Visible light excitation type nitrogen dioxide gas sensor based on Bi2S3 / SnS2 heterostructure as well as preparation method and application of visible light excitation type nitrogen dioxide gas sensor

Abstract

The invention belongs to the technical field of gas sensors, and discloses a visible light excitation type nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure and preparation and application thereof, and the gas sensor comprises a gas sensitive material, an interdigital electrode and an LED light source. The preparation method specifically comprises the following steps: preparing bismuth sulfide with the microstructure of a nanorod structure and tin disulfide with the microstructure of a micron sheet structure by adopting a hydrothermal method to form a heterostructure composite material, uniformly coating the gas sensitive material on the surface of an interdigital electrode taking an aluminum oxide substrate as a substrate, and vertically placing an LED light source right above the gas sensitive material. The invention has the advantages of low price, simple preparation process, compatibility with CMOS (Complementary Metal Oxide Semiconductor) process, easiness in microminiaturization and integration with other microelectronic devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a visible light-excited nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure, its preparation method, and its application. Background Technology

[0002] Nitrogen dioxide (NO2) is a typical toxic and harmful gas, widely present in vehicle exhaust, fossil fuel combustion, and industrial emissions. It not only contributes to photochemical smog and acid rain but also harms the human respiratory system. Studies have shown that long-term exposure to low concentrations of NO2 can lead to chronic lung damage. The U.S. Environmental Protection Agency (EPA) lists NO2 as a major air pollutant, stipulating that its hourly average concentration should not exceed 100 ppb and its annual average limit is 53 ppb. This indicates that even extremely low concentrations of NO2 can endanger human health. Therefore, developing highly sensitive, low-power NO2 detection technologies is of great significance for both environmental protection and health monitoring. However, traditional metal oxide gas sensors require operation at high temperatures of 200℃ to 400℃, resulting in high energy consumption, complex structures, and a tendency to decay material surface activity and shorten device lifespan, making it difficult to meet the requirements of low power consumption and portable devices. To reduce operating temperature and improve sensor sensitivity and selectivity, research teams have recently proposed using photoexcitation instead of thermal excitation to drive gas sensing responses. Photoexcited gas sensors generate electron-hole pairs through light illumination, enabling target gas adsorption and charge transfer at room temperature. Compared to traditional thermally excited sensors, photoexcited devices offer lower power consumption, better stability, faster response recovery, and better preservation of material structure. Visible light excitation is more energy efficient and compatible than ultraviolet light excitation, and can be driven by sunlight or LEDs, avoiding damage to materials from high-energy ultraviolet radiation. For example, Chinese patent document (application number 201811451692.6) discloses a nitrogen dioxide gas sensor based on a flower-shaped SnSe2 / SnO2 heterojunction. The preparation method of the flower-shaped SnSe2 / SnO2 heterojunction includes: first preparing flower-shaped SnSe2 nanomaterials, then placing them in a tube furnace and heating them at a rate of 2–6 °C / min while simultaneously introducing a dry gas with an oxygen / nitrogen volume ratio of 0.17–0.25. When the temperature reaches 350 °C–650 °C, calcination is maintained for 0.5–4 hours, followed by natural cooling to room temperature to obtain a white powder of the flower-shaped SnSe2 / SnO2 heterojunction. However, this flower-shaped heterojunction is structurally unstable during use, easily collapsing and stacking, clogging the pores; therefore, its stability in use is limited. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects in the prior art and provide a visible light-excited nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure, its preparation method, and its application. The Bi2S3 / SnS2 heterostructure uses two-dimensional sheet-like SnS2 as a substrate to induce the generation of nanorod-shaped Bi2S3, which is uniformly distributed on the surface of the SnS2 sheet, and has higher structural stability. Furthermore, the sensor based on this heterojunction has good selectivity, high response value, and strong stability for low concentrations of NO2 gas, and can operate at room temperature under visible light excitation.

[0004] To achieve the objectives of this invention, the following technical solution is adopted: A visible-light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure includes interdigitated electrodes and a Bi₂S₃ / SnS₂ heterostructure composite material coated on the surface of the interdigitated electrodes. It also includes an LED light source. The gas-sensitive material is uniformly coated on the surface of the interdigitated electrodes with a coating thickness of 20 μm. m~40 m; The Bi2S3 / SnS2 heterostructure composite material includes a micron-sized two-dimensional sheet structure SnS2 and a nanorod structure Bi2S3 uniformly distributed on the surface of the SnS2 two-dimensional sheet, with a molar ratio of Bi2S3 to SnS2 of 0.1 to 0.4:1; The LED light source is placed vertically above the gas-sensitive material at a height of 1 cm to 3 cm.

[0005] As a preferred technical solution, the preparation of Bi2S3 / SnS2 heterostructure composite material includes the following steps: dispersing SnS2 powder in an ethylene glycol solution and continuously stirring to obtain a uniform suspension with a concentration of 0.01 mol / L to 0.05 mol / L; then, slowly adding a bismuth nitrate / ethylene glycol solution to the SnS2 suspension and stirring to achieve uniform mixing (stirring time is generally 10 min to 30 min); then adding a sodium sulfide / ethylene glycol solution dropwise to the above precursor and stirring to achieve uniform mixing (stirring time is generally 10 min to 30 min); transferring the resulting mixture to a reaction vessel and hydrothermally reacting at a temperature of 100℃ to 200℃ for 5 h to 15 h; collecting the product, washing and drying it to obtain the Bi2S3 / SnS2 heterostructure material.

[0006] Furthermore, the concentrations of the bismuth nitrate / ethylene glycol solution and the sodium sulfide / ethylene glycol solution are 0.01 mol / L~0.04 mol / L and 0.015 mol / L~0.06 mol / L, respectively.

[0007] To further improve the response value and response rate, the following preferred scheme can also be adopted: As a preferred technical solution, the size of the Bi2S3 / SnS2 heterostructure composite material is 2. m~10 m.

[0008] As a preferred technical solution, the interdigitated electrode has a thickness of 400 mm. m~600 The alumina substrate has a pre-patterned pure gold material on the front side, with 5-8 pairs of interdigitated fingers and a finger spacing of 100. m~300 m.

[0009] As a preferred technical solution, the wavelength of the LED light source is 500nm~550nm, and the power density is 1mW / cm². 2 ~50mW / cm 2 .

[0010] The method for preparing the above-mentioned nitrogen dioxide gas sensor includes the following steps: The Bi2S3 / SnS2 heterostructure composite material is ground in a mortar to make the obtained powder easier to disperse (grinding time is generally 10 min to 30 min). The ground powder is then dispersed in deionized water and ultrasonically treated to obtain a dispersion of 4 mg / mL to 8 mg / mL. 3 μL to 6 μL of the dispersion is coated onto the surface of the interdigital electrode and then placed in a vacuum drying oven at 60℃ to 80℃ for 10 h to 24 h to obtain the nitrogen dioxide gas sensor.

[0011] Working principle of the invention: This invention relates to a nitrogen dioxide gas sensor, which is a chemiluminescent resistive semiconductor gas sensor. Its working principle is based on the fact that when the semiconductor sensing material comes into contact with the target gas, the redox reaction on the surface causes a change in carrier concentration, resulting in a corresponding change in the semiconductor resistance value. This allows for the detection of the type and concentration of the target gas. Because the work function of the semiconductor sensing material used in this invention is lower than the affinity of nitrogen dioxide gas molecules for carriers, when nitrogen dioxide molecules are adsorbed on the material surface, they capture free electrons from the semiconductor to form negative ion adsorption states. This leads to a decrease in the carrier concentration in the semiconductor, which macroscopically manifests as a change in the sensor's resistance value. This change in resistance serves as the sensor's real-time detection signal output.

[0012] The beneficial effects of this invention are: 1. This invention uses a hydrothermal method to prepare a Bi2S3 / SnS2 heterostructure composite material. The raw materials are readily available and inexpensive, and the preparation process is simple. It is a semiconductor heterostructure preparation scheme with low equipment investment and simple process flow.

[0013] 2. The composite material of this invention features uniformly distributed Bi2S3 nanorods on its surface, which partially contact micron-sized sheet-like SnS2, forming a heterojunction. This increases the active sites on the composite surface, promoting the adsorption of more gas molecules and thus enhancing the gas-sensing performance. Therefore, the composite material of this invention has the advantages of chemical stability and excellent detection performance for nitrogen dioxide gas. In its preparation, two-dimensional sheet-like SnS2 material is used as the substrate. Compared with the three-dimensional flower-like SnS2 clusters in existing technologies, its flat and continuous layered structure is more conducive to the uniform loading of Bi2S3 nanoparticles, thereby constructing a stable and large-area contact heterojunction interface. The regular exposed crystal faces and layered structure of the sheet-like SnS2 facilitate smoother electron transport at the interface, avoiding the stacking collapse, pore blockage, or surface reconstruction phenomena that may occur in flower-like structures during long-term testing, effectively improving the stability and repeatability of the heterostructure during gas-sensing testing.

[0014] 3. The interdigitated electrodes used in this invention can be made from an alumina substrate as the base material, with metal interdigitated electrodes fabricated on its surface. The synthesized Bi2S3 / SnS2 heterostructure composite material is then coated onto the electrode gap region to form a stable gas-sensitive thin film. This structure not only possesses good conductivity and adhesion but also offers advantages such as compatibility with CMOS processes, simple fabrication process, ease of miniaturization, and integration with other microelectronic devices.

[0015] 4. The LED light source used in this invention provides external photoexcitation for the nitrogen dioxide gas sensor, enhancing the photogenerated carrier concentration of the Bi2S3 / SnS2 heterostructure composite material, thereby improving the sensor's gas-sensing performance at room temperature. The selected LED light source can be a visible light source with a wavelength range of 500nm~550nm, which can effectively excite electron transitions and promote the generation of electron-hole pairs. This LED light source has advantages such as small size, low energy consumption, fast response, long lifespan, and ease of integration with the sensor. Attached Figure Description

[0016] Figure 1 This is an X-ray diffraction pattern of the Bi2S3 / SnS2 heterostructure composite material of the present invention.

[0017] Figure 2 The image shows the scanning electron microscope (SEM) microstructure of the Bi2S3 / SnS2 heterostructure composite material of this invention.

[0018] Figure 3 The image shows the transmission electron microscope (TEM) microstructure of the Bi2S3 / SnS2 heterostructure composite material of this invention.

[0019] Figure 4This is a comparison chart showing the response of the Bi2S3 / SnS2 heterostructure composite material and the gas sensor prepared by the single-component Bi2S3 and SnS2 of this invention to 5 ppm nitrogen dioxide under the optimal power density of the LED light source. In the figure, x in Bi2S3 / SnS2-x refers to the molar ratio of Bi2S3 to SnS2 in the composite material, and x = 0.1, 0.2, 0.3, 0.4.

[0020] Figure 5 This is a comparison chart of the responses of the Bi2S3 / SnS2 heterostructure composite gas sensor of the present invention to several common volatile interfering gases and nitrogen dioxide gas. Detailed Implementation

[0021] To further understand the purpose, content, and advantages of this invention, specific embodiments of the invention are described in detail below. However, these embodiments are not limited to the examples described below and should be freely combined according to actual circumstances. The endpoints and values ​​of the ranges disclosed herein are not limited to the precise ranges and values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The present invention will be further described in detail below with reference to the embodiments: The two-dimensional sheet-like SnS2 in the following embodiments was provided by Sichuan Liuzu Semiconductor Materials Co., Ltd. Example 1

[0023] A nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure composite material comprises a semiconductor gas-sensitive material, interdigitated electrodes, and an LED light source. The gas-sensitive material is uniformly coated on the surface of the interdigitated electrodes, with a coating thickness of 40 mm. m. The LED light source is placed vertically above the gas-sensitive material at a height of 1 cm. The gas-sensitive material is a heterostructure composite material formed by nanorod-shaped bismuth sulfide and micron-shaped sheet-like tin disulfide prepared by hydrothermal method. The preparation method includes the following steps: Step 1: Preparation of the Bi₂S₃ / SnS₂ heterostructure: First, bismuth nitrate and sodium sulfide powders were dissolved in ethylene glycol solution, with the concentrations of bismuth nitrate and sodium sulfide controlled at 0.02 mol / L and 0.03 mol / L, respectively. Then, an appropriate amount of SnS₂ powder was weighed and dispersed in the ethylene glycol solution, and stirred continuously to obtain a uniform suspension with a concentration of 0.05 mol / L. Next, the bismuth nitrate / ethylene glycol solution was slowly added to the SnS₂ dispersion, and stirring was continued for 30 min. Then, the sodium sulfide / ethylene glycol solution was added dropwise to the above precursor, and stirring was continued for another 30 min. The resulting mixture was transferred to a reaction vessel and subjected to hydrothermal reaction at 180℃ for 12 h. After naturally cooling to room temperature, the product was washed multiple times and dried in a vacuum drying oven at 60℃ for 14 h to obtain the Bi₂S₃ / SnS₂ heterostructure material (Bi₂S₃ / SnS₂-0.2). Step 2, preparation of the gas sensor: The Bi2S3 / SnS2 heterostructure composite material obtained in Step 1 is ground in a mortar for 10 min to 30 min, and then the ground powder is dispersed in deionized water and ultrasonically treated to obtain a dispersion of 4 mg / mL to 8 mg / mL; 3 μL to 6 μL of the dispersion is coated onto the surface of the interdigitated electrode and then placed in a vacuum drying oven at 60 °C for 14 h to obtain the nitrogen dioxide gas sensor.

[0024] Figure 1 X-ray diffraction patterns of the Bi2S3 / SnS2 heterostructure composite material prepared in Example 1 are given.

[0025] Figure 2 Scanning electron microscopy images of the Bi2S3 / SnS2 heterostructure composite material prepared in Example 1 are provided.

[0026] Figure 3 Transmission electron microscopy (TEM) images of the Bi2S3 / SnS2 heterostructure composite material prepared in Example 1 are provided. Example 2

[0027] A nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure composite material comprises a semiconductor gas-sensitive material, interdigitated electrodes, and an LED light source. The gas-sensitive material is uniformly coated on the surface of the interdigitated electrodes, with a coating thickness of 40 mm. m. The LED light source is placed vertically above the gas-sensitive material at a height of 1 cm. The gas-sensitive material is a heterostructure composite material formed by nanorod-shaped bismuth sulfide and micron-shaped sheet-like tin disulfide prepared by hydrothermal method. The preparation method includes the following steps: Step 1: Preparation of the Bi₂S₃ / SnS₂ heterostructure: First, bismuth nitrate and sodium sulfide powders were dissolved in ethylene glycol solution, with the concentrations of bismuth nitrate and sodium sulfide controlled at 0.04 mol / L and 0.06 mol / L, respectively. Then, an appropriate amount of SnS₂ powder was weighed and dispersed in the ethylene glycol solution, and stirred continuously to obtain a uniform suspension with a concentration of 0.05 mol / L. Next, the bismuth nitrate / ethylene glycol solution was slowly added to the SnS₂ dispersion, and stirring was continued for 30 min. Then, the sodium sulfide / ethylene glycol solution was added dropwise to the above precursor, and stirring was continued for another 30 min. The resulting mixture was transferred to a reaction vessel and subjected to hydrothermal reaction at 180℃ for 12 h. After naturally cooling to room temperature, the product was washed multiple times and dried in a vacuum drying oven at 60℃ for 14 h to obtain the Bi₂S₃ / SnS₂ heterostructure material (Bi₂S₃ / SnS₂-0.4). Step 2, preparation of the gas sensor: The Bi2S3 / SnS2 heterostructure composite material obtained in Step 1 is ground in a mortar for 10 min to 30 min, and then the ground powder is dispersed in deionized water and ultrasonically treated to obtain a dispersion of 4 mg / mL to 8 mg / mL; 3 μL to 6 μL of the dispersion is coated onto the surface of the interdigitated electrode and then placed in a vacuum drying oven at 60 °C for 14 h to obtain the nitrogen dioxide gas sensor.

[0028] The preparation methods of Bi2S3 / SnS2-0.1 and Bi2S3 / SnS2-0.3 are the same as in Example 1, except that the concentrations of the bismuth nitrate ethylene glycol solution and the sodium sulfide ethylene glycol solution are changed to 0.01 mol / L and 0.015 mol / L, and 0.03 mol / L and 0.045 mol / L, respectively. Example 3

[0029] Performance testing of nitrogen dioxide gas sensor: The Bi2S3 / SnS2 heterostructure composite gas sensor prepared in step two of Example 1 was placed in an air atmosphere, with the LED light source using an optimal power density of 20 mW / cm². 2 Nitrogen dioxide gas was introduced under the specified conditions. The resistance change of the sensor in air and in a 5 ppm nitrogen dioxide atmosphere with air as the background was measured using a digital multimeter and used as the sensor signal.

[0030] Figure 4 The response of the Bi2S3 / SnS2 heterostructure composite material prepared in Example 1 and the gas sensor prepared by single-component Bi2S3 and SnS2 to 5 ppm nitrogen dioxide under the optimal power density of the LED light source is shown in the comparison graph. Figure 5A comparative graph showing the response of the Bi2S3 / SnS2 heterostructure composite gas sensor prepared in Example 1 to several common volatile interfering gases and nitrogen dioxide gas is provided.

[0031] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

Claims

1. A visible light-excited nitrogen dioxide gas sensor based on a Bi2S3 / SnS2 heterostructure, comprising a gas-sensitive material, interdigitated electrodes, and an LED light source, characterized in that, The gas-sensitive material is a Bi2S3 / SnS2 heterostructure composite material, uniformly coated on the surface of the interdigitated electrode, with a coating thickness of 20 mm. m~40 m; The LED light source is placed vertically directly above the gas-sensitive material; The Bi2S3 / SnS2 heterostructure composite material comprises a micron-sized two-dimensional sheet structure SnS2 and a nanorod structure Bi2S3 uniformly distributed on the surface of the SnS2 two-dimensional sheet, with a molar ratio of Bi2S3 to SnS2 of 0.1 to 0.4:

1.

2. The visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 1, characterized in that, The size of the Bi2S3 / SnS2 heterostructure composite material is 2. m~10 m.

3. The visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 1, characterized in that, The interdigitated electrodes are made of pre-patterned pure gold material on the front side, with 5 to 8 pairs of interdigitates and a spacing of 100mm between them. m~300 m, thickness 400 m~600 m-sized alumina substrate.

4. A visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 1, characterized in that, The LED light source has a wavelength of 500nm~550nm and a power density of 1mW / cm². 2 ~50mW / cm 2 .

5. A visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 1, characterized in that, The Bi2S3 / SnS2 heterostructure composite material was prepared by a hydrothermal method.

6. A visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 1, characterized in that, The preparation method of Bi2S3 / SnS2 heterostructure composite material includes the following steps: First, bismuth nitrate and sodium sulfide powders were dissolved separately in ethylene glycol solution. Then, SnS2 powder was dispersed in ethylene glycol solution and stirred continuously to obtain a uniform suspension. Next, bismuth nitrate / ethylene glycol solution was slowly added to the uniform suspension while stirring continuously. Then, sodium sulfide / ethylene glycol solution was added dropwise under stirring conditions. The resulting mixture was transferred to a reaction vessel and subjected to hydrothermal reaction at 100℃~200℃ for 5h~15h. After naturally cooling to room temperature, the product was washed multiple times and vacuum dried to obtain the Bi2S3 / SnS2 heterostructure composite material.

7. A method for fabricating a visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to any one of claims 1 to 6, characterized in that, Includes the following steps: The Bi2S3 / SnS2 heterostructure composite material was ground in a mortar to make the obtained powder easier to disperse. The ground powder was then dispersed in deionized water and ultrasonically treated to obtain a dispersion. The dispersion was then coated onto the surface of the interdigitated electrode and placed in a vacuum drying oven at 60℃~80℃ for 10h~24h to obtain the nitrogen dioxide gas sensor.

8. The method for fabricating a visible light-excited nitrogen dioxide gas sensor based on a Bi₂S₃ / SnS₂ heterostructure according to claim 7, characterized in that, The concentration of the dispersion is 4 mg / mL to 8 mg / mL.

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