Circularly polarized room-temperature phosphorescent material based on marine polysaccharide as well as preparation and application of circularly polarized room-temperature phosphorescent material

Abstract

The invention belongs to the technical field of phosphorescent materials, and particularly relates to a circularly polarized room-temperature phosphorescent material based on marine polysaccharides and preparation and application thereof.The circularly polarized room-temperature phosphorescent material based on marine polysaccharides is prepared by the steps that 4-(4-bromophenyl)-pyridine and methyl iodide are dissolved in absolute ethyl alcohol, a reflux reaction is performed to prepare bromophenyl pyridinium, and the bromophenyl pyridinium is dissolved in absolute ethyl alcohol; dissolving the chiral marine polysaccharide lambda-type carrageenan containing the negative sulfate radical group and an achiral phosphorescent color body bromophenyl pyridinium containing the positive pyridine group in deionized water, performing ultrasonic heating until the solution is clear, and then gradually cooling and self-assembling to form a lambda-type carrageenan and bromophenyl pyridinium suspension; finally, the lambda-type carrageenan and bromophenylpyridinium suspension is subjected to vacuum drying, the circularly polarized room-temperature phosphorescent thin film material based on the marine polysaccharide is obtained, the material property is stable, the circularly polarized room-temperature phosphorescent thin film material can be applied to phosphorescent digital encryption, optical anti-counterfeiting and the like, the preparation method is simple and novel, the raw material source is wide, the cost is low, and industrial production is facilitated. The method has important significance for designing and preparing CP-RTP materials based on natural macromolecules.

Description

Technical field:

[0001] The invention belongs to the technical field of phosphorescent materials, and in particular relates to a circularly polarized room temperature phosphorescent material based on marine polysaccharides and a preparation method and application thereof. Background technology:

[0002] Circularly polarized luminescence (CPL) is a phenomenon in which a chiral luminescent material emits left-handed and right-handed circularly polarized light of different intensities under the excitation of monochromatic excitation light. It has potential application prospects in 3D display, biological imaging, anti-counterfeiting encryption, etc.

[0003] At present, the research on CPL active materials mainly focuses on circularly polarized fluorescence and circularly polarized phosphorescence, which involve singlet excited states and triplet excited states, respectively. Circularly polarized room temperature phosphorescence (CP-RTP) materials combine the advantages of room temperature phosphorescence and efficient circularly polarized luminescence, with the properties of large Stokes shift and long-lifetime emission. Chiral components, rigid microenvironment and phosphors are prerequisites for the realization of CP-RTP. However, due to the inherent instability of the triplet excited state and the complex chirality transfer problem between the chiral center and the phosphorescent unit, the design and preparation of CP-RTP materials are still challenging.

[0004] Polysaccharides are widely present in organisms. They are a class of natural high molecular weight polymers composed of aldose or ketose connected by glycosidic bonds. They are important biomacromolecules in organisms and one of the basic substances to maintain the normal operation of life activities. Polysaccharides are abundant, renewable, cheap and easy to obtain. Polysaccharides can be used to prepare room temperature phosphorescent (RTP) materials. Their abundant hydroxyl groups can provide a rigid microenvironment and stabilize non-chiral organic phosphors through non-covalent interactions, thereby achieving RTP emission.

[0005] However, there are no reports on the use of marine polysaccharides to prepare circularly polarized room temperature phosphorescent materials. Summary of the invention:

[0006] The purpose of the present invention is to solve the technical problems existing in the prior art, such as the inherent instability of the triplet excited state, the complex chiral transfer problem between the chiral center and the phosphorescent unit, and the complex synthesis process of the chiral phosphor or copolymer. The present invention provides a circularly polarized room temperature phosphorescent material based on marine polysaccharides, and a preparation method and application thereof. The chiral polysaccharide λ-carrageenan (λ-Car) and the non-chiral phosphorescent chromophore bromophenylpyridinium (PYI) are co-assembled by supramolecular co-assembly technology to form a right-handed chiral λ-carrageenan@bromophenylpyridinium (λ-Car@PYI) spiral assembly, which prevents RTP quenching in the solid state, thereby constructing a luminescent material that stimulates the emission of left-handed circularly polarized phosphorescence at room temperature. The circularly polarized room temperature phosphorescent material does not require a complex synthesis process, and effectively solves the inherent instability of the triplet excited state and the complex chiral transfer problem between the chiral center and the phosphorescent unit. The material has stable properties and can be applied to applications such as phosphorescent digital encryption and optical anti-counterfeiting.

[0007] In order to achieve the above object, the present invention provides a method for preparing a circularly polarized room temperature phosphorescent material based on marine polysaccharides, and the specific steps are as follows:

[0008] S1: Preparation of phosphorescent chromophore bromophenylpyridinium:

[0009] Dissolve 4-(4-bromophenyl)-pyridine and iodomethane in anhydrous ethanol and heat under reflux for 12-36 hours; after cooling to room temperature, concentrate the reaction mixture by rotary evaporation to obtain a light golden precipitate, wash with dichloromethane and vacuum dry to obtain a light golden solid, which is the phosphorescent color body bromophenylpyridinium;

[0010] S2: Preparation of circularly polarized room temperature phosphorescent thin film materials:

[0011] S2.1: Dissolve λ-carrageenan and the phosphorescent chromophore bromophenylpyridinium prepared in step S1 in deionized water to obtain an aqueous solution; subject the aqueous solution to ultrasonic treatment, heating until it is clear, and then gradually cooling to self-assemble to form a λ-Car@PYI suspension, wherein the λ-Car@PYI suspension contains helical microfibers with circularly polarized room temperature phosphorescence properties;

[0012] S2.2: Take the λ-Car@PYI suspension prepared in step S2.1 onto a cleaned substrate, and evenly spin-coat the suspension on the substrate using a spin coater. After vacuum drying in a vacuum drying oven at 25°C, a λ-Car@PYI film with circularly polarized room temperature phosphorescent properties is obtained, which is a circularly polarized room temperature phosphorescent material based on marine polysaccharides.

[0013] When preparing the phosphor chromophore bromophenylpyridinium in step S1 of the present invention, the mass volume ratio of 4-(4-bromophenyl)-pyridine and iodomethane dissolved in anhydrous ethanol is (0.25-1g): (2-5mL): (50-100mL); the reflux temperature is 85-90°C.

[0014] In step S2 of the present invention, the diameter of the spiral micron fibers in the λ-Car@PYI suspension is 2.5 μm.

[0015] When preparing the circularly polarized room temperature phosphorescent film material in step S2 of the present invention, the concentration of the phosphorescent color body bromophenylpyridinium in the aqueous solution is 6-25 mM / L, and the concentration of λ-type carrageenan is 15-25 mM / L.

[0016] In step S2.1 of the present invention, the ultrasonic frequency is 40-60 Hz and the ultrasonication is performed for 5-15 min.

[0017] In step S2.1 of the present invention, the heating temperature is 95-105° C. and the heating time is 5-10 min.

[0018] In step S2.2 of the present invention, the acceleration of the spin coater is 1000-2000 rpm, the speed is 300-400 rpm, and the time is 30-60 s.

[0019] In step S2.2 of the present invention, the drying time in the vacuum drying oven is at least 3 hours, and the temperature is controlled at 15-35°C.

[0020] The substrate of the present invention is a quartz glass sheet.

[0021] The present invention also provides a circularly polarized room temperature phosphorescent material based on marine polysaccharide prepared by the preparation method, and the absolute value of the circularly polarized fluorescence luminescence asymmetry factor is 4.1×10 -3 .

[0022] The present invention provides application of the circularly polarized room temperature phosphorescent material based on marine polysaccharide in digital encryption.

[0023] The present invention provides application of the circularly polarized phosphorescent material based on marine polysaccharide in optical anti-counterfeiting, and the circularly polarized room temperature phosphorescent material is used as an optical label in optical anti-counterfeiting.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention adopts a chiral co-assembly strategy to hierarchically co-assemble chiral anionic polysaccharide λ-Car and achiral cationic phosphor PYI in water through electrostatic interaction to form helical microfibers, and then spin-coats and dries the helical microfibers to form λ-Car@PYI thin films, which prevent RTP from being affected by H in the solid state. 2 O, O2 By taking advantage of the influence of quenchers such as quenchers, a luminescent material with stimulated emission of left-handed circularly polarized phosphorescence at room temperature was constructed, and the inherent instability of the triplet excited state and the complex chiral transfer problem between the chiral center and the phosphorescent unit were effectively solved. The material properties are stable and can be suitable for applications such as phosphorescent digital encryption and optical anti-counterfeiting.

[0026] (2) Wide sources of raw materials: The marine polysaccharide λ-Car used in the present invention is extracted from red algae, which reduces the cost.

[0027] (3) Simple preparation method: The present invention adopts a supramolecular co-assembly strategy and does not require a complicated synthesis process.

[0028] (4) High innovation: The present invention utilizes polysaccharides through non-covalent bonds, which expands a new perspective for the design and preparation of CP-RTP materials.

[0029] (5) Excellent optical properties: The present invention forms a material with circularly polarized room temperature phosphorescence properties by co-assembling the anionic polysaccharide λ-Car and the non-chiral cationic phosphor PYI, which imparts circular polarization properties to non-polarized light, and has the advantages of excellent optical properties and room temperature emission.

[0030] In summary, the present invention co-assembles the chiral polysaccharide λ-Car with the achiral phosphorescent chromophore PYI through the supramolecular co-assembly technology to form a λ-Car@PYI spiral assembly with right-handed chirality, and prevents the room temperature phosphorescence quenching in the solid state, thereby constructing a luminescent material that emits left-handed circularly polarized phosphorescence under stimulated emission at room temperature; the inherent instability of the triplet excited state and the complex chirality transfer problems between the chiral center and the phosphorescent unit are solved, the material properties are stable, and it can be suitable for applications such as phosphorescent digital encryption and optical anti-counterfeiting; the preparation method is simple and novel, the raw material source is wide, and the cost is low, which is of great significance for the design and preparation of CP-RTP materials based on natural macromolecules. Description of the drawings:

[0031] Figure 1 (a) UV-visible absorption spectrum, (b) fluorescence spectrum of the PYI solution described in Example 1 of the present invention, and (c) phosphorescence spectrum of the PYI powder.

[0032] Figure 2 Circular dichroism spectrum (CD) of the λ-Car@PYI suspension described in Example 1 of the present invention and its photograph under sunlight.

[0033] Figure 3 This is a high-resolution scanning electron microscope image of the λ-Car@PYI spiral microfiber obtained in Example 1 of the present invention.

[0034] Figure 4(a) Fluorescence spectrum and photograph at 365 nm excitation wavelength, and (b) laser confocal image of the λ-Car@PYI suspension described in Example 1 of the present invention.

[0035] Figure 5 This is the circularly polarized fluorescence spectrum of the λ-Car@PYI suspension described in Example 1 of the present invention.

[0036] Figure 6 Schematic diagram of the principle of circularly polarized fluorescence emission by the λ-Car@PYI suspension described in Example 1 of the present invention.

[0037] Figure 7 This is the circular dichroism spectrum of the λ-Car@PYI film described in Example 1 of the present invention and its photograph under sunlight and 365nm excitation.

[0038] Figure 8 (a) phosphorescence spectrum and (b) laser confocal image of the λ-Car@PYI film described in Example 1 of the present invention.

[0039] Fig. 9 This is the phosphorescence lifetime test result of the λ-Car@PYI film described in Example 1 of the present invention.

[0040] Fig.10 This is the circularly polarized phosphorescence spectrum of the λ-Car@PYI film described in Example 1 of the present invention.

[0041] Fig.11 This is a schematic diagram of the principle of the λ-Car@PYI film emitting circularly polarized room temperature phosphorescence described in Example 1 of the present invention.

[0042] Fig.12 This is a picture of the λ-Car@PYI circularly polarized room temperature phosphorescent thin film material described in Example 1 of the present invention being used for digital encryption display. Specific implementation method:

[0043] The technical solution of the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0044] Embodiment 1:

[0045] (1) Preparation of phosphorescent chromophore phenylpyridinium bromophosphate (PYI):

[0046] 4-(4-bromophenyl)-pyridine (1 g) and iodomethane (2 mL) were dissolved in 50 mL of anhydrous ethanol and heated under reflux for 24 h at a reflux temperature of 85°C; after cooling to room temperature, the reaction mixture was concentrated by rotary evaporation to obtain a light golden precipitate, which was washed with dichloromethane and then dried under vacuum to obtain a light golden solid, which was the phosphorescent color body bromophenylpyridinium (PYI), with a yield of 50%;

[0047] PYI was dissolved in a certain amount of DMSO to obtain a PYI-DMSO solution, and its UV-visible absorption spectrum and fluorescence spectrum were tested. The phosphorescence spectrum of the synthesized PYI solid powder was measured. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that the UV-visible absorption spectrum of PYI-DMSO solution shows a strong absorption peak at 302nm ( Figure 1 a), emits blue fluorescence at 380 nm ( Figure 1 b), while PYI solid powder shows orange phosphorescence at 580nm under 302nm UV light ( Figure 1 c);

[0048] (2) Preparation of circularly polarized room temperature phosphorescent thin film materials:

[0049] (a) The chiral marine polysaccharide λ-carrageenan and the achiral phosphorescent chromophore PYI were weighed in a molar ratio of 1:0.4 and then dissolved in deionized water to make the concentration of λ-carrageenan in the aqueous solution 20 mM / L and the concentration of phosphorescent chromophore PYI 8 mM / L; the solution was ultrasonicated for 10 min, heated at 100°C for 10 min until clear, and then gradually cooled to self-assemble into a λ-carrageenan@bromophenylpyridinium (λ-Car@PYI) milky white suspension, wherein the λ-Car@PYI milky white suspension contained helical microfibers with circularly polarized room temperature phosphorescence properties;

[0050] The circular dichroism spectrum of the λ-Car@PYI milky white suspension was tested at room temperature and photographed under sunlight. The results are as follows: Figure 2 As shown, the results show that at the corresponding absorption wavelength of 302nm, CD presents a right-handed chiral signal that is first positive and then negative, and the λ-Car@PYI suspension appears milky white under sunlight; at the same time, the suspensions prepared by different molar ratios of λ-carrageenan and PYI (1:0, 1:0.2, 1:0.6, 1:0.8, 1:1.0) were tested by circular dichroism spectroscopy according to the above method, and the results are shown in Figure 2 As shown, there is no chiral signal when the molar concentration ratio of λ carrageenan to PYI is 1:0 and 1:0.2.

[0051] The λ-Car@PYI milky white suspension was dried and then tested by high-resolution scanning electron microscopy. Figure 3 The scanning electron micrographs show that the helical microfibers formed by the co-assembly of λ-Car and PYI have a diameter of about 2.5 μm.

[0052] Samples were taken for fluorescence spectroscopy of the λ-Car@PYI suspension at room temperature, laser confocal imaging, and photo shooting at an excitation wavelength of 365 nm. The results are as follows: Figure 4 As shown, the results show that the fluorescence position is at 380nm ( Figure 4 a), λ-Car@PYI suspension emits blue fluorescence at 365nm excitation wavelength ( Figure 4 a), laser confocal imaging of helical microfibers that emit blue fluorescence but no yellow phosphorescence ( Figure 4 b);

[0053] The circular polarization fluorescence spectrum of the λ-Car@PYI suspension was tested and the principle diagram was inferred. The results are shown in Figure 5 and Figure 6 The results show that CPL presents a positive signal at the fluorescence position of 380nm, and the absolute value of its luminescence asymmetry factor is 4.1×10 -3 , no CPL signal was detected at 580 nm at the phosphorescence position; this is due to the presence of H 2 O, O 2 The quencher quenches the triplet excitons, causing them to return to the ground state in a non-radiative relaxation state without being able to emit phosphorescence.

[0054] (b) Take 30 μL of λ-Car@PYI suspension on a cleaned quartz glass sheet, and evenly spin-coat the suspension on the quartz glass sheet using a spin coater. After vacuum drying in a vacuum drying oven at 25°C for at least 3 hours, a λ-Car@PYI film with circularly polarized room temperature phosphorescent properties is obtained, which is a circularly polarized room temperature phosphorescent material based on marine polysaccharides.

[0055] The λ-Car@PYI film was tested for circular dichroism spectrum at room temperature and photographed under sunlight and 365nm excitation. The results are as follows: Figure 7 As shown, the results show that at the corresponding absorption wavelength of 302nm, the CD presents a right-handed chiral signal that is first positive and then negative, which is consistent with the CD measured for the λ-Car@PYI suspension; compared with sunlight, the λ-Car@PYI film emits yellow phosphorescence under 365nm excitation.

[0056] The λ-Car@PYI film was taken for phosphorescence spectrum, laser confocal imaging and phosphorescence lifetime test. The results are as follows: Figure 8 and 9 As shown, the results show that its phosphorescence characteristic emission is at 580nm ( Figure 8 a), phosphorescence lifetime is 7.88ms ( Fig. 9 ), laser confocal imaging of yellow phosphorescent helical microfibers ( Figure 8 b).

[0057] The circularly polarized phosphorescence spectrum of the λ-Car@PYI film was tested and the principle diagram was inferred. The results are shown in Fig.10 and Fig.11 As shown. Fig.10 It can be seen that at the phosphorescence position of 580nm, CPL presents a positive signal. The circularly polarized room temperature phosphorescence of λ-Car@PYI film in the solid state is due to the prevention of H 2 O, O 2 The quencher has a triplet state (T 1 ) exciton quenching, promoting intersystem crossing (S 1 →T 1 ), suppressing non-radiative relaxation and returning to the ground state in the form of light (T 1 →S 0 ) emits phosphorescence.

[0058] A certain amount of λ-Car aqueous solution and λ-Car@PYI suspension with a concentration of 20 mM / L were injected into different parts of the 3D printed digital “8888” mold for digital encryption display, such as Fig.12 As shown, after the solution in the mold naturally dried into a thin film, it was irradiated under sunlight and it was found that the mold displayed the number "8888". However, when excited by 365nm ultraviolet light, the mold displayed the encrypted number "2024" of orange phosphorescence.

[0059] As described above, the circularly polarized room temperature phosphorescent material based on marine polysaccharides prepared in the present invention has the characteristics of circularly polarized room temperature phosphorescence, imparts circular polarization to non-polarized light, and has the advantages of superior optical properties, room temperature emission, etc.

Claims

1. A method for preparing a circularly polarized room temperature phosphorescent material based on marine polysaccharides, characterized in that: The specific steps are as follows: S1: Preparation of phosphorescent chromophore bromophenylpyridinium: Dissolve 4-(4-bromophenyl)-pyridine and iodomethane in anhydrous ethanol and heat under reflux; after cooling to room temperature, concentrate the reaction mixture to obtain a light golden precipitate, wash and dry to obtain a light golden solid, which is the phosphorescent color body bromophenylpyridinium; S2: Preparation of circularly polarized room temperature phosphorescent thin film materials: S2.1: dissolving λ carrageenan and the phosphorescent color body bromophenylpyridinium in step S1 in deionized water to obtain an aqueous solution; subjecting the aqueous solution to ultrasonic treatment, heating until it is clear, and then cooling to self-assemble to form a λ carrageenan@bromophenylpyridinium suspension, wherein the λ carrageenan@bromophenylpyridinium suspension contains helical microfibers with circularly polarized room temperature phosphorescence properties; S2.2: After the λ-carrageenan@bromophenylpyridinium suspension prepared in step S2.1 is vacuum dried, a circularly polarized room temperature phosphorescent material based on marine polysaccharides is obtained.

2. The method for preparing circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 1, characterized in that: In step S1, 4-(4-bromophenyl)-pyridine and iodomethane are dissolved in anhydrous ethanol in a mass volume ratio of 0.25-1 g: 2-5 mL: 50-100 mL; the reflux temperature is 85-90° C., and the reflux time is 12-36 h.

3. The method for preparing circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 1, characterized in that: The vacuum drying time in step S2 is at least 3 hours, and the temperature is controlled at 15-35°C.

4. The preparation method according to claim 1, characterized in that: In step S2.1, the concentration of the phosphorescent color body bromophenylpyridinium in the aqueous solution is 6-25 mM / L, and the concentration of λ carrageenan is 15-25 mM / L; the ultrasonic frequency is 40-60 Hz, and the ultrasonication is performed for 5-15 min; the heating temperature is 95-105° C., and the heating is performed for 5-10 min.

5. The method for preparing circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 1, characterized in that: Before the vacuum drying in step S2.2, the λ-carrageenan@bromophenylpyridinium suspension is spin-coated on the substrate using a spin coater.

6. The method for preparing circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 5, characterized in that: The acceleration of the spin coater is 1000-2000 rpm, the speed is 300-400 rpm, and the time is 30-60 s.

7. A circularly polarized room temperature phosphorescent material based on marine polysaccharides prepared by the preparation method according to any one of claims 1 to 6.

8. The circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 7, characterized in that: The absolute value of the circularly polarized fluorescence luminescence asymmetry factor of the circularly polarized room temperature phosphorescent material is 4.1×10 -3 .

9. Use of the circularly polarized room temperature phosphorescent material based on marine polysaccharides according to claim 7 in digital encryption.

10. Use of the circularly polarized phosphorescent material based on marine polysaccharides according to claim 7 in optical anti-counterfeiting, characterized in that: The circularly polarized room temperature phosphorescent material is used as an optical label in optical anti-counterfeiting.

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