An electrochemical gas sensor for detecting linalool and a method for manufacturing the same

Abstract

The application relates to the technical field of analytical detection, in particular to an electrochemical gas sensor for detecting linalool and a preparation method thereof. The preparation method is to prepare the electrochemical gas sensor after modifying a molecular imprinting film-zeolite imidazolate framework-8-multi-walled carbon nanotube-zinc oxide (MIP-ZIF-8-MWCNT-ZnO) composite material on the surface of an electrode. The electrochemical gas sensor can sensitively and accurately detect the content of linalool gas released by plants, realizes stable and accurate detection of linalool with high specificity and high sensitivity in a complex environment, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of analytical detection technology, and in particular to an electrochemical gas sensor for detecting linalool and its preparation method. Background Technology

[0002] Linalool is a volatile monoterpene compound widely distributed in plants, present in varying concentrations in leaves, flowers, fruits, and epidermal tissues. As a key component of plant secondary metabolites, linalool not only imparts unique aromas to plants (such as lavender and citrus fruits) but also participates in physiological processes such as insect defense, pathogen inhibition, and responses to abiotic stress. Linalool has been reported to possess antibacterial activity against Staphylococcus aureus and Escherichia coli. When plants are infected by pathogens, they release more linalool. For example, the release of linalool gas increases in strawberries infected with Botrytis cinerea.

[0003] Currently, the mainstream methods for linalool detection include gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-mass spectrometry (HPLC-MS). However, these methods require destructive sampling of plant tissues (such as grinding and solvent extraction), making it difficult to achieve in-situ detection in vivo. In addition, the sample pretreatment steps are cumbersome (such as derivatization and solid-phase extraction), which may lead to the loss or oxidative degradation of volatile linalools, affecting the accuracy of quantification.

[0004] In contrast, electrochemical methods offer advantages such as fast response, high sensitivity, good selectivity, and wide detection range, demonstrating excellent application potential in in-situ in vivo plant detection. Therefore, developing an electrochemical sensor capable of in-situ in vivo detection of linalool released from plants has become a pressing technical challenge in this field. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a method for preparing an electrochemical gas sensor for detecting linalool, comprising: dispersing the template molecule linalool in a polyvinyl alcohol solution, adding a crosslinking agent to obtain a molecularly imprinted polymer, and removing the template molecule linalool to obtain MIP powder.

[0006] Multi-walled carbon nanotubes were dispersed in a zeolite imidazolium ester framework material-8 alcohol solution to prepare ZIF-8-MWCNT solution; ZnO was dispersed in ZIF-8-MWCNT solution to prepare ZIF-8-MWCNT-ZnO composite material.

[0007] MIP powder was dispersed in ZIF-8-MWCNT-ZnO composite material to prepare MIP-ZIF-8-MWCNT-ZnO composite material; the MIP-ZIF-8-MWCNT-ZnO composite material was coated on the electrode surface and dried to obtain the electrochemical gas sensor for detecting linalool.

[0008] Among them, MIP-ZIF-8-MWCNT-ZnO is a composite nanomaterial composed of MIP, ZIF-8, MWCNT, and ZnO. Molecularly imprinted (MIP) is a molecularly imprinted powder made by adding a cross-linking agent to polyvinyl alcohol (PVA) as a functional monomer and linalool as a template molecule. When the template molecule is removed, cavities with the same size and structure as the target molecule are formed on the surface of the MIP, which can efficiently recognize and bind linalool. This is the first layer of recognition of the target molecule.

[0009] On the other hand, a key feature of zeolite imidazole framework-8 (ZIF-8) is the structural flexibility resulting from the wiggling of the -CH-3 group and the imidazole salt linker, allowing for a tunable microporous structure (pore size approximately 3.4 Å). Its pore size matches the linalool molecule (molecular size approximately 5.2 Å), enabling a size sieving effect, preferentially adsorbing linalool and excluding large molecular interferences (such as terpenes). Furthermore, the nitrogen-containing group of the imidazole ligand in ZIF-8 can bind to the hydroxyl and double bonds of linalool through hydrogen bonding and π-π stacking, enhancing the sensor's specificity and further improving its selectivity. ZIF-8 achieves a second layer of recognition for target molecules.

[0010] The high conductivity of multi-walled carbon nanotubes (MWCNTs) enables them to rapidly transmit charge transfer signals induced by adsorbed molecules. Zinc oxide (ZnO), as a representative nanomaterial, possesses a wide band gap and excellent structural controllability, and has been widely used in gas sensing. Furthermore, ZnO is an n-type semiconductor, sensitive to gas adsorption; the adsorption of linalool molecules causes changes in surface oxygen species, leading to a significant change in conductivity, thus achieving a highly sensitive response. Through the catalytic effect and dual recognition effect of MWCNTs and ZnO, the sensor exhibits excellent sensitivity and selectivity.

[0011] In summary, this invention uses ZIF-8, MWCNT, and ZnO as modifying materials and combines them with molecular imprinting technology. Through the synergistic effect of heterojunction charge separation, hierarchical pore diffusion, and dual recognition mechanism, the sensitivity and selectivity of the linalool gas sensor are improved.

[0012] In some embodiments, the molar ratio of the template molecule linalool to polyvinyl alcohol is 1:(1~5), preferably 1:2.

[0013] In some embodiments, the concentration of linalool in the mixture of linalool and polyvinyl alcohol solutions is 0.5 to 2 mM, preferably 1 mM.

[0014] In some implementations, the polyvinyl alcohol solution is an aqueous solution of polyvinyl alcohol.

[0015] In some embodiments, the crosslinking agent is glutaraldehyde.

[0016] Preferably, the crosslinking agent is a 50% glutaraldehyde aqueous solution.

[0017] In some embodiments, a molecularly imprinted polymer is prepared by reacting the addition of a crosslinking agent at 80°C to 90°C (preferably 85°C).

[0018] In some implementations, MIP powder is prepared by removing the template molecule linalool using an alcohol solvent.

[0019] In some embodiments, the alcohol solvent is methanol.

[0020] In some embodiments, the zeolite imidazole ester framework material-8 alcohol solution is an ethanol solution of zeolite imidazole ester framework material-8.

[0021] In some embodiments, the concentration of zeolite imidazole ester backbone material-8 in the zeolite imidazole ester backbone material-8 alcohol solution is 1~5 mg / mL (preferably 3 mg / mL), and the concentration of alcohol is 2%~10% (v / v) (preferably 5%).

[0022] In some embodiments, the concentration of multi-walled carbon nanotubes in the mixture of multi-walled carbon nanotubes and zeolite imidazole ester framework material-8 alcohol solution is 0.1~0.5 mg / mL (preferably 0.2 mg / mL).

[0023] In some embodiments, the concentration of ZnO in the mixture of ZnO and ZIF-8-MWCNT solution is 0.1~1 mg / mL (preferably 0.5 mg / mL).

[0024] In some embodiments, the concentration of MIP powder in the mixture of MIP powder and ZIF-8-MWCNT-ZnO composite material is 0.1~2 mg / mL (preferably 1 mg / mL).

[0025] In some implementations, the electrode is an IDE electrode.

[0026] In some embodiments, the electrode is activated by a potentiostatic method in a sulfuric acid solution before use.

[0027] Preferably, the electrode is placed in a 0.1-0.5 M sulfuric acid solution and activated by cyclic voltammetry at -0.2-1.5 V (preferably 5 cycles).

[0028] Furthermore, the present invention provides an electrochemical gas sensor for detecting linalool prepared by the aforementioned method.

[0029] Furthermore, the present invention provides the application of the electrochemical gas sensor for detecting linalool in the detection of linalool; preferably, its application in in situ in vivo detection of linalool released by plants.

[0030] In the specific implementation process, the plant can be any plant that releases linalool, including but not limited to fruits, vegetables, flowers, and crops.

[0031] Furthermore, the present invention provides a method for in situ in vivo detection of linalool released from plants, comprising: placing the electrochemical gas sensor into a gas chamber and attaching it to the surface of the plant, and then connecting it to an electrochemical workstation for detection.

[0032] In practice, the parts of a plant include, but are not limited to, the stem, leaves, and fruit.

[0033] In the specific implementation process, the concentration of linalool can be obtained by establishing a standard curve.

[0034] In the specific implementation process, after connecting to the electrochemical workstation, it scan (potential 1V, sampling interval 0.1s) is used for detection.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] This invention provides an electrochemical sensor capable of in-situ, in vivo detection of linalool released by plants. This sensor can sensitively and accurately detect the content of linalool gas released from plants, achieving stable and accurate detection of linalool with high specificity and sensitivity in complex environments. This technology can enable early detection of plant diseases and prevent their infection and spread, thus mitigating crop losses and showing broad application prospects.

[0037] Furthermore, this technology can effectively reduce detection costs and is simple and convenient to operate. When integrated with smart agriculture applications, this technology can support unmanned, intelligent, real-time dynamic monitoring, thereby providing an efficient and convenient solution for modern agriculture. Attached Figure Description

[0038] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention.

[0039] Figure 2This is the linear curve of Embodiment 1 of the present invention and the comparative sensor.

[0040] Figure 3 This is a graph showing the selective test results of the sensor in Embodiment 1 of the present invention.

[0041] Figure 4 This is a schematic diagram of the in-situ detection of linalool released from plants by the sensor in Embodiment 1 of the present invention. Detailed Implementation

[0042] 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. The IDE electrode in the following embodiments was purchased from Changchun Beirun Electronic Technology Co., Ltd., with specifications of 10*5*0.635mm. The ZIF-8 and MWCNT in the following embodiments were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. The polyvinyl alcohol (PVA) in the following embodiments has a molecular weight of 9000~10000 and was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0043] Example 1

[0044] This embodiment provides an electrochemical gas sensor for detecting linalool, and the preparation process is shown in the schematic diagram below. Figure 1 As shown, the preparation method is as follows:

[0045] (1) Place the IDE electrode in a 0.5 M sulfuric acid solution and activate it by cyclic voltammetry (CV) at -0.2 to 1.5 V for 5 cycles to remove impurities from the electrode surface.

[0046] (2) Preparation of molecularly imprinted polymer solution using ultrapure water: The molar ratio of linalool to PVA is 1:2, and the concentration of linalool is 1 mM. First, the weighed PVA is dispersed in 5 mL of ultrapure water and ultrasonically dispersed at 45 °C for 1 h. Then, linalool is added to the prepared PVA solution and stirred at 45 °C for 1 h. After uniform dispersion, 50 μL of 50% glutaraldehyde solution is added to the solution as a crosslinking agent, and stirred at 85 °C for another 3 h. Finally, the obtained polymer is dried. The polymer and methanol are mixed at a mass-volume ratio of 1 g: 20 mL and stirred in a water bath. The eluent is changed every 2 h for 10 h to remove the template molecules. After removing the template molecules, the polymer is dried again to obtain MIP powder.

[0047] (3) Dissolve ZIF-8 (final concentration of 3 mg / mL) in 10 mL of 5% (v / v) ethanol solution. After ZIF-8 is completely dissolved, ZIF-8 solution is obtained.

[0048] (4) Slowly add MWCNT (final concentration of 0.2 mg / mL) to ZIF-8 solution, sonicate for 30 minutes, and obtain ZIF-8-MWCNT solution after uniform dispersion.

[0049] (5) Slowly add ZnO (final concentration of 0.5 mg / mL) to the ZIF-8-MWCNT solution and continue to ultrasonically disperse until a stable suspension is formed, thereby obtaining the ZIF-8-MWCNT-ZnO composite material.

[0050] (6) Slowly add MIP powder (final concentration of 1 mg / mL) to the ZIF-8-MWCNT-ZnO composite material solution and ultrasonically disperse until a stable suspension is formed, thereby obtaining the MIP-ZIF-8-MWCNT-ZnO composite material.

[0051] (7) Use a pipette to take 30 μL of MIP-ZIF-8-MWCNT-ZnO composite material and drop it onto the IDE electrode, cover the electrode surface and put it into a 40℃ oven to dry for 10 minutes, thus obtaining the electrochemical gas sensor MIP-ZIF-8-MWCNT-ZnO / IDE.

[0052] Example 2

[0053] This embodiment tests the detection performance of the electrochemical gas sensor prepared in Example 1, and the steps are as follows:

[0054] (1) Using 50ppm linalool 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 linalool gas flowing into the gas chamber by adjusting the flow rates of linalool and high-purity nitrogen. The sensor was placed in a 10mL sealed gas chamber, and the response of the sensor in 5ppm, 10ppm, 15ppm, 20ppm, 25ppm, 30ppm, 35ppm, 40ppm, 45ppm and 50ppm linalool gas was tested at 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 the air (R0), and then the absolute value was taken. Figure 2 As shown, the linear equation of the sensor is y = 0.59x + 0.14(R). 2 =0.965), R 2 =0.965, detection range 5-50ppm.

[0055] (2) Interference verification was performed on the electrochemical gas sensor prepared in Example 1 using 50 ppm of limonene, menthol, geraniol, and phenylethanol. The selectivity test results are as follows: Figure 3 As shown, the electrochemical gas sensor prepared in Example 1 only exhibits a high response to linalool.

[0056] (3) In-situ detection of linalool release from plants (citrus): After connecting the electrochemical gas sensor prepared in Example 1 to a portable electrochemical workstation—EmStat4R electrochemical workstation (PalmSens, Netherlands), an it scan was performed (potential 1V, sampling interval 0.1s). After testing in clean air for 100s, the sensor was attached to the surface of the plant tissue and placed in the gas chamber. After stabilization, the plant surface was tested for 100s. The in-situ detection method is as follows: Figure 4 As shown. The concentration of linalool released by the detected citrus fruit was calculated by substituting the obtained response signal into the standard curve, and the detection results were compared with the GC-MS detection results. The specific steps are as follows:

[0057] GC-MS was used as a control to detect the gases produced by the same fruit sample. The specific method is as follows: First, the sampled gas underwent primary thermal desorption, with the temperature gradually increased from 40℃ to 260℃ to release the volatile components. Then, a secondary desorption was performed, with the temperature increased to 300℃. The gas was then concentrated, injected into the chromatographic column, and finally analyzed by the instrument.

[0058] Chromatographic column used: DB-624 capillary column (30m × 0.25mm × 0.25μm) or equivalent weakly polar column. Temperature program: Initial 40℃ (hold for 2 min) → 4℃ / min to 120℃ → 8℃ / min to 240℃ (hold for 5 min). Injector: 250℃ (splitless mode), injection volume 1μL. Detector: FID (flame ionization detector), 260℃. Carrier gas: high-purity helium (He), flow rate 1.0mL / min.

[0059] Five tests were performed on the gas sample produced by the same fruit. The results are shown in Table 1. The results show that the RSD of the detection result of Example 1 is 6.33%, the results are consistent and similar to the concentration detected by gas chromatography-mass spectrometry, indicating that the detection results of the sensor in Example 1 are accurate and reliable.

[0060] Table 1 Comparison of linalool levels (ppm) determined by different detection methods

[0061]

[0062] Comparative Example 1

[0063] This comparative example provides an electrochemical gas sensor for detecting linalool, the preparation method of which differs from that of Example 1 only in that ZIF-8 is replaced with an equal amount of ZIF-67.

[0064] 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 10~35ppm, and the detection effect is not as good as that of Example 1.

[0065] Comparative Example 2

[0066] This comparative example provides an electrochemical gas sensor for detecting linalool, the preparation method of which differs from that of Example 1 only in that MWCNT is replaced with an equal amount of graphene (GO).

[0067] 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 5~25 ppm, and the detection effect is not as good as that of Example 1.

[0068] 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 an electrochemical gas sensor for detecting linalool, characterized in that, include: The template molecule linalool was dispersed in a polyvinyl alcohol solution, and a crosslinking agent was added to obtain a molecularly imprinted polymer (MIP). After removing the template molecule linalool, MIP powder was obtained. Multi-walled carbon nanotubes were dispersed in a zeolite imidazolium ester framework material-8 alcohol solution to prepare ZIF-8-MWCNT solution; ZnO was dispersed in ZIF-8-MWCNT solution to prepare ZIF-8-MWCNT-ZnO composite material. MIP powder was dispersed in ZIF-8-MWCNT-ZnO composite material to prepare MIP-ZIF-8-MWCNT-ZnO composite material; the MIP-ZIF-8-MWCNT-ZnO composite material was coated on the electrode surface and dried to obtain the electrochemical gas sensor for detecting linalool.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the template molecule linalool to polyvinyl alcohol is 1:(1~5). And / or, in a mixture of linalool and polyvinyl alcohol solutions, the concentration of linalool is 0.5~2 mM; And / or, the polyvinyl alcohol solution is an aqueous solution of polyvinyl alcohol.

3. The preparation method according to claim 1 or 2, characterized in that, The crosslinking agent is glutaraldehyde.

4. The preparation method according to claim 3, characterized in that, After adding a crosslinking agent, the molecularly imprinted polymer was prepared by reacting at 80℃~90℃.

5. The preparation method according to claim 1 or 2, characterized in that, MIP powder was prepared by removing the template molecule linalool using an alcohol solvent.

6. The preparation method according to claim 5, characterized in that, The alcohol solvent is methanol.

7. The preparation method according to claim 1 or 2, characterized in that, The zeolite imidazole ester framework material-8 alcohol solution is an ethanol solution of zeolite imidazole ester framework material-8.

8. The preparation method according to claim 7, characterized in that, In the ethanol solution of zeolite imidazole ester framework material-8, the concentration of zeolite imidazole ester framework material-8 is 1~5 mg / mL, and the volume percentage concentration of ethanol is 2%~10%.

9. The preparation method according to claim 7, characterized in that, In the mixture of multi-walled carbon nanotubes and zeolite imidazole ester framework material-8 alcohol solution, the concentration of multi-walled carbon nanotubes is 0.1~0.5 mg / mL.

10. The preparation method according to claim 7, characterized in that, In the mixture of ZnO and ZIF-8-MWCNT solutions, the concentration of ZnO is 0.1~1 mg / mL.

11. The preparation method according to claim 7, characterized in that, In the mixture of MIP powder and ZIF-8-MWCNT-ZnO composite material, the concentration of MIP powder is 0.1~2 mg / mL.

12. The preparation method according to claim 1 or 2, characterized in that, The electrode is an IDE electrode.

13. The preparation method according to claim 12, characterized in that, Before use, the electrode is activated in a sulfuric acid solution using a constant potential method.

14. An electrochemical gas sensor for detecting linalool prepared by the preparation method according to any one of claims 1 to 13.

15. The application of the electrochemical gas sensor for detecting linalool according to claim 14 in the detection of linalool, characterized in that, The application is in the in situ in vivo detection of linalool released by plants.

16. A method for in situ in vivo detection of linalool released from plants, characterized in that, include: The electrochemical gas sensor described in claim 14 is placed in the gas chamber and attached to the surface of the plant, and then connected to an electrochemical workstation for detection.

Images