Ethanol flexible gas sensor as well as preparation method and application thereof

Abstract

The invention relates to the technical field of analysis and detection, in particular to an ethanol flexible gas sensor as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing an aniline solution with an MXene suspension, and then dropwise adding an ammonium persulfate solution for polymerization reaction to prepare an MXene / PANI composite material; and dissolving Fe2O3 and the MXene / PANI composite material in an alcohol solvent, and coating the surface of the flexible interdigital electrode with the obtained solution to prepare the ethanol flexible gas sensor. The ethanol flexible gas sensor disclosed by the invention can adapt to irregular surfaces of plant tissues, and does not cause essential damage to a detection part, so that in-situ and in-vivo detection of ethanol released by a plant body is realized. Through combination with an intelligent agriculture application scene, the ethanol flexible gas sensor also supports unmanned and intelligent in-situ dynamic monitoring, and an efficient and convenient ethanol detection solution is provided for modern agriculture.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of analytical detection, in particular to an ethanol flexible gas sensor and a preparation method and application thereof. BACKGROUND

[0002] Fruit freshness detection is a key link of postharvest quality control and food safety supervision of agricultural products. During postharvest storage, transportation and sales, the respiratory metabolism of fruits (such as mangoes) will produce volatile organic compounds (VOCs) represented by ethanol, and the concentration of which is significantly positively correlated with the maturity of fruits, mechanical damage and the degree of microbial corruption, which can be used as an important biomarker to evaluate the freshness of fruits. Therefore, the detection of ethanol gas is crucial for monitoring the quality of fruits.

[0003] Traditional ethanol detection methods such as sensory evaluation and gas chromatography-mass spectrometry have the problems of strong subjectivity, sample destruction and expensive equipment, which are difficult to meet the in-situ and non-destructive detection needs in modern supply chain. In contrast, electrochemical gas sensors are attracting attention due to their fast response, simple operation and low cost.

[0004] However, most of the gas sensors currently used have the characteristics of large size, poor flexibility and not wear-resistant, making it difficult to detect the ethanol concentration released by individual fruits. The introduction of a flexible substrate in a typical gas sensor can make the sensor have good flexibility and adapt to the curved surface of fruits, allowing in-situ detection of target gases at room temperature. Therefore, how to develop an ethanol flexible gas sensor has become a technical problem that needs to be solved in the field. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a preparation method of an ethanol flexible gas sensor, comprising: mixing an aniline solution and a MXene suspension to prepare a composite material mixture; adding an ammonium persulfate solution dropwise to the composite material mixture for polymerization reaction to prepare a MXene / PANI composite material; dissolving Fe2O3 and the MXene / PANI composite material in an alcohol solvent to prepare a mixed solution; coating the mixed solution on the surface of a flexible interdigital electrode to prepare the ethanol flexible gas sensor.

[0006] The present application prepares a new type of nanocomposite material by compounding p-type MXene-polyaniline (PANI) and n-type Fe2O3 nanoparticles. The heterojunction formed between the p-type and n-type semiconductors can significantly enhance the response to ethanol gas. MXene provides high conductivity for the composite material, and its rich functional groups on the surface provide adsorption sites for ethanol gas molecules. The above material is drop-coated on the electrode to obtain an electrochemical flexible sensor that can detect ethanol gas in-situ.

[0007] In some embodiments, the aniline solution is a hydrochloric acid solution of aniline; preferably, the concentration of aniline in the aniline solution is 0.05-0.2 g / ml (more preferably 0.1 g / ml).

[0008] In some embodiments, the concentration of the MXene suspension is 1-5 mg / ml (preferably 1 mg / ml).

[0009] In some embodiments, the volume ratio of the aniline solution to the MXene suspension is (2-10):1 (preferably 4:1).

[0010] In some embodiments, the concentration of the ammonium persulfate solution is 0.5-3 mM (preferably 1.3 mM).

[0011] In some embodiments, the polymerization reaction is carried out in an ice bath.

[0012] Preferably, the time of the polymerization reaction is 4-8 h (preferably 6 h).

[0013] Preferably, the MXene / PANI composite material is prepared after the polymerization reaction, followed by washing with pure water and drying.

[0014] In some embodiments, the mass ratio of Fe2O3 to the MXene / PANI composite material is (1-12):1 (preferably 6:1).

[0015] In some embodiments, the alcohol solvent is 2-propanol.

[0016] In some embodiments, in the mixed solution, the concentration of Fe2O3 is 1-5 mg / ml; and the concentration of the MXene / PANI composite material is 0.1-1 mg / ml.

[0017] In some embodiments, the preparation method of the flexible interdigital electrode comprises: adhering a gold foil to a polyethylene terephthalate plate as a flexible substrate, then constructing an interdigital electrode on the gold foil by laser direct writing, and covering the conductive parts on both sides of the interdigital electrode with a polyimide solution to encapsulate the electrode.

[0018] In some embodiments, the flexible interdigital electrode is activated in a sulfuric acid solution using the constant potential method (preferably 1.7 V) before use.

[0019] Preferably, the time of the activation is 100-300 s (preferably 180 s) to remove impurities on the surface of the electrode.

[0020] Further, the present application provides an ethanol flexible gas sensor prepared by the preparation method.

[0021] Further, the application provides the application of the ethanol flexible gas sensor in detecting ethanol; preferably in situ and in vivo detecting ethanol released by plants.

[0022] In the specific implementation process, the plants are any plants releasing ethanol, including but not limited to fruits, vegetables, flowers, crops and the like.

[0023] Further, the application provides a method for in situ and in vivo detecting ethanol released by plants, comprising: attaching the ethanol flexible gas sensor to the surface of a plant in a closed gas chamber, and then connecting an electrochemical workstation to detect ethanol.

[0024] In the specific implementation process, the parts of the plant include but are not limited to stems, leaves, fruits and the like of the plant.

[0025] In the specific implementation process, the concentration of ethanol can be obtained by establishing a standard curve.

[0026] In the specific implementation process, the electrochemical workstation is connected to detect ethanol by using i-t scanning (potential 1V, sampling interval 0.1 s).

[0027] In the specific implementation process, the fruits are packaged with packaging materials such as preservative films during storage or sale, and the space of the packaged fruits is limited, while the flexible sensor of the application can be attached to the surface of the fruits or more easily integrated into the packaging materials, without occupying space, and the flexible substrate can withstand mechanical stress, so that the sensor can be prevented from being damaged due to vibration during transportation, and the service life is prolonged.

[0028] Compared with the prior art, the application has the following beneficial effects: The application provides an ethanol flexible gas sensor and a preparation method thereof, and the ethanol flexible gas sensor of the application can adapt to the irregular surface of plant tissues, does not cause essential damage to the detection site, and thus realizes in situ and in vivo detecting ethanol released by plants.

[0029] In addition, the preparation method of the ethanol flexible gas sensor of the application is simple and has low manufacturing cost, and the MXene / PANI@Fe2O3 composite material prepared by the method realizes high selectivity and high stability in detecting ethanol. By being combined with the intelligent agricultural application scene, the ethanol flexible gas sensor of the application also supports in situ dynamic monitoring without people and intelligently, and provides an efficient and convenient ethanol detection solution for modern agriculture. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a process flow chart of embodiment 1 of the application.

[0031] Figure 2 is a standard curve of the sensor of embodiment 1 and comparative examples.

[0032] Figure 3 are the interference verification experimental results of the sensor of Example 1. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. In the embodiments provided in the present specification, the specific techniques or conditions not mentioned are carried out according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not mentioned by the manufacturer are conventional products that can be purchased through a regular channel. In the following examples, MXene is Ti3C2, which is purchased from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd. with the item number 104661.

[0034] Example 1 The present embodiment provides an ethanol flexible gas sensor, and a process flow chart is as shown in Figure 1 The preparation method is as follows: (1) The gold foil is adhered to the polyethylene terephthalate (PET), and then heated for 2 minutes until the hot melt adhesive on the PET substrate is completely melted.

[0035] (2) Then the interdigital electrode pattern is constructed on the gold foil by laser direct writing, and the printing power is 53% and the printing speed is 2.7 cm / s.

[0036] (3) The conductive part on both sides of the interdigital electrode is covered with a polyimide (PI) solution (50%), and is cured at 60°C for 30 minutes.

[0037] (4) The electrode is placed in a sulfuric acid solution (0.5 mM), and is activated by constant potential method (1.7 V) for 180 s to remove impurities on the surface of the electrode.

[0038] (5) Aniline solution of 0.1 g / ml is prepared using 1M HCl solution, 10 ml of which is added to 2.5 ml of MXene suspension of 1 mg / ml, and 15 ml of 1.3 mM ammonium persulfate solution is added dropwise to the above solution. After polymerization in an ice bath for 6 hours, the powder is filtered, washed with pure water and dried to obtain MXene / PANI composite material.

[0039] (6) 3 mg of Fe2O3 and 0.5 mg of MXene / PANI composite material (mass ratio of 6:1) are dissolved in 1 mL of 2-propanol, and ultrasonic treatment is performed for 30 minutes to uniformly mix them.

[0040] (7) Using a pipette to pipette 10 μL of the mixed solution to the flexible interdigital electrode sensor test area, dry at room temperature, and prepare an ethanol flexible gas sensor.

[0041] Example 2 The detection performance of the ethanol flexible gas sensor prepared in Example 1 was tested, and the steps were as follows: (1) 100 ppm ethanol standard gas was used as the gas source, and high-purity nitrogen was used as the carrier gas. A double-channel mass flow controller was used to control the ethanol gas concentration flowing into the gas chamber by adjusting the flow rates of ethanol gas and high-purity nitrogen. The sensor was placed in a 20 ml sealed gas chamber, and the i-t method was used to test the sensor response in 1 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, and 100 ppm ethanol gas at 1 V potential, and a standard curve was drawn. The definition of sensor response is the change in resistance (ΔR) of the sensor exposed to the target gas divided by the initial resistance (R0) of the sensor in air, and then taking its absolute value. The linear equation of the sensor is shown in Figure 2 . The linear equation is y = 0.21x + 1.93, the detection range is 1-100 ppm, the detection limit is 0.4 ppm (S / N = 3), and the correlation coefficient is 0.98.

[0042] (2) In-situ detection of ethanol released by fruits The ethanol flexible sensor was connected to the IVIUM portable electrochemical workstation (pocketSTAT), mango was selected as the experimental material, i-t scanning was performed (potential 1 V, sampling interval 0.1 s), after 100 s test in clean air, the sensor was attached to the surface of the fruit and placed in a 150 ml sample chamber for 5 minutes, after stabilization, 100 s test was performed, and the response signal was obtained. The concentration of ethanol released by the measured fruit was calculated by introducing the standard curve.

[0043] At the same time, the same fruit sample was tested by gas chromatography-mass spectrometry (GC-MS) as a control. The mango was placed in a 150 ml sample chamber of a gas sensing system for 5 minutes to generate enough headspace gas, and then the headspace gas in the sample chamber was purged into a gas sampling bag with high-purity nitrogen. The aged solid-phase microextraction head was inserted into the gas sampling bag, adsorbed for 30 minutes, and then desorbed at the inlet of GC-MS for 10 minutes. The conditions of gas chromatography-mass spectrometry are as follows: (1) Chromatographic column: polyethylene glycol stationary phase (30 m x 0.32 mm x 0.25 μm) chromatographic column; column temperature: 42°C for 3 min, then increased to 120°C at a rate of 25°C / min and maintained for 4 min; (2) Carrier gas: Helium; (3) Flow rate: 1.25 mL / min; (4) Injection volume: 0.4 mL; (5) Split ratio: 10:1; (6) Injection port temperature: 160°C; (7) EI source voltage: 70 eV; (8) Solvent delay: 1.50 min; (9) Ion source temperature: 230°C; (10) Quadrupole temperature: 150°C; (11) Interface temperature: 180°C; (12) Acquisition mode: Full scan (SCAN).

[0044] The same fruit sample was detected for 6 times, and the results are shown in Table 1. The results show that the RSD of the detection results of Example 1 is 5.53%, the results are good in consistency and close to the concentration detected by gas chromatography-mass spectrometry, indicating that the detection results of the sensor of Example 1 are accurate and reliable.

[0045] Table 1 Test results of ethanol in fruit samples

[0046] (3) Interference verification experiment: 100 ppm of ethanol, methanol, isopropyl alcohol, acetone, ammonia were used to verify the interference of the sensor of Example 1.

[0047] The results are shown in Table 2. The sensor of Example 1 only showed a high response to ethanol. Figure 3

[0048] Comparative Example 1 The present comparative example provides a flexible gas sensor for detecting ethanol, and the preparation method is only different from Example 1 in that PANI is replaced by an equal amount of poly-3-hexylthiophene (P3HT).

[0049] The detection performance of the sensor was tested by the method in Example 2, and the results are shown in Table 2. The detection range of the sensor is 30-80 ppm, and the detection effect is not as good as that of Example 1. Figure 2

[0050] Comparative Example 2 The present comparative example provides a flexible gas sensor for detecting ethanol, and the preparation method is different from Example 1 in that Fe2O3 is replaced by an equal amount of ZnO.

[0051] The detection performance of the sensor was tested by the method in Example 2, and the results are shown in Table 2. The detection range of the sensor is 30-80 ppm, and the detection effect is not as good as that of Example 1. Figure 2 ​​As shown, the detection range of the sensor is 20-60 ppm, and the detection effect is not as good as that of Example 1.

[0052] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a flexible ethanol gas sensor, characterized in that, include: Aniline solution and MXene suspension were mixed to prepare a composite material mixture; ammonium persulfate solution was added dropwise to the composite material mixture to carry out a polymerization reaction, thereby obtaining an MXene / PANI composite material; Fe2O3 and the MXene / PANI composite material were dissolved in an alcohol solvent to prepare a mixed solution; The mixed solution was coated onto the surface of a flexible interdigitated electrode to obtain the ethanol flexible gas sensor.

2. The preparation method according to claim 1, characterized in that, The aniline solution is a hydrochloric acid solution of aniline; preferably, the concentration of aniline in the aniline solution is 0.05~0.2g / ml.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of the MXene suspension is 1~5 mg / ml; And / or, the volume ratio of aniline solution to MXene suspension is (2~10):1; And / or, the concentration of the ammonium persulfate solution is 0.5~3mM.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The polymerization reaction was carried out in an ice bath.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The mass ratio of Fe2O3 to the MXene / PANI composite material is (1~12):1; And / or, the alcohol solvent is 2-propanol; Preferably, the concentration of Fe2O3 in the mixed solution is 1~5 mg / ml; and the concentration of the MXene / PANI composite material is 0.1~1 mg / ml.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The method for preparing the flexible interdigitated electrode includes: attaching gold foil to a polyethylene terephthalate plate as a flexible substrate, then constructing the interdigitated electrode by laser direct writing on the gold foil, and encapsulating the electrode by covering the conductive parts on both sides of the interdigitated electrode with a polyimide solution.

7. The preparation method according to claim 6, characterized in that, The flexible interdigitated electrode is activated in sulfuric acid solution using a constant potential method before use.

8. An ethanol flexible gas sensor prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the flexible ethanol gas sensor according to claim 8 in the detection of ethanol; preferably in the in-situ in vivo detection of ethanol released by plants.

10. A method for in situ in vivo detection of ethanol released from plants, characterized in that, include: In a sealed gas chamber, the flexible ethanol gas sensor of claim 8 is attached to the surface of a plant and then connected to an electrochemical workstation to detect ethanol.

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