A high-stable room temperature phosphorescence composite material with excitation wavelength and time double dependence characteristics, and a preparation method and application thereof

Abstract

This invention discloses a highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics, its preparation method, and its applications. The composite material is prepared from ionic organic phosphorescent molecules (AQN), polyvinyl alcohol (PVA), and boric acid. The ionic organic phosphorescent molecules are dispersed in a PVA matrix, and boric acid is introduced to construct a cross-linked network based on the synergistic effect of dynamic hydrogen bonds and B–O coordination bonds. This material exhibits a unique ability to synergistically regulate the excitation wavelength and time dimension. Under excitation in the 250–340 nm wavelength range, it exhibits an afterglow behavior that evolves from yellow to blue-green over time, while under excitation in the 350–390 nm wavelength range, it exhibits a stable orange afterglow. Thanks to the rigid network constructed by the boric acid cross-linking effectively suppressing non-radiative transitions and blocking water molecules, this material exhibits excellent environmental stability, maintaining significant phosphorescence emission characteristics even after high-temperature treatment at 160 °C or immersion in water for 10 hours.

Description

Technical Field

[0001] This invention relates to the field of functional luminescent materials technology, specifically to a highly stable room-temperature phosphorescent composite material with dual excitation wavelength-dependent and time-dependent modulation characteristics, its preparation method, and its application in multidimensional encryption and flexible displays. Background Technology

[0002] With the development of information technology, higher demands are being placed on high-performance luminescent materials in fields such as information security, anti-counterfeiting identification, and dynamic optical coding. Organic room temperature phosphorescent (RTP) materials, due to their long afterglow lifetime, low toxicity, and large Stokes shift, show promising application prospects in fields such as biosensing, information storage, and flexible displays.

[0003] Currently, researchers primarily employ molecular engineering (such as the halogen atom effect) or physical matrix encapsulation (such as polymer matrices and crystal engineering) to suppress nonradiative transitions, thereby achieving long-lived afterglow. However, in practical applications, especially in high-level anti-counterfeiting and complex bioimaging, existing RTP materials still face the following limitations: 1. Limited response modes: Existing materials mostly exhibit static luminescence or a single excitation response, lacking the ability to synergistically regulate excitation wavelength, time dimension, and environmental stimuli, resulting in limited information storage density and anti-counterfeiting security. 2. Environmental stability bottleneck: Due to the extreme sensitivity of organic triplet excitons to temperature and moisture, most RTP systems experience rapid decay or even quenching of phosphorescence lifetime under high temperature or high humidity environments due to intensified molecular motion and oxygen quenching effects. 3. The contradiction between rigid structure and processability: Obtaining high-performance RTPs typically requires extremely high crystal stiffness, but this often limits the material's compatibility in flexible displays and ink printing.

[0004] Therefore, how to construct an RTP material that can achieve excitation / time-dependent multidimensional luminescence regulation and maintain high stability in harsh environments (high temperature, water environment) is a key technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] This invention aims to overcome the challenge of balancing multifunctionality and environmental stability in existing organic room-temperature phosphorescent (RTP) materials. By introducing boronic acid into an ionic organic phosphor / PVA system, a reinforced rigid cross-linked network is constructed using BO coordination and dynamic hydrogen bonding. The DA structure of the ionic compound facilitates the synergistic regulation of the material's luminescence properties through both wavelength-dependent and time-dependent modulation. Furthermore, the introduced BO bonds not only further enhance the system's rigidity and suppress non-radiative transitions but also significantly improve the material's luminescence stability in high-temperature and aqueous environments. Thus, the resulting RTP material possesses both multidimensional luminescence modulation capabilities and excellent environmental adaptability.

[0006] To achieve the above objectives, in a first aspect, the present invention provides an ionic organic phosphorescent small molecule, the molecular structure of which is shown in formula (1): (1).

[0007] According to a second aspect of the present invention, the present invention also provides a highly stable room temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics, comprising a cross-linked network formed by the reaction of boric acid with a polyhydroxy polymer compound and an ionic organic phosphorescent small molecule of formula (1) doped in the cross-linked network.

[0008] As a further preferred technical solution of the present invention, the polyhydroxy polymer compound is at least one of cellulose, starch, chitosan, chitin, polyvinyl alcohol, and polyacrylic acid, and is more preferably polyvinyl alcohol with a degree of alcoholysis of 98-99%.

[0009] According to a third aspect of the present invention, the present invention also provides a method for preparing a highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics, comprising the following steps: S1. The ionic organic phosphorescent small molecule with the structure of formula (1) is obtained by reacting 1,4,5,8-naphthalenetetracarboxylic anhydride and 4-aminoquinoline in anhydrous ethanol solvent. S2. Dissolve the polyhydroxy polymer in a solvent and add the ionic organic phosphorescent small molecule to prepare a mixed solution. S3. Boric acid is added to the mixed solution for structural engineering control to construct a crosslinked network with dynamic hydrogen bonding and BO coordination synergistic effect. After drying, a highly stable room temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics is obtained.

[0010] As a further preferred technical solution of the present invention, the reaction temperature for preparing ionic organic phosphorescent small molecules is 70~90℃ and the reaction time is 3~8h.

[0011] As a further preferred embodiment of the present invention, the mass ratio of the polyhydroxy polymer to boric acid is 100:(1~20); and / or, the mass ratio of the polyhydroxy polymer to organic phosphorescent molecules is 1000:(1~20).

[0012] As a further preferred technical solution of the present invention, when boric acid is added to the mixed solution for reaction, the density and rigidity of the cross-linked network are controlled by adjusting the pH value of the system. The pH value is 8-10, and hydrochloric acid or sodium hydroxide is used to adjust the pH value.

[0013] As a further preferred technical solution of the present invention, the drying is performed by drying in a forced-air drying oven at 50~60℃ for 8-12 hours.

[0014] According to a fourth aspect of the present invention, the present invention also provides an application of a highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics in the fields of information security, anti-counterfeiting identification, dynamic optical coding, multi-dimensional information encryption, or smart display. Specifically, by utilizing the synergistic luminescence behavior of the room-temperature phosphorescent composite material with excitation wavelength dependence and time dependence, multi-channel, high-security-level information encryption can be achieved.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: 1) This invention proposes a room-temperature phosphorescent material based on boric acid-crosslinked polyvinyl alcohol (PVA) composite ionic organic phosphorescent small molecules. By constructing a synergistic crosslinking network of hydrogen bonds and B-O coordination bonds, it achieves coordinated regulation of excitation wavelength-dependent luminescence and time-dependent luminescence evolution. Utilizing PVA as a flexible matrix, combined with the ionic organic phosphorescent small molecules and the boric acid crosslinking structure, it stabilizes multiple emission centers while restricting molecular motion, effectively improving intersystem crossing (ISC) efficiency and suppressing non-radiative transition processes, thereby significantly enhancing the material's long-afterglow luminescence performance. The constructed system can produce afterglow emission of different colors under different excitation wavelengths, and exhibits dynamic color evolution over time, providing a new material design strategy for multi-dimensional information encryption and high-level anti-counterfeiting.

[0016] 2) In terms of material structure design, this invention significantly improves the structural rigidity and environmental stability of the system by introducing a boric acid crosslinking network. Compared to traditional organic room-temperature phosphorescent materials that rely on crystal engineering or heavy atom effects, this invention eliminates the need for complex molecular design and stringent preparation conditions, achieving high-performance, long-afterglow luminescence simply through solution mixing and low-temperature film formation. The constructed dynamic crosslinking network not only effectively suppresses the quenching effect of oxygen and moisture on triplet excitons but also enhances the material's stability in high-temperature and high-humidity environments. Experimental results show that the material maintains significant phosphorescence emission even at 160 °C and after prolonged immersion in water, providing reliable technical support for flexible optical devices, anti-counterfeiting labels, and smart displays.

[0017] 3) The multi-emission center collaborative system constructed in this invention achieves dual control over luminescence behavior in both the "excitation wavelength dimension" and the "time dimension." By adjusting the excitation wavelength, afterglow output ranging from blue-green to orange can be achieved; by utilizing the differences in lifetime of different luminescence centers, the luminescence color can dynamically change over time, thereby significantly improving information expression capabilities and encryption complexity. Compared to traditional single-emission mode RTP materials, this invention can achieve multi-level dynamic information display and time-resolved anti-counterfeiting, meeting the requirements for high-security information storage and dynamic optical encoding. Furthermore, the material structure of this invention is simple, has low manufacturing costs, and excellent processability, allowing for further expansion into fields such as flexible thin films, erasable and rewritable devices, and intelligent optical response devices.

[0018] Therefore, the design scheme of organic room-temperature phosphorescent materials based on a boric acid crosslinking enhancement strategy proposed in this invention effectively achieves synergistic enhancement of excitation-dependent and time-dependent long afterglow luminescence behavior by constructing a rigid network structure, optimizing the energy level matching relationship between multiple emission states, and suppressing non-radiative energy loss. This method not only significantly improves the phosphorescence lifetime, quantum efficiency, and environmental stability of the material, but also effectively solves the key problem of "difficulty in balancing luminescence performance and stability" in existing multifunctional RTP systems, providing a new technical path for developing highly stable, multidimensionally tunable organic room-temperature phosphorescent materials with practical application value. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a single-crystal structure diagram of AQN in Example 1.

[0021] Figure 2 The schematic diagram of the preparation mechanism of BA-AQN-PVA composite material in Example 2 is as follows: Ionic luminescent molecules are doped into the PVA matrix and cross-linked by introducing boric acid to construct a rigid network structure with the combined action of hydrogen bonds and B–O coordination.

[0022] Figure 3 Phosphorescence emission spectra of AQN-PVA systems with different AQN doping concentrations (0.1–2.0 wt.%).

[0023] Figure 4 Images showing the afterglow evolution of AQN-PVA systems with different AQN doping concentrations (0.1–2.0 wt.%) under 254 nm excitation.

[0024] Figure 5 Fourier transform infrared (FT-IR) spectra of six samples: PVA, AQN-PVA, and BA-AQN-PVA with different doping ratios (1%-20%).

[0025] Figure 6 (a) A comparison of the phosphorescence emission spectra of AQN-PVA in Comparative Example 1 and BA-AQN-PVA in Example 2 shows that the luminescence intensity and spectral distribution changed after the introduction of boric acid; (b) the crosslinking of boric acid significantly improved the phosphorescence lifetime (from 1.12 s to 1.36 s) and quantum efficiency (from 22.1% to 30.2%) of the material.

[0026] Figure 7 The normalized emission spectra of the BA-AQN-PVA system in Example 2 at different delay times show that the luminescent components evolve over time; and the changes in CIE color coordinates corresponding to different delay times reveal that the afterglow color gradually migrates from a short time to a long time.

[0027] Figure 8 The emission spectra of the BA-AQN-PVA system in Example 2 at different excitation wavelengths (254 nm and 365 nm) show obvious excitation-dependent luminescence characteristics; and the CIE trajectory changes at different excitation wavelengths (220–390 nm) indicate that the emission color is continuously adjustable with the excitation wavelength.

[0028] Figure 9 The images show afterglow photographs of the BA-AQN-PVA system in Example 2 under different excitation wavelengths (254, 310, 365 nm) and delay times, visually demonstrating the excitation-dependent and time-dependent multidimensional phosphorescence behavior of the system.

[0029] Figure 10 The phosphorescence emission spectra of the BA-AQN-PVA system in Example 2 at different temperatures (273–433 K) under excitation conditions of 254 nm and 365 nm show that the luminescence intensity gradually decreases with increasing temperature.

[0030] Figure 11These are afterglow photographs of the BA-AQN-PVA system under different temperatures and excitation conditions in Example 2, visually demonstrating the effect of temperature on the regulation of luminescence intensity and color.

[0031] Figure 12 For the water resistance stability characterization of the BA-AQN-PVA system in Example 2, (a) the phosphorescence intensity change monitored at 570 nm during the immersion of the BA-AQN-PVA sample in water shows that the system still maintains stable luminescence under long-term immersion conditions; (b) the comparison of luminescence photographs of BA-AQN-PVA and AQN-PVA samples before and after immersion in water (0 and 90 min) shows that the boric acid crosslinked system still has obvious afterglow after immersion in water, while the luminescence of the uncrosslinked system is significantly quenched, proving that the crosslinked network effectively improves the water resistance stability of the material.

[0032] Figure 13 The BA-AQN-PVA system of Example 2 was used to prepare a security label with phosphorescent ink through screen printing. The label exhibited different afterglow characteristics under ultraviolet excitation and off excitation conditions, thus realizing visual anti-counterfeiting identification.

[0033] Figure 14 This diagram illustrates the information writing-reading-erasing cycle of the BA-AQN-PVA system rewritable thin film in Example 2, demonstrating that the material can achieve controllable information encoding through ultraviolet light and masking. The diagram also shows the afterglow evolution behavior of different patterns during multiple writing / erasing cycles, demonstrating the system's information reading capability and good cycle stability under time-resolved conditions.

[0034] Figure 15 The phosphorescent fiber constructed by wet spinning of the BA-AQN-PVA system in Example 2 and its luminescence performance exhibit tunable afterglow color under different excitation wavelengths (254 nm and 365 nm) and delay times, demonstrating its potential in flexible photonic devices and textile applications.

[0035] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0036] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0037] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0038] Example 1: Synthesis and Characterization of Ionic Organophosphorescent Small Molecules (AQN) 1. Synthesis Procedure: 2.0 g of 1,4,5,8-naphthalenetetracarboxylic anhydride and 2.68 g of 4-aminoquinoline were placed in a 250 mL three-necked flask. 120 mL of anhydrous ethanol was added as a solvent, and the mixture was refluxed at 80 °C for 5 hours. During the reaction, the solution gradually changed from a suspension to a clear brown solution. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and a grayish-white solid precipitated. The product was collected by filtration and washed repeatedly with cold ethanol to remove unreacted starting materials. The product was then dried in a vacuum oven at 60 °C for 12 hours to obtain ionic organophosphorescent small molecule (AQN) powder. The synthesis equation for AQN is as follows:

[0039] 2. Structure Verification: Single crystals of AQN were obtained by slow solvent evaporation, and their structure is as follows. Figure 1 As shown, the molecular structure of AQN was determined by single-crystal X-ray diffraction. The results indicate that AQN is a typical ionic compound, and the strong electrostatic interaction between its positive and negative ions lays the foundation for the subsequent construction of a stable energy level structure in a polymer matrix.

[0040] Example 2: Preparation of room temperature phosphorescent (BA-AQN-PVA) composite material 1. Preparation of PVA aqueous solution: Weigh 0.6 g of polyvinyl alcohol (PVA) with a degree of alcoholysis of 98-99%, add it to 9.4 g of deionized water, and stir vigorously at 90 ℃ until completely dissolved to form a uniform and transparent solution with a mass fraction of 6 wt.%.

[0041] 2. Host-guest doping: Add 5 mg of AQN powder prepared in Example 1 (the mass fraction of AQN in the AQN-PVA system is 5.0 wt.%) to the above PVA solution, and sonicate for 30-60 minutes to ensure that the ionic luminescent molecules are dispersed at the molecular level in the polymer matrix to obtain the AQN-PVA mixed system.

[0042] 3. Structural engineering crosslinking: Slowly add boric acid (BA) aqueous solution to the above mixture, controlling the mass ratio of PVA to BA to be 100:20, and adjust the pH of the system to 8 to promote the synergistic construction of B–O coordination bonds and dynamic hydrogen bonds (e.g., Figure 2 As shown in the figure, the BA-AQN-PVA composite material system was obtained. After the system was coated into a film, it was dried in a 60°C forced-air oven for 8 hours to obtain the BA-AQN-PVA film.

[0043] The equation for the crosslinking reaction of boric acid in this mixed system is as follows:

[0044] Comparative Example 1 1. Preparation of PVA aqueous solution: Weigh 0.6 g of polyvinyl alcohol (PVA) with a degree of alcoholysis of 98-99%, add it to 9.4 g of deionized water, and stir vigorously at 90 ℃ until completely dissolved to form a uniform and transparent solution with a mass fraction of 6 wt.%.

[0045] 2. Host-guest doping: 5 mg of AQN powder prepared in Example 1 (the mass fraction of AQN in the AQN-PVA system is 5.0 wt.%) was added to the above PVA solution, and the mixture was ultrasonically treated for 30-60 minutes to ensure that the ionic luminescent molecules were dispersed at the molecular level in the polymer matrix. Finally, the system was coated into a film and dried in a 60°C oven for 8 hours to obtain an AQN-PVA thin film.

[0046] Based on the technical solutions of Example 2 and Comparative Example 1, the following experimental tests were further conducted: Test 1. In the scheme of Example 2, the mass fraction of AQN in the AQN-PVA system was adjusted by only changing the amount of AQN used (0.1 wt.%, 0.5 wt.%, 1.0 wt.%, 1.5 wt.%, 2.0 wt.%), such as... Figure 3 As shown, the intensity and distribution of the phosphorescence emission spectrum of the AQN-PVA system change accordingly. This indicates that the aggregation state of AQN molecules has a significant regulatory effect on the multiple emission states of the system.

[0047] Test 2. AQN-PVA systems prepared in Test 1 with different AQN mass fractions (0.1 wt.%, 0.5 wt.%, 1.0 wt.%, 1.5 wt.%, 2.0 wt.%) were excited at 254 nm. All samples exhibited a clear time-dependent phosphorescence evolution behavior (TDPC) from yellow to blue, as shown in Figure 4. It can be seen that with increasing AQN concentration, the afterglow color and duration show non-linear changes. With increasing doping concentration, the afterglow color and duration of the system change significantly, exhibiting a time-dependent luminescence evolution behavior from yellow to blue, indicating that the molecular aggregation state and the interaction between luminescent centers have a significant impact on the phosphorescence process.

[0048] Test 3. Following the scheme of Example 2, by simply changing the percentage of boric acid added relative to PVA (0 wt.%, 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%), the infrared spectra of the prepared series of BA-AQN-PVA films and pure PVA films are as follows: Figure 5 As shown. It can be seen that pure PVA films at 3000–3600 and 2850–2950 cm⁻¹...- The absorption peak at ¹ is attributed to the characteristic stretching vibrations of the hydroxyl (-OH) and methylene (-CH2) groups. In contrast, with increasing boric acid content in the hybrid film, two new absorption peaks gradually appear at approximately 1285 and 665 cm⁻¹. - At position ¹, these correspond to the stretching vibration of the O–B–O bond and the bending vibration of the B–O–C bond, respectively. Simultaneously, in 20% BA-AQN-PVA, at 3300 cm⁻¹… - The intensity of the stretching vibration of the hydroxyl group near ¹ is significantly reduced.

[0049] Test 4. A comparative test was conducted between the uncrosslinked AQN-PVA of Comparative Example 1 and the BA-AQN-PVA crosslinked with boric acid in Example 2. Figure 6 As shown in a, compared to uncrosslinked AQN-PVA, the phosphorescence intensity of the BA-AQN-PVA system after introducing boric acid crosslinking is significantly improved, and the spectral distribution is richer. Figure 6 As shown in b, the construction of the cross-linked network extended the phosphorescence lifetime from 1.12 s to 1.36 s, while increasing the phosphorescence quantum efficiency from 22.1% to 30.2%. This quantitatively demonstrates the significant effect of structural engineering control in suppressing non-radiative losses.

[0050] Test 5. The BA-AQN-PVA final product film of Example 2 was used as the test object to verify its time-dimensional luminescence evolution and excitation wavelength-dependent luminescence behavior, and the AQN-PVA film of Comparative Example 1 was used as the control sample.

[0051] Specifically, in a room temperature air environment, delayed emission spectra of the samples were measured using a phosphorescence spectrometer. The excitation source was 254 nm ultraviolet light, and the delay times were set to 50 ms, 100 ms, 200 ms, 500 ms, and 1000 ms, respectively. The normalized afterglow emission spectra and corresponding CIE color coordinates were recorded for different delay times. Figure 7 As shown in a, the normalized emission spectrum of the BA-AQN-PVA film showed a significant blue shift as the delay time increased from 50 ms to 1000 ms, indicating that there are different lifetime luminescent centers in the system and they compete for decay during the afterglow decay process. Figure 7 The CIE chromaticity locus in b further reveals that the afterglow color of BA-AQN-PVA exhibits a continuous dynamic drift over time. Similarly, the AQN-PVA film also shows a certain time-dependent afterglow color change, indicating that the AQN structure itself can endow the system with multi-lifetime luminescence characteristics, while the introduction of BA further enhances this luminescence regulation behavior and its stability.

[0052] Furthermore, under room temperature air conditions, wavelength-dependent afterglow tests were performed on AQN-PVA and BA-AQN-PVA films. The excitation wavelength was adjusted within the range of 220–390 nm, and the delayed emission spectra and CIE color coordinates at each excitation wavelength were recorded. Figure 8 As shown in a, BA-AQN-PVA exhibits significantly different initial afterglow emission spectra under excitation at 254 nm and 365 nm. Figure 8 b and Figure 9 Further, it was shown that as the excitation wavelength was switched within the range of 220–390 nm, the afterglow color of BA-AQN-PVA could be continuously and visually adjusted within the range of blue-green to orange. The AQN-PVA sample also exhibited a similar excitation wavelength-dependent afterglow variation trend, indicating that this characteristic mainly originates from the ionic DA structure of AQN. BA, through BO coordination and dynamic hydrogen bonding, constructs a rigid cross-linked network, further enhancing the luminescence stability of the final product BA-AQN-PVA in high-temperature and aqueous environments.

[0053] Test 6. The BA-AQN-PVA final product film of Example 2 was used as the test object to verify its high-temperature luminescence resistance and water quenching resistance, and the AQN-PVA film of Comparative Example 1 was used as the control sample.

[0054] 1) In the high-temperature resistance test, the sample was placed on a temperature-controlled sample stage, and the temperature was gradually increased within the range of 273–433 K. At each temperature point, the sample was excited with 254 nm and 365 nm ultraviolet light, and the delayed emission spectrum, phosphorescence intensity changes, and visible afterglow photographs were recorded. For example... Figure 10 As shown, during the heating process of BA-AQN-PVA to 433 K (approximately 160 ℃), although the phosphorescence intensity decreased due to the thermal quenching effect, it still maintained a significant excitation wavelength-dependent afterglow characteristic; as Figure 11 The phosphorescence properties and thermal stability of AQN-PVA and BA-AQN-PVA films under high-temperature conditions were compared. Figure 10 In the figure, 'a' represents the delayed phosphorescence emission spectra of the two samples measured at 433 K (approximately 160 °C). The results show that the AQN-PVA sample without boric acid crosslinking exhibits only extremely weak phosphorescence emission at high temperatures, with its emission peak intensity nearly completely quenched. In contrast, BA-AQN-PVA maintains a significant and relatively strong phosphorescence emission signal under the same conditions, with characteristic emission peaks still observable near approximately 570 nm and 620 nm. This indicates that the BO coordination and dynamic hydrogen bond crosslinking network formed after the introduction of boric acid can effectively enhance the rigidity of the system and suppress non-radiative transitions caused by molecular thermal motion under high-temperature conditions, thereby significantly improving the high-temperature phosphorescence stability of the material. Figure 10Figure b further illustrates the afterglow image changes of AQN-PVA and BA-AQN-PVA within the temperature range of 293–433 K. As the temperature gradually increases, the afterglow brightness of the AQN-PVA sample decreases rapidly and almost completely disappears under high-temperature conditions; while the BA-AQN-PVA sample still exhibits significant afterglow emission even at 433 K, indicating its excellent thermoluminescence resistance. These results further demonstrate that the AQN structure endows the system with room-temperature phosphorescence properties, while the dense, rigid network formed by boric acid crosslinking further enhances the material's luminescence stability and resistance to thermal quenching in high-temperature environments.

[0055] 2) In the water resistance test, AQN-PVA and BA-AQN-PVA films were immersed in deionized water, and the changes in delayed phosphorescence intensity under different immersion times were monitored in real time at room temperature. The afterglow emission state was observed by ultraviolet light excitation. Figure 12 In the figure, 'a' represents the change in the delayed phosphorescence emission spectrum of the AQN-PVA film after immersion in water. The results show that the phosphorescence intensity of the uncrosslinked AQN-PVA sample rapidly decreases after immersion in water. After only 5 minutes of immersion, its characteristic phosphorescence peak has significantly decreased, and after 10 minutes of immersion, the afterglow almost completely disappears, indicating that water molecules easily enter the system and have a significant quenching effect on the phosphorescence centers. Figure 12 In Figure b, the phosphorescence intensity of the BA-AQN-PVA film at 570 nm as a function of time during immersion in water is shown. It can be seen that although the phosphorescence intensity decreases to some extent in the initial stage, it can remain relatively stable for a long time afterward. Even after immersion for hundreds of minutes, it still maintains a significant phosphorescence signal, indicating that the BO coordination and dynamic hydrogen bond crosslinking network formed after the introduction of boric acid effectively improves the system's resistance to water quenching. Figure 12 The image c further compares the actual luminescence images of the two samples before and after immersion in water under "light on / light off" conditions. BA-AQN-PVA still showed a noticeable orange afterglow after immersion for 90 min, while the afterglow of the AQN-PVA sample basically disappeared under the same conditions. This further proves that the dense rigid network constructed by boric acid crosslinking can effectively block the intrusion of water molecules, thereby significantly improving the luminescence stability of the material in the water environment.

[0056] The following provides multi-scenario processing and practical applications of the BA-AQN-PVA composite material of the present invention: Application Example 1: Screen Printing Labels like Figure 13As shown, a BA-AQN-PVA composite material system (10 g of 6wt.% PVA aqueous solution was mixed with 3 mg of AQN powder using ultrasonication, followed by the addition of 60 mg of boric acid, and the pH was adjusted to 8 with sodium hydroxide) was prepared as a security ink. The prepared ink was then placed on a 100-mesh screen and printed with a giraffe pattern. Even after 2 seconds of UV shutdown, the ink maintained a refined outline and vibrant afterglow, making it suitable for visual anti-counterfeiting.

[0057] Application Example 2: Flexible Erasable Writable Film like Figure 14 As shown, information was written into the BA-AQN-PVA film of Example 2 using a photomask and UV lamp irradiation. It is evident that the film exhibits excellent cycle stability, the information can be read, and it possesses time-resolved characteristics, making it suitable for reusable encrypted displays.

[0058] Application Example 3: Organic Long Afterglow Fibers like Figure 15 As shown, the fibers prepared by the BA-AQN-PVA composite material system through a wet spinning process (taking 10 g of 6wt.% PVA solution, adding 3 mg of AQN powder and 120 mg of boric acid, and ultrasonically mixing them to obtain a spinning solution, and using a saturated sodium sulfate solution as the coagulation bath and adjusting its pH to 10) exhibit distinctly different afterglow colors at different excitation wavelengths (254 nm and 365 nm), and demonstrate extremely high color purity, providing possibilities for flexible photonic devices and smart textiles.

[0059] This invention utilizes boric acid to structurally engineer an ionic organic phosphorescent molecule (AQN) and polyvinyl alcohol (PVA) system, successfully constructing a tightly cross-linked network with dynamic hydrogen bonding and B–O coordination synergy. This strategy not only effectively suppresses nonradiative transitions of molecules, enabling the system to exhibit excellent high-temperature resistance (up to 160 °C) and water immersion stability, but also endows the material with unique multi-dimensional phosphorescence modulation characteristics based on excitation wavelength and time. Experimental data show that the composite material prepared by this invention can achieve color switching at different excitation wavelengths and dynamic afterglow evolution with increasing delay time, greatly enriching the expression dimensions of optical information. Furthermore, this system possesses excellent processing adaptability and can be transformed into various forms such as thin films, patterned labels, and functional fibers through various processes such as casting, screen printing ink preparation, and wet spinning. This material system, which combines stability in high-temperature and high-humidity environments with multi-dimensional luminescence modulation capabilities, resolves the contradiction between multifunctionality and stability in existing organic room-temperature phosphorescent materials, providing a high-performance, low-cost, and easily mass-producible ideal solution for fields such as high-security anti-counterfeiting, complex data encryption, and flexible display devices.

[0060] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. An ionic organic phosphorescent small molecule, characterized in that, Its molecular structure is shown in formula (1): （1）。 2. A highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics, characterized in that, It includes a cross-linked network formed by the reaction of boric acid and a polyhydroxy polymer compound, and the ionic organic phosphorescent small molecule as described in claim 1 doped into the cross-linked network.

3. The highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics according to claim 2, characterized in that, The polyhydroxy polymer compound is at least one of cellulose, starch, chitosan, chitin, polyvinyl alcohol, and polyacrylic acid.

4. The method for preparing the highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics as described in claim 2 or 3, characterized in that, Includes the following steps: S1. The ionic organic phosphorescent small molecule with the structure of formula (1) is obtained by reacting 1,4,5,8-naphthalenetetracarboxylic anhydride and 4-aminoquinoline in anhydrous ethanol solvent. S2. Dissolve the polyhydroxy polymer in a solvent and add the ionic organic phosphorescent small molecule to prepare a mixed solution. S3. Boric acid is added to the mixed solution for structural engineering control to construct a crosslinked network with dynamic hydrogen bonding and BO coordination synergistic effect. After drying, a highly stable room temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics is obtained.

5. The preparation method according to claim 4, characterized in that, The reaction temperature for preparing ionic organophosphorescent small molecules is 70~90℃, and the reaction time is 3~8h.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the polyhydroxy polymer to boric acid is 100:(1~20); and / or, the mass ratio of the polyhydroxy polymer to organic phosphorescent molecules is 1000:(1~20).

7. The preparation method according to claim 4, characterized in that, When boric acid is added to the mixed solution for reaction, the density and rigidity of the cross-linked network are controlled by adjusting the pH value of the system, wherein the pH value is 8-10.

8. The preparation method according to claim 4, characterized in that, The drying process involves drying in a forced-air oven at 50-60℃ for 8-12 hours.

9. The application of the highly stable room-temperature phosphorescent composite material with dual excitation wavelength and time dependence characteristics as described in claim 2 or 3 in the fields of information security, anti-counterfeiting identification, dynamic optical coding, multi-dimensional information encryption, or intelligent display. Specifically, by utilizing the synergistic luminescence behavior of the room-temperature phosphorescent composite material with excitation wavelength dependence and time dependence, multi-channel, high-security-level information encryption can be achieved.

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