A circularly polarized luminescent composite material based on helical silica-rare earth fluorides, its preparation method and application

Abstract

The application discloses a kind of based on helical silica-rare earth fluoride circular polarization luminescence composite material and its preparation method and application, belong to luminescent material technical field;The circular polarization luminescence composite material based on helical silica-rare earth fluoride includes helical silica and rare earth fluoride in situ growth on the surface of helical silica, wherein helical silica includes left-hand helical silica and right-hand helical silica, and the rare earth cation of rare earth fluoride can be any one or more combinations of Ce 3+ 、Tb 3+ 、Nd 3+ 、Eu 3+ ;The application is in situ assembled strategy and the NaHF2 introduced, so that rare earth fluoride nanoparticles grow in situ on the surface of helical silica after carboxyl modification, and the circular polarization luminescence composite material is prepared;The circular polarization luminescence material can realize multicolor circular polarization luminescence and time-resolved photoluminescence, and has wide application prospect in the field of preparing anti-fake pattern and information encryption.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, specifically relating to a circularly polarized luminescent composite material based on helical silica-rare earth fluorides, its preparation method, and its application. Background Technology

[0002] Circularly polarized light is a special type of polarized light whose light vector rotates around the direction of propagation, and the end of the light vector traces a circular trajectory in a plane perpendicular to the direction of the light. Circularly polarized light can be considered as the synthesis of two plane-polarized lights with equal amplitude, orthogonal vibration directions, and a phase difference of ±π / 2. Based on the direction of rotation of the light vector, circularly polarized light is classified into left-handed and right-handed circularly polarized light. Due to its unique polarization characteristics, circularly polarized light has attracted increasing attention from researchers, and obtaining high-performance circularly polarized light has become a research hotspot in the field of optics.

[0003] Circularly polarized light has wide applications in many fields. For example, in 3D movie projection, circularly polarized light is used to achieve a stereoscopic effect; the polarized glasses worn by viewers can receive different polarized light separately, thus producing stereoscopic vision. Furthermore, circularly polarized light also has important applications in optical communication, data storage, measurement, and biomedical imaging. By manipulating and detecting the polarization state of light, circularly polarized light technology provides higher measurement accuracy and better anti-interference performance, driving development in multiple fields.

[0004] Due to the unique luminescent properties of circularly polarized light, circularly polarized light (CPL) materials have attracted increasing attention in recent years. When excited, these materials emit both left-handed and right-handed circularly polarized light with differing intensities. This unique property makes CPL materials promising for applications in various fields. CPL materials have important applications in 3D displays, information encryption, and photoelectric detection. For example, in 3D displays, CPL materials can provide stereoscopic visual effects; in information encryption, their circular polarization properties can be used to achieve secure information transmission and storage, offering higher concealment, security, and difficulty in replication.

[0005] Although numerous circularly polarized luminescent materials have been reported, developing circularly polarized luminescent materials with multiple photoresponse characteristics and stable properties remains challenging. Current research on circularly polarized luminescent materials mainly focuses on small organic molecules, polymers, and organometallic complexes. Compared to organic circularly polarized luminescent materials, inorganic circularly polarized luminescent materials exhibit better structural stability. A chiral assembly strategy is commonly used to construct inorganic circularly polarized luminescent materials, which involves assembling a non-chiral luminescent guest with a chiral host. This strategy, due to the diversity of luminescent guest selection, is more conducive to constructing circularly polarized luminescent materials with controllable emission.

[0006] Researchers are continuously optimizing the performance of CPL materials to meet the needs of different fields by designing molecular structures and controlling chiral centers. For example, chiral silica has the advantages of diverse morphologies, a rigid framework, and ease of modification of its inner and outer surfaces, making it an ideal chiral host. Chinese patent CN112300778A, filed on July 30, 2019, provides a circularly polarized luminescent material, its preparation method, and its application. This patent introduces chiral nanostructures into the field of circularly polarized luminescence for the first time. It forms a core-shell structure by coating dispersed chiral nanostructures with a silica shell, while simultaneously utilizing the silica shell to adsorb fluorescent substances, forming a host-guest structure. The chiral nanostructure core acts as a chiral source, generating near-field induced fluorescence to produce circularly polarized luminescence. However, this system requires chiral-shaped noble metals or similar materials as the chiral nanostructure core for silica coating, and the guest fluorescent substance is a small organic molecule dye, which is prone to photobleaching, thus affecting the stability of circularly polarized luminescence.

[0007] Rare-earth fluoride nanoparticles possess advantages such as long lifetime, low phonon energy, multicolor tunability, time-resolved photoluminescence, and good photostability. They also exhibit a rich electronic energy level structure with numerous transitions between energy levels, making them a promising class of inorganic luminescent materials. They also hold great potential in developing multi-level response circularly polarized luminescent composite materials. Chinese patent CN114621766A, filed on April 1, 2022, discloses circularly polarized luminescent chiral rare-earth phosphate nanomaterials, their preparation method, and applications. The preparation method involves combining rare-earth inorganic compounds with chiral molecules to synthesize chiral rare-earth phosphate nanocrystals with circularly polarized luminescence properties. However, this system does not employ a chiral host-luminescent guest assembly strategy. The binding force between the chiral small molecules and the rare-earth inorganic compounds may not be strong enough, and prolonged use or exposure to external environmental influences may lead to the destruction of the chiral structure, thus affecting the circularly polarized luminescence performance.

[0008] Limited by suitable and effective composite strategies, there are no reports on the construction of circularly polarized luminescent materials by combining chiral silica with rare-earth fluorides and exploring their application potential. Therefore, establishing a universal synthesis strategy to effectively combine chiral silica with rare-earth fluorides and construct circularly polarized luminescent materials capable of achieving multicolor circularly polarized emission and time-resolved photoluminescence has significant reference value and application potential in the preparation of anti-counterfeiting patterns and information encryption. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a circularly polarized luminescent composite material based on helical silica-rare earth fluorides, its preparation method, and its application. The circularly polarized luminescent material can achieve multicolor circularly polarized luminescence and time-resolved photoluminescence, and has broad application prospects in the fields of preparing anti-counterfeiting patterns and information encryption.

[0010] The technical solution of the present invention is as follows:

[0011] One of the objectives of this invention is to provide a circularly polarized light-emitting composite material based on helical silica-rare earth fluorides. The circularly polarized light-emitting composite material includes helical silica and rare earth fluorides grown in situ on the surface of helical silica. The helical silica is a carboxyl-modified helical silica nanoribbon, including left-handed helical silica L-HS and right-handed helical silica R-HS.

[0012] Furthermore, the pitch of the spiral silicon dioxide is 30–200 nm, and the diameter is 10–60 nm.

[0013] Furthermore, the pitch of the spiral silicon dioxide is 50–100 nm, and the diameter is 15–40 nm.

[0014] Furthermore, the rare earth cation in the rare earth fluoride may be Ce. 3+ 、Tb 3+ 、Nd 3+ Eu 3+ Any one or more combinations thereof.

[0015] The second objective of this invention is to provide a method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluorides, comprising the following steps:

[0016] S1. Spiral silica was prepared by sol-gel transcriptional synthesis and the surface was modified with carboxyl groups to obtain spiral silica with carboxyl groups on the surface.

[0017] S2. Using electrostatic interaction, rare earth cations are adsorbed on the surface of the spiral silica prepared in S1. Sodium hydrogen fluoride (NaHF2) is introduced to allow rare earth fluorides to grow in situ on the surface of the spiral silica, thus obtaining the circularly polarized light-emitting composite material based on spiral silica-rare earth fluorides.

[0018] Further, S1 includes the following steps:

[0019] S11. Using hexadecyl bromide and tetramethylethylenediamine in a molar ratio of 2:1 as raw materials, the mixture was stirred at 80°C for 36-48 h, then recrystallized and dried to synthesize the gemini surfactant N,N'-bis(hexadecyldimethyl)-1,2-dibromo-ethylenediammonium salt GS16-2-16.

[0020] S12. Add tartaric acid and silver carbonate in a mass ratio of approximately 1:1 to 10-20 mL of methanol and stir at 50 °C for 1.5-24 h. Then, introduce GS16-2-16 prepared in S11 into the system and continue stirring for 3-24 h.

[0021] S13. Filter the mixed solution after stirring in S12, take the supernatant, evaporate by rotary evaporation, recrystallize, and dry to obtain GS16-2-16-tartrate.

[0022] S14. Stir the GS16-2-16-tartrate obtained in S13 at 60℃~80℃ for 0.2~1h, and place it in a thermostat at 20℃ for 3~90h.

[0023] S15. Dissolve 7.5 mg tartaric acid in 5 mL of water, mix with 0.5 mL of tetraethyl silicate, add to the GS16-2-16-tartrate system described in S14, stir and react for 14-60 h, centrifuge at 12000 rpm for 5 min, centrifuge with anhydrous ethanol and wash three times with alcohol, and remove the supernatant.

[0024] S16. Disperse the intermediate product A obtained in S15 in an ethanol solution containing 3-aminopropyltriethoxysilane, stir at 60-80°C for 0.1-24 h, centrifuge and wash with alcohol three times, and remove the supernatant.

[0025] The volume ratio of 3-aminopropyltriethoxysilane to anhydrous ethanol is 1:200; the mass ratio of intermediate product A to anhydrous ethanol is 1:400.

[0026] S17. Disperse the intermediate product B obtained in S16 again in an N,N-dimethylformamide solution containing succinic anhydride, stir at room temperature for 0.1-24 h, centrifuge at 12000 rpm for 5 min, wash three times with anhydrous ethanol, remove the supernatant, and obtain spiral silica with carboxyl groups on the surface.

[0027] The mass ratio of intermediate product B, succinic anhydride, and N,N-dimethylformamide is 1:3:190.

[0028] Furthermore, the tartaric acid in S12 is L-tartaric acid or D-tartaric acid;

[0029] When the tartaric acid is L-tartaric acid, the GS16-2-16-tartrate in S14 is GS16-2-16L-tartrate and self-assembles into a right-handed helical structure.

[0030] When tartaric acid is D-tartaric acid, the GS16-2-16-tartrate in S14 is GS16-2-16D-tartrate and self-assembles into a left-handed helical structure.

[0031] Furthermore, when GS16-2-16-tartrate in S15 is GS16-2-16L-tartrate, L-tartaric acid is added; when GS16-2-16-tartrate is GS16-2-16D-tartrate, D-tartaric acid is added.

[0032] Furthermore, the spiral silica in S17 can be left-handed spiral silica L-HS or right-handed spiral silica R-HS;

[0033] Left-handed helical silica L-HS is transcribed into the GS16-2-16D-tartrate self-assembly, and right-handed helical silica R-HS is transcribed into the GS16-2-16L-tartrate self-assembly.

[0034] Further, in step S2, the spiral silica prepared by step S1 is added to an aqueous solution containing rare earth nitrates, and the reaction is carried out at an ultrasonic power of 200W for 0.05-24h. Then, an aqueous solution of sodium hydrogen fluoride (NaHF2) is added and the reaction is continued to be ultrasonicated for 0.05-24h. After centrifugation at 8000rpm for 5min, the supernatant is removed after washing three times with water to obtain the circularly polarized light-emitting composite material based on spiral silica-rare earth fluoride.

[0035] The mass ratio of spiral silica, rare earth nitrate and sodium hydrogen fluoride is 1:66:12.

[0036] The third objective of this invention is to provide an application of a circularly polarized luminescent composite material based on helical silica-rare earth fluorides in the preparation of anti-counterfeiting patterns and information encryption.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. This invention innovatively develops a circularly polarized luminescent composite material based on helical silica-rare earth fluorides. This circularly polarized luminescent composite material is an inorganic chiral nanomaterial with a luminescence asymmetry factor reaching 10. -3 The light emission is on the order of magnitude and is stable with adjustable color, retaining CPL activity even after calcination at 400℃. The sign of circularly polarized luminescence depends on the chirality of the spiral silica. In this invention, rare earth fluorides are spirally arranged on the surface of spiral silica. Taking advantage of the low phonon energy, good luminescence stability, ease of doping, and long fluorescence lifetime of rare earth fluorides, multi-color tunable circularly polarized luminescence and time-resolved photoluminescence can be achieved simultaneously.

[0039] 2. This invention provides a method for preparing a circularly polarized luminescent composite material based on helical silica and rare earth fluorides. An in-situ assembly strategy is employed to arrange rare earth fluorides helically on the surface of the helical silica. The modified helical silica surface is rich in carboxyl groups, exhibiting a strong negative charge, which facilitates the attraction of rare earth cations to the rare earth fluoride surface via electrostatic interactions, thereby achieving in-situ growth of rare earth fluorides on the surface of the helical silica strip. This composite process is simple and easy to operate, with mild reaction conditions and good versatility.

[0040] 3. The circularly polarized luminescent composite material based on helical silica-rare earth fluorides prepared in this invention not only possesses excellent optical properties but also exhibits the unique advantages of multi-color circularly polarized luminescence and time-resolved photoluminescence. This circularly polarized luminescent composite material emits circularly polarized light of multiple colors, providing a novel means for anti-counterfeiting technology. By precisely controlling the luminescence color, it can create anti-counterfeiting labels that are difficult to replicate, effectively combating counterfeit and substandard products. Furthermore, the time-resolved photoluminescence characteristics of this circularly polarized luminescent composite material make it highly promising in the field of information encryption. Utilizing the differences in luminescence at different points in time, complex information can be encoded, enabling the hiding and transmission of information and providing strong protection for information security. Attached Figure Description

[0041] Figure 1 This is a transmission electron microscope image of the left-handed / right-handed spiral silica L / R-HS prepared in the embodiments of the present invention;

[0042] Figure 2 This is a transmission electron microscope image of the circularly polarized luminescent composite material L / R-HS@CeF3:Tb prepared in Example 1 of the present invention;

[0043] Figure 3 The circularly polarized emission spectrum of the circularly polarized luminescent composite material L / R-HS@CeF3:Tb prepared in Example 1 of this invention is shown.

[0044] Figure 4 The circularly polarized emission spectrum of the circularly polarized luminescent composite material L / R-HS@CeF3:25%Tb,1%Eu prepared in Example 2 of this invention is shown below.

[0045] Figure 5 The circularly polarized emission spectrum of the circularly polarized luminescent composite material L / R-HS@CeF3:25%Tb,4%Eu prepared in Example 3 of this invention is shown.

[0046] Figure 6 This is a test pattern for the anti-counterfeiting pattern of a circularly polarized luminescent composite material based on spiral silica-rare earth fluoride in the performance test of this invention.

[0047] Figure 7This is a test diagram of information encryption of the circularly polarized luminescent composite material based on helical silica-rare earth fluoride in the performance test of this invention;

[0048] Figure 8 The circularly polarized emission spectra of the circularly polarized luminescent composite material R-HS@CeF3:Tb prepared in Example 1 of this invention after calcination at different temperatures are shown. Detailed Implementation

[0049] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0050] Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0051] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0052] Example 1

[0053] This embodiment provides a method for preparing a right-handed helical silica-rare earth fluoride circularly polarized luminescent composite material R-HS@CeF3:Tb, including the following steps:

[0054] S1. Weigh tetramethylethylenediamine and hexadecane bromide according to a molar ratio of 1:2 and add them to the same flask. Place the flask in an oil bath, raise the temperature to 80°C, and stir continuously for 40 hours. After the reaction is complete, a pale yellow product is obtained. Place the product in a vacuum drying oven and dry for 24 hours.

[0055] S2. The dried product from S1 is recrystallized three times with acetone / isopropanol. The crystals are purified by vacuum filtration. The purified product is placed in a vacuum drying oven until a constant weight is reached to obtain the gemini surfactant N,N'-bis(hexadecyldimethyl)-1,2-dibromo-ethylenediammonium salt (GS16-2-16).

[0056] S3. Add 300 mg L-tartaric acid and 303 mg silver carbonate to methanol and stir at 50 °C for 2 hours. Then add 685 mg GS16-2-16 to the above system and continue stirring for 5 hours. Filter and take the supernatant. After rotary evaporation, recrystallize with chloroform / methanol (v / v, 9 / 1) and dry to obtain GS16-2-16 L-tartaric acid salt.

[0057] S4. Weigh 3.6 mg of GS16-2-16L-tartrate prepared in S3 and dissolve it in 5 mL of water. Stir at 60 °C for 20 min and then place in a thermostat at 20 °C for 72 h.

[0058] S5. Dissolve 7.5 mg L-tartaric acid in 5 mL of water, mix with 0.5 mL of tetraethyl silicate solution, and add to the system described in S4. Stir and react for 24 h, then centrifuge and wash with alcohol 3 times to remove the supernatant and obtain right-handed spiral silica (R-HS).

[0059] S6. Disperse the right-handed spiral silica (R-HS) obtained in S5 in 20 mL of ethanol solution containing 0.1 mL of 3-aminopropyltriethoxysilane, stir at 80 °C for 12 h, centrifuge, wash three times with alcohol, and remove the supernatant.

[0060] S7. The product obtained in S6 was redispersed in 20 mL of N,N-dimethylformamide solution containing 100 mg succinic anhydride. After stirring at room temperature for 6 h, the mixture was centrifuged and washed three times with alcohol to remove the supernatant, yielding helical silica with carboxyl groups on the surface; its transmission electron microscopy (TEM) results are as follows. Figure 1 As shown in the right figure, the R-HS has uniform dimensions, with a pitch of approximately 66 nm and a diameter of approximately 35 nm.

[0061] S8. In an aqueous solution containing 24.5 mg cerium nitrate and 8.6 mg terbium nitrate, 0.5 mg of the right-handed helical silica with carboxyl groups on the surface prepared in S7 was added. After sonication for 10 min, 1 mL of an aqueous solution containing 6.2 mg sodium hydrogen fluoride was added and sonication was continued for 5 min. After centrifugation, the silica was washed three times with water to remove the supernatant, thus obtaining the right-handed helical silica-rare earth fluoride circularly polarized luminescent composite material R-HS@CeF3:Tb.

[0062] Transmission electron microscopy image of R-HS@CeF3:Tb as shown below Figure 2 As shown in the right figure; in this embodiment, D-tartaric acid can also be used to synthesize left-handed helical silica (L-HS), and then to prepare a left-handed helical silica-rare earth fluoride circularly polarized luminescent composite material L-HS@CeF3:Tb, the transmission electron microscope image of which is shown below. Figure 2 As shown in the left figure. Figure 2 As shown, CeF3:Tb grows in an array on the surface of spiral silica.

[0063] Example 2

[0064] This embodiment provides a method for preparing a left-handed helical silica-rare earth fluoride circularly polarized luminescent composite material L-HS@CeF3:25%Tb,1%Eu, including the following steps:

[0065] S1. Weigh tetramethylethylenediamine and hexadecane bromide according to a molar ratio of 1:2 and add them to the same flask. Place the flask in an oil bath, raise the temperature to 80°C, and stir continuously for 40 hours. After the reaction is complete, a pale yellow product is obtained. Place the product in a vacuum drying oven and dry for 24 hours.

[0066] S2. The dried product from S1 is recrystallized three times with acetone / isopropanol. The crystals are purified by vacuum filtration. The purified product is placed in a vacuum drying oven until a constant weight is reached to obtain the gemini surfactant N,N'-bis(hexadecyldimethyl)-1,2-dibromo-ethylenediammonium salt (GS16-2-16).

[0067] S3. Add 300 mg D-tartaric acid and 303 mg silver carbonate to methanol and stir at 50 °C for 2 hours. Then add 685 mg GS16-2-16 to the above system and continue stirring for 5 hours. Filter and take the supernatant. After rotary evaporation, recrystallize with chloroform / methanol (v / v, 9 / 1) and dry to obtain GS16-2-16 D-tartaric acid salt.

[0068] S4. Weigh 3.6 mg of GS16-2-16D-tartrate prepared in S3 and dissolve it in 5 mL of water. Stir at 60 °C for 20 min and then place in a thermostat at 20 °C for 72 h.

[0069] S5. Dissolve 7.5 mg D-tartaric acid in 5 mL of water, mix with 0.5 mL of tetraethyl silicate solution, and add to the system described in S4. Stir and react for 24 h, then centrifuge and wash with alcohol 3 times to remove the supernatant and obtain left-handed spiral silica (L-HS).

[0070] S6. Disperse the left-handed helical silica (L-HS) obtained in S5 in 20 mL of ethanol solution containing 0.1 mL of 3-aminopropyltriethoxysilane, stir at 80 °C for 12 h, centrifuge, wash three times with alcohol, and remove the supernatant.

[0071] S7. The product obtained in S6 was redispersed in 20 mL of N,N-dimethylformamide solution containing 100 mg succinic anhydride. After stirring at room temperature for 6 h, the mixture was centrifuged and washed three times with alcohol to remove the supernatant, yielding helical silica with carboxyl groups on the surface; its transmission electron microscopy (TEM) results are as follows. Figure 1 As shown in the left figure, the L-HS has uniform dimensions, with a pitch of approximately 66 nm and a diameter of approximately 35 nm.

[0072] S8. In an aqueous solution containing 24.1 mg cerium nitrate, 8.6 mg terbium nitrate and 0.3 mg europium nitrate, 0.5 mg of the left-handed helical silica with carboxyl groups on the surface prepared in S7 was added. After sonication for 10 min, 1 mL of an aqueous solution containing 6.2 mg sodium hydrogen fluoride was added and sonication was continued for 5 min. After centrifugation, the mixture was washed three times with water to remove the supernatant, thus obtaining the left-handed helical silica-rare earth fluoride circularly polarized luminescent composite material L-HS@CeF3:25%Tb,1%Eu.

[0073] In this embodiment, L-tartaric acid can also be used to synthesize right-handed helical silica (R-HS), and then to prepare right-handed helical silica-rare earth fluoride circularly polarized light-emitting composite material R-HS@CeF3:25%Tb,1%Eu.

[0074] Example 3

[0075] This embodiment provides a method for preparing a left-handed helical silica-rare earth fluoride circularly polarized luminescent composite material L-HS@CeF3:25%Tb,4%Eu, including the following steps:

[0076] S1. Weigh tetramethylethylenediamine and hexadecane bromide according to a molar ratio of 1:2 and add them to the same flask. Place the flask in an oil bath, raise the temperature to 80°C, and stir continuously for 40 hours. After the reaction is complete, a pale yellow product is obtained. Place the product in a vacuum drying oven and dry for 24 hours.

[0077] S2. The dried product from S1 is recrystallized three times with acetone / isopropanol. The crystals are purified by vacuum filtration. The purified product is placed in a vacuum drying oven until a constant weight is reached to obtain the gemini surfactant N,N'-bis(hexadecyldimethyl)-1,2-dibromo-ethylenediammonium salt (GS16-2-16).

[0078] S3. Add 300 mg D-tartaric acid and 303 mg silver carbonate to methanol and stir at 50 °C for 2 hours. Then add 685 mg GS16-2-16 to the above system and continue stirring for 5 hours. Filter and take the supernatant. After rotary evaporation, recrystallize with chloroform / methanol (v / v, 9 / 1) and dry to obtain GS16-2-16 D-tartaric acid salt.

[0079] S4. Weigh 3.6 mg of GS16-2-16D-tartrate prepared in S3 and dissolve it in 5 mL of water. Stir at 60 °C for 20 min and then place in a thermostat at 20 °C for 72 h.

[0080] S5. Dissolve 7.5 mg D-tartaric acid in 5 mL of water, mix with 0.5 mL of tetraethyl silicate solution, and add to the system described in S4. Stir and react for 24 h, then centrifuge and wash with alcohol 3 times to remove the supernatant and obtain left-handed spiral silica (L-HS).

[0081] S6. Disperse the left-handed helical silica (L-HS) obtained in S5 in 20 mL of ethanol solution containing 0.1 mL of 3-aminopropyltriethoxysilane, stir at 80 °C for 12 h, centrifuge, wash three times with alcohol, and remove the supernatant.

[0082] S7. The product obtained in S6 was redispersed in 20 mL of N,N-dimethylformamide solution containing 100 mg succinic anhydride. After stirring at room temperature for 6 h, the mixture was centrifuged and washed three times with alcohol to remove the supernatant, yielding helical silica with carboxyl groups on the surface; its transmission electron microscopy (TEM) results are as follows. Figure 1 As shown in the left figure, the L-HS has uniform dimensions, with a pitch of approximately 66 nm and a diameter of approximately 35 nm.

[0083] S8. In an aqueous solution containing 23.2 mg cerium nitrate, 8.6 mg terbium nitrate, and 1.4 mg terbium nitrate, 0.5 mg of the left-handed helical silica with carboxyl groups on its surface prepared in S7 was added. After sonication for 10 min, 1 mL of an aqueous solution containing 6.2 mg sodium hydrogen fluoride was added, and sonication was continued for 5 min. After centrifugation, the mixture was washed three times with water to remove the supernatant, thus obtaining the left-handed helical silica-rare earth fluoride circularly polarized luminescent composite material L-HS@CeF3:25%Tb,4%Eu.

[0084] In this embodiment, L-tartaric acid can also be used to synthesize right-handed helical silica (R-HS), and then to prepare right-handed helical silica-rare earth fluoride circularly polarized light-emitting composite material R-HS@CeF3:25%Tb,4%Eu.

[0085] Performance testing

[0086] 1. Circularly polarized luminescence test

[0087] The circularly polarized luminescence of the spiral silica-rare earth fluoride circularly polarized luminescent composite materials L / R-HS@CeF3:Tb, L / R-HS@CeF3:25%Tb,1%Eu, and L / R-HS@CeF3:25%Tb,4%Eu prepared in Examples 1-3 was tested, and the test results are as follows: Figure 3-5 As shown.

[0088] Among them, L / R-HS@CeF3:Tb emits green light, which is composed of... Figure 3It can be seen that L-HS@CeF3:Tb can obtain a negative CPL signal, indicating that right-handed CPL emission has been obtained, and R-HS@CeF3:Tb can obtain a positive CPL signal, indicating that left-handed CPL emission has been obtained.

[0089] L / R-HS@CeF3:25% Tb, 1% Eu. The luminescent color is yellow. Figure 4 It can be seen that L-HS@CeF3:25%Tb,1%Eu can obtain a negative CPL signal, indicating that right-handed CPL luminescence has been obtained, while R-HS@CeF3:25%Tb,1%Eu can obtain a positive CPL signal, indicating that left-handed CPL luminescence has been obtained.

[0090] L / R-HS@CeF3: 25% Tb, 4% Eu. The luminescent color is orange. Figure 5 It can be seen that L-HS@CeF3:25%Tb,4%Eu can obtain a negative CPL signal, indicating that right-handed CPL luminescence has been obtained, while R-HS@CeF3:25%Tb,4%Eu can obtain a positive CPL signal, indicating that left-handed CPL luminescence has been obtained.

[0091] 2. Anti-counterfeiting pattern test

[0092] The L / R-HS@CeF3:25%Tb, R-HS@CeF3:25%Tb,1%Eu, and R-HS@CeF3:25%Tb,4%Eu prepared in Examples 1-3 were respectively added to a 10wt% polyvinyl alcohol solution. After stirring and mixing evenly, the mixture was dried to form a film. The obtained film was cut into the target pattern, with green luminescent material as green leaves, yellow luminescent material as petals, and orange luminescent material as stamens, to create a pattern as shown below. Figure 6 The anti-counterfeiting "flower" pattern shown.

[0093] This pattern appears as a transparent film under sunlight, only revealing different luminescent colors under 254nm handheld ultraviolet light. Time-resolved luminescence tests on the petals and stamens revealed time-dependent luminescence characteristics. CPL testing of the pattern showed different CPL signals in different wavelengths. This demonstrates that utilizing the circularly polarized luminescent composite material based on helical silica-rare earth fluorides described in this invention, along with time-resolved luminescence and CPL as covert signals, can increase the security and difficulty in replication of anti-counterfeiting measures.

[0094] 3. Information encryption test

[0095] The circularly polarized light-emitting composite materials with different color emissions obtained in Examples 1-3 were filled into a 96-well plate to prepare multi-color codes, simulating the information encryption and decryption process, such as... Figure 7 As shown.

[0096] The information is encrypted under sunlight; the number "968" can only be observed under 254nm ultraviolet light, achieving first-level decryption. Due to energy transfer between rare-earth ions in the material, the emitted color is dynamic over time. When the delay time is set to 1.5 milliseconds, the yellow number serves as second-level encryption, decrypting the number "8". Using the positive signal of CPL as third-level encryption, the number "356" is decrypted. By sequentially reading the codes, the encoded "9688356" is finally decrypted. This multi-level decryption process ensures a high level of security for the protected information.

[0097] 4. Stability Test

[0098] The circularly polarized luminescent composite material R-HS@CeF3:Tb prepared in Example 1 was calcined at 200℃, 300℃, and 400℃, respectively, and the circularly polarized luminescence was tested using the calcined R-HS@CeF3:Tb.

[0099] Test results are as follows Figure 8 As shown, R-HS@CeF3:Tb still exhibits CPL activity after calcination at different temperatures, indicating that the circularly polarized luminescent composite material of spiral silica-rare earth fluoride described in this invention has good stability.

[0100] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A helical silica-rare earth fluoride based circularly polarized luminescent composite material, characterized in that, The circularly polarized luminescent composite material comprises helical silica and rare earth fluoride grown in situ on the surface of the helical silica, wherein the helical silica is carboxyl-modified helical silica nanobelt, including left-handed helical silica L-HS and right-handed helical silica R-HS.

2. The helical silica-rare earth fluoride based circularly polarized luminescent composite material according to claim 1, characterized in that, The helical silica has a pitch of 30-200 nm and a diameter of 10-60 nm.

3. The helical silica-rare earth fluoride based circularly polarized luminescent composite material according to claim 1, wherein The rare earth cation in the rare earth fluoride can be Ce 3+ , Tb 3+ , Nd 3+ , Eu 3+ , or any combination of one or more thereof.

4. A method for preparing a helical silica-rare earth fluoride-based circularly polarized luminescent composite material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, preparing helical silica by a sol-gel transcription synthesis method, and modifying the surface with a carboxyl group to obtain helical silica with a carboxyl group on the surface; S2, using electrostatic action to make the helical silica prepared in S1 adsorb rare earth cations on the surface, introducing sodium hydrogen fluoride NaHF2 to make the rare earth fluoride grow in situ on the surface of the helical silica, and obtaining the circularly polarized luminescent composite material based on helical silica-rare earth fluoride.

5. The method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluoride according to claim 4, characterized in that, The S1 comprises the following steps: S11, synthesizing a gemini surfactant N,N'-bis(hexadecyl dimethyl)-1,2-dibromo-ethylenediamine salt GS16-2-16 by using bromohexadecane and tetramethylethylenediamine as raw materials in a molar ratio of 2:1, stirring at 80℃ for 36-48 h, recrystallizing and drying; S12, adding tartaric acid and silver carbonate in a mass ratio of 1:1 into 10-20 mL of methanol, stirring at 50℃ for 1.5-24 h, and then introducing the GS16-2-16 prepared in S11 into the system to continue stirring for 3-24 h; S13, filtering the mixed solution after stirring in S12, rotating evaporation of the supernatant, recrystallizing, and drying to obtain GS16-2-16-tartaric acid salt; S14, stirring the GS16-2-16-tartaric acid salt prepared in S13 at 60-80℃ for 0.2-1 h, and placing in a thermostat at 20℃ for 3-90 h; S15, dissolving 7.5 mg of tartaric acid in 5 mL of water, mixing with 0.5 mL of tetraethyl silicate, adding to the GS16-2-16-tartaric acid salt system in S14, stirring for 14-60 h, centrifuging at 12000 rpm for 5 min, and washing three times with anhydrous ethanol to remove the supernatant; S16, dispersing the intermediate product A prepared in S15 in an ethanol solution containing 3-aminopropyl triethoxysilane, stirring at 60-80℃ for 0.1-24 h, centrifuging at 12000 rpm for 5 min, washing three times with anhydrous ethanol, and removing the supernatant; The volume ratio of 3-aminopropyl triethoxysilane to anhydrous ethanol is 1:200, and the mass ratio of the intermediate product A to anhydrous ethanol is 1:400; S17, dispersing the intermediate product B prepared in S16 again in an N,N-dimethylformamide solution containing succinic anhydride, stirring at room temperature for 0.1-24 h, centrifuging at 12000 rpm for 5 min, washing three times with anhydrous ethanol to remove the supernatant, and obtaining helical silica with a carboxyl group on the surface; The mass ratio of the intermediate product B to succinic anhydride to N,N-dimethylformamide is 1:3:

190.

6. The method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluoride according to claim 5, characterized in that, The tartaric acid in S12 is L-tartaric acid or D-tartaric acid; When the tartaric acid is L-tartaric acid, the GS16-2-16-tartaric acid salt in S14 is GS16-2-16L-tartaric acid salt, and self-assembles into a right-handed helical structure; When the tartaric acid is D-tartaric acid, the GS16-2-16-tartaric acid salt in S14 is GS16-2-16D-tartaric acid salt, and self-assembles into a left-handed helical structure.

7. The method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluoride according to claim 6, characterized in that, When the GS16-2-16-tartaric acid salt in S15 is GS16-2-16L-tartaric acid salt, L-tartaric acid is added; when the GS16-2-16-tartaric acid salt is GS16-2-16D-tartaric acid salt, D-tartaric acid is added.

8. The method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluoride according to claim 7, characterized in that, The helical silica in S17 can be left-handed helical silica L-HS or right-handed helical silica R-HS; The left-handed helical silica L-HS is transcribed in the GS16-2-16D-tartaric acid salt self-assembly, and the right-handed helical silica R-HS is transcribed in the GS16-2-16L-tartaric acid salt self-assembly.

9. The method for preparing a circularly polarized luminescent composite material based on helical silica-rare earth fluoride according to claim 4, characterized in that, The S2 is prepared by adding the helical silica prepared by S1 in an aqueous solution containing rare earth nitrate, under 200W ultrasonic power for 0.05-24h, adding sodium hydrogen fluoride NaHF2 aqueous solution and continuing to ultrasonic for 0.05-24h, centrifuging at 8000rpm for 5min, washing with water for three times, removing the supernatant, and obtaining the helical silica-rare earth fluoride-based circularly polarized luminescent composite material; The mass ratio of the helical silica, the rare earth nitrate and the sodium hydrogen fluoride is 1:66:

12.

10. The helical silica-rare earth fluoride-based circularly polarized luminescent composite material prepared by the preparation method of any one of claims 4-9 is applied in the preparation of anti-counterfeiting patterns and information encryption.

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