Preparation method and application of sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticide

Abstract

The invention relates to a preparation method and application of a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides, according to the method, carboxylated cellulose nanofiber mediated defect type UiO-66-OH is used as a core functional material, sprayable slurry is prepared in cooperation with an aqueous film-forming matrix, and a continuous compact film layer is formed through a synchronous spraying process. The method is simple in processing, manufacturing tools are easy to obtain, and batch production and preparation can be realized; the packaging film obtained through the method can provide a stable and independent reaction and fluorescence response environment for in-situ detection and preliminary degradation of organophosphorus pesticides, the detection-degradation-protection integrated function is achieved, the problems that in-situ fitting performance is poor, the function is single, operation is tedious, and pollution is prone to occurring in the prior art are solved, and the packaging film has good application prospects. The paper achieves multiple functions, is suitable for detecting organophosphorus pesticide residues on the surfaces of various fruits and vegetables, and is environment-friendly, high in stability, easy to store and low in cost.

Description

Technical Field

[0001] This invention relates to the field of sprayable packaging film processing technology and in-situ pesticide detection, specifically to a method for preparing and using a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides. Background Technology

[0002] Organophosphorus pesticides are widely used in fruit and vegetable cultivation due to their highly effective insecticidal and fungicidal properties. However, their residues can easily accumulate through the food chain, posing potential harm to the human nervous and endocrine systems. Therefore, achieving rapid in-situ detection of organophosphorus pesticides on fruit and vegetable surfaces is of great significance for ensuring food safety. Currently, the main methods for detecting organophosphorus pesticides include gas chromatography, liquid chromatography-mass spectrometry, and enzyme inhibition methods. Among these, chromatographic methods offer high detection accuracy but require specialized equipment, cumbersome pretreatment, and skilled operators, making them unsuitable for rapid in-situ detection. Enzyme inhibition methods are simple to operate, but enzyme activity is easily affected by temperature and humidity, resulting in poor stability and insufficient detection specificity.

[0003] Fluorescence sensing technology has attracted much attention in the field of in-situ detection due to its advantages such as rapid response, high sensitivity, and strong visualization. Zirconium-based metal-organic frameworks (UiO-66-OH), as a typical metal-organic framework (MOF) material, possess controllable pore structures, excellent optical properties, and zirconium coordination vacancy active sites. Its fluorescence properties can be modulated through defect engineering to achieve specific recognition of organophosphorus pesticides. Carboxylated cellulose nanofibers (CNFs) combine good self-assembly properties, biocompatibility, and green renewable characteristics, and can be used as dispersion media and film-forming aids to improve the stability and film-forming properties of MOF materials. Combining these two technologies to prepare sprayable film materials can leverage the fluorescence sensing advantages of MOFs while utilizing the film-forming properties of carboxylated cellulose nanofibers (CNFs) to adapt to the complex surfaces of fruits and vegetables, achieving integrated packaging protection and in-situ detection, which has become a current research hotspot.

[0004] Sprayable packaging films have great potential in food preservation and functional packaging due to their convenient construction, strong surface adaptability (able to fit the uneven surfaces of fruits and vegetables), and the lack of complex molding equipment. Existing sprayable films mostly focus on preservation and barrier functions; the technology of combining fluorescent sensing functions with sprayable packaging films is still in the exploratory stage. Current fluorescent sensing films are mostly prepared using dip-coating and blade-coating processes, resulting in poor uniformity of film thickness and difficulty in adapting to complex surfaces such as curved and wrinkled surfaces of fruits and vegetables. Furthermore, most sensing films only have a single detection function, failing to consider packaging protection performance, and the sensing material is prone to detachment and lacks stability, making it difficult to meet the needs of practical handheld operation and long-term storage.

[0005] To achieve the integration of fluorescence sensing and sprayable packaging functions, existing technologies have proposed several improvement schemes, such as: Publication number CN 114544574A discloses a method for detecting organophosphorus pesticides using a microfluidic chip based on a fluorescent sensing film. The method utilizes platinum nanoparticles@oxalate-organometallic framework composite material and porous two-dimensional nanosheets to construct a porous fluorescent sensing film through layer-by-layer self-assembly. The microfluidic chip consists of a sample channel, an injection channel, a reaction chamber, a microfluidic channel, a detection chamber, and an optical fiber channel. Then, an organophosphorus pesticide detection system is built by combining a portable constant-pressure syringe pump, a laser, a spectrometer, a signal transmitter, and a signal display, thus miniaturizing and integrating the detection equipment and standardizing organophosphorus pesticide detection.

[0006] Publication No. CN 117723519A discloses a dual-modal indicator for visually monitoring the freshness of meat and its application. The indicator is designed in an hourglass shape and uses a fluorescent sensing gel with aggregation-induced emission (AIE) properties—a dual-ligand silver nanocluster—as a sensitive sensing material for detecting putrefactive amine gases. This gel is placed in one of the chambers. As the meat spoils within the packaging, the fluorescent sensing gel comes into contact with and reacts with the volatile amine compounds. Its ordered aggregation structure is disrupted, the luminescence intensity weakens, leading to the recovery of its flow dynamics and fluorescence quenching. The fluidized fluorescent sensing gel then drips into the other chamber of the hourglass-shaped indicator for measurement. Users can visually determine the freshness of the product by observing the weakening and quenching of fluorescence intensity, as well as the flow and dripping amount of the fluorescent sensing gel within the indicator.

[0007] Publication No. CN 120446069A discloses a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, its preparation method, and its application. The sensor encapsulates the organic dye molecule 4-MU with the zeolite imidazole ester backbone ZIF-8 to form core-shell structured 4-MU@ZIF-8 nanoparticles, which are then doped into the polymer PLA-PEG to form a fluorescent sensing film. This film enables fast response, low detection limit, and visual detection of TCs, while also possessing certain mechanical and antibacterial properties. Therefore, it provides a new approach for the field of intelligent packaging for detecting TCs in food.

[0008] Publication No. CN 117343054A discloses a fluorescent probe and fluorescent tag for real-time non-destructive visual monitoring of meat freshness, as well as their preparation method and application. The fluorescent probe HBT-Bz, which is sensitive to amine compounds, is used as the sensing unit. Solid supports such as filter paper, cotton, non-woven fabric, and woven fabric are immersed in the solution of the fluorescent probe, removed and dried to obtain the fluorescent tag. When placed in meat packaging, the freshness of the food can be monitored in real-time non-destructively with accurate and reliable results.

[0009] Publication number CN 117304528A discloses a hydrogel film for pollutant removal and fluorescence detection in water and its preparation method. The method involves mixing a metal-organic framework material, a thickener, a modifier, and a solvent, coating the mixture onto a glass substrate using a scraping process, and then molding and cleaning to obtain the film for pollutant removal and fluorescence detection in water. This film preparation method is simple, the film thickness is controllable, and it possesses good flexibility, high porosity, and high specific surface area. It can achieve rapid adsorption and removal of pollutants in water and highly sensitive fluorescence detection, and the preparation cost is low, showing good prospects for practical applications.

[0010] While the aforementioned existing technologies attempt to combine fluorescence sensing with membrane materials, their core focus remains on pre-fabricated membrane preparation or the realization of a single sensing function. They generally suffer from the following shortcomings: First, the film-forming processes (dipping, casting, pre-fabrication) cannot adapt to the complex surfaces of fruits and vegetables, and in-situ spraying exhibits poor adhesion. Second, the sensing materials suffer from poor dispersion and insufficient stability, easily agglomerating or detaching, affecting detection accuracy and membrane lifespan. Third, most materials only possess detection capabilities, lacking packaging protection and interference resistance, and do not incorporate the degradation characteristics of organophosphorus pesticides, resulting in limited functionality. Fourth, some solutions utilize fluorescent materials (quantum dots, organic dyes) with poor photostability and weak specificity, or complex preparation processes and high costs, making mass production difficult.

[0011] To address the aforementioned problems, this invention proposes a sprayable, surface-adaptive packaging film for in-situ detection of organophosphorus pesticides. Carboxylated cellulose nanofibers (CNFs) serve as the dispersion and self-assembly medium, combined with a defective UiO-66-OH fluorescent sensing material. A sprayable slurry is prepared using an aqueous film-forming matrix, and a continuous, dense packaging film layer is formed on the surface of fruits and vegetables through a spraying process. The self-assembly properties of carboxylated cellulose nanofibers (CNFs) enhance the dispersion stability and film adhesion of UiO-66-OH. Their carboxyl groups can synergistically interact with the zirconium coordination vacancies of UiO-66-OH, strengthening the specific recognition of organophosphorus pesticides. The defective UiO-66-OH not only possesses highly sensitive fluorescence response but can also preliminarily degrade organophosphorus pesticides through coordination interactions, achieving a synergistic detection-degradation function.

[0012] The sprayable coating process used in this invention is simple to operate, requiring no complex equipment. The film layer can closely adhere to complex surfaces such as curved and wrinkled surfaces of fruits and vegetables, exhibiting strong surface adaptability. The film layer combines packaging protection (blocking moisture and contaminants) with in-situ fluorescence detection functions. It is not easily damaged or contaminated during handheld operation, requiring no additional support equipment. The preparation materials (carboxylated cellulose nanofibers, UiO-66-OH, and aqueous film-forming matrix) are inexpensive, readily available, and environmentally friendly. The process is simple and controllable, making it suitable for mass production. This packaging film can rapidly respond to organophosphorus pesticide residues on the surface of fruits and vegetables (second-level response, detection limit as low as 0.014 mg / kg), exhibits strong resistance to 17 common interfering substances, and enables semi-quantitative visual detection. Simultaneously, it degrades organophosphorus pesticides into low-toxicity products, making it suitable for in-situ detection and protection of various fruits and vegetables. This solves the problems of poor surface adaptability, limited functionality, insufficient stability, and difficulty in widespread application of existing technologies. Summary of the Invention

[0013] The purpose of this invention is to provide a method for preparing a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides and its application. This method uses carboxylated cellulose nanofibers-mediated defect-type UiO-66-OH as the core functional material, combined with an aqueous film-forming matrix to prepare a sprayable slurry, and forms a continuous, dense film layer through a simultaneous spraying process. This method is simple to process, uses readily available tools, and can be mass-produced. The packaging film obtained by this invention provides a stable and independent reaction and fluorescence response environment for in-situ detection and preliminary degradation of organophosphorus pesticides, achieving an integrated function of detection-degradation-protection. It overcomes the problems of poor in-situ adhesion, single function, cumbersome operation, and easy contamination in existing technologies, achieving single-step spraying and forming, and completing multiple functions with a single sheet. It is suitable for detecting organophosphorus pesticide residues on the surfaces of various fruits and vegetables, and the material is green, environmentally friendly, highly stable, easy to store, and inexpensive.

[0014] The present invention discloses a method for preparing a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides. The packaging film is made from defect-type UiO-66-OH, sodium alginate, and calcium chloride solution. The specific operation is carried out according to the following steps: Preparation of defective UiO-66-OH aqueous solution: a. Dissolve carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 100-150 °C, and react for 1-3 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 50-80 ℃, react for 1-2 hours, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold, and the transparent packaging film is obtained by self-assembly at room temperature. Alternatively, the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j can be directly sprayed onto fruits and vegetables, and after film formation, they can self-assemble into a transparent packaging film.

[0015] The packaging film obtained by the method is used in the preparation of a test for organophosphorus pesticides glyphosate, dichlorvos, or dimethoate.

[0016] This invention discloses a method for preparing a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides and its applications. The sprayable surface-adaptive packaging film obtained by this method is mainly used for the rapid in-situ detection and preliminary degradation of organophosphorus pesticide residues (glyphosate, dichlorvos, dimethoate, etc.) on the surfaces of various fruits and vegetables such as apples, pears, cucumbers, tomatoes, lettuce, and spinach. It can be widely used for on-site testing in scenarios such as homes, farmers' markets, fruit and vegetable planting bases, and food testing institutions. It can also be used as a functional layer for fruit and vegetable preservation packaging, achieving simultaneous protection, detection, and degradation.

[0017] This invention combines carboxylated cellulose nanofibers-mediated defect-type UiO-66-OH with an aqueous film-forming matrix. Leveraging the self-assembly properties of carboxylated cellulose nanofibers and the fluorescence sensing and degradation characteristics of UiO-66-OH, along with a simultaneous spraying process, it achieves a close fit between the packaging film and the complex surfaces of fruits and vegetables. Simultaneously, it possesses multiple functional advantages, as detailed below: 1. Excellent surface adaptability: The film layer can be closely adhered to the curved and wrinkled surfaces of fruits and vegetables by using a sprayable process combined with a surface adaptation layer design. It is bubble-free and does not fall off, which solves the problem of poor adhesion of existing pre-made films and dip-coated films. It can be formed in situ without secondary processing. 2. Integrated Functional Synergy: Breaking through the limitations of single detection functions, the defective UiO-66-OH membrane can achieve second-level fluorescence response for organophosphorus pesticides (detection limit as low as 0.014 mg / kg), has strong resistance to 17 common interfering substances, and can perform semi-quantitative visual detection. It can also degrade pesticides into low-toxicity products through zirconium coordination vacancy interaction. The membrane layer also has packaging protection (blocking moisture and contaminants) function, realizing the three-in-one function of detection-degradation-protection. 3. Significant advantages in process and cost: Only ordinary sprayers, constant temperature drying ovens and other conventional equipment are required. The raw materials (carboxylated cellulose nanofibers, UiO-66-OH, water-based film-forming matrix) are inexpensive, readily available and environmentally friendly, with no harmful solvent residues. The process steps are simple, can be operated in batches, have low learning costs, and are suitable for large-scale promotion and application. 4. High stability and practicality: After curing, the membrane has a dense structure that is not easily damaged or contaminated. It is easy to operate by hand without the need for additional equipment. It can be stored at room temperature for more than 6 months while still maintaining excellent fluorescence performance. The reagents are locked in the membrane to prevent them from penetrating and contaminating the fruits and vegetables. This solves the problems of easy contamination and poor stability of existing detection membranes.

[0018] A method and application for preparing and applying a defect-engineered zirconium-based metal-organic framework (UiO-66-OH) material mediated by carboxylated cellulose nanofibers (CNFs) with fluorescence sensing properties, combined with a sprayable film-forming matrix, and sprayed onto the surface of fruits and vegetables to form an adaptive packaging film, thereby realizing in-situ fluorescence detection and preliminary degradation of organophosphorus pesticides. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the packaging film and the film-forming mechanism of the present invention; Figure 2 This is a scanning electron microscope image of the packaging film of the present invention; Figure 3 This is the Fourier transform infrared spectrum of the packaging film of the present invention; Figure 4 This is a diagram showing the contact angles and the angles of advance and retreat of the packaging film of the present invention. Figure 5 The diagram shows the stress-strain of the packaging film of this invention. The small image in the upper left corner is a picture of the folded film, and the small image in the lower right corner is a diagram showing the relationship between modulus and tensile stress. Figure 6 The image shows the ultraviolet transmittance of the packaging film of this invention. The inset image is a comparison of the obtained film before and after being applied to the pattern. Figure 7 The fluorescence spectra of glyphosate at different concentrations detected in the packaging film of this invention are shown. Figure 8 This is a comparison of the ultraviolet absorption spectrum of the packaging film of the present invention with potentially degradable substances; Figure 9 This is a schematic diagram and a physical image of the self-assembly of a packaging film sprayed onto strawberries according to the present invention; Figure 10 Statistical analysis of the cytotoxicity results of the packaging film of this invention; Figure 11 The present invention provides images of the packaging film applied to strawberries to detect different concentrations of glyphosate, and RGB extraction images of the film after extraction and detection. Figure 12 The images show actual photos of the packaging film of this invention applied to strawberries to detect different concentrations of glyphosate, and RGB linear graphs of the film after extraction and detection. Detailed Implementation

[0020] The present invention will be further described and explained below with reference to the accompanying drawings and actual embodiments. Example 1

[0021] Preparation of defective UiO-66-OH aqueous solution: a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide and stir until completely dissolved to obtain a ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 100 °C, and react for 3 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 50 °C, react for 2 hours, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare a calcium chloride aqueous solution with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold simultaneously, and the transparent packaging film will be obtained by self-assembly at room temperature. Example 2

[0022] Preparation of defective UiO-66-OH aqueous solution: a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 110 °C, and react for 2 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 60 ℃, react for 1 hour, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold simultaneously, and the transparent packaging film will be obtained by self-assembly at room temperature. Example 3

[0023] Preparation of defective UiO-66-OH aqueous solution: a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 115 °C, and react for 2 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 55 °C, react for 1 hour, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. The defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j are directly sprayed onto fruits and vegetables. After film formation, they can self-assemble into a transparent packaging film. Example 4

[0024] Preparation of defective UiO-66-OH aqueous solution: a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 130 °C, and react for 1 hour. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 65 °C, react for 1 hour, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold, and the transparent packaging film is obtained by self-assembly at room temperature. Example 5

[0025] Preparation of defective UiO-66-OH aqueous solution: a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 140 °C, and react for 3 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 70°C, react for 1.5 hours, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. The defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j are directly sprayed onto fruits and vegetables. After film formation, they can self-assemble into a transparent packaging film. Example 6

[0026] a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 140 °C, and react for 2 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 75°C, react for 2 hours, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold, and the transparent packaging film is obtained by self-assembly at room temperature. Example 7

[0027] a. Dissolve 1.5 g of carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve 21 mg of zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 hours to obtain a mixture solution; d. Dissolve 65.64 mg of 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 150 °C, and react for 2.5 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 80 °C, react for 1 hour, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare an aqueous solution of calcium chloride with a concentration of 0.1 mg / mL: k. The defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j are directly sprayed onto fruits and vegetables. After film formation, they can self-assemble into a transparent packaging film.

[0028] The sprayable packaging film obtained by the method described in this invention is suitable for in-situ pesticide detection, featuring simple preparation, high biocompatibility, accurate detection results, and convenient operation. In an application example of detecting glyphosate on strawberries, the packaging film exhibited a clear fluorescence response, a linear concentration gradient change, and excellent bioadhesion performance. This product can be used for pesticide residue detection in various fruits, vegetables, and other agricultural products. By directly spraying to form a detection film layer, it can achieve intuitive and rapid on-site screening based on fluorescence changes under excitation light. Its film-forming mechanism ensures sufficient contact and stable response between the reagent and the analyte, while avoiding contamination or damage to the sample, making it suitable for real-time safety monitoring in the circulation and consumption of agricultural products.

Claims

1. A method for preparing a sprayable surface-adaptive packaging film for in-situ detection of organophosphorus pesticides, characterized in that, The packaging film is made from a solution of defective UiO-66-OH, sodium alginate, and calcium chloride. The specific operation is carried out according to the following steps: Preparation of defective UiO-66-OH aqueous solution: a. Dissolve carboxylated cellulose in N,N-dimethylformamide and stir thoroughly at room temperature until completely dissolved to obtain a mixture; b. Dissolve zirconium chloride in 1.5 mL of N,N-dimethylformamide to obtain a mixture; c. Add the mixture obtained in step b to the carboxylated nanocellulose dispersion obtained in step a and stir for 4 h to obtain a mixture solution; d. Dissolve 2-hydroxyterephthalic acid in 1.5 mL of N,N-dimethylformamide solution and stir until completely dissolved to obtain the ligand solution; f. Add the ligand solution obtained in step d to the mixture solution obtained in step c, and stir thoroughly for 1 h until the mixture solution is homogeneous and free of stratification; g. Add 6.4 mL of acetic acid and 0.25 mL of deionized water to the solution obtained in step f, stir for 10 min, and obtain a mixture; h. Transfer the mixture obtained in step g to a polyvinyl fluoride reactor and react in an oven preheated to 120 °C for 1 hour. After the reaction, transfer the solution to a centrifuge tube, place it in the inner liner of the reactor, heat it to 100-150 °C, and react for 1-3 hours. After the reaction, cool and let it stand. Use N,N-dimethylformamide and pure water to repeatedly centrifuge and wash 3 times until there is no fluorescence to obtain a defective UiO-66-OH aqueous solution. Preparation of defective UiO-66-OH / sodium alginate: i. Slowly pour sodium alginate into pure water that is being stirred, and stir for at least 24 hours until it is evenly dispersed. Then slowly add it into the defective UiO-66-OH aqueous solution obtained in step h, heat to 50-80 ℃, react for 1-2 hours, and after the reaction is completed, cool to room temperature to obtain defective UiO-66-OH / sodium alginate. j. Prepare a calcium chloride aqueous solution with a concentration of 0.1 mg / mL: k. Spray the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j onto the mold, and the transparent packaging film is obtained by self-assembly at room temperature. Alternatively, the defective UiO-66-OH / sodium alginate obtained in step i and the calcium chloride aqueous solution obtained in step j can be directly sprayed onto fruits and vegetables, and after film formation, they can self-assemble into a transparent packaging film.

2. The use of a packaging film obtained by the method of claim 1 in the preparation of a test for organophosphorus pesticides glyphosate, dichlorvos, or dimethoate.

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