Preparation method and application of pillared molybdenite / ZnO nanorods

Abstract

The present invention discloses a preparation method and application of a pillared molybdenite / ZnO nanorod, which belongs to the field of gas sensing technology. The specific steps are as follows: (1) dispersing commercially available molybdenite into a zinc acetate methanol solution to obtain solution A; (2) adding a sodium hydroxide methanol solution to solution A to obtain molybdenite / ZnO nanoparticles; (3) dispersing the molybdenite / ZnO nanoparticles into deionized water to obtain a molybdenite / ZnO nanoparticle suspension; (4) adding the molybdenite / ZnO nanoparticle suspension to a sodium hydroxide solution of ε-Zn(OH)2, heating and aging, stirring, washing, and drying overnight to obtain a heterogeneous pillared molybdenite / ZnO nanorod. The gas-sensitive material of the present invention has the characteristics of simple preparation method, low cost, etc., and has good response performance to ppb level NO2.

Description

Technical Field

[0001] The present invention relates to the field of gas sensing technology, and more particularly to a preparation method of pillared molybdenite / ZnO nanorods and their application in NO2 monitoring. Background Art

[0002] Nitrogen dioxide (NO2) is one of the most toxic air pollutants, and its main sources are the burning of fossil fuels and industrial production. In addition to forming acid rain, photochemical smog and damaging the ozone layer, it also has a significant impact on human health. For example, respiratory diseases: irritation of the respiratory tract, triggering or aggravation of diseases such as asthma and bronchitis, and increasing the risk of cardiovascular disease. Immune system damage: reduced immune function and increased risk of infection. Nitrogen dioxide (NO2) is seriously harmful even at the ppb level. The U.S. Environmental Protection Agency sets the NO2 standard for air quality control at 53 ppb. Continuous or frequent exposure to NO2 concentrations above the air quality standard of 53 ppb may lead to an increased incidence of acute respiratory and olfactory paralysis. Therefore, it is of great significance to achieve convenient and timely monitoring of trace NO2.

[0003] The detection of nitrogen dioxide (NO2) is achieved by adsorbing and activating the adsorption sites and active sites on the sensitive material. After activation, the charge of the sensitive material is transferred, causing the resistivity of the sensitive material to change. However, the materials commonly used for nitrogen dioxide (NO2) detection are mainly based on metal oxide semiconductors, which are widely studied due to their simple preparation methods and low cost. In particular, ZnO has become one of the most promising NO2 sensing materials due to its high sensitivity and high selectivity to NO2. However, metal oxides usually require higher operating temperatures (150-400°C), which limits their application at low temperatures. UV activation is considered to be an effective strategy to achieve NO2 sensing through various semiconductor nanostructures at room temperature, but this strategy still requires relatively harsh ultraviolet light irradiation.

[0004] Research has found that MoS2, the primary component of molybdenite, possesses high surface area, abundant active sites, excellent electrical properties, and ease of integration with other materials. It has recently been widely used in lubricants, catalysts, photocatalysts, electronic devices, energy storage devices, and gas sensors. MoS2 exhibits high sensitivity, good selectivity, and low operating temperature for NO2 detection, and its multilayered structure facilitates NO2 adsorption and transport. However, current methods for preparing MoS2 primarily rely on mechanical exfoliation, liquid-phase exfoliation, and hydrothermal / solvothermal methods. These methods require high energy consumption, complex equipment, and low MoS2 yields. The present invention, however, directly utilizes commercially available molybdenite as a raw material to prepare gas-sensitive materials, reducing material preparation costs. However, the stacking and aggregation of molybdenite (MoS2) leads to insufficient gas permeability and a shortage of surface active sites involved in the sensing process. Therefore, the construction of pillared structures is considered a promising strategy to address the stacking and agglomeration issues of two-dimensional materials. This can be achieved by inserting and growing specialized nanostructures between layers. Pillared structures offer the advantages of a larger surface area, increasing the exposure of active sites and enhancing charge carrier transfer.

[0005] Therefore, providing a pillared molybdenite / ZnO gas sensing material that can respond to ppb-level NO2 and a preparation method thereof is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In light of this, the present invention provides a method for preparing pillared molybdenite / ZnO nanorods and their application. This method features a simple preparation process that does not require the use of advanced equipment, facilitating industrial production of the material. The resulting molybdenite / ZnO heterogeneous pillared structure responds to ppb-level NO2 under simulated sunlight at room temperature.

[0007] One of the purposes of the present invention is to provide a method for preparing pillared molybdenite / ZnO nanorods, comprising the following steps:

[0008] (1) Commercially available molybdenite was dispersed into a zinc acetate methanol solution under stirring until adsorption equilibrium was achieved to obtain solution A for subsequent use;

[0009] (2) adding sodium hydroxide methanol solution to solution A, stirring continuously, centrifuging, washing and drying to obtain molybdenite / ZnO nanoparticles;

[0010] (3) dispersing the molybdenite / ZnO nanoparticles into deionized water and stirring uniformly to obtain a molybdenite / ZnO nanoparticle suspension for standby use;

[0011] (4) The molybdenite / ZnO nanoparticle suspension was added to a sodium hydroxide solution of ε-Zn(OH)2 under stirring, stirred for 10 min, aged at elevated temperature, stirred again, washed, and dried overnight to obtain heterogeneous pillared molybdenite / ZnO nanorods.

[0012] Furthermore, the purity of MoS2 in the commercially available molybdenite is ≥99%.

[0013] Furthermore, in step (1), the solid-to-liquid ratio of the commercially available molybdenite to the zinc acetate methanol solution is 1 mg:1 mL; and the concentration of the zinc acetate methanol solution is 2.0 mol / L.

[0014] Furthermore, in step (2), the concentration of the sodium hydroxide methanol solution is 2.0-16.0 mol / L; the molar ratio of zinc ions to sodium ions in step (2) is 1:6.25-25; the stirring speed is 0-600 rpm, the centrifugal speed is 2000 rpm, and the drying is performed at 20-30° C. for 12-24 h.

[0015] The beneficial effect of adopting the above technical solution is that under this process, the zinc oxide nanoparticles form a better pillared structure between the layers of molybdenite. The low speed centrifugation is to avoid destroying the pillared structure.

[0016] Furthermore, in step (3), the solid-liquid ratio of the molybdenite / ZnO nanoparticles to deionized water is 10 mg:1 mL; and the stirring speed is 0-600 rpm.

[0017] Furthermore, in step (4), the preparation method of ε-Zn(OH)2 is: adding sodium hydroxide solution dropwise to zinc sulfate solution under stirring, reacting fully, washing and drying the precipitate to obtain ε-Zn(OH)2; the stirring speed is 0-600rpm; the aging temperature is 60-100°C, and the aging time is 0.5 hour.

[0018] Furthermore, the concentration of the sodium hydroxide solution is 2.0-4.0 mol / L, the concentration of the zinc sulfate solution is 1.0-2.0 mol / L, and the molar ratio of the sodium hydroxide to the zinc sulfate is 2:1; the stirring speed is 100-700 rpm, and the drying is carried out at 15-20° C. for 22-26 hours.

[0019] Furthermore, in step (4), the mass ratio of the ε-Zn(OH)2 to the molybdenite / ZnO nanoparticles is 3.48:0.1, the liquid-solid ratio of the sodium hydroxide solution to the molybdenite / ZnO nanoparticles is 200 mL:0.1 g, and the concentration of the sodium hydroxide solution is 4.0 mol / L; the stirring speed is 200-800 rpm, and the stirring is repeated for 20-40 min, and the drying condition is 60°C.

[0020] The beneficial effects of the above technical solution are as follows: Under this process condition, the pillared structure of molybdenite / ZnO nanorods prepared using ε-Zn(OH)2 as a precursor and molybdenite / ZnO nanoparticles as seeds is more stable, with higher sensing sensitivity and lower detection limit. In addition, the zinc oxide nanoparticles grown between the molybdenite sheets increase electron transport channels, adsorption sites, and active sites, thereby improving stability and sensitivity. The formation of zinc oxide nanorods on the molybdenite / ZnO surface increases adsorption sites and active sites, resulting in better sensing performance.

[0021] Further preferably, the purity of zinc acetate dihydrate used to prepare the zinc acetate methanol solution is ≥99%, and the purity of methanol is ≥99.5%; the purity of the sodium hydroxide is ≥99.5%, and the purity of the zinc sulfate is ≥99%.

[0022] The technical concept of the present invention is as follows: MoS2 has a high specific surface area and abundant active sites. MoS2 has high sensitivity, good selectivity and low operating temperature for NO2 detection, and MoS2 has a multilayer structure, which is conducive to the adsorption and transmission of NO2. However, due to the stacking of the layered structure, the reduction of its active sites reduces the gas-sensing performance, and the pillared structure can effectively solve the problem of MoS2 stacking. Zinc oxide nanorods have the characteristics of high specific surface area, excellent electronic properties, rich morphology and size controllability, good chemical stability and thermal stability, low cost and easy preparation, so pillared MoS2 is combined with zinc oxide nanorods to prepare high-performance gas-sensitive materials.

[0023] The active sites of the molybdenite / ZnO nanorod composite material are oxygen sites. When NO2 is adsorbed by the composite, it is oxidized by the oxygen sites, causing a change in the material's resistivity. The formation mechanism is that the molybdenite / ZnO nanoparticles and zinc oxide nanorods form a heterostructure. Changing the morphology of zinc oxide on the surface of the molybdenite / ZnO nanoparticles also increases their specific surface area and active sites.

[0024] The second purpose of the present invention is to provide an application of pillared molybdenite / ZnO nanorods, which can monitor 50 ppb NO2 under simulated sunlight conditions at room temperature.

[0025] Because molybdenite with a lamellar structure has good adsorption capacity and abundant active sites, NO2 is easily oxidized on the surface of the material. The pillared structure improves the stability of the material and enhances its electron transport ability and sensitivity. The growth of zinc oxide nanorods on the surface of molybdenite / ZnO nanoparticles increases the active sites and enhances the sensitivity and low-temperature activity of the material.

[0026] The key factors in forming pillared molybdenite / ZnO nanoparticles are the stirring speed, the concentrations of the zinc acetate methanol solution and the sodium hydroxide methanol solution, and the rate at which the zinc acetate methanol solution is added. The formation of pillared molybdenite / ZnO nanorods is determined by a combination of the stirring speed, the sodium hydroxide solution concentration, the amount of molybdenite / ZnO seed crystals, the amount of the ε-Zn(OH)2 precursor, the aging time, and the aging temperature.

[0027] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The gas-sensitive material of the present invention has the characteristics of simple preparation method and low cost. The molybdenite / ZnO nanorods prepared by the above method have good NO2 response performance.

[0029] (2) This method uses an adjustable molar ratio of zinc ions to sodium ions, which can adjust its adsorption and transmission capacity for NO2, and at the same time regulate the number of active sites and electron transmission capacity, which is of great value in the field of NO2 room temperature sensing.

[0030] (3) The synthesis temperature of this method is low. Except for the high aging temperature, the rest of the synthesis process is completed at room temperature, which is more environmentally friendly than other synthesis methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0032] Figure 1 This is the SEM image of the molybdenite / ZnO nanorods prepared in Example 3.

[0033] Figure 2 This is the response diagram of the molybdenite / ZnO nanorods prepared in Example 3 to 50 ppb NO2. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] In the embodiments of the present invention, the purity of MoS2 in molybdenite is ≥99%, the purity of zinc acetate dihydrate is ≥99%, the purity of methanol is ≥99.5%, the purity of sodium hydroxide is ≥99.5%, and the purity of zinc sulfate is ≥99%.

[0036] Example 1

[0037] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0038] (1) 100 mg of molybdenite was dispersed in 100 mL of a 2.0 mol / L methanol solution of zinc acetate dihydrate, stirred at room temperature for 1 h until adsorption equilibrium was reached, and 312.5 mL of a 4.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:6.25. The mixture was stirred at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and dried in vacuum at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0039] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0040] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0041] The molar ratio of zinc ions to sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 1 is 1:6.25. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation, and responds after NO2 is introduced into the gas chamber for 35 seconds. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 50% of the initial state, and the stability is general.

[0042] Example 2

[0043] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0044] (1) 100 mg of molybdenite was dispersed in 100 mL of a 2.0 mol / L methanol solution of zinc acetate dihydrate, stirred at room temperature for 1 h until adsorption equilibrium was reached, and 312.5 mL of an 8.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:12.5. The mixture was stirred at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and dried in vacuum at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0045] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0046] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0047] The molar ratio of zinc ions to sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 2 is 1:12.5. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation. It responds 19 seconds after NO2 is introduced into the gas chamber. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 76% of its initial state, and its stability is general.

[0048] Example 3

[0049] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0050] (1) 100 mg of molybdenite was dispersed in 100 mL of a 2.0 mol / L methanol solution of zinc acetate dihydrate, stirred at room temperature for 1 h until adsorption equilibrium was reached, and 625 mL of an 8.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:25. The mixture was stirred at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and dried in vacuum at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0051] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0052] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 ml of deionized water, added to 200 ml of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0053] The molar ratio of zinc ions to sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 3 is 1:25. The material responds to a NO2 concentration of 50 ppb and responds after NO2 is introduced into the gas chamber for 5 seconds. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 95% of its initial state, and its stability is very good.

[0054] Example 4

[0055] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0056] (1) 100 mg of molybdenite was dispersed in 100 mL of a 2.0 mol / L methanol solution of zinc acetate dihydrate, stirred at room temperature for 1 h until adsorption equilibrium was reached, and 312.5 mL of a 16.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:25. The mixture was stirred at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and dried in vacuum at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0057] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0058] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0059] The molar ratio of zinc ions to sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 4 is 1:25. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation, and responds when NO2 is introduced into the gas chamber for 30 seconds. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 60% of its initial state, and its stability is general.

[0060] Example 5

[0061] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0062] (1) 100 mg of MoS2 prepared by hydrothermal method was dispersed in 100 mL of 2.0 mol / L methanol solution of zinc acetate dihydrate and stirred at room temperature for 1 h until it reached adsorption equilibrium. 625 mL of 8.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:25. After stirring at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and vacuum dried at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0063] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0064] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0065] The molar ratio of zinc ions and sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 5 is 1:25. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation, and responds after NO2 is introduced into the gas chamber for 5 seconds. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 96% of the initial state, and the stability is very good.

[0066] Example 6

[0067] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0068] (1) 100 mg of 90% pure molybdenite was dispersed in 100 mL of 2.0 mol / L methanol solution of zinc acetate dihydrate and stirred at room temperature for 1 h until adsorption equilibrium was reached. 625 mL of 8.0 mol / L methanol solution of sodium hydroxide was added, where the molar ratio of zinc ion to sodium hydroxide was 1:25. The mixture was stirred at 300 rpm for 2 h and centrifuged at 2000 rpm for 5 min. The mixture was washed with deionized water 5 times and then washed with ethanol 2 times. The mixture was vacuum dried at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0069] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0070] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, heated to 80°C and aged for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0071] The molar ratio of zinc ions and sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 6 is 1:20. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation, and responds 13 seconds after NO2 is introduced into the gas chamber. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 86% of its initial state, and has good stability.

[0072] Example 7

[0073] A method for preparing a gas-sensitive material with a molybdenite / ZnO heterogeneous pillared structure:

[0074] (1) 100 mg of molybdenite was dispersed in 100 mL of a 2.0 mol / L methanol solution of zinc acetate dihydrate, stirred at room temperature for 1 h until adsorption equilibrium was reached, and 625 mL of an 8.0 mol / L methanol solution of sodium hydroxide was added, wherein the molar ratio of zinc ion to sodium hydroxide was 1:25. The mixture was stirred at 300 rpm for 2 h, centrifuged at 2000 rpm for 5 min, washed with deionized water 5 times and then washed with ethanol twice, and dried in vacuum at 25 °C for 24 h to obtain pillared molybdenite / ZnO nanoparticles.

[0075] (2) 100 mL of 2.0 mol / L zinc sulfate solution was added dropwise to 100 mL of 4.0 mol / L sodium hydroxide solution at 300 rpm, stirred for two hours, filtered, and dried at 18°C ​​for 24 hours.

[0076] (3) 100 mg of molybdenite / ZnO nanoparticles were dispersed in 10 mL of deionized water, added to 200 mL of 4.0 mol / L sodium hydroxide solution containing 3.48 g of ε-Zn(OH)2 and stirred at 300 rpm for ten minutes, aged at 60°C and 100°C for 0.5 h, then stirred at 300 rpm, washed, and dried at 60°C overnight to obtain molybdenite / ZnO nanorods.

[0077] The molar ratio of zinc ions and sodium hydroxide in the pillared molybdenite / ZnO nanorod gas sensing nanomaterial synthesized in Example 7 is 1:25. The material responds to a NO2 concentration of 50 ppb under simulated sunlight irradiation. After NO2 is introduced into the gas chamber, it responds 20s and 25s later, respectively. When NO2 and other reactants are removed from the gas chamber, the resistance of the pillared molybdenite / ZnO nanorod pillared heterojunction material can return to 80% and 78% of the initial state, and has good stability.

[0078] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing pillared molybdenite / ZnO nanorods, characterized in that: The following steps are involved: (1) under agitation, molybdenite is dispersed into zinc acetate methanol solution until adsorption equilibrium is obtained to obtain solution A, for subsequent use; (2) adding sodium hydroxide methanol solution to solution A, stirring continuously, centrifuging, washing and drying to obtain molybdenite / ZnO nanoparticles; (3) dispersing the molybdenite / ZnO nanoparticles into deionized water and stirring uniformly to obtain a molybdenite / ZnO nanoparticle suspension for standby use; (4) The molybdenite / ZnO nanoparticle suspension was added to a sodium hydroxide solution of ε-Zn(OH)2 under stirring, stirred for 10 min, aged at elevated temperature, stirred again, washed, and dried overnight to obtain heterogeneous pillared molybdenite / ZnO nanorods.

2. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: The purity of MoS2 in the molybdenite is ≥99%.

3. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: In step (1), the solid-to-liquid ratio of the molybdenite to the zinc acetate methanol solution is 1 mg: 1 mL; The concentration of the zinc acetate methanol solution is 2.0 mol / L.

4. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: In step (2), the concentration of the sodium hydroxide methanol solution is 2.0-16.0 mol / L; The molar ratio of zinc ion to sodium ion in step (2) is 1:6.25-25; The stirring speed is 0-600 rpm, the centrifugal speed is 2000 rpm, and the drying temperature is 20-30° C. for 12-24 hours.

5. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: In step (3), the solid-liquid ratio of the molybdenite / ZnO nanoparticles to deionized water is 10 mg:1 mL; and the stirring speed is 0-600 rpm.

6. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: In step (4), the preparation method of the ε-Zn(OH)2 is: adding a sodium hydroxide solution dropwise to a zinc sulfate solution under stirring, reacting fully, washing and drying the precipitate to obtain ε-Zn(OH)2; The stirring speed is 0-600 rpm; the aging temperature is 60-100° C., and the aging time is 0.5 hours.

7. The method for preparing pillared molybdenite / ZnO nanorods according to claim 6, wherein: The concentration of the sodium hydroxide solution is 2.0-4.0 mol / L, the concentration of the zinc sulfate solution is 1.0-2.0 mol / L, and the molar ratio of the sodium hydroxide to the zinc sulfate is 2:1; The stirring speed is 100-700 rpm, and the drying is carried out at 15-20° C. for 22-26 hours.

8. The method for preparing pillared molybdenite / ZnO nanorods according to claim 1, wherein: In step (4), the mass ratio of described ε-Zn(OH)2 and molybdenite / ZnO nanoparticles is 3.48:0.1, the liquid-solid ratio of described sodium hydroxide solution and molybdenite / ZnO nanoparticles is 200mL:0.1g, and the concentration of described sodium hydroxide solution is 4.0mol / L; The stirring speed is 200-800 rpm, and the stirring is repeated for 20-40 minutes. The drying condition is 60°C.

9. The method for preparing pillared molybdenite / ZnO nanorods according to any one of claims 1 to 8, characterized in that: The purity of zinc acetate dihydrate used to prepare the zinc acetate methanol solution is ≥99%, and the purity of methanol is ≥99.5%; the purity of the sodium hydroxide is ≥99.5%, and the purity of the zinc sulfate is ≥99%.

10. An application of pillared molybdenite / ZnO nanorods, characterized in that: Monitoring of ppb-level NO2 at room temperature by the pillared molybdenite / ZnO nanorods obtained by the preparation method according to any one of claims 1 to 9.

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