A room temperature ammonia sensor based on PtS-WS2 heterojunction nanocomposite and a preparation process thereof

Abstract

This invention belongs to the field of nanomaterials technology, and provides a room-temperature ammonia sensor based on a PtS-WS2 heterojunction nanocomposite material and its preparation process. H2PtCl6 and L-lysine are added to a WS2 solution. [PtCl6] in the solution... 2‑ It combines with WS2 to form [PtCl6]. 2‑ / WS2 cluster, after introducing Na3cit, [PtCl6] 2‑ PtS seeds are reduced to form PtS, which grow on WS2 to complete the preparation of a PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets. This method is simple, the sensor structure is small and portable, requires no external heater or light source, has low power consumption, fast response speed, and long service life. The resulting sensor exhibits high response to ammonia at room temperature, fast response and recovery speed, and good selectivity, making it suitable for ammonia sensor applications.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a room temperature ammonia sensor based on PtS-WS2 heterojunction nanocomposite material and its preparation process. Background Technology

[0002] Ammonia has wide applications in chemical synthesis, such as in the production of fertilizers and explosives, and plays an important role in agricultural and industrial production. It can also serve as a green energy source for power generation, maritime shipping, and as a hydrogen carrier, helping to decarbonize the shipping industry and other industrial chains. Therefore, it helps reduce air pollution, alleviate the energy crisis, and maintain economic growth. However, to use ammonia in a wider range of fields, the issue of ammonia leakage must be carefully considered, as its leakage can potentially threaten human health. For example, low-concentration ammonia exposure can cause respiratory, skin, blood, and liver dysfunction, while high-concentration exposure can even cause acute liver failure in workers. Therefore, real-time ammonia monitoring is crucial. To provide real-time ammonia early warning, a large number of ammonia sensors need to be deployed in the aforementioned industrial sectors. These sensors can help industries meet production safety requirements. Currently, portable, low-cost, low-power, low-operating-temperature, high-response, easy-to-operate, and easily compatible sensors with other electronic devices are favored in the sensor market. Chemi-resistive gas sensors can meet these requirements.

[0003] Choosing the right material is the most crucial step in preparing an ideal gas sensor. Two-dimensional transition metal chalcogenides (TMDs) with graphene and graphene-like structures have attracted considerable attention. However, despite graphene's excellent electronic properties, its zero bandgap structure limits its application in gas sensors. Therefore, researchers have turned their attention to novel TMD materials such as WS2 and MoS2. These two-dimensional materials not only possess superior electron transport properties but also have a relatively wide bandgap, indicating greater potential for applications in chemical gas sensors. Furthermore, these two-dimensional materials have high specific surface areas and abundant active sites, which can promote gas adsorption and desorption processes. Ouyang (C.Ouyang, Y.Sang, H.Wang, C.Wu, Qin, Ziyu, T.Zhou, D.Zeng, C.Xie, High selectivity for room temperature detection of ammonia viain-situ Raman spectroscopy based on Pt quantum dots modified WS2 nanosheets, Applied Surface Science 485(2019)22-28.) et al. discovered that a Pt quantum dot modified WS2 nanosheet-based sensor exhibits excellent response characteristics and faster recovery speed to ammonia at room temperature. Liu et al. (S.Liu, Y.Xu, D.Chanda, L.Tan, R.Xing, X.Li, L.Mao, N.Kazuya, A.Fujishima, Ultrathin WS2 nanosheets vertically aligned on TiO2 nanobelts as efficient alkaline hydrogenevolution electrocatalyst, International Journal of Hydrogen Energy 45(2020)1697-1705.) studied TiO2@WS2 composite materials, demonstrating their higher efficiency and durability as electrocatalysts in hydrogen production. Therefore, introducing noble metal modification or a second modification to WS2 can improve gas-sensing performance and catalytic properties. In this study, we used an in-situ reduction method to prepare PtS nanoparticle-modified WS2 microsheet nanocomposites and investigated their gas-sensing properties. Summary of the Invention

[0004] The purpose of this invention is to realize ammonia gas sensing at room temperature, and to provide an ammonia gas sensor based on PtS-WS2 nanocomposite material that has high response, fast response recovery, good selectivity and can operate at room temperature.

[0005] The technical solution of this invention:

[0006] A room-temperature ammonia gas sensor based on a PtS-WS2 heterojunction nanocomposite material is disclosed. The sensor mainly comprises a gas-sensitive material and an interdigitated electrode plate. The gas-sensitive material is coated on the surface of the interdigitated electrode plate with a coating thickness of 50–100 μm. The gas-sensitive material is a PtS-WS2 heterojunction nanocomposite material, wherein PtS accounts for 0.5–5 mol% of the gas-sensitive material.

[0007] The diameter of the WS2 micron sheet is 0.4-4.3 microns, and the PtS is an irregular nanoparticle.

[0008] A fabrication process for a room-temperature ammonia sensor based on PtS-WS2 heterojunction nanocomposite material, comprising the following steps:

[0009] The PtS-WS2 heterojunction nanocomposite material was mixed with deionized water to form a uniform paste. The paste was then coated onto gold interdigitated electrodes, which were gold electrodes pre-printed on an alumina ceramic substrate (size: 15×8×0.6mm, finger width 0.4mm, finger spacing 0.2mm, 8 pairs of electrodes), with a coating thickness of 50-100μm. The electrodes were then placed in a drying oven and dried at 60℃ for 12 hours to obtain a room temperature ammonia sensor based on the PtS-WS2 heterojunction nanocomposite material.

[0010] A method for preparing a PtS-WS2 heterostructure nanocomposite material, comprising the following steps:

[0011] WS2 was dissolved in deionized water and sonicated for 15 minutes to obtain a homogeneous 0.01M WS2 aqueous solution; 0.01M L-lysine solution (C 11 H 23 N3O6 and a 0.01M chloroplatinic acid solution (H2PtCl6) were sequentially added to the above mixed solution, sonicated for 15 minutes, and then stirred for 20 minutes; here, L-lysine acts as a temporary binder. Next, a 0.1M sodium citrate solution (Na3cit) was slowly added dropwise to the stirred mixture, and stirring was continued for 30 minutes to obtain a PtS / WS2 heterostructure nanocomposite material with a PtS content of 0.5-5 mol%.

[0012] The volume ratio of WS2 solution, L-lysine solution, chloroplatinic acid solution and sodium citrate solution is 20:0.1:0.1:0.01 to 20:1:1:0.1.

[0013] The PtS / WS2 heterojunction nanocomposite material was centrifuged and washed several times with deionized water and anhydrous ethanol. The washed product was then placed in a drying oven and dried at 60°C for 12 hours.

[0014] A room-temperature ammonia sensor based on a PtS-WS2 heterojunction nanocomposite material is disclosed. The PtS-WS2 heterojunction nanocomposite material is obtained by an in-situ chemical reduction method. This in-situ chemical reduction method involves adding H2PtCl6 and L-lysine to a WS2 solution. The [PtCl6] in the solution... 2- It combines with WS2 to form [PtCl6]. 2- / WS2 cluster, after introducing Na3cit, [PtCl6] 2- PtS seeds are reduced to form PtS, which then grow on WS2, completing the preparation of the PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets.

[0015] Working principle: When the WS2 micron-sized chip sensor is placed in the air at room temperature, oxygen molecules in the air adsorb onto the WS2 surface and gain electrons transferred from the WS2 conduction band to form O2. - As the hole concentration in the WS2 microsheet increases, the electrical resistance decreases. After ammonia gas is injected, the ammonia gas and adsorbed O2... - The reaction produces NO2, H2O, and electrons. The electrons return to WS2, causing a decrease in the hole concentration in WS2 and an increase in its electrical resistance.

[0016] The improved gas-sensing performance of the PtS-WS2 heterojunction nanocomposite is due to the electron sensitization effect generated during the preparation of the PtS-WS2 heterojunction. Electrons are transferred from PtS to WS2. As the PtS content in the heterojunction nanomaterial increases, the sensor resistance decreases, which is beneficial to improving the gas-sensing response of the nanocomposite. On the other hand, the introduction of PtS can act as a catalyst to promote the adsorption of oxygen in the PtS-WS2 heterojunction nanocomposite, allowing the reaction to release more free electrons that return to the WS2 microsheets, further enhancing its gas-sensing performance.

[0017] The beneficial effects of this invention are:

[0018] 1. This invention utilizes PtS-WS2 to form a heterojunction nanocomposite material for ammonia gas sensors, which can operate at room temperature, avoiding wear and aging of gas-sensitive materials caused by long-term high-temperature operation, reducing safety hazards during long-term operation, and improving service life.

[0019] 2. This invention employs an in-situ chemical reduction method to obtain PtS-WS2 heterojunction nanocomposites. The raw materials are readily available, the preparation process is simple, and the preparation cost is low, making it suitable for low-cost semiconductor heterojunction fabrication. The successfully loaded PtS nanoparticles act as a catalyst, increasing the adsorbed oxygen concentration on the surface of the nanocomposite material, which is key to improving its gas-sensing performance.

[0020] 3. This invention requires no external heater, no external light source, and no external power supply. The product circuit design is simple when manufacturing the sensor, reducing the product manufacturing cost, usage cost, and energy consumption. It is a new type of energy-saving, portable, and green commercial sensor. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the synthesis of PtS-WS2 nanocomposite materials using a chemical in-situ reduction method. (a) Pure WS2 microsheets, ○ represents W, ● represents S; (b) WS2 microsheets and [PtCl6] in chloroplatinic acid solution. 2- They combine to form [PtCl6] 2- / WS2 cluster, It is [PtCl6] 2- (c)[PtCl6] 2- / WS2 clusters are reduced by sodium citrate to generate PtS seeds, which grow on WS2 microsheets to form PtS / WS2 heterojunction nanocomposite materials. It consists of irregular PtS nanoparticles.

[0022] Figure 2 (a) SEM image of pure WS2 microsheets; (b) SEM image of PtS-WS2 nanocomposite with PtS nanoparticle content of 5 mol%; (c) TEM image of PtS-WS2 nanocomposite with PtS nanoparticle content of 5 mol%; (d) HRTEM image of PtS-WS2 nanocomposite with PtS nanoparticle content of 5 mol%.

[0023] Figure 3 The response recovery curves of a sensor based on PtS-WS2 nanocomposite material and a sensor based on pure WS2 are compared for different concentrations of ammonia.

[0024] Figure 4 This study compares the responses of a PtS-WS2 nanocomposite sensor and a pure WS2 sensor to different gases. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] A room-temperature ammonia sensor was prepared using a PtS-WS2 heterojunction nanocomposite material, which was obtained by an in-situ chemical reduction method. The in-situ chemical reduction method involved adding 50 mg of WS2 to 20 ml of deionized water and sonicating for 15 minutes to form a homogeneous mixture of powder and deionized water. Appropriate amounts (0.1 ml) of a 0.01 M L-lysine solution (C0.01) were then added. 11 H 23 N3O6 and a suitable amount (0.1 ml) of 0.01 M chloroplatinic acid solution (H2PtCl6) were added to the above mixed solution, and the mixture was sonicated for 15 minutes and stirred for 20 minutes. L-Lysine acts as a temporary binder. Then, a suitable amount (0.01 ml) of 0.1 M sodium citrate solution (Na3cit) was slowly added dropwise to the stirred mixture, and the mixture was stirred for 30 minutes. In the PtS / WS2 heterojunction nanocomposite material to be prepared, the content of PtS nanoparticles in the gas-sensitive material was controlled to be 0.5 mol%. After the above steps, the product was subjected to routine centrifugation and washing several times with deionized water and anhydrous ethanol. The washed product was then placed in a drying oven and dried at 60°C for 12 hours. The formation process of the composite material is [PtCl6] in solution. 2- It combines with WS2 to form [PtCl6]. 2- The / WS2 cluster, after the introduction of sodium citrate (Na3cit), [PtCl6] 2- PtS seeds are reduced to form PtS, which then grow on WS2, completing the preparation of the PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets.

[0028] Example 2

[0029] A room-temperature ammonia sensor was prepared using a PtS-WS2 heterojunction nanocomposite material, which was obtained by an in-situ chemical reduction method. The in-situ chemical reduction method involved adding 50 mg of WS2 to 20 ml of deionized water and sonicating for 15 minutes to form a homogeneous mixture of powder and deionized water. Appropriate amounts (0.2 ml) of a 0.01 M L-lysine solution (C0.01) were then added. 11 H 23N3O6 and a suitable amount (0.2 ml) of 0.01 M chloroplatinic acid solution (H2PtCl6) were added to the above mixed solution, and the mixture was sonicated for 15 minutes and stirred for 20 minutes. L-Lysine acts as a temporary binder. Then, a suitable amount (0.02 ml) of 0.1 M sodium citrate solution (Na3cit) was slowly added dropwise to the stirred mixture, and the mixture was stirred for 30 minutes. In the PtS / WS2 heterojunction nanocomposite material to be prepared, the content of PtS nanoparticles in the gas-sensitive material was controlled to be 1 mol%. After the above steps, the product was subjected to routine centrifugation and washing several times with deionized water and anhydrous ethanol. The washed product was then placed in a drying oven and dried at 60°C for 12 hours. The formation process of the composite material is [PtCl6] in solution. 2- It combines with WS2 to form [PtCl6]. 2- The / WS2 cluster, after the introduction of sodium citrate (Na3cit), [PtCl6] 2- PtS seeds are reduced to form PtS, which then grow on WS2, completing the preparation of the PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets.

[0030] Example 3

[0031] A room-temperature ammonia sensor was prepared using a PtS-WS2 heterojunction nanocomposite material, which was obtained by an in-situ chemical reduction method. The in-situ chemical reduction method involved adding 50 mg of WS2 to 20 ml of deionized water and sonicating for 15 minutes to form a homogeneous mixture of powder and deionized water. Appropriate amounts (0.6 ml) of a 0.01 M L-lysine solution (C0.01) were then added. 11 H 23 N3O6 and a suitable amount (0.6 ml) of 0.01 M chloroplatinic acid solution (H2PtCl6) were added to the above mixed solution, and the mixture was sonicated for 15 minutes and stirred for 20 minutes. L-Lysine acts as a temporary binder. Then, a suitable amount (0.06 ml) of 0.1 M sodium citrate solution (Na3cit) was slowly added dropwise to the stirred mixture, and the mixture was stirred for 30 minutes. In the PtS / WS2 heterojunction nanocomposite material to be prepared, the content of PtS nanoparticles in the gas-sensitive material was controlled to be 3 mol%. After the above steps, the product was subjected to routine centrifugation and washing several times with deionized water and anhydrous ethanol. The washed product was then placed in a drying oven and dried at 60°C for 12 hours. The formation process of the composite material is [PtCl6] in solution. 2- It combines with WS2 to form [PtCl6]. 2- The / WS2 cluster, after the introduction of sodium citrate (Na3cit), [PtCl6]2- PtS seeds are reduced to form PtS, which then grow on WS2, completing the preparation of the PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets.

[0032] Example 4

[0033] A room-temperature ammonia sensor was prepared using a PtS-WS2 heterojunction nanocomposite material, which was obtained by an in-situ chemical reduction method. The in-situ chemical reduction method involved adding 50 mg of WS2 to 20 ml of deionized water and sonicating for 15 minutes to form a homogeneous mixture of powder and deionized water. Appropriate amounts (1 ml) of a 0.01 M L-lysine solution (C0.01) were then added. 11 H 23 N3O6 and a suitable amount (1 ml) of 0.01 M chloroplatinic acid solution (H2PtCl6) were added to the above mixed solution, and the mixture was sonicated for 15 minutes and stirred for 20 minutes. L-Lysine acts as a temporary binder. Then, a suitable amount (0.1 ml) of 0.1 M sodium citrate solution (Na3cit) was slowly added dropwise to the stirred mixture, and the mixture was stirred for 30 minutes. In the PtS / WS2 heterojunction nanocomposite material to be prepared, the content of PtS nanoparticles in the gas-sensitive material was controlled to be 5 mol%. After the above steps, the product was subjected to routine centrifugation and washing several times with deionized water and anhydrous ethanol. The washed product was then placed in a drying oven and dried at 60°C for 12 hours. The formation process of the composite material is [PtCl6] in solution. 2- It combines with WS2 to form [PtCl6]. 2- The / WS2 cluster, after the introduction of sodium citrate (Na3cit), [PtCl6] 2- PtS seeds are reduced to form PtS, which then grow on WS2, completing the preparation of the PtS-WS2 heterojunction nanocomposite material. The nanocomposite material is composed of PtS nanoparticles and WS2 micron-sized sheets.

Claims

1. A room temperature ammonia gas sensor based on PtS-WS2 heterojunction nanocomposite characterized in that, The room temperature ammonia sensor is mainly composed of a gas sensitive material and an interdigital electrode plate, wherein the gas sensitive material is coated on the surface of the interdigital electrode plate with a coating thickness of 50-100 microns; and the gas sensitive material is a PtS-WS2 heterojunction nanocomposite.

2. The room temperature ammonia sensor of claim 1, wherein, The PtS accounts for 0.5-5 mol% in the gas sensitive material.

3. The room temperature ammonia sensor of claim 1, wherein, The WS2 microparticle has a diameter of 0.4-4.3 microns, and the PtS is irregular nanoparticles.

4. A process for the preparation of room temperature ammonia sensor based on PtS-WS2 heterojunction nanocomposite material, characterized in that, The steps are as follows: The PtS-WS2 heterojunction nanocomposite is mixed with deionized water to form a uniform paste; the paste is coated on the gold interdigital electrode with a coating thickness of 50-100 microns; and then dried at 60°C for 12 hours to obtain a room temperature ammonia sensor based on the PtS-WS2 heterojunction nanocomposite.

5. The manufacturing process of claim 4, wherein, The preparation method of the PtS-WS2 heterojunction nanocomposite is as follows: WS2 is dissolved in deionized water and ultrasonically treated for 15 minutes to obtain a 0.01M uniform WS2 aqueous solution; a 0.01M L-type lysine solution and a 0.01M chloroplatinic acid solution are sequentially added to the above mixed solution, ultrasonically treated for 15 minutes, and then stirred for 20 minutes; then a 0.1M sodium citrate solution is slowly added dropwise to the stirring mixed solution, and the stirring is continued for 30 minutes to obtain a PtS / WS2 heterojunction nanocomposite with a PtS content of 0.5-5 mol%.

6. The manufacturing process according to claim 5, characterized in that, In the formula, V1, V2, V3 and V4 represent the volume of the WS2 solution, the L-type lysine solution, the chloroplatinic acid solution and the sodium citrate solution, respectively. The volume ratio of the WS2 solution, the L-type lysine solution, the chloroplatinic acid solution and the sodium citrate solution is 20:0.1:0.1:0.01-20:1:1:0.1.

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