Preparation of an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials and its products and applications

Abstract

The present invention discloses a preparation of an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials, and its products and applications. Co-doped WO3 nanomaterials are prepared by adding ZIF-67 during the preparation of gel, and then calcining at high temperature in an air atmosphere. The porosity of the nanomaterials is further increased by utilizing the high porosity of ZIF-67. The samples prepared by the method can be used for the detection of ammonia. The preparation method of the present invention is simple. The sensitivity and selectivity of the WO3 nanomaterial to the gas response are improved by increasing the material porosity and Co doping. The MEMS device is made of the material, and the stability of the gas sensor under long-term working conditions can be increased.

Description

Technical Field

[0001] The present invention relates to the field of gas detection, and in particular to the preparation of an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials, its products and applications, and a preparation method for growing a sensitive material for ammonia detection on the surface of a MEMS device. Background Art

[0002] Ammonia is a toxic gas widely used in industry. It is colorless and has a pungent odor. It can burn the skin, eyes, and respiratory mucosa. Excessive inhalation can cause lung swelling and even death. The "Indoor Air Quality Standard" GB / T18883-2002 stipulates that the maximum allowable concentration of ammonia in indoor air is 0.26 ppm. The "Industrial Enterprise Design Hygiene Standard" TJ36-79 stipulates that the maximum allowable concentration of ammonia in workshop air is 39.5 ppm. Therefore, real-time monitoring of low-concentration ammonia is very important.

[0003] WO3 has become a gas-sensitive material for detecting a variety of toxic, harmful, flammable and explosive gases due to its good stability, easy synthesis and regulation of surface properties. However, pure WO3 material is not satisfactory in terms of selectivity and long-term stability. By constructing nanomaterials and doping, on the one hand, the specific surface area of ​​the material can be increased and the active sites of the surface reaction can be increased. On the other hand, a heterojunction can be formed to improve the sensitivity of the gas response. Combining it with MEMS devices can improve the long-term stability and consistency of gas sensors and further reduce energy consumption.

[0004] The present invention dopes WO3 with ZIF-67 having a MOF structure. During the heat treatment process, the ZIF-67 organic framework is pyrolyzed to form a Co-doped WO3 nanomaterial. The Co-doped WO3 prepared by this method has a large specific surface area. The Co-doped WO3 is combined with a MEMS device to prepare a MEMS gas sensor for ammonia detection. Summary of the invention

[0005] The present invention aims to provide a method for preparing an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials, which can achieve high-sensitivity detection of ammonia.

[0006] Another object of the present invention is to provide an ammonia MEMS gas sensor product based on Co-doped tungsten trioxide nanomaterials prepared by the above method.

[0007] Another object of the present invention is to provide an application of the above product.

[0008] The object of the present invention is achieved by the following scheme: A method for preparing an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial comprises the following steps:

[0009] (1) Take 50 mL of deionized water and place it in a beaker. Then add 3-8 mmol of citric acid. After dissolving, add glucose at a molar ratio of 1:1.3-2. After stirring for 30 min, add sodium tungstate at a molar ratio of 1:2-3. After stirring for 30 min, add 0.3-0.6 g of ZIF-76 and 2-5 mmol of ethylene glycol. Seal the beaker with plastic wrap, place it in a water bath, and stir at 80-90 °C until the solution becomes a colloid.

[0010] The ZIF-67 preparation method is as follows:

[0011] 1 mmol of Co(NO3)2・6H2O and 4 mmol of 2-methylimidazole were dissolved in 25 mL of methanol, respectively, and then the two were mixed, stirred at room temperature for 10 min, and then allowed to stand at room temperature for 24 h. The precipitate was centrifuged and dried to obtain ZIF-67.

[0012] (2) Take an appropriate amount of the colloid obtained in step 1 and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at a temperature of 400-450°C for 1-2 h at a heating rate of 1-2°C / min. After cooling to room temperature, an ammonia MEMS gas sensor made of Co-doped WO3 nanomaterials is obtained.

[0013] The present invention provides an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial, which is prepared according to any of the above methods.

[0014] The present invention provides an application of an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial in preparing an ammonia MEMS gas sensor material.

[0015] The method prepares Co-doped WO3 nanomaterials by adding ZIF-67 during the preparation of gel and then calcining at high temperature in an air atmosphere. The porosity of the nanomaterials is further increased by utilizing the high porosity of ZIF-67. The samples prepared by the method can be used for the detection of ammonia. The preparation method of the present invention is simple. The sensitivity and selectivity of the WO3 nanomaterials to gas response are improved by increasing the porosity of the material and doping with Co. The WO3 nanomaterials are made into MEMS devices, which can increase the stability of the gas sensor under long-term working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1: is the response-recovery curve of the gas sensor of the present invention to ammonia gas with a concentration of 1 ppm at an operating temperature of 150°C. DETAILED DESCRIPTION

[0017] The ZIF-67 preparation method used in the present invention is:

[0018] 1 mmol of Co(NO3)2・6H2O and 4 mmol of 2-methylimidazole were dissolved in 25 mL of methanol, respectively, and then the two were mixed and stirred at room temperature for 10 min, and then allowed to stand at room temperature for 24 h. The precipitate was centrifuged and dried to obtain ZIF-67.

[0019] Example 1

[0020] An ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared according to the following steps:

[0021] (1) Take 50 mL of deionized water and place it in a beaker. Then add 8 mmol of citric acid. After dissolving, add glucose in a molar ratio of glucose to citric acid of 1:2. After stirring for 30 min, add sodium tungstate in a molar ratio of sodium tungstate to citric acid of 1:3. After stirring for 30 min, add 0.6 g of ZIF-76 and 5 mmol of ethylene glycol. Seal the beaker with plastic wrap, place it in a water bath, and stir at 90°C until the solution becomes a colloid.

[0022] (2) Take an appropriate amount of the colloid obtained in step (1) and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at 450°C for 1 h with a heating rate of 1°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

[0023] Figure 1 The gas sensor of the device obtained in this embodiment has a hydrogen response-recovery curve to ammonia with a concentration of 1 ppm at an operating temperature of 150° C., and a response sensitivity of 21.86, indicating that the gas sensor has very excellent response characteristics.

[0024] Example 2

[0025] An ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared in the following steps similar to those in Example 1:

[0026] (1) Take 50 mL of deionized water and place it in a beaker. Then add 3 mmol of citric acid. After dissolving, add glucose at a molar ratio of 1:1.5. After stirring for 30 min, add sodium tungstate at a molar ratio of 1:2. After stirring for 30 min, add 0.5 g of ZIF-76 and 3 mmol of ethylene glycol. Seal the beaker with plastic wrap and place it in a water bath. Stir at 80°C until the solution becomes a colloid.

[0027] (2) Take an appropriate amount of the colloid obtained in step (1) and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at 400°C for 1.5 h with a heating rate of 1°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

[0028] The device obtained in this embodiment has a response sensitivity of 18.5 to ammonia gas with a concentration of 1 ppm at an operating temperature of 150°C.

[0029] Example 3

[0030] An ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared in the following steps similar to those in Example 1:

[0031] (1) Take 50 mL of deionized water and place it in a beaker. Then add 5 mmol of citric acid. After dissolving, add glucose at a molar ratio of 1:2. After stirring for 30 min, add sodium tungstate at a molar ratio of 1:2.5. After stirring for 30 min, add 0.6 g of ZIF-76 and 5 mmol of ethylene glycol. Seal the beaker with plastic wrap and place it in a water bath. Stir at 80-90 °C until the solution becomes a colloid.

[0032] (2) Take an appropriate amount of the colloid obtained in step 1 and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at a temperature of 450°C for 1 h at a heating rate of 2°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

[0033] The device obtained in this embodiment has a response sensitivity of 19.4 to ammonia gas with a concentration of 1 ppm at an operating temperature of 150°C.

Claims

1. An application of an ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial in detecting ammonia, characterized in that: The preparation method of ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials includes the following steps: (1) Take 50 mL of deionized water and place it in a beaker. Then add 3-8 mmol of citric acid. After dissolving, add glucose at a molar ratio of 1:1.3-2. After stirring for 30 min, add sodium tungstate at a molar ratio of 1:2-3. After stirring for 30 min, add 0.3-0.6 g of ZIF-67 and 2-5 mmol of ethylene glycol. Seal the beaker with plastic wrap, place it in a water bath, and stir at 80-90 °C until the solution becomes a colloid. (2) Taking an appropriate amount of the colloid obtained in step (1) and uniformly coating it on the MEMS substrate of the Pt interdigitated electrode, then placing it in a tube furnace and calcining it in an air atmosphere at a temperature of 400-450°C for 1-2 h at a heating rate of 1-2°C / min, and after cooling to room temperature, obtaining the Co-doped WO3 nanomaterial ammonia MEMS gas sensor; The preparation method of ZIF-67 described in step (1) is: 1 mmol of Co(NO3)2・6H2O and 4 mmol of 2-methylimidazole were dissolved in 25 mL of methanol respectively, and then the two were mixed, stirred at room temperature for 10 min, and then allowed to stand at room temperature for 24 h. The precipitate was centrifuged and dried to obtain ZIF-67.

2. The application of the ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial in detecting ammonia according to claim 1 is characterized in that: The preparation method of ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared according to the following steps: (1) Take 50 mL of deionized water and place it in a beaker. Then add 8 mmol of citric acid. After dissolving, add glucose in a molar ratio of 1:

2. After stirring for 30 min, add sodium tungstate in a molar ratio of 1:

3. After stirring for 30 min, add 0.6 g of ZIF-67 and 5 mmol of ethylene glycol. Seal the beaker with plastic wrap, place it in a water bath, and stir at 90°C until the solution becomes a colloid. (2) Take an appropriate amount of the colloid obtained in step (1) and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at 450°C for 1 h with a heating rate of 1°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

3. The application of the ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial in detecting ammonia according to claim 1 is characterized in that: The preparation method of ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared according to the following steps: (1) Take 50 mL of deionized water and place it in a beaker. Then add 3 mmol of citric acid. After dissolving, add glucose at a molar ratio of 1:1.

5. After stirring for 30 min, add sodium tungstate at a molar ratio of 1:

2. After stirring for 30 min, add 0.5 g of ZIF-67 and 3 mmol of ethylene glycol. Seal the beaker with plastic wrap, place it in a water bath, and stir at 80°C until the solution becomes a colloid. (2) Take an appropriate amount of the colloid obtained in step (1) and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at 400°C for 1.5 h with a heating rate of 1°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

4. The application of the ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterial in detecting ammonia according to claim 1 is characterized in that: The preparation method of ammonia MEMS gas sensor based on Co-doped tungsten trioxide nanomaterials is prepared according to the following steps: (1) Take 50 mL of deionized water and place it in a beaker. Then add 5 mmol of citric acid. After dissolving, add glucose in a molar ratio of glucose to citric acid of 1:

2. After stirring for 30 min, add sodium tungstate in a molar ratio of sodium tungstate to citric acid of 1:2.

5. After stirring for 30 min, add 0.6 g of ZIF-67 and 5 mmol of ethylene glycol. Seal the beaker with plastic wrap and place it in a water bath. Stir at 80-90 °C until the solution becomes a colloid. (2) Take an appropriate amount of the colloid obtained in step (1) and evenly coat it on the MEMS substrate of the Pt interdigitated electrode, then place it in a tube furnace and bake it in an air atmosphere at a temperature of 450°C for 1 h at a heating rate of 2°C / min. After cooling to room temperature, a Co-doped WO3 nanomaterial ammonia MEMS gas sensor is obtained.

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