Inorganic liquid crystal composite material, optical film and preparation method and application thereof

Abstract

The application discloses an inorganic liquid crystal composite material, an optical film and a preparation method and application thereof. The inorganic liquid crystal composite material comprises a solvent, titanium dioxide-based nanosheets dispersed in the solvent, and quantum dots loaded on surfaces of the titanium dioxide-based nanosheets. The inorganic liquid crystal composite material can be arranged under the induction of an electric field or a magnetic field, and has the functions of light modulation, polarized light emission and quantitative detection of ultraviolet light. The application further provides an optical film, a preparation method of the inorganic liquid crystal composite material and the optical film, and application of the inorganic liquid crystal composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic luminescent materials, in particular to an inorganic liquid crystal composite material, an optical film and a preparation method and application thereof. BACKGROUND

[0002] The research on luminescent liquid crystals originated from the continuous exploration of liquid crystal materials and display technology. Liquid crystal display requires an optical liquid crystal material capable of controlling light through an electric field. However, traditional liquid crystals need external light sources and color polarizing plates to display images, and the function is relatively single, and there is a waste of light energy consumption. In order to simplify the display device and reduce energy consumption, researchers began to explore the introduction of luminescent materials into the liquid crystal layer, so that the display itself can have the dual functions of luminescence and dimming. This innovation makes the display no longer dependent on external backlight, thereby realizing a thinner, lighter and more power-saving design.

[0003] Traditional liquid crystal materials are mainly organic luminescent liquid crystal materials. Compared with organic luminescent liquid crystal materials, inorganic composite liquid crystal materials have better system compatibility, high magnetic / electric field sensitivity, easy solution processing and other characteristics, and have considerable application potential. At present, there are few reports on inorganic liquid crystal materials, and their performance is difficult to meet the use requirements of background light sources.

[0004] Therefore, it is of great significance to develop an inorganic liquid crystal material to fill the research gap in the field of inorganic luminescent liquid crystals and expand the application field of inorganic liquid crystal materials. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides an inorganic liquid crystal composite material which can be arranged under the induction of an electric field or a magnetic field, realizing the light adjusting ability of visible light, the polarized light luminescent property and the quantitative detection of ultraviolet light.

[0006] The present application also provides a preparation method of the inorganic liquid crystal composite material.

[0007] The present application also provides an application of the inorganic liquid crystal composite material.

[0008] The present application also provides a fluorescent film.

[0009] The present application also provides a preparation method of the fluorescent film.

[0010] Specifically, the first aspect of the present application relates to an inorganic liquid crystal composite material, comprising:

[0011] a solvent;

[0012] a titanium dioxide-based nanosheet, the titanium dioxide-based nanosheet being dispersed in the solvent, and the diameter-thickness ratio of the titanium dioxide-based nanosheet being ≥1000;

[0013] Quantum dots are loaded on the surface of the titanium dioxide-based nanosheet.

[0014] The inorganic liquid crystal composite material according to the first aspect of the present application has at least the following beneficial effects:

[0015] Zero-dimensional quantum dots are loaded on the surface of two-dimensional titanium dioxide-based nanosheets through chemical bonds and electrostatic adsorption, a heterojunction is formed between titanium dioxide and quantum dots, the light-emitting ability of quantum dots is utilized, so that a wider band of incident light is responded by titanium dioxide, and light modulation ability for visible light, polarized light emission characteristics, and quantitative detection for ultraviolet light are realized.

[0016] The diameter-thickness ratio of the titanium dioxide-based nanosheet is greater than or equal to 1000, and the titanium dioxide-based nanosheet has a great geometric anisotropy ratio. The titanium dioxide-based nanosheet can be dispersed in a solvent to form a uniform and stable dispersion system, and then can be arranged in a direction under the induction of an electric field or a magnetic field to form a highly ordered heterojunction fluorescent film. If the diameter-thickness ratio is reduced, the dispersion stability in the solvent cannot be guaranteed, and electromagnetic orientation cannot be realized.

[0017] The titanium dioxide-based nanosheet has a birefringence effect due to the great geometric anisotropy ratio, and can have different phase delay abilities for light rays of different colors in the visible light band, so that modulation for a long wavelength band is achieved. Under ultraviolet excitation, the circular dichroism absorption of the nanosheet is utilized to effectively modulate the polarization state of the carbon dot light emission in the constructed heterojunction. If the diameter-thickness ratio is insufficient, the size effect required for polarized light modulation cannot be met, polarized light emission cannot be realized, and light modulation ability for visible light and quantitative detection for ultraviolet light cannot be realized.

[0018] According to some embodiments of the present application, the solvent is a polar solvent.

[0019] According to some embodiments of the present application, the solvent is selected from a combination of one or more of water, ethylene glycol, N,N-dimethylformamide, and dimethyl sulfoxide.

[0020] According to some embodiments of the present application, the material of the titanium dioxide-based nanosheet is selected from doped or undoped titanium dioxide.

[0021] In the doped titanium dioxide, the doping element is selected from one or more elements having an ionic radius close to Ti 4+ Doping with an element having an ionic radius close to Ti4+ is conducive to uniform doping.

[0022] According to some embodiments of the present application, the doping element is selected from a combination of one or more of Fe, Co, Mn, Ni, and Sn.

[0023] According to some embodiments of the present application, the doping element is selected from one or both of Fe and Co.

[0024] According to some embodiments of the present application, the doping element is selected from Co.

[0025] According to some embodiments of the present application, the doping element has a molar ratio of 1-5:25 with Ti in the TiO2-based nanosheet, for example, specifically, 1:25, 2:25, 3:25, 4:25, 1:5 or any ratio therebetween.

[0026] According to some embodiments of the present application, the TiO2-based nanosheet has a thickness of 1-2 nm. That is, the TiO2-based nanosheet is a single-layer or few-layer structure.

[0027] According to some embodiments of the present application, the TiO2-based nanosheet has a sheet diameter ≥2 μm.

[0028] According to some embodiments of the present application, the TiO2-based nanosheet has a diameter-to-thickness ratio ≥1100.

[0029] According to some embodiments of the present application, the inorganic liquid crystal composite material has a solid content of 0.1-15 mg / mL. For example, 0.1 mg / mL, 0.2 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL or any value therebetween.

[0030] According to some embodiments of the present application, the quantum dots are selected from carbon-based, cadmium-based or silicon-based quantum dots.

[0031] The inorganic liquid crystal composite material can be modulated for different light-emitting behaviors of quantum dots, and is suitable for quantum dots with light-emitting energy equal to or less than 400 nm (when the photon energy is about 400 nm, the nanosheet has a certain degree of absorption).

[0032] According to some embodiments of the present application, the carbon-based quantum dots are selected from carbon quantum dots, graphene quantum dots, carbon nitride quantum dots.

[0033] According to some embodiments of the present application, the cadmium-based quantum dots are selected from cadmium sulfide, cadmium selenide or cadmium telluride quantum dots.

[0034] According to some embodiments of the present application, the silicon-based quantum dots are selected from silicon quantum dots, silicon oxide quantum dots, silicon carbide quantum dots.

[0035] According to some embodiments of the present application, the average particle size of the quantum dots is 1-20 nm.

[0036] According to some embodiments of the present application, the average particle size of the quantum dots is 2-10 nm.

[0037] According to some embodiments of the present application, the mass ratio of the quantum dots to the titanium dioxide-based nanosheet is 0.001-0.1:1000. For example, it can be specifically 0.001:1000, 0.005:1000, 0.01:1000, 0.02:1000, 0.05:1000, 0.1:1000 or any ratio therebetween.

[0038] The second aspect of the present application is directed to a method for preparing the inorganic liquid crystal composite material as described above, comprising the steps of:

[0039] S1, mixing preparation raw materials including titanium source, potassium source and lithium source, calcining to obtain ion intercalation titanium dioxide-based nanosheet composite;

[0040] S2, performing proton exchange and solution swelling and exfoliation on the ion intercalation titanium dioxide-based nanosheet composite to obtain a titanium dioxide-based nanosheet dispersion;

[0041] S3, mixing quantum dot dispersion and the titanium dioxide-based nanosheet dispersion, solid-liquid separation to obtain quantum dot @ titanium dioxide-based nanosheet composite;

[0042] S4, dispersing the quantum dot @ titanium dioxide-based nanosheet composite in a solvent to obtain the inorganic liquid crystal composite material.

[0043] The method for preparing the inorganic liquid crystal composite material according to the second aspect of the present application has at least the following beneficial effects:

[0044] Mixing preparation raw materials including titanium source, potassium source and lithium source, calcining to obtain ion intercalation titanium dioxide-based nanosheet composite having a layered stacking structure, replacing K + and Li + in the ion intercalation titanium dioxide-based nanosheet composite by proton exchange, and then performing solution swelling and exfoliation to obtain a titanium dioxide-based nanosheet dispersion.

[0045] Using K + , Li + mixed ion source doping can improve doping uniformity, control the growth of titanium dioxide-based nanosheets, obtain single-layer or few-layer titanium dioxide nanosheets, and improve the aspect ratio. Among them, K + with a larger ionic radius meets the intercalation ion structure required for preparing stacked titanium dioxide nanosheet crystal structure. Although adding one kind of ion source can also synthesize stacked titanium dioxide nanosheet structure, it cannot achieve uniform embedding and is prone to produce pure titanium dioxide crystal structure. The final exfoliated nanosheet structure cannot be effectively controlled, including the diameter and atomic layer thickness of the nanosheet, which affects the exfoliation effect of the final nanosheet. The introduction of Li +The problem can be perfectly solved, and smaller Li+ions can be better embedded between different titanium dioxide layers to prevent the formation of pure titanium dioxide crystal structures, which is beneficial to K + Better incorporation, and then the thickness of the obtained single-atom layer or few-layer titanium oxide nanosheet is 1-2 nm, and a higher aspect ratio is obtained. Therefore, K + , Li + The mixed ion source can be used to effectively control the growth of titanium dioxide nanosheets.

[0046] The potassium source and the lithium source are cheap and easy to obtain, which is beneficial to large-scale production.

[0047] According to some embodiments of the present application, the titanium source is selected from one or a combination of two of titanium dioxide, titanium hydroxide or titanium chloride.

[0048] According to some embodiments of the present application, the lithium source is selected from one or a combination of two of lithium chloride, lithium oxide or lithium carbonate.

[0049] According to some embodiments of the present application, the potassium source is selected from one or a combination of two of potassium chloride, potassium oxide or potassium carbonate.

[0050] According to some embodiments of the present application, the molar ratio of the titanium source, the potassium source and the lithium source is 25:4-7:0.7-1.3.

[0051] By controlling the addition ratio of the potassium source and the lithium source, the crystallization and directional growth of the titanium dioxide nanosheet are better controlled, so as to obtain an ideal nanosheet particle size and size. Controlling the amount of ion source in a suitable range can better ensure the growth of the nanosheet. For example, if the amount of ion source is too small, the intercalation ion is reduced, which is easy to cause the stacking of titanium oxide and the collapse of the nanosheet structure, and the full exfoliation of the nanosheet cannot be realized. If the amount of ion source is increased, the growth process of the nanosheet is inhibited, and the size of the nanosheet bulk (i.e. the ion intercalation titanium dioxide-based nanosheet composite) is reduced.

[0052] According to some embodiments of the present application, the preparation raw material further comprises a doping source.

[0053] According to some embodiments of the present application, the doping element of the doping source is selected from one or a combination of two of Fe, Co, Mn, Ni and Sn.

[0054] According to some embodiments of the present application, the doping source is selected from one or a combination of two of oxides, chlorides, carbonates or hydroxides of the corresponding doping elements.

[0055] According to some embodiments of the present application, in step S1, the calcination temperature is 900-1200°C, and the calcination time is 8-20h.

[0056] According to some embodiments of the present application, in step S1, the mixing comprises grinding.

[0057] According to some embodiments of the present application, the grinding time is 20-60 min.

[0058] According to some embodiments of the present application, in step S2, the proton exchange is performed in an acid solution.

[0059] According to some embodiments of the present application, the acid solution is hydrochloric acid.

[0060] According to some embodiments of the present application, the concentration of the acid solution is 1-1.5 M.

[0061] According to some embodiments of the present application, the solid-liquid ratio of the ion intercalation titanium dioxide-based nanosheet composite and the acid solution is 5-30 mg / mL.

[0062] According to some embodiments of the present application, the proton exchange time is 30-50 h.

[0063] According to some embodiments of the present application, in step S2, it further comprises standing precipitation and drying after the proton exchange.

[0064] According to some embodiments of the present application, in step S2, the solution swelling exfoliation comprises stirring the product after the proton exchange in an exfoliating agent solution.

[0065] According to some embodiments of the present application, the exfoliating agent solution is a tetrabutylammonium hydroxide (TBAOH) solution.

[0066] According to some embodiments of the present application, the concentration of the exfoliating agent solution is 3-20 mg / mL.

[0067] According to some embodiments of the present application, the solid-liquid ratio of the product after the proton exchange and the exfoliating agent solution is 1-10 mg / mL.

[0068] According to some embodiments of the present application, the stirring time is 24-36 h.

[0069] According to some embodiments of the present application, in step S2, it further comprises standing the product after the solution swelling exfoliation, and taking the upper liquid to obtain a titanium dioxide-based nanosheet dispersion.

[0070] Wherein, standing is used to remove the impurities in the lower layer of the precipitate.

[0071] According to some embodiments of the present application, in step S2, the concentration of the titanium dioxide-based nanosheet dispersion is 0.1-20 mg / mL.

[0072] According to some embodiments of the present application, in step S2, the concentration of the titanium dioxide-based nanosheet dispersion liquid is 0.1-10 mg / mL. For example, it can be 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 5 mg / mL, 10 mg / mL or any value between them.

[0073] According to some embodiments of the present application, in step S3, the volume fraction of the quantum dot dispersion liquid relative to the titanium dioxide-based nanosheet dispersion liquid is 0.02 vol‰-2 vol‰. For example, it can be 0.02 vol‰, 0.05 vol‰, 1 vol‰, 2 vol‰ or any value between them. When the concentration of quantum dots is less than the lower limit percentage, the luminescence intensity is weak; when the concentration of quantum dots is too high, it is easy to cause excessive loading to appear flocculation and precipitation.

[0074] According to some embodiments of the present application, in step S3, the concentration of quantum dots in the quantum dot dispersion liquid is 0.1-20 mg / mL. The quantum dot solution can be obtained by market or prepared by known methods.

[0075] According to some embodiments of the present application, in step S3, the mixing is stirring, the stirring speed is 500-1000 rpm, and / or the stirring time is 15-60 min.

[0076] According to some embodiments of the present application, in step S3, the mixing temperature is 25-60℃, which is conducive to the loading of quantum dots on the titanium dioxide-based nanosheet to form a heterojunction structure.

[0077] According to some embodiments of the present application, in step S3, the solid-liquid separation is centrifugal separation.

[0078] According to some embodiments of the present application, the centrifugal separation speed is 5000-12000 rpm, and the centrifugal separation time is 5-20 min.

[0079] According to some embodiments of the present application, in step S4, the dispersion is shock dispersion, and the shock dispersion time can be selected as 3-15 min.

[0080] According to some embodiments of the present application, the short-wave detection wavelength range of the inorganic liquid crystal composite material is 305-480 nm, which is greater than the wavelength corresponding to the band gap of the titanium-based nanosheet carrier and less than the wavelength corresponding to the band gap of the loaded quantum dots, covering the ultraviolet A region and the entire blue light region.

[0081] According to some embodiments of the present application, the long-wave band detection wavelength range of the inorganic liquid crystal composite material is 450-780 nm, which is greater than the wavelength corresponding to the loaded quantum dot band gap and covers almost the entire visible light region.

[0082] According to some embodiments of the present application, the wavelength range of the polarization modulation of the inorganic liquid crystal composite material is 430-650 nm, and the ability to modulate the polarization state of the light emission is 30%-50%.

[0083] The modulation range of the polarization behavior of the light emission band depends on the light emission wavelength of the quantum dots. The ability to modulate the polarization state of the light emission is calculated by applying an electric field and measuring the change in the intensity of the carbon dot light emission spectrum (including 90° vertical linearly polarized light and 0° vertical linearly polarized light) before and after the oriented polarizer.

[0084] It should be noted that the above wavelength range is related to the light emission behavior of the quantum dots and is not related to the loading amount of the quantum dots. The loading amount of the quantum dots mainly affects the light emission intensity and does not affect the modulation of the light emission band.

[0085] The third aspect of the present application relates to the use of the above-mentioned inorganic liquid crystal composite material in the preparation of a fluorescent film or an optical device.

[0086] The above-mentioned inorganic liquid crystal composite material has electromagnetic orientation characteristics and dual functions of light emission and light modulation, and can be used to prepare a fluorescent film or an optical device.

[0087] According to some embodiments of the present application, the optical device includes a display device, an optical detector, or a multifunctional optical device.

[0088] The multifunctional optical device includes a multifunctional optical device that integrates light emission, light modulation, and detection. Specifically, by using a polarizer, short-wave band detection, long-wave band modulation, and polarization control of the light emission band can be achieved.

[0089] The fourth aspect of the present application relates to a fluorescent film, and the preparation raw material thereof includes the above-mentioned inorganic liquid crystal composite material.

[0090] The fluorescent film of the present embodiment, due to the use of the above-mentioned inorganic liquid crystal composite material, at least has all the beneficial effects brought by the embodiments of the inorganic liquid crystal composite material.

[0091] According to some embodiments of the present application, the area of the fluorescent film is ≥1 cm 2 .

[0092] According to some embodiments of the present application, the area of the fluorescent film is 1-4 cm 2 .

[0093] The fifth aspect of the present application relates to a method for preparing the fluorescent film, comprising the steps of:

[0094] The substrate is placed in the inorganic liquid crystal composite material, and the fluorescent film is prepared by a pulling process under the action of an electric field or a magnetic field.

[0095] The inorganic liquid crystal composite material has good electromagnetic orientation characteristics, and a highly ordered fluorescent film structure can be prepared by a pulling process, which can ensure the film preparation area and production efficiency.

[0096] According to some embodiments of the present application, the strength of the electric field is > 60 V / cm.

[0097] According to some embodiments of the present application, the strength of the magnetic field is > 200 mT.

[0098] According to some embodiments of the present application, the substrate is selected from glass, silicon wafer, ITO or FTO.

[0099] According to some embodiments of the present application, the pulling speed is ≤ 0.3 cm / min.

[0100] Other features and advantages of the present application will be set forth in the specification, and in part will become apparent from the specification, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0101] Figure 1 X-ray diffraction pattern of the inorganic liquid crystal composite material prepared in Example 1 of the present application;

[0102] Figure 2 Transmission electron microscopy images of CDs (a) and inorganic liquid crystal composite material (b) in Example 1 of the present application;

[0103] Figure 3 Atomic force microscopy image of the inorganic liquid crystal composite material prepared in Example 1 of the present application;

[0104] Figure 4 Absorption spectrum of the inorganic liquid crystal composite material prepared in Example 1 of the present application;

[0105] Figure 5 X-ray photoelectron spectroscopy of the inorganic liquid crystal composite material prepared in Example 1 of the present application;

[0106] Figure 6 Schematic diagram of the device for preparing the highly ordered CDs / CTO nanosheet heterojunction composite film in Example 4 of the present application;

[0107] Figure 7 Optical photograph of the highly ordered CDs / CTO nanosheet heterojunction composite film prepared in Example 4 of the present application;

[0108] Figure 8 Deposition optical image (Ex = 365 nm) of highly ordered CDs / CTO nanosheet heterojunction composite film prepared for Example 5 of the present application;

[0109] Figure 9 Schematic diagram of optical device for Example 6 of the present application;

[0110] Figure 10 Luminescence polarization modulation performance of inorganic liquid crystal composite material prepared for Example 1 of the present application;

[0111] Figure 11 Luminescence polarization modulation performance of inorganic liquid crystal composite material prepared for Example 2 of the present application;

[0112] Figure 12 Luminescence polarization modulation performance (a) and intensity change value (b) of inorganic liquid crystal composite material prepared for Example 3 of the present application;

[0113] Figure 13 Ultraviolet light detection performance of inorganic liquid crystal composite material prepared for Example 1 of the present application. DETAILED DESCRIPTION

[0114] The embodiments of the present application are described in detail below, the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0115] In the following examples and comparative examples, part of the raw materials are described as follows, and the remaining raw materials are all conventional commercially available raw materials unless otherwise specified.

[0116] CoO, CAS#: 1307-96-6, Aladdin Co. Ltd.

[0117] TiO2, CAS#: 13463-67-7, Aladdin Co. Ltd.

[0118] K2CO3, CAS#: 6381-79-9, Aladdin Co. Ltd.

[0119] Li2CO3, CAS#: 554-13-2, Aladdin Co. Ltd.

[0120] TBAOH, CAS#: 2052-49-5, Sigma-Aldrich Co. Ltd.

[0121] CdSe quantum dots: CAS: 1306-24-7 Sigma-Aldrich Co. Ltd.

[0122] Carbon quantum dots (CDs), Catalog#R-GQ-002, Xi'an Ruixi Biological Technology Co., Ltd.

[0123] Example 1

[0124] This embodiment prepares an inorganic liquid crystal composite material, which is a CDs / cobalt-doped titanium dioxide (CTO) nanosheet heterojunction composite liquid crystal material, and its preparation process includes:

[0125] (1) Weigh and mix TiO2, CoO, K2CO3 and Li2CO3 powders with a molar ratio of 25:3:6:1, grind them thoroughly for 30 min, place them in a muffle furnace and calcine them at 1100℃ for 5 h to obtain solid blocks.

[0126] (2) Place the solid block in a 1M hydrochloric acid solution (solid-liquid ratio 10mg / mL) and stir slowly for 3 days to allow for full proton exchange, let it stand to precipitate, and then dry.

[0127] (3) Take 1g of dried powder and add 10mL of LTA BAOH solution (10mg / mL). Stir again for 1 day to allow the stacked nanosheets to fully expand and fall off. Let stand to remove the lower layer impurities and form a 0.8mg / mL CTO nanosheet dispersion.

[0128] (4) Pour a high-concentration CDs solution (0.1 mg / mL) into the CTO nanosheet dispersion obtained in step (3). The volume fraction of the CDs solution relative to the CTO nanosheet dispersion is 0.3 vol‰. Heat to 35°C and stir at 800 rpm for 30 min to ensure thorough mixing. Then centrifuge at 8000 rpm for 10 min to obtain a heterojunction solid. The CDs loading was tested to be 0.02:1000. Loading test method: Shake the sample for about 5 min, let it stand for 30 min, centrifuge the mixture at 12000 rpm for 10 min, dry the collected centrifuged material, and compare it with the original CTO nanosheet mass.

[0129] (5) Add 10 mL of water to 20 mg of heterojunction solid and shake manually for 10 min to obtain 0.2 mg / mL CDs / CTO nanosheet heterojunction composite liquid crystal material.

[0130] The basic structure of the fluorescent composite material prepared in Example 1 was tested, and the test results are as follows: Figures 1-4 As shown.

[0131] Depend on Figure 1 It can be seen that the predicted phase structure of CDs, CTO nanosheets and their composites is consistent with expectations. From Figure 2(a) TEM images show that CDs have a diameter of about 7 nm; Figure 2 (b) is a TEM image of the resulting CDs / CTO nanoplatelet heterojunction composite liquid crystal material, showing that quantum dots are successfully bonded to the surface of CTO nanoplatelets.

[0132] Figure 3 It can be seen that the entire nanoplatelet is a single-layer or few-layer structure, and the size of CTO is 2 μm and the thickness is about 1.8 nm.

[0133] Figure 4 is an absorption spectrum of the CDs / CTO nanoplatelet heterojunction composite liquid crystal material, and the results show that the presence of CTO nanoplatelets has little effect on the ultraviolet light absorption performance of CDs.

[0134] Figure 5 The structural characterization of the CDs / CTO nanoplatelet heterojunction composite liquid crystal material is given, and from the XPS image it can be seen that a new C-O-Ti bond is generated in the composite material, indicating the reason for the formation of the heterojunction.

[0135] Example 2

[0136] The difference from Example 1 is only that in step (1), CoO is not added. The remaining raw materials and preparation methods are the same as in Example 1, and thus a CDs / TiO2 nanoplatelet heterojunction composite liquid crystal material is obtained.

[0137] Example 3

[0138] The difference from Example 1 is only that the CDs in step (4) are replaced by CdSe quantum dots, and the concentration is kept unchanged. The remaining raw materials and preparation methods are the same as in Example 1, and thus a CdSe / CTO nanoplatelet heterojunction composite liquid crystal material is obtained.

[0139] Example 4

[0140] This example prepares a highly ordered CDs / CTO nanoplatelet heterojunction composite film, and the preparation process includes:

[0141] A 6 V / mm electric field is applied to the CDs / CTO nanoplatelet heterojunction composite liquid crystal material of Example 1 to assist in directional arrangement, a hydrophilic ITO substrate is inserted, and then a highly ordered CDs / CTO nanoplatelet heterojunction composite film is obtained by slowly pulling at a speed of 0.3 cm / min, with an area of 1.5 cm 2 .

[0142] Figure 6 shows a schematic diagram of the preparation of a highly ordered CDs / CTO nanoplatelet heterojunction composite film, showing the electric field-assisted pulling method for preparing the film technology. Figure 7 shows a 1.5 cm 2Blue photoluminescence heterojunction thin film of CdSe / ZnS.

[0143] Example 5

[0144] The difference from Example 4 is that the 60V / cm electric field is replaced by a 200mT magnetic field, and other conditions remain unchanged, and the CDs / CTO nanosheet heterojunction composite thin film can also be obtained, as shown in Figure 8 .

[0145] Example 6

[0146] An optical device comprising the heterojunction composite liquid crystal material prepared in Example 1 or Example 2 or Example 3. The structure and principle of the optical device are shown in Figure 9 , the prepared heterojunction composite liquid crystal material is loaded into a cuvette, electrodes are implanted at both ends, and a polarizer is installed at the receiving end of the probe signal. A 365nm broadband ultraviolet light is given above the device perpendicular to the electric field, and the incident light and emission data are collected by rotating the polarizer in the parallel direction perpendicular to the electric field and the incident light. The specific operation process is as follows: without external voltage, the linear emission intensity of the sample is tested under the conditions of 90° and 0° of the polarizer. Under the condition of applying voltage (6V / mm), the linear emission intensity of the sample is tested under the conditions of 90° and 0° of the polarizer.

[0147] Figures 10-12 The emission intensity change diagram of the sample in the 90° vertical and 0° horizontal state of linearly polarized light before and after applying voltage. Figures 10-12 Corresponding to the sample Example 1, Example 2, Example 3 in turn. It can be seen that under the condition of applying voltage, the directional nanosheet arrangement makes the linearly polarized light intensity stronger, and the linearly polarized emission of the heterojunction in the 90° vertical direction is weaker than that in the 0° horizontal direction after directional modulation. From the above data, it can be seen that the blue light emission of quantum dots is realized under the assistance of the directional arrangement of titanium dioxide-based nanosheets.

[0148] Figure 13 The ultraviolet light detection ability of the optical device is shown (taking the inorganic liquid crystal composite material of Example 1 as an example). It can be seen that the difference in absorption ability of the ultraviolet electromagnetic light incident in the horizontal direction and the vertical direction (i.e. circular dichroism absorption characteristics) of the CTO nanosheet with a band gap (>4.0eV) leads to the fact that the incident ultraviolet light can also be detected, and linear detection of 360-410nm is realized.

[0149] The embodiments of the application are described in detail above with reference to the drawings, but the application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application. In addition, the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0150] The embodiments of the present application are described in detail above with reference to the accompanying drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims

1. An inorganic liquid crystal composite material, characterized by: Comprise: a solvent; a titanium dioxide-based nanosheet dispersed in the solvent, the titanium dioxide-based nanosheet having a diameter-to-thickness ratio ≥1000, a thickness of 1-2 nm, and a sheet diameter ≥2 μm; quantum dots loaded on the surface of the titanium dioxide-based nanosheet.

2. The inorganic liquid crystal composite material according to claim 1, characterized by: The material of the titanium dioxide-based nanosheet is selected from doped or non-doped titanium dioxide.

3. The inorganic liquid crystal composite material according to claim 2, characterized by: The material of the titanium dioxide-based nanosheet is selected from doped titanium dioxide, and the doping element is selected from one or more of the combination of Fe, Co, Mn, Ni, and Sn.

4. The inorganic liquid crystal composite material according to claim 3, characterized by: The molar ratio of the doping element to Ti in the titanium dioxide-based nanosheet is 1-5:

25.

5. The inorganic liquid crystal composite material according to claim 1, wherein: The quantum dots are selected from carbon-based, cadmium-based, or silicon-based quantum dots; and / or, the average particle size of the quantum dots is 1-20 nm; and / or, the mass ratio of the quantum dots to the titanium dioxide-based nanosheet is 0.001-0.1:1000.

6. The inorganic liquid crystal composite material according to claim 1, wherein: The inorganic liquid crystal composite has a solid content of 0.1-15 mg / mL; and / or, the solvent is selected from one or more of the combination of water, ethylene glycol, N,N-dimethylformamide, and dimethyl sulfoxide.

7. An inorganic liquid crystal composite material according to any one of claims 1 to 6, characterized by: The short-wave detection wavelength range of the inorganic liquid crystal composite is 305-480 nm; and / or, the long-wave detection wavelength range is 450-780 nm; and / or, the wavelength range of polarization modulation is 430-650 nm, and the ability to modulate the polarization state of luminescence is 30%-50%.

8. The method for preparing an inorganic liquid crystal composite material according to any one of claims 1 to 7, characterized by: Comprise steps: S1, mixing preparation raw materials including a titanium source, a potassium source, and a lithium source, calcining, to obtain an ion intercalated titanium dioxide-based nanosheet composite; S2, performing proton exchange and solution swelling exfoliation on the ion intercalated titanium dioxide-based nanosheet composite, to obtain a titanium dioxide-based nanosheet dispersion; S3, mixing a quantum dot dispersion and the titanium dioxide-based nanosheet dispersion, solid-liquid separation, to obtain a quantum dot@titanium dioxide-based nanosheet composite; S4, dispersing the quantum dot@titanium dioxide-based nanosheet composite in a solvent, to obtain the inorganic liquid crystal composite.

9. The method of claim 8, wherein: The titanium source is selected from one or both of titanium dioxide, titanium hydroxide, or titanium chloride; and / or, the lithium source is selected from one or more of the combination of lithium chloride, lithium oxide, or lithium carbonate; and / or, the potassium source is selected from one or more of the combination of potassium chloride, potassium oxide, or potassium carbonate; and / or, the molar ratio of the titanium source, the potassium source, and the lithium source is 25:4-7:0.7-1.

3.

10. The method of claim 8, wherein: The preparation raw materials further comprise a doping source, and the doping element of the doping source is selected from one or more of the combination of Fe, Co, Mn, Ni, and Sn.

11. The method of claim 8, wherein: In step S1, the calcination temperature is 900-1200 ℃, and the calcination time is 4-8 h.

12. The method of claim 8, wherein: In step S2, the proton exchange is performed in an acid solution.

13. The method of claim 12, wherein: The acid solution is hydrochloric acid with a concentration of 1-1.5 M.

14. The method of claim 12, wherein: The solid-liquid ratio of the ion intercalated titanium dioxide-based nanosheet composite to the acid solution is 5-30 mg / mL.

15. The method of claim 12, wherein: The proton exchange time is 30-50 h.

16. The method of claim 8, wherein: The solution swelling exfoliation comprises stirring the product after the proton exchange in a stripping agent solution.

17. The method of claim 16, wherein: The peeling agent solution is a tetrabutylammonium hydroxide solution.

18. The method of claim 16, wherein: The concentration of the peeling agent solution is 3-20 mg / mL.

19. The method of claim 16, wherein: The stirring time is 24-36 h.

20. The method of claim 16, wherein: The solid-liquid ratio of the product after proton exchange to the peeling agent solution is 1-10 mg / mL.

21. The method of claim 8, wherein: The concentration of the titanium dioxide-based nanosheet dispersion liquid is 0.1-20 mg / mL; and / or, the volume fraction of the quantum dot dispersion liquid relative to the titanium dioxide-based nanosheet dispersion liquid is 0.02 vol‰-2 vol‰; and / or, the concentration of quantum dots in the quantum dot dispersion liquid is 0.1-20 mg / mL.

22. The method of claim 8, wherein: In step S3, the mixing is stirring, and the stirring speed is 500-1000 rpm.

23. The method of claim 22, wherein: The stirring time is 15-60 min.

24. The method of claim 22, wherein: The mixing temperature is 25-60℃.

25. The method of claim 8, wherein: In step S3, the solid-liquid separation is centrifugal separation, the centrifugal separation speed is 5000-12000 rpm, and the centrifugal separation time is 5-20 min.

26. Use of the inorganic liquid crystal composite material according to any one of claims 1-7 in the preparation of a fluorescent film or optical device.

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