Organic long-afterglow magnetic microsphere as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional materials, and discloses organic long-afterglow magnetic microspheres as well as a preparation method and application thereof. The organic long-afterglow magnetic microsphere comprises a subject component, and guest molecules and magnetic nanoparticles doped in the subject component, wherein the main component is prepared from melamine formaldehyde resin; the guest molecule comprises a polycyclic aromatic hydrocarbon derivative; the magnetic nanoparticles comprise at least one of magnetic metal oxide, magnetic metal or magnetic alloy nanoparticles. After the material is activated by ultraviolet light, the afterglow life can reach a second level, the afterglow quantum yield can reach 25.72% at most, and the afterglow wavelength, the afterglow life and the quantum yield can be flexibly regulated and controlled through guest molecules; a rigid hydrogen bond network of the melamine formaldehyde resin effectively inhibits non-radiative transition and isolates oxygen, so that the stability of triplet excitons is remarkably improved; the microspheres are uniform in morphology, controllable in particle size and excellent in magnetic responsiveness, and directional movement and enrichment can be achieved under an external magnetic field.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, and in particular to an organic long afterglow magnetic microsphere, its preparation method, and its application. Background Technology

[0002] Long-afterglow materials are a class of special functional materials that continue to emit light after the excitation source has ceased. Because they effectively eliminate interference from short-lived background light and significantly improve the signal-to-noise ratio of detection signals, they show broad application prospects in fields such as bioimaging, information encryption, anti-counterfeiting labels, road signs, and optoelectronic devices. Traditional long-afterglow materials are mainly based on inorganic systems, such as aluminates and silicates doped with rare-earth ions, or organometallic complexes containing noble metals. While these materials possess excellent luminous efficiency and long afterglow lifetimes, their preparation costs are high, the synthesis conditions are demanding (usually requiring high-temperature solid-state reactions), and some materials pose potential biotoxicity or environmental risks, severely limiting their application and promotion in emerging fields such as biomedicine and flexible electronics.

[0003] In recent years, pure organic long-afterglow materials have attracted widespread attention due to their advantages such as strong structural tunability, low synthesis cost, good biocompatibility, and excellent processing performance. Currently, the main strategies for achieving room-temperature organic long-afterglow include: (1) using crystal engineering to form a rigid stack of organic molecules in the crystal lattice to suppress molecular motion and nonradiative relaxation; (2) introducing organic light-emitting units into the polymer backbone or side chain through covalent bonds, using the rigid environment of the polymer to stabilize triplet excitons; (3) adopting a host-guest doping strategy to disperse organic light-emitting molecules (guests) into a rigid polymer matrix (host), using the rigid environment and physical isolation provided by the host to restrict the vibration, rotation, and contact with oxygen of the guest molecules, thereby inducing long-afterglow luminescence at room temperature. Among these, the host-guest doping method is considered the most promising technical path for practical application because of its simple preparation, mild conditions, ease of scaling, and the ability to flexibly adjust the luminescence color, efficiency, and lifetime by controlling the structure and doping concentration of the guest molecules.

[0004] However, current host-guest doped polymer-based organic long afterglow materials still generally face three major bottlenecks: First, the afterglow efficiency is low and the lifetime is short. This is mainly due to the insufficient intersystem crossing efficiency of the selected guest molecules, the poor stability of the triplet excited state, and the insufficient protection of the polymer matrix for the guest molecules, which cannot effectively suppress nonradiative transitions and oxygen quenching. Second, the materials have limited functions. Most materials only have a single luminescent function and cannot achieve additional functions such as magnetic response and directional manipulation.

[0005] Furthermore, existing organic long-afterglow materials are mostly in powder or thin film form, lacking microsphere structures, resulting in poor processability and adaptability, making it difficult to meet the needs of emerging applications such as micro / nano-scale devices and intelligent control systems. Therefore, designing and developing an organic long-afterglow magnetic material with a microsphere structure that also possesses high quantum yield, long afterglow lifetime, excellent stability, and controllable magnetic response is of significant theoretical and practical value for promoting the practical application of organic long-afterglow materials. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide an organic long-afterglow magnetic microsphere.

[0007] The second objective of this invention is to provide a method for preparing such organic long afterglow magnetic microspheres.

[0008] The third objective of this invention is to provide applications for such organic long-afterglow magnetic microspheres.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an organic long-afterglow magnetic microsphere, comprising a host component, and guest molecules and magnetic nanoparticles doped in the host component; wherein, The main component includes melamine-formaldehyde resin; The guest molecules include polycyclic aromatic hydrocarbon derivatives; The magnetic nanoparticles include at least one of magnetic metal oxide, magnetic metal, or magnetic alloy nanoparticles.

[0010] In some embodiments of the present invention, the mass fraction of the guest molecule in the organic long afterglow magnetic microsphere is 0.01%-0.5%; the mass ratio of the magnetic nanoparticle to the guest molecule is (8-12):1.

[0011] In some preferred embodiments of the present invention, the mass fraction of the guest molecule in the organic long afterglow magnetic microsphere is 0.05%-0.1%; the mass ratio of the magnetic nanoparticle to the guest molecule is (9-11):1.

[0012] In some embodiments of the present invention, the guest molecule is selected from at least one compound of formula I, formula II, and formula III: .

[0013] In some embodiments of the present invention, the magnetic nanoparticles are selected from at least one of Fe3O4 nanoparticles, γ-Fe2O3 nanoparticles, NiFe2O4 nanoparticles, CoFe2O4 nanoparticles, and Fe nanoparticles.

[0014] In some preferred embodiments of the present invention, the magnetic nanoparticles are Fe3O4 nanoparticles.

[0015] In some embodiments of the present invention, the particle size of the organic long afterglow magnetic microspheres is 0.1-8 μm.

[0016] In some preferred embodiments of the present invention, the particle size of the organic long afterglow magnetic microspheres is 1-3 μm.

[0017] A second aspect of the present invention provides a method for preparing the organic long afterglow magnetic microspheres described in the first aspect of the present invention, comprising the following steps: S1. Mix the guest molecule with an organic solvent to obtain solution A; mix melamine with an aqueous formaldehyde solution and react under alkaline conditions to obtain solution B; disperse magnetic nanoparticles with a silane coupling agent in an alcohol solvent and react under acidic conditions to obtain solution C; S2. Mix solutions A, B and C, then mix with an emulsifier, adjust the pH value with acid, and react to obtain a polymer emulsion. S3. The polymer emulsion is centrifuged, washed, and dried to obtain the organic long afterglow magnetic microspheres.

[0018] In some embodiments of the present invention, in step S1, the solid-liquid ratio of the guest molecule to the organic solvent is (8-15) mg: 1 mL.

[0019] In some preferred embodiments of the present invention, in step S1, the solid-liquid ratio of the guest molecule to the organic solvent is (8-12) mg: 1 mL.

[0020] In some embodiments of the present invention, in step S1, the organic solvent is selected from methanol, ethanol, acetone, dimethyl sulfoxide, N,N At least one of dimethylformamide, tetrahydrofuran, and acetonitrile.

[0021] In some preferred embodiments of the present invention, in step S1, the organic solvent is tetrahydrofuran.

[0022] In some embodiments of the present invention, in step S1, the concentration of the formaldehyde aqueous solution is 1wt%-55wt%.

[0023] In some preferred embodiments of the present invention, in step S1, the concentration of the formaldehyde aqueous solution is 30wt%-40wt%.

[0024] In some embodiments of the present invention, in step S1, the solid-liquid ratio of the melamine to the formaldehyde aqueous solution is 1g:(0.8-1.5)mL.

[0025] In some preferred embodiments of the present invention, in step S1, the solid-liquid ratio of the melamine to the formaldehyde aqueous solution is 1g:(0.9-1.1)mL.

[0026] In some embodiments of the present invention, in step S1, the reaction is carried out under alkaline conditions, with a system pH of 7-11, a reaction temperature of 70-110°C, and a reaction time of 5-20 min.

[0027] In some preferred embodiments of the present invention, in step S1, the reaction is carried out under alkaline conditions, the pH value of the system is 8-9, the reaction temperature is 80-100℃, and the time is 5-15 min.

[0028] In some embodiments of the present invention, step S1, the reaction under alkaline conditions, includes adding an alkali to adjust the pH of the system to alkaline; the alkali is selected from at least one of organic amines, alkali metal hydroxides, and alkali metal carbonates.

[0029] In some preferred embodiments of the present invention, in step S1, the alkali is selected from at least one of diethylamine, triethylamine, triethanolamine, sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0030] In some more preferred embodiments of the present invention, in step S1, the base is triethanolamine.

[0031] In some embodiments of the present invention, in step S1, the ratio of the magnetic nanoparticles, silane coupling agent and alcohol solvent is (16-24) mg: 1 mg: (1-5) mL.

[0032] In some preferred embodiments of the present invention, in step S1, the ratio of the magnetic nanoparticles, silane coupling agent and alcohol solvent is (18-22) mg: 1 mg: (1-3) mL.

[0033] In some embodiments of the present invention, in step S1, the silane coupling agent includes γ-aminopropyltriethoxysilane (KH-550).

[0034] In some embodiments of the present invention, in step S1, the alcohol solvent is selected from at least one of methanol, ethanol, and isopropanol.

[0035] In some preferred embodiments of the present invention, in step S1, the alcohol solvent is ethanol.

[0036] In some embodiments of the present invention, in step S1, the reaction is carried out under acidic conditions, with a system pH of 2-5, a reaction temperature of 35-55°C, and a reaction time of 2-5 hours.

[0037] In some preferred embodiments of the present invention, in step S1, the reaction is carried out under acidic conditions, with a system pH of 4-5, a reaction temperature of 40-50°C, and a reaction time of 2-4 hours.

[0038] In some embodiments of the present invention, step S1, the reaction under acidic conditions, includes adding an acid to adjust the pH of the system to acidic; the acid is selected from at least one of acetic acid, oxalic acid, formic acid, citric acid, hydrochloric acid, and sulfuric acid.

[0039] In some preferred embodiments of the present invention, in step S1, the acid is oxalic acid.

[0040] In some embodiments of the present invention, in step S2, the concentration of the emulsifier is 2-30 mg / mL; the volume ratio of solution A, solution B, solution C to emulsifier is 1: (5-10): (5-15): (50-150).

[0041] In some preferred embodiments of the present invention, in step S2, the concentration of the emulsifier is 2-10 mg / mL; the volume ratio of solution A, solution B, solution C to emulsifier is 1: (5-8): (8-12): (80-120).

[0042] In some embodiments of the present invention, in step S2, the emulsifier is selected from at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0043] In some embodiments of the present invention, in step S2, the pH is adjusted to 3-6 by adding acid, the reaction temperature is 50-70°C, and the reaction time is 15-60 min.

[0044] In some preferred embodiments of the present invention, in step S2, the pH is adjusted to 5-6 by adding acid, the reaction temperature is 55-65°C, and the time is 20-40 min.

[0045] In some embodiments of the present invention, in step S2, the acid is selected from at least one of acetic acid, oxalic acid, formic acid, citric acid, hydrochloric acid, and sulfuric acid.

[0046] In some preferred embodiments of the present invention, in step S2, the acid is oxalic acid.

[0047] In some embodiments of the present invention, in step S2, the reaction process is aided by stirring at a speed of 500-800 r / min.

[0048] In some embodiments of the present invention, in step S3, the centrifugation speed is 4000-6000 r / min and the time is 5-15 min.

[0049] In some preferred embodiments of the present invention, in step S3, the centrifugation speed is 4500-5500 r / min and the time is 5-10 min.

[0050] In some embodiments of the present invention, in step S3, the washing reagent includes deionized water; the number of washing cycles is 3-4.

[0051] In some embodiments of the present invention, in step S3, the drying temperature is 40-60°C and the time is 20-30 hours.

[0052] In some preferred embodiments of the present invention, in step S3, the drying temperature is 45-55°C and the time is 20-25 hours.

[0053] The third aspect of the present invention provides the application of the organic long afterglow magnetic microspheres described in the first aspect of the present invention in bioimaging, environmental pollutant capture, anti-counterfeiting, data encryption, functional inks or road markings.

[0054] Compared with the prior art, the beneficial effects of the present invention are: 1) The organic long-afterglow magnetic microspheres provided by this invention use melamine-formaldehyde resin as a rigid host and physically dopants polycyclic aromatic hydrocarbon derivatives as guest molecules, while simultaneously introducing magnetic nanoparticles, to achieve synergistic integration of long-afterglow luminescence and magnetic response. After activation by ultraviolet light, the afterglow lifetime can reach the second level (up to 2.77s), and the afterglow quantum yield can reach up to 25.72%. The afterglow wavelength, lifetime, and quantum yield can be flexibly controlled by the guest molecules. The rigid hydrogen bond network of melamine-formaldehyde resin effectively suppresses nonradiative transitions and isolates oxygen, significantly improving the stability of triplet excitons. The microspheres have uniform morphology, controllable particle size, and excellent magnetic responsiveness, and can achieve directional movement and enrichment under an external magnetic field. 2) The method for preparing organic long afterglow magnetic microspheres provided by the present invention adopts solution blending and dispersion polymerization process, which is mild, does not require precious metals or rare earth elements, and is low in cost and environmentally friendly. 3) The organic long-afterglow magnetic microspheres provided by this invention have both efficient and persistent luminescence and controllable magnetic response functions, showing broad application prospects in fields such as biomedical imaging, intelligent anti-counterfeiting, information encryption and magnetic separation and recovery of environmental pollutants. Attached Figure Description

[0055] Figure 1 The 1H NMR spectrum of the compound of formula I prepared in Example 1; Figure 2 The 1H NMR spectrum of the compound of formula II prepared in Example 2; Figure 3 The 1H NMR spectrum of the compound of formula III prepared in Example 3; Figure 4 The steady-state emission spectra of the solid powders of compounds of formulas I-III prepared in Examples 1-3 are shown. Figure 5 The graphs show the luminescence decay curves of the solid powders of compounds of formulas I-III prepared in Examples 1-3; Figure 6 This is a scanning electron microscope image of the polymer microsphere organic long afterglow material prepared in Example 1; Figure 7 This is a scanning electron microscope image of the polymer microsphere organic long afterglow material prepared in Example 2; Figure 8 This is a scanning electron microscope image of the polymer microsphere organic long afterglow material prepared in Example 3; Figure 9 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 1; Figure 10 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 2; Figure 11 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 3; Figure 12 The excitation spectrum, steady-state photoluminescence spectrum, and delayed photoluminescence spectrum of the polymer microsphere organic long afterglow materials prepared in Examples 1(a), 2(b), and 3(c) are shown. Figure 13 The delayed emission decay curves are for the polymer microsphere organic long afterglow materials prepared in Examples 1(a), 2(b), and 3(c). Figure 14 The images show the afterglow luminescence phenomenon of the polymer microsphere organic long afterglow materials prepared in Examples 1-3; Figure 15 The photoluminescence spectrum (a) and afterglow decay curve (b) of the organic long afterglow magnetic microspheres prepared in Example 2 are shown. Figure 16 The photoluminescence spectrum (a) and afterglow decay curve (b) of the organic long afterglow magnetic microspheres prepared in Example 3 are shown. Figure 17 The motion state of the organic long afterglow magnetic microspheres prepared in Examples 2 and 3 under the action of an external magnetic field; Figure 18 This is a binary cryptographic encryption diagram of the organic long afterglow magnetic microspheres prepared in Example 2. Detailed Implementation

[0056] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0057] Example 1 This embodiment prepares a compound of formula I and uses it to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres: The synthetic steps for compound I are as follows: Under an argon atmosphere, 2-bromotriene (0.50 g, 1.63 mmol) and phenylboronic acid (0.24 g, 1.96 mmol) were dissolved in 20 mL of tetrahydrofuran solution, and then added to 5 mL of 2 mol / L K₂CO₃ aqueous solution. The mixture was then bubbled and ventilated for 30 min, followed by the addition of an appropriate amount of tetra(triphenylphosphine)palladium. The reaction solution was stirred at 90 °C for 24 h, and TLC analysis indicated that the reaction was essentially complete. After the reaction solution cooled to room temperature, it was extracted with water and dichloromethane to separate the aqueous and organic phases. The organic solvent was then removed by vacuum distillation, and the residue was purified by column chromatography using dichloromethane / petroleum ether (9:1, v / v) as the mobile phase. After reprecipitation and vacuum drying, 0.292 g of white powder, representing compound I, was obtained, with a yield of 59%.

[0058] The synthetic route for compound I is shown below:

[0059] Figure 1 The 1H NMR spectrum of the compound of formula I prepared in Example 1 is shown below. Figure 1 It can be seen that the compound of formula I was successfully synthesized and can be further used to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres.

[0060] The preparation steps of polymer microsphere organic long afterglow material are as follows: 1) Weigh 10 mg of compound I and dissolve it in 2 mL of tetrahydrofuran to prepare a solution a with a concentration of 10 mg / mL; 2) Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution b; 3) Add 1 mL of solution a to 10 mL of solution b, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. 4) Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it with deionized water 3-4 times, and then vacuum dry it at 50℃ for 24 h to obtain polymer microsphere organic long afterglow material with a particle size of 2 μm.

[0061] The preparation steps of organic long afterglow magnetic microspheres are as follows: S11. Weigh 10 mg of compound I and dissolve it in 2 mL of tetrahydrofuran to prepare solution A with a concentration of 10 mg / mL; S12. Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution B. S13. Disperse 100 mg Fe3O4 nanoparticles and 5 mg KH-550 in 10 mL ethanol, adjust the pH to 4-5 with acetic acid, and heat at 45 °C for 3 h to obtain solution C. S21. Add 1 mL of solution A and 10 mL of solution C to 10 mL of solution B, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. S31. Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it 3-4 times with deionized water, and then vacuum dry it at 50℃ for 24 h to obtain organic long afterglow magnetic microspheres with a particle size of 2.7 μm.

[0062] Example 2 This embodiment prepares a compound of formula II and uses it to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres: The synthetic steps for compound II are as follows: Under an argon atmosphere, 4-dibenzofuranboronic acid (0.50 g, 2.36 mmol) and 2,2'-dibromobisbenzene (2.2 g, 7.07 mmol) were dissolved in 20 mL of tetrahydrofuran solution, and then added to 5 mL of 2 mol / L K₂CO₃ aqueous solution. The mixture was then bubbled and ventilated for 30 min, followed by the addition of an appropriate amount of tetra(triphenylphosphine)palladium. The reaction solution was stirred at 85 °C for 24 h, and TLC analysis indicated that the reaction was essentially complete. After the reaction solution cooled to room temperature, it was extracted with water and dichloromethane to separate the aqueous and organic phases. The organic solvent was then removed by vacuum distillation, and the residue was purified by column chromatography using dichloromethane / petroleum ether (5:1, v / v) as the mobile phase. After reprecipitation and vacuum drying, 0.150 g of a white powder was obtained, which was the intermediate product of formula II, with a yield of 59%. Under an argon atmosphere, the intermediate product of formula II (0.15 g, 0.38 mmol) was dissolved in 15 mL of xylene solution, and then Cs2CO3 (0.49 g, 1.50 mmol) was added. After bubbling and aeration for 30 min, an appropriate amount of bis(dibenzylacetone)palladium was added, and the reaction solution was stirred at 140 °C for 24 h. TLC detection showed that the reaction was basically complete. After the reaction solution was cooled to room temperature, it was extracted with water and dichloromethane to separate the aqueous phase and the organic phase. The organic solvent was then removed by vacuum distillation, and the residue was separated and purified by column chromatography using dichloromethane / petroleum ether (9:1, v / v) as the mobile phase. After reprecipitation and vacuum drying, 0.09 g of white powder was obtained, which is the compound of formula II, with a yield of 76%.

[0063] The synthetic route for compound II is shown below:

[0064] Figure 2 The 1H NMR spectrum of the compound of formula II prepared in Example 2 is shown below. Figure 2 It is evident that the compound of formula II has been successfully synthesized and can be further used to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres.

[0065] The preparation steps of polymer microsphere organic long afterglow material are as follows: 1) Weigh 10 mg of compound II and dissolve it in 2 mL of tetrahydrofuran to prepare a solution a with a concentration of 10 mg / mL; 2) Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution b; 3) Add 1 mL of solution a to 10 mL of solution b, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. 4) Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it with deionized water 3-4 times, and then vacuum dry it at 50℃ for 24 h to obtain polymer microsphere organic long afterglow material with a particle size of 2 μm.

[0066] The preparation steps of organic long afterglow magnetic microspheres are as follows: S11. Weigh 10 mg of compound II and dissolve it in 2 mL of tetrahydrofuran to prepare solution A with a concentration of 10 mg / mL; S12. Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution B. S13. Disperse 100 mg Fe3O4 nanoparticles and 5 mg KH-550 in 10 mL ethanol, adjust the pH to 4-5 with acetic acid, and heat at 45 °C for 3 h to obtain solution C. S21. Add 1 mL of solution A and 10 mL of solution C to 10 mL of solution B, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. S31. Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it 3-4 times with deionized water, and then vacuum dry it at 50℃ for 24 h to obtain organic long afterglow magnetic microspheres with a particle size of 2.7 μm.

[0067] Example 3 This embodiment prepares a compound of formula III and uses it to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres: The synthetic steps for compound III are as follows: Under an argon atmosphere, 4-dibenzofuranthiophene (0.50 g, 2.19 mmol) and 2,2'-dibromobisphenylene (2.05 g, 6.58 mmol) were dissolved in 20 mL of tetrahydrofuran solution, and then added to 5 mL of 2 mol / L K2CO3 aqueous solution. The mixture was then bubbled and ventilated for 30 min, followed by the addition of an appropriate amount of tetra(triphenylphosphine)palladium. The reaction solution was stirred at 85 °C for 24 h, and TLC analysis showed that the reaction was essentially complete. After the reaction solution cooled to room temperature, it was extracted with water and dichloromethane to separate the aqueous and organic phases. The organic solvent was then removed by vacuum distillation, and the residue was purified by column chromatography using dichloromethane / petroleum ether (3:1, v / v) as the mobile phase. After reprecipitation and vacuum drying, 0.560 g of white powder was obtained, which was the intermediate product of formula III, with a yield of 62%. Under an argon atmosphere, the intermediate product of Formula III (0.56 g, 1.36 mmol) was dissolved in 15 mL of xylene solution, followed by the addition of Cs₂CO₃ (1.77 g, 5.44 mmol) and a small amount of triphenylphosphine. After bubbling and aeration for 30 min, an appropriate amount of bis(dibenzylacetone)palladium was added, and the reaction solution was stirred at 140 °C for 24 h. TLC analysis showed that the reaction was essentially complete. After the reaction solution cooled to room temperature, it was extracted with water and dichloromethane to separate the aqueous and organic phases. The organic solvent was then removed by vacuum distillation, and the residue was purified by column chromatography using dichloromethane / petroleum ether (9:1, v / v) as the mobile phase. After reprecipitation and vacuum drying, 0.07 g of white powder, which is the compound of Formula III, was obtained, with a yield of 17%.

[0068] The synthetic route for compound III is shown below:

[0069] Figure 3 The 1H NMR spectrum of the compound of formula III prepared in Example 3 is shown below. Figure 3 It is evident that the compound of formula III has been successfully synthesized and can be further used to prepare polymer microsphere organic long afterglow materials and organic long afterglow magnetic microspheres.

[0070] The preparation steps of polymer microsphere organic long afterglow material are as follows: 1) Weigh 10 mg of compound III and dissolve it in 2 mL of tetrahydrofuran to prepare a solution a with a concentration of 10 mg / mL; 2) Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution b; 3) Add 1 mL of solution a to 10 mL of solution b, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. 4) Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it with deionized water 3-4 times, and then vacuum dry it at 50℃ for 24 h to obtain polymer microsphere organic long afterglow material with a particle size of 2 μm.

[0071] The preparation steps of organic long afterglow magnetic microspheres are as follows: S11. Weigh 10 mg of compound III and dissolve it in 2 mL of tetrahydrofuran to prepare solution A with a concentration of 10 mg / mL; S12. Add 5.224g of melamine to 5.34mL of 37wt% formaldehyde aqueous solution, then add triethanolamine to adjust the pH of the solution to 8-9, heat at 90℃ for 10min to obtain clear solution B. S13. Disperse 100 mg Fe3O4 nanoparticles and 5 mg KH-550 in 10 mL ethanol, adjust the pH to 4-5 with acetic acid, and heat at 45 °C for 3 h to obtain solution C. S21. Add 1 mL of solution A and 10 mL of solution C to 10 mL of solution B, and then add the resulting mixture to 100 mL of 10 mg / mL PVA aqueous solution at 60 °C. Quickly adjust the pH value to 5-6 with acetic acid, and stir at 500 r / min for 30 min to obtain a polymer emulsion. S31. Centrifuge the polymer emulsion at 5000 r / min for 5 min, then wash it 3-4 times with deionized water, and then vacuum dry it at 50℃ for 24 h to obtain organic long afterglow magnetic microspheres with a particle size of 2.7 μm.

[0072] Characterization and performance testing The optical properties and microsphere particle size of the polymer microsphere organic long afterglow materials prepared in Examples 1-3 were tested to investigate the particle size, afterglow emission spectrum, and afterglow lifetime. All tests were performed on an Edinburgh FLS980 steady-state and transient fluorescence spectrometer with an integrating sphere and an Ocean Optics QE65 Pro CCD fiber optic spectrometer. Figure 4 The steady-state emission spectra of the solid powders of compounds of formulas I-III prepared in Examples 1-3 are shown below. Figure 4 It can be seen that the solid powders of Formula I-III prepared in Examples 1-3 did not produce long afterglow luminescence after being excited by ultraviolet light. They only had high luminescence intensity in the wavelength range of 350-450nm and emitted only transient fluorescence. That is, the solid powders of Formula I-III do not have afterglow properties.

[0073] Figure 5 The graphs show the luminescence decay curves of the solid powders of formulas I-III prepared in Examples 1-3. Figure 5 It can be seen that the luminescence duration of the solid powders of Formula I-III prepared in Examples 1-3 after ultraviolet light excitation is very short, and the fitted lifetime value is less than 30 ns. That is, the solid powders of Formula I-III do not have afterglow properties and the luminescence intensity decays rapidly.

[0074] Figure 6 This is a scanning electron microscope image of the polymer microsphere organic long afterglow material prepared in Example 1. Figure 7This is a scanning electron microscope image of the polymer microsphere organic long afterglow material prepared in Example 2. Figure 8 This is a scanning electron microscope (SEM) image of the polymer microsphere organic long afterglow material prepared in Example 3. Figures 6-8 As can be seen, the organic long afterglow materials prepared in Examples 1-3 all exhibit a regular spherical morphology with a smooth surface and no obvious protrusions. The microspheres have a uniform particle size (about 2 μm), with no agglomeration or adhesion, and good dispersibility. This breaks through the morphological limitation of existing organic long afterglow materials, which are mostly monolithic polymers. It proves that the preparation process provided by this invention can achieve uniform microsphere molding and controllable particle size, laying a morphological foundation for the subsequent processing and dispersion application of the material.

[0075] Figure 9 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 1. Figure 10 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 2. Figure 11 This is a transmission electron microscope (TEM) image of the polymer microsphere organic long afterglow material prepared in Example 3. Figures 9-11 It can be seen that the organic long-afterglow materials prepared in Examples 1-3 have a dense, spherical structure with no obvious cavitation or pore defects inside. The guest molecules do not show obvious phase separation or aggregation in the polymer matrix and exhibit a uniform dispersion state. This indicates that the guest molecules have been successfully dispersed in the melamine-formaldehyde resin network without local aggregation causing luminescence quenching. This explains the structural reason for the material's efficient long-afterglow luminescence and also proves that the microspheres have a dense internal structure and good stability, providing structural assurance for the subsequent introduction of magnetic particles.

[0076] Figure 12 The excitation spectrum, steady-state photoluminescence spectrum, and delayed photoluminescence spectrum of the polymer microsphere organic long afterglow materials prepared in Examples 1(a), 2(b), and 3(c) are given by [the relevant data]. Figure 12It can be seen that the polymer microsphere organic long-afterglow materials prepared in Examples 1-3, after being irradiated with 330nm ultraviolet light, all exhibited strong characteristic absorption peaks in the 300-400nm ultraviolet region. Matching the ultraviolet excitation source, this proves that the materials can be effectively activated by ultraviolet light. The organic long-afterglow materials prepared in Examples 1 and 2 using compounds of formula I / II as guest molecules have steady-state photoluminescence spectra in the wavelength range of 350-450nm. After the excitation source is removed, the delayed photoluminescence spectra show a significant redshift to the 450-600nm range. The fact that the peak positions do not overlap with the steady-state peaks indicates that the two originate from singlet fluorescence and triplet phosphorescence, respectively. In Example 3, the organic long-afterglow material prepared with compound III as the guest molecule has a steady-state photoluminescence spectrum in the wavelength range of 450-600 nm. After the excitation source is removed, a significant emission peak still appears at the wavelength position that matches the steady-state spectrum, indicating that the heavy atom effect of the S heteroatom reduces the energy difference between the singlet and triplet states, and the excited states are mixed. This verifies the mechanism of the present invention to stabilize triplet excitons through host-guest recombination and achieve long-afterglow luminescence.

[0077] Figure 13 The delayed emission decay curves are shown for the polymer microsphere organic long afterglow materials prepared in Examples 1(a), 2(b), and 3(c). Figure 13 It can be seen that all curves exhibit a slow decay characteristic with a long lifetime, meaning that the polymer microsphere organic long-afterglow materials can all produce significant long-afterglow luminescence, and the afterglow lifetime can reach up to 2.77s.

[0078] Table 1. Photophysical property data of the polymer microsphere organic long afterglow materials prepared in Examples 1-3

[0079] Table 1 shows the photophysical properties of the polymer microsphere organic long-afterglow materials prepared in Examples 1-3. As can be seen from Table 1, under the same doping concentration, the polymer microsphere organic long-afterglow materials prepared in Examples 1-3 all exhibit dual emission peaks in the 460-520 nm visible light region. Among them, the material in Example 2 has the shortest emission peak wavelength (460 nm / 500 nm), while the material in Example 1 has the longest emission peak wavelength (485 nm / 520 nm). The polymer microsphere organic long-afterglow materials prepared in Examples 1-3 can all achieve second-level long-lasting luminescence, with a maximum afterglow lifetime of 2.77 s, a maximum total quantum yield of 53.73%, and a maximum afterglow quantum yield of 25.72%. This indicates that the afterglow wavelength, lifetime, and quantum yield of the material can be controlled by selecting different guest molecules.

[0080] Figure 14 These are images showing the afterglow luminescence phenomena of the polymer microsphere organic long afterglow materials prepared in Examples 1-3. Figure 14It can be seen that the materials in Examples 1-3 can all produce a bright cyan-green afterglow after being activated by ultraviolet light, and the brightness is uniform. This indicates that the organic long afterglow material provided by the present invention has uniform dispersion of guest molecules in the polymer, and the material has good application potential in fields such as anti-counterfeiting, data encryption, functional inks, and road markings.

[0081] Figure 15 The photoluminescence spectrum (a) and afterglow decay curve (b) of the organic long afterglow magnetic microspheres prepared in Example 2 are shown. Figure 16 The photoluminescence spectrum (a) and afterglow decay curve (b) of the organic long-afterglow magnetic microspheres prepared in Example 3 are shown. Figure 15 and Figure 16 It is known that after doping with magnetic nanoparticles, the steady-state photoluminescence spectrum of the material is still in the wavelength range of 350-450 nm, consistent with that of the undoped material. After the excitation source is removed, the delayed photoluminescence spectrum of the material in Example 2 also shows a significant red shift to the 450-600 nm range, while the delayed photoluminescence spectrum of the material in Example 3 overlaps with the steady-state photoluminescence spectrum. In addition, the materials in Examples 2 and 3 maintain a long afterglow lifetime in the millisecond range, with quantum yields of 40.45% and 24.22%, respectively. This indicates that the introduction of magnetic nanoparticles did not damage the long afterglow luminescence performance of the material. The melamine-formaldehyde resin matrix effectively isolates the magnetic nanoparticles from the guest molecules, avoiding their adverse interactions. This achieves a synergistic integration of magnetic response function and long afterglow luminescence function, and the luminescence performance is excellent, meeting the requirements of multifunctional applications.

[0082] Figure 17 The motion state of the organic long afterglow magnetic microspheres prepared in Examples 2 and 3 under the action of an external magnetic field is shown by... Figure 17 It is evident that the materials in Examples 2 and 3 can be rapidly enriched in a liquid medium under the guidance of an external magnetic field and move directionally along the direction of the magnetic field. During the movement, they can still maintain the afterglow emission after photoactivation, realizing the visual control of motion + emission. This proves that the magnetic microspheres prepared by this invention can be precisely controlled by an external magnetic field and have the ability to move and enrich rapidly in a directional manner, which is convenient for subsequent separation, recycling and targeted application. In addition to the common applications of organic long afterglow materials such as anti-counterfeiting, data encryption, functional inks, and road markings, they have the potential for use in fields such as biological imaging and environmental pollutant capture.

[0083] The organic long-afterglow magnetic microspheres prepared in Example 2 were arranged according to binary rules. After ultraviolet excitation, they produced long-afterglow luminescence, which was still visible after the light was turned off. A binary password string was formed according to "long afterglow = 1, no long afterglow = 0". After binary translation, the hidden information was obtained. Figure 18 The binary cryptographic encryption diagram of the organic long afterglow magnetic microspheres prepared in Example 2 is obtained from... Figure 18It is known that the encrypted information "SCNU" can be obtained through the translation process. Compared with pure organic long afterglow materials, magnetic microspheres can be oriented, enriched and fixed in position by magnetic fields, and can be made into a dynamic password that is movable / recombinable. Microspheres can be quickly collected by magnetic fields and repeatedly arranged into new passwords, supporting dynamic encryption and multiple uses.

Claims

1. An organic long-afterglow magnetic microsphere, characterized in that, It includes a main component, as well as guest molecules and magnetic nanoparticles doped into the main component; wherein, The main component includes melamine-formaldehyde resin; The guest molecules include polycyclic aromatic hydrocarbon derivatives; The magnetic nanoparticles include at least one of magnetic metal oxide, magnetic metal, or magnetic alloy nanoparticles.

2. The organic long afterglow magnetic microspheres according to claim 1, characterized in that, In the organic long afterglow magnetic microspheres, the mass fraction of the guest molecules is 0.01%-0.5%; the mass ratio of the magnetic nanoparticles to the guest molecules is (8-12):

1.

3. The organic long afterglow magnetic microspheres according to claim 2, characterized in that, The guest molecule is selected from at least one of compounds of formula I, formula II, and formula III: 。 4. The organic long afterglow magnetic microspheres according to claim 2, characterized in that, The magnetic nanoparticles are selected from at least one of Fe3O4 nanoparticles, γ-Fe2O3 nanoparticles, NiFe2O4 nanoparticles, CoFe2O4 nanoparticles, and Fe nanoparticles.

5. The organic long afterglow magnetic microspheres according to any one of claims 1-4, characterized in that, The organic long afterglow magnetic microspheres have a particle size of 0.1-8 μm.

6. The method for preparing organic long-afterglow magnetic microspheres according to claim 5, characterized in that, Includes the following steps: S1. Mix the guest molecule with an organic solvent to obtain solution A; mix melamine with an aqueous formaldehyde solution and react under alkaline conditions to obtain solution B; disperse magnetic nanoparticles with a silane coupling agent in an alcohol solvent and react under acidic conditions to obtain solution C; S2. Mix solutions A, B and C, then mix with an emulsifier, adjust the pH value with acid, and react to obtain a polymer emulsion. S3. The polymer emulsion is centrifuged, washed, and dried to obtain the organic long afterglow magnetic microspheres.

7. The preparation method according to claim 6, characterized in that, In step S1, the solid-liquid ratio of the guest molecule to the organic solvent is (8-15) mg: 1 mL; And / or, the molar ratio of melamine to formaldehyde is 1: (1-5); And / or, the ratio of the magnetic nanoparticles, silane coupling agent and alcohol solvent is (16-24) mg: 1 mg: (1-5) mL.

8. The preparation method according to claim 7, characterized in that, In step S1, the reaction is carried out under alkaline conditions, with a system pH of 7-11, a reaction temperature of 70-110℃, and a reaction time of 5-20 min. And / or, the reaction is carried out under acidic conditions, with a system pH of 2-5, a reaction temperature of 35-55℃, and a reaction time of 2-5 hours.

9. The preparation method according to claim 8, characterized in that, In step S2, the concentration of the emulsifier is 2-30 mg / mL; the volume ratio of solution A, solution B, solution C to emulsifier is 1: (5-10): (5-15): (50-150); And / or, the pH is adjusted to 3-6 by adding acid, the reaction temperature is 50-70℃, and the time is 15-60 min.

10. The application of the organic long afterglow magnetic microspheres according to any one of claims 1-5 in bioimaging, environmental pollutant capture, anti-counterfeiting, data encryption, functional inks or road markings.

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