Method for physically regulating and controlling afterglow time of room-temperature phosphorescent material through optical excitation and application of method in dynamic information display

Abstract

The invention belongs to the technical field of functional materials, and discloses a method for physically regulating and controlling the afterglow time of a room-temperature phosphorescent material through optical excitation and application of the method in dynamic information display. By using the method, the afterglow emitting RGB three primary colors and the afterglow with red and green time resolution are prepared respectively. The material is quick and energy-saving to prepare and stable in performance, multiple dynamic information encryption can be realized by controlling the wavelength and irradiation time of ultraviolet light, and the material has a wide application prospect in the fields of intelligent anti-counterfeiting and information storage.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to a method for physically controlling the afterglow time of room temperature phosphorescent materials through photoexcitation and its application in dynamic information display. Background Technology

[0002] Room-temperature phosphorescent materials, due to their unique photophysical properties such as long lifetime, large Stokes shift, and high exciton utilization, have broad application prospects in fields such as data encryption, environmental sensing, information storage, bioimaging, and color display, making them one of the research hotspots in the field of organic optoelectronic functional materials. Currently, the afterglow time of room-temperature phosphorescent materials remains constant after fabrication, making dynamic control virtually impossible. While this static characteristic satisfies basic application scenarios, it also limits the material's functional scalability and intelligent response capabilities. Achieving dynamic control of the afterglow time through external stimuli would greatly promote its application in intelligent response devices.

[0003] Using lignin as the luminescent chromophore and polylactic acid as the matrix, the phosphorescence of the material was initially quenched by residual oxygen (O2), resulting in an afterglow lifetime of only 3.0 ms. After 20 s of irradiation with 365 nm ultraviolet light, the lignin triplet excitons consumed the residual O2, activating the phosphorescence and increasing the lifetime to 221.1 ms. However, the phosphorescence color was uniform, and the afterglow lifetime was short. (Jingyi Zhou, BingTian, ​​Yingxiang Zhai, MinWang, Shouxin Liu, JianLi, Shujun Li, Tony D. James & Zhijun Chen, Photoactivated room temperature phosphorescence from lignin)

[0004] This invention utilizes a dual matrix of polyvinylpyrrolidone and boric acid to prepare RGB tri-color materials and room-temperature phosphorescent materials with time-resolved red-to-green transitions by adjusting the precursor structure. The duration of afterglow can be dynamically controlled by varying the photoexcitation time. In the field of intelligent anti-counterfeiting, "photo-controlled afterglow duration switching" can be used to achieve dynamic encryption and decryption of information, significantly improving the complexity and security of anti-counterfeiting measures. By triggering color switching at different afterglow stages through photoexcitation of specific durations, the concealed storage and precise decryption of information can be achieved, adapting to the needs of high-end information security scenarios. The prepared RGB tri-color afterglow emission can achieve maximum color coverage with the smallest color unit, realizing full-gamut photoactivated RTP, becoming a key support for promoting the development of intelligent optoelectronic functional materials towards high integration and high flexibility. Summary of the Invention

[0005] This invention provides a method for controlling afterglow time using photoexcitation physics, enabling dynamic information display and enhancing the intelligent application of room-temperature phosphorescent materials in information encryption and security anti-counterfeiting fields. Using polyvinylpyrrolidone (PVP) and boric acid as a matrix, the afterglow time can be dynamically controlled by changing the photoexcitation time. Furthermore, room-temperature phosphorescent materials with RGB afterglow emission can be prepared by adjusting the conjugation degree of the precursor. Additionally, red-green time-resolved room-temperature phosphorescent materials can be prepared using the precursor pyrene with large π conjugation. The red afterglow material exhibits afterglow visible to the naked eye for 1s, 1s, and 3s after photoexcitation at 1s, 5s, and 10s, respectively; similarly, the green afterglow material exhibits afterglow visible to the naked eye for 2s, 4s, and 13s, respectively; and the blue afterglow material exhibits afterglow visible to the naked eye for 1s, 2s, and 5s, respectively. Moreover, the prepared red-green time-resolved afterglow material exhibits afterglow visible to the naked eye for 1s, 3s, and 7s, with red afterglow for the first 2s and green afterglow for the last 5s. The duration of afterglow, which is perceptible to the naked eye, is directly related to the triplet exciton radiation decay behavior of a material. Room-temperature phosphorescence lifetime, as a core parameter for quantifying this photophysical process, can accurately characterize the dynamic luminescence performance of materials with different colored afterglows. RGB room-temperature phosphorescent materials, after full UV activation, exhibit lifetimes of 187.18 ms, 1195.24 ms, and 135.85 ms, respectively. The red-green time-resolved room-temperature phosphorescent material, after full UV activation, has a red luminescent center lifetime of 204.32 ms and a green luminescent center lifetime of 284.63 ms. This invention features a simple preparation method, dynamically adjustable afterglow duration, and achieves not only the RGB primary colors but also red-green time-resolved colors, greatly enriching its applications in intelligent anti-counterfeiting and information encryption.

[0006] The technical solution of this invention:

[0007] A method for physically controlling the afterglow time of room-temperature phosphorescent materials through photoexcitation includes the following steps:

[0008] Step 1: Dissolve boric acid in deionized water and heat in an 80°C water bath until completely dissolved to obtain a boric acid solution;

[0009] Step 2: Add polyvinylpyrrolidone to a boric acid solution, and add 1-pyreneboric acid, 9-phenanthreneboric acid, salicylic acid and pyrene respectively. Place the well mixed solution in a microwave oven and microwave for 4 minutes. After cooling to room temperature, red, green, blue and red-green time-resolved room temperature phosphorescent materials are obtained respectively.

[0010] In step 1, the concentration of the boric acid solution is 10~20 mg / mL, preferably 15 mg / mL;

[0011] In step 1, the mass ratio of polyvinylpyrrolidone to boric acid is 10:1 to 50:1, preferably 20:1.

[0012] In step 2, the mass ratio of polyvinylpyrrolidone to 1-pyreneboronic acid is 12:1 to 60:1, preferably 15:1; the mass ratio of polyvinylpyrrolidone to 9-phenanthreneboronic acid is 12:1 to 60:1, preferably 15:1; the mass ratio of polyvinylpyrrolidone to salicylic acid is 12:1 to 60:1, preferably 15:1; and the mass ratio of polyvinylpyrrolidone to pyrene is 12:1 to 60:1, preferably 15:1.

[0013] Application of room-temperature phosphorescent materials obtained by the method of this invention in dynamic information display.

[0014] In this invention, the molecular structure of polyvinylpyrrolidone contains a large number of lactam groups (–C=O–N–), which can form hydrogen bonds with the precursor molecule, effectively restricting intramolecular vibrations and thus suppressing the nonradiative inactivation of triplet excitons. Boric acid (BA) forms dynamic B–O covalent bonds with the –OH functional groups in the precursor molecule, constructing a three-dimensional cross-linked network, thereby enhancing structural rigidity, further restricting the movement of the luminescent group, and extending the phosphorescence lifetime. The empty p orbitals of boron atoms can accept electrons, promoting n-π transitions, enhancing SOC, and improving ISC efficiency. The initial RTP is quenched by O2 in the air. After UV irradiation, the triplet exciton converts O2 into singlet oxygen (…). 1 O2) consumes local oxygen, thus "activating" the RTP. Precursors containing easily oxidized groups, such as phenolic hydroxyl groups, can also participate in... 1 O2 scavenging accelerates oxygen depletion. The PVP matrix effectively inhibits the penetration of external O2. Under continuous ultraviolet irradiation, residual O2 within the matrix is ​​gradually consumed, thereby stabilizing the O2-sensitive triplet excitons and ultimately resulting in a significant enhancement of phosphorescence intensity. This process achieves the goal of modulating phosphorescence intensity through irradiation time. The PVP matrix is ​​heat-sensitive; heating enhances the movement of PVP segments, opening O2 diffusion channels, allowing O2 to re-enter and quench the triplet excitons, thus returning them to an inactive state. This endows the material with reversibility and multiple response characteristics.

[0015] The beneficial effects of this invention are as follows: This invention successfully prepared a smart luminescent material whose afterglow duration can be controlled by ultraviolet light irradiation time. By adjusting the precursor structure, not only was a room-temperature phosphorescent material with RGB emission and a single luminescent center achieved, but also a room-temperature phosphorescent material with red-green time-resolved emission and two luminescent centers was prepared. By controlling the wavelength and irradiation time of ultraviolet light, dynamic information display can be achieved. This strategy not only paves the way for building a simple, efficient, and commercially viable long-lifetime RTP polymer system, but also expands the application range of stimulus-responsive materials. In the field of smart anti-counterfeiting, its characteristics of "controllable photoactivation, multi-color output, and time resolution" can be used to construct a multi-level anti-counterfeiting system. By controlling the ultraviolet light irradiation time, the dynamic display and hiding of different color information can be achieved, and the time resolution characteristic can further improve anti-counterfeiting security, preventing counterfeiters from achieving counterfeiting simply by copying colors. In the field of information storage, the combination of the three primary colors of RGB and the time resolution characteristic can be used to achieve high-density information storage. For example, different information fragments can be triggered to display by different irradiation times, or overlapping stored information can be distinguished by using time resolution technology, breaking through the capacity limitation of traditional single-color storage. Attached Figure Description

[0016] Figure 1 The excitation and emission spectra of the photoactivated red room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 1 are shown.

[0017] Figure 2 The excitation and emission spectra of the photoactivated green room temperature phosphorescent material prepared under the optimal reaction conditions in Example 2 are shown.

[0018] Figure 3 The excitation and emission spectra of the photoactivated blue room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 3 are shown.

[0019] Figure 4 The excitation and emission spectra of the photoactivated time-resolved room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 4 are shown.

[0020] Figure 5 The diagram shows the changes in phosphorescence intensity of the photoactivated red room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 1 at different photoactivation times in an air argon atmosphere.

[0021] Figure 6 The diagram shows the changes in phosphorescence intensity of the photoactivated green room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 2 at different photoactivation times in an air argon atmosphere.

[0022] Figure 7 The diagram shows the changes in phosphorescence intensity of the photoactivated blue room-temperature phosphorescent material prepared under the optimal reaction conditions in Example 3 at different photoactivation times in an air argon atmosphere.

[0023] Figure 8 This shows the change in phosphorescence intensity of the time-resolved room temperature phosphorescent material prepared under the optimal reaction conditions in Example 4 at different photoactivation times in an air argon atmosphere.

[0024] Figure 9 The text indicates that afterglow emission was visible to the naked eye under the optimal reaction conditions in Examples 1, 2, 3, and 4. Among them, (A) represents PVP@1-Bor@BA, (B) represents PVP@9-Phe@BA, (C) represents PVP@SAD@BA, and (D) represents PVP@PYR@BA.

[0025] Figure 10 The dynamic digital encryption and anti-counterfeiting patterns represent the patterns, wherein (A) represents the digital encryption information presented under different light activation times produced in Examples 1, 2, and 3, (B) represents the anti-counterfeiting patterns produced in Examples 2, 3, and 4, with the flower part produced in Example 4, and (C) represents the information encryption produced in Examples 1 and 4. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described below in conjunction with the technical solutions and accompanying drawings.

[0027] Example 1

[0028] This embodiment discloses a preparation method for a photoactivated red afterglow room temperature phosphorescent material prepared by using boric acid and polyvinylpyrrolidone together as a rigid matrix and 1-pyreneboronic acid:

[0029] Dissolve 150 mg of boric acid in 10 mL of deionized water and heat in an 80°C water bath until completely dissolved. Add 300 mg of polyvinylpyrrolidone to the boric acid solution, with a mass ratio of polyvinylpyrrolidone to 1-pyreneboric acid of 12:1 to 60:1. Microwave for 4 min.

[0030] Table 1 records the afterglow time of different mass ratios of the matrix and 1-pyreneboric acid in Example 1 under a 365nm UV lamp, with a fixed microwave time of 4 min.

[0031]

[0032] As shown in Table 1, the material with the longest afterglow after full photoactivation and a mass ratio of 20:1 is compared to other materials, with a visible red afterglow of 3 seconds.

[0033] Table 2 records the afterglow of the sample after preparation under the optimal reaction conditions of Example 1, under different durations of irradiation with a 365nm ultraviolet lamp.

[0034]

[0035] As shown in Table 2, when the UV excitation time in Example 1 was controlled at 1s, 5s, 10s, and 15s, the afterglow was 1s, 1s, 3s, and 3s, respectively. The complete UV activation time was 10s.

[0036] Example 2

[0037] This embodiment discloses a preparation method for a photoactivated green afterglow room temperature phosphorescent material prepared by using boric acid and polyvinylpyrrolidone together as a rigid matrix and 9-phenanthreneboronic acid:

[0038] Dissolve 150 mg of boric acid in 10 mL of deionized water and heat in an 80°C water bath until completely dissolved. Add 300 mg of polyvinylpyrrolidone to the boric acid solution, with a mass ratio of polyvinylpyrrolidone to 9-phenanthreneboronic acid of 12:1 to 60:1. Microwave for 4 min.

[0039] Table 3 records the afterglow time of the matrix and 9-phenanthroline boric acid of Example 1 at different mass ratios under a 365nm UV lamp, with a fixed microwave time of 4min.

[0040]

[0041] As shown in Table 3, the material with the longest afterglow after full photoactivation and a mass ratio of 20:1 is compared with other materials, with a visible green afterglow of 13 seconds.

[0042] Table 4 records the afterglow of the sample after preparation under the optimal reaction conditions of Example 2, under different durations of irradiation with a 365nm ultraviolet lamp.

[0043]

[0044] As shown in Table 4, when the UV excitation time in Example 2 was controlled at 1s, 5s, 10s, and 15s, the afterglow was 2s, 4s, 13s, and 13s, respectively. The complete UV activation time was 10s.

[0045] Example 3

[0046] This embodiment discloses a preparation method for a photoactivated blue afterglow room temperature phosphorescent material prepared by using boric acid and polyvinylpyrrolidone together as a rigid matrix and salicylic acid:

[0047] Dissolve 150 mg of boric acid in 10 mL of deionized water and heat in an 80°C water bath until completely dissolved. Add 300 mg of polyvinylpyrrolidone to the boric acid solution, with a polyvinylpyrrolidone to salicylic acid mass ratio of 12:1 to 60:1. Microwave for 4 min.

[0048] Table 5 records the afterglow time of different mass ratios of matrix and salicylic acid in Example 1 under a 365nm UV lamp, with a fixed microwave time of 4 min.

[0049]

[0050] As shown in Table 5, the material with the longest afterglow after full photoactivation and a mass ratio of 20:1 is compared with other materials, with a visible green afterglow of 13 seconds.

[0051] Table 6 records the afterglow of the sample after preparation under the optimal reaction conditions of Example 3, under 365nm UV lamp irradiation for different durations.

[0052]

[0053] As shown in Table 6, when the UV excitation time in Example 1 was controlled at 1s, 5s, 10s, and 15s, the afterglow was 1s, 2s, 5s, and 5s, respectively. The complete UV activation time was 10s.

[0054] Example 4

[0055] This embodiment discloses a preparation procedure for photoactivated red-green time-resolved room temperature phosphorescent materials prepared by using boric acid and polyvinylpyrrolidone together as a rigid matrix and pyrene:

[0056] Dissolve 150 mg of boric acid in 10 mL of deionized water and heat in an 80°C water bath until completely dissolved. Add 300 mg of polyvinylpyrrolidone to the boric acid solution, with a polyvinylpyrrolidone to pyrene mass ratio of 12:1 to 60:1. Microwave for 4 min.

[0057] Table 7 records the afterglow time of different mass ratios of matrix and pyrene in Example 1 under a 365nm UV lamp, with a fixed microwave time of 4 min.

[0058]

[0059] As shown in Table 7, when the mass ratio is 20:1 after full photoactivation, the afterglow is the longest compared to other materials, with a visible green afterglow of 7 seconds.

[0060] Table 8 records the afterglow of the sample after preparation under the optimal reaction conditions of Example 4, under 365nm UV lamp irradiation for different durations.

[0061]

[0062] As shown in Table 8, when the UV excitation time in Example 4 was controlled at 1s, 5s, 10s, and 15s, the afterglow was 1s, 3s, 7s, and 7s, respectively. The complete UV activation time was 10s.

[0063] Phosphorescence excitation and emission spectra of light-activated RGB room-temperature phosphorescent materials, such as Figure 1-3As shown in the figure. The synthesized materials were excited at wavelengths of 373 nm, 318 nm, and 344 nm, and emitted at wavelengths of 612 nm, 522 nm, and 452 nm, respectively, thus realizing the preparation of photoactivated RGB room-temperature phosphorescent materials. The excitation and emission spectra of the photoactivated time-resolved room-temperature phosphorescent materials are shown in the figure. Figure 4 As shown. The synthesized material was excited at a wavelength of 343 nm and emitted at wavelengths of 400 nm and 594 nm.

[0064] The photophysical properties of the material under argon gas conditions were investigated experimentally, further demonstrating that this radiation-dependent RTP is a result of an oxygen consumption mechanism. Figure 5-8 The values ​​represent the phosphorescence intensity of photoactivated RGB and time-resolved room-temperature phosphorescent materials after UV irradiation for different durations in an argon-air atmosphere, respectively. Under argon conditions, the material directly produces bright RTP, and there is no significant increase in phosphorescence intensity after 365nm UV irradiation. However, in an air atmosphere, the highest phosphorescence intensity is achieved after UV activation times of 6s, 8s, 12s, and 6s, respectively.

[0065] like Figure 9 As shown, the red afterglow material exhibits visible afterglow for 1s, 1s, and 3s after UV irradiation for 1s, 5s, and 10s, respectively; similarly, the green afterglow material exhibits visible afterglow for 2s, 4s, and 13s; the blue afterglow material exhibits visible afterglow for 1s, 2s, and 5s; and the red-green dual-color time-resolved afterglow material exhibits visible afterglow for 1s, 3s, and 7s, with a red afterglow for the first two seconds and a green afterglow for the last 5 seconds. After photoactivation by 10s irradiation under a 365nm UV lamp, the red, green, blue, and red-green color changes of the RGB and time-resolved room-temperature phosphorescent materials are visible to the naked eye for approximately 3s, 13s, 5s, and 7s, respectively.

[0066] Leveraging its unique dynamic response characteristics, this invention applies it to information storage. By adjusting the ultraviolet irradiation time, it achieves precise control over the duration, color, and switching sequence of afterglow, constructing a three-dimensional dynamic luminescence system of "time-color-intensity." This system requires no complex equipment; only a portable ultraviolet lamp is needed to complete information writing, reading, and erasing. It combines high security, high information capacity, reversibility, and environmental friendliness, providing a novel solution for next-generation intelligent anti-counterfeiting and information storage technology. Figure 10(a) Initially, after rapid excitation with 365nm ultraviolet light, almost no information is visible. As the irradiation time increases, localized numbers appear. For example, after 8 seconds of irradiation, only the number 12092459 is displayed. With further increases in irradiation time, complete numerical information can be observed. Time-resolved imaging typically refers to using the differences in the lifetime of luminescence of substances to distinguish different luminescent species and reduce background interference. In the field of anti-counterfeiting, time-resolved imaging using carbon dots can achieve higher security because counterfeiters find it difficult to replicate lifetime characteristics, making it more reliable than simple color-based anti-counterfeiting. Figure 10 (b) is a security pattern made using time-resolved materials prepared with a pyrene precursor. The flower part displays red for the first two seconds, then green. Figure 10 (c) uses the PVP@PYR@BA composite material to write the correct information, while PVP@1-Bor@BA is used to encrypt the information. Under 365nm ultraviolet excitation, the error message "8888" jointly encoded by the PVP@1-Bor@BA composite material and PVP@PYR@BA will be displayed. After turning off the 365nm light source for two seconds, the correct information "1949" encoded separately by the PVP@PYR@BA composite material will be displayed in blue.

[0067] Comparative Example 1: 300 mg PVP and 20 mg 1-pyreneboric acid were dissolved in 10 mL of water (without boric acid) and microwaved for 4 min. The resulting film showed no significant phosphorescence enhancement after 365 nm UV irradiation, and the afterglow was not visible.

[0068] Comparative Example 2: 150 mg of boric acid and 20 mg of 1-pyreneboric acid were dissolved in 10 mL of water (without PVP) and microwaved for 4 min. The resulting product was a brittle solid with no film-forming properties, extremely weak phosphorescence intensity, and no photoactivated response.

[0069] Experimental results show that using only polyvinylpyrrolidone (PVP) as a single matrix in combination with precursors (such as 1-pyreneboronic acid, 9-phenanthreneboronic acid, salicylic acid or pyrene), or using only boric acid (BA) mixed with precursors, cannot simultaneously achieve the following three key properties: (1) tunable room temperature phosphorescence emission of red, green and blue primary colors; (2) significant photoactivated response behavior; and (3) long afterglow duration perceptible to the naked eye.

[0070] Comparative Examples 1 and 2 demonstrate that PVP and BA must coexist to achieve the photoactivated RGB and time-resolved RTP performance described in this invention. While a PVP system alone provides some hydrogen bond rigidity, it lacks effective oxygen barrier capabilities and covalent anchoring, making triplet excitons easily quenched by ambient oxygen and difficult to reversibly activate via UV irradiation. A boric acid system alone, lacking polymer network support, cannot form a stable and rigid microenvironment, resulting in extremely low phosphorescence efficiency and no color modulation capability. Only by synergistically constructing a bifunctional matrix with PVP and boric acid in a specific ratio, through the combined action of the PVP hydrogen bond network and the dynamic B–O covalent crosslinking of boric acid, can the oxygen-depleted photoactivation mechanism, efficient and stable triplet excitons, and full RGB color gamut emission be simultaneously achieved.

[0071] Comparative Example 3: Table 1 records the main observations of Comparative Example 3 PVP and BA at different mass ratios under a 365nm UV lamp, with a fixed microwave time of 4min.

[0072]

[0073] As shown in Table 1, when the mass ratio of PVP to boric acid is 10:1 to 1:1, the material can achieve photoactivated room temperature phosphorescence. Among them, the performance is best when the mass ratio is 2:1 (i.e., the boric acid solution concentration is 15 mg / mL), exhibiting the longest afterglow time, the best film-forming properties, and the highest activation efficiency.

Claims

1. A method for physically controlling the afterglow time of room-temperature phosphorescent materials through photoexcitation, characterized in that, Includes the following steps: Step 1: Dissolve boric acid in deionized water and heat in an 80°C water bath until completely dissolved to obtain a boric acid solution; Step 2: Add polyvinylpyrrolidone to a boric acid solution, and then add 1-pyreneboric acid, 9-phenanthrolineboric acid, salicylic acid, and pyrene to obtain a well-mixed solution. Place the solution in a microwave oven and microwave for 4 minutes. After cooling to room temperature, red, green, blue, and red-green time-resolved room temperature phosphorescent materials are obtained.

2. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 1, the concentration of the boric acid solution is 10~20 mg / mL.

3. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 1, the mass ratio of polyvinylpyrrolidone to boric acid is 10:1 to 50:

1.

4. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 2, the mass ratio of polyvinylpyrrolidone to 1-pyreneboronic acid is 12:1 to 60:

1.

5. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 2, the mass ratio of polyvinylpyrrolidone to 9-phenanthreneboronic acid is 12:1 to 60:

1.

6. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 2, the mass ratio of polyvinylpyrrolidone to salicylic acid is 12:1 to 60:

1.

7. The method for physically controlling the afterglow time of room-temperature phosphorescent materials by photoexcitation according to claim 1, characterized in that, In step 2, the mass ratio of enpyrrolidone to pyrene is 12:1 to 60:

1.

8. The application of the room-temperature phosphorescent material obtained by the method of any one of claims 1-7 in dynamic information display.

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