A fluorescent film based on micro-nano topological structure for enhancing aggregation-induced emission and a preparation method and application thereof

Abstract

The application discloses a fluorescent film based on micro-nano topological structure enhanced aggregation-induced emission and a preparation method and application thereof, and relates to the technical field of fluorescent materials. The application first prepares a photosensitive layer / fluorescent layer double-layer composite film, and then performs selective exposure on the double-layer composite film; during the exposure, photochemical reaction occurs in photosensitive units in the photosensitive polymer of an exposed area, hydrogen bonds are formed between the photosensitive units and a polymer main chain, stress generated by the photochemical reaction causes the photosensitive film layer below the area to shrink and recess, the fluorescent film layer above the area synchronously sinks, and the construction of a periodic micro-nano topological structure is realized. The periodic micro-nano topological structure can utilize the synergistic spatial confinement effect generated by the stress field superposition between adjacent recessed units, force aggregation-induced emission units to significantly inhibit intramolecular rotation and vibration and block non-radiative transition channels in a high-density and orderly stacking state, so that the fluorescence intensity is greatly improved without additional access to chemical modification groups and introduction of foreign additives.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials technology, and in particular to a fluorescent thin film based on micro / nano topological structure to enhance aggregation-induced emission, its preparation method and application. Background Technology

[0002] Aggregation-induced emission (AIE) has overcome the limitation of fluorescence quenching caused by aggregation of traditional fluorescent molecules due to their significantly enhanced fluorescence in the aggregated state, opening up new avenues for high-efficiency solid-state luminescent materials and showing broad application prospects in optoelectronic devices, bioimaging, chemical sensing, and anti-counterfeiting. However, the fluorescence intensity of existing AIE molecules is still relatively low, and how to achieve a secondary amplification of the solid-state luminescence efficiency of AIE molecules remains a current research hotspot.

[0003] Although various strategies have been attempted to address this issue, they are generally difficult to scale up for production. Most of them rely on chemical modification of aggregation-induced emission molecules (such as adding large-volume substituents or other additional groups) or blending with foreign components, which not only increases the complexity of the system but may also affect the intrinsic properties of the material.

[0004] Therefore, there is an urgent need in this field for a method that can be mass-produced to achieve enhanced aggregation-induced emission without chemical modification or blending, but only through physical structure regulation. Summary of the Invention

[0005] The purpose of this invention is to provide a fluorescent thin film based on micro-nano topology to enhance aggregation-induced emission, as well as its preparation method and application, in order to solve the problem that existing aggregation-induced emission thin films rely on chemical modification of aggregation-induced emission molecules (i.e. aggregation-induced emission units) or blending with foreign components to achieve fluorescence gain, resulting in complex systems, high costs and difficulty in large-scale production.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention is a method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission, comprising the following steps:

[0008] A photosensitive polymer solution is coated onto the substrate surface and then dried to form a photosensitive thin film layer.

[0009] A fluorescent polymer solution is coated on the surface of the photosensitive thin film layer and dried to form a fluorescent thin film layer, thus obtaining a photosensitive layer / fluorescent layer bilayer composite film.

[0010] By selectively exposing the photosensitive layer / fluorescent layer bilayer composite film, a periodic micro-nano topological structure is constructed on the surface of the film, thereby obtaining the fluorescent thin film based on the micro-nano topological structure-enhanced aggregation-induced emission.

[0011] The photosensitive polymer in the photosensitive polymer solution is obtained by covalently attaching a photosensitive compound to the polymer backbone;

[0012] The fluorescent polymer in the fluorescent polymer solution is obtained by covalently attaching an aggregation-induced emission compound to the polymer backbone.

[0013] This invention first prepares a photosensitive / fluorescent bilayer composite film, then selectively exposes it. During exposure, the photosensitive units in the photosensitive polymer in the exposed region undergo photochemical reactions to form hydrogen bonds with the polymer backbone. The resulting stress causes the photosensitive film layer below this region to shrink and sink, and the fluorescent film layer above it sinks synchronously, forming a recessed structure on the composite film, thus realizing the construction of a periodic micro / nano topological structure. The periodic micro / nano topological structure can utilize the synergistic spatial confinement effect generated by the superposition of stress fields between adjacent recessed units to force aggregation-induced emission units to significantly suppress intramolecular rotation and vibration and block non-radiative transition channels in a high-density, ordered stacking state, thereby greatly improving fluorescence intensity without the addition of chemical modification groups or the introduction of external additives.

[0014] Furthermore, the structural formula of the photosensitive compound is as follows: ;

[0015] The structural formula of the aggregation-induced emission compound is: ;

[0016] The polymer includes polyurethane or polyamic acid.

[0017] When a photosensitive compound is incorporated into the polyurethane backbone, photosensitive polyurethane is obtained, with the photosensitive compound serving as the photosensitive unit of the photosensitive polyurethane. Similarly, when a photosensitive compound is incorporated into the polyamic acid backbone, photosensitive polyamic acid is obtained, with the photosensitive compound serving as the photosensitive unit of the photosensitive polyamic acid. When an aggregation-induced emission (AIE) compound is incorporated into the polyurethane backbone, fluorescent polyurethane is obtained, with the AIE serving as the AIE unit of the fluorescent polyurethane. Likewise, when an AIE compound is incorporated into the polyamic acid backbone, fluorescent polyamic acid is obtained, with the AIE serving as the AIE unit of the fluorescent polyamic acid.

[0018] Furthermore, the preparation step of the photosensitive polymer solution includes: mixing the photosensitive compound with a monomer that forms a polyurethane or polyamic acid backbone and a solvent, and then reacting to obtain the photosensitive polymer solution.

[0019] Furthermore, the preparation step of the fluorescent polymer solution includes: mixing the aggregation-induced emission compound with monomers that form polyurethane or polyamic acid backbones and solvents, and obtaining the fluorescent polymer solution after reaction.

[0020] Further, the monomers forming the polyurethane main chain include polyisocyanates and polyols; the monomers forming the polyamic acid main chain include dianhydride monomers and diamine monomers; the solvent includes N,N-dimethylformamide or N,N-dimethylacetamide.

[0021] Optionally, the polyisocyanate includes at least one of toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and p-phenylene diisocyanate; the polyol includes at least one of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,8-octanediol.

[0022] Optionally, the dianhydride monomer includes at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4-oxydiphthalic anhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride; the diamine monomer includes at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxyphenyl)]hexafluoropropane, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl and 1,3-bis(3-aminophenoxy)benzene.

[0023] Optionally, when preparing the photosensitive polyurethane solution, the molar ratio of the polyisocyanate, the photosensitive compound and the polyol is 10:a:(10-a), where 0<a≤3; the total mass fraction of the polyisocyanate, the photosensitive compound and the polyol in the reaction system is 20-40% (that is, the mass fraction of the solvent is 60-80%); the reaction conditions include: stirring and reacting in an ice water bath at 0-5°C for 9-12h, then heating up to 60°C and continuing the stirring reaction for 12-15h.

[0024] Optionally, when preparing the photosensitive polyamic acid solution, the molar ratio of the dianhydride monomer, the photosensitive compound and the diamine monomer is 7:b:(7-b), where 0<b≤2; the total mass fraction of the dianhydride monomer, the photosensitive compound and the diamine monomer in the reaction system is 20-40%; the reaction conditions include: stirring and reacting in an ice water bath at 0-5°C for 12-15h.

[0025] Optionally, when preparing the fluorescent polyurethane solution, the molar ratio of the polyisocyanate, the aggregation-induced emission compound and the polyol is 10:c:(10-c), where 0<c≤0.5; the total mass fraction of the polyisocyanate, the aggregation-induced emission compound and the polyol in the reaction system is 20-40%; the reaction conditions include: stirring and reacting in an ice water bath at 0-5°C for 9-12h, then heating up to 60°C and continuing the stirring reaction for 12-15h.

[0026] Optionally, when preparing the fluorescent polyamic acid solution, the molar ratio of the dianhydride monomer, the aggregation-induced emission compound and the diamine monomer is 7:d:(7-d), where 0<d≤0.3; the total mass fraction of the dianhydride monomer, the aggregation-induced emission compound and the diamine monomer in the reaction system is 20-40%; the reaction conditions include stirring and reacting in an ice water bath at 0-5°C for 12-15h.

[0027] Preferably, the structural formula of the photosensitive polymer is or .

[0028] Preferably, the structural formula of the fluorescent polymer is or .

[0029] Further, before coating the photosensitive polymer solution on the surface of the substrate, the method further comprises pretreating the substrate, and the pretreatment includes ultrasonic cleaning and ultraviolet ozone treatment.

[0030] Optionally, the substrate comprises glass, a silicon wafer or a quartz wafer.

[0031] Optionally, the ultrasonic cleaning is specifically ultrasonic cleaning in acetone, isopropanol and water in sequence, and after the ultrasonic cleaning, a step of drying with nitrogen is further included.

[0032] Optionally, the ultraviolet ozone treatment is specifically performed by jointly irradiating with dual-wavelength ultraviolet light of 185 nm and 254 nm for 10-20 min.

[0033] Optionally, the coating method comprises spin coating, blade coating or solution casting.

[0034] Further, constructing a periodic micro-nano topological structure on the surface of the photosensitive layer / fluorescent layer double-layer composite film through selective exposure comprises: closely attaching an ultraviolet light-transmitting mask with a micron-scale periodic pattern to the upper surface of the photosensitive layer / fluorescent layer double-layer composite film, and performing selective exposure by using ultraviolet light to form an initial recessed structure on the photosensitive layer / fluorescent layer double-layer composite film; the line width of the micron-scale periodic pattern is 1 μm-10 μm, the line spacing is 1 μm-10 μm (the period, that is, "line width + line spacing" is 2 μm-20 μm); the wavelength range of the light source for the selective exposure is 100 nm-400 nm, the exposure time is 10 s-600 s, and the exposure power is 20 W-30 W.

[0035] When selective exposure is performed with ultraviolet light, the photosensitive units in the photosensitive polymer in the exposed area undergo a photochemical reaction to form hydrogen bonds with the polymer main chain, the generated stress causes the photosensitive thin film layer in this area to shrink and recess, and the overlying fluorescent thin film layer sinks synchronously accordingly, so as to form an initial recessed structure (that is, an initial periodic micro-nano topological structure) on the composite film.

[0036] Furthermore, after the selective exposure is completed, the process further includes immersing the selectively exposed photosensitive layer / fluorescent layer bilayer composite film in an organic solvent and then drying it, so as to further deepen the recessed structure of the exposed area.

[0037] Optionally, the organic solvent includes at least one selected from methanol, ethanol, propanol, acetonitrile, acetone, and petroleum ether.

[0038] Organic solvents can dissolve the residual solvent in the photosensitive film layer, inducing the polymer network to become denser, thereby further deepening the recessed structure of the exposed area, and the upper fluorescent film layer sinks synchronously.

[0039] Furthermore, the depth of the periodic micro / nano topology (i.e., the depth of the recessed structure) is 10nm-1000nm.

[0040] Furthermore, the thickness of the photosensitive thin film layer is 1-50 μm.

[0041] Furthermore, the thickness of the fluorescent thin film layer is 1-50 μm.

[0042] Optionally, the drying temperature is 80°C.

[0043] The second technical solution of the present invention: a fluorescent thin film based on micro-nano topology-enhanced aggregation-induced emission prepared by the above-described method for preparing fluorescent thin films based on micro-nano topology-enhanced aggregation-induced emission.

[0044] The third technical solution of the present invention: the application of the above-mentioned fluorescent thin film based on micro-nano topology-enhanced aggregation-induced emission in the fields of pattern anti-counterfeiting or sensing.

[0045] This invention utilizes photoinduced bilayer composite film deformation technology, employing a mask with micrometer-level linewidth and spacing to precisely control geometric parameters. This allows for the construction of micro / nano topologies (i.e., recessed arrays) with controllable periodicity and morphology on the surface of polymer films containing aggregation-induced emission units (AIEs). These periodic micro / nano topologies create a large-area, uniformly distributed localized geometric constraint environment on the film surface. Compared to isolated or randomly distributed micro / nano structures, the periodically arranged micro / nano topologies (i.e., recessed arrays) generate a synergistic spatial confinement effect: the stress fields between adjacent recessed units superimpose, forming a more uniform and intense compressive force field, forcing AIEs to achieve high-density, ordered stacking throughout the patterned region. This ordered periodic structure significantly enhances the intramolecular motion confinement effect, utilizing physical spatial confinement to significantly suppress intramolecular rotation and vibration, and block non-radiative transition channels. This results in a substantial increase in fluorescence intensity without the addition of any additives or chemical modification groups, maximizing the advantages of physical spatial confinement for fluorescence amplification.

[0046] The present invention discloses the following technical effects:

[0047] This invention eliminates the need for chemical modification or blending of aggregate-induced emission units (AELs). Instead, it constructs periodic micro / nano topologies on the surface of a fluorescent polymer film. Utilizing the synergistic spatial confinement effect generated by the superposition of stress fields between adjacent recessed units, the AELs are forced into a high-density, ordered stacking state, significantly suppressing intramolecular rotation and vibration and blocking non-radiative transition channels. This results in a substantial increase in fluorescence intensity without the addition of chemical modification groups or external additives. Furthermore, this method simultaneously achieves fluorescence enhancement and high-precision patterning. The process is simple, low-cost, and easily scalable, avoiding the complex processes and high costs of existing technologies. This provides a novel technical solution for the preparation of high-performance solid-state luminescent films and their applications in patterned anti-counterfeiting and sensing. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 An atomic force microscope image of the fluorescent thin film prepared in Example 1.

[0050] Figure 2 The fluorescence emission spectrum of the fluorescent thin film prepared in Example 1 is shown.

[0051] Figure 3 The image shows the fluorescent film prepared in Example 1 under 365nm ultraviolet light irradiation.

[0052] Figure 4 An atomic force microscope image of the fluorescent thin film prepared in Example 2.

[0053] Figure 5 The fluorescence emission spectrum of the fluorescent thin film prepared in Example 2 is shown.

[0054] Figure 6 This is a photograph of the fluorescent thin film prepared in Example 2 under 365nm ultraviolet light irradiation.

[0055] Figure 7 An atomic force microscope image of the fluorescent thin film prepared for Comparative Example 1.

[0056] Figure 8 The fluorescence emission spectrum of the fluorescent thin film prepared in Comparative Example 1 is shown.

[0057] Figure 9 The UV-Vis absorption spectra of the fluorescent thin film prepared for Comparative Example 1 before and after irradiation with 365nm UV light are shown.

[0058] Figure 10 This is a schematic diagram illustrating the principle of the internal filtration effect of the fluorescent thin film prepared for Comparative Example 1 after irradiation with 365nm ultraviolet light.

[0059] Figure 11 A photograph of the fluorescent thin film prepared for Comparative Example 1 under 365nm ultraviolet light irradiation. Detailed Implementation

[0060] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0061] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0062] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0063] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0064] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0065] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0066] In specific embodiments of the present invention, room temperature is referred to as 20-30°C unless otherwise specified.

[0067] All raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0068] Example 1

[0069] A fluorescent thin film based on micro / nano topological structure to enhance aggregation-induced emission is prepared by the following steps:

[0070] (1) Substrate pretreatment: The glass was ultrasonically cleaned in acetone, isopropanol and deionized water for 10 min (ultrasonic power of 200W), dried with nitrogen, and then subjected to ultraviolet ozone treatment (using 185nm and 254nm dual-wavelength ultraviolet light for 15 min) to enhance the adhesion of subsequent coatings.

[0071] (2) Photosensitive compound (i.e. photosensitive unit) is covalently attached to the polyurethane backbone to obtain photosensitive polyurethane solution; the photosensitive polyurethane solution is spin-coated onto the pretreated glass surface and baked at 80°C for 5 min to form a photosensitive thin film layer with an average thickness of 3 μm.

[0072] The specific preparation steps of the photosensitive polyurethane solution are as follows: Under anhydrous and nitrogen-protected conditions, 22.18 kg (20 mol) of the photosensitive compound, 34.83 kg (200 mol) of toluene-2,4-diisocyanate, and 21.27 kg (180 mol) of 1,6-hexanediol were added to a reactor containing 182.65 kg of N,N-dimethylformamide. The mixture was stirred and reacted in an ice-water bath at 0-5°C for 9 h, followed by heating to 60°C and continuing stirring for 12 h to obtain the photosensitive polyurethane solution. The specific synthetic route is as follows:

[0073] .

[0074] (3) The aggregation-induced emission compound (i.e. aggregation-induced emission unit) is covalently attached to the polyurethane backbone to obtain a fluorescent polyurethane solution; the fluorescent polyurethane solution is spin-coated onto the photosensitive film layer and baked at 80°C for 5 min to form a fluorescent film layer with an average thickness of 3 μm, thus obtaining a photosensitive layer / fluorescent layer bilayer composite film.

[0075] The specific preparation steps of the fluorescent polyurethane solution are as follows: Under anhydrous and nitrogen-protected conditions, 0.72 kg (2 mol) of aggregation-induced luminescence compound, 34.83 kg (200 mol) of toluene-2,4-diisocyanate, and 23.4 kg (198 mol) of 1,6-hexanediol were added to a reactor containing 137.55 kg of N,N-dimethylformamide. The mixture was stirred in an ice-water bath at 0-5°C for 9 h, and then the temperature was raised to 60°C and the reaction was continued with stirring for 12 h. The specific synthetic route is as follows:

[0076] .

[0077] (4) A UV photomask with a periodic pattern (the line width of the transparent part is 2.5 μm, the line spacing is 2.5 μm, and the period is 5 μm) is attached tightly to the upper surface of the photosensitive layer / fluorescent layer double composite film (i.e. the surface of the fluorescent thin film layer). UV light with a wavelength of 365 nm is used as the exposure source. For easy comparison, the right side of the film is selectively exposed to UV light for 10 s with an exposure power of 30 W. The left side of the film is not exposed as a control.

[0078] (5) After the photosensitive layer / fluorescent layer double-layer composite film was exposed, it was immersed in acetonitrile for 2 seconds and then dried to obtain a fluorescent film with a periodic micro-nano topological structure, which is a fluorescent film based on micro-nano topological structure to enhance aggregation-induced emission.

[0079] Figure 1The images shown are atomic force microscopy (AFM) images of the fluorescent thin film prepared in Example 1. The left side represents the region without micro / nano topological structures, while the right side represents the region with periodic micro / nano topological structures. It can be seen that after selective ultraviolet exposure and immersion in an organic solvent, the right side of the fluorescent thin film forms a periodic micro / nano topological structure with a linewidth of 2.5 μm, a line spacing of 2.5 μm, and an average depth of 145 nm. The untreated area on the left side remains flat. This indicates that the exposed area causes the photosensitive thin film layer to cause indentation in the fluorescent thin film layer, while the unexposed area remains unchanged.

[0080] Figure 2 The fluorescence emission spectrum of the fluorescent film prepared in Example 1 shows that the periodic micro-nano topological structure on the right (i.e., 2.5 μm-2.5 μm in the figure) suppresses the intramolecular motion of aggregation-induced emission units through the physical spatial confinement effect, resulting in a significant increase in fluorescence intensity of 61513 CPS compared to the region without micro-nano topological structure on the left (171432 CPS and 109919 CPS, respectively), thereby achieving enhanced aggregation-induced emission.

[0081] Figure 3 The image shows a photograph of the fluorescent film prepared in Example 1 under 365nm ultraviolet light irradiation. The left side represents the region without micro / nano topological structures, while the right side represents the region with periodic micro / nano topological structures. It can be seen that the fluorescence intensity of the periodic micro / nano topological structure region on the right is significantly stronger than that of the flat region without micro / nano topological structures on the left.

[0082] Example 2

[0083] A fluorescent thin film based on micro / nano topological structure to enhance aggregation-induced emission is prepared by the following steps:

[0084] (1) Substrate pretreatment: The quartz sheet was ultrasonically cleaned in acetone, isopropanol and deionized water for 10 min (ultrasonic power of 200W), dried with nitrogen, and then subjected to ultraviolet ozone treatment (irradiated with 185nm and 254nm dual-wavelength ultraviolet light for 15 min) to enhance the adhesion of subsequent coatings.

[0085] (2) Photosensitive compound (i.e. photosensitive unit) is covalently attached to the polyamic acid backbone to obtain photosensitive polyamic acid solution; the photosensitive polyamic acid solution is cast onto the surface of the pretreated quartz sheet and baked at 80°C for 120 min to form a photosensitive thin film layer with an average thickness of 30 μm.

[0086] The specific preparation steps of the photosensitive polyamic acid solution are as follows: Under anhydrous and nitrogen-protected conditions, 22.18 kg (20 mol) of the photosensitive compound, 30.54 kg (140 mol) of pyromellitic dianhydride, and 24.03 kg (120 mol) of 4,4'-diaminodiphenyl ether were added to a reaction vessel containing 179.08 kg of N,N-dimethylacetamide, and the mixture was stirred and reacted in an ice-water bath at 0-5℃ for 12 h. The specific synthetic route is as follows:

[0087] .

[0088] (3) The aggregation-induced emission compound (i.e. aggregation-induced emission unit) is covalently attached to the polyamic acid backbone to obtain a fluorescent polyamic acid solution; the fluorescent polyamic acid solution is cast on the photosensitive film layer and baked at 80°C for 120 min to form a fluorescent film layer with an average thickness of 30 μm, thus obtaining a photosensitive layer / fluorescent layer bilayer composite film.

[0089] The specific preparation steps of the fluorescent polyamic acid solution are as follows: Under anhydrous and nitrogen-protected conditions, 0.72 kg (2 mol) of aggregation-induced emission compound, 30.54 kg (140 mol) of pyromellitic dianhydride, and 27.63 kg (138 mol) of 4,4'-diaminodiphenyl ether were added to a reactor containing 137.41 kg of N,N-dimethylacetamide, and the mixture was stirred in an ice-water bath at 0-5°C for 12 h. The specific synthetic route is as follows:

[0090] .

[0091] (4) A UV photomask with a periodic pattern (the line width of the transparent part is 6μm, the line spacing is 6μm, and the period is 12μm) is attached tightly to the upper surface of the photosensitive layer / fluorescent layer double-layer composite film (i.e. the surface of the fluorescent thin film layer). UV light with a wavelength of 365nm is used as the exposure source. The central square pattern area of ​​the photosensitive layer / fluorescent layer double-layer composite film is selectively exposed to UV light for 60s and the exposure power is 30W. The area outside the central square pattern is not exposed as a control.

[0092] (5) After the photosensitive layer / fluorescent layer double-layer composite film was exposed, it was soaked in ethanol for 5 seconds and then dried to obtain a fluorescent film with a periodic micro-nano topological structure, which is a fluorescent film based on micro-nano topological structure to enhance aggregation-induced emission.

[0093] Figure 4 The image shown is an atomic force microscope image of the fluorescent thin film prepared in Example 2. It can be seen that after selective ultraviolet exposure and immersion in organic solvent, the central square pattern region of the thin film forms a periodic micro-nano topological structure with a linewidth of 6 μm, a line spacing of 6 μm, and an average depth of 175 nm.

[0094] Figure 5 The fluorescence emission spectrum of the fluorescent film prepared in Example 2 shows that the periodic micro-nano topological structure in the square pattern region (i.e., 6μm-6μm in the figure) suppresses the intramolecular motion of aggregation-induced emission units through the physical spatial confinement effect, making its fluorescence intensity significantly increased by 29713 CPS compared with the region without micro-nano topological structure outside the square pattern (the two are 137199 CPS and 107486 CPS, respectively), thereby achieving enhanced aggregation-induced emission.

[0095] Figure 6 The image shows a photograph of the fluorescent film prepared in Example 2 under 365nm ultraviolet light irradiation. The central square pattern represents a periodic micro / nano topological structure region, while the areas outside the central square pattern are regions without micro / nano topological structures. It can be seen that the fluorescence intensity of the micro / nano topological structure region within the square pattern is significantly stronger than that of the flat areas outside the square pattern without micro / nano topological structures.

[0096] Comparative Example 1

[0097] (1) Substrate pretreatment: The glass was ultrasonically cleaned in acetone, isopropanol and deionized water for 10 min (ultrasonic power of 200W), dried with nitrogen, and then subjected to ultraviolet ozone treatment (using 185nm and 254nm dual-wavelength ultraviolet light for 15 min) to enhance the adhesion of subsequent coatings.

[0098] (2) The photosensitive compound (i.e., the photosensitive unit) is covalently linked to the polyurethane backbone to obtain a photosensitive polyurethane solution. The specific preparation steps of the photosensitive polyurethane solution are as follows: Under anhydrous and nitrogen-protected conditions, 22.18 kg (20 mol) of the photosensitive compound, 34.83 kg (200 mol) of toluene-2,4-diisocyanate and 21.27 kg (180 mol) of 1,6-hexanediol are added to a reactor containing 182.65 kg of N,N-dimethylformamide. The mixture is stirred in an ice-water bath at 0-5℃ for 9 h, and then heated to 60℃ and stirred for another 12 h to obtain the photosensitive polyurethane solution. The specific synthetic route is as follows:

[0099] .

[0100] (3) The aggregation-induced emission compound (i.e., aggregation-induced emission unit) was covalently attached to the polyurethane backbone to obtain a fluorescent polyurethane solution. The specific preparation steps of the fluorescent polyurethane solution are as follows: Under anhydrous and nitrogen-protected conditions, 0.72 kg (2 mol) of the aggregation-induced emission compound, 34.83 kg (200 mol) of toluene-2,4-diisocyanate and 23.4 kg (198 mol) of 1,6-hexanediol were added to a reactor containing 137.55 kg of N,N-dimethylformamide and stirred in an ice-water bath at 0-5℃ for 9 h, followed by heating to 60℃ and stirring for another 12 h. The specific synthetic route is as follows:

[0101] .

[0102] (4) The above photosensitive polyurethane solution and fluorescent polyurethane solution are mixed and stirred for 5 hours. The resulting mixed solution is spin-coated onto the pretreated glass surface and then baked at 80°C for 5 minutes to form a photosensitive / fluorescent monolayer film with an average thickness of 3 μm.

[0103] (5) A UV photomask with a periodic pattern (the line width of the transparent part is 2.5 μm, the line spacing is 2.5 μm, and the period is 5 μm) is attached tightly to the surface of the photosensitive / fluorescent monolayer film. UV light with a wavelength of 365 nm is used as the exposure source. For easy comparison, the right side of the film is selectively exposed to UV light for 10 s with an exposure power of 30 W. The left side of the film is not exposed as a control.

[0104] (6) The exposed photosensitive / fluorescent monolayer film was immersed in acetonitrile for 2 seconds and then dried to obtain a fluorescent film with a periodic micro-nano topological structure.

[0105] Figure 7 The image shown is an atomic force microscope image of the fluorescent thin film prepared in Comparative Example 1. It can be seen that after selective ultraviolet exposure and immersion in organic solvent, a periodic micro-nano topological structure with a linewidth of 2.5 μm, a line spacing of 2.5 μm, and an average depth of 145 nm is formed on the right side of the fluorescent thin film.

[0106] Figure 8The fluorescence emission spectrum of the fluorescent film prepared in Comparative Example 1 is shown. The results show that although the periodic micro / nano topological structure on the right (i.e., 2.5 μm-2.5 μm in the figure) can suppress the intramolecular motion of aggregation-induced emission units through physical spatial confinement, the fluorescence intensity in the right region is significantly lower than that in the left region without the micro / nano topological structure by 58043 CPS (63766 CPS on the right, 121809 CPS on the left). This phenomenon is attributed to the structural transformation of the photosensitive unit after irradiation with 365 nm ultraviolet light. Specifically, the 1,4-dihydropyridine structure is transformed into the 2,6-dimethylpyridine structure, and this transformation product exhibits characteristic absorption in the 430-500 nm range (e.g., ...). Figure 9 The UV-Vis absorption spectra of the fluorescent film prepared in Comparative Example 1 before and after 365 nm UV irradiation are shown in the figure. This absorption band overlaps with the emission spectrum of the aggregation-induced emission unit, thus establishing an internal filtering effect, causing the emitted fluorescent photons to be absorbed by the 2,6-dimethylpyridine structure (e.g., ...). Figure 10 The schematic diagram shown in Comparative Example 1 illustrates the principle of the internal filtering effect after irradiation with 365nm ultraviolet light, which in turn causes a significant decrease in fluorescence intensity.

[0107] Figure 11 The image shows a photograph of the fluorescent film prepared in Comparative Example 1 under 365nm ultraviolet light irradiation. The left side represents the region without micro / nano topological structures, while the right side represents the region with periodic micro / nano topological structures. It can be seen that the fluorescence intensity on the right side is significantly weaker than that on the left.

[0108] In summary, the fabrication of a photosensitive / fluorescent bilayer composite film offers the following significant advantages: First, the spatial separation of the photosensitive and fluorescent thin film layers effectively avoids direct internal filtering interference from the photoconversion products of the photosensitive unit on fluorescence emission. Simultaneously, the shrinkage deformation of the photosensitive thin film layer can be precisely transferred to the fluorescent thin film layer, enabling simultaneous construction of the micro / nano topology and independent control of fluorescence performance. Second, the bilayer structure provides greater structural design freedom. The photosensitive thin film layer can focus on stress response and deformation-driven processes, while the fluorescent thin film layer specializes in efficient luminescence. Their functions are complementary and independent, thus ensuring both fluorescence enhancement and precise control of the micro / nano topological morphology.

[0109] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission, characterized in that, Includes the following steps: A photosensitive polymer solution is coated onto the substrate surface and then dried to form a photosensitive thin film layer. A fluorescent polymer solution is coated on the surface of the photosensitive thin film layer and dried to form a fluorescent thin film layer, thus obtaining a photosensitive layer / fluorescent layer bilayer composite film. By selectively exposing the photosensitive layer / fluorescent layer bilayer composite film, a periodic micro-nano topological structure is constructed on the surface of the film, thereby obtaining the fluorescent thin film based on the micro-nano topological structure-enhanced aggregation-induced emission. The photosensitive polymer in the photosensitive polymer solution is obtained by covalently attaching a photosensitive compound to the polymer backbone; The fluorescent polymer in the fluorescent polymer solution is obtained by covalently attaching an aggregation-induced luminescence compound to the polymer backbone. The polymer is polyurethane or polyamic acid; The structural formula of the photosensitive compound is: ; The structural formula of the aggregation-induced emission compound is: ; The preparation steps of the photosensitive polymer solution include: mixing the photosensitive compound with a monomer that forms a polyurethane or polyamic acid backbone and a solvent, and then reacting to obtain the photosensitive polymer solution. The preparation steps of the fluorescent polymer solution include: mixing the aggregation-induced emission compound with monomers that form polyurethane or polyamic acid backbones and solvents, and then reacting to obtain the fluorescent polymer solution.

2. The method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission as described in claim 1, characterized in that, The monomers forming the polyurethane backbone include polyisocyanates and polyols; the monomers forming the polyamic acid backbone include dianhydride monomers and diamine monomers; the solvent includes N,N-dimethylformamide or N,N-dimethylacetamide.

3. The method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission as described in claim 1, characterized in that, Before coating the substrate surface with the photosensitive polymer solution, the substrate is pretreated, including ultrasonic cleaning and ultraviolet ozone treatment.

4. The method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission as described in claim 1, characterized in that, Constructing a periodic micro / nano topological structure on the surface of the photosensitive / fluorescent bilayer composite film by selective exposure includes: attaching an ultraviolet-transmitting mask with a micrometer-scale periodic pattern tightly to the upper surface of the photosensitive / fluorescent bilayer composite film, and selectively exposing it with ultraviolet light; the linewidth of the micrometer-scale periodic pattern is 1μm-10μm, and the line spacing is 1μm-10μm; the wavelength range of the light source for selective exposure is 100nm-400nm, the exposure time is 10s-600s, and the exposure power is 20W-30W.

5. The method for preparing a fluorescent thin film based on micro / nano topological structure-enhanced aggregation-induced emission as described in claim 4, characterized in that, After the selective exposure is completed, the process also includes immersing the selectively exposed photosensitive layer / fluorescent layer bilayer composite film in an organic solvent and then drying it.

6. A fluorescent thin film based on micro-nano topology-enhanced aggregation-induced emission prepared by the method described in any one of claims 1-5.

7. The application of a fluorescent thin film based on micro / nano topology-enhanced aggregation-induced emission as described in claim 6 in the fields of pattern anti-counterfeiting or sensing.

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