A circularly polarized luminescent multilayer assembly film and preparation method thereof

Abstract

The present invention provides a circularly polarized luminescent multilayer assembled film and a preparation method thereof. The circularly polarized luminescent multilayer assembled film comprises a fluorescent layer and an optically active layer stacked together; the fluorescent layer comprises a first flexible polymer film and a fluorescent dye distributed within the first flexible polymer film; the optically active layer comprises at least two layers of hybrid oriented films, each comprising a second flexible polymer film and a one-dimensional metal nanomaterial distributed within the second flexible polymer film and arranged in an oriented manner, wherein both the second flexible polymer film and the one-dimensional metal nanomaterial are achiral; the layers of the hybrid oriented films are stacked and arranged at a preset deflection angle along the orientation axis of the one-dimensional metal nanomaterial. The circularly polarized luminescent multilayer assembled film can achieve full parameter control of CPL wavelength, intensity, and handedness.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of circularly polarized luminescent chiral thin film materials, and relates to a circularly polarized luminescent multilayer assembly film with multicolor and efficient controllability and a preparation method thereof. Background Art

[0002] Chiral optical materials, due to their unique ability to control the circular polarization of light (including circularly polarized absorption (CD) and circularly polarized luminescence (CPL)), play an increasingly important role in polarization display, information encryption, and smart sensing. Compared with conventional fluorescent materials, CPL materials can significantly improve information security because they can deeply modulate fluorescence in a higher-dimensional polarization state. However, this also places higher demands on the basic performance of CPL materials, such as: high luminescence asymmetry factor ( g lum ), multicolor CPL, excellent environmental stability, etc. In recent years, researchers have done a lot of research on circularly polarized luminescent materials, including chiral organic small molecules, chiral inorganic nanoparticles, supramolecular assemblies and bulk films ( CCS Chem. 2024, 6, 518-527, Angew. Chem. Int. Ed. 2024, e202407385 However, for most chiral molecules and even supramolecular materials, the available g lum Values ​​are usually weak (10 -4 -10 -2 ), and the regulation of CPL is difficult and complicated. In addition, it is relatively difficult to obtain multi-color CPL covering multiple bands.

[0003] Using a multilayer assembly strategy based on the “matching rule”, CPL can be easily and efficiently obtained by utilizing the overlap of the emission-absorption bands of the fluorescent layer and the chiral layer without any chemical interaction between the two ( Macromolecules 2019, 52, 376-384 This strategy breaks the shortcomings of traditional methods of using chemical / physical interactions to construct CPL materials, which are complex and poorly controllable, making the design and preparation of CPL materials simpler and richer. g lum Can reach 10 -1 However, since the chirality comes from intrinsic chiral materials such as chiral polymers and supramolecular materials, it is still impossible to efficiently adjust the CPL characteristic parameters such as sign, intensity, and wavelength. In addition, higher CPL can be obtained by assembling fluorescent dye molecules with cholesteric liquid crystals (such as cellulose nanocrystals CNC) layer by layer. g lum (>10 0However, the inherent environmental stability of liquid crystal materials (such as water resistance and high temperature resistance) hinders their application in many practical scenarios. Secondly, due to the inherent chirality (left-handed structure) formed during the assembly process of cholesteric liquid crystals, the direction of CPL is difficult to adjust (only right-handed CPL is produced). Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a circularly polarized luminescent multilayer assembly film and a preparation method thereof, wherein the circularly polarized luminescent multilayer assembly film can achieve full parameter control of CPL wavelength (i.e., color), intensity and rotation direction.

[0005] The present invention is achieved through the following technical solutions:

[0006] A circularly polarized luminescent multilayer assembled film comprises a fluorescent layer and an optically active layer stacked together; the fluorescent layer comprises a first flexible polymer film and a fluorescent dye distributed in the first flexible polymer film; the optically active layer comprises at least two layers of hybrid oriented films, each comprising a second flexible polymer film and a one-dimensional metal nanomaterial distributed in the second flexible polymer film and arranged in an orientation, wherein both the second flexible polymer film and the one-dimensional metal nanomaterial are achiral; the layers of the hybrid oriented films are stacked and arranged at a preset deflection angle along the orientation axis of the one-dimensional metal nanomaterial.

[0007] Preferably, the fluorescent dye is Nile red, coumarin, fluoroboron dipyrrole or rhodamine.

[0008] Preferably, the first flexible polymer film is a polymethyl methacrylate film or a polyvinyl alcohol film, and the second flexible polymer film is a polyvinyl alcohol film.

[0009] Preferably, the mass of the fluorescent dye accounts for 0.01% to 1% of the mass of the first flexible polymer film.

[0010] Preferably, the mass of the one-dimensional metal nanomaterial accounts for 0.08% to 0.24% of the mass of the second flexible polymer film.

[0011] Preferably, the one-dimensional metal nanomaterial is gold or silver.

[0012] Preferably, the one-dimensional metal nanomaterial has a morphology of nanorods or nanowires.

[0013] Preferably, the deflection angle between the uppermost hybrid alignment film and the lowermost hybrid alignment film is in the range of 0° to ±180°, and is not 0°±A90°, where A is a constant.

[0014] The method for preparing the circularly polarized luminescent multilayer assembled film of the present invention comprises:

[0015] Mixing a fluorescent dye and a first polymer in a solvent to obtain a first mixed solution; drying the first mixed solution to form a film to obtain a fluorescent layer;

[0016] Mixing a second polymer and a one-dimensional metal nanomaterial in a solvent to obtain a second blend solution; drying the second blend solution to form a film to obtain a hybrid film; axially stretching the hybrid film in one direction at a preset stretch ratio to obtain a hybrid oriented film; stacking a plurality of the hybrid oriented films along the orientation axis at a preset deflection angle to obtain an optically active layer;

[0017] The fluorescent layer and the optically active layer are stacked together in sequence to obtain a circularly polarized luminescent multilayer assembly film.

[0018] Preferably, the preset draft ratio is 100% to 500%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The circularly polarized luminescent multilayer assembled film of the present invention does not rely on any chiral template. It is based on completely non-chiral building units, utilizes single-layer orientation, "matching rules" to assemble layer by layer, and is obtained by an efficient method of twisted stacking. The CPL of the circularly polarized luminescent multilayer assembled film of the present invention is generated by the optical coupling of the fluorescent layer and the optically active layer. The fluorescent layer is first excited by ultraviolet light to produce fluorescent color. The optically active layer can selectively absorb left-handed / right-handed fluorescence of the corresponding band and output the corresponding right-handed / left-handed fluorescence to achieve circularly polarized luminescence. The one-dimensional metal nanomaterial is uniformly distributed in the second flexible polymer film instead of being concentrated and distributed on the surface of the film, so that the CD peak band of the optically active layer matches the band emitted by the fluorescent layer, thereby obtaining a circularly polarized luminescent multilayer assembled film with high CPL intensity. The circularly polarized luminescent multilayer assembled film of the present invention has high CPL intensity (>1000 mdeg), high g lum (>0.3). By selecting fluorescent layers with different emission wavelengths, multicolor and white CPL covering the entire visible range can be achieved. By adjusting the content of fluorescent dyes and one-dimensional metal nanomaterials and the deflection angle, the direction, size, and other characteristic parameters of the CPL can be simply and efficiently controlled. Furthermore, this circularly polarized luminescent multilayer assembled film exhibits excellent thermal stability, with a maximum operating temperature of 110°C without any degradation of its optical properties. It also exhibits excellent light resistance and environmental durability. After 72 hours of irradiation with UV-365nm light and 50 days of exposure to ambient conditions, the CPL spectrum of the circularly polarized luminescent multilayer assembled film shows little change. Finally, the excellent mechanical properties of this circularly polarized luminescent multilayer assembled film (tensile strength: 216 MPa, elongation at break: 27%) will greatly enhance the material's basic performance and application range.

[0021] Furthermore, by selecting fluorescent dyes with different emission wavelengths, the CPL color of the circularly polarized luminescent multilayer assembly film can be controlled to obtain circularly polarized luminescent multilayer assembly films with different CPL colors.

[0022] Furthermore, by regulating the content of fluorescent dyes and one-dimensional metal nanomaterials, the CPL intensity of the circularly polarized luminescent multilayer assembled film can be controlled.

[0023] Furthermore, the rotational regulation of the deflection angle of the hybrid oriented film can realize the control of the intensity and direction (left-handed / right-handed) of the circularly polarized luminescent multilayer assembled film CPL.

[0024] The preparation method of the circularly polarized luminescent multilayer assembly film of the present invention is simple, low-cost, and highly universal, and has great application potential in the fields of information encryption, polarization display, and the like in the future.

[0025] Furthermore, the CPL intensity can be controlled by regulating the degree of orientation (drawing ratio) in the hybrid oriented film. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is an SEM image of the PVA-AuNRs hybrid film after axial stretching described in Example 1 of the present invention.

[0028] Figure 2 Polarization extinction spectra of PVA-AuNRs stacked films at different deflection angles (a) and the variation statistics of extinction intensity with deflection angle (b).

[0029] Figure 3 : These are the CD spectra corresponding to the PVA-AuNRs stacked film described in Example 1 of the present invention at different interlayer angles (±15°, ±30°, ±45°).

[0030] Figure 4 The CD spectrum (a) of the PVA-AuNRs stacked film obtained by surface coating of AuNR solution in Comparative Example 1 and the CPL spectrum (b) of its circularly polarized luminescent multilayer assembled film.

[0031] Figure 5 1 and 2. The fluorescence emission spectra (a) of the different fluorescent layers described in Example 2 of the present invention and the fluorescence color images (b) of the corresponding fluorescent solutions under 365 nm ultraviolet excitation are shown.

[0032] Figure 6 The CPL spectra (a) and the CPL intensity and direction variation statistics (b) of the circularly polarized luminescent multilayer assembled film prepared from PVA-AuNRs stacked films with different deflection angles (±15°, ±30°, ±45°) in Example 3 of the present invention.

[0033] Figure 7 This is the CPL spectrum of the circularly polarized luminescent multilayer assembled film based on different fluorescent layers and PVA-AuNRs stacked films in Example 4 of the present invention.

[0034] Figure 8 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film of the present invention, which is assembled with a Nile red fluorescent layer and a PVA-AuNRs stacked film with an angle of -30°, at different operating temperatures.

[0035] Figure 9 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film obtained by the present invention under different UV-365nm irradiation time.

[0036] Figure 10 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film obtained by the present invention when placed in a standard environment (RH=50%, T=25°C) for different time periods.

[0037] Figure 11 This is the stress-strain curve of the single-layer PVA-AuNRs stacked film of the present invention with a stretching ratio of 450%, as well as a physical picture showing its bendability and flexibility.

[0038] Figure 12 These are the CPL spectra (a) of the circularly polarized luminescent multilayer assembled films with different fluorescent dye contents in Example 5, the CPL spectra (b) of the circularly polarized luminescent multilayer assembled films with different AuNRs contents in Example 6, and the CPL spectra (c) of the circularly polarized luminescent multilayer assembled films with different stretching ratios in Example 7. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0041] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the invention.

[0042] Furthermore, it should be noted that the terms "first," "second," and the like are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Furthermore, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, for example, to mean a fixed connection or a detachable connection; a direct connection or an indirect connection through an intermediate medium; or internal communication between two components.

[0043] The circularly polarized luminescent multilayer assembled film described in the present invention includes a fluorescent layer and an optically active layer stacked together; the fluorescent layer includes a first flexible polymer film and a fluorescent dye distributed in the first flexible polymer film; the optically active layer includes at least two layers of hybrid oriented films, each of which includes a second flexible polymer film and a one-dimensional metal nanomaterial distributed in the second flexible polymer film matrix and arranged in an oriented manner, wherein the second flexible polymer film and the one-dimensional metal nanomaterial are both achiral; each layer of the hybrid oriented film is stacked and arranged at a preset deflection angle along the orientation axis of the one-dimensional metal nanomaterial.

[0044] In the present invention, the deflection angle between the topmost hybrid alignment film and the bottommost hybrid alignment film is within the range of 0° to ±180°, and is not 0°±A90°, where A is a constant. Preferably, each layer of the hybrid alignment film deflects clockwise or counterclockwise.

[0045] In the circularly polarized luminescent multilayer assembled film of the present invention, the fluorescent dye accounts for 0.01% to 1% of the mass of the first flexible polymer film; the one-dimensional metal nanomaterial accounts for 0.08% to 0.24% of the mass of the second flexible polymer film. The fluorescent dye content affects the FL intensity, which in turn affects the CPL. The amount of gold nanorods used affects the CD intensity, which in turn affects the CPL.

[0046] The fluorescent dye in the fluorescent layer of the present invention can be a common commercial fluorescent dye, such as Nile Red, rhodamine, coumarin, and BODIPY. In specific implementation, the fluorescent dye with the corresponding emission wavelength is selected according to the desired fluorescent color.

[0047] The first flexible polymer film for loading the fluorescent dye in the present invention may be a polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA) film.

[0048] The optically active layer of the present invention preferably comprises a PVA-AuNRs stacked film, which is formed by stacking at least two layers of PVA-AuNRs hybrid oriented films at a predetermined deflection angle along the orientation axis of the one-dimensional metal nanomaterial. The PVA-AuNRs hybrid oriented film is obtained by wet-stretching a PVA-AuNRs hybrid film of a certain thickness obtained by casting, followed by drying and shaping. The PVA-AuNRs hybrid film is obtained by physically blending an AuNRs solution and a PVA solution in a certain ratio, followed by drying to form a film.

[0049] In a specific embodiment of the present invention, the aspect ratio of AuNRs is preferably 1 to 4, and the aspect ratio is not 1 and 4, but preferably 2.

[0050] The circularly polarized luminescent multilayer assembled film of the present invention is prepared by a method comprising:

[0051] Mixing a fluorescent dye and a first polymer in a solvent to obtain a first mixed solution; drying the first mixed solution to form a film to obtain a fluorescent layer;

[0052] Mixing a second polymer and a one-dimensional metal nanomaterial in a solvent to obtain a second blend solution; drying the second blend solution to form a film to obtain a hybrid film; axially stretching the hybrid film in one direction at a preset stretch ratio to obtain a hybrid oriented film; stacking a plurality of the hybrid oriented films along the orientation axis at a preset deflection angle to obtain an optically active layer;

[0053] The fluorescent layer and the optically active layer are stacked together to obtain a circularly polarized luminescent multilayer assembly film.

[0054] As a preferred embodiment, the specific preparation method of the circularly polarized luminescent multilayer assembled film of the present invention comprises the following steps:

[0055] (1) Preparation of the fluorescent layer: According to the desired fluorescent color, take a fluorescent dye with the corresponding emission wavelength, stir it thoroughly and dissolve it in dichloromethane or water at room temperature to obtain a fluorescent dye solution of a certain concentration. Then weigh a certain amount of PMMA or PVA solution and blend it with the fluorescent dye solution in a certain proportion. Finally, pour a certain amount of the blended solution into a Petri dish and place it in an oven to dry to form a film.

[0056] (2) Preparation of PVA-AuNRs hybrid membrane: Physically blend the AuNRs solution with the PVA solution to obtain a uniform PVA-AuNRs solution. Pour a certain amount of the blended solution into a culture dish and place it in an oven to dry it into a membrane.

[0057] (3) Preparation of PVA-AuNRs hybrid oriented film: The PVA-AuNRs hybrid film was cut into rectangles and clamped on both sides of the homemade stretching device. After the hybrid film was fully wetted with pure water, it was axially stretched at a certain stretching ratio (100%~500%) and finally dried and shaped to obtain a PVA-AuNRs hybrid oriented film with a certain degree of orientation.

[0058] (4) Preparation of PVA-AuNRs stacked film: Take two or more PVA-AuNRs hybrid oriented films with a certain degree of orientation prepared in step (3), stack them along their axial orientation direction at a certain deflection angle (for example, 0°, ±15°, ±30°, ±45°) to obtain a PVA-AuNRs stacked film with a certain optical activity.

[0059] (5) Preparation of circularly polarized luminescent multilayer assembled film: The fluorescent layer of the required color segment and the PVA-AuNRs stacked film are stacked layer by layer to obtain a circularly polarized luminescent multilayer assembled film.

[0060] When in use, the fluorescent layer is placed in front of the excitation light path. When ultraviolet light excites the fluorescent layer to produce corresponding fluorescence, the optically active layer selectively absorbs the fluorescence to obtain circularly polarized luminescence.

[0061] Efficient control of the circularly polarized luminescent multilayer assembled film CPL:

[0062] First, by adjusting the fluorescence emission wavelength, the CPL color can be controlled, thereby achieving the aforementioned multicolor CPL goal. Second, by regulating the fluorescence intensity of the fluorescent layer, the CPL intensity can be regulated, and the fluorescence intensity can be controlled by the fluorescent dye content. Third, by rotating the hybrid oriented film, the CPL intensity and direction (left-handed / right-handed) can be controlled. Controlling the AuNRs content and the degree of orientation (drawdown ratio) in the hybrid oriented film can also control the CPL intensity. Finally, by adjusting the aspect ratio of the AuNRs in the hybrid oriented film, the CPL response band of the material can be controlled.

[0063] In the embodiment of the present invention, the basic optical activity (including CPL intensity, glum, coverage wavelength width, etc.) of the obtained circularly polarized light-emitting film is characterized using commercial CPL spectroscopy.

[0064] Example 1 Stacked films with different deflection angles

[0065] 5g of PVA particles were weighed and poured into 95g of pure water. The mixture was heated at 90°C and magnetically stirred at 1500 rpm for 3 hours. After the particles were completely dissolved, a PVA solution with a solid content of 5wt% was obtained. 20g of the prepared PVA solution was physically blended with 25mL of a solution of AuNRs with an aspect ratio of 2 at a certain concentration (0.1mg / mL). The mixture was magnetically stirred at 1500 rpm for 12 hours to obtain a PVA-AuNRs solution. The resulting PVA-AuNRs solution was poured into a 10cm×10cm Petri dish and dried in a 45°C oven. After drying, a uniform PVA-AuNRs hybrid film with a thickness of approximately 100μm was obtained.

[0066] The PVA-AuNRs hybrid film was cut into 4×1.5cm rectangular strips, clamped at both ends to a stretching device, and the central 1.5cm width of the rectangular strip was fully moistened with pure water before axial stretching at a magnification of 450%. Finally, the strip was dried and shaped by evaporation to obtain an anisotropic PVA-AuNRs hybrid oriented film with a certain degree of orientation. Two PVA-AuNRs hybrid oriented films were stacked along the axial direction at deflection angles of 0°, ±15°, ±30°, and ±45° (the orientation direction of the upper film relative to the lower film was defined as clockwise rotation (positive (+), counterclockwise rotation (negative (-))), ultimately obtaining double-layer stacked PVA-AuNRs films with different deflection angles.

[0067] Example 2 Fluorescent solutions and fluorescent layers with different fluorescent colors

[0068] Weigh 10 mg of commercial Nile Red-625 nm (FL-625 nm) powder and dissolve it in 10 g of dichloromethane (DCM) to obtain a 0.1% Nile Red dye solution. For dyes with different fluorescence emission wavelengths (coumarin 120-440 nm, coumarin 151-490 nm, coumarin 153-530 nm, pyrrolidone BODIPY-560 nm, and rhodamine-6G-585 nm), add them to their respective soluble solvents (water / DCM) at the same concentration to prepare the corresponding fluorescent solutions. Specifically, rhodamine-6G-585 nm was dissolved in 10 g of water, while the other coumarins (120-440 nm, coumarin 151-490 nm, coumarin 153-530 nm, and pyrrolidone BODIPY-560 nm) were dissolved in DCM.

[0069] Blend 2 mL of each approximately 0.1% fluorescent solution (coumarin 120-440 nm, coumarin 151-490 nm, coumarin 153-530 nm, pyrrolidone-boronopyrrolidone-560 nm, and Nile Red 625 nm) with 20 g of a 5 wt% polymethyl methacrylate (PMMA) solution to obtain a uniform blend. Pour the blend into a 10 cm × 10 cm Petri dish and dry it in a 45°C oven. Once the film is completely dry, remove it and set aside. Blend 2 mL of a 0.1% fluorescent solution of rhodamine-6G 585 nm with 20 g of a 5 wt% polyvinyl alcohol (PVA) solution to obtain a uniform blend. Pour the blend into a 10 cm × 10 cm Petri dish and dry it in a 45°C oven. Once the film is completely dry, remove it and set aside.

[0070] Through this embodiment, fluorescent layers formed by Nile Red-625 nm, coumarin 120-440 nm, coumarin 151-490 nm, coumarin 153-530 nm, BODIPY-560 nm, and Rhodamine-6G-585 nm were obtained, which were sequentially recorded as: the first fluorescent layer, the second fluorescent layer, the third fluorescent layer, the fourth fluorescent layer, the fifth fluorescent layer, and the sixth fluorescent layer.

[0071] Example 3 Circularly polarized luminescent multilayer assembled films obtained by stacking films with different deflection angles

[0072] The first fluorescent layer formed by Nile Red-625nm in Example 2 and the PVA-AuNRs stacked films with different deflection angles obtained in Example 1 were stacked and assembled to obtain a circularly polarized luminescent multilayer assembled film containing PVA-AuNRs stacked films with different deflection angles.

[0073] The red fluorescence emitted by the Nile Red fluorescent film was used as the fluorescence source of the circularly polarized luminescent multilayer assembled film, and the fluorescent layer was used as the upper layer incident with the excitation light source to characterize the CPL of each circularly polarized luminescent multilayer assembled film.

[0074] Example 4 Circularly polarized luminescent multilayer assembled films with different fluorescence emission bands

[0075] The first fluorescent layer, second fluorescent layer, third fluorescent layer, fourth fluorescent layer, fifth fluorescent layer, and sixth fluorescent layer of different fluorescent colors obtained in Example 2 were assembled with PVA-AuNRs stacked films with a deflection angle of ±45° to obtain circularly polarized luminescent multilayer assembled films with different emission bands. The CPL of the circularly polarized luminescent multilayer assembled film was characterized using a CPL spectrometer.

[0076] Example 5 Circularly polarized luminescent multilayer assembled films with different fluorescent dye contents

[0077] 10 mg of commercial Nile Red-625 nm dye powder was weighed and dissolved in 10 g of DCM (dichloromethane) to obtain a Nile Red dye solution with a concentration of approximately 0.1%.

[0078] 0.1 mL, 1 mL, and 10 mL of a Nile red dye solution with a concentration of approximately 0.1% were taken, respectively, and blended with 20 g of a prepared polymethyl methacrylate (PMMA) solution with a concentration of 5 wt % to obtain a uniform blended solution. The solution was poured into a 10 cm × 10 cm Petri dish and dried in a 45°C oven. After the film was completely dry, it was peeled off and set aside to obtain fluorescent layers with a fluorescent dye mass content of 0.01%, 0.1%, and 1%, respectively.

[0079] The fluorescent layers with different fluorescent dye contents were respectively assembled with the PVA-AuNRs stacked films with a deflection angle of ±45° in Example 1 to form circularly polarized luminescent multilayer assembled films.

[0080] Example 6 Circularly polarized luminescent multilayer assembled films with different AuNR contents

[0081] 5g of PVA particles were weighed and poured into 95g of pure water. The mixture was heated at 90°C and magnetically stirred at 1500 rpm for 3 hours. After the particles were completely dissolved, a PVA solution with a solid content of 5wt% was obtained. 20g of the prepared PVA solution was weighed and physically blended with 8mL, 16mL, and 24mL of AuNRs solutions with an aspect ratio of 2 and a concentration of 0.1mg / mL. The mixture was magnetically stirred at 1500 rpm for 12 hours to obtain PVA-AuNRs solutions. The resulting PVA-AuNRs solutions were poured into a 10cm×10cm Petri dish and dried in a 45°C oven. After drying, PVA-AuNRs hybrid membranes with AuNR contents of 0.08%, 0.16%, and 0.24%, respectively, were obtained.

[0082] The PVA-AuNRs hybrid film was cut into 4×1.5cm rectangular strips, clamped at both ends to a stretching device, and the central 1.5cm width of the rectangular strip was fully moistened with pure water before axial stretching at a magnification of 450%. Finally, the strips were dried and shaped by evaporation to obtain an anisotropic PVA-AuNRs hybrid oriented film with a certain degree of orientation. Two PVA-AuNRs hybrid oriented films were stacked along the axial direction at a deflection angle of ±45°, resulting in PVA-AuNRs stacked films with AuNRs contents of 0.08%, 0.16%, and 0.24%, respectively.

[0083] The first fluorescent layer formed by Nile Red-625nm in Example 2 was assembled with the PVA-AuNRs stacked films with different AuNRs contents in Example 6 to form circularly polarized luminescent multilayer assembled films.

[0084] Example 7 PVA-AuNRs stacked films with different stretching ratios

[0085] 5g of PVA particles were weighed and poured into 95g of pure water. The mixture was heated at 90°C and magnetically stirred at 1500 rpm for 3 hours. After the particles were completely dissolved, a PVA solution with a solid content of 5wt% was obtained. 20g of the prepared PVA solution was weighed and physically blended with 25mL of a 0.1mg / mL AuNRs solution with an aspect ratio of 2. The mixture was magnetically stirred at 1500 rpm for 12 hours to obtain a PVA-AuNRs solution. The resulting PVA-AuNRs solution was poured into a 10cm×10cm Petri dish and dried in a 45°C oven. After drying, a PVA-AuNRs hybrid membrane was obtained.

[0086] The PVA-AuNRs hybrid film was cut into 4×1.5cm rectangular strips, clamped at both ends to a stretching device, and the central 1.5cm width of the rectangular strip was fully moistened with pure water. The strips were then axially stretched at ratios of 200%, 350%, and 500%. Finally, the strips were dried and shaped by evaporation to obtain anisotropic PVA-AuNRs hybrid oriented films with different degrees of orientation. PVA-AuNRs hybrid oriented films with the same degree of orientation were stacked in pairs at a deflection angle of ±45° along the axial direction to obtain PVA-AuNRs stacked films with different optical activities.

[0087] The first fluorescent layer formed by Nile Red-625nm in Example 2 was assembled with the PVA-AuNRs stacked films with different stretching ratios in Example 7 to form circularly polarized luminescent multilayer assembled films.

[0088] Comparative Example 1

[0089] Weigh 5g of PVA particles and pour them into 95g of pure water. Heat at 90°C with magnetic stirring at 1500 rpm for 3 hours until the particles are completely dissolved, obtaining a PVA solution with a 5% solids content. Weigh 20g of the prepared PVA solution and pour it into a 10cm x 10cm Petri dish. Place it in a 45°C oven and dry it. Once dried, a PVA film is obtained.

[0090] 6 mL of AuNRs solution with a concentration of 0.1 mg / mL and an aspect ratio of 2 was drop-coated on the surface of the PVA film. After the solvent was fully evaporated, a PVA-AuNRs hybrid film was obtained.

[0091] The PVA-AuNRs hybrid film was cut into 4×1.5cm rectangular strips, clamped at both ends to a stretching device, and the central 1.5cm width of the rectangular strip was fully moistened with pure water before axial stretching at a magnification of 450%. Finally, the strip was dried and shaped after water evaporation to obtain an anisotropic PVA-AuNRs hybrid oriented film with a certain degree of orientation. Two PVA-AuNRs hybrid oriented films were stacked along the axial direction at a deflection angle of ±45°, ultimately obtaining a PVA-AuNRs stacked film with a certain degree of optical activity.

[0092] Figure 1 This is the distribution of gold nanorods on the surface of the PVA-AuNRs hybrid film after axial stretching described in the present invention. As can be seen from the figure, the dispersed AuNRs after stretching are arranged in an orderly manner along the stretching direction. Since they are dispersed in the entire PVA film matrix, the surface content of the PVA-AuNRs hybrid film photographed by the electron scanning electron microscope is relatively small and the density is not high.

[0093] Figure 2Figure a shows the polarization extinction spectra of the PVA-AuNRs hybrid oriented film at different deflection angles. Since the AuNRs are uniformly distributed in the PVA film rather than aggregated, the absorption peak has hardly changed relative to the wavelength of the AuNRs solution. The inset shows the relative direction of the linearly polarized light and the arrangement of the AuNRs. Figure 2 As can be seen in Figure b, the extinction intensity of the PVA-AuNRs hybrid oriented film varies periodically with the deflection angle (wavelength 650 nm) due to its anisotropic structure. The extinction intensity of the non-oriented PVA-AuNRs hybrid film hardly changes with the deflection angle due to its isotropic structure. Figure 2 The inset in b is the corresponding polar coordinate plot.

[0094] Figure 3 The CD spectra of the PVA-AuNRs stacked films with different deflection angles (±15°, ±30°, ±45°) described in Example 1 of the present invention are shown in FIG. Figure 3 As can be seen in a, the CD peak band is Figure 2 The absorption band in the α-AuNRs layer is consistent, and this band also matches the subsequent emission band of the fluorescent layer. It can be seen that due to the structural advantage of the twisted stacking of the PVA-AuNRs oriented hybrid film, the intensity and direction of the CD signal can be controlled by simply adjusting the deflection angle between the layers. Figure 3 Figure b in the figure is the statistical value of the CD intensity changing with the angle, and an effective fit was obtained using the sine function.

[0095] Figure 4 This is the CD spectrum of the PVA-AuNRs stacked film obtained by surface coating of AuNRs solution in Comparative Example 1. Figure 4 As can be seen in Figure a, due to the aggregation of AuNRs, the strongest CD peak band of this structure has been significantly red-shifted to the infrared band (700-1600nm), which is almost incompatible with the emission band of the fluorescent layer used later. The intensity of the corresponding circularly polarized luminescent multilayer assembled film obtained by the "matching rule" is extremely low ( Figure 4 Middle b).

[0096] Figure 5 Figure 2 shows the fluorescence emission spectra of different fluorescent layers described in Example 2 of the present invention (a) and the fluorescence colors of the corresponding fluorescent solutions under 365nm UV excitation (b). This figure demonstrates that fluorescent components (including fluorescent layers and fluorescent solutions) can be prepared with different fluorescent colors covering the entire visible light band (380-780nm).

[0097] Figure 6 The CPL spectra of the circularly polarized luminescent multilayer assembled films prepared from PVA-AuNRs stacked films with different deflection angles (±15°, ±30°, ±45°) in Example 3 of the present invention are shown in FIG. Figure 6 As shown in Figure a, when the PVA-AuNRs stack is assembled with the fluorescent layer, it exhibits high-intensity CPL due to the "matching rule" theory. This indicates that when the interlayer angle of the PVA-AuNRs stack is set to a value other than 0° ± 90°, the resulting optical activity (CD intensity) can selectively absorb left-handed / right-handed fluorescence and output the corresponding right-handed / left-handed fluorescence. Figure 6 Figure (b) shows the statistical value of the CPL intensity as the interlayer angle changes, and is effectively fitted using a sine function. As the interlayer angle of the PVA-AuNRs stack changes, the CPL intensity of the circularly polarized luminescent multilayer assembled film also changes accordingly. When the deflection direction of the upper PVA-AuNRs hybrid oriented film in the PVA-AuNRs stack changes, the CPL direction of the circularly polarized luminescent multilayer assembled film also changes simultaneously. Therefore, by regulating the interlayer angle of the PVA-AuNRs stack, efficient control of the CPL intensity and direction of the circularly polarized luminescent multilayer assembled film is achieved.

[0098] Figure 7 This is the CPL spectrum of the circularly polarized luminescent multilayer assembled film based on different fluorescent layers and PVA-AuNRs stacked films in Example 4 of the present invention. Figure 7 It can be seen that the circularly polarized luminescent multilayer assembled films formed by assembling different fluorescent layers with the PVA-AuNRs stacked film have different CPL colors, indicating that the present invention can control the CPL color of the circularly polarized luminescent multilayer assembled film by selecting fluorescent layers with different emission wavelengths, thereby achieving multicolor and white CPL covering the entire visible color range. Compared to the red fluorescent layer, the other fluorescent colors are not as well matched with the PVA-AuNRs stacked film, resulting in relatively low CPL.

[0099] Chiral optical devices with practical application value are particularly critical for controlling environmental stability such as light, temperature, and durability. Therefore, the present invention conducted temperature, light, and environmental durability tests on the circularly polarized luminescent multilayer assembled film composed of a Nile red fluorescent layer and a PVA-AuNRs stacked film with an angle of -30°. The specific results are as follows: Figures 8-10 shown.

[0100] Figure 8 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film obtained by the present invention at different operating temperatures. Figure 8As can be seen, the CPL spectral intensity of the circularly polarized luminescent multilayer assembled film begins to decrease after 120°C as the ambient temperature increases. At 150°C, the CPL intensity decreases to 70% of the original intensity (at 25°C), and the glum value is 80% of the original intensity. Similarly, at 150°C, the CD intensity decreases to 80% of the original intensity. This demonstrates that the circularly polarized luminescent multilayer assembled film of the present invention has excellent thermal stability, with a maximum operating temperature of 120°C with virtually no impact on its optical properties. Its thermal stability between 120°C and 150°C also exceeds that of most chiral liquid crystal materials.

[0101] Figure 9 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film obtained by the present invention under different UV-365nm irradiation time. Figure 7 It can be seen that after 72 hours of UV-365nm light irradiation, the CPL spectrum of the circularly polarized luminescent multilayer assembly film has almost no change, indicating that the circularly polarized luminescent multilayer assembly film of the present invention has excellent optical stability and can greatly enhance the application value of the circularly polarized luminescent multilayer assembly film.

[0102] Figure 10 The CPL spectrum changes of the circularly polarized luminescent multilayer assembled film obtained by the present invention under standard environment (RH=50%, T=25℃) for different time periods. Figure 10 It can be seen that after being placed in the environment for 50 days, the CPL spectrum of the circularly polarized luminescent multilayer assembled film remains unchanged, indicating that the circularly polarized luminescent multilayer assembled film of the present invention has good environmental durability.

[0103] Figure 11 The stress-strain curve of the PVA-AuNRs hybrid oriented film with a stretch ratio of 450% for the single layer of the present invention and the actual image showing its bendability and flexibility. Traditional optical devices are often difficult to achieve wider applications due to their high brittleness, especially in the field of wearable smart materials. In contrast, Figure 11 It can be seen that the PVA-AuNRs hybrid oriented film of the present invention exhibits impressive mechanical properties, with a strength of 216 MPa while maintaining good flexibility (elongation at break 27%), which is extremely rare in current optically active layer materials.

[0104] Figure 12 Figure a is the CPL spectrum of the circularly polarized luminescent multilayer assembly film with different fluorescent dye contents obtained in Example 5. It can be seen from the figure that the CPL intensity can also be regulated by adjusting the fluorescence intensity of the fluorescent layer (i.e., the content of the fluorescent dye). Within a certain range, the CPL intensity increases significantly with the increase of the dye content.

[0105] Figure 12Figure b is the CPL spectrum of the circularly polarized luminescent multilayer assembled films with different AuNRs contents obtained in Example 6. It can be seen from the figure that by regulating the AuNRs concentration in the PVA-AuNRs stacked film, the optical activity of the PVA-AuNRs stack can be affected, thereby achieving the regulation of the CPL of the circularly polarized luminescent multilayer assembled film. The results show that the CPL intensity increases with the increase of AuNRs concentration.

[0106] Figure 12 Figure c is the CPL spectrum of the circularly polarized luminescent multilayer assembly film with different stretching ratios obtained in Example 7. It can be seen from the figure that as the stretching ratio increases, the CPL intensity gradually increases, that is, the CPL intensity of the circularly polarized luminescent multilayer assembly film can be changed by adjusting the stretching ratio.

Claims

1. A circularly polarized luminescent multilayer assembled film, characterized in that: The invention comprises a fluorescent layer and an optically active layer stacked together; the fluorescent layer comprises a first flexible polymer film and a fluorescent dye distributed in the first flexible polymer film; the optically active layer comprises at least two layers of hybrid orientation films, the hybrid orientation films comprising a second flexible polymer film and a one-dimensional metal nanomaterial distributed in the second flexible polymer film and arranged in an orientation, wherein both the second flexible polymer film and the one-dimensional metal nanomaterial are achiral; the layers of the hybrid orientation films are stacked and arranged at a preset deflection angle along the orientation axis of the one-dimensional metal nanomaterial.

2. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The fluorescent dye is Nile red, coumarin, fluoroboron dipyrrole or rhodamine.

3. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The first flexible polymer film is a polymethyl methacrylate film or a polyvinyl alcohol film, and the second flexible polymer film is a polyvinyl alcohol film.

4. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The mass of the fluorescent dye accounts for 0.01% to 1% of the mass of the first flexible polymer film.

5. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The mass of the one-dimensional metal nanomaterial accounts for 0.08%~0.24% of the mass of the second flexible polymer film.

6. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The one-dimensional metal nanomaterial is gold or silver.

7. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The one-dimensional metal nanomaterial has a morphology of nanorods or nanowires.

8. The circularly polarized luminescent multilayer assembled film according to claim 1, characterized in that: The deflection angle between the uppermost hybrid alignment film and the lowermost hybrid alignment film is within the range of 0° to ±180° and is not 0°±A90°, where A is a constant.

9. The method for preparing the circularly polarized luminescent multilayer assembled film according to any one of claims 1 to 8, wherein: include: mixing the fluorescent dye and the first polymer in a solvent to obtain a first blend solution; drying the first blended solution into a film to obtain a fluorescent layer; mixing a second polymer and the one-dimensional metal nanomaterial in a solvent to obtain a second blend solution; Drying the second blend solution into a film to obtain a hybrid film; axially stretching the hybrid film in one direction at a preset stretch ratio to obtain a hybrid oriented film; stacking a plurality of the hybrid oriented films along the orientation axis at a preset deflection angle to obtain an optically active layer; The fluorescent layer and the optically active layer are stacked together in sequence to obtain a circularly polarized luminescent multilayer assembly film.

10. The method for preparing the circularly polarized luminescent multilayer assembled film according to claim 9, wherein: The preset draft ratio is 100% to 500%.

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