Preparation method of aiegen doped pla electrospun nanofiber membrane with pH fluorescence color change property

Abstract

The application belongs to the technical field of functional material preparation, and particularly relates to a preparation method of an AIEgen-doped PLA electrospinning nanofiber membrane with pH fluorescence color change property. The preparation method comprises the following steps: (1) synthesizing an aggregation-induced emission body 5-(4-((4-(1,2,2-triphenylstyryl) benzylidene) amino) isoindoline-2-yl) piperidin-2-one (TPE-LAN); (2) preparing a TPE-LAN electrospinning solution; and (3) preparing the AIEgen-doped PLA electrospinning nanofiber membrane with pH fluorescence color change property. The AIEgen-doped PLA electrospinning nanofiber membrane with pH fluorescence color change property prepared by the preparation method has the aggregation-induced emission property, biocompatibility and antibacterial property, and overcomes the problem of light quenching caused by aggregation, and can be applied to the field of food monitoring.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional material preparation, and particularly relates to a preparation method of an AIEgen-doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change properties. BACKGROUND

[0002] With the increasing demand of consumers for the freshness and safety of aquatic products, the development of efficient and sensitive real-time monitoring technology for food freshness has become an important research direction in the field of food science and materials engineering. Fang's group (Ziqi Fang, Yanfen Xu, Lian Duan, et al, Freshness evaluation of grass carp by volatile biogenic amines monitored by secondary electrospray ionization ion mobility spectrometry, Microchemical Journal, Volume 195, 2023, 109483.) used the secondary electrospray ionization ion mobility spectrometry method with ammonium acetate to rapidly determine the content of various volatile biogenic amines in grass carp. The ammonium ions produced by the electrospray ionization source were used as reactant ions to react with volatile biogenic amines in the gas phase and were separated in the drift tube. Li's group (Yanlei Li, Xiuying Tang, Zhixiong Shen, et al, Prediction of total volatile basic nitrogen (TVB-N) content of chilled beef for freshness evaluation by using viscoelasticity based on airflow and laser technique, Food Chemistry, Volume 287, 2019, Pages 126-132.) conducted viscoelasticity experiments to detect the total volatile basic nitrogen (TVB-N) content of chilled beef for freshness evaluation and further analyzed the growth trend of TVB-N under extended storage time. Then, a six-element viscoelasticity model was established by fitting the deformation data using universal global optimization. The viscoelasticity parameters, including elastic moduli E1, E2, E3 and viscosity coefficients η1, η2, η3, were applied to construct the TVB-N content prediction model using partial least squares regression (PLSR) and support vector machine regression (SVR).Hao's team (Jiahui Hao, Jingyi Wang, Jie Wang, et al, A novel multifunctional bioactive film based on Gelidium amauslipolysaccharide incorporated with lingonberry anthocyanin for fish freshness monitoring and preservation, LWT, Volume 215,2025,117173.) developed a sustainable bioactive film with activity and intelligent characteristics, using polysaccharide as the film-forming matrix and lingonberry anthocyanin as the indicator, a polysaccharide-based anthocyanin composite film with excellent physical and mechanical properties was constructed. The film showed significant colorimetric response to pH 3-12 buffer and volatile ammonia, and could be used for intelligent analysis and characterization of fish freshness monitoring.

[0003] However, the above-mentioned traditional fish freshness detection methods (such as determination of volatile nitrogen and microbial culture method) have the limitations of complex operation, long time consumption, dependence on large instruments, etc., which are difficult to meet the real-time monitoring needs of modern cold chain logistics and intelligent packaging. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of AIEgen doped PLA electrospinning nanofiber film with pH fluorescence color change property. The nanofiber film prepared by the method has aggregation-induced emission characteristics, biocompatibility and antibacterial property, overcomes the problem of light quenching caused by aggregation, and can be applied to the field of food monitoring.

[0005] The preparation method of the AIEgen doped PLA electrospinning nanofiber film with pH fluorescence color change property comprises the following steps:

[0006] (1) 4-(1,2,2-triphenylvinyl) benzaldehyde and 3-(7-amino-3-oxo-1H-isoindol-2-yl) piperidin-2,6-dione are dissolved in anhydrous ethanol to synthesize an aggregation-induced emitter 5-(4-((4-(1,2,2-triphenylvinyl) benzylidene) amino) isoindolin-2-yl) piperidin-2-one, i.e. TPE-LAN;

[0007] (2) polylactic acid is dissolved in dichloromethane solvent for stirring reaction to prepare a polylactic acid solution, and TPE-LAN is dissolved in N,N-dimethylformamide solvent for stirring reaction to prepare a TPE-LAN solution;

[0008] (3) mixing the polylactic acid solution prepared in step (2) and the TPE-LAN solution uniformly, then using an electrospinning instrument, electrospinning the obtained mixed solution, and finally drying to prepare an AIEgen-doped PLA electrospinning nanofiber membrane with pH fluorescent color-changing properties.

[0009] The molar ratio of 4-(1,2,2-triphenylvinyl)benzaldehyde to 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione in step (1) is 0.60-0.75:1.

[0010] In step (1), the reaction conditions are refluxing at 78°C for 16-18 hours under a nitrogen atmosphere, then placing the obtained solution at 25°C for 24 hours, and after the reaction is completed, performing suction filtration to prepare 5-(4-((4-(1,2,2-triphenylvinyl)benzylidene)amino)isoindolin-2-yl)piperidin-2-one (TPE-LAN).

[0011] In step (1), 4-(1,2,2-triphenylvinyl)benzaldehyde and 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione are respectively dissolved in anhydrous ethanol, then the two mixed solutions are respectively subjected to ultrasonic treatment until completely dissolved, and then the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde is added dropwise into the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione for reaction, wherein the mass-volume ratio of 4-(1,2,2-triphenylvinyl)benzaldehyde to anhydrous ethanol in the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde is 0.0835-0.104:50, with the unit of g / mL, and the mass-volume ratio of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione to anhydrous ethanol in the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione is 0.100:50, with the unit of g / mL.

[0012] In step (2), the mass-volume ratio of polylactic acid (PLA) to dichloromethane is 3.47:20, with the unit of g / mL.

[0013] In step (2), the mass-volume ratio of TPE-LAN to N,N-dimethylformamide is 0.0156-0.0469:5, with the unit of g / mL. When the mass-volume ratio is less than 0.0156:5, the fluorescence change is not obvious due to the low content of the fluorescent source. Similarly, when the mass-volume ratio is greater than 0.0469:5, the fluorescence quenching part is easily covered by the fluorescence appearing part due to the excessive content of the fluorescent source, which also leads to the fluorescence change not being easily perceived.

[0014] The stirring speed of the stirring reaction in step (2) is 800 r / min, the stirring reaction temperature is normal temperature, and the stirring reaction time is 1-2 hours.

[0015] The volume ratio of the TPE-LAN solution to the polylactic acid solution in step (3) is 1:4.

[0016] The electrospinning parameters in step (3) are as follows: a voltage of 12 kV, a flow rate of 2 mL / h, a receiving distance of 20 cm, and a cylinder rotation speed of 100 r / min.

[0017] When the electrospinning voltage is lower than 12 kV, the diameter of the nanofiber is relatively large, because the voltage is relatively low, so that the fiber stretching force is insufficient; when the voltage is higher than 12 kV, the diameter of the nanofiber is also relatively large, because in the process of increasing the voltage, the electric field force is continuously enhanced, and the solution is "sucked" out of the needle too fast, which initially causes the fiber diameter to decrease, but the over-high voltage causes the polymer droplets ejected per unit time to increase, which causes insufficient stretching, and part of the solution is dried before it is fully refined, thereby causing the fiber diameter to become thick, and even a string of beads phenomenon occurs. Therefore, the preferred electrospinning voltage is 12 kV.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] (1) The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color change property has process parameters easy to control, simple operation, and the prepared AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color change property has stable performance.

[0020] (2) The AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color change property prepared by the preparation method has aggregation-induced emission characteristics, biocompatibility and antibacterial properties, overcomes the problem of light quenching caused by aggregation, and can be applied to the field of food monitoring.

[0021] (3) The AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color change property prepared by the preparation method is used for detecting fish spoilage characteristic gas, and under a closed environment, with the extension of the fish meat storage time, the color of the fiber membrane under ultraviolet lamp irradiation gradually changes from bright yellow-green fluorescence to the milk white color of the fiber membrane itself, and the contrast is high.

[0022] (4) The preparation method of the AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property, fully utilizes the AIE characteristics of 4-(1,2,2-triphenylvinyl) benzaldehyde to realize visual signal output, captures the biological amine substances generated by fish spoilage through the dynamic response characteristics of the imine bond, simultaneously plays the antibacterial function of lenalidomide, constructs a system integrating "detection-indication-antibacterial" in one, breaks through the single function limitation of traditional detection technology, provides a new solution for aquatic product quality monitoring, has important social and economic benefits for guaranteeing food safety and reducing food waste.

[0023] (5) The AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property prepared by the preparation method has a weak alkaline environment suitable for amine substances released after fish spoilage, the pH value changes in the range of 6.0-7.8, the fluorescence signal change needs to be detected under the condition of 365nm ultraviolet light irradiation, the temperature is room temperature, and too high temperature will affect the stability of the PLA electrostatic spinning nanofiber membrane. With the aggravation of fresh fish spoilage, the fiber membrane has a visible fluorescence color change, i.e., from bright yellow-green fluorescence to the milk white color of the fiber membrane itself. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a nuclear magnetic hydrogen spectrum of the aggregation-induced emission body TPE-LAN prepared in Example 1;

[0025] Figure 2 It is a scanning electron microscope picture of the AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property prepared in Example 1 under different receiving voltages, wherein A, B, C, D and E respectively represent the scanning electron microscope pictures of the nanofiber membrane under voltages of 8kV, 10kV, 12kV, 14kV and 16kV;

[0026] Figure 3 It is a fish freshness monitoring real object picture of the AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property prepared in Example 1;

[0027] Figure 4 It is a fish freshness monitoring real object picture of the AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property prepared in Comparative Example 2;

[0028] Figure 5 It is a fish freshness monitoring real object picture of the AIEgen doped PLA electrostatic spinning nanofiber membrane with pH fluorescence color change property prepared in Example 2;

[0029] Figure 6The AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescent color change property prepared in Example 3 is used for fish freshness monitoring.

[0030] Figure 7 The fluorescence microscope image of the TPE-LAN synthesized in Example 1 as a filler dispersed in rubber. DETAILED DESCRIPTION

[0031] The application is further described below in conjunction with examples.

[0032] Example 1

[0033] The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescent color change property described in Example 1 is composed of the following steps:

[0034] (1) 4-(1,2,2-triphenylvinyl)benzaldehyde (0.100 g) and 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione (0.100 g) are respectively dissolved in ethanol (50 mL), and the two mixed solutions are respectively subjected to ultrasonic treatment until completely dissolved, then the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde is added dropwise to the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione for reaction, and refluxed at 78°C under nitrogen atmosphere for 16 hours. The obtained solution is placed in an environment at 25°C for 24 hours, and then filtered to obtain 5-(4-((4-(1,2,2-triphenylvinyl)benzylidene)amino)isoindolin-2-yl)piperidin-2-one (TPE-LAN) in yellow solid powder. Figure 1 The nuclear magnetic hydrogen spectrum shown proves that the TPE-LAN aggregation-induced emission body is successfully synthesized.

[0035] (2) Polylactic acid (3.47 g) is dissolved in dichloromethane solvent (20 mL) for stirring reaction to prepare a PLA solution, and TPE-LAN (0.0313 g) is dissolved in N,N-dimethylformamide solvent (5 mL) for stirring reaction to prepare a TPE-LAN solution; the stirring speed of the stirring reaction is 800 r / min, the stirring reaction temperature is room temperature, and the stirring reaction time is 1.5 hours.

[0036] (3) The PLA solution prepared in step (2) is mixed evenly with the TPE-LAN ​​solution prepared in step (2). The volume ratio of TPE-LAN ​​solution to polylactic acid solution is 1:4. Then, the mixed solution is electrospun using an electrospinning instrument. Finally, it is dried at a temperature of 70°C to prepare an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties. The parameters of the electrospinning technology are a voltage of 12kV, a flow rate of 2mL / h, a receiving distance of 20cm, and a cylinder rotation speed of 100r / min. Figure 2 Scanning electron microscope (SEM) images of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties prepared in Example 1 at different receiving voltages. Among them, at voltages below 12 kV (… Figure 2 In cases A and B, the fiber diameter is too large due to uneven fiber stretching caused by a weak electric field; when the voltage is higher than 12kV ( Figure 2 The electric fields (D and E) in the process are relatively strong. Excessive voltage will increase the number of polymer droplets ejected per unit time, resulting in uneven fiber stretching and excessively large fiber diameter. Therefore, 12kV is adopted as the optimal process parameter.

[0037] When the prepared pH-fluorescent color-changing fiber membrane is used to monitor the freshness of fish, a petri dish (60 mm in diameter) is used. A freshly cut fish sample (approximately 20 g) is placed inside the dish, and an AIEgen-doped PLA electrospun nanofiber membrane (2 × 2 cm in size) with pH-fluorescent color-changing properties is placed on the surface of the sample. The petri dish is sealed and placed in a constant temperature environment (25°C to accelerate spoilage). The fiber membrane area is irradiated with a UV flashlight (365 nm), and the fluorescence color change is recorded daily. Figure 3 As shown, when the fish meat was left for less than 12 hours, the pH value remained unchanged at 6.0 because the fish meat was not rotten. Therefore, the fluorescence color of the film remained bright yellow-green. As the storage time increased, bacteria decomposed the proteins and other nitrogenous substances (such as amino acids) in the fish meat, leading to an increase in pH. Under alkaline conditions, the ring-opening reaction of the o-dicarboximide bond in TPE-LAN ​​prevented the intramolecular charge transfer process from TPE to LAN, resulting in a significant decrease in the film fluorescence intensity. When the storage time reached 48 hours, the fish meat began to rot, and the pH value measured by a puncture pH meter was 7.1. At this point, the film only showed a weak yellow-green fluorescence. When the storage time continued to increase to 60 hours, the fish meat showed obvious signs of rot, and the pH value measured was 7.8. At this point, the film fluorescence was completely quenched, showing only the milky white color of the film itself. Moreover, compared with fish meat that begins to rot after 24 hours under normal circumstances, fish meat with the nanofiber membrane fixed to it only begins to rot after 48 hours, and the rot time is significantly delayed, indicating that the fiber membrane has a significant antibacterial effect.

[0038] Based on the aggregation-induced emission (AIE) fluorescence behavior of TPE-LAN, it can be used as a fluorescently labeled filler for in-situ non-destructive testing of rubber. Combined with fluorescence microscopy, the three-dimensional dispersion morphology of the fluorescently labeled filler in the polymer matrix can be accurately characterized, such as... Figure 7 As shown.

[0039] Example 2

[0040] The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties described in Example 2 consists of the following steps:

[0041] (1) 0.0835 g of 4-(1,2,2-triphenylvinyl)benzaldehyde and 0.100 g of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione were dissolved in 50 mL of ethanol. The two mixed solutions were sonicated until completely dissolved. Then, the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde was added dropwise to the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione and refluxed at 78 °C for 17 hours under a nitrogen atmosphere. The resulting solution was placed at 25 °C for 24 hours and filtered to obtain a yellow solid powder of 5-(4-(4-(1,2,2-triphenylyl)benzylmethyl)amino)isoindololin-2-yl)piperidin-2-one (TPE-LAN).

[0042] (2) Polylactic acid (3.47g) was dissolved in dichloromethane solvent (20mL) and stirred to prepare PLA solution. TPE-LAN ​​(0.0156g) was dissolved in N,N-dimethylformamide solvent (5mL) and stirred to prepare TPE-LAN ​​solution. The stirring speed of the stirring reaction was 800r / min, the stirring temperature was room temperature, and the stirring time was 1 hour.

[0043] (3) The PLA solution prepared in step (2) is mixed evenly with the TPE-LAN ​​solution prepared in step (2). The volume ratio of TPE-LAN ​​solution to polylactic acid solution is 1:4. Then, the mixed solution is electrospun using an electrospinning instrument. Finally, it is dried at a temperature of 70°C to prepare an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties. The parameters of the electrospinning technology are a voltage of 12kV, a flow rate of 2mL / h, a receiving distance of 20cm, and a cylinder rotation speed of 100r / min. Figure 5 This is a photograph of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties, prepared in Example 2, used for monitoring the freshness of fish meat. Figure 5As shown, when the fish meat was left for less than 12 hours, the pH value was 6.0 because the fish meat had not yet rotted, and therefore the fluorescence color of the film remained unchanged, still a bright yellow-green. As the storage time of the fish meat increased, bacteria decomposed the proteins and other nitrogenous substances (such as amino acids) in the fish meat, leading to an increase in pH value and a significant decrease in the fluorescence intensity of the film. When the storage time reached 48 hours, the fish meat began to rot, and the pH value measured by a puncture pH meter was 7.1. At this time, the film only showed a weak yellow-green fluorescence. When the storage time of the fish meat continued to increase to 60 hours, the fish meat showed obvious signs of rot, and the pH value measured was 7.8. At this time, the fluorescence of the film was completely quenched, showing only the milky white color of the film itself. Moreover, compared with the fish meat under normal conditions that begins to rot after 24 hours, the fish meat with this nanofiber membrane fixed to it only began to rot after 48 hours, a significantly delayed rot time, indicating that the fiber membrane has a significant antibacterial effect.

[0044] Based on the aggregation-induced emission (AIE) fluorescence behavior of TPE-LAN, it can be used as a fluorescent labeling filler for in-situ non-destructive testing of rubber. Combined with fluorescence microscopy, the three-dimensional dispersion morphology of the fluorescent labeling filler in the polymer matrix can be accurately characterized.

[0045] Example 3

[0046] The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties described in Example 3 consists of the following steps:

[0047] (1) 0.104 g of 4-(1,2,2-triphenylvinyl)benzaldehyde and 0.100 g of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione were dissolved in 50 mL of ethanol. The two mixed solutions were sonicated until completely dissolved. Then, the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde was added dropwise to the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione and refluxed at 78 °C for 18 hours under a nitrogen atmosphere. The resulting solution was placed at 25 °C for 24 hours and filtered to obtain a yellow solid powder of 5-(4-(4-(1,2,2-triphenylyl)benzylmethyl)amino)isoindololin-2-yl)piperidin-2-one (TPE-LAN).

[0048] (2) Polylactic acid (3.47g) was dissolved in dichloromethane solvent (20mL) and stirred to prepare PLA solution. TPE-LAN ​​(0.0469g) was dissolved in N,N-dimethylformamide solvent (5mL) and stirred to prepare TPE-LAN ​​solution. The stirring speed of the stirring reaction was 800r / min, the stirring temperature was room temperature, and the stirring time was 2 hours.

[0049] (3) The PLA solution prepared in step (2) is mechanically mixed with the TPE-LAN ​​solution prepared in step (2) in a volume ratio of 1:4. Then, the mixed solution is electrospun using an electrospinning instrument and dried at 70°C to obtain an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties. The parameters of the electrospinning technology are a receiving voltage of 12kV, a flow rate of 2mL / h, a receiving distance of 20cm, and a cylinder rotation speed of 100r / min. Figure 6 This is a photograph of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties, prepared in Example 3, used for monitoring the freshness of fish meat. Figure 6 As shown, when the fish meat was left for less than 12 hours, the pH value was 6.0 because the fish meat had not yet rotted, and therefore the fluorescence color of the film remained unchanged, still a bright yellow-green. As the storage time of the fish meat increased, bacteria decomposed the proteins and other nitrogenous substances (such as amino acids) in the fish meat, leading to an increase in pH value and a significant decrease in the fluorescence intensity of the film. When the storage time reached 48 hours, the fish meat began to rot, and the pH value measured by a puncture pH meter was 7.1. At this time, the film only showed a weak yellow-green fluorescence. When the storage time of the fish meat continued to increase to 60 hours, the fish meat showed obvious signs of rot, and the pH value measured was 7.8. At this time, the fluorescence of the film was completely quenched, showing only the milky white color of the film itself. Moreover, compared with the fish meat under normal conditions that begins to rot after 24 hours, the fish meat with this nanofiber membrane fixed to it only began to rot after 48 hours, a significantly delayed rot time, indicating that the fiber membrane has a significant antibacterial effect.

[0050] Based on the aggregation-induced emission (AIE) fluorescence behavior of TPE-LAN, it can be used as a fluorescent labeling filler for in-situ non-destructive testing of rubber. Combined with fluorescence microscopy, the three-dimensional dispersion morphology of the fluorescent labeling filler in the polymer matrix can be accurately characterized.

[0051] Comparative Example 1

[0052] The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties described in Comparative Example 1 consists of the following steps:

[0053] (1) 0.100 g of 4-(1,2,2-triphenylvinyl)benzaldehyde and 0.100 g of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione were dissolved in 50 mL of ethanol. The two mixed solutions were sonicated until completely dissolved. The anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde was then added dropwise to the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione and refluxed at 78 °C for 16 hours under a nitrogen atmosphere. The resulting solution was placed at 25 °C for 24 hours and filtered to obtain a yellow solid powder of 5-(4-(4-(1,2,2-triphenylyl)benzylmethyl)amino)isoindololin-2-yl)piperidin-2-one (TPE-LAN).

[0054] (2) Dissolve polylactic acid (PLA) (3.47 g) in a mixed solvent consisting of 20 mL of dichloromethane and 5 mL of N,N-dimethylformamide and stir to prepare PLA solution.

[0055] (3) The PLA solution prepared in step (2) was mixed evenly with the TPE-LAN ​​powder (0.0313 g) prepared in step (1). It was found that the TPE-LAN ​​product dissolved slowly in the PLA solution, resulting in the formation of a gel in the PLA solution. Due to the formation of the gel, it was impossible to prepare a fiber membrane using electrospinning technology, and thus subsequent experiments could not be carried out.

[0056] In Comparative Example 1, when TPE-LAN ​​solid powder was mixed with PLA solution, the product TPE-LAN ​​was in solid form, while PLA was in solution. When the added product TPE-LAN ​​was in solid form, PLA dissolved in a mixed solvent composed of dichloromethane and N,N-dimethylformamide easily formed hydrogen bonds, thereby forming a network structure. This resulted in significant steric hindrance, making it difficult to disperse TPE-LAN. PLA formed a gel and could not form a stable electrospinning solution, thus making it impossible to prepare fiber membranes and therefore unsuitable for fish freshness detection.

[0057] Comparative Example 2

[0058] The preparation method of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties described in Comparative Example 2 consists of the following steps:

[0059] (1) Dissolve 0.324 g of 1-(4-(1,2,2-triphenylvinyl)benzyl)hydrazine and 0.200 g of acetylferrocene in 50 mL of ethanol. Sonicate the two mixed solutions until completely dissolved. Then add the anhydrous ethanol solution of 1-(4-(1,2,2-triphenylvinyl)benzyl)hydrazine dropwise to the anhydrous ethanol solution of acetylferrocene and reflux at 78 °C for 16 hours under a nitrogen atmosphere. Place the resulting solution at 25 °C for 24 hours and filter to obtain a light brown solid powder of (1E)-1-((1-(4-(1,2,2-triphenylvinyl)benzyl)hydrazine-1-ethyl)ferrocene (FcMe-TPE).

[0060] (2) Polylactic acid (3.47g) was dissolved in dichloromethane solvent (20mL) and stirred to prepare PLA solution. FcMe-TPE (0.0313g) was dissolved in N,N-dimethylformamide solvent (5mL) and stirred to prepare FcMe-TPE solution. The stirring speed of the stirring reaction was 800r / min, the stirring temperature was room temperature, and the stirring time was 2 hours.

[0061] (3) The PLA solution prepared in step (2) is mechanically mixed with the FcMe-TPE solution prepared in step (2) in a uniform manner. The volume ratio of FcMe-TPE solution to polylactic acid solution is 1:4. Then, the mixed solution is electrospun using an electrospinning instrument and finally dried at a temperature of 70°C to prepare an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties. The parameters of the electrospinning technology are a receiving voltage of 12kV, a flow rate of 2mL / h, a receiving distance of 20cm, and a cylinder rotation speed of 100r / min.

[0062] Although Comparative Example 2 has AIE properties, it lacks a lenalidomide structure, resulting in extremely low antibacterial performance of the electrospun nanofiber membrane and rapid spoilage of the fish meat. Figure 4 This is a photograph of the AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties, prepared in Comparative Example 2, used for monitoring the freshness of fish meat. The test was conducted at 25°C. Figure 4As shown, due to the change in the fluorescent molecule structure in Comparative Example 2, the fluorescence intensity of the obtained nanofiber membrane was weak, showing only a dark yellow color under ultraviolet light. Because the fluorescent molecules in the fiber membrane lacked the lenalidomide structure, the antibacterial performance was significantly weakened. When the fish meat was left for only 24 hours, it had already rotted noticeably, and its pH value was measured to be 7.0 by a puncture pH meter. The fluorescence color of the membrane also changed to some extent, from dark yellow to a weak yellowish-green, but the color change was not significant compared to Example 1. When the fish meat was left for 60 hours, it was almost completely rotten, and its pH value reached 8.0. However, the fluorescence color of the membrane still did not change significantly, showing a weak yellowish-green fluorescence under ultraviolet light. In other words, the fiber membrane prepared using Comparative Example 2 had no significant inhibitory effect on fish meat rot, and the fluorescence color was not sensitive enough to pH.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties, characterized in that: It consists of the following steps: (1) 4-(1,2,2-triphenylvinyl)benzaldehyde and 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidin-2,6-dione were reacted in anhydrous ethanol to synthesize aggregation-induced luminescent material 5-(4-((4-(1,2,2-triphenylyl)benzylmethyl)amino)isoindololin-2-yl)piperidin-2-one, i.e., TPE-LAN; (2) Polylactic acid was dissolved in dichloromethane solvent and stirred to prepare a polylactic acid solution. TPE-LAN ​​was dissolved in N,N-dimethylformamide solvent and stirred to prepare a TPE-LAN ​​solution. (3) Mix the polylactic acid solution prepared in step (2) with the TPE-LAN ​​solution evenly, then use an electrospinning instrument to electrospin the resulting mixed solution, and finally dry it to prepare an AIEgen-doped PLA electrospun nanofiber membrane with pH fluorescence color-changing properties. In step (1), the reaction conditions are: reflux at 78°C for 16-18 hours under a nitrogen atmosphere, then place the resulting solution at 25°C for 24 hours, filter after the reaction is complete, and prepare 5-(4-((4-(1,2,2-tristyryl)benzylmethyl)amino)isoindololin-2-yl)piperidin-2-one; In step (1), 4-(1,2,2-triphenylvinyl)benzaldehyde and 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione were dissolved in anhydrous ethanol, respectively. The two mixed solutions were then sonicated until completely dissolved. The anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde was then added dropwise to the anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione for reaction. The mass-to-volume ratio of 4-(1,2,2-triphenylvinyl)benzaldehyde to anhydrous ethanol in the anhydrous ethanol solution of 4-(1,2,2-triphenylvinyl)benzaldehyde was 0.0835–0.

104. 50, in g / mL, refers to the mass-to-volume ratio of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione to anhydrous ethanol in an anhydrous ethanol solution of 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione to anhydrous ethanol of 0.100 : 50, in g / mL.

2. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: In step (1), the molar ratio of 4-(1,2,2-triphenylvinyl)benzaldehyde to 3-(7-amino-3-oxo-1H-isoindol-2-yl)piperidine-2,6-dione is 0.60-0.75 :

1.

3. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: In step (2), the mass-to-volume ratio of polylactic acid (PLA) to dichloromethane is 3.47:20, with units of g / mL.

4. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: In step (2), the mass-to-volume ratio of TPE-LAN ​​to N,N-dimethylformamide is 0.0156-0.0469:5, with units of g / mL.

5. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: The stirring speed of the stirring reaction in step (2) is 800 r / min, the stirring temperature is room temperature, and the stirring time is 1-2 hours.

6. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: In step (3), the volume ratio of TPE-LAN ​​solution to polylactic acid solution is 1:

4.

7. The method for preparing AIEgen-doped PLA electrospun nanofiber membranes with pH fluorescence color-changing properties according to claim 1, characterized in that: In step (3), the electrospinning parameters are a voltage of 12kV, a flow rate of 2mL / h, a receiving distance of 20cm, and a cylinder rotation speed of 100r / min.

Images