Semiconductor gas-sensitive material and its preparation method, sensor and quadruped robot application

Abstract

The present invention discloses a semiconductor gas-sensitive material and a preparation method thereof, a sensor and a quadruped robot application. The present invention relates to the field of gas detection technology. The preparation method of the semiconductor gas-sensitive material comprises the following steps: S1, preparing ZIF-67; S2, ultrasonically dispersing ZIF-67 powder in methanol to form a white uniform suspension, then sequentially adding silver nitrate and chloropalladic acid to the white uniform suspension, stirring, standing, centrifuging, and drying to obtain a white powder; S3, calcining the white powder to obtain a semiconductor gas-sensitive material Ag-Pa / CoO. The semiconductor gas-sensitive material of the multi-metal composite structure of the present invention can show higher sensitivity and selectivity. The multi-metal has more active sites, which can increase the reaction rate between toxic gases and oxygen anions, resulting in a rapid change in the state of the electron depletion layer, thereby realizing rapid detection of gas concentration.

Description

Technical Field

[0001] The present invention relates to the field of gas detection technology, and in particular to a semiconductor gas-sensitive material and a preparation method thereof, a sensor and a quadruped robot application. Background Art

[0002] In today's era of rapid technological development, it is particularly important to conduct efficient and accurate detection of toxic and harmful gases such as ammonia and carbon monoxide in complex environments such as deep wells, tunnels, and confined spaces. Such environments are often difficult to implement with traditional detection methods due to space limitations, harsh environmental conditions, and high risks of manual operations. With its unique bionic design, the quadruped robot can move flexibly in complex terrains, overcoming the problem that traditional wheeled or tracked robots are limited in certain special environments. At the same time, combined with advanced gas detection technology, the quadruped robot can detect and transmit toxic and harmful gas data in the environment in real time, providing timely and accurate information support for staff to ensure operational safety. In addition, the application of quadruped robots can effectively reduce manpower input, improve operational efficiency, and reduce production costs, which is of great significance for promoting the development of related industries.

[0003] The continuous development of sensor technology has improved the detection accuracy and sensitivity of toxic gas detectors. The application of new sensors has made the detection instruments respond faster, have lower false alarm rates, and can detect multiple harmful gases at the same time. Many works have made unremitting efforts to develop high-performance room-temperature gas sensors, such as synthesizing a variety of nanostructures to utilize the unique sensing mechanism of low-dimensional structures. However, the sensing performance of these gas sensors at room temperature is limited, especially for toxic gas detection. For example, some sensors show sufficient sensitivity, but the response / recovery time is very long, and they cannot even recover to the initial resistance. Some sensors have high sensitivity and short response / recovery time, but show poor stability and gas selectivity. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a semiconductor gas-sensitive material and a preparation method thereof, a sensor and a quadruped robot application.

[0005] A method for preparing a semiconductor gas-sensitive material of the present invention comprises the following steps:

[0006] S1. Dissolve cobalt nitrate hexahydrate and 2-methylimidazole ligand in a solvent respectively; then slowly add the 2-methylimidazole solution dropwise to the cobalt nitrate solution. After the reaction is completed, centrifuge, wash, and dry the product to obtain ZIF-67;

[0007] S2, ultrasonically dispersing ZIF-67 powder in methanol to form a white uniform suspension, then sequentially adding silver nitrate and chloropalladic acid to the white uniform suspension, stirring, standing, centrifuging, and drying to obtain a white powder;

[0008] S3. Calcine the white powder at 400-600°C for 2-4 h and obtain the semiconductor gas-sensitive material Ag-Pa / CoO after natural cooling.

[0009] Furthermore, in the semiconductor gas-sensitive material Ag-Pa / CoO, the molar ratio of Co, Ag and Pa is 1~3:1~3:1~3.

[0010] Furthermore, in step S2, the mixture is stirred for 1 to 3 hours and then allowed to stand for 24 to 48 hours.

[0011] Furthermore, in step S3, the heating rate is 1-2°C / m.

[0012] A semiconductor gas-sensitive material prepared by the above-mentioned preparation method.

[0013] A gas sensor based on the semiconductor gas-sensitive material mentioned above.

[0014] Furthermore, the gas sensor of the semiconductor gas-sensitive material is prepared by the following steps:

[0015] S1, dispersing the semiconductor gas-sensitive material Ag-Pa / CoO in deionized water to obtain an Ag-Pa / CoO conductive solution;

[0016] S2. The Ag-Pa / CoO conductive solution is transferred to a dilute polylactic acid solution and mixed evenly, and then the solution is evenly coated on a substrate with a pair of gold electrodes, and dried to obtain a gas sensor.

[0017] The invention discloses a quadruped robot equipped with a gas sensor for detecting reducing toxic gases.

[0018] Furthermore, the toxic gas includes ammonia and VOCs.

[0019] The present invention introduces Ag and Pa bimetallics into the porous crystalline material ZIF-67 containing Co metal clusters through ion exchange method to obtain a trimetallic Co, Ag, Pa porous crystalline material Ag-Pa / ZIF-67. Subsequently, Ag-Pa / ZIF-67 is used as a template agent and calcined at high temperature to obtain Ag-Pa / CoO as a sensing material; the present invention forms a trimetallic Co, Ag, Pa porous metal semiconductor material Ag-Pa / CoO by introducing the combination of Ag and Pa bimetallics and Co metal clusters. When the Ag-Pa / CoO material is exposed to the air, oxygen molecules in the air will be adsorbed on the surface of the Ag-Pa / CoO material and take electrons from the Ag-Pa / CoO material to form oxygen anions (such as O - , O 2- When toxic gases (such as ammonia, VOCs, etc.) come into contact with the sensor, these gases react with the oxygen anions on the surface of the Ag-Pa / CoO material, causing the state of the electron depletion layer to change, thereby causing the conductivity of the semiconductor gas-sensitive material to change. By measuring this change in conductivity, toxic gases can be detected.

[0020] The three metals Ag, Pa and Co can form a complex electronic structure in the composite material, including charge transfer, orbital hybridization, etc. These effects not only change the band structure of the material, but also affect the surface chemical properties of the material, thereby improving the sensitivity and selectivity to the gas, so that the semiconductor gas-sensitive material of the multi-metal composite structure of the present invention shows higher sensitivity and selectivity. Multi-metals have more active sites, which can enhance the rapid reaction between toxic gases and oxygen anions, resulting in rapid changes in the state of the electron depletion layer, thereby realizing rapid detection of gas concentration.

[0021] The semiconductor gas-sensitive material Ag-Pa / CoO prepared by the present invention is a porous nanomaterial. The three-metal element composite structure can significantly increase the specific surface area and porosity of the material, thereby increasing the contact area between the material and the target gas and improving the gas adsorption efficiency. Its high specific surface area helps to form more oxygen anions, increase the reaction space between toxic gases and oxygen anions, and absorb more toxic gases, thereby improving the response and recovery time of the sensor device.

[0022] Ag-Pa / CoO is used as a semiconductor gas-sensitive material and is prepared with polylactic acid in a slurry and loaded on a substrate with a pair of gold electrodes as a gas sensor. The test results show that the sensitivity of the Ag-Pa / CoO gas sensor to ammonia extends to 5ppm, and the response and recovery times are 1s and 88s respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD patterns of CoO and Ag-Pa / CoO prepared in Example 1;

[0024] Figure 2 This is a graph showing the N2 adsorption-desorption curve of the Ag-Pa / CoO semiconductor gas-sensitive material prepared in Example 1;

[0025] Figure 3 This is a SEM image of the Ag-Pa / CoO semiconductor gas-sensitive material prepared in Example 1;

[0026] Figure 4 The response curves of the Ag-Pa / CoO gas sensor prepared in Example 1 and the CoO gas sensor prepared in Comparative Example 1 as a function of ammonia concentration;

[0027] Figure 5 Response time and recovery time of Ag-Pa / CoO detection device to ammonia. DETAILED DESCRIPTION

[0028] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0029] The preparation method of Ag-Pa / CoO in the present invention is as follows:

[0030] 1. Synthesis of ZIF-67 powder

[0031] 1.5~2.5 g of cobalt nitrate metal salt and 1.5~2.5 g of 2-methylimidazole ligand were successively added to 100~200 ml of anhydrous methanol solution, stirred at room temperature for 10~20 min to completely dissolve them, ultrasonicated in an ultrasonic cleaner for 10~20 min to fully combine the metal ions and ligand molecules, and then continued to stir and react at room temperature for 6~8 h to obtain a white powder reaction product. The white particles after the reaction were collected by centrifugation, clarified with methanol three times, and then dried in an oven at 60~80°C to obtain the required ZIF-67 powder.

[0032] 2. Preparation of Ag-Pa / CoO semiconductor gas-sensitive materials

[0033] First, dissolve ZIF-67 powder in 60~80ml of methanol, stir for 10~20min, and transfer to an ultrasonic cleaner for 10~20min to form a white uniform suspension. Then use a pipette to measure 30~60 μL of silver nitrate solution and chloropalladic acid, respectively, and add them to the solution containing ZIF-67 in turn. After continuous stirring for 1~3 hours, let it stand for 24~48 hours. After centrifugation and drying, the resulting white powder is obtained.

[0034] The mixture was transferred to a tube furnace and calcined at 400-600°C for 2-4 h with a heating rate of 1°C / m. After natural cooling, the desired Ag-Pa / CoO semiconductor gas sensing material was obtained.

[0035] The preparation method of the gas sensor is as follows:

[0036] Weigh 200-300 mg of the Ag-Pa / CoO semiconductor gas-sensitive material prepared above, add it to 50-100 ml of deionized water, and ultrasonicate it for 10-20 min to evenly disperse it to obtain a Ag-Pa / CoO conductive solution.

[0037] Pour 0.3-0.5 g of polylactic acid particles into 20-30 mL of dichloromethane solvent and obtain a polylactic acid dilute solution by magnetic stirring for 10-20 min. Transfer the Ag-Pa / CoO conductive solution to the polylactic acid dilute solution and magnetically stir for 10-20 min to mix it evenly. Then evenly coat it on a ceramic tube with a pair of gold electrodes as a sensing material layer. After drying, put the ceramic tube with the sensing material into a drying oven at 80 ° C and dry it for 2 h to obtain the Ag-Pa / CoO gas sensor.

[0038] The gas sensor can be connected to the electrical components. The four metal electrodes of the dried ceramic tube are soldered to four pins on the hexagonal base with solder, and the metal coil heater (a nickel-chromium alloy coil heater for temperature regulation) is passed through the ceramic tube and soldered to the corresponding pins. The prepared device is placed on the base of the aging table and aged for several days to stabilize the device resistance value.

[0039] Integration of gas sensors on quadruped robots

[0040] Gas sensors are usually used as a sensing module of quadruped robots and are connected to the robot's control system through an interface or bus (this is the existing technology). When designing the robot, the corresponding interface and installation position are reserved so that the gas sensor can be integrated into the robot to perform environmental monitoring in dangerous or complex environments.

[0041] Example 1

[0042] 1. Synthesis of ZIF-67 powder

[0043] 1.5 g of cobalt nitrate metal salt and 1.5 g of 2-methylimidazole ligand were successively added to 100 ml of anhydrous methanol solution, stirred at room temperature for 20 min to completely dissolve them, and ultrasonicated in an ultrasonic cleaner for 20 min to fully combine the metal ions and ligand molecules. The stirring reaction was continued at room temperature for 6 h to obtain a white powder reaction product. The white particles after the reaction were collected by centrifugation, washed with methanol three times, and then dried in an oven at 60~80°C to obtain the required ZIF-67 powder.

[0044] 2. Preparation of Ag-Pa / CoO semiconductor gas-sensitive materials

[0045] First, the ZIF-67 powder prepared above was dissolved in 80 ml of methanol, stirred for 20 min, and then transferred to an ultrasonic cleaner for 20 min to form a white uniform suspension. Then, 60 μL of silver nitrate solution and chloropalladic acid were measured with a pipette, and added to the solution containing ZIF-67 in turn. After continuous stirring for 1 to 3 h, it was allowed to stand for 24 to 48 h. After centrifugation and drying, the resulting white powder was obtained.

[0046] The mixture was transferred to a tube furnace and calcined at 500°C for 2-4 h with a heating rate of 1°C / m. After natural cooling, the desired Ag-Pa / CoO semiconductor gas sensing material was obtained.

[0047] 3. Use Ag-Pa / CoO semiconductor gas-sensitive material to prepare an Ag-Pa / CoO gas sensor according to the above-mentioned gas sensor preparation method.

[0048] Example 2

[0049] In step 2, 30 μL of silver nitrate solution and 30 μL of chloropalladic acid were measured with a pipette, and the rest was the same as in Example 1.

[0050] Example 3

[0051] In step 2, 45 μL of silver nitrate solution and 45 μL of chloropalladic acid were measured with a pipette, and the rest was the same as in Example 1.

[0052] Comparative Example 1

[0053] In step 2, the silver nitrate solution and chloropalladic acid are not added, and the rest are the same as in Example 1.

[0054] Comparative Example 2

[0055] In step 2, only the silver nitrate solution was added, and the rest was the same as in Example 1.

[0056] Comparative Example 3

[0057] In step 2, only the chloropalladic acid solution was added, and the rest was the same as in Example 1.

[0058] Figure 1 XRD diagrams of CoO and Ag-Pa / CoO prepared by the present invention; As can be seen from Figure 1, the diffraction peaks of all samples are consistent with the standard card of CoO (JCPDS: 43-1004), and no other impurity peaks are observed. This shows that their main components are cobalt oxide, and the products are relatively pure. At the same time, the diffraction peaks of CoO after Ag-Pd modification have not changed, indicating that Ag-Pd modification has not changed the structure of CoO itself, which may be caused by too little modified content.

[0059] Figure 2 is the N2 adsorption-desorption curve of Ag-Pa / CoO; Figure 2 As can be seen in the figure, the Ag-Pa / CoO semiconductor gas-sensitive material prepared in the present invention is a porous material with a BET specific surface area of ​​425 m 2 / g, has a large surface area.

[0060] Figure 3 is the scanning electron microscope image of Ag-Pa / CoO, such as Figure 3 As shown, Ag-Pa / CoO has a dodecahedral structure with relatively uniform particle size and good dispersion, which helps to improve the sensitivity and response speed of the sensor.

[0061] The Ag-Pa / CoO gas sensor prepared by the Ag-Pa / CoO semiconductor gas-sensitive material of Example 1 and the CoO gas sensor prepared by CoO of Comparative Example 1 were used to detect the response performance to NH3:

[0062] Figure 4 The response curves of the Ag-Pa / CoO gas sensor and the CoO gas sensor prepared by the present invention with respect to the ammonia concentration are shown in FIG. Figure 4 It can be seen that the responses of the two groups of sensors to ammonia increase approximately linearly at low concentrations, but become gentle and approach saturation at high concentrations. Moreover, at the same concentration, the response of the CoO gas sensor to ammonia is significantly lower than that of the Ag-Pa / CoO gas sensor. This fully demonstrates that the dual modification improves the gas-sensing performance of the pure material.

[0063] Figure 5 is the response time and recovery time of Ag-Pa / CoO gas sensor to ammonia; Figure 5In the experiment, it can be found that the response and recovery time of the Ag-Pa / CoO gas sensor based on the device modified with bimetallic Ag and Pd are 1s and 88s respectively. Because the catalytic effect of bimetallic Ag and Pd reduces the activation energy required for the reaction and accelerates the interaction between ammonia molecules and oxygen ions, the Ag-Pa / CoO gas sensor exhibits a faster response characteristic.

[0064] For matters not mentioned above, the prior art applies.

[0065] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a semiconductor gas-sensitive material, characterized in that: The steps include: S1. Dissolve cobalt nitrate hexahydrate and 2-methylimidazole ligand in a solvent respectively; then slowly add the 2-methylimidazole solution dropwise to the cobalt nitrate solution. After the reaction is completed, centrifuge, wash, and dry the product to obtain ZIF-67; S2, ultrasonically dispersing ZIF-67 powder in methanol to form a white uniform suspension, then sequentially adding silver nitrate and chloropalladic acid to the white uniform suspension, stirring, standing, centrifuging, and drying to obtain a white powder; S3. Calcine the white powder at 400-600°C for 2-4 h and obtain the semiconductor gas-sensitive material Ag-Pa / CoO after natural cooling.

2. The preparation method according to claim 1, characterized in that: In the semiconductor gas-sensitive material Ag-Pa / CoO, the molar ratio of Co, Ag and Pa is 1~3:1~3:1~3.

3. The preparation method according to claim 1, characterized in that: In step S2, stirring is continued for 1 to 3 hours and then allowed to stand for 24 to 48 hours.

4. The preparation method according to claim 1, characterized in that: In step S3, the heating rate is 1-2°C / m.

5. A semiconductor gas-sensitive material prepared by the preparation method according to any one of claims 1 to 4.

6. A gas sensor based on the semiconductor gas-sensitive material according to claim 5.

7. The gas sensor according to claim 6, characterized in that: The preparation was carried out in the following steps: S1, dispersing the semiconductor gas-sensitive material Ag-Pa / CoO in deionized water to obtain an Ag-Pa / CoO conductive solution; S2. The Ag-Pa / CoO conductive solution is transferred to a polylactic acid dilute solution and mixed evenly, and then the solution is evenly coated on a substrate with a pair of gold electrodes to form a sensing material layer, and then dried to obtain a gas sensor.

8. A quadruped robot equipped with the gas sensor as claimed in claim 7, characterized in that: Used to detect reducing toxic gases.

9. The quadruped robot according to claim 8, characterized in that: The toxic gases include ammonia and VOCs.

Images