Gas sensitive material, gas sensor as well as preparation method and application of gas sensor

Abstract

The invention relates to the technical field of gas sensing, and particularly provides a gas sensitive material, a gas sensor and a preparation method and application thereof. The gas sensitive material comprises a functional phase, a binding phase and an organic phase, the functional phase comprises SnO2 and WO3; the binding phase comprises a low-melting-point oxide; the organic phase comprises a high-boiling-point organic solvent. According to the invention, SnO2 and WO3 are mixed as a functional phase, so that the gas sensitive material can meet an appropriate gas detection function; the low-melting-point oxide is used as a binding phase, the sintering temperature is reduced, and the adhesive force is improved; a high-boiling-point organic solvent is used as an organic phase, so that the organic phase fully disperses and envelops powder; the prepared gas sensitive material is stable and reliable, is not easy to settle, can adapt to different dispensing processes, and is small in thickness and high in sensitivity after being transferred to form a film.

Description

Technical Field

[0001] The present invention relates to the field of gas sensing technology, and in particular to a gas sensitive material, a gas sensor, and a preparation method and application thereof. Background Art

[0002] Metal oxide semiconductor gas sensors are a type of gas sensing device that uses a gas-sensitive material to form a film on a suitable substrate and uses the contact between the surface film and the target gas to achieve gas sensing response. The working mechanism of metal oxide semiconductor gas sensors is mainly based on the redox reaction of the gas on the semiconductor surface, which causes the resistance value of the sensitive element to change. At present, the materials used in the processing and manufacturing process of gas sensors based on microsystem devices are difficult to mass produce, and it is difficult to prepare low-thickness gas-sensitive materials during the preparation process.

[0003] Therefore, there is an urgent need to develop a gas sensitive material, a gas sensor, and a preparation method and application thereof. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a gas sensitive material, a gas sensor and a preparation method and application thereof. The gas sensitive material of the present invention has good stability, is not easy to settle, has a small thickness after transfer film formation, and is more conducive to the adsorption and binding of specific gas molecules.

[0005] To this end, the first aspect of the present invention provides a gas sensitive material, comprising: a functional phase, a bonding phase and an organic phase;

[0006] The functional phase includes SnO2 and WO3;

[0007] The bonding phase includes a low melting point oxide;

[0008] The organic phase includes a high boiling point organic solvent.

[0009] The invention provides a gas sensitive material, which includes three-phase components. The invention mixes SnO2 and WO3 as functional phases, so that the gas sensitive material can meet the appropriate gas detection function. The invention uses low-melting-point oxides as bonding phases to reduce the sintering temperature and improve its adhesion. The invention uses high-boiling-point organic solvents as organic phases, so that the organic phase fully disperses and envelops powder. The gas sensitive material of the invention has good stability, is not easy to settle, has a small thickness after transfer and film formation, is more conducive to the adsorption and bonding of specific gas molecules, improves the sensitivity and stability of subsequent gas sensors, and can realize wafer-level mass production of gas sensors based on microsystem devices.

[0010] In some embodiments of the present invention, the mass ratio of the functional phase, the binder phase and the organic phase is (5-7): (0.5-1.5): (2-4).

[0011] In some embodiments of the present invention, the mass ratio of SnO2 to WO3 is (1-20): 1. In some other preferred embodiments of the present invention, the mass ratio of SnO2 to WO3 is 14:1.

[0012] In some embodiments of the present invention, the particle size of SnO2 is 200 to 1000 nm.

[0013] In some embodiments of the present invention, the particle size of WO3 is 200-1000 nm.

[0014] In some embodiments of the present invention, the low melting point oxide includes at least one of bismuth oxide, lead oxide, tin oxide, copper oxide, zinc oxide, calcium oxide, aluminum oxide, iron oxide, sodium oxide, magnesium oxide and chromium oxide.

[0015] In some embodiments of the present invention, the high boiling point organic solvent includes at least one of terpineol, butyl carbitol acetate and dibutyl phthalate.

[0016] In some embodiments of the present invention, the organic phase further comprises a thickener and a dispersant.

[0017] A second aspect of the present invention provides a gas sensor, comprising:

[0018] A micro-hotplate; the upper surface of the micro-hotplate has a detection electrode layer;

[0019] Gas sensitive material layer; the gas sensitive material is arranged on the upper surface of the detection electrode layer.

[0020] When the gas sensor reacts with the gas to be measured, the gas-sensitive material will adsorb and chemically react with the target gas, causing a reversible change in the capacitance or resistance of the gas-sensitive material. By measuring the change in the capacitance or resistance of the gas-sensitive material, the concentration of the gas to be measured can be determined.

[0021] The gas sensor of the present invention can detect gases including hydrogen sulfide, acetone and the like.

[0022] The third aspect of the present invention provides a method for preparing the above-mentioned gas sensor, comprising the following steps: preparing a micro-hotplate; the upper surface of the micro-hotplate has a detection electrode layer; dispensing the above-mentioned gas sensitive material and / or the gas sensitive material obtained by the preparation method of the above-mentioned gas sensitive material on the detection electrode layer; after the dispensing is completed, heat treating the system.

[0023] In some preferred embodiments of the present invention, the heat treatment temperature is 400-600°C and the time is 1-2 hours. The heat treatment sintering and curing of the gas-sensitive material under a temperature-controlled environment ensures that it has good stability and durability in actual use, and is also beneficial to improving the sensitivity and response speed of the gas sensor.

[0024] A fourth aspect of the present invention provides the use of the above-mentioned gas sensor and / or the gas sensor prepared by the above-mentioned method for preparing the gas sensor in detecting hydrogen sulfide or acetone gas.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 A schematic diagram of the dispensing film forming process in the embodiment is shown;

[0028] Figure 2 The structure diagram of the valve seat and valve body and related components of the automatic dispensing machine in the embodiment and the comparative example is shown;

[0029] Figure 3 (a) shows the light microscopic image of the glue spots obtained by batch dispensing in Example 2; Figure 3 (b) shows a characterization diagram of the film thickness of the glue dots obtained by batch dispensing in Example 2;

[0030] Figure 4 shows a SEM image of the gas sensor film in Example 1;

[0031] Figure 5 shows scratch images of the sensors of Example 1 and Comparative Example 1;

[0032] Figure 6 (a) shows a gas film thickness characterization diagram of the gas sensor of Example 3; Figure 6 (b) shows the 20 ppm hydrogen sulfide test gas response graph of the sensor of Example 3;

[0033] Figure 7 (a) shows the 5 ppm hydrogen sulfide test gas response diagram of the gas sensor of Comparative Example 3; Figure 7 (b) shows the 5 ppm hydrogen sulfide test gas response diagram of the gas sensor of Example 3;

[0034] Figure 8The gas response diagram of the hydrogen sulfide gas gradient concentration of the gas sensor of Example 3 and Comparative Example 3 is shown;

[0035] Fig. 9 The gas response diagram of the gas sensor of Example 3 under different gas environments of 5 ppm is shown;

[0036] Fig.10 The gas response diagram of the test of 10 ppm hydrogen sulfide gas in each specific gravity in Example 3 and Comparative Example 1 is shown;

[0037] Fig.11 The gas response diagrams of the 10 ppm hydrogen sulfide gas test in Example 3 and Comparative Example 2 are shown;

[0038] Fig.12 (a) shows the resistance change diagram of the gas sensor of Comparative Example 4 in a 5 ppm hydrogen sulfide test; Fig.12 (b) shows the resistance change graph of the gas sensor of Example 3 in a 5 ppm hydrogen sulfide test. DETAILED DESCRIPTION

[0039] The embodiments of the present disclosure are described in detail below. The embodiments described below are exemplary and are only used to explain the present disclosure, and should not be construed as limiting the present disclosure. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in the art or in the product manual shall be followed.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0042] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0044] The method of synthesizing gas sensitive materials (precursors) was applied in the electronics field as conductive materials in the early 21st century. At present, the method of synthesizing precursors is mainly used in the field of conductive pastes, which mainly consists of three parts: functional phase, bonding phase and organic phase. The functional phase is the main part of the precursor, which enables the precursor to achieve the corresponding functional effect; the bonding phase is a component of the precursor, which can improve the adhesion of the precursor film, making the precursor more reliable after sintering; the organic phase is the main solvent in the precursor, so that the functional phase and the bonding phase can be fully dispersed, which is conducive to better play a role. The precursor has leveling properties during processing, which can better form a conductive film on the surface of the device, and is often used to prepare various types of sensor devices.

[0045] To this end, the first aspect of the present invention provides a gas sensitive material, comprising: a functional phase, a bonding phase and an organic phase;

[0046] The functional phase includes SnO2 and WO3;

[0047] The bonding phase includes a low melting point oxide;

[0048] The organic phase includes a high boiling point organic solvent.

[0049] The invention provides a gas sensitive material, which includes three-phase components. The invention uses a mixed gas of SnO2 and WO3 as a functional phase, so that the gas sensitive material can meet a suitable gas detection function. The invention uses a low melting point oxide as a bonding phase to reduce the sintering temperature and improve its adhesion. The invention uses a high boiling point organic solvent as an organic phase, so that the organic phase fully disperses and envelops the powder. The prepared gas sensitive material is stable and reliable, not easy to settle, can be adapted to different dispensing processes, has a small thickness after transfer and high sensitivity. The gas sensitive material of the invention has better stability, is more conducive to the adsorption and bonding of specific gas molecules, improves the sensitivity and stability of subsequent gas sensors, and can realize wafer-level mass production of gas sensors based on microsystem devices.

[0050] In some embodiments of the present invention, the mass ratio of the functional phase, the binder phase and the organic phase is (5-7): (0.5-1.5): (2-4).

[0051] In some embodiments of the present invention, in the gas sensitive material, the mass fraction of the functional phase is 47% to 73%.

[0052] In some embodiments of the present invention, in the gas sensitive material, the mass fraction of the binder phase is 4% to 17%.

[0053] In some embodiments of the present invention, in the gas sensitive material, the mass fraction of the organic phase is 19% to 40%.

[0054] In some other preferred embodiments of the present invention, the mass ratio of the functional phase, the adhesive phase and the organic phase is 6:1:2.5.

[0055] In some embodiments of the present invention, the mass ratio of SnO2 to WO3 is (1-20): 1. In some other preferred embodiments of the present invention, the mass ratio of SnO2 to WO3 is 14:1.

[0056] In some embodiments of the present invention, the particle size of SnO2 is 200-1000 nm. As an example, the particle size of SnO2 can be 200, 300, 400, 500, 600, 700, 800, 900 or 1000 nm.

[0057] In some embodiments of the present invention, the particle size of WO3 is 200-1000 nm. As an example, the particle size of WO3 can be 200, 300, 400, 500, 600, 700, 800, 900 or 1000 nm.

[0058] In some embodiments of the present invention, the low melting point oxide includes at least one of bismuth oxide, lead oxide, tin oxide, copper oxide, zinc oxide, calcium oxide, aluminum oxide, iron oxide, sodium oxide, magnesium oxide and chromium oxide.

[0059] In some embodiments of the present invention, the binder phase comprises bismuth oxide.

[0060] In some embodiments of the present invention, the high boiling point organic solvent includes at least one of terpineol, butyl carbitol acetate and dibutyl phthalate.

[0061] Butyl Carbitol Acetate is an ester solvent made by the reaction of Butyl Carbitol and acetic acid, with a boiling point of about 245°C. Butyl Carbitol Acetate is a polar solvent with good dissolving power, suitable for dissolving a variety of resins, coatings, inks and certain polymers.

[0062] Dibutyl Phthalate (DBP) is an ester of phthalic acid with a boiling point of about 340°C. Dibutyl Phthalate has high solubility and is usually used as a plasticizer for plastics and rubbers, and is also used to dissolve certain resins and paints.

[0063] In some embodiments of the present invention, the organic phase further comprises a thickener and a dispersant.

[0064] In some embodiments of the present invention, the thickener includes ethyl cellulose. Ethyl cellulose (EC) can effectively increase the viscosity of the liquid in an organic solvent. Ethyl cellulose interacts with solvent molecules to change the rheological properties of the solution, thereby increasing the viscosity of the liquid and playing a thickening role.

[0065] The dispersant includes Siban 85; Siban 85, also known as sorbitan oleate, is a non-ionic surfactant that can help disperse and stabilize solid particles in liquids and prevent aggregation and precipitation of particles.

[0066] In some other preferred embodiments of the present invention, the organic phase comprises terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose and Span 85.

[0067] In other preferred embodiments of the present invention, the mass ratio of pineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose and Span 85 is (2.1-2.6): (1-1.5): (0.2-0.6): (0.3-0.6): (0.2-0.4).

[0068] In some embodiments of the present invention, the method for preparing the above-mentioned gas sensitive material comprises the following steps:

[0069] The functional phase, the binder phase and the organic phase are mixed to obtain a gas sensitive material.

[0070] In some embodiments of the present invention, the functional phase, the adhesive phase and the organic phase are ground before mixing. The grinding process can not only further improve the uniformity of the gas sensitive material, but also ensure that it is suitable for the subsequent dispensing process.

[0071] In some embodiments of the present invention, the functional phase, the binder phase and the organic phase are mixed under stirring; the stirring speed is 1200-1800 rpm / min; the mixing temperature is 65-85°C; and the mixing time is 3.5-5.5h.

[0072] In some embodiments of the present invention, the mixing of the functional phase, the adhesive phase and the organic phase specifically includes: first mixing the functional phase and the adhesive phase, and then mixing with the organic phase.

[0073] In some embodiments of the present invention, the method for preparing the functional phase comprises: mixing SnO2 and WO3 in the presence of a solvent; the solvent may be an organic solvent having a diluting effect, for example, ethanol.

[0074] In some embodiments of the present invention, the method for preparing the organic phase comprises: mixing a high boiling point organic solvent, a thickener and a dispersant; the mixing is carried out under stirring; the stirring speed is 1200 to 1800 rpm / min; the mixing temperature is 65 to 85°C; and the mixing time is 3.5 to 5.5 hours.

[0075] In some embodiments of the present invention, the method for preparing the gas sensitive material comprises:

[0076] S1: Mix the raw materials of the functional phase.

[0077] The mixing includes mechanical mixing. The raw materials of the functional phase include SnO2 and WO3, which together constitute the functional phase in the gas sensitive material. During the application process, the gas sensitive material forms a film and combines specifically with the target gas to produce a change in the film resistance value. The sensing function of the specific gas is achieved by calibrating the degree of the change. The response value and stability of the gas sensor can be improved by uniformly mixing these nanoparticles using a mechanical method.

[0078] S2: Mix the binder phase with the product obtained in S1.

[0079] The mixing includes mechanical mixing. The raw materials of the bonding phase include low melting point oxides; the low melting point oxides constitute the bonding phase in the gas sensitive material. During the application process, the material is transformed into a molten state through heat treatment. The low melting point oxides in the molten state can be tightly combined with the substrate, thereby improving the film-base bonding strength of the gas sensitive material after film formation, thereby improving the stability of the gas sensor.

[0080] In some embodiments of the present invention, the low melting point oxide includes at least one of bismuth oxide, lead oxide, tin oxide, copper oxide, zinc oxide, calcium oxide, aluminum oxide, iron oxide, sodium oxide, magnesium oxide and chromium oxide; further, the binding phase includes bismuth oxide; the bismuth oxide and the product obtained from S1 are uniformly mixed by a mechanical method, and the contraction of the bismuth oxide in the molten state can make the product obtained from S1 form a more effective conductive network, thereby improving the sensing performance of the gas sensor.

[0081] S3: Mix the raw material of the organic phase with the product obtained in S2.

[0082] In some embodiments of the present invention, the organic phase comprises a high boiling point organic solvent.

[0083] In some embodiments of the present invention, the high boiling point organic solvent includes at least one of terpineol, butyl carbitol acetate and dibutyl phthalate.

[0084] In some embodiments of the present invention, the organic phase further comprises a thickener and a dispersant.

[0085] In some embodiments of the present invention, the thickening agent comprises ethylcellulose.

[0086] The dispersant includes Span 85.

[0087] In some embodiments of the present invention, the organic phase includes terpineol, ethyl cellulose, butyl carbitol acetate, dibutyl phthalate, and Span 85.

[0088] In some embodiments of the present invention, the product obtained in S2 is fully stirred and mixed with the organic phase.

[0089] The raw materials for obtaining the organic phase include pinene alcohol, ethyl cellulose, butyl carbitol acetate, dibutyl phthalate and Span 85, which together constitute the organic phase in the gas-sensitive material; the organic phase can disperse and stabilize the product obtained from S2, while improving the process compatibility. The organic phase and the product obtained from S2 are uniformly mixed by stirring, so that the functional phase, the adhesive phase and the organic phase can be mixed to prepare the gas-sensitive material, which ensures the stability of the sensing function and has good process compatibility, thereby realizing the high-volume production and integration of gas sensors.

[0090] In some embodiments of the present invention, it is specifically stated that step S1 comprises:

[0091] S11, weighing SnO2 and WO3 nanoparticles in a preset ratio.

[0092] In this step, the key is to weigh the SnO2 and WO3 nanoparticles in a suitable ratio. This material mixture system is the functional phase in the gas sensitive material, aiming to achieve the gas sensing performance of the final gas sensitive material particles. The correct ratio can ensure that the gas sensitive material has a high response value and selectivity when sensing hydrogen sulfide gas.

[0093] S12, putting the weighed SnO2 and WO3 nanoparticles into a mortar, and mechanically grinding them until the particles are fully mixed and uniform, so as to obtain mixed particles;

[0094] The two metal oxide particles are mixed thoroughly by mechanical grinding to ensure that each particle is evenly distributed in the mixed material to avoid agglomeration of particles, which may lead to differences in sensor performance. Physical grinding allows particles of different materials to be in close contact at the microscopic scale, which helps to form a uniform solid structure and improve the uniformity and repeatability of the material.

[0095] In some embodiments of the present invention, it is specifically stated that step S2 includes:

[0096] S21, weighing a preset proportion of bismuth-based glass powder.

[0097] In this step, the key is to weigh the bismuth glass powder in the right proportion. This material is the binding phase in the gas sensitive material, which is intended to improve the electrical properties of the gas sensitive material and the film-base bonding strength after film formation. The correct proportion can ensure that the gas sensitive material maintains a high film-base bonding strength without sacrificing conductive properties, thereby improving the stability of the gas sensor.

[0098] S22, putting the mixed particles obtained in S1 and the bismuth-based glass powder into a mortar, and mechanically grinding them until the particles are fully mixed and uniform, so as to obtain mixed particles;

[0099] The weighed binder phase and functional phase are thoroughly mixed by mechanical grinding to ensure that each particle is evenly distributed in the mixed powder. The uniform mixing helps the formation of a conductive network. Through physical grinding, the particles of different materials are in close contact at the microscopic scale, which helps to form a gas sensor with high stability in the subsequent sintering step.

[0100] In some embodiments of the present invention, it is specifically stated that step S3 includes:

[0101] S31, weighing a preset proportion of terpineol, ethyl cellulose, butyl carbitol acetate, dibutyl phthalate and Span 85, and stirring and mixing them to obtain a mixed solution.

[0102] In this step, the key lies in the appropriate proportion of the mixed solution components: terpineol, ethyl cellulose, butyl carbitol acetate, dibutyl phthalate and Span 85. After fully mixing until the insoluble ethyl cellulose is completely dissolved, a mixed solution is obtained, which is the organic phase in the gas sensitive material. The specific proportion of these materials in the mixture and after being fully mixed can disperse the powder obtained in S2 to the greatest extent and ensure process compatibility, aiming to achieve the stability of the process and film quality of the final gas sensitive material film.

[0103] S32, stirring and mixing the powder in S2 with the mixed solution to obtain a mixed suspension.

[0104] The weighed binder phase, functional phase and organic phase are fully mixed by stirring to ensure that each substance is evenly distributed in the organic phase to obtain a mixed suspension. The mixed suspension has better rheological properties in terms of rheology, high plasticity in the film-forming process, and higher process compatibility, which helps to form a gas sensor with high stability and mass production in the film-forming process.

[0105] A second aspect of the present invention provides a gas sensor, comprising:

[0106] A micro-hotplate; the upper surface of the micro-hotplate has a detection electrode layer;

[0107] Gas sensitive material layer; the gas sensitive material is arranged on the upper surface of the detection electrode layer.

[0108] When the gas sensor reacts with the gas to be measured, the gas-sensitive material will adsorb and chemically react with the target gas, causing a reversible change in the capacitance or resistance of the gas-sensitive material. By measuring the change in the capacitance or resistance of the gas-sensitive material, the concentration of the gas to be measured can be determined.

[0109] The gas sensor of the present invention can detect gases including hydrogen sulfide, acetone and the like.

[0110] In some embodiments of the invention, the micro-hotplate comprises:

[0111] Quartz substrate;

[0112] A silicon oxide support layer, located on the quartz substrate;

[0113] One or more platinum heating electrode layers, disposed on the silicon oxide support layer, for providing a heating source for controlling the temperature;

[0114] A silicon oxide isolation insulating layer, covering the platinum heating electrode layer, for electrically isolating and protecting the platinum heating electrode layer;

[0115] The platinum detection electrode layer is arranged on the silicon oxide isolation insulating layer and is used to detect the resistance change induced by the gas sensitive material layer.

[0116] A third aspect of the present invention provides a method for preparing the above-mentioned gas sensor, comprising the following steps:

[0117] S100: preparing a micro-hotplate, wherein the upper surface of the micro-hotplate has a detection electrode layer.

[0118] In some embodiments of the invention, the micro-hotplate comprises:

[0119] Quartz substrate;

[0120] A silicon oxide support layer, located on the quartz substrate;

[0121] One or more platinum heating electrode layers, disposed on the silicon oxide support layer, for providing a heating source for controlling the temperature;

[0122] A silicon oxide isolation insulating layer, covering the platinum heating electrode layer, for electrically isolating and protecting the platinum heating electrode layer;

[0123] The platinum detection electrode layer is arranged on the silicon oxide isolation insulating layer and is used to detect the resistance change induced by the gas sensitive material layer.

[0124] In this embodiment, it is specifically described that S100 includes:

[0125] A pre-fabricated micro-hotplate is provided; wherein the micro-hotplate comprises a platinum electrode for detection, an interdigitated electrode for forming an ohmic contact with a sensing layer, and a serpentine electrode for heating.

[0126] Optionally, a pre-prepared micro-hot plate is used, and ultrasonic cleaning is performed in sequence using acetone, ethanol, and deionized water, and then dried with nitrogen gas.

[0127] The pre-prepared micro-hotplate substrate provided is BF33 glass, which contains platinum electrodes for detection, interdigitated electrodes for forming ohmic contact with the sensing layer, and serpentine electrodes for heating; these components provide the necessary foundation for realizing the core sensing function of the gas sensor and are the basic structure for high-response and high-precision detection.

[0128] S200: dispensing the gas sensitive material and / or the gas sensitive material obtained by the preparation method of the gas sensitive material onto the detection electrode layer; after the dispensing is completed, heat-treating the system.

[0129] In some embodiments of the present invention, the gas sensitive material is applied to the electrode layer by dispensing, and sintered under controlled temperature and atmosphere to form a gas sensor. The obtained gas sensor device is packaged.

[0130] In some embodiments of the present invention, the temperature and time of the heat treatment are set according to the final curing degree and sensing performance of the desired gas sensitive material. In some preferred embodiments of the present invention, the temperature of the heat treatment is 400-600°C, the time is 1-2h; the heating rate of the heat treatment is 1-5°C / min. Heat treatment sintering and curing of gas sensitive materials in a temperature-controlled environment ensures that they have good stability and durability in actual use, and is also conducive to improving the sensitivity and response speed of gas sensors.

[0131] In some embodiments of the present invention, after the heat treatment is completed, the system is cooled; in other preferred embodiments of the present invention, the system is cooled to room temperature. In the preparation process of the gas sensor, the cooling step after the heat treatment can stabilize the material, avoid cracks or structural damage caused by too fast temperature changes, and improve the adhesion and structural integrity of the material.

[0132] In some embodiments of the present invention, during the dispensing process, the valve opening time is 0.20-0.50 ms, the piezoelectric frequency is 300-600 Hz, the force is 9-15, and the material chamber temperature is 20-60°C.

[0133] The gas sensitive material is accurately applied to the electrode layer using dispensing equipment to form a sensing layer. The dispensing method can accurately control the position, area and thickness of the sensing layer. Sintering under controlled temperature and atmosphere can make the adhesive in the gas sensitive material melt and the organic phase volatilize, ensuring that it has good stable sensing performance in actual use and improving the stability of the gas sensor. The sintered gas sensor device is transferred using a metal tube shell and package and an adapter board (PCB) to achieve electrical level connection between the gas sensor device and the test platform, which is convenient for subsequent testing of the sensor.

[0134] In this embodiment, specifically, step S200 includes:

[0135] S201: Use a dispensing device to apply the mixed suspension prepared in S3 to a predetermined position of the interdigitating electrode on the micro-hotplate to ensure that the mixed suspension forms an effective ohmic contact with the interdigitating electrode and to ensure uniformity of film formation.

[0136] Optionally, the parts used in the dispensing equipment are ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and blown dry with nitrogen.

[0137] The use of dispensing equipment can accurately control the film formation position and thickness of the material, which is conducive to ensuring the uniformity and mass production of gas sensors; effective film formation can form a uniform and stable sensing layer during the sintering process.

[0138] S202: placing the micro-hotplate having the gas-sensitive material sensing layer in a dry environment, performing a drying process using an infrared lamp, and then controlling the temperature and atmosphere to perform a heat treatment on the micro-hotplate to form a gas sensor device.

[0139] Drying and sintering are aimed at removing the organic phase and the binding phase in the gas sensitive material by increasing the temperature, so that the gas sensitive material forms a stable, uniform, porous gas sensor at the predetermined interdigitated electrode position of the micro-hotplate. The sintering temperature and time need to be optimized according to the boiling point of the organic phase in the gas sensitive material, the initial temperature of the binding phase and the electrical properties of the device. Optimizing the sintering process helps to improve the response value and stability of the gas sensor and achieve better gas sensing.

[0140] S203: Encapsulate the gas sensor device using a metal tube shell and a PCB adapter board to achieve electrical connection.

[0141] The use of metal tube shells and PCB adapter boards to package gas sensor devices can enable the devices to be electrically interconnected with subsequent test platforms, thereby achieving data transmission and testing.

[0142] During the preparation of metal oxide semiconductor gas sensors, the transfer method of the gas sensor will greatly affect the quality of the gas sensor. In the film transfer process, the current traditional uniform coating and manual coating are unable to meet the film formation requirements of highly integrated MEMS devices due to their limited film forming accuracy. The mainstream film forming processes are screen printing and soft lithography guidance. Screen printing uses a mesh-like printing plate to pre-form the required material pattern on the template. During printing, the mesh holes of the patterned part of the printing plate are transparent to the material, while the mesh holes of the non-patterned part are not transparent to the material. During printing, the material is poured into one end of the printing plate, and a certain pressure is applied to the material part on the printing plate with a scraper, while moving toward the other end of the printing plate. During the movement, the material is squeezed from the mesh holes of the patterned part to the substrate by the scraper. The screen printing process can efficiently and batch-transfer the film, but the existing screen printing process in China has low precision. When the printing line width is reduced to 50μm, the line edge will be blurred and overflow will occur. The screen printing process cannot meet the requirements of miniaturization and high integration of gas sensors based on microsystem devices, and the contact film formation has a destructive effect on the device itself based on the microsystem device. Soft lithography technology uses a flexible engraved soft mold made of a flexible polymer material, and then uses hot pressing and other methods to transfer the prefabricated material pattern to the bottom of the mold, and then transfers the mold to the top of the substrate, aligns it and slowly presses it down, and transfers the pattern on the prefabricated template to the required substrate surface to form a thin film to complete the film transfer. This method can achieve high-precision and high-integration film transfer of gas-sensitive materials, but the soft mold of soft lithography technology is expensive, the material to mold pattern transfer process is difficult to control, the overall process flow is long, the process is complicated, and the soft mold needs to be replaced every time the pattern is changed, which is not suitable for mass production.

[0143] The present invention utilizes dispensing to perform film transfer in the preparation process of the gas sensor. The dispensing process can be mass-produced in the high-precision, high-sensitivity in-situ film-forming process, and the process flow is simple and easy to operate, and it is suitable for in-situ film-forming processing of gas sensors based on microsystem devices. Dispensing is a film-forming method that utilizes a jet valve dispensing machine to spray sensitive materials onto the surface of a substrate for non-contact film formation. The jet valve dispensing machine is mainly composed of a valve body and a valve seat, wherein the valve body is composed of a retaining ring, a sealing ring, a top screw, a striker and a valve body base; the valve seat is composed of a control line, a Luer connector, a piezoelectric drive assembly, and a non-contact ceramic valve seat. The working mechanism of the jet valve dispensing machine is to first send the material into the valve body and valve seat through the Luer connector, and use the control line to transmit high and low level signals to control the piezoelectric drive component. When the piezoelectric drive component receives a high level signal, it lifts up and drives the striker to lift up. When the piezoelectric drive component receives a low level signal, it drops and drives the striker back. The striker pushes the material and the valve body base opens at the same time, so that the material is sprayed out of the valve body and the valve seat and attached to the substrate surface. At the same time, the mechanical structure controls the precise movement of the valve body so that the sensitive material is uniformly and stably filmed in the material attachment area of ​​the gas sensor micro-hot plate based on the micro-system device. The dispensing film forming process is completed. The schematic diagram of the dispensing film forming process is shown in the figure. Figure 1 , the structure diagram of valve seat, valve body and related parts is as follows Figure 2 ,in Figure 2 (a) is the valve seat structure diagram, Figure 2 (b) is a structural diagram of the valve body and related components. This dispensing process can reduce the thickness of the gas sensor, improve the gas sensing performance of the gas sensor, and greatly increase the yield rate, thus realizing mass production of gas sensors.

[0144] In view of the fact that the current production of gas sensors is difficult in batches, the present invention analyzes that the key technology is the in-situ film formation and transfer of gas sensors. The film is formed on the gas sensor substrate in a non-contact manner through an automatic dispensing process, which optimizes the film formation stability of the gas-sensitive material, thereby achieving high-quality in-situ film formation of the gas-sensitive material and batch production of in-situ film formation.

[0145] In some embodiments of the present invention, during processing, the functional phase is fully mechanically mixed; the bismuth-based glass is then fully mechanically mixed with the above-mentioned mixed particles; pineneol, ethyl cellulose, butyl carbitol acetate, dibutyl phthalate and Span 85 are fully stirred and mixed to obtain a mixed solution; the mixed solution is fully mixed with the mixed powder to obtain a gas sensitive material, which is applied to a pre-prepared electrode layer by dispensing, and sintered under controlled temperature and atmosphere to form a gas sensor and packaged; the gas sensitive material is prepared by a three-phase mixing method and applied to the sensor substrate by dispensing, thereby improving the response value and stability of the gas sensor, increasing the process compatibility of the gas sensor, and realizing high-volume and high-integration production of the gas sensor.

[0146] A fourth aspect of the present invention provides the use of the above-mentioned gas sensor and / or the gas sensor prepared by the above-mentioned method for preparing the gas sensor in detecting hydrogen sulfide or acetone gas.

[0147] The scheme of the present disclosure will be explained below in conjunction with the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in the field or the product instructions shall be followed. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially. The bismuth oxide used in the embodiments of the present invention and the comparative examples is produced by Anmi Micro-Nano New Materials (Guangzhou) Co., Ltd., with a purity of 98%.

[0148] Example 1

[0149] The method for preparing the gas sensor of this embodiment specifically includes the following steps:

[0150] (1) Preparation process of gas sensitive materials:

[0151] The gas sensitive material of this embodiment adopts a three-phase mixing process, and the three phases are a functional phase, a bonding phase and an organic phase.

[0152] The functional phases are SnO2 and WO3 powders, the particle size of SnO2 is 500nm, and the particle size of WO3 is 500nm; 7g WO3 powder and 0.5g SnO2 powder are respectively measured, placed in a mortar, and a proper amount of ethanol is added for grinding to mix the powders thoroughly and evenly. After all the ethanol is evaporated, the mixed powder is collected as the functional phase.

[0153] The binder phase is bismuth oxide.

[0154] The main components of the organic phase are organic solvent, thickener, plasticizer, and dispersant; in this embodiment, terpineol is used as an organic solvent; ethyl cellulose is used as a thickener; butyl carbitol acetate and dibutyl phthalate are used as plasticizers; and Span 85 is used as a dispersant. First, 0.3g of ethyl cellulose is measured and placed in an empty beaker, and the beaker is labeled as 1. Then, 2.1g of terpineol, 1.0g of butyl carbitol acetate, 0.2g of dibutyl phthalate, and 0.2g of Span 85 are measured and added to beaker 1, and a magnetic stirrer is used to heat and stir at 65°C for 3.5h at a speed of 1200rpm / min to dissolve all the ethyl cellulose in the organic solvent to obtain a mixed solution A.

[0155] 6.5 g of the functional phase and 1.0 g of the binding phase were measured respectively, the two powders were placed in a mortar, and an appropriate amount of ethanol was added for grinding to mix the powders thoroughly and evenly. After all the ethanol was evaporated, the mixed powder A was collected and placed in an empty beaker, and the beaker was labeled 2; 2.5 g of the organic phase was measured and added to beaker 2, and a magnetic stirrer was used to heat and stir at 65 ° C at a speed of 1200 rpm / min for 3.5 h to form a light yellow suspension A, and the light yellow suspension A was cooled to room temperature to obtain a gas sensitive material.

[0156] (2) Preparation process of gas sensor:

[0157] The gas sensor of this embodiment adopts the dispensing method for film transfer.

[0158] The dispensing machine used in this embodiment is mainly composed of a valve body and a valve seat, wherein the valve body is composed of a retaining spring, a sealing ring, a top screw, a striker and a valve body base; the valve seat is composed of a control line, a Luer connector, a piezoelectric drive assembly, and a non-contact ceramic valve seat. The working mechanism of the jet valve dispensing machine is to first send the material into the valve body and the valve seat through the Luer connector, and use the control line to transmit high and low level signals to control the piezoelectric drive assembly. When the piezoelectric drive assembly receives a high level signal, it lifts up to drive the striker to lift up, and when the piezoelectric drive assembly receives a low level signal, it falls down to drive the striker back. The striker pushes the material and the valve body base opens at the same time, so that the material sprays out of the valve body and the valve seat and adheres to the substrate surface. At the same time, the mechanical structure controls the precise movement of the valve body so that the sensitive material is uniformly and stably formed into a film in the material attachment area of ​​the gas sensor micro-hot plate based on the micro-system device.

[0159] Clean the BF33 glass slide with acetone, isopropanol and distilled water in turn and treat the film-forming surface of the device with a plasma cleaner. Install the dispensing equipment on the valve body seat and lock it. Take 8ml of the gas-sensitive material prepared in step (1) and pour it into the dispensing machine channel. Turn on the dispensing machine power supply and air pump to provide driving pressure for the channel. Turn on the dispensing machine controller, adjust the working parameters of the dispensing machine, control the valve opening time to 0.50ms, the piezoelectric frequency to 600Hz, the force to 9, and the material chamber temperature to 20℃, turn on the dispensing machine for single dispensing, calibrate the dispensing position and calibrate. Place the glass slide at the dispensing position, perform batch dispensing, and repeat the dispensing action 16 times to transfer the film. After completing the dispensing of all devices, reset the dispensing machine, turn off the dispensing machine power supply and air pump, disassemble the dispensing equipment, and use acetone, alcohol and distilled water to clean the dispensing equipment's material chamber, nozzle, striker, piston, clean them and seal them for storage, and discard the disposable channel.

[0160] The glass slide was baked under an infrared lamp until the gas sensitive material was dry. The glass slide was placed in a muffle furnace and sintered at 600°C for 1 hour with a heating rate of 1°C / min.

[0161] Example 2

[0162] The method for preparing the gas sensor of this embodiment specifically includes the following steps:

[0163] (1) Preparation process of gas sensitive materials:

[0164] The gas sensitive material of this embodiment adopts a three-phase mixing process, wherein the three phases are a functional phase, a bonding phase and an organic phase. The specific method is the same as that of embodiment 1 and will not be described in detail.

[0165] (2) Preparation process of gas sensor:

[0166] The gas sensor of this embodiment adopts the dispensing method for film transfer.

[0167] The ceramic flat plate electrode with gold electrode printed on the front and heating electrode printed on the back and Pt lead wire was cleaned with acetone, isopropyl alcohol and distilled water in turn, and the device film-forming surface was treated with a plasma cleaner. Install the dispensing device on the valve seat of the valve body and lock it. Install the dispensing device on the valve seat of the valve body and lock it. Take 10ml (1) of the prepared gas-sensitive material and pour it into the dispensing machine channel. Turn on the power supply and air pump of the dispensing machine to provide driving pressure for the channel. Turn on the dispensing machine controller, adjust the working parameters of the dispensing machine, control the valve opening time to 0.20ms, the piezoelectric frequency to 300Hz, the force to 13, and the material chamber temperature to 60℃, turn on the dispensing machine for single dispensing, calibrate the dispensing position and calibrate. Place the ceramic flat plate electrode sheet at the dispensing position, perform batch dispensing, and repeat the dispensing action 16 times for film transfer. After completing the dispensing of all devices, reset the dispensing machine, turn off the power and air pump of the dispensing machine, disassemble the dispensing equipment, and clean the material cavity, nozzle, striker, and piston of the dispensing equipment with acetone, alcohol, and distilled water in turn, clean them, and seal them for storage, and discard the disposable material channel.

[0168] Bake the flat electrode under an infrared lamp until the gas sensitive material is dry. Place the flat electrode in a muffle furnace and sinter at 600°C for 1.5 hours with a heating rate of 5°C / min. After sintering, cool the flat electrode to room temperature and weld the gold electrode and the heating electrode to a universal indirect-heated hexagonal tube socket through a Pt wire wire; thus, a gas sensor made of gas sensitive material is obtained, and the sensor is subjected to a gas-sensitive test.

[0169] Example 3

[0170] The method for preparing the gas sensor of this embodiment specifically includes the following steps:

[0171] (1) Preparation process of gas sensitive materials:

[0172] The gas sensitive material of this embodiment adopts a three-phase mixing process, wherein the three phases are a functional phase, a bonding phase and an organic phase. The specific method is the same as that of embodiment 1 and will not be described in detail.

[0173] (2) Preparation process of gas sensor:

[0174] The gas sensor of this embodiment uses a dispensing method to perform film transfer.

[0175] Clean the 3.5*3.5mm glass substrate and Pt electrode micro-hotplate with acetone, isopropyl alcohol and distilled water in turn, and treat the device film-forming surface with a plasma cleaner. Install the dispensing equipment on the valve body seat and lock it. Take 12ml (1) of the prepared gas-sensitive material and pour it into the dispensing machine channel. Turn on the power supply and air pump of the dispensing machine to provide driving pressure for the channel. Turn on the dispensing machine controller, adjust the working parameters of the dispensing machine, control the valve opening time to 0.30ms, the piezoelectric frequency to 400Hz, the force to 11, the material chamber temperature to 40℃, turn on the dispensing machine for single dispensing, calibrate the dispensing position and calibrate. Place the glass slide at the dispensing position, perform batch dispensing, and repeat the dispensing action 16 times for film transfer. After completing the dispensing of all devices, reset the dispensing machine, turn off the power and air pump of the dispensing machine, disassemble the dispensing equipment, and clean the material cavity, nozzle, striker, and piston of the dispensing equipment with acetone, alcohol, and distilled water in turn, clean them, and seal them for storage, and discard the disposable material channel.

[0176] Bake the micro hot plate under an infrared lamp until the gas sensitive material is dry, and then place it in a muffle furnace and sinter it at 500°C for 1.5 hours with a heating rate of 2°C / min.

[0177] (3) In order to facilitate the subsequent gas-sensing test, the gas sensor was packaged. The micro-hotplate device was cooled to room temperature after sintering, and the device leads were packaged using a 5*5mm metal tube shell and a wire bonding machine. The tube shell was transferred to the PCB, and the device was connected to a universal indirect-heated hexagonal tube socket on the PCB board using flying wires, and the sensor was subjected to a gas-sensing test.

[0178] Comparative Example 1

[0179] The preparation method of the gas sensor of this comparative example is different from that of Example 3 only in that: in this comparative example, the binder phase is added with different specific gravities, and the mass fraction of the binder phase in the gas sensitive material is set to a gradient of 0wt%, 20wt%, and 30wt%. The remaining steps are carried out by referring to the method in Example 3.

[0180] Comparative Example 2

[0181] The preparation method of the gas sensor of this comparative example is different from that of Example 3 only in that no organic phase is added in this comparative example, and the remaining steps are carried out with reference to the method of Example 3.

[0182] Comparative Example 3

[0183] The preparation method of the gas sensor of this comparative example is different from that of Example 3 only in that: this comparative example omits step (2), and adopts a coating method to directly brush the gas sensitive material onto the surface of the micro-hotplate for film transfer, and the remaining steps are carried out according to the method in Example 3.

[0184] Coating methods include:

[0185] The 3.5*3.5mm glass substrate and Pt electrode micro-hotplate were cleaned with acetone, isopropanol, and distilled water in turn, and the electrode surface was treated with a plasma cleaner; 15μL of the precursor was dripped on the center of the micro-hotplate using a 25μL pipette to level it to form a uniform sensitive film and completely cover the gold electrode; the micro-hotplate was baked under an infrared lamp until the gas sensitive material was dry. It was placed in a muffle furnace and sintered at 500℃ for 1.5h, with a heating rate of 2℃ / min.

[0186] Comparative Example 4

[0187] The preparation method of the gas sensor of this comparative example is different from that of Example 3 only in that the SnO2 and WO3 mixed nanoparticles in the functional phase are replaced with In2O3 particles (the particle size of In2O3 is 500nm), and the mass of In2O3 particles and SnO2 and WO3 mixed nanoparticles is equal. The remaining steps are carried out with reference to the method in Example 3.

[0188] Test Case

[0189] The gas sensors obtained in the embodiments and comparative examples were tested.

[0190] 1. Step meter test

[0191] The experimental results are as follows Figure 3 shown. Figure 3 (a) is the morphology of the glue dots obtained by batch dispensing in Example 2. From the optical microscope image, it can be seen that the glue dots are round with a diameter between 356-507 μm. Six of the glue dots in Example 2 were characterized using a step profiler to obtain a film thickness map of the gas sensor as shown below: Figure 3 (b) The film thickness is stable between 35-51μm, which shows the stability and consistency of the dispensing process after batch processing. The size and thickness of the glue dots obtained by the dispensing process meet the actual needs of gas sensors based on microsystem devices and can realize the batch production of gas sensors.

[0192] 2. Scanning electron microscope

[0193] The experimental results are as follows Figure 4 shown. Figure 4(a)(b)(c)(d) are 500, 1000, 5000 and 10000 times SEM magnification images of the gas sensor in Example 1. The gas sensors all have loose porous structures, and the pore structures range from micrometer to nanometer scale. The formation of the pore structure proves that the organic phase is fully volatilized during the sintering process. The formed pore structure makes the contact area between the functional phase and the target gas larger in the gas response, and the response is more sufficient and rapid.

[0194] 3. Scratch measurement

[0195] Scratch measurement of gas sensors with different bonding ratios in Example 1 and Comparative Example 1. Measurement principle: A linear tangential load is applied to the gas sensor using a probe and scratched to produce a straight scratch. The load at the scratch break is the membrane-base bonding force. The measurement results are shown in Figure 5 , Figure 5 (a) is the scratch image of 10wt% bonding weight in Example 1, Figure 5 (b) is a scratch image of 0wt% bonding phase in comparative example 1. As shown in the figure, the gas sensor with 0wt% bonding phase produced obvious fracture during measurement, and the critical load at the fracture was 35mN, while the gas sensor with 10wt% bonding phase did not produce fracture during the measurement, that is, its membrane-based bonding force was greater than the maximum range of the nano scratch tester, 100mN, which proves that the added bonding phase has greatly improved the membrane-based bonding force of the gas sensor, which can solve the problem of poor reliability in the gas sensor.

[0196] 4. Gas adsorption / desorption test

[0197] When conducting gas adsorption / desorption tests, the present invention uses a multi-channel test system for dynamic testing, and sets the gas type, gas flow rate, concentration and time through a program for automatic control. In this test example, the ventilation method is target gas / background gas cycle ventilation, which is intended to test the adsorption capacity and response degree of the device during the target gas ventilation and the desorption capacity of the device during the background gas ventilation. During the test, the gas flow rate is fixed at 400sccm, the target gas is the test gas, and the ventilation time is 600s; the background gas is air, and the ventilation time is 1800s; the test relative humidity is controlled to 20%, the ambient temperature is 24°C, and the device operating temperature is 250°C.

[0198] The experimental results are as follows Figure 6-12 shown.

[0199] Figure 6The gas response diagram and film thickness diagram of Example 3, where (a) is the film thickness diagram; (b) is the gas response diagram. In Example 3, five groups of sensors with different thicknesses were prepared by the dispensing method, and the sensors were numbered 1#, 2#, 3#, 4#, and 5#. The film thickness and size were characterized by a step meter. It can be seen from the figure that the dispensing diameter of the five groups of sensors is approximately 400μm, the error fluctuation is ±11μm, and the dispensing thickness is 42.421μm, 36.416μm, 31.394μm, 26.384μm, and 22.462μm, respectively. The five groups of sensors were subjected to a gas sensitivity test using 20ppm hydrogen sulfide gas, and the test results are as follows: Figure 6 (b). As can be seen from the figure, the dynamic response curves of the five groups of sensors are similar, and sensors 1# to 5# show an increasing trend in response values. Combining the film thickness and diameter data for analysis, the glue dot thickness and response value of the five groups of sensors show an obvious negative correlation trend. This is because the gas sensors prepared by the glue dispensing method are stacked in a trapezoidal shape. After the film thickness increases, the stacking volume increases, and the sensitive materials accumulated inside increase. The sensitive materials inside have low reaction efficiency when participating in the redox reaction in gas sensing, which affects the performance of the gas sensor. Therefore, an excessively thick film thickness will lead to a decrease in the response value of the gas sensor. The glue dispensing process of the present invention can form thinner gas sensors, which is of great significance in improving the performance of the sensor.

[0200] Figure 7 The resistance change diagram of the 5ppm hydrogen sulfide gas test of Example 3 and Comparative Example 3, wherein (a) is Comparative Example 3; (b) is Example 3. It can be seen from the figure that the two devices have similar response curves. When the hydrogen sulfide environment is first exposed, the resistance drops rapidly to a certain value and then remains unchanged; when the hydrogen sulfide environment is withdrawn, the resistance slowly recovers to the baseline resistance. The difference is that Example 3 has a higher resistance value in the air. This is because the gas sensor prepared by the dispensing method is thinner and the conductive network formed is worse, so the electrical performance is worse than that of the coating method. However, the response value of Example 3 is 29.2, the response time is 40s, and the recovery time is 389s, while the response value of Comparative Example 3 is 23.4, the response time is 94s, and the recovery time is 831s. The response value, response time, and recovery time of the device prepared by the dispensing method are better than those of the sensor prepared by the coating method, especially the response time and recovery time, which are shortened by nearly 50% compared with the coating method. This is because thinner gas sensors improve the efficiency of gas exchange and accelerate the speed of gas reaction, thus having shorter response time and recovery time.

[0201] Figure 8The gas response diagram of the hydrogen sulfide gas gradient concentration of Example 3 and Comparative Example 3. Example 3 and Comparative Example 3 were placed in the same environment for dynamic gas testing. The response values ​​of Comparative Example 3 to 0.5ppm, 1ppm, 2ppm, 5ppm, 10ppm, and 20ppm hydrogen sulfide gas were 5.1, 10.0, 16.8, 23.7, 64.1, and 125.0, respectively; the corresponding hydrogen sulfide gas response values ​​of Example 3 were 5.9, 9.6, 18.0, 29.7, 85.8, and 204.5. It can be seen from the figure that the response values ​​of the gas sensors prepared by the two different film transfer processes are linearly related to the gas concentration, and a wider detection range is presented in the detection of hydrogen sulfide gas. In Example 3, the response values ​​of all other concentrations except 1ppm are higher than those of Comparative Example 3, which indicates that the sensing film prepared by the dispensing method has a higher sensing ability in gas sensing. In the detection of hydrogen sulfide gas at a lower concentration, the gas sensor of Comparative Example 3 has response values ​​of 1.6, 1.7, 1.7, 2.8, 3.9, and 5.1 to 10ppb, 20ppb, 50ppb, 0.1ppm, 0.2ppm, and 0.5ppm hydrogen sulfide gas, respectively; the corresponding response values ​​of the gas sensor of Example 3 are 1.9, 1.9, 2.1, 3.5, 4.2, and 5.9. As can be seen from the figure, the sensor prepared by the dispensing method shows better performance in response to low-concentration hydrogen sulfide, and the lowest detection limit is also lower than that of the sensor prepared by the coating method.

[0202] Fig. 9 It is the gas response diagram of Example 3 under different gas environments of 5ppm, wherein (a)(b)(c)(d)(e) are respectively the gas response diagrams of Example 3 under 5ppm hydrogen sulfide, acetone, carbon dioxide, ethanol, and ammonia environments, and (f) is a bar graph of the response values ​​of the five gases. As shown in the figure, the response values ​​of the gas sensor of Example 3 to 5ppm hydrogen sulfide, carbon dioxide, ammonia, ethanol, and acetone gases are 29.2, 1.6, 1.4, 3.4, and 4.3, respectively. It can be seen from the figure that regardless of the film transfer method, the gas sensor shows the highest sensitivity to hydrogen sulfide gas, which is higher than other gases of the same concentration. Among them, the hydrogen sulfide response value of Example 3 is 29.2, which is more than five times higher than the response values ​​of other gases.

[0203] Fig.10The gas response diagram of the test of 10ppm hydrogen sulfide gas in each specific gravity in Example 3 and Comparative Example 1. Example 3 and Comparative Example 1 explore the effect of the bonding phase density in the heat treatment process on the gas-sensitive response of the gas sensor. Specifically, four bonding phase density gradients of 0wt%, 10wt%, 20wt% and 30wt% were set to test the sensor using 10ppm hydrogen sulfide gas. The corresponding response values ​​of 0wt%, 10wt%, 20wt% and 30wt% bonding phase density were 76, 94, 37 and 24 respectively. With the increase of bonding phase density, the gas response of the gas sensor showed a trend of first increasing and then decreasing. This is because when the bonding phase is low-doped, the bonding phase content is insufficient, the functional phase cannot be effectively wetted, and the conductive network cannot be formed, so the response is low. As the bonding phase doping ratio increases, the wetting effect is enhanced, the bonding phase is tightly combined together to form an effective conductive network, so the response is improved. As the bonding phase doping ratio is further increased, the bonding phase itself is an insulator, and the excessive insulator doping affects the overall conductive performance of the gas sensor, so the response is reduced again.

[0204] Fig.11 The gas response diagram of the test of hydrogen sulfide gas with a specific gravity of 10ppm in Example 3 and Comparative Example 2. Example 3 and Comparative Example 2 explore the effect of the organic specific gravity on the gas-sensitive response of the gas sensor in the heat treatment process. Two gradients of organic specific gravity of 0wt% and 25wt% were set, and the sensor was tested using 10ppm hydrogen sulfide gas. The corresponding response values ​​of 0wt% and 25wt% organic specific gravity were 42 and 69, respectively. The test results show that the presence or absence of the organic phase greatly affects the sensing performance of the device. The reason for this phenomenon is that under the optimal heat treatment process conditions determined previously, the organic phase can be completely volatilized, so that only particles of the functional phase and the bonding phase remain in the gas sensor. Therefore, in the extreme case where there is no organic phase, the functional phase and the bonding phase that have not been dispersed by the organic phase will show serious agglomeration, affecting the gas exchange efficiency, and the particles that have not been treated with the organic phase have poor compatibility with the process during the film formation process, and the resulting gas sensor has poor stability, which is not conducive to the mass production of gas sensors.

[0205] Fig.12The resistance change diagram of the 5ppm hydrogen sulfide gas test of Example 3 and Comparative Example 4, wherein (a) is Comparative Example 4; (b) is Example 3. It can be seen from the figure that the two devices have similar response curves. When they are first exposed to the hydrogen sulfide environment, the resistance drops rapidly to a certain value and then remains unchanged; when the hydrogen sulfide environment is withdrawn, the resistance slowly recovers to the baseline resistance. The difference is that the response value of Example 3 is 29.2, the response time is 40s, and the recovery time is 389s, while the response value of Comparative Example 4 is 17.4, the response time is 188s, and the recovery time is 893s. This shows that the gas sensing performance of the mixed nanoparticles of SnO2 and WO3 as the functional phase is better than that of In2O3, and the mixed nanoparticles of SnO2 and WO3 are more suitable for the high-volume and high-stability preparation of gas sensors.

[0206] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", "some implementation schemes" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0207] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A gas sensitive material, characterized in that: include: Functional phase, adhesive phase and organic phase; The functional phase includes SnO2 and WO3; The bonding phase includes a low melting point oxide; The organic phase includes a high boiling point organic solvent.

2. The gas sensitive material according to claim 1, characterized in that: The mass ratio of the functional phase, the adhesive phase and the organic phase is (5-7): (0.5-1.5): (2-4).

3. The gas sensitive material according to claim 1, characterized in that: The mass ratio of SnO2 to WO3 is (1-20):

1.

4. The gas sensitive material according to claim 1, characterized in that: The particle size of SnO2 is 200-1000nm; The particle size of the WO3 is 200-1000 nm.

5. The gas sensitive material according to claim 1, characterized in that: The low melting point oxide comprises at least one of bismuth oxide, lead oxide, tin oxide, copper oxide, zinc oxide, calcium oxide, aluminum oxide, iron oxide, sodium oxide, magnesium oxide and chromium oxide; The high boiling point organic solvent includes at least one of terpineol, butyl carbitol acetate and dibutyl phthalate.

6. The gas sensitive material according to claim 1, characterized in that: The organic phase also includes a thickener and a dispersant.

7. A gas sensor, characterized in that: include: Micro hot plate; The upper surface of the micro-hotplate has a detection electrode layer; Gas sensitive material layer; The gas sensitive material is arranged on the upper surface of the detection electrode layer.

8. The method for preparing the gas sensor according to claim 7, characterized in that: The following steps are involved: A micro-hotplate is prepared; the upper surface of the micro-hotplate has a detection electrode layer; the gas sensitive material and / or the gas sensitive material obtained by the preparation method of the gas sensitive material is glued on the detection electrode layer; after the glue is glued, the system is heat-treated.

9. The method for preparing a gas sensor according to claim 8, characterized in that: The heat treatment temperature is 400-600° C. and the time is 1-2 hours.

10. Use of the gas sensor according to claim 7 and / or the gas sensor prepared by the preparation method of the gas sensor according to claim 8 or 9 in detecting hydrogen sulfide or acetone gas.

Images