Preparation method of aquatic product freshness monitoring electronic nose with rapid biogenic amine response characteristic

Abstract

The invention discloses a preparation method of an aquatic product freshness monitoring electronic nose with a rapid biogenic amine response characteristic and application of the aquatic product freshness monitoring electronic nose in real-time detection of aquatic product freshness, and belongs to the field of self-powered aquatic product freshness indication. According to the technical scheme, ZnO grows on filter paper in situ, and then defects are created on ZnO crystals through acetic acid gas phase etching, so that the acid-etched ZnO paper is obtained. The filter paper is adopted as a substrate material, the technological process is simple and environmentally friendly, and trace biogenic amine can be rapidly detected. The coordination effect between an oxygen-containing group on the cellulose fiber and Zn < 2 + > becomes a connection point for fixedly growing ZnO nano particles, and the mechanical strength between the nano material and a substrate is improved. Defects are created on ZnO crystals through acetic acid gas phase etching, and the adsorption energy and sensitivity of the electronic nose to biogenic amine are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of self-powered aquatic product freshness monitoring, and in particular relates to a method for preparing an electronic nose for monitoring aquatic product freshness with high dielectric properties, high sensitivity, and biodegradability, and rapid biogenic amine response characteristics, by in-situ growing ZnO on filter paper and using acetic acid vapor etching. Specifically, the present invention relates to a method for preparing an electronic nose for monitoring aquatic product freshness with rapid biogenic amine response characteristics. Background Art

[0002] In current research, the rapid deterioration of aquatic products is a global problem, leading to waste of resources, economic losses and increased food safety risks. Therefore, real-time non-destructive monitoring of the quality of aquatic products in the supply chain is crucial. Biogenic amines are marker gases for the deterioration of aquatic products. The development of efficient biogenic amine detection sensors can assess the quality of cold chain food, reduce waste, and prevent the occurrence of foodborne diseases. Compared with traditional detection methods, electronic nose technology has shown obvious advantages in the detection of freshness of aquatic products due to its simple operation and rapid and non-destructive detection capabilities. Despite this, the high price and maintenance costs of commercial electronic noses, as well as the limitation of having to be connected to a wired power supply, restrict their widespread application in the field of aquatic product testing.

[0003] Cellulose is one of the most abundant natural polymers on earth. Due to its excellent biodegradability, biocompatibility and flexibility, it has been widely studied in recent years as an ideal friction material for environmentally friendly triboelectric nanogenerators. The unique molecular structure and polymer properties of cellulose give it good chemical reaction properties, especially the abundant hydroxyl groups on the fiber can effectively react with Zn 2+ Coordination forms stable connection points for metal nanoparticles. In traditional methods, directly loading zinc oxide nanoparticles on cellulose may cause the particles to fall off easily. However, the strategy of in-situ growth of zinc oxide can significantly improve the mechanical strength between the nanoparticles and the cellulose substrate, thereby enhancing its stability. In addition, the hydrogen bond network inside cellulose and between adjacent molecules can effectively control the growth size of zinc oxide and optimize its gas-sensing performance. Moreover, the pore structure of cellulose makes it easier for zinc oxide grown on its surface to adsorb target gases. Therefore, the method of in-situ growth of zinc oxide can effectively solve the problem of easy shedding of nanoparticles and enhance the overall performance of cellulose as a friction material.

[0004] Currently, common gas sensors can be categorized as electrochemical, optical, solid electrolyte, and metal oxide semiconductor (MOS) gas sensors. MOS have been extensively studied due to their high sensitivity, reproducible and stable performance, simple operation, low cost, and ease of use. ZnO, an important n-type semiconductor material with a large binding energy (60 meV) and wide bandgap (3.37 eV), has attracted considerable attention due to its high sensitivity, chemical stability, high carrier mobility, and non-toxic properties. ZnO exhibits high sensitivity and strong gas adsorption capacity for NH₃ sensing. Furthermore, ZnO-based gas sensors typically have low power consumption, making them suitable for applications in portable devices and wireless sensor networks. ZnO is also easy to prepare, using methods such as solution deposition, sol-gel deposition, and vapor deposition. These methods are relatively simple and low-cost, making them suitable for large-scale production. However, the sensitivity of sensors based on single metal oxides is insufficient to meet the requirements for everyday use, hindering the detection of trace gases. Consequently, some researchers have sought to improve the sensing performance of gas-sensing materials through compositional modification, such as doping with expensive nanomaterials. However, current research on improving the gas-sensing performance of sensors lacks the ability to manipulate the structure of the gas-sensing material itself. In theory, semiconductor crystal defects play a key role in the gas adsorption process, and the presence of defects generally leads to increased sensor sensitivity to gases. Creating defects by acid-etching metal semiconductors can improve the sensitivity of gas-sensing materials to ammonia. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide an electronic nose with rapid biogenic amine response characteristics and its application in real-time detection of freshness of aquatic products.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The steps include:

[0008] Soak the qualitative filter paper in zinc chloride solution and sodium hydroxide solution successively. 2+ It is anchored to the hydroxyl groups of cellulose and then reacts with sodium hydroxide to deposit zinc hydroxide in situ on the cellulose. The zinc hydroxide deposited on the paper is pyrolyzed at high temperature into water vapor and zinc oxide, and finally etched with acetic acid vapor to obtain acid-etched zinc oxide paper.

[0009] A method for preparing an electronic nose for monitoring the freshness of aquatic products with a rapid response to biogenic amines, characterized by comprising the following steps:

[0010] 1) Soak filter paper c in ZnCl2 solution at 22-30°C for 30-60 minutes;

[0011] 2) Soak the treated filter paper in NaOH solution;

[0012] 3) Dry the Zn(OH)2 loaded paper and place it in a muffle furnace;

[0013] 4) Placing the ZnO paper and the acetic acid solution in a sealed container, and performing vapor phase etching of the ZnO supported on the paper using acetic acid vapor;

[0014] 5) Acid-etched ZnO paper and PVDF (polyvinylidene fluoride) were used as the positive electrode of TENG to prepare an electronic nose for monitoring the freshness of aquatic products with rapid biogenic amine response characteristics.

[0015] In the step (1), the concentration of the ZnCl2 solution is 0.1-0.4 mol / L, the pH value of the solution is in the range of 3-6.0, and the filter paper is a qualitative filter paper with an area of 9x9-15x15 mm in length and width. 2 , the mass of ZnCl2 solution is 30g-50g.

[0016] In the step (1), the reaction temperature is room temperature, and in the step (1), the oxygen-containing groups on the cellulose fibers are reacted with Zn 2+ The coordination effect between Zn 2+ Anchored on cellulose fibers.

[0017] In the step (2), the concentration of the NaOH solution is 0.5-0.7 mol / L; the chemical reaction time is 20-40 minutes, the reaction temperature is 20-30 degrees Celsius, and the Zn on the cellulose in the step (2) 2+ Will react with OH in the solution - A chemical reaction occurs, generating Zn(OH)2 on the paper.

[0018] In the step (3), the temperature of the muffle furnace is 180-250° C., preferably 200-220° C., and the reaction time is 40-80 min, preferably 60-65 min. In the step (3), Zn(OH) 2 is pyrolyzed to generate H 2 O and ZnO due to the high temperature.

[0019] In the step (4), the etching process is carried out at 80-90° C., the etching time is 1-7 hours, the concentration of acetic acid is 12.5 mol / L-14.3 mol / L, and the amount of acetic acid is greater than or equal to 60 mL, preferably 60-100 mL.

[0020] In step (5), the positive and negative electrodes are both 50×50-70×70 mm in area. 2 .

[0021] The prepared electronic nose for monitoring the freshness of aquatic products has the characteristics of rapid response to biogenic amines.

[0022] The invention discloses an application of an electronic nose for monitoring the freshness of aquatic products in the detection of the freshness of aquatic products.

[0023] The electronic nose for monitoring the freshness of aquatic products outputs electrical signals through TENG, which has a good linear relationship with the changes in the concentration of biogenic amines produced during the spoilage of aquatic products. The freshness of aquatic products can be detected in real time based on the changes in the electrical signals.

[0024] Based on the above technical solution, preferably, the concentration of zinc chloride in the zinc chloride solution in the step is 0.1 to 0.4 mol / L, preferably 0.2 to 0.3 mol / L.

[0025] Based on the above technical solution, preferably, the concentration of sodium hydroxide in the step is 0.4 to 0.8 mol / L, preferably 0.6 to 0.7 mol / L.

[0026] Based on the above technical solution, preferably, the pyrolysis temperature of the zinc hydroxide loaded paper in the muffle furnace in the step is 180-250° C., preferably 200-220° C.; the pyrolysis time is 40-80 min, preferably 60-65 min.

[0027] Based on the above technical solution, preferably, the acetic acid concentration in this step is 10-15 mol / L, preferably 12.5-14.3 mol / L, and the amount of acetic acid is greater than or equal to 60 mL, preferably 60-100 mL. The ambient temperature during etching is 70-90°C, preferably 80-85°C. The etching time is 1-7 hours, preferably 3-4 hours.

[0028] The present invention also relates to a high-performance cellulose friction material (paper-based friction nanogenerator) with rapid biogenic amine response characteristics prepared by the protection method.

[0029] The present invention also relates to the application of the high-performance cellulose friction material prepared by the above method in the field of aquatic product freshness indication (real-time detection), especially in the field of self-powered aquatic product freshness indication.

[0030] Based on the above technical solution, preferably, the acid-etched zinc oxide paper (high-performance cellulose friction material) prepared above is used as the positive friction material, and the commercial electrode polyvinylidene fluoride (PVDF) is used as the negative friction material to construct a TENG, and the freshness of aquatic products is detected by detecting the changes in the concentration of biogenic amines in the packaging microenvironment.

[0031] The present invention in situ grows zinc oxide on paper and then uses acetic acid gas to etch the nanoparticles to obtain acid-etched zinc oxide paper. In situ growth of zinc oxide on paper can significantly improve the surface roughness of the paper. At the same time, the in situ growth strategy can achieve a stable combination of ZnO nanoparticles and cellulose substrate, effectively overcoming the problem of weak interfacial interaction between the two and avoiding the shedding of nanoparticles caused by friction. The acid etching treatment causes anion defects in the zinc oxide crystals, and the crystal surface potential increases, which is beneficial to the triboelectric properties of the material and improves the electron supply capacity of the paper. The obtained acid-etched zinc oxide paper is used as a positive triboelectric material, and the commercial electrode polyvinylidene fluoride (PVDF) is used as a negative triboelectric material to prepare a paper-based friction nanogenerator (TENG). The output electrical signal of the TENG shows a significant linear correlation with the change in the concentration of biogenic amines in the microenvironment of aquatic product storage, and the freshness of the aquatic product can be reflected by real-time monitoring of the electrical signal change. On this basis, the TENG detection data is compared with the food safety threshold specified in the standard to evaluate whether the aquatic product meets the national edible physical and chemical standards. This method realizes the integration of the entire process from real-time monitoring of biogenic amine concentration to determination of food safety compliance, providing an innovative technical means for quality control during the storage and transportation of aquatic products. The product prepared by the present invention has the advantages of simple process flow, low energy consumption, easy batch and large-scale production, and good reproducibility between product batches. The selection of cellulose as the base of the gas-sensitive material is not only green and environmentally friendly, but the air permeability of cellulose can also improve the gas diffusion efficiency, greatly reducing the detection limit of the gas-sensitive material for ammonia, thereby effectively improving the sensitivity of the sensor, facilitating a rapid and accurate response to trace ammonia, and realizing the monitoring of the freshness status of aquatic products.

[0032] Compared with the prior art, the preparation method provided by the present invention has the following advantages:

[0033] The gas-sensitive TENG fabricated in this paper uses cellulose as its gas-sensitive substrate. Its permeability improves gas diffusion efficiency, which effectively enhances the sensor's response and recovery speed. The in-situ growth strategy enables a stable bond between ZnO and the cellulose substrate, effectively overcoming the weak interfacial interaction between the two. This promising approach is expected to find widespread application in the field of aquatic product freshness indication.

[0034] 2. The gas-sensitive material prepared by the present invention adopts a vapor phase etching method to adjust the structure of the semiconductor crystal, effectively improving the adsorption energy of the material to the target gas and enhancing the sensitivity of the sensor.

[0035] 3. The production method of the paper-based TENG prepared in the present invention has the advantages of simple production process, low energy consumption, easy batch and large-scale production, and good repeatability between product batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1The triboelectric signal output of the acid-etched zinc oxide paper TENG prepared in Example 1-4. In the figure: The acid etching treatment increases the dielectric constant and surface roughness of the material, and the generated V OC , I SC and Q SC When the acid etching time reaches 3h, the maximum V OC is 107.32V, maximum I SC 4.56μA, maximum Q SC It is 35.85nC.

[0037] Figure 2 The dielectric constant of the paper prepared in Examples 1 and 5 changes. In the figure: the dielectric constant of the acid-etched zinc oxide paper is better than that of the zinc oxide paper and the blank paper. The dielectric constant is related to the polarity of the molecule. The increase in the dielectric constant of the paper loaded with zinc oxide is mainly due to the fact that zinc oxide itself has a certain dielectric constant (usually between 2.5 and 3.5). Its loading increases the polarization ability of the material, thereby improving the overall dielectric constant. The acid-etched zinc oxide paper obtained after the acid etching treatment has defects in the zinc oxide loaded, resulting in an uneven distribution of the electric field inside the zinc oxide and an increase in the dielectric constant of the material.

[0038] Figure 3 This is a stability test of the acid-etched zinc oxide paper TENG prepared in Example 1. The figure shows that the voltage did not decrease during 1600 cycles of repeated measurements in an air environment with room temperature and a relative humidity of 20-30%.

[0039] Figure 4 The electrical signal changes of the acid-etched zinc oxide paper TENG prepared in Example 1 under different ammonia concentrations (0-100 ppm) at room temperature.

[0040] Figure 5 Fitting curves of ammonia concentration responses measured by TENG under different ammonia concentration conditions (0-100 ppm) at room temperature for the sample TENG prepared in Example 1 and Example 5.

[0041] Figure 6 Fitting curves of the ammonia concentration responses of the acid-etched zinc oxide paper TENG prepared in the comparative example and Examples 2-4 were measured at room temperature under different ammonia concentration conditions (0-100 ppm).

[0042] Figure 7 Schematic diagram of TENG prepared from samples prepared in Examples 1-4, where the example sample in the figure is acid-etched zinc oxide paper.

[0043] Figure 8 Comparison of the real-time response recovery time of the samples prepared in Examples 1-8 to ammonia gas in a 100 ppm atmosphere.

[0044] Figure 9 The acid-etched zinc oxide paper TENG prepared in Example 1 was used to monitor the freshness of scallops placed at room temperature in real time.

[0045] Figure 10 Evaluation of the electrical signal indicating the freshness of aquatic products from 0 to 20 h using the acid-etched zinc oxide paper TENG prepared in Example 1, as well as the changes in the TVB-N (volatile basic nitrogen) content of aquatic products during the storage time. DETAILED DESCRIPTION

[0046] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0047] Unless otherwise specified in the examples, all experimental procedures or conditions were carried out according to conventional experimental procedures or conditions described in the literature in the field. All reagents or instruments used without specifying the manufacturer were commercially available conventional reagents.

[0048] The experimental material filter paper of the present invention is a qualitative filter paper containing cellulose fibers.

[0049] Example 1

[0050] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 10.9 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH of the zinc chloride solution with a pH meter. The pH of the solution should be in the range of 4.5 to 5.0, and the pH value here is 5.

[0051] Accurately weigh 9.6g of sodium hydroxide and dissolve it in 400ml of deionized water to prepare a sodium hydroxide solution. Soak the qualitative filter paper in 30g of zinc chloride solution for 30 minutes. Then transfer the soaked qualitative filter paper to 30g of sodium hydroxide solution and soak it for another 20 minutes. After the reaction, remove the filter paper. Soak the reacted filter paper in deionized water again. Repeat the deionized water soaking process three times for 5 minutes to completely dissolve the sodium chloride produced in the reaction. Then, place the washed filter paper in a 60°C oven to dry.

[0052] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0053] (3) Preparation of acid-etched zinc oxide paper: The pyrolyzed loaded zinc oxide paper and 70 mL of 13 mol / L acetic acid solution were placed in an airtight box (30x30x20 cm 3 ), set the ambient temperature to 80°C and the etching time to 3h.

[0054] (4) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 A square of 1.5-1.5 mm in diameter was used. Acid-etched zinc oxide paper was adhered to a piece of conductive silver tape to serve as the triboelectric positive electrode layer. The triboelectric negative electrode was composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape.

[0055] Arrange the acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) in parallel face to face, with a spacing of 2-3 mm between them. A gas-sensitive paper-based TENG is obtained. The positive and negative electrodes are respectively led out through copper wires and connected to a voltmeter. When the positive and negative electrodes contact and rub to generate current, the TENG output voltage can be measured by the voltmeter. The working mode of TENG adopts the vertical contact separation mode, that is, applying force in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0056] Example 2

[0057] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 10.9 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH of the zinc chloride solution with a pH meter. The pH of the solution should be in the range of 4.5 to 5.0, and the pH value here is 5.

[0058] Accurately weigh 9.6g of sodium hydroxide and dissolve it in 400ml of deionized water to prepare a sodium hydroxide solution. Soak the qualitative filter paper in 30g of zinc chloride solution for 30 minutes. Then transfer the soaked qualitative filter paper to 30g of sodium hydroxide solution and soak it for another 20 minutes. After the reaction, remove the filter paper. Soak the reacted filter paper in deionized water three times for 5 minutes to completely dissolve the sodium chloride produced in the reaction. Then, dry the washed filter paper in a 60°C oven.

[0059] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0060] (3) Preparation of acid-etched zinc oxide paper: The pyrolyzed loaded zinc oxide paper and 70 mL of 13 mol / L acetic acid solution were placed in an airtight box (30x30x20 cm3 ), set the ambient temperature to 80°C and the etching time to 1h.

[0061] (4) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 A square of 1.5-1.5 mm in diameter was used. Acid-etched zinc oxide paper was adhered to a piece of conductive silver tape to serve as the triboelectric positive electrode layer. The triboelectric negative electrode was composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape.

[0062] Arrange the acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) in parallel face to face, with a spacing of 2-3 mm between them. A gas-sensitive paper-based TENG is obtained. The positive and negative electrodes are respectively led out through copper wires and connected to a voltmeter. When the positive and negative electrodes contact and rub to generate current, the TENG output voltage can be measured by the voltmeter. The working mode of TENG adopts the vertical contact separation mode, that is, applying force in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0063] Example 3

[0064] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 10.9 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value of the solution should be in the range of 4.5 to 5.0, and the pH value here is 5. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water to prepare a sodium hydroxide solution. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 minutes, then transfer the soaked qualitative filter paper to 30 g of sodium hydroxide solution and continue soaking for 20 minutes. After the reaction, remove the filter paper. Soak the reacted filter paper in deionized water again, soaking the filter paper three times for 5 minutes, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0065] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0066] (3) Preparation of acid-etched zinc oxide paper: The pyrolyzed loaded zinc oxide paper and 70 mL of 13 mol / L acetic acid solution were placed in an airtight box (30x30x20 cm 3 ), set the ambient temperature to 80°C and the etching time to 5h.

[0067] (4) Cut the conductive silver tape into two pieces of 5x5 cm 2Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 The acid-etched zinc oxide paper is adhered to a piece of conductive silver tape as the friction positive electrode layer. The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. A gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of TENG can be measured by a voltmeter. The working mode of TENG adopts vertical contact separation, that is, force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0068] Example 4

[0069] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 10.9 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value should be in the range of 4.5 to 5.0, and the pH value here is 5. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water to prepare a sodium hydroxide solution. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 min, then transfer the soaked qualitative filter paper to 30 g of sodium hydroxide solution and continue soaking for 20 min. After the reaction, remove the filter paper. Soak the reacted filter paper in deionized water again, soaking the filter paper three times for 5 min, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0070] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0071] (3) Preparation of acid-etched zinc oxide paper: The pyrolyzed loaded zinc oxide paper and 70 mL of 13 mol / L acetic acid solution were placed in an airtight box (30x30x20 cm 3 ), set the ambient temperature to 80°C and the etching time to 7h.

[0072] (4) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2The acid-etched zinc oxide paper is adhered to a piece of conductive silver tape as the friction positive electrode layer. The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. A gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of TENG can be measured by a voltmeter. The working mode of TENG adopts vertical contact separation, that is, force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0073] Example 5

[0074] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 10.9 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value should be in the range of 4.5 to 5.0, and the pH value here is 5. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water to prepare a sodium hydroxide solution. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 min, then transfer the soaked qualitative filter paper to 30 g of sodium hydroxide solution and continue soaking for 20 min. After the reaction, remove the filter paper. Soak the reacted filter paper in deionized water again, soaking the filter paper three times for 5 min, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0075] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0076] (3) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 A square of the same size was used. The acid-etched zinc oxide paper was adhered to a piece of conductive silver tape to serve as the tribo-positive electrode layer.

[0077] The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to a conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. The gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of the TENG can be measured by a voltmeter. The working mode of TENG adopts a vertical contact separation type, that is, a force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0078] Example 6

[0079] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 5.45 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value should be in the range of 4.5 to 5.0, and the pH value here is 5. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 min, then transfer it to 30 g of sodium hydroxide solution and continue soaking for 20 min. After the reaction, remove the filter paper. Soak the filter paper after the reaction in deionized water again, soaking the filter paper three times for 5 min, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0080] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0081] (3) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 The acid-etched zinc oxide paper is adhered to a piece of conductive silver tape as the friction positive electrode layer. The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. A gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of TENG can be measured by a voltmeter. The working mode of TENG adopts vertical contact separation, that is, force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0082] Example 7

[0083] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 16.35 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value should be in the range of 3.5 to 4.0, and the pH value here is 4. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 min, then transfer it to 30 g of sodium hydroxide solution and continue soaking for 20 min. After the reaction, remove the filter paper. Soak the filter paper after the reaction in deionized water again, soaking the filter paper three times for 5 min, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0084] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0085] (3) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 The acid-etched zinc oxide paper is adhered to a piece of conductive silver tape as the friction positive electrode layer. The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. A gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of TENG can be measured by a voltmeter. The working mode of TENG adopts vertical contact separation, that is, force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0086] Example 8

[0087] (1) Preparation of zinc hydroxide loaded paper: Accurately weigh 21.80 g of zinc chloride and dissolve it in 400 ml of deionized water. Add 0.1 mol / L hydrochloric acid dropwise until the zinc chloride is completely dissolved. Measure the pH value of the zinc chloride solution with a pH meter. The pH value should be in the range of 3.0 to 3.5, and the pH value here is 3. Accurately weigh 9.6 g of sodium hydroxide and dissolve it in 400 ml of deionized water. Soak the qualitative filter paper in 30 g of zinc chloride solution for 30 min, then transfer it to 30 g of sodium hydroxide solution and soak it for 20 min. After the reaction, remove the filter paper. Soak the filter paper after the reaction in deionized water again, soaking the filter paper three times for 5 min, so that the sodium chloride produced in the reaction is completely dissolved in the deionized water. Then place the washed filter paper in a 60°C oven to dry.

[0088] (2) Preparation of zinc oxide loaded paper: Place the dried filter paper loaded with zinc hydroxide in a muffle furnace, set the heating rate to 5°C / min, heat to 200°C, and pyrolysis time to 60 min.

[0089] (3) Cut the conductive silver tape into two pieces of 5x5 cm 2 Cut the acid-etched zinc oxide paper and PVDF into 5x5 cm squares. 2 The acid-etched zinc oxide paper is adhered to a piece of conductive silver tape as the friction positive electrode layer. The friction negative electrode is composed of polyvinylidene fluoride (PVDF) adhered to the conductive silver tape. The acid-etched zinc oxide paper (positive electrode friction layer) and the PVDF film (negative electrode friction layer) are arranged in parallel face to face, with a spacing of 2-3 mm in between. A gas-sensitive paper-based TENG can be obtained. The positive and negative electrodes are respectively led out and connected to a voltmeter through copper wires. When the positive and negative electrodes contact and rub to generate current, the output voltage of TENG can be measured by a voltmeter. The working mode of TENG adopts vertical contact separation, that is, force is applied in the vertical direction of the electrode to make the positive and negative electrodes contact each other, forming a current in the circuit.

[0090] Comparative Example 1

[0091] The preparation was carried out according to the method of Example 1, except that the etching time was 0, that is, the loaded zinc oxide paper did not undergo the acid etching process and was directly used as the positive electrode friction layer of TENG.

[0092] Comparative Example 2

[0093] The preparation was carried out according to the method of Example 1, except that zinc oxide was not loaded, and blank paper material was used as the positive electrode friction layer of the paper-based TENG, that is, a blank paper-based friction nanogenerator.

[0094] Example 9: Performance test of high-performance gas-sensitive paper-based triboelectric nanogenerator and evaluation of aquatic product freshness indication:

[0095] 1. Triboelectric output performance

[0096] Test method:

[0097] Acid-etched zinc oxide paper was used as the positive triboelectric layer, and polyvinylidene fluoride (PVDF) was used as the negative triboelectric layer. The acid-etched zinc oxide paper and a piece of PVDF film were cut into 50 mm x 50 mm rectangles and adhered to two silver tapes, respectively, to form acid-etched zinc oxide paper / Ag electrodes and PVDF / Ag electrodes. At room temperature, the acid-etched zinc oxide paper / Ag electrode served as the positive electrode, and the PVDF / Ag electrode served as the negative electrode. The acid-etched zinc oxide paper (positive triboelectric layer) and the PVDF film (negative triboelectric layer) were arranged face-to-face in parallel, with a 2-3 mm gap between them. Conductive silver tape was used to connect the positive and negative electrode leads. Copper wires were connected to the electrode leads and connected in series to an electrometer. The positive and negative electrodes were connected to a linear motor with an impact frequency of 1 Hz and an impact force of 5 N. During the test, mechanical pressure applied by the motor brought the electrodes into contact and compressed them. The pressure was then released, separating them, and this process was repeated to generate current.

[0098] The output effects of the zinc oxide paper-based TENG prepared in the above-mentioned Example 1, Examples 2-4 and Comparative Examples at different etching times are compared. The results are as follows: Figure 1 , from the different etching times in the superscript of the figure, we can know that the sample prepared in Example 1 (etching time is 3 hours) has the best output performance, with an output voltage of up to 107.32V, a short-circuit current of up to 4.56μA, and an output charge of up to 35.85nC. The etching time in Example 2 is 1h, and the TENG prepared therefrom has an output voltage of 96V, a short-circuit current of 4.11μA, and an output charge of 31.46nC. In Examples 3 and 4, as the etching time is extended to 5h and 7h, the output voltage of the TENG prepared by these two samples decreases, but the TENG with an etching time of 0 in Comparative Example 1 has an output voltage of 84.5V, a short-circuit current of 3.85μA, and an output charge of 28.67nC, which is significantly the lowest. Therefore, the step of acid etching of the loaded zinc oxide has a great influence on the results. Figure 1 It can be seen that the output voltage of the acid-etched zinc oxide paper obtained in Example 1 is significantly better than that in Comparative Example 1, that is, the triboelectric performance of the TENG prepared with the acid-etched zinc oxide paper obtained in Example 1 is significantly better than that in Comparative Example 1.

[0099] Likewise, the acid-etched zinc oxide papers prepared in Examples 1-4 have good triboelectric output performance.

[0100] 2. Dielectric properties

[0101] The dielectric properties of the paper-based TENG prepared in Example 1, Example 5 and Comparative Example 2 were investigated. Figure 2As shown in the figure, the dielectric constant of acid-etched zinc oxide (AZP) paper is significantly greater than that of zinc oxide paper (ZP) and blank paper (Paper). The dielectric constant is related to the polarity of the molecule. The increase in the dielectric constant of paper loaded with zinc oxide is mainly due to the fact that zinc oxide itself has a certain dielectric constant (usually between 2.5 and 3.5). Its loading increases the polarization ability of the material, thereby improving the overall dielectric constant. The acid-etched zinc oxide paper obtained after acid etching has defects in the loaded zinc oxide, resulting in an uneven electric field distribution within the zinc oxide and an increase in the dielectric constant of the material.

[0102] Depend on Figure 2 It can be seen that the product prepared in Example 1 has excellent dielectric properties. The increase in dielectric constant means that the acid-etched zinc oxide paper TENG has a higher capacitance than the zinc oxide paper TENG prepared in Example 5 and the blank paper TENG in Comparative Example 2. Figure 2 It can be seen that the sample prepared in Example 1 has the highest dielectric constant and excellent dielectric properties.

[0103] Similarly, the gas-sensitive paper-based TENG prepared in Examples 2-4 also has good dielectric properties, which are higher than those in Examples 5-8.

[0104] 3. Stability

[0105] Test method:

[0106] The positive and negative electrodes collided with each other 1600 times in an air environment with room temperature and relative humidity of 27-30% RH. The acid-etched zinc oxide paper / Ag electrode was used as the positive electrode and the PVDF / Ag electrode was used as the negative electrode. The stability performance of the product was investigated using the acid-etched zinc oxide paper TENG prepared in Example 1. The results are as follows: Figure 3 As shown. When the positive and negative electrodes of TENG collided with each other for 800s (1600 cycles), the output voltage fluctuation of TENG was only 9.09%, which shows that TENG has stable output performance and meets the stability performance requirements of TENG in practical applications. ( Figure 3 The horizontal axis is the TENG working time)

[0107] Similarly, the gas-sensitive paper-based TENGs prepared in Examples 2-4 and the comparative example all have good stability.

[0108] 4. Ammonia sensitivity characteristics:

[0109] The acid-etched zinc oxide paper TENG prepared in Example 1 was used to investigate the ammonia sensitivity of the product. Figure 4 shown.

[0110] This product was placed in an ammonia environment at 0, 5, 10, 20, 40, 60, 80, and 100 ppm. At room temperature, the acid-etched zinc oxide paper / Ag electrode was used as the positive electrode and the PVDF / Ag electrode was used as the negative electrode. The TENG instrument was placed in the above ammonia environment and the voltage meter was used to obtain the voltage. Figure 4 Conclusion, (two cycles per second, i.e. the impact frequency is 1Hz);

[0111] Depend on Figure 4 It can be seen that the product prepared in Example 1 has good ammonia sensitivity characteristics, which meets the ammonia sensitivity requirements in its practical application of indicating the freshness of aquatic products. When the ammonia concentration is only 5 ppm, the voltage can be seen to fluctuate, that is, the product can respond to ammonia and realize trace detection of the target gas.

[0112] Depend on Figure 5-6 It can be seen that the output voltages of the products prepared in Comparative Examples 1 and 2 and Examples 2-4 at different ammonia concentrations were linearly fitted. The slope of the fitting curve represents the sensitivity of the sample to ammonia. The larger the slope, the higher the sensitivity of the sample to ammonia. 2 The closer the value is to 1, the better the fitting degree. The products prepared in Comparative Example 2 and Examples 2-4 have good ammonia sensitivity and can respond when the ammonia concentration is as low as 5 ppm, but their sensitivity is obviously inferior to that of Example 1.

[0113] Figure 7 Schematic diagram of TENG connected to a voltmeter. Figure 7 As can be seen, the functional paper prepared in the example serves as the positive electrode of the TENG, and the PVDF serves as the negative electrode of the TENG, connected by a copper wire. The two are triboelectrically charged, and the voltmeter displays a value. However, when the TENG is placed in an ammonia atmosphere, the TENG output voltage decreases.

[0114] Depend on Figure 8 It can be seen that when this product is placed in an ammonia 100ppm environment, the acid-etched zinc oxide paper / Ag electrode is used as the positive electrode and the PVDF / Ag electrode is used as the negative electrode, the product prepared in Example 1 can respond quickly to ammonia. In an ammonia atmosphere of 100ppm, the response recovery time is only 20 / 24s. In Examples 2-4, based on the change in the acid etching time, the prepared sample response / recovery times are 32 / 40s, 35 / 42s, and 44 / 56s, respectively. The products prepared in Examples 5-8 are not acid-etched, and their response recovery times are extended to 72 / 86s, 90 / 98s, 73 / 88s, and 75 / 90s in an ammonia atmosphere of 100ppm. The sample prepared from blank paper in Comparative Example 2 is not loaded with gas-sensitive material, so it cannot respond quickly to ammonia. In summary, the samples prepared in Examples 1-4 have excellent fast ammonia response recovery characteristics compared to the comparative samples, Examples 5-8, and Comparative Example 2.

[0115] 5. Aquatic product freshness indication effect:

[0116] Test method:

[0117] Fresh scallops and acid-etched zinc oxide paper TENG were placed together in a sealed container and kept at room temperature. Photos were taken regularly to observe changes in the appearance of the scallops.

[0118] The acid-etched zinc oxide paper TENG prepared in Example 1 was used to investigate the freshness indication effect of the product. Figure 9 and Figure 10 shown.

[0119] The acid-etched zinc oxide paper TENG prepared with the acid-etched zinc oxide paper / Ag electrode as the positive electrode and the PVDF / Ag electrode as the negative electrode was placed in an airtight box containing scallops, and the corresponding pressure gauge value was recorded every 4 hours.

[0120] Depend on Figure 9 and Figure 10 As can be seen, the product prepared in Example 1 demonstrates excellent freshness indicator performance for aquatic products, enabling real-time monitoring of changes in trace biogenic amine concentrations within the packaging microenvironment, enabling timely monitoring of aquatic product deterioration. In accordance with the national standard GB2733-2015 for food safety physical and chemical indicators for fresh and frozen animal-derived aquatic products, scallops are considered spoiled when their volatile basic nitrogen content is ≥15 mg / 100 g. In other words, a 55-60% drop in voltage for the product prepared in Example 1 indicates that the scallops do not meet national edible physical and chemical standards. This meets the requirements for real-time monitoring of aquatic product freshness in practical applications.

[0121] Similarly, the gas-sensitive TENGs prepared in Examples 2-4 all have good freshness indication effects for aquatic products.

[0122] This invention provides a method for preparing a high-performance cellulose friction material with high dielectric properties, high sensitivity, and biodegradability, and a rapid biogenic amine response. The material's application in real-time aquatic product freshness detection, and its application in self-powered aquatic product freshness indication, falls within the field of self-powered aquatic product freshness indication. Experimental results demonstrate that the prepared acid-etched zinc oxide paper TENG exhibits excellent biocompatibility, simple preparation, environmental friendliness, and low cost. It also responds quickly to trace ammonia levels as low as 5 ppm, making it amenable to large-scale production.

Claims

1. A method for preparing an electronic nose for monitoring the freshness of aquatic products with a rapid response to biogenic amines, characterized in that: The steps include: 1) Soak filter paper c in ZnCl2 solution at 22-30°C for 30-60 minutes; 2) Soak the treated filter paper in NaOH solution; 3) Dry the Zn(OH)2 loaded paper and place it in a muffle furnace; 4) Placing the ZnO paper and the acetic acid solution in a sealed container, and performing vapor phase etching of the ZnO supported on the paper using acetic acid vapor; 5) Acid-etched ZnO paper and PVDF (polyvinylidene fluoride) were used as the positive electrode of TENG to prepare an electronic nose for monitoring the freshness of aquatic products with rapid biogenic amine response characteristics.

2. The method according to claim 1, characterized in that: In the step (1), the concentration of the ZnCl2 solution is 0.1-0.4 mol / L, the pH value of the solution is within the range of 3-6.0, and the filter paper is a qualitative filter paper with an area of 9x9-15x15mm in length and width. 2 , the mass of ZnCl2 solution is 30g-50g.

3. The method according to claim 1, wherein: In the step (1), the reaction temperature is room temperature, and in the step (1), the oxygen-containing groups on the cellulose fibers are reacted with Zn 2+ The coordination effect between Zn 2+ Anchored on cellulose fibers.

4. The method according to claim 1, wherein: In the step (2), the concentration of the NaOH solution is 0.5-0.7 mol / L; the chemical reaction time is 20-40 minutes, the reaction temperature is 20-30 degrees Celsius, and the Zn on the cellulose in the step (2) 2+ Will react with OH in the solution - A chemical reaction occurs, generating Zn(OH)2 on the paper.

5. The method according to claim 1, characterized in that: In the step (3), the temperature of the muffle furnace is 180-250° C., preferably 200-220° C., and the reaction time is 40-80 min, preferably 60-65 min. In the step (3), Zn(OH) 2 is pyrolyzed to generate H 2 O and ZnO due to the high temperature.

6. The method according to claim 1, characterized in that: In the step (4), the etching process is carried out at 70-90° C., the etching time is 1-7 hours, the concentration of acetic acid is 10-15 mol / L, preferably 12.5 mol / L-14.3 mol / L, and the amount of acetic acid is greater than or equal to 60 mL, preferably 60-100 mL.

7. The method according to claim 1, characterized in that: In step (5), the positive and negative electrodes are both 50×50-70×70 mm in area. 2 .

8. An electronic nose for monitoring the freshness of aquatic products having a rapid biogenic amine response characteristic prepared by the method of any one of claims 1 to 7.

9. Use of the electronic nose for monitoring freshness of aquatic products according to claim 8 in detecting the freshness of aquatic products.

10. The use according to claim 9, characterized in that: The electronic nose for monitoring the freshness of aquatic products outputs electrical signals through TENG, which has a good linear relationship with the changes in the concentration of biogenic amines produced during the spoilage of aquatic products. The freshness of aquatic products can be detected in real time based on the changes in the electrical signals.

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