High-performance degradable smart fluorescent response film and preparation method thereof

Abstract

The present application relates to the technical field of degradable high molecular material, and particularly relates to a high-performance degradable intelligent fluorescent response film and a preparation method thereof, the present application utilizes degradable high molecular material, self-assembled organic filler and intelligent fluorescent response carbon dot material, realizes the stabilization of the carbon dot material and the two-dimensional sheet-shaped self-assembled organic filler through a solvothermal method-self-assembled organic filler technology, significantly improves the mechanical performance of the composite film by utilizing the two-dimensional organic sheet layer structure characteristics after being compounded with the degradable high molecular material, realizes the accurate and visual monitoring of trace mercaptan markers in the rotting process of tropical fruits by adjusting and controlling the distribution of the self-assembled organic filler, the multiple hydrogen bond structure of the degradable high molecular material and the carbon quantum dot nanostructure in the composite film network, and breaks through the bottleneck of high performance and multifunction of bio-based and degradable films.

Description

Technical Field

[0001] This invention relates to the field of biodegradable polymer materials technology, specifically to a high-performance biodegradable smart fluorescent responsive thin film and its preparation method. Background Technology

[0002] The evolution of packaging materials has profoundly reshaped food industry practices and significantly driven the development of preservation and transportation technologies. However, reliance on non-biodegradable petroleum-based plastics has led to severe plastic pollution and microplastic risks. Nearly 500 billion plastic bags are used annually, and 18 billion pounds of plastic waste end up in the ocean. Therefore, sustainable and biodegradable polymers have garnered significant attention for decades; however, widely used biodegradable plastic packaging often suffers from deficiencies in mechanical properties and biodegradability (only under industrial composting conditions). Therefore, developing high-performance, multifunctional, and sustainable packaging materials is crucial to balancing performance and cost.

[0003] Chinese invention patent application number 201710265928.6 discloses a method for modifying bacterial cellulose membranes. The method first involves a substitution reaction between bacterial cellulose and epichlorohydrin to introduce epoxy groups onto the bacterial cellulose. Then, under alkaline conditions, β-cyclodextrin is grafted onto the cellulose to introduce hydrophilic molecules with hydrophobic cavities. This process, without damaging the original properties of the bacterial cellulose, allows it to contain both hydrophilic and hydrophobic molecules, thus exhibiting amphiphilic properties. The bacterial cellulose modified by this patent method significantly improves the natural and transdermal release rates of hydrophobic small molecules such as vitamin E and tea tree oil, showing great promise for applications in the skincare industry.

[0004] Chinese invention patent application number 201910294186.9 discloses a method for preparing bacterial cellulose / polymeric cyclodextrin composite materials. The method first involves crosslinking cyclodextrin monomers with terephthaloyl chloride to form polymeric cyclodextrin. Then, the polymeric cyclodextrin is activated with sodium hydride in N,N-dimethylformamide to obtain sodium salt of polymeric cyclodextrin. Finally, the cyclodextrin polymer is grafted onto a bacterial cellulose membrane using a silane coupling agent to obtain the bacterial cellulose / polymeric cyclodextrin composite material. This patent is simple, convenient, and has low synthesis costs. The prepared bacterial cellulose / polymeric cyclodextrin composite material exhibits good adsorption effects on small organic molecule pollutants in water, and the membrane material is easy to separate and recover, making it reusable.

[0005] The growing trends in packaging science towards intelligence (real-time monitoring) and sustainability (biodegradability and bioavailability) have spurred a huge demand for smart packaging materials. However, existing film materials cannot monitor damage or spoilage of packaged food, and their mechanical and antibacterial properties need improvement. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention aims to provide a high-performance biodegradable smart fluorescent response film with high mechanical properties, biodegradability and the ability to visualize food spoilage monitoring.

[0007] The purpose of this invention is to provide a method for preparing a high-performance biodegradable smart fluorescent responsive film. The operation steps are simple, the conditions are easy to achieve, and it can effectively improve the mechanical properties of the material. At the same time, carbon quantum dots achieve a balance between applicability and degradation performance.

[0008] The objective of this invention is achieved through the following technical solution: a high-performance biodegradable smart fluorescent responsive film, wherein the smart fluorescent responsive film comprises the following raw materials in parts by weight:

[0009] 80-120 parts of biodegradable polymer materials

[0010] 20-40 parts of self-assembled organic filler

[0011] 5-15 parts of carbon dot material.

[0012] Preferably, the biodegradable polymer material includes at least one of cellulose, starch, chitosan, and protein. Alternatively, in addition to the above-mentioned natural biodegradable polymer materials, the biodegradable polymer material can also be a synthetic biodegradable polymer material such as polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA), polylactic acid-glycolic acid copolymer (PGLA), and polyhydroxyalkanoate (PHA).

[0013] Preferably, the cellulose is nanocellulose with a single filament diameter of 1-100 nm. Nanocellulose has a rigid rod-like or fibrous structure formed by hydrogen bond networks of its molecular chains, characterized by high crystallinity (54%-88%) and specific surface area (150-250 m² / g). The nanocellulose includes at least one of cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). Cellulose nanocrystals (CNC) are extracted from plant cellulose, possessing high crystallinity and excellent mechanical properties, and are widely used in energy storage, composite materials, and other fields. Their high specific surface area and mechanical strength make them outstanding in functional materials. Cellulose nanofibers (CNF) are obtained through mechanical or chemical treatment of plant cellulose, featuring a high aspect ratio and good flexibility, and are commonly used in membrane materials, electrode materials, etc. Surface modification techniques can optimize dispersibility and processing performance. Bacterial cellulose (BC) is biosynthesized by bacteria, possessing high purity and biocompatibility, as well as high crystallinity and high mechanical strength, making it suitable for medical, food packaging, and other fields.

[0014] Natural cellulose refers to fiber systems extracted directly from living organisms without chemical modification. Based on their source, they can be divided into three categories: plant cellulose, bacterial cellulose, and animal cellulose. Compared to plant cellulose, bacterial cellulose (BC) has characteristics such as high purity (up to 90% or more), high crystallinity (up to 60%), and high mechanical strength (tensile strength up to 50 MPa). Therefore, BC has broad potential in medical and biomedical applications, packaging, electronics, and other fields.

[0015] Alternatively, the nanocellulose may be modified to obtain modified nanocellulose, wherein the modifying groups of the modified nanocellulose include at least one selected from alkyl, hydroxyalkyl, amino, carboxyl, aldehyde, sulfonic acid, boric acid, and phosphate groups. The modified nanocellulose can be nanofibers such as methylcellulose, carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, cellulose acetate, sulfonated cellulose, or phosphorylated cellulose. Additionally, bacterial cellulose can also be modified.

[0016] Preferably, the intelligent fluorescent responsive film further includes 0.05-0.15 parts of a fluorescent marker. The fluorescent marker includes any one of 2,3-pyrazinediamine, tyrosine, tryptophan, vitamin B2, adenosine triphosphate, reduced coenzyme I, porphyrin, and collagen.

[0017] Preferably, the material of the self-assembling organic filler includes at least one of coconut oil, polyvinylpyrrolidone, and cyclodextrin.

[0018] Preferably, the precursor of the carbon dot material includes at least one of gelatin, citric acid, glucose, and urea.

[0019] Another objective of this invention is achieved through the following technical solution: a method for preparing a high-performance degradable smart fluorescent responsive thin film, comprising the following steps:

[0020] (1) Preparation of carbon dot materials: The precursor required for carbon dot materials is dissolved in an appropriate amount of anhydrous ethanol or deionized water and stirred to form a homogeneous precursor solution; the solution is heated and cooled to room temperature naturally, then centrifuged, the supernatant is collected, and solid carbon dot materials are obtained by solvent evaporation under reduced pressure; the carbon dot materials are dissolved in distilled water to form an aqueous solution of carbon dot materials, and an aqueous solution of silver ions is added to the aqueous solution of carbon dot materials to quench the carbon dots, thereby forming Ag. + @CDs solution;

[0021] (2) Preparation of self-assembled organic filler: The material of self-assembled organic filler and sodium dodecyl sulfate are dissolved in deionized water at a certain molar ratio, stirred evenly, and the uniform mixture is incubated to obtain two-dimensional sheet-like self-assembled organic filler.

[0022] (3) Dispersion of biodegradable polymer materials: The biodegradable polymer materials are added to deionized water and dispersed to obtain a biodegradable polymer material dispersion.

[0023] (4) Preparation of intelligent fluorescent responsive thin film: The Ag obtained above is used to prepare the film. + @CDs aqueous solution, cyclodextrin assembly and biodegradable polymer material dispersion are mixed and stirred, the uniformly dispersed mixture is poured onto a flat polytetrafluoroethylene plate and dried in an oven. After drying, it is peeled off to form the smart fluorescent responsive film.

[0024] Preferably, in step (1), the mass-to-volume ratio of the precursor required for the carbon dot material to anhydrous ethanol or deionized water is 1:20-40; the stirring time is 20-40 min; the heating temperature is 160-180℃; the heating time is 4-12 h; the centrifugation rate is 4000-8000 r / min; the mass concentration of the carbon dot aqueous solution is 0.05-0.15 mg / mL; and the molar amount of Ag+ in the silver ion aqueous solution is 1-5 mmol.

[0025] Preferably, in step (2), the molar ratio of the self-assembled organic filler material to sodium dodecyl sulfate is 2-4:1, the stirring temperature is 50-60℃, the stirring time is 2-4h, the incubation temperature is 20-30℃, and the time is 36-60h; in step (4), the stirring time is 0.2-0.8h, the oven temperature is 50-70℃, and the drying time is 4-8h.

[0026] This invention utilizes biodegradable polymer materials, self-assembled organic fillers, and intelligent fluorescently responsive carbon dot materials. A solvothermal method-organic filler self-assembly technique is used to stabilize the carbon dot materials and two-dimensional sheet-like organic fillers. After being composited with biodegradable polymers to form a film, the mechanical properties of the composite film are significantly improved by leveraging its two-dimensional organic sheet structure. By controlling the distribution of the self-assembled organic fillers, the multiple hydrogen bond structure of the biodegradable polymer materials, and the carbon quantum dot nanostructures within the composite film network, precise and visual monitoring of trace thiol markers during the spoilage process of tropical fruits is achieved, overcoming the bottlenecks in the high performance and multifunctionality of bio-based and biodegradable films.

[0027] The beneficial effects of this invention are as follows: Based on carbon dots loaded with cyclodextrin assemblies and bacterial cellulose, this invention successfully prepared a smart fluorescent responsive film with high mechanical properties, biodegradability, and the ability to visually monitor food spoilage. Benefiting from interfacial hydrogen bonding interactions and the corresponding closely packed micro / nano structures, the prepared smart fluorescent responsive film exhibits excellent mechanical properties and the required water vapor barrier properties. Furthermore, the quenching of carbon dots based on the competitive reaction of silver ions to thiol groups provides the resulting smart fluorescent responsive film with antibacterial properties and smart fluorescent responsiveness. Through an optical recognition system, it can be used for quantitative analysis of visual signals, which may open up new avenues for real-time monitoring of tropical fruit spoilage during transportation. In addition, the obtained smart fluorescent responsive film can be rapidly biodegraded within 5 days under enzymatic conditions, and a mung bean germination test proved that it has no adverse effects on plant growth. This invention provides valuable new insights into the high-value utilization of bio-based materials and enhancing their multifunctional properties by adjusting material structure.

[0028] The preparation method of this invention has simple operation steps and easy-to-achieve conditions, which can effectively improve the mechanical properties of the material. At the same time, the carbon dot material achieves a balance between applicability and degradation performance, and the product has broad application prospects in the fields of green biodegradable packaging. Attached Figure Description

[0029] Figure 1 This is the physical characterization of the intelligent fluorescent responsive film of the present invention; wherein, A is the surface morphology of the dried cyclodextrin nanosheets under SEM, B is the cross-sectional morphology of the original bacterial cellulose, C is the cross-sectional morphology of the film prepared in Example 1, D is the potential measurement of the film prepared in Example 1, and E is the FTIR image.

[0030] Figure 2 This is a mechanical property test of the intelligent fluorescent responsive film of the present invention; wherein, A is a stress-strain curve, B is a graph showing the relationship between Young's modulus and cyclodextrin assembly content, C is a graph showing the relationship between tensile strength and cyclodextrin assembly content, D is a graph showing the relationship between toughness and cyclodextrin assembly content, and E is a graph showing the relationship between tensile strain capacity and cyclodextrin assembly content.

[0031] Figure 3 This is a barrier test of the intelligent fluorescent responsive film of the present invention; wherein, A is the thermogravimetric curve, B is the derivative thermogravimetric curve, C is the oxygen and carbon dioxide barrier properties, and D is the water vapor barrier properties.

[0032] Figure 4 This is an antibacterial test of the intelligent fluorescent responsive film of the present invention; wherein, AB are the inhibition zones of the film against Staphylococcus aureus and Escherichia coli, respectively, C is the statistical analysis of the diameter of the inhibition zone, and D is the antibacterial rate of the film.

[0033] Figure 5This is a fluorescence response diagram obtained when the intelligent fluorescent responsive film of the present invention is used to package durian.

[0034] Figure 6 This is a degradation diagram of the intelligent fluorescent responsive film of the present invention in an aqueous cellulase solution.

[0035] Figure 7 The diagram shows the results of an experiment on the germination and growth of mung beans using the intelligent fluorescent responsive film of this invention; where A represents the growth at 0, 3, 7, and 10 days, and B represents the root and stem growth after 10 days. Detailed Implementation

[0036] To facilitate understanding by those skilled in the art, the following description is provided in conjunction with embodiments and appendices. Figure 1-7 The present invention will be further described below, and the content mentioned in the embodiments is not intended to limit the present invention. Example

[0037] (1) Preparation of carbon dot materials: 1 g of citric acid and 0.01 g of 2,3-pyrazinediamine were dissolved in 30 ml of anhydrous ethanol and stirred for 30 min to form a homogeneous precursor solution; the solution was transferred to a polytetrafluoroethylene reactor and heated at 170 °C for 4 h. After naturally cooling to room temperature, the crude product was centrifuged at 4000 r / min to remove large insoluble particles. The supernatant was collected and obtained as solid carbon dot materials (CDs) by solvent evaporation under reduced pressure; 1 g of carbon dot material was dissolved in distilled water to form a carbon dot material aqueous solution with a concentration of 0.1 mg / ml. 2 mmol of silver nitrate aqueous solution was added to the carbon quantum dot aqueous solution to quench the carbon dots, thereby forming Ag + @CDs solution.

[0038] (2) Preparation of self-assembled organic filler: β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) were dissolved in deionized water at a molar ratio of 2:1. The mixture was continuously magnetically stirred at 60°C for 2 h. The homogeneous mixture was incubated at 25°C for 48 h to obtain a two-dimensional sheet-like cyclodextrin assembly β-CD@SDS.

[0039] (3) Dispersion of biodegradable polymer materials: 10g of bacterial cellulose (BC) was added to deionized water for dispersion to obtain bacterial cellulose dispersion.

[0040] (4) Preparation of intelligent fluorescent responsive thin film: The Ag obtained above is used to prepare the film. + @CDs aqueous solution, 2.75g cyclodextrin assembly and bacterial cellulose dispersion were mixed and stirred for 0.5h. The uniformly dispersed mixture was poured onto a flat polytetrafluoroethylene plate and dried in an oven at 50°C for 6h. After drying, it was peeled off to form the smart fluorescent responsive film BCCF. Example

[0041] (1) Preparation of carbon dot materials: 1g of glucose was dissolved in deionized water and stirred for 30min to form a homogeneous precursor solution; the solution was transferred to a polytetrafluoroethylene reactor and heated at 180℃ for 12h. After naturally cooling to room temperature, the crude product was centrifuged at 6000r / min to remove large insoluble particles. The supernatant was collected and obtained as solid carbon dot materials (CDs) by solvent evaporation under reduced pressure; 1g of carbon dot material was dissolved in distilled water to form a carbon dot material aqueous solution with a concentration of 0.1mg / ml. 2mmol of silver nitrate aqueous solution was added to the carbon quantum dot aqueous solution to quench the carbon dots, thereby forming Ag + @CDs solution.

[0042] (2) Preparation of organic filler: β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) were dissolved in deionized water at a molar ratio of 3:1. The mixture was continuously magnetically stirred at 55°C for 3 hours. The homogeneous mixture was then incubated at 25°C for 36 hours to obtain a two-dimensional sheet-like cyclodextrin assembly β-CD@SDS.

[0043] (3) Dispersion of biodegradable polymer materials: 10g of bacterial cellulose (BC) was added to deionized water for dispersion to obtain bacterial cellulose dispersion.

[0044] (4) Preparation of intelligent fluorescent responsive thin film: The Ag obtained above is used to prepare the film. + @CDs aqueous solution, 3.67g cyclodextrin assembly and bacterial cellulose dispersion were mixed and stirred for 0.5h. The uniformly dispersed mixture was poured onto a flat polytetrafluoroethylene plate and dried in an oven at 60℃ for 4h. After drying, it was peeled off to form the smart fluorescent responsive film BCCF. Example

[0045] (1) Preparation of carbon dot materials: 1g of urea was dissolved in deionized water and stirred for 30min to form a homogeneous precursor solution; the solution was transferred to a polytetrafluoroethylene reactor and heated at 160℃ for 8h. After naturally cooling to room temperature, the crude product was centrifuged at 8000r / min to remove large insoluble particles. The supernatant was collected and obtained as solid carbon dot materials (CDs) by solvent evaporation under reduced pressure; 1g of carbon dot material was dissolved in distilled water to form a carbon dot material aqueous solution with a concentration of 0.1mg / ml. 2mmol of silver nitrate aqueous solution was added to the carbon quantum dot aqueous solution to quench the carbon dots, thereby forming Ag + @CDs solution.

[0046] (2) Preparation of organic filler: β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) were dissolved in deionized water at a molar ratio of 4:1. The mixture was continuously magnetically stirred at 50°C for 4 hours. The homogeneous mixture was then incubated at 25°C for 60 hours to obtain a two-dimensional sheet-like cyclodextrin assembly β-CD@SDS.

[0047] (3) Dispersion of biodegradable polymer materials: 10g of bacterial cellulose (BC) was added to deionized water for dispersion to obtain bacterial cellulose dispersion.

[0048] (4) Preparation of intelligent fluorescent responsive thin film: The Ag obtained above is used to prepare the film. + @CDs aqueous solution, 3g cyclodextrin assembly and bacterial cellulose dispersion were mixed and stirred for 0.5h. The uniformly dispersed mixture was poured onto a flat polytetrafluoroethylene plate and dried in an oven at 60℃ for 4h. After drying, it was peeled off to form the smart fluorescent responsive film BCCF.

[0049] Comparative Example 1

[0050] 10g of bacterial cellulose (BC) was added to deionized water and dispersed to obtain a bacterial cellulose dispersion. The dispersion was poured onto a flat polytetrafluoroethylene plate and dried in an oven at 50°C for 6 hours. After drying, the dispersion was peeled off to form a film.

[0051] Comparative Example 2

[0052] β-Cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) were dissolved in deionized water at a molar ratio of 2:1. The mixture was continuously magnetically stirred at 60°C for 2 h, and the homogeneous mixture was incubated at 25°C for 48 h to obtain a two-dimensional sheet-like cyclodextrin assembly β-CD@SDS.

[0053] 10g of bacterial cellulose (BC) was added to deionized water and dispersed to obtain a bacterial cellulose dispersion.

[0054] Mix 2.75g of cyclodextrin assembly and bacterial cellulose dispersion and stir for 0.5h. Pour the uniformly dispersed mixture onto a flat polytetrafluoroethylene plate and dry it in an oven at 50℃ for 6h. After drying, peel it off to form a film.

[0055] Comparative Examples 3-5

[0056] The difference between Comparative Examples 3-5 and Example 1 above is that the amount of cyclodextrin assembly used is 1.22g, 1.94g and 4.71g, respectively.

[0057] Performance testing: The films prepared in Comparative Example 1 (labeled as BC), Comparative Example 2 (labeled as 2β-BC), Comparative Example 3 (10% cyclodextrin assembly content, labeled as BCCF-0.10), Comparative Example 4 (15% cyclodextrin assembly content, labeled as BCCF-0.15), Comparative Example 1 (20% cyclodextrin assembly content, labeled as BCCF-0.20), Comparative Example 2 (25% cyclodextrin assembly content, labeled as BCCF-0.25), and Comparative Example 5 (30% cyclodextrin assembly content, labeled as BCCF-0.30) were tested respectively.

[0058] I. Physical Characterization

[0059] 1. SEM measurement

[0060] Cyclodextrin nanosheets, bacterial cellulose, and the thin film prepared in Example 1 were subjected to SEM analysis. The microstructure of the samples was observed using a Hitachi JSM-6710F scanning electron microscope (SEM) and an energy-dispersive X-ray spectroscopy (EDS) instrument. The experimental results are as follows: Figure 1 As shown in A-1C. Figure 1 A represents the surface morphology of dried cyclodextrin nanosheets under SEM. Figure 1 B represents the cross-sectional morphology of the original bacterial cellulose. Figure 1 C represents the cross-sectional morphology of the film prepared in Example 1. It can be seen that the film prepared in Example 1 exhibits a significantly enhanced degree of cross-linking, thereby constructing a denser three-dimensional network structure. The increase in the degree of cross-linking directly improves the mechanical properties of the film, including higher tensile strength, elastic modulus, and compressive strength.

[0061] 2. Potential Measurement

[0062] The zeta potentials of the films prepared in Example 1 and Comparative Example 1 were measured using a Zetasizer nano ZS90 (UK) potentiometer. The experimental results are as follows: Figure 1 As shown in Figure D, it can be seen that the film prepared in Example 1 has a higher potential value and better stability compared with the film prepared in Comparative Example 1.

[0063] 3. FTIR detection

[0064] The carbon dot materials CDs, cyclodextrin assemblies β-CD@SDS, bacterial cellulose BC, and thin film BCCF prepared in Example 1 were analyzed by FTIR. FTIR analysis was performed using a Frontier Dual Ranger spectrometer (PerkinElmer, Waltham, MA, USA) in attenuated total reflectance (ATR) mode at room temperature from 400 to 4000 cm⁻¹. -1 The resolution is 4cm. -1 The scan was performed 32 times, and the experimental results are as follows: Figure 1 As shown in E, Figure 1 E is the FTIR image. It can be seen that the film prepared in Example 1 retains a large amount of the basic chemical structure of β-CD@SDS and adds new groups, resulting in a completely new composite material.

[0065] II. Mechanical Performance Testing

[0066] The films prepared in Examples 1-2 and Comparative Examples 1 and 3-5 were subjected to mechanical property tests. Stress-strain curves of the films were obtained using an electromechanical testing machine (INSTRON 3367 USA). The film thickness was 40 µm, and dumbbell-shaped specimens with a width of 3 mm were cut before measurement. The tensile speed was set to 5 mm / min. The experimental results are as follows: Figure 2 As shown in A-2E. Figure 2 A is the stress-strain curve. It can be seen that as the content of cyclodextrin assemblies increases, the strength, stiffness, and toughness of the film are comprehensively improved, reaching the optimal level when the content of cyclodextrin assemblies is 20%. As the content of cyclodextrin assemblies further increases, the strength, stiffness, and toughness of the film gradually decrease. Figure 2 B is the graph showing the relationship between Young's modulus and the content of cyclodextrin assemblies. It can be seen that as the content of cyclodextrin assemblies increases, the Young's modulus of the film gradually increases, reaching a maximum of 4.93 GPa when the content of cyclodextrin assemblies is 20%. As the content of cyclodextrin assemblies further increases, the Young's modulus of the film gradually decreases. Figure 2 C is the graph showing the relationship between tensile strength and cyclodextrin assembly content. It can be seen that as the cyclodextrin assembly content increases, the tensile strength of the film gradually increases, reaching a maximum of 126.84 MPa when the cyclodextrin assembly content is 20%. As the cyclodextrin assembly content further increases, the tensile strength of the film gradually decreases. Figure 2 D is the relationship between toughness and cyclodextrin assembly content. It can be seen that as the cyclodextrin assembly content increases, the film toughness first increases and then decreases, reaching a maximum of 4.37 MJ / m when the cyclodextrin assembly content is 20%. 3 . Figure 2E is a graph showing the relationship between tensile strain capacity and cyclodextrin assembly content. It can be seen that as the cyclodextrin assembly content increases, the tensile strain capacity of the film first increases and then decreases, reaching its maximum value when the cyclodextrin assembly content is 20%.

[0067] III. Barrier Test

[0068] The films prepared in Example 1 and Comparative Example 1 were subjected to thermogravimetric analysis (Tg) using a STA449 F5 Jupiter® simultaneous thermal analyzer (NETZSCH-Gerätebau GmbH, Selb, Germany). The Tg and derivative TG were recorded simultaneously. The film (approximately 4 mg) was placed in an aluminum pot and heated at 50 cm⁻¹. 3 At a nitrogen flow rate of / min, the temperature was increased from 30℃ to 600℃ at a rate of 10℃ / min. The experimental results are as follows: Figure 3 As shown in A-3B. Figure 3 A is the thermogravimetric curve. Figure 3 B is the thermogravimetric curve of the microstructure. It can be seen that the film prepared in Example 1 has better thermal stability than the film prepared in Comparative Example 1.

[0069] The films prepared in Example 1 and Comparative Example 1 were subjected to barrier tests. The water vapor transmission rate of the gel film and G-OCSI was measured using a water vapor transmission rate tester (W3 / 060, Jinan Labthink Electromechanical Technology Co., Ltd.), with three repeated tests. The parameters of the testing instrument were adjusted to ensure a temperature of 38℃ and a relative humidity of 90%. The oxygen and carbon dioxide permeability of the composite film was measured using a gas transmission meter. Rectangular specimens (10×10mm²) were installed in the test chamber. The tests were conducted at 23℃ and 50% relative humidity, using high-purity oxygen (99.999%) and carbon dioxide (99.999%) as permeating gases. The experimental results are as follows: Figure 3 As shown in C-3D. Figure 3 C represents the oxygen and carbon dioxide barrier properties. It can be seen that, compared to the film prepared in Comparative Example 1, the film prepared in Example 1 achieves a barrier value of 432 cm⁻¹ for both oxygen and carbon dioxide. 3 / m 2 / Tianhe 1186cm 3 / m 2 / sky. Figure 3 D represents water vapor barrier properties. Compared to the film prepared in Comparative Example 1, the film prepared in Example 1 exhibits ideal water vapor barrier properties (168.9 g / m² / day).

[0070] IV. Antibacterial Test

[0071] The films prepared in Example 1 and Comparative Examples 1-2 were subjected to antibacterial tests. The antibacterial activity of the bacterial cellulose (BC)-based composite films against Escherichia coli and Staphylococcus aureus was tested by measuring the diameter of the inhibition zone after exposure to the samples. A concentration of approximately 10% was prepared using sterile physiological saline. -5 -10 -6 A bacterial suspension of CFU / mL was prepared. Subsequently, the BC-based composite film was cut into 15 mm discs and sterilized by UV irradiation for 30 min. 10 mL of beef extract peptone agar medium was added to a sterile petri dish, followed by inoculation with 50 µL of the bacterial suspension.

[0072] Staphylococcus aureus and Escherichia coli were used as model microorganisms to evaluate the antimicrobial efficacy of BCCF. All samples were sterilized using a pressure steam sterilizer (115°C, 30 min) (YXQ-LB-30SII, Shanghai Boxun, China). 500 μL of bacterial suspension (strain density 1 × 10⁻⁶) was placed in each well of a 24-well plate. -7 (CFU / mL) was added to the completely sterilized sample and incubated at 37°C for 2 hours. The experimental results are as follows: Figure 4 As shown in A-4D.

[0073] Figure 4 A-4B represent the inhibition zones of the membrane against Staphylococcus aureus and Escherichia coli, respectively. Figure 4 C represents the statistical analysis of the diameter of the inhibition zone. It can be seen that, compared with the films of Comparative Examples 1-2 without the addition of carbon dot materials, the film prepared in Example 1 exhibits excellent antibacterial properties (the diameter of the inhibition zone is 2.46 mm). Figure 4 D represents the antibacterial rate of the film. It can be seen that the film prepared in Example 1 has an antibacterial rate of 99.20% against Staphylococcus aureus and an antibacterial rate of 99.52% against Escherichia coli, demonstrating excellent antibacterial properties.

[0074] V. Fluorescence Response Test

[0075] The thin film prepared in Example 1 was subjected to fluorescence response testing, and the experimental results are as follows: Figure 5 As shown, Figure 5 The image shows the fluorescence response obtained when the film is used to package durian. It can be seen that the film prepared by this invention can be used for quantitative analysis of visual signals, which may open up new avenues for real-time monitoring of tropical fruit spoilage during transportation.

[0076] VI. Biodegradation Test

[0077] The thin film prepared in Example 1 was subjected to a biodegradation test, and the experimental results are as follows: Figure 6 As shown, Figure 6The graph shows the degradation of the film in an aqueous cellulase solution. It can be seen that the film prepared by this invention can be degraded by cellulase solution, and the degradation time is about 5 days.

[0078] VII. Mung Bean Germination and Growth Experiment

[0079] The film prepared in Example 1 was used in a mung bean germination and growth experiment. The experimental results are as follows: Figure 7 As shown, Figure 7 Tap water (blank control) and the presence of a film in the water were used to evaluate the growth of mung bean sprouts hydroponically grown at room temperature for 10 days. It can be seen that the growth, color and root length of the bean sprouts were not significantly affected.

[0080] This invention develops a smart fluorescent responsive film using biodegradable polymer materials and carbon dot materials (CDs). This film not only monitors fruit damage but also possesses high strength. Tensile testing results show that the synergistic effect between the bacterial cellulose hydrogen-bonded network and the cyclodextrin assembly (β-CD@SDS) endows the composite film with excellent mechanical properties (tensile strength exceeding 120 MPa, Young's modulus of 4.93 GPa) and ideal water vapor barrier properties (168.9 g / m² / day). Furthermore, density functional theory (DFT) studies confirm the existence of numerous non-covalent interactions (hydrogen bonds) within the smart fluorescent responsive film (BCCF) network. By adding a quenched carbon dot solution, the smart fluorescent responsive film exhibits thiol-based luminescence response characteristics, enabling visualization and monitoring of tropical fruit damage. Notably, this smart fluorescent responsive film degrades rapidly (within 5 days) under the action of cellulase without any negative impact on plant growth. Due to the presence of silver ions, the film exhibits excellent antibacterial properties (inhibition zone diameter of 2.46 mm). This invention provides a valuable example for fruit packaging films, offers a feasible strategy for achieving high-strength, monitorable smart films, and also provides important examples and ideas for designing novel fruit packaging film network structures.

[0081] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A high-performance degradable smart fluorescent response film, characterized in that: The intelligent fluorescent responsive film comprises the following raw materials in parts by weight: 100 parts of biodegradable polymer material 27.5-36.7 parts of self-assembled organic filler 5-15 parts of carbon dot material; The biodegradable polymer material includes at least one of cellulose, starch, chitosan, and protein; the self-assembling organic filler material is cyclodextrin; the precursor of the carbon dot material includes at least one of gelatin, citric acid, glucose, and urea. The preparation method of the intelligent fluorescent responsive thin film includes the following steps: (1) Preparation of carbon dot materials: Dissolve the precursor required for carbon dot materials in an appropriate amount of anhydrous ethanol or deionized water and stir to form a uniform precursor solution; The solution was heated and allowed to cool naturally to room temperature. It was then centrifuged, and the supernatant was collected. Solid carbon dots were obtained by solvent evaporation under reduced pressure. The carbon dots were dissolved in distilled water to form an aqueous solution. Adding an aqueous solution of silver ions quenched the carbon dots, thus forming Ag. + @CDs solution; (2) Preparation of self-assembled organic filler: The material of self-assembled organic filler and sodium dodecyl sulfate are dissolved in deionized water at a certain molar ratio, stirred evenly, and the uniform mixture is incubated to obtain two-dimensional sheet-like self-assembled organic filler. (3) Dispersion of biodegradable polymer materials: The biodegradable polymer materials are added to deionized water and dispersed to obtain a biodegradable polymer material dispersion. (4) Smart fluorescent responsive film: The Ag obtained above is used to prepare the film. + @CDs aqueous solution, cyclodextrin assembly and biodegradable polymer material dispersion are mixed and stirred, the uniformly dispersed mixture is poured onto a flat polytetrafluoroethylene plate and dried in an oven. After drying, it is peeled off to form the smart fluorescent responsive film. 2.The high-performance degradable smart fluorescent response film according to claim 1, characterized in that: The cellulose is nanocellulose with a single filament diameter of 1-100 nm.

3. The high-performance degradable smart fluorescent response film according to claim 2, characterized in that: The nanocellulose includes at least one of cellulose nanofibers, cellulose nanocrystals, and bacterial cellulose. 4.The high-performance degradable smart fluorescent response film according to claim 1, characterized in that: The intelligent fluorescent responsive film also includes 0.05-0.15 parts of fluorescent marker.

5. The high-performance degradable smart fluorescent response film according to claim 1, characterized in that: In step (1), the mass-to-volume ratio of the precursor required for the carbon dot material to anhydrous ethanol or deionized water is 1:20-40; the stirring time is 20-40 min; the heating temperature is 160-180℃; the heating time is 4-12 h; the centrifugation rate is 4000-8000 r / min; the mass concentration of the carbon dot aqueous solution is 0.05-0.15 mg / mL; and the Ag in the silver ion aqueous solution is... + The molar amount is 1-5 mmol. 6.The high-performance degradable smart fluorescent response film according to claim 1, characterized in that: In step (2), the molar ratio of the self-assembled organic filler material to sodium dodecyl sulfate is 2-4:1, the stirring temperature is 50-60℃, the stirring time is 2-4h, the incubation temperature is 20-30℃, and the time is 36-60h; in step (3), the stirring time is 0.2-0.8h, the oven temperature is 50-70℃, and the drying time is 4-8h.

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