A hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite and its preparation method

Abstract

This invention proposes a palladium sulfide-molybdenum disulfide composite hierarchical nanostructure-based nitrogen dioxide sensor and its fabrication method, belonging to the fields of sensor technology and composite nanomaterials technology. The sensor of this invention includes a substrate and a gas-sensitive layer loaded on the substrate. The gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial, in which PdS nanoparticle clusters are embedded on the surface of MoS2 nanoflowers. PdS and MoS2 form a heterojunction, improving the separation and transport rate of charge carriers, thereby enhancing the gas-sensitive performance of the nitrogen dioxide sensor. This results in a higher response value and faster response recovery time for NO2 concentrations at the ppm level.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and composite nanomaterials technology, and particularly relates to a nitrogen dioxide sensor based on a hierarchical nanostructure of palladium sulfide composite molybdenum disulfide and its preparation method. Background Technology

[0002] Nitrogen dioxide (NO2) is a colorless gas that is present in daily life for a long time. It is also a toxic and harmful pollutant, mainly originating from manufacturing production, vehicle emissions, and fuel combustion. Its production cannot be completely controlled, posing a significant threat to the environment and human health. Prolonged exposure to high concentrations of NO2 can irritate the respiratory tissues and eyes, and even cause irreversible damage to other vital parts of the body. When it comes into contact with other pollutants or water, it reacts, leading to natural disasters such as smog and acid rain, causing unavoidable damage to the living environment. Therefore, accurate and rapid detection of NO2 concentration is crucial. Developing NO2 gas sensors with rapid response, high sensitivity, and wide detection range is of great significance for protecting human health and monitoring the atmospheric environment.

[0003] Gas sensors based on metal-oxide-semiconductor (MOS) materials have seen rapid development due to their low cost, low power consumption, simple fabrication, high sensitivity, and fast response. For semiconductor sensors, selecting materials sensitive to the target gas is a crucial step in fabricating high-performance gas sensors. Currently, many high-performance two-dimensional materials have been developed and applied in various fields. Research has shown that two-dimensional transition metal chalcogenide (TMD) nanomaterials are considered excellent sensing materials for room-temperature gas sensors, which can reduce the sensor's detection limit. Among them, MoS2 possesses excellent electrical properties and a large specific surface area, providing more adsorption sites and improving carrier mobility, making it a promising p-type TMD material for gas sensing. However, poor selectivity and slow response / recovery time are among the key issues limiting the practical gas sensing applications of single-MoS2 gas sensors. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of the present invention:

[0007] A nitrogen dioxide sensor based on a hierarchical nanostructure of palladium sulfide and molybdenum disulfide composite includes a substrate and a gas-sensitive layer loaded on the substrate, wherein the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial (PdS / MoS2 composite nanomaterial).

[0008] Furthermore, the thickness of the gas-sensitive layer is 1-500 μm.

[0009] Furthermore, the palladium sulfide-molybdenum disulfide composite nanomaterial comprises palladium sulfide nanoparticles (PdS nanoparticles) and nanoflower-shaped molybdenum disulfide (nanoflower-shaped MoS2) in a mass ratio of 1:(0.5-5).

[0010] Furthermore, the palladium sulfide-molybdenum disulfide composite nanomaterial is prepared by mixing palladium sulfide nanoparticles and nanoflower-like structures in ethanol, and the mixing includes one of mechanical composite, ultrasonic composite, and in-situ growth.

[0011] Furthermore, both the palladium sulfide nanoparticles and the nanoflower-like structures are prepared using a hydrothermal method; more specifically, the hydrothermal method includes conventional hydrothermal or microwave hydrothermal; when the hydrothermal method is conventional hydrothermal, the hydrothermal reaction temperature is 120-250℃ and the hydrothermal reaction time is 5-30h; when the hydrothermal method is microwave hydrothermal, the microwave power is 100-800W.

[0012] Furthermore, the raw materials for preparing the palladium sulfide nanoparticles include palladium hydrochloride (H2PdCl4) and thiourea (CH4N2S); the raw materials for preparing the nanoflower-like structures include sodium molybdate (Na2MoO4·2H2O) and thiourea (CH4N2S).

[0013] Furthermore, the substrate is a rigid substrate or a flexible substrate.

[0014] Furthermore, the rigid substrate is one of a silicon-based substrate, a zirconium oxide substrate, and an aluminum oxide substrate; the flexible substrate is one of a polyimide (PI) substrate, a polyethylene terephthalate (PET) substrate, a polyurethane (PU) substrate, and a paper-based substrate.

[0015] The second technical solution of the present invention:

[0016] A method for preparing the aforementioned palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor includes the following steps:

[0017] The substrate is pretreated, and then coated with palladium sulfide-molybdenum disulfide composite nanomaterials. After drying, the palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor is obtained.

[0018] Furthermore, the coating method includes one of screen printing, drop coating, spray coating, spin coating, and inkjet printing.

[0019] Furthermore, the substrate pretreatment process includes cleaning and drying steps; specifically, the substrate is ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60-80℃ for 6-12 hours.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] In this invention, the NO2 gas-sensitive material in the palladium sulfide-molybdenum disulfide hierarchical nanostructure-based nitrogen dioxide sensor is a palladium sulfide-molybdenum disulfide composite nanomaterial. In the palladium sulfide-molybdenum disulfide composite nanomaterial, PdS nanoparticle clusters are embedded on the surface of MoS2 nanoflowers. PdS and MoS2 form a heterojunction, which improves the separation and transport rate of charge carriers, thereby improving the gas-sensing performance of the nitrogen dioxide sensor. This results in a higher response value and faster response recovery time for NO2 concentrations at the ppm level. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 This is a scanning electron microscope image of the palladium sulfide-molybdenum disulfide composite nanomaterial prepared in Example 1;

[0024] Figure 2 The real-time resistance change curve of the PdS / MoS2 composite nanomaterial-based NO2 gas sensor prepared in Example 1 against 50-10 ppm NO2 at room temperature;

[0025] Figure 3 The image shows the repeatability curve of the PdS / MoS2 composite nanomaterial-based NO2 gas sensor prepared in Example 1 for 50 ppm NO2 at room temperature. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] This invention proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a substrate and a gas-sensitive layer loaded on the substrate, wherein the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial (PdS / MoS2 composite nanomaterial).

[0032] The thickness of the gas-sensitive layer directly affects the surface area of ​​the sensor in contact with the gas. A thinner gas-sensitive layer may provide a larger effective sensitive interface, thereby increasing the contact opportunities between gas molecules and the sensor surface and improving the adsorption and reaction efficiency of the gas. However, if the gas-sensitive layer is too thin, it may lead to unstable sensor response or reduced sensitivity. A thicker gas-sensitive layer may restrict the diffusion of gas molecules into the sensor interior, thus affecting the response speed and recovery time. The thickness of the gas-sensitive layer is optimized by forming a heterogeneous structure based on its composition and matching it with the thickness of the electron depletion layer to improve the gas-sensitive performance of the sensor. Based on this, in a preferred embodiment of the present invention, the thickness of the gas-sensitive layer is 1-500 μm.

[0033] When palladium sulfide nanoparticles and molybdenum disulfide nanoparticles combine to form a heterostructure, electrons will transfer from the material with the lower work function to the material with the higher work function due to their different work functions, until the Fermi levels of the two materials are equal. This electron transfer leads to the formation of an electron depletion layer or an electron accumulation layer at the interface of the heterostructure, thereby affecting the conductivity and gas-sensing performance of the sensor. The formation of the heterostructure can increase the number of active sites at the interface. The increased active sites can promote the participation of more NO2 molecules in the reaction, resulting in a larger resistance change and thus improving the sensor response. The amount of palladium sulfide nanoparticles and molybdenum disulfide nanoparticles affects the density of active sites in the heterostructure, thereby affecting the adsorption capacity and reaction rate of gas molecules. Based on this, in a preferred embodiment of the present invention, the palladium sulfide-molybdenum disulfide composite nanomaterial includes palladium sulfide nanoparticles (PdS nanoparticles) and nanoflower-shaped molybdenum disulfide (nanoflower-shaped MoS2) in a mass ratio of 1:(0.5-5).

[0034] In a preferred embodiment of the present invention, the palladium sulfide-molybdenum disulfide composite nanomaterial is prepared by mixing palladium sulfide nanoparticles and molybdenum disulfide nanoflora in ethanol. The mixing includes one of mechanical mixing, ultrasonic mixing, and in-situ growth. Mechanical mixing refers to the process of uniformly mixing palladium sulfide nanoparticles and molybdenum disulfide nanoparticles using mechanical stirring (such as paddle stirring, turbine stirring, magnetic stirring, etc.); ultrasonic mixing refers to the process of uniformly mixing palladium sulfide nanoparticles and molybdenum disulfide nanoparticles under ultrasonic treatment conditions; in-situ growth refers to using molybdenum disulfide nanoflora prepared by hydrothermal method as raw material, and then growing palladium sulfide nanoparticles on the surface of molybdenum disulfide nanoflora again by hydrothermal method. The morphology of the PdS nanoparticles prepared by hydrothermal method is a nanoparticle cluster. By dispersing molybdenum disulfide nanoflora and PdS nanoparticles in ethanol, the PdS nanoparticle clusters are embedded on the surface of the MoS2 nanoflora.

[0035] In a preferred embodiment of the present invention, both the palladium sulfide nanoparticles and the nano-flower-like molybdenum disulfide are prepared by a hydrothermal method; more specifically, the hydrothermal method includes conventional hydrothermal or microwave hydrothermal; when the hydrothermal method is conventional hydrothermal, the hydrothermal reaction temperature is 120-250℃ and the hydrothermal reaction time is 5-30h; when the hydrothermal method is microwave hydrothermal, the microwave power is 100-800W.

[0036] In a preferred embodiment of the present invention, the raw materials for preparing the palladium sulfide nanoparticles include palladium hydrochloride (H2PdCl4) and thiourea (CH4N2S), and the raw materials for preparing the nanoflower-like molybdenum disulfide include sodium molybdate (Na2MoO4·2H2O) and thiourea (CH4N2S).

[0037] For example, in this embodiment of the invention, the method for preparing the palladium sulfide nanoparticles (PdS nanoparticles) is as follows:

[0038] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 120-250 °C for 5-30 h. After cooling, the product was removed and collected by centrifugation at 8000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 10 h to obtain PdS nanoparticles.

[0039] For example, in this embodiment of the invention, the preparation method of the nano-flower-like molybdenum disulfide (nano-flower-like molybdenum disulfide MoS2) is as follows:

[0040] 5 mmol of Na₂MoO₄·2H₂O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was then adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and kept at 120-250 °C for 5-30 h. After cooling, the mixture was removed and centrifuged at 6000 rpm to collect the final product. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 12 h to obtain nano-flower-like molybdenum disulfide (MoS₂).

[0041] In a preferred embodiment of the present invention, the substrate is a rigid substrate or a flexible substrate. More specifically, the rigid substrate is one of a silicon-based substrate, a zirconium oxide substrate, and an aluminum oxide substrate; the flexible substrate is one of a polyimide (PI) substrate, a polyethylene terephthalate (PET) substrate, a polyurethane (PU) substrate, and a paper-based substrate.

[0042] This invention also proposes a method for preparing the aforementioned palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based nitrogen dioxide sensor, comprising the following steps:

[0043] The substrate is pretreated, and then coated with palladium sulfide-molybdenum disulfide composite nanomaterials. After drying, the palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor is obtained.

[0044] In a preferred embodiment of the present invention, the coating method includes one of screen printing, drop coating, spray coating, spin coating and inkjet printing.

[0045] In a preferred embodiment of the present invention, the substrate pretreatment process includes cleaning and drying steps; specifically, the substrate is ultrasonically cleaned sequentially with acetone, alcohol and deionized water, and then dried at 60-80°C for 6-12 hours.

[0046] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0047] In this embodiment of the invention, room temperature refers to 25±2℃.

[0048] All raw materials used in the embodiments of this invention were purchased commercially.

[0049] The technical solution of the present invention will be further illustrated by the following embodiments.

[0050] Example 1

[0051] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, including a sensor substrate and a gas-sensitive layer. The substrate is made of aluminum oxide-based platinum interdigitated electrodes, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 1 μm.

[0052] The preparation method of the hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite includes the following steps:

[0053] (1) Substrate pretreatment

[0054] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 8 hours for later use.

[0055] (2) Preparation of PdS nanoparticle materials

[0056] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The mixture was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 160 °C for 12 h. After cooling, the product was collected by centrifugation at 8000 rpm and washed three times with ethanol and three times with deionized water. The product was then dried in a 60 °C oven for 10 h to obtain PdS nanoparticles.

[0057] (3) Preparation of nanoflower-like MoS2

[0058] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and kept at 210 °C for 24 h. After cooling, the product was collected by centrifugation at 6000 rpm and washed three times with ethanol and three times with deionized water. The product was then dried in a 60 °C oven for 12 h to obtain nano-flower-like MoS2.

[0059] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0060] Five mg of a mixture of 1:1 MoS2 and PdS nanoparticles in a 1:1 mass ratio were weighed, mixed with 1 mL of ethanol, and sonicated for 10 min to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then screen-printed onto a pretreated alumina-based platinum interdigitated electrode to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0061] Example 2

[0062] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a sensor substrate and a gas-sensitive layer. The substrate is a zirconium oxide-based platinum interdigitated electrode, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 10 μm. The specific preparation method includes the following steps:

[0063] (1) Substrate pretreatment

[0064] The zirconium oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 8 hours for later use.

[0065] (2) Preparation of PdS nanoparticle materials

[0066] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 140 °C for 15 h. After cooling, the product was collected by centrifugation at 8000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 10 h to obtain PdS nanoparticles.

[0067] (3) Preparation of nanoflower-like MoS2

[0068] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and kept at 210 °C for 30 h. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a drying oven at 60 °C for 12 h to obtain nano-flower-like MoS2.

[0069] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0070] 10 mg of a mixture of flower-shaped MoS2 and PdS nanoparticles in a mass ratio of 1:2 was weighed, mixed with 1 mL of ethanol, and sonicated for 10 min to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then coated onto a pretreated substrate using a drop-coating process to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0071] Example 3

[0072] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a sensor substrate and a gas-sensitive layer. The substrate is made of polyimide-based platinum interdigitated electrodes, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 10 μm. The specific preparation method includes the following steps:

[0073] (1) Substrate pretreatment

[0074] The polyimide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 8 hours before use.

[0075] (2) Preparation of PdS nanoparticle materials

[0076] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 180 °C for 10 h. After cooling, the product was collected by centrifugation at 8000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a drying oven at 60 °C for 10 h to obtain PdS nanoparticles.

[0077] (3) Preparation of nanoflower-like MoS2

[0078] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and kept at 230 °C for 20 h. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a drying oven at 60 °C for 12 h to obtain nano-flower-like MoS2.

[0079] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0080] 10 mg of a mixture of flower-shaped MoS2 and PdS nanoparticles in a mass ratio of 1:0.5 was weighed, mixed with 1 mL of ethanol, and ultrasonically treated to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then spin-coated onto a pretreated substrate to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0081] Example 4

[0082] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a sensor substrate and a gas-sensitive layer. The substrate is made of polyurethane-based platinum interdigitated electrodes, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 500 μm. The specific preparation method includes the following steps:

[0083] (1) Substrate pretreatment

[0084] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 80°C for 6 hours for later use.

[0085] (2) Preparation of PdS nanoparticle materials

[0086] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The mixture was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 250 °C for 5 h. After cooling, the product was collected by centrifugation at 8000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a drying oven at 60 °C for 10 h to obtain PdS nanoparticles.

[0087] (3) Preparation of nanoflower-like MoS2

[0088] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and kept at 250 °C for 5 h. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 12 h to obtain nano-flower-like MoS2.

[0089] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0090] 50 mg of a mixture of flower-shaped MoS2 and PdS nanoparticles in a mass ratio of 1:5 was weighed, mixed with 1 mL of ethanol, and ultrasonically treated to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then coated onto a pretreated substrate using spin coating and inkjet printing to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0091] Example 5

[0092] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a sensor substrate and a gas-sensitive layer. The substrate is a polyethylene terephthalate-based platinum interdigitated electrode, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 300 μm. The specific preparation method includes the following steps:

[0093] (1) Substrate pretreatment

[0094] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 12 hours for later use.

[0095] (2) Preparation of PdS nanoparticle materials

[0096] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The mixture was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 120 °C for 30 h. After cooling, the product was collected by centrifugation at 8000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 10 h to obtain PdS nanoparticles.

[0097] (3) Preparation of nanoflower-like MoS2

[0098] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and kept at 120 °C for 30 h. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 12 h to obtain nano-flower-like MoS2.

[0099] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0100] 30 mg of a mixture of flower-shaped MoS2 and PdS nanoparticles in a mass ratio of 1:0.5 was weighed, mixed with 1 mL of ethanol, and ultrasonically treated to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then coated onto a pretreated substrate using inkjet printing to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0101] Example 6

[0102] This embodiment proposes a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite, comprising a sensor substrate and a gas-sensitive layer. The substrate is made of silicon-based platinum interdigitated electrodes, and the gas-sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial with a thickness of 300 μm. The specific preparation method includes the following steps:

[0103] (1) Substrate pretreatment

[0104] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 12 hours for later use.

[0105] (2) Preparation of PdS nanoparticles

[0106] 0.75 mmol of chloropalladium acid and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The mixture was then kept at 160 °C for 1 h in a microwave hydrothermal synthesizer with a power of 200 W. After cooling, the product was collected by centrifugation at 8000 rpm and washed three times with ethanol and deionized water, respectively. The product was then dried in a 60 °C oven to obtain PdS nanoparticles.

[0107] (3) Preparation of nanoflower-like MoS2

[0108] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then heated at 210 °C for 2 h in a microwave hydrothermal synthesizer with a power of 200 W. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C oven for 12 h to obtain nano-flower-like MoS2.

[0109] (4) Preparation of a hierarchical nanostructured nitrogen dioxide sensor based on palladium sulfide and molybdenum disulfide composite

[0110] 30 mg of a mixture of flower-shaped MoS2 and PdS nanoparticles in a mass ratio of 1:0.5 was weighed, mixed with 1 mL of ethanol, and ultrasonically treated to obtain a palladium sulfide-molybdenum disulfide composite nanomaterial. The palladium sulfide-molybdenum disulfide composite nanomaterial was then spin-coated onto a pretreated substrate to obtain a gas-sensitive layer. After drying, a palladium sulfide composite molybdenum disulfide hierarchical nanostructured nitrogen dioxide sensor (PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor) was obtained.

[0111] Comparative Example 1

[0112] Same as Example 1, except that the thickness of the gas-sensitive layer is 0.1 μm.

[0113] Comparative Example 2

[0114] Same as Example 1, except that the thickness of the gas-sensitive layer is 800 μm.

[0115] Comparative Example 3

[0116] Same as Example 1, except that flower-shaped MoS2 nanoparticles and PdS nanoparticles were weighed in a mass ratio of 1:10.

[0117] Comparative Example 4

[0118] Same as Example 1, except that the gas-sensitive layer is made of molybdenum disulfide nanomaterials, specifically:

[0119] This comparative example presents a molybdenum disulfide nanostructured nitrogen dioxide sensor, comprising a sensor substrate and a gas-sensitive layer. The substrate is an aluminum oxide-based platinum interdigitated electrode, and the gas-sensitive layer has a thickness of 1 μm. The fabrication method specifically includes the following steps:

[0120] (1) Substrate pretreatment

[0121] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 8 hours for later use.

[0122] (2) Preparation of nanoflower-like MoS2

[0123] 5 mmol of Na2MoO4·2H2O and 5 mmol of thiourea were added to a reaction vessel containing 50 mL of deionized water. The mixture was magnetically stirred for 30 min until completely dissolved. The pH of the mixture was adjusted to 3 using hydrochloric acid solution. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and kept at 210 °C for 24 h. After cooling, the product was collected by centrifugation at 6000 rpm. The product was washed three times with ethanol and three times with deionized water, and then dried in a 60 °C drying oven for 12 h to obtain nano-flower-like MoS2.

[0124] (3) Preparation of molybdenum disulfide nanostructured nitrogen dioxide sensor

[0125] 5 mg of MoS2 nanoflora was weighed, mixed with 1 mL of ethanol, and ultrasonically treated to obtain molybdenum disulfide nanomaterials. The molybdenum disulfide nanomaterials were then screen-printed onto a pretreated substrate to obtain a gas-sensitive layer. After drying, a molybdenum disulfide nanostructure-based nitrogen dioxide sensor (MoS2 nanomaterial membrane-based NO2 gas sensor) was obtained.

[0126] Comparative Example 5

[0127] Same as Example 1, except that the gas-sensitive layer is made of palladium sulfide nanomaterials, specifically:

[0128] This comparative example presents a palladium sulfide nanostructured nitrogen dioxide sensor, comprising a sensor substrate and a gas-sensitive layer. The substrate is an aluminum oxide-based platinum interdigitated electrode, and the gas-sensitive layer has a thickness of 1 μm. The fabrication method specifically includes the following steps:

[0129] (1) Substrate pretreatment

[0130] The aluminum oxide-based platinum interdigitated electrodes were ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, and then dried at 60°C for 8 hours for later use.

[0131] (2) Preparation of PdS nanoparticles

[0132] 0.75 mmol of H2PdCl4 and 1 g of thiourea were added to a reaction vessel containing 80 mL of deionized water. The mixture was magnetically stirred for 30 min until fully dissolved. The mixture was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and kept at 160 °C for 12 h. After cooling, the product was collected by centrifugation at 8000 rpm and washed three times with ethanol and three times with deionized water. The product was then dried in a 60 °C oven for 10 h to obtain PdS nanoparticles.

[0133] (3) Preparation of palladium sulfide nanostructured nitrogen dioxide sensor

[0134] 5 mg of PdS nanoparticles were weighed and mixed with 1 mL of ethanol and ultrasonically treated to obtain palladium sulfide nanomaterials. Then, the palladium sulfide nanomaterials were screen printed onto a pretreated substrate to obtain a gas-sensitive layer. After drying, a palladium sulfide nanostructure-based nitrogen dioxide sensor (PdS nanomaterial film-based NO2 gas sensor) was obtained.

[0135] Performance testing

[0136] The scanning electron microscope image of the palladium sulfide-molybdenum disulfide composite nanomaterial prepared in Example 1 is shown below. Figure 1 As can be seen, PdS nanoparticle clusters are embedded on the surface of MoS2 nanoflowers.

[0137] The performance tests of the nitrogen dioxide sensors prepared in Examples 1-6 and Comparative Examples 1-5 of this invention were conducted according to methods disclosed in the art. A Keithley 2700 data acquisition unit was used to test the resistance signals of the sensors prepared above. The specific steps are as follows:

[0138] (1) Connect the sensor to the gas-sensitive testing equipment, introduce air into the equipment until it stabilizes, and record the resistance value R of the device in the air. a (2) Introduce NO2 into the device until the resistance value stabilizes again, and record the resistance value R of the device in NO2. g (3) Re-introduce air into the device until the resistance reaches a stable level, and the device completes one response recovery process.

[0139] Response value = (R) a -R g ) / R a ×100%, where R a R is the sensor output resistance value in air atmosphere. g This is the sensor output resistance value under NO2 atmosphere.

[0140] Different NO2 concentrations were obtained by gas dilution method, with test concentrations ranging from 0 to 50 ppm.

[0141] The real-time resistance change curve of the PdS / MoS2 composite nanomaterial membrane-based NO2 gas sensor prepared in Example 1 for 50-10 ppm NO2 at room temperature is shown in the figure. Figure 2 As can be seen, after NO2 is introduced, the sensor resistance decreases as the NO2 concentration increases, and it shows a response value of 46.4% for 50ppm NO2 gas, with a response / recovery time of 42 / 52s.

[0142] Under the same test method, the gas sensor prepared in Example 2 showed a response value of 45.3% to 50ppm NO2 gas, with a response / recovery time of 40 / 52s;

[0143] The gas sensor prepared in Example 3 showed a response value of 44.6% to 50 ppm NO2 gas, with a response / recovery time of 45 / 58 s;

[0144] The gas sensor prepared in Example 4 showed a response value of 47.1% to 50 ppm NO2 gas, with a response / recovery time of 50 / 61 s.

[0145] The gas sensor prepared in Example 5 showed a response value of 46.5% to 50ppm NO2 gas, with a response / recovery time of 48 / 59s.

[0146] The gas sensor prepared in Example 6 exhibited a response value of 45.8% to 50 ppm NO2 gas, with a response / recovery time of 51 / 66 s. This demonstrates that the performance of the gas sensors prepared in Examples 1-6 is quite similar.

[0147] The gas sensor prepared in Comparative Example 1 showed a response value of 2.4% to 50 ppm NO2 gas, with a response / recovery time of 91 / 124 s;

[0148] The gas sensor prepared in Comparative Example 2 showed a response value of 12.1% to 50 ppm NO2 gas, with a response / recovery time of 187 / 196 s;

[0149] The gas sensor prepared in Comparative Example 3 showed a response value of 10.3% to 50 ppm NO2 gas, with a response / recovery time of 120 / 121 s;

[0150] The gas sensor prepared in Comparative Example 4 showed a response value of 8.1% to 50 ppm NO2 gas, with a response / recovery time of 187 / 196 s.

[0151] The gas sensor prepared in Comparative Example 5 showed a response value of 19.3% to 50 ppm NO2 gas, with a response / recovery time of 122 / 129 s.

[0152] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based nitrogen dioxide sensor comprising a substrate and a gas sensitive layer loaded on the substrate, characterized in that, The gas sensitive layer is a palladium sulfide-molybdenum disulfide composite nanomaterial; The thickness of the gas sensitive layer is 1-500 μm; The palladium sulfide-molybdenum disulfide composite nanomaterial comprises palladium sulfide nanoparticles and molybdenum disulfide nanoparticles in a mass ratio of 1:(0.5-5); The palladium sulfide-molybdenum disulfide composite nanomaterial is prepared by mixing palladium sulfide nanoparticles and nanoflower molybdenum disulfide in ethanol; The mixing preparation method is mechanical compounding, ultrasonic compounding or in-situ growth.

2. The palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based N02 sensor according to claim 1, wherein, Both the palladium sulfide nanoparticles and the nanoflower molybdenum disulfide are prepared by a hydrothermal method.

3. The palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based N02 sensor according to claim 2, wherein, The hydrothermal method is a conventional hydrothermal method or a microwave hydrothermal method.

4. The palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based N02 sensor according to claim 1, wherein, The substrate is a rigid substrate or a flexible substrate.

5. A method for preparing the palladium sulfide composite molybdenum disulfide hierarchical nanostructure-based NO2 sensor according to any one of claims 1-4, characterized in that, The method comprises the following steps: The substrate is pretreated, the palladium sulfide-molybdenum disulfide composite nanomaterial is coated on the substrate, and the nitrogen dioxide sensor with a palladium sulfide-molybdenum disulfide composite hierarchical nanostructure is obtained after drying.

6. The method of claim 5, wherein the method is characterized by: The coating method comprises one of silk screen printing, drop coating, spraying, spin coating and inkjet printing.

7. The method of claim 5, wherein the method is characterized by: The substrate pretreatment process comprises the steps of cleaning and drying.

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