Photoresponse dynamic phosphorescent polymer doped film material, preparation method thereof and application of photoresponse dynamic phosphorescent polymer doped film material in phosphorescent visual monitoring of shelf life of chilled food

Abstract

The invention belongs to the technical field of room-temperature phosphorescent film materials, and particularly relates to preparation of a doped film material with polyvinyl alcohol or polyacrylonitrile as a subject and polycyclic aromatic hydrocarbon as an object and application of the doped film material in phosphorescent visual monitoring of the shelf life of chilled food. Phenanthrene (or benzophenanthrene) is used as an object to be doped with polyvinyl alcohol (or polyacrylonitrile) according to a certain proportion, and a uniform and transparent doped film material is obtained. The material has a light activation characteristic, and after the material is illuminated for 120 seconds, the phosphorescence service life is as long as 3.4 seconds, the afterglow time is as long as 70 seconds, and the phosphorescence quantum efficiency is as high as 25.8%. The material has an unusual memory effect, can be kept for 5 hours at room temperature and can be kept for 36 hours at 4 DEG C. According to the phosphorescent doped film material provided by the invention, the range of a photoresponse dynamic organic lasting room-temperature phosphorescent material system is expanded, and a brand-new method for monitoring the shelf life of the chilled food is provided through phosphorescent visualization.

Description

Technical Field

[0001] The present invention relates to the technical field of room temperature phosphorescent film materials, and particularly relates to a light-responsive dynamic phosphorescent polymer-doped film material, a preparation method thereof, and an application thereof in the phosphorescent visualization monitoring of the shelf life of chilled fresh food. Background Art

[0002] The light-responsive dynamic room-temperature phosphorescent materials and their applications have been reported. In 2018, Yang Chaolong, Zhao Yanli and others doped the organic guest molecule hexakis(4-carboxyphenoxy)cyclotriphosphazene into polyvinyl alcohol. Under persistent ultraviolet irradiation, non-covalent cross-linking bonds formed between the host and the guest, causing a photoactivation phenomenon in the doped film. In 2020, the Jinsang Kim research group doped a metal-free pure organic phosphor 2,5-dihexyloxy-4-bromobenzaldehyde into polymethyl methacrylate. Under continuous 365-nm ultraviolet irradiation, the phosphorescence emission of the doped system was significantly enhanced. This is because under ultraviolet irradiation, triplet oxygen is continuously converted into singlet oxygen, resulting in a unique phosphorescence enhancement phenomenon. This organic phosphorescent film has the ability to visualize hidden information and can therefore be used in new security information communication applications (Adv. Optic. Mater. 2020, 8, 2000654). In 2021, the Ma Xiang research group doped a series of organic small molecules based on a single benzene structure into a polymethyl methacrylate matrix, generating photoactivation characteristics. Finally, using the photoactivated phosphorescent properties of the doped film, it can be prepared into anti-counterfeiting labels or used for information storage (Adv. Funct. Mater. 2021, 2010659). In 2021, Li Zhen, Tang Benzhong and others utilized the photo-stimulus response characteristics of polymethyl methacrylate, using phenothiazine derivatives as the luminescent guest and polymethyl methacrylate as the polymer host, to develop a series of photoinduced RTP systems. Through continuous ultraviolet activation, their RTP efficiency can be increased from 0% to 22%. Since these doped film materials exhibit excellent photostability, they have potential applications in leakage testing, microcrack detection, programmable information storage and encryption (Adv. Funct. Mater. 2021, 31, 2101719). In 2021, Li Zhen, Fang Manman and others designed and synthesized a series of triphenylamine derivatives with different aryl substituents to study the influence of the π-conjugated structure on the optical properties of light-responsive materials. With the change of the substituent from a benzene to a naphthalene unit, after dispersing them into a polymethyl methacrylate matrix, the competition between the formation of triplet excitons and cation radicals under light irradiation results in their different light-responsive behaviors (Adv. Mater. 2021, 33, 2104002). In 2022, the Yang Chaolong research group doped biphenyl derivatives substituted with different lengths of alkyl chains into a polyacrylic acid matrix to prepare a series of long-lived photoactivated phosphorescent films. After ultraviolet irradiation for a period of time, the phosphorescence lifetime of the film can reach 2234 ms. This intelligent and light-time-dependent long-lived phosphorescent material has broad application prospects in the field of multi-level information encryption (Nat. Commun. 2021, 12, 2297). In 2023, the Tao Xutang research group used polymethyl methacrylate or polycarbonate as a rigid matrix for doping polycyclic aromatic hydrocarbons to achieve full-color phosphorescence exceeding 5 seconds under ambient conditions.In addition, the afterglow emission of polycarbonate-doped polycyclic aromatic hydrocarbon systems exhibits sensitivity to oxygen, which makes them promising candidates for dynamic phosphorescence-based oxygen sensors (Mater. Horiz., 2023, 10, 197). In 2024, Yang Zhiyong et al. doped terphenyl derivatives into polyvinyl butyral resin, showing reversible photoactivated RTP with a lifetime of up to 5.82 s, and used it as an in-situ modulated anti-counterfeiting label (Sci. Adv. 2024, 10, eadk3354).

[0003] For photo-responsive dynamic room-temperature phosphorescent materials, the structures of guest molecules are mostly complex and the synthesis steps are cumbersome. Secondly, the practical applications of the prepared phosphorescent materials in the food field are scarce. Therefore, the research on organic room-temperature phosphorescent materials still faces the dual challenges of developing dynamic photo-responsive phosphorescent materials with excellent performance and expanding their practical applications in food safety monitoring. Summary of the Invention

[0004] In view of the insufficient number of current photo-responsive dynamic phosphorescent systems and the lack of practical applications, further expansion is still needed. The present invention provides an organic small molecule-polymer doped room-temperature phosphorescent system with a simple guest molecule structure, inexpensive and easily available materials, a simple preparation method, and long lifetime. The present invention uses the means of organic small molecule-polymer doping to achieve ultra-long lifetime photo-responsive dynamic phosphorescence through a low guest doping concentration, and obtains phosphorescent film materials with the longest phosphorescent lifetime of 3.4 s and a phosphorescent quantum efficiency as high as 25.8%, respectively. In addition, by using the "memory effect" of the doped film, it is successfully applied to a method for visually monitoring the shelf life of chilled fresh food through phosphorescence.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A photo-responsive dynamic phosphorescent polymer doped film material, characterized in that the guest molecule is a polycyclic aromatic hydrocarbon and the polymer matrix is polyvinyl alcohol or polyacrylonitrile.

[0006] For the above photo-responsive dynamic phosphorescent polymer doped film material, the mass of the polycyclic aromatic hydrocarbon guest molecule accounts for 0.17 - 6.67% of the mass of the polyvinyl alcohol or polyacrylonitrile main molecule.

[0007] For the above photo-responsive dynamic phosphorescent polymer doped film material, the molecular structures of the main polyvinyl alcohol or polyacrylonitrile are:

[0008]

[0009] For the above photo-responsive dynamic phosphorescent polymer doped film material, the polycyclic aromatic hydrocarbon guest is phenanthrene or terphenyl, and its molecular structure is:

[0010]

[0011] The preparation method of the above-mentioned light-responsive dynamic phosphorescent polymer-doped film material comprises the following steps: Prepare a solution of polyvinyl alcohol or polyacrylonitrile, stir to obtain a polymer solution, prepare a tetrahydrofuran solution of polycyclic aromatic hydrocarbon, mix the polymer solution with the tetrahydrofuran solution of polycyclic aromatic hydrocarbon, drop-coat on a quartz sheet, dry and cool to obtain a polymer-doped film material.

[0012] In the preparation method of the above-mentioned light-responsive dynamic phosphorescent polymer-doped film material, the stirring is carried out at 95 °C for 2 h.

[0013] In the preparation method of the above-mentioned light-responsive dynamic phosphorescent polymer-doped film material, the concentration of the tetrahydrofuran solution of polycyclic aromatic hydrocarbon is 0.5 mg / mL, the concentration of the polymer solution is 30 mg / mL, and the volume ratio of the two is 1:1.

[0014] Application of the above-mentioned light-responsive dynamic phosphorescent polymer-doped film material in phosphorescence visualization for monitoring the shelf life of chilled fresh food.

[0015] In the above application, the doped material is prepared into a time-sensitive anti-counterfeiting label and pasted on the packaging of chilled fresh food. Information is written in situ through a 254 nm ultraviolet lamp, and the freshness supervision of chilled fresh food is carried out by using phosphorescence visualization to trace the non-fresh history of chilled fresh food.

[0016] The light-responsive dynamic phosphorescent polymer-doped film material provided by the present invention has a unique "memory effect", and can be maintained for 5 hours at room temperature and 36 hours at 4 °C. Therefore, the thin film can be prepared into a time-sensitive anti-counterfeiting label and can be used for the freshness supervision of chilled fresh food. The specific operation steps are as follows: Stick the thin film on the packaging of chilled fresh food, write information in situ on the packaging with an ultraviolet lamp and put it in the refrigerator for freshness preservation. Within 36 hours, the label pattern on the packaging is clearly visible under instantaneous irradiation, indicating that the storage meets the regulations. If the chilled fresh food is placed at room temperature for more than 3 hours and then put back into the refrigerator, the pattern will become blurred, indicating that the chilled fresh food is not edible.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The Phen@PVA doped thin film of the present invention can produce dark blue luminescence under instantaneous irradiation of a room temperature ultraviolet lamp. As the irradiation time increases, the luminescence color changes from dark blue to green. After turning off the excitation light source, green phosphorescence can be produced, and the afterglow time is up to 20 seconds. The TP@PVA doped thin film can produce dark blue luminescence under instantaneous irradiation of a room temperature ultraviolet lamp. As the irradiation time increases, the luminescence color changes from dark blue to light blue. After turning off the excitation light source, light blue phosphorescence can be produced, and the afterglow time is up to 70 seconds.

[0019] 2. The photo-responsive dynamic phosphorescent polymer doped film material of the present invention does not require rare elements, has no heavy atoms, is low-cost, has low consumables and simple composition, and does not cause pollution to the environment, providing new theoretical data information for photo-responsive dynamic organic phosphorescent materials and also expanding the types and numbers of photo-responsive dynamic organic phosphorescent material systems.

[0020] 3. The photo-responsive dynamic phosphorescent polymer doped film material provided by the present invention has a photo-activation property. As the illumination time increases, the phosphorescent intensity increases. And after a continuous illumination, only an instantaneous irradiation is needed within a few hours to observe bright phosphorescence, that is, the material has a "memory effect".

[0021] 4. The "memory effect" of the photo-responsive dynamic phosphorescent polymer doped film material provided by the present invention can be maintained for 5 hours at room temperature and for 36 hours at 4 °C, which better meets the actual application requirements. Brief Description of the Drawings

[0022] Figure 1 is the photoluminescence spectrum of the Phen@PVA doped film under different UV irradiation times (λ ex = 254 nm).

[0023] Figure 2 is the photoluminescence spectrum of the TP@PVA doped film under different UV irradiation times (λ ex = 254 nm).

[0024] Figure 3 is the phosphorescence lifetime decay curve of the Phen@PVA doped film under different UV irradiation times (λ ex = 254 nm, delay time = 8 ms).

[0025] Figure 4 is the phosphorescence lifetime decay curve of the TP@PVA doped film under different UV irradiation times (λ ex = 254 nm, delay time = 8 ms).

[0026] Figure 5 are the luminescence photos of the Phen@PVA doped film before and after turning off the excitation light source under different UV irradiation times.

[0027] Figure 6 are the luminescence photos of the TP@PVA doped film before and after turning off the excitation light source under different UV irradiation times.

[0028] Figure 7 are the CIE chromaticity coordinates of the Phen@PVA doped film under different UV irradiation times.

[0029] Figure 8CIE chromaticity coordinates of the TP@PVA doped film under different UV irradiation times.

[0030] Figure 9 Phosphorescence spectra of the TP@PAN doped film under different UV irradiation times in vacuum (λ ex = 254 nm).

[0031] Figure 10 Photoluminescence photos of the Phen@PVA doped film with "memory effect" at room temperature.

[0032] Figure 11 Application of the Phen@PVA doped film in monitoring the shelf life of food through phosphorescence visualization. Detailed implementation mode

[0033] The present invention will be further described in detail below in conjunction with the embodiments.

[0034] Example 1

[0035] Phenanthrene and polyvinyl alcohol doped film (Phen@PVA)

[0036] (I) Materials

[0037] The guest molecule is phenanthrene (Phen), and the polymer host molecule is polyvinyl alcohol (PVA-1788).

[0038] (II) The preparation method is as follows:

[0039] Weigh 0.001 g of phenanthrene and place it in a 5 mL centrifuge tube. Then add 2 mL of tetrahydrofuran and perform ultrasonic treatment at room temperature to prepare a homogeneous tetrahydrofuran solution of phenanthrene with a concentration of 0.5 mg / mL. Weigh 1.2 g of polyvinyl alcohol and place it in a 100 mL round-bottom flask. Add 40 mL of deionized water and stir it at 95 °C for 2 h to prepare an aqueous solution of polyvinyl alcohol with a concentration of 30 mg / mL.

[0040] Mix the above-mentioned tetrahydrofuran solution of phenanthrene and the aqueous solution of polyvinyl alcohol according to a volume ratio of 1:1, and perform ultrasonic treatment to obtain a homogeneous host-guest mixed solution. Take an appropriate amount of the host-guest mixed solution (about 0.5 mL) and evenly drop-coat it on a quartz sheet of 2 cm × 2 cm × 0.1 cm. Then dry it in a blast drying oven at 80 °C for 2 h, take it out and cool it to room temperature to obtain the polymer doped film material (Phen@PVA), where the mass percentage: (mass of phenanthrene molecule / mass of polyvinyl alcohol molecule) × 100% = 1.67%.

[0041] (III) Detection

[0042] 1. Place the Phen@PVA room temperature phosphorescent film material prepared in Example 1 under a 254 nm ultraviolet lamp for excitation to obtain a photoluminescence spectrum. The results are asFigure 1 As shown in the figure. With the increase of the ultraviolet irradiation time, the fluorescence emission intensity of Phen@PVA at 407 nm decreased slightly, while the phosphorescence emission intensities at 470 nm, 503 nm and 541 nm increased significantly. The phosphorescence ratio increased from 17% to 80%.

[0043] 2. The room temperature phosphorescent film material of Phen@PVA prepared in Example 1 was excited under a 254 nm ultraviolet lamp to obtain a phosphorescence lifetime decay curve. The results are as Figure 3 shown. When the ultraviolet irradiation time was 2 min, the phosphorescence lifetime of Phen@PVA increased from the initial 533 ms to 1864 ms; the luminescence photograph of the Phen@PVA film showed that under continuous ultraviolet irradiation, the green afterglow duration exceeded 20 s( Figure 5 ).

[0044] 3. The room temperature phosphorescent film material of Phen@PVA prepared in Example 1 was excited under a 254 nm ultraviolet lamp, and the CIE color coordinates were plotted according to the photoluminescence spectrum. The results are as Figure 7 shown. With the continuous ultraviolet irradiation, the emission color changed from blue-violet (CIE(0.191, 0.153)) to green (CIE(0.237, 0.381)).

[0045] Example 2

[0046] Triptycene and polyvinyl alcohol doped film (TP@PVA)

[0047] (I) Materials

[0048] The guest molecule is triptycene (TP), and the polymer host molecule is polyvinyl alcohol (PVA-1788).

[0049] (II) The preparation method is as follows:

[0050] Replace phenanthrene (Phen) in Example 1 with triptycene (TP), and the remaining preparation steps are the same as those in Example 1 to obtain the phosphorescent doped film material TP@PVA.

[0051] (III) Detection

[0052] 1. The doped film material of TP@PVA prepared in Example 2 was excited under a 254 nm ultraviolet lamp to obtain a photoluminescence spectrum. The results are as Figure 2 shown. With the increase of the illumination time, the fluorescence peak of TP@PVA at 407 nm decreased slightly, and the phosphorescence emission intensities at 432 nm, 465 nm and 495 nm increased significantly. The phosphorescence ratio increased significantly from 10% to 74%.

[0053] 2. The TP@PVA doped membrane material prepared in Example 2 was excited under a 254 nm ultraviolet lamp to obtain a phosphorescence lifetime decay curve, and the results are as Figure 4 shown. When the ultraviolet irradiation time was 2 min, the phosphorescence lifetime of Phen@PVA increased from the initial 606 ms to 3397 ms; the luminescence photograph of the TP@PVA thin film showed that under continuous ultraviolet irradiation, the light blue afterglow lasted for more than 70 s( Figure 6 ).

[0054] 3. The TP@PVA doped membrane material prepared in Example 2 was excited under a 254 nm ultraviolet lamp, and the CIE color coordinates were plotted according to the photoluminescence spectrum, and the results are as Figure 8 shown. With the continuous irradiation of ultraviolet light, the emission color changed from dark blue (CIE(0.168,0.061)) to light blue (CIE(0.169,0.140)).

[0055] Example 3

[0056] Triptycene and polyacrylonitrile doped thin film (TP@PAN)

[0057] (I) Materials

[0058] The guest molecule is triptycene (TP), and the polymer host molecule is polyacrylonitrile (PAN) with M w = 150000 g / mol.

[0059] (II) The preparation method is as follows:

[0060] Weigh 0.001 g of triptycene and place it in a 5 mL centrifuge tube, then add 2 mL of tetrahydrofuran, and perform ultrasonic treatment at room temperature to prepare a uniform tetrahydrofuran solution of triptycene with a concentration of 0.5 mg / mL. Weigh 1.2 g of polyacrylonitrile and place it in a 100 mL round-bottom flask, add 40 mL of N,N-dimethylformamide, and stir it at 95 °C for 2 h to prepare a polyacrylonitrile solution with a concentration of 30 mg / mL.

[0061] Mix the above tetrahydrofuran solution of triptycene and the polyacrylonitrile solution in a volume ratio of 1:1, and after ultrasonic treatment, obtain a uniform host-guest mixed solution. Take an appropriate amount of the host-guest mixed solution (about 0.5 mL) and evenly drop-coat it on a 2 cm × 2 cm × 0.1 cm quartz sheet, then dry it in a forced-air drying oven at 100 °C for 2 h, take it out and cool it to room temperature to obtain a polymer-doped membrane material (TP@PAN), where the mass percentage: (molecular mass of triptycene / molecular mass of polyacrylonitrile) × 100% = 1.67%.

[0062] (II) Detection

[0063] 1. The TP@PAN doped film material prepared in Example 3 was excited under a 254 nm ultraviolet lamp to obtain the phosphorescence spectrum under vacuum. The results are as Figure 9 shown. With the increase of the ultraviolet irradiation time, the phosphorescence emission of TP@PAN was significantly enhanced.

[0064] Example 4

[0065] The Phen@PVA doped film material prepared in Example 1 was excited under a 254 nm ultraviolet lamp for one minute. Within 5 hours, the doped film no longer needed to be continuously irradiated with ultraviolet light for the second time under ambient conditions. Obvious afterglow could be observed under instantaneous ultraviolet irradiation, indicating that the doped film had a "memory effect" ( Figure 10 ).

[0066] Example 5

[0067] The doped material of Example 1 (Phen@PVA) was made into a time-sensitive anti-counterfeiting label, and phosphorescence visualization was used to supervise the freshness preservation of chilled foods. The specific operation steps are as follows: The preparation steps of the doped film were the same as those in Example 1. A mask plate was covered on the Phen@PVA, and information was written by in-situ activation with a 254 nm ultraviolet lamp for 2 minutes. The activated film was pasted on the chilled food packaging and put into the refrigerator for freshness preservation. Within 36 hours, the label pattern on the chilled food packaging was still clearly visible under instantaneous ultraviolet irradiation, indicating that the storage met the regulations. If the chilled food was placed at room temperature for more than 3 hours and then put back into the refrigerator, the pattern would become blurred, indicating that the food was not edible. Thus, the ability of this light-responsive dynamic phosphorescent doped film to store data has potential application value in the supervision of chilled food freshness preservation ( Figure 11 ).

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A photoresponsive dynamic phosphorescent polymer doped film material, characterized in that: The guest molecules are polycyclic aromatic hydrocarbons, and the polymer matrix is ​​polyvinyl alcohol or polyacrylonitrile.

2. The photoresponsive dynamic phosphorescent polymer doped film material according to claim 1, characterized in that: The molecular weight of the guest polycyclic aromatic hydrocarbons accounts for 0.17 to 6.67% of the molecular weight of the main polyvinyl alcohol or polyacrylonitrile.

3. The photoresponsive dynamic phosphorescent polymer doped film material according to claim 1, characterized in that: The molecular structure of the main polyvinyl alcohol or polyacrylonitrile is:

4. The photoresponsive dynamic phosphorescent polymer doped film material according to claim 1, characterized in that: The polycyclic aromatic hydrocarbon guest is phenanthrene or triphenylene, and its molecular structure is:

5. The method for preparing the light-responsive dynamic phosphorescent polymer doped film material according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: preparing polyvinyl alcohol or polyacrylonitrile into a solution, stirring to obtain a polymer solution, preparing a tetrahydrofuran solution of polycyclic aromatic hydrocarbons, mixing the polymer solution with the tetrahydrofuran solution of polycyclic aromatic hydrocarbons, dripping the mixture on a quartz sheet, drying and cooling to obtain a polymer doped film material.

6. The method for preparing the light-responsive dynamic phosphorescent polymer doped film material according to claim 5, characterized in that: The stirring is stirring at 95° C. for 2 h.

7. The method for preparing the light-responsive dynamic phosphorescent polymer doped film material according to claim 5, characterized in that: The concentration of the tetrahydrofuran solution of polycyclic aromatic hydrocarbons is 0.5 mg / mL, and the concentration of the polymer solution is 30 mg / mL, and the volume ratio of the two is 1:

1.

8. Application of the light-responsive dynamic phosphorescent polymer-doped film material according to any one of claims 1 to 4 in monitoring the shelf life of chilled food by phosphorescence visualization.

9. According to the application of claim 8, the doped material is prepared into an anti-counterfeiting label with time validity and pasted on the packaging of chilled food. Information is written in situ by a 254nm ultraviolet lamp, and phosphorescence visualization is used to monitor the freshness of chilled food and trace the history of staleness of chilled food.

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