8 will absorb electrons from the gas-sensitive particles 3, thereby further deepening the thickness of the electron depletion layer near the surface of the gas-sensitive particles 3, causing the conductivity of the gas-sensitive particles 3 to decrease, and the gas-sensitive particles 3 are in a high-resistance state. When a reducing gas appears, the adsorbed oxygen on the surface of the catalytic particles 8 is reduced, and the absorbed electrons return to the interior of the gas-sensitive particles 3, causing the resistance of the material to decrease. The surface of the catalytic particles 8 has an uneven surface potential energy, and the change in the adsorption potential energy is uneven. When the thermal motion energy exceeds the boundary potential barrier, the adsorbed electrons will be transferred from the original position to the surface of the catalytic particles 8. That is, when the gas molecules to be detected are adsorbed and accumulated on the surface of the catalytic particles 8 and then overflow to the surface of the gas-sensitive particles 3, the catalytic particles 8 are like reactive active sites, which will significantly promote the gas-sensitive reaction rate of the gas-sensitive particles 3. The catalytic particles 8 can be set on the surface of the gas-sensitive particles 3 by sputtering. Sputtering is the phenomenon that energetic particles bombard the surface of the target material, causing the target atoms (or molecules) to scatter from the surface. However, sputtering deposition has high requirements on equipment, and requires the use of coating chambers, magnetron sputtering targets, vacuum systems, gas circuits and even water cooling systems, and the production cost is relatively high.

[0050] A method for loading gas-sensitive catalytic materials for high-performance gas sensors, based on the above-mentioned loading system, can use electrochemical deposition to deposit catalytic particles 8 on the surface where gas-sensitive particles 3 have been deposited. Electrochemical deposition is a process in which a redox reaction occurs at the interface between an electrode and an electrolyte under the action of an electric field and the product is deposited on the working electrode. Cations in the solution are usually precipitated and adsorbed on the cathode surface by cathode electrodeposition. Under appropriate deposition voltage (current) conditions, molecules or atomic groups that are easily reduced in the solution, under certain conditions such as temperature, pH value and electrolyte concentration, deposit corresponding particles on the cathode surface. After electrolysis continues for a period of time, the particles are adsorbed into agglomerates to form a thin film covering the cathode. Compared with other preparation methods, the electrochemical deposition method has certain advantages. It can be operated at a lower temperature and has a faster deposition rate. It can grow materials on substrates with complex morphology. The material growth temperature is low and materials with different microstructures can be obtained by regulating electrochemical parameters.

[0051] Specifically, the steps of loading the catalytic particles 8 are as follows:

[0052] S1: The single-pass porous alumina template with gas-sensitive particles 3 deposited on the surface is used as a cathode and immersed in an electrolyte containing catalytic particles 8 for a first time, and catalytic particles 8 with a first dispersion density are deposited on the surface of the gas-sensitive particles 3; wherein the first time should be controlled to be less than the time required for the catalytic particles 8 to precipitate and form a film from the surface of the gas-sensitive particles 3, and the first dispersion density is the dispersion density of the catalytic particles 8 on the surface of the gas-sensitive particles 3 only when the reaction time lasts for the first time. The reaction process that exceeds the time required for the catalytic particles 8 to precipitate and form a film from the surface of the gas-sensitive particles 3 will form a metal film structure that completely covers the gas-sensitive particles 3 on the surface of the gas-sensitive particles 3, so that the gas-sensitive particles 8 cannot adsorb or are difficult to adsorb the gas molecules to be detected for detection.

[0053] S2: Immerse at least a portion of the single-pass porous alumina template with catalytic particles 8 deposited on the surface, including the nanotube orifice, in the same electrolyte for a second time to encourage the formation of a second dispersed density of catalytic particles 8 at the nanotube orifice; wherein the sum of the second time and the first time is less than the time required for the catalytic particles 8 to precipitate and form a film on the surface of the gas-sensitive particles 3, and the second dispersed density refers to the dispersed density of the catalytic particles 8 on the surface of the gas-sensitive particles 3 when the reaction time lasts for the sum of the first time and the second time, wherein the second dispersed density is greater than the first dispersed density.

[0054] The catalytic particles 8 at the first dispersion density are used to contact the gas-sensitive particles 3 and significantly improve the gas-sensitive performance of the gas-sensitive particles 3. The catalytic particles 8 at the second dispersion density are directly in contact with the sensing electrode 1 at least at the nanotube orifice position, and encourage the gas-sensitive particles 3 to form an ohmic contact with the sensing electrode 1 based on the catalytic particles 8. By increasing the dispersion density of the catalytic particles 8 deposited at the nanotube orifice, the sensing electrode 1 can have more points for ohmic contact with the gas-sensitive particles 3. Further, the gas-sensitive particles 3 at the nanotube orifice position are directly electrically connected to the sensing electrode 1 based on the catalytic particles 8, so that the changes in the electrical properties of the gas-sensitive particles 3 at the nanotube orifice when the sensing reaction occurs can be conducted to the sensing electrode 1 more quickly than the gas-sensitive particles 3 on the inner wall of the nanotube, and the gas-sensitive particles 3 at the nanotube orifice position often preferentially contact the gas-sensitive particles 3 when the sensor detects the gas molecules to be detected. The nanotube orifice position of the catalytic particles 8 with the second dispersion density can more quickly react with the gas molecules to be detected and accurately transmit the changes in electrical parameters in the sensing process based on the sensing electrode 1 in ohmic contact with the catalytic particles 8.

[0055] According to a preferred embodiment, the catalytic particles 8 can also be loaded on the surface of the gas-sensitive particles 3 by spin coating. Specifically, the method of loading the catalytic particles 8 in the alumina template on which the gas-sensitive particles 3 have been deposited is as follows:

[0056] A1. Chemical bath deposition precursor solution configuration: dissolving a compound capable of obtaining catalytic particles 8 based on a reaction in an alcohol solution;

[0057] A2, catalytic particle deposition: based on the precursor liquid, a hydrothermal method is used to grow catalytic particles 8 on the surface of the layer structure formed by the gas-sensitive particles 3;

[0058] A3. Spin coating is used to disperse the catalytic particles 8 on the alumina template onto the surface of the gas-sensitive particles 3.

[0059] Catalytic particles 8 are grown on the surface of the gas-sensitive particles 3 using a precursor liquid, and the alumina template is rotated during a single growth process so that the catalytic particles 8 cannot agglomerate to form large-sized particles during the growth process. Specifically, after the single-pass porous alumina template is completely immersed in the precursor liquid and pulled once, it is dried at a condition not higher than 100 degrees Celsius (preferably 80 degrees Celsius) for half an hour. During the drying process, the single-pass porous alumina template is rotated so that the catalytic particles 8 are evenly dispersed on the surface of the gas-sensitive particles 3. There are three ways to control the rotation of the single-pass porous alumina template: the first way: the rotation of the single-pass porous alumina template is controlled by taking the axis of rotation parallel to any nanotube axis on the single-pass porous alumina template, wherein the nanotube orifice is facing downward; the second state: the rotation of the single-pass porous alumina template is controlled by taking the straight line perpendicular to any nanotube axis as the axis of rotation; the third state: the rotation of the single-pass porous alumina template is controlled by taking any straight line that is neither parallel to nor perpendicular to the axis of the nanotube as the axis of rotation;

[0060] When the single-pass porous alumina template rotates in the first mode, due to the centrifugal force, the catalytic particles 8 will be self-calibrated and arranged and evenly distributed on the surface of the gas-sensitive particles 3. The alcohol solution as a solute can be quickly discharged from the nanotube due to its low density, further accelerating the deposition of the catalytic particles 8. After the catalytic particles 8 are dispersed, the excess catalytic particles 8 and the alcohol solution will be thrown out from the tube mouth at one end of the nanotube under the action of gravity during the deposition process, avoiding the problem of agglomeration of catalytic particles 8 in the nanotube causing a larger diameter. Preferably, in order to avoid the torque of nanotubes at different positions having a greater impact on the deposition of catalytic particles 8, the axis of the nanotube as close to the middle position as possible should be selected as the axis of rotation for rotation, thereby reducing the dispersion difference between the nanotubes with the minimum torque and the maximum torque.

[0061] When the single-pass porous alumina template in the second mode rotates, the centrifugal force on the catalytic particles 8 is directed to the two ends of the nanotube, and the catalytic particles 8 will slide on the nanotube wall toward the nanotube mouth in a direction parallel to the axis of the nanotube. The catalytic particles 8 will be evenly distributed along the direction parallel to the axis, but unevenly distributed in the circumferential direction around the inner wall of the nanotube.

[0062] When the double-pass porous alumina template in the third mode rotates, due to the difference in torque at different positions in a single nanotube, the catalytic particles 8 at different positions on the nanotube are subjected to different forces, and satisfactory and uniform catalytic particles cannot be obtained on the surface of the gas-sensitive particles 3. In addition, the alcohol solution cannot be discharged smoothly from the nanotube.

[0063] The use of the spin coating method can prevent the catalytic particles 8 from agglomerating during the deposition process, so that small-sized catalytic particles 8 are finally obtained. The small-sized catalytic particles 8 allow the unit area of ​​the surface of the gas-sensitive particles 3 to accommodate more catalytic particles 8, so that the surface of the gas-sensitive particles 3 has more reactive sites, thereby promoting the gas-sensitive reaction rate of the gas-sensitive particles 3. The first method under the spin coating method used in the present invention during the deposition film formation process can form small-sized and evenly distributed catalytic particles 8. The small-sized catalytic particles 8 have a large specific surface area and are easy to adsorb gas molecules, further increasing the reaction sensitivity and sensing efficiency of the gas-sensitive particles 3. Furthermore, the small-sized gas-sensitive particles 3 can reduce the impact of the space occupied by the gas-sensitive particles 3 on the adsorption of gas molecules to be detected.

[0064] According to a preferred embodiment, when a double-pass porous alumina template is used to implement a spin coating method. Under the action of centrifugal force, the precursor liquid under the first method forms evenly distributed high-quality catalytic particles 8 on the surface of the gas-sensitive particles 3. At this time, the excess catalytic particles 8 and alcohol solution required will be discharged from the nanotube orifice. The catalytic particles 8 under the second and third methods are poorly dispersed, unevenly distributed and easily agglomerated to form large-sized particles. Therefore, for the double-pass porous alumina template, the spin coating method under the first method can also obtain small-sized and evenly dispersed catalytic particles 8.

[0065] According to a preferred embodiment, by controlling the rotation speed during the spin coating method, the agglomeration tendency and dispersion effect of the catalytic particles 8 can be controlled. For example, the agglomeration tendency of the catalytic particles 8 at a high rotation speed is greatly restricted, and they cannot aggregate to form a large-sized particle aggregate that affects the response sensitivity of the gas-sensitive particles 3, and the catalytic particles 8 can be evenly dispersed to the surface of the layer structure formed by the gas-sensitive particles 3 under the action of centrifugal force. However, the aggregation tendency between the catalytic particles 8 at a low rotation speed is less restricted or unrestricted, and they can aggregate during the deposition process, and the aggregation tendency is controlled by the rotation speed, and the distribution effect is also related to the rotation speed.

[0066] It should be noted that the above specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention description and its drawings are illustrative and do not constitute a limitation of the claims. The protection scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for loading gas-sensitive catalytic materials for high-performance gas sensors, characterized in that: include: Chemical bath deposition precursor solution configuration: dissolving two or more compounds capable of obtaining catalytic particles (8) based on a reaction in an alcohol solution; Catalytic particles (8) deposition: Based on the precursor liquid, a single-pass porous alumina template with gas-sensitive particles (3) deposited on the surface is used as a cathode and immersed in an electrolyte containing the catalytic particles (8) for a first time by a hydrothermal method, and catalytic particles (8) with a first dispersion density are grown on the surface of the layer structure formed by the gas-sensitive particles (3), wherein the first time is controlled to be less than the time required for the catalytic particles (8) to precipitate from the surface of the gas-sensitive particles (3) to form a film, and the first dispersion density refers to the dispersion density of the catalytic particles (8) on the surface of the gas-sensitive particles (3) when the reaction time lasts for the first time; and Immersing at least a portion of the single-pass porous alumina template with the catalytic particles (8) deposited on the surface thereof, including the nanotube orifice, in the same electrolyte for a second time, encouraging the formation of the catalytic particles (8) with a second dispersed density at the nanotube orifice, wherein the sum of the second time and the first time is less than the time required for the catalytic particles (8) to precipitate and form a film on the surface of the gas-sensitive particles (3), and the second dispersed density refers to the dispersed density of the catalytic particles (8) on the surface of the gas-sensitive particles (3) when the reaction time lasts for the sum of the first time and the second time; wherein the second dispersion density is greater than the first dispersion density; The gas-sensitive particles (3) are arranged on the inner wall of the nanotubes and the surface layer of the nanotube pores of the alumina template by adsorption deposition, and the spin coating method under the first method encourages the catalytic particles (8) to be evenly dispersed on the surface of the layer structure and limits the agglomeration tendency of the catalytic particles (8). The spin coating method under the first method refers to controlling the rotation of the porous alumina template based on a straight line parallel to the axis of any nanotube on the porous alumina template as a rotation axis, so that the catalytic particles (8) are dispersed and deposited on the surface of the layer structure under the action of centrifugal force, and the excess catalytic particles (8) and the alcohol solution after dispersion are discharged from the tube mouth of the nanotube under the action of their own gravity.

2. A high performance gas sensor, characterized in that: It includes the following parts stacked from top to bottom: A sensing electrode (1), which is arranged at the top of the entire sensor and is used to transmit an electrical signal when the sensor has a sensing reaction; The sensing layer (2) prepared by the method for loading gas-sensitive catalytic materials for high-performance gas sensors according to claim 1 is arranged on the bottom layer of the sensing electrode (1) in a manner of at least partially vertically overlapping with the sensing electrode (1), and has gas-sensitive particles (3) for sensing reactions with the gas to be detected; An isolation layer (4), which is arranged on a side of the sensing layer (2) opposite to the sensing electrode (1) and is used to uniformly and stably transmit heat required for the gas-sensitive particles (3) to generate a sensing reaction to the sensing layer (2); A heating layer (5) is arranged at the bottom of the isolation layer (4) and is used to provide heat to the sensing layer (2), and the heat can be evenly conducted to the sensing layer (2) after being blocked by the isolation layer (4); a support layer (6), which is arranged on a side of the heating layer (5) opposite to the isolation layer (4) and is used to prevent the heat generated by the heating layer (5) from being dissipated from the side located on the support layer (6); and The substrate (7) is arranged at the bottom layer of the entire sensor structure and serves as a carrier structure for carrying all the above layer structures.

3. The high performance gas sensor according to claim 2, characterized in that: A sensing electrode (1) is deposited on the sensing layer (2) formed by the gas-sensitive particles (3), the catalytic particles (8) and the porous alumina template, and the sensing electrode (1) is electrically connected to the layer structure formed by the gas-sensitive particles (3), so that the change in the electrical properties of the gas-sensitive particles (3) when a sensing reaction occurs can be conducted based on the sensing electrode (1).

4. The high performance gas sensor according to claim 3, characterized in that: The sensing electrode (1) comprises at least a pair of structurally matched interdigital electrodes (11), the interdigital electrodes (11) being centrally symmetrically arranged on the porous alumina template without contact, and the interdigital electrodes (11) being electrically connected to the gas-sensitive particles (3) on the surface of the porous alumina template.

5. The high performance gas sensor according to claim 3, characterized in that: The isolation layer (4) is arranged between the heating layer (5) and the sensing layer (2), and a heating electrode hole (42) is reserved on the isolation layer (4) for leading the heating layer (5) to an external heating power source.

6. The high performance gas sensor according to claim 5, characterized in that: The device further comprises a heating layer (5), wherein the heating layer (5) comprises a heating electrode (51) and a thermal resistance wire (53), wherein the heating electrode (51) is electrically connected to the thermal resistance wire (53) via a connecting wire (52), and the shape of the heating electrode (51) matches the heating electrode hole (42), so that the heating electrode (51) can be arranged in the heating electrode hole (42) in a nested manner and maintain electrical connection with the external heating power source.

7. The high performance gas sensor according to claim 2, characterized in that: The substrate (7) is provided with a groove hole (71) penetrating from top to bottom, the groove hole (71) is in the shape of a triangle with a stable structure, and the substrate (7) is used to improve the physical strength of the sensor.

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