A hydrogen sulfide gas sensor and its preparation method

Abstract

The present invention discloses a hydrogen sulfide gas sensor, comprising an electrode, wherein a sensitive layer formed of a BP / SnO2 composite material is covered on the surface of the electrode. The BP / SnO2 composite material is prepared from a BP / SnO2 composite material solution formed by uniformly dispersing black phosphorus (BP), tin tetrachloride pentahydrate (SnCl4·5H2O), and polyvinylpyrrolidone (PVP) in deionized water. Among the BP / SnO2 composite materials, a black phosphorus nanosheet / single-layer SnO2 quantum dot composite material is preferably used as the sensitive layer of the hydrogen sulfide gas sensor. The hydrogen sulfide gas sensor disclosed in the present invention achieves a lower detection limit (0.2 ppm), ultrahigh sensitivity (response (Ra / Rg) to 5 ppm of H2S is 233.8), and fast response (16.4 s) for H2S detection, thereby solving the technical problems of low accuracy and low sensitivity of hydrogen sulfide gas sensors in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen sulfide detection, and in particular to a hydrogen sulfide gas sensor with high sensitivity and accuracy and a preparation method thereof. Background Art

[0002] Hydrogen sulfide is an inorganic compound with the chemical formula H2S and a molecular weight of 34.076. Under standard conditions, it is a flammable, acidic gas. It is colorless and has a rotten egg odor at low concentrations, and a sulfurous odor at extremely low concentrations. It is highly toxic. Its aqueous solution is hydrosulfuric acid, which is weakly acidic, weaker than carbonic acid but stronger than boric acid. It is soluble in water and readily soluble in alcohols, petroleum solvents, and crude oil. Hydrogen sulfide is a flammable and hazardous chemical that can form explosive mixtures with air and can cause combustion and explosion when exposed to open flames or high temperatures. Hydrogen sulfide is an important chemical raw material. It is commonly used in the synthesis of phosphors, electroluminescent materials, photoconductors, and photoelectric exposure meters. It is also used as a reducing agent in organic synthesis, in metal refining, pesticides, pharmaceuticals, and catalyst regeneration. It is also used in the manufacture of inorganic sulfides and in chemical analysis, such as the identification of metal ions.

[0003] Furthermore, hydrogen sulfide (H2S), a foul-smelling gas, is a hallmark of halitosis in the exhaled breath of individuals with the condition. Its concentration typically ranges from less than 1 ppm. Common oral diseases that cause halitosis include tongue coating, tooth decay, and periodontal disease. Currently, over 10% of the population in my country suffers from halitosis. Therefore, measuring H2S concentrations in the exhaled breath of individuals with halitosis can facilitate clinical diagnosis. Therefore, real-time monitoring of H2S concentrations in various scenarios is crucial for workplace safety and human health. Current methods for detecting hydrogen sulfide include silver nitrate colorimetry, gas chromatography, iodine titration, and methylene blue. However, these methods require large, expensive, and complex instruments with long detection times, making them incapable of real-time monitoring across multiple scenarios. Gas sensors are compact, inexpensive, and easy to operate, making them widely used.

[0004] Tin dioxide (SnO2) is a common gas sensor material in existing technologies. However, current SnO2-based gas sensors often suffer from low sensitivity and high reaction temperatures, significantly limiting their development and practical application. For example, Chinese Patent CN 108318542 A discloses a gas sensor based on a SnO2-based hydrogen sulfide-sensitive material. However, its sensitivity is low, with a response of only 4 to 5 ppm H2S. Chinese Patent CN 104502413 A discloses a SnO2-based hydrogen sulfide gas sensor doped with copper oxide, but its shortcomings include low sensitivity and high operating temperature (the response to 10 ppm H2S is only 20, and the operating temperature is greater than 240°C). Chinese Patent CN 112067666A discloses a hydrogen sulfide gas sensor based on a SnO2-doped silver phosphate-based gas sensor. However, its sensitivity (response to 10 ppm H2S is 118) still needs to be improved. Summary of the Invention

[0005] The present invention aims to provide a hydrogen sulfide gas sensor and a preparation method thereof, so as to solve the technical problem of low accuracy and low sensitivity of hydrogen sulfide gas sensors in the prior art.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A hydrogen sulfide gas sensor includes an electrode, characterized in that a sensitive layer formed by a BP / SnO2 composite material is covered on the surface of the electrode; the BP / SnO2 composite material is prepared from a BP / SnO2 composite material solution formed by uniformly dispersing black phosphorus (BP), tin tetrachloride pentahydrate (SnCl4·5H2O) and polyvinylpyrrolidone (PVP) in deionized water.

[0008] Preferably, in the BP / SnO2 composite material, the weight ratio of BP to SnO2 ranges from BP / SnO2=0.008:1 to 0.031:1.

[0009] Preferably, in the BP / SnO2 composite material, the weight ratio of BP to SnO2 is BP / SnO2=0.016:1.

[0010] Preferably, the weight ratio of the tin tetrachloride pentahydrate and polyvinyl pyrrolidone is SnCl4·5H2O / PVP=1.7:1.

[0011] Preferably, the electrodes are MEMS interdigital electrodes.

[0012] Preferably, in the BP / SnO2 composite material, the BP is a black phosphorus nanosheet, the length of the black phosphorus nanosheet is 200nm~5μm, and the thickness is 4~8nm; the SnO2 is a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2~3nm.

[0013] The present invention also discloses a method for preparing a hydrogen sulfide gas sensor, which utilizes the hydrogen sulfide gas sensor described above and is characterized in that it comprises the following steps:

[0014] Step 1: exfoliate a preset mass of black phosphorus into nanosheets, and disperse the obtained black phosphorus nanosheets into an aqueous solution to obtain a black phosphorus dispersion with a black phosphorus mass fraction of 0.5 mg / mL.

[0015] Step 2: dissolving a preset amount of tin tetrachloride pentahydrate and polyvinyl pyrrolidone in deionized water and mixing and stirring to obtain a mixed solution;

[0016] Step 3: mixing the black phosphorus dispersion in step 1 and the mixed solution in step 2 and stirring to obtain a doping mixed solution;

[0017] Step 4: transferring the doped mixed solution obtained in step 3 to the lining of the reactor for hydrothermal reaction to obtain a mixed solution containing the BP / SnO2 composite material;

[0018] Step 5: washing the BP / SnO2 composite material produced in step 4 and drying it to obtain a dry BP / SnO2 composite material;

[0019] Step 6: using a drop coating method, the dried BP / SnO2 composite material obtained in step 5 is dispersed in deionized water and drop-coated onto the surface of the electrode device to prepare an electrode device covered with a BP / SnO2 composite film;

[0020] Step 7: Drying the electrode device having the BP / SnO2 composite material film to obtain a hydrogen sulfide gas sensor based on the BP / SnO2 composite material.

[0021] Preferably, in step 1, the black phosphorus block is exfoliated into nanosheets by ultrasonic liquid phase exfoliation, with an ultrasonic duration of 12 hours and an ultrasonic frequency of 20 kHz to 23 kHz.

[0022] Preferably, in the BP / SnO2 composite material obtained in step 5, the weight ratio of BP and SnO2 is in the range of BP:SnO2=0.008:1~0.031:1; the BP is a black phosphorus nanosheet, the length of the black phosphorus nanosheet is 200nm~5μm, and the thickness is 4~8nm; the SnO2 is a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2~3nm.

[0023] Preferably, the electrode device described in step 6 is a MEMS interdigital electrode device.

[0024] The present invention has the following beneficial effects:

[0025] 1. This paper proposes, for the first time, a method for detecting H2S using a black phosphorus nanosheet / monolayer SnO2 quantum dot (BP / SnO2) composite material. Compared to SnO2 gas-sensing materials alone, the steric barrier effect of the BP nanosheets during synthesis limits the growth of SnO2. This results in a single-layer SnO2 quantum dot morphology of several nanometers on the BP nanosheets, significantly smaller than that of the single SnO2 material. According to the general principle of metal oxide gas-sensing materials, the smaller the material size, the greater the gas-sensing effect. As the gas sensing center in the BP / SnO2 composite, the single-layer SnO2 quantum dot morphology can effectively improve gas-sensing responsivity and the utilization efficiency of the gas-sensing material. Furthermore, the introduction of BP into the BP / SnO2 composite creates a large number of BP-SnO2 heterojunctions, increasing the material's specific surface area and the number of adsorption sites for gas molecules. This promotes the adsorption and diffusion of gas molecules within the sensitive film, thereby enhancing the sensor's response strength and adsorption / desorption rates.

[0026] 2. The preparation method of the BP / SnO2 composite material disclosed in the present invention is based on hydrothermal reaction, and the material preparation method is simple, green and low-cost.

[0027] 3. The hydrogen sulfide gas sensor disclosed in this invention achieves a low detection limit (0.2 ppm), high sensitivity (response (Ra / Rg) of 233.8 to 5 ppm of H2S), and fast H2S detection response (16.4 s). Furthermore, the sensor exhibits excellent moisture resistance and can operate in high-humidity environments.

[0028] 4. The sensor designed in the present invention is based on MEMS devices, and its energy consumption (10 mW) is much lower than that of gas sensors based on ceramic tube devices (400 mW-1 W). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the purpose, technical solutions and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0030] Figure 1 This is the SEM surface morphology of the BP / SnO2 composite material of the present invention.

[0031] Figure 2This is a resistance dynamic change diagram of the hydrogen sulfide gas sensor based on the BP / SnO2 composite material of the present invention in the repeatability test of 200 ppb H2S.

[0032] Figure 3 This is the real-time dynamic response diagram of the hydrogen sulfide gas sensor based on the BP / SnO2 composite material of the present invention to 200 ppb~9 ppm H2S.

[0033] Figure 4 The hydrogen sulfide gas sensor based on the BP / SnO2 composite material of the present invention responds to 5 ppm H2S at different relative humidity.

[0034] Figure 5 This is a dynamic response diagram of the hydrogen sulfide gas sensor based on the BP / SnO2 composite material of the present invention to 200-350 ppb H2S in simulated bad breath.

[0035] Figure 6 The linear fitting curve of the hydrogen sulfide gas sensor based on the BP / SnO2 composite material of the present invention to the H2S response in bad breath and the gas concentration. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not require further definition or explanation in subsequent figures. In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the figures, or the orientations or positional relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and are not to be construed as indicating or implying relative importance. Furthermore, terms such as "horizontal" and "vertical" do not imply that a component must be absolutely horizontal or overhanging, but rather may be slightly tilted. For example, "horizontal" simply refers to a direction that is more horizontal than "vertical," and does not imply that the structure must be completely horizontal, but rather may be slightly tilted. In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0038] The present invention aims to solve the technical problem of low accuracy and low sensitivity of hydrogen sulfide gas sensors in the prior art.

[0039] Based on the above technical problems to be solved, the present invention discloses a hydrogen sulfide gas sensor, comprising an electrode, the surface of which is covered with a sensitive layer formed by a BP / SnO2 composite material; the BP / SnO2 composite material is prepared from a BP / SnO2 composite material solution formed by uniformly dispersing black phosphorus (BP), tin tetrachloride pentahydrate (SnCl4·5H2O) and polyvinyl pyrrolidone (PVP) in deionized water.

[0040] Specifically, the BP material refers to black phosphorus (BP), which is an allotrope of elemental phosphorus.

[0041] Preferably, in the BP / SnO2 composite material, black phosphorus is a nanosheet, SnO2 is a single-layer SnO2 quantum dot, and black phosphorus is in the form of a nanosheet in the composite material. The length of the black phosphorus nanosheet is 200nm~5μm, and the thickness is 4~8nm; the SnO2 refers to a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2~3nm, that is, the SnO2 material can be attached to the black phosphorus nanosheet and present a quantum dot form.

[0042] Quantum dots are an important nanoscale, low-dimensional semiconductor material whose dimensions in any three dimensions are no greater than twice the exciton Bohr radius of the corresponding semiconductor material. Quantum dots are generally spherical or quasi-spherical, with diameters typically ranging from 2 to 20 nm. Common examples include silicon quantum dots, germanium quantum dots, and cadmium sulfide quantum dots.

[0043] The low density of states and sharp energy levels in quantum dots result in a three-dimensional quantum confinement effect on carriers within the quantum dot structure, which alters their electrical and optical properties. Furthermore, quantum dots can undergo significant intra-band transitions under normal incidence. Electronic devices using quantum dots are gaining increasing attention due to their small size and low power consumption.

[0044] According to the general rules of metal oxide gas-sensitive materials, the smaller the material size, the greater the gas-sensitive effect. In this application document, a composite material formed by combining a single-layer SnO2 quantum dot material and black phosphorus nanosheets is used as the sensitive layer of the hydrogen sulfide gas sensor. This can achieve high sensitivity while also having a small size, enabling the hydrogen sulfide gas sensor to have a wider range of applications.

[0045] The devices disclosed in this application document are preferably MEMS devices, specifically resistive gas sensors based on interdigital electrodes. The MEMS device refers to a micro-electro-mechanical-system, which integrates information sensing, processing, mechanical actuators and other micro devices in a high-density, low-cost manner in a microsystem according to the manufacturing principles of integrated circuits.

[0046] The advantages of the MEMS device are small size, light weight, stable performance, mass production through IC and other processes, low cost, good performance consistency, low power consumption, high resonant frequency, short response time, high comprehensive integration, high added value, and multiple energy conversion and transmission functions, including force, heat, sound, magnetism, chemical, and bioenergy.

[0047] The optimal operating temperature of the hydrogen sulfide gas sensor disclosed in this application document is 130 degrees Celsius.

[0048] Preferably, in the BP / SnO2 composite material, the weight ratio of BP to SnO2 ranges from BP:SnO2=0.008:1 to 0.031:1.

[0049] Preferably, in the BP / SnO2 composite material, the weight ratio of BP to SnO2 is BP:SnO2=0.016:1.

[0050] Preferably, the weight ratio of the tin tetrachloride pentahydrate and polyvinyl pyrrolidone is SnCl4·5H2O / PVP=1.7:1.

[0051] Preferably, the calculation formula of the response value of the hydrogen sulfide gas sensor to a specific hydrogen sulfide gas concentration is: Ra / Rg;

[0052] Where: Ra is the stable resistance of the sensor in dry air, and Rg is the stable resistance of the sensor in H2S.

[0053] Preferably, the electrodes are MEMS interdigital electrodes.

[0054] The present invention also discloses a method for preparing a hydrogen sulfide gas sensor, which utilizes the hydrogen sulfide gas sensor described above and is characterized in that it comprises the following steps:

[0055] Step 1: peeling a preset mass of black phosphorus into nanosheets, and dispersing the obtained black phosphorus nanosheets into an aqueous solution to obtain a black phosphorus dispersion;

[0056] Step 2: dissolving a preset amount of tin tetrachloride pentahydrate and polyvinyl pyrrolidone in deionized water and mixing and stirring to obtain a mixed solution;

[0057] Step 3: mixing the black phosphorus dispersion in step 1 and the mixed solution in step 2 and stirring to obtain a doping mixed solution;

[0058] Step 4: transferring the doped mixed solution obtained in step 3 to the lining of the reactor for hydrothermal reaction to obtain a mixed solution containing the BP / SnO2 composite material;

[0059] Step 5: washing the BP / composite material produced in step 4 and drying the same to obtain a dry BP / SnO2 composite material;

[0060] Step 6: using a drop coating method, the dried BP / SnO2 composite material obtained in step 5 is dispersed in deionized water and drop-coated onto the surface of the electrode device to prepare an electrode device covered with a BP / SnO2 composite film;

[0061] Step 7: Drying the electrode device having the BP / SnO2 composite material film to obtain a hydrogen sulfide gas sensor based on the BP / SnO2 composite material.

[0062] The tin tetrachloride pentahydrate, also known as Stannic chloride, pentahydrate in English, has a molecular formula of SnCl4·5H2O, a molecular weight of 350.598, a melting point of 56°C, and a boiling point of 114.1°C (under standard atmospheric pressure). It is commonly used as an analytical reagent and mordant. Other names include tin tetrachloride pentahydrate, crystalline tin tetrachloride, and tin tetrachloride pentahydrate.

[0063] The polyvinylpyrrolidone, also known as Polyvinylpyrrolidone (PVP), has a molecular formula of (C6H9NO)n, a molecular weight of 111.143, a melting point of 130°C, and a boiling point of 90-93°C (under standard atmospheric pressure). It is often used as a dispersant for the synthesis of metal oxide nanomaterials. Its other names include 1-vinyl-2-pyrrolidone polymer, polyvinylpyrrolidone series, polyvinyl polypyrrolidone copper, polyvinylpyrrolidone, pivaloside, povidone, and polyvinylpyrrolidone K-17.

[0064] Preferably, in step 1, the black phosphorus is stripped into nanosheets by ultrasonic liquid phase stripping, with an ultrasonic duration of 12 hours and an ultrasonic frequency of 20 kHz-23 kHz.

[0065] Specifically, the initial form of the black phosphorus in step 1 is bulk black phosphorus.

[0066] Specifically, in step 4, the temperature of the hydrothermal reaction is 120 degrees Celsius, and the hydrothermal reaction time is 12 hours.

[0067] Preferably, in the BP / SnO2 composite material obtained in step 5, the weight ratio of BP to SnO2 ranges from BP:SnO2=0.008:1 to 0.031:1, preferably BP:SnO2=0.016:1.

[0068] Preferably, in the BP / SnO2 composite material obtained in step 5, black phosphorus is a nanosheet, SnO2 is a single-layer SnO2 quantum dot, and black phosphorus is in the form of a nanosheet in the composite material, and the length of the black phosphorus nanosheet is 200nm~5μm, and the thickness is 4~8nm; the SnO2 refers to a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2~3nm, that is, the SnO2 material can be attached to the black phosphorus nanosheet and present a quantum dot form.

[0069] Specifically, in step 5, the cleaning method adopts centrifugal cleaning, and the number of cleaning times is several times; the drying treatment adopts vacuum oven drying, the vacuum oven temperature is 60 degrees Celsius, and the drying time is 12 hours.

[0070] Preferably, the electrode device described in step 6 is a MEMS interdigital electrode device.

[0071] In step 7, the drying process is carried out in a vacuum environment, the vacuum drying temperature is 60 degrees Celsius, and the drying time is 12 hours.

[0072] The hydrogen sulfide gas sensor and preparation method disclosed in the present invention have the following technical effects: the H2S sensor based on the black phosphorus (BP) / tin dioxide (SnO2) composite material disclosed in the present invention achieves rapid, highly sensitive, and highly selective detection of 0.2-9 ppm H2S, and can sensitively detect trace amounts of H2S in simulated bad breath. At the same time, the device preparation process is simple, low-cost, easy to operate, and has a fast detection speed, overcoming the shortcomings of traditional detection methods such as high cost, complex operation, and long testing time. The present invention proposes for the first time a method for detecting H2S based on a BP / SnO2 composite material. Compared with a single SnO2 gas-sensitive material, the introduction of BP in the BP / SnO2 composite material enables the construction of a large number of heterojunctions, increases the specific surface area, increases the adsorption sites of gas molecules, and promotes the adsorption and diffusion of gas molecules in the sensitive film, thereby improving the response strength and adsorption / desorption speed of the sensor. The preparation method of the BP / SnO2 composite material of the present invention is based on a hydrothermal reaction, and the material preparation method is simple, green, and low-cost. The hydrogen sulfide gas sensor designed by the present invention achieves a lower detection limit (0.2 ppm), high sensitivity (response (Ra / Rg) to 5 ppm of H2S is 233.8), and fast response (16.4 s) H2S detection. The sensor designed by the present invention is based on a MEMS device and has low energy consumption (10 mW). Example

[0073] A hydrogen sulfide gas sensor disclosed in the present invention is applied to detect the H2S content in human exhaled breath. It should be noted that the hydrogen sulfide gas sensor disclosed in the present invention can be applied in many occasions and is not limited to this application embodiment.

[0074] In terms of oral hydrogen sulfide (H2S) gas, hydrogen sulfide, as a foul-smelling gas, is a characteristic gas in the exhaled breath of patients with bad breath. Its concentration range is usually less than 1 ppm. Currently, the clinical methods used to diagnose bad breath are mainly based on gas chromatography, ion chromatography, selected ion flow tube mass spectrometry and other technical methods. However, these analytical methods are often expensive, have complex operating procedures, long testing times, and high instrument maintenance costs, making them unsuitable for convenient home detection of bad breath.

[0075] The hydrogen sulfide gas sensor disclosed in the present invention can diagnose bad breath in real time and efficiently by detecting H2S concentration, exhibiting excellent selectivity and moisture resistance. It can detect H2S concentrations below 1 ppm in the exhaled breath of simulated bad breath patients, and has the ability to clinically diagnose bad breath.

[0076] The device used in this embodiment is a resistive gas sensor based on interdigital electrodes prepared by the above-mentioned method for preparing a hydrogen sulfide gas sensor. The sensitive layer is a BP / SnO2 composite material, and the optimal operating temperature is 130 degrees Celsius.

[0077] The specific preparation method is as follows:

[0078] Step 1: Ultrasonic liquid phase exfoliation is used to exfoliate a predetermined mass of black phosphorus (BP) into nanosheets. The ultrasonic treatment lasts for 12 hours at an ultrasonic frequency of 20 kHz to 23 kHz, and the resulting BP nanosheets are dispersed in an aqueous solution.

[0079] Step 2: dissolving a preset amount of tin tetrachloride pentahydrate (SnCl4·5H2O) and polyvinylpyrrolidone (PVP) in deionized water and mixing and stirring to obtain a mixed solution;

[0080] Step 3: mixing the black phosphorus dispersion in step 1 and the mixed solution in step 2 and stirring to obtain a doping mixed solution;

[0081] Step 4: Transfer the doped mixed solution obtained in step 3 to the inner lining of the reactor and perform a hydrothermal reaction at 120 degrees Celsius for 12 hours to obtain a mixed solution containing the BP / SnO2 composite material;

[0082] Step 5, centrifugally washing the BP / SnO2 composite material generated in step 4 several times, and then placing it in a vacuum oven for drying to obtain a dry BP / SnO2 composite material;

[0083] Step 6: using a drop coating method, the dried BP / SnO2 composite material obtained in step 5 is dispersed in deionized water and drop coated onto the surface of the MEMS electrode device to prepare an electrode device covered with a BP / SnO2 composite material film;

[0084] Step 7: Drying the electrode device having the BP / SnO2 composite material film to obtain a hydrogen sulfide gas sensor based on the BP / SnO2 composite material.

[0085] In step 5, the vacuum oven temperature is 60 degrees Celsius, the drying time is 12 hours, and the mass ratio of the prepared BP:SnO2 composite material ranges from BP:SnO2=0.008:1 to 0.031:1, with the optimal ratio being BP:SnO2=0.016:1.

[0086] The SEM surface morphology of the prepared BP / SnO2 composite material is shown in Figure 2. Figure 1 As shown, Figure 1 The BP in the middle is in the form of nanosheets, and a large number of uniformly sized SnO2 quantum dots (about 3nm in diameter) can be observed attached to the surface of the BP nanosheets. The structural morphology of the BP / SnO2 composite material is good.

[0087] Next, the performance of the hydrogen sulfide gas sensor based on BP / SnO2 composite material was tested. The test results are as follows: Figure 2 and Figure 3 As shown, Figure 2 This is the dynamic change diagram of the resistance of the hydrogen sulfide gas sensor based on BP / SnO2 composite material for 200 ppb H2S repeatability test. Figure 3 This is the real-time dynamic response diagram of the hydrogen sulfide gas sensor based on BP / SnO2 composite material to 200 ppb~9ppm H2S.

[0088] from Figure 2 It can be observed that when the concentration of hydrogen sulfide gas is high, the resistance of the hydrogen sulfide gas sensor becomes smaller. When the concentration of hydrogen sulfide gas is zero, the resistance of the hydrogen sulfide gas sensor gradually increases until it reaches the maximum value. As the concentration of hydrogen sulfide gas appears regularly or becomes zero, the resistance of the hydrogen sulfide gas sensor can change regularly according to the change of hydrogen sulfide gas concentration, and all have good response states.

[0089] from Figure 3 It can be observed that the hydrogen sulfide gas sensor based on the BP / SnO2 composite material has a good response state to different concentrations of hydrogen sulfide gas, and the response value increases with the increase of the hydrogen sulfide gas concentration. Among them, the hydrogen sulfide gas concentration range used in this embodiment is 200 ppb~9 ppm, and the response is defined as Ra / Rg, where Ra and Rg are the stable resistance of the sensor in dry air and H2S, respectively.

[0090] from Figure 4 The response values ​​of the hydrogen sulfide gas sensor based on BP / SnO2 composite material to 5ppm hydrogen sulfide gas at different relative humidity can be observed. As the background humidity increases from dry air (0.3%RH) to 80%RH, the H2S response value decreases slightly. However, at 80%RH, the response value still remains at 75% of the dry air background response value, demonstrating good moisture resistance. The response is defined as R RH / R g , R RH and R g They are the stable resistance of the sensor in different humidity backgrounds and after H2S is introduced.

[0091] Next, the exhalation states of healthy and pathological individuals were simulated. The simulated exhalation of normal individuals included about 75% nitrogen, about 20% oxygen, about 4% carbon dioxide, and about 60% relative humidity. Compared with the exhalation of normal individuals, the exhalation of pathological individuals contained more H2S gas.

[0092] like Figure 5 The figure shows the dynamic response of the hydrogen sulfide gas sensor based on BP / SnO2 composite material to 200~350ppb H2S in simulated bad breath. The dynamic response in the figure is defined as R n / R h , R n and R h are the stable resistance of the sensor in simulated normal breathing and simulated bad breath, respectively. Figure 5 It can be seen that when the hydrogen sulfide gas sensor based on the BP / SnO2 composite material recognizes the presence of hydrogen sulfide gas, the resistance of the sensor decreases, and the response value of the sensor is proportional to the concentration of the hydrogen sulfide gas. It can be concluded that the hydrogen sulfide gas sensor disclosed in the present invention has good performance in detecting the H2S content in human exhaled breath under the condition of simulated bad breath patients.

[0093] Then, four H2S concentrations were selected for testing, the four concentration values ​​were 200 ppb, 250 ppb, 300 ppb and 350 ppb respectively. Figure 6 The linear fitting curve of the hydrogen sulfide gas sensor based on BP / SnO2 composite material to the H2S response in bad breath and gas concentration is shown in Figure 2. Figure 6 As shown in Figure 2, it can be observed that the response of the hydrogen sulfide gas sensor increases with the increase of hydrogen sulfide gas concentration, and the slope of the fitting curve is 0.003 / ppb and the linearity is r 2 =0.93, showing Figure 6 Shown is better sensitivity.

[0094] This example demonstrates that the hydrogen sulfide gas sensor disclosed in the present invention achieves rapid, highly sensitive, and highly selective detection of hydrogen sulfide gas concentrations of 0.2 to 9 ppm, can sensitively detect trace amounts of H2S in simulated halitosis breath, and has good detection performance for weak H2S gas in the breath of pathological individuals. Furthermore, the device has a simple fabrication process, low cost, easy operation, and fast detection speed, overcoming the shortcomings of traditional detection methods such as high cost, complex operation, and long testing time.

[0095] It will be understood that the present invention is described through some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Under the guidance of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. The embodiments described in the present invention are some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

Claims

1. A hydrogen sulfide gas sensor comprising an electrode, characterized in that: A sensitive layer formed by a BP / SnO2 composite material is covered on the surface of the electrode; the BP / SnO2 composite material is prepared from a BP / SnO2 composite material solution formed by uniformly dispersing black phosphorus, tin tetrachloride pentahydrate and polyvinyl pyrrolidone in deionized water; the weight ratio of BP to SnO2 ranges from BP / SnO2=0.008:1 to 0.031:1; in the BP / SnO2 composite material, the BP is a black phosphorus nanosheet, the length of the black phosphorus nanosheet is 200nm~5μm, and the thickness is 4~8nm; the SnO2 is a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2~3nm.

2. A hydrogen sulfide gas sensor according to claim 1, characterized in that: In the BP / SnO2 composite material, the weight ratio of BP to SnO2 is BP / SnO2=0.016:

1.

3. A hydrogen sulfide gas sensor according to claim 1, characterized in that: The weight ratio of the tin tetrachloride pentahydrate and polyvinyl pyrrolidone is SnCl4·5H2O / PVP=1.7:

1.

4. A hydrogen sulfide gas sensor according to claim 1, characterized in that: The electrodes are MEMS interdigital electrodes.

5. A method for preparing a hydrogen sulfide gas sensor, comprising preparing a hydrogen sulfide gas sensor as claimed in claim 1, characterized in that: The following steps are involved: Step 1: exfoliating a predetermined mass of black phosphorus into nanosheets, and dispersing the obtained black phosphorus nanosheets into an aqueous solution to obtain a black phosphorus dispersion having a black phosphorus mass fraction of 0.5 mg / mL; Step 2: dissolving a preset amount of tin tetrachloride pentahydrate and polyvinyl pyrrolidone in deionized water and mixing and stirring to obtain a mixed solution; Step 3: mixing the black phosphorus dispersion in step 1 and the mixed solution in step 2 and stirring to obtain a doping mixed solution; Step 4: transferring the doped mixed solution obtained in step 3 to the lining of the reactor for hydrothermal reaction to obtain a mixed solution containing the BP / SnO2 composite material; Step 5: washing the BP / SnO2 composite material generated in step 4 and drying it to obtain a dry BP / SnO2 composite material; in the BP / SnO2 composite material, the weight ratio of BP to SnO2 ranges from 0.008:1 to 0.031:1; the length of the black phosphorus nanosheets is 200 nm to 5 μm, and the thickness is 4 to 8 nm; the SnO2 is a single-layer SnO2 quantum dot, and the diameter of the single-layer SnO2 quantum dot is 2 to 3 nm; Step 6: using a drop coating method, the dried BP / SnO2 composite material obtained in step 5 is dispersed in deionized water and drop-coated onto the surface of the electrode device to prepare an electrode device covered with a BP / SnO2 composite film; Step 7: Drying the electrode device having the BP / SnO2 composite material film to obtain a hydrogen sulfide gas sensor based on the BP / SnO2 composite material.

6. The method for preparing a hydrogen sulfide gas sensor according to claim 5, wherein: In step 1, the black phosphorus is stripped into nanosheets by ultrasonic liquid phase stripping, with an ultrasonic time of 12 hours and an ultrasonic frequency of 20 kHz-23 kHz.

7. The method for preparing a hydrogen sulfide gas sensor according to claim 5, characterized in that: The electrode device described in step 6 is a MEMS interdigital electrode.

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