A Co-BDC / MXene nanocomposite material, preparation method and application

Abstract

The present invention discloses a Co-BDC / MXene nanocomposite material, a preparation method and an application, which belong to the field of gas sensors. The present invention provides a Co-BDC / MXene nanocomposite material and an application. The Co-BDC / MXene-based sensor has good sensitivity to acetone gas, a low detection limit and a wide detection range. The stability of the Co-BDC / MXene composite material is also improved compared to the pure MXene material, so the stability of the Co-BDC / MXene-based acetone sensor will be better. At the same time, due to the good flexibility and plasticity of the MXene material, the Co-BDC / MXene composite material has the possibility of preparing a flexible wearable gas sensor. Finally, the conductivity of the Co-BDC / MXene composite material is significantly improved compared to traditional MOFs.

Description

Technical Field

[0001] The present invention belongs to the field of gas sensors, and in particular to a Co-BDC / MXene nanocomposite material, a preparation method and an application thereof. Background Art

[0002] As an extension of human senses, gas sensors have broad application prospects in a variety of fields, including environmental monitoring, food safety, industrial safety, and aerospace. As the core components of gas sensors, gas-sensitive materials are urgently needed to develop gas-sensitive materials with high sensitivity, high stability, high selectivity, low power consumption, and slow response time to target gases.

[0003] MXene nanomaterials are a class of metal carbides and metal nitrides with a two-dimensional layered structure. Due to their similar structure to graphene, they are also called "graphene-like." This material has a large specific surface area and a large number of functional groups on its surface, providing abundant active sites for gas adsorption and surface reactions. Lee et al. reportedly discovered for the first time that Ti3C2MXene has excellent gas-sensing properties, and its optimal operating temperature is much lower than that of common semiconductor gas-sensing materials, exhibiting good gas-sensing performance even at room temperature. However, due to the presence of surface functional groups on MXene materials and other factors, MXene materials are prone to oxidation reactions in oxidizing atmospheres, resulting in the collapse of their two-dimensional structure. Therefore, MXene materials have the disadvantage of poor stability when used as gas-sensing materials, which seriously limits their further development in the sensor field.

[0004] Currently, common gas sensors using metal oxide semiconductors as sensitive materials suffer from low gas sensitivity, low conductivity, high operating temperature, high energy consumption, and long response / recovery times, which limit their application. While MOFs offer advantages such as a large surface area and numerous active sites, their poor conductivity hinders further development in gas sensors. Summary of the Invention

[0005] In order to further improve the performance of existing gas-sensitive materials, the present invention provides a Co-BDC / MXene nanocomposite material, a preparation method and an application.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a Co-BDC / MXene nanocomposite material comprises the following steps:

[0008] MXene was dispersed in N,N-dimethylformamide, and then Co(NO3)2·6H2O was added to perform electrostatic adsorption self-assembly to obtain a mixed solution;

[0009] Dispersing a DMF solution of terephthalic acid in the mixture, and then adding ethanol and water in sequence, and mixing them together to form a precursor;

[0010] The precursor was placed in a reactor, filled with inert gas, and then reacted at a temperature of 140°C for 12 hours. After the reaction, the precipitate was collected to obtain a Co-BDC / MXene nanocomposite material.

[0011] Furthermore, 0.035 g MXene and 0.291 g Co(NO3)2·6H2O were dispersed in every 15 ml N,N-dimethylformamide;

[0012] In the DMF solution of terephthalic acid, 0.166 g of terephthalic acid is dispersed per 10 ml of DMF.

[0013] Furthermore, when dispersing the DMF solution of terephthalic acid in the mixed solution, the mixture was mixed at a ratio of 10 ml of DMF to every 15 ml of N,N-dimethylformamide.

[0014] Furthermore, when adding ethanol and water, 2 ml of ethanol and 2 ml of water were added per 15 ml of N,N-dimethylformamide.

[0015] A Co-BDC / MXene nanocomposite material, characterized in that it is prepared according to the preparation method of the present invention.

[0016] Furthermore, it is used as a gas-sensitive material to detect the concentration of VOCs gas.

[0017] Furthermore, the Co-BDC / MXen nanocomposite material was placed in a mortar, ethanol was added, and then ground into a paste-like liquid;

[0018] The paste liquid is applied to the counter electrode, and after the ethanol evaporates, the Co-BDC / MXene gas sensor is obtained.

[0019] Furthermore, the test was performed at an operating temperature of 110°C.

[0020] Furthermore, it is used to detect the concentrations of acetone, methanol, n-propanol, toluene, ethanol and formaldehyde.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a Co-BDC / MXene nanocomposite material and its application. The Co-BDC / MXene-based sensor has good sensitivity to acetone gas, a low detection limit, and a wide detection range. Compared with pure MXene materials, the stability of the Co-BDC / MXene composite material is also improved, so the stability of the Co-BDC / MXene-based acetone sensor will be better. At the same time, due to the good flexibility and plasticity of the MXene material, the Co-BDC / MXene composite material has the potential to be used to prepare flexible wearable gas sensors. Finally, the conductivity of the Co-BDC / MXene composite material is significantly improved compared to traditional MOFs.

[0023] The present invention provides a method for preparing a Co-BDC / MXene nanocomposite material, which has simple steps and controllable reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The relationship between the sensitivity of Co-BDC / MXene gas sensor to 100ppm acetone gas and operating temperature;

[0025] Figure 2 The response diagram of Co-BDC / MXene gas sensor to six different VOC gases including acetone, methanol, n-propanol, toluene, ethanol and formaldehyde at an operating temperature of 110°C;

[0026] Figure 3 This is the dynamic response diagram of the Co-BDC / MXene gas sensor to different concentrations of acetone gas at an operating temperature of 110°C. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] The present invention is described in further detail below with reference to the accompanying drawings:

[0030] The application of MXene materials in gas sensors is still in its infancy, with many questions still to be explored, both in terms of reaction mechanism research and practical applications. However, due to the advantages of MXene materials such as large specific surface area, high electron mobility, and good plasticity, the application of MXene materials in gas sensors has broad prospects. To promote the further application of MXene materials in gas sensors, it is necessary to solve problems such as how to improve the stability of MXene materials and how to promote gas adsorption reactions. The present invention combines MXene materials and MOFs materials to form a composite nanomaterial—Co-BDC / MXene material—to improve the performance of MXene materials and prepare gas-sensitive materials with even better performance.

[0031] This invention provides a method for fabricating a VOC gas sensor based on a Co-BDC / MXene composite material. The Co-BDC / MXene material is first synthesized using the following method. The resulting material is then uniformly coated onto the electrodes of a indirectly heated gas sensor. Finally, the sensor's performance is tested for acetone gas. The experimental results demonstrate that the Co-BDC / MXene-based acetone gas sensor exhibits excellent sensitivity, detection limit, and detection range.

[0032] Example

[0033] (1) Synthesis of MXene materials

[0034] First, use a graduated cylinder to measure 20 ml of 12 mol / L HCl and transfer it to a centrifuge tube for later use. Next, use a weighing balance to weigh 1.2 g of 99% LiF and transfer it to the HCl. Place the solution in an oil bath until the liquid reaches 40°C and stir for 20 minutes (18 seconds). Use a balance to weigh 1.0 g of MAX (Ti3AlC2) solid and add it to the system in small amounts over ten minutes. After adding the raw materials, fill the centrifuge tube with Ar gas, seal it with plastic wrap, tightly cap it, and place it in a 40°C water bath. Stir and react at 18 seconds per minute for 48 hours. After the reaction is complete, remove the centrifuge tube and transfer the contents evenly to two new tubes. Add a small amount of water to each tube and place it in a centrifuge at 3000 rpm for 2 minutes until the liquid becomes sticky. Discard the supernatant, add water to 45 ml, and centrifuge again at 3500 rpm for 5 minutes. After four centrifugations, the precipitate becomes sticky and the pH of the supernatant is near neutral. The clay-like precipitate is then stirred and mixed with water to form a homogeneous liquid. The mixture is then transferred to a round-bottom flask and sonicated in an ice bath for 4 hours while stirring. After sonication, centrifuge at 3500 rpm for 1 hour, and the supernatant is collected. The collected liquid is pre-frozen and freeze-dried. After drying, the MXene (Ti3C2) is collected and stored frozen in a vacuum freezer.

[0035] (2) Synthesis of Co-BDC / MXene nanocomposites

[0036] 0.035g of MXene solid was weighed and transferred to 15ml of N,N-dimethylformamide (DMF) solution. Ultrasonication was performed in an ice bath for 20 minutes to achieve uniform dispersion. 0.291g of Co(NO₃)₂·6H₂O was then added to the MXene dispersion and ultrasonicated for 15 minutes to induce electrostatic adsorption self-assembly. 0.166g of terephthalic acid (BDC) was transferred to 10ml of DMF solution and ultrasonicated for 15 minutes to fully dissolve it. The BDC solution was poured into the MXene dispersion containing dissolved cobalt ions while stirring. 2ml of ethanol and 2ml of water were then quickly added, followed by stirring at room temperature for 30 minutes. The solution was then transferred to a 100ml polytetrafluoroethylene (PTFE) reactor, filled with inert Ar gas, and placed in a muffle furnace maintained at 140°C for 12 hours. After the reaction is complete, the solution, which has cooled to room temperature, is placed in a centrifuge tube and centrifuged three times in a centrifuge at 7500 rpm using DMF and ethanol alternately. The resulting precipitate is pre-frozen and freeze-dried for later use.

[0037] (3) Preparation of Co-BDC / MXene gas sensor

[0038] The frozen Co-BDC / MXen sample was scraped from the bottom of a glass dish. The collected solid particles were placed in a sealed bag and placed in a mortar. A binder solution in ethanol was added to evenly disperse the solids in the solution. The mixture was then ground into a uniform paste. Using a brush, the prepared paste was carefully applied to two pairs of gold electrodes, ensuring even and complete coverage. After the binder completely evaporated, the Co-BDC / MXene gas sensor was obtained.

[0039] The performance of the Co-BDC / MXene gas sensor is tested below:

[0040] The performance of Co-BDC / MXene composite nanomaterials to acetone gas was tested using relevant instruments under experimental conditions of temperature 27°C and humidity 33%. The response values ​​of Co-BDC / MXene materials to acetone gas with a concentration of 100ppm at five different temperatures (80°C, 100°C, 110°C, 120°C and 140°C) were tested using instruments. The data obtained are shown in Figure 1 ,from Figure 1 It can be seen that the optimal working temperature of the material is 110℃.

[0041] The response value of the sensor to acetone gas with a concentration of 100 ppm at different temperatures was tested. By adjusting the temperature of the Co-BDC / MXene-based sensor (80℃, 100℃, 110℃, 120℃ and 140℃), the experimental results showed that (e.g. Figure 1 ) At 110℃, the sensor's response value reaches its maximum, which is 30.8. From this point on, the sensor's response value will decrease regardless of whether the temperature increases or decreases. Therefore, the optimal operating temperature of the acetone sensor is 110℃, which is much lower than that of common metal oxide-based gas sensors on the market. Secondly, the dynamic response of the sensor to different concentrations of acetone at 110℃ was tested. The experimental results ( Figure 3 ) It can be seen that in the range of 30ppm-300ppm, there is a good linear relationship between the sensor response value and the acetone gas concentration. It is worth noting that the sensor's response value to 10ppm acetone gas is still greater than 2, so the sensor has a good detection limit and detection range. Finally, the response value of the VOCs sensor to multiple gases was tested. The experimental method was to test the sensor's response value to six different gases (acetone, methanol, n-propanol, toluene, ethanol and formaldehyde) at 110℃ (the target analyte concentration was 100ppm). The experimental results ( Figure 2 ) shows that the sensor response values ​​are 31, 4, 28, 19, 24 and 4, respectively. The highest response value of the sensor to acetone gas is 31, and the response values ​​to n-propanol and ethanol are both above 20, so the material shows good response values ​​to various gases.

[0042] Based on the above experimental results, it can be found that the Co-BDC / MXene-based sensor has good sensitivity to acetone gas, a low detection limit, and a wide detection range. The Co-BDC / MXene composite material also has improved stability compared to pure MXene material, which may lead to a Co-BDC / MXene-based VOC gas sensor with better stability. Furthermore, due to the excellent flexibility and plasticity of MXene materials, the Co-BDC / MXene composite material has the potential to be used in the preparation of flexible wearable gas sensors. Finally, the Co-BDC / MXene composite material has a significant improvement in electrical conductivity compared to traditional MOFs.

[0043] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An application of a Co-BDC / MXene nanocomposite material, characterized in that: Used as a gas-sensitive material to detect the concentration of VOCs gas; The preparation method of the Co-BDC / MXene nanocomposite material comprises the following operations: MXene was dispersed in N,N-dimethylformamide, and then Co(NO3)2·6H2O was added to perform electrostatic adsorption self-assembly to obtain a mixed solution; Dispersing a DMF solution of terephthalic acid in the mixture, and then adding ethanol and water in sequence, and mixing them together to form a precursor; The precursor was placed in a reactor, filled with inert gas, and then reacted at a temperature of 140°C for 12 hours. After the reaction, the precipitate was collected to obtain a Co-BDC / MXene nanocomposite material; The mixture contained 0.035 g MXene and 0.291 g Co(NO3)2·6H2O dispersed in every 15 ml N,N-dimethylformamide; In the DMF solution of terephthalic acid, 0.166 g of terephthalic acid is dispersed in every 10 ml of DMF; When dispersing the DMF solution of terephthalic acid in the mixed solution, mix according to the ratio of 15 ml N, N-dimethylformamide to 10 ml DMF; When adding ethanol and water, add 2 ml of ethanol and 2 ml of water per 15 ml of N,N-dimethylformamide.

2. The use of the Co-BDC / MXene nanocomposite material according to claim 1, characterized in that: The Co-BDC / MXen nanocomposite material was placed in a mortar, ethanol was added, and then ground into a paste-like liquid; The paste liquid is applied to the counter electrode, and after the ethanol evaporates, the Co-BDC / MXene gas sensor is obtained.

3. The use of the Co-BDC / MXene nanocomposite material according to claim 2, characterized in that: The test was carried out at an operating temperature of 110°C.

4. The use of the Co-BDC / MXene nanocomposite material according to claim 3, characterized in that: Used to detect the concentration of acetone, methanol, n-propanol, toluene, ethanol and formaldehyde.

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