Single-component room-temperature phosphorescent organogel based on dibenzofuran and its anti-counterfeiting application

Abstract

The present invention provides an organic light-emitting material with reversible room temperature phosphorescence (RTP). This phosphorescent material is a pure organic light-emitting material that exhibits reversible room temperature phosphorescence (RTP) under external stimulation and has attracted widespread attention due to its potential application in dynamic anti-counterfeiting. The present invention synthesized a single-component organic RTP molecule (DBF‑dPh) based on dibenzofuran, and studied its stimulus response characteristics and application in the field of anti-counterfeiting. DBF‑dPh can form a stable gel in a mixed solvent of DMSO and water, and exhibits a long room temperature phosphorescence lifetime (35.2 ms) in the gel state; when heated to 85°C, the gel transforms into a sol state, and the phosphorescence is quenched, thereby showing dynamic RTP characteristics. This work provides a reference for the design of single-component room temperature phosphorescent gels and expands the application of room temperature phosphorescent materials in the field of dynamic anti-counterfeiting.

Description

Technical Field

[0001] The invention relates to phosphorescent materials and applies the phosphorescent materials to anti-counterfeiting materials. Background Art

[0002] With the development of modern science and technology and the economy, optical anti-counterfeiting materials for information security are gaining increasing attention due to their efficiency, cost-effectiveness, and ease of use. Fluorescence has a short lifetime, typically on the nanosecond scale, and rapidly disappears once the excitation light ceases. In contrast, phosphorescence has a much longer lifetime, typically on the microsecond scale, and its afterglow can be detected even after the excitation light is turned off. This long-lasting luminescence is of immeasurable value in various fields, including light-emitting devices, sensing, anti-counterfeiting, bioimaging, and photocatalysis. Therefore, the development of materials capable of room-temperature phosphorescence is of considerable scientific and practical significance. Currently, the most common inorganic phosphorescent materials are those containing sulfides doped with heavy metals, transition metals, or rare earth elements, but their high price and poor processing properties limit their practical applications. In contrast, organic materials are gaining popularity due to their wide availability, versatile synthesis methods, and cost-effectiveness. However, organic materials suffer from weak spin-orbit coupling (SOC) of excited triplet states and forbidden radiative (triplet-to-singlet) relaxation. Furthermore, the triplet excited states of organic molecules are susceptible to nonradiative relaxation through thermal and collisional processes and are also sensitive to the presence of atmospheric oxygen. Supramolecular gels are emerging stimuli-responsive materials with a wide range of applications, widely acclaimed for their large surface area, sensitive response to stimuli, ideal reproducibility, and ease of manipulation. In recent years, gel fiber structures have been found to be ideal media for constructing stimuli-responsive RTP materials. In the gel state, these organic supramolecular structures form a rigid microenvironment that not only confines the vibration of the phosphor but also hinders the quenching of triplet excitons by quenchers such as oxygen, thereby maintaining room-temperature phosphorescence. However, when heated to the sol state, the phosphorescence can be effectively quenched, making organogels excellent candidates for thermally responsive dynamic phosphorescence applications. Summary of the Invention

[0003] Based on the above technical problems, the present invention provides an organic light-emitting material with reversible room temperature phosphorescence (RTP), the structural formula of which is:

[0004] , named DBF-dPh.

[0005] The present invention also provides a method for preparing an organic light-emitting material of reversible room temperature phosphorescence (RTP), and the reaction formula is as follows:

[0006]

[0007] The method comprises the following steps: adding chloroform solvent to anhydrous AlCl3 under an inert nitrogen atmosphere, then adding benzoyl chloride to obtain a reaction mixture, then gradually introducing dibenzo[b,d]furan dissolved in the chloroform solvent into the previous reaction mixture, and stirring the reaction at room temperature. After the reaction is completed, an organic light-emitting material with reversible room temperature phosphorescence (RTP) is obtained through post-treatment.

[0008] The molar ratio of benzoyl chloride to dibenzo[b,d]furan is 5-10:1; and the amount of anhydrous AlCl3 used is 40-60% of the total molar amount of the reaction raw materials.

[0009] The post-treatment includes quenching the product after the reaction with dilute hydrochloric acid, extracting with dichloromethane, combining the organic extracts, washing with water, drying, vacuum concentrating, and then purifying by column chromatography to obtain the product DBF-dPh.

[0010] The present invention also provides application of an organic light-emitting material with reversible room temperature phosphorescence (RTP) in preparing a room temperature phosphorescent material.

[0011] In some specific embodiments, the room temperature phosphorescent material is obtained after the obtained reversible room temperature phosphorescent (RTP) organic light-emitting material is formed into a gel material.

[0012] A room temperature phosphorescent organic gel is an organic gel formed by an organic luminescent material of reversible room temperature phosphorescence (RTP) in a DMSO aqueous solution.

[0013] The DBF-dPh of the present invention can form a stable gel in a mixed solvent of DMSO and water, and exhibits a long room-temperature phosphorescence lifetime in the gel state (the longest phosphorescence lifetime can be achieved 35.2 ms); when heated to 85°C, the gel transforms into a sol state and the phosphorescence is quenched, thereby displaying dynamic RTP characteristics.

[0014] The DBF-dPh of the present invention can only dissolve in DMSO and cannot form a gel product. Even at a concentration of 30 mg / mL, only a homogeneous mixed solution is formed, demonstrating excellent solubility. However, in the presence of water, such as a 2:1 ratio of DMSO to water, a stable gel product can be formed.

[0015] In some preferred cases, a stable gel product is formed by forming a mixed solvent of DMSO and water (hereinafter referred to as DMSO / H2O gel) at a volume ratio of 2:1, and then adding DBF-dPh.

[0016] Another technical solution of the present invention is to use the room temperature phosphorescent organogel in a material having room temperature phosphorescent properties. The room temperature phosphorescent organogel is a stable gel formed by DBF-dPh in a mixed solvent of DMSO and water (hereinafter referred to as DBF-dPh gel).

[0017] The room-temperature phosphorescence characteristic refers to the phosphorescence effect produced at 25°C, specifically manifesting as a yellow phosphorescence effect. DBF-dPh in a DMSO / H2O gel at 25°C can achieve a phosphorescence effect lasting over 30ms, with a long-lived phosphorescence band with a visible afterglow. The DBF-dPh of the present invention exhibits an even better phosphorescence lifetime in a DMSO / H2O gel at low temperatures, such as over 120ms at 77K.

[0018] In the present invention, the room temperature phosphorescent organogel is used in materials having room temperature phosphorescent properties under external stimulation, wherein the external stimulation includes light stimulation and / or temperature stimulation, wherein the light stimulation includes ultraviolet light; and the temperature stimulation includes stimulation within the range of 25-65°C.

[0019] The light stimulation is the phosphorescence phenomenon formed when the gel formed by DBF-dPh in DMSO / H2O is exposed to ultraviolet light for 0 min-25 min, as shown in this case, which shows a significant enhancement of phosphorescence.

[0020] The temperature stimulation causes the phosphorescence phenomenon formed by the gel formed by DBF-dPh in DMSO / H2O at 25°C to 65°C, which, in this case, shows an effect of significantly reducing phosphorescence.

[0021] A photoresponsive anti-counterfeiting material, wherein the phosphorescence intensity gradually increases upon exposure to ultraviolet light, comprises the room temperature phosphorescent organogel. The ultraviolet light intensity is 300-380 nm. In some embodiments, the irradiation is performed at an ultraviolet light intensity of 365 nm. The phosphorescence phenomenon is formed under the enhanced ultraviolet light irradiation for a duration of 0 to 25 minutes.

[0022] A temperature-responsive anti-counterfeiting material realizes a reversible process of heating into a solvent and cooling into a gel by heating from 25°C to 65°C and cooling from 65°C to 25°C. The material includes the room temperature phosphorescent organic gel.

[0023] The present invention also provides a single-component dynamic phosphorescent anti-counterfeiting material based on dibenzofuran, which uses a yellow fluorescent dye to surround the room-temperature phosphorescent organic gel to form an anti-counterfeiting mark, so that under ultraviolet light, the room-temperature phosphorescent organic gel and the yellow fluorescent dye have similar luminescence, and the dynamic anti-counterfeiting process is realized under ultraviolet light on, ultraviolet light off, room temperature, and heating to 45°C-85°C.

[0024] The yellow fluorescent dye is the known fluorescent dye BO-TPA (chemical structure: ; Synthesis see reference: Chem. Commun., 2014, 50, 2569).

[0025] In some embodiments, the DBF-dPh gel obtained above is formed into an anti-counterfeiting label and then coated with a yellow fluorescent dye to form a composite anti-counterfeiting label. Under ultraviolet light, the gel and the dye exhibit similar luminescence, hindering the identification of the anti-counterfeiting label. When the ultraviolet light is turned off, the dye's fluorescence disappears, while the DBF-dPh gel emits a yellow afterglow, allowing identification of the anti-counterfeiting label.

[0026] Alternatively, DBF-dPh gel is molded into an anti-counterfeiting label, and yellow fluorescent dye also forms an anti-counterfeiting label. After the two are superimposed, under ultraviolet light, the anti-counterfeiting label molded by DBF-dPh gel appears, and when the ultraviolet light is turned off, the anti-counterfeiting label of the yellow fluorescent dye appears.

[0027] Alternatively, DBF-dPh gel is mixed with a yellow fluorescent dye to form a security label, and then DBF-dPh gel is applied to a portion of this security label to form the final security label. Under ultraviolet light, the security label is revealed. When the ultraviolet light is turned off, the formed portion of the security label is revealed. When heated to 45°C, the displayed portion of the security label weakens until it disappears at 85°C. After cooling to room temperature, the formed portion of the security label is revealed.

[0028] In summary, we designed and synthesized a non-classical organogel, DBF-dPh, with a rigid chemical structure. Balanced intermolecular π-π interactions enable it to form a stable gel in DMSO / H₂O. The DBF-dPh gel emits long-lived yellow phosphorescence at room temperature and is responsive to UV light and heat, endowing it with multi-level anti-counterfeiting capabilities and making it suitable for dynamic anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 From left to right: DBF-dPh sol-gel transition photo (a), frequency sweep analysis (b), 6.28 rad·s -1 Strain sweep analysis under (c), OM of wet gel and SEM image of dry gel (20 mg mL -1 ) (d).

[0030] Figure 2 is the temperature-dependent change in the sol-gel transition process 1 H NMR spectroscopy and photoluminescence spectroscopy.

[0031] Figure 3(a) Steady-state and delayed emission spectra of DBF-dPh gel; (b) Photoluminescence decay curves of DBF-dPh gel at different temperatures; (c) Photoluminescence and afterglow images (λ ex : 400 nm; delay 1 ms).

[0032] Figure 4 (a) Delayed emission spectra and afterglow images of DBF-dPh gel under 365 nm light irradiation; (b) DBF-dPh gel (20 mg mL -1 ) delayed emission spectrum and afterglow image. (λ ex : 400 nm; delay 1 ms).

[0033] Figure 5 The encrypted information for using DBF-dPh gel includes: (a) the QR code “CTGU”, (b) the numbers “365” and the word “if”. DETAILED DESCRIPTION

[0034] Example 1

[0035] Synthesis of DBF-dPh products:

[0036]

[0037] DBF-dPh: Under an inert nitrogen atmosphere, chloroform (10 mL) was added to anhydrous AlCl₃ (3.19 g, 24.0 mmol, 4.0 eq), followed by the slow addition of benzoyl chloride (4.16 mL, 36.0 mmol, 6.0 eq). Subsequently, dibenzo[b,d]furan (1.01 g, 6.0 mmol, 1.0 eq) dissolved in chloroform (20 mL) was gradually introduced into the reaction mixture and stirred at room temperature for 6 hours. Upon completion of the reaction, the mixture was quenched with dilute hydrochloric acid (HCl) and extracted three times with dichloromethane (DCM). The combined organic extracts were washed with water, dried over anhydrous Na₂SO₄, and the crude product was concentrated in vacuo. The final product, DBF-dPh, was purified by column chromatography as a light yellow solid (65%). 1H NMR (400 MHz, CDCl3): δ 8.45 (d, J =1.2 Hz, 2H), 8.06 (m, 2H), 7.85 (d, J = 7.2 Hz, 4H), 7.72 (d, J = 8.8 Hz, 2H), 7.65 (t, J = 7.4 Hz, 2 H), 7.55 (t, J = 7.6 Hz, 4H). 13C NMR (100 MHz, CDCl3): δ 195.95, 159.20, 137.83, 133.29, 132.45, 130.46, 129.99, 128.42,123.86, 123.78, 111.87. HRMS (ESI) m / z: [M+H] + calcd for C 26 H 17 O3377.1178, found377.1219.

[0038] Example 2

[0039] The gelation behavior of DBF-dPh prepared in Example 1 in conventional solvents was investigated using heating and cooling methods. If the material did not flow when the vial was inverted, the sample was considered a gel. However, even at a concentration of 30 mg / mL, DBF-dPh remained a homogeneous solution in DMSO, demonstrating good solubility.

[0040] DBF-dPh was added to DMSO / H2O (2:1 v / v) to form a stable gel ( Figure 1 (a, lower panel). The gel concentration (CGC) of DBF-dPh is 20 mg mL -1 When heated above 85°C, a sol state can be obtained, showing perfect reversibility ( Figure 1 (a, upper picture).

[0041] In order to further verify the formation of gel, rheological experiments were carried out on DBF-dPh gel. Figure 1 As shown in Figure 2, the storage modulus (G') of DBF-dP in DMSO / H2O gel gradually decreases with the increase of strain, while the loss modulus (G'') changes irregularly. Figure 1 In (b), the loss modulus (G'') exceeds the storage modulus (G'), indicating that the gel is gradually destroyed. In addition, the frequency sweep experiment shows that the storage modulus (G') of DBF-dPh gel always exceeds the loss modulus (G''), indicating that the organogel has good tolerance to external forces ( Figure 1 Middle c).

[0042] Then, optical microscopy (OM) was used ( Figure 1 d upper) and scanning electron microscopy (SEM) ( Figure 1 The aggregation morphology and microstructure of the DBF-dPh organogel (middle d, lower panel) were investigated. OM analysis revealed that DBF-dPh in the DMSO / H2O wet gel formed elongated nanofibers approximately 100 μm in length. The resulting xerogel consisted of 5-8 μm nanoparticles with no aggregation tendency, indicating uniform distribution of DBF-dPh throughout the xerogel system. Comparison of micrographs of the wet and xerogels reveals crystallization during freeze-drying to prepare the xerogel.

[0043] Example 3

[0044] For the DBF-dPh gel prepared in Example 2, in order to further explore the self-assembly of DBF-dPh gel in DMSO / H2O, this example tested the temperature-related 1 H NMR spectrum ( Figure 2 For DBF-dPh gel, as the temperature increases, the protons on the dibenzofuran units shift upfield. In particular, at 65°C, a new resonance signal appears around 7.7 ppm, which was unresolved at 25°C. This suggests that the DBF-dPh gel molecules experience multiple intermolecular interactions in the gel state. Considering that the steric hindrance of the two terminal phenyl groups of the DBF-dPh gel molecules may inhibit intermolecular stacking between dibenzofuran units, stacking between the benzene ring and dibenzofuran, or even CH interactions, may be the primary cause of the NMR signal changes. It is important to note that the solvent also plays a significant role in gelation, as the NMR signal of water changes significantly with temperature. Figure 2The temperatures from bottom to top in a are 25℃, 35℃, 45℃, 55℃, 65℃, 75℃, and 85℃. Figure 2 The reagent bottles in B show the fluorescence effects of the gel-like product under ultraviolet light and the sol-like product under ultraviolet light respectively.

[0045] Example 4

[0046] The phosphorescence properties of the DBF-dPh gel prepared in Example 2 were studied in the gel state. The 3D network of nanofibers within the gel provides a rigid environment that inhibits molecular motion and reduces non-radiative decay, potentially enhancing the RTP properties in the gel state. DBF-dPh in DMSO / H2O gels exhibits a primary emission band centered at 565 nm, manifesting as yellow phosphorescence ( Figure 3 a). The phosphorescence lifetime of DBF-dPh in DMSO / H2O gel is 35.2 ms at 25°C and extends to 127.0 ms at 77 K ( Figure 3 b), indicating that DBF-dPh in DMSO / H2O gel exhibits good room temperature phosphorescence properties. In addition, a long-lived phosphorescence band with visible afterglow at room temperature was observed in DBF-dPh gel ( Figure 3 c).

[0047] Example 5

[0048] As a soft nanofiber material, RTP gel generally exhibits flexibility and high sensitivity to external stimuli. The phosphorescence intensity can be significantly enhanced by consuming oxygen through light irradiation of the phosphorescent gel. For the DBF-dPh gel prepared in Example 2, the phosphorescence intensity of DBF-dPh in DMSO / H2O gel gradually increased when it was exposed to UV light from 0 minutes to 25 minutes ( Figure 4 a), showing light-responsive anti-counterfeiting capabilities. Secondly, considering the reversible process of heating to sol and cooling to gel, the effect of temperature on the phosphorescence properties of DBF-dPh gel was studied. As the temperature increased from 25°C to 65°C, the phosphorescence intensity decreased significantly and was negligible above 65°C ( Figure 4 b). Furthermore, after turning off the 365nm UV light at 25°C, the phosphorescence exhibited a bright yellow afterglow, which dimmed to a dark yellow at 65°C. These results demonstrate that the DBF-dPh gel exhibits excellent thermoresponsive phosphorescence, making it an ideal candidate for dynamic anti-counterfeiting applications.

[0049] Example 6

[0050] In view of the dynamic phosphorescence properties of the DBF-dPh gel system (DBF-dPh in DMSO / H2O gel prepared in Example 2), this example demonstrates its potential application in anti-counterfeiting.

[0051] like Figure 5 As shown in Figure a, DBF-dPh gel was molded into a QR code and filled with a specific yellow fluorescent dye, BO-TPA. Under 365nm ultraviolet light, the gel and dye exhibit similar luminescence, preventing WeChat from scanning and identifying any information. When the UV light is turned off, the dye's fluorescence disappears, while the DBF-dPh gel emits a yellow afterglow. Scanning with WeChat revealed the hidden message "CTGU."

[0052] In addition, if Figure 5 As shown in Figure b, a cipher with both numbers and patterns was also fabricated. The number "888" is made of DBF-dPh gel and the yellow fluorescent dye BO-TPA, while "365" consists solely of DBF-dPh gel. Under 365nm UV light, "888" appears; when the UV light is turned off, only "365" is visible, enabling digital encryption related to phosphorescence lifetime. After 30 minutes of UV irradiation, the visibility of "365" is significantly enhanced. Thus, the DBF-dPh gel exhibits dual anti-counterfeiting properties, responsive to both the excitation light duration and the phosphorescence lifetime.

[0053] In addition, the word "gift" was created using DBF-dPh gel and a similarly colored non-RTP fluorescent dye, and "if" was made from DBF-dPh gel. Under 365nm UV light, "gift" was visible, but in the absence of UV light, only "if" remained visible, indicating that phosphorescence lifetime can be applied to word encryption. When heated to 45℃, the yellow afterglow of "if" was significantly weakened and disappeared at 85℃, but it could be restored after cooling to room temperature ( Figure 5 b). In summary, DBF-dPh gel has multi-level anti-counterfeiting capabilities that can respond to phosphorescence lifetime, excitation light time, and thermal stimulation ( Figure 5 c).

Claims

1. A room temperature phosphorescent organogel, characterized in that: An organic gel is formed by dissolving an organic light-emitting material of reversible room temperature phosphorescence (RTP) in an aqueous solution of DMSO. The structural formula of the organic light-emitting material is: , named DBF-dPh.

2. The room temperature phosphorescent organogel according to claim 1, characterized in that The preparation method of an organic light-emitting material with reversible room temperature phosphorescence (RTP) includes the following steps: adding chloroform to anhydrous AlCl3 under an inert nitrogen atmosphere, then adding benzoyl chloride to obtain a reaction mixture, then gradually introducing dibenzo[b,d]furan dissolved in chloroform into the previous reaction mixture, and stirring the reaction at room temperature. After the reaction is completed, the organic light-emitting material with reversible room temperature phosphorescence (RTP) is obtained through post-treatment.

3. The room temperature phosphorescent organogel according to claim 2, characterized in that The molar ratio of benzoyl chloride to dibenzo[b,d]furan is 5-10:1; the amount of anhydrous AlCl3 is 40-60% of the total molar amount of the reaction raw materials; The post-treatment includes quenching the product after the reaction with dilute hydrochloric acid, extracting with dichloromethane, combining the organic extracts, washing with water, drying, vacuum concentrating, and then purifying by column chromatography to obtain the product DBF-dPh.

4. Use of the room temperature phosphorescent organogel according to claim 1 in materials with room temperature phosphorescent properties.

5. The use according to claim 4, characterized in that The room temperature phosphorescent organic gel is used in materials having room temperature phosphorescent properties under external stimulation, wherein the external stimulation includes light stimulation and / or temperature stimulation, wherein the light stimulation includes ultraviolet light; and the temperature stimulation includes stimulation within the range of 25-65°C.

6. A light-responsive anti-counterfeiting material, wherein the phosphorescence intensity gradually increases when exposed to ultraviolet light, the material comprising the room temperature phosphorescent organogel according to claim 1.

7. A temperature-responsive anti-counterfeiting material, which realizes a reversible process of heating to a solvent and cooling to a gel by heating from 25°C to 65°C and cooling from 65°C to 25°C, wherein the material comprises the room temperature phosphorescent organogel according to claim 1.

8. A single-component dynamic phosphorescent anti-counterfeiting material based on dibenzofuran, characterized in that: The anti-counterfeiting label formed by surrounding the room temperature phosphorescent organic gel according to claim 1 with yellow fluorescent dye makes the room temperature phosphorescent organic gel and the yellow fluorescent dye have similar luminescence under ultraviolet light, and realizes a dynamic anti-counterfeiting process under ultraviolet light on, ultraviolet light off, room temperature, and heating to 45°C-85°C.

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