Microwave hydrothermal method for growing palladium sulfide nanoparticle gas sensing material, and preparation method and application thereof

Abstract

The application discloses a microwave hydrothermal method for growing a palladium sulfide nanoparticle gas-sensitive material and a preparation method and application thereof, and belongs to the technical field of nanometer materials and electronic devices. The palladium sulfide nanoparticle gas-sensitive material is composed of a substrate layer with an electrode and a gas-sensitive layer; wherein the gas-sensitive layer is prepared from palladium sulfide nanoparticles. The specific preparation method comprises the following steps: taking chloropalladic acid and thiourea as precursors, generating palladium sulfide nanoparticles through a chemical reaction under microwave hydrothermal conditions, mixing the palladium sulfide nanoparticles with ethanol, coating the mixture on a pretreated substrate material to form a gas-sensitive film, and obtaining the palladium sulfide nanoparticle gas-sensitive material. The material has high gas sensitivity and selectivity, and can play a role in the application of NO2 gas sensors.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterials and electronic devices, and particularly relates to a microwave hydrothermal method for growing a palladium sulfide nanoparticle gas sensing material and a preparation method and application thereof. BACKGROUND

[0002] Metal oxide semiconductors (MOS) are widely used in gas sensor materials for monitoring various gases in the environment due to their low cost and simple manufacturing process. However, most NO2 gas sensors need to work at a relatively high temperature to have a good response value to NO2. For example, the patent for invention with publication number CN111812161A discloses a NO2 gas sensor based on metal oxide and a preparation method thereof. The prepared NiO-In2O3 metal oxide nanosphere coating has a high response value of 140 to 500 ppb of NO2 at a working temperature of 100℃. For example, the patent for invention with publication number CN109490391A discloses a preparation method of a zirconium oxide composite tungsten oxide nanotube NO2 gas sensor. The zirconium oxide sheet is subjected to secondary anodic oxidation, and tungsten oxide is filled into the zirconium oxide nanotube by the dipping method to obtain a zirconium oxide composite tungsten oxide nanotube, and the nanotube is used to assemble a sensor. The sensitivity of the sensor to 30-500 ppm of NO2 reaches 269.2 mV / decade at the optimal working temperature of 300℃. Therefore, it is still a great challenge to develop a room temperature NO2 sensor based on a new type of sensitive material with high response, good selectivity and stability. SUMMARY

[0003] In view of the above technical problems, the present application provides a microwave hydrothermal method for growing a palladium sulfide nanoparticle gas sensing material and a preparation method and application thereof. It can meet the development needs of the new generation of low-power and wearable electronic devices.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] One of the technical purposes of the present application is to provide a microwave hydrothermal method for growing a palladium sulfide nanoparticle gas sensing material. The palladium sulfide nanoparticle gas sensing material is composed of a substrate layer with an electrode and a gas sensitive layer. The gas sensitive layer is prepared from palladium sulfide nanoparticles.

[0006] Further, the preparation of the palladium sulfide nanoparticles includes the following steps: mixing chloropalladic acid (H2PdCl4) and thiourea (CS(NH2)2) with water, then performing a microwave hydrothermal reaction, cooling, centrifuging, washing, drying, and obtaining palladium sulfide nanoparticles.

[0007] The microwave hydrothermal method is a wet chemical synthesis method using microwave heating, which can promote chemical reactions at relatively low temperatures and pressures. In the present application, chloropalladic acid provides the palladium source, and thiourea provides the sulfur source. The chloropalladic acid and thiourea are used as precursors to undergo a chemical reaction under microwave hydrothermal conditions. The microwave heating can provide uniform heat, accelerate the reaction rate, and help form uniform nanostructures, ultimately generating palladium sulfide nanoparticles.

[0008] Further, the microwave hydrothermal reaction conditions are as follows: temperature 120-200℃, power 100-500W, and time 0.5-4h.

[0009] The temperature, time, and power during the microwave hydrothermal reaction are controlled to control the morphology, size, and crystallinity of the product.

[0010] Further, the amount ratio of chloropalladic acid to thiourea is 0.75mmol:1g.

[0011] Further, the substrate layer is a rigid substrate or a flexible substrate. The material of the rigid substrate is aluminum oxide, zirconium oxide, or silicon-based. The material of the flexible substrate is flexible polyimide (PI) or polyethylene terephthalate (PET).

[0012] The present application selects different substrate materials according to different physical properties of materials to adapt to different application scenarios.

[0013] The second technical purpose of the present application is to provide a preparation method of a palladium sulfide nanoparticle gas-sensitive material grown by a microwave hydrothermal method, which comprises the following steps: mixing the palladium sulfide nanoparticles with ethanol, coating the mixture on a pretreated substrate material to form a gas-sensitive film, and drying to obtain the palladium sulfide nanoparticle gas-sensitive material.

[0014] Further, the pretreatment specifically refers to ultrasonic cleaning the substrate material with acetone, alcohol, and deionized water in sequence, and drying.

[0015] The pretreatment of the substrate is to remove impurities and oil stains on the surface to ensure that the palladium sulfide nanoparticles can be uniformly attached to the substrate, thereby improving the performance of the gas-sensitive material.

[0016] Further, the thickness of the gas-sensitive film is 1-100μm.

[0017] Further, the drying parameters are as follows: temperature 50-80℃, and drying time 6-12h.

[0018] The third technical purpose of the present application is to provide an application of a palladium sulfide nanoparticle gas-sensitive material grown by a microwave hydrothermal method in the field of sensors.

[0019] The fourth technical objective of the present application is to provide a NO2 gas sensor made of the palladium sulfide nanoparticle gas sensing material grown by the microwave hydrothermal method.

[0020] The palladium sulfide nanoparticle has a high specific surface area, and contains a large number of surface active sites which can interact with gas molecules to change the electrical conductivity or other electronic properties of the material. When the gas molecules contact the surface of the palladium sulfide nanoparticle, adsorption or chemical reaction occurs, causing electrons to transfer from the gas molecules to the palladium sulfide nanoparticle, thereby achieving the purpose of detecting gas molecules.

[0021] Compared with the prior art, the present application has the following advantages and technical effects:

[0022] The method for preparing the palladium sulfide nanoparticle gas sensing material grown by the microwave hydrothermal method of the present application is a technology for controlling particle size by changing reaction conditions. This method uses microwave energy (i.e. high-frequency oscillating electromagnetic field) as a catalyst under high temperature, medium power and high-frequency oscillation conditions to cause the formation and breaking of chemical bonds in the raw materials, and finally generate palladium sulfide nanoparticles. The generated palladium sulfide nanoparticles have high gas sensitivity and selectivity, and can play a role in the application of NO2 gas sensors.

[0023] The method of the present application can complete the reaction at room temperature without the need for heating to a high temperature or high pressure, saving energy. At the same time, the reaction process can be carried out in a normal pressure container without the need for special equipment, and the operation is simple. In addition, the types of reactants are fewer, only two raw materials of chloropalladic acid and thiourea are needed, and the cost is lower. Therefore, this method has the advantages of energy saving, environmental protection, low cost and simple operation. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The illustrations are shown to explain the present application and are not intended to limit the present application unduly.

[0025] Figure 1 It is a scanning electron microscope image of the palladium sulfide nanoparticles in Example 1 of the present application.

[0026] Figure 2 It is a repeatable curve graph of the gas sensor at room temperature for 50ppm NO2 in Example 1 of the present application. DETAILED DESCRIPTION

[0027] The various illustrative embodiments of the present application will now be described in detail below. This detailed description is not intended to be taken in a limiting sense, but rather to provide a more detailed description of certain aspects, features and embodiments of the present application.

[0028] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, a parameter, an individual value or subrange within that range is also specifically disclosed. Each of the smaller ranges is also individually and specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also endpoints of the range, subject to any specifically excluded endpoint. All ranges disclosed herein are also individually and specifically disclosed.

[0029] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are related to the present application. In the case of conflict between the present specification and any document incorporated herein by reference, the present specification will control.

[0030] Many modifications and variations of the present application described in the specific embodiments of the application can be made by those skilled in the art without departing from the spirit or scope of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0031] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0032] The present application is a microwave hydrothermal reaction of raw materials chloropalladic acid and thiourea in aqueous solution. Under high temperature (120-200°C), medium power (100-500W) and high frequency oscillation conditions, they will form and break chemical bonds, thereby generating palladium sulfide nanoparticles. This is a technique for controlling particle size by changing reaction conditions, called "microwave catalysis", and the catalyst used is microwave energy, i.e. high frequency oscillation electromagnetic field. Microwave energy can excite chemical bonds, making atomic vibrations more intense and increasing reaction rates. The present application uniformly distributes the generated palladium sulfide nanoparticles on the substrate material to form a gas sensitive material. The resulting palladium sulfide nanoparticle gas sensitive material has high gas sensitivity and selectivity, and can be used in gas sensor applications, especially for NO2 gas.

[0033] In one specific embodiment, a preparation method of a microwave hydrothermal method for growing a palladium sulfide nanoparticle gas sensing material includes the following steps: chloropalladic acid and thiourea are added to deionized water for mixing, magnetic stirring (30 min) until fully dissolved, microwave hydrothermal reaction in a microwave hydrothermal synthesis instrument, cooling to room temperature, centrifugation at 8000 rpm, washing with ethanol and deionized water in sequence, drying in a 60℃ drying oven, and obtaining palladium sulfide nanoparticles.

[0034] In some preferred embodiments of the present application, the temperature of the microwave hydrothermal reaction is 120-200℃. Illustratively, in the following preferred embodiments of the present application, the temperature of the microwave hydrothermal reaction is 120℃, 160℃, 200℃, or any value within the aforementioned range.

[0035] In some preferred embodiments of the present application, the power of the microwave hydrothermal reaction is 100-500W. Illustratively, in the following preferred embodiments of the present application, the power of the microwave hydrothermal reaction is 200W, 300W, 500W, or any value within the aforementioned range.

[0036] In some preferred embodiments of the present application, the time of the microwave hydrothermal reaction is 0.5-4h. Illustratively, in the following preferred embodiments of the present application, the time of the microwave hydrothermal reaction is 1h, 2h, 4h, or any value within the aforementioned range.

[0037] In some preferred embodiments of the present application, the ratio of the amount of chloropalladic acid, thiourea, and deionized water is 0.75mmol:1g:80mL.

[0038] The preparation method of the microwave hydrothermal method for growing a palladium sulfide nanoparticle gas sensing material includes the following steps: palladium sulfide nanoparticles are mixed with ethanol to obtain a mixed coating of 1-20mg / mL, which is then coated on a pretreated substrate material to form a gas sensitive film, and dried to obtain a palladium sulfide nanoparticle gas sensing material. Illustratively, in the following preferred embodiments of the present application, the palladium sulfide nanoparticles are mixed with ethanol to obtain a mixed coating of 5mg / mL, 10mg / mL, or 20mg / mL.

[0039] In some preferred embodiments of the present application, the pretreatment specifically refers to ultrasonic cleaning the substrate material with acetone, alcohol, and deionized water in sequence, and drying. The drying temperature is 50-80℃, and the drying time is 6-12h. The specific drying temperature and time are not specifically limited as long as the purpose of drying can be achieved. Illustratively, in the following preferred embodiments of the present application, a drying temperature of 60℃ and a drying time of 8h are used as examples for effect verification.

[0040] In some preferred embodiments of the present application, the substrate material is a rigid substrate or a flexible substrate. The rigid substrate is aluminum oxide, zirconium oxide or silicon-based; illustratively, in the following preferred embodiments of the present application, the rigid substrate is aluminum oxide or zirconium oxide. The flexible substrate is flexible polyimide (PI) or polyethylene terephthalate (PET); illustratively, in the following preferred embodiments of the present application, the flexible substrate is flexible polyimide or polyethylene terephthalate.

[0041] In some preferred embodiments of the present application, the thickness of the gas sensitive film is 1-100 μm. Illustratively, in the following preferred embodiments of the present application, the thickness of the gas sensitive film is 1 μm, 10 μm, 20 μm or any value within the aforementioned range.

[0042] In some preferred embodiments of the present application, the drying temperature is 50-80 °C and the drying time is 6-12 h. The specific drying temperature and time are not specifically limited as long as the purpose of drying can be achieved. Illustratively, in the following preferred embodiments of the present application, the drying temperature is 60 °C and the drying time is 8 h are taken as examples for effect verification.

[0043] In some preferred embodiments of the present application, the coating method can be selected from one of the conventional screen printing, drop coating, spraying and spin coating processes. Illustratively, in the following preferred embodiments of the present application, the screen printing and drop coating processes are taken as examples for effect verification.

[0044] The screen printing process is also known as "squeegee coating" or "squeegee application", which is a method of applying liquid to a substrate using a squeegee or similar tool. The liquid is applied to a substrate that has been dried and prepared.

[0045] The drop coating process is a common coating technique that uses a small ball (called a drop) to evenly apply liquid paint to a substrate. The ball moves under the action of gravity, evenly applying the paint to the surface of the substrate.

[0046] The spraying process is a method of using compressed air to spray liquid paint onto a substrate. The paint is sprayed in a mist form and is captured and absorbed by the substrate.

[0047] The spin coating process is a special coating technique that involves rotating a substrate and applying liquid paint to its surface. Due to the movement of the substrate during the application process, very uniform application can be achieved, and large or irregular substrates can be processed.

[0048] The microwave hydrothermal method for growing palladium sulfide nanoparticle gas sensitive materials can be used for a sensor for detecting NO2 gas at room temperature.

[0049] The "room temperature" in the present application refers to 20-30°C unless otherwise specified.

[0050] The raw materials used in the present application are commercially available.

[0051] The technical solutions of the present application are further illustrated by the following examples.

[0052] Example 1

[0053] A preparation method of a palladium sulfide nanoparticle gas sensing material by a microwave hydrothermal method, comprising the following steps:

[0054] (1) sequentially use acetone, alcohol, deionized water to ultrasonically clean the substrate material (alumina-based platinum interdigital electrode), and then dry at 60°C for 8h for standby;

[0055] (2) add 0.75mmol of chloropalladic acid and 1g of thiourea to a reaction container containing 80mL of deionized water, magnetically stir for 30min until fully dissolved, then in a microwave hydrothermal synthesis instrument, control the power at 200W, keep at 160°C for 2h, after cooling, take out, centrifuge at 8000rpm to collect the final product, and then wash with ethanol and deionized water for 3 times respectively, and then place in a 60°C drying oven to dry to obtain palladium sulfide nanoparticles;

[0056] (3) mix 5mg of palladium sulfide nanoparticles with 1mL of ethanol (anhydrous ethanol, the same below) to obtain a mixed coating of 5mg / mL, and use screen printing process to apply the mixed coating on the alumina-based platinum interdigital electrode substrate material to form a gas sensitive film (the thickness of the gas sensitive film is about 1μm); then place the substrate material with the gas sensitive film in an oven and dry at 60°C for 8h to prepare a palladium sulfide nanoparticle gas sensing material, i.e. a gas sensor (PdS).

[0057] Figure 1 For the scanning electron microscope image of the palladium sulfide nanoparticles in Example 1, it can be seen that the particle size of the palladium sulfide nanoparticles is between 50-100nm.

[0058] Example 2

[0059] A preparation method of a palladium sulfide nanoparticle gas sensing material by a microwave hydrothermal method, comprising the following steps:

[0060] (1) sequentially use acetone, alcohol, deionized water to ultrasonically clean the substrate material (alumina-based platinum interdigital electrode), and then dry at 60°C for 8h for standby;

[0061] (2) 0.75 mmol of chloropalladic acid and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water, and magnetic stirring was performed for 30 min until complete dissolution. Then, in a microwave hydrothermal synthesis instrument, the power was controlled at 300 W, and the temperature was maintained at 200°C for 1 h. After cooling, the final product was collected by centrifugation at 8000 rpm, washed with ethanol and deionized water for 3 times respectively, and then placed in a 60°C drying oven for drying to obtain palladium sulfide nanoparticles;

[0062] (3) 5 mg of palladium sulfide nanoparticles were mixed with 1 mL of ethanol to obtain a mixed coating of 5 mg / mL. The mixed coating was applied to the zirconia-based platinum interdigital electrode substrate material to form a gas sensitive film (the thickness of the gas sensitive film was about 10 μm) by using a drop coating process. Then, the substrate material with the gas sensitive film was placed in an oven and dried at 60°C for 8 h to prepare a palladium sulfide nanoparticle gas sensitive material, i.e. a gas sensor (PdS).

[0063] The microstructure of the palladium sulfide nanoparticles prepared in Example 2 was similar to that of Example 1.

[0064] Example 3

[0065] A preparation method of a palladium sulfide nanoparticle gas sensitive material by a microwave hydrothermal method, comprising the following steps:

[0066] (1) The substrate material (polyimide-based platinum interdigital electrode) was ultrasonically cleaned with acetone, alcohol and deionized water in sequence, and then dried at 60°C for 8 h for standby;

[0067] (2) 0.75 mmol of chloropalladic acid and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water, and magnetic stirring was performed for 30 min until complete dissolution. Then, in a microwave hydrothermal synthesis instrument, the power was controlled at 300 W, and the temperature was maintained at 120°C for 4 h. After cooling, the final product was collected by centrifugation at 8000 rpm, washed with ethanol and deionized water for 3 times respectively, and then placed in a 60°C drying oven for drying to obtain palladium sulfide nanoparticles;

[0068] (3) 20 mg of palladium sulfide nanoparticles were mixed with 1 mL of ethanol to obtain a mixed coating of 20 mg / mL. The mixed coating was applied to the polyimide-based platinum interdigital electrode substrate material to form a gas sensitive film (the thickness of the gas sensitive film was about 20 μm) by using a drop coating process. Then, the substrate material with the gas sensitive film was placed in an oven and dried at 60°C for 8 h to prepare a palladium sulfide nanoparticle gas sensitive material, i.e. a gas sensor (PdS).

[0069] The microstructure of the palladium sulfide nanoparticles prepared in Example 3 was similar to that of Example 1.

[0070] Example 4

[0071] A preparation method of a palladium sulfide nanoparticle gas sensing material by a microwave hydrothermal method, comprising the following steps:

[0072] (1) sequentially use acetone, alcohol, and deionized water to ultrasonically clean a substrate material (polyethylene terephthalate-based platinum interdigital electrode), and then dry at 60°C for 8 hours for standby;

[0073] (2) add 0.75 mmol of chloropalladic acid and 1 g of thiourea to a reaction container containing 80 mL of deionized water, magnetically stir for 30 min until fully dissolved, then in a microwave hydrothermal synthesis instrument, control the power to be 500 W, keep at 160°C for 1 h, after cooling, take out to centrifugally collect the final product at 8000 rpm, and then wash with ethanol and deionized water for 3 times respectively, and then place in a 60°C drying oven to dry to obtain palladium sulfide nanoparticles;

[0074] (3) mix 10 mg of palladium sulfide nanoparticles with 1 mL of ethanol to obtain a mixed coating of 10 mg / mL, and use a screen printing process to apply the mixed coating on the polyethylene terephthalate-based platinum interdigital electrode substrate material to form a gas sensitive film (the thickness of the gas sensitive film is about 10 μm); then place the substrate material with the gas sensitive film in an oven, dry at 60°C for 8 hours, to prepare a palladium sulfide nanoparticle gas sensing material, i.e. a gas sensor (PdS).

[0075] The palladium sulfide nanoparticles prepared in Example 4 have a similar microstructure to that of Example 1.

[0076] Comparative Example 1

[0077] The same as Example 1, except that the amount of chloropalladic acid is adjusted to 0.1 mmol.

[0078] Comparative Example 2

[0079] The same as Example 1, except that the temperature of the microwave hydrothermal reaction is 110°C.

[0080] Comparative Example 3

[0081] The same as Example 1, except that the power of the microwave hydrothermal reaction is 700 W.

[0082] Comparative Example 4

[0083] (1) weigh 0.3 mmol of palladium chloride (PdCl2), add concentrated hydrochloric acid (the volume ratio of concentrated hydrochloric acid to palladium chloride is 2:1) and 5 mL of deionized water, and stir in a water bath at 60°C until fully dissolved to form a palladium chloro acid hydrate (H2PdCl4·nH2O) solution;

[0084] Weigh cetyltrimethylammonium bromide (CTAB) and dissolve it in 5 mL of deionized water to obtain a cetyltrimethylammonium bromide solution;

[0085] Palladium chlorate hydrate (H2PdCl4.nH 20 ) solution was mixed with cetyltrimethylammonium bromide solution (palladium chlorate hydrate solution was mixed with cetyltrimethylammonium bromide solution in a molar ratio of 1:1 of palladium chloride to cetyltrimethylammonium bromide), and titrated with 0.5 mol / L NaOH aqueous solution to pH=10 under magnetic stirring, and the mixed solution was stirred for 30 min until it was mixed uniformly, the prepared solution was transferred into a 50 mL polytetrafluoroethylene liner, the liner was transferred into a stainless steel high-pressure reaction kettle, and the kettle was sealed and placed in a constant temperature drying oven, the temperature of the drying oven was set to 100°C, and the constant temperature reaction was carried out for 12 h, and the temperature was naturally cooled to room temperature to obtain black PdO powder, which was repeatedly washed with deionized water and ethanol for 3 times, and was placed in a drying oven at 80°C to obtain black PdO powder.

[0086] (2) 10 mg of black PdO powder was mixed with 1 mL of ethanol to obtain a 10 mg / mL mixed coating, and the mixed coating was applied on a polyethylene terephthalate-based platinum interdigital electrode substrate material by screen printing process to form a gas sensitive film (the thickness of the gas sensitive film was about 10 μm); then the substrate material with the gas sensitive film was placed in an oven and dried at 60°C for 8 h to prepare a gas sensor.

[0087] Test Example 1

[0088] The performance parameters of the prepared gas sensor were tested on a gas sensitive test equipment (KLUM-QM-104), and the specific method was as follows: (1) the gas sensor was connected to the gas sensitive test equipment, air was introduced into the equipment to reach stability, and the resistance value R a of the device in air was recorded; (2) NO2 was introduced into the equipment until the resistance value reached stability again, and the resistance value R g of the device in NO2 was recorded; (3) air was introduced into the equipment again until the resistance reached stability, and the device completed a response recovery process. Different NO2 concentrations were obtained by gas dilution method, the test concentration was 0-100 ppm, and the response value (Response) was defined as: Response=(R a -R g ) / R g ×100%, wherein R a was the output resistance value of the sensor in air atmosphere, and R g was the output resistance value of the sensor in NO2 atmosphere.

[0089] Figure 2 Figure 2 is a repeatability curve of the gas sensor in Example 1 at room temperature and 50% humidity for 50 ppm NO2, which was obtained by Figure 2It can be seen that after the NO2 is introduced, the resistance value of the sensor decreases with the increase of the NO2 concentration, and the sensor exhibits a response value of 28.4% to the NO2 gas, and the response / recovery time is 112 / 109 s.

[0090] Under the same test method, the gas sensor prepared in Example 2 exhibits a response value of 27.8% to the NO2 gas, and the response / recovery time is 115 / 112 s; the gas sensor prepared in Example 3 exhibits a response value of 26.9% to the NO2 gas, and the response / recovery time is 118 / 121 s; the gas sensor prepared in Example 4 exhibits a response value of 27.3% to the NO2 gas, and the response / recovery time is 117 / 112 s. It can be seen that the performances of the gas sensors prepared in Examples 1-4 are all close. The gas sensor prepared in Comparative Example 1 exhibits a response value of 10.4% to the NO2 gas, and the response / recovery time is 201 / 224 s; the gas sensor prepared in Comparative Example 2 exhibits a response value of 11.1% to the NO2 gas, and the response / recovery time is 187 / 196 s; the gas sensor prepared in Comparative Example 3 exhibits a response value of 12.3% to the NO2 gas, and the response / recovery time is 180 / 181 s; the gas sensor prepared in Comparative Example 4 exhibits a response value of 1.2% to the NO2 gas, and the response / recovery time is 387 / 396 s.

[0091] The above merely describes preferred specific embodiments of the present application. However, the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A microwave hydrothermal method for growing palladium sulfide nanoparticle gas sensing material, characterized in that, The palladium sulfide nanoparticle gas sensitive material is composed of a substrate layer with an electrode and a gas sensitive layer; The gas sensitive layer is prepared from palladium sulfide nanoparticles; The preparation of the palladium sulfide nanoparticles comprises the following steps: mixing chloropalladic acid and thiourea with water, then performing a microwave hydrothermal reaction, cooling, centrifuging, washing, drying, and obtaining palladium sulfide nanoparticles; The microwave hydrothermal reaction is performed under the following conditions: temperature 120-200℃, power 100-500W, and time 0.5-4h; The amount ratio of the chloropalladic acid to the thiourea is 0.75mmol:1g; The substrate layer is a rigid substrate or a flexible substrate; the material of the rigid substrate is aluminum oxide, zirconium oxide or silicon-based; the material of the flexible substrate is flexible polyimide or polyethylene terephthalate.

2. A method for preparing a palladium sulfide nanoparticle gas sensing material by a microwave hydrothermal method according to claim 1, characterized in that, The method comprises the following steps: The palladium sulfide nanoparticles are mixed with ethanol, then coated on a pretreated substrate material to form a gas sensitive film, dried, and then obtained is the palladium sulfide nanoparticle gas sensitive material.

3. The method for preparing palladium sulfide nanoparticle gas sensing material by microwave hydrothermal method according to claim 2, characterized in that, The pretreatment specifically refers to: sequentially ultrasonic cleaning the substrate material with acetone, alcohol and deionized water, and drying.

4. The method for preparing palladium sulfide nanoparticle gas sensing material by microwave hydrothermal method according to claim 2, characterized in that, The thickness of the gas sensitive film is 1-100μm.

5. Application of the palladium sulfide nanoparticle gas sensitive material grown by the microwave hydrothermal method in the field of sensors.

6. A NO2 gas sensor characterized by comprising: The palladium sulfide nanoparticle gas sensitive material grown by the microwave hydrothermal method is made of the palladium sulfide nanoparticles.

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