An ethanol flexible gas sensor and a preparation method and application thereof

Abstract

The present application relates to the technical field of analytical detection, and particularly relates to an ethanol flexible gas sensor and a preparation method and application thereof.The preparation method is that aniline solution is mixed with MXene suspension, then ammonium persulfate solution is added dropwise to carry out polymerization reaction, and a MXene / PANI composite material is prepared; Fe2O3 is dissolved in an alcohol solvent together with the MXene / PANI composite material, and then is coated on the surface of a flexible interdigital electrode to prepare the ethanol flexible gas sensor.The ethanol flexible gas sensor can adapt to the irregular surface of plant tissues, does not cause essential damage to the detection part, and thus realizes in-situ and in-vivo detection of ethanol released by plants.Combined with the intelligent agricultural application scene, the ethanol flexible gas sensor also supports unmanned and intelligent in-situ dynamic monitoring, and provides an efficient and convenient ethanol detection solution for modern agriculture.

Description

Technical Field

[0001] This invention relates to the field of analytical detection technology, and in particular to an ethanol flexible gas sensor, its preparation method, and its application. Background Technology

[0002] Fruit freshness testing is a crucial step in post-harvest quality control and food safety supervision of agricultural products. During post-harvest storage, transportation, and sales, the respiration and metabolism of fruits (such as mangoes) produce volatile organic compounds (VOCs), with ethanol being a prime example. The concentration of VOCs is significantly positively correlated with fruit maturity, mechanical damage, and the degree of microbial spoilage, serving as an important biomarker for assessing fruit freshness. Therefore, the detection of ethanol gas is essential for monitoring fruit quality.

[0003] Traditional methods for ethanol detection, such as sensory evaluation and gas chromatography-mass spectrometry, suffer from high subjectivity, sample destruction, and expensive equipment, making them unsuitable for the in-situ, non-destructive detection requirements of modern supply chains. In contrast, electrochemical gas sensors have attracted significant attention due to their advantages of rapid response, ease of operation, and low cost.

[0004] However, the large size, poor flexibility, and lack of wear resistance of most currently used gas sensors make it difficult to detect the concentration of ethanol released from individual fruits. Introducing a flexible substrate into a typical gas sensor can give the sensor good flexibility, allowing it to adapt to the curved surface of the fruit and enabling in-situ detection of target gases at room temperature. Therefore, developing a flexible ethanol gas sensor has become a pressing technical challenge in this field. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention provides a method for preparing a flexible ethanol gas sensor, comprising: mixing an aniline solution with an MXene suspension to form a composite material mixture; and adding an ammonium persulfate solution dropwise to the composite material mixture to carry out a polymerization reaction, thereby obtaining an MXene / PANI composite material.

[0006] Fe2O3 and the MXene / PANI composite material were dissolved in an alcohol solvent to prepare a mixed solution;

[0007] The mixed solution was coated onto the surface of a flexible interdigitated electrode to obtain the ethanol flexible gas sensor.

[0008] This invention prepares a novel nanocomposite material by combining p-type MXene-polyaniline (PANI) with 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 to the composite material, and its abundant functional groups on the surface provide adsorption sites for ethanol gas molecules. The above material is drop-coated onto an electrode to obtain an electrochemical flexible sensor that can detect ethanol gas in situ.

[0009] In some embodiments, the aniline solution is a hydrochloric acid solution of aniline; preferably, the concentration of aniline in the aniline solution is 0.05~0.2g / ml (more preferably 0.1g / ml).

[0010] In some embodiments, the concentration of the MXene suspension is 1 to 5 mg / ml (preferably 1 mg / ml).

[0011] In some embodiments, the volume ratio of aniline solution to MXene suspension is (2~10):1 (preferably 4:1).

[0012] In some embodiments, the concentration of the ammonium persulfate solution is 0.5 to 3 mM (preferably 1.3 mM).

[0013] In some embodiments, the polymerization reaction is carried out in an ice bath.

[0014] Preferably, the polymerization reaction takes 4 to 8 hours (preferably 6 hours).

[0015] Preferably, the MXene / PANI composite material is obtained by washing and drying with pure water after the polymerization reaction.

[0016] In some embodiments, the mass ratio of Fe2O3 to the MXene / PANI composite material is (1~12):1 (preferably 6:1).

[0017] In some embodiments, the alcohol solvent is 2-propanol.

[0018] In some embodiments, the concentration of Fe2O3 in the mixed solution is 1~5 mg / ml; the concentration of the MXene / PANI composite material is 0.1~1 mg / ml.

[0019] In some embodiments, 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 portions on both sides of the interdigitated electrode with a polyimide solution.

[0020] In some embodiments, the flexible interdigitated electrode is activated in a sulfuric acid solution using a potentiostatic method (preferably 1.7V) before use.

[0021] Preferably, the activation time is 100~300s (preferably 180s) to remove impurities from the electrode surface.

[0022] Furthermore, the present invention provides an ethanol flexible gas sensor prepared by the aforementioned preparation method.

[0023] Furthermore, the present invention provides the application of the aforementioned flexible ethanol gas sensor in the detection of ethanol; preferably, its application in in-situ in vivo detection of ethanol released by plants.

[0024] In the specific implementation process, the plant can be any plant that releases ethanol, including but not limited to fruits, vegetables, flowers, and crops.

[0025] Furthermore, the present invention provides a method for in-situ in vivo detection of ethanol released from plants, comprising: attaching the ethanol flexible gas sensor to the surface of the plant in a sealed gas chamber, and then connecting it to an electrochemical workstation to detect ethanol.

[0026] In practice, the parts of a plant include, but are not limited to, the stem, leaves, and fruit.

[0027] In practice, the concentration of ethanol can be obtained by establishing a standard curve.

[0028] In the specific implementation process, after connecting to the electrochemical workstation, ethanol was detected by it scan (potential 1V, sampling interval 0.1s).

[0029] In practice, fruits are packaged with plastic wrap or other packaging materials during storage or sale. The space of the packaged fruit is limited. The flexible sensor of this invention can fit the surface of the fruit or be more easily integrated into the packaging material without taking up space. Furthermore, the flexible substrate can withstand mechanical stress, which can prevent the sensor from being damaged by vibration during transportation and extend its service life.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention provides a flexible ethanol gas sensor and its preparation method. The flexible ethanol gas sensor of this invention can adapt to the irregular surface of plant tissues and will not cause essential damage to the detection site, thereby realizing in-situ and in vivo detection of ethanol released by plants.

[0032] Furthermore, the fabrication method of the flexible ethanol gas sensor of this invention is simple and low-cost. Through the fabricated MXene / PANI@Fe2O3 composite material, high selectivity and high stability in ethanol detection are achieved. By combining with smart agriculture applications, the flexible ethanol gas sensor of this invention also supports unmanned, intelligent in-situ dynamic monitoring, providing a highly efficient and convenient ethanol detection solution for modern agriculture. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention.

[0034] Figure 2 This is the standard curve of Example 1 and the comparative sensor.

[0035] Figure 3 This is the result of the interference verification experiment of the sensor in Example 1. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. In the embodiments provided in this specification, unless specific techniques or conditions are specified, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. MXene in the following embodiments is Ti3C2, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., item number 104661.

[0037] Example 1

[0038] This embodiment provides a flexible ethanol gas sensor, and the process flow diagram is as follows: Figure 1 As shown, the preparation method is as follows:

[0039] (1) Adhere the gold foil to polyethylene terephthalate (PET) and heat for 2 minutes until the hot melt adhesive on the PET substrate is completely melted.

[0040] (2) Then, the interdigitated electrode pattern was constructed on the gold foil by laser direct writing with a printing power of 53% and a printing speed of 2.7 cm / s.

[0041] (3) Cover the conductive parts on both sides of the interdigital electrode with a polyimide (PI) solution (50%) and cure at 60°C for 30 minutes.

[0042] (4) Place the electrode in a sulfuric acid solution (0.5 mM) and activate it for 180 s using a constant potential method (1.7 V) to remove impurities from the electrode surface.

[0043] (5) Prepare a 0.1 g / ml aniline solution using 1M HCl solution, take 10 ml and add 2.5 ml of 1 mg / ml MXene suspension, add 15 ml of 1.3 mM ammonium persulfate solution dropwise to the above solution, polymerize in an ice bath for 6 hours and filter to obtain powder, wash with pure water and dry to obtain MXene / PANI composite material.

[0044] (6) Take 3 mg of Fe2O3 and 0.5 mg of MXene / PANI composite material (mass ratio of 6:1) and dissolve them in 1 mL of 2-propanol, and sonicate for 30 minutes to make them uniformly mixed.

[0045] (7) Use a pipette to transfer 10 μL of the mixed solution onto the test area of ​​the flexible interdigital electrode sensor and dry it at room temperature to obtain the ethanol flexible gas sensor.

[0046] Example 2

[0047] This embodiment tests the detection performance of the flexible ethanol gas sensor prepared in Example 1, and the steps are as follows:

[0048] (1) Using 100ppm ethanol standard gas as the gas source and high-purity nitrogen as the carrier gas, a dual-channel mass flow controller was used to control the concentration of ethanol gas flowing into the gas chamber by adjusting the flow rates of ethanol gas and high-purity nitrogen gas. The sensor was placed in a 20ml sealed gas chamber, and the response of the sensor in 1ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm and 100ppm ethanol gas was tested at a potential of 1V using the it method, and a standard curve was plotted. The sensor response was defined as the change in resistance of the sensor exposed to the target gas (ΔR) divided by the initial resistance of the sensor in air (R0), and then the absolute value was taken. The linear equation of the sensor is as follows: Figure 2 As shown in the figure. 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.

[0049] (2) In-situ detection of ethanol release from fruit

[0050] The flexible ethanol sensor was connected to the IVIUM portable electrochemical workstation (pocketSTAT). Mango was selected as the experimental material, and an it scan was performed (potential 1V, sampling interval 0.1 s). After testing in clean air for 100 s, the sensor was attached to the surface of the fruit and placed in a 150 mL sample chamber for 5 minutes. After stabilization, a 100 s test was performed. The obtained response signal was used to calculate the concentration of ethanol released by the tested fruit by substituting it into a standard curve.

[0051] Meanwhile, gas chromatography-mass spectrometry (GC-MS) was used to test the same fruit sample as a control. The mango was placed in the 150 mL sample chamber of the gas sensing system for 5 minutes to generate sufficient headspace gas. Then, the headspace gas in the sample chamber was purged into the gas sampling bag with high-purity nitrogen. An aged solid-phase microextraction head was inserted into the gas sampling bag for adsorption for 30 minutes, followed by desorption at the GC-MS inlet for 10 minutes. The GC-MS conditions were as follows:

[0052] (1) Chromatographic column: polyethylene glycol stationary phase (30m×0.32mm×0.25μm) chromatographic column; column temperature: 42℃ for 3min, then increase to 120℃ at 25℃ / min and hold for 4min;

[0053] (2) Carrier gas: Helium;

[0054] (3) Flow rate: 1.25 mL / min;

[0055] (4) Injection volume: 0.4 mL;

[0056] (5) Diversion ratio: 10:1;

[0057] (6) Inlet temperature: 160℃;

[0058] (7) EI source voltage: 70eV;

[0059] (8) Solvent delay: 1.50 min;

[0060] (9) Ion source temperature: 230℃;

[0061] (10) Quadrupole temperature: 150℃;

[0062] (11) Interface temperature: 180℃;

[0063] (12) Acquisition method: full scan (SCAN).

[0064] The same fruit sample was tested 6 times, and the results are shown in Table 1. The results show that the RSD of the test result of Example 1 is 5.53%, the consistency of the results is good and close to the concentration detected by gas chromatography-mass spectrometry, indicating that the detection results of the sensor in Example 1 are accurate and reliable.

[0065] Table 1. Test results of ethanol in fruit samples

[0066]

[0067] (3) Interference verification experiment:

[0068] The sensor in Example 1 was subjected to interference verification using 100 ppm of ethanol, methanol, isopropanol, acetone, and ammonia.

[0069] The results are as follows Figure 3 As shown, the sensor in Example 1 only exhibits a high response to ethanol.

[0070] Comparative Example 1

[0071] This comparative example provides a flexible gas sensor for detecting ethanol, the preparation method of which differs from that of Example 1 only in that PANI is replaced with an equal amount of poly(3-hexylthiophene) (P3HT).

[0072] The sensor's detection performance was tested using the method described in Example 2, such as... Figure 2 As shown, the detection range of this sensor is 30~80ppm, and the detection effect is not as good as that of Example 1.

[0073] Comparative Example 2

[0074] This comparative example provides a flexible gas sensor for detecting ethanol. The preparation method differs from that in Example 1 in that Fe2O3 is replaced with an equal amount of ZnO.

[0075] The sensor's detection performance was tested using the method described in Example 2, such as... Figure 2 As shown, the detection range of this sensor is 20~60ppm, and the detection effect is not as good as that of Example 1.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

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 dispersed 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.

3. The preparation method according to claim 2, characterized in that, The concentration of aniline in the aniline solution is 0.05~0.2g / ml.

4. The preparation method according to claim 1, 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.

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

6. 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.

7. The preparation method according to claim 6, characterized in that, In the mixed solution, the concentration of Fe2O3 is 1~5 mg / ml; the concentration of the MXene / PANI composite material is 0.1~1 mg / ml.

8. The preparation method according to any one of claims 1 to 4, 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.

9. The preparation method according to claim 8, characterized in that, The flexible interdigitated electrode is activated in sulfuric acid solution using a constant potential method before use.

10. An ethanol flexible gas sensor prepared by any one of claims 1 to 9.

11. The application of the flexible ethanol gas sensor according to claim 10 in the detection of ethanol.

12. The application according to claim 11, characterized in that, The application is in the in-situ in vivo detection of ethanol released by plants.

13. 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 10 is attached to the surface of a plant and then connected to an electrochemical workstation to detect ethanol.

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