A chiral polyacid composite material, its preparation method and application

Abstract

This invention provides a chiral polyoxometalate composite material, its preparation method, and its application. The preparation method includes the following steps: (1) mixing a surfactant with a polyoxometalate to obtain a surfactant-embedded polyoxometalate; (2) mixing the surfactant-embedded polyoxometalate with a cellulose nanocrystal solution to obtain a suspension, and evaporating the suspension to obtain the chiral polyoxometalate composite material. In the preparation method of the chiral polyoxometalate composite material provided by this invention, a surfactant is used to non-covalently modify a large anionic polyoxometalate. The surfactant-embedded polyoxometalate is more easily co-assembled with a chiral template cellulose nanocrystal to obtain a chiral nematic structure. Furthermore, the pitch of the chiral polyoxometalate composite material can be controlled by the surfactant, resulting in a chiral polyoxometalate composite material with uniform thickness, high quantum yield, and excellent circularly polarized luminescence brightness.

Description

Technical Field

[0001] This invention belongs to the field of chiral polyoxometalate preparation technology, specifically relating to a chiral polyoxometalate composite material, its preparation method, and its application. Background Technology

[0002] Polyoxometalates (POMs) are anionic nanoscale transition metal-oxygen clusters, often used as inorganic ligands to construct novel polyoxometalate derivatives, with wide applications in optics, magnetism, catalysis, and biology. The oxygen-rich surface and abundant substitution sites of POMs enable the insertion of covalent or non-covalent active sites and chemical modification. Through surface modification, POMs can exist as soluble large anions in many solvent systems and exhibit solution self-assembly behavior. Polyoxometalate cluster assembled materials, due to their sub-nanometer structural units, can achieve unprecedented structural tunability and polymer-like properties. In 2020, Professor Lan Yaqian's research group synthesized a novel 240-core giant polymolybdate cage, which exhibited good stability in solution and extremely high proton conductivity (J Am Chem Soc, 2020, 142(32): 13982-13988). In 2008, Professor Liu Tianbo's research group first reported the synthesis of hybrid POM clusters and their self-assembly into capsule-like structures in acetonitrile / water mixed solvent (JAm Chem Soc, 2008, 130(44): 14408–14409). Covalent modification of polyoxometalate clusters has enriched the self-assembly of polyoxometalate clusters, but the self-assembly of the aforementioned novel 240-core giant polymolybdate cage and POM clusters into capsule-like structures has resulted in relatively limited self-assembled structures due to the complex organic synthesis reactions and steps.

[0003] Most polyoxometallic clusters have highly symmetrical structures, and a few chiral polyoxometallic clusters in solution are also prone to racemization. Therefore, the chirification of polyoxometallic clusters is also an important topic in the synthesis of polyoxometallic clusters. In 2017, Professor Zhang Jie's team at Peking University reported a method for achieving circularly polarized light emission (CPL) by electrostatic assembly of non-chiral europium (Eu)-containing POMs and chiral diblock copolymers, which was enhanced by sodium chloride (ChemCommun, 53(31):4390, 2017). Cellulose nanocrystal suspensions can be evaporated to obtain cellulose nanocrystal film materials. These film materials retain the self-assembled chiral nematic structure in the suspension. The left-handed circular polarization and the colored light generated within a certain wavelength range are determined by the pitch structure of the cellulose nanocrystal film material. When the pitch of the prepared cellulose nanocrystal film material is in the visible light range, the reflected wavelength produces visible colorful colors. Different film-forming conditions can affect the phase shape and the pitch of the fingerprint structure of the prepared cellulose nanocrystalline film material, thereby affecting the surface color of the prepared cellulose nanocrystalline film material and its chiral signal intensity.

[0004] Existing techniques for preparing chiral POMs involve complex experimental conditions, low yields, and uneven thickness, with a tendency for aggregation. Therefore, there is an urgent need to develop a simpler method to prepare chiral POMs while simultaneously achieving high CPL brightness. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a chiral polyacid composite material, its preparation method, and its application. By designing the raw materials and process steps, the synthesis steps of the chiral polyacid composite material are simplified, while the prepared chiral polyacid composite material has an adjustable photonic bandgap, uniform thickness, high quantum yield, and high CPL brightness.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a chiral polyacid composite material, the method comprising the following steps:

[0008] (1) Mix the surfactant with the polyoxometalate to obtain the surfactant-encapsulated polyoxometalate;

[0009] (2) The surfactant-embedded polyoxometalate is mixed with a cellulose nanocrystal solution to obtain a suspension, and the suspension is evaporated to obtain the chiral polyoxometalate composite material.

[0010] In the preparation method of the chiral polyoxometalate composite material provided by this invention, polyoxometalates (POMs) have a well-defined structure and good solubility, and can be enriched with surfactants to form surfactant-embedded polyoxometalates (SEPs). Simultaneously, POMs can be well dispersed by surfactants. This invention uses surfactants to non-covalently modify large anionic POMs. Compared with covalent modification methods, non-covalent modification of POMs is simpler and more convenient. Furthermore, through non-covalent modification with surfactants, the inherent properties of POMs are preserved, and the ionic strength of the cellulose nanocrystals (CNCs)-surfactant-embedded polyoxometalate mixed solution is reduced, allowing for better interaction between POMs and the chiral template. In addition, the pitch of the chiral nematic structure obtained by co-assembling POMs and CNCs can change significantly with the addition of surfactants, thus allowing the pitch of the chiral polyoxometalate composite material to be controlled by surfactants.

[0011] The present invention provides a method for preparing chiral polyacid composite materials. POMs can interact with CNCs to form a complex, resulting in a self-assembled nanoscale structure in aqueous solution. This allows the prepared chiral polyacid composite material to possess excellent mechanical and optical properties, showing broad application prospects in drug delivery, material preparation, and sensors. Furthermore, the self-assembly of POMs and CNCs can also be used to prepare nanomaterials with specific morphologies and properties, such as nanospheres and nanotubes, providing new avenues for research in nanoelectronics and biomedicine.

[0012] The method for preparing chiral polyacid composite materials provided by this invention can be carried out through simple experimental operations at room temperature and pressure with very high repeatability. The prepared chiral polyacid composite materials have high quantum yield, uniform thickness, high CPL brightness, and significantly improved CPL performance.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] The surfactant described in this invention requires the presence of more than 10 alkyl groups in its molecular structure. The surfactant includes, but is not limited to, any one or a combination of at least two of sodium dodecyl sulfate, tridecyl ammonium bromide, tetradecyl ammonium bromide, tetrabutyl ammonium bromide, dioctadecyl dimethyl ammonium bromide, or hexadecyl trimethyl ammonium bromide. The surfactant provided by this invention is a cationic surfactant with hydrophobic properties. By non-covalently modifying POMs with this hydrophobic surfactant, SEPs acquire a hydrophobic surface, making SEPs a very good and stable dispersion carrier.

[0015] Preferably, the polyoxometalate includes Na₂[EuW₂]₃. 10 O 36 ]6H2O, Na9[LaW 10 O 36 ]6H2O, Na9[TbW 10 O 36 ]6H2O, Na9[SmW 10 O 36 ]6H2O or Na9[DyW 10 O 36 Any one or at least two of 6H2O.

[0016] The polyoxometalate provided by this invention is a weakly-type rare-earth polyoxometalate, selected from Eu. 3+ La + 、Tb 3+ 、Sm 3+ or Dy 3+ As luminescent centers, cationic surfactants are electrostatically modified onto polyoxometalates (POMs) to form surfactant-embedded polyoxometalates (SEPs). These SEPs exhibit good self-assembly properties in solvents of a certain polarity. Using them as supports, they self-assemble with chiral templates (CNCs). Under the combined protection and guidance of the surfactants and POMs, Eu... 3+ La + 、Tb 3+ 、Sm 3 + or Dy 3+ Uniform dispersion with small particle size was achieved. Typically, high concentrations of nanoparticles loaded onto CNCs can lead to quenching, chiral morphological distortion, and severe phase separation due to nanoparticle aggregation, resulting in a significant reduction in iridescence and luminescence. However, since POMs are regularly arranged in the SEP self-assembly and achieve a narrower particle size distribution, and are also protected by surfactants, nanoparticle aggregation is effectively prevented, reducing losses.

[0017] The polyoxometalate salt described in this invention uses Na9[EuW] 10 O 36 Taking 6H2O as an example, [EuW 10 O 36 ] 9-- Eu 3+ and O 2- Each with [WO4] 2- Coordinate bonds are formed. In this coordination system, photoexcitation in the O→W LMCT (coordinate bond charge transfer from oxygen atom to tungsten ion) band can promote intramolecular energy transfer, thereby generating Eu in the crystal lattice. 3+This indicates that electrons from the oxygen atom transitioned from their coordinate bonds to the d orbitals of the tungsten ion, and that the energy of these electrons was transferred to Eu. 3+ This intramolecular energy transfer is of great significance for the preparation and application of certain optoelectronic materials. The above-described mechanism of intramolecular energy transfer also applies to other polyoxometalates of this invention.

[0018] Preferably, the polyoxometalate is prepared by the following method, which includes: mixing an aqueous solution of sodium tungstate dihydrate and an aqueous solution of metal nitrate hexahydrate, heating the mixture to allow it to react, and then cooling the mixture to obtain the polyoxometalate.

[0019] Preferably, the concentration of the sodium tungstate dihydrate aqueous solution is 1-10 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0020] Preferably, the aqueous solution of metal nitrate hexahydrate includes any one of europium nitrate hexahydrate, lanthanum nitrate hexahydrate, terbium nitrate hexahydrate, samarium nitrate hexahydrate, or dysprosium nitrate hexahydrate.

[0021] Preferably, the concentration of the aqueous solution of the metal nitrate hexahydrate is 1-10 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0022] Preferably, the molar ratio of the sodium tungstate dihydrate to the metal nitrate hexahydrate is (2-20):1, for example, it can be 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1, etc., and more preferably (10-10.2):1, for example, it can be 10:1, 10.11:1, 10.12:1, 10.13:1, 10.14:1, 10.15:1, 10.16:1, 10.17:1, 10.18:1, 10.19:1 or 10.2:1, etc.

[0023] Preferably, before mixing the sodium tungstate dihydrate aqueous solution with the metal nitrate hexahydrate aqueous solution, the pH value of the sodium tungstate dihydrate aqueous solution is adjusted to 7-7.5 using a pH adjuster, for example, 7, 7.1, 7.2, 7.3, 7.4 or 7.5.

[0024] Preferably, the pH adjuster includes any one or a combination of at least two of glacial acetic acid, citric acid, bio-acid, phosphoric acid, dilute hydrochloric acid, dilute sulfuric acid, or formic acid.

[0025] Preferably, the molar ratio of the pH adjuster to the sodium tungstate dihydrate is (1-3):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, etc.

[0026] Preferably, the temperature is raised to 80-90°C, for example, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0027] Preferably, the reaction time is 10-30 min, for example, it can be 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min or 30 min, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0028] Preferably, the temperature is reduced to 5-10℃, for example, 5℃, 5.5℃, 6℃, 6.5℃, 7℃, 7.5℃, 8℃, 8.5℃, 9℃, 9.5℃ or 10℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, the molar ratio of the polyoxometalate to the surfactant is (0.01-10):1, for example, it can be 0.01:1, 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. A further preferred molar ratio is (0.02-0.2):1.

[0030] Preferably, the surfactant in step (1) is dissolved in water and then mixed in the form of a surfactant solution.

[0031] Preferably, the mass fraction of the surfactant solution is 10-50%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0032] This invention allows for easy adjustment of the loading of SEPs by controlling the mass fraction of the surfactant solution, and also allows for control of the pitch of chiral polyacid composite materials.

[0033] Preferably, the polyoxometalate in step (1) is dissolved in water and then mixed in the form of a polyoxometalate solution.

[0034] Preferably, the concentration of the polyoxometalate solution is 0.01-10 mol / L, for example, it can be 0.01 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, or 10 mol / L, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0035] Preferably, the mixing in step (1) is carried out under stirring.

[0036] Preferably, the stirring time is 10-30 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0037] Preferably, after the mixing in step (1) is completed, the steps of standing, filtration, extraction and drying are also performed in sequence.

[0038] Preferably, the extractant comprises a combination of water and ethanol.

[0039] Preferably, the mass ratio of water to ethanol is 1:(4-10), for example, it can be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc.

[0040] Preferably, the drying temperature is 40-60℃, for example, it can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] Preferably, the drying time is 2-3 days, for example, 2 days, 2.1 days, 2.2 days, 2.3 days, 2.4 days, 2.5 days, 2.6 days, 2.7 days, 2.8 days, 2.9 days or 3 days, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0042] Preferably, the cellulose nanocrystal solution comprises a combination of water and cellulose nanocrystals.

[0043] Preferably, the length of the cellulose nanocrystals is 150-200 nm, for example, it can be 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm or 200 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0044] The diameter of the cellulose nanocrystals is 15-20 nm, for example, it can be 15 nm, 16 nm, 17 nm, 18 nm, 19 nm or 20 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0045] Preferably, the cellulose nanocrystals in the cellulose nanocrystal solution have a mass percentage content of 3-3.5%, for example, 3%, 3.1%, 3.2%, 3.3%, 3.4% or 3.5%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0046] The cellulose nanocrystal solution described in this invention is a commercially available product. For example, the cellulose nanocrystal solution can be purchased from Maclean's reagent.

[0047] Preferably, the mass ratio of the surfactant-embedded polyoxometalate to the cellulose nanocrystals is (0.001-0.03):1, for example, it can be 0.001:1, 0.004:1, 0.006:1, 0.008:1, 0.002:1, 0.004:1, 0.006:1, 0.008:1, 0.01:1, 0.012:1, 0.014:1, 0.016:1, 0.018:1, 0.02:1, 0.022:1, 0.024:1, 0.026:1, 0.028:1, or 0.03:1, etc.

[0048] Preferably, the evaporation time is 2-3 days, for example, it can be 2 days, 2.1 days, 2.2 days, 2.3 days, 2.4 days, 2.5 days, 2.6 days, 2.7 days, 2.8 days, 2.9 days or 3 days, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0049] Preferably, the evaporation temperature is 20-30℃, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0050] Preferably, the preparation method specifically includes the following steps:

[0051] (1) The surfactant solution and the polyoxometalate solution are mixed under stirring, then allowed to stand, and then filtered to obtain a white precipitate. The white precipitate is extracted with an extractant and then dried to obtain the surfactant-embedded polyoxometalate. The surfactant solution is obtained by dissolving the surfactant in water. The mass fraction of the surfactant solution is 10-50%. The polyoxometalate solution is obtained by dissolving the polyoxometalate in water. The concentration of the polyoxometalate solution is 0.01-10 mol / L. The molar ratio of the polyoxometalate to the surfactant is (0.01-10):1, preferably (0.02-0.2):1. The stirring time is 10-30 min. The drying temperature is 40-60℃. The drying time is 2-3 days.

[0052] (2) The surfactant-embedded polyoxometalate is mixed with a cellulose nanocrystal solution to obtain a suspension. The suspension is evaporated at 20-30°C for 2-3 days to obtain the chiral polyoxometalate composite material. The cellulose nanocrystal solution comprises a combination of water and cellulose nanocrystals. The length of the cellulose nanocrystals is 150-200 nm and the diameter is 15-20 nm. The mass percentage of cellulose nanocrystals in the cellulose nanocrystal solution is 3-3.5%. The mass ratio of the surfactant-embedded polyoxometalate to the cellulose nanocrystals is (0.001-0.03):1.

[0053] In a second aspect, the present invention provides a chiral polyacid composite material, which is prepared by the preparation method described in the first aspect.

[0054] Thirdly, the present invention provides an application of the chiral polyacid composite material as described in the second aspect, wherein the chiral polyacid composite material is used in optoelectronic devices.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The method for preparing chiral polyacid composite materials provided by this invention utilizes the self-assembly of CNCs to induce the chiral arrangement of rare-earth-containing POMs, constructing a supramolecular structure of rare-earth-containing POMs. The circular polarization luminescence performance is controlled by adjusting the rare-earth-containing POMs and surfactants, combined with CNCs. A simple co-assembly method is used to combine achiral rare-earth-containing POMs-based surfactants with CNCs, inducing achiral POMs to achieve a chiral sequence, thus simplifying the preparation process.

[0057] (2) Negatively charged POMs can bind to surfactants through electrostatic interactions. When co-assembled with chiral templates, the ionic strength of the mixed solution decreases, resulting in a higher yield of chiral polyacid composite materials.

[0058] (3) Using the preparation method of the chiral polyacid composite material provided by the present invention, the prepared chiral polyacid composite material has tunable multicolor, uniform thickness, high quantum yield, circular polarization fluorescence activity, and high CPL brightness. Attached Figure Description

[0059] Figure 1 It is the EuW embedded in tetrabutylammonium bromide in Example 1. 10 Fluorescence spectrum;

[0060] Figure 2 It is the EuW embedded in tetrabutylammonium bromide in Example 1. 10 Absorption spectrum;

[0061] Figure 3These are the CPL spectra of the chiral polyacid composite materials provided in Examples 1, 2, and 1;

[0062] Figure 4 It is EuW 10 Infrared spectrum;

[0063] Figure 5 It is the EuW embedded in tetrabutylammonium bromide in Example 1. 10 Infrared spectrum;

[0064] Figure 6 It is the EuW embedded in tetrabutylammonium bromide in Example 1. 10 TEM image;

[0065] Figure 7 These are polarized light microscope images of the chiral polyacid composite material provided in Example 1;

[0066] Figure 8 This is a SEM image of the cross-section of the chiral polyacid composite material provided in Comparative Example 1;

[0067] Figure 9 This is a SEM image of the cross-section of the chiral polyacid composite material provided in Example 1;

[0068] Figure 10 This is the fluorescence spectrum of the chiral polyacid composite material provided in Example 1;

[0069] Figure 11 This is a quantum yield diagram of the chiral polyacid composite material provided in Example 1;

[0070] Figure 12 The graph shows the quantum yield of chiral polyacid composite materials as a function of different mass fractions of tetrabutylammonium bromide solutions.

[0071] Figure 13 This is a bar chart showing the change in CPL brightness of chiral polyacid composite materials with different mass fractions of tetrabutylammonium bromide solution.

[0072] Figure 14 This is a graph showing the pitch of chiral polyacid composite materials as a function of the mass fraction of different tetrabutylammonium bromide solutions. Detailed Implementation

[0073] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0074] The sources of some components in the following examples and comparative examples are as follows:

[0075] (1)Na9[EuW10 O 36 ]6H2O: Its preparation method includes: dissolving 0.025 mol of sodium tungstate dihydrate in 20 mL of deionized water, and after complete dissolution, adjusting the pH of the solution to 7 with 0.05 mol of glacial acetic acid; dissolving 0.0025 mol of europium nitrate hexahydrate in 2 mL of deionized water, and after complete dissolution, slowly adding it dropwise to the pH-adjusted sodium tungstate dihydrate aqueous solution; stirring evenly and heating the mixed solution to 80℃, reacting for 30 min, and then precipitating crystals at 5℃, filtering, and drying in a vacuum drying oven at 60℃ for 24 h to obtain white solid Na9[EuW 10 O 36 ]6H2O (abbreviated as EuW) 10 Store at room temperature. White solid Na₂[EuW₂] 10 O 36 After being dissolved in 6H2O, it exhibits red fluorescence under a 254nm ultraviolet light.

[0076] (2)Na9[TbW 10 O 36 ]6H2O: Its preparation method is similar to that of EuW 10 The only difference in the preparation method is that europium nitrate hexahydrate is replaced with terbium nitrate hexahydrate in equal amounts; all other raw materials, process parameters, and steps are the same as those in the EuW series. 10 The preparation method is the same.

[0077] (3)Na9[DyW 10 O 36 ]6H2O: Its preparation method is similar to that of EuW 10 The only difference in the preparation method is that europium nitrate hexahydrate is replaced with dysprosium nitrate hexahydrate in equal amounts; all other raw materials, process parameters, and steps are the same as those used in EuW. 10 The preparation method is the same.

[0078] (4) Cellulose nanocrystal solution: purchased from Maclean's reagent, the length of the microcrystalline cellulose in the solution is 150-200 nm, the diameter is 15-20 nm, and the mass fraction is 3%.

[0079] Example 1

[0080] A chiral polyacid composite material and its preparation method, wherein the preparation method specifically includes the following steps:

[0081] (1) Dissolve 1.25g of tetrabutylammonium bromide in 5mL of deionized water to form a solution, then take 0.00035mol EuW 10 Dissolve in 5 mL of deionized water, stir thoroughly to dissolve, and then slowly add the tetrabutylammonium bromide solution dropwise to EuW. 10After stirring for 30 minutes, the solution gradually became turbid. Upon standing, a white precipitate formed. The precipitate was filtered and purified by extraction with a mixture of deionized water and ethanol (mass ratio 1:6). The precipitate was collected and dried under vacuum at 60°C for 48 hours to obtain tetrabutylammonium bromide-embedded EuW. 10 ;

[0082] (2) Take 3 mL of a 3% (w / w) cellulose nanocrystal solution and add 0.0005 g of tetrabutylammonium bromide-embedded EuW 10 The suspension was obtained and placed in a polystyrene petri dish with a diameter of about 35 mm. The suspension was evaporated and concentrated at 25°C for 2 days to obtain the chiral polyacid composite material.

[0083] Examples 2-5

[0084] A chiral polyacid composite material and its preparation method are disclosed. The only difference between this material and Example 1 is that the amount of tetrabutylammonium bromide used in step (1) is 0.56g, 2.14g, 3.33g, and 5.00g, respectively. The other raw materials, process parameters, and steps are the same as in Example 1.

[0085] Examples 6-9

[0086] A chiral polyacid composite material and its preparation method, which differs from Example 1 only in that the tetrabutylammonium bromide-embedded EuW in step (2) is used. 10 The amounts were 0.00025g, 0.001g, 0.0012g, and 0.0015g, respectively, and the other raw materials, process parameters, and steps were the same as in Example 1.

[0087] Examples 10-11

[0088] A chiral polyacid composite material and its preparation method are disclosed, differing from Example 1 only in that EuW is used. 10 Equal amount replaced with Na9[TbW 10 O 36 ]6H2O, Na9[DyW 10 O 36 The other raw materials, process parameters and steps are the same as in Example 1.

[0089] Example 12

[0090] A chiral polyacid composite material and its preparation method are disclosed. The only difference between this material and Example 1 is that the surfactant tetrabutylammonium bromide in step (1) is replaced with benzoic acid in an equal amount. All other raw materials, process parameters and steps are the same as in Example 1.

[0091] Comparative Example 1

[0092] A chiral polyacid composite material and its preparation method are disclosed. The difference between this method and Example 1 is that the preparation method specifically includes the following steps: Take 3 mL of a 3% (w / w) cellulose nanocrystal solution and add 0.00045 g of EuW... 10 The suspension was obtained and placed in a polystyrene petri dish with a diameter of about 35 mm. The suspension was evaporated and concentrated at 25°C for 2 days to obtain the chiral polyacid composite material.

[0093] Product characterization and performance testing:

[0094] (1) Tests were performed using a steady-state transient fluorescence spectrometer (Edinburgh Instruments FLS1000) and a UV-NIR-Vis spectrometer (PerkinElmer Lambda 750); the test results are as follows: Figure 1 EuW embedded in tetrabutylammonium bromide in Example 1 10 fluorescence spectrum and Figure 2 EuW embedded in tetrabutylammonium bromide in Example 1 10 The absorption spectrum is shown in the figure; by Figure 1 and Figure 2 It can be seen that the tetrabutylammonium bromide-embedded EuW 10 Two strong absorption peaks D0 are observed at 316 nm and 394 nm, and corresponding emission signals can be observed at 595 nm, 620 nm, 652 nm, 692 nm, and 700 nm under optimal excitation at 316 nm, consistent with Eu. 3+ The luminescence characteristics of ions. [EuW] 10 O 36 ] 9- Photoexcitation in the O→W LMCT (coordinate bond charge transfer from oxygen atom to tungsten ion) band produced Eu. 3+ This indicates that electrons from the oxygen atom transitioned from their coordinate bonds to the d orbitals of the tungsten ion, and that the energy of these electrons was transferred to Eu. 3+ Ions. The strong emission band at 595 nm corresponds to... 5 D0→ 7 The F1 emission transition corresponds to the emission transition at 620nm. 5 D0→ 7 The F2 emission transition occurs in the weak 652nm band. 5 D0→ 7 The emission transition of F3, and the strong emission bands at 692 and 700 nm correspond to 5 D0→ 7 F4 launch transition.

[0095] The chiral polyacid composite material provided in Example 1 was subjected to fluorescence spectroscopy testing, and the test results are as follows: Figure 10The fluorescence spectrum of the chiral polyacid composite material provided in Example 1 is shown in the figure. It can be seen from the figure that the interaction between SEPs and CNCs did not affect Eu. + The luminescence of the ions did not shift, and the red luminescence of the chiral polyacid composite material was due to Eu. + It comes from ions.

[0096] (2) The CPL spectra of the chiral polyacid composite materials provided in Example 1, Example 2, and Comparative Example 1 were tested using a circularly polarized emission spectrometer (JASCO CPL-300). The test results are as follows: Figure 3 As shown in the CPL spectra of the chiral polyacid composite materials provided in Examples 1, 2 and Comparative Example 1, when the overlap between the emission peak and the photon bandgap is high, the CPL signal of the chiral polyacid composite material provided in Example 1 is stronger.

[0097] (3) Scan the EuW using a Fourier transform infrared spectrometer (BRUKER VERTEX 80). 10 EuW encapsulated with tetrabutylammonium bromide in Example 1 10 The test results are as follows Figure 4 EuW 10 infrared spectrum and Figure 5 EuW embedded in tetrabutylammonium bromide in Example 1 10 The infrared spectrum is shown at 947 cm⁻¹. -1 (W=O) d ), 871cm -1 (WO b -W), 817cm -1 and 784cm -1 (W-Oc-W) (where b, c, and d represent the letters of the vertices of the polyoxometalate polyhedral structure, and these characteristic absorption peaks are respectively attributed to WO) d (944cm -1 )WO b (848cm -1 W-Oc (776cm) -1 694cm -1 Characteristic vibration bands were observed at the point where the stretching vibrations were absorbed, indicating that EuW 10 The successful preparation of [the substance] and the unchanged framework after its encapsulation with tetrabutylammonium bromide; from […]. Figure 5 It can be seen that at 2954cm -1 and 2869cm -1 The positions represent the asymmetric and symmetric vibrations of CH and C-H2, respectively, proving that the alkyl chain of tetrabutylammonium bromide is successfully linked to EuW. 10 The surface.

[0098] (4) The tetrabutylammonium bromide-embedded EuW in Example 1 was scanned using TEM (HITACHI-HT7700). 10 The test results are as follows Figure 6 EuW embedded in tetrabutylammonium bromide in Example 1 10 The TEM image shows that the alkyl chain of tetrabutylammonium bromide connects EuW 10 The clusters are tightly wrapped, forming a spherical structure, without any aggregation.

[0099] (5) The chiral polyacid composite material provided in Example 1 was observed using a polarizing microscope (Nikon, Ci-POL). The test results are as follows: Figure 7 A polarized light microscope image of the chiral polyacid composite material provided in Example 1 is shown. Figure 7 As can be seen, the chiral polyacid composite material provided in Example 1 exhibits obvious chiral nematic fingerprint texture features under a polarizing microscope.

[0100] (6) The chiral polyacid composite materials provided in Example 1 and Comparative Example 1 were scanned using SEM (ZEISS-Merlin), and the test results are as follows: Figure 8 SEM images of the cross-section of the chiral polyacid composite material provided in Comparative Example 1 and Figure 9 The SEM image of the cross-section of the chiral polyacid composite material provided in Example 1 shows that the pitch of the chiral polyacid composite material provided in Example 1 is smaller than that of the chiral polyacid composite material provided in Comparative Example 1. This is because tetrabutylammonium bromide reduces the electrostatic repulsion between cellulose nanocrystals, thereby reducing the pitch.

[0101] The chiral polyacid composite materials provided in Examples 1-5 and Comparative Example 1 were scanned using SEM (ZEISS-Merlin). The pitch of the chiral polyacid composite materials provided in Examples 1-5 and Comparative Example 1 was measured. The test results are as follows: Figure 14 The pitch of the chiral polyacid composite material varies with the mass fraction of different tetrabutylammonium bromide solutions, as shown in the graph. The results indicate that the pitch of the chiral polyacid composite material provided in Example 1 is relatively small, and the pitch of the chiral polyacid composite material first decreases and then increases with the increase of the mass fraction of the tetrabutylammonium bromide solution.

[0102] (7) The chiral polyacid composite material provided in Example 1 was scanned using a steady-state transient fluorescence spectrometer (Edinburgh Instruments FLS1000). The test results are as follows: Figure 11 The fluorescence spectrum of the chiral polyacid composite material provided in Example 1 is shown in the figure. Figure 11 It can be seen that the chiral polyacid composite material provided in Example 1 has a relatively high quantum yield of about 84%.

[0103] The quantum yields of the chiral polyacid composites provided in Examples 1-5 and Comparative Example 1 were tested using a steady-state transient fluorescence spectrometer (Edinburgh Instruments FLS1000). The test results are as follows: Figure 12 The graph shows the quantum yield (quantum yield describes the fluorescence efficiency of a sample, which is the ratio of the number of emitted photons to the number of photons absorbed by the sample) of the chiral polyacid composite material with different mass fractions of tetrabutylammonium bromide solution. As can be seen from the graph, the quantum yield of the chiral polyacid composite material first increases and then basically stabilizes with the increase of the mass fraction of surfactant solution.

[0104] (8) The chiral polyacid composite materials provided in Examples 1-5 and Comparative Example 1 were scanned using a circularly polarized emission spectrometer (JASCO CPL-300). The results were obtained using the formula... Where ε abs and The CPL brightness of Examples 1-5 and Comparative Example 1 was calculated based on the molecular extinction coefficient and emission quantum yield measured at the excitation wavelength, respectively. The results are as follows: Figure 13 The bar chart shows the change in CPL brightness of the chiral polyacid composite material with different mass fractions of tetrabutylammonium bromide solution. The results show that the CPL brightness in Example 1 is relatively high, and the CPL brightness of the chiral polyacid composite material first increases and then decreases with the increase of the mass fraction of surfactant solution.

[0105] Using a circularly polarized emission spectrometer (JASCO CPL-300) to scan Example 12, the CPL brightness of Example 12 was calculated to be approximately 7.6, which is lower than the CPL brightness of the chiral polyacid composite material provided in Example 1. Using benzoic acid as a surfactant cannot effectively improve the CPL brightness of the chiral polyacid composite material.

[0106] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing a chiral polyacid composite material, characterized in that, The preparation method includes the following steps: (1) The surfactant is mixed with the polyoxometalate to obtain the surfactant-encapsulated polyoxometalate; (2) The surfactant-embedded polyoxometalate is mixed with a cellulose nanocrystal solution to obtain a suspension, and the suspension is evaporated to obtain the chiral polyoxometalate composite material; The surfactant is tetrabutylammonium bromide; The surfactant described in step (1) is dissolved in water and then mixed in the form of a surfactant solution; the mass fraction of the surfactant solution is 20-50%. The mass ratio of the surfactant-embedded polyoxometalate to the cellulose nanocrystals is (0.001-0.03):1; The polyoxometalate includes Na9[EuW] 10 O 36 ]6H2O, Na9[LaW 10 O 36 ]6H2O, Na9[TbW 10 O 36 ]6H2O, Na9[SmW 10 O 36 ]6H2O or Na9[DyW 10 O 36 Any one or at least two of the following: 6H2O; The molar ratio of the polyoxometalate to the surfactant is (0.02-0.2):

1.

2. The preparation method according to claim 1, characterized in that, The polyoxometalate described in step (1) is dissolved in water and then mixed in the form of a polyoxometalate solution.

3. The preparation method according to claim 2, characterized in that, The concentration of the polyoxometalate solution is 0.01-10 mol / L.

4. The preparation method according to claim 1, characterized in that, The mixing in step (1) is carried out under stirring.

5. The preparation method according to claim 4, characterized in that, The stirring time is 10-30 minutes.

6. The preparation method according to claim 1, characterized in that, After the mixing in step (1) is completed, the steps of settling, filtration, extraction and drying are also performed in sequence.

7. The preparation method according to claim 6, characterized in that, The extractant used in the extraction includes a combination of water and ethanol.

8. The preparation method according to claim 7, characterized in that, The mass ratio of water to ethanol is 1:(4-10).

9. The preparation method according to claim 6, characterized in that, The drying temperature is 40-60 ℃.

10. The preparation method according to claim 6, characterized in that, The drying time is 2-3 days.

11. The preparation method according to claim 1, characterized in that, The cellulose nanocrystal solution comprises a combination of water and cellulose nanocrystals.

12. The preparation method according to claim 11, characterized in that, The cellulose nanocrystals have a length of 150-200 nm and a diameter of 15-20 nm.

13. The preparation method according to claim 1, characterized in that, The cellulose nanocrystal solution contains 3-3.5% cellulose nanocrystals by mass.

14. The preparation method according to claim 1, characterized in that, The evaporation time is 2-3 days.

15. The preparation method according to claim 1, characterized in that, The evaporation temperature is 20-30 ℃.

16. The preparation method according to claim 1, characterized in that, The preparation method specifically includes the following steps: (1) The surfactant solution and the polyoxometalate solution are mixed under stirring, then allowed to stand, and then filtered to obtain a white precipitate. The white precipitate is extracted with an extractant and then dried to obtain the surfactant-embedded polyoxometalate. The surfactant solution is obtained by dissolving the surfactant in water; The polyoxometalate solution is obtained by dissolving the polyoxometalate in water; the concentration of the polyoxometalate solution is 0.01-10 mol / L. The stirring time is 10-30 min; The drying temperature is 40-60℃; The drying time is 2-3 days; (2) The surfactant-embedded polyoxometalate is mixed with cellulose nanocrystal solution to obtain a suspension, and the suspension is evaporated at 20-30 °C for 2-3 days to obtain the chiral polyoxometalate composite material; The cellulose nanocrystal solution comprises a combination of water and cellulose nanocrystals; The cellulose nanocrystals have a length of 150-200 nm and a diameter of 15-20 nm. The cellulose nanocrystal solution contains 3-3.5% cellulose nanocrystals by mass.

17. A chiral polyacid composite material, characterized in that, The chiral polyacid composite material is prepared by the preparation method described in any one of claims 1 to 16.

18. The application of the chiral polyacid composite material as described in claim 17 in optoelectronic devices.

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