Antibacterial and hydrophilic dual-functional ionic liquid double-layer membrane as well as preparation method and application thereof

Abstract

The invention discloses an antibacterial and hydrophilic dual-functional ionic liquid double-layer membrane as well as a preparation method and application thereof. According to the double-layer film, corn starch (ST) and polyvinyl alcohol (PVA) serve as substrates, and natural dye alizarin (AL) is mixed to serve as a hydrophilic layer; chitosan (CS), corn protein (Zein) and vanillin (VA) serve as a supporting layer; meanwhile, the ionic liquid is doped, so that the double-layer film is endowed with a fresh-keeping function and sensitive detection capability, the limitation of a single detection function is broken through, and a new thought is provided for food safety.

Description

Technical Field

[0001] This invention relates to an antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane and its preparation method, as well as its application in the preservation of food and the rapid, sensitive, and portable detection of biogenic amines. Background Technology

[0002] In recent years, traditional detection methods for aquatic products have faced limitations such as destructive sampling and time lag due to the spoilage and accumulation of toxic biogenic amines caused by the proliferation of microorganisms during storage and distribution. To address this, embedding pH-sensitive indicators into a biopolymer matrix can create intelligent packaging films for non-destructive, real-time freshness detection. To extend the shelf life of aquatic products, some studies have incorporated various antimicrobial agents to impart antimicrobial properties to sensors. However, the release of some inherently acidic or alkaline antimicrobial agents (such as potassium sorbate) can alter the environmental pH, superimposing or masking the effects of target biogenic amines and affecting the accuracy of target analyte detection. It is noteworthy that antimicrobial substances typically require loading onto specific carriers, leading to a decline in the material's basic properties and impacting the reliability and lifespan of practical applications. Therefore, it is necessary to find a suitable antimicrobial substance that can meet the rapid detection requirements of aquatic product freshness while ensuring membrane performance.

[0003] Ionic liquids, with their high thermal stability and chemical designability, are known as "designer solvents." They can form hydrogen bonds and electrostatic interactions with membrane material molecules, resulting in tighter molecular chains and enhanced mechanical strength. Furthermore, the presence of positive ions in ionic liquids gives them an affinity for negatively charged bacterial cell membranes. Modifying bilayer membranes with ionic liquids can enhance resistance to bacterial cells, achieving highly efficient sterilization. In addition, amines volatilized from aquatic products are hydrophilic; increasing the hydrophilicity of the bilayer membrane will facilitate the capture of target analytes, improving detection sensitivity.

[0004] In this invention, the hydrophilic layer, through the introduction of an ionic liquid, forms hydrogen bonds and electrostatic interactions with the membrane material molecules, resulting in a tighter molecular chain connection, enhanced mechanical strength, and a transformation from brittle to tough. Due to the excellent water solubility of the imidazole ionic liquid, the hydrophilicity of the bilayer membrane is enhanced, significantly increasing the capture and diffusion efficiency of polar NH3 molecules on the membrane surface. This, combined with the alizarin (AL) indicator loaded within the membrane, ensures sufficient contact with NH3, improving detection sensitivity. The antibacterial layer, through the introduction of an ionic liquid C... 16 MImCl forms a clear inhibition zone against Staphylococcus aureus, demonstrating that the ionic liquid bilayer membrane possesses certain antibacterial properties. Therefore, this smart label overcomes the limitations of single-function applications, enabling both food sample preservation and visual detection. Summary of the Invention

[0005] This invention discloses an antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane, its preparation method, and its applications. The bilayer membrane of this invention uses corn starch (ST) and polyvinyl alcohol (PVA) as a base, mixed with the natural dye alizarin (AL) as a hydrophilic layer; chitosan (CS), zein, and vanillin (VA) form the support layer; and simultaneously incorporates an ionic liquid, endowing the bilayer membrane with preservation function and sensitive detection capability, overcoming the limitations of single detection functions and providing a new approach to food safety.

[0006] Based on the fact that hydrophilicity is beneficial for improving detection sensitivity, 1-hexadecyl-3-methylimidazolium chloride C 16 MImCl(IL4) ionic liquid exhibits optimal detection performance and demonstrates excellent sensitivity. This invention preferably uses C... 16 MImCl ionic liquid is a functionalized ionic liquid applied to the preservation of aquatic products and the rapid, sensitive quantitative detection of biogenic amines. Utilizing the irreversible bactericidal effect of long-chain alkyl groups in the ionic liquid on bacterial cell membranes, the ionic liquid bilayer membrane can extend the shelf life of aquatic products. Furthermore, the amines volatilized from aquatic products are hydrophilic; by improving the hydrophilicity of the membrane, the capture of target substances by the bilayer membrane is enhanced, improving detection sensitivity and enabling non-destructive on-site spoilage monitoring. Therefore, the bilayer membrane sensor of this invention is a smart tag that combines detection and antibacterial properties, which is of great significance for the real-time monitoring of the freshness and preservation of aquatic products.

[0007] The technical solution of the present invention is as follows: An antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane was prepared by the following method: (1) Preparation of hydrophilic film-forming solution Corn starch and polyvinyl alcohol are dissolved in deionized water, and glycerol is added and mixed (preferably stirred for 4 h in an 80 ℃ water bath) to obtain ST-PVA mixture. Then, an ethanol solution of alizarin is added and mixed (preferably stirred for 30 min) to obtain ST-PVA-AL mixture. Subsequently, an ionic liquid is added and mixed (preferably stirred for 30 min) to obtain ST-PVA-AL-IL film-forming solution. In the preferred ST-PVA mixture, the mass fraction of corn starch is 1%, the mass fraction of polyvinyl alcohol is 4%, the mass fraction of glycerol is 0.3%, and the balance is deionized water; In the preferred ethanol solution of alizarin, the concentration of alizarin is 10. -2 M; The preferred volume ratio of alizarin ethanol solution to ST-PVA mixture is 1:10; The preferred volume molar ratio of ST-PVA-AL mixture to ionic liquid is 50:1, mL / mmol; Ionic liquids are selected from one of IL1 to IL5:

[0008] (2) Preparation of antibacterial film-forming solution

[0009] Chitosan was dissolved in acetic acid solution (preferably stirred at 50 °C for 1.5 h) to obtain a chitosan solution; corn protein was dissolved in ethanol solution (preferably stirred at 25 °C for 30 min) to obtain a corn protein solution; at room temperature, the chitosan solution and corn protein solution were mixed, and vanillin and glycerol were added to obtain a CS-ZN-VA mixture, and ionic liquid IL4 was added and mixed (preferably stirred for 30 min) to obtain a CS-ZN-VA-IL4 film-forming solution; The preferred mass-to-volume ratio of chitosan to acetic acid solution is 1:50, g / mL; the acetic acid solution is an aqueous solution of 1.0 wt% acetic acid. The preferred mass-to-volume ratio of corn protein to ethanol solution is 1:50, g / mL; the ethanol solution is an aqueous solution of 80wt% ethanol. The preferred volume ratio of chitosan solution to corn protein solution is 1:1; The preferred CS-ZN-VA mixture contains 2 wt% vanillin and 2 wt% glycerol. The preferred volume molar ratio of the CS-ZN-VA mixture to the ionic liquid IL4 is 50:1, mL / mmol; (3) Preparation of bilayer membrane Take the CS-ZN-VA-IL4 film-forming solution obtained in step (2) and pour it into a petri dish. After drying (preferably in a 40 ℃ oven for 8 h), an antibacterial layer (also a support layer) is obtained. The ST-PVA-AL-IL film-forming solution obtained in step (1) is poured onto the antibacterial layer and dried (preferably at 25 ℃ for 48 h) to obtain a double-layer film. The preferred volume ratio of CS-ZN-VA-IL4 film-forming solution to ST-PVA-AL-IL film-forming solution is 5:3.

[0010] The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane described in this invention can be used for food preservation and rapid, sensitive, and portable detection of biogenic amines.

[0011] The specific testing methods are as follows: (1) Determination of antibacterial activity of the antibacterial layer CS-ZN-VA-IL4 Antimicrobial activity against Staphylococcus aureus was tested on CS-ZN-VA membranes and CS-ZN-VA-IL4 layers without ionic liquids. Inhibition zones were recorded to assess antimicrobial activity. Prior to testing, the membrane samples were sterilized by high-temperature, high-pressure steam sterilization (121℃, 20 min). 6A CFU / mL bacterial suspension was inoculated onto a nutrient agar plate. Sample films were cut into 6 mm circles, placed on the nutrient agar plate, and incubated at 37°C for 48 h. The diameter of the inhibition zone around the film was recorded. The experiment was conducted in three groups. Finally, the diameter of the inhibition zone was photographed to assess antibacterial activity.

[0012] (2) Ammonia gas comparison experiment

[0013] When the CS-ZN-VA / ST-PVA-AL bilayer film without ionic liquid and the CS-ZN-VA-IL4 / ST-PVA-AL-IL bilayer film with ionic liquid were exposed to the same concentration of pure ammonia gas, they were photographed under the same light using the same equipment, the RGB values ​​were extracted, the ΔED value was calculated, and the comparison was performed at fixed points on the color wheel.

[0014] (3) Real sample testing

[0015] Live shrimp were transported to the laboratory via freezing within 30 minutes and stored at -16℃ to ensure freshness. Shrimp of similar size and volume were randomly selected and divided into three groups, which were placed in environments of 25℃, 4℃, and -16℃ respectively. A 1 cm × 3 cm double-layer smart tag was cut and placed in a petri dish of shrimp, sealed with plastic wrap, and the color change of the smart tag and the freshness of the shrimp were observed within a time range of 0 to 5 days. The images were photographed and recorded. Based on the images taken by the smartphone, the RGB extraction function of PowerPoint was used to record the values, and the color difference of the film was calculated according to equation (1).

[0016] (1)

[0017] Where x is the number of storage days, R X G X and B X The values ​​are the film color characteristic values ​​at different storage times, where R0, G0, and B0 are the original color characteristic values ​​of the film. The color difference value ΔED of the film is calculated according to the equation. Simultaneously, at different times, the total volatile basic nitrogen (TVB-N) of shrimp samples was measured according to the Chinese standard GB 5009.228-2016 to verify the detection results of the smart tag. The shrimp meat was deshelled, peeled, and headed; the edible part was taken, minced, and stirred evenly. 5 g of the sample was weighed, accurately added to 50.0 mL of deionized water, shaken for 10 min to ensure even dispersion, and soaked for 30 min before filtration as a reserve solution. Subsequently, the determination was performed using the titration method according to the national standard, with three parallel experiments set up.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention successfully synthesized an ionic liquid bilayer membrane and applied it to the rapid, sensitive, and portable detection of food (e.g., aquatic products) preservation and freshness. In particular, the screened IL4 (C 16 MImCl), after incorporating this ionic liquid into the bilayer membrane, endows the bilayer membrane with antibacterial properties and higher detection sensitivity, while simultaneously improving its mechanical properties and antioxidant capacity. 16 The ionic liquid bilayer membrane made by incorporating MImCl into the bilayer membrane provides a new approach for portable, real-time detection of aquatic products.

[0019] In this invention, the hydrophilic layer incorporates an ionic liquid (IL1~IL5) to form hydrogen bonds and electrostatic interactions with the membrane material molecules, resulting in tighter molecular chain connections, enhanced mechanical strength, and a transformation from brittle to tough. Due to the excellent water solubility of the imidazole ionic liquid, the hydrophilicity of the bilayer membrane is enhanced, significantly increasing the capture and diffusion efficiency of polar NH3 molecules on the membrane surface. This, combined with the alizarin (AL) indicator loaded within the membrane, ensures sufficient contact with NH3, improving detection sensitivity. The antibacterial layer incorporates the ionic liquid IL4 (C... 16 The ionic liquid bilayer membrane (MImCl) formed a clear inhibition zone against Staphylococcus aureus, demonstrating its antibacterial properties. Therefore, this smart label overcomes the limitations of single-function applications, enabling both food sample preservation and visual detection.

[0020] This invention employs a multi-effect strategy using ionic liquids, enabling the identification of food freshness through smart label indicators. Simultaneously, the double-layer membrane possesses antibacterial properties, extending the shelf life of food. Furthermore, the membrane's antioxidant and mechanical properties are simultaneously enhanced, demonstrating promising applications in practical food preservation and freshness detection. Attached Figure Description

[0021] Figure 1 Comparison of contact angles of ST-PVA and its modified form with ionic liquids IL1~IL5 in Example 2.

[0022] Figure 2 Comparison images of the bilayer membrane without ionic liquid and the bilayer membrane with ionic liquid before and after the response to NH3 in Example 3, and the color gamut of the extracted RGB values.

[0023] Figure 3 Stress-strain curves of six thin films in Example 4.

[0024] Figure 4 Comparison of tensile strength (MPa) and elongation at break (%) of the six films in Example 4.

[0025] Figure 5Image showing the inhibition diameter of CS-ZN-VA and CS-ZN-VA-IL4 against Staphylococcus aureus in Example 5.

[0026] Figure 6 Example 6: Comparison of the antioxidant properties of the hydrophilic layer ST-PVA and the antibacterial layer CS-ZN-VA before and after the incorporation of IL4.

[0027] Figure 7 In Example 7, visual detection images of shrimp were obtained from the CS-ZN-VA / ST-PVA-AL dual-layer smart tag at three temperature conditions: 25℃, 4℃, and -16℃.

[0028] Figure 8 Example 7: The relationship between TVB-N values, color difference values ​​ΔED, and storage time of shrimp samples at different temperatures.

[0029] Figure 9 : Schematic diagram of the antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane of the present invention and its effect. Detailed Implementation

[0030] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] In the following embodiments, Chitosan (CS, low viscosity < 200 mPa·s), zein (from Corn), vanillin (AR, 99%), glycerol (Glycerol, AR, 99%), polyvinyl alcohol (Mw ~ 67,000), sodium alginate (AR, 90%), alizarin (AR, 97%), and 1-hexadecyl-3-methylimidazolium chloride (96.0%) were purchased from Aladdin Reagent Co., Ltd.; nisin (900 IU / mg), 2,2-biphenyl-1-picrylhydrazyl (DPPH, 99%), 2,2''-hydrazine-bis(3-ethylbenzothiazoline-6-sulfonic acid)diamine (ABTS, 99% biotechnology grade), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (99%), and tetrahydroxymethylphosphorus chloride (Ca. 80% in) Water, 1-carboxymethyl-3-methylimidazolium chloride (98%), and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6], 97%) were purchased from Ron Reagent Co., Ltd.; corn starch (98%) was purchased from Shanghai Yuanye Biotechnology Co., Ltd.; Staphylococcus aureus (No.: ATCC29213); and aquatic products were purchased from the local market.

[0032] Example 1

[0033] Preparation of different types of membrane materials

[0034] Preparation of the hydrophilic layer ST-PVA for testing basic properties: 1 g corn starch and 4 g polyvinyl alcohol were dissolved in deionized water, and 0.3 g glycerol was added, bringing the total mass to 100 g. The mixture was stirred in an 80°C water bath for 4 h until the solution was homogeneous, yielding the ST-PVA film-forming solution. 5 mL of the ST-PVA film-forming solution was poured into an 80 mm petri dish and dried in a ventilated area at 25°C for 48 h to obtain ST-PVA.

[0035] The method for preparing a bilayer membrane without ionic liquid is as follows: Preparation of the antibacterial layer CS-ZN-VA film-forming solution: First, 1 g of chitosan (CS) was stirred and dissolved in 50 mL of acetic acid solution (1.0 wt%) at 50 °C for 1.5 h. Simultaneously, 1 g of zein was dissolved in 50 mL of ethanol (80 wt%) at 25 °C for 30 min. The prepared chitosan and zein solutions were mixed at room temperature. Then, vanillin (2 wt%) was added to the mixture, followed by glycerol (2 wt%) with continuous stirring to obtain the CS-ZN-VA film-forming solution.

[0036] Preparation of the hydrophilic layer ST-PVA-AL film-forming solution: Dissolve 1 g of corn starch and 4 g of polyvinyl alcohol in deionized water, add 0.3 g of glycerol, for a total mass of 100 g, and stir in an 80℃ water bath for 4 h until the solution is homogeneous to obtain the ST-PVA mixture. Take 20 mL of the ST-PA mixture and add 2 mL of alizarin ethanol solution (10... -2 (M AL solution), stir thoroughly for 30 min to obtain ST-PVA-AL film-forming solution.

[0037] Preparation of the bilayer membrane: 5 mL of CS-ZN-VA film-forming solution was poured into an 80 mm petri dish and dried in an oven at 40℃ for 8 h to obtain an antibacterial layer. Then, 3 mL of ST-PVA-AL film-forming solution was poured onto the antibacterial layer and dried at 25℃ for 48 h to obtain the bilayer membrane CS-ZN-VA / ST-PVA-AL.

[0038] The method for preparing ionic liquid bilayer films is as follows: Preparation of the hydrophilic layer ST-PVA-AL-IL film-forming solution: Take 50 mL of ST-PVA-AL film-forming solution and transfer it to a centrifuge tube. Add 1 mmol of 1-butyl-3-methylimidazolium hexafluorophosphate (IL1), 1-butyl-3-methylimidazolium di(trifluoromethanesulfonyl)imide (IL2), tetrahydroxymethylphosphoric acid (IL3), 1-hexadecyl-3-methylimidazolium chloride (IL4), and 1-carboxymethyl-3-methylimidazolium chloride (IL5). Stir for 30 min to obtain five film-forming solutions: ST-PVA-AL-IL1, ST-PVA-AL-IL2, ST-PVA-AL-IL3, ST-PVA-AL-IL4, and ST-PVA-AL-IL5.

[0039] Preparation of antibacterial layer CS-ZN-VA-IL4 film-forming solution: Take 50 mL of CS-ZN-VA film-forming solution and transfer it to a centrifuge tube. Add 1 mmol of 1-hexadecyl-3-methylimidazolium chloride (IL4) and stir for 30 min to obtain CS-ZN-VA-IL4 film-forming solution.

[0040] Preparation of ionic liquid bilayer membrane: 5 mL of CS-ZN-VA-IL4 film-forming solution was poured into an 80 mm petri dish and dried in an oven at 40 °C for 8 h to obtain an antibacterial layer. Then, 3 mL of ST-PVA-AL-IL film-forming solution was poured onto the antibacterial layer and dried at 25 °C for 48 h to obtain the ionic liquid bilayer membrane CS-ZN-VA-IL4 / ST-PVA-AL-IL.

[0041] Example 2

[0042] The specific steps for testing the hydrophilicity of ionic liquid membranes with hydrophilic layers include: Five ionic liquids were screened: (a) 1-butyl-3-methylimidazolium hexafluorophosphate, (b) 1-butyl-3-methylimidazolium di(trifluoromethanesulfonyl)imide, (c) tetrahydroxymethylphosphoric acid chloride, (d) 1-hexadecyl-3-methylimidazolium chloride, and (e) 1-carboxymethyl-3-methylimidazolium chloride. These were added to the ST-PVA film-forming solution to prepare the ST-PVA-IL layer. The hydrophilicity of the membrane was determined by measuring the contact angle between water and the membrane. The results are as follows: Figure 1 As shown.

[0043] Among them, IL4 (1-hexadecyl-3-methylimidazolium chloride) showed the most significant modification effect, reducing the membrane contact angle from 77.75° to 41.63°, a decrease of 46%. This demonstrates that long-alkyl chain imidazolium ionic liquids have a prominent entanglement effect on ammonia molecules, which will be beneficial for subsequent rapid detection.

[0044] Example 3

[0045] The specific steps for testing the sensitivity of ionic liquid bilayer membranes to ammonia include: When a CS-ZN-VA / ST-PVA-AL bilayer film without ionic liquid and a CS-ZN-VA-IL4 / ST-PVA-AL-IL4 bilayer film with ionic liquid were exposed to the same concentration of pure ammonia gas, they were photographed under the same light using the same equipment. RGB values ​​were extracted, ΔED values ​​were calculated, and the results were compared at fixed points on a color wheel. The results are as follows: Figure 2 As shown.

[0046] When both bilayer films were exposed to the same concentration of pure ammonia gas, the CS-ZN-VA-IL4 / ST-PVA-AL-IL4 bilayer film containing the ionic liquid exhibited a deeper color and a wider color difference gradient. Calculations showed that the color difference value (ΔED) of the film without the ionic liquid was 64.15, while the color difference value (ΔED) of the film containing the ionic liquid was 130.73, an increase of 103.79%. This is likely because the improved hydrophilicity of the film enhances the capture and diffusion efficiency of polar NH3 molecules on the film surface. Synergistically, the AL indicator loaded in the film can fully contact NH3, thereby accelerating the deprotonation color reaction process and improving detection sensitivity.

[0047] Example 4

[0048] The mechanical property testing of hydrophilic ionic liquid membranes includes the following specific steps: The tensile strength and elongation at break of the double-layer film were tested according to GB / T13022-91 "Test Method for Tensile Properties of Plastic Films". The film was cut into 1cm×4cm pieces with a utility knife, the thickness of the film was measured with a high-precision micrometer, and the length and width of the film were measured and recorded with a Guanglu digital vernier caliper.

[0049] After the basic hydrophilic layer ST-PVA is incorporated with ionic liquid, it generally undergoes a transition from brittle to ductile. Figure 3 In comparison, the modification effect of ST-PVA-IL4 was the most prominent, consistent with the improvement in hydrophilicity, indicating that IL4 had the best modification effect on the hydrophilic membrane matrix ST-PVA. Specifically, after modification with IL4, the tensile strength of ST-PVA decreased from 12.17 MPa to 6.70 MPa, while the elongation at break increased from 34.14% to 142.23%. Figure 4 ).

[0050] Example 5

[0051] The antibacterial performance test of the antibacterial layer ionic liquid membrane includes the following specific steps: Before testing, the film samples were sterilized by high temperature and high pressure (121℃, 20min) steam sterilization, containing 106 A CFU / mL bacterial suspension was inoculated onto a nutrient agar plate. Sample films were cut into 6mm circles, placed on the nutrient agar plate, and incubated at 37°C for 48 hours. The diameter of the inhibition zone around the film was recorded. The experiment was conducted in three groups. Finally, the diameter of the inhibition zone was photographed to assess antibacterial activity.

[0052] like Figure 5 As shown, the inhibition zone size test of the double membrane against Staphylococcus aureus was carried out. The comparison showed that after the addition of IL4, CS-ZN-VA-IL4 had an inhibition zone of 4 mm against Staphylococcus aureus, while the original CS-ZN-VA did not produce an inhibition zone.

[0053] Example 6

[0054] The specific steps for determining the antioxidant properties of ionic liquid bilayer membranes include: The antioxidant capacity of ST-PVA and CS-ZN-VA membranes was determined by DPPH and ABTS free radical scavenging experiments. 0.1 g of the membrane was immersed in 10 mL of deionized water for 1 h and centrifuged. DPPH solution (3 mL, 0.1 mM) was added to 1 mL of the supernatant, and the mixture was treated in the dark for 30 min. The absorbance of the reaction solution at 517 nm was measured.

[0055] DPPH free radical scavenging rate (%) = [1-(A1-A2) / A0)]×100 (2)

[0056] Where A1 is the absorbance value of the DPPH solution after the sample reaction; A2 is the absorbance value of the sample with anhydrous ethanol; and A0 is the absorbance value of the DPPH solution with distilled water.

[0057] The prepared ABTS mixture (7.4 mM ABTS + 2.6 mM potassium persulfate) was stored overnight. The ABTS mixture was diluted with distilled water to adjust its absorbance at 734 nm to 0.70 ± 0.01 before testing. The diluted ABTS mixture (3 mL) was mixed with the membrane supernatant or distilled water (1 mL). After incubation in the dark for 10 min, the absorbance at 734 nm was measured. The ABTS radical scavenging rate of the membrane was calculated according to formula (3).

[0058] ABTS free radical scavenging activity (%) = [1-(A a -A b ) / A c )]×100(3)

[0059] Among them, A a A represents the absorbance value of the ABTS mixture after the sample was added and reacted; bA represents the absorbance values ​​of distilled water and the sample. c The absorbance value is for a mixture of ABTS and distilled water.

[0060] like Figure 6 As shown, the ABTS radical scavenging rate of the ST-PVA hydrophilic layer increased from 34.80% to 82.95% and the DPPH radical scavenging rate increased from 61.38% to 87.41% before and after the incorporation of ionic liquid; the ABTS radical scavenging rate of the CS-ZN-VA antibacterial layer increased from 26.11% to 48.12% and the DPPH radical scavenging rate increased from 60.47% to 74.52% before and after the incorporation of ionic liquid.

[0061] Example 7

[0062] Take a 1cm×3cm double-layer smart tag and place it in a shrimp culture dish. Seal it with plastic wrap and observe the color change of the smart tag and the freshness of the shrimp within a time range of 0-5 days. Take pictures and record the data. Based on the pictures taken by the smartphone, import them into the computer and use the RGB extraction function of PowerPoint to record the values. Calculate the color difference of the film according to equation (1).

[0063] (1)

[0064] Where x is the number of storage days, R X G X and B X The values ​​are the film color characteristic values ​​for different storage times, where R0, G0, and B0 are the original color characteristic values ​​of the film. The color difference value ΔED of the film is calculated according to the equation.

[0065] The results are as follows Figure 7 , Figure 8 As shown, the double membrane was originally pale yellow; when the shrimp showed slight spoilage but remained within the edible range, it turned dark yellow; when the shrimp samples were spoiled and inedible, the double membrane turned reddish-brown. The above analysis demonstrates that the CS-ZN-VA / ST-PVA-AL sensor can be used to detect the freshness of fresh shrimp, enabling real-time and visual freshness detection.

Claims

1. A bifunctional ionic liquid bilayer membrane with antibacterial and hydrophilic properties, characterized in that, It is prepared according to the following method: (1) Preparation of hydrophilic film-forming solution Corn starch and polyvinyl alcohol were dissolved in deionized water, and glycerol was added and mixed to obtain ST-PVA mixture. Then, an ethanol solution of alizarin was added and mixed to obtain ST-PVA-AL mixture. Finally, an ionic liquid was added and mixed to obtain ST-PVA-AL-IL film-forming solution. Ionic liquids are selected from one of IL1 to IL5: (2) Preparation of antibacterial film-forming solution Chitosan was dissolved in acetic acid solution to obtain chitosan solution; corn protein was dissolved in ethanol solution to obtain corn protein solution; at room temperature, chitosan solution and corn protein solution were mixed, vanillin and glycerol were added to obtain CS-ZN-VA mixture, ionic liquid IL4 was added and mixed to obtain CS-ZN-VA-IL4 film-forming solution; (3) Preparation of bilayer membrane Pour the CS-ZN-VA-IL4 film-forming solution obtained in step (2) into a culture dish, dry it to obtain an antibacterial layer, pour the ST-PVA-AL-IL film-forming solution obtained in step (1) onto the antibacterial layer, dry it to obtain a double-layer membrane.

2. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (1), the mass fraction of corn starch in the ST-PVA mixture is 1%, the mass fraction of polyvinyl alcohol is 4%, the mass fraction of glycerol is 0.3%, and the remainder is deionized water.

3. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, Step (1) In the ethanol solution of alizarin, the concentration of alizarin is 10. -2 The volume ratio of the ethanol solution of alizarin to the ST-PVA mixture is 1:

10.

4. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (1), the volume molar ratio of the ST-PVA-AL mixture to the ionic liquid is 50:1, mL / mmol.

5. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (2), the mass-to-volume ratio of chitosan to acetic acid solution is 1:50, g / mL; the acetic acid solution is an aqueous solution of 1.0 wt% acetic acid; the mass-to-volume ratio of corn protein to ethanol solution is 1:50, g / mL; the ethanol solution is an aqueous solution of 80 wt% ethanol; and the volume ratio of chitosan solution to corn protein solution is 1:

1.

6. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (2), the CS-ZN-VA mixture contains 2 wt% vanillin and 2 wt% glycerol.

7. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (2), the volume molar ratio of the CS-ZN-VA mixture to the ionic liquid IL4 is 50:1, mL / mmol.

8. The antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1, characterized in that, In step (3), the volume ratio of CS-ZN-VA-IL4 film-forming solution to ST-PVA-AL-IL film-forming solution is 5:

3.

9. The application of the antibacterial and hydrophilic bifunctional ionic liquid bilayer membrane as described in claim 1 in food preservation and biogenic amine detection.

Images