A high responsivity gas sensor gas sensitive particle loading method and system

Abstract

The application relates to a high-response gas sensor gas-sensitive particle loading system and method, wherein the method comprises the following steps: chemical bath precursor solution configuration: at least two or more compounds capable of obtaining gas-sensitive particles based on a reaction are dissolved in an alcohol solution; supernatant of the precursor solution is removed under a heating condition to increase the concentration of the gas-sensitive particles; gas-sensitive particle film deposition: a gas-sensitive particle film is grown on an alumina template based on the precursor solution by using a hydrothermal method; and a spin coating method under the first method encourages the gas-sensitive particles on the alumina template to form a gas-sensitive particle film with small-sized gas-sensitive particles and uniform film thickness distribution. The application limits the agglomeration of the gas-sensitive particles in the deposition process by using the spin coating method, and the excess gas-sensitive particles and the alcohol solution are discharged from the nanotube orifice under the action of centrifugal force, the film forming process is accelerated, and the deposition process of the gas-sensitive material can be carried out under a lower temperature condition, so that heat loss in the loading process is reduced.

Description

Technical Field

[0001] This invention relates to the field of sensor devices, and more particularly to a method and system for loading gas-sensitive particles into a high-response gas sensor. Background Technology

[0002] With the development of the times, the gaseous environment people encounter in modern life and production is becoming increasingly complex, making the detection of various toxic and harmful gases that are not easily detected by people increasingly important. Since the last century, researchers at home and abroad have devoted considerable effort to studying how to detect whether various hazardous gases have leaked or exceeded standards. Based on a large number of research results, gas sensors have emerged.

[0003] After decades of rapid development, gas sensors are no longer limited to detecting toxic and harmful gases. Their applications have expanded from initial safety detection to various aspects closely related to daily life, such as detecting gases like trimethylamine and ethyl acetate related to food freshness, and detecting alcohol content in drunk drivers. As the applications of gas sensors have become more widespread, people have begun to focus on improving their performance. Typically, the selectivity of a gas sensor for different gases, its sensitivity to specific gases, and its long-term stability are important indicators for evaluating its gas-sensing performance. Furthermore, considering the practical application of gas sensors in real life, the design process also needs to consider whether the sensor has practical value, a suitable cost-performance ratio, and the feasibility of large-scale production. Through long-term scientific research, metal-oxide-semiconductor (MOS) gas sensors have emerged as one of the most widely used gas sensors among various types.

[0004] Existing technology, such as patent document CN112730527A, discloses a gas detection system based on a MEMS gas sensor array, including: a MEMS gas sensor array, a time-division multiplexed multi-channel resistance-to-frequency conversion circuit, a programmable heater circuit, an EEPROM, a trimmable on-chip oscillator, a power-on self-reset circuit, and a digital control circuit; the MEMS gas sensor array includes multiple gas sensors; the gas sensors include heater resistors and gas-sensitive particle resistors; wherein, the MEMS gas sensor array is used to convert gas information in the environment into changes in the resistance of gas-sensitive particles; the multi-channel resistance-to-frequency conversion circuit is used to convert the resistance value of the gas-sensitive particles of the selected channel into a square wave signal of the corresponding frequency; the on-chip oscillator is used to generate a stable clock signal required by the system.

[0005] Chinese patent CN110455875B discloses a gas-sensitive particle and a gas sensor, and a method for preparing the same. The gas-sensitive particle includes an aqueous solution of black phosphorus for primary deposition and a benzyl viologen solution for secondary deposition. The gas sensor includes an interdigitated electrode with gas-sensitive particles deposited on its surface, thereby forming a benzyl viologen-doped black phosphorus gas-sensitive film on the interdigitated electrode. The structure of the gas-sensitive film is as follows: black phosphorus partially covers the interdigitated electrode, and a portion of benzyl viologen connects the black phosphorus and the interdigitated electrode, forming a circuit for transferring electrons from benzyl viologen to black phosphorus; furthermore, a portion of benzyl viologen covers some high-energy adsorption sites on the surface of the black phosphorus. A method for preparing a gas sensor involves depositing black phosphorus on an interdigitated electrode and then depositing benzyl viologen a second time, thereby doping the black phosphorus with benzyl viologen.

[0006] The aforementioned prior art proposes a technical solution of placing gas-sensitive particles in a high-temperature environment to detect target gases. However, during the deposition process, the gas-sensitive particles are prone to agglomeration due to van der Waals forces. This agglomeration prevents the internal gas-sensitive particles from participating in the reaction, reducing the recognition ability of the gas-sensitive particles and resulting in low detection efficiency.

[0007] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0008] To address at least some of the shortcomings of the prior art, this application provides a method for loading gas-sensitive particles into a high-response gas sensor. The loading method includes at least the following steps: preparation of a chemical bath deposition precursor solution: dissolving at least two or more compounds capable of generating gas-sensitive particles based on a reaction in an alcohol solution; removing the supernatant of the precursor solution under heating conditions to increase the concentration of gas-sensitive particles; gas-sensitive particle film deposition: growing a gas-sensitive particle film on an alumina template using a hydrothermal method based on the precursor solution; and encouraging the formation of a gas-sensitive particle film with small-sized particles and uniform film thickness distribution on the alumina template using a spin-coating method based on the first method. This invention forms gas-sensitive particles in an alcohol solution, avoiding the problems of large particle size, poor stability, and small surface area of ​​gas-sensitive particles formed in traditional water-based methods. Furthermore, the gas-sensitive particle loading process in this invention has lower environmental temperature requirements and does not require the high-temperature loading methods of traditional loading processes, thus saving energy and offering high practicality. Furthermore, choosing non-toxic ethanol as the solute reduces the use of toxic and harmful substances during the loading process, further improving the safety of the loading process.

[0009] Preferably, removing the supernatant of the precursor solution encourages the spherical gas-sensitive particles to increase their collision frequency under heating conditions, thereby forming rod-shaped gas-sensitive particles with polar crystal planes at both ends. Removing the supernatant increases the number of seed crystals per unit volume, thus suppressing the overgrowth of the rod-shaped gas-sensitive particles. This invention encourages the formation of more rod-shaped gas-sensitive particles with ±(0001) crystal planes and superior gas-sensing performance, achieving optimal gas-sensing performance. Furthermore, concentration suppresses the aggregation of gas-sensitive particles into large-sized particles, ensuring that as many gas-sensitive particles as possible are small-sized, highly sensitive particles unaffected by contact barriers.

[0010] Preferably, the spin coating method in the first method refers to controlling the rotation of the porous alumina template by using a straight line parallel to the axis of rotation of any nanotubes on the template. This allows the gas-sensitive particles to deposit on the inner wall of the nanotubes under centrifugal force, forming a gas-sensitive particle film. Gas-sensitive particles that cannot form a film and the alcohol solution are discharged from the nanotube opening under centrifugal force. In this invention, spin coating is used to control the uniform formation of a film of gas-sensitive particles on the inner wall of the nanotubes. Furthermore, the spin coating method in the first method can prevent the gas-sensitive particles from agglomerating during film formation, ensuring that the gas-sensitive particles maintain a small morphology and are deposited on the inner wall of the nanotubes. Excess gas-sensitive particles and alcohol solution that fail to form a film are discharged from the nanotube opening under their own gravity, further accelerating the film formation process. Furthermore, to avoid the significant impact of the torque of nanotubes at different positions on the film formation process, the axis of rotation of the nanotube closest to the center is selected, thereby reducing the film formation difference between nanotubes with minimum and maximum torque.

[0011] Preferably, small-sized gas-sensitive particles possess extremely small grain size, large specific surface area, and a large number of unsaturated bonds, enabling the gas-sensitive particle film formed by these particles to adsorb gas molecules and exhibit a response sensitivity dependent on the particle size, which increases as the particle size decreases. Grains with a grain size greater than twice the Debye length are considered large-sized grains. In this case, the gas-sensing performance of the material mainly depends on the grain boundary barrier height and is independent of the grain size. When the grain size shrinks to approximately twice the Debye length, a contracting conductive channel is formed within the grain due to the presence of an electron depletion layer around the neck. The conductivity of the material is then related to the cross-sectional area of ​​this conductive channel. The electron depletion layer changes with different atmospheres; therefore, variations in the electron depletion layer thickness and the grain boundary barrier height both affect the gas-sensing performance. When the grain size is less than twice the Debye constant, the electron depletion layer extends throughout the entire grain, causing the conductive channel to disappear and the resistivity of the material to decrease significantly. In this case, the gas-sensing performance also improves as the grain size decreases. Spin coating can prevent the gas-sensitive particles from agglomerating during the deposition process, so that the gas-sensitive particles on the nanotube film are mostly composed of small-sized gas-sensitive particle grains.

[0012] Preferably, a first electrode and a second electrode are deposited on the sensing layer formed by the gas-sensitive particles and the porous alumina template. The first electrode and the second electrode are electrically connected to the gas-sensitive particle film, so that the change in electrical properties when the gas-sensitive particles undergo a sensing reaction can be conducted based on the first electrode and the second electrode.

[0013] Preferably, the sensing layer includes functional areas and non-functional areas, which are connected by a suspension, and the shape of the non-functional areas matches the first electrode and the second electrode.

[0014] Preferably, the loading method further includes setting a heating layer and an isolation layer. The isolation layer is set between the heating layer and the sensing layer. The isolation layer can transfer the heat generated by the heating layer to the functional area in a uniform conduction manner. The isolation layer has reserved heating electrode holes for the heating layer to be led out 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 via a connecting wire. The shape of the heating electrode matches the heating electrode hole, so that the heating electrode can be nested in the heating electrode hole and maintain electrical connection with an external heating power supply. The heating area formed by the meandering thermal resistance wire matches the shape of the functional area, so that the thermal resistance wire can heat the functional area as a whole.

[0016] A high-response gas sensor gas-sensitive particle loading system is disclosed, wherein the gas-sensitive particles are deposited on the inner wall of a porous alumina template by spin coating according to the first method to form a gas-sensitive particle film. The gas-sensitive particle film has small-sized gas-sensitive particles and uniform film thickness distribution.

[0017] Preferably, the spin coating method in the first method refers to controlling the rotation of the porous alumina template based on a straight line parallel to the axis of rotation of any nanotube on the porous alumina template, so that the gas-sensitive particles are deposited on the inner wall of the nanotube under the action of centrifugal force to form a gas-sensitive particle film. The gas-sensitive particles that cannot form a film and the alcohol solution are discharged from the opening of the nanotube under the action of centrifugal force. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a top view of the sensing electrode of the present invention;

[0020] Figure 3 This is a schematic diagram of the heating layer of the present invention;

[0021] Figure 4 This is a schematic diagram of the sensor layer partitioning of the present invention;

[0022] Figure 5 This is a flowchart of the gas-sensitive particle loading steps of the present invention.

[0023] List of reference numerals

[0024] 1: First electrode; 11: Interdigitated electrode; 12: Interdigitated region; 13: Interdigitated end; 14: Interdigitated panel; 2: Sensing layer; 21: Functional area; 22: Non-functional area; 23: Suspension; 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: Hole; 8: Second electrode. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a high-response gas sensor gas-sensitive particle loading system (taking a dual-channel porous alumina template as an example). Figure 1 As shown, it can include the following parts stacked from top to bottom:

[0028] The first electrode 1 is located at the very top of the entire sensor and is used to transmit electrical signals when the sensor generates a sensing response.

[0029] The sensing layer 2 is disposed on the bottom layer of the first electrode 1 in such a way that it at least partially overlaps the first electrode 1 vertically, and has sensing particles 3 for sensing reactions with the gas to be detected.

[0030] The second electrode 8, together with the first electrode 1, makes contact electrical connection between the sensing layer 2 and the first electrode 1, so that changes in the electrical properties of the sensing particles 3 can be conducted through the first electrode plate 1 and the second electrode plate 8.

[0031] An isolation layer 4 is disposed on the other side of the second electrode 8 relative to the sensing layer 2, for uniformly and stably transmitting the heat required for the sensing particles 3 to undergo a sensing response to the sensing layer 2.

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

[0033] A support layer 6 is disposed on the side of the heating layer 5 opposite to the isolation layer 4 to prevent the heat generated by the heating layer 5 from being lost from the side located on the support layer 6.

[0034] Substrate 7, which is located at the bottom layer of the entire sensor structure, serves as a carrier structure to support all the layers above.

[0035] According to a preferred embodiment, such as Figure 1 As shown, the first electrode 1 is disposed on the surface of the sensing layer 2, and the second electrode 8 is disposed on the opposite side of the sensing layer 2 relative to the surface. The first electrode 1 and the second electrode 8 are respectively in contact with and electrically connected to the gas-sensitive particles 3 on the sensing layer 2. Under the premise that the voltage across the first electrode 1 and the second electrode 8 is constant, when the gas-sensitive particles 3 come into contact with the gas to be detected that can react with them, a sensing reaction occurs, causing a change in their own resistance, and further changing the current in the circuit. By monitoring the change in current within the circuit, it can be determined whether there is a gas capable of being sensed in the scene where the sensor is located. Preferably, as... Figure 1The first electrode 1 and the second electrode 8 can be composed of a pair of interdigitated electrodes 11 with an interlaced structure. The interdigitated electrodes 11 are arranged vertically without overlapping, and the interdigitated interval 12 between the two interdigitated electrodes 11 is electrically connected to the interdigitated ends 13 of the interdigitated electrodes 11 through the gas-sensitive particles 3 on the sensing layer 2, so that a closed loop is formed between the two interdigitated electrodes 11.

[0036] According to a preferred embodiment, such as Figure 1 As shown, the first electrode 1 and the second electrode 8 are respectively deposited on two vertical surfaces of the sensing layer 2. The sensing layer 2 is preferably a double-perforated porous alumina template, wherein the orifices of the double-perforated porous alumina template face the first electrode 1 and the second electrode 8, respectively. Two interdigitated electrodes 11, formed by interlocking vertically without overlapping, are deposited at the orifice positions on both sides of the double-perforated porous alumina template. The two interdigitated electrodes 11 are electrically connected by being deposited on both sides of the sensing layer 2 and contacting the gas-sensitive particles 3 within the interdigitated interval 12. The gas-sensitive particles 3 within the interdigitated interval 12 include gas-sensitive particles on the surface outside the orifices and gas-sensitive particles deposited on the inner wall of the alumina template within the orifices. Preferably, the interdigitated interval 12 can be any shape conceived by those skilled in the art, matching the contour formed by its mating interdigitated electrodes 11. Here, it is set as a triangle. The two interdigitated electrodes 11 are led out through their respective interdigitated panels 14, which are used to connect to an external voltage source.

[0037] According to a preferred embodiment, the sensing layer 2 is formed from a porous alumina template with gas-sensitive particles 3 deposited on its surface. The porous single-pass alumina template consists of multiple nanotubes connected at both ends, each nanotube having an opening communicating with the outside. Specifically, the double-pass alumina template consists of multiple openings connected at both ends. Common porous double-pass alumina templates have a honeycomb structure, composed of hundreds, thousands, or even tens of thousands of regular hexagonal prism-shaped oxide units. Taking the porous double-pass alumina template as an example, each regular hexagon has a circular channel in the center. The channel size is generally at the nanometer level, and the channel is roughly perpendicular to the surface. The pore size is uniform yet relatively adjustable, resulting in a simple and orderly array structure. This special structure makes the preparation method of the alumina template in a nano-ordered array simple, inexpensive, and suitable for the assembly of various materials. The ratio between the morphology of the material and particles assembled and deposited within the template is closely related to the performance of the nanomaterial. The porous double-pass alumina template can be prepared using a two-step anodic oxidation method. Because this template has the characteristics of high temperature resistance, high strength and monodisperse pore size, this method is an ideal method for preparing nano-alumina materials.

[0038] Preferably, the gas-sensitive particles 3 are nano-zinc oxide materials. Preferably, the gas-sensitive particles 3 can also be tin dioxide or tungsten trioxide, etc. (when a gas comes into contact with the gas-sensitive particles, it can cause changes in the electrical properties of the gas-sensitive particles, such as an increase or decrease in resistance). They are deposited on the inner wall of the nanotubes and the surface of the nanotube pores of the alumina template through adsorption deposition. The alumina template has a high specific surface area, enabling it to contact and adsorb as many gas-sensitive particles 3 as possible and greatly increasing the spread area of ​​the gas-sensitive particles 3, making it easier for the gas molecules to be detected to contact the gas-sensitive particles 3 and react with them.

[0039] According to a preferred embodiment, when the gas-sensitive particle 3 comes into contact with the target gas molecules that can trigger a sensing reaction, the target gas gains or loses electrons due to its oxidizing and reducing properties. This changes the electrical properties of the gas-sensitive particle 3, such as its resistance, and the current flowing through it also changes. Consequently, the magnitude of the current on the sensing electrode 1, which is electrically connected to the gas-sensitive particle 3, also changes. Therefore, by monitoring the degree of current change, it can be determined whether the gas-sensitive particle 3 has come into contact with the target gas molecules that can trigger a sensing reaction. Furthermore, by controlling the temperature environment, the gas-sensitive particle 3 can be controlled to only trigger a sensing reaction with the target molecules that need to be detected.

[0040] The alumina template of the sensing layer 2 can be divided into functional area 21 and non-functional area 22. Functional area 21 and non-functional area 22 are connected by suspension 23. Gas-sensitive particles 3 are deposited on both functional area 21 and non-functional area 22. The shape of functional area 21 is adapted to the shape of sensing electrode 1, so that the shape of functional area 21 can match the interdigitated area 12. Here, the shape of functional area 21 is set as a triangle matching the contour of sensing electrode 1. Non-functional area 22 is used for angular compensation when functional area 21 deforms in a high-temperature environment. Only a single suspension 23 is set to connect with functional area 21 to reduce heat loss of functional area 22. Functional area 21 needs to be at a high temperature when sensing response occurs. Due to the difference in Young's modulus and thermal expansion coefficient of the constituent materials of functional area 21 and sensing electrode 1 and isolation layer 4 stacked on both sides, the surface stress of functional area 21 will increase under high temperature conditions. The stress at the connection with suspension 23 is relatively large, which is prone to cracking and damage. This can be improved by angular compensation. The non-functional area 22, suspension 23, and functional area 21 are integrally formed structures. Preferably, the non-functional area 22, suspension 23, and functional area 21 can be cut and separated from the complete alumina template by cutting.

[0041] According to a preferred embodiment, the sensing current during the sensing response is mainly distributed on the gas-sensitive particles 3, including the gas-sensitive particles on the surface of the alumina pores and within the alumina nanopores. In this invention, the contact surface between the sensing electrode 1 and the sensing layer 2 is the overlapping area of ​​the interdigitated region of the sensing electrode 1 and the functional area of ​​the sensing layer 2. That is, the area where the sensing response occurs is mostly concentrated on the nanopore walls with a high unfolded area, with a small portion located within the interdigitated region of the sensing electrode 1.

[0042] According to a preferred embodiment, an isolation layer 4 is disposed at the bottom of the sensing layer 2 to isolate the sensing layer 2 from the heating layer 5. The isolation layer 4 prevents the gas-sensitive particles 3 from malfunctioning due to excessively rapid temperature changes in the heating layer 5. Excessive temperature changes can lead to large variations in thermal stress and rapid thermal expansion, easily causing material deformation and fracture. The isolation layer 4, while ensuring heat conduction, also maintains electrical isolation between the sensing layer 2 and the heating layer 5. The isolation layer 4 can be formed from a silicon oxide layer structure.

[0043] The isolation layer 4 is provided with a mating functional area 21, a suspension 23, and an interdigital electrode 11 for connecting the wires of the interdigital panel 14 to a first overlapping area 41. For example... Figure 1 As shown, the first overlapping area 41 is formed by cutting away several trapezoids from the isolation layer, where the perpendicular bisectors intersect at a point and the shorter sides face each other. In this invention, the first overlapping area 41 is formed by removing three trapezoids. The triangular region enclosed by the trapezoids matches the shape of the functional area 21, and the area of ​​the triangular region is slightly larger than the area of ​​the functional area 21 to ensure that the functional area 21 is completely within the triangular region. A reserved area is reserved between adjacent trapezoids for matching and overlapping with some of the wires of the suspension 23 and the interdigitated electrode 11.

[0044] According to a preferred embodiment, the heating layer 5 is disposed on the side of the isolation layer 4 opposite 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 via a connecting wire 52. The present invention primarily utilizes the thermal resistance wire 53 to provide the heat source required for the entire sensor's sensing response. The thermal resistance wire 53 is formed by meandering along a triangular region matching the first overlapping area 41 from a material with high resistivity, allowing the thermal resistance wire 53 to have a relatively long length to concentrate heating of the functional area 21 of the sensing layer 2 through the isolation layer 4, given a fixed overall shape. The connecting wire 52 can be made of the same material as the thermal resistance wire 53. Even though the connecting wire 52 generates heat when current passes through it, the relatively long heat-generating length of the thermal resistance wire 53 results in more concentrated heat, thus minimizing the impact of the heat from the connecting wire 52 on the sensing response of the functional area 21. The economic benefits of integrally generating the thermal resistance wire 53 and the connecting wire 52 without needing to select other wires for electrical connection to the thermal resistance wire 53 are the highest, and material waste during manufacturing is saved. The connecting wire 52 is led out to the heating electrode 51 by overlapping it into the reserved area. The heating electrode 51 is preferably rectangular in structure, and has a relatively large area to facilitate electrical connection with a voltage source. The heating electrode 51 is nested in the isolation layer 4 through the reserved heating electrode hole and is disposed on the isolation layer 4, so that one side of the heating electrode 51 is exposed, which facilitates the connection of the voltage source.

[0045] The heat generated by the thermal resistance wire 53 can be collected 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, thus avoiding the functional area 21 from deforming or falling off due to uneven heating and thermal stress imbalance.

[0046] According to a preferred embodiment, a support layer 6 is disposed below the heating layer 5. A second overlapping region 61 is disposed on the support layer 6 corresponding to the first overlapping region 41. The shape and size of the second overlapping region 61 match those of the first overlapping region 41. The second overlapping region 61 serves as a carrier region for the thermal resistance wire 53 when the heating layer 5 is deposited on the support layer 6. The second overlapping region 61 includes three cantilever beams for connecting to the remaining areas of the support layer 6. When the heat generated by the heating layer 5 is transferred to the carrier region, the heat conduction rate of the carrier region through the cantilever beams is relatively slow because the carrier region is only connected by three cantilever beams. This allows the carrier region to concentrate the heat radiated from the heating layer 5 towards the support layer 6, facilitating the temperature of the functional area 21 adapted to the first overlapping region 41 and the second overlapping region 61 to reach the sensing temperature. The support layer 6 can be formed by slotting a silicon nitride or silicon oxide layer structure.

[0047] According to a preferred embodiment, the substrate 7 is located at the bottom layer of the entire sensor device to improve the overall physical strength of the sensor. For example... Figure 1 As shown, the substrate 7 is a cubic structure with a relatively high thickness. A slotted hole 71 is formed on the substrate 7, extending vertically through the entire substrate. In this invention, the slotted hole 71 is shaped as a triangular structure with high stability. Preferably, the shape of the slotted hole 71 can also be square, trapezoidal, or other shapes conceived by those skilled in the art. By slotting the substrate 7, its bending resistance can be increased, further avoiding the risk of the sensor device bending upon impact, thereby further improving the reliability of the sensor device.

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

[0049] A method for loading gas-sensitive particles into a high-response gas sensor, based on the above-mentioned loading system, comprises the following steps when loading gas-sensitive particles 3 into an alumina template:

[0050] S1. Preparation of chemical bath deposition precursor solution: Dissolve the compound that can obtain gas-sensitive particles 3 based on the reaction in an alcohol solution;

[0051] S2. Under heating conditions, the supernatant of the precursor solution is removed to increase the concentration of the gas-sensitive particles 3;

[0052] S3. Deposition of gas-sensitive particle film: Based on the aforementioned precursor solution, a gas-sensitive particle film is grown on an alumina template using a hydrothermal method.

[0053] S4. The gas-sensitive particles 3 on the alumina template are coated onto the alumina template by spin coating.

[0054] The prepared precursor solution is allowed to stand for a period of time, and then the supernatant is removed to encourage the spherical gas-sensitive particles to increase their collision frequency under heating conditions, forming rod-shaped gas-sensitive particles 3.

[0055] Traditionally, when using gas-sensitive particles 3, they are often first formed in water and then deposited onto a carrier surface under high temperature conditions. However, the gas-sensitive particles 3 formed by dissolving in water are relatively large in size and have poor stability. The presence of surfactants on the surface of the gas-sensitive particles reduces their surface area, and they are also highly sensitive to ambient temperature. This invention uses alcohols as precursor solvents, which enhances the polarity of the solute zinc oxide molecules under the dipole interaction of alcohols. Therefore, the interaction between the alcohol solvent and zinc oxide results in a decrease in the electron cloud density and an increase in polarity on the zinc oxide surface. Specifically, the preparation process of the chemical bath deposition precursor solution is as follows (taking zinc oxide as the gas-sensitive particle as an example): Prepare an alcohol solution of Zn(CH3COO)2·2H2O, dissolve it in a water bath, and set it aside; prepare an alcohol solution of NaOH, dissolve it in a water bath, and set it aside. Place the completely dissolved sodium hydroxide alcohol solution in 0°C ice water to cool it to the same temperature, and then magnetically stir it at 0°C, slowly adding an equal volume of zinc acetate alcohol solution to form a transparent zinc oxide suspension. Preferably, the alcohol can be one or a combination of methanol, ethanol, and isopropanol. Furthermore, ethanol has higher reducing power than methanol and isopropanol. Under similar preparation conditions, zinc oxide prepared in ethanol solvent exhibits faster surface charge transfer efficiency, and the preparation process in ethanol has the lowest toxicity. Therefore, ethanol solution can be selected as the alcohol solvent.

[0056] After allowing the zinc oxide sol to stand at a temperature not exceeding 100 degrees Celsius (preferably 70 degrees Celsius), the supernatant is removed using a pipette. Increasing the concentration of the suspension encourages more frequent collisions of the nanosphere-shaped gas-sensitive particles 3 under further heating conditions, thereby generating nanorod-shaped gas-sensitive particles 3. The high concentration of zinc oxide solution increases the number of seed crystals per unit volume, thus inhibiting the excessive growth of nanorods. Further heating the concentrated solution at 70 degrees Celsius to encourage the remaining spherical gas-sensitive particles 3 to further generate rod-shaped nanorods yields a precursor solution containing ZnO nanorods. The rod-shaped nanorods, due to their polar ±(0001) crystal plane, exhibit higher gas-sensing performance, further enhancing the sensor's responsiveness.

[0057] A gas-sensitive particle film is grown on an alumina template using a precursor solution, and the alumina template is rotated during the single film formation process to ensure uniform film formation. Specifically, taking a dual-channel porous alumina template as an example, the template is completely immersed in the precursor solution and then lifted once, followed by drying at a temperature not exceeding 100 degrees Celsius (preferably 80 degrees Celsius) for half an hour. During the drying process, the template is rotated to ensure uniform film formation of the gas-sensitive particle film on the template. This process is repeated multiple times to form a gas-sensitive particle film of the target thickness on the inner wall of the nanotubes. There are three ways to control the rotation of the dual-channel porous alumina template: First, the template is rotated using an axis parallel to any nanotube axis; Second, the template is rotated using a straight line perpendicular to any nanotube axis; Third, the template is rotated using an axis neither parallel nor perpendicular to the nanotube axis.

[0058] In the first method, when the dual-channel porous alumina template rotates, the gas-sensitive material 3 self-aligns and uniformly forms a film on the inner wall of the dual-channel porous alumina due to centrifugal force. The alcohol solution, being a solute, has a low density and is located on the surface of the gas-sensitive particle film, allowing it to be quickly expelled from the nanotubes, further accelerating the film formation of the gas-sensitive particles 3. After the gas-sensitive particle film is formed, excess gas-sensitive particles 3 and alcohol solution, unable to adhere to the inner wall of the porous alumina template during film formation, are ejected from the openings at both ends of the nanotubes under gravity, avoiding uneven film thickness within the nanotubes. Preferably, to avoid significant influence of the torque of nanotubes at different positions on the film formation process, the axis of rotation of the nanotube closest to the center is selected, thereby reducing the film formation difference between nanotubes with minimum and maximum torque.

[0059] In the second method, when the dual-channel porous alumina template rotates, the centrifugal force on the gas-sensitive particles 3 points towards the two ends of the tube. The gas-sensitive particles 3 slide along the nanotube wall towards the tube openings in a direction parallel to the nanotube's axis. A thin film of gas-sensitive particles is formed on the inner wall of the nanotube, uniformly distributed along the axis but unevenly distributed circumferentially around the inner wall. It is worth noting that, due to the uniform temperature inside the tube, excess gas-sensitive particles 3 in the middle section of the nanotube travel a longer distance towards both ends, making them more prone to film formation during this process. This results in the final gas-sensitive particle film having a thickness less in the nanotube sections than the film near the tube openings, further contributing to the uneven deposition of the gas-sensitive particle film on the nanotube.

[0060] In the third method, the dual-channel porous alumina template experiences varying torque at different locations within a single nanotube during rotation. Consequently, the gas-sensitive particles 3 at different positions on the nanotube experience different forces, making it impossible to obtain a satisfactorily uniformly distributed film of gas-sensitive particles on the inner wall of the nanotube. Furthermore, the alcohol solution cannot accumulate on the film of gas-sensitive particles inside the tube, nor can it be smoothly discharged from the nanotube.

[0061] Spin coating avoids the agglomeration of gas-sensitive particles 3 during film formation, resulting in small-sized gas-sensitive particles 3. These small particles are less than twice the Debye length. During gas sensing, oxygen adsorption on the surface of the gas-sensitive particles 3 leads to the formation of a space charge layer. When the size of the formed gas-sensitive particles 3 is close to (or less than) twice the Debye length, the sensitivity response primarily depends on the particle size. The reaction sensitivity increases exponentially with decreasing particle size. However, as the size decreases, van der Waals forces intensify the agglomeration effect between gas-sensitive particles. When these particles agglomerate, internal particles cannot participate in the reaction, thus reducing the recognition ability of the gas-sensitive particles 3. Furthermore, it affects the response speed of the gas-sensitive particle film, non-stoichiometric oxides, and the exposure of high-energy crystal planes. The present invention uses a spin-coating method during the deposition process to form a high-quality rod-shaped nanorod film with small size and uniform thickness distribution. The small-sized gas-sensitive particles have extremely small grain size and large specific surface area, as well as high surface energy and a large number of unsaturated bonds, which can easily adsorb gas molecules, further increasing the reaction sensitivity and sensing efficiency of the gas-sensitive particles 3.

[0062] According to a preferred embodiment, when using a single-channel porous alumina template for spin coating: In the first method, under centrifugal force, the gas-sensitive particles 3 can form a uniform, high-quality gas-sensitive particle film on the inner wall of the nanotube. In this case, the orifice of the single-channel porous alumina template needs to be oriented downwards to facilitate the discharge of excess gas-sensitive particles 3 and alcohol solution. In the second method, the gas-sensitive particles form a film structure with aggregates at one end and uneven thickness at the other end. In the third method, the gas-sensitive particle film formation is poor. Therefore, for a single-channel porous alumina template, the spin coating method in the first method can also obtain a small-sized and uniformly distributed gas-sensitive particle film.

[0063] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention. These solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A method for loading gas-sensitive particles into a high-response gas sensor, characterized in that, include: Two or more compounds that can obtain gas-sensitive particles (3) based on the reaction are dissolved in an alcohol solution to prepare a chemical bath deposition precursor solution. The gas-sensitive particles are zinc oxide. The preparation process of the chemical bath deposition precursor solution is as follows: prepare an alcohol solution of Zn(CH3COO)2·2H2O, dissolve it in a water bath for later use, prepare an alcohol solution of NaOH, dissolve it in a water bath for later use, put the completely dissolved sodium hydroxide alcohol solution into 0 degrees Celsius ice water to cool it to the same temperature, and then stir it magnetically at 0 degrees Celsius and slowly add it to the same volume of zinc acetate alcohol solution to form a transparent zinc oxide suspension. At a temperature not exceeding 100 degrees Celsius, after allowing the transparent zinc oxide suspension to stand, remove the supernatant using a pipette. Gas-sensitive particle film deposition: Gas-sensitive particle films are grown on an alumina template using the aforementioned precursor solution via a hydrothermal method; The gas-sensitive particles (3) on the alumina template are formed into a gas-sensitive particle film composed of gas-sensitive particles (3) by spin coating in the first mode; The first method involves controlling the rotation of the double-pass porous alumina template by using the axis of rotation of any nanotube parallel to the center line of the double-pass porous alumina template.

2. The gas-sensitive particle loading method according to claim 1, characterized in that, During the process of removing the supernatant of the precursor liquid under heating conditions, the heating temperature is set in the following manner: at this heating temperature, the collision frequency of the spherical gas-sensitive particles (3) increases to form rod-shaped gas-sensitive particles (3) with polar crystal planes at both ends. The amount of supernatant removed is set in such a way that the number of seed crystals of the gas-sensitive particles (3) per unit volume is increased, thereby inhibiting the excessive growth of the rod-shaped gas-sensitive particles (3).

3. The gas-sensitive particle loading method according to claim 1 or 2, characterized in that, The spin coating method in the first mode 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, so that the gas-sensitive particles (3) are deposited on the inner wall of the nanotube under the action of centrifugal force to form the gas-sensitive particle film. The gas-sensitive particles (3) that cannot form a film and the alcohol solution are discharged from the opening of the nanotube under their own gravity.

4. A gas sensor, characterized in that, include: The sensing layer (2) is formed by gas-sensitive particles (3) and a porous alumina template, wherein the porous alumina template has a gas-sensitive particle film composed of the gas-sensitive particles (3); A first electrode (1) and a second electrode (8) are deposited on the sensing layer (2), and the first electrode (1) and the second electrode (8) are electrically connected to the gas-sensitive particle film, so that the change in electrical properties of the gas-sensitive particle (3) when it undergoes a sensing response can be conducted from the first electrode (1) and the second electrode (8). The gas-sensitive particle film is prepared using the gas-sensitive particle loading method as described in any one of claims 1 to 3.

5. The gas sensor according to claim 4, characterized in that, The sensing layer (2) includes a functional area (21) and a non-functional area (22), which are connected by a suspension (23). The shape of the non-functional area (22) is matched to the first electrode (1) and the second electrode (8).

6. The gas sensor according to claim 5, characterized in that, It also includes a heating layer (5) and an isolation layer (4). The isolation layer (4) is disposed between the heating layer (5) and the sensing layer (2). The isolation layer (4) can transfer the heat generated by the heating layer (5) to the functional area (21) in a uniform conduction manner. The isolation layer (4) has reserved heating electrode holes (42) for the heating layer (5) to be led out to an external heating power supply.

7. The gas sensor according to claim 6, characterized in that, The heating layer (5) includes a heating electrode (51) and a thermal resistance wire (53). The heating electrode (51) is electrically connected to the thermal resistance wire (53) through a connecting wire (52). The shape of the heating electrode (51) matches the heating electrode hole (42), so that the heating electrode (51) can be nested in the heating electrode hole (42) and maintain an electrical connection with the external heating power supply. The shape of the heating area formed by the meandering thermal resistance wire (53) matches the functional area (21), so that the thermal resistance wire (53) can heat the functional area (21) as a whole.

8. A high-response gas sensor gas-sensitive particle loading system, configured to perform the gas-sensitive particle loading method according to any one of claims 1 to 3, characterized in that, The system is configured to deposit gas-sensitive particles (3) onto the inner wall of a porous alumina template using a spin-coating method in a first mode to form a gas-sensitive particle film.

9. The gas-sensitive particle loading system according to claim 8, characterized in that, The spin coating method in the first mode 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, so that the gas-sensitive particles (3) are deposited on the inner wall of the nanotube under the action of centrifugal force to form the gas-sensitive particle film. The gas-sensitive particles (3) that cannot form a film and the alcohol solution are discharged from the opening of the nanotube under their own gravity.

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