A long afterglow composite based on polyvinyl alcohol and xanthan gum and a preparation method and application thereof

Abstract

The application discloses a long afterglow composite based on polyvinyl alcohol and xanthan gum and a preparation method and application thereof. The specific steps of the method are as follows: S1: polyvinyl alcohol PVA is poured into a beaker and deionized water is added to stir until completely dissolved, and is prepared for use; S2: xanthan gum XG is poured into a beaker and deionized water is added to stir until completely dissolved, and is prepared for use; S3: after the polyvinyl alcohol PVA and the xanthan gum XG solution are mixed, a long afterglow composite guest molecule is added and is uniformly stirred to obtain a mixed solution; and S4: the mixed solution is placed on a substrate and is dried to obtain a long afterglow composite film doped with polyvinyl alcohol and xanthan gum. The blending strategy of the method has a better network structure, effectively inhibits the vibration of a chromophore, and inhibits non-radiative transition. The long afterglow composite based on polyvinyl alcohol and xanthan gum is applied to information encryption and preparation of anti-counterfeiting patterns.

Description

Technical Field

[0001] This invention relates to the field of organic light-emitting materials, specifically to a long afterglow composite material based on polyvinyl alcohol and xanthan gum, its preparation method, and its application. Technical Background

[0002] In the field of solid-state luminescent materials physics and chemistry, persistent luminescent materials, as a special class of photoelectric energy storage materials, have always occupied an important position in basic research and practical applications due to their ability to continue emitting light radiation after excitation ceases. Inorganic persistent luminescent materials achieve long-persistent luminescence based on the trapping of photogenerated carriers by trap energy levels and thermally stimulated release. Their outstanding advantages are long luminescence lifetime, high chemical stability, and excellent afterglow brightness, and they are mainly used in fields such as nighttime safety indication, emergency lighting, and high-energy ray detection. The long-persistent phenomenon of organic persistent luminescent materials originates from the radiative transition after the intersystem crossing (ISC) of excited-state molecules to the triplet excited state. To achieve efficient and sustained long-persistent emission, organic molecules usually need to be assembled or doped in a rigid host matrix (such as small molecule crystals, polymer matrices, or macrocyclic compounds). This rigid environment can effectively suppress non-radiative transitions (such as molecular vibration and rotation) and oxygen quenching that triplet excitons are susceptible to, thereby stabilizing the triplet excited state and extending the luminescence lifetime.

[0003] Compared to inorganic systems, organic long-afterglow materials exhibit extremely high design freedom and functional plasticity at the molecular level due to the tunability of their conjugated molecular structures. Through precise molecular engineering and assembly control, not only can controllable emission across the entire spectrum of red, green, and blue wavelengths be achieved under mild conditions, but more importantly, their inherent flexibility, solution processability, and biocompatibility give them unparalleled advantages in cutting-edge applications such as bioimaging, anti-counterfeiting encryption, and flexible optoelectronic devices. In-depth exploration of the excited-state regulation mechanisms and structure-property relationships in organic long-afterglow materials is of significant scientific importance and application value for promoting original innovation in next-generation intelligent luminescent materials.

[0004] Currently, organic long-afterglow materials generally face problems such as severe non-radiative transition losses, short afterglow lifetime (usually less than 10 seconds), and low luminous efficiency; some inorganic long-afterglow materials containing heavy metals have limitations such as poor biocompatibility and insufficient environmental friendliness; at the same time, most long-afterglow materials rely on a single matrix system, which has limited effect on fixing the luminescent object, making it difficult to achieve both multi-color tunable emission and high performance.

[0005] Polyvinyl alcohol (PVA), a typical water-soluble polymer, possesses excellent film-forming properties, transparency, and mechanical flexibility, making it an ideal candidate material for constructing flexible composite matrices. Although the PVA molecular chain itself does not contain luminescent chromophores and does not produce intrinsic long-afterglow emission, the abundant hydroxyl groups in its side chains enable it to form a dense intramolecular / intermolecular hydrogen bond network. This characteristic allows it to construct a highly rigid local microenvironment for the luminescent guests doped within it, effectively suppressing nonradiative transitions of excited states through spatial confinement effects, thus providing the necessary prerequisite for activating and stabilizing organic long-afterglow luminescence.

[0006] Xanthan gum (XG), an anionic polysaccharide produced by microbial fermentation, further enriches the construction dimensions of dual-host systems. This material not only possesses excellent colloidal stability, maintaining structural integrity across a wide pH range (2-12), high-salt environments, and even short-term high temperatures (120°C), but its abundant carboxyl and hydroxyl groups on its molecular chain also endow it with a strong ability to construct three-dimensional hydrogen-bonded networks. Although xanthan gum itself does not possess photoelectric activity, its rich active functional groups can form complementary cross-linked or interpenetrating network structures with PVA, allowing for precise control over the system's rigidity and water solubility through chemical modification or physical doping.

[0007] Based on the good compatibility of the two in aqueous solution and their ability to synergistically construct hydrogen bond networks, this invention proposes a long afterglow composite material based on polyvinyl alcohol and xanthan gum, its preparation method and application. By constructing a PVA / XG dual-matrix doping system, the film-forming properties and basic framework provided by PVA, as well as the additional crosslinking sites and microenvironment stability contributed by XG, are used to jointly construct a more dense and uniform rigid matrix. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a long-afterglow composite material based on polyvinyl alcohol (PVA) and xanthan gum, its preparation method, and its applications. PVA and Xanthan gum are blended to form a dual-host system, and different long-afterglow guest molecules are in-situ doped to achieve multicolor long-afterglow emission. By constructing a dual-host synergistic system with a multi-component hydrogen-bonded network, the dispersion stability and excited-state protection capability of long-afterglow guest molecules can be significantly improved. Compared to a single PVA or Xanthan gum host, this blending strategy has a better network structure, effectively suppressing chromophore vibrations and non-radiative transitions.

[0009] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing a long afterglow composite material based on polyvinyl alcohol and xanthan gum, specifically comprising the following steps:

[0010] S1: Pour polyvinyl alcohol (PVA) into a beaker and add deionized water, stirring until completely dissolved. Set aside.

[0011] S2: Pour xanthan gum XG into a beaker and add deionized water, stirring until completely dissolved. Set aside.

[0012] S3: Mix polyvinyl alcohol (PVA) and xanthan gum (XG) solutions, add long afterglow composite material guest molecules, mix and stir until homogeneous to obtain a mixed solution;

[0013] S4: The mixed solution is placed on a substrate and dried to obtain a long afterglow composite film doped with polyvinyl alcohol and xanthan gum.

[0014] Using the above technical solution, polyvinyl alcohol (PVA) and xanthan gum (XG) are dissolved separately in water and mixed. Long-afterglow composite material guest molecules are then added and stirred until completely dissolved and uniformly mixed. After depolymerization, a polymer film doped with the guest is obtained, which is the long-afterglow composite material. In other words, by blending PVA and XG to form a dual-host system, the long-afterglow composite material is in-situ doped, thereby achieving multicolor long-afterglow emission. The dual-host system contains abundant hydroxyl groups, which can form various intramolecular and intermolecular hydrogen bonds with guest molecules. During the blending process, the guest is incorporated into the system. After the reaction is complete, the hydrogen bond network is formed, at which point the guest is almost uniformly embedded and more firmly and stably. Compared to a single PVA or XG host, the blending strategy designed in this way has a better network structure, effectively suppressing chromophore vibrations and non-radiative transitions. By constructing a composite matrix system of polyvinyl alcohol (PVA) and xanthan gum (XG), and utilizing the hydrogen bonding interactions and synergistic network structure between their molecular chains, efficient encapsulation and rigid environmental control of long-afterglow guest molecules are achieved. This significantly suppresses non-radiative transition losses, extends afterglow lifetime, and improves luminous efficiency. This composite matrix combines the excellent film-forming properties of PVA with the biocompatibility, hydrophilicity, and shear-thickening properties of XG. Flexible composite films can be prepared through simple solution blending and drying processes. This not only solves the problem of insufficient fixation of guest molecules by traditional single matrices but also enables multi-color long-afterglow emission by controlling the types and doping ratios of guest molecules, providing a new avenue for expanding the application of long-afterglow materials in fields such as information encryption and anti-counterfeiting.

[0015] Preferably, the mass ratio of polyvinyl alcohol (PVA) to xanthan gum (XG) is (1~10):1.

[0016] Preferably, the guest molecule in the long afterglow composite material accounts for 1 to 10 wt% of the sum of the masses of polyvinyl alcohol (PVA) and xanthan gum (XG). The doping ratio refers to the mass ratio of the guest molecule to the two host molecules.

[0017] Preferably, the doping ratio of the guest molecules in the long afterglow composite material is 1wt%, 3wt%, 5wt%, 8wt%, or 10wt%.

[0018] Preferably, the general structural formula of the guest molecules in the long afterglow composite material is:

[0019] .

[0020] Preferably, the guest molecules of the long afterglow composite material are selected from one or more of NPBA, CzPBA, PyBA, DPCZ, BCz, NL, and CZ.

[0021] The structure of PyBA is as follows:

[0022] ;

[0023] The structural formula of DPCZ is:

[0024] ;

[0025] The structural formula for CZ is:

[0026] ;

[0027] The structural formula of BCz is:

[0028] ;

[0029] The structural formula of NL is:

[0030] ;

[0031] The structural formula for NPBA is:

[0032] ;

[0033] The structural formula for CzPBA is:

[0034] .

[0035] Preferably, the stirring temperature in step S1 is 60-90℃; and the stirring time in step S3 is 30 minutes.

[0036] Preferably, after stirring in step S4, the mixed solution is poured onto the substrate and dried at room temperature for 12 hours; then placed in a 50°C forced-air drying oven and dried for 12 hours to finally obtain a long afterglow composite film doped with polyvinyl alcohol and xanthan gum.

[0037] A second aspect of the present invention is to provide a long afterglow composite material based on polyvinyl alcohol and xanthan gum as described in the first aspect of the present invention, wherein the long afterglow composite material comprises polyvinyl alcohol (PVA), xanthan gum (XG) and long afterglow composite material guest molecules; the mass ratio of polyvinyl alcohol (PVA) to xanthan gum (XG) is (1~10):1; and the doping ratio of the sum of the masses of polyvinyl alcohol (PVA) and xanthan gum (XG) in the long afterglow composite material is 1~10 wt%.

[0038] Using the above technical solution, no chemical reaction occurs between the components. Instead, a stable composite system is formed only through physical interactions such as hydrogen bonds, van der Waals forces, and π–π stacking. Long-afterglow guest molecules are uniformly dispersed and fixed in a rigid matrix formed by polyvinyl alcohol and xanthan gum, and long-afterglow luminescence is achieved by suppressing non-radiative molecular transitions.

[0039] Preferably, the total mass of polyvinyl alcohol (PVA) and xanthan gum (XG) in the long afterglow composite material is 1 wt%, 3 wt%, 5 wt%, 8 wt%, or 10 wt%.

[0040] A third aspect of the present invention is to provide an application of a long afterglow composite material based on polyvinyl alcohol and xanthan gum, as described in the first and second aspects of the present invention, in realizing information encryption and preparing anti-counterfeiting patterns.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) For the first time, the PVA-XG dual-matrix network was applied to long afterglow materials, and a stable composite system was constructed through physical interaction, which is fundamentally different from existing long afterglow materials with single polymer matrix or inorganic matrix.

[0043] (2) This method blends PVA and XG to form a dual-host system, and in-situ doping with different guest molecules achieves multicolor long afterglow emission. The dual-host system contains abundant hydroxyl groups, which can form a variety of intramolecular and intermolecular hydrogen bonds with guest molecules. During the blending process, the guest molecules are incorporated into the system. After the reaction is complete, the hydrogen bond network is formed, at which point the guest molecules are almost uniformly embedded and are more robust and stable. Compared with a single PVA or XG host, this blending strategy has a better network structure, effectively suppressing chromophore vibrations and nonradiative transitions. It solves the technical problem of short afterglow lifetime and biocompatibility that are difficult to balance in traditional materials.

[0044] (3) The long-afterglow composite material based on polyvinyl alcohol and xanthan gum can be used to realize information encryption and prepare anti-counterfeiting patterns. It can also be extended to fields such as bio-imaging (using its biocompatibility to realize long-term light emission tracking in vivo), flexible display (preparing flexible long-afterglow light-emitting devices), and emergency indication (such as safety signs in low-light environments). Attached Figure Description

[0045] Figure 1 This is a graph showing the afterglow duration variation of PVA@XG@DPCZ films with different doping ratios under 254 nm excitation in Example 1;

[0046] Figure 2 This is a graph showing the afterglow duration variation of PVA@XG@BCZ films with different doping ratios under 365 nm excitation in Example 2;

[0047] Figure 3 This is a graph showing the afterglow duration variation of PVA@XG@CZ films with different doping ratios under 254 nm excitation in Example 3;

[0048] Figure 4 This is a graph showing the afterglow duration variation of PVA@XG@NL films with different doping ratios under 254 nm excitation in Example 4;

[0049] Figure 5 This is a graph showing the afterglow duration variation of PVA@DPCZ, XG@DPCZ, and PVA@XG@DPCZ films with a 5wt% ratio under 254 nm excitation.

[0050] Figure 6 The images show the XRD patterns of PVA, PVA@XG, PVA@XG@BCZ, PVA@XG@CZ, PVA@XG@DPCZ, and PVA@XG@NL; (a) is the XRD pattern of the PVA film; (b) is the XRD pattern of the PVA@XG film; (c) is the XRD pattern of the PVA@XG@BCZ film; (d) is the XRD pattern of the PVA@XG@CZ film; (e) is the XRD pattern of the PVA@XG@DPCZ film; and (f) is the XRD pattern of the PVA@XG@NL film.

[0051] Figure 7 The UV-Vis absorption spectra of guest molecules DPCZ, BCZ, CZ, and NL in dilute dichloromethane solution are shown below: (a) is the UV-Vis absorption spectrum of DPCZ, with absorption peaks at 256.5 nm and 288.5 nm; (b) is the UV-Vis absorption spectrum of BCZ, with absorption peaks at 263.5, 284.5, 323, and 358.5 nm; (c) is the UV-Vis absorption spectrum of CZ, with absorption peaks at 256, 291, 319, and 332.5 nm; and (d) is the UV-Vis absorption spectrum of NL, with absorption peaks at 279.5, 332, and 341 nm.

[0052] Figure 8The excitation-emission two-dimensional spectra of DPCZ, BCZ, CZ, and NL in dilute dichloromethane solution are shown in Figure 1; (a) is the excitation-emission two-dimensional spectrum of DPCZ; (b) is the excitation-emission two-dimensional spectrum of BCZ; (c) is the excitation-emission two-dimensional spectrum of CZ; and (d) is the excitation-emission two-dimensional spectrum of NL.

[0053] Figure 9 The images show the steady-state and transient spectra of PVA@XG@DPCZ films with different ratios, respectively; where (a) is the steady-state spectrum and (b) is the transient spectrum.

[0054] Figure 10 These are the lifetime decay curves of PVA@XG@DPCZ films with different ratios;

[0055] Figure 11 These are the steady-state and transient spectra of PVA@XG@CZ films with different ratios, where (a) is the steady-state spectrum and (b) is the transient spectrum.

[0056] Figure 12 These are the lifetime decay curves of PVA@XG@CZ films with different ratios;

[0057] Figure 13 These are the steady-state and transient spectra of PVA@XG@BCZ films with different proportions, where (a) is the steady-state spectrum and (b) is the transient spectrum.

[0058] Figure 14 These are the lifetime decay curves of PVA@XG@BCZ films with different proportions;

[0059] Figure 15 These are the steady-state and transient spectra of PVA@XG@NL films with different ratios, where (a) is the steady-state spectrum and (b) is the transient spectrum.

[0060] Figure 16 These are the lifetime decay curves of PVA@XG@NL films with different ratios;

[0061] Figure 17 The process involves sequentially coating a decorative item with 1 wt% PVA@XG@BCZ, 1 wt% PVA@XG@BCZ, 3 wt% PVA@XG@CZ, and 5 wt% PVA@XG@DPCZ films to give it afterglow properties.

[0062] Figure 18 This is a simple application of encrypting information using three combinations: the first line is 1wt% PVA@XG@BCZ, the second and third lines are both 1wt% PVA@XG@BCZ, 3wt% PVA@XG@NL, and 5wt% PVA@XG@DPCZ.

[0063] Figure 19 The material was molded into different shapes, demonstrating its strong plasticity. The first column is 5wt% PVA@XG@DPCZ, the second column is 1wt% PVA@XG@BCZ, the third column is 3wt% PVA@XG@CZ, and the fourth column is 1wt% PVA@XG@BCZ.

[0064] Figure 20 Comparison of luminescence effects of thin films prepared by different doping of the same luminescent object with the same proportion;

[0065] Figure 21 The stress-strain curve of the PVA film in this invention;

[0066] Figure 22 The stress-strain curve of the PVA@XG thin film in this invention;

[0067] Figure 23 The stress-strain curve of the PVA@XG@DPCz film in this invention;

[0068] Figure 24 This is a graph showing the afterglow duration variation of PVA@XG@CzPBA films with different doping ratios under 254 nm excitation in this invention.

[0069] Figure 25 This is a graph showing the afterglow duration variation of PVA@XG@NPBA films with different doping ratios under 254 nm excitation in this invention.

[0070] Figure 26 This is a graph showing the afterglow duration variation of PVA@XG@PyBA films with different doping ratios under 365 nm excitation in this invention. Detailed Implementation

[0071] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0072] Unless otherwise specified, the preparation methods and usage conditions used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0073] To avoid excessive and unnecessary detail, well-known structures or functions will not be described in detail in the following embodiments. The approximate language used in the following embodiments is for quantitative purposes, indicating that variations in quantity are permissible without altering the basic function. Unless otherwise defined, the technical and scientific terms used in the following embodiments have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0074] DPCZ: 3,6-diphenyl-9H-carbazole, 3,6-diphenylcarbazole or 3,6-diphenyl-9H-carbazole;

[0075] NPBA: naphthalen-1-ylboronic acid, 1-naphthalenoboronic acid or naphthalen-1-ylboronic acid;

[0076] CzPBA: (4-(9H-carbazol-9-yl)phenyl)boronic acid, 4-(9H-carbazol-9-yl)phenylboronic acid or 4-carbazol-9-ylphenylboronic acid;

[0077] PyBA: pyren-1-ylboronic acid, 1-pyrenoboronic acid or pyren-1-ylboronic acid;

[0078] BCZ: 7H-benzo[c]carbazole, benzo[c]carbazole or 7H-benzo[c]carbazole or benzo[c]carbazole;

[0079] NL: 1H-benzo[de]isoquinoline-1,3(2H)-dione, 1,8-naphthylimide or naphthalenediamine or 1H-benzo[de]isoquinoline-1,3(2H)-dione;

[0080] CZ: Carbazole, carbazole.

[0081] Example 1 (PVA@XG@DPCZ film): The preparation of this long afterglow composite material based on polyvinyl alcohol and xanthan gum is as follows:

[0082] S1: Weigh 0.5g of polyvinyl alcohol (PVA) and pour it into a beaker. Add 10mL of deionized water and stir magnetically in an 80℃ constant temperature water bath for 30min until completely dissolved. Cool to room temperature and set aside.

[0083] S2: Weigh 0.05g xanthan gum XG into a beaker, add 10mL of deionized water, and stir magnetically for 60min at room temperature until completely dissolved. Set aside.

[0084] S3: Mix the polyvinyl alcohol (PVA) solution obtained in step S1 and the xanthan gum (XG) solution obtained in step S2. Weigh out 0.0055g, 0.0165g, 0.0275g, 0.0440g, and 0.0550g of DPCZ respectively and pour them directly into the mixed solution and stir for 30min.

[0085] S4: After stirring, pour the mixture onto a stainless steel plate and dry it at room temperature for 12 hours, then place it in a 50℃ forced-air drying oven and dry it for another 12 hours. Finally, samples with proportions of 1wt%, 3wt%, 5wt%, 8wt%, and 10wt% are obtained.

[0086] like Figure 1 The figure shows the afterglow duration variation of PVA@XG@DPCZ films with different doping ratios under 254 nm excitation. Under this wavelength of excitation, it can be clearly seen that the 5wt% ratio has a better effect.

[0087] Example 2 (PVA@XG@BCZ film): The difference from Example 1 is that the long afterglow composite material guest molecules in step S3 are replaced with BCZ. The specific steps are the same as those in Example 1.

[0088] like Figure 2 The figure shows the afterglow duration variation of PVA@XG@BCZ films with different doping ratios under 365 nm excitation. Under this wavelength of excitation, it can be clearly seen that the 4wt% ratio has a better effect.

[0089] Example 3 (PVA@XG@CZ film): The difference from Example 1 is that the long afterglow composite material guest molecule in step S3 is replaced with CZ, and the other operations are the same as in Example 1.

[0090] like Figure 3 The figure shows the afterglow duration variation of PVA@XG@CZ films with different doping ratios under 254 nm excitation. Under this wavelength excitation, it can be seen that the 1wt% ratio has a better effect.

[0091] Example 4 (PVA@XG@NL film): The difference from Example 1 is that the long afterglow composite material guest molecule in step S3 is replaced with NL, and the other operations are the same as in Example 1.

[0092] like Figure 4 The figure shows the afterglow duration variation of PVA@XG@NL films with different doping ratios under 254 nm excitation. Under this wavelength excitation, a 5wt% doping ratio can produce a relatively good effect.

[0093] Example 5 (PVA@XG@CzPBA film): The difference from Example 1 is that the long afterglow composite material guest molecule in step S3 is replaced with CzPBA, and the other operations are the same as in Example 1.

[0094] Figure 24 This is a graph showing the afterglow duration variation of PVA@XG@CzPBA films with different doping ratios under 254 nm excitation in Example 5. From... Figure 24As can be seen, the afterglow duration varies with different doping ratios, with 3% and 5% showing relatively better performance.

[0095] Example 6 (PVA@XG@NPBA film): The difference from Example 1 is that the long afterglow composite material guest molecule in step S3 is replaced with NPBA, and the other operations are the same as in Example 1.

[0096] Figure 25 This is a graph showing the afterglow duration variation of PVA@XG@NPBA films with different doping ratios under 254 nm excitation in Example 6. Figure 25 As can be seen, the afterglow duration varies with different doping ratios, with 4% showing relatively better performance.

[0097] Example 7 (PVA@XG@PyBA film): The difference from Example 1 is that the long afterglow composite material guest molecule in step S3 is replaced with PyBA, and the other operations are the same as in Example 1.

[0098] Figure 26 This is a graph showing the afterglow duration variation of PVA@XG@PyBA films with different doping ratios under 365 nm excitation in Example 7. From... Figure 26 As can be seen, the afterglow duration varies with different doping ratios, with 3% showing relatively better performance.

[0099] Comparative Example 1 (PVA@DPCz film): The specific preparation steps of this PVA@DPCz film are as follows:

[0100] Weigh 0.5g of PVA into a beaker, add 10mL of deionized water, stir at 80℃ until completely dissolved, and cool to room temperature. Weigh 0.0250g of DPCZ and add it directly to the PVA solution, stirring for 30min. After stirring, pour the solution onto a stainless steel plate and dry at room temperature for 12 hours, then place it in a 50℃ forced-air drying oven for another 12 hours to obtain a 5wt% sample.

[0101] Comparative Example 2 (XG@DPCz film): The specific preparation steps of this XG@DPCz film are as follows: Weigh 0.5g of XG and pour it into a beaker, add 20mL of deionized water, and stir at room temperature until completely dissolved. Weigh 0.0250g of DPCz and pour it directly into the XG solution, stirring for 30min. After stirring, pour it onto a stainless steel plate and dry at room temperature until fully formed, then place it in a 50℃ forced-air drying oven for 12 hours to obtain a sample with a final concentration of 5wt%.

[0102] like Figure 5The figure shows the afterglow duration variation of Comparative Example 1 (PVA@DPCZ film), Comparative Example 2 (XG@DPCZ film), and Example 1 (PVA@XG@DPCZ film) under 254nm excitation at a 5wt% ratio. Here we can see that XG alone as the host has no afterglow, PVA alone has afterglow but the duration is relatively short, while the duration of the dual-host PVA@XG@DPCZ film is much longer than that of the single-host film.

[0103] like Figure 6 The figures shown are XRD patterns of PVA, PVA@XG, PVA@XG@DPCZ, Example 2 (PVA@XG@BCZ), Example 3 (PVA@XG@CZ), and Example 4 (PVA@XG@NL). Figure 6 As can be seen from the XRD test of PVA, a broad peak appears at 19.3°, which is a unique characteristic of PVA. The crystallinity of the film did not change after the addition of XG. After the addition of DPCZ, crystallization peaks appeared at 7°, 10°, 11°, 19.9°, and 27.8°. After the addition of BCZ, crystallization peaks appeared at 9°, 10°, 13°, 18°, and 22.5°. After the addition of CZ, crystallization peaks appeared at 9.1°, 18.4°, and 27.9°. After the addition of NL, crystallization peaks appeared at 8.6°, 11.8°, 17.3°, and 24.3°. The shift in diffraction peaks may be due to the incorporation of guest molecules into the polymer system, affecting the polymer arrangement. Simultaneously, dispersed doping of guest molecules makes it difficult to form large crystal morphologies. The combination of these two factors leads to the shift in diffraction peaks. This shift indicates that the guest molecules are fully incorporated into the polymer matrix and are constrained and protected by the network structure of the polymer matrix.

[0104] Figure 7 The images show the absorption spectra of DPCZ, BCZ, CZ, and NL in dilute solutions. CZ exhibits absorption peaks at 256, 291, 319, and 332.5 nm, and the absorption in the 250-300 nm region is attributed to high-energy π−π. ∗The absorption peaks in the 300-350 nm region, characterized by weak transitions and distinct fine vibrational structures, are typical spectral features of rigid planar molecules. DPCZ exhibits absorption peaks at 256.5 and 288.5 nm. Compared to the CZ structure, the elongation of the conjugated system in DPCZ reduces the band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and the outer benzene ring can rotate freely through single bonds, reducing the overall rigidity of the molecule. This causes the fine vibrational structure previously present in CZ at >300 nm to disappear, resulting in a broader absorption band. BCZ shows absorption peaks at 263.5, 284.5, 323, 339.5, and 358.5 nm. The introduction of the fused ring structure significantly increases the delocalization range of π electrons (leading to a significant redshift), while maintaining high planar rigidity. Therefore, some fine vibrational absorption can still be observed in the long-wavelength region. NL exhibits absorption peaks at 279.5, 332, and 341 nm. The introduction of strong electron-withdrawing groups significantly lowers the LUMO energy level of the molecule, resulting in lower energy required for π−π∗ transitions. Therefore, its main absorption band appears directly in the lower energy (long wavelength) region.

[0105] Figure 8 The excitation-emission two-dimensional spectra of DPCZ, BCZ, CZ, and NL in dilute solutions are shown. All four samples exhibit obvious fluorescence emission characteristics. The optimal excitation wavelength (Ex) of DPCZ, BCZ, and CZ is between 240-300 nm, and the main emission wavelength (Em) is concentrated in the range of 350-450 nm. Specifically, the main emission peaks of DPCZ and BCZ are located in the longer wavelength region (approximately 380-420 nm), showing a redshift compared to CZ (340-370 nm), which is attributed to a lower energy emission state or a stronger excited state relaxation effect. The excitation wavelength of NL appears between 320-350 nm, significantly different from the other three, attributable to its different molecular structure. The diagonal line near Em≈Ex is attributed to first-order Rayleigh scattering, and the diagonal line near Em≈2Ex is attributed to second-order Rayleigh scattering.

[0106] Figure 9 These are the steady-state and transient spectra of Example 1 (PVA@XG@DPCZ thin film) with different doping ratios, from... Figure 9 As can be seen in (a), the steady-state luminescence intensity reaches its maximum at around 388 nm for different doping ratios, with the peak intensity occurring when the doping ratio is 8 wt%. Meanwhile, as... Figure 9 As shown in (b), the transient spectral intensity reaches its maximum at around 440 nm, and the steady-state luminescence intensity reaches its peak at a doping ratio of 5 wt%. This represents an improvement of approximately 220% compared to an 8 wt% doping ratio.

[0107] Figure 10 These are lifetime decay curves for PVA@XG@DPCZ films with different proportions at the emission peak of 484 nm. The lifetime of the 1wt% sample reached 2431.19 ms, the 3wt% sample reached 2504.39 ms, the 5wt% sample reached 2774.38 ms, the 8wt% sample reached 2323.13 ms, and the 10wt% sample reached 2299.8 ms. Based on the lifetime results, the 5wt% sample exhibited the best performance.

[0108] Figure 11 These are the steady-state and transient spectra of PVA@XG@CZ films with different proportions. The steady-state spectra were excited using a 348 nm light source, with the optimal emission peak at 420 nm. The emission peak intensity was lowest at 0.5 wt% and highest at 6 wt%. The transient spectra were excited using a 298 nm light source, with the optimal emission peak at 440 nm. The emission peak intensity was lowest at 0.5 wt% and highest at 2 wt%.

[0109] Figure 12 These are the lifetime decay curves for PVA@XG@CZ films with different proportions. The 2wt% sample has the longest lifetime, while the 0.5wt% sample has the shortest lifetime.

[0110] Figure 13 These are the steady-state and transient spectra of PVA@XG@BCZ films with different proportions. The steady-state spectra were excited using a 320 nm light source, with the optimal emission peak at 394 nm. The emission peak intensity was lowest at 0.5 wt% and highest at 4 wt%. The transient spectra were excited using a 365 nm light source, with the optimal emission peak at 528 nm. The emission peak intensity was lowest at 0.5 wt% and highest at 4 wt%.

[0111] Figure 14 These are the lifetime decay curves for PVA@XG@BCZ films with different proportions. The 1wt% sample has the longest lifetime, while the 8wt% sample has the shortest lifetime.

[0112] Figure 15 These are the steady-state and transient spectra of PVA@XG@NL films with different proportions. The steady-state spectra, excited by a 320 nm light source, show two optimal emission peaks at 406 and 592 nm, with the lowest intensity at 0.1 wt% and the highest intensity at 10 wt%. The transient spectra, excited by a 350 nm light source, show two peaks at 540 and 590 nm. At both 540 and 590 nm, the lowest intensity is at 0.1 wt%, while the highest intensity is at 540 nm (10 wt%) and at 590 nm (3 wt%).

[0113] Figure 16 These are the lifetime decay curves for PVA@XG@NL films with different proportions. The 10wt% sample has the longest lifetime, while the 5wt% sample has the shortest lifetime.

[0114] Application Example 1 (Anti-counterfeiting label):

[0115] Following the method in Example 1, doping solutions with proportions of 1 wt% PVA@XG@BCZ, 3 wt% PVA@XG@CZ, and 5 wt% PVA@XG@DPCZ were prepared for use. Several commercially available plastic decorative items of different shapes were selected. Before treatment, none of them emitted fluorescence or phosphorescence after UV excitation. The decorative items were slowly immersed in the prepared doping solutions and dried at room temperature until the film completely covered and shaped the item. Then, they were placed in a 50°C forced-air drying oven for further drying until fully formed. After removal, the desired result was obtained. Figure 17 The decorative item shown has afterglow properties. From Figure 17 The image shows that wrapping the decorative item with a thin film allows the originally non-luminous item to emit a glow.

[0116] Application Example 2 (Information Encryption):

[0117] like Figure 18 The image illustrates a simple application of this material for encrypted information transmission. Following the method in Example 1, doping solutions of 1 wt% PVA@XG@BCZ, 3 wt% PVA@XG@CZ, and 5 wt% PVA@XG@DPCZ were prepared for use. Using a perforated stainless steel mold "8", materials with longer afterglow durations were arranged in a shape resembling the number "2", while those with shorter afterglow durations were placed elsewhere. Under UV light, the material displays an "8" shape; after the UV light is removed, the afterglow displays a "2" shape. The second row shows the fabrication of an afterglow encryption device with color and time resolution based on the differences in afterglow color and afterglow duration between different doped guest molecules. The image shows that the material has three colors: blue, green, and yellow. Under UV light excitation, it displays the number "8", and after the UV light is removed, the number changes from "8" to "9" and then to "3" over time. The third row follows a similar principle, changing from "8" to "3" and then to "1". This allows for the fabrication of advanced multi-dimensional information encryption devices.

[0118] Figure 19The demonstration showed that the material could be molded into different shapes, showcasing its exceptional plasticity. Following the method in Example 1, doping solutions were prepared in proportions of 1 wt% PVA@XG@BCZ, 3 wt% PVA@XG@CZ, and 5 wt% PVA@XG@DPCZ. The solutions were poured into prepared letter molds and allowed to dry at room temperature. Then, they were placed in a 50°C forced-air drying oven for 12 hours to dry further, yielding three-dimensional models of the corresponding letters.

[0119] Figure 20 The image shows a comparison of the luminescence effects of thin films prepared by different host materials doped with the same long-afterglow composite material luminescent guest at the same ratio. Compared with the traditional PVA as a single host film, the dual host film with XG has a better phosphorescence effect.

[0120] Figure 21 The stress-strain curves of the PVA film are shown. The film exhibits extremely high tensile strength and typical rigid fracture characteristics. The ultimate tensile strength (UTS) is approximately 1400 MPa, indicating the possible existence of highly oriented molecular chains or a dense hydrogen bond network within the material. The film yields at approximately 2% strain, followed by significant strain softening, and finally fractures at approximately 7.5% strain. Overall, the film possesses high initial stiffness and strength, but low elongation at break, exhibiting typical high-strength, low-toughness mechanical behavior.

[0121] Figure 22 The stress-strain curves of the PVA@XG thin film are shown. The PVA@XG composite film exhibits excellent strength and toughness characteristics. The ultimate tensile strength reaches approximately 2650 MPa, and the elongation at break reaches 140%. The broad cold stretching plateau (strain 10%~110%) in the curves indicates that significant molecular chain orientation and slippage occurred under stress. This high strength and high toughness are mainly attributed to the dense hydrogen bond network formed between PVA and XG. Its dynamic dissociation and recombination during stretching effectively dissipate strain energy, significantly improving the fracture toughness of the film.

[0122] Figure 23The stress-strain curves of the PVA@XG@DPCz film are shown. After doping with the guest molecule DPCZ, the PVA@XG@DPCZ composite film exhibits ultra-high strength and moderate toughness. The stress-strain curves show that the ultimate tensile strength (UTS) of the composite film jumps to approximately 3800 MPa, significantly enhanced compared to the undoped system. The film reaches its yield peak at approximately 5% strain, followed by a brief plastic deformation phase, and finally fractures at approximately 20% strain. This surge in strength and decrease in ductility is mainly attributed to the introduction of rigid DPCZ molecules. DPCZ may form strong interfacial interactions with the PVA / XG matrix through hydrogen bonding or hydrophobic interactions, acting as physical crosslinking points and effectively limiting polymer chain slippage. This allows for a breakthrough in material stiffness and load-bearing capacity at the expense of some elongation at break.

[0123] By comparison Figure 21-23 It can be observed that the stress and strain of the PVA film are the lowest. The strain of the PVA@XG film is 17 times higher than that of the PVA film, and the maximum stress it can withstand is also increased by more than 1000MPa. Although the strain decreased significantly after adding DPCz, it still far exceeded that of the PVA film, with the maximum stress it can withstand being 2.5 times higher than that of the PVA film.

[0124] The above results show that by adjusting the doping ratio of the PVA / XG dual host and the types of guest molecules, long afterglow emission with different colors and lifetimes can be achieved. Moreover, the composite film has good mechanical flexibility and environmental stability, laying an experimental foundation for its application in information encryption, anti-counterfeiting patterns and other fields.

[0125] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0126] For those skilled in the art, the specific embodiments are merely illustrative descriptions of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution, such as changing the mass of a substance or a reaction parameter, or directly applying the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for preparing a long afterglow composite material based on polyvinyl alcohol and xanthan gum, characterized in that, Specifically, the following steps are included: S1: Pour polyvinyl alcohol (PVA) into a beaker and add deionized water, stirring until completely dissolved. Set aside. S2: Pour xanthan gum XG into a beaker and add deionized water, stirring until completely dissolved. Set aside. S3: Mix polyvinyl alcohol (PVA) and xanthan gum (XG) solutions, add long afterglow composite material guest molecules, mix and stir until homogeneous to obtain a mixed solution; S4: The mixed solution is placed on a substrate and dried to obtain a long afterglow composite film doped with polyvinyl alcohol and xanthan gum.

2. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol (PVA) to xanthan gum (XG) is (1~10):

1.

3. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 1, characterized in that, The combined mass of polyvinyl alcohol (PVA) and xanthan gum (XG) in the long afterglow composite material is 1-10 wt%.

4. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 3, characterized in that, The combined mass of polyvinyl alcohol (PVA) and xanthan gum (XG) in the long afterglow composite material is 1 wt%, 3 wt%, 5 wt%, 8 wt%, and 10 wt%.

5. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 3, characterized in that, The guest molecules of the long afterglow composite material are selected from one or more of NPBA, CzPBA, PyBA, DPCZ, BCz, NL, and CZ.

6. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 3, characterized in that, The stirring temperature in step S1 is 60-90℃; the stirring time in step S3 is 30 minutes.

7. The method for preparing the long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 3, characterized in that, After stirring in step S4, the mixed solution is poured onto the substrate and dried at room temperature for 12 hours; then it is placed in a 50°C forced-air drying oven and dried for 12 hours to finally obtain a long afterglow composite film doped with polyvinyl alcohol and xanthan gum.

8. A long afterglow composite material based on polyvinyl alcohol and xanthan gum as described in any one of claims 1-7, characterized in that, The long afterglow composite material includes polyvinyl alcohol (PVA), xanthan gum (XG), and long afterglow composite material guest molecules; the mass ratio of PVA to xanthan gum (XG) is (1~10):1; the doping ratio of the sum of the masses of PVA and xanthan gum (XG) in the long afterglow composite material is 1~10wt%.

9. The long afterglow composite material based on polyvinyl alcohol and xanthan gum according to claim 8, characterized in that, The combined mass of polyvinyl alcohol (PVA) and xanthan gum (XG) in the long afterglow composite material is 1 wt%, 3 wt%, 5 wt%, 8 wt%, and 10 wt%.

10. The application of a long afterglow composite material based on polyvinyl alcohol and xanthan gum as described in any one of claims 1-9 in realizing information encryption and preparing anti-counterfeiting patterns.

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