Green, stable and long-life RTP-coated IPA material as well as preparation method and application thereof

Abstract

The invention provides a green, stable and long-life RTP-coated IPA material and a preparation method and application thereof.The method comprises the steps that 1, lignin is catalytically degraded through ternary DES comprising a hydrogen bond acceptor, a hydrogen bond donor and an enhancer, and lignin degraded through DES is obtained; wherein in the DES, the hydrogen bond acceptor is choline chloride or allyltrimethylammonium chloride, the hydrogen bond donor is lactic acid, and the enhancer is ethylene glycol or manganese chloride; (2) carrying out carbonization reaction on the lignin degraded by the DES and boric acid to obtain CDs doped with an element B; (3) crosslinking the CDs with a polymer matrix to obtain an RTP material; and (4) carrying out a cross-linking reaction on the RTP material and isophthalic acid to obtain the green, stable and long-life RTP-coated IPA material. The green, stable and long-life RTP-coated IPA material disclosed by the invention has excellent phosphorescence life and stability in a solvent, and has important application potential.

Description

A green, stable, and long-life RTP@IPA material, its preparation method, and its application. Technical Field

[0001] This invention relates to the field of phosphorescent materials technology, specifically to a green, stable, and long-life RTP@IPA material, its preparation method, and its applications. Background Technology

[0002] Room temperature phosphorescent materials have wide applications in anti-counterfeiting, information encryption, sensing, and bioimaging. In the anti-counterfeiting field, inks are widely used due to their relatively low cost. Currently, the application of widely used ultraviolet-excited fluorescent inks is limited to some extent by their limited luminescence lifetime. Long-life room temperature phosphorescent (RTP) materials provide a reliable solution for anti-counterfeiting.

[0003] Traditional RTP materials have certain drawbacks, such as humidity sensitivity, high cost, demanding synthesis conditions, resource scarcity, high toxicity, and short luminescence lifetime. For example, traditional RTP materials include rare earth and precious metals, which typically require extremely high temperatures and suffer from high prices, resource scarcity, and significant biotoxicity. The refining and separation of rare earth ores consumes large amounts of sulfuric acid or liquid alkali reagents, causing serious environmental pollution. Pure organic RTP materials have a short lifetime at room temperature, and their phosphorescence can only be observed in liquid nitrogen and inert environments, greatly limiting their applications. In addition, current anti-counterfeiting materials generally suffer from instability. If RTP materials are placed in the environment and exposed to moisture and oxygen in the air for a long time, their phosphorescence lifetime and intensity will decrease to a certain extent. This is because the non-radiative decay caused by high concentrations of dissolved oxygen in water and molecular motion significantly quenches triplet excitons, further limiting the application of RTP materials.

[0004] Therefore, developing a green RTP material that exhibits afterglow luminescence in water and other solvents, is non-biotoxic, and has a long phosphorescence lifetime is an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a green, stable, and long-life RTP@IPA material, its preparation method, and its applications. The RTP@IPA material exhibits excellent phosphorescence lifetime and solvent stability, and its preparation method is green, environmentally friendly, and economical.

[0006] To achieve the above technical objectives, this invention proposes a method for preparing a green, stable, and long-life RTP@IPA material, which includes the following steps:

[0007] (1) Lignin is degraded by ternary DES (deep eutectic solvent) including hydrogen bond acceptor, hydrogen bond donor and reinforcing agent to obtain lignin after DES degradation; wherein, the hydrogen bond acceptor in the DES is choline chloride (ChCl) or allyltrimethylammonium chloride (ATMAC), the hydrogen bond donor is lactic acid (LA) and the reinforcing agent is ethylene glycol (EG) or manganese chloride (MnCl2);

[0008] (2) The lignin obtained in step (1) after DES degradation is reacted with boric acid to obtain CDs doped with B element;

[0009] (3) The CDs obtained in step (2) are crosslinked with a polymer matrix to obtain an RTP material;

[0010] (4) The RTP material is cross-linked with isophthalic acid (IPA) to obtain the green, stable and long-life RTP@IPA material.

[0011] The above technical solution uses lignin, a widely available bio-based material, as a raw material to prepare CDs, which is green and environmentally friendly, and improves the environmental friendliness and economy of the preparation process.

[0012] Carbon dots (CDs) are a novel type of RTP material. To improve the phosphorescence lifetime of RTP materials, the surface of CDs needs to have abundant functional groups, which then interact with the matrix to achieve RTP emission. The above technical solution incorporates several technical features to enhance the phosphorescence lifetime and solvent stability of RTP materials:

[0013] First, the lignin used in this invention contains aromatic ring structures and conjugated groups, which is beneficial to improving the lifetime of the prepared RTP material. Second, the research team of this invention, through quantum mechanical simulation and a large number of exploratory experiments, further set up a ternary DES catalytic degradation of lignin using choline chloride or allyltrimethylammonium chloride as hydrogen bond acceptors, lactic acid as hydrogen bond donors, and ethylene glycol or manganese chloride as reinforcing agents. This allows lignin to generate hydroxyl and carboxyl groups through depolymerization, thereby enriching the groups on the surface of CDs and improving the lifetime of RTP materials. Third, effectively enhancing the intersystem crossing (ISC) process from S1 (first electron excited singlet state) to Tn (triplet state) in RTP materials and suppressing the nonradiative transition of T1 are key to obtaining long-life RTP materials. In step (2), this invention further doped the degraded lignin with boron (B) through a carbonization reaction. B atoms are electrophilic, and introducing B into CDs reduces the band gap between the singlet and triplet states, ultimately promoting the ISC process and thus improving the lifetime of RTP materials. Fourth, the lifespan of RTP materials can also be improved by introducing a rigid environment. In step (3), this invention further introduces a polymer matrix with many advantages such as flexibility, stretchability, and easy processing. The polymer matrix and the CDs doped with B form a highly entangled rigid environment that effectively suppresses the vibration and rotation of phosphorescent molecules, thereby shielding the quenching effect caused by oxygen and moisture in the environment, thus improving the strength and lifespan of the RTP material. In addition, the RTP material prepared in step (3) of this invention introduces a crystalline substance IPA, forming a coated crystal structure, which can hinder the contact between the prepared RTP material and the surrounding environment and improve the stability of the RTP material. Moreover, IPA is slightly soluble in water and does not easily interact with water, further reducing the contact between the RTP material and moisture and oxygen, so that the green, stable, and long-life RTP@IPA material of this invention can maintain stable performance in solvents.

[0014] Through the synergistic optimization of the above-mentioned technical features, the technical solution effectively improves the phosphorescence lifetime and solvent stability of the prepared green, stable, and long-lived RTP@IPA material. The embodiments of this invention demonstrate the excellent phosphorescence lifetime and solvent stability of the prepared green, stable, and long-lived RTP@IPA material.

[0015] In a further example of the present invention, the proportions of the ternary components of the DES were explored and optimized. Optionally, the molar ratio of hydrogen bond acceptor, hydrogen bond donor, and reinforcing agent in the DES is (0.5-2):(0.5-4):(0.5-2). This improves the lignin degradation reaction rate and reaction efficiency, and promotes the improvement of the phosphorescence lifetime of the prepared RTP material. In some optional examples of the present invention, the molar ratio of hydrogen bond acceptor, hydrogen bond donor, and reinforcing agent in the DES is preferably 1:(1-3):1. The embodiments of the present invention illustrate the optimization process of the DES components and proportions through quantum mechanical simulation and exploratory verification.

[0016] In a further example of the present invention, the hydrogen bond acceptor may be ATMAC; further still, the DES is [ATMAC][LA][EG] with a component molar ratio of 1:3:1, or [ATMAC][LA][MnCl2] with a component molar ratio of 1:3:1.

[0017] In a further example of the invention, the ratio of DES to lignin was explored and optimized. Optionally, the mass ratio of DES to lignin is (30-15):1, which promotes sufficient degradation of lignin, and the process cost can be reduced by optimizing the amount of DES used. In some optional examples of the invention, the mass ratio of DES to lignin is preferably 20:1.

[0018] In a further example of the present invention, the conditions for the catalytic degradation reaction were explored and optimized. Optionally, the temperature of the catalytic degradation reaction is 190℃-220℃, and the time is 4-12h. By controlling the conditions of the catalytic degradation reaction, it is beneficial to regulate the overall reaction process and improve the operability of the process. In some optional examples of the present invention, the time of the catalytic degradation reaction is preferably 8h.

[0019] It should be noted that, due to the high viscosity of DES, in the specific process, step (1) may involve adding an appropriate amount of water as a co-solvent to promote the mixing of lignin and DES. Those skilled in the art will understand that vigorous stirring can be performed during the catalytic degradation process to promote the degradation reaction.

[0020] In a further example of the present invention, step (1) further includes: after the catalytic degradation reaction is completed, separating DES from the reacted material and recycling it. DES is a low-toxicity, recyclable catalyst, and the recycling of DES enhances the environmental friendliness and economy of the preparation process of the present invention.

[0021] It should be noted that the present invention does not limit the method for separating DES and lignin after DES degradation from the material after the catalytic degradation reaction. For example, solvent extraction can be used to recover DES and separate the lignin after DES degradation.

[0022] In a further example of the present invention, the ratio of lignin degraded by DES to boric acid in step (2) was explored and optimized. Optionally, the mass ratio of lignin degraded by DES to boric acid in step (2) is 1:(5-15), thereby promoting the effective doping of element B into the lignin degraded by DES and improving the phosphorescence lifetime of the obtained RTP material. In some optional examples of the present invention, the mass ratio of lignin degraded by DES to boric acid in step (2) is preferably 1:(9-11).

[0023] In a further example of the present invention, the control conditions for the carbonization reaction were explored and optimized. Optionally, the temperature of the carbonization reaction is 190-220°C; the exploration process of the carbonization temperature is shown in the embodiments of the present invention; the reaction time is 5-36 h. Controlling the carbonization reaction conditions is beneficial for regulating the efficiency and effect of boron doping. In some optional examples of the present invention, the temperature of the carbonization reaction is preferably 200°C. In some optional examples of the present invention, the reaction time of the carbonization reaction is preferably 12 h.

[0024] It should be noted that in the actual preparation process, step (2) of this invention may involve dissolving the lignin degraded by DES and boric acid in a first solvent for carbonization reaction. The first solvent may be water or an organic solvent, including one or a mixture of methanol, ethanol, dichloromethane, and ethyl acetate. After the reaction, the material is separated and dried to obtain B-doped CDs powder. It should be noted that this invention does not limit the specific operation for separating the material after the reaction in step (2). Filtration, dialysis, centrifugation, and other operations that can achieve the same technical effect can be used for separation. Heating, calcination, vacuum freeze-drying, or other operations that can achieve the same technical effect can be used for drying. Those skilled in the art can choose according to their needs, and this does not limit the scope of protection of this invention.

[0025] In a further example of the present invention, the ratio of CDs to polymer matrix in step (3) was explored and optimized. Optionally, the mass ratio of CDs to polymer matrix in step (3) is 1:(500-2000), and optimizing the amount of reaction raw materials is beneficial to improving reaction efficiency and yield. In some optional examples of the present invention, the mass ratio of CDs to polymer matrix in step (3) is preferably 1:1000.

[0026] In a further example of the present invention, the polymer matrix may be selected from one or more of acrylic resin (PAA), polyvinyl alcohol (PVA), and polyacrylamide (PAM), and may further be selected from PAM.

[0027] In a further example of the present invention, the temperature of the crosslinking reaction in step (3) is 50℃-90℃ and the reaction time is 2-4h.

[0028] In a further example of the present invention, the crosslinking reaction in step (3) is carried out under the action of a crosslinking agent and an initiator. Optionally, the mass ratio of the crosslinking agent to the polymer matrix is ​​1:(30-100). Optimizing this mass ratio can improve the mechanical properties and stability of the obtained RTP material and increase the phosphorescence lifetime of the obtained RTP material. In some optional examples of the present invention, the mass ratio of the crosslinking agent to the polymer matrix is ​​preferably 1:(35-85), more preferably 1:(35-65), and even more preferably 1:50.

[0029] Optionally, the crosslinking agent includes one or more of N,N'-methylenebisacrylamide (MBA), N,N,N',N'-tetramethylethylenediamine, ethylenediamine, polyacrylic acid, formaldehyde, polyacrylamide, and polyethylene glycol.

[0030] Optionally, the mass ratio of the initiator to the polymer matrix is ​​1:(30-100), which is beneficial for controlling the reaction rate of crosslinking polymerization and improving the operability of the process. In some optional examples of the present invention, the mass ratio of the initiator to the polymer matrix is ​​preferably 1:35.

[0031] Optionally, the initiator includes one or more of ammonium persulfate (APS), sodium persulfate, potassium persulfate, and monomethyl persulfate.

[0032] It should be noted that in the actual preparation process, step (3) can be used to mix the reaction raw materials, crosslinking agent, and initiator in a second solvent. The second solvent can be water or an organic solvent, including one or a mixture of methanol, ethanol, dichloromethane, and ethyl acetate. The material after the reaction is a hydrogel-like RTP material. The present invention does not limit the drying method of the hydrogel-like RTP material; for example, vacuum freeze-drying or other methods that can achieve the same technical effect can be used to obtain dried RTP material. Furthermore, in some examples of the present invention, those skilled in the art can grind the dried RTP material into powder for subsequent use.

[0033] It should be noted that in the actual process, the present invention does not limit the specific methods for promoting the mixing or dissolution of reactants. Those skilled in the art can choose methods such as stirring, ultrasound, or other methods to promote the mixing of materials as needed, without limiting the scope of protection of the present invention.

[0034] In a further example of the present invention, the crosslinking reaction in step (4) includes: mixing the RTP@IPA material with isophthalic acid uniformly, and maintaining the mixture at a temperature of 120-140°C for 0.5-1 h. Optionally, the RTP material and IPA are mixed uniformly in a third solvent, wherein the third solvent may be water or an organic solvent, and the organic solvent includes one or a mixture of methanol, ethanol, dichloromethane, and ethyl acetate.

[0035] In another aspect, the present invention proposes a green, stable, and long-lifetime RTP@IPA material, which is prepared by the above-mentioned method for preparing green, stable, and long-lifetime RTP@IPA material. Its phosphorescence lifetime reaches 728.96 ms, and its stability is greatly improved. Afterglow can still be observed in different solvents for more than 30 days.

[0036] The embodiments of the present invention demonstrate the phosphorescence lifetime of the green, stable, and long-lived RTP@IPA of the present invention, and its performance is stable, exhibiting excellent phosphorescence lifetime performance even in solvents.

[0037] In another aspect, the present invention proposes the application of the above-mentioned green, stable and long-life RTP@IPA material in anti-counterfeiting, information encryption, sensing, bioimaging and fabrication of organic light-emitting devices.

[0038] The green, stable, and long-life RTP@IPA material of this invention provides a reliable solution for anti-counterfeiting due to its excellent optical properties, and is suitable for the field of anti-counterfeiting inks.

[0039] The green, stable, and long-life RTP@IPA material of this invention is a material with time-dependent phosphorescent color. It can provide higher security protection than ordinary information encryption methods through the design of multi-layer dynamic phosphorescent color three-dimensional encoding and other technologies, and can be used for advanced dynamic information encryption.

[0040] This invention provides a green, stable, and long-lived RTP@IPA material as a CDs-based RTP, which can effectively capture target analytes and has been widely used in the field of luminescence analysis. Furthermore, phosphorescence detection avoids interference from short-lived scattered light or fluorescent background, exhibiting a high signal-to-noise ratio and detection sensitivity in complex media.

[0041] This invention presents a green, stable, and long-lived RTP@IPA material. As a CDs-based RTP, it exhibits excellent biocompatibility and stability, and has significant application prospects in the biomedical field. In bioimaging, compared to fluorescent probes, phosphorescent probes have a longer luminescence lifetime and can distinguish autofluorescence interference.

[0042] In addition, the green, stable, and long-life RTP@IPA material of this invention can be used in the fabrication of organic light-emitting devices, such as light-emitting diodes.

[0043] Compared with existing technologies, the beneficial effects of this invention are as follows: The preparation method of the green, stable, and long-life RTP@IPA material of this invention uses bio-based lignin, which is widely available and has aromatic ring structures and conjugated groups on its surface, as raw material. It adopts ternary DES catalytic degradation of lignin to enrich the groups on the surface of CDs. Combined with the doping of boron element and the introduction of polymer matrix with many advantages such as flexibility, stretchability, and easy processing, and through the synergistic improvement of IP crosslinking and other technical features, the phosphorescence lifetime and stability in solvents of the prepared green, stable, and long-life RTP@IPA material are improved. Its lifetime reaches 728.96 ms, and afterglow can still be observed in different solvents for more than 30 days, which has broad application value. The raw materials used in the preparation method of this invention are green and low in cost, and the preparation process is environmentally friendly, safe, and economical. Attached Figure Description

[0044] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0045] Figure 1 shows a schematic diagram of the structure of the RTP material in Example 1;

[0046] Figure 2 shows the infrared spectra of CDs, PAM and RTP materials in Example 1;

[0047] Figure 3 shows (a) TEM and high-resolution images and (b) particle size distribution of CDs in Example 1;

[0048] Figure 4 shows (a) the XPS full spectrum of CDs doped with B; (b) high-resolution energy dispersive spectroscopy analysis; (c) the 1s level spectrum of oxygen; and (d) the 1s level spectrum of B.

[0049] Figure 5 shows the effect of different ternary DES on the binding energy of the system in quantum mechanical simulation;

[0050] Figure 6 shows the frontier orbital energy differences of different ternary DES and model compounds in quantum mechanical simulations.

[0051] Figure 7 shows (a) degradation rate and (b) PDI value of lignin catalyzed by different ternary DES.

[0052] Figure 8 shows the determination of hydroxyl content in lignin obtained by different ternary DES catalytic degradation.

[0053] Figure 9 shows the phosphorescence emission spectra and phosphorescence lifetimes of RTP materials prepared by lignin degradation using different ternary DES catalysts, λ. ex =365nm;

[0054] Figure 10 shows the CIE colorimetric diagrams of RTP materials prepared by lignin degradation using different ternary DES catalysts: (a) IV'-RTP material; (b) VIII'-RTP material.

[0055] Figure 11 shows the SEM image and elemental mapping of the green, stable, and long-life RTP@IPA material prepared in Example 1, where (a) is the SEM image of the RTP@IPA material; (b) is the overall elemental mapping of the RTP@IPA material; and (cf) is a sub-map of the elemental mapping of the RTP@IPA material.

[0056] Figure 12 shows the intensity variation of the optimal phosphorescence emission spectral position of the green, stable, and long-lived RTP@IPA material in aqueous solution for 60 min;

[0057] Figure 13 shows the afterglow phenomenon of the green, stable, and long-lived RTP@IPA material in different solvents, λ ex =365nm(a); Comparison with phosphorescence lifetime of RTP materials in existing literature(b);

[0058] Figure 14 shows the phosphorescence emission spectrum (a) and phosphorescence lifetime (b) of the green, stable, and long-lived RTP@IPA material. ex =365nm;

[0059] Figure 15 shows the afterglow phenomenon of the green, stable, and long-life RTP@IPA material;

[0060] Figure 16 shows the phosphorescence emission spectra (a) and lifetime plots (b) at different carbonization temperatures in Example 2. ex =365nm;

[0061] Figure 17 shows the phosphorescence emission spectrum (a) and phosphorescence lifetime spectrum (b) of the RTP materials prepared using different polymer matrices in Example 3. ex =365nm;

[0062] Figure 18 shows the emission spectrum (a) and phosphorescence lifetime spectrum (b) of RTP materials with different crosslinking agent contents in Example 4. ex =365nm. Detailed Implementation

[0063] To facilitate understanding of the present invention, a more comprehensive description will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of protection of the invention.

[0064] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0065] The equipment and characterization methods used in the following examples include: X-ray photoelectron spectroscopy (XPS); field emission electron microscopy (SEM); Edinburgh FLS1000 steady-state / transient fluorescence spectrometer; ultraviolet-visible spectrophotometer; transmission electron microscopy (TEM); nanoparticle size and zeta potential analyzer; a third-order fitting equation was used to calculate the phosphorescence lifetime, and the formula for calculating the phosphorescence lifetime is as follows:

[0066]

[0067] In the formula, τ is the average phosphorescence lifetime (ms), τ1, τ2 and τ3 are the fitted phosphorescence lifetimes (ms), and A1, A2 and A3 are the weights of τ1, τ2 and τ3, respectively.

[0068] Example 1

[0069] A method for preparing a green, stable, and long-life RTP@IPA material, specifically comprising the following steps (1)-(4):

[0070] (1) Preparation of DES-degraded lignin: Sodium lignin sulfonate and DES raw material in a mass ratio of 1:20 were weighed and placed in a three-necked flask. An appropriate amount of water was added as a co-solvent, and the mixture was stirred vigorously and refluxed at 130°C for 8 hours. After the catalytic degradation reaction was completed, the DES-degraded lignin was obtained. The DES was [ATMAC][LA][EG] with a molar ratio of 1:3:1.

[0071] The reactants were cooled to room temperature, and the resulting solution was extracted three times with ethyl acetate (1:1 volume ratio). The extract was then rotary evaporated to recover the ethyl acetate, yielding a light brown lignin degraded by DES. The centrifuged solution was further rotary evaporated to remove ethanol, yielding DES, which could be reused. Alternatively, anhydrous ethanol was added to the raffinate to precipitate unreacted lignin. The precipitate was then centrifuged, dried in an oven, and weighed to calculate the lignin degradation rate. The centrifuged solution was also rotary evaporated to remove ethanol, yielding DES, which could be reused.

[0072] (2) Preparation of B-doped CDs: Weigh 0.3g of lignin degraded by DES and dissolve it in 5mL of deionized water; weigh 3g of boric acid and dissolve it in 50mL of deionized water, and sonicate for 15min to dissolve it; then mix the two solutions and continue sonicating for 10min to promote dissolution and mixing; then place the dissolved solution on a magnetic stirrer and stir for 30min. After stirring, transfer the solution to a 100mL liner and place it in a reaction vessel, and carbonize it in an oven at 200℃ for 12h to obtain the B-doped CDs. The reacted material was filtered through a 0.22μm microporous membrane, and the filtrate was transferred to a 500Da dialysis bag and dialyzed for 48h, with the water changed every 6h. The dialyzed solution was then freeze-dried under vacuum for 48h to obtain B-doped CDs powder.

[0073] Figure 2 shows the infrared spectra of CDs, PAM, and the RTP material of this embodiment. A comparative analysis was performed at 3200 cm⁻¹. -1 The stretching vibration peak of -OH at 1500 cm⁻¹ -1 The stretching vibration peak of CN at 1190 cm⁻¹ -1 The stretching vibration peak of BO (asymmetric stretched oxygen atom connecting the trigonal crystal system) at 948 cm⁻¹ -1 The characteristic BC bond absorption peak confirms that element B was successfully doped into CDs. The presence of the PAM characteristic peak indicates that PAM was introduced into the RTP material, which serves to suppress the rotation and vibration of CDs.

[0074] Figure 3 shows the TEM and high-resolution images of CDs and their particle size. As can be seen from Figure 3, the CDs are almost spherical and completely dispersed, with an average particle size of 4.12 ± 1.28 nm, indicating that the ternary DES promotes the effective degradation of lignin.

[0075] Figure 4 shows the XPS analysis of CDs doped with boron. The figure verifies that the boron content in the CDs is 2.1%, proving the successful introduction of boric acid. Further analysis shows that the CDs exhibit three peaks in the high-resolution C1s spectrum, two peaks in the O1s spectrum, and two fitted peaks in the B1s spectrum, confirming that a covalent coupling reaction occurs between the CDs and boric acid, forming BC and BO bonds.

[0076] (3) Preparation of RTP material: Weigh 2.5 mg of CDs obtained in step (2) and add 5 mL of deionized water. Weigh 2.5 g of acrylamide, 50 mg of MBA and 70 mg of APS, and dissolve each in 5 mL of deionized water. Sonicate for 3 min to dissolve. Then mix the above four raw materials and sonicate for 10 min to dissolve completely. Stir magnetically for 5 min to promote the reaction. Then place it in a vacuum drying oven at 70 °C for 2 h to react. After crosslinking reaction, a hydrogel-like RTP material is obtained. The structural schematic diagram of the RTP material is shown in Figure 1. Subsequently, the dried RTP material is obtained by vacuum freeze-drying and then ground into powder for testing.

[0077] (4) Weigh 50 mg of the RTP material prepared in step (3) and dissolve it in 20 mL of water. Sonicate for 30 min to ensure complete dissolution. Weigh 0.25 g of IPA and dissolve it in 10 mL of water. Sonicate for 3 min to ensure complete dissolution. Then mix the two solutions and sonicate for 15 min to ensure complete mixing. Stir magnetically for 30 min. Transfer the dissolved solution to a 100 mL three-necked flask and reflux at 130 °C for 30 min. Pour out the reacted solution and cool it to room temperature to obtain a white substance. Wash the substance three times with water to obtain the green, stable, and long-life RTP@IPA material.

[0078] Furthermore, the research and development team of this invention used quantum mechanical simulations combined with numerous exploratory experiments to explore and optimize the types and component ratios of the DES. Specifically:

[0079] On the one hand, this embodiment utilizes quantum mechanical simulations to design the molecular structure of DES, predict its catalytic activity using binding energy and frontier orbital theory, and optimize its structure, thereby optimizing the composition and component ratio of DES. The quantum mechanical simulations are performed using Gaussian 09D software, with the functional and basis set being B3LYP and 6-311+G(d,p). The optimized composition and component ratio of the DES are shown in Table 1.

[0080] Table 1

[0081] The molar ratios of the components in the DES composition are as follows: Ⅰ'[ChCl][LA][EG] 1:1:1 Ⅱ'[ChCl][LA][EG] 1:3:1 Ⅲ'[ATMAC][LA][EG] 1:1:1 Ⅳ'[ATMAC][LA][EG] 1:3:1 Ⅴ'[ChCl][LA][MnCl2] 1:1:1 Ⅵ'[ChCl][LA][MnCl2] 1:3:1 Ⅶ'[ATMAC][LA][MnCl2] 1:1:1 Ⅷ'[ATMAC][LA][MnCl2] 1:3:1 surface

[0082] Figure 5 illustrates the effect of different ternary DES on the binding energy of the system obtained through quantum mechanical simulation. In this embodiment, the catalytic activity of the ternary DES was predicted based on frontier orbital theory. The catalytic activity of the DES was determined by judging the degree of energy barrier reduction after the addition of the DES; the greater the reduction, the better the catalytic effect of the DES. The HOMO and LUMO energy differences of each system are shown in Figure 6. Generally, the smaller the binding energy of the system, the weaker the intermolecular interaction forces, making it easier to overcome the energy barrier and allow the reaction to occur; the smaller the frontier orbital energy difference, the better the catalytic activity of the DES. Based on the calculations of binding energy (Figure 5) and frontier orbital theory (Figure 6), the order of catalytic activity of the DES from high to low is predicted to be: IV'>II'>VIII'>VI'>III'>VII'>I'>V'. After the addition of the ternary DES, the energy barriers of the systems were significantly reduced, indicating that the designed DES has excellent catalytic effect.

[0083] On the other hand, in this embodiment, an exploratory experiment was conducted based on the eight types of DES shown in Table 1.

[0084] Catalytic degradation experiment The eight ternary DES in Table 1 were used to degrade lignin, and the degradation rate was calculated. The PDI value of the degraded lignin was also tested (the results are shown in Figure 7). As can be seen from Figure 7(a), all eight DES can effectively catalyze the degradation of lignin. The decreasing trend of PDI in Figure 7(b) is consistent with the changing trend of the degradation rate.

[0085] In addition, the hydroxyl content of lignin after DES degradation was tested (the results are shown in Figure 8). As can be verified from Figure 8, the trend of hydroxyl content of lignin obtained after degradation by different DES is basically consistent with the order of DES catalytic activity, which verifies the accuracy of theoretical calculation.

[0086] Performance testing of RTP materials prepared from lignin degraded by different DESThe phosphorescence emission spectra and phosphorescence lifetimes of RTP materials prepared by lignin degradation using EG-based and MnCl2-based DES as reinforcing agents were determined using steady-state transient fluorescence spectroscopy (results are shown in Figure 9). The emission spectra of the materials could be captured with a 1 ms delay under 365 nm excitation. The phosphorescence emission peaks of the RTP materials prepared by EG-based DES were concentrated around 500-510 nm. The phosphorescence lifetimes of the RTP materials prepared by DES catalytic degradation of lignin using [ChCl][LA][EG] 1:1:1, [ChCl][LA][EG] 1:3:1, [ATMAC][LA][EG] 1:1:1, and [ATMAC][LA][EG] 1:3:1 were 401.38 ms, 434.80 ms, 415.93 ms, and 451.05 ms, respectively. The phosphorescence lifetime of the RTP material prepared using [ATMAC] as an HBA (hydrogen bond acceptor) was also higher than that of choline chloride, which is consistent with the results calculated based on frontier orbital theory, verifying the accuracy of the theoretical calculations. The phosphorescence emission peak of the RTP material prepared by MnCl2-based DES degradation of lignin is located at approximately 510-530 nm. The phosphorescence lifetimes of the RTP materials prepared by DES catalytic degradation of lignin using [ChCl][LA][MnCl2]1:1:1, [ChCl][LA][MnCl2]1:3:1, [ATMAC][LA][MnCl2]1:1:1, and [ATMAC][LA][MnCl2]1:3:1 are 406.73 ms, 431.29 ms, 407.98 ms, and 435.05 ms, respectively. This lifetime order is basically consistent with the order of hydroxyl and carboxyl group content after ternary DES degradation of lignin, which is consistent with the catalytic activity of DES, verifying the accuracy of the theoretical calculation.

[0087] As can be seen, the phosphorescence lifetime of the RTP material prepared by ternary DES degradation of lignin in this invention reaches the range of 401.38-451.05 ms. Compared with the phosphorescence lifetime of traditional RTP materials of about 100-300 ms, the phosphorescence lifetime of the green, stable and long-lived RTP@IPA material of this invention is significantly improved and the phosphorescence performance is more stable.

[0088] Figure 9 also confirms that the DES used in the preparation method of the green, stable, and long-lifetime RTP@IPA material of this invention introduces a third-component reinforcing agent, which inhibits the formation of condensation-type lignin. The degraded lignin exhibits a higher content of hydroxyl functional groups, resulting in a higher functional group content on the surface of the prepared CDs. Further blending with the polymer matrix leads to more hydrogen bond interactions, suppressing the non-radiative transition process of triplet excitons and promoting the radiative transition process, thus improving the phosphorescence lifetime of the prepared RTP material. Simultaneously, compared to traditional doping with N and S elements, B element can both promote intersystem crossing and enhance phosphorescence lifetime.

[0089] Furthermore, this embodiment also plotted the CIE chromaticity diagrams (as shown in Figure 10) of RTP materials prepared by DES catalytic degradation of lignin using [ATMAC][LA][EG] with a component molar ratio of 1:3:1 and [ATMAC][LA][MnCl2] with a component molar ratio of 1:3:1, respectively, with coordinates of (0.288, 0.407) and (0.283, 0.397). Figure 10 verifies that different DESs do not significantly differ in the emission color of the RTP materials; all exhibit a yellowish-green emission, which coincides with the position of the optimal emission peak in the emission spectrum.

[0090] The results of quantum mechanical simulations and exploratory examples confirm that in the preparation method of the green, stable, and long-lived RTP@IPA material of the present invention, the hydrogen bond acceptor in the DES is choline chloride or allyltrimethylammonium chloride, the hydrogen bond donor is lactic acid, and the reinforcing agent is ethylene glycol or manganese chloride; furthermore, the molar ratio of the hydrogen bond acceptor, hydrogen bond donor, and reinforcing agent in the DES is (0.5-2):(0.5-4):(0.5-2), preferably 1:(1-3):1; furthermore, the hydrogen bond acceptor can be ATMAC; even further, the DES is [ATMAC][LA][EG] with a component molar ratio of 1:3:1, or [ATMAC][LA][MnCl2] with a component molar ratio of 1:3:1.

[0091] Furthermore, Figure 11 shows the SEM image and elemental mapping of the green, stable, and long-lived RTP@IPA material prepared in this embodiment. Figure 11 confirms that the green, stable, and long-lived RTP@IPA material of this invention exhibits a three-dimensional shell structure. Additionally, only very small amounts of N (Figure e) and B (Figure f) are visible in the elemental mapping, indicating that the IPA structure encapsulates the RTP material, forming a coating structure. The RTP material achieves isolation from the air in the environment; therefore, this material effectively extends the stability of the RTP@IPA material, achieving a stable lifetime and enabling luminescence even in aqueous solutions.

[0092] Furthermore, this embodiment also verifies the stability of the green, stable, long-lifetime RTP@IPA material in different solvents. Specifically:

[0093] To verify the stability of the RTP@IPA material in water, the material was immersed in water for 1 hour, and its quenching was observed. As shown in Figure 12, the material exhibits a bright afterglow emission phenomenon in water, and it also maintains a bright emission effect after 1 hour of immersion. This indicates that the intensity of the phosphorescence emission spectrum of the RTP material did not change significantly, confirming that the material not only exhibits afterglow in solid powder but also has a stable afterglow phenomenon in aqueous solution.

[0094] To verify the stability of the RTP@IPA material of this invention in different solvents, the prepared RTP@IPA powder was dispersed in common solvents such as acetonitrile, isopropanol, sulfolane, n-propanol, glycerol, and water. After ultraviolet excitation, the afterglow phenomenon was observed, and the luminescence was recorded over a long period (the results are shown in Figure 13). As can be verified by Figure 13, the afterglow time of the RTP@IPA material varies in different solvents, with the longest time in acetonitrile and the shortest time in n-propanol. Furthermore, after 30 days of continued ultraviolet excitation, a bright afterglow phenomenon could still be observed after the excitation was turned off, proving that the green, stable, and long-lived RTP@IPA material of this invention has significant and long-lasting stability.

[0095] This embodiment also tested the phosphorescence performance of the green, stable, and long-lifetime RTP@IPA material. Specifically, as shown in Figure 14, the optimal emission peak of the RTP@IPA material of this invention is located at 510 nm, and its phosphorescence lifetime reaches 728.96 ms. The afterglow phenomenon of the RTP@IPA material after the UV lamp is turned off (Figure 15) shows that it emits a bright yellow-green light, and the afterglow time can reach 8 s. This verifies that the green, stable, and long-lifetime RTP@IPA material of this invention is a green, environmentally friendly, long-lifetime phosphorescent material with excellent solvent stability at room temperature.

[0096] Example 2

[0097] Based on the preparation method of the green, stable and long-life RTP@IPA material shown in Example 1, the carbonization temperature in step (2) was explored and optimized in this example.

[0098] Specifically, taking the RTP material prepared by degrading lignin with a DES catalyst containing [ATMAC][LA][EG] in a molar ratio of 1:3:1 as an example, this embodiment tested the effect of different carbonization temperatures on the phosphorescence emission spectrum and lifetime of the RTP material, and the results are shown in Figure 16. As can be verified from Figure 16, the carbonization temperature in step (2) of this invention can be selected as 190-220℃. At 200℃, the phosphorescence lifetime of the RTP material reached a maximum of 451.05ms. As the carbonization temperature further increases, the phosphorescence lifetime of the RTP material decreases. Therefore, the carbonization temperature can be further selected as 200℃.

[0099] Example 3

[0100] Based on the preparation method of the green, stable and long-life RTP@IPA material shown in Example 1, this example explores and optimizes the types of polymer matrices in step (3).

[0101] Specifically, taking the RTP material prepared by degrading lignin with a DES catalyst containing [ATMAC][LA][EG] in a molar ratio of 1:3:1 as an example, this embodiment tested the effect of different polymer matrix types on the phosphorescence emission spectrum and lifetime of the RTP material, and the results are shown in Figure 18. As can be verified by Figure 17, the polymer matrix can be selected from one or more of acrylic resin (PAA), polyvinyl alcohol (PVA), and polyacrylamide (PAM), and PAM can be further selected.

[0102] Example 4

[0103] Based on the preparation method of the green, stable and long-life RTP@IPA material shown in Example 1, the amount of crosslinking agent in step (3) was explored and optimized in this example.

[0104] Specifically, taking the RTP material prepared by degrading lignin with a DES catalyst containing [ATMAC][LA][EG] in a molar ratio of 1:3:1 as an example, this embodiment tested the effect of different amounts of crosslinking agent on the phosphorescence emission spectrum and lifetime of the RTP material, and the results are shown in Figure 18. Generally, a higher crosslinking agent content leads to a higher crosslinking density, that is, the connection between crosslinking points in the gel is more compact, which helps to form a more rigid structure and is beneficial to the non-radiative transition process of fixing CDs. As can be verified by Figure 18, the crosslinking agent to the polymer matrix in the preparation method of the green, stable and long-lifetime RTP@IPA material of the present invention is 1:(30-100), preferably 1:(35-85), even more preferably 1:(35-65), and more preferably 1:50.

[0105] It should be noted that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple improvements can be made without departing from the concept of the present invention, and all such improvements should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a green, stable, and long-life RTP@IPA material, characterized in that, Includes the following steps: (1) Lignin is degraded by ternary DES catalysis including hydrogen bond acceptor, hydrogen bond donor and reinforcing agent to obtain lignin after DES degradation; wherein, the hydrogen bond acceptor in the DES is choline chloride or allyltrimethylammonium chloride, the hydrogen bond donor is lactic acid, and the reinforcing agent is ethylene glycol or manganese chloride; (2) The lignin obtained by DES degradation in step (1) is carbonized with boric acid to obtain CDs doped with B element; (3) The CDs obtained in step (2) are crosslinked with the polymer matrix to obtain the RTP material; (4) The RTP material is crosslinked with isophthalic acid to obtain the green, stable and long-life RTP@IPA material.

2. The preparation method of the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, The molar ratio of hydrogen bond acceptor, hydrogen bond donor, and reinforcing agent in the DES is (0.5-2):(0.5-4):(0.5-2), preferably 1:(1-3):1; and / or, the hydrogen bond acceptor is allyltrimethylammonium chloride; and / or, the mass ratio of DES to lignin in step (1) is (30-15):1, preferably 20:1; and / or, the temperature of the catalytic degradation reaction is 190℃-220℃, and the time is 4-12h.

3. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, In step (2), the mass ratio of lignin degraded by DES to boric acid is 1:(5-15), preferably 1:(9-11.

4. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, The carbonization reaction temperature is 190℃-220℃, preferably 200℃; the reaction time is 5-36h, preferably 12h.

5. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, In step (3), the mass ratio of CDs to polymer matrix is ​​1:(500-2000), preferably 1:1000; and / or, the polymer matrix includes one or more of acrylic resin, polyvinyl alcohol, and polyacrylamide; and / or, the temperature of the crosslinking reaction in step (3) is 50-90℃, and the reaction time is 2-4h.

6. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, The crosslinking reaction in step (3) is carried out under the action of a crosslinking agent and an initiator; preferably, the mass ratio of the crosslinking agent to the polymer matrix is ​​1:(30-100), more preferably 1:(35-85); preferably, the crosslinking agent includes one or more of N,N'-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, ethylenediamine, polyacrylic acid, polyacrylamide, and polyethylene glycol; preferably, the mass ratio of the initiator to the polymer matrix is ​​1:(30-100), more preferably 1:35; preferably, the initiator includes one or more of ammonium persulfate, sodium persulfate, potassium persulfate, and monomethyl persulfate.

7. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, Step (1) further includes: after the catalytic degradation is completed, separating DES from the reacted material and recycling it.

8. The method for preparing the green, stable, and long-life RTP@IPA material according to claim 1, characterized in that, The crosslinking reaction in step (4) includes: mixing the RTP@IPA material with isophthalic acid evenly and maintaining the mixture at 120-140℃ for 0.5-1h.

9. A green, stable, and long-life RTP@IPA material, characterized in that, The RTP@IPA material was prepared using the method described in any one of claims 1-8.

10. The application of the green, stable, and long-life RTP@IPA material as described in claim 9 in anti-counterfeiting, information encryption, sensing, bioimaging, and the fabrication of organic light-emitting devices.

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