Preparation method and application of pure organic fluorescent long-lasting film excited by visible light

Abstract

The present invention provides a method for preparing a pure organic fluorescent long-lasting film excited by visible light, comprising: preparing a host solution using a polyhydroxy polymer matrix material and a solvent; preparing a guest solution using fluorescent dye molecules and a solvent; preparing a target solution using a mixture of the host solution and the guest solution; and dropwise adding the target solution onto a glass sheet to remove the solvent from the target solution, thereby obtaining a pure organic fluorescent long-lasting film excited by visible light. The method comprises forming hydrogen bonds between the polyhydroxy polymer matrix material and the fluorescent dye molecules. The present invention also provides applications of the pure organic fluorescent long-lasting film excited by visible light in the fields of color-tunable lighting sources, industrial product manufacturing, and anti-counterfeiting labels.

Description

Technical Field

[0001] The present invention relates to the field of long-lasting fluorescence, and in particular to a preparation method and application of a pure organic fluorescent long-lasting fluorescence film excited by visible light. Background Art

[0002] Whether it's room-temperature phosphorescence (RTP) or thermally activated delayed fluorescence (TADF) afterglow, stabilizing triplet excitons is essential for efficient afterglow emission. RTP afterglow has long been a hot research topic in pure organic optoelectronics, while the construction of ultralong organic phosphorescent (UOP) materials depends heavily on the surrounding environment, such as the matrix and temperature. Furthermore, the spin-forbidden transition between the lowest excited triplet state (T1) and the ground state (S0) typically reduces emission efficiency. Achieving a low triplet radiative transition rate often makes it difficult to simultaneously achieve a high triplet emission efficiency. Furthermore, the excitation process of UOP materials typically requires a high-energy excitation source, such as ultraviolet excitation, to reach the lowest excited singlet state (S1), where triplet excitons are subsequently retrieved via intersystem crossing (ISC). In contrast, the radiative decay of TADF afterglow is a spin-allowed process from S1 to S0. Furthermore, increasing the temperature can even enhance TADF emission. The charge transfer (CT) properties of TADF molecules also contribute to their absorption of light in the visible region, thus facilitating the generation of visible light-excited afterglow. However, currently, there is a relative lack of pure organic fluorescent long-lasting glow materials excited by visible light. Summary of the Invention

[0003] In view of this, the main purpose of the present invention is to provide a method for preparing a pure organic fluorescent long-lasting film excited by visible light and its application, in order to at least partially solve one of the above-mentioned technical problems.

[0004] As one aspect of the present invention, a method for preparing a pure organic fluorescent long-lasting film excited by visible light is provided, comprising:

[0005] A main solution is prepared by using a polyhydroxy polymer matrix material and a solvent;

[0006] A guest solution is prepared by using fluorescent dye molecules and solvent;

[0007] A target solution is prepared by using a mixed solution of the host solution and the guest solution;

[0008] The target solution is added dropwise onto a glass sheet to remove the solvent in the target solution, thereby obtaining a pure organic fluorescent long-lasting film excited by visible light;

[0009] The polyhydroxy polymer matrix material forms hydrogen bond interactions with the fluorescent dye molecules.

[0010] According to an embodiment of the present invention, the mass fraction ratio of the polyhydroxy polymer matrix material to the fluorescent dye molecules is 100:1.

[0011] According to an embodiment of the present invention, the fluorescent dye molecules include: acridine yellow, rhodamine B, acridine orange, and a mixture of acridine yellow and rhodamine B.

[0012] According to an embodiment of the present invention, in the mixture of acriflavine and rhodamine B, the mass fraction ratio of acriflavine to rhodamine B is 1:2 to 10:1.

[0013] According to an embodiment of the present invention, in the mixture of acriflavine and rhodamine B, the mass fraction ratio of acriflavine to rhodamine B is 1:2.

[0014] According to an embodiment of the present invention, the polyhydroxy polymer matrix material includes: polyvinyl alcohol, agarose, polyacrylic acid, polyvinyl pyrrolidone, and cellulose.

[0015] According to an embodiment of the present invention, the solvent comprises an aqueous solution.

[0016] As another aspect of the present invention, there is also provided an application of a visible light excited pure organic fluorescent long afterglow film prepared by a method for preparing a visible light excited pure organic fluorescent long afterglow film in the field of color tunable lighting sources.

[0017] As another aspect of the present invention, there is provided an application of a visible light excited pure organic fluorescent long afterglow film prepared by a method for preparing a visible light excited pure organic fluorescent long afterglow film in the field of industrial product manufacturing.

[0018] As another aspect of the present invention, there is provided an application of a visible light excited pure organic fluorescent long afterglow film prepared by a method for preparing a visible light excited pure organic fluorescent long afterglow film in the field of visible light identification anti-counterfeiting labels.

[0019] Based on the above technical solutions, it can be seen that the preparation method of the visible light excited pure organic fluorescent long afterglow film and its application of the present invention have at least one or part of the following beneficial effects compared with the prior art:

[0020] (1) The present invention provides a method for preparing a pure organic fluorescent long-lasting film material excited by visible light by dispersing fluorescent dye molecules into a polyhydroxy polymer matrix, thereby obtaining a simple and environmentally friendly material preparation strategy. The matrix material used is only required to be a polyhydroxy polymer, which is relatively wide to choose from. For example, PVA, agarose, starch, cellulose, etc. can all be used as the main matrix material to achieve fluorescent long-lasting emission. The product is cheap and easy to obtain. The guest material used, such as acridinium yellow Acf, can produce fluorescent long-lasting emission before and after purification. The cost is low and the raw materials are easy to obtain. Both the host and guest materials have good water solubility. Therefore, the solvent required for material preparation is only water, which is green, environmentally friendly and pollution-free, and the cost is also low. The material obtained after host-guest doping exhibits bright green fluorescent long-lasting emission after stopping white light excitation. The afterglow lasts for nearly 10 seconds and the color is adjustable, which has a wide range of applicability.

[0021] (2) The fluorescent long-lasting film material prepared by the present invention has relatively few requirements for sample conditions. A simple physical mixing method is used to mix the guest molecules with the host material, and the corresponding material is obtained after the water evaporates. No single crystal or eutectic cultivation is required. Furthermore, by regulating the matrix or further incorporating other molecules, the color and duration of the fluorescent afterglow can be controlled, thereby expanding the material's application range.

[0022] (3) The fluorescent long-lasting film material prepared by the present invention can exhibit long-lasting fluorescent emission even after white light excitation ceases. Therefore, based on this characteristic of the material, it can be used to develop color-tunable lighting sources. The resulting light-emitting diodes (LEDs) can still exhibit afterglow emission of different colors even after power is turned off, and can be used in energy-saving light sources and decorative light sources.

[0023] (4) The fluorescent long afterglow film material prepared by the present invention only requires the fluorescent dye molecules to be concentrated at an extremely low concentration (0.5 mg mL -1 ) can be mixed with a polyhydroxy polymer matrix to achieve material development. Therefore, by applying or dripping an aqueous solution of dye molecules onto the surfaces of various substrates, such as paper, wood, cotton, cotton rope, and cellulose, a variety of industrial products with long-lasting fluorescence can be produced. Low-cost anti-counterfeiting labels that can be identified by visible light can also be prepared. For example, using an aqueous solution of ACF to directly draw a corresponding label on a paper box, the resulting pattern exhibits a long-lasting green fluorescence after white light excitation, enabling anti-counterfeiting applications.

[0024] (5) The method of the present invention is simple and easy to prepare. The excellent long-lasting fluorescence emission of the material under visible light excitation can be used to prepare lighting sources, luminous products, anti-counterfeiting labels, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A flow chart schematically illustrates a method for preparing a pure organic fluorescent long-lasting film excited by visible light according to an embodiment of the present invention;

[0026] Figure 2 (a) shows the normalized delayed luminescence spectra of the Acf@PVA film at room temperature and 77K according to Example 4 of the present invention;

[0027] Figure 2 (b) shows a schematic diagram of the afterglow photograph and delayed luminescence spectrum of the Acf@PVA film during the heating process according to Example 4 of the present invention;

[0028] Figure 3 (a) shows the time-resolved delayed luminescence spectra of Acf@PVA, Acf@PVP and Acf@PAA films under white light excitation according to Example 5 of the present invention;

[0029] Figure 3 (b) shows the normalized delayed luminescence spectra of Acf@PVA, Acf@PVP and Acf@PAA films at room temperature and 77K and their S1 and T1 energy level differences according to Example 5 of the present invention;

[0030] Figure 4 The afterglow kinetic decay curve of Acf at the maximum emission wavelength of delayed fluorescence in different polyhydroxy polymer matrices according to Example 5 of the present invention is shown;

[0031] Figure 5 (a) shows the normalized afterglow excitation spectra of Acf@PVA and 1-2@PVA films according to Example 6 of the present invention;

[0032] Figure 5 (b) shows the normalized afterglow excitation spectra of Acf@agarose and 1-2@agarose films according to Example 6 of the present invention;

[0033] Figure 6 The time-resolved delay spectra of 10-1@agarose (a), 5-1@agarose (b), 2-1@agarose (c), 1-1@agarose (d), and 1-2@agarose (e) films under 365 nm ultraviolet light excitation according to Example 6 of the present invention are shown;

[0034] Figure 7 The time-resolved delay spectra of 10-1@agarose (a), 5-1@agarose (b), 2-1@agarose (c), 1-1@agarose (d) and 1-2@agarose (e) films under white light excitation according to Example 6 of the present invention are shown;

[0035] Figure 8 The time-resolved delay spectra of 10-1@PVA (a), 5-1@PVA (b), 2-1@PVA (c), 1-1@PVA (d) and 1-2@PVA (e) films under 365 nm ultraviolet light excitation according to Example 6 of the present invention are shown;

[0036] Figure 9 The time-resolved delay spectra of 10-1@PVA(a), 5-1@PVA(b), 2-1@PVA(c), 1-1@PVA(d) and 1-2@PVA(e) films under white light excitation according to Example 6 of the present invention are shown;

[0037] Figure 10 (a) shows the CIE coordinate change diagram corresponding to the fluorescence afterglow color in the agarose matrix at different mass ratios of Acf and RhB according to Example 6 of the present invention;

[0038] Figure 10 (b) shows the CIE coordinate change diagram corresponding to the fluorescence afterglow color in the PVA matrix at different mass ratios of Acf and RhB according to Example 6 of the present invention;

[0039] Figure 11 (a) shows a physical diagram of a printed circuit board (PCB) mounted with a light-emitting diode (LED) and a NE555 timer according to Example 7 of the present invention;

[0040] Figure 11 (b) shows a schematic diagram of photos taken when the LED lamp coated with the Acf@PVA solution according to Example 7 of the present invention is turned on and off (wherein, top: vertical view; bottom: top view);

[0041] Figure 11 (c) shows a schematic diagram of photos of an LED bulb coated with a PVA aqueous solution of Acf and RhB taken with the LED light on and off according to Example 7 of the present invention;

[0042] Figure 12 Schematic diagrams of steady-state luminescence and afterglow photographs of various products with long-lasting fluorescent emission under 365nm ultraviolet light and white light excitation according to Example 8 of the present invention are shown (the products include luminescent fibers, fabrics, cotton, and paper, etc.);

[0043] Figure 13 A low-cost anti-counterfeiting label made of an Acf aqueous solution according to Example 9 of the present invention and a detection effect diagram under white light are shown. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0045] Related research shows that great progress has been made in the research of new luminescent materials. Different materials, including aggregation-induced emission (AIE), RTP and TADF materials, have been continuously developed. However, pure organic fluorescent long-lasting materials excited by visible light have rarely been reported.

[0046] In the process of implementing the present invention, it was found that pure organic fluorescent long-lasting materials that can be excited by visible light are rarely reported. Part of the reason is that it is difficult to simultaneously control the energy gap (ΔE) between S1 and T1. ST ) and increase the transient fluorescence decay rate (k PF ) is still unclear.

[0047] The present invention takes into account that the previous research on TADF materials mainly focused on the application of organic light emitting diodes (OLEDs), which requires the materials to have a short delayed fluorescence lifetime (τ DF ) and the fast reverse intersystem crossing (RISC) rate (k RISC However, for long afterglow luminescent materials, the material needs to have a longer τ DF According to the molecular design strategy of TADF molecules, it is possible to increase ΔE ST , reduce k RISC and improve k PF To achieve long fluorescence afterglow emission. In addition, to achieve afterglow emission stimulated by visible light, the material needs to have strong absorption in the visible light region, which also means that the material needs to have a strong 0-0 absorption band, that is, a large absorption oscillator strength (f) and orbital overlap degree (S if ). Due to S if and ΔE ST Proportional to τ, so using the same design principle, we can also achieve the extension of τ DF The purpose of enhancing the absorption intensity of visible light by the material can provide a good opportunity for constructing fluorescent long-afterglow materials excited by visible light.

[0048] Furthermore, fluorescent dyes possess intramolecular charge transfer properties and exhibit strong absorption and emission efficiencies for visible light. Currently, a variety of fluorescent dyes have been developed, covering the entire visible light range. Therefore, if strategies can be employed to suppress the fluorescence quenching effect of solid-state materials, commercial dyes have the potential to be used in the development of long-lasting fluorescent materials.

[0049] Furthermore, the long-chain structure of high-molecular-weight polymers facilitates the encapsulation of small molecules. Furthermore, the special functional groups on the polymer side chains can form strong intermolecular interactions with small organic molecules, thereby restricting molecular motion and inhibiting non-radiative transitions. Doping small-molecule dyes into a polymer matrix can enhance the structural rigidity of the material while effectively isolating factors such as water and oxygen that can easily cause triplet exciton quenching. Therefore, combining fluorescent dye molecules with high-molecular-weight polymers is a feasible strategy for constructing long-lasting fluorescent materials excited by visible light.

[0050] Based on this, the present invention provides a method for preparing a pure organic fluorescent long-lasting film excited by visible light, comprising: preparing a host solution using a polyhydroxy polymer matrix material and a solvent; preparing a guest solution using fluorescent dye molecules and a solvent; preparing a target solution using a mixture of the host solution and the guest solution; and dropwise adding the target solution onto a glass slide to remove the solvent from the target solution, thereby obtaining a pure organic fluorescent long-lasting film excited by visible light. The method involves hydrogen bonding between the polyhydroxy polymer matrix material and the fluorescent dye molecules. The present invention also provides applications of the pure organic fluorescent long-lasting film excited by visible light in the fields of color-tunable lighting sources, industrial product manufacturing, and anti-counterfeiting labels.

[0051] The following schematically illustrates the preparation method and application of a pure organic fluorescent long-lasting film excited by visible light. It should be noted that the example is only a specific embodiment of the present invention and does not limit the scope of protection of the present invention.

[0052] As one aspect of the present invention, a method for preparing a pure organic fluorescent long-afterglow film excited by visible light is provided.

[0053] Figure 1 The flowchart of the method for preparing a pure organic fluorescent long-afterglow film excited by visible light according to an embodiment of the present invention is schematically shown.

[0054] like Figure 1 As shown, the method for preparing the pure organic fluorescent long-afterglow film excited by visible light includes S101 to S104.

[0055] In operation S101 , a main solution is prepared by using a polyhydroxy polymer matrix material and a solvent.

[0056] In operation S102 , a guest solution is prepared using fluorescent dye molecules and a solvent.

[0057] In operation S103 , a target solution is prepared by using a mixed solution of the host solution and the guest solution.

[0058] In operation S104 , the target solution is dropped onto a glass sheet to remove the solvent in the target solution, thereby obtaining a pure organic fluorescent long-lasting film excited by visible light.

[0059] It should be noted that hydrogen bonding is formed between the polyhydroxy polymer matrix material and the fluorescent dye molecules, which can inhibit non-radiative transitions and protect triplet excitons.

[0060] According to an embodiment of the present invention, a method for preparing a pure organic fluorescent long afterglow material excited by visible light is obtained by dispersing fluorescent dye molecules into a polyhydroxy polymer matrix, thereby obtaining a simple and environmentally friendly material preparation strategy. The matrix material used is only required to be a polyhydroxy polymer, and the selection is relatively wide. For example, polyvinyl alcohol, agarose, starch, cellulose, etc. can all be used as matrix materials to achieve fluorescent long afterglow emission. The price is cheap and the product is easy to obtain. The guest material fluorescent dye molecules used, such as acridinium yellow, can produce fluorescent long afterglow emission before and after purification. The cost required is low and the raw materials are easy to obtain. The pure organic fluorescent long afterglow material excited by visible light obtained after host-guest doping exhibits bright green fluorescent long afterglow emission after stopping white light excitation. The afterglow lasts for nearly 10s and the color is adjustable, which has a wide range of applicability.

[0061] According to embodiments of the present invention, when preparing the target solution, the host solution and the guest solution are mixed without requiring a specific order of addition; physical stirring can be used for mixing. After the target solution is dropwise added to a glass slide, it can be naturally evaporated and air-dried at room temperature. Therefore, the visible-light-excited pure organic fluorescent long-lasting fluorescent material prepared by the method for preparing a visible-light-excited pure organic fluorescent long-lasting fluorescent film provided by the present invention has relatively few requirements for sample conditions. The guest molecules are mixed with the host material using a simple physical mixing method, and the corresponding material is obtained after the water evaporates, without the need for single crystal or eutectic cultivation.

[0062] According to an embodiment of the present invention, the mass fraction ratio of the polyhydroxy polymer matrix material to the fluorescent dye molecules may be 100:1.

[0063] According to an embodiment of the present invention, the fluorescent dye molecules may include: acridine yellow (Acf), rhodamine B (RhB), acridine orange (Aco), and a mixture of acridine yellow and rhodamine B. The chemical structures of acridine yellow (Acf), rhodamine B (RhB), and acridine orange (Aco) are shown in the following formulas (I) to (III), respectively:

[0064]

[0065] According to an embodiment of the present invention, the fluorescent dye molecules may further include: HyC, AFC, Fluo, and Con. The chemical structures of HyC, AFC, Fluo, and Con are shown in the following formulas (IV) to (VII), respectively:

[0066]

[0067] It should be noted that acridinium yellow dyes with a relatively rigid chemical structure have the best long-lasting fluorescence emission performance.

[0068] According to the embodiments of the present invention, the fluorescent dye molecules can exhibit fluorescent afterglow emission before and after purification, and the use cost is low.

[0069] According to an embodiment of the present invention, in the mixture of acriflavine and rhodamine B, the mass fraction ratio of acriflavine to rhodamine B may be 1:2 to 10:1. For example, the mass fraction ratio of acriflavine to rhodamine B may be, but is not limited to, 1:2, 1:1, 2:1, 5:1, 10:1, etc.

[0070] Preferably, in the mixture of acriflavine and rhodamine B, the mass fraction ratio of acriflavine to rhodamine B is 1:2.

[0071] According to an embodiment of the present invention, by changing the mass ratio of acriflavine to rhodamine B in a mixture of acriflavine and rhodamine B, the color and duration of the fluorescent afterglow can be adjusted, thereby expanding the application range of the material. For example, the fluorescent color can be adjusted from green to red.

[0072] According to an embodiment of the present invention, the polyhydroxy polymer matrix material may include: polyvinyl alcohol (PVA), agarose, polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), and cellulose.

[0073] The chemical structure of polyvinyl alcohol (PVA) is shown in the following formula (VIII):

[0074]

[0075] According to an embodiment of the present invention, the solvent may include an aqueous solution.

[0076] According to the embodiment of the present invention, since both the host and guest materials have good water solubility, when preparing pure organic fluorescent long-lasting thin film materials excited by visible light, the required solvent can be only water, which is green, environmentally friendly and pollution-free, and the cost is also low.

[0077] For example, the main polyhydroxy polymer matrix material such as polyvinyl alcohol (PVA) can be weighed into a clean and dry container, and water is added to prepare 100 mg mL -1Weigh the guest molecule fluorescent dye (such as HyC, AFC, Acf, Fluo, RhB, Con or Aco) into a clean and dry container, and add water to make 0.5 mg mL -1 A guest solution is prepared by mixing 2 mL of the guest solution with 1 mL of the host solution. After stirring thoroughly, 0.6 mL of the mixed solution is dropped onto a glass slide and allowed to evaporate the water. This yields a pure organic fluorescent long-lasting film excited by visible light. The fluorescence long-lasting properties of this pure organic fluorescent long-lasting film material excited by visible light can be characterized at room temperature.

[0078] As another aspect of the present invention, there is also provided an application of a visible light excited pure organic fluorescent long afterglow film prepared by a method for preparing a visible light excited pure organic fluorescent long afterglow film in the field of color tunable lighting sources.

[0079] According to embodiments of the present invention, a pure organic fluorescent long-lasting thin film material excited by visible light exhibits long-lasting fluorescence emission even after white light excitation ceases. This characteristic of the material can be used in the development of color-tunable lighting sources. The resulting light-emitting diodes (LEDs) can continue to emit afterglow in different colors even after power is removed, enabling applications such as energy-saving and decorative lighting.

[0080] As another aspect of the present invention, a method for preparing a pure organic fluorescent long-lasting film excited by visible light is also provided, and the film is used in the production of industrial products. For example, the film can be used in the production of various industrial products such as luminous fibers and luminous newspapers.

[0081] According to an embodiment of the present invention, the prepared visible light excited pure organic fluorescent long afterglow thin film material only requires the fluorescent dye molecules to be at an extremely low concentration (0.5 mg mL -1 ) can be mixed with a polyhydroxy polymer matrix to develop materials. Therefore, by applying or dripping an aqueous solution of dye molecules onto the surface of various substrates, such as paper, wood, cotton, cotton rope, and cellulose, different industrial products that emit long-lasting fluorescence can be obtained.

[0082] As another aspect of the present invention, there is provided an application of a visible light excited pure organic fluorescent long afterglow film prepared by a method for preparing a visible light excited pure organic fluorescent long afterglow film in the field of visible light identification anti-counterfeiting labels.

[0083] According to embodiments of the present invention, methods for preparing pure organic fluorescent long-lasting films excited by visible light can also be used to produce low-cost anti-counterfeiting labels that can be identified by visible light. For example, a label can be directly drawn on a paper box using an aqueous solution of ACF. The resulting pattern exhibits a long-lasting green fluorescence after white light excitation, enabling anti-counterfeiting applications.

[0084] The following examples illustrate the preparation method, its preparation method, and its application. It should be noted that the examples are only specific embodiments of the present invention and do not limit the scope of protection of the present invention. The raw materials and reagents used are all commercially available or purified using conventional methods in the literature.

[0085] It should be noted that in the following embodiments and figures, "on" can represent an operating state; "off" can represent a non-operating state. "Wavelength" represents wavelength; "Time" represents time; "Normalized Intensity" represents normalized intensity; "Intensity" represents intensity; and "Delayed Intensity" represents delayed intensity.

[0086] Example 1: Preparation of the main solution (wherein the polyhydroxy polymer matrix material is polyvinyl alcohol)

[0087] Weigh 2 g of PVA and place it in a dry and clean 25 mL sample bottle. Add 20 mL of deionized water, tighten the bottle cap, heat and stir to completely dissolve the PVA, and obtain a concentration of 100 mg mL -1 Colorless transparent solution.

[0088] Example 2: Preparation of guest solution (wherein the fluorescent dye molecule is Acf)

[0089] Add methanol to the round-bottom flask containing Acf, heat, and continue to add methanol until the solid is completely dissolved. Add ten times the volume of tetrahydrofuran, cool and let stand to allow the solid to precipitate. Filter, wash the solid with tetrahydrofuran five times, and centrifuge to obtain a solid. Repeat the above steps four times to obtain purified Acf solid. Weigh 10 mg of Acf into a dry and clean 25 mL sample bottle, add 20 mL of deionized water, and stir to completely dissolve the solid to obtain a concentration of 0.5 mg mL -1 A yellow transparent solution.

[0090] Example 3: Preparation of pure organic fluorescent long-lasting thin film material excited by visible light

[0091] 1 mL of the host solution in Example 1 and 2 mL of the guest solution in Example 2 were measured and mixed and stirred for 1 hour. Then 0.6 mL of the solution was dropped onto a glass slide. After the water evaporated completely, a pure organic fluorescent long-afterglow thin film material excited by visible light was obtained.

[0092] According to the embodiments of the present invention, a series of commercial fluorescent dyes can be incorporated into polyvinyl alcohol for study. In particular, since the afterglow of purified Acf has not been studied, the present invention purifies acriflavine to eliminate the influence of impurities on the mechanism study. By calculating the integral area (S) of the 0-0 absorption band of the dye after doping in PVA, the abs ), it was found that the abs The Acf, rhodamine B and acridine orange with different values of Acf exhibit fluorescence afterglow emission with different intensities and durations after stopping white light excitation. ST Value and k PF The value promotes the realization of long-lasting fluorescence emission. In addition, compared with the purified Acf, the commercial Acf exhibits a blue-shifted fluorescence, indicating that it has a larger ΔE ST value, which also leads to its slower k RISC Value (about 10 0 s -1 ) and longer τ DF For RhB dye, although it only exhibits weak afterglow emission, it can also emit bright red fluorescence with long afterglow with the help of energy transfer process.

[0093] According to an embodiment of the present invention, a common impurity in commercial Acf is proflavin sulfate. When commercial Acf is directly incorporated into PVA without purification, the resulting film can also exhibit long-lasting fluorescence emission under white light excitation. In both steady-state and delayed modes, the commercial Acf@PVA film can detect a fluorescence emission peak that is blue-shifted compared to the purified Acf@PVA film. However, the phosphorescence emission peaks of the two films are not much different. Therefore, the ΔE of the commercial Acf@PVA film is ST The larger the size, the longer the afterglow duration. In addition, when incorporated into agarose, the phosphorescence emission peak in the delayed spectrum of the commercial Acf film disappears, indicating a greener afterglow.

[0094] Example 4: Verification of thermally activated delayed fluorescence performance

[0095] The film material in Example 3 exhibits long afterglow green fluorescence emission under white light irradiation. At room temperature (RT), the delayed luminescence spectrum of the film is as follows: Figure 2 As shown in (a), the spectrum shows an emission peak with a maximum wavelength at 523 nm and a shoulder at 598 nm. When the thin film is frozen in liquid nitrogen to 77 K, the emission peak around 523 nm significantly weakens, while the emission peak at 595 nm becomes the dominant emission peak. This indicates that TADF emission occurs primarily at 523 nm, while RTP emission occurs primarily at 598 nm.

[0096] The delayed luminescence spectrum of the thin film material changes from 77K to 313K. Figure 2 As shown in (b), as the temperature increases, the emission peak intensity in the short-wavelength region increases, while the emission peak in the long-wavelength region gradually becomes negligible. Therefore, the afterglow in the short-wavelength region is TADF emission, while the afterglow in the long-wavelength region is RTP emission.

[0097] According to an embodiment of the present invention, at room temperature, a film doped with Acf and PVA exhibits green fluorescence under white light excitation. After turning off the white light excitation light source, the film shows green fluorescence long afterglow emission. When the temperature rises from 77K to 313K, the afterglow emission color of the film gradually changes from red to orange, yellow and green. In addition, the delayed luminescence spectrum of the compound Acf in a dilute solution of ethanol (concentration of 50μM) also shows that it emits strong red phosphorescence at 77K with a lifetime of 2.51s. This result proves that the T1 of Acf should be in the red light region, and its green afterglow emission at room temperature should belong to fluorescent long afterglow emission.

[0098] Example 5: Regulation of long afterglow emission properties using solid-state solvent effects

[0099] According to the method in Example 1, 100 mg mL -1 of PVP and PAA solution.

[0100] Acf@PVP and Acf@PAA films were prepared according to the method in Example 3.

[0101] like Figure 3 As shown in (a), compared with Acf@PVA film, the time-resolved delayed spectra of Acf@PVP and Acf@PAA films clearly show a shorter duration and red-shifted fluorescence afterglow emission. Figure 3 As shown in (b), in the retardation spectra at room temperature and 77K, the energy level of S1 of Acf in PVP and PAA matrices is significantly reduced, while the energy level of T1 changes only slightly. Figure 4 As shown, with the increase of the polarity of the solid solvent, the ΔE of Acf ST As the size of the delayed fluorescence decreases, the lifetime of the delayed fluorescence also decreases.

[0102] According to the embodiments of the present invention, the present invention also proves that the solvent effect in the solid state can change ΔE ST In a more polar environment, the energy of the CT emission peak will be reduced, while the energy of the LE emission peak will be less affected, which may lead to the material ΔE STThe value decreases, so the RISC process is accelerated, τ DF The films prepared from Acf and polyvinyl pyrrolidone or polyacrylic acid exhibited red-shifted fluorescence emission and shortened delayed fluorescence duration under white light excitation compared with Acf@PVA films.

[0103] Example 6: Color Control of Long-Persistence Fluorescence Excited by Visible Light

[0104] According to the method in Example 2, mixed solutions of Acf and RhB with mass ratios of 10:1, 5:1, 2:1, 1:1 and 1:2 were prepared, and the total concentration of the two was 0.5 mg mL -1 .

[0105] 10-1@PVA, 10-1@agarose, 5-1@PVA, 5-1@agarose, 2-1@PVA, 2-1@agarose, 1-1@PVA, 1-1@agarose, 1-2@PVA and 1-2@agarose films were prepared according to the method in Example 3.

[0106] like Figure 5 (a) and Figure 5 As shown in (b), when the mass ratio of Acf and RhB is 1:2 (1-2@agarose and 1-2@PVA films), the excitation spectrum recorded in the delayed mode is almost exactly the same as the excitation spectrum recorded in the delayed mode of Acf@agarose or Acf@PVA films. In addition, 1-2@agarose and 1-2@PVA films have faster afterglow decay rates than Acf@agarose and Acf@PVA films. According to the exponential fitting results of the afterglow decay kinetics curve, the afterglow lifetime of Acf in Acf@PVA film is 0.60s, while the afterglow lifetime of Acf in 1-2@PVA film is 0.38s. The above results indicate that a reaction may have occurred between Acf and RhB. Resonance energy transfer.

[0107] like Figures 6 to 9 As shown in Figure 1, the time-resolved delay spectra measured after stopping UV and white light excitation are shown. It can be seen that the afterglow intensity of the two dyes Acf and RhB will change at different mass ratios. It is worth noting that more obvious color changes can be seen in the agarose matrix, which can be demonstrated by the CIE coordinates of the afterglow spectrum. The 1931 CIE coordinate diagram of the afterglow color in the agarose matrix is shown in Figure 1. Figure 10 (a) It can be found that its CIE coordinates change from (0.32, 0.61) to (0.59, 0.39), and as shown in Figure 10As shown in (b), in the PVA matrix, the CIE coordinates of the afterglow color change from (0.32, 0.57) to (0.53, 0.45).

[0108] According to an embodiment of the present invention, when RhB and Aco are dispersed in a PVA matrix, the resulting film exhibits only weak red afterglow emission under white light excitation at room temperature. When the temperature is lowered to 77 K, a new emission peak belonging to the T1 state is revealed in the delayed luminescence spectrum, while the maximum afterglow emission peak measured at room temperature is weakened or becomes invisible at 77 K. This indicates that the afterglow emission from the film obtained in the present invention at room temperature exhibits TADF properties. Other films did not exhibit strong TADF-type afterglow when excited by white light.

[0109] According to an embodiment of the present invention, the introduction of RhB into a film made from commercially available Acf and PVA or agarose allows for the color of the long-lasting fluorescence afterglow induced by white light to be tuned over a wider range. As the RhB content in the film increases, the characteristic RhB absorption peak at 556nm gradually intensifies. Steady-state spectra also reveal a decrease in Acf emission intensity and a slight red-shift in the RhB emission peak with increasing RhB content. Similar changes in afterglow intensity are also observed. RhB afterglow emission increases with increasing concentration in either agarose or PVA matrices. Thus, the color of the afterglow can be manipulated. Commercially available Acf@PVA films emit a long-lasting green fluorescence afterglow lasting approximately 10 seconds. When the mass ratio of Acf to RhB reaches 1:2, the resulting film produces an orange-red fluorescence afterglow lasting approximately 8 seconds.

[0110] Example 7: Development of color-tunable lighting sources

[0111] Mount the LED bulb emitting visible light and the NE555 timer on a printed circuit board (PCB), as shown in Figure 11 As shown in (a).

[0112] PVA aqueous solutions with different mass ratios of Acf and RhB were prepared and coated on the surface of the LED.

[0113] The timer NE555 is used to control the switch of the light. After turning off the light, the long-life cyan fluorescence can be clearly observed, such as Figure 11 (b) Even if the power is cut off, the LED bulb can still continue to emit light for a period of time. In addition, the light color can be switched between cyan, yellow-green, yellow, orange and red, as shown in Figure 11 (c). Among them, Figure 11 In (c), “colortunable light sources” refer to color-tunable light sources. Therefore, Acf and RhB can be used to construct energy-saving and decorative light sources with adjustable color.

[0114] Example 8: Development of Luminous Industrial Products

[0115] Prepare 0.5 mg mL -1 The ACF aqueous solution is then used to paint on various surfaces or to directly drop the aqueous solution onto these materials. The materials can include clothing, cotton, filter paper, printing paper, cotton rope, wood, cellulose, starch, chitosan, sodium alginate, etc.

[0116] When the material is irradiated with ultraviolet light (UV) or white light (Daylight) and then the excitation is stopped, it can be found that the areas containing Acf on the surface of these materials will produce strong fluorescence with long afterglow emission, such as Figure 12 shown.

[0117] Example 9: Development of low-cost anti-counterfeiting labels

[0118] Take 40 μL of Acf aqueous solution (0.5 mg mL -1 ) is used to draw anti-counterfeit labels and draw patterns on ordinary paper boxes.

[0119] like Figure 13 As shown in the figure, a pattern was painted on the box using an Acf solution (Painting with Acf), while another pattern was painted using a common yellow pigment (Painting with a crayon). When irradiated with white light (Whitelight on), only the pattern painted with the Acf solution showed a bright green afterglow after the white light was turned off, while the pattern painted with the common yellow pigment did not produce any afterglow.

[0120] According to an embodiment of the present invention, 1 gram of commercially available ACF material can be used to create over 50,000 2 cm x 2 cm anti-counterfeiting labels, with an estimated cost of approximately $2. Therefore, ACF can be conveniently used on a variety of materials at a very low cost to play an important anti-counterfeiting role.

[0121] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a pure organic fluorescent long-lasting film excited by visible light, comprising: A main solution is prepared by using a polyhydroxy polymer matrix material and a solvent, wherein the polyhydroxy polymer matrix material includes: polyvinyl alcohol, agarose, polyacrylic acid, polyvinyl pyrrolidone, and cellulose; A guest solution is prepared by using fluorescent dye molecules and the solvent, wherein the fluorescent dye molecules include: acridine yellow, rhodamine B, acridine orange, and a mixture of the acridine yellow and rhodamine B; A target solution is prepared by using a mixed solution of the host solution and the guest solution; Adding the target solution dropwise onto a glass sheet to remove the solvent in the target solution, thereby obtaining a pure organic fluorescent long-lasting film excited by visible light; Wherein, hydrogen bonds are formed between the polyhydroxy polymer matrix material and the fluorescent dye molecules.

2. The preparation method according to claim 1, wherein The mass fraction ratio of the polyhydroxy polymer matrix material to the fluorescent dye molecules is 100:

1.

3. The preparation method according to claim 1, wherein In the mixture of the acriflavine and the rhodamine B, the mass fraction ratio of the acriflavine to the rhodamine B is 1:2 to 10:

1.

4. The preparation method according to claim 1, wherein In the mixture of the acriflavine and the rhodamine B, the mass fraction ratio of the acriflavine to the rhodamine B is 1:

2.

5. The preparation method according to any one of claims 1 to 2, wherein The solvent includes an aqueous solution.

6. Use of a pure organic fluorescent long-lasting film excited by visible light prepared by the preparation method according to any one of claims 1 to 5 in the field of color-tunable lighting sources.

7. Use of a pure organic fluorescent long-lasting film excited by visible light prepared by the preparation method according to any one of claims 1 to 5 in the field of industrial product production.

8. Use of a pure organic fluorescent long-lasting film excited by visible light prepared by the preparation method according to any one of claims 1 to 5 in the field of visible light identification anti-counterfeiting labels.

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