Room-temperature phosphorescent film as well as preparation method and application thereof

Abstract

The invention provides a room-temperature phosphorescent film as well as a preparation method and application thereof, and relates to the technical field of room-temperature phosphorescent anti-counterfeiting. The preparation method of the room-temperature phosphorescent film comprises the following steps: mixing phosphorescent molecules, polyacrylonitrile and an organic solvent to obtain a room-temperature phosphorescent film precursor solution, then coating the surface of a substrate material with the room-temperature phosphorescent film precursor solution, and carrying out curing treatment to obtain the room-temperature phosphorescent film, and the phosphorescent molecules comprise one or more of DBrC, BrPBC and TCB. The phosphorescent film prepared by the invention can emit blue fluorescence and yellow fluorescence, has long phosphorescent life, and can show different information under different illumination conditions after being prepared into a composite film material with a fluorescent monomer, thereby forming a triple optical encryption dimension.

Description

Technical Field

[0001] This invention relates to the field of room temperature phosphorescent anti-counterfeiting technology, and in particular to a room temperature phosphorescent thin film, its preparation method and application. Background Technology

[0002] Against the backdrop of a rapid increase in global data volume, developing novel information storage materials that combine high stability with low energy consumption has become a crucial issue in materials science. Despite significant advancements in information technology, numerous challenges remain in key areas such as suppressing electromagnetic interference, improving data encryption reliability, and optimizing storage density. Optical materials, with their excellent resistance to electromagnetic interference and efficient information storage capabilities, demonstrate unique advantages in information encryption. However, traditional fluorescent materials are limited by short luminescence lifetimes, small Stokes shifts, and susceptibility to ambient light interference, making it difficult to meet the application requirements of high-density storage and complex environments. In this context, developing luminescent materials with high brightness, long lifetimes, and stable performance, particularly room-temperature phosphorescent (RTP) materials, has become an important means to overcome current storage challenges. RTP materials, due to their unique photophysical properties, including millisecond-level luminescence lifetimes, large Stokes shifts, and lack of background fluorescence interference, show broad application prospects in fields such as information encryption.

[0003] Currently, high-performance RTP materials mainly rely on metal-containing complex systems, which suffer from drawbacks such as high cost, high toxicity, and poor biocompatibility. In contrast, metal-free organic RTP materials have gradually become a research hotspot due to their advantages such as low cost, low toxicity, and excellent biocompatibility. However, current organic RTP systems face significant challenges, including weak spin-orbit coupling (SOC) leading to low intersystem crossing (ISC) efficiency and excessively fast triplet exciton nonradiative transition rates. Recent studies have demonstrated that efficient and durable RTP materials can be effectively developed by synergistically enhancing the spin-orbit coupling effect and suppressing nonradiative decay (e.g., through crystal engineering, halogen bonding, heavy atom effects, H-aggregation regulation, and n-π* transition optimization). However, the harsh growth conditions and poor processing performance of crystalline materials limit their practical applications (Wu, H., Wang, D., Zhao, Z., Wang, D., Xiong, Y., Tang, BZ. Tailoring noncovalent interactions to activate persistent room-temperature phosphorescence from doped polyacrylamide films. Advanced Functional Materials, 2021, 31(32): 2101656.). Currently, although amorphous flexible organic RTP materials have potential in the fields of bioimaging and flexible electronics, achieving efficient RTP in amorphous phases remains challenging. Studies have shown that embedding organic phosphors into rigid matrices or macrocyclic host materials can effectively activate the RTP properties of amorphous films. For example, Yang Chaolong's team successfully achieved efficient RTP in amorphous organic systems through host-guest interactions between hexa-(4-carboxy-phenoxy)-cyclotriphosphazene and polyvinyl alcohol (PVA) (Su,Y.,Phua,SZF,Li,Y.,Zhou,X.,Jana,D.,Liu,G.,Lim,WQ,Ong,WK,Yang,C.,Zhao,Y.Ultralongroomtemperaturephosphorescencefromamorphousorganicmaterialstowardconfidentialinformationencryptionanddecryption[J].ScienceAdvances,2018,4(5):eaas9732).

[0004] The above attempts provide new ideas for the development of RTP-based information storage materials. Although substantial progress has been made, many existing RTP materials suffer from drawbacks such as short afterglow lifetime and instability, which severely restrict their practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a room temperature phosphorescent thin film, its preparation method and application, in order to solve the problems of short afterglow lifetime and instability of existing metal-free organic room temperature phosphorescent materials.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a room-temperature phosphorescent thin film, comprising the following steps:

[0008] Phosphorescent molecules, polyacrylonitrile, and organic solvents are mixed to obtain a room temperature phosphorescent film precursor solution. The room temperature phosphorescent film precursor solution is then coated onto the surface of a substrate material to obtain a room temperature phosphorescent film.

[0009] The phosphorescent molecules include one or more of DBrC, BrPBC and TCB;

[0010] The structural formula of DBrC is as follows: The structural formula of BrPBC is The structural formula of TCB is:

[0011] Preferably, the mixing ratio of the phosphorescent molecules, polyacrylonitrile, and organic solvent is 1-5 mg: 50-150 mg: 5-15 mL.

[0012] This invention provides a room temperature phosphorescent thin film prepared by the above-described preparation method.

[0013] The present invention also provides an application of the above-mentioned room temperature phosphorescent thin film in the field of information encryption, comprising the following steps:

[0014] 1) The fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile and organic solvent were mixed and reacted to obtain a copolymer of fluorescent monomer HBopa and acrylamide, poly(HBopa-co-AM);

[0015] A room-temperature phosphorescent film precursor solution was obtained by mixing phosphorescent molecules, polyacrylonitrile, and an organic solvent.

[0016] 2) By utilizing the fluorescence properties of poly(HBopa-co-AM) solution and the afterglow properties of room temperature phosphorescent film precursor solution, different information was plotted using the two to obtain films exhibiting different information under different conditions.

[0017] Preferably, the structural formula of the fluorescent monomer HBop a in step 1) is as follows:

[0018]

[0019] Preferably, the ratio of the fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile and organic solvent in step 1) is 0.32g~0.5g: 0.70~1.0g: 7.00~10mg: 10mL.

[0020] Preferably, the temperature of the mixing reaction in step 1) is 40–90°C and the time is 10–15 h.

[0021] The present invention has at least the following beneficial effects:

[0022] In this invention, BrPBC-PAN doped thin films are combined with Al 3+ A responsive poly(HBopa-co-AM) thin film was used to construct a composite information encryption system, which extended the encryption to the time dimension and demonstrated excellent performance in anti-counterfeiting applications, providing a new solution for RTP materials in the field of information security. Attached Figure Description

[0023] Figure 1 The 1H NMR spectrum of BrPBC prepared in Example 1;

[0024] Figure 2 The photophysical properties of the BrPBC-PAN room temperature phosphorescent thin film prepared in Example 1 are shown in the figure. Figure 2 In the figure, 'a' represents the luminescence of the BrPBC-PAN room temperature phosphorescent film when irradiated with 365nm ultraviolet light and within 12 seconds after the ultraviolet light is turned off. Figure 2 In the figure, b represents the normalized fluorescence and phosphorescence spectra of the BrPBC-PAN room temperature phosphorescent film. Figure 2 In the figure, c represents the lifetime decay curve of the BrPBC-PAN room temperature phosphorescent film at the phosphorescence emission peak at 549 nm. Figure 2 In the figure, d represents the position of fluorescence emission and phosphorescence emission of the BrPBC-PAN room temperature phosphorescent film on the 1931 CIE color coordinates.

[0025] Figure 3 The 1H NMR spectrum of DBrC prepared in Example 2;

[0026] Figure 4 The image shows the photophysical properties of the DBrC-PAN room temperature phosphorescent thin film prepared in Example 2. Figure 4 In the figure, 'a' represents the luminescence of the DBrC-PAN room temperature phosphorescent film when irradiated with 365nm ultraviolet light and within 8 seconds after the ultraviolet light is turned off. Figure 4 In the figure, b represents the normalized fluorescence and phosphorescence spectra of the DBrC-PAN room temperature phosphorescent film.

[0027] Figure 5The TCB nuclear magnetic resonance hydrogen spectrum obtained in Example 3;

[0028] Figure 6 The image shows the photophysical properties of the TCB-PAN room temperature phosphorescent thin film prepared in Example 3. Figure 6 In the figure, 'a' represents the luminescence of the TCB-PAN room-temperature phosphorescent film when irradiated with 365nm ultraviolet light and within 5 seconds after the ultraviolet light is turned off. Figure 6 In the figure, b represents the normalized fluorescence and phosphorescence spectra of the TCB-PAN room temperature phosphorescent film.

[0029] Figure 7 The graph shows the phosphorescence lifetime decay of the DBrC-PAN room temperature phosphorescent film and the TCB-PAN room temperature phosphorescent film prepared in Examples 2 and 3. Figure 7 In the figure, 'a' represents the lifetime decay curve of the DBrC-PAN room temperature phosphorescent film at the phosphorescence emission peak at 549 nm. Figure 7 In the figure, b represents the lifetime decay curve of the TCB-PAN room temperature phosphorescent film at the phosphorescence emission peak at 547 nm.

[0030] Figure 8 The 1H NMR spectrum of HBopa prepared in Example 4;

[0031] Figure 9 The encrypted “8” pattern of the phosphorescent thin film with encrypted information prepared in Example 4 was photographed under different lighting conditions. Detailed Implementation

[0032] This invention provides a method for preparing a room-temperature phosphorescent thin film, comprising the following steps:

[0033] Phosphorescent molecules, polyacrylonitrile, and organic solvents are mixed to obtain a room temperature phosphorescent film precursor solution. The room temperature phosphorescent film precursor solution is then coated onto the surface of a substrate material to obtain a room temperature phosphorescent film.

[0034] The phosphorescent molecules include one or more of DBrC, BrPBC and TCB;

[0035] The structural formula of DBrC is as follows: The structural formula of BrPBC is The structural formula of TCB is:

[0036] In this invention, the mixing ratio of the phosphorescent molecules, polyacrylonitrile, and organic solvent is 1-5 mg: 50-150 mg: 5-15 mL, preferably 2-4 mg: 70-130 mg: 7-13 mL, more preferably 2.5-3.5 mg: 90-110 mg: 9-11 mL, and even more preferably 3 mg: 100 mg: 10 mL.

[0037] In this invention, the organic solvent includes one or more of N,N-dimethylformamide dimethyl sulfoxide and acetonitrile.

[0038] In this invention, the method for preparing DBrC includes the following steps:

[0039] DBrC was obtained by reacting a mixture of carbazole, 1,3,5-tribromobenzene, copper iodide, 1,10-phenanthroline, potassium carbonate, and an organic solvent under a protective atmosphere.

[0040] The synthesis route is as follows:

[0041]

[0042] The mixing ratio of carbazole, 1,3,5-tribromobenzene, copper iodide, 1,10-phenanthroline, potassium carbonate, and organic solvent was 2.50 g: 7.05 g: 0.29 g: 0.14 g: 4.15 g: 30 mL; the mixing reaction temperature was 180 °C and the reaction time was 24 h.

[0043] In this invention, the preparation method of BrPBC includes the following steps:

[0044] Under a protective atmosphere, carbazole, 1,3,5-tribromobenzene, cuprous iodide, 1,10-phenanthroline, potassium carbonate, and an organic solvent were mixed and reacted to obtain BrPBC.

[0045] The synthesis route is as follows:

[0046]

[0047] The mixing ratio of carbazole, 1,3,5-tribromobenzene, cuprous iodide, 1,10-phenanthroline, potassium carbonate, and organic solvent was 2.90 g: 2.50 g: 0.09 g: 0.14 g: 4.40 g: 25 mL; the mixing reaction temperature was 180 °C and the reaction time was 24 h.

[0048] In this invention, the method for preparing the TCB includes the following steps:

[0049] TCB was obtained by reacting a mixture of carbazole, 1,3,5-tribromobenzene, copper iodide, 1,10-phenanthroline, potassium carbonate, and an organic solvent under a protective atmosphere.

[0050] The synthesis route is as follows:

[0051]

[0052] The mixing ratio of carbazole, 1,3,5-tribromobenzene, copper iodide, 1,10-phenanthroline, potassium carbonate, and organic solvent was 2.80 g: 1.25 g: 0.80 g: 0.08 g: 2.80 g: 40 mL; the mixing reaction temperature was 180 °C and the reaction time was 24 h.

[0053] This invention provides a room temperature phosphorescent thin film prepared by the above-described preparation method.

[0054] The present invention also provides an application of the above-mentioned room temperature phosphorescent thin film in the field of information encryption, comprising the following steps:

[0055] 1) The fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile and organic solvent were mixed and reacted to obtain a copolymer of fluorescent monomer HBopa and acrylamide, poly(HBopa-co-AM);

[0056] A room-temperature phosphorescent film precursor solution was obtained by mixing phosphorescent molecules, polyacrylonitrile, and an organic solvent.

[0057] 2) By utilizing the fluorescence properties of poly(HBopa-co-AM) solution and the afterglow properties of room temperature phosphorescent film precursor solution, different information was plotted using the two to obtain films exhibiting different information under different conditions.

[0058] In this invention, the structural formula of the fluorescent monomer HBopa in step 1) is as follows:

[0059]

[0060] In this invention, the ratio of the fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile, and organic solvent in step 1) is 0.32g-0.5g: 0.70-1.0g: 7.00-10mg: 10mL, preferably 0.35-0.45g: 0.75-0.95g: 7.5-9.5mg: 10mL, further preferably 0.38-0.42g: 0.80-0.90g: 8.0-9.0mg: 10mL, and even more preferably 0.40g: 0.85g: 8.5mg: 10mL.

[0061] In this invention, the temperature of the mixing reaction in step 1) is 40-90°C, preferably 50-80°C, more preferably 60-85°C, and even more preferably 70°C; the time is 10-15h, preferably 11-14h, and even more preferably 12-13h.

[0062] In this invention, the preparation method of the fluorescent monomer HBopa includes the following steps:

[0063] (a) The compound DHBH was obtained by reacting methyl 2,5-dihydroxybenzoate, hydrazine hydrate and an organic solvent;

[0064] (b) HBopo was obtained by reacting DHBH, phthalaldehyde and ethanol together.

[0065] (c) HBopa is obtained by mixing HBopo, triethylamine, acetic acid and N,N-dimethylformamide.

[0066] In this invention, the mixing ratio of methyl 2,5-dihydroxybenzoate, hydrazine hydrate and organic solvent in step (a) is 0.02 mol: 0.03 mol: 80 mL;

[0067] The temperature of the mixing reaction in step (a) is 0–30°C and the time is 6–10 h.

[0068] In this invention, the ratio of DHBH, phthalaldehyde and ethanol in step (b) is 0.02 mol: 0.02 mol: 50 mL;

[0069] The temperature of the mixing reaction in step (b) is 60–100°C and the time is 10–14 h.

[0070] In this invention, the ratio of HBopo, triethylamine, acetic acid, and N,N-dimethylformamide mixed in step (c) is 1 mmol: 300 μL: 1.42 mmol: 10 mL.

[0071] The temperature of the mixing reaction in step (c) is 0–30°C and the time is 2–6 h.

[0072] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0073] Example 1

[0074] Under nitrogen protection, carbazole (2.90 g, 17.95 mmol), 1,3,5-tribromobenzene (2.50 g, 7.95 mmol), cuprous iodide (0.076 g, 0.40 mmol), 1,10-phenanthroline (0.14 g, 0.80 mmol), potassium carbonate (4.40 g, 32.00 mmol), and 25 mL of dry DMF were mixed in a three-necked flask. The reaction mixture was heated to 180 °C and refluxed for 24 h. After the reaction was complete, the solvent DMF was removed by rotary evaporation. Then, the residue was extracted with an appropriate amount of dichloromethane. Separation was performed by silica gel column chromatography using a 1:10 v / v mixture of ethyl acetate / dichloromethane as the eluent, finally yielding a white powdery solid BrPBC (1.68 g, yield 43.5%). The 1H NMR spectrum is shown below. Figure 1 As shown, 1 HNMR (400MHz, CDCl3, ppm): δ8.15 (d, J = 7.7Hz, 4H), 7.87 (d, J = 1.9Hz, 2H), 7.80 (t,J=1.9Hz,1H),7.56(d,J=8.2Hz,4H),7.50–7.44(m,4H),7.37–7.31(m,4H). 13 CNM R (100MHz, CDCl3, ppm): δ140.57,140.39,128.74,126.54,124.21,124.03,123.90,120.96,120.72,120.61,109.76.

[0075] The prepared BrPBC, PAN (polyacrylonitrile), and N,N-dimethylformamide were mixed in a ratio of 2 mg:100 mg:10 mL, heated to 80 °C, and stirred for 30 min to obtain a transparent room temperature phosphorescent film precursor solution. This precursor solution was then used at a concentration of 0.001 g / cm³. 2 The coating amount was applied to the surface of the substrate (quartz glass plate), and dried at 110°C for 1 hour to obtain a BrPBC-PAN room temperature phosphorescent film.

[0076] The photophysical properties of the BrPBC-PAN room temperature phosphorescent thin film prepared in this embodiment were tested, and the test results are as follows: Figure 2 As shown. Figure 2 In Figure 'a', the light emission of the BrPBC-PAN room temperature phosphorescent film is observed when it is irradiated with 365nm ultraviolet light and within 12s after the ultraviolet light is turned off. Under ultraviolet excitation, the material exhibits unique blue fluorescence emission (λem = 421nm) accompanied by observable yellow phosphorescence emission (λem = 549nm). The dynamic transition process is not only visible to the naked eye but can also be completely recorded by taking pictures. The phosphorescence emission exhibits typical RTP material characteristics. Figure 2 In this context, b represents the normalized fluorescence spectrum (prompt) and phosphorescence spectrum (delayed) of the BrPBC-PAN room-temperature phosphorescent film, and (λ) ex =365nm, delay time: 10ms), it can be seen that the fluorescence spectrum and phosphorescence spectrum show a shift of up to 128nm, confirming an effective intersystem crossing process. Figure 2 In the figure, c represents the lifetime decay curve of the phosphorescence emission peak at 549 nm of the BrPBC-PAN room temperature phosphorescent film. Combined with time-resolved spectroscopy analysis, the phosphorescence lifetime of the BrPBC-PAN film reaches 624.19 ms and the phosphorescence quantum yield (ΦP) is 3.64% (Table 1). These data together verify that the material has excellent RTP characteristics. Figure 2 In the figure, d represents the position of fluorescence emission and phosphorescence emission of the BrPBC-PAN room temperature phosphorescent film on the 1931 CIE color coordinates. The 1931 CIE color coordinates of fluorescence emission and phosphorescence emission are located in the (0.16, 0.05) and (0.45, 0.54) regions, respectively. This high-contrast color span makes multi-mode luminescence applications possible, giving this material application potential in the fields of anti-counterfeiting and optical information encoding.

[0077] Example 2

[0078] Under nitrogen protection, carbazole (2.50 g, 14.95 mmol), 1,3,5-tribromobenzene (7.05 g, 22.33 mmol), copper iodide (0.29 g, 1.50 mmol), 1,10-phenanthroline (0.14 g, 1.50 mmol), potassium carbonate (4.15 g, 29.90 mmol), and 30 mL of dry DMF were mixed in a three-necked flask. The reaction mixture was heated to 180 °C and refluxed for 24 h. After the reaction was complete, the solvent DMF was removed by rotary evaporation. Then, the residue was extracted with an appropriate amount of dichloromethane. Separation was performed by silica gel column chromatography using ethyl acetate / dichloromethane at a volume ratio of 1:10 as the eluent. The final product was dried to obtain a white solid powder DBrC (2.80 g, yield 46.7%). The 1H NMR spectrum is shown below. Figure 3 As shown, 1 HNMR (400MHz, CDCl3, ppm): δ8.13(d,J=7.8Hz,2H),7.77(t,J=1.7Hz,1H),7.71(d,J=1.7Hz,2H),7.46–7.41(m,4H),7.32(ddd,J=8.0,6.5,1.7Hz,2H). 13CNMR (100MHz, CDCl3, ppm): δ140.33, 140.19, 133.07, 128.89, 126.41, 123.84, 120.82, 120.61, 109.60.

[0079] The prepared DBrC, PAN (polyacrylonitrile), and N,N-dimethylformamide were mixed in a ratio of 2 mg:100 mg:10 mL, heated to 80 °C, and stirred for 30 min to obtain a transparent room temperature phosphorescent film precursor solution. This precursor solution was then used at a concentration of 0.001 g / cm³. 2 The coating amount was applied to the surface of the substrate (quartz glass plate), and dried at 110°C for 1 hour to obtain a DBrC-PAN room temperature phosphorescent film.

[0080] The photophysical properties of the DBrC-PAN room temperature phosphorescent thin film prepared in this embodiment were tested, and the test results are as follows: Figure 4 As shown. Figure 4 In the figure, 'a' represents the luminescence of the DBrC-PAN room temperature phosphorescent film when it is irradiated with 365nm ultraviolet light and within 8s after the ultraviolet light is turned off. The afterglow emission time ranges from 0s to 8s. Figure 4 In the figure, b represents the normalized fluorescence (prompt) and phosphorescence (delayed) spectra of the DBrC-PAN room temperature phosphorescent film (λex = 365 nm, delay time: 10 ms). The fluorescence emission peak is located at 427 nm, exhibiting typical blue light emission characteristics, while the phosphorescence emission is located at 549 nm, exhibiting obvious yellow light emission characteristics. Figure 4 The observed thin film luminescence phenomenon is consistent with that observed in a.

[0081] Example 3

[0082] Under nitrogen protection, carbazole (2.80 g, 16.00 mmol), 1,3,5-tribromobenzene (1.25 g, 4.00 mmol), copper iodide (0.80 g, 4.00 mmol), 1,10-phenanthroline (0.08 g, 0.40 mmol), potassium carbonate (2.80 g, 20.00 mmol), and 40 mL of dry DMF were mixed in a three-necked flask. The reaction mixture was heated to 180 °C and refluxed for 24 h. After the reaction was complete, the solvent DMF was removed by rotary evaporation. Then, the residue was extracted with an appropriate amount of dichloromethane. Separation was performed by silica gel column chromatography using a 1:10 v / v mixture of ethyl acetate / dichloromethane as the eluent to give a white powdery solid TCB (1.24 g, yield 53.9%). The 1H NMR spectrum is shown below. Figure 5 As shown, 1HNMR (400MHz, CDC l3, ppm): δ8.17(d,J=7.8Hz,6H),7.97(s,3H),7.67(d,J=8.2Hz,6H),7.48(t,J=7.3Hz,6H),7.34(t,J=7.4Hz,6H). 13 CNMR (100MHz, CDCl3, ppm): δ140.91, 140.44, 126.44, 123.97, 123.64, 120.94, 120.78, 120.67, 109.79.

[0083] The prepared TCB, PAN (polyacrylonitrile), and N,N-dimethylformamide were mixed in a ratio of 2 mg:100 mg:10 mL, heated to 80 °C, and stirred for 30 min to obtain a transparent room temperature phosphorescent film precursor solution. This precursor solution was then used at a concentration of 0.1 g / cm³. 2 The coating amount was applied to the surface of the substrate (quartz glass plate), and dried at 110°C for 1 hour to obtain a TCB-PAN room temperature phosphorescent film.

[0084] The photophysical properties of the TCB-PAN room temperature phosphorescent thin film prepared in this embodiment were tested, and the test results are as follows: Figure 6 As shown. Figure 6 In the figure, 'a' represents the luminescence of the TCB-PAN room temperature phosphorescent film when it is irradiated with 365nm ultraviolet light and within 5s after the ultraviolet light is turned off. The observable afterglow emission time ranges from 0s to 5s. Figure 6 In the figure, b represents the normalized fluorescence (prompt) and phosphorescence (delayed) spectra of the TCB-PAN room temperature phosphorescent film (λex = 365 nm, delay time: 10 ms). The fluorescence emission peak is located at 417 nm, exhibiting typical blue light emission characteristics, while the phosphorescence emission is located at 547 nm, exhibiting obvious yellow light emission characteristics. This is also consistent with... Figure 6 The observed thin film luminescence phenomenon is consistent with that observed in a.

[0085] Figure 7 The graph shows the phosphorescence lifetime decay of the DBrC-PAN room temperature phosphorescent film and the TCB-PAN room temperature phosphorescent film prepared in Examples 2 and 3. Figure 7 In the figure, 'a' represents the lifetime decay curve of the DBrC-PAN room temperature phosphorescent film at the phosphorescence emission peak at 549 nm (λex = 365 nm). Figure 7 In the figure, b represents the lifetime decay curve of the TCB-PAN room-temperature phosphorescent film at the phosphorescence emission peak at 547 nm (λex = 365 nm); from Figure 7 As can be seen, the phosphorescence lifetimes of DBrC-PAN and TCB-PAN are as long as 341.92 and 128.56 ms, respectively.

[0086] The photophysical properties of the BrPBC-PAN room temperature phosphorescent films, DBrC-PAN room temperature phosphorescent films, and TCB-PAN room temperature phosphorescent films prepared in Examples 1-3 at room temperature are shown in Table 1.

[0087] Table 1. Photophysical properties at room temperature of the BrPBC-PAN, DBrC-PAN, and TCB-PAN room-temperature phosphorescent films prepared in Examples 1-3.

[0088]

[0089]

[0090] λ F : Maximum fluorescence value; λ P : Maximum phosphorescence value; τ F Fluorescence lifetime; Φ F Fluorescence quantum efficiency; τ P Phosphorescence lifetime; Φ P Phosphorescence quantum efficiency.

[0091] Example 4

[0092] 1. Synthesis of DHBH:

[0093] In a 250 mL three-necked flask, 80 mL of anhydrous ethanol and methyl 2,5-dihydroxybenzoate (3.36 g, 0.02 mol) were added, followed by dropwise addition of hydrazine hydrate (1.88 g, 0.03 mol), yielding a clear and transparent solution. The solution was stirred under reflux for 8 h, and after cooling to room temperature, a pale yellow precipitate formed. The precipitate was collected by filtration, washed three times with anhydrous ethanol and distilled water, and dried under vacuum. Recrystallization with anhydrous ethanol yielded a pale yellow powder, DHBH (2.68 g, yield 79.7%). 1 HNMR(400MHz,DMSO-d6,ppm): δ11.56(s,1H),9.86(s,1H),8.99(s,1H),7.1 8(d,J=2.9,1H),6.83(dd,J=8.8,2.9,1H),6.72(d,J=8.8,1H),4.58(s,2H);

[0094] 2. Synthesis of HBopo:

[0095] (1) In a 250 mL three-necked flask, DHBH (3.36 g, 0.02 mol) was dissolved in 30 mL of ethanol to obtain a DHBH solution; o-phthalaldehyde (2.68 g, 0.02 mol) was dissolved in 20 mL of ethanol and added dropwise to the above DHBH solution. The resulting mixture was stirred at 80 °C for 12 h. After cooling to room temperature, the volatile components were removed by rotary evaporation to obtain a viscous liquid.

[0096] (2) 100 mL of deionized water was added to the viscous liquid, resulting in the precipitation of pink particles. The precipitate was collected by filtration, washed with water, and dried under vacuum to obtain a white powder containing the blue fluorescent molecule HBopo (3.69 g, yield 69.4%). ¹H NMR (400 MHz, DMSO-d6, ppm): δ 9.70 (s, 1H), 7.86 (s, 1H), 7.75–7.55 (m, 4H), 7.33–7.24 (m, 1H), 7.13–7.05 (m, 2H), 7.01 (s, 1H). 13 CNMR (100MHz, DMSO-d6, ppm): δ160.07,153.65,149.02,140.40,132.62,127.63,127 .24,126.99,123.93,123.67,123.43,119.63,118.61,113.58,113.32,82.56,82.29.

[0097] 3. Synthesis of HBopa

[0098] Under nitrogen protection, HBopo (0.27 g, 1.00 mmol), 300 μL of triethylamine, and 5 mL of DMF were added to a 50 mL three-necked flask. The mixture was stirred and cooled in an ice-water bath, and then 5 mL of DMF solution containing Ac (100.00 μL, 1.42 mmol) was slowly added dropwise over 30 min. After the solution was added, the ice-water bath was removed, and the mixture was allowed to continue reacting for 4 h. After the reaction was complete, the solvent DMF was removed by rotary evaporation. Then, an appropriate amount of dichloromethane was added to the residue for extraction. Separation was performed using ethyl acetate / petroleum ether at a volume ratio of 2:1 as the eluent, finally yielding a white powdery solid HBopo (0.23 g, yield 71.9%). The 1H NMR spectrum is shown below. Figure 8 As shown, 1HNMR (400MHz, DMSO-d6, ppm): δ7.91(s,1H),7.79–7.57(m,5H),7.53(dd,J=8.8,2.9Hz,1H),7.33(d,J=8.8Hz ,1H),7.20(s,1H),6.57(dd,J=17.3,1.3Hz,1H),6.43(dd,J=17.3,10.3Hz,1H),6.18(dd,J=10.3,1.3Hz,1H); 13 CNMR (100MHz, DMSO-d6, ppm): δ 164.74, 159.46, 153.78, 146.07, 140.80, 134.43, 132.83, 131.33, 129.90, 127.98, 127.41, 127.26, 127.20, 123.35, 121.61, 119.81, 118.86, 82.67; The synthetic route is as follows:

[0099]

[0100] 4. Preparation of stimulus-responsive fluorescent thin film poly(HBopa-co-AM):

[0101] (1) HBopa (0.32 g, 1.00 mmol), AM (0.70 g, 10.00 mmol), and azobisisobutyronitrile (AIBN) (7.00 mg, 0.04 mmol) were dissolved in 10 mL of tetrahydrofuran (THF). The mixture was then transferred to a dry three-necked flask and protected with nitrogen (N2). The reaction flask was placed in an oil bath at 70 °C and the reaction was maintained for 10 h. After the reaction was complete, the mixture was added dropwise to 30 mL of n-hexane, the precipitate was collected by filtration, and dried under vacuum to obtain a pale yellow solid product, poly(HBopa-co-AM). The synthetic route is as follows:

[0102]

[0103] (2) Dissolve 0.05 g of poly(HBopa-co-AM) in 5 mL of ultrapure water to prepare a solution with a mass concentration of 1.0%. Then, pour the mixture into a self-made mold (i.e., a 1 mm thick "1"-shaped hollow silicone sheet is attached to the top of a glass plate) to form the pattern "1", and dry it at room temperature for 24 h to prepare a fluorescent film.

[0104] 5. Preparation of phosphorescent thin films

[0105] 2 mg of three organic phosphorescent molecules (DBrC, BrPBC, TCB) and 100 mg of PAN were dissolved in 10 mL of DMF to obtain a solution of the three organic phosphorescent molecules. The solution was heated and stirred until transparent. The mixture was then poured into a self-made mold (i.e., a 1 mm thick "1"-shaped perforated silicone sheet was attached to the top of a glass plate) to form the pattern "1". The solution was dried at 110 °C for 1 h to obtain a thin film.

[0106] Figure 9 The encrypted phosphorescent film prepared in this embodiment is shown in the images, photographed under different lighting conditions (sunlight, UV light on, and UV light off), displaying an "8"-shaped pattern of the encrypted information. The left side of the "8" pattern is composed of poly(HBopa-AM), while the right side is composed of a BrPBC-PAN film. Figure 9 As shown, under natural light conditions, the composite pattern of the number "8" appears transparent. When subjected to 365nm ultraviolet excitation, the left poly(HBopa-AM) region shows no obvious fluorescence emission, while the right BrPBC-PAN region exhibits blue fluorescence, displaying the decryption information "1," forming the initial encryption information. (The text then repeats itself, seemingly unrelated to the previous sentence.) -2 M's Al 3+ After solution spraying, the system exhibits a stimulus-response fluorescence enhancement effect, enabling the secondary information decryption information "8". Furthermore, after UV excitation termination, the BrPBC-PAN region emits a yellow afterglow, continuously displaying the decryption information "1", successfully achieving a triple optical encryption dimension.

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a room-temperature phosphorescent thin film, characterized in that, Includes the following steps: Phosphorescent molecules, polyacrylonitrile, and organic solvents are mixed to obtain a room temperature phosphorescent film precursor solution. The room temperature phosphorescent film precursor solution is then coated onto the surface of a substrate material and cured to obtain a room temperature phosphorescent film. The phosphorescent molecules include one or more of DBrC, BrPBC and TCB; The structural formula of DBrC is as follows: The structural formula of BrPBC is The structural formula of TCB is:

2. The method for preparing a room-temperature phosphorescent thin film according to claim 1, characterized in that, The mixing ratio of the phosphorescent molecules, polyacrylonitrile, and organic solvent is 1-5 mg: 50-150 mg: 5-15 mL.

3. The room temperature phosphorescent thin film prepared by the method for preparing a room temperature phosphorescent thin film according to any one of claims 1 to 2.

4. The application of the room temperature phosphorescent thin film according to claim 3 in the field of information encryption, characterized in that, Includes the following steps: 1) The fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile and organic solvent are mixed and reacted to obtain a copolymer of fluorescent monomer HBopa and acrylamide, poly(HBopa-co-AM); 2) Utilizing the fluorescence properties of poly(HBopa-co-AM) solution and the afterglow property of room temperature phosphorescent film precursor solution, different information was plotted using both, resulting in films exhibiting different information under different conditions; The room temperature phosphorescent film precursor solution is the room temperature phosphorescent film precursor solution according to claim 1 or 2.

5. The application of a room-temperature phosphorescent thin film according to claim 4 in the field of information encryption, characterized in that, The structural formula of the fluorescent monomer HBopa mentioned in step 1) is as follows:

6. The application of a room-temperature phosphorescent thin film according to claim 5 in the field of information encryption, characterized in that, The ratio of the fluorescent monomer HBopa, acrylamide, azobisisobutyronitrile and organic solvent in step 1) is 0.32g~0.5g: 0.70~1.0g: 7.00~10mg: 10mL.

7. The application of a room-temperature phosphorescent thin film according to claim 5 or 6 in the field of information encryption, characterized in that, The reaction in step 1) is carried out at a temperature of 40–90°C for 10–15 hours.

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