A preparation method and application of molybdenum trioxide nanosheet semiconductor

Abstract

The present application discloses a preparation method and application of molybdenum trioxide nanosheet semiconductors. The preparation method of the present application includes adding α-MoO3 and sulfur powder into an organic solvent, mixing evenly, reacting at 120-150 °C for 20-24 h, centrifuging to take the supernatant and storing it in the dark to obtain a MoO3 QDs solution, and drying to obtain sulfided MoO 3‑x QDs powder; dispersing the MoO 3‑x QDs powder in water to make a slurry, coating it on a substrate, and heating at 300-350 °C for 1-2 h to obtain semiconductor molybdenum trioxide nanosheets; the mass ratio of α-MoO3 to sulfur powder is 1:0.5-2. The method of the present application adds sulfur powder for doping during the preparation process, and different morphologies and performance characteristics of molybdenum trioxide nanosheets can be prepared by simply adjusting the amount of sulfur powder. The operation is simple and convenient, with stronger flexibility and practicability, providing a new scheme and approach for the preparation of molybdenum trioxide nanosheets with different morphologies and performances.

Description

Technical Field

[0001] This application relates to the technical field of metal oxide semiconductors, and particularly to a preparation method and application of molybdenum trioxide nanosheet semiconductors. Background Art

[0002] Molybdenum trioxide (MoO 3 ) As an n-type semiconductor metal oxide, it has been rated as a research hotspot material in recent years due to its practicality in a wide range of important technical applications. MoO 3 Due to its wide bandgap (2.39 - 2.9 eV), it has become one of the most promising semiconductor materials for applications in sensors, photocatalysts, solar cells, and thin film electrodes. As an n-type semiconductor oxide, MoO 3 In the field of gas sensors, it is often limited by its low conductivity, high operating temperature, and low sensitivity. And MoO 3 The emergence and application of various nanostructures can effectively solve the above problems. Due to the progress of synthesis technology, many novel nanostructures can already be explored and used in various application fields. Currently, there are various preparation methods for MoO 3 nanostructures in the literature and patents, but they are all single methods corresponding to single structures, lacking flexibility and practicality. Summary of the Invention

[0003] The purpose of this application is to provide an improved preparation method of molybdenum trioxide nanosheet semiconductors, the prepared molybdenum trioxide nanosheets, and their applications.

[0004] To achieve the above purpose, this application adopts the following technical solutions:

[0005] One aspect of this application discloses a preparation method of semiconductor molybdenum trioxide nanosheets, including adding α-MoO 3 and sulfur powder into an organic solvent, mixing evenly; then, reacting at 120 - 150 °C for 20 - 24 h; after the reaction is completed, centrifuging to take the supernatant and storing it away from light to obtain a MoO 3 QDs solution; drying the MoO 3 QDs solution to obtain sulfided MoO 3-x QDs powder; dispersing the MoO 3-x QDs powder in water to make a coating slurry; coating the coating slurry on a substrate and heating at 300 - 350 °C for 1 - 2 h until the coating does not change color, to obtain semiconductor molybdenum trioxide nanosheets; wherein, the mass ratio of α-MoO 3 and sulfur powder is 1:0.5 - 2, and different morphologies and performance characteristics of molybdenum trioxide nanosheets (MoO 3nanoflakes). Among them, dispersing MoO 3-x The QDs powder in water, preferably deionized water, is used.

[0006] It should be noted that the research of this application finds that when preparing semiconductor molybdenum trioxide nanosheets, adding sulfur powder to them and adjusting the amount of sulfur powder can change the morphology and performance characteristics of the obtained molybdenum trioxide nanosheets. For example, in one implementation of this application, molybdenum trioxide nanosheets with completely different morphologies are obtained only by changing the amount of sulfur powder; moreover, as the amount of sulfur powder increases, the aspect ratio of the molybdenum trioxide nanosheets gradually increases, and the highest response to ethanol gas is also higher. The preparation method of this application can prepare molybdenum trioxide nanosheets with different morphologies and properties by simply adjusting the amount of sulfur powder, and has stronger flexibility and practicability.

[0007] In one implementation of this application, the organic solvent is an aqueous solution of at least one of N-methylpyrrolidone (NMP), acetonitrile, methanol, ethanol, and isopropanol.

[0008] It should be noted that NMP, acetonitrile, methanol, ethanol, and isopropanol can all be used as the organic solvent of this application, but they have different polarities and surface tensions. In one implementation of this application, an aqueous solution of NMP is preferably used, and the effect is the best.

[0009] Preferably, the organic solvent is an aqueous solution with a volume ratio of N-methylpyrrolidone to water of 1:1.

[0010] It should be noted that the ratio of NMP to water being 1:1 is to maximize the exfoliation effect of the nanosheets and maintain their stability; it can be understood that under relatively low requirements, this ratio can also be appropriately adjusted to meet different production needs.

[0011] In one implementation of this application, α-MoO 3 and sulfur powder are mixed evenly in the organic solvent. The specific method includes adding α-MoO 3 and sulfur powder to the organic solvent, and then circulating and cooling with ultrasound at 20 - 25°C for 3 - 5 min to obtain a stable and uniform milky white turbid liquid.

[0012] In one implementation of this application, the conditions for centrifugation after the reaction are centrifugation at 10000 - 12000 rpm for 5 - 15 min.

[0013] In one implementation of this application, the drying conditions for the MoO 3 QDs solution are drying at 100 - 120°C for 36 - 48 h.

[0014] It should be noted that the drying conditions of this application are related to the amount of the sample. As long as it is ensured that the moisture is completely evaporated and the solid is completely dried; therefore, under the condition of ensuring the quality of MoO 3 QDs, it is preferably dried at 100-120 °C. As for the drying time, it is based on the complete drying of all the solids. For example, it is dried for 36-48 h.

[0015] In one implementation manner of this application, the substrate is a ceramic chip.

[0016] It should be noted that this application uses a ceramic chip as the substrate mainly considering directly using it for preparing a gas sensor later. The key lies in directly leading out a heating electrode on the back of the substrate to directly pass a heating current through the ceramic chip for heating. It can be understood that if only preparing semiconductor molybdenum trioxide nanosheets without considering the application of gas sensors, other materials can also be used as the substrate; specifically, it is determined according to specific applications or production, and no specific limitation is made here.

[0017] In one implementation manner of this application, the preparation method of this application further includes connecting a pair of gold electrodes to the front and back of the ceramic chip respectively, leading out platinum wires as leads, and heating through the back heating electrode, that is, heating at 300-350 °C for 1-2 h.

[0018] It should be noted that heating at 300-350 °C for 1-2 h, this combination of temperature and time is to make MoO 3-x completely converted into MoO 3 , the higher the temperature, the shorter the time, and the lower the temperature, the longer the time. As long as it is ensured that MoO 3-x is all changed into MoO 3 that's okay.

[0019] On the other hand, this application discloses molybdenum trioxide nanosheets obtained by the preparation method of this application.

[0020] On yet another aspect, this application discloses the application of the molybdenum trioxide nanosheets of this application in gas sensors.

[0021] On yet another aspect, this application discloses a gas sensor using the molybdenum trioxide nanosheets of this application as a semiconductor gas-sensitive material.

[0022] It should be noted that this application has found through research that using the molybdenum trioxide nanosheets of this application as a semiconductor gas-sensitive material in the sensor probe, the resulting gas sensor has better response. For example, for ethanol gas, the highest response of the molybdenum trioxide nanosheets prepared by sulfur powder doping can reach 76.9; and for methanol gas, the highest response of the molybdenum trioxide nanosheets prepared by sulfur powder doping can be increased by more than ten times compared with the molybdenum trioxide prepared without sulfur powder doping.

[0023] Due to the above technical solutions, the beneficial effects of the present application are as follows:

[0024] In the preparation method of semiconductor molybdenum trioxide nanosheets of the present application, sulfur powder is added for doping during the preparation process of molybdenum trioxide nanosheets. By simply adjusting the amount of sulfur powder, molybdenum trioxide nanosheets with different morphologies and performance characteristics can be prepared. The operation is simple and convenient, with stronger flexibility and practicability, providing a new solution and approach for preparing molybdenum trioxide nanosheets with different morphologies and properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the scanning electron microscope observation results and partial EDS mapping diagrams of MoO 3 nanoflakes prepared by doping different amounts of sulfur powder in the embodiments of the present application;

[0026] Figure 2 It is the gas-sensing performance test results diagram of MoO 3 nanoflakes prepared by doping different amounts of sulfur powder in the embodiments of the present application for ethanol;

[0027] Figure 3 It is the gas-sensing performance test results diagram of MoO 3 nanoflakes prepared by doping different amounts of sulfur powder in the embodiments of the present application for methanol. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present application will be further described in detail below in conjunction with the accompanying drawings through specific embodiments. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of these features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification to avoid the core part of the present application being overwhelmed by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the descriptions in the specification and general technical knowledge in the art.

[0029] Using existing methods, MoO 3 nanoflakes with various morphologies or properties can also be prepared. However, generally, a single method corresponds to a single structure. When preparing MoO 3 nanoflakes with different morphologies or structures, different methods need to be used, which is not conducive to industrial production.

[0030] The present application creatively discovers that when preparing semiconductor molybdenum trioxide nanosheets, adding sulfur powder to α-MoO 3Sulfur powder is added, and by adjusting the amount of sulfur powder, the morphology and performance characteristics of the prepared MoO 3 nanoflakes can be changed.

[0031] Based on the above research and findings, the present application has developed a method for preparing semiconductor molybdenum trioxide nanosheets, including adding α-MoO 3 and sulfur powder into an organic solvent, mixing evenly; then, reacting at 120 - 150 °C for 20 - 24 h; after the reaction is completed, centrifuging to take the supernatant and storing it in the dark, thus obtaining the MoO 3 QDs solution; drying the MoO 3 QDs solution to obtain sulfided MoO 3- x QDs powder; dispersing the MoO 3-x QDs powder in water to make a coating slurry; coating the coating slurry on a substrate and heating at 300 - 350 °C for 1 - 2 h until the color of the coating does not change, thus obtaining semiconductor molybdenum trioxide nanosheets; wherein, the mass ratio of α-MoO 3 and sulfur powder is 1:0.5 - 2, and different morphologies and performance characteristics of molybdenum trioxide nanosheets can be prepared by adjusting the amount of sulfur powder.

[0032] The preparation method of the present application, without changing other process conditions and using the same process equipment, only needs to simply adjust the amount of sulfur powder and control the proportion of raw materials, then different morphologies and performance characteristics of MoO 3 nanoflakes can be prepared. The operation is simple and convenient, and it has stronger flexibility and practicability.

[0033] The present application will be further described in detail below through specific examples and drawings. The following examples are only for further illustration of the present application and should not be construed as a limitation of the present application.

[0034] Example

[0035] 0.3 g of α-MoO 3 powder is separately mixed with 0.15 g, 0.3 g, and 0.6 g of sulfur powder, and then respectively added into 20 mL of a mixed solvent with a volume ratio of NMP / H 2 O of 1:1. The mixed solution is placed in an ultrasonic cleaner, and ultrasonic cooling is cycled at 20 °C for 5 min to obtain a relatively stable and uniform milky white turbid liquid. Then, the milky white liquid is transferred to a 20 mL hydrothermal reaction kettle, the temperature is controlled at 120 °C, the sample is reacted in a vacuum drying oven for 24 h, the obtained liquid is allowed to stand and cool, then transferred to a centrifuge tube, centrifuged at a speed of 12,000 rpm in a centrifuge for 10 min, and the supernatant is taken and stored in the dark to obtain MoO 3NMP / aqueous solution of QDs. The solution was taken in a petri dish and placed in a vacuum drying oven to be dried under vacuum at 120 °C for 48 hours until a dark blue to black powder was obtained. The obtained powder was sulfided MoO 3-x QDs powder. The black powder sample was mixed with deionized water to form a slurry, which was coated on a ceramic sheet (1.5 mm * 1.5 mm * 0.25 mm), namely a common four-legged electrode sheet of a ceramic substrate. A pair of gold electrodes were connected to the front and back respectively, and a platinum wire was led out as a wire. It was heated by the back heating electrode at 350 °C for about 1 h. During the heating process, the surface sample gradually turned white and no longer changed after about 1 h, thus obtaining MoO 3 nanoflakes of this example.

[0036] In addition, only 0.3 g of α-MoO 3 powder was used in this example, and no sulfur powder was added. The same treatment was carried out according to the aforementioned method to prepare MoO 3 as a comparison.

[0037] The prepared MoO 3 nanoflakes were observed by scanning electron microscopy (SEM) respectively, and the results are as Figure 1 shown. Figure 1 Among them, Figure (a) is MoO 3 without sulfur powder doping as a comparison, Figure (b) is MoO 3 nanoflakes prepared with a mass ratio of α-MoO 3 to sulfur powder of 1:0.5, Figure (c) is MoO 3 nanoflakes prepared with a mass ratio of α-MoO 3 to sulfur powder of 1:1, and Figure (d) is MoO 3 nanoflakes prepared with a mass ratio of α-MoO 3 to sulfur powder of 1:2. Figure 1 The results of Figure (a) to Figure (d) show that MoO 3 nanoflakes with different morphologies can be prepared by adding different amounts of sulfur powder. Moreover, with the increase of the amount of sulfur powder, the aspect ratio of the nanosheets gradually increases and the thickness gradually decreases.

[0038] The EDS mapping images obtained from the SEM image of Figure (d) are as shown in Figure 1 Figures (e) to (g). The results of Figures (e) to (g) show that Mo and O elements are uniformly distributed in the prepared MoO 3 nanoflakes.

[0039] When the S doping amounts during the preparation process are 0.5, 1, and 2 respectively, the prepared MoO 3MoO nanoflakes with different morphologies 3 In this example, the responses of different S-doped MoO 3 nanoflakes to ethanol and methanol were tested using the static gas mixing method on an intelligent gas sensing test system (Weisheng WS-30B).

[0040] (1) Detection of gas sensing performance to ethanol

[0041] In this example, the responses of MoO prepared without S doping at 350 °C 3 and MoO nanoflakes prepared with S doping amounts of 0.5, 1, and 2 respectively 3 to 500 ppm ethanol were tested, and the test results are as Figure 2 shown.

[0042] Figure 2 In the figure, MO represents MoO without sulfur powder doping for comparison 3 , MO-S(0.5) represents MoO 3 prepared with a mass ratio of α-MoO to sulfur powder of 1:0.5 3 nanoflakes, MO-S(1) represents MoO 3 prepared with a mass ratio of α-MoO to sulfur powder of 1:1 3 nanoflakes, and MO-S(2) represents MoO 3 prepared with a mass ratio of α-MoO to sulfur powder of 1:2 3 nanoflakes.

[0043] Figure 2 The results show that the response of the S-doped samples to ethanol at 350 °C is higher than that of the non-S-doped samples to ethanol, and the response to ethanol increases with the increase of the S doping amount. Among them, the response of MO-S(2) to 500 ppm ethanol reaches 76.9. Moreover, the responses of MO, MO-S(0.5), MO-S(1), and MO-S(2) are 27.5, 39.6, 57.0, and 76.9 in sequence; thus, it can be seen that the responses of the samples prepared with S doping to ethanol gas reach approximately 1.5 times, 2.1 times, and 2.8 times that of the samples prepared without S doping respectively.

[0044] (2) Detection of gas sensing performance to methanol

[0045] In this example, the responses of MoO prepared without S doping at 200 - 400 °C 3 and MoO nanoflakes prepared with S doping amounts of 0.5, 1, and 2 respectively 3 to 500 ppm methanol were tested, and the test results are as Figure 3 shown.

[0046] Figure 3 Among them, MO represents MoO without sulfur powder doping for comparison 3 , MO-S(0.5) represents α-MoO 3 nanoflakes prepared with a mass ratio of α-MoO to sulfur powder of 1:0.5 3 , MO-S(1) represents α-MoO 3 nanoflakes prepared with a mass ratio of α-MoO to sulfur powder of 1:1 3 , MO-S(2) represents α-MoO 3 nanoflakes prepared with a mass ratio of α-MoO to sulfur powder of 1:2 3 nanoflakes.

[0047] Figure 3 The results show that the responses of the S-doped samples to methanol at 200 °C, 250 °C, 300 °C, 350 °C, and 400 °C are all improved compared to the non-S-doped samples; moreover, as the S-doping amount increases, the improvement factor of the response to methanol also increases. Especially at 350 °C, the improvement factor of MO-S(2) reaches more than ten times that of the non-S-doped sample.

[0048] The above content is a further detailed description of the present application in combination with specific implementation manners, and it cannot be determined that the specific implementation of the present application is only limited to these descriptions. For those of ordinary skill in the technical field to which the present application belongs, without departing from the concept of the present application, several simple deductions or substitutions can still be made.

Claims

1. A method for preparing semiconductor molybdenum trioxide nanosheets, characterized in that: The method comprises adding α-MoO3 and sulfur powder into an organic solvent and mixing them evenly; then, reacting at 120-150°C for 20-24h; after the reaction is completed, centrifuging and taking out the supernatant and storing it in the dark to obtain a MoO3QDs solution; drying the MoO3QDs solution to obtain sulfurized MoO3-xQDs powder; dispersing the MoO3-xQDs powder in water to prepare a coating slurry; coating the coating slurry on a substrate, heating at 300-350°C for 1-2h until the coating does not change color, to obtain semiconductor molybdenum trioxide nanosheets; wherein the mass ratio of α-MoO3 to sulfur powder is 1:0.5-2, and molybdenum trioxide nanosheets with different morphologies and performance characteristics are obtained by adjusting the amount of sulfur powder, and the organic solvent is a mixed solvent of N-methylpyrrolidone and water in a volume ratio of 1:

1.

2. The preparation method according to claim 1, characterized in that: The α-MoO3 and sulfur powder are uniformly mixed in an organic solvent. The specific method includes: adding the α-MoO3 and sulfur powder into the organic solvent, circulating cooling and ultrasonicating at 20-25° C. for 3-5 minutes to obtain a stable and uniform milky white turbid liquid.

3. The preparation method according to claim 1, characterized in that: After the reaction is completed, the centrifugation condition is 10000-12000 rpm for 5-15 min.

4. The preparation method according to claim 1, characterized in that: The drying conditions of the MoO3QDs solution are 100-120°C for 36-48h.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The substrate is a ceramic sheet.

6. The preparation method according to claim 5, characterized in that: The method also includes connecting a pair of gold electrodes at the front and back of the ceramic sheet, leading out a platinum wire as a conductor, and heating it through a back heating electrode, that is, heating it at 300-350° C. for 1-2 hours.

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