Preparation method of gas-sensitive material for grain storage quality detection based on heterovalent doping, product and application of gas-sensitive material

Abstract

The invention discloses a preparation method of a gas-sensitive material for grain storage quality detection based on heterovalent doping, a product and application of the gas-sensitive material, the gas-sensitive material comprises tungsten atoms and antimony molybdate three-dimensional grading materials in different valence states, the thickness of Sb2MoO6 nanosheets is 15 nm, the tip angle is 80-85 degrees, and the thickness of the Sb2MoO6 nanosheets is 20-30 nm. Tungsten atoms simultaneously have alternative doping and interstitial doping on Mo atoms in the antimony molybdate material; the gas sensitive material disclosed by the invention has a regularly-changed graded morphology, and W atoms of 4 +, 5 + and 6 + are used for alternative doping and gap doping, so that the electron mobility is improved, and the generation of a donor energy level is facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of gas-sensitive materials, and specifically relates to a preparation method and product of a gas-sensitive material for detecting stored grain quality based on heterovalent doping, and application thereof. Background Art

[0002] Mildew in rice can cause serious waste of stored grain and various food safety problems. Gas detection of volatile organic compounds (VOCs) produced by mildew is a non-destructive detection method that can be used to judge the quality of rice and prevent mildew in rice. If the newly harvested rice is stored for more than 3 months, its quality will decline. Rice with excessive storage and reduced quality can be used as feed in livestock and poultry production, which has good application prospects. Among them, ethylene is a typical VOC produced by the metabolism of several common fungi. Its content increases continuously during the storage of rice. However, when the ethylene concentration is between 0.1 and 1 ppm, it will have a significant impact on the production of stored grain. At present, no research reports on ethylene in the application of gas detection of mildew in rice have been found. Therefore, the detection of ethylene gas produced during the storage of rice has become a non-destructive detection method for the degree of mildew in rice with simple operation, rapid response and high sensitivity.

[0003] In recent years, metal oxide semiconductor materials have been used as gas-sensitive materials to detect ethylene. For example, the paper entitled “Materials Chemistry and Physics 254 (2020) 123540” discloses a SnO2 and CeO2 gas-sensitive material prepared by a double reactant co-precipitation method. x The response of the nanocomposite to 10 ppm ethylene at 350°C reached 5.8, with a detection limit of 0.3 ppm, showing good selectivity and stability for ethylene. However, the final product prepared by the above method has a poor room temperature response value to ethylene and cannot be used for the detection of ethylene in rice mold gas. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above and / or existing problems in the prior art in detecting ethylene in rice mildew gas, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a gas-sensitive material for storing grain quality detection based on heterovalent doping.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a gas-sensitive material for detecting stored grain quality based on heterovalent doping, comprising: It includes tungsten atoms with different valence states and antimony molybdate three-dimensional hierarchical materials. The thickness of the Sb2MoO6 nanosheets is 15 nm, and the tip angle is 80-85°. Tungsten atoms exist in the antimony molybdate material as both alternative doping and interstitial doping of Mo atoms.

[0008] Another object of the present invention is to overcome the deficiencies in the prior art and provide a novel method based on heterovalent doping. The method for preparing a gas-sensitive material for detecting stored grain quality comprises the following steps: The tin source and the molybdenum source are uniformly dissolved in ethanol and deionized water respectively, and stirred thoroughly until transparent, and mixed to obtain a suspension A with a light yellow flocculent precipitate; A certain amount of tungsten source was added to the obtained light yellow suspension, and sodium hydroxide solution was added to adjust the pH value of the solution while stirring to obtain a uniform suspension B; After the uniform suspension B was transferred into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, a solvent thermal reaction was carried out at 180°C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, centrifuged, washed, and dried in sequence to obtain a gas-sensitive material.

[0009] As a preferred embodiment of the preparation method of the present invention, the tin source is antimony trichloride, the molybdenum source is sodium molybdate dihydrate, and each 70 ml of ethanol aqueous solution in the suspension A includes 16 mmol SbCl3 and 8 mmol Na2MoO4·2H2O.

[0010] As a preferred embodiment of the preparation method of the present invention, the molar ratio of the tin source to the molybdenum source is 2:1.

[0011] As a preferred embodiment of the preparation method of the present invention, the volume ratio of ethanol to deionized water is 1:1.

[0012] As a preferred embodiment of the preparation method of the present invention, the tungsten source is antimony tungstate, and the added amount is 0-0.8 mmol.

[0013] As a preferred embodiment of the preparation method of the present invention, the concentration of the sodium hydroxide solution is 20wt% and the pH value is 3.

[0014] As a preferred embodiment of the preparation method of the present invention, the drying refers to drying at 80°C for 12 hours, the centrifugal speed is 3000 r / min, and the washing refers to alternating washing with anhydrous ethanol and deionized water for 6 times.

[0015] Another object of the present invention is to overcome the deficiencies in the prior art and provide a gas-sensitive material for detecting stored grain quality based on heterovalent doping for use in the preparation of a gas-sensitive element for detecting ethylene.

[0016] As a preferred solution of the application of the present invention, it includes: The gas-sensitive material is added to deionized water and ground to form a paste, and then the paste is evenly coated on the outer surface of the gas sensor substrate to completely cover the platinum electrode, and dried at 70° C. for 20 h to form a gas-sensitive coating to obtain the ethylene gas sensor.

[0017] Compared with the prior art, the present invention has the following technical effects: (1) The present invention prepares an asymmetric W atom-doped Sb2MoO6 hierarchical nanostructured material by combining a simple one-step hydrothermal method, which has a regularly changing hierarchical morphology. The doped material has 4+, 5+ and 6+ W atom substitution doping and interstitial doping, which improves electron mobility and is beneficial to the generation of donor energy levels.

[0018] (2) The preparation method of the present invention is simple, safe, low-cost and highly practical. It fills the blank of using ternary metal oxide doped materials to detect ethylene ppb-level gas-sensitive response under high humidity and room temperature conditions, and achieves high selective response. The prepared ethylene gas sensor exhibits good gas-sensitive performance for 10-1 ppm ethylene gas at room temperature and high relative humidity (80% RH). It can be used as an optimal new material for detecting the degree of mildew in rice reserves, and shows great application potential in the field of rapid and non-destructive detection of characteristic gas (ethylene) of rice mildew. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them: Figure 1 SEM images and Raman spectra of Sb2MoO6 hierarchical nanostructured materials doped with heterovalent W atoms: (a) SEM image before W atom doping, (b) SEM image after 5 mol% W doping, (c) SEM image after 7.5 mol% W doping, and (d) Raman images before and after 5 mol% W doping.

[0020] Figure 2W 4f orbital XPS images of W atoms-doped Sb2MoO6 hierarchical nanostructured materials: (a) 2.5 mol%, (b) 5 mol%, (c) 7.5 mol%, and (d) 10 mol%.

[0021] Figure 3 Dynamic response of heterovalent W atom-doped Sb2MoO6 hierarchical nanostructured materials to ethylene at room temperature (a) Dynamic response diagram to 10-2 ppm ethylene, (b) Response to 10-2 ppm ethylene at 80% relative humidity and calculation of detection limit.

[0022] Figure 4 The response of 5 mol% W atom-doped Sb2MoO6 hierarchical nanostructured materials to the characteristic interfering gas of rice mildew. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0026] The chemical raw materials required for the present invention can all be purchased from the market.

[0027] The gas sensor substrate used in the present invention is a sensor Pt electrode sample piece produced by Wuhan Huachuang Ruike Technology Co., Ltd.

[0028] A gas-sensitive material for detecting stored grain quality based on heterovalent doping, comprising tungsten atoms of different valence states and Antimony molybdate three-dimensional hierarchical material, the thickness of Sb2MoO6 nanosheets is 15 nm, the tip angle is 80-85°, and tungsten atoms exist in the antimony molybdate material as both replacement doping and interstitial doping of Mo atoms.

[0029] The method for preparing the above-mentioned gas-sensitive material comprises the following steps: (1) Preparation of hierarchical Sb2MoO6 nanosheets: 16 mmol SbCl3 and 8 mmol Na2MoO4·2H2O were uniformly dissolved in 32 mL ethanol and 32 mL deionized water, respectively, and magnetically stirred at room temperature of 25°C for 15 min until transparent, and a suspension with light yellow flocculent precipitate was obtained; (2) Preparation of heterovalent W atom-doped Sb2MoO6 hierarchical nanostructured materials: The light yellow suspension obtained in step (1) was uniformly mixed with a certain amount of Sb2WO6 powder, and magnetically stirred at room temperature of 25°C for 15 min, followed by adding 20 wt% NaOH solution, and adjusting the pH value to 3 while stirring. After obtaining the suspension, it was transferred into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and subjected to solvent thermal reaction at 180°C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, and then centrifuged, washed, and dried in sequence to obtain a gas-sensitive material.

[0030] Application of the prepared gas-sensitive material in the preparation of ethylene gas-sensitive elements: the gas-sensitive material is added to deionized water and ground into a paste, which is then evenly coated on the outer surface of the gas sensor substrate and completely covers the platinum electrode, and dried at 70°C for 20 h to form a gas-sensitive coating to obtain a gas-sensitive element.

[0031] Example 1 refer to Figure 1 This embodiment provides a method for preparing a gas-sensitive material for storing grain quality detection based on heterovalent doping, which prepares a gas-sensitive material with both substitution doping and interstitial doping.

[0032] A method for preparing a gas-sensitive material for detecting stored grain quality based on heterovalent doping comprises the following steps: (1) At room temperature, 16 mmol SbCl3 and 8 mmol Na2MoO4·2H2O were uniformly dissolved in 32 mL ethanol and 32 mL deionized water, respectively, and magnetically stirred at room temperature of 25°C for 15 min until transparent. Suspension A with light yellow flocculent precipitate was obtained. (2) Sb2WO6 powder with a mass of 0, 0.4 mmol and 0.6 mmol were added to three parts of suspension A, respectively. After magnetic stirring at room temperature of 25°C for 15 min, 20 wt% NaOH solution was added respectively. The pH value of the solution was adjusted to obtain uniform suspension B1, uniform suspension B2 and uniform suspension B3. The uniform suspension B1, uniform suspension B2 and uniform suspension B3 were transferred into a polytetrafluoroethylene-lined stainless steel high-pressure reactor, and solvothermally reacted at 180°C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged, washed and dried to obtain gas-sensitive material 1, gas-sensitive material 2 and gas-sensitive material 3, respectively.

[0033] The prepared gas-sensitive materials 1, 2 and 3 are used to prepare gas-sensitive elements for detecting ethylene, respectively. The steps specifically include the following steps: adding deionized water to the gas-sensitive materials 1, 2 and 3 to form a paste, respectively; then coating the paste evenly on the outer surfaces of two gas sensor substrates and completely covering the platinum electrodes; and drying at 70°C for 20 h to form a gas-sensitive coating, and finally obtaining gas-sensitive elements 1, 2 and 3.

[0034] The obtained sample powder was subjected to morphological characterization and Raman testing. Figure 1 (a) is the SEM image of the pure Sb2MoO6 microstructure before W atom doping. Figure 1 (b) is a microscopic SEM image of the W atom doping amount of 5 mol%. It is found that the pure Sb2MoO6 nanosheets are vertically divergent, while the morphology after doping becomes a layer-by-layer stacked nanosheet structure. The larger porosity produced by the doped morphology helps to obtain a higher response during the test; Figure 1 (c) The Raman peak of the sample after doping shifts to low frequency. This is because the incorporation of larger atoms leads to a moderate expansion of the interatomic distance and weakens the bond strength in the crystal structure. In addition, due to the weakening of the coherence of the vibration mode, the Raman peak becomes wider and the intensity decreases, which also proves the existence of lattice defects (such as vacancies and dislocations). It can be inferred that it comes from the simultaneous existence of substitutional doping and interstitial doping, thereby changing the properties of the host material to a greater extent. Because interstitial doping interacts with multiple adjacent atoms and significantly distorts the lattice, the interaction with a large number of atoms will form multi-center bonds, thereby improving the complex interaction of electronic forces and resulting in strong adsorption of the target gas. Existing dislocations can act as point defects to interact with interstitial W atoms and oxygen defects, and accelerate the reaction process by establishing favorable reaction areas or effective oxygen diffusion pathways, thereby producing local large distortions and high strain energy, adjusting defect concentrations, and thus improving chemical activity and producing good gas-sensitive responses on a macroscopic scale.

[0035] Example 2 refer to Figure 2 This embodiment provides a method for preparing a gas-sensitive material for detecting stored grain quality based on heterovalent doping, comprising the following steps: A method for preparing a gas-sensitive material for detecting stored grain quality based on heterovalent doping comprises the following steps: (1) At room temperature, 16 mmol SbCl3 and 8 mmol Na2MoO4·2H2O were uniformly dissolved in 32 mL ethanol and 32 mL deionized water, respectively, and magnetically stirred at room temperature of 25°C for 15 min until transparent. Suspension A with light yellow flocculent precipitate was obtained. (2) 0.2 and 0.8 mmol of Sb2WO6 powder were added to two parts of suspension A, respectively. After magnetic stirring at room temperature of 25°C for 15 min, 20 wt% NaOH solution was added to each part. The pH value of the solution was adjusted to obtain uniform suspensions B3 and B4. The uniform suspensions B3 and B4 were transferred into a polytetrafluoroethylene-lined stainless steel high-pressure reactor, respectively, and subjected to solvent thermal reaction at 180°C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged, washed and dried to obtain gas-sensitive materials 4 and 5.

[0036] The prepared gas-sensitive materials 4 and 5 are used to prepare gas-sensitive elements for detecting ethylene, respectively, which specifically include the following steps: adding deionized water to gas-sensitive materials 4 and 5 to grind them into pastes, then uniformly coating the pastes on the outer surface of the gas sensor substrate and completely covering the platinum electrode, and drying them at 70°C for 20 h to form a gas-sensitive coating, and finally obtaining gas-sensitive elements 4 and 5.

[0037] This embodiment characterizes the surface element composition and chemical state of gas-sensitive materials 2 to 5, and performs peak fitting on W4f (4f atomic orbital of W) through XPS analysis, such as Figure 2 As shown, it was found that the doping valence states of W atoms included 4+, 5+ and 6+, among which W4+ had the highest content, and the content of W4+ when the doping amount was 5 mol% was significantly higher than the contents when the doping amounts were 2.5 mol%, 7.5 mol% and 10 mol% respectively. The alivalent doping of larger atoms is conducive to the generation of defects, thereby increasing the carrier density and providing more active sites, which helps the sample with a doping amount of 5 mol% to obtain a higher response during testing.

[0038] Example 3 Reference Figure 3 The difference between this embodiment and embodiment 2 is that it can further verify the response of the gas sensor when detecting ethylene.

[0039] Gas sensors 2 to 5 are placed in the gas chamber respectively, and high-purity air is introduced at room temperature to stabilize the gas sensors. After the electrical signals are stabilized, different concentrations of ethylene are introduced to observe the resistance changes.

[0040] In the dynamic response curves of gas sensors made from gas-sensitive materials 2 to gas-sensitive elements 5 to different concentrations of ethylene at room temperature, 5 mol% W-doped Sb2MoO6 showed the best response. Compared with pure Sb2MoO6, the response values ​​increased by 84 and 12 times at 10 ppm and 2 ppm concentrations, respectively. Based on the high humidity characteristics of the actual rice mildew detection environment, the response value of 5 mol% W-doped Sb2MoO6 to 2-10 ppm ethylene at 80% relative humidity was measured, and its detection limit was calculated to be 31 ppb, which is conducive to the application of actual detection scenarios.

[0041] Example 4 Reference Figure 3 The difference between this embodiment and embodiment 2 is that it can further verify that the gas sensor prepared by the present invention has excellent selectivity for ethylene detection.

[0042] The gas-sensitive element corresponding to gas-sensitive element 2 is placed in the gas chamber, and high-purity air is introduced into it for stabilization at room temperature. After the electrical signal is stable, benzaldehyde, 1-octen-3-ol, geranyl acetone, n-octanol, n-hexanal, tetradecane, linalool, n-pentanol, n-nonanal, 2-pentylfuran and carbon dioxide are introduced into it respectively to observe its resistance change.

[0043] The selectivity of 5 mol% W-doped Sb2MoO6 at room temperature was measured by adjusting the flowmeter to introduce eleven interfering gases volatilized during the mildew process of rice. Figure 4 As shown, the gas sensor 2 has poor responses to different types of interfering gases at room temperature, and its detection sensitivity to ethylene is more than 100 times better.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A gas-sensitive material for detecting stored grain quality based on heterovalent doping, characterized in that: include Three-dimensional hierarchical materials of tungsten atoms and antimony molybdate with different valence states. The thickness of Sb2MoO6 nanosheets is 15 nm, and the tip angle is 80-85°. Tungsten atoms exist in the antimony molybdate material as both alternative doping and interstitial doping of Mo atoms.

2. A method for preparing the ethylene gas-sensitive material according to claim 1, characterized in that: The following steps are included: The tin source and the molybdenum source are uniformly dissolved in ethanol and deionized water respectively, and stirred thoroughly until transparent, and mixed to obtain a suspension A with a light yellow flocculent precipitate; A certain amount of tungsten source was added to the obtained light yellow suspension, and sodium hydroxide solution was added to adjust the pH value of the solution while stirring to obtain a uniform suspension B; After the uniform suspension B was transferred into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, a solvent thermal reaction was carried out at 180°C for 24 hours. After the reaction was completed, it was naturally cooled to room temperature, and centrifuged, washed, and dried in sequence to obtain a gas-sensitive material.

3. The preparation method according to claim 2, characterized in that: The tin source is antimony trichloride, the molybdenum source is sodium molybdate dihydrate, and each 70 ml of ethanol aqueous solution in the suspension A includes 16 mmol SbCl3 and 8 mmol Na2MoO4·2H2O.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the tin source to the molybdenum source is 2:

1.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The volume ratio of the ethanol to the deionized water is 1:

1.

6. The preparation method according to any one of claims 2 to 4, characterized in that: The tungsten source is antimony tungstate, and the added amount is 0-0.8 mmol.

7. The preparation method according to any one of claims 2 to 4, characterized in that: The concentration of the sodium hydroxide solution is 20 wt %, and the pH value is 3.

8. The preparation method according to claim 1, characterized in that: The drying process was performed at 80° C. for 12 h, the centrifugal speed was 3000 r / min, and the washing process was performed by alternating anhydrous ethanol and deionized water for 6 times.

9. Use of the gas-sensitive material as claimed in claim 1 in preparing a gas-sensitive element for detecting ethylene.

10. The use according to claim 9, characterized in that: include, The gas-sensitive material is added to deionized water and ground to form a paste, and then the paste is evenly coated on the outer surface of the gas sensor substrate to completely cover the platinum electrode, and dried at 70° C. for 20 h to form a gas-sensitive coating to obtain the ethylene gas sensor.

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