Sensor for detecting occupational exposure of ammonia gas as well as preparation method and application of sensor

Abstract

The invention discloses a sensor for ammonia gas occupational exposure detection and a preparation method and application thereof, and particularly relates to the technical field of ammonia gas detection. According to the invention, the MXene gas-sensitive material is loaded on the spandex in a spraying manner. Furthermore, an electrodeposition process is adopted, and an MXene-PPy composite material is prepared on MXene through in-situ polymerization, so that the flexible ammonia gas sensor is constructed. High-sensitivity, low-detection-limit and high-selectivity detection of the ammonia gas is realized. The invention provides the preparation method of the sensor for ammonia gas occupational exposure detection, and the method is simple and controllable and has relatively high practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia gas detection, and in particular to a sensor for detecting occupational exposure to ammonia gas, and a preparation method and application thereof. Background Art

[0002] Ammonia is widely present in industrial production, medical health, food safety and other fields. However, in the workplace, long-term inhalation of excessive ammonia by the human body can cause a series of serious diseases such as uremia, liver cirrhosis and renal failure. Lower concentrations of ammonia cannot be identified by the human body's own olfactory system alone. Therefore, there is an urgent need for an ammonia detection device that not only meets the stringent performance requirements of sensitivity, selectivity and detection limit, but also needs to have special advantages such as multi-point continuous monitoring, no impact on workers' operations, and mass production.

[0003] Among the many ammonia detection technologies, semiconductor material-based sensors have shown significant advantages in cost control, room temperature operation, sensor performance adjustment and system integration, and are the most ideal gas-sensitive materials for building wearable ammonia sensors. Among them, MXene materials have rich functional groups, ultra-high signal-to-noise ratio and excellent conductivity, which makes them have the potential to detect gases at extremely low concentrations. Conductive polymers have the advantages of customizable sensing functions, flexibility, and room temperature sensing, and are also particularly suitable for the construction of wearable ammonia sensors. However, sensors based on single gas-sensitive materials still have problems such as poor long-term stability, low sensitivity, and poor selectivity. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a method for preparing a MXene-PPy composite material-based ammonia sensor and its application in occupational exposure detection.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a sensor for detecting occupational exposure to ammonia gas, wherein the sensor is prepared by the following method: (1) Mix the HF solution and Ti3AlC2 and then fully react and etch. After the reaction is completed, wash, ultrasonicate and centrifuge in sequence. Collect the upper liquid and freeze-dry it in vacuum to obtain a powdered MXene material. (2) The spandex substrate is placed in an alkaline solution for alkalization treatment, washed and dried, and then an aqueous solution of MXene material prepared from MXene material is sprayed on the substrate and dried at 55-65°C for 0.5-1.5h to obtain spandex anchored with MXene; (3) Prepare a mixed electrodeposition solution containing pyrrole, Na2HPO4, and NaClO4, and perform electrodeposition using an electrolytic cell with a three-electrode system to in-situ polymerize a MXene-PPy composite material on the spandex anchored with MXene; (4) Dry the substrate loaded with MXene-PPy and cut it into electrodes, fix the electrodes using silver paste and copper tape, and construct a complete flexible sensor.

[0006] In the above preparation method: in step (1), the HF solution is generated by reacting concentrated hydrochloric acid with LiF; the mass ratio of Ti3AlC2, concentrated hydrochloric acid, and LiF is 0.5~1.5:15~25:1~3.

[0007] In the above preparation method: in step (1), the etching temperature is 35~45 °C and the time is 24~48 h.

[0008] In the above preparation method: in step (1), the ultrasonic conditions are to perform 2~5 ultrasonic treatments on the solution in an ice-water bath under N2 protection, with each ultrasonic treatment time of 15~25 min and the interval time between two consecutive ultrasonic treatments of 15~25 min; The centrifugation speed is 3500~4000 r / min and the time is 10~60 min; The temperature of vacuum freeze-drying is -70~-50 °C, the time is 3~5 days, and the vacuum degree is 0.5~1.5 Pa.

[0009] In the above preparation method: in step (2), the alkaline solution is a NaOH solution with a concentration of 0.5~1.5 mol / L, the alkalization treatment time is 0.5~1.5 h, and the alkalization treatment temperature is 70~85 °C.

[0010] In the above preparation method: in step (2), the concentration of the MXene material aqueous solution is 5~15 mg / mL, the nozzle diameter of the spray gun used for spraying is 0.1~0.5 mm, and the spraying time is 1~5 s.

[0011] In the above preparation method: in step (3), the concentration of Na2HPO4 in the mixed electrodeposition solution is 0.10~0.30 mol / L, the concentration of pyrrole is 0.1~0.2 mol / L, and the concentration of NaClO4 is 0.001~0.003 mol / L.

[0012] In the above preparation method: in step (3), in the three-electrode system, the spandex anchored with MXene is used as the working electrode, the counter electrode is a Pt sheet, and the reference electrode is an Ag / AgCl electrode; the electrodeposition voltage is 0.8~1.2 V and the electrodeposition time is 30~50 s.

[0013] A sensor for detecting occupational ammonia exposure, which is prepared by the above method.

[0014] In the technical solution of the present invention, the application of the sensor prepared by the method in detecting the ammonia content in the workplace.

[0015] In the technical solution of the present invention: The detection is carried out in a closed space. Except for the real sample test experiment, the temperature and humidity conditions are the same. The bubbling method is used to simulate the volatile gas environment of real samples with different concentrations.

[0016] The present invention uses concentrated hydrochloric acid and LiF to react to generate hydrofluoric acid. The reasons for doing this are as follows: 1. The hydrofluoric acid HF solution itself is highly toxic and has extremely strong corrosiveness. Direct use is harmful to both humans and the environment.

[0017] 2. Using concentrated hydrochloric acid and lithium fluoride to synthesize the HF solution, the MXene material etched and synthesized by this method is monolayer. Using the HF solution, the etching effect is not as good as this method.

[0018] 3. Reacting concentrated hydrochloric acid with lithium fluoride can control the concentration of HF.

[0019] The present invention uses a spraying method to load the MXene gas-sensitive material on spandex. Further, an electrodeposition process is used to in-situ polymerize on MXene to prepare an MXene-PPy composite material, thereby constructing a flexible ammonia sensor. High-sensitivity, low-detection limit, and high-selectivity detection of ammonia are achieved. The invention provides a preparation method for a sensor for detecting occupational ammonia exposure, which method is simple and controllable and has strong practicability. Description of the Drawings

[0020] Figure 1 Long-term stability image of the MXene-PPy-based ammonia sensor.

[0021] Figure 2 Gas selectivity image of the MXene-PPy-based ammonia sensor.

[0022] Figure 3 Test image of the silicon wafer cleaning agent of the MXene-PPy-based ammonia sensor. Detailed Embodiments

[0023] The following further illustrates the present invention in conjunction with embodiments, but the protection scope of the present invention is not limited thereto: In the embodiment of the present invention, the model of the silver paste is Ausbond 3813. Example 1

[0024] The specific preparation method of the synthesis method of MXene is as follows: Add 1.6 g of LiF to 20 mL of concentrated hydrochloric acid, and dissolve it thoroughly under stirring. Then, add 1 g of Ti3AlC2 to the solution in small portions multiple times. Subsequently, react at 40 °C for 36 h. After that, add deionized water to the solution and centrifuge to wash away impurities such as unreacted Ti3AlC2 and multi-layered MXene in the solution until the pH of the solution reaches 6. After collecting the solution, ultrasonically treat the solution in an ice-water bath under nitrogen protection (ultrasonically treat the solution 4 times in an ice-water bath under N2 protection, with each ultrasonic treatment lasting for 20 min and the interval between two consecutive ultrasonic treatments being 20 min). Finally, centrifuge the solution for 1 h (at a rotation speed of 3800 r / min), collect the upper liquid, and freeze-dry it to obtain a powdered MXene material (using a freeze dryer (model SCIENTZ-10N / A of Ningbo Xinzhi Freeze-drying Equipment Co., Ltd.). The cold trap temperature is -60 °C, the vacuum degree is 1.0 Pa, and the time is 72 hours); Second step, ammoniated treatment of spandex, and the specific preparation method is as follows: Place the textile in an aqueous solution of 1 mol / L NaOH, heat it in a water bath for 1 h (80 °C), then wash the textile with deionized water until it is neutral, and then place it in a constant-temperature forced-air drying oven for drying for later use; Third step, spray MXene on spandex, and the specific preparation method is as follows: Set the relative distance between the spandex substrate and the spray gun to 15 cm, the caliber of the spray gun used for spraying to 0.3 mm, and control the spraying time to 3 s. The concentration of the MXene aqueous solution (dissolve the powdered MXene material in water and mix evenly) is 10 mg / mL. After spraying, dry it at 60 °C for 1 h to obtain spandex anchored with MXene; Fourth step, prepare the electrodeposition solution, and the specific preparation method is as follows: Prepare a mixed electrodeposition solution with a concentration of 0.20 mol / L of Na2HPO4, 0.15 mol / L of pyrrole monomer, and 0.0015 mol / L of NaClO4 in the mixed electrodeposition solution.

[0025] Fifth step, prepare the MXene-PPy composite gas-sensitive material by electrodeposition, and the specific preparation method is as follows: Use spandex anchored with MXene as the working electrode (15 mm × 10 mm), select a Pt sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Take 20 mL of the electrodeposition solution in a three-electrode system, set the electrodeposition potential to 0.9 V, and control the electrodeposition time to 40 s, and thus construct an ammonia gas sensor.

[0026] Step 6: Prepare a complete flexible sensor. The specific preparation method is as follows: Dry and cut the spandex loaded with the gas-sensitive material into electrodes with a size of 15 mm × 10 mm, and fix the electrodes using silver paste and copper tape to obtain a fabric-based ammonia sensor.

[0027] Step 7: Detect the performance of the sensor. Figure 1 It is the long-term stability image of the MXene-PPy-based ammonia sensor. The sensor was placed in ammonia gas at concentrations of 10, 20, 30, 40, and 50 ppm for a stability test lasting up to 14 days. Its response values were measured on the 5th day and the 14th day respectively. The results show that the sensor can still maintain approximately 90% of its original response value at each concentration after 5 days, and approximately 80% of its original response value at each concentration after 14 days, indicating excellent long-term stability. Figure 2 It is the gas selectivity image of the MXene-PPy-based ammonia sensor. The response values of the sensor to acetone, methanol, dichloromethane, ethanol, and hydrochloric acid are 15.77%, 3.40%, 16.70%, 2.67%, and 3.80% of the response value to ammonia gas at the same concentration respectively, showing excellent anti-interference ability. Figure 3 It is the test image of the MXene-PPy-based ammonia sensor for silicon wafer cleaning agent. The sensor achieved a response value of over 544.98% in five consecutive cycles of testing, showing significant real sample detection ability.

Claims

1. A method for preparing a sensor for detecting occupational exposure to ammonia, characterized in that: The sensor was prepared by the following method: (1) Mix the HF solution and Ti3AlC2 and then fully react and etch. After the reaction is completed, wash, ultrasonicate and centrifuge in sequence. Collect the upper liquid and freeze-dry it in vacuum to obtain a powdered MXene material. (2) The spandex substrate is placed in an alkaline solution for alkalization treatment, washed and dried, and then an aqueous solution of MXene material prepared from MXene material is sprayed on the substrate and dried at 55-65°C for 0.5-1.5h to obtain spandex anchored with MXene; (3) Preparing a mixed electrodeposition solution containing pyrrole, Na2HPO4 and NaClO4, and using a three-electrode system electrolytic cell for electrodeposition, in situ polymerization is performed on the spandex anchored with MXene to form a MXene-PPy composite material; (4) Dry the MXene-PPy-loaded substrate and cut it into electrodes. Use silver paste and copper tape to fix the electrodes to construct a complete flexible sensor.

2. The method for preparing the sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: In step (1), the HF solution is generated by reacting concentrated hydrochloric acid and LiF; the mass ratio of Ti3AlC2, concentrated hydrochloric acid and LiF is 0.5~1.5:15~25:1~3.

3. The method for preparing a sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: The etching temperature in step (1) is 35-45°C and the etching time is 24-48 hours.

4. The method for preparing a sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: The ultrasonic condition in step (1) is to perform ultrasonic treatment on the solution 2 to 5 times in an ice water bath under N2 protection, each ultrasonic treatment lasts for 15 to 25 minutes, and the interval between two consecutive ultrasonic treatments is 15 to 25 minutes; The centrifugal speed is 3500~4000r / min, and the time is 10~60min; The temperature of vacuum freeze drying is -70~-50℃, the time is 3~5 days, and the vacuum degree is 0.5~1.5 Pa.

5. The method for preparing the sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: In step (2), the alkaline solution is a NaOH solution with a concentration of 0.5-1.5 mol / L, the alkalization treatment time is 0.5-1.5 h, and the alkalization treatment temperature is 70-85°C.

6. The method for preparing the sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: In step (2), the concentration of the MXene material aqueous solution is 5-15 mg / mL, the caliber of the spray gun used for spraying is 0.1-0.5 mm, and the spraying time is 1-5 s.

7. The method for preparing the sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: In step (3), the concentration of Na2HPO4 in the mixed electrodeposition solution is 0.10-0.30 mol / L, the concentration of pyrrole is 0.1-0.2 mol / L, and the concentration of NaClO4 is 0.001-0.003 mol / L.

8. The method for preparing a sensor for occupational exposure detection of ammonia according to claim 1, characterized in that: In step (3), in the three-electrode system, the spandex anchored with MXene is used as the working electrode, the counter electrode is a Pt sheet, and the reference electrode is an Ag / AgCl electrode; the electrodeposition voltage is 0.8-1.2 V, and the electrodeposition time is 30-50 s.

9. A sensor for detecting occupational exposure to ammonia, characterized in that: The sensor is prepared by the method described in any one of claims 1 to 8.

10. Use of the sensor prepared by the method of claim 1 in detecting ammonia content in workplaces.

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